Chapter 5
PLANT DESIGN
CONTENTS:
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Chemical Engineering Plant Design
•
Sequence of Steps in Developing a Project
•
Plant Location
•
Plant Layout
•
Storage of materials
•
Materials Handling
•
Utilities
Chemical Engineering Plant Design
The general term plant design includes all
engineering aspects involved in the
development of either a new, modified, or
expanded industrial plant. In this development,
the chemical engineer will be making economic
evaluations of new processes, designing
individual pieces of equipment, or developing a
plant layout. Because of these many design
duties, the chemical engineer is many times
referred to as a design engineer.
Chemical Engineering Plant Design Cont’d
On the other hand, a chemical engineer
specializing in the economic aspects of the
design is often referred to as a cost engineer.
The term process engineering is used in
connection with economic evaluation and
general economic analyses of industrial
processes, while process design refers to the
actual design of the equipment and facilities
necessary for carrying out the process.
Similarly, the meaning of plant design is limited
by some engineers to items related directly to
the complete plant, such as plant layout,
general service facilities, and plant location.
Sequence of steps in developing a project
Time sequence
Project Steps
Process identification
Laboratory scale process research
Bench scale investigations
Preliminary economic evaluation
Process development
Mass and energy balance
Detailed process design
Site selection
Refined economic evaluation
Design Fixed
Detailed economic evaluation
Engineering flow scheme
Basic design
Detailed construction plan
Detail design
Procurement
Construction
Startup
Plant Location
The geographical location of any industrial plant
has strong influence on the success of the
project. Considerable care must be exercised in
selecting the plant site, and many different
factors must be considered. Primarily, the plant
should be located where the minimum cost of
production and distribution can be obtained, but
other factors, such as room for expansion and
safe living conditions for plant operators as well
as the surrounding community, are also
important.
Plant Location Factors
1.
Raw materials availability
2.
Markets
3.
Energy availability
4.
Climate conditions
5.
Transportation facilities
6.
Water supply
7.
Waste disposal
8.
Labor supply
9.
Taxation and legal restrictions
10.
Site Characteristics
11.
Flood and fire protection
12.
Community factors
Individual risk: --- Risk Contours
PLANT LOCATION AND RISK:
ISO-risk contours represent the geographical variation of the risk for a hypothetical
individual who is positioned at a pacticular location for 24 hrs/day, 365 days / year
LSIR: Location specific individual risk
Plant Layout
After the process flow diagrams are completed and
before detailed piping, structural, and electrical design
can begin, the layout of process units in a plant and the
equipment within these process units must be planned.
This layout can play an important part in determining
construction and manufacturing costs, and thus must be
planned carefully with attention being given to future
problems that may arise. Since each plant differs in
many ways and no two plant sites are exactly alike,
there is no one ideal plant layout. However, proper
layout in each case will include arrangement of
processing areas, storage areas, and handling areas in
efficient coordination and with regard to such factors as:
Plant Layout Cont’d
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12.
New site development or addition to previously
developed site
Type and quantity of products to be produced
Type of process and product control
Operational convenience and accessibility
Economic distribution of utilities and services
Type of buildings and building-code requirements
Health and safety considerations
Waste-disposal requirements
Auxiliary equipment
Space available and space required
Roads and railroads
Possible future expansion
Typical Master Plot Plan
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Future Process Area
xLandscaped
Area
Chemical
processing
Area
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Packing
and
shipping
area
Parking
Area
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Picking-plant
area (extend lot
200 ft east
)
Reservoir
Neutralizing tanks
x
Future
Storage
Area
Power-point
Area
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Loading
Railroad siding
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ISCO Chemical Company
Ferrous Sulfate Recovery Plant
Master Plot Plan: Scale ½”=10 ft
List of plant units in a typical layout
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Process units
Tank farms
Loading and unloading facilities
Flares
Power, boilers and incinerators
Cooling towers
Substations, large electrical switch yards
Central control houses
Warehouses
Analytical laboratories
Incoming utility metering and block systems
Fire hoses, fixed monitors, reservoirs and emergency fire pumps
Waste treatment areas
Maintenance buildings and areas
Administrative buildings
Storage
Adequate storage facilities for raw materials,
intermediate products, final products, recycle
materials, off-grade materials, and fuels are
essential to the operation of a process plant. A
supply of raw materials permits operation of the
process plant regardless of temporary procurement
or delivery difficulties. Storage of intermediate
products may be necessary during plant shutdown
for emergency repairs while storage of final
products makes it possible to supply the customer
even during a plant difficulty or unforeseen
shutdown. An additional need for adequate storage
is often encountered when it is necessary to meet
seasonal demands from steady production.
Storage Cont’d
Bulk storage of liquids is generally handled by
closed spherical or cylindrical tanks to prevent
the escape of volatiles and minimize
contamination. Liquids with vapor pressures
above atmospheric must be stored in vaportight tanks capable of withstanding internal
pressure. If flammable liquids are stored in
vented tanks, flame arresters must be installed
in all openings except connections made below
the liquid level.
Storage Cont’d
Gases are stored at atmospheric pressure in wetor dry-seal gas holders. The wet-gas holder
maintains a liquid seal of water or oil between the
top movable inside tank and the stationary
outside tank. In the dry-seal holder the seal
between the two tanks is made by means of a
flexible rubber or plastic curtain.
Solid products and raw materials are either stored
in weather-tight tanks with sloping floors or in
outdoor bins and mounds. Solid products are
often packed directly in bags, sacks, or drums.
Vertical tank installation
Materials Handling
Materials-handling equipment is logically divided
into continuous and batch types, and into classes
for the handling of liquids, solids, and gases.
Liquids and gases are handled by means of
pumps and blowers; in pipes, flumes, and ducts;
and in containers such as drums, cylinders, and
tank cars. Solids may be handled by conveyors,
bucket elevators, chutes, lift trucks, and
pneumatic systems. The selection of materialshandling equipment depends upon the cost and
the work to be done. Factors that must be
considered in selecting such equipment include:
Materials Handling Cont’d
1. Chemical and physical nature of material
being handled
2. Type and distance of movement of material
3. Quantity of material to be moved per unit time
4. Nature of feed and discharge from materialshandling equipment
5. Continuous or intermittent nature of materials
handling
Perry
pumping
Rotary blower
Vacuum pump selection
Perry
Belt conveyors
Bucket elevator
Utilities
1. In the chemical industries, power is supplied primarily in
the form of electrical energy. Agitators, pumps, blowers,
compressors, and similar equipment are usually
operated by electric motors.
2. When a design engineer is setting up the specifications
for a new plant, a decision must be made on whether to
use purchased power or have the plant set up its own
power unit. It may be possible to obtain steam for
processing and heating as a by-product from the selfgeneration of electricity, and this factor may influence
the final decision.
3. Power can be transmitted in various forms, such as
mechanical energy, electrical energy, heat energy, and
pressure energy. The engineer should recognize the
different methods for transmitting power and must
choose the ones best suited to the particular process
under development.
Utilities Cont’d
4. Steam is generated from whatever fuel is the cheapest,
usually at pressures of 450 psig (3100 kPa) ore more,
expanded through turbines or other prime movers to
generate the necessary plant power, and the exhaust
steam is used in the process as heat. The quantity of
steam used in a process depends upon the thermal
requirements, plus the mechanical power needs, if such
a power is generated in the plant.
5. Water for industrial purposes can be obtained from one
of two general sources: the plant’s own source or a
municipal supply. If the demands for water are large, it
is more economical for the plant to provide its own
water source. Such a supply may be obtained from
ground water or surface water sources. Before a
company agrees to go ahead with any new project, it
must ensure itself of a sufficient supply of water for all
industrial, sanitary, and safety demands, both present
and future.
List of utilities
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Compressed Air: Plant and Instrument
Natural Gas
Fire Protection
City and Process Water
Chilled Water
Wastewater
Welder Water
Hot Water Heating
Steam and Condensate
Fuel Handling: Gasoline, Diesel, …
Cooling and Tower Water
Motor/Hydraulic/Cutting Oil
Process Gases: N, H2 and CO2
Tube boiler