I Basic Concept of Process Design

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Dr.Eng. Yulius Deddy Hermawan

Department of Chemical Engineering

UPN “Veteran” Yogyakarta

I

Basic Concept of Process Design

Outline

1. Formulation of The Design Problem

2. Chemical Process Design and I ntegration

3. The Hierarchy of Chemical Process Design

4. Onion Model

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Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

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FORMULATI ON OF THE

DESI GN PROBLEM

How does Chemical Process Plant come into being?

1. An idea:

a. Completely new product

b. I mprovement of an existing product 2. Feasibility Study: reasonable profit?

3. Research and Development: collect data (information) such as the operating condition (P, T, F)

4. Process Design: in this step, a Chemical Engineer:

a. decides what kind of equipments will be needed for each operation

b. calculates size of each item

c. organizes all information in the flow sheet (PFD and/ or P&I D) 5. Project Engineering: pilot plant and full scale

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Formulation of The Design Problem

Design

Problem

Process

Design

Need product specification: Purify spec.

for a specialty product (the functional properties rather than chemical properties): require aproduct design stage

Flowsheet

Operating and reacting condition Capacity, energy Recycle, heat integration

Chemical Product

(Smith, R, 2005)

•

essential to modern living standards

•

almost all aspects of everyday life are supported by

chemical products in one way or another.

•

3 broad classes of chemical product:

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Commodity or Bulk Chemicals

(Smith, R, 2005)

These are produced in large volumes and purchased on the basis of chemical composition, purity and price.

Examples are:



sulfuric acid,



nitrogen,



oxygen,



ethylene and



chlorine.

Fine Chemicals

(Smith, R, 2005)

These are produced in small volumes and purchased on the basis of chemical composition, purity and price.

Examples:

•

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

•

n-butyric acid: used in beverages, ﬂavorings, fragrances

and other products)

•

barium titanate powder: used for the manufacture of

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Specialty or effect or functional chemicals

(Smith, R, 2005)

These are purchased because of their effect (or function), rather than their chemical composition.

Examples:

•

Pharmaceuticals

•

Pesticides

•

Dyestuffs

•

perfumes

•

ﬂavorings.

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Chemical Process Design and I ntegration

(Smith, R, 2005)

•

Transformation

of raw material into desired products

usually can not be achieve in a single step, but trough some steps as follows:

1. Reaction 2. Separation 3. Mixing 4. Heating 5. Cooling

6. Pressure change

7. Particle size reduction and enlargement 8. etc.

Chemical Process Design and I ntegration

(Smith, R., 2005)

•

Synthesis

of chemical process involves two broad activities:

1. Selection of individual transformation step

2. I nterconnect individual transformation step to form complete structures that achieves the required overall transformation.

•

Flow sheet

: diagrammatic representation of the process

steps with their interconnection.

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HI ERARCHY OF CHEMI CAL

PROCESS DESI GN AND

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Hierarchy of Chemical Process Design and I ntegration

(Smith, R, 2005)

•

Process Starts with the reactor.

•

The process requires a reactor to transform the FEED into

PRODUCT

Unfortunately, not all theFEED reacts. Also,part of theFEED reacts to form

BYPRODUCT instead ofthe desired

PRODUCT.

Hierarchy of Chemical Process Design and I ntegration

A separation system is needed to isolate the PRODUCT at the required purity.

• Reactor design dictates the

separation and recycle problem

• this flowsheet is probably too

inefficient in its use of energy

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For a given reactor and separator design there are different possibilities for heat integration.

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Changing the reactor dictates a different separation and recycle problem

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A different reactor design not only leads to a different separation system but additional possibilities for heat integration.

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Simplify Onion Model

(Smith, R, 2005)

Reflect !!

1. What does it mean? Process’ circle < operation circle < utility circle 2. in case, if I ndustries do not involve the process/ reaction? How about the

onion model?

3. Does it possible if industries with un-concentred the onion model? Give its examples

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Raw materials Products

I . Process/ Reaction I I . Operation

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V

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Batch and Continuous Processes

(Smith, R, 2005)

•

However, not all processes operate continuously.

•

I n a batch process, the main steps operate discontinuously.

•

I n contrast with a continuous process, a batch process does

not deliver its product continuously but in discrete amounts. This means that heat, mass, temperature, concentration and other properties vary with time.

•

I n practice, most batch processes are made up of a series of

batch and semicontinuous steps.

•

A semicontinuous step runs continuously with periodic

start-ups and shutdowns.

A Simple Batch Proc

ess (Smith, R, 2005)

Requires heating

Requires cooling

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Batch Processes:

(R. Smith)

•

are economical for small volumes;

•

are ﬂexible in accommodating changes in product formulation;

•

are ﬂexible in changing production rate by changing the

number of batches made in any period of time;

•

allow the use of standardized multipurpose equipment for the

production of a variety of products from the same plant;

•

are best if equipment needs regular cleaning because of fouling

or needs regular sterilization;

•

are amenable to direct scale-up from the laboratory and

•

allow product identiﬁcation.

Batch Processes:

(

R. Smith)

One of the major problems with batch processing is batch to-batch conformity.

•

Minor changes to the operation can mean slight changes

in the product from batch to batch.

•

Fine and specialty chemicals are usually manufactured in

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Batch Processes:

(James M. Dauglas)

Select batch, if: 1. Production rate

a. Sometimes batch if less than 10million lb/ year b. Usually batch if 1million lb/ year

c. Multiproduct plant 2. Market forces:

a. Seasonal production b. Short product lifetime 3. Scale up problems:

a. Very long reaction times

b. Handling slurries at low flowrates c. Rapidly fouling materials

VI

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Production Capacity

(Smith, R, 2005)

Production capacity is an important factor that needs to be calculated to:

•

determine equipment size

•

satisfy contractual requirements

•

aid supply chain management

•

benchmark against competitors

•

obtain operating permits from regulator.

Production capacity is a central concept in:

•

production planning and scheduling

•

operations management

Production capacity depends on:

•

market

•

raw material availability

Production System Performance

(Smith, R, 2005)

•

The production capacity of a chemical plant is a fundamental

measure of its economic potential.

•

A simple definition of capacity is the maximum through-put

for a single processing step

•

For chemical manufacturing operations, the production

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The important things to Determine Production Rates

(James M. Dauglas)

1. I f we want to design a new plant to meet an expanding market condition, first guess of the production rate based on the largest plant that has ever been built.

• The greatest economy of scale

• Normally things are cheaper per unit if we buy them in

large quantitiies

2. The maximum size of a plant is usually fixed by the maximum size of one or more pieces of equipment to the plant site. 3. The production rate specified for the plant might change

during a design because of the market conditions are constantly changing _ we must be responsive to these changes

4. Product purity normally is also fixed by marketing consideration.

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VI I

PRETREATMENT OF

RAW MATERI ALS

Raw Material Handling

(James M. Dauglas) 1. Phase: a. solid b. liquid c. gas d. slurry e. solution f. etc.

2. I mpurity a. inert

b. will affect to the reactions? c. I ts separation and recycle

3. I ts Properties: a. Density/ viscosity b. volatility

c. corrosive d. etc.

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Solid Feeder

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Belt Conveyor

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Liquid Tank

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Preparing of Vapor/ Gas Feed

Control strategies would be discussed

next

Preparing of High Pressure Gas Feed

dry gas (FG)

coolant (FC)

condensate (FL)

SEPARATOR CONDENSOR

COMPRESSOR

flare (Fflare)

high pressure gas

gas feed (FF)

comp. suction

(Fsuct)

to oil pit

T, P

SPLITTER Control strategies