Study On The Decomposition Reaction Of Ammonium Chloride With High Concentration Calcium Oxide

Ammonia-soda process is a main method to produce soda.In this process,low concentration ammonium chloride,the by-product,is decomposed into calcium chloride and ammonia by adding lime milk to the solution.Ammonia is evaporated out through ammonia still process and then circulated back to soda carbonate system.At the same time,large amount of waste solution of the concentration of 10 percent calcium chloride was produced,which made a serious pollution on the environment.The union soda production is another industrual method of producing soda carbonate.In this process,the ammonium chloride will be isolated from the system in a solid form through cold precipitation and salting-out processes,avoiding the pollution of effluent.At present,95%of ammonium chloride is used as fertilizer in the agriculture.However,the sweetness of fruits will be weaken,because ammonium chloride is a kind of acidic and chloride-containing fertilizer.The soil will be hardened.Therfore,ammonium chloride fertilizer has a large number of surplus,which makes a waste of resources.Because of the problems mentioned above,this paper propose that ammonium chloride is reacted with calcium oxide in the solid form or under high concentration solution.In this process,ammonia is cyclic used.At the same time,high concentration calcium chloride is produced,which is directly used as snow-melting agent and in other aspect.This method not only avoids the enviroment pollution,but also make cyclic utilization of ammonium,which is of great significance for the development of soda carbonate industry.The major contents of this paper are listed as bellow:1)The small-scale experiments that decomposed the ammonium chloride using calcium oxide/calcium hydroxide by dry method was carried out.Results showed that the decomposition of ammonium chloride reached above 99.5%through the solid-solid phase reaction by using the small mill as the reaction equipment.But the production was proved as alkai type calcium chloride instead of anhydrous calcium chloride.And then the appearance,structure,hydrolysis resistance and carbonation reaction of alkai type calcium chloride was stuided.2)Base on the results of small-scale experiments,middle-scale experiments of dry method of ammonium chloride decomposition reaction was performed.Based on the design and calculation of experiment equipment of ball mill,the middle-scale experiment device with 900mm diameter and 400mm width was built.The volume of wear-resisting ball,discharging port and exhaust hole was optimized designed.Experiment results showed that the dry method middle-scale experiment device had amplification effect,and the maximum decomposition of ammonium chloride of calcium oxide method was about 80%.The maximum decomposition of ammonium chloride of calcium hydroxide method was about 88%3)Because of the problems of dry decomposition method,the high concentration wet decomposion method of ammonium chloride by calcium oxide/calcium hydroxide were studied.It had been found that ammoniun chloride cannot be decomposed by calcium oxide comletely,even water was existed in the system.The surface of calcium oxide was wrapped,which hindered the reaction process,resulting in the uncomplete decomposion of ammonium chloride by the comparison of calcium oxide before and after the reaction via SEM.But the ammonium chloride could be decomposion completely by dry calcium hydroxide and ammonium chloride saturated solution,even under higher concentration.In this process,gas state ammonium was reused,and high concentration solution of calcium chloride was obtained.4)Based on the results of wet method high concentration experiments,the inner-agitating-vavle-type horizontal middle-scale experiment reactor was designed,which was used in the wet method reaction of calcium hydroxide and ammoniun chloride.The relevant study of middle-scale experiment was carried out,and the decomposion law of the reaction of calcium hydroxide and ammoniun chloride was discussed.It was found that the amplification effect of reaction could be eliminated by calcium hydroxide method,which could decompose ammoniun chloride completely.