| China is the world’s top producer of steel, and a large amount of steel slag was emissions every year. And for a long time, due to the low utilization, the domestic steel slag has deposited more than100million tons, and still thousands of tons volume increment per year. A large slag heaped into a slag heap, not only takes a lot of land, but also China’s major industrial solid waste which creates a source of atmospheric pollution. In addition, the steel production process also emited large quantities of carbon dioxide. Therefore, the use of calcium and magnesium component of the salg carbonated with carbon dioxide to produce a stable carbonate product, can not only large-scale fixe CO2, but also can make the physical and chemical changes of steel slag. Then the comprehensive utilization of slag resources can be achieved, which is of great significance of environmental protection causes and recycling economy. In view of the above situation, CO2sequestration and resource utilization of the slag was studied based on carbonation technology. Dilute alkali medium system enhanced steel slag direct CO2sequestration, leaching behavior of steel slag in multiphase composite medium system of indirect CO2sequestration, and preparation of new building materials using the two kinds of steel slag produced during the carbonated processes, were systematically investigated. Specifically as follows:(1) As a new process, dilute alkali medium carbonation system to enhanced steel slag direct CO2sequestration has been studied, and the process conditions and mechanism were discussed in depth. The results show that:under the optimal conditions that reaction temperature of80℃, alkial to slag ratio of4%, liquid to solid ratio of2:1, stirring speed of450rpm, and reaction time of2h,16.67g CO2can be fixed in100g slag, more than50%improvement over the aqueous system. It was found that calcium silicate is the main activity group of steel slag direct CO2sequestration process, while calcium ferrite was difficult in occuring carbonation reaction.(2) Around the new technology that multiphase composite system enhancing steel slag indirect CO2sequestration generated high added value carbonate products, leaching behavior of the major elements and the kinetics of the slag selective leaching reaction were studied in the cycling process of multiphase composite media. The results show that calcium acetate content in the multiphase composite reaction medium has large effect on the leaching behavior of magnesium, manganese, and has little effect on calcium, aluminum, iron, silicon, toxic heavy metal elements such as vanadium, chromium were almost no leaching during the process. Reaction dynamics model of multi-phase composite medium selective leaching slag was built. The results showed that the slag selective leaching process controlled by the chemical reaction and the apparent activation energy were27.53-40.04kJ/mol correspond to the different initial concentrations of calcium acetate.(3) Explore the possibility of using both direct carbonation slag and leach residue of indirect CO2sequestration into sound-absorbing materials prepared. The results showed that thickness, cement ratio, preparation pressure and particle size of the steel slag were the influence factors on product performance of sound-absorbing materials. Sound-absorbing materials with good absorption properties and compressive properties can be prepared by using direct carbonation slag replaced part of cement. |
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