| Stainless steel pickling sludge is a toxic solid waste containing Cr6+produced from the stainless steel pickling process.This kind of sludge is usually used in manufacturing of industrial materials or curing in disposal field,which however cannot effectively use the secondary resources such as nickel and chromium in acid wash sludge.Therefore,how to realize the effective use of stainless steel pickling sludge is an urgent problem for metallurgical enterprises.Based on this,the group presents the idea of returning the stainless steel acid to the smelting process of stainless steel and recovering the metal.In this paper,based on the characteristics of high S content in stainless steel pickling sludge,with stainless steel pickling sludge return to use as a starting point,analysis the sludge of stainless steel chemical composition,microstructure,physical and chemical properties such as melting point,granularity.It is found that the acid sludge in yellow has small particle size,mainly contains about 46%of the total sulfur,calcium,iron.And nickel,chromium content is about 3.7%,the main crystalline phase in the sludge is CaF2,CaSO4,CrF2,a small amount of lime particles,as well as some amorphous metal oxide.Melting point of pickling sludge is 1205℃.According to the analysis of sludge characteristics,combined theoretical calculation results with experiment,transformation performance of sulfur and valuable metal were investigated,under the condition of different smelting stage,sludge S content and different ratio of sludge.It is found that when the acid sludge was added to the initial stage of the stainless steel smelting process,the recovery of the metal elements of Fe,Cr,Ni was better,and the recovery rate was above 98%,50%and 99%respectively.With the same amount of sludge added,the sludge with high sulfur content is more obvious.In the process of blowing oxygen,the higher the carbon content in the steel,the lower the return S rate of the sludge.Under the same amount of sludge,return S of raw sludge is high for sludge containing high sulfur.And after proper sludge desulphurization pretreatment,S content in liquid steel can be significantly reduced.The amount of pre-treated sludge is five times as large as the original sludge in the same case as the amount of the steel liquid.For example in 100t AOD furnace process,if sulfur content in liquid steel caused by sludge increased from 0.01%to 0.025%,the amount of recycled acid sludge into liquid steel can be added up to 6.5 t.This article research is helpful to realize the recovery of valuable metal of pickling sludge and rational utilization of the slag material such as calcium fluoride,calcium oxide,which make it possible that stainless steel pickling sludge return to use in the stainless steel smelting process. |
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