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Introduction and application of calcium carbide
The chemical name of calcium carbide is calcium carbide (CaC2), and the main component is CaC2, accounting for 70-80% of the total content of calcium carbide. The remaining component Cao accounts for about 20%, and others such as C, Si, Fe account for about 6%. Calcium carbide is an inorganic compound, white crystal, industrial products for gray black block, section for purple or gray. In case of water, it will react violently to form acetylene and give off heat.
1、 Acetylene gas is produced by the reaction of calcium carbide with water
The chemical property of calcium carbide is very active. When it meets water, it will decompose to produce acetylene gas to synthesize many organic compounds and give off a lot of heat. For example: synthetic rubber, artificial resin, acetone, ketene, carbon black, etc.; at the same time, acetylene oxygen flame is widely used in metal welding and cutting. Acetylene gas can also be processed into propargyl alcohol (C3H4O) for pharmaceutical use.
2、 Production of PVC
In the production of PVC by calcium carbide method, acetylene (C2H2) is produced by calcium carbide (CaC2) in contact with water. Vinyl chloride monomer (CH2 = CHCl) is synthesized from acetylene and hydrogen chloride (HCl), and then vinyl chloride is polymerized to produce polyvinyl chloride - [ch-chci] n -.
3、 Calcium carbide desulfurizer / deoxidizer
Calcium carbide is an economic and efficient desulfurizing and deoxidizing agent in steel production. Calcium carbide is usually used to reduce FeO, Cr2O3 and MnO in slag during steelmaking and refining. This is the so-called white slag making process. When fine calcium carbide is added into slag, CaC2 is decomposed into calcium and carbon. Carbon continues to produce CO2 gas in the reaction of FeO, MnO and Cr2O3 in the reduction slag, so as to form foams in the slag. The foaming slag means that the thickness of the slag increases and produces the arc burying effect. This brings three advantages. One is to protect the lining from prolonging life by arc radiation. The second is to improve the efficiency of power input, save power consumption and shorten smelting time. The third is to form reducing atmosphere, reduce the secondary oxidation of steel to air and absorb moisture in air. Calcium is a strong reducing agent, which can reduce FeO and Cr2O3 in slag maximally. After forming white slag, it can react directly with sulfur in molten steel to form CAS. Therefore, some people mix calcium carbide with lime, bauxite and fluorite as desulfurizer. It has the advantages of good fluidity, fast desulfurization and deoxidization reaction speed, strong desulfurization depth, short reduction time (refining), small temperature drop of molten steel, low consumption of desulfurizer and material consumption. Because of the reasonable price, it has become the substitute of aluminum in iron and steel industry. The desulphurization and deoxidization of primary steel can not only reduce the consumption of aluminum and the inclusion of alumina, but also reduce the cost. Compared with the reducing agent SiC, the reduction ability is strong and the weakness of reducing slag basicity by SiC reduction is avoided. It is best used in electric furnace, refining furnace and converter, which can reduce energy saving and cost in iron and steel industry. Because of its excellent desulfurization and deoxidation performance, it is also an ideal desulfurizing and deoxidizing agent in foundry industry, which is widely used in foundry industry.
4、 Calcium cyanamide produced by calcium carbide reaction
Calcium cyanamide, namely lime nitrogen, is formed by the reaction of powdered calcium carbide and nitrogen. Lime nitrogen is an important raw material for the preparation of cyanamide. The melt formed by the reaction of heated lime nitrogen and salt is used in gold mining and nonferrous metal industry. Lime nitrogen is also an efficient soil disinfectant. Its disinfection principle refers to the monocyandiamide and liquid dicyandiamide, which generate gas after the decomposition of calcium cyanide in water, has a broad-spectrum killing effect on fungi, bacteria and other harmful organisms in the soil, and can control a variety of soil borne diseases and underground pests, and has a certain control effect on root knot nematode, which has been plagued by facility agricultural production. In addition to quicklime, the intermediate products of the decomposition of calcium cyanamide, monocyandiamide and dicyandiamide finally form urea, which has the advantages of no residue and no environmental pollution. The outstanding role of calcium cyanamide disinfection technology is to promote organic matter decomposition, improve soil structure, regulate soil acidity, eliminate soil hardening, increase soil permeability, reduce the harm of Cordyceps sinensis, and reduce the content of nitrite in vegetables.
Calcium carbide is mainly used in industrial gas, pharmaceutical, PVC, steel smelting, fluorine chemical raw materials, gold mining and nonferrous metal industry, soil disinfectant, fruit ripening, etc. the domestic output is about 2.3 million tons / month.