1998 AIChE design competition
Transcript of 1998 AIChE design competition
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ChE 4185 Final Design Project: 1998 AIChE Design Competition
Jacob Rendall & Kody Cobb 11/18/2016
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Table of Contents Executive Summary ...................................................................................................................... 6
Figure 1: Effect of Product Sale Price on ROR .................................................................................... 8
Introduction ................................................................................................................................... 8
Problem Statement ...................................................................................................................... 8
Figure 2: System Flow Schematic ........................................................................................................ 9
Figure 3: System Stream Requirements .............................................................................................. 10
Objectives .................................................................................................................................. 10
Analysis Tools ........................................................................................................................... 10
Discussion..................................................................................................................................... 10
Process Concepts ....................................................................................................................... 10
Figure 4: ANC/TOL X-Y Diagram ..................................................................................................... 11
Figure 5: TOL/XYL X-Y Diagram ..................................................................................................... 11
Process Overview ...................................................................................................................... 12
Figure 6: Initial Flowsheet .................................................................................................................. 12
Acetonitrile Column .................................................................................................................. 12
Figure 7: Effect of Pressure on ACN/TOL Seperation ....................................................................... 13
Figure 8: ACN Column Composition Profile ..................................................................................... 14
Figure 9: Tray vs Packed Column Design .......................................................................................... 15
Toluene Column ........................................................................................................................ 15
Figure 10: Effect of Pressure on TOL/XYL Separation ..................................................................... 16
Figure 11: Toluene Column Composition Profile ............................................................................... 16
Flash Drum ................................................................................................................................ 17
Mixer ......................................................................................................................................... 17
Heat Exchanger and Cooler Network ........................................................................................ 18
Table 1: Integrated Process Streams ................................................................................................... 18
Figure 12: Grand Composite Curve .................................................................................................... 19
Figure 13: Hot and Cold Composite Curves ....................................................................................... 20
Figure 14: Heat Content Diagram ....................................................................................................... 21
Figure 15: Final Heat Exchanger Path ................................................................................................ 22
Pumps ........................................................................................................................................ 22
Piping Design ............................................................................................................................ 23
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Process Description ..................................................................................................................... 23
Figure 16: Final Process Flowsheet .................................................................................................... 23
Equipment Summary.................................................................................................................. 25
Column Design .......................................................................................................................... 25
Figure 17: Structured Packing Selection ............................................................................................. 25
Table 2: Column Design Specifications .............................................................................................. 26
Table 3: Condenser and Reboiler Specifications ................................................................................ 27
Figure 18: Reflux Drum Sizing Chart ................................................................................................. 28
Table 4: Reflux Drum Specifications .................................................................................................. 28
Flash Drum Design.................................................................................................................... 29
Table 5: Flash Drum Specifications .................................................................................................... 29
Mixer Design ............................................................................................................................. 30
Table 6: Mixer Specifications ............................................................................................................. 30
Heat Exchanger and Cooler Network Design ........................................................................... 30
Table 7: Heat Exchanger Specifications ............................................................................................. 31
Table 8: Cooler Specifications ............................................................................................................ 32
Storage Tank Design ................................................................................................................. 32
Table 9: Storage Tank Specifications ................................................................................................. 33
Pump Design ............................................................................................................................. 33
Table 10: Process Pump Specification ................................................................................................ 33
Figure 19: Vacuum Pump Sizing ........................................................................................................ 34
Table 11: Vacuum Pump Specification .............................................................................................. 34
Piping Design ............................................................................................................................ 35
Figure 20: Piping Specifications ......................................................................................................... 35
Utility Summary ........................................................................................................................ 35
Table 12: Utility Costs ........................................................................................................................ 36
Table 13: Annual Utility Usage .......................................................................................................... 36
Table 14: Annual MEK Material Costs .............................................................................................. 37
Table 15: MEK Chiller Justification ................................................................................................... 38
Process Flow Diagram (PFD) ..................................................................................................... 38
Figure 21: Control Loop Hardware ..................................................................................................... 38
Figure 22: Piping and Instrumentation Diagram ................................................................................. 39
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Mass and Energy Balances ......................................................................................................... 40
Table 16: Process Stream Tables ........................................................................................................ 40
Safety, Environmental and Health Issues ................................................................................. 47
Pressure and Vessel Analysis .................................................................................................... 47
Table 17: MAWP ................................................................................................................................ 48
Table 18: MAWT ................................................................................................................................ 49
Fire Protection ........................................................................................................................... 49
Health Considerations ............................................................................................................... 50
Spill Containment ...................................................................................................................... 50
Inherently Safer Checklist ......................................................................................................... 50
HAZOP...................................................................................................................................... 53
Potential Concerns..................................................................................................................... 53
Figure 23: Example Risk Matrix ......................................................................................................... 54
Figure 24: HAZOP Case Summary .................................................................................................... 55
Figure 24a: HAZOP for ACNCOL ..................................................................................................... 56
Figure 24b: HAZOP for TOLCOL ..................................................................................................... 57
Figure 24f: HAZOP for Heat Exchanger Network ............................................................................. 60
Figure 24g: HAZOP for Pipes ............................................................................................................ 61
Figure 24h: HAZOP for Pumps .......................................................................................................... 61
Figure 24j: HAZOP for Makeup ......................................................................................................... 63
FMEA ........................................................................................................................................ 63
Figure 25: FMEA severity ranking ..................................................................................................... 63
Figure 26: FMEA occurrence ranking ................................................................................................ 64
Figure 27: FMEA detection ranking ................................................................................................... 64
Figure 24: FMEA ................................................................................................................................ 68
Process Economics ...................................................................................................................... 68
Table 19: Process Equipment Costs .................................................................................................... 69
Table 21: Additional Cost Allowances ............................................................................................... 70
Table 21: Total Capital Investment ..................................................................................................... 71
Table 22: Xylene Purchase Cost ......................................................................................................... 71
Table 23: Waste Disposal Cost ........................................................................................................... 72
Table 24: Labor Costs ......................................................................................................................... 72
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Table 25: Operating Costs................................................................................................................... 72
Table 26: Annual Revenue .................................................................................................................. 73
Table 27: Annual Depreciation Allowance ......................................................................................... 73
Table 28: Cash-Flow for Solvent Recovery System ........................................................................... 74
Improvement Recommendations ............................................................................................... 74
Acknowledgments ....................................................................................................................... 75
References .................................................................................................................................... 77
Appendix ...................................................................................................................................... 78
Heat Exchanger Network .......................................................................................................... 78
Piping Design ............................................................................................................................ 79
Vacuum Pump Sizing ................................................................................................................ 83
Flash Drum Sizing ..................................................................................................................... 84
Mixer Sizing .............................................................................................................................. 85
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Executive Summary
In this report, we summarize our design for a solvent recovery system. We process waste streams
from our siloxane process into reusable acetonitrile and toluene streams. Our design reduces the
amount of raw materials we need to buy and the amount of waste we produce.
We investigate several different options for separating pure acetonitrile and toluene from a
system containing acetonitrile, toluene, xylene, and siloxane. We create a safe design with three
separation units that complete the required separations. We use two distillation columns and a
flash tank. We break an azeotrope between acetonitrile and toluene in the first column by
operating at a vacuum and by adding xylene as an extractive agent. We cool all product and
waste streams below flash points in order to operate safely.
We optimize each aspect of the design to minimize costs. We analyze operating pressure, feed
location, and reflux ratio on each column. We use pinch analysis to integrate our heat streams in
order to reduce utility cost, and use utilities only where necessary. We reduce our Xylene feed to
the process to an optimum point where the separation occurs without incurring excess material
costs.
We complete an in depth safety analysis in this report to ensure safe operations. We complete a
HAZOP in Figure 24 and a FMEA in Figure 27. We also provide safety recommendations
regarding fire and chemical safety.
We recommend the purchase of two packed distillation columns with reflux drums, reboilers and
condensers, one flash drum, five heat exchangers, four coolers, a mixer, a chiller, and a tank farm
in order to recycle the solvent coming out of the process. We size and summarize the equipment
specifications in the Equipment Summary section. We provide a list of process equipment costs
in Table 19 in the Process Economics section.
We need plant cooling water, electricity, low-pressure steam, and high-pressure steam to
complete this process. We purchase an MEK chiller and recovery system in order to provide
further utilities to the solvent recovery process.
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We provide a detailed process economic evaluation on associated costs, revenue, and cash flow.
We recommend a SOYD depreciation scheme and calculate the economic benefit of
implementing this solvent recovery system. Table 28 shows our cash flow analysis.
We attain our process information using Aspen Plus v9.0. We create a detailed process flowsheet
and use the simulation engine to calculate mass and energy information about our process. We
leverage the software to provide accurate sizing on all of our equipment. We use EconExpert
(http://www.ulrichvasudesign.com/econ.html) to estimate purchase costs for all of our
equipment. We use a price index of 544 based on prices in August 2016.
The solvent recovery system recovers acetonitrile at a rate of 158.2 kg/hr and toluene at a rate of
362.8 kg/hr. These numbers correspond to annual recovery rates of 1265600 kg/ year of
acetonitrile and 2902697 kg/ year of toluene. We show all process stream flows in our mass
balance in Table 16.
We estimate that the implementation of this solvent recovery system will yield a rate of return of
102.9 %. The process requires a $4.6 million total capital investment and $2.2 million annual
product costs but generates $9.7 million in annual revenue. The solvent recovery system will pay
itself back within the first year, and generate almost $90 million dollars of profit through its 20-
year life span. We highly encourage the purchase of this system.
We find that the system is a good investment regardless of material price fluctuation. We see the
effect of material sale price on our rate of return in Figure 1:
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Figure 1: Effect of Product Sale Price on ROR
We see that even when the products approach low sale prices we still achieve greater than 10%
ROR. We recommend that you purchase, install, and operate this system as soon as possible. We
do not include a specific timeline but recommend an aggressive one in order to realize cost
savings as soon as possible.
Introduction
Problem Statement
We complete the task of designing a solvent recovery system. The system contains acetonitrile,
toluene, xylene, and siloxane. Feeds A, B and C enter the solvent recovery system. Feed stream
A has a flow rate of 270 kg/hr consisting of 98.5% toluene and 1.5% siloxane. Feed B has a flow
rate of 60 kg/hr consisting of 96.5% toluene, 2% acetonitrile, and 1.5% siloxane. Feed C has a
flow rate of 200 kg/hr consisting of 19.5% toluene, 78.5% acetonitrile, and 2% siloxane. These
feeds produce two recycle streams and one waste stream. Figure 2 shows the feed streams
entering the solvent recovery system from the process:
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Figure 2: System Flow Schematic
Figure 2 also shows the recycle streams flowing from the solvent recovery process. One recycle
stream has a flow rate of 158.2 kg/hr and an acetonitrile composition of 99.87%. Another
recycle stream has a flow rate of 362.84 kg/hr and a toluene composition of 99.92%. The waste
stream purges the system of siloxane. The waste stream flows at 36.11 kg/hr and consists of
about 75% xylene and 25% siloxane. The waste stream has these compositions to avoid siloxane
precipitation in the system, which occurs at concentrations above 25%. A final make-up feed
adds xylene back into the system. Figure 3 summarizes the flow requirements:
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Figure 3: System Stream Requirements
Objectives
These objectives are the drivers for this project and process optimization.
Maximize solvent recovery and cost savings.
Minimize capital requirements.
Minimize utility usage and variable costs.
Minimize process waste and remediation related costs.
Facilitate a safe operating environment.
We focus on these objectives while completing this project. The basis of all objectives lie in
either economics or safety, so in addition to an extensive design section, we also provide
economic and safety evaluations.
Analysis Tools
We design and analyze this process primarily with Aspen Plus v9.0. This software leverages a
powerful simulation engine to carry out many complex calculations. We model the physical
properties of all the relevant components except for siloxane using Aspen Plus databases. We
receive the physical properties of siloxane from Dr. Liu and manually input them into Aspen
Plus. We use the NRTL-RK thermodynamic equation of state to perform thermodynamic
analysis.
We design the necessary equipment using Aspen Plus, engineering heuristics, several
professional sources, and common sense. We acquire pricing information from EconExpert’s
online database. We use a cost index to extrapolate pricing information from years past.
Discussion
Process Concepts
We face the challenge of overcoming an azeotrope between acetonitrile and toluene in this
system. We investigate how pressure affects this azeotrope in Figure 4:
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Figure 4: ANC/TOL X-Y Diagram
As we lower the pressure in the column, the azeotrope moves further to the right and we can
obtain a higher mole fraction of acetonitrile. We operate at 0.1 bar in our first column, and use
xylene as an extractive agent to fully break the azeotrope and reach the acetonitrile purity
specification.
We separate toluene and xylene in a second column. We investigate the effect of pressure on this
separation in Figure 5:
Figure 5: TOL/XYL X-Y Diagram
We operate the toluene column at atmospheric pressure. We do not gain a large enough benefit
from changing the pressure so we stay at ambient conditions.
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We complete our final separation between xylene and siloxane with a flash tank. We use a flash
tank instead of a column because it is much cheaper and can complete the required separation.
We operate the flash drum in a manner so that the weight percent of siloxane in the liquid bottom
stream does not go over 25%. At concentrations above 25% siloxane precipitates out of the
solution and causes process problems.
Process Overview
We propose using a process with three separation units, an extractive vacuum column, an
ordinary distillation column, and a flash tank. The first column separates acetonitrile from the
system at the required rate. The second column separates Toluene from the system. The flash
tank separates Xylene from a waste stream. We utilize coolers to cool product and waste streams
to safe temperatures (below their flash points). Figure 6 shows our initial basic flowsheet:
Figure 6: Initial Flowsheet
This flowsheet meets all process requirements and is the basis of our final design. We optimize
the initial design by applying engineering heuristics. We manipulate feed locations, reflux ratios,
and heat paths to meet our project objectives.
Acetonitrile Column
The two columns make up the bulk of the design and capital investment. Therefore, we take
careful considerations while we design them. We first consider how to address a boiling point
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azeotrope between acetonitrile and toluene. We separate acetonitrile from the other components
using vacuum extractive distillation, with xylene being the extractive agent. The vacuum requires
more input cost, but provides necessary benefit. Using Aspen Plus binary component analysis,
we find that switching the operating pressure from 1 bar to 0.1 bars moves the azeotrope from
82% pure acetonitrile to 87% acetonitrile. This 5% difference lowers the temperature profile of
the column from 80-110oC to 20-45oC and reduces steam consumption. Figure 7 shows the effect
of pressure on the separation of acetonitrile and toluene:
Figure 7: Effect of Pressure on ACN/TOL Seperation
Further analysis shows that the separation of acetonitrile at 99.87% is impossible without
operating at a vacuum. The addition of xylene eliminates the azeotrope from our range of
operation, and allows us to reach the desired specification.
We decide the feed locations of the fist column based on the composition profile inside the
column, and ease of separation within that profile. We use Aspen Plus to analyze the
composition profile of multiple scenarios. Figure 8 shows the composition profile of the final
design:
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Figure 8: ACN Column Composition Profile
We utilize the height of the column as efficiently as possible by placing the B and C feed
locations toward the bottom (stage 25). We use the top of the column to achieve the final 2%
separation between acetonitrile and toluene. Figure 6 shows the clear effect that xylene has on
the equilibrium between acetonitrile and toluene. We add xylene at stage 10 and there is an
immediate jump in the acetonitrile liquid composition, and a small jump in the vapor
composition.
We adjust the reflux ratio in the column until we achieve the required distillate composition of
acetonitrile in the distillate. The simulation then meets the specified distillate rate by adjusting
the reboiler duty. Our final design uses 28 theoretical stages, a mass reflux ratio of 2.8, and a
distillate rate of 158.2 kg/hr.
We decide to use a packed column instead of a tray column because the flow rates through the
column are relatively low in this system. This causes the diameter of the acetonitrile column to
be small (0.62 meters). We show the difference between a tray and packed column in Figure 9:
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Figure 9: Tray vs Packed Column Design
The packed column has fixed structured packing inside instead of weir trays. The packing
influences the flow profile inside the column and maximizes vapor liquid interactions. Packed
columns are favored in columns with small diameters. Our final acetonitrile column is a 5.98
meter packed column with 5.2 meters of Sulzer MellaPak 750Y structured packing having an
HETP of 0.2 meters, and a partial reboiler. This is the equivalent of 28 theoretical stages.
Toluene Column
The second column separates toluene from xylene and siloxane. We carry this separation out at
atmospheric conditions using ordinary distillation. This column operates at atmospheric pressure
to avoid costly pressure manipulation systems. The temperature gradient within the column is
110oC to 145oC, which we manage using plant utility streams. Figure 10 shows the effects of
pressure on the toluene/xylene separation:
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Figure 10: Effect of Pressure on TOL/XYL Separation
Figure 7 confirms that there is no advantage to operating at non-ambient pressures. We choose
feed locations to best utilize the height of the column. We choose feed locations of 3 and 16 for
the A feed and the feed from the bottom of the first column respectively. These feed locations
give a broad composition profile. Figure 11 shows the composition profile of the toluene
column:
Figure 11: Toluene Column Composition Profile
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We utilize the top of the toluene column to achieve the final few percent of the separation much
like the acetonitrile column. Feed A comes in towards the top of the column and acts as internal
reflux, which minimizes the reflux ratio. We use 23 stages, a reflux ratio of 2.3, and a distillate
rate of 362.8 kg/hr in our final column design.
We decide to use a packed column for the internals of the toluene column because of the column
size (0.45 meter diameter). Our final toluene column is a 4.83 meter packed column with 4.2
meters of Sulzer MellaPak 750Y structured packing having an HETP of 0.2 meters, and a partial
reboiler. This is the equivalent of 23 theoretical stages.
Flash Drum
We utilize a flash block as a low cost option to separate the bottom feed of the second distillation
column into two streams. The liquid waste stream purges the system of siloxane. The stream
leaves the flash tank at siloxane’s solubility limit, 25 wt%. We prevent siloxane precipitation and
potential safety issues by implementing this purge. This stream classifies as Option B waste, and
costs 1.5 $/kg to process.
We recycle the vapor xylene coming off the top of the flash tank. We condense the vapor and
then feed it to a mixer with fresh xylene, and eventually back into the first column. The flash
block meets the 25% siloxane concentration requirement using operating conditions of 140.5oC
and 1 atm. We control the flash tank temperature using a jacket.
Mixer
We use a mixer to mix the condensed recycled xylene with a fresh make up xylene stream. We
choose a makeup flow rate to restore the pure xylene flowrate to 100 kg/hr. We assume that the
xylene make up stream is at ambient conditions. We choose a holding time of 5 minutes to
ensure the makeup stream and recycle stream reach composition and temperature equilibrium.
We use the xylene feed leaving the mixture as the xylene feed to the first distillation column.
This xylene acts as the essential extractive agent.
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Heat Exchanger and Cooler Network
We implement the biggest changes from our initial process flowsheet to our final flowsheet by
integrating our heat streams. We do this through Pinch analysis. We first identify all of our
process streams that need heating or cooling, and designate target temperatures for each stream.
We identify our feed streams as potential cold streams if we preheat them. In order to optimize
our preheat temperature designation we look at our column temperature profiles. We have a
temperature profile of 21oC – 54oC in our fist column so we decide not to preheat feeds B and C.
The second column has a temperature distribution of 110oC to 138oC, but we use the A feed
stream as internal reflux so we only preheat it to 84oC. We include the condensation of the
xylene recycle stream, by including the latent heat of condensation in its heat capacity flow.
Table 1 shows the streams we integrate and their relevant properties:
Table 1: Integrated Process Streams
We use Pinch analysis and a 5oC minimum temperature approach to analyze the heat flow
through the system and to determine the minimum duty required from utilities. We find a Pinch
temperature of 137.9oC indicating that below this temperature, we need only cooling, and above
the pinch temperature we need only heating. Our process operates below the pinch temperature
so we only need cooling. We calculate a minimum cooling duty of 20.81 kW. We create a grand
composite curve in Figure 12 to visualize the heat flow through the system:
Hot Streams Cp, J/kg*K m, kg/hr mCp, W/C Temp Change, K Duty Req, kW Temp In Temp Out
ACNProd 2018.97 158.2 88.72 16 1.42 21.4 5.4
TOLProd 1820.95 362.84 183.53 105.6 19.38 110 4.3
Waste 1447.24 36.11 14.52 115.5 1.68 140.4 27.1
XYLRec --- 72.55 2986.96 2.30 6.87 140.4 138.10
Cold Streams Cp, J/kg*K m, kg/hr mCp, W/C Temp Change, K Duty Req, kW Temp In Temp Out
Feed A 1659 270 132.76 64 8.55 20 84
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Figure 12: Grand Composite Curve
We see that the process does not extend past the pinch temperature and only requires cooling.
We also verify that this minimum cooling requirement is 21.81 kW. We conduct further analysis
and graph the hot and cold composites in Figure 13:
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Figure 13: Hot and Cold Composite Curves
We see again that the process requires no heating, and only 21.81 kW of cooling. We calculate a
minimum number of exchangers of 5 based on 4 hot streams, 1 cold streams, and 1 cooling
utility requirement. We use the minimum 5 exchangers, broken down into 2 heat exchangers and
3 coolers. We designate our exchangers in Figure 14 using a heat content diagram:
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Figure 14: Heat Content Diagram
We designate the heat exchangers based on the heuristic of matching heat blocks on the top of
the hot side with heat blocks on the top of the cold side. We summarize our final heat exchanger
network in Figure 15:
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Figure 15: Final Heat Exchanger Path
We use this heat exchanger path to meet the required temperatures summarized in Table 1. All
coolers cooling process streams below 45oC use MEK as a coolant, otherwise they use cooling
water. This ensures a minimum temperature approach of 10oC for all utility streams.
We save $2,672 annually through heat integration. Through the 20-year life span of the project,
we save $53,440 because of our heat integration. We also reduce the number of exchangers
necessary by one.
Pumps
We use three pumps in our final process to change process pressures. We need a pump on each
of the two outlet streams coming off the first column. The first pump is on the bottoms stream
and brings the pressure up to 1 bar before the bottoms stream enters the second column. The
second pump pressurizes the distillate flow to 1 bar before it arrives at the product storage tank.
We need a vacuum pump on the outlet of the condenser in the first column to control operating
pressure. In addition to the three process pumps, we use 7 pumps to move process material from
one unit operation to the next. We also buy back up pumps for all pump applications to avoid
shutting down operations in the event of a pump failure.
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Piping Design
We use a design heuristic1 to calculate what schedule piping to use, assuming room temperature
operation. We use the largest flow rate that flows in the piping and assume properties similar to
water. We use 316 SS Schedule 5S 3” diameter. We show calculations below:
Largest flowrate = 31.03 𝑚3
ℎ𝑟= 136.6 𝑔𝑝𝑚
Assume water velocity of 5𝑓𝑡
𝑠
V = 0.408𝑄
𝐷2
D = 3.3 in
44 ksi max stress
Schedule = 1000 𝑃
𝑆= 1000 (
14.7
44000) = 0.3 → Schedule 5S
Process Description
We make changes from our initial process flowsheet to increase cost savings, safety, and overall
ease of operating. Figure 16 shows our final process flowsheet:
Figure 16: Final Process Flowsheet
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The major change we made from the initial flowsheet is heat integration. This makes the flow
sheet harder to follow but results in cost savings in relation to utilities. We use E1 and E2 to
exchange heat between feed stream A which needs heating, and product streams that need
cooling. We also use three coolers, C1, C2, and C3 to provide additional cooling to the process
streams. We operate at the minimum cooling duty found in our pinch analysis.
The ACNCOL distillation column separates acetonitrile from other components. PUMP2
pressurizes the distillate stream to 1 bar before it is cooled by MEK in C1 and leaves the process.
PUMP1 pressurizes the bottoms stream from the first column to atmospheric pressure. The
bottoms stream then enters the second column. We use MEK in our ACNCOL condenser and
low pressure steam in our reboiler.
The TOLCOL distillation column separates toluene from xylene and siloxane. The TOL product
stream flows through coolers C2, and C3 until it reaches a temperature below toluene’s
flashpoint. C2 cools the toluene product to 45oC using cooling water. C3 cools the toluene
product to 4.3oC with MEK. The bottoms stream is a mixture of xylene and siloxane. This stream
flows to a flash drum, FLASH for further separation. We use cooling water in our TOLCOL
condenser and high-pressure steam in the reboiler.
The separation of xylene and siloxane does not require a third distillation column. The relative
volatilities between components is great enough so that we complete the separation with a flash
drum. The liquid stream, WASTE1, flows from the flash drum just below 25% siloxane.
WASTE1 flows through E1 and leaves the process at 27oC, which is below the flash point of
xylene.
XYLVAP leaves the flash drum as a vapor and condenses in E2. From this cooler, XYLMID
flows into the mixer, MIX and combines with makeup xylene. XYLREC flows from the mixer to
the first distillation block and completes the internal recycle stream. We reduce the amount of
xylene recycle from 200 kg/hr to 100 kg/hr. This results in equipment, material, and utility cost
savings while maintaining the required separation.
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Equipment Summary
Column Design
We size our column diameters based on the vapor flowrates in the column, and the height based
on the required number of stages to complete the separation. We sized the diameters so that no
section would experience greater than 80% flooding. We use the tower heuristic in table 9-13
from the heuristic handout that suggests structured packing with diameters less than 0.9m.
We pack both columns with stainless steel Sulzer Mellapak 750Y structured packing. This
packing performs well at various temperatures and pressures, which works well with both
columns. We choose MellaPak 750Y because it has a low and constant HETP (0.2 m) at our
ranges of operation. We show this in Figure 17:
Figure 17: Structured Packing Selection
We design the columns using these packings specifications and the operating conditions from the
discussion section. Table 2 shows the final column designs:
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Table 2: Column Design Specifications
We run the columns so that we achieve product concentrations slightly greater than necessary to
avoid for any variation in the feed streams or unforeseen problems. We calculate a total height
for each column by multiplying the height of packing by a factor of 1.15. We use stainless steel
in the construction of each column and in the packing to avoid process side corrosion.
We use a total condenser and partial reboiler in both of our columns. Both condensers are shell
and tube heat exchangers with the process tube side and the coolant shell side. The tubes are
316SS and the shells carbon steel. We use partial kettle reboilers. The reboiler on the first
column uses low-pressure steam (25psig) and the reboiler on the second column uses high-
pressure steam (150psig). We construct the reboilers with SS316. Table 3 shows the condenser
and reboiler specifications:
Specifications
Bottom Temperature [°C]
Top Temperature [°C]
Reflux Ratio
Pressure [bar]
# of Stages
HETP
Diameter [m]
Height [m]
Pack Height [m]
Packing Vendor
Packing Type
Material
Cost
Component Weight Percent Component Weight Percent
Acetonitrile 0.9990 Acentonitrile 0.0005
Toluene 0.0007 Toluene 0.9995
Siloxane trace Siloxane trace
p-Xylene 0.0003 p-Xylene trace
Water 0 Water 0
Acetonitrile 0.0008 Acentonitrile trace
Toluene 0.4804 Toluene 0.0046
Siloxane 0.0249 Siloxane 0.0830
p-Xylene 0.4940 p-Xylene 0.9124
Water 0 Water 0
316SS 316SS
Distillate Stream Compositions (wt%)
Bottoms Stream Compositions (wt%)
Sulzer Sulzer
MellaPak 725 MellaPak 725
$89,744 $60,779
0.62 0.45
5.98 4.83
5.2 4.2
0.2 0.2
21.39 110.01
Distillation Towers with Total Condenser and Reboiler
Column 1 Column 2
53.85 138.29
2.8 2.3
0.1 1
28 23
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Table 3: Condenser and Reboiler Specifications
We use EconExpert to do cost estimates, however, for a kettle reboiler there is a 10m3 minimum
volume in the software. We assume this is a minimum reboiler cost and use the cost for 10m3.
We determine the flow rates of coolant to the condenser on the basis that the MEK outlet
temperature cannot exceed -19oC, and that the plant-cooling tower recovers cooling water at
temperatures less than 45oC.
We determine steam flow rates to the condenser so that the steam fully condenses at the outlet of
the exchanger with very little superheating. This ensures the most efficient heat exchange
between steam and the process side (latent heat is better than specific heat). This also minimizes
potential problems with the condensate recovery system.
We size our reflux drums in each column assuming a holding time of 5 minutes. We calculate a
total flowrate into the reflux drums by combining the distillate and reflux streams leaving. We
use these numbers and the procedure in our project handout. We assume a liquid space of 50%.
We use Figure 18 to size our reflux tanks:
Specifications
Area [m2]
Heat Duty [kW]
U [W/m2C]
Type
Cost
StreamACN
ProcessMEK
TOL
Process
Cooling
Water
ACN
Process
Low P
Steam
TOL
Process
High P
Steam
Pressure in [bar] 0.1 1 1 1 0.1 2.74 1 11.35
Pressure out [bar] 0.1 1 1 1 0.1 2.74 1 11.35
Temperature in [°C] 21.39 -29 110.2 35 52.18 130.5 138.3 185.6
Temperature out [°C] 21.39 -19 110.2 45 53.85 130.5 138.3 185.6
Vapor Fraction in 1 0 1 0 0 1 0 1
Vapor Fraction out 0 0 0 0 0.85 0 0.93 0
Flow rate [kg/hr] 601 25236 1197 10446 1313 211 1507 241
$8,490 $6,463 $19,373 $19,373
126.1
1140
KettleShell and Tube Shell and Tube Kettle
850 850 1140
Reboilers
TOL-REB
2.43
131.9135.6 120.5
Condensers
3.53 2.03 1.39
ACN-COND TOL-CON ACN-REB
28
Figure 18: Reflux Drum Sizing Chart
We get a diameter and length for each tank from this chart. We extrapolate the length of the
length axis in order to intersect our line. Table 4 summarizes our flash tank specifications:
Table 4: Reflux Drum Specifications
We construct our drums with stainless steel. Both drums are relatively small but this makes sense
with the given process flowrates.
Specification Column 1 Column 2
Diameter (m) 0.152 0.457
Length (m) 1.524 1.524
Volume (m^3) 0.028 0.25
flow rate (gal/hr) 202.9 404.7
Reflux Ratio 2.8 2.3
Liquid Space (%) 50% 50%
Material 316SS 316SS
Purchased Cost $6,574 $9,240
Reflux Drums
29
Flash Drum Design
We size the flash drum using the procedure from “Flash distillation: examples-flash drum,
sizing” by P.C. Wankat. We include all of the calculations in the appendix. We follow the design
heuristics outlined in “Chemical Process Equipmet” by James R. Couper to orientate our vessel.
These heuristics call for a vertical drum in liquid/gas separation applications.
We assumed a liquid hold up time of 5 min in our calculations. We calculate a diameter less than
a foot, so we round up to a minimum diameter of 1 ft. We use the liquid hold up and diameter to
calculate a diameter of 5 ft. We get an H/D of 5, which is consistent with the heuristics. We also
consider a 50% fill percentage and double our volume. Table 5 summarizes the flash drum
design excluding the 50% fill percentage factor:
Table 5: Flash Drum Specifications
Specification
Temperature [C]
Pressure [bar]
Diameter [m]
Height [m]
Volume [m^3]
Heat Duty [kW]
Type
Material
Cost
Component Weight Percent
Acetonitrile trace
Toluene 0.0058
Siloxane 0.0019
p-Xylene 0.9923
Water 0
Acetonitrile trace
Toluene 0.0023
Siloxane 0.2421
p-Xylene 0.7556
Water 0
$24,094
Vapor Stream
Compositions
(wt%)
Liquid Stream
Compositions
(wt%)
1.925
0.224
6.9
Vertical with Demister Pad
316SS
Drum Separator
Flash Drum
140.4
1.01
0.385
30
The final volume including the 50% liquid fill percentage is 0.224m3. We include a demister pad
in our design to help with the efficiency of the separation and to maximize entrainment removal.
We ensure that the siloxane composition leaving the drum is well below its solubility limit of
25%. We fulfill the flash drum heating requirement (6.9 kW) with an electrical heating jacket.
We calculate the electrical demand of the flash drum using a conservative efficiency of 0.5. The
flash drum requires 1192 MJ/day of electricity.
Mixer Design
We use a motionless mixer because both the xylene recycle stream and make up stream are
predominately xylene (we do not need agitation). We use a hold up time of 5 minutes and a
liquid level of 70%. We assume a length/diameter ratio of 3:1. Table 6 shows the mixer
specifications:
Table 6: Mixer Specifications
We calculate the make-up flow rate of pure xylene so that 100 kg/hr of xylene flows from the
mixer at all times.
Heat Exchanger and Cooler Network Design
We use Aspen Plus to size our integrated heat exchangers and coolers. We get relatively small
areas so we use double pipe heat exchangers for all our exchangers and coolers. We do this in
accordance with the heuristics proved in table 9.11 from the heuristics handout. Table 7 shows
the heat exchanger specifications:
Specification
Hold time [mins]
Volume [m3]
Diameter [m]
Length [m]
Material
Cost
Outgoing Streams
Recycle Make Up Xylene Feed
Pressure [bar] 1 1 1
Temperature [°C] 138.145 25 108.99
Mass Flow Rate [kg/hr] 72.46 28.06 100.5
Incoming Streams
$13,148
316SS
Motionless Mixer
5
0.0153
0.1867
0.56
31
Table 7: Heat Exchanger Specifications
We use the minimum heat exchanger cost in EconExpert, which specifies a minimum area of
0.65m3. We use overall heat transfer coefficients that correspond with liquid-liquid heat transfer
from the heuristics handout. We save 17.1 kW of heating and cooling utilities by the use of this
heat exchanger network. This heat integration saves $2,673 annually on utilities. We have
process flow on both sides of the heat exchangers so all parts are made of 316SS.
We save money on utilities through implementation of this heat integration network, but we have
to take special considerations with process start up since we cool feed streams with product
streams. We resolve this issue by using utilities to cool both of the product streams.
We use 2 MEK coolers and a water cooler to finish cooling our process streams. We cool the
process below potentially hazardous flash point temperatures with these coolers. Table 8 shows
all cooler specifications:
Specifications
Area [m2]
Heat Duty [kW]
U [W/m2C]
Type
Cost
Stream Waste A FeedXylene
RecycleA Feed
Pressure in [bar] 1 1 1 1
Pressure out [bar] 1 1 1 1
Temperature in [°C] 140.4 20 140.4 33.6
Temperature out [°C] 27 33.6 138.1 84.4
Vapor Fraction in 0 0 1 0
Vapor Fraction out 0 0 0 0
Flow rate [kg/hr] 37 270 73 270
$7,422 $7,422
0.104
1.70 6.87
E1 E2
Heat Exchangers
280 850
Double Pipe Double Pipe
0.166
32
Table 8: Cooler Specifications
We designate all of the MEK flowrates so that MEK leaves the process at -29oC, and we set the
cooling water flowrate so that it leaves at 45oC.
Storage Tank Design
We follow the storage heuristics outlined in the heuristics handout to size our storage tanks. We
have 12 storage tanks total plus a spill container. We have 6 primary process storage tanks, one
for each feed stream and one for each product or waste stream. Feed streams B and C enter the
first distillation column at the same feed stage location so we use the same storage tank for these
streams. We purchase a backup storage tank for each primary stream as well in case we need to
clean a tank, require additional storage, or some other unknown factor.
We assume that the maximum level in any tank is 80% for 15 days of operation. We assume a
length/diameter ratio of 3/1. We size the spill container so that it is 1.5x the size of the largest
process storage tank. We use a cone roof design because it is the most cost effective. Table 9
summarizes the storage tank specifications:
Specifications
Area [m2]
Heat Duty [kW]
U [W/m2C]
Type
Cost
StreamACN
ProductMEK
TOL
Product
Cooling
Water
TOL
ProductMEK
Pressure in [bar] 1 1 1 1 1 1
Pressure out [bar] 1 1 1 1 1 1
Temperature in [°C] 21.4 -29 110 35 45 -29
Temperature out [°C] 5.4 -19 45 45 4.3 -19
Flow rate [kg/hr] 158 264 363 1082 363 1285
C3
$4,206 $4,206
Double Pipe Double Pipe
850 850
C1 C2
Coolers
$4,206
Double Pipe
850
6.91
0.525
1.42 12.52
0.136 0.501
33
Table 9: Storage Tank Specifications
Pump Design
We size our pumps based on the power they add to the system. Both process pumps are rotary
pumps. We use rotary pumps because our flow rates are too small for centrifugal pumps.
Centrifugal pumps are inefficient with flow rates below 15 gpm, our flow rates are both 1 gpm.
We show our process pump in Table 10:
Table 10: Process Pump Specification
We size our vacuum pump using the procedure outlined in the project handout. We need to
maintain a rough vacuum at 75 torr. Our operating requirements favor a one-stage liquid ring
pump. We use Figure 19 to size our pump:
L/D
liquid level
holding time (days)
Specifications A Feed B and C Feeds Waste TOL Product ACN Product Make Up Xylene Spill Container
Type cone roof cone roof cone roof cone roof cone roof cone roof cone roof
Diameter (m) 3.91 4.01 2.01 4.28 3.40 1.84 4.90
Height (m) 11.72 12.04 6.04 12.84 10.20 5.52 14.70
Volume (m^3) 140.63 152.40 19.27 184.80 92.63 14.68 277.20
Flow Rate (m^3/day) 7.5 8.128 1.02759 9.856 4.94 0.7827 N/A
Material 316SS 316SS 316SS 316SS 316SS 316SS 316SS
Cost $67,409 $70,349 $25,270 $78,007 $54,206 $22,341 $97,332
Storage Tank Design
3
80%
15
Streams
Specification PUMP-1 PUMP-2
Fluid Power [kW] 0.0062 0.0051
Flow Rate [cum/hr] 0.243 0.202
Head developed [m] 11.16 11.73
Pressure in [bar] 0.1 0.1
Pressure out [bar] 1.01 1
Net Work [kW] 0.021 0.017
Total Efficiency 0.54 0.54
Electrical Demand [kJ/day] 3360 2736
Cost $5,249 $5,023
Pump Sizing
34
Figure 19: Vacuum Pump Sizing
We use Figure 19 to arrive at a 22 HP requirement. We use this and the following HP/cost
relationship to calculate cost:
𝐼𝑛𝑠𝑡𝑎𝑙𝑙 𝐶𝑜𝑠𝑡 = $28,000 (𝐻𝑃
10)
0.5
(544
297)
We place the vacuum pump coming off the condenser in the first column. We summarize our
vacuum pump specifications in Table 11:
Table 11: Vacuum Pump Specification
Specification One Stage Liquid Ring
Vaccum Pressure [bar] 0.1
Vacuum Pressure [torr] 75
Horse Power 22
Total Efficiency 0.54
Electrical Demand [MJ/day] 2625
Cost $76,070
Vacuum Pump
35
We calculate an electrical demand in all of our pumps using a driver efficiency of 90% and a
pump efficiency of 60%. We combine these to get an overall efficiency of 54% for our pumps.
We use 2631 MJ/day of electricity with our pumps.
We purchase an additional 6 pumps which are specified in our process flow diagram. We use
these pumps to move material between storage tanks and the process and from one unit operation
to another. We assume a price of $4,000 per pump based on our first two pumps.
We purchase back up pumps in addition to the primary process pumps so we are ready if a pump
breaks. Pumps are relatively cheap and are an integral to operations. Pumps need to be replaced
more frequently than other equipment so we pay more to insure ourselves in the event of a pump
failure.
Piping Design
We choose to use 316SS piping. Our sizing follows Aspen Plus resulting flow rates, design
heuristics, and 316 SS testing data. We provide specifications for the piping in Figure 20:
Figure 20: Piping Specifications
Utility Summary
We use low-pressure steam, high-pressure steam, cooling water, MEK, and electricity as utilities
in our process. We calculate our annual utility cost using given utility costs. We summarize our
utility costs in Table 12:
Diameter [in] 3.3
Mas Stress [ksi] 44
Schedule 5S
Material 316SS
Piping Specifications
36
Table 12: Utility Costs
We use cooling water and electricity instead of MEK and steam wherever possible because of
cheaper costs. We show our annual utility usage in Table 13:
Table 13: Annual Utility Usage
We notice that the major utility consumption comes from the ACNCOL condenser. This cost is
so high because the first column has a low temperature profile because of its operating pressure.
We need to operate the column with its current specifications to meet the acetonitrile spec so we
cannot reduce this condenser cost.
Utility Cost Amount Units
Cooling Water $0.03 1000 L
MEK $19.70 1000000 kJ
Low P Steam $21.10 1000 kg
High P Steam $24.40 1000 kg
Electricity $0.02 1000 kJ
Cost of Utilities
Equipment Utility Amount Units Cost
Reboiler 1 low P steam 1688 1000 kg/yr $35,617
Reboiler 2 high P steam 1926 1000 kg/yr $46,996
$82,613
Condenser 2 cooling water 84906 1000 L/yr $2,547
C2 cooling water 8795 1000 L/yr $264
$2,811
Condenser 1 MEK 3905 1000 MJ/yr $76,934
C1 MEK 41 1000 MJ/yr $806
C3 MEK 199 1000 MJ/yr $3,920
$81,660
Flash Drum electricity 397440 1000 kJ/yr $7,949
Pump 1 electricity 1120 1000 kJ/yr $22
Pump 2 electricity 912 1000 kJ/yr $18
Vac Pump electricity 874955 1000 kJ/yr $17,499
$25,489
$192,573Total Yearly Utility Cost:
Total Steam Cost:
Total Cooling Water Cost:
Total MEK Cost:
Total Electricity Cost:
37
The reboilers in each column also drive up the utility cost. The high distillation related costs
show the benefit of operating without a third distillation column. They also verify the cost
savings achieved from lowering the xylene recycle flow rate.
We recycle and reuse our coolant. We do this to comply with coolant recovery laws and to attain
cost savings by reducing coolant disposal. In order to recycle and reuse our coolant we include
an MEK chiller in our process investment. We set aside a $250,000 allowance for the purchase
of a chiller system.
We purchase the MEK material initially, and then purchase more annually to make up for
coolant lost through leaks in the coolant system. We use 28,171 kg/hr of MEK and estimate a
total mass of MEK in our system as 50% of our hourly rate. We use MEK pricing from an online
market overview which reports MEK material costs at 0.551 $/ kg. We estimate MEK leakage at
a rate of 5% annually based on another online report. We use these assumptions to estimate our
initial and annual MEK material costs, which we summarize in Table 14:
Table 14: Annual MEK Material Costs
We find that the MEK material costs are very low relative to the cost of our system. This is
because we allocate a large amount of capital on the MEK chiller, which allows us to recycle and
reuse our MEK. We also comply with EPA regulations because of this coolant recovery system.
We justify the cost of the MEK chiller by looking at costs without one. Without a reuse/recycle
stream, we need to purchase large amounts of MEK annually and pay large disposal fees. We
summarize the cost of operating with and without an MEK chiller in Table 15:
Price [$/kg] 0.551
Total Mass [kg] $14,086
Annual Make-up [kg] $704
Start-up Cost $7,761
Annual Make-up Cost $388
MEK Material Cost
38
Table 15: MEK Chiller Justification
We find that the continuous purchase and disposal of MEK would cost $500 million dollars
annually, which is obviously infeasible. We decide to purchase the cooler in order to recycle and
reuse our MEK coolant.
Process Flow Diagram (PFD)
We present a piping and instrumentation diagram to show a holistic view of our process with
instrumentation specifics shown. The red dots represent thermocouples and flowmeters around
heat exchangers, coolers, storage tanks, reboilers, reflux drums, flash tanks, mixers, and
condensers. Control loop hardware has mechanical and electrical devices to perform functions
of the actuator, sensor and controller. The sensor converts the temperature to a voltage and sends
information to the controller, which then causes the actuator (valves) to make adjustments12. We
show the instrument in Figure 21:
Figure 21: Control Loop Hardware
Annual Flow [ Gg] $225
Annual Purchase Cost $124,178,870
Annual Disposal Cost $382,935,893
Annual Cost $507,114,763
MEK Recycle Justification
39
The green dots on the schematic below represent level sensors that monitor the storage vessels to
protect against the possibility of overflow and exposure to hazardous waste. Blue dots represent
pressure gauges. These monitor the pressure around columns, pumps, and storage tanks. Our
piping and instrumentation diagram shows our integrated control scheme in Figure 22:
Figure 22: Piping and Instrumentation Diagram
40
Mass and Energy Balances
We include the mass and energy data for all the streams in our process flowsheet. All the names
correspond with the names in Figure 16 from the process description. Table 16 includes all final
process and utility streams:
Table 16: Process Stream Tables
A ACN ACNSAFE ACOLD AMID B
MIXED Substream
Temperature C 84.4 21.4 5.4 20.0 33.6 75.0
Pressure bar 1.01325 0.1 0.1 1.01325 1.01325 1.01325
Mass Vapor Fraction 0 0 0 0 0 0
Mass Liquid Fraction 1 1 1 1 1 1
Mole Flows kmol/hr 2.893 3.851 3.851 2.893 2.893 0.659
Mole Fractions
Mass Density kg/cum 806.95 782.66 800.72 868.54 856.03 818.42
Volume Flow cum/hr 0.33 0.20 0.20 0.31 0.32 0.07
Mass Flows kg/hr 270.00 158.20 158.20 270.00 270.00 60.00
ACN kg/hr 0 158.0361282 158.0361282 0 0 1.2
TOL kg/hr 265.95 0.11691243 0.11691243 265.95 265.95 57.9
XYL kg/hr 0 0.04695937 0.04695937 0 0 0
SILOXANE kg/hr 4.05 1.45E-46 1.45E-46 4.05 4.05 0.9
WATER kg/hr 0 0 0 0 0 0
MEK kg/hr 0 0 0 0 0 0
ACN 0 0.998964148 0.998964148 0 0 0.02
TOL 0.985 0.000739017 0.000739017 0.985 0.985 0.965
XYL 0 0.000296835 0.000296835 0 0 0
SILOXANE 0.015 9.16E-49 9.16E-49 0.015 0.015 0.015
WATER 0 0 0 0 0 0
MEK 0 0 0 0 0 0
Mass Enthalpy kcal/kg 54.4468 180.8219 173.1130 27.1536 32.5657 53.6760
Mass Entropy cal/gm-K -0.8102 -0.8967 -0.9229 -0.8937 -0.8758 -0.8182
Enthalpy Flow Gcal/hr 0.0147 0.0286 0.0274 0.0073 0.0088 0.0032
Mass heat capacity, mixture cal/gm-K 0.4563 0.4905 0.4737 0.3911 0.4051 0.4490
Properties
Mass Fractions
Energy Streams
Component Mass Flows
41
BOT1 BOT2 C COND1OUT COND2OUT
MIXED Substream
Temperature C 48.4 137.5 75.0 21.4 109.9
Pressure bar 0.1 1 1.01325 0.1 1
Mass Vapor Fraction 0 0 0 0 0
Mass Liquid Fraction 1 1 1 1 1
Mole Flows kmol/hr 13.729 14.137 4.254 14.635 13.002
Mole Fractions
Mass Density kg/cum 841.50 754.53 753.61 782.66 781.53
Volume Flow cum/hr 1.56 2.00 0.27 0.77 1.53
Mass Flows kg/hr 1313.34 1506.77 200.00 601.16 1197.37
ACN kg/hr 6.827882063 8.63E-08 157 600.5372873 0.54077841
TOL kg/hr 903.6515289 13.91220063 39 0.444267234 1196.740366
XYL kg/hr 397.8218195 1483.063995 0 0.178445604 0.090846152
SILOXANE kg/hr 5.042266972 9.797836259 4 5.51E-46 9.55E-06
WATER kg/hr 0 0 0 0 0
MEK kg/hr 0 0 0 0 0
ACN 0.005198855 5.73E-11 0.785 0.998964148 0.000451638
TOL 0.688054215 0.009233104 0.195 0.000739017 0.999472483
XYL 0.302907671 0.984264371 0 0.000296835 7.59E-05
SILOXANE 0.00383926 0.006502525 0.02 9.16E-49 7.97E-09
WATER 0 0 0 0 0
MEK 0 0 0 0 0
Mass Enthalpy kcal/kg 14.8555 -3.1643 172.7838 180.8219 69.6428
Mass Entropy cal/gm-K -0.8822 -0.8693 -0.8046 -0.8967 -0.7743
Enthalpy Flow Gcal/hr 0.0195 -0.0048 0.0346 0.1087 0.0834
Mass heat capacity, mixture cal/gm-K 0.4319 0.5083 0.5165 0.4905 0.4886
Properties
Mass Fractions
Energy Streams
Component Mass Flows
42
CW1COLD CW1HOT CW2COLD CW2HOT FEED-1
MIXED Substream
Temperature C 35.0 45.0 35.0 45.0 53.8
Pressure bar 1 1 1.01325 1.01325 0.1
Mass Vapor Fraction 0 0 0 0 0
Mass Liquid Fraction 1 1 1 1 1
Mole Flows kmol/hr 579.822 579.822 60.062 60.062 2.009
Mole Fractions
Mass Density kg/cum 984.26 974.48 984.26 974.45 834.47
Volume Flow cum/hr 10.61 10.72 1.10 1.11 0.24
Mass Flows kg/hr 10445.65 10445.65 1082.03 1082.03 202.36
ACN kg/hr 0 0 0 0 0.163872246
TOL kg/hr 0 0 0 0 97.20110822
XYL kg/hr 0 0 0 0 99.95304003
SILOXANE kg/hr 0 0 0 0 5.037010851
WATER kg/hr 10445.64938 10445.64938 1082.033781 1082.033781 0
MEK kg/hr 0 0 0 0 0
ACN 0 0 0 0 0.000809825
TOL 0 0 0 0 0.480349352
XYL 0 0 0 0 0.493948875
SILOXANE 0 0 0 0 0.024891948
WATER 1 1 1 1 0
MEK 0 0 0 0 0
Mass Enthalpy kcal/kg -3779.2804 -3769.3645 -3779.2801 -3769.3319 -3.6134
Mass Entropy cal/gm-K -2.1305 -2.0989 -2.1305 -2.0988 -0.9021
Enthalpy Flow Gcal/hr -39.4770 -39.3735 -4.0893 -4.0785 -0.0007
Mass heat capacity, mixture cal/gm-K 0.9903 0.9993 0.9903 0.9994 0.4237
Properties
Mass Fractions
Energy Streams
Component Mass Flows
43
FEED-3 MAKEUP MEKCOLD1 MEKCOLD2 MEKCOLD3
MIXED Substream
Temperature C 54.2 25.0 -29.0 -29.0 -29.0
Pressure bar 2.0265 1.01325 1.01325 1 1.01325
Mass Vapor Fraction 0 0 0 0 0
Mass Liquid Fraction 1 1 1 1 1
Mole Flows kmol/hr 2.009 0.264 3.663 350.034 17.825
Mole Fractions
Mass Density kg/cum 834.14 860.55 855.34 855.34 855.34
Volume Flow cum/hr 0.24 0.03 0.31 29.51 1.50
Mass Flows kg/hr 202.36 28.00 264.13 25239.84 1285.28
ACN kg/hr 0.163872246 0 0 0 0
TOL kg/hr 97.20110822 0 0 0 0
XYL kg/hr 99.95304003 28.00486665 0 0 0
SILOXANE kg/hr 5.037010851 0 0 0 0
WATER kg/hr 0 0 0 0 0
MEK kg/hr 0 0 264.125179 25239.84371 1285.28285
ACN 0.000809825 0 0 0 0
TOL 0.480349352 0 0 0 0
XYL 0.493948875 1 0 0 0
SILOXANE 0.024891948 0 0 0 0
WATER 0 0 0 0 0
MEK 0 0 1 1 1
Mass Enthalpy kcal/kg -3.4269 -54.7532 -931.9387 -931.9389 -931.9387
Mass Entropy cal/gm-K -0.9017 -1.0163 -1.4433 -1.4433 -1.4433
Enthalpy Flow Gcal/hr -0.0007 -0.0015 -0.2461 -23.5220 -1.1978
Mass heat capacity, mixture cal/gm-K 0.4240 0.4080 0.4588 0.4588 0.4588
Properties
Mass Fractions
Energy Streams
Component Mass Flows
44
MEKHOT1 MEKHOT2 MEKHOT3 OH1 OH2
MIXED Substream
Temperature C -19.0 -19.0 -19.0 21.4 110.2
Pressure bar 1.01325 1 1.01325 0.1 1
Mass Vapor Fraction 0 0 0 1 1
Mass Liquid Fraction 1 1 1 0 0
Mole Flows kmol/hr 3.663 350.034 17.825 14.635 13.002
Mole Fractions
Mass Density kg/cum 845.53 845.53 845.53 0.17 2.97
Volume Flow cum/hr 0.31 29.85 1.52 3570.40 402.71
Mass Flows kg/hr 264.13 25239.84 1285.28 601.16 1197.37
ACN kg/hr 0 0 0 600.5372873 0.54077841
TOL kg/hr 0 0 0 0.444267234 1196.740366
XYL kg/hr 0 0 0 0.178445604 0.090846152
SILOXANE kg/hr 0 0 0 5.51E-46 9.55E-06
WATER kg/hr 0 0 0 0 0
MEK kg/hr 264.125179 25239.84371 1285.28285 0 0
ACN 0 0 0 0.998964148 0.000451638
TOL 0 0 0 0.000739017 0.999472483
XYL 0 0 0 0.000296835 7.59E-05
SILOXANE 0 0 0 9.16E-49 7.97E-09
WATER 0 0 0 0 0
MEK 1 1 1 0 0
Mass Enthalpy kcal/kg -927.3213 -927.3203 -927.3188 374.7367 156.1466
Mass Entropy cal/gm-K -1.4248 -1.4248 -1.4248 -0.2383 -0.5486
Enthalpy Flow Gcal/hr -0.2449 -23.4054 -1.1919 0.2253 0.1870
Mass heat capacity, mixture cal/gm-K 0.4654 0.4654 0.4654 0.3029 0.3544
Properties
Mass Fractions
Energy Streams
Component Mass Flows
45
REB1COND REB1OUT REB1STM REB2COND REB2OUT
MIXED Substream
Temperature C 130.5 53.9 130.5 185.6 138.3
Pressure bar 2.736939323 0.1 2.736939323 11.35538594 1
Mass Vapor Fraction 0.009994699 0.846399205 1 0.010000278 0.928618183
Mass Liquid Fraction 0.990005301 0.153600795 0 0.989999722 0.071381817
Mole Flows kmol/hr 11.713 13.729 11.713 13.364 14.137
Mole Fractions
Mass Density kg/cum 127.98 0.41 1.49 335.36 3.44
Volume Flow cum/hr 1.65 3174.19 141.36 0.72 437.73
Mass Flows kg/hr 211.01 1313.34 211.01 240.76 1506.77
ACN kg/hr 0 6.827882063 0 0 8.63E-08
TOL kg/hr 0 903.6515289 0 0 13.91220063
XYL kg/hr 0 397.8218195 0 0 1483.063995
SILOXANE kg/hr 0 5.042266972 0 0 9.797836259
WATER kg/hr 211.0098108 0 211.0098108 240.7560472 0
MEK kg/hr 0 0 0 0 0
ACN 0 0.005198855 0 0 5.73E-11
TOL 0 0.688054215 0 0 0.009233104
XYL 0 0.302907671 0 0 0.984264371
SILOXANE 0 0.00383926 0 0 0.006502525
WATER 1 0 1 1 0
MEK 0 0 0 0 0
Mass Enthalpy kcal/kg -3674.4263 97.4281 -3160.4875 -3611.1432 72.1271
Mass Entropy cal/gm-K -1.8387 -0.6276 -0.5654 -1.6971 -0.6861
Enthalpy Flow Gcal/hr -0.7753 0.1280 -0.6669 -0.8694 0.1087
Mass heat capacity, mixture cal/gm-K 1.1007 0.3216 0.4619 1.1999 0.3953
Properties
Mass Fractions
Energy Streams
Component Mass Flows
46
REB2STM RECYCLE1 TOL TOLMID2 TOLSAFE
MIXED Substream
Temperature C 185.6 138.3 110.0 45.0 4.3
Pressure bar 11.35538594 1 1 1 1
Mass Vapor Fraction 1 0 0 0 0
Mass Liquid Fraction 0 1 1 1 1
Mole Flows kmol/hr 13.364 0.962 3.940 3.940 3.940
Mole Fractions
Mass Density kg/cum 5.63 753.31 781.41 846.18 883.49
Volume Flow cum/hr 42.75 0.15 0.46 0.43 0.41
Mass Flows kg/hr 240.76 109.52 362.84 362.84 362.84
ACN kg/hr 0 7.39E-10 0.163872245 0.163872245 0.163872245
TOL kg/hr 0 0.5025125 362.6485957 362.6485957 362.6485957
XYL kg/hr 0 99.92551089 0.027529137 0.027529137 0.027529137
SILOXANE kg/hr 0 9.087007958 2.89E-06 2.89E-06 2.89E-06
WATER kg/hr 240.7560472 0 0 0 0
MEK kg/hr 0 0 0 0 0
ACN 0 6.75E-12 0.000451638 0.000451638 0.000451638
TOL 0 0.004588525 0.999472483 0.999472483 0.999472483
XYL 0 0.912436491 7.59E-05 7.59E-05 7.59E-05
SILOXANE 0 0.082974984 7.97E-09 7.97E-09 7.97E-09
WATER 1 0 0 0 0
MEK 0 0 0 0 0
Mass Enthalpy kcal/kg -3139.9311 -13.7738 69.6998 40.0330 23.6683
Mass Entropy cal/gm-K -0.6699 -0.8822 -0.7741 -0.8584 -0.9134
Enthalpy Flow Gcal/hr -0.7560 -0.0015 0.0253 0.0145 0.0086
Mass heat capacity, mixture cal/gm-K 0.4858 0.4694 0.4887 0.4232 0.3810
Properties
Mass Fractions
Energy Streams
Component Mass Flows
47
Safety, Environmental and Health Issues
Pressure and Vessel Analysis
We perform a pressure analysis by using a design heuristic MAWP formula. To do so, we add
50 psi to the highest pressure in our system. We specify a piping schedule of 5316 SS pipe that
follows a design heuristic and accounts for the allowable working stress and operating pressure.
We find the maximum allowable working pressure (MAWP) using a design heuristic;
Design pressure (psig) = (1.1 x operating pressure in psia) -14.7
or
50 psi + operating pressure in psig, whichever is greater
WASTE1 WASTE2 XYLMID XYLREC XYLVAP
MIXED Substream
Temperature C 140.4 27.0 138.1 109.1 140.4
Pressure bar 1.01325 1.01325 1.01325 1.01325 1.01325
Mass Vapor Fraction 0 0 0 0 1
Mass Liquid Fraction 1 1 1 1 0
Mole Flows kmol/hr 0.279 0.279 0.683 0.947 0.683
Mole Fractions
Mass Density kg/cum 754.20 864.84 754.00 783.36 3.23
Volume Flow cum/hr 0.05 0.04 0.10 0.13 22.47
Mass Flows kg/hr 36.96 36.96 72.55 100.56 72.55
ACN kg/hr 3.57E-11 3.57E-11 7.04E-10 7.03E-10 7.04E-10
TOL kg/hr 0.084531133 0.084531133 0.417981367 0.418021236 0.417981367
XYL kg/hr 27.93037754 27.93037754 71.99513335 100 71.99513335
SILOXANE kg/hr 8.950007897 8.950007897 0.137000061 0.137010881 0.137000061
WATER kg/hr 0 0 0 0 0
MEK kg/hr 0 0 0 0 0
ACN 9.65E-13 9.65E-13 9.70E-12 6.99E-12 9.70E-12
TOL 0.002286794 0.002286794 0.005761278 0.004157139 0.005761278
XYL 0.755591521 0.755591521 0.992350371 0.994480315 0.992350371
SILOXANE 0.242121685 0.242121685 0.001888351 0.001362546 0.001888351
WATER 0 0 0 0 0
MEK 0 0 0 0 0
Mass Enthalpy kcal/kg -35.1946 -74.7254 -2.5163 -17.0635 78.9158
Mass Entropy cal/gm-K -0.9083 -1.0121 -0.8686 -0.9053 -0.6707
Enthalpy Flow Gcal/hr -0.0013 -0.0028 -0.0002 -0.0017 0.0057
Mass heat capacity, mixture cal/gm-K 0.3886 0.3093 0.5113 0.4843 0.3909
Properties
Mass Fractions
Energy Streams
Component Mass Flows
48
Our MAWP is 4.35 bar
Table 17 shows our MAWP analysis:
Table 17: MAWP
We perform a temperature analysis by using a design heuristic MAWT formula. To do so, we
add 50 degrees Fahrenheit to the highest temperature in our system.
We find the maximum allowable working temperature (MAWT) using a design heuristic;
Design Temperature (F) = (50 + operating temperature in Fahrenheit) or 600F minimum.
Our MAWP is 600 Fahrenheit.
Table 18 shows our MAWT analysis:
49
Table 18: MAWT
Fire Protection
For passive fire protection, we cool all product and waste streams below their flash point
temperatures and bring them back to atmospheric pressure. Vermiculite cement fireproofs all of
our columns vessels and flash drum as they have the greatest potential for fire. The vermiculite
cement covers all equipment up to 10 meters from ground level. The main objective for the 10m
cement is to prevent failure in the event of a fire in proximity of flammable materials. We place
all storage tanks at a minimum distance of 25 feet away from any other equipment to minimize
their likelihood of fire exposure.
For active fire protection, we put out liquid fires using Monnex powder fire extinguishers
because we can’t put out low flash point liquid materials with water. Our fire detection system
includes flammable gas detectors to detect leaks, infrared detectors to detect flames, and smoke
detectors for smoke detection. We put out non-chemical fires using a sprinkler system. We put
50
out chemical fires using fluoroprotein foam. We put out electrical fires using CO2 fire
extinguishers.
We recommend emergency material transfer for our plant. It is necessary to have arrangements
so that in the event of a fire it is possible to transfer flammable material away from the parts of
the plant on fire. A relief header leading to a vent stack allows vapor to vent safely away from
pressure vessels.
We make all fire protection in accordance with NFPA, Dow Minimum Preventive and Protective
Features, and the project handout.
Health Considerations
We provide operators and other employees with safety mandates to ensure our process runs
safely. As part of these mandates, all operators and employees meet certain expectations. All
operators and employees wear personal protective equipment including goggles, non-conductive
work boots, gloves, and hard hats. Work boots protect against heavy objects falling on the foot,
but also prevent electrical conductivity. Gloves protect against burns from hot pipes and heated
streams/equipment. Goggles will serve as eye protection against harmful chemicals within the
plant. We provide safety stations, eyewash stations, and first aid stations for all workers and
operators in the plant.
Spill Containment
We have a spill containment system that is 1.5 times the size of our largest storage container.
This allows us a good margin of safety to redirect streams to a safe place that will not result in
environmental damage. We install grates on the floor that direct any spills to a header, which
leads to the spill containment tank. As a result, the spill container is underground. The volume
of our spill container is 277.2 m3.
Inherently Safer Checklist
To help us think about possible safety issues we utilize the Inherently Safer Checklist. We
explain relevant checklist items via bullet point. We take topics for this checklist from CCPS,
Guidelines for Engineering Design for Process Safety, AIChE, New York, 1996. We note here
51
that some of the items are broad concepts of inherent safety. We do not use the checklist as a
“yes/no” manner. We decide what might be possible and then decide what is feasible.
1.) Intensification/Minimization
1.1 – Do the following strategies reduce inventories of hazardous raw materials, intermediates,
and/or finished products?
We use a recycle stream to save as much solvent p-xylene as possible. This reduces the
overall amount of waste from our process.
1.3 – Can other types of unity operations or equipment reduce material inventories?
We use continuous distillation over batch distillation.
1.7 – Can we change process conditions to avoid handling flammable liquids above their flash
points?
We cool products below their flash points to prevent the handling of flammable liquids.
1.8 – Can we change process conditions to reduce production of hazardous wastes or by-
products?
We can’t reduce production of hazardous waste because we have no control over the
composition of the feed streams.
2.) Substitution / Elimination
2.4 – Is it possible to use utilities with lower hazards?
We minimize the use of methyl ethyl keytone because it is hazardous and use it only
when we can’t cool products with cooling water. We use high pressure steam only when
we can’t heat a stream using the lower pressure steam.
3.) Attenuation / Moderation
3.3 – Can we operate at less severe conditions using any other route?
We operate at atmospheric conditions when possible.
4.) Limitation of Effects
52
4.1 – Can we design and construct vessels and piping to be strong enough to withstand the
largest overpressure that we can generate within the process?
We design pipes and vessels to handle excess pressure that follows MAWP calculations
4.2 – Can we design equipment to totally contain the materials that might be present inside at
ambient temperature or the maximum?
We design pipes and vessels to handle excess temperatures that follows MAWT
calculations.
4.4-4.5 – Can we locate process units to reduce or eliminate adverse effects from other adjacent
hazardous installations?
We will keep storage vessels away from the process vessels. This eliminates the
possibility of accidental heating
4.6 – For processes handling flammable materials, is it possible to design the facility layout to minimize
the number and size of confined areas and to limit the potential for serious overpressures in the event of a
loss of containment and subsequent ignition?
We operate the process outdoors so we can avoid small spaces by spreading out the
process
We also have a spill container.
4.7 – Can we locate the plant to minimize the need for transportation of hazardous materials?
We minimize the transportation costs because we are recycling toluene and acetonitrile to
a process upstream in our process plant.
5.) Simplification / Error Tolerance
5.2 – Can we design equipment so that it is difficult to create a potentially hazardous situation
due to an operating or maintenance error?
We use Stainless Steel 316 for all process equipment to prevent damage and corrosion.
We size piping to be much stronger than normal because we want a safe process and to
avoid leaks which may be difficult to identify.
53
We design our vessels according to heuristics
5.3 – Can we design procedures so that it is difficult to create a potentially hazardous situation
due to an operating or maintenance error?
We will train operators to perform maintenance safely.
HAZOP
We provide a hazard and operability analysis (HAZOP) for our plant to ensure a maximum level
of safety. HAZOP requires steady-state operating, well-built equipment, competent operators,
and clear standard procedures. Operators will adhere to HAZOP protocols during plant
operating to minimize risk. We assume and require continuous maintenance on all plant
equipment.
HAZOP Key Finding
We look at the HAZOP case summary and risk analysis in figure 24 for specific trends. We find
that each unit is susceptible to ruptures or leaks. We assume and require continuous maintenance
on all plant equipment to prevent this problem. We also have back up equipment incase
operators cannot prevent equipment breakdown. Other major concerns include temperatures
becoming too high causing explosions and compositions of products becoming out of
specification. We have instrumentation to monitor temperatures and pressures of the system and
operators monitoring the system around the clock. Operators follow a clear set of standard
procedures to ensure safety and specified product outcomes.
Potential Concerns
We use a Risk Matrix to assign qualitative and quantitative values to each potential concern
within the plant. We show an example of a risk matrix in Figure 19:
54
Figure 23: Example Risk Matrix
Columns 1 and 2 contain dangerous chemicals. Operators maintain operating conditions within
design specifications and perform maintenance and preventative disaster techniques.
Maintenance employees follow standard operating procedures when performing maintenance to
minimize their exposure to chemicals. High temperatures can cause a fire or explosion in the
column and results in our largest risk. We show our HAZOP case summary in Figure 24:
55
Figure 24: HAZOP Case Summary
We do a complete HAZOP risk analysis in Figure 24:
Parameter Deviation ACNCOL TOLCOL Storage Vessels Mixer Heat Exchangers Pipes Coolers Pumps Streams
High
Low
No
Reverse
High
Low
High
Low
High
Low
Less
More
other than
Less
More
Electrical No
Leak
Rupture
Unit
Flow
Pressure
Level
Temperature
Composition
Separation
56
Figure 24a: HAZOP for ACNCOL
57
Figure 24b: HAZOP for TOLCOL
The flash drum can leak or clog. We operate the process within design specifications to prevent
blockage. Operators perform routine maintenance to minimize the risks of a leak. High
temperatures cause a fire or explosion in the flash drum and results in our largest risk.
58
Figure 24c: HAZOP for FLASH
The storage vessels can leak, overflow, or explode. Operators perform routine maintenance to
minimize the risks of a leak. We have storage vessels made to have a 15 day holding time, an
80% liquid level to be cautious against liquid surge, and a length to diameter ratio of 3:1.
Routine emptying prevents overflow. Operators operate the process within design specifications
to ensure temperatures stay below flashpoints within the storage vessels. High temperatures can
cause a fire or explosion in the storage vessels and results in our largest risk.
59
Figure 24d: HAZOP for Storage Vessels
The mixer can overflow or explode. We expose hazardous material if the mixer overflows.
Operators operate within design specifications to prevent mixer overflow. The liquid has
potential to explode if it is above the flash point. Exchangers must operate correctly to cool
liquids effectively. Too high of a temperature can cause a fire or explosion in the mixer and
results in our largest risk.
Figure 24e: HAZOP for Mixer
60
We have hazardous chemicals within all of the exchangers. Operators must perform regular
maintenance to ensure leaks do not occur. If exchangers do not operate correctly, components
raise above their flash points. Engineers can increase cooling flow rates to ensure temperatures
stay flash points. High temperatures can cause a fire or explosion in the heat exchanger network
and results in our largest risk.
Figure 24f: HAZOP for Heat Exchanger Network
61
We do pipe design to ensure all pipes operate well within process conditions to prevent leaking.
Operators must perform routine maintenance to ensure there is no leaking. Low flow or lack of
containment leads to overflow of hazardous material, which results in our largest risk.
Figure 24g: HAZOP for Pipes
If pumps fail mechanically, cavitation can occur and permanently damage equipment. Operators
must make sure pumps run effectively through continuous maintenance. Stream pressure and
flash point problems are our largest risk factors according to the risk matrix for our pumps.
Figure 24h: HAZOP for Pumps
Impurities, poor flow rate and volatile temperatures in the feed streams can disrupt design
specifications. A number of possibilities relating to feed streams A, B and C affect the separation
effectiveness within the columns. We find it critical that operators will inspect incoming feed
and monitor separation results in the column. Operators have a requirement to perform routine
maintenance to ensure correct circulation, purity, and temperature.
62
Figure 24i: HAZOP for Feed Streams
Impurities, poor flow rate and volatile temperatures in the feed streams can disrupt design
specifications. A number of possibilities relating to the make-up stream affect the separation
effectiveness within the columns. We find it critical that operators inspect incoming feed and
monitor separation results in the column. Operators have a requirement to perform routine
maintenance to ensure correct circulation, purity, and temperature. Calculation error is the most
common error for make-up stream being ineffective. Engineers monitor these calculations
regularly.
63
Figure 24j: HAZOP for Makeup
FMEA
We use Failure Mode and Effects Analysis to systematically review our process and determine
all sources of failure defects. An effective FMEA identifies corrective actions to prevent failures
from reaching the customer; and to assure the highest possible yield, quality, and reliability. We
account for failures before implementation to ensure a safe operation. We calculate risk priority
numbers using the tables below:
Figure 25: FMEA severity ranking
64
Figure 26: FMEA occurrence ranking
Figure 27: FMEA detection ranking
We calculate initial RPN values by multiplying severity, occurrence, and detection values. We
rank RPN values as the lowest being the most safe and highest having the most dangerous
potentials. We make improvements to threatening RPN values that decrease the original RPN
value (Resulting RPN). Improvement and corrective action must continue until the resulting
RPN is at an acceptable level for all potential failure modes. We calculate Resulting RPN values
until they meet a safe range.
65
FMEA Key Findings
We have our largest risk at column one, the A.CN pump and the bottoms pump per the RPN
numbers calculated. Column one can have a material leak due to cracks or broken seals. As a
result, the plant has exposure to hazardous material. Operators, flowmeters, and vapor sensors
are put into place to monitor the issue. When column one has a material leak we shut down the
plant and provide safety showers to the operators. The pumps are flowing out of spec due to
irregular pressures and temperatures. This causes impurities in the final product. The duties are
monitored as well as flowmeters put in place to monitor the process. When the pumps are
flowing out of spec we check the reboiler and condenser.
66
67
68
Figure 24: FMEA
Process Economics
We calculate the cost of all equipment with EconExpert. EconExpert is an online version of
Chemical Engineering Process Design and Economics. We cost our equipment using a cost
index of 544, which correlates to August 2016. We determine equipment cost by multiplying
purchase cost by pressure and material factors. We use a 10% delivery and freight cost for all
equipment. We use the F.O.B purchase costs reported in the specification tables in our
equipment summary.
We include employee safety and fire protection in addition to basic equipment. We use cement
as a fire retardant to protect each column and flash drum. The cement covers the equipment and
extends an additional 10.7 meters above the equipment. We provide safety such as eye
protection, hearing protection, hand protection, and hazardous shower and eye wash stations for
our employees. We add an additional ten percent to the safety and equipment to account for
miscellaneous items such as piping, supports, sprinklers, fire extinguishers, smoke detectors, and
valves. We summarize all our costs in Table 19:
69
Table 19: Process Equipment Costs
Purchase Cost Material Factor Pressure Factor FOB Cost Delivered Cost
Column 1 $16,553 4 1 $81,585 $89,744
Packing 1 $15,373
Column 2 $12,127 4 1 $55,254 $60,779
Packing 2 $6,746
E1 $2,249 3 1 $6,747 $7,422
E2 $2,249 3 1 $6,747 $7,422
C1 $2,249 1.7 1 $3,823 $4,206
C2 $2,249 1.7 1 $3,823 $4,206
C3 $2,249 1.7 1 $3,823 $4,206
Reboiler 1 $10,360 1.7 1 $17,612 $19,373
Reboiler 2 $10,360 1.7 1 $17,612 $19,373
Condenser 1 $4,540 1.7 1 $7,718 $8,490
Condenser 2 $3,456 1.7 1 $5,875 $6,463
Pump 1 $2,386 2 1 $4,772 $5,249
Pump 2 $2,283 2 1 $4,566 $5,023
Vac Pump $76,070 1 1 $76,070 $83,677
Extra Pumps $16,669 2 1 $33,338 $36,672
Flash Drum $5,331 4 1 $21,904 $24,094
Reflux Drum 1 $1,494 4 1 $5,976 $6,574
Reflux Drum 2 $2,100 4 1 $8,400 $9,240
Mixer $4,534 $3 $13,149 $14,463
A Storage $19,260 3.5 1 $67,409 $74,150
B+C Storage $20,100 3.5 1 $70,349 $77,384
Waste Storage $7,220 3.5 1 $25,270 $27,797
TOL Storage $22,288 3.5 1 $78,007 $85,808
ACN Storage $15,487 3.5 1 $54,206 $59,627
Xylene Storage $6,383 3.5 1 $22,341 $24,575
Spill Conatiner $27,809 3.5 1 $97,332 $107,065
Chiller $250,000 $250,000 $275,000
MEK $7,761 $7,761 $8,537
Fire Protection $2,814 $2,814 $3,095
Saftey shower $2,705 $2,705 $2,976
Hearing Protection $91 $91 $100
Eye Protection $180 $180 $198
Gloves $80 $80 $88
Misc $111,057 $111,057 $111,057
$1,274,130
Columns
Miscillaneous
Total Equipment Cost:
Flash Drum
Pumps
Condenser
Reboiler
Heat Exchanger
Fire and Safety Protection
MEK Recovery System
Storage Vessel
Mixer
70
We include a miscellaneous allowance of 10% of all other costs. We allocate this for costs
associated with structural support, piping, minor equipment, back up pumps, and any other
expenditure we overlooked in the cost estimation. We use large material factors to account for
the usage of stainless steel in all of our process equipment.
We use the cost of our equipment as a basis to calculate our total capital investment. We use a
modified Lang Factor based on the fluid processing plant model. We take out expenditures that
are not applicable to a plant expansion, and decrease factors that would not require as large of an
investment as a new plant. We assume that the plant already has service, maintenance, office
buildings, and free land. We use an installation factor of 43% and use reasonable numbers for
our other factors. We summarize our additional costs in Table 20:
Table 21: Additional Cost Allowances
We use a total Lang Factor of 3.5, which is reasonable in a plant improvement or modification
setting. We summarize our total capital investment cost break down in Table 21
Additional Costs
Percent of
Equipment
Cost
Equipment Installation 43%
Instrumentation and Controls (Installed) 17%
Piping (Installed) 22%
Electrical (Installed) 12%
Yard Improvements 5%
Engineering and Supervision 31%
Construction Expense 27%
Contractors Fee 21%
Contingency 20%
71
Table 21: Total Capital Investment
We estimate a total capital investment of about $4.5 million. Of this investment, 15% is working
capital investment and 85% is fixed capital investment. We invest a majority of our money on
the actual installation and construction of our equipment relative to the purchase cost.
We predict an operating cost based on the variable costs that will incur with our process. We get
our A, B, and C feed streams from an existing process, but we still buy make-up xylene and
MEK. We calculate our xylene cost in Table 22:
Table 22: Xylene Purchase Cost
We pay for the waste disposal of our siloxane purge stream. This stream contains more than 25%
siloxane by weight so we dispose of it as class B waste (1.50 $/kg). We show our waste cost
calculation in Table 23:
Total Equipment Cost (F.O.B) $1,158,300
Delivered Equipment Costs (1.1*TEC) $1,274,130
Equipment Installation $547,876
Instrumentation and Controls (Installed) $216,602
Piping (Installed) $280,309
Electrical (Installed) $152,896
Yard Improvements $63,706
Engineering and Supervision $394,980
Construction Expense $344,015
Contractors Fee $267,567
Contingency $254,826
Fixed Capital Investment (FCI) $3,796,906
Working Capital Investment (15% TCI) $670,042
Total Capital Investment (TCI) $4,466,948
Total Capital Investment
Raw Material Cost [$/kg] $1.70
p-Xylene Flow Rate [kg/hr] 28.07
Annual Operation Hours [hr] 8000
Annual Cost $381,714
Cost of p-Xylene
72
Table 23: Waste Disposal Cost
We use these calculations to calculate our total raw material purchase and disposal costs. We
need to calculate our labor costs. To complete this we estimate two operators per shift for 8
shifts. We pay our operators 32 $/hr and include a benefits factor of 1.7. We show our labor cost
calculations in Table 24:
Table 24: Labor Costs
We use these calculations and other estimates to calculate our total annual operating cost. We
allocate 6% of FCI for maintenance costs and 15% of maintenance costs for operating supplies.
We summarize our operating costs in Table 25:
Table 25: Operating Costs
Waste Type B
Cost [$/kg] $1.50
Flow Rate of Waste [kg/hr] 37.028
Annual Operation Hours [hr] 8000
Annual Cost $444,336
Cost of Waste Stream Disposal
Shifts 4
Operators 2
Annual Employee Hours 2000
Houly Wage $32
Total Labor Cost per year $512,000
Benefits Factor 1.70
Total Labor Cost $870,400
Labor Cost
Item Cost
Operating Labor $870,400
Utilities $192,573
Maintenance (6% FCI) $227,814
Operating Supplies (15% Maint.) $34,172
Waste Disposal (Class B) $444,336
Raw Materials (Xylene and MEK) $382,102
Total $2,151,397
Operating Cost
73
We use the price of ACN and TOL to calculate the cost savings of our solvent recovery system.
We assume 8000 operating hours per year. We summarize our annual revenue in Table 26:
Table 26: Annual Revenue
We generate annual revenue of over $9 million. We run a cash flow analysis using all of our
costs and revenue to find the rate of return of our solvent recovery system. We use a SOYD
depreciation scheme in order to minimize our annual taxable income. We calculate our annual
depreciation allowance in Table 27:
Table 27: Annual Depreciation Allowance
Annual Revenue Value [$/kg] Recovered [kg/hr] Recovered [kg/yr] Sale [$/yr]
ACN 3.3 158.2 1265600 $4,176,480
TOL 1.9 362.8 2902720 $5,515,168
Total $9,691,648For 8000 operating hours per year:
Year SOYD Factor Depreciation
0
1 0.095 $361,610
2 0.090 $343,530
3 0.086 $325,449
4 0.081 $307,369
5 0.076 $289,288
6 0.071 $271,208
7 0.067 $253,127
8 0.062 $235,047
9 0.057 $216,966
10 0.052 $198,886
11 0.048 $180,805
12 0.043 $162,725
13 0.038 $144,644
14 0.033 $126,564
15 0.029 $108,483
16 0.024 $90,403
17 0.019 $72,322
18 0.014 $54,242
19 0.010 $36,161
20 0.005 $18,081
74
We assume no salvage value after a 20-year lifespan. We calculate our cash flow using a 40%
income tax rate. We show our cash flow diagram in Table 28:
Table 28: Cash-Flow for Solvent Recovery System
We convert each annual after tax cash flow to present day value in order to solve for rate of
return. The correct ROR value yields a net present day value equal to the total capital invested.
Using this analysis, we calculate a ROR of 102.9%. This value is much higher than 10%, which
leads us to recommend the adoption of this solvent recovery system.
We recommend purchasing the equipment on July 1, 2017. This is the first day of the third
quarter and allows us to claim bonus depreciation that year. We buy on this date and not later so
that we can install our system as fast as possible and start recovering solvent immediately.
Improvement Recommendations
We designed a very profitable solvent recovery system, but there is always room for
improvement. We recommend exploring further heat integration. We can heat feed A up to 75oC
before lowering the pinch temperature and requiring steam heating. We plan to investigate this
option to reduce our MEK consumption.
Year Total Product Cost Revenue Before Tax Cash-Flow Depreciation Taxable Income Income Tax (40%) After Tax Cash Flow Present Value of ATCF
0 -$4,466,948 -$4,466,948
1 -$2,366,537 $9,691,648 $7,325,111 $361,610 $6,963,501 $2,785,400 $4,539,711 $2,237,459
2 -$2,151,397 $9,691,648 $7,540,251 $343,530 $7,196,721 $2,878,688 $4,661,562 $1,132,362
3 -$2,151,397 $9,691,648 $7,540,251 $325,449 $7,214,802 $2,885,921 $4,654,330 $557,235
4 -$2,151,397 $9,691,648 $7,540,251 $307,369 $7,232,882 $2,893,153 $4,647,098 $274,214
5 -$2,151,397 $9,691,648 $7,540,251 $289,288 $7,250,963 $2,900,385 $4,639,866 $134,940
6 -$2,151,397 $9,691,648 $7,540,251 $271,208 $7,269,043 $2,907,617 $4,632,633 $66,403
7 -$2,151,397 $9,691,648 $7,540,251 $253,127 $7,287,124 $2,914,849 $4,625,401 $32,677
8 -$2,151,397 $9,691,648 $7,540,251 $235,047 $7,305,204 $2,922,082 $4,618,169 $16,080
9 -$2,151,397 $9,691,648 $7,540,251 $216,966 $7,323,285 $2,929,314 $4,610,937 $7,913
10 -$2,151,397 $9,691,648 $7,540,251 $198,886 $7,341,365 $2,936,546 $4,603,705 $3,894
11 -$2,151,397 $9,691,648 $7,540,251 $180,805 $7,359,446 $2,943,778 $4,596,472 $1,916
12 -$2,151,397 $9,691,648 $7,540,251 $162,725 $7,377,526 $2,951,010 $4,589,240 $943
13 -$2,151,397 $9,691,648 $7,540,251 $144,644 $7,395,607 $2,958,243 $4,582,008 $464
14 -$2,151,397 $9,691,648 $7,540,251 $126,564 $7,413,687 $2,965,475 $4,574,776 $228
15 -$2,151,397 $9,691,648 $7,540,251 $108,483 $7,431,768 $2,972,707 $4,567,544 $112
16 -$2,151,397 $9,691,648 $7,540,251 $90,403 $7,449,848 $2,979,939 $4,560,311 $55
17 -$2,151,397 $9,691,648 $7,540,251 $72,322 $7,467,929 $2,987,171 $4,553,079 $27
18 -$2,151,397 $9,691,648 $7,540,251 $54,242 $7,486,009 $2,994,404 $4,545,847 $13
19 -$2,151,397 $9,691,648 $7,540,251 $36,161 $7,504,090 $3,001,636 $4,538,615 $7
20 -$2,151,397 $10,361,690 $12,513,088 $18,081 $12,495,007 $4,998,003 $7,515,085 $5
$4,466,948.44TCI at yr 0:
75
We also recommend investigating a better waste treatment plan. We can purchase a dryer or
evaporator to dry out purged siloxane to reduce waste disposal costs. If we dry out siloxane and
dispose of that as class B waste, we can then either recycle the rest of our xylene or condense it
and dispose of it as class A waste for much cheaper.
We design the system to cool streams down to 0.1oC below their flash point temperatures, but to
operate as safely as possible we recommend cooling the streams down further.
Acknowledgments
We acknowledge Dr. Liu for his invaluable lectures, notes, and knowledge. We thank Dr. Liu for
his patience and guidance throughout this project and thank him for the opportunity to design
this system.
Thank You Dr. Liu!!
76
77
References
1. “Analysis, Synthesis, and Design of Chemical Processes,” by Turton, Bailie, Whiting, and Shaeiwitz. Prentice Hall, 1998.
2. “ChE 4185 Process and Product Design I, Fall 2015, 1998 AIChE National Student Design Competition,” Dr. Liu ChE 4185. Virginia Tech Chemical Engineering. 2016.
3. “Notes on Equipment Sizing October 2016,” Dr. Liu ChE 4185. Virginia Tech Chemical Engineering. 2016.
4. Humphrey, J. L. and George E. Keller, Separation Process Technology, McGraw-Hill, New York (1997).
5. “Structured Packings: Energy-efficient, innovative and profitable,” Sulzer Chemtech - Mass Transfer Technology. pg. 6.
6. “ChE 4185 Process and Product Design I Process Economics,” Professor Y. A. Liu Department of Chemical Engineering Virginia Tech. pages 192-193, 304, 325f-325g
7. G.D. Ulrich and P. T. Vasudevan. Chemical Engineering Process Design and Economics, A Practical Guide, 2nd Edition.
8. 1982 AIChE National Student Design Competition Problem. 9. Lees, F.P., Loss Prevention in the Process Industries. Volumes 1 and 2 Pages 528-544.
Buttersworths, Boston (1983). 10. Wankat, Phillip C. Separation Process Engineering: Includes Mass Transfer Analysis. Upper
Saddle River, NJ: Prentice Hall, 2012. Print. 11. Guidelines for Hazard Evaluation Procedures, 3rd. Ed. 2008 AIChE New York. 12. Washington Faculty, Chapter 2 “Control Loop Hardware”
http://faculty.washington.edu/baneyx/436/Orifice.pdf 11/16/2016 13. Sschundler Construction Co. “Schundler Vermiculite Concrete Light Weight and Insulating”
http://www.schundler.com/vermcon.htm 11/16/2016 14. Wayfair, “Speakman Safe-T-Zone Traditional Series Emergency Combination Shower”
https://www.wayfair.com/Speakman-Safe-T-Zone-Traditional-Series-Emergency-Combination-Shower-SE-697-SPK1445.html?source=hotdeals 11/16/2016
15. ULINE, “Uline Reusable Earplugs-Corded” https://www.uline.com/Product/Detail/S-19874/Hearing-Protection/Uline-Reusable-Earplugs-Corded?pricode=WY633&gadtype=pla&id=S-19874&gclid=CMmQlL_0rtACFQZLDQod7RYGcQ&gclsrc=aw.ds 11/16/2016
16. ULINE, “Charguard Gloves – Large” https://www.uline.com/Product/Detail/S-13387L/Heat-Resistant-Gloves/Charguard-Gloves-Large?pricode=WY635&gadtype=pla&id=S-13387L&gclid=CLm64cr1rtACFYtLDQodVAYCWQ&gclsrc=aw.ds 11/16/2016
17. Discount Safety Gear, “Rugged Blue Diablo Safety Glasses” http://www.discountsafetygear.com/rugged-blue-diablo-safety-glasses.html?utm_source=googlepepla&utm_medium=adwords&id=110076584658&gclid=CObTtfj2rtACFZpMDQodcz4BfA 11/16/2016
18. ICIS, “Methyl Ethyl Ether (MEK) Prices and Pricing information” http://www.icis.com/resources/news/2007/11/05/9076042/methyl-ethyl-ketone-mek-prices-and-pricing-information/ 11/16/2016
19. ChemWorld, “Closed Loop Water Leaks” http://www.chemworld.com/Closed-Loop-Water-Leaks-s/1570774.htm 11/16/2016
20. Pinch Analysis Tool, Institution of Chemical Engineers, United Kingdom.
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Appendix
Heat Exchanger Network
79
Piping Design
80
81
82
83
Vacuum Pump Sizing
84
Flash Drum Sizing
85
Mixer Sizing
86
Reflux Drum Sizing
87