Study Of Chromium Recycling From Stainless Steel Sludge To Product Chromium Trioxide

Up to know, the common measure to deal with these residues produced in stainless industry is to dispose as landfill. Because of the higher content of Cr3+ and Cr6+, which is toxic to human being health, especially Cr6+, which is a deadly toxic one. So it is an important subject of relevant researchers that recovery and utilization of valuable elements in solid waste stainless steel plant resources to create considerable economic benefit and has the function of environmental protection, prevent secondary pollution. It will have great theoretic and practical significance. But up to now it has not mature efficient process flows used in industrial production of recovering chromium from this characteristic stainless steel residue in this research. Although calcium roasting has widely used in chromium ore, it is few in application of recovering chromium from stainless steel residue.It is mainly studied in this paper that extracting high-purity chromium oxide from a kind of scrap containing chromium named stainless steel residue. Through lots of exploratory tests, the final testing program:roasting-leaching-restore-precipitate-calcine. Through the whole process of the each stage, we make sure of this experiment technology conditions. At first, it is the concrete technological parameters of roasting stage:the dosage of sodium carbonate is 1.5 times of theory dosage, dolomite dosage is 10 percent, roasting temperature is 1000℃, roasting time is 60 minutes. Secondly, water leaching time is 60 minutes, leaching liquid-solid ratio is 4, leaching temperature is 80℃.Thirdly, the conditions of reduction stage is pH is from 2.5 to 3.0, restore time is 45 minutes, quality rate of Cr(Ⅵ) and Na2SO3 is 1:5.Then,the technological parameters of precipitation are pH is from 8.5 to 9.0,time is 20 minutes. Last the calcinate conditions are temperature is 1000℃and time is 2 hours. Under of these technological parameters, we obtain the final product index of the research and obtain the final chromic oxide product. Its purity is 99.631%.These conditions lay a good foundation for the project research and development.Water leaching dynamic of chromium is discussed in this study. The result indicates that this water leaching reaction belongs to diffusion resistance model.