Recycling Use Of Dust And Chromium Containing Sludge From Stainless Steel-maker

With the development of stainless industry, the output of waste residue and sludge increased steadily. Up to know, the common measure to deal with these substances is to dispose as landfill. Because of the higher content of Cr³⁺and Cr⁶⁺, which is toxic to humanbeing health, especially Cr⁶⁺, a deadly toxic one, and valuable metal such as Ni in these substances, so the treatment and recycling use is causing more and more attention. The relevant research will have great theoretic and practical significance. The method of reducing at high temperature is used to recycle the valuable elements in scale, dust and chromium containing sludge from stainless steel-maker. The essential technological process is to mix scale, dust, sludge containing chromium and coke at appropriate ratio and makes the mixed material agglomerated by pressing, then smelt the agglomerate in submerged arc furnace. It is the anticipant aim that the Cr⁶⁺ is eliminated and the alloy elements which are chromium, nickel and manganese etc. are recoveried. In correspondance of this consideration, the following works were carried out:(1) Dust and chromium containing sludge were investigated and analyzed. The element of scale, dust, chromium containing sludge and coke which is reducer, size distribution of dust and scale and water content of dust and chromium containing sludge were meansured.(2) The compressive strength of the briquets of dust and scale were measured and analyzed with different water and powdered coke contents. The appropriate process parameters were selected. It was found that to reach the good compressive strength, the appropriate water content in briquetting is 12% for dust; when the content of scale is decreased, the compressive strength of scale and dust is largened; the appropriate powdered coke content is 12% in dust, and the appropriate water content is 14% correspondingly.(3) Material and heat equilibrium were calculated base on the parameters submerged arc furnace. The appropriate technological parameters of smelting were ascertained and the quantificational data was offered for improving economic indicator of smelting. The academic content of coke is 12%, when the ration of scale, dust and chromium containing sludge is 1:9:10. The content of silica is 10%, when the basicity is 1.5.(4) The mixed material was smelted with the 19% and 23% content of coke. The element was measured and the metallurgical structure was analyzed. The influencing factors of metal recovery, which are the condition of thermodynamics, the content of reducer, property of furnace slag and the condition of dynamics, were analyzed. Furthermore, the influencing factors of sulfur content were discussed. The condition of reducing the metal oxide adequately was selected.The advice of furthermore study on the idea of recycling use of dust and chromium containing sludge were put forward based on the experimental study. Some problems in the process of experimental study were analyzed, and the resolving methods which can offer definite reference for the future study were put forward.