Experimental Study On Sintering Of Sludgeceramsite By Avoiding Drying Andnon-preheating Process

With the development of social economy,China’s annual sludge output has grown rapidly.The composition of sludge in China is relatively complex,which contains a large number of germs,heavy metals and organic matter.Improper treatment will cause harm to the environment and human health.At present,sludge is mainly treated by sanitary landfill,land use,incineration and other ways,but these treatment methods cannot fundamentally solve the harm of sludge to the natural environment as well as human and animal health.It is the topical issue to use sludge as the raw material for sintering sludge ceramsite at present.In the process of sintering sludge ceramsite,bacteria and organic matters in the sludge are completely killed in the high temperature,and heavy metal substances will be consolidated in the ceramsite,realizing harmless and resource-based treatment of sludge,and achieving certain economic benefits.Adopting the method of sintering sludge ceramsite to solve the sludge treatment also has shortcomings.This method is cumbersome and energy-intensive,when drying sludge,it will produce pungent smell,which will seriously affect the air Quality around the factory.These disadvantages restrict the further development and application of this sludge treatment method.According to the shortcomings of sludge ceramsite preparation at present,the following work would be done.（1）In this experiment,sludge and clay were used as test raw materials and the chemical composition of the raw materials was analyzed by XRF to determine the ratio range of testing raw materials.This test was optimized based on the disadvantages and deficiencies of the traditional roasting sludge ceramsite process,a new technology was put forward,which avoids drying and does not preheat the fired sludge ceramsite.（Hereinafter referred to as the new process）The sludge content commonly used in the actual production of sludge ceramsite was adopted,and the sludge ceramsite was sintered by using the new process and the traditional process respectively.It is found that the water absorption rate and compressive strength of the sludge ceramsite sintered by the new process are basically the same as that of the traditional process,and the accumulation density of the sludge ceramsite of the new process is lower,which proves that the new process is feasible to sinter sludge ceramsite,and can achieve the purpose of saving production cost and reducing production energy consumption.（2）Product density is the measurement index.The influence of various factors on the performance of sludge ceramsite was analyzed by single factor test and orthogonal test.Give the result as follows:With the increase of smoisture content of dehydrated sludge,the water absorption rate of sludge ceramsite increased first and then decreased,the accumulation density of sludge ceramsite decreased,and the single compressive strength of sludge ceramsite is independent of the moisture content of dehydrated sludge.With the increase of sintering temperature,the water absorption rate of sludge ceramsite increased first and then decreased,the accumulation density of sludge ceramsite decreased,and the single compressive strength of sludge ceramsite also decreased.With the increase of the incubation time of sludge ceramsite,the water absorption rate of sludge ceramsite decreased,the accumulation density of sludge ceramsite decreased,and the compressive strength of sludge ceramsite decreased.With the increase of the dehydration sludge content,the water absorption rate of sludge ceramsite decreased,the accumulation density of sludge ceramsite increased,and the compressive strength of sludge ceramsite increased.Through the orthogonal test,it can be concluded that for the accumulation density of sludge ceramsite,the influence of three horizontal factors is from large to small:the incubation temperature,incubation time and the content of dehydrated sludge.The optimal process is:sludge content of 30%,incubation temperature of 1200℃,incubation time of 15min,its accumulation density of 244Kg·m^-3.For the water absorption rate of sludge and sludge ceramsite,the influence of three horizontal factors ranged from large to small:the incubation time,incubation temperature and the content of dehydrated sludge.The optimal process for the maximum water absorption rate is:sludge content 40%,calcination temperature 1150℃,calcination time 10min,the water absorption rate is 15.62%,the optimal process for the minimum water absorption rate is:sludge content 50%,calcination temperature 1200℃,calcination time 15min,the water absorption rate is 4.88%.For the single compressive strength of sludge ceramsite,the influence of three horizontal factors ranged from large to small:firing temperature,firing time and dehydration sludge content.The optimal calcination process is:the sludge content is 50%,the calcination temperature is 1150℃,the calcination time is5min,the single compressive strength is 1.47MPa.（3）Through XRD and SEM scanning,it can be found that the mineral composition of sludge ceramsite sintered by the new process is basically the same as that of the traditional process.The mineral composition of sludge ceramsite was less affected by the new process,the preheating and the traditional process.After drying treatment of sludge,the particle size inside the raw pellets of sludge ceramsite was more uniform.The pre-heating process would make the sludge ceramsite embryo body more compact,compared with the sludge ceramsite sintered by the new process,the internal pores of sludge ceramsite produced by the traditional process is less than 5μm,while the pore pore size of the sludge ceramsite produced by the new process is close to that of the sludge ceramsite produced by the new process,with the pore size of most pores ranging from 10μm to 20μm.（4）Taking Chong Qing Hechuan sludge ceramsite as an example,the annual output of sludge ceramsite is 180,000 tons.Compared with the traditional process to sinter sludge ceramsite,the new process can save the energy of drying and crushing sludge and clay,and effectively reduce the production cost of sludge ceramsite.According to the calculation,the factory can save 547,840 yuan a year by adopting the new process to sinter sludge ceramsite,recover the factory construction cost and production and operation cost 0.6 years in advance,and improve the production efficiency of sludge ceramsite,which can achieve good economic benefits.To sum up,sludge and clay were used as raw materials to sinter sludge ceramsite in this research,putting forward a new sludge ceramsite burning process,verifying the feasibility of the new technology,the technology can guarantee the performance of sludge ceramsite and at the same time,save energy,reduce cost,improve production efficiency.In order to provide some reference value for the actual production of sludge ceramsite in the future.