Basic Study On Activation Separation And Resource Utilization Of Al-Si Components In Coal Gasification Residue

Coal gasification,as a kind of coal conversion technology,has been developed rapidly.This process will produce a large number of coal gasification slag,and the potential environmental harm will be great.There are abundant Al-Si-C resources in coal gasification slag.The large-scale utilization of it can effectively solve the problem of environmental pollution and reduce the exploitation of primary mineral.In this paper,a systematic analysis of the Erdos coal gasification fine slag including that mineral phase structure,element distribution and characteristics of gasification slag was carried out.The characteristics of gasification slag phase,the distribution of element and the reactivity of ash slag were clarified.The technical idea of producing polyaluminum chloride and high modulus sodium silicate solution by cyclic acid activation and dilute alkali desilication was put forward,and the optimization of this process was carried out.The mechanism of activation and desilication of gasification slag was further clarified by 29Si solid state NMR and particle pore structure analysis.The main conclusions are as follows:(1)The analysis of the original slag from Erdos was carried out,and it's physical and chemical characteristics have been clarified.Results show that the main component is A1 and Si with its concentration up to 45%and the content of C could reach to 30%.Amorphous aluminosilicate is the main mineral phase while some quartz and cal cite exist in the slag.The particle size is mainly between 10?m and 100?m.The morphology of the particles is mainly amorphous carbon and irregular inorganic particles.The element of Al,Si and impurity elements are uniformly distributed on the surface of inorganic particles,some elements enriched in the slag.(2)The optimization of cyclic acid leaching process for the preparation of polyaluminum chloride was carried out and the optimal process conditions were clarified.Further study on activation mechanism was carried out.It is clear that the leaching of aluminum and other impurity ions cause the openning of the particle pores,The structure of the particles is changed greatly with specific surface area of 279.52 m2/g,and the specific surface area of micropores and mesoporoUs particles is 44.44 m2/g and 235.07 m2/g,respectively.The Al-Si coordination structure of the original particles changes from Q4(2Al)to Q4(1Al).When Al and the impurity elements Fe and Ca enter into the liquid phase,the chemical bonds that Si-O-Al and Si-O-Ca on the surface of the particles are transformed into more reactive bond that Si-O-H.Based on the characteristics of high alumina content and low basicity in high aluminate solution,the process of preparing polyaluminum chloride was put forward and optimized.The polyaluminum chloride product with aluminum content more than 10%and basicity exceeding 30%can be prepared.(3)According to the high reactivity of acid activation slag,a dilute alkali desilication process of acid activation slag was put forward and optimized.Sodium silicate solution with a modulus of 3.5 can be prepared.Compared with the direct desilication without acid activation,the desilication ratio of activated slag was improved to 56.3%.Desilication slag contains a large number of zeolite with excellent morphology.The specific surface area is 323.43 m2/g,The specific surface area of micropores and mesoporous particles are 45.48 m2/g and 289.04 m2/g,respectively.(4)The morphology and species of the particles were investigated.The carbon content over 75?m was higher.The large size and the irregular carbon particles were main particle in it.The carbon content under 75?m was lower,and the morphology of the particles was complicated.The utilization of residual carbon was put forward.High carbon slag can be used for circulating combustion.Further research on the preparation of foamed ceramics was carried out.The effects of different raw materials,calcination temperature and calcination time on the properties of foamed ceramics were studied.Based on the optimization of the whole process,the material balance estimation of the process is carried out.