| In this study,two typical hazardous wastes,namely petroleum sludge and fly ash were used as Raw materials,clay and municipal sludge were used as additive for preparing high-strength ceramsite by high temperature sintering process.According to the chemical composition and phase composition of the material,the effects of,Explore the influence of hazardous waste content and sintering processes,such as sintering temperature,sintering time on the properties of ceramsite cylinder compression strength,1 h water absorption,bulk density,loss on ignition,etc,and the corresponding mechanism was analyzed.By detecting the concentration of heavy metal leaching in raw materials and ceramsite,combined with SEM,XRD,BCR continuous leaching and other testing methods,the stable curing mechanism of heavy metals was explored.The main studies are as follows:(1)Taking oilfield sludge as the main raw material,loess,yellow sand and clay as additives,the effects of sludge content,sintering temperature and sintering time on the compressive strength,1 h water absorption,bulk density and sintering loss of ceramsite were studied by single factor experiments.With the increase of sintering temperature,the 1h water absorption and sintering loss of the ceramsite decrease,while the bulk density and cylindrical compressive strength first increase and then decrease.Finally,the optimal sludge content was 60%,the optimal sintering temperature was 1140℃,and the optimal sintering time was 20 min.Under this process,the 1 h water absorption of the ceramsite was 0.32%,the bulk density was1020.3 kg/m~3,the burning loss was 15.95%,and the cylinder compressive strength was 40.992 MPa.At that time,the content of oil sludge reached the maximum,all performance indicators meet the performance requirements of high-strength ceramsite in GB/T 17431.1-2010"Lightweight Aggregate and Its Experimental Standard".(2)Fly ash as the main raw material,municipal sludge,clay as additives to prepare high strength ceramsite,The effects of fly ash content,preheating temperature,sintering temperature and sintering time on the properties of ceramsite were investigated by single factor experiment.It could be concluded that the optimal mixing amount of waste incineration fly ash was 30%,the sintering process was preheated for 30 min at 400℃,and sintering for 20 min at 1150℃.the water absorption of the ceramsite for 1 h was 0.42%,the bulk density was 975.2 kg/m~3,the cylinder compressive strength was 31.8 MPa,and the burning loss was 18.23%.The orthogonal experiment further showed that the best properties of the ceramsite were obtained under the conditions of fly ash content of 30%,preheating temperature of380℃,sintering temperature of 1155℃and sintering time of 25 min.The cylinder compressive strength was 34.90 MPa,water absorption rate was 0.15%for 1 h,bulk density was 988.2 kg/m~3and sintering loss was 18.2%.(3)The BCR continuous extraction technology combined with SEM and XRD characterization was used to explore the stable solidification mechanism of heavy metals.The heavy metals in the ceramsite obtained by BCR continuous extraction technology mostly changed from the unstable forms of exchangeable and reducible states before sintering to the stable forms of oxidized and residual states.SEM results showed that the sintered ceramsite presents smooth and shiny molten glass phase and produces needle-like mullite structure.XRD results showed that new phases of mullite or pyroxene were produced.These results indicated that the heavy metals in the ceramsite were vitreous encased or fixed in the new crystalline phase.At the same time,heavy metal leaching concentration of the ceramsite before and after sintering was tested.It was found that the leaching concentration of all kinds of heavy metals in the ceramsite decreased after sintering at high temperature.It was further proved that heavy metals sintered at high temperature can be stably solidified inside the ceramsite. |
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