What is the difference between the combined soda-making process and the ammonia-soda process?

This post was last edited by mkp369 on 2017-3-11 08:14. The combined alkali production method was invented by Hou Debang, a renowned Chinese chemist. A method that combines the synthesis of ammonia with the ammonia-alkali process for soda ash production in order to manufacture both soda ash and ammonium chloride simultaneously. The raw materials are table salt, ammonia, and carbon dioxide. It includes two processes. The first process is the same as that used in the ammonia-alkali method for producing soda ash: ammonia is introduced into saturated brine to form an ammonium brine solution, after which carbon dioxide is added to produce sodium bicarbonate precipitate. Pure soda ash is obtained through filtration, washing, and calcination. The filtrate is mother liquor I containing ammonium chloride. The second process involves introducing ammonia into mother liquor I, freezing it, and adding fine powdered table salt to cause ammonium chloride to precipitate; ammonium chloride is then obtained through filtration, washing, and drying. Mother liquor II after the precipitation of ammonium chloride is saturated with table salt, and ammonia and carbon dioxide can be introduced again to recycle for soda production. Compared with the ammonia-alkali process, its advantages are: (1) the utilization rate of sodium chloride reaches over 96% ； (2) Carbon dioxide from ammonia synthesis plants was utilized comprehensively ； (3) Saved equipment such as ammonia vaporization towers and lime kilns ； (4) There is no difficult-to-treat calcium chloride waste coming from the ammonia vaporization tower. But washed table salt powder must be used. The ammonia-alkali process, also known as the Solvay process, is a method for producing soda ash invented in 1892 by the Belgian engineer Solvay (1838–1922). Soda ash is produced using table salt (sodium chloride), limestone (which, when calcined, produces quicklime and carbon dioxide), and ammonia as raw materials. Ammonia is first introduced into saturated salt water to form an ammonium salt solution, after which carbon dioxide is added, resulting in the formation of sodium bicarbonate precipitate, which has a lower solubility, and an ammonium chloride solution. NaCl + NH3 + H2O + CO2 = NaHCO3↓ + NH4Cl. The tiny crystals of NaHCO3 obtained after filtration and washing are then heated and calcined to produce soda ash. Calcination of 2NaHCO3 yields Na2CO3 + H2O + CO2 ↑; the carbon dioxide gas produced can be recovered and reused. The filtrate containing ammonium chloride is mixed with lime milk [2] and heated; the ammonia gas released can be recovered and reused. CaO + H2O = Ca(OH)2 (slaked lime) 2NH4Cl + Ca(OH)2 △ CaCl2 + 2NH3↑ + 2H2O

Learned it. Thank you, OP, for sharing

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