Chemical plant

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A chemical plant is an

manufacturer
to be effectively a chemical plant.

minimize transportation costs for the feedstocks produced by the refinery. Speciality chemical[3] and fine chemical plants are usually much smaller and not as sensitive to location. Tools have been developed for converting a base project cost from one geographic location to another.[4]

Chemical processes

Kemira's chemical plant in Oulu, Finland

Chemical plants use chemical processes, which are detailed industrial-scale methods, to transform feedstock chemicals into products. The same chemical process can be used at more than one chemical plant, with possibly differently scaled capacities at each plant. Also, a chemical plant at a site may be constructed to utilize more than one chemical process, for instance to produce multiple products.

A chemical plant commonly has usually large vessels or sections called units or lines that are interconnected by piping or other material-moving equipment which can carry streams of material. Such material streams can include fluids (gas or liquid carried in piping) or sometimes solids or mixtures such as slurries. An overall chemical process is commonly made up of steps called unit operations which occur in the individual units. A raw material going into a chemical process or plant as input to be converted into a product is commonly called a feedstock, or simply feed. In addition to feedstocks for the plant, as a whole, an input stream of material to be processed in a particular unit can similarly be considered feed for that unit. Output streams from the plant as a whole are final products and sometimes output streams from individual units may be considered intermediate products for their units. However, final products from one plant may be intermediate chemicals used as feedstock in another plant for further processing. For example, some products from an oil refinery may be used as feedstock in petrochemical plants, which may in turn produce feedstocks for pharmaceutical plants.

Either the feedstock(s), the product(s), or both may be individual compounds or mixtures. It is often not worthwhile separating the components in these mixtures completely; specific levels of purity depend on product requirements and process economics.

Operations

Chemical processes may be run in continuous or batch operation.

Batch operation

In batch operation, production occurs in time-sequential steps in discrete batches. A batch of feedstock(s) is fed (or charged) into a process or unit, then the chemical process takes place, then the product(s) and any other outputs are removed. Such batch production may be repeated over again and again with new batches of feedstock. Batch operation is commonly used in smaller scale plants such as pharmaceutical or specialty chemicals production, for purposes of improved traceability as well as flexibility. Continuous plants are usually used to manufacture

petrochemicals while batch plants are more common in speciality and fine chemical production as well as active pharmaceutical ingredient
(API) manufacture.

Continuous operation

In continuous operation, all steps are ongoing continuously in time.

crude oil refined per day; alternatively chemical plant capacity may be given in tons
of product produced per day. In actual daily operation, a plant (or unit) will operate at a percentage of its full capacity. Engineers typically assume 90% operating time for plants which work primarily with fluids, and 80% uptime for plants which primarily work with solids.

Units and fluid systems

Specific

heat produced or absorbed by chemical reactions must be considered. Some plants may have units with organism cultures for biochemical processes such as fermentation or enzyme
production.

Distillation unit in Italy

oil depot
.

Fluid systems for carrying liquids and gases include piping and tubing of various diameter sizes, various types of

reactants
or materials such as solids for extraction or leaching, to provide a suitable medium for certain chemical reactions to run, or so they can otherwise be treated as fluids.

Chemical plant design

Flow diagram for a typical oil refinery

Today, the fundamental aspects of designing chemical plants are done by chemical engineers. Historically, this was not always the case, and many chemical plants were constructed haphazardly before the discipline of chemical engineering became established. Chemical engineering was first established as a profession in the United Kingdom when the first chemical engineering course was given at the University of Manchester in 1887 by George E. Davis in the form of twelve lectures covering various aspects of industrial chemical practice.[6] As a consequence George E. Davis is regarded as the world's first chemical engineer. Today chemical engineering is a profession and those professional chemical engineers with experience can gain "Chartered" engineer status through the Institution of Chemical Engineers.

In plant design, typically less than 1 percent of ideas for new designs ever become commercialized. During this solution process, typically, cost studies are used as an initial screening to eliminate unprofitable designs. If a process appears profitable, then other factors are considered, such as safety, environmental constraints, controllability, etc.[2] The general goal in plant design, is to construct or synthesize “optimum designs” in the neighborhood of the desired constraints.[7]

Many times

electrical engineers may become involved with mechanical or electrical details, respectively. Structural engineers may become involved in the plant design to ensure the structures can support the weight
of the units, piping, and other equipment.

The units, streams, and fluid systems of chemical plants or processes can be represented by

heats of reaction, heat capacities, expected temperatures, and pressures at various points to calculate amounts of heating and cooling needed in various places and to size heat exchangers. Chemical plant design can be shown in fuller detail in a piping and instrumentation diagram
(P&ID) which shows all piping, tubing, valves, and instrumentation, typically with special symbols. Showing a full plant is often complicated in a P&ID, so often only individual units or specific fluid systems are shown in a single P&ID.

In the plant design, the units are sized for the maximum capacity each may have to handle. Similarly, sizes for pipes, pumps, compressors, and associated equipment are chosen for the flow capacity they have to handle. Utility systems such as

pressure reducing valve
or sample cooler.

Units and fluid systems in the plant including all vessels, piping, tubing, valves, pumps, compressors, and other equipment must be rated or designed to be able to withstand the entire range of pressures, temperatures, and other conditions which they could possibly encounter, including any appropriate

Hazop or fault tree analysis
, to ensure that the plant has no known risk of serious hazard.

Within any constraints the plant is subject to, design parameters are optimized for good economic performance while ensuring the safety and welfare of personnel and the surrounding community. For flexibility, a plant may be designed to operate in a range around some optimal design parameters in case feedstock or economic conditions change and re-optimization is desirable. In more modern times, computer simulations or other computer calculations have been used to help in chemical plant design or optimization.

Plant operation

Process control

In

Electrical controls are now common. A plant often has a control room
with displays of parameters such as key temperatures, pressures, fluid flow rates and levels, operating positions of key valves, pumps, and other equipment, etc. In addition, operators in the control room can control various aspects of the plant operation, often including overriding automatic control. Process control with a computer represents more modern technology. Based on possible changing feedstock composition, changing products requirements or economics, or other changes in constraints, operating conditions may be re-optimized to maximize profit.

Workers

As in any industrial setting, there are a variety of workers working throughout a chemical plant facility, often organized into departments, sections, or other work groups. Such workers typically include engineers, plant operators, and maintenance technicians. Other personnel at the site could include chemists, management/administration, and office workers. Types of engineers involved in operations or maintenance may include chemical process engineers, mechanical engineers for maintaining mechanical equipment, and electrical/computer engineers for electrical or computer equipment.

Transport

Large quantities of fluid feedstock or product may enter or leave a plant by

tanker truck. For example, petroleum commonly comes to a refinery by pipeline. Pipelines can also carry petrochemical feedstock from a refinery to a nearby petrochemical plant. Natural gas is a product which comes all the way from a natural gas processing plant to final consumers by pipeline or tubing. Large quantities of liquid feedstock are typically pumped into process units. Smaller quantities of feedstock or product may be shipped to or from a plant in drums. Use of drums about 55 gallons in capacity is common for packaging
industrial quantities of chemicals. Smaller batches of feedstock may be added from drums or other containers to process units by workers.

Maintenance

In addition to feeding and operating the plant, and packaging or preparing the product for shipping, plant workers are needed for taking samples for routine and troubleshooting analysis and for performing routine and non-routine maintenance.

Routine maintenance
can include periodic inspections and replacement of worn catalyst, analyzer reagents, various sensors, or mechanical parts. Non-routine maintenance can include investigating problems and then fixing them, such as leaks, failure to meet feed or product specifications, mechanical failures of valves, pumps, compressors, sensors, etc.

Statutory and regulatory compliance

When working with chemicals,

U. S. Chemical Safety and Hazard Investigation Board
has become operational.

Clustering of commodity chemical plants

Chemical Plants used particularly for

Northeast of England Process Industry Cluster (NEPIC).[8] Approximately 50% of the UK's petrochemicals, which are also commodity chemicals, are produced by the industry cluster companies on Teesside at the mouth of the River Tees on three large chemical parks at Wilton,[9] Billingham and Seal Sands
.

Corrosion and use of new materials

BS4994
is widely used for design and construction of the vessels, tanks, etc.

See also

References

  1. ^ Ellison-Taylor; et al. (1970). Chemical Plant Technology: An Introductory Manual. Longmans.
  2. ^
    ISBN 978-0-07-017762-8
    .
  3. ^ Stork, William (2004). "Speciality Chemicals" (PDF). Chemical & Engineering News supplement 82. pp. 35–39.
  4. ^ Plant Construction Location Factor - Intratec Knowledge Base Archived 6 March 2014 at the Wayback Machine
  5. ^ NetSuite.com (29 June 2023). "Continuous Operations Explained". Oracle NetSuite. Retrieved 31 August 2023.
  6. ^ Delgass; et al. "Seventy Five Years of Chemical Engineering". Purdue University. Retrieved 13 August 2013.
  7. ^ Cussler, Moggridge and Moggridge (2001). Chemical product design. Cambridge University Press.
  8. ^ UK Trade&Investment. "Chemicals–the UK advantage" (PDF). pp. 9–10. Archived from the original (PDF) on 29 October 2013. Retrieved 10 July 2013.
  9. ISBN 978-1872339016
    .

Further reading
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