Chemical process
Encyclopedia
In a "scientific
" sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compound
s. 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. In an "engineering
" sense, a chemical process is a method intended to be used in manufacturing
or on an industrial scale (see Industrial process
) to change the composition of chemical(s) or material(s), usually using technology similar or related to that used in chemical plant
s or the chemical industry
.
Neither of these definitions is exact in the sense that one can always tell definitively what is a chemical process and what is not; they are practical definitions. There is also significant overlap in these two definition variations. Because of the inexactness of the definition, chemists and other scientists use the term "chemical process" only in a general sense or in the engineering sense. However, in the "process (engineering)" sense, the term "chemical process" is used extensively. The rest of the article will cover the engineering type of chemical process.
Although this type of chemical process may sometimes involve only one step, often multiple steps, referred to as unit operation
s, are involved. In a plant
, each of the unit operations commonly occur in individual vessels or sections of the plant called units. Often, one or more chemical reaction
s are involved, but other ways of changing chemical (or material) composition may be used, such as mixing
or separation process
es. The process steps may be sequential in time or sequential in space along a stream of flowing or moving material; see Chemical plant. For a given amount of a feed (input) material or product (output) material, an expected amount of material can be determined at key steps in the process from empirical data and material balance calculations. These amounts can be scaled up or down to suit the desired capacity or operation of a particular chemical plant built for such a process. More than one chemical plant may use the same chemical process, each plant perhaps at differently scaled capacities.
Such chemical processes can be illustrated generally as block flow diagram
s or in more detail as process flow diagram
s. Block flow diagrams show the units as blocks and the streams flowing between them as connecting lines with arrowheads to show direction of flow.
In addition to chemical plants for producing chemicals, chemical processes with similar technology and equipment are also used in oil refining
and other refineries
, natural gas processing
, polymer
and pharmaceutical manufacturing, food processing
, and water
and wastewater
treatment.
. Together with unit operation
s it forms the main principle of the varied chemical industries. Each genre of unit processing follows the same chemical law much as each genre of unit operation
s follows the same physical law.
Chemical engineering unit processing consists of the following important processes:
Process (science)
In science, a process is every sequence of changes of a real object/body which is observable using the scientific method. Therefore, all sciences analyze and model processes....
" sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s. Such a chemical process can occur by itself or be caused by somebody. Such a chemical process commonly involves a chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
of some sort. In an "engineering
Process (engineering)
In engineering a process is a set of interrelated tasks that, together, transform inputs into outputs. These tasks may be carried out by people, nature, or machines using resources; so an engineering process must be considered in the context of the agents carrying out the tasks, and the resource...
" sense, a chemical process is a method intended to be used in manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
or on an industrial scale (see Industrial process
Industrial process
Industrial 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....
) to change the composition of chemical(s) or material(s), usually using technology similar or related to that used in chemical plant
Chemical plant
A 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,...
s or the chemical industry
Chemical industry
The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials into more than 70,000 different products.-Products:...
.
Neither of these definitions is exact in the sense that one can always tell definitively what is a chemical process and what is not; they are practical definitions. There is also significant overlap in these two definition variations. Because of the inexactness of the definition, chemists and other scientists use the term "chemical process" only in a general sense or in the engineering sense. However, in the "process (engineering)" sense, the term "chemical process" is used extensively. The rest of the article will cover the engineering type of chemical process.
Although this type of chemical process may sometimes involve only one step, often multiple steps, referred to as 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, are involved. In a plant
Factory
A factory or manufacturing plant is an industrial building where laborers manufacture goods or supervise machines processing one product into another. Most modern factories have large warehouses or warehouse-like facilities that contain heavy equipment used for assembly line production...
, each of the unit operations commonly occur in individual vessels or sections of the plant called units. Often, one or more chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
s are involved, but other ways of changing chemical (or material) composition may be used, such as mixing
Mixing (process engineering)
In industrial process engineering, mixing is a unit operation that involves manipulating a heterogeneous physical system, with the intent to make it more homogeneous...
or separation process
Separation process
In chemistry and chemical engineering, a separation process, or simply a separation, is any mass transfer process used to convert a mixture of substances into two or more distinct product mixtures, at least one of which is enriched in one or more of the mixture's constituents. In some cases, a...
es. The process steps may be sequential in time or sequential in space along a stream of flowing or moving material; see Chemical plant. For a given amount of a feed (input) material or product (output) material, an expected amount of material can be determined at key steps in the process from empirical data and material balance calculations. These amounts can be scaled up or down to suit the desired capacity or operation of a particular chemical plant built for such a process. More than one chemical plant may use the same chemical process, each plant perhaps at differently scaled capacities.
Such chemical processes can be illustrated generally as block flow diagram
Block diagram
Block diagram is a diagram of a system, in which the principal parts or functions are represented by blocks connected by lines, that show the relationships of the blocks....
s or in more detail as process flow diagram
Process Flow diagram
A 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...
s. Block flow diagrams show the units as blocks and the streams flowing between them as connecting lines with arrowheads to show direction of flow.
In addition to chemical plants for producing chemicals, chemical processes with similar technology and equipment are also used in oil refining
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
and other refineries
Refinery
A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value.-Types of refineries:Different types of refineries are as follows:...
, natural gas processing
Natural gas processing
Natural-gas processing is a complex industrial process designed to clean raw natural gas by separating impurities and various non-methane hydrocarbons and fluids to produce what is known as pipeline quality dry natural gas.-Background:...
, polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
and pharmaceutical manufacturing, food processing
Food processing
Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...
, and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
treatment.
Unit processing in chemical engineering
Unit processing is the basic processing in chemical engineeringChemical 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...
. Together with 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 it forms the main principle of the varied chemical industries. Each genre of unit processing follows the same chemical law much as each genre of 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 follows the same physical law.
Chemical engineering unit processing consists of the following important processes:
- Oxidation
- ReductionRedoxRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
- HydrogenationHydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
- DehydrogenationDehydrogenationDehydrogenation is a chemical reaction that involves the elimination of hydrogen . It is the reverse process of hydrogenation. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures....
- HydrolysisHydrolysisHydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
- Hydration reactionHydration reactionIn organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group and a hydrogen cation are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous...
- DehydrationDehydrationIn physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
- HalogenationHalogenationHalogenation is a chemical reaction that incorporates a halogen atom into a molecule in substitution of hydrogen atom. Halogenation takes place in the gas phase. There are four types of halogenation: fluorination, chlorination, bromination, and iodination...
- NitrificationNitrificationNitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. Degradation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil...
- Sulfonation
- Ammoniation
- Alkaline fusion
- AlkylationAlkylationAlkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
- Dealkylation
- Esterification
- PolymerizationPolymerizationIn polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
- Polycondensation
- CatalysisCatalysisCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
See also
- 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,...
- 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....
- Process (engineering)Process (engineering)In engineering a process is a set of interrelated tasks that, together, transform inputs into outputs. These tasks may be carried out by people, nature, or machines using resources; so an engineering process must be considered in the context of the agents carrying out the tasks, and the resource...
- Foam fractionationFoam fractionationFoam fractionation is a chemical process in which hydrophobic molecules are preferentially separated from a liquid solution using rising columns of foam. It is commonly used, albeit on a small scale, for the removal of organic waste from aquariums; these units are known as "protein skimmers"...