Process for reprocessing slags from metallurgical processes with recovery of soda

摘要

The invention relates to a process for reprocessing slags from metallurgical processes with recovery of soda (sodium carbonate). In processes customary hitherto, the soda-containing slag from a pig iron desulphurisation and/or dephosphorisation is leached at relatively low pH values with simultaneous addition of carbon dioxide or treated under increased pressure (superatmospheric pressure). Sodium hydrogen carbonate is largely formed here, and only slags formed in soda desulphurisation can be used. In contrast, according to the process of the invention other slags from metallurgical processes, in particular including calcium carbide slags and/or magnesium slags can also be used. The slags are leached with hot water at from 80 to 100@C and pH values between 12 and 13.5. Subsequently, precipitation with carbon dioxide is carried out in the presence of one or more additives, with the additives very largely preventing adsorption or deposition of sodium on the precipitation products. Hydrogen sulphide formed is processed to give sulphur or sulphuric acid, and soda is recovered from the soda solution of the precipitation stage.