Optimization And Evaluation On Lightweight Aggregate Produced By Sewage Sludge/Fly Ash/Coal Gangue

As the typical MSW,sewage sludge,coal sludge and fly ash,which have always been the focus of attention.Therefore,the sludge,coal gangue and fly ash are mixed in different ratio to synergistically prepare artificial lightweight aggregates.This way not only achieves the objective of resource-reducing,harmless,and reducing the sludge,but also solves the problem of coal gangue and fly ash land occupation problem and realize the utilization of the MSW.In this paper,sludge,coal gangue and fly ash are raw materials.Firstly,TG-DSC analysis is tested on these three raw materials to determine the suitable temperature range for sintering and the possible temperature range for producting gas.The result is around 1200°C.Then,the three raw materials were made into 16 groups according to different blending ratios.Thermodynamic simulations were performed on each group of samples to analyze the crystal components in the sintered body,and the XRD analysis of the sintered body was performed to verify the simulation results.In addition,16 groups of samples were tested for mechanical properties and environmental safety to determine their actual performance.The results of thermodynamic simulation are basically consistent with the results of XRD analysis of the sintered body.It is shown that when the amount of sludge mixed is higher than 50%,more than 40%of mullite is produced at a high temperature(1250°C).The sample with high sludge content has better mechanical properties and better water resistance,according to the later experiment.This also confirms the stability of mullite and the hydrophobicity of the ceramic surface.In the sintering experiment,the mixing ratio and sintering temperature of the three materials were different.And then,the sintered body were tested for mechanical properties,water absorption,and heavy metal leaching characteristics.The results show that at the sintering temperature on 1200°C,and the sludge content is 60%,the density of the sintered body is 383.99kg/m~3;the compressive strength is 4~6MPa;the water absorption is below 3%;the specific surface area is around 20m~2/gFinally,the concept of OPTI was introduced which was used to evaluate the environmental pollution of the sintered body.It was result that the OPTI value of the sintered body is less than 350,which satisfies the OPTI tested by TCLP method:1512.24.