Thermodynamics analysis and response surface methodology to investigate decomposition behaviors for lepidolite sulfation products in presence of coal

Abstract

The process consisting of sulfation and decomposition has been proved to utilize lepidolite efficiently, while the conditions of sulfation products are relatively harsh. In this paper, the decomposition behaviors for lepidolite sulfation products in presence of coal were studied to optimize the conditions required. The feasibility was first verified theoretically by calculating the thermodynamic equilibrium composition with different amounts of carbon addition. The priority of each component reacted with carbon was concluded as Al2(SO4)3, KAl(SO4)2, RbAl(SO4)2, and FeSO4. Based on the batch experimental results, response surface methodology was purposed to simulate and predict the effect of various parameters. The verification experimental results showed the extraction of Al and Fe were only 0.05 % and 0.01 % under the optimal conditions of 750 °C, 20 min, and 20 % coal dosage. The separation of alkali metals and impurities was realized. The decomposition behaviors for lepidolite sulfation products in presence of coal was clarified by discussing the contradiction between theoretical thermodynamic calculation and actual experimental results. It indicated that carbon monoxide was more active than carbon in promoting decomposition. The addition of coal decreased the temperature and time required, which not only cut the energy consumption, but also reduced the operation difficulty. This study provided more theoretical and technical support for the application of sulfation and decomposition process.