Chemical Industry, also known as the chemical processing industry, refers to the process industry where chemical methods are dominant in the production process. The chemical industry is an industrial sector that has been formed since the early 19th century and has developed rapidly. The chemical industry is a knowledge and capital intensive industry. With the development of science and technology, it has gradually developed into a multi-industry and multi-species production department, which only produced a few inorganic products such as soda ash and sulfuric acid and organic products mainly derived from the extraction of alizarin from plants at first. A large number of chemical enterprises arise which comprehensively utilize resources and scale up, including the basic chemical industry and plastics, synthetic fibers, petroleum, rubber, pharmaceuticals, dyes and so on. It is a department that utilizes chemical reactions to change the structure, composition, and morphology of a chemical product, such as: inorganic acids, alkalis, salts, rare elements, synthetic fibers, plastics, synthetic rubber, dyes, paints, fertilizers, pesticides, etc.
The chemical industry is a multi-species basic industry. In order to meet the various needs of chemical production, there are many types of chemical equipment, and the operating conditions of the equipment are also complicated. According to the operating pressure, it is divided into vacuum, normal pressure, low pressure, medium pressure, high pressure and ultra high pressure; according to the operating temperature, it is divided into low temperature, normal temperature, medium temperature and high temperature. Most of the treated medium is corrosive or flammable, explosive, toxic and poisonous etc. Sometimes for a specific device, there are requirements about temperature, pressure and corrosion resistance. Sometimes these requirements are mutually restrictive , and sometimes certain conditions often change.