Preparation of bauxite mixed with calcium aluminate Polymeric aluminum chloride is calcium aluminate is rich in AL2O3 but difficult to dissolve the aluminum ore plus limestone sintered products, and some are produced by sintering AL2O3 solid waste, the chemical formula can be written CA (ALO2) 2, or CaO · AL2O3, aluminum-bearing ores should be crushed, roasted, finely ground and calcined at 1200-1400 ° C with limestone to become the more easily dissolved calcium aluminate. Originally an intermediate product of the cement industry, the market price is only about one-third of that of aluminum hydroxide gel and is therefore very attractive to the polymetallic industry for use as a premix for industrial applications. In the current production often use calcium aluminate two-stage method, the first one is similar to the acid-soluble one-step method, in the reaction tank with roasting activated bauxite and hydrochloric acid to elute the molten aluminum, the second paragraph in the reaction tank was added aluminate Calcium powder, reaction at atmospheric pressure of less than 100 ℃, on the one hand to improve the aluminum content of the reaction solution, but also improve the basicity of the salt. At present, China generally uses bauxite and calcium aluminate two-step production of polyaluminum chloride. Shandong, Henan, Jiangsu and other large enterprises are using this technology. The product of the base degree of 60% -90%, alumina mass fraction of 25% -31%. Two-step acid dissolution method can be used atmospheric dissolution method, you can also use pressurized dissolution method. The former dissolves for a long time, the dissolution rate is low, but can be mass-produced, which dissolves a short time, high dissolution rate, but the general use of 5m3 reactor, the output less than the former. Adding the calcium aluminate powder in the second paragraph may increase the insoluble content in the product. There are strict requirements for insolubles in the national standard. In order to reduce the content of insolubles, the mixed liquid after one-step or two-step production of polyaluminium chloride is usually left for 4-10 days or filtered by a frame filter press. Tongji University, the successful development of a new polyacrylamide Polyacrylamide, 1t suspension in 1-3kg modified polyacrylamide aqueous solution, you can quickly reduce the insoluble content, usually one day after standing, insoluble content can reach the national standard , The cost per ton of liquid handling generally 2-3 yuan. At present, this technology has been applied in Shandong Zibo, Henan Gongyi and other places. If the calcium aluminate in the heavy metal ions is relatively high, you must take measures to further reduce heavy metals.