Preparation Of Fuel Particle And Resource Utilization Of Brick With Depth Dewatered Sludge

“Circular on strengthening prevention of the urban sewage treatment plantsludge pollution”was issued in November2012by National EnvironmentalProtection Ministry in China. The circular clearly requires moisture content ofurban wastewater sludge <50%. Domestic sewage treatment plants upgraded theplate and frame filter press technology for sludge dewatering, which generated alarge number of depth dewatered sludge. But there are rarely researches on depthdewatered sludge utilization technology.In this paper, depth dewatered sludge utilization technology was carried out bya series of studies. Fired brick, water permeable brick, fuel particle were preparedwith depth dewatered sludge. Besides, fuel particle insulating brick was preparedwith fuel particle. Compressive strength, insulation performance, leaching ofheavy metals of brick was characterized. The results were as followed:With the increasing dosage of the depth dewatered sludge, LOI (weight losson ignition), water absorption, porosity of the depth dewatered sludge bricksincreased, but the compressive strength decreased. The most optimized dosage ofthe depth dewatered sludge was20%, at this time, LOI, porosity, compressivestrength was5%,40%,33MPa respectively. Heavy metals leaching test resultsindicated that nine heavy metals in the depth dewatered sludge brick reached“Identification standards for hazardous waste-Identification for extractiontoxicity”(GB5085.3-2007) standard.Dewatered sludge fuel particles were prepared. When the sludge dosageincreased from0%to100%, calorific value of the fuel particles increased from902kJ/kg to4514kJ/kg. The fuel particles could achieve complete combustion at1000℃.Fuel particle insulating brick was prepared with fuel particle. LOI, waterabsorption, porosity of this brick increased with the supplementation of sludge infuel particle, nevertheless, compressive strength decreased. When the dosage of sludge was50%, LOI, water absorption, porosity of fuel particle insulating brickcould reach "Fired common brick"(GB5101-2003) standard. The thermalconductivity was≤1.5W/(m2·K), could reach the standard of “Designstandard for energy efficiency of residential buildings in hot summer and coldwinter area”(JGJ134-2010), revealed excellent insulating performance. Thefreeze-thaw cycle results indicated that mass loss rate of the brick was0.55%,compressive strength loss rate was14.21%after25freeze-thaw cycles. TCLPresults indicated that heavy metals in the brick reached “Identification standardsfor hazardous waste-Identification for extraction toxicity”(GB5085.3-2007)standard.Urea and Gravel was used as pore-forming agent for preparation of waterpermeable brick, Gravel revealed a better pore-forming properties. When thedosage of Gravel≤20%, compressive strength and coefficient of permeability ofthe brick could reached "Water permeable brick"(JC/T945-2005) standard.Freeze-thaw cycle results indicated that compresssive strength loss rate of Gravelpermeable brick≤20%. Heavy metals leaching test results indicated the brickreached “Identification standards for hazardous waste-Identification for extractiontoxicity”(GB5085.3-2007) standard.Through economic and technical assessment and emission reductionaccounting，the production of1million dewatered sludge brick and fuel particlesbrick could achieve economic effect of76,000RMB, and reduce SO2emission2.203tones and3.126tones respectively, effectively achieve depth dewateredsludge resource utilization.