| In recent years,with the continuous development of soda ash industry,the byproduct production of ammonium chloride has been increasing year by year.Soda ash as a product is sold all over the place,ammonium chloride is because of its low price and a lot of accumulation,seriously restricted the development of soda ash enterprises.Therefore,it is of great significance to treat a large amount of accumulated ammonium chloride and adopt an appropriate process to produce products with high added value.As a basic chemical raw material,calcium carbonate is widely used in cement,coating,plastics,papermaking and other industries.Therefore,this paper designed a roasting-water leaching-carbonization method to treat ammonium chloride,and by regulating the carbonization process to prepare fine calcium carbonate products,so as to achieve high value utilization of resources.This paper first studied the roasting process of ammonium chloride and natural limestone,investigated the effects of roasting temperature,reactant molar ratio and roasting time on the conversion rate of ammonium chloride,and obtained the best roasting conditions to improve the conversion rate of ammonium chloride.Under optimal conditions,the conversion rate of ammonium chloride can reach 96.9%,which indicates that the natural limestone with low price can effectively treat ammonium chloride,and the conversion rate of ammonium chloride is very high.In the process of roasting,ammonium chloride reacts with excessive carbonate rock to produce a large amount of calcium chloride.The effects of water immersion temperature,time and liquid-solid ratio were investigated.Under the optimal conditions,the leaching rate of calcium chloride reached 98.6%.At the same time,carbon dioxide and ammonia were also produced in the roasting process,and the carbon dioxide and ammonia produced in the roasting process were introduced into the aqueous solution to prepare high-quality calcium carbonate,so as to realize the comprehensive utilization of resources.The results show that in the carbonization process,the initial concentration and carbonation temperature of the aqueous solution can produce pure calcite calcium carbonate,while the increase of gas flow rate can produce mixed crystal of calcite and aragonite,which is not conducive to the large-scale production of enterprises.Finally,the relationship between the induction period and supersaturation of precipitated calcium carbonate in calcium chloride-ammonium carbonate system was studied by focused beam reflection measurement(FBRM)on-line in situ technique.And combined with the classical nucleation theory to analyze.Subsequently,an extended study was carried out on the polymorphism of calcium carbonate.The influence of alkanolamide 6502,a nonionic surfactant,on the precipitation of calcium carbonate was investigated.The effects of surfactant dosage,crystallization temperature and stirring rate on calcium carbonate were investigated.The results show that alkanolamide 6502 could change the polymorphism of calcium carbonate,and the larger the dosage,the greater the ratio of pellet aragonite.At the same time,various forms of calcium carbonate crystals are also prepared,such as hollow spherical,spherical,layered dandelion and so on.In addition,the addition of surface activity can also produce a hydrophobic layer on the surface of calcium carbonate crystal,which changes the surface properties of calcium carbonate. |
