Technological Research On High-temperature Firing Of Ceramsite From River Sediment

In cities and towns with developed river networks,the discharge of river sediment and urban sludge will inevitably increase with the development of the city.In order to solve the solid wastes such as river sediment brought by the"a total treatment of Five Water"policy,based on the analysis of the material composition of the river sediment and related representative urban sludge,and follow principles of harmlessness,reduction,and recycling,research was carried out on the preparation of ceramsite light aggregates with river sediment and urban sludge as the main materials.In this paper,based on the analysis of the material characteristics of river sediment,waste mud and sewage sludge,laboratory experiments on the high-temperature firing of ceramsite from river sediment and various types of urban sludge are carried out.And cooperated with Huzhou Dadongwu New Material Ceramsite Manufacturing Company of Zhejiang Province about pilot test of the production line,through the pilot test to determine the best producted conditions for the firing of ceramsite light aggregates.Material property research showed that the content of the river channel sediment and waste mud are similar in composition of clay content.The silicon aluminum oxide content of sewage sludge is low but the organic content is more than 5 times of the first two materials.Adding a small amount of clay as a binder can reach the composition requirements of ceramsite firing.Through the measurement of the plasticity index of all raw materials and mixtures,it is founded that the weighted average model can be used to roughly estimate the plasticity index of the mixture.After comparing the model calculation and actual measurement results,it can be determined that the river sediment and various urban sludges used in this research satisfied the plasticity requirements of ceramsite granulation.Through TG analysis of various raw materials,the preheating temperature range was 300～350℃,the high temperature swell temperature range was 1150～1200℃,and the heating rate range was 20℃/min～40℃/min.In the laboratory pilot study,the material mixing range was initially determined through the mixture trial burning experiment:the river sediment plus waste mud:clay:sewage sludge=(40%～60%):(20%～30%):(20%～30%).The river sediment and various types of urban sludge were mixed and shaped according to the prescribed ratio and placed in a high-temperature rotary reactor to carry out orthogonal and single-factor experiments,focusing on the calcination(swelling)temperature,material ratio,insulation(swelling)influence of factors such as time,heating rate and gas flow into the reactor on the main performance indicators(apparent density,water absorption rate and compressive strength)of ceramsite light aggregate,the suitable craft conditions for the laboratory test of ceramsite firing from the river sediment are:calcination(expansion)temperature 1175℃,heat preservation(expansion)time 20minutes,heating rate 35℃/min,gas flow rate 60ml/min,the material ratio was river sediment:clay:waste mud:sewage sludge=47:17:16:20.During the pilot test,the detailed craft and equipment parameters of the large-scale collection and dewatering of river sediment,the various process links and related equipment parameters of the production line of ceramsite were summarized.The raw materials used in the pilot test were different from the laboratory tests,mainly discussing the craft conditions for firing ceramsite using raw materials such as river sediment,printing and dyeing sludge,and mulberry field humus.From the research results,we can see that the best production line firing temperature was about1200℃.The best material ratio was river sediment:printing and dyeing sludge:mulberry field humus was 40:47:13.The best performance of ceramsite obtained by firing is loose bulk density(bulk density)was only 316.33kg/m~3,the compressive strength was 1.3MPa and the other indexes satisfied the industry specifications.The large-scale production of ceramsite made from the river sediment has made the enterprise save nearly half of its production cost;it is conducive to the promotion and use of clean energy and the efficient use of energy;it’s also provides indirect protection for land resources such as cultivated land.A series of research results showed that it’s not only feasible to burn ceramsite using river sediment and urban sludge,but also produces benign benefits in many aspects such as economy,ecology,and society,it was worth developing and promoting.