The Study On Engineering Application Of Chromium Slag Wet Detoxification

With the rapid development of economic and social, the industrialization process accelerate human activity intensifies and the expansion of city, which bring about serious environmental problems. Especially, the soil heavy metal pollution problem has got more and more the attention. Hunan is known as the hometown of nonferrous metal and has the heavy historical burden of heavy metal pollution for a long time."The Embodiment of heavy metal pollution governance in Xiangjiang river" authorized by the state council on March2011makes the river basin become the first national demonstration area of heavy metal pollution governance. For a long time, considerable chromium slag were discarded and stacked disorderly in the important water source and densely populated areas creating heavy metal pollution of the surrounding soil and groundwater due to the hexavalent chromium movement, thus threatening seriously environment safety and human health. Therefore, the study on harmless treatment technology of chrome slag and its pollution soil has become a priority for protection of groundwater resources and human health. Aim to the discarded chromium residue by history in hengyang city, the batch experiments about program comparison and engineering application investigation, which determined the final treatment process of wet detoxication-safety landfill. The main conclusions are as follows:â… .The comparison, selection and argumentation of the detoxification program in Laboratory1) Compare of the dry method such as chromic slag as cement mineralizer, used as a substitute for dolomite in sintering and ironmaking production, cyclone furnace, as coloring agent for glass with the wet detoxification technology for roughing. Taking full account of the current situation of chromic slag, the governance effect, the stability after management, the operating conditions, the features, the technical maturity, the economic cost and the applicability of this subject, the preselected project is wet detoxification treatment process.2) Design the following experiments to set out further governance programmes scientificly. The direct cement solidification test of chromic slag, the chromic slag alkaline detoxification test, the chromic slag acid detoxification test, chromium acid, the cement solidification test after the slag is detoxified by acid method. It chooses chromic slag acid method to detoxification based on the economic cost and the features of the slag according to the test results. Besides, the best detoxification condition according to the test is that the addition of sulfuric acid is0.02ml/g, the granularity is100mesh, the ratio of solid to liquid is1:3, the leaching time is2h, the ferrous sulfate accounts for10%of the slag amount.II. Main conclusions of engineering applications1) The final technological processes of this project:enter jaw crusherâ†'wet grindâ†'chute feedâ†'stirring reaction in contact tankâ†'↗the filtrate to recycle pressure filtration↘the filter cake to safe landfill site2) The main affecting factors of this project:the granularity of chromium slag, the injection rate of concentrated sulfuric acid, the addition of reducing agent, the response time of stirring, and the order and the of the articulation time of each step in practical engineering operation. the main technical parameters determined by the process trail run:particle size-100meshâ†'feed0.5hâ†'stirring0.5hâ†'adding sulfuric acid to adjust pH from5.0to5.5â†'stirring0.5hâ†'adding ferrous sulfate of which is10%of the quantity of the slagâ†'stirring reaction1h3) The laboratory inspects itself a total of850samples from the production commissioning until the end of the project. The qualified rate percent of pass is98.7%including11samples of hexavalent chromium unqualified.850samples of the total chromium are tested. The qualified rate percent of pass is100%, and the qualified rate percent of pass of PH and moisture content is100%.The monitoring results of Hengyang environmental monitoring station, the third-party monitoring agency is that a total of515samples. The qualified rate percent of pass is94.8%with which contains seven samples of hexavalent chromium that is unqualified. The qualified rate of the total chromium, pH, and moisture content is100%. Monitoring results show that, each indicator of the chromic slag meets the requirements of non hazardous industrial solid waste landfill after wet detoxification. The engineering project has been accepted smoothly by Hunan Provincial Environmental Department in January2013.