| In this paper, a solidification/stabilization method, which can safely dispose sludge in a short term, was used to treat the sludge from Beijing Tanzhou Sewage Treatment Plant. Meanwhile, sludge ceramists were made by using the sludge as the main raw material, which opened a new way of sludge utilization based on the reduction and harmlessness.A kind of curing agent(MC4), purchased from Anhui, was used to solidify dewatering sludge in this study. The results showed that the moisture content in cured block reduced dramatically with the lengthening curing period and the increasing addition of curing agent. The lowest moisture content was less than 50% after 7 days curing. pH value of the cured blocks were generally increased and stabilized at 11.The pH Could be significantly reduced when aluminum sulfate was added.Results showed aluminum sulfate had little effect on the sludge dewatering properties. The curing effect could effectively reduce the content of organic matter in sludge. However, the low heat value of cured block was still higher than2500 kJ/kg and it could be used as a fuel. The compressive strength of block could reach395.8 kPa after 7 days curing,and it could meet the construction standards(GB/T 23485-2009). The surface characteristics of the cured bloc were observed through scanning electron microscopy(SEM). Results of SEM indicated that the addition of the curing agent can enhance the compactness of curing block granules, which could improve the mechanical properties of the cured block and prevent the heavy metals from leaching.In this self curing study to self-made curing agent, Cement and MgO were selected as the main skeleton of solidified sludge. And bentonite, triethanolamine and aluminum sulfate were used as additives. The results showed that cement and MgO could increase the expansion rate and mechanical strength. When cement was added,the unconfined compressive strength wasn’t improved greatly, while the expansion rate was increased notably. In contrast, when MgO was added, the unconfined compressive strength of cured block was significantly improved and the expansion rate was kept below 1.5, which was much lower than that of the cement. When the cement and MgO were added together, their synergistic effectcould greatly reduce the amount of cement, effectively improving themechanical strength of cured body and reducing the covers area of curing place, therefore, the cost of sludge treatment and disposalwas decreased.raw sludge, clay, slag and glass powder were chose as the main raw material to make sintered ceramist.Result showed the optimal proportioning for sintered ceramist were 35% of sludge, 30% of clay, 25% of slag and 10% of glass powder. The optimum operating conditions parameters the preheating temperature was 450 ℃,warm-up time was 15 min, the firing temperature was 1125 ℃ and the firing time was30 min were determinedfor the preparation of ceramist for the preparation of ceramist.The characteristics of obtained ceramist were as follows: the compressive strength was 4.2 MPa, the 1hour water absorption was 14.4%, the apparent density was 1.46g/cm3 and packing density was 0.39 g/cm3. By investigating the impacts of process the parameters and the quanlity of mixed sludge on sludge ceramsite performance, the mechanism of burning ceramsiteceramist with organic in sludge was revealed.SEM analysis of ceramsite surface morphology and the internal pore structure showed that:if the sintering temperature was too high, the ceramsite surface of the ceramist would have too many pores which were communicated with each other. As a result of,these communicated pores lead to the ceramist would have a loosen structure and a higher water absorption rate. If the addition of the sludge was inceased, the surfaces of the ceramist would have less porosity and could not form the glass phase wrapping the surface of the ceramsit.As a result, the ceramsite would have a of higher water absorption rate and lower compressive strength. |
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