Research On Mechanism And Technology In Sintering Sewage Sludge For Haydite

Sewage sludge is a kind of solid waste which is generated from the process of urban sewage treatment. It contains large amount of pathogens and microorganism and can cause great harm to the environment. Without suitable treatment, sludge can lead to secondary pollution easily. At present, the main sewage sludge treatment and disposal methods are landfill, land use and combustion, which are not scientific. Therefore, searching for a new way for resource utilization of sludge is particularly important. In this paper, a process of sewage sludge sintering for haydite is proposed, which is a new way for sludge resource utilization and bring about great economic benefits.First of all, chemical composition and thermal analysis are studied. Results show that inorganic component of sludge is similar to clay. However, the ignition loss is large, so auxiliary material is added. Fly ash and clay are selected as auxiliary material. Results show that ignition loss of fly ash and clay is less than 10%.The feasibility of two granulation technologies by sintering municipal sewage sludge (pressure-assisted sintering and pressureless sintering) is studied. The influences of mixture ratio, sintering temperature and sintering temperature holding time on the compression strength, water absorption and density of haydite are analyzed. At the same time the sintering mechanism of sludge haydite is analyzed. Considering performance and economy, the proper mixture ratio is 50% dry sludge, 30% fly ash and 20% clay, the sintering temperature is 1150℃,the holding time is half an hour. Under these conditions, the compressive strength of pressure-assisted sintering haydite is 27MPa, water absorption can be controlled at about 12%, packing density can be controlled at 900kg/m3, according to national standard GB/T1743.1-1998, the performance of pressure-assisted sintering haydite is qualified. water absorption of pressureless sintering haydite exceeds related standard.Heavy metals immobilization during sintering process is studied. Fixed rate of Cu,Ni,Zn is about60%-80%, fixed rate of Pb,Cd is about 20%-30%. The content of Pb and Cd in sludge is small. So the fixed rates of heavy metals in this process are relatively good.Combining sludge drying with sintering technology, the whole haydite manufacturing system is designed. This system has the features of inner loop of material and energy. This design not only minimizes sludge emissions and energy consumption, but also obtains standard haydite. From this process, both environmental and economic benefits can be brought.