Characteristics of coal sludge slurry prepared by a wet-grinding process

Coal sludge slurry(CSS) is an alternative fuel and a potential competitive method for sludge reduction.Based on the researches of coal water slurry, we studied CSSs by using a wet-grinding process with different types of regional municipal sludge(sludge) in an orthogonal experiment. The sludge type,sludge mixing proportion, dosage of dispersant, and grinding time were tested in this study. The results show that water content and its occurrence characteristics in the sludge have primary hindering influences on slurry ability. The range of fixed-viscosity concentrations with raw wet sludge is from 50.78%to 44.40%(by weight), while the range is from 53.35% to 51.51%(by weight) with dry sludge. All of the CSSs exhibit shear-thinning behaviors with different variation trends, especially the CSSs with more than 15%(by weight) raw wet sludge in it. Adding the same proportion of raw wet sludge increases the thixotropic properties of CSSs and the highest area of thixotropy loop is 3065 Pa/s, while the highest value of dry sludge is 1798 Pa/s. Hydrophilic group plays an important role in adsorbing water and building three-dimension networks with other particles, which is the main reason for CSS properties.Therefore, the mechanism can be used to find the way for making high quality CSS.

Experimental study on the partial preheating combustion characteristic of Yankuang coal sludge

Coal sludge is a seriously polluted solid waste,and the rational utilization of its resources has long being an undoubtedly important research topic.This paper mainly studies the coal sludge partial preheating characteristic,combustion characteristic and the process of migration and conversion of nitrogen with preheating combustion technology.The experimental results indicate that most of the elements in the coal sludge are released during preheating,and the ratio of the fuel-N converted to the N_(2),NH_(3) and HCN are 75.5%,6.74%and 0.64%,respectively.Compared with the coal sludge,the BET surface area and cumulative pore area of preheated char are increased.The surface of preheated char is loose and porous with many fine particles,while raw coal is dense with larger particles.Meantime,the quantity of carbon defect structure,the active sites and the reactivity of preheated char are all increased.In the whole process,the NO_(x) emission is about 156 mg/m3(@6%O2),the ratio of fuel-N converted to NO_(x) was 2.98%,and the combustion efficiency is 96.5%.This experiment results will play a vital role in efficient and clean utilization of coal sludge.

Combustion of Sewage Sludge as Alternative Fuel for Cement Industry

The combustion of sewage sludge and coal was studied by thermogravimetric analysis.Both differential scanning calorimetric analysis and derivative thermogravimetric profiles showed differences between combustion of sewage sludge and coal,and non-isothermal kinetics analysis method was applied to evaluate the combustion process.Based on Coats-Redfern integral method,some reaction models were tested,the mechanism and kinetics of the combustion reaction were discussed.The results show that the combustion of sewage sludge is mainly in the low temperature stage,meanwhile the ignition temperature and Arrhenius activation energy are lower than that of coal.The combustion of sewage sludge has the advantage over coal in some aspects,thus sewage sludge can partly replace coal used as cement industry fuel.