Study On The Preparation And Slurry Mechanism Of Modified Sludge-CWS

In order to make full use of an amount of water contained in municipal sewage sludge and its calorific value of sludge, mixing the sludge into Coal Water Slurry(CWS) to prepare the Sludge-Coal Water Slurry(S-CWS), which selects from the Wang Lou gas coal and dewatered sludge produced in Xuzhou Guozhen Water Operations Ltd.as the research object. In this paper, sludge was modified by alkali and S-CWS was prepared with gas coal. The slurry mechanism of modified S-CWS was studied.Through the comparison of pulping properties of S-CWS and CWS, the slurry concentration of S-CWS become low, liquidity become worse, but stability is better. With the sludge addition increased, the flow pattern of slurry changes from yield dilatant fluid to Bingham plastic fluid. The slurry concentration decreased rapidly. When the sludge added to 5%(The sludge dry basis accounting for the quality of coal dry basis percentage), the slurry concentration has been reduced to 54.11%, but the stability of slurry is improved.With the fixed viscosity concentration of S-CWS, the water-saving rate and the free humic acid yield as the indicators of sludge modified. The pulping properties of modified S-CWS under different alkali conditions was studied. The results show that pulping properties of modified S-CWS with Na OH as modifier, modified time 1.5 h and conditions 20% modifier accounting for the quality of sludge dry basis percentage is best. The slurry concentration, stability and liquidity of S-CWS are greatly improved. In the modified sludge add ratio was 5%, the slurry concentration was 57.55%, increased by 3.44%. Modified release of bound water in sludge floc structure and have an effect on water-saving. When the modified sludge add ratio was 20%, the water saving rate as high as 25.76%.The slurry mechanism of modified S-CWS were studied by analyzing changes of the dispersant adsorption mechanism and kinetics on coal and sludge surface, effect of modified on the surface properties and spatial structure of sludge and effect of modified on the existing forms of water in sludge. The results show that adsorption of dispersant on gas coal, sludge and modified sludge accord with Langmuir isothermal adsorption model. The relationship among adsorption constant KL is modified sludge> Sludge> gas coal, the relationship of adsorption amount is modified sludge> sludge> gas coal. The adsorption process on the surface accord with second-order kinetic adsorption model, indicated that the adsorption process was mainly chemical adsorption. The relationship among adsorption rate constant k2 is modified sludge> Sludge> gas coal. Modified enhanced sludge’s electronegativity and after adsorption NSF electronegative further enhanced. It increased the electrostatic repulsion between the particles in SCWS system, improved the slurry liquidity and stability. The sludge’s floc structure was damaged by the strong alkaline of Na OH and becomes more compact and less pore structure. The water adsorbed in floc structure were released. It reduced the binding energy of the sludge water and the bound water content from 0.96 kg water/kg DS down to 0.53 kg water/kg DS. So modified on sludge can improved the utilization rate of water in the sludge and decreased the viscosity of S-CWS.