Gypsum crystallization and hydrochloric acid regeneration by reaction of calcium chloride solution with sulfuric acid

被引:33
作者
Al-Othman, Amani [1 ]
Demopoulos, George R. [1 ]
机构
[1] McGill Univ, Dept Min & Mat Engn, Montreal, PQ, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
Crystallization; Gypsum; HCl regeneration; Chloride hydrometallurgy;
D O I
10.1016/j.hydromet.2008.08.010
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
In this work, the crystallization of gypsum(CaSO4 center dot 2H(2)O) in the temperature range of 20-60 degrees C is investigated along with the simultaneous regeneration of HCl by the reaction of concentrated CaCl2 solution (3-3.5 M) with H2SO4 at a concentration range of 2.6-8.0 M. Fast addition of H2SO4 proved counter productive as it yielded a gel-like fine crystal suspension. Slower addition via titration or in multiple steps over 2 to 4 h followed by 2 h of equilibration proved successful in producing well developed columnar gypsum crystals of similar to 50+ mu m long and 5+ mu m thick. It was determined that for the purpose of producing high strength HCl (4 M), with minimum soluble CaSO4 (5 g/L at 40 degrees C), 8.0 M H2SO4 has to be used at a molar ratio (SO4/Ca)= 0.8. Upon the elevation of temperature or by using seed and recycling, crystal growth was promoted yielding crystals as large as 100+ mu m in length and 20+ mu m in thickness. Crystallization tests in the presence of several metal chlorides showed that metal impurity uptake is not a problem except for lead, which was present at 95 ppm (or mg/kg). Filtration rates higher than 4000 kg of solids deposited m(-2) h(-1) were obtained. (C) 2008 Elsevier B.V. All rights reserved.
引用
收藏
页码:95 / 102
页数:8
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