David R. Shonnard Department of Chemical Engineering ...

Michigan Technological University1

Waste Generation and Release Estimation from Chemical Processes - Chapter 8.3

David R. ShonnardDepartment of Chemical Engineering

Michigan Technological University


Outline

l Educational goals and topics covered in the module

l Identify and estimate emissions from process units -Chapter 8, section 3

After screening out a number of environmentally and economically inferiorreaction pathways and raw materials, the design engineer can begin toidentify unit operations in a relatively small number of flowsheets. An

environmental evaluation should again be considered using emission estimation.


Educational goals and topics covered in this lecture

Students will:l estimate air emissions and other releases from process units

after developing a preliminary process flowsheet, using software and hand calculations

l have a better understanding of the mechanisms for pollutant generation and release from process units


Identifying and estimating air emissions and other releases from process units

1. Identify waste release sources in process flowsheets and mechanisms for unit operations

2. Methods for estimating air emissions from chemical processes

3. Case study - Benzene to Maleic Anhydride process evaluation

Chapter 8.3


1. Waste streams from process units2. Major equipment - vents on reactors, column separators, storage tanks,

vacuum systems, ..3. Fugitive sources - large number of small releases from pumps, valves,

fittings, flanges, open pipes, ..4. Loading/unloading operations5. Vessel clean out, residuals in drums and tanks6. Secondary sources - emissions from wastewater treatment, other waste

treatment operations, on-site land applications of waste, ..7. Spent catalyst residues, column residues and tars, sludges from tanks,

columns, and wastewater treatment, …8. Energy consumption - criteria air pollutants, traces of hazardous air

pollutants, global warming gases,

Typical waste emission sources from chemical processes - Ch 8


1. Actual measurements of process waste stream contents and flow rates or indirectly estimated based on mass balance and stoichiometry. (most preferred but not always available at the design stage)

2. Release data for a surrogate chemical or process or emission factors based on measured data

3. Mathematical models of emissions (emission correlations, mass transfer theory, process design software, etc.)

4. Estimates based on best engineering judgment or rules of thumb

Process waste release estimation methods


Waste stream summaries based on past experience

1. Hedley, W.H. et al. 1975, “Potential Pollutants from Petrochemical

Processes”, Technomics, Westport, CT

2. AP-42 Document, Chapters 5 and 6 on petroleum and chemical industries, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

3. Other sourcesi. Kirk-Othmer Encyclopedia of Chemical Technology, 1991-ii. Hydrocarbon Processing, “Petrochemical Processes ‘99”, March 1999.

Emission estimation methods: based on surrogate processes


Distillation column emission and waste generation mechanisms

FeedTank

Distillation Column

Condenser

Vent air emissions

Reboiler

DistillateD, xD, xD,I

BottomsB, xB, xB,I=0

FeedF, xF, xF,I

N2

Still Bottoms Waste (sludges)

High temperature degradation reactions

Inert gas for safety


Distillation column emissions: Vent air emissions - N2 mass balance

∆Moles N2 = F xF, I − DxD, I − B xB ,I D = F (xF − xB

xD − xB

)

xF, I =0.98{exp[xF ln(HEtOH ) +(1− xF )ln(HH2 O)]}−1

xD,I = 0.98{exp[xD ln(HEtOH ) +(1− xD)ln( HH2O)]}−1

F: Moles of feed.xF: Mole fraction of ethanol in the feed.xF,I: Mole fraction nitrogen in the feed.D: Moles of overhead product.xD: Mole fraction of ethanol in the overheads produc t.xD,I: Mole fraction of nitrogen in the overheads product.B: Moles of bottoms product.xB: Mole fraction of ethanol in the bottoms product.xB,I: Mole fraction of nitrogen in the bottoms product = 0

Vent emissions of EtOH = (∆Moles N2)(VPEtOH/1 atm)

Vapor pressure of EtOH at condenser Temp.


Liquid storage tank air emissions and waste generation mechanisms

Vertical Fixed Roof Storage Tank

Tank Bottoms Waste (sludges)

Vent air emissions


Liquid storage tank emissions and waste generation mechanisms

Domed External Roof Storage Tank

Tank Bottoms Waste (sludges)

Vent air emissions


Emission Mechanisms; Fixed Roof TankLTOTAL = LSTANDING + LWORKING

Roof Column

Vent

∆T

∆P

LiquidLevel

- Weather, paint color/quality

- Weather

- liquid throughput, volume oftank

Vapor pressure of liquid drives emissions

Mechanisms of air emissions from storage tanks


Module 4: Storage tank comparison -TANKS 4.0 Demonstration

Storage Tank TypeStorage Tank TypeStorage Tank TypeStorage Tank Type VerticalVerticalVerticalVertical InternalInternalInternalInternal Domed ExternalDomed ExternalDomed ExternalDomed External

Fixed Roof Fixed Roof Fixed Roof Fixed Roof Floating Roof Floating Roof Floating Roof Floating Roof Floating RoofFloating RoofFloating RoofFloating Roof

Annual Emissions (lb)Annual Emissions (lb)Annual Emissions (lb)Annual Emissions (lb)

White PaintWhite PaintWhite PaintWhite Paint 337.6 66.2 42.8

Grey (Medium) PaintGrey (Medium) PaintGrey (Medium) PaintGrey (Medium) Paint 489.1 85.1 52.4

Heated (White)Heated (White)Heated (White)Heated (White) 313.5

Poor (Grey/MediumPoor (Grey/MediumPoor (Grey/MediumPoor (Grey/Medium 509.7 81.0 51.5

Toluene Storage Tank Calculation• Toluene emissions only• 516,600 gal/yr flowrate of toluene• 15,228.5 gallon tank for each comparison


Wastewater generation and RCRA sludges

10 kg sludge/kg pptRCRA waste

Petroleum refinerywater processes


Wastewater generation and RCRA sludges

10 kg sludge/kg pptRCRA waste

Petroleum refinerywater processes

PreventPollution

ReverseOsmosisDevice


Emission Factors -major equipment

Table 8.3.2 Average Emission Factors for Chemical Process UnitsCalculated from the US EPA L&E Database

Process Unit EFav ; (kg emitted/103 kg throughput) Reactor Vents 1.50 Distillation Columns Vents 0.70 Absorber Units 2.20 Strippers 0.20 Sumps/Decanters 0.02 Dryers 0.70 Cooling Towers 0.10

Estimates Only: Accuracy is only order-of-magnitude


Emission factors -fugitive sources; minor equipment

Ei (kg i / yr) = mi × EFav × Ns × 24 ×365


l 1,400 valves (168 in gas service), 3,048 flanges/connectors, 27 pumps in liquid service, 20 pressure relief valves, 20 sampling valves

Example 8.3-3 -fugitive emissions from a chemical facility

valves in gas service

168 valves( ) 0.00597 kg VOChr - valve

2.2

lbkg

24 hr

day

365 days

yr

= 19,300

lb VOCyr

valves in liquid service

1400 -168 valves( ) 0.00403 kg VOChr - valve

2.2

lbkg

24 hr

day

365 days

yr

= 95,700

lb VOCyr


Example 8.3-3 - Summary table fugitive emissions from a chemical facility

Equipment type Emissions, lb/yr % of emissions byequipment type

Valves 115,000 41

Flanges 108,000 38

Pumps 10,300 3.7

Pressure relief valves 40,200 14

Open-ended lines 700 .3

Sample connections 5,700 3

Total 276,000 100


Emission factors -criteria pollutants from energy consumption

Ei (lb i / yr) =EFav (lb i / 103gal) × ED(Btu / yr)

HV(Btu / 103 gal) × BEAP-42, Chapter 1, section 1.3, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm


Emission factors -CO2 from energy consumption

Ei (lb i / yr) =EFav (lb i / 103gal) × ED(Btu / yr)

HV(Btu / 103 gal) × BE

AP-42, Chapter 1, section 1.3, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm


Software Tools

Storage tanksTANKS 4.0 - program from EPA - www.epa.gov/ttn/chief/tanks.html

Wastewater treatmentWATER8 - on Air CHIEF CD - www.epa.gov/ttn/chief/airchief.htmlEPI Suite - Epiwin

Treatment storage and disposal facility (TSDF) processesCHEMDAT8 - on Air CHIEF CD

Emission correlations/models -storage tanks and waste treatment


Benzene to MA process

AP-42, Chapter 6, section 6.14, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

V2O52 C6H6 + 9 O2 ----------> 2 C4H2O3 + H2O + 4 CO2

MoO3


Air emission and releases sources:Benzene to MA process

Source Identification1. Product recovery absorber vent

2. Vacuum system vent

3. Storage and handling emissions

4. Secondary emissions from water out, spent catalyst, fractionation column residues

5. Fugitive sources (pumps, valves, fittings, ..)

6. Energy consumption


Process data for energy consumption• 0.15 lb fuel oil equivalent per lb Maleic Anhydride product• fuel oil #6 in a Normally Fired Utility Boiler• 1% sulfur• Boiler efficiency included in the energy usage data

Emissions from energy consumption:Criteria pollutants (SO2, SO3, NOx, CO, PM)

AirCHIEF Software


Emissions from energy consumption:continued

SO2

157 lb SO2

%S 103 gal #6

1%S( ) 1 gal #66.68 lb #6

0.15 lb #6lb MA

= 3.53x10-3

lb SO2

lb MA = 3.53

lb SO2

103 lb MA

SO3

5.7 lb SO3

%S 103 gal #6

1%S( ) 1 gal #66.68 lb #6

0.15 lb #6lb MA

= 1.28x10-4

lb SO3

lb MA = 0.13

lb SO3

103 lb MA

NOx

67 lb NOx103 gal # 6

1 gal #66.68 lb #6

0.15 lb #6lb MA

= 1.50x10-3

lb NOxlb MA

= 1.50 lb NOx

103 lb MA

CO

5 lb CO103 gal # 6

1 gal #66.68 lb #6

0.15 lb #6lb MA

= 1.12x10-4

lb COlb MA

= 0.11 lb CO

103 lb MA

PM

9.19 lb PM%S 103 gal #6

1%S( ) 1 gal #66.68 lb #6

0.15 lb #6lb MA

= 2.06x10-4

lb PMlb MA

= 0.21 lb PM

103 lb MA


Uncontrolled Air emission / releasesBenzene to MA Process (lb/103 lb MA)

Release Source

i Methods used

MaleicAnhydride(MA)

Benzene Xylene CriteriaPollutants

CO2 Tars andoxygenates

Venting fromstorage tanks 1 0.03 0.14

Absorber columnvent 2 100 700 (CO) 972 20

Vacuum systemvent 2 0.02 0.02

FugitiveEmissions 3 0.2 0.2 0.1

Loading/unloadingoperations 4 0.2 2.0

Wastes fromvacuum columns 5 3.8 26.5

Energy useemissions 6 5.5 562

Total 4.2 102.3 0.1 705 1,534 46.51 Vertical fixed-roof tank; surrogate for MA is perchloroethylene; Tanks 4.0 program from EPA www.epa.gov/ttn/chief/tanks/html2 Hedley et al. 1975. Potential Pollutants from Petrochemical Processes. Technomic, West Port, CT AP-42 chapter 6 section 6.14, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm3 Typical chemical industry emission factor from Berglund and Hansen, 1990.4 Equation 8.3-4, chapter 8, Green Engineering textbook.5 Hedley et al. 1975. Potential Pollutants from Petrochemical Processes. Technomic, West Port, CT6 AP-42, Chapter 1, section 1.3, Table 1.3-11, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm


Flowsheet evaluation -n-butane to maleic anhydride

Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 15, pp. 893-927. 1991


Module 4: Uncontrolled Air emission / releasesn-butane to MA Process (lb/103 lb MA)

Release Source

i Methods used

MaleicAnhydride(MA)

n-butane CriteriaPollutants

CO2 Tars andoxygenates

Venting fromstorage tanks 1 1.0

Absorber columnvent 2 8.0 251.4 761 (CO) 1033

Vacuum systemvent 3 9.6

FugitiveEmissions 4 0.2 0.2

Loading/unloadingoperations 5 0.2

Wastes fromvacuum columns 6 3.8

Energy useemissions 7 2.9 600

Total 22.6 251.6 764 1,6331 Vertical fixed-roof tank; Tanks 4.0 program within the Environmental Fate and Risk Ass essment Tool (EFRAT) (see module 6)2 from stream information using a commercial process simulator, HYSYS3 from emission estimation program in EFRAT using the emission factor for a vacuum distillation column.4 Typical chemical industry emission factor from Berglund and Hansen, 1990.5 Equation 8.3-4, chapter 8, Green Engineering textbook.6 Hedley et al. 1975. Potential Pollutants from Petrochemical Processes. Technomic, West Port, CT7 from emission estimation program in EFRAT using emission factors for energy consumption, AP-42, Chapter 1, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm , bituminous coal for electricity demand only


Tier 2 environmental assessment indexes

1. Energy: [total energy (Btu/yr)] / [production rate (MM lb/yr)]

2. Materials: [raw materials (MM lb/yr)] / [production rate (MM lb/yr)]

3. Water: [process water (MM lb/yr)] / [production rate (MM lb/yr)]

4. Emissions: [total emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)]

5. Targeted emissions: [total targeted emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)]


Benzene to MA ProcessConclusions from emissions summary

1. Chemical profile: CO2 > CO > benzene > tars-oxygenates > MA

2. Toxicity profile: Benzene > MA > CO > tars-oxygenates > CO2

3. Unit operations profile: Absorber vent > energy consumption > vacuum system vent

- Pollution prevention and control opportunities are centeredon benzene, the absorber unit, and energy consumption -


Summary/Conclusions

1. Methodologies/software tools - process synthesis:

• emission factors• surrogate process information from historical sources• emission estimation software: TANKS 4.0, AirCHIEF 7.0, process

simulator packages, • Tier 2 environmental assessment

David R. Shonnard Department of Chemical Engineering ...

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