Utilization of stainless steel pickling sludge using the blast furnace molten slag
Stainless steel pickling sludge is a by-product of pickling and passivation of stainless steel in the produc-tion process of stainless steel,which is a hazardous waste.The paper proposes a technology of using blast furnace molten slag to treat stainless steel pickling sludge,which is expected to realize the resource utilization of stainless steel pickling sludge.The melting point temperature of pickling sludge added to blast furnace slag with different pro-portions was determined by hemispherical method,and the reasons for the change of melting point temperature were analyzed by drawing phase diagram with FactSage,and the mortar blocks were carried out by the ground granulated blast furnace slag(GGBS)mixed with 425 Portland cement.The results showed that,the melting temperature of molten slag increases with increasing sludge ratio.With the increase of the ratio of stainless steel pickling sludge,the CaO content of the slag decreases and the melting point temperature increases.Inorganic salts such as CaSO4 in stainless steel pickling sludge play an inorganic grinding role in GGBS.When the proportion of stainless steel pick-ling sludge is increased from 0 to 5%,the specific surface area of GGBS increased from 379.70 m2/kg to 415.28 m2/kg,the 7 d activity index of mortar blocks increased from 79.45%to 89.94%,and the 28 d activity index increased from 94.64%to 99.96%,and all of them met the requirements of S95 GGBS.Finally,the industrial application of blast furnace slag treatment of stainless steel pickling sludge was preliminarily designed based on the blast furnace with vol-ume of 1 680 m3.According to the heat balance calculation,the excess heat of blast furnace slag can treat 11.28%of stainless steel pickling sludge under the conditions of considering heat loss and ensuring that no crusting occurs in blast furnace slag,which provides a technical guidance for the application of stainless steel pickling sludge.
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