ChE Design CORREL

includes all engineering aspects involved in the development of a new, modified, or expanded commercial process in a chemical or biochemical plant.

Plant design

used in connection with economic evaluation and general economic analyses of commercial processes

Process engineering

actual design of the equipment and facilities necessary for providing the desired products and services

Process design

Inception of basic idea

PROCESS DESIGN DEVELOPMENT

small-scale replica of the full-scale final plant

PILOT PLANT

usually constructed from odd pieces of equipment that are already available and is not meant to duplicate the exact setup to be used in the full-scale plant

COMMERCIAL DEVELOPMENT PLANT

• Chemical engineer creates one or more solutions

• Different feeds and intermediates

• Performs mass and energy balances

FLOWSHEET DEVELOPMENT

Allows rapid calculations, large storage

COMPUTER AIDED DESIGN

Allow examination of effect that various design variables will have on the process or plant design more rapidly than manual calculation

COMPUTER AIDED DESIGN

Provide basis for company management to decide to infuse further capital

Pre-design cost estimation

Optimum Design

• Cost

• Profit

• Capacity

Optimum Design

• Cost Minimization

• Profit Maximization

• Capacity Maximization

The best design with the least total cost

Optimum Economic Design

Optimization Applications
Fluid Flow

Economic Diameter

Optimization Applications
Heat Transfer

Insulation thickness

Optimization Applications
Evaporation

Number of effects

Optimization Applications
Drying

Temperature difference

Optimization Applications
Distillation

Reflux Ratio

Optimization Applications
Condenser

Cooling Water Flow Rate

Optimization Applications
Filtration

Filter capacity

Optimization Applications
Leaching

SF Ratio

Optimization Applications
Solvent extraction

SF Ratio

Optimization Applications
Adsorption

Adsorption to Solution Ratio

Optimization Applications
Scale Formation

Cycle Time

Optimization Applications
Reactor

Reactant conversion

Optimization Applications
Humidification

Mass velocity of vapor

Optimization Applications
Gas absorption

Mass velocity of liquid

Optimization Applications
Ion exchange

Mass velocity of liquid/gas

Expenses under Total Capital Investment

FCI and WC

Subcategories under FixedCapital Investment

Manufacturing and Non-Manufacturing Expense

Allocation of FCI

80-85%

equipment, installation, instrumentation, piping, insulation, site preparation etc. directly related to process operation

manufacturing capital investment

land, offices, warehouses, utility generation, waste disposal etc.

non-manufacturing capital investment

All are depreciable except this

Land

raw materials and supplies, finished and semi-finished products, accounts receivable, cash for expenses/accounts payable, taxes payable, non depreciable

WC

Allocation of WC

15-20%

a value for a given point of time showing the cost at that time relative to a certain base time (usually in the past)

Cost Index

How often is CEPCI and MS published?

Every month

Base value of CEPCI

100 in 1957-1959

Value of CEPCI in 2001

395.4

Base value of MS

100 in 1926

Value of MS in 2001

1092

Other cost indices

• Nelson-Farrar Refinery Construction Cost Index

• Engineering News –Record Construction Index

Good approximations in capacity scaling are often obtained using an exponent of

0.6

Actual exponents in capacity scaling vary from

0.2 to >1

Two conditions of when to use capacity scaling

• Withing tenfold range of capacity

• Similar equipment

Percentage of installation costs

20-90%

Instrumentation and Control are estimated as a fraction of

• Purchased equipment cost (preliminary)

• P&ID’s and instrument index (detailed and definitive)

Insulation are estimated as a fraction of

• Purchased equipment cost (preliminary)

• Material take-offs (detailed and definitive)

Buildings and Yard Improvements are estimated as a fraction of

Purchased equipment cost

Service Facilities and Land are estimated as a fraction of

Purchased equipment cost

purchase may be needed for grass-roots plant

Land

Engineering Supervision and Services are estimated as a percentage of

Fixed capital investment

Range and typical value of Allocation percentage of engineering Supervision and Services

4-21% (8.1%)

Range and typical value of Allocation percentage of Construction Expense and Contractor’s Fee

4.2-16.6% (8.1%)

Cost necessary to produce and sell the product

Total Product Cost

Total Product Cost consists of:

• Manufacturing expenses

• General expenses

Directly related to the manufacturing process

Manufacturing Costs

not directly related to manufacturing, but necessary for running the business

General Expenses

Fixed Charges

• depreciation

• local taxes

• insurance

• rent

chemical or electrochemical attack

Corrosion

What metals to choose to lessen corrosion?

choose combination of metals that are close as possible in the galvanic series

dissolves rapidly in either acidic and basic solutions

aluminum and zinc

powerful accelerator of corrosion

oxidizing agents

widely used in the protection of underground pipes and tanks from external soil corrosion and in water systems.

cathodic protection

Commonly used steel

Carbon steel

Types of stainless steel

• Martensitic

• Ferritic

• Austenitic

Factors considered in selection of materials

• Chemical

• Physical

• Economic

Resistance to corrosion is considered as

CHEMICAL FACTOR

Ability to resist expansion

PHYSICAL FACTOR

Material properties: elasticity, machinability, porosity, hardness, softness, conductivity of heat and elasticity, etc.

PHYSICAL FACTOR

WELDED JOINT EFFICIENCY

Single-Welded Butt Joint with Bonding Strips

• 0.90 - fully radiographed

• 0.80 - spot examined

• 0.65 - not radiographed

WELDED JOINT EFFICIENCY

Double-Welded Butt Joint

• 1.00 - fully radiographed

• 0.85 - spot examined

• 0.70 - not radiographed

General rule of thumb for spot examined without precise data

• Electric resistance weld

• Lap welded

• Single butt welded

• Electric resistance weld - 0.85

• Lap welded - 0.80

• Single butt welded - 0.60

• Seamless shells and heads - 1.00

Allowance for design pressure

Whichever is greater

• 10% of max operating P

• 70–175 kPa

Standard Design P

Design P = max operating P + Allowance

When no data is available for max operating P,

Design P = normal operating P + 175 kPa

For vessels operating at 0.32–1 atm and 316 - 538 C

Design P = 377 kPa

Conditions for vessels with Design P = 377 kPa

P = 0.32 - 1 atm

T = 316- 538 C

For vacuum operation Design P inside and outside

design P is 200 kPa outside and full vacuum inside

Standard Design T

For operating temperature between –30 to 350 C

Design T = Operating T + 30 C

Below –30 C metal

Special Steel

Above 350 C

allowable design stress falls sharply

Compare Piping and Tubing

Walls

Piping

• Heavy

Tubing

• Thin

Compare Piping and Tubing

Length

Piping

• 20 - 40 ft

Tubing

• 100+ ft

Compare Piping and Tubing

Surface

Piping

• Rough

Tubing

• Smooth

Compare Piping and Tubing

Connection

Piping

• Screwed, Welded, Flanged

Tubing

• Compression, Flaring, Soldering

Compare Piping and Tubing

Manufacture

Piping

• Welding, Casting, Piercing

Tubing

• Extrusion or Cold-Drawn

Compare Piping and Tubing

Size

Piping

• Relatively Large

Tubing

• Smaller

Relationship of Friction Factors

f_darcy = 4f_fanning

Fans

• Pressure

• Volume

– Low-pressure service of up to 0.5 psi

– Volume service of up to 130,000 ft³/min

Gas compressibility usually assumed negligible

Fans

Blowers

• Pressure

• Volume

– Pressure service of up to 1.5 psi

– Volume service of up to 200,000 ft3/min

For large volume and higher-pressure service

Compressors