PLANT DESIGN AND ECONOMICS - Ferdowsi...

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١٢/١۶/١۴٣۶ ١ PLANT DESIGN AND ECONOMICS Zahra Maghsoud 1 Course objectives Introduces the concepts and methods of plant design and economic evaluation: General design considerations Process design development Cost estimation Interest and Investment Costs Depreciation Profitability, Alternative Investments, and Replacements Practice these in the context of a term-project 2

Transcript of PLANT DESIGN AND ECONOMICS - Ferdowsi...

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PLANT DESIGN AND ECONOMICS

Zahra Maghsoud1

Course objectives

Introduces the concepts and methods of plant design and economic evaluation: General design considerations Process design development Cost estimation Interest and Investment Costs DepreciationProfitability, Alternative Investments, and

Replacements Practice these in the context of a term-project

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Grading

Midterm 40%

Final exam 35%

Project 25% Topics: Build-up and design a process tomeet the goals that will be announced during the course.

Attendance will be followed according to the university policy. Complete class attendance 2.5% +

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References

1. Plant Design and Economics for Chemical Engineers, M. S. Peters and K. D. Timmerhaus McGraw-Hill, 1991, 2005.

2. Product and Process Design Principles, W. D. Seider, J. D. Seader, D. R. Lewin, Wiley, 2003.

3. Process Engineering Economics, Chemical engineering, J. R. Couper, Marcel Dekker, 2003.

4. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design, G. Towler and R. Sinnott, Elsevier, 2008.

5. Analysis, Synthesis and Design of Chemical Processes, Turton R., Bailie R. C., Whiting W. B., Shaeiwitz J. A., Prentice Hall, 2009

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References

Plant Design and Economics for Chemical Engineers, M. S. Peters and K. D. Timmerhaus McGraw-Hill, 1991, 2005.

ن طراحی کارخانه و تحلیل مباحث اقتصادي براي مهندسیر، ، ترجمه دکتر مجتبی سمنانی رهبچهارمشیمی، ویرایش

)ع(ساناز پورمند، انتشارات دانشگاه امام حسین

طراحی کارخانه و برآورد اقتصادي براي مهندسین شیمی ،، ترجمه دکتر جالل الدین شایگانپنجمویرایش

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Introduction to Process Design

Design is a creative process whereby an innovative solution fora problem is conceived.

Fluoride containing toothpastes Frozen concentrated orange juice Ready-to-eat breakfast cereals

All of these items resulted from research followed by design.

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Process Design

Most companies: continuous change of product to compete with others

In the late 1950s the dairy industry consumed 220,000 tons per year of petroleum waxes for coating paperboard cartons and milk bottle tops. This was 35% of the total U.S. wax production. By 1966 this market had dropped to 14% of its former level (25,000 tons/yr) because polyethylene and other coatings had replaced it.

Wax coated paperboard Polyethylene coated paperboard

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Process Design

Research Prevent changes that completely destroy a product’s markets.

• Improving the product• Finding new uses for it• Reducing its costs (improving the method of producing)

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Research

Basic research: Exploratory studies into things for which an end use cannot be specified. a study to determine the effect of chlorine molecules on the diffusivity of

hydrocarbons a study of the dissolution of single spheres in a flowing stream.

Applied research: Has a definite goal. a new approach to manufacture polystyrene. designing a new waste recovery system

studying the feasibility of replacing conventional controllers in an existing plant with direct digital control.

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Chemical engineering design

Chemical plants are a series of operations that take raw materials and convert them into desired products, salable by-products, and unwanted wastes.

When considering the design of processes for the manufacture of chemical products, the market into which they are being sold fundamentally influences the objectives and priorities in the design.

Chemical products can be divided into three broad classes:

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Chemical Products

Commodity or bulk chemicals Fine chemicals

Specialty effect or functional

chemicals

Produced in large volumes and purchased on the basis of chemical composition, purity and price. Examples are sulfuric acid, nitrogen, oxygen, ethylene and chlorine.

Produced in small volumes and purchased on the basis of chemical composition, purity and price. Examples are chloropropylene oxide (used for the manufacture of epoxy resins, ion-exchange resins and other products), dimethyl formamide (used, for example, as a solvent, reaction medium and intermediate in the manufacture of pharmaceuticals),

These are purchased because of their effect (or function), rather than their chemical composition. Examples are pharmaceuticals, pesticides, dyestuffs, perfumes and flavorings.

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Chemical Products

Commodity or bulk chemicals Fine chemicals

Specialty effect or functional

chemicals

There is nothing to choose between 99.9% benzene made by one manufacturer and that made by another manufacturer, other than price and delivery issues.

Production< 1000 t·y−1. Polymers are purchased on the basis of their mechanical properties, but can be produced in quantities significantly higher than 1000 t·y−1.

High added value

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http://www.vat.ir/

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Chemical products

For the most part, innovations regarding manufacture of commodity chemicals have occurred a long time in the past.

More profit by lower ancillary costs: favorable union contract better deal on the costs of different sources of energy superior automation better catalyst

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When a new chemical product is first developed, it can often be protected by a Patent in the early years of commercial exploitation.

Chemical products

• Novel• Useful• Unobvious

Product Patented Product

a monopoly for commercial exploitation of the product

until patent expiration Once the patent expires (20 years), competitorscan join in and manufacture the product.

If competitors cannot wait until the patentexpires, then alternative competing products mustbe developed.

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Samsung-Apple lawsuit16

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Chemical products

Protection by secrecy: The formula for Coca- Cola has been kept a secret for over 100

years. Potentially, there is no time limit on such protection.

However, for the protection through secrecy to be viable, competitors must not be able to reproduce the product from chemical analysis.

This is likely to be the case only for certain classes of specialty and food products for which the properties of the product depend on both the chemical composition and the method of manufacture.

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Chemical products

Product life cycles The general trend is that when a new product is introduced into the market, the sales grow slowly until the market is established and then more rapidly once the market is established.

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Chemical Product Design

Strategies for Chemical Product Design1. Needs2. Ideas3. Selection4. Manufacture

The future of chemical engineering-that is, the place where chemical engineers can innovate-is in chemical product design

Brainstorming

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Problem Identification and Requirements Specification

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Needs Identification

How the customer explained it

How the project leader understood it

How the analyst designed it

What the customer really needed!

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Requirements Specification

Identifies requirements design must satisfy for success

1. Marketing requirements Customer needs

2. Engineering requirements Applies to technical aspects Performance requirements

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Origins of design problems

Explorations of chemists, biochemists, and engineers in research labs to satisfy the desires of customers to obtain chemicals with improved properties for many applications or Accidents like Teflon

The engineer himself, who often has a strong inclination that a new chemical or route to produce an existing chemical can be very profitable.

An inexpensive source of a raw material(s) becomes available.

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The Design ProcessProblem statement

Implementation

PlanFinancialoutcome

XYZ Co.

© 2007 G.P. Towler / UOP. For educational use in conjunction with Sinnott & Towler Chemical Engineering Design only.

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OPTIMUM DESIGN

In almost every case encountered by a chemical engineer, there are several alternative methods which can be used for any given process or operation.

Formaldehyde

Catalytic dehydrogenation of methanol

Controlled oxidation of natural gas

Direct reaction between CO and H2

+variables

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Optimum Economic Design

If there are two or more methodsfor obtaining exactly equivalentfinal results, the preferred methodwould be the one involving theleast total cost.

This is the basis of an optimumeconomic design.

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Optimum Operation Design

Many processes require definite conditions of temperature, pressure, contact time, or other variables if the best results are to be obtained.

It is often possible to make a partial separation of these optimum conditions from direct economic considerations. In cases of this type, the best design is designated as the optimum operation design.

The chemical engineer should remember, however, that economic considerations ultimately determine most quantitative decisions.

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Optimum Operation Design

Determination of operating conditions for the catalytic oxidation of sulfur dioxide to sulfur trioxide:

2SO2(g)+O2(g) <--> 2SO3(g)

Suppose that all the variables, such asconverter size, gas rate, catalystactivity, and entering-gasconcentration, are tied and the onlypossible variable is the temperatureat which the oxidation occurs.

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PRACTICAL CONSIDERATIONS IN DESIGN

The chemical engineer must never lose sight of the practical limitations involved in a design.

It may be possible to determine an exact pipe diameter for an optimum economic design, but this does not mean that this exact size must be used in the final design.

Optimum diameter: 3.43 in. (8.71 cm)

recommended pipe size:standard 3 ½ in.-diameter pipe

Id: 3.55 in. (9.02 cm)

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PRACTICAL CONSIDERATIONS IN DESIGN

The engineer: the optimum economic diameter is only an exact mathematical number and may vary from month to month as prices or operating conditions change.“A standard 3-in.-diameter pipe would require less investment and would probably only increase the total cost slightly.”

Theoretically, the conscientious engineer is correct in this case.

total cost

3 1/2 in. pipe: $5000

3-in. pipe: $4500

total yearly savings on power and fixed charges

$25 (5%)

invest the extra $500 elsewhere

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PRACTICAL CONSIDERATIONS IN DESIGND

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t Access to key control valves

Sufficient space should be for maintenance workers to check, take part and repair equipment

Scale-forming fluid through the tubes in tube-and-shell heat exchanger for cleaning operations

Including inlets on several trays above and below the calculated feed point in a distillation tower

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THE DESIGN APPROACH

Make assumptions & approximate estimates when exact values are notavailable in order to save time and energy.

Assumptions are made only when they are necessary and essentiallycorrect.

The engineer must also consider costs and probable profits andeconomic conditions and limitations constantly throughout all the work.

The general approach in any plant design involves a careful balanced combination of theory, practice, originality, and plain common sense.

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Continuous and Batch Processes

Continuous processes are designed to operate 24 hours a day, 7 days a week, throughout the year. Some downtime will be allowed for maintenance and, for some processes, catalyst regeneration. The plant attainment or operating rate is the percentage of the available hours in a year that the plant operates, and is usually between 90 and 95%.

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Continuous and Batch Processes

Batch processes are designed to operate intermittently, with some, or all, of the process units being frequently shut down and started up.

It is quite common for batch plants to use a combination of batch and continuous operations. For example, a batch reactor may be used to feed a continuous distillation column.

Continuous processes will usually be more economical for large-scale production. Batch processes are used when some flexibility is wanted in production rate or product specifications.

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Continuous and Batch Processes

The advantages of batch processing areA. Batch processing allows production of multiple different

products or different product grades in the same equipment.B. The production rate of batch plants is very flexible.C. Batch plants are easier to clean and maintain sterile

operation.D. Batch processes are easier to scale up from chemist’s

recipes.E. Batch plants have low capital for small production volumes.

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Continuous and Batch Processes

The drawbacks of batch processing areA. The scale of production is limited.B. Batch-to-batch quality can vary, leading to high production

of waste products or off-spec product.C. Recycle and heat recovery are harder, making batch plants

less energy efficient and more likely to produce waste byproducts.

D. Asset utilization is lower for batch plants, as the plant almost inevitably is idle part of the time.

E. The fixed costs of production are much higher for batch plants on a $/unit mass of product basis.

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Choice of Continuous versus Batch Production

Given the higher fixed costs and lower plant utilization of batch processes, batch processing usually makes sense only for products that have high value and are produced in small quantities. Batch plants are commonly used for

Food products Pharmaceutical products such as drugs, vaccines, and hormones Specialty chemicals

Even in these sectors, continuous production is favored if the process is well understood, the production volume is large, and the market is competitive.

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The Structure of a project

Process Research

Process Development

Process Design

Plant Design and Construction

Plant Operations

Marketing

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The Structure of a project

Process Research 1. Process Evaluation

The objective is to evaluate the technical, economic, and financial feasibility of a process.

a) Construct a preliminary process flow diagram b) Approximate equipment sizing c) Economic evaluation d) Locate areas requiring research

2. Bench Scale StudiesThe objective is to obtain additional design data for process

evaluation. a) Plan experiments d) Revise flow diagram b) Design experimental setup e) Revise economic evaluation c) Correlate data f) Locate areas requiring

development

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The Structure of a project

Process Development Objective: To obtain more design data and possibly

product for market research. a) Plan development program e) Correlate data b) Design pilot plant f) Revise flow diagram c) Supervise pilot-plant construction g) Revise economic

evaluation d) Supervise pilot-plant operations

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The Structure of a project

Process Design Objective: To establish process and equipment

specifications. a) Construct flow diagram b) Perform mass and energy balances c) Consider alternative process designs d) Size equipment e) Design control systems studies f) Conduct economic studies g) Conduct optimization studies h) Evaluate safety and health i) Conduct environmental impact

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The Structure of a project

Plant Design and ConstructionObjective: To implement the process design.

a) Specify equipment b) Design vessels (mechanical design of reactors, separators, tanks) c) Design structures d) Design process piping system e) Design data acquisition and control system f) Design electric-power distribution system g) Design steam-distribution system h) Design cooling-water distribution system i) Purchase equipment j) Coordinate and schedule project k) Monitor progress

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The Structure of a project

Plant Operations

Objective: To produce the product. a) Plant startup d) Production

b) Trouble shooting e) Plant engineering c) Process improvement

Marketing

Objective: To sell the product. a) Market research

b) Product sales c) Technical customer service

d) Product development

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Sample of a process and plant-design schedule

A Gantt chart

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Schedule – Gantt Chart45