Studies On The Preparation Of High Purity And Whiteness Calcium Carbonate By Calcium Carbide Residue

Calcium carbide residue is one kind of industry waste residue produced in the preparation of acetylene gas by the hydration of calcium carbide. If we take no treatment, it not only takes up land, but also causes the serious pollution to the environment. At present, the comprehensive treatments of calcium carbide residue generally still have some problems, such as small process load and not high added value for product. As a sort of cheap and high-quality padding and white pigment, the calcium carbonate has been widely used in many industries, for example, plastic, rubber, papermaking, coating, commodity chemistry and so on. Especially, the nanometer calcium carbonate can enable the physical performance of product to get an enormous improvement. Therefore the preparation of light calcium carbonate, which has a big market demand, will become a good approach of the comprehensive treatments of calcium carbide residue.This research used the calcium carbide residue, removed the impurity thoroughly through leaching, then adopted gas-liquid intermittence carbonization method and liquid-liquid continuous reaction method to prepare the high-purity, high-whiteness, light calcium carbonate and nanometer calcium carbonate respectively. After the reaction, the filtrate was returned and used to leach the calcium carbide residue to obtain the circulation using.This article studied the process characteristics of leaching and precipitation reaction, the effect of craft parameter on the reaction process and product performance, and then determined the best craft conditions of each working procedure using experimental method.The results of research show that the impurity of infusibility and metal ion has been removed after the leaching of calcium carbide residue, and the transform rate of hydrated lime up to about 88%. The calcium carbonate prepared by the gas-liquid intermittence carbonization reaches the excellent index requirement of HG/T2226-2000 by examination, the purity of which is 99.2%, whiteness is 94 degree, crystal shape is virgulate. The nanometer calcium carbonate prepared by liquid-liquid continuous reaction method gets up to the first-class index requirement of HG/T2776-1996, crystal shape is cube, the purity and whiteness is 98.9% and 93 degree.This article studied the reaction and crystallization mechanism that the calcium carbonate was prepared by the calcium carbide residue, and analyzed the difference between the calcium carbide residue method and the iimestone method, the difference between gas-liquid intermittence carbonization method and liquid-liquid continuous reaction method. This article also analyzed the behavior and the innovation of this research.All in all, the research has provided comprehensive treatments of calcium carbide residue with the new method and technology, and it may obtain high added-value, widely used products, getting remarkable benefit of environmental protection and economy as well.