钙基脱硫剂对污泥流变特性的影响

Effect of calcium based desulfurizers on rheological properties of sludge

污泥流变特性的改善对高水分污泥大规模资源化利用至关重要。系统研究了加入钙基脱硫剂石灰石、电石渣对污泥流变特性的影响。采用旋转流变仪探究了石灰石或电石渣比例和粒径、剪切时间对污泥流变特性的影响规律。结果表明:脱硫剂石灰石或电石渣掺加比例越大,混合膏体的表观黏度和剪切应力相对越大,脱硫剂掺加比例大于15%后,混合膏体的流变特性变化较显著;石灰石掺加比例>15%后流体由屈服假塑性流体转变为宾汉性流体,混合膏体的表观黏度在同一剪切速率下随剪切时间增大而减小,呈剪切变稀的现象;2种脱硫剂的掺加比例越小剪切变稀现象越显著,且在低剪切速率35 s^(-1)下,表观黏度下降趋势更显著。在同一剪切速率下对相同掺加比例的混合膏体进行分析发现粒径0~0.075 mm的混合膏体,混合后表观黏度更大,说明脱硫剂粒径越小,对混合物的流变特性影响越显著。通过污泥混合钙基脱硫剂泵送可降低混合膏体含水率,且泵送入炉后起到炉内脱硫作用,脱硫剂最佳掺加比例为15%~20%。本研究为污泥在循环流化床中大规模燃烧利用和泵送方案优化设计提供理论指导。

The improvement of sludge rheological properties is very important for large-scale resource utilization of high-moisture sludge.The effects of adding calcium desulphurizer such as limestone and calcium carbide slag on the rheological properties of sludge were systematically studied.The effects of limestone or calcium carbide slag ratio,particle size and shear time on the rheological characteristics of sludge were investigated by using a rotating rheometer.The results show that the apparent viscosity and shear stress of the mixture increase with the proportion of desulfurizer limestone or calcium carbide slag,and the rheological properties of the mixture change significantly when the proportion of desulfurizer is greater than 15%.The fluid changes from a yield pseudoplastic fluid to a Bingham fluid when the proportion of limestone is more than 15%.The apparent viscosity of the mixed paste decreases with the increase of shear time at the same shear rate,showing the phenomenon of shear thinning.The smaller the proportion of two desulfurizers is,the more obvious the shear thinning phenomenon is,and the apparent viscosity decreasing trend is more significant at the lower shear rate of 35 s^(-1).The analysis of desulfurizer mixed paste with the same proportion at the same shear rate is found that the apparent viscosity of the mixed paste with the particle size of 0-0.075 mm is greater,indicating that the smaller the particle size of the desulfurizer is,the more significant the effect on the rheological properties of the mixture is.The moisture content of the mixed paste can be reduced by pumping the sludge with calcium-based desulfurizer,and the desulfurization function can be played in the furnace after pumping into the furnace.The optimal proportion of desulfurizer is 15%-20%.This study provides theoretical guidance for sludge combustion utilization and optimal design of pumping scheme in circulating fluidized bed.