Study On Leaching Of Sodium Aluminate From Clinker Of High-alumina Fly Ash Low Calcium Soda Lime

At present,China's bauxite resources are increasingly exhausted,as a potential aluminum resource,the development and utilization of high-alumina fly ash can not only solve the negative problems caused by large amount of fly ash storage,but also alleviate the contradiction between supply and demand of bauxite resources shortage.Alumina clinker is an intermediate product of high-alumina fly ash sintering process to produce alumina,and is a raw material for studying the leaching of sodium aluminate.The leaching of sodium aluminate in clinker is a crucial link in the technological process of extracting alumina from high-alumina fly ash.In this paper,alumina clinker sintered by high-alumina fly ash and low calcium soda lime is used as raw material,and the standard leaching conditions of bauxite are used as reference to explore the suitable leaching conditions of sodium aluminate in alumina clinker.The optimal leaching parameters of sodium aluminate in clinker are determined through single factor test and orthogonal test,which provides the basis for industrial production.On this basis,the sodium-calcium-silicon slag is preliminarily treated with dealkalization to obtain calcium silicate hydrate.The specific research contents are as follows:(1)Exploration of leaching conditions of sodium aluminate in alumina clinker.The effects of leaching temperature,leaching time,liquid-solid ratio and alkali liquor concentration on the leaching rate of sodium aluminate were studied experimentally.Through the combination of single factor test and orthogonal test,it is found that the leaching temperature has the most significant effect on the leaching rate of sodiumaluminate,followed by leaching time.The leaching rate of sodium aluminate does not change with the change of alkali concentration within the alkali concentration range explored in the test,which shows that the leaching of sodium aluminate is a solid phase dissolution process and does not react with alkali.Finally,through the verification of the optimal combination of orthogonal tests,the optimal technological parameters of sodium aluminate leaching are obtained as follows: leaching temperature T=65?,leaching time t=7 min,liquid-solid ratio L/S=5 mL/g,alkali liquor concentration C=0.Under these conditions,the leaching rate of sodium aluminate can reach above 94%.(2)Dealkalization treatment of sodium-calcium-silicon slag.According to the exploration of sodium aluminate leaching test,when the liquid-solid ratio L/S=5 mL/g,the liquid phase and solid phase can be fully dispersed and have good fluidity.Therefore,the dealkalization test does not explore the liquid-solid ratio any more,but only studies the influence of temperature and time on the dealkalization of sodium-calcium-silicon slag.The test results show that when the temperature is 175?and the dealkalization is 150 min,the alkali content in sodium-calcium-silicon slag is reduced from 24.75% to about 1.80%,and the dealkalization effect is very obvious.The microscopic particles of dealkalization products are like silkworm chrysalis,and the interior of the particles are intricately interconnected by irregular needle-like tobermorite monomers.This structure makes the inside of the alkaline residue have larger pores,resulting in small bulk density and large specific surface area of the alkaline residue.