热水解-厌氧消化工艺中污泥的触变性分析

采用触变动力学系数作为评价指标,通过流变试验研究了热水解-厌氧消化联合工艺中污泥标准化黏度和触变性的变化规律,并探讨了屈服应力和触变性二者间的联系,从触变性角度为热水解-厌氧消化污泥的处理处置提供参考依据。结果表明:与滞后环相比,用触变动力学系数K更适合表征污泥的触变性;调配污泥、热水解污泥和厌氧消化污泥的标准化黏度均随时间增大逐渐减小;3种污泥的触变性随TSS质量分数增大而减小,经热水解-厌氧消化后污泥的触变性增大,流动性增强;污泥屈服应力越大,触变性越小,稳定性越强。

Analysis on thixotropy of sludge in processing of thermal hydrolysis-anaerobic digestion

The present paper is aimed at making an investigation of the variation of the normalized viscosity and thixotropy of the sludge in the integrated process of the thermal hydrolysis and mesophilic anaerobic digestion through the rheological experiments.And,then,there comes the need to discuss the relationship between the yield stress and thixotropyby using the thixotropic kinetic coefficient as the evaluation indicator of the sludge thixotropy.The purpose of the discussion is to provide a reference for the treatment and disposal of the thermal hydrolysis-anaerobic digestion sludge from the perspective of thixotropy.The results of our discussion indicate that the hysteresis loop area method fails to reflect the respective dynamic features of the process of the rupture and reconstruction of the sludge flock,for there exist indeed some inconvenience and limitations in the exploitation of the hysteresis ring area to compare the thixotropy of the sludge samples in different types and different ranges of shearing rates.Nevertheless,the thixotropic kinetic coefficient method can help to define the change of the structural parameters with time as the dynamic coefficient of the structural decomposition and reconstruction.The application of the thixotropic kinetic coefficient to specifying the thixotropy of sludge can better reflect the dynamic process of the internal structure.Besides,the normalized viscosity of the mixture,the thermal hydrolysis and the anaerobic digestion sludge tend to decrease gradually with time,whereas the normalized viscosity can decrease sharply in the initial stage of shearing,and then the viscosity gets to be stable slowly and eventually.The K value of the 3 kinds of sludge tends to increase with the increase of TSS,that is,the thixotropy may decrease with the increase of TSS,signifying that it is easier for the sludge to reach a stable state under the action of the external force.As a result of the thermal hydrolysis-anaerobic digestion,the internal structural strength of the sludge tends to be reduced.And,then,with the decrease of viscosity,the flow resistance may get reduced to promote the improvement of the thixotropic property and strengthen the fluidity.As a kind of thixotropic yield stress fluid,the stress yield of the sludge serves as the symbol of the fracture of the network structure.In the graph of the yield stress change with K,the value of K also increases with the increase of the yield stress,that is to say,there ought to exist a positive correlation between the thixotropy dynamic coefficient and the yield stress.And,just for this correlation,the greater the yield stress of the sludge,the greater the thixotropy kinetic coefficient and the smaller the thixotropy would be.Thus,in turn,the stronger the steric hindrance in the internal structure of the sludge,the greater the stability and the more difficult and less likely the liquid flows.