Study On Making Clean Fuel By Mixing Sludge And Coal

Sludge are largely produced in the sewage treatment process of municipalsewage plants. At present, the treatment and disposal of sludge is given priority tolandfill, resource utilization is low (less than20%). This way not only occupy a lotland resource, but also brings secondary pollution to environment. Therefore, how toproperly dispose the sludge or to realize resource utilization of the sludge, hasbecome one of the key technical problems which need to be resolved in the field ofenvironmental protection in China.The moisture content of sludge is higher, and after mechanical dewatering thewater is about80%. High moisture content is the key factors that restrict sludgerecycling use. This paper innovated a new way of the resource utilization of thesludge. Sludge was modified by semi-coke which was conditioner. The sludge wasdewatered by gravity concentration. Then the concentrated sludge was mixed withcoal to prepare clean fuel. It opened a new way of resource utilization of the sludge. Ithad important significance in conserving resources and protecting the environment.Therefore, for the related technical problems of using sludge and coal to prepare cleanfuel, We conducted the preliminary research work. The main contents were asfollows:(1) The lignite semi-coke’s effect on modifying and deep concentrateddewatering of sludge was explored by the method of gravity concentrated dewatering.The results showed that the dewatering property, the settling property and themechanical dewatering property of sludge had been improved greatly through addingsemi-coke into the sludge. When2g of semi-coke was added to100g of sludge, thewater content of concentrated sludge was reduced from91.13%to78.05%aftermodified treatment. What’s more, the water content of filter cake was reduced from65.00%to49.50%by vacuum filtration. In20minutes, the average sedimentation rateof sludge was increased from2.67mL/min to3.25mL/min. We also studied the effectof particle size of semi-coke on modifying of sludge. It concluded that the bestparticle size of semi-coke was between325mesh to200mesh. This study exploredthe mechanism of semi-coke on the modifying and deep concentrated dewatering of sludge. The mechanism mainly manifested in semi-coke’s adsorption on sludge andweakening hydrophilic properties of sludge.(2) Combustion characteristic of mixed-ligand complexes of sludge andbituminous coal had been researched by thermo-gravimetric analysis, and thendynamic analysis of combustion for TG-DTG curves of every experimental samplehad been completed by Coats-Redfern integral method. The results showed that, thereexisted a great difference from the TG-DTG curves of respective sample. There werethree obvious weight-loss peaks on the DTG curve of sludge, and there was only onedistinct weight-loss peak on the DTG of Zhuzhou bituminous coal. The TG-DTGcurves of mixed-ligand complexes of the sludge and the coal were between theTG-DTG curve of the coal and the sludge. Owing to addition of the sludge, theignition point of coal and activation energy of the mixed-ligand complexes waseffectively reduced.(3) After modifying, the concentrated sludge was directly mixed with coal toprepare sludge-coal-water slurry. The slurryability experimental methods were used tostudy the effects of some factors such as coal quality, additive dosage, sludgeproportion, particle size distribution on slurryability of coal-water-sludge slurry. Theresults indicated that preparing sludge-coal-water slurry by Xiangtan sludge andbituminous coal was technically feasible. As the sludge proportion increased, theapparent viscosity of the sludge-coal-water slurry gradually increased with the poorliquidity of the sludge-coal-water slurry, while the stability of the sludge-coal-waterslurry was significantly improved. The maximum adding ratio of sludge underdifferent concentration was determined by the experiment. When the pulpingconcentration was55%, the maximum adding ratio of sludge was less than10%.When the pulping concentration was60%, the maximum adding ratio of sludge wasless than6%. If the addition was higher than the maximum value, the viscosity ofsludge-coal-water slurry would not be able to meet the industrial application of alower viscosity than1200mPa s.