Process design
Encyclopedia
Process design is the design of processes for desired physical and/or chemical transformation of materials. Process design is central to chemical engineering
and it can be considered to be the summit of chemical engineering, bringing together all of the components of that field.
Process design can be the design of new facilities or it can be the modification or expansion of existing facilities. The design starts at a conceptual level and ultimately ends in the form of fabrication and construction plans.
Process design is distinct from equipment design, which is closer in spirit to the design of unit operations. Processes often include many unit operation
s.
In order of increasing detail, process design documents include:
Process designers also typically write operating manuals on how to start-up, operate and shut-down the process.
Documents are maintained after construction of the process facility for the operating personnel to refer to. The documents also are useful when modifications to the facility are planned.
A primary method of developing the process documents is process flowsheeting
.
Objectives that a design may strive to include:
Constraints include:
Other factors that designers may include are:
data available or data from full-scale operating facilities. Other sources of information include proprietary design criteria provided by process licensors, published scientific data, laboratory experiments, and input.
However, engineers still rely on heuristics, intuition, and experience when designing a process. Human creativity is an element in complex designs.
Chemical engineering
Chemical engineering is the branch of engineering that deals with physical science , and life sciences with mathematics and economics, to the process of converting raw materials or chemicals into more useful or valuable forms...
and it can be considered to be the summit of chemical engineering, bringing together all of the components of that field.
Process design can be the design of new facilities or it can be the modification or expansion of existing facilities. The design starts at a conceptual level and ultimately ends in the form of fabrication and construction plans.
Process design is distinct from equipment design, which is closer in spirit to the design of unit operations. Processes often include many unit operation
Unit operation
In chemical engineering and related fields, a unit operation is a basic step in a process.Unit operation involves bringing a physical change such as separation, crystallization, evaporation, filtration etc.. For example in milk processing, homogenization, pasteurization, chilling, and packaging are...
s.
Documentation
Process design documents serve to define the design and they ensure that the design components fit together. They are useful in communicating ideas and plans to other engineers involved with the design, to external regulatory agencies, to equipment vendors and to construction contractors.In order of increasing detail, process design documents include:
- Block Flow Diagrams (BFD): Very simple diagrams composed of rectangles and lines indicating major material or energy flows.
- Process Flow Diagrams (PFD's)Process Flow diagramA process flow diagram is a diagram commonly used in engineering to indicate the general flow of plant processes and equipment.The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations...
: Typically more complex diagrams of major unit operations as well as flow lines. They usually include a material balance, and sometimes an energy balance, showing typical or design flowrates, stream compositions, and stream and equipment pressures and temperatures.
- Piping and Instrumentation Diagrams (P&ID's)Piping and instrumentation diagramA piping and instrumentation diagram/drawing is a diagram in the process industry which shows the piping of the process flow together with the installed equipment and instrumentation.-Contents and Function:...
: Diagrams showing each and every pipeline with piping class (carbon steel or stainless steel) and pipe size (diameter). They also show valving along with instrument locations and process control schemes.
- Specifications: Written design requirements of all major equipment items.
Process designers also typically write operating manuals on how to start-up, operate and shut-down the process.
Documents are maintained after construction of the process facility for the operating personnel to refer to. The documents also are useful when modifications to the facility are planned.
A primary method of developing the process documents is process flowsheeting
Process flowsheeting
Process flowsheeting is the use of computer aids to perform steady-state heat and mass balancing, sizing and costing calculations for a chemical process.The process design effort may be split into three basic steps* synthesis* analysis and* optimization....
.
Design Considerations
Designs have objectives and constraints, and even a simple process requires a trade-off among such factors.Objectives that a design may strive to include:
- Throughput rate
- Process yieldYield (chemistry)In chemistry, yield, also referred to as chemical yield and reaction yield, is the amount of product obtained in a chemical reaction. The absolute yield can be given as the weight in grams or in moles...
- Product purity
Constraints include:
- Capital cost
- Available space
- Safety concerns
- Environmental impactEnvironmental impact assessmentAn environmental impact assessment is an assessment of the possible positive or negative impact that a proposed project may have on the environment, together consisting of the natural, social and economic aspects....
and projected effluentEffluentEffluent is an outflowing of water or gas from a natural body of water, or from a human-made structure.Effluent is defined by the United States Environmental Protection Agency as “wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers...
s and emissionFlue gasFlue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants...
s - Waste production
- Operating and maintenance costs
Other factors that designers may include are:
- ReliabilityReliability engineeringReliability engineering is an engineering field, that deals with the study, evaluation, and life-cycle management of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often measured as a probability of...
- RedundancyRedundancy (engineering)In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
- Flexibility
- Anticipated variability in feedstock and allowable variability in product.
Sources of Design Information
Designers usually do not start from scratch, especially for complex projects. Often the engineers have pilot plantPilot plant
A pilot plant is a small chemical processing system which is operated to generate information about the behavior of the system for use in design of larger facilities....
data available or data from full-scale operating facilities. Other sources of information include proprietary design criteria provided by process licensors, published scientific data, laboratory experiments, and input.
Computer Help
The advent of low cost powerful computers has aided complex mathematical simulation of processes, and simulation software is often used by design engineers. Simulations can identify weaknesses in designs and allow engineers to choose better alternatives.However, engineers still rely on heuristics, intuition, and experience when designing a process. Human creativity is an element in complex designs.
See also
- Chemical engineerChemical engineerIn the field of engineering, a chemical engineer is the profession in which one works principally in the chemical industry to convert basic raw materials into a variety of products, and deals with the design and operation of plants and equipment to perform such work...
- Chemical plantChemical plantA chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use special equipment,...
- Chemical processChemical processIn a "scientific" sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by somebody. Such a chemical process commonly involves a chemical reaction of some sort...
- Process integrationProcess integrationProcess integration is a term in chemical engineering which has two possible meanings.1. A holistic approach to process design which emphasizes the unity of the process and considers the interactions between different unit operations from the outset, rather than optimising them separately. This...
- Process simulationProcess simulationProcess simulation is used for the design, development, analysis, and optimization of technical processes and is mainly applied to chemical plants and chemical processes, but also to power stations, and similar technical facilities.- Main principle :...
- Chemical process modelingChemical process modelingChemical process modeling is a computer modeling technique used in chemical engineering process design. It typically involves using purpose-built software to define a system of interconnected components, which are then solved so that the steady-state or dynamic behavior of the system can be...
- Environmental engineeringEnvironmental engineeringEnvironmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...
- Industrial processIndustrial processIndustrial processes are procedures involving chemical or mechanical steps to aid in the manufacture of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry....
- List of Chemical Process Simulators
- List of Dynamic Process Simulators
- Process engineeringProcess engineeringProcess engineering focuses on the design, operation, control, and optimization of chemical, physical, and biological processes through the aid of systematic computer-based methods...
- Process safetyProcess safetyProcess safety focuses on preventing fires, explosions and accidental chemical releases in chemical process facilities or other facilities dealing with hazardous materials such as refineries, and oil and gas production installations.Occupational safety and health primarily covers the management of...
- Unit processUnit processA Unit Process is a step in manufacturing in which chemical reaction takes place, e.g, the oxidation of paraxylene to terephthalic acid is a unit process, the hydrogenation of vegetable oil to ghee is a unit process. In 1930 P.H. Groggins introduced Unit processes in order to classify and...