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Experimental Research on Sludge and Pulverized Coal Mixture Pulping and Combustion Characteristics of the Slurry

Author: SuZuo
Tutor: FanHaiHong
School: Xi'an University of Architecture and Technology
Course: Materials Science
Keywords: Sludge Structure Viscosity Mix slurry Combustion characteristic
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 51
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Abstract

Sludge is the inevitable product of the sewage disposal process. If not properly handled, large amounts of harmful substances in sludge can inevitably cause secondary serious pollution. Combustion is the most efficient and cleanest way in the current disposal approach. Combustion of Sludge and pulverized coal mixture can overcome the sludge’s low calorific value and the problem that high water content can’t meet the need of its own water evaporation. However, due to the high viscosity of the sludge, the slurry is difficult to meet the viscosity requirements of pumping and?atomization. Based on the observation of microstructure of sludge, this paper analyzes the causes of sludge’s high viscosity, studies viscosity-reduction mechanism by use of physical and chemical methods, and proposes a method of preparing sludge slurry fuel. The results are as follows:The structure analysis shows that basic structure of sludge is a network structure formed by overlapping and entangling of filamentous microorganisms. Their own waste EPS (extracellular polymer) dissolved in water to form gels, together filling in the network structure, which leads to high viscosity of sludge.Physical forces will damage sludge’s network structure and reduce sludge viscosity. The compressing method has the maximal viscosity reduction effect, the final viscosity can reach 2.64Pa·S, viscosity reduction rate 83.66%. Chemical methods can damage the cell walls of microorganisms, release cell water and thus reduce sludge viscosity. Add 5% NaOH, sludge viscosity value can reach 0.73Pa·S, viscosity reduction rate 96.23%.Add pulverized coal to sludge to make slurry. When the amount of pulverized coal are above 40% , the slurry viscosity obviously rises. It shows that adding less than 40% of pulverized coal is reasonable.Add 10% of pulverized coal to sludge to make slurry, heat of the slurry can meet the needs of the water evaporation and the combustion process can proceed steadily. Add 40% of pulverized coal, slurry heat value can reach 1.38×10~4mJ / g, equivalent to heat of low quality coal;Adding alkali to the slurry has little effect on sludge combustion process, ignition temperature increased slightly, and burnout temperature did not change much, indicating that viscosity reduction combustion is feasible when adding alkali to the slurry.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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