Technology Of Non-burned Brick Using Msw Gasification Slag And Ecological Risk Evaluation

As the speeding pace of urbanization, the problem of Municiple Solid Waste(MSW) disposal is urgent. The treatment is also growing, which combains the traditional way with a new way to disposing. As a result of reduction affect remarkable(about 90% volume), the gasification treatment technology is as one of main treatment in the future. However, there are still 15%-25% mass of inorganic slag need to disposal in the landfill. The inorganic gasification slag which belongs to the category of general solid waste can be directly for recycling use. The research purpose of this test is that adopting MSW gasification slag used in preparation of non-burned bricks which can reduce the consumption of mineral materials in cement-based materials in the one hand and solve the bottleneck of all the recycling problem in MSW on the other hand. It is beneficial to realize in the true sense of spam "zero landfill".The MSW RDF(refuse derived fuel) in Beijing was physical and chemical researched and analysed, the result is as followed. The MSW gasification slag is composed of inorganic slag, residual carbon, muck, glass, ceramics, bricks and stones. The particle size range is mainly concentrated in the 0.16 to 2.5 mm. Its density and moisture are 2g/cm3 and 17%. The mineral compositions of this are mainly of the alpha quartz, calcite and labradorite. Chemical compositions of this are mainly SiO2, CaO, Al2O3 and Fe2O3; there contain a small amount of MgO, K2 O and Na2 O, etc. The MSW gasification slag is a non-radioactive material, which belongs to the potential activity of residual waste containing active silica and alumina, needing to be motivated. Using chromatography analysis method determines the MSW gasification slag disposal ideal way which is preparating non-burned brick in the building materials.By researching the MSW gasification slag non-burned bricks, it was analysed the effect which are dosage of raw materials, molding pressure, moisture content, curing process, the time. At the same time, the microscopic informations were analysed by the detection methods such as XRD, SEM and EDS. The research results showed that:(1) The optimum proportion of using MSW gasification slag in Beijing to prepare non-burned bricks is carbide slag: fly ash: cement: gasification slag =10:10:10:70; through the grey correlation analysis, it is concluded that the same result in complete accord with experimental results.(2) The optimum experiment technology is that molding pressure is 20 MPa,molding moisture is 12%, curing period is 28 days in curing box, ambient temperature 19 to 21℃, the relative humidity is 90%.(3) The performance of product meets the standard of JC/T422-2007 MU20.(4) In the process of preparation, the MSW gasification slag content can reach 70%.(5) Various kinds of gel material are intertwined, filling, forming dense three-dimensional network structure.The heavy metals in non-burnt bricks made from MSW(municipal solid waste) gasification slags with a modified BCR(European Community Bureau of Reference) procedure were studied. It was found that heavy metals were present in the form of oxidizable and residual fractions. The heavy metal of Cd is about 67.00% of total fraction existed as oxidize and residual, the rest of heavy metals account for more than 92.51%, which were stable and not easy to dissolve. The preparation process of non-burnt bricks had prominent solidification effect for some heavy metals in the gasification slag. The solidified rate for metals such as As, Cd, Cr, Ni and Zn would reach 89.82%, 79.57%, 73.64%, 66.73% and 88.05%, respectively. On the basis of these observations, the risk of heavy metals in the non-burnt bricks were evaluated using the solidification formula and the leaching concentration of heavy metals combined with the assessments of the Hakanson potential ecological risk and pollution of RSP(ratio of minor phase and progenetic phase). Analysis results showed that the preparation of MSW gasification slag non-burnt bricks was not harmful to the environment, but attention should be paid to the possible migration of heavy metal Cd in the long term, which could result in an indirect impact on the ecological environment.