Reasonable Process Of Sludge As Alternative Fuel For Cement Industry

In the urban sewage treatment industry,sludge is an inevitable product.With high water content,easily corrupt,containing heavy metals and other characteristics,and contains high organic matter,with a certain amount of heat.In recent years,with the continuous development of urban economy and society,urban sewage treatment capacity is increasing,resulting in sludge production is also rising.A sewage treatment plant on the sludge treatment capacity,has gradually become the decisive factor in the quality of its sewage treatment.In this paper,the sludge from different sources in the city was used as the object of study.The drying process of the sludge was analyzed and the physical and chemical properties,combustion characteristics and heavy metal toxicity were measured and compared with the traditional fuel pulverized coal.All aspects of its feasibility as an alternative fuel.On the basis of this,the paper further studies the reasonable process of sludge as an alternative fuel in the cement industry,analyzes the optimum water content range and the reasonable range of adding rate,and provides the theoretical basis for the actual utilization of the sludge in the cement kiln system.Different kinds of sludge were treated with different drying temperature to study the changes of volume and shape in the process of sludge dryingThe results show that in a certain temperature range,the higher the temperature is,the higher the rate of water cut is.But the high temperature will cause the sludge to be cemented and lead to the precipitation of volatile matter.Thermal analysis technology to study the wet sludge with the temperature to increase the sludge itself changes,the conclusion of the two concluded that the drying temperature of the sludge should be controlled at 100 ?-140 ?.Through the chemical composition analysis,industrial analysis,calorific value analysis and elemental analysis of four aspects of dry sludge research,and compared with the traditional fuel coal powder,concluded that the main chemical composition of the sludge and coal similar to most of the heavy metals There were no significant differences in elemental content and content.There is a clear gap between the dry sludge and pulverized coal in the industrial analysis.Dry sludge volatile content is higher,while the fixed carbon content in coal is much higher than the dry sludge.The heat of dry sludge is about 8.5-20kJ/g,the average heat is about-13.69kJ/g,the calorific value is relatively high,and it has high utilization value.In the case of hydrogen and sulfur,The difference between dry sludge and pulverized coal is not obvious,and the nitrogen in the sludge is generally higher than that of coal.In terms of carbon element,the content of pulverized coal is much higher than that of dry sludge.Through the thermal analysis method,the thermal analysis curve was drawn,and the quality change and the heat dissipation and heat dissipation of the dry sludge and pulverized coal were analyzed.The results show that the combustion of dry sludge and pulverized coal is divided into three stages.The heat release of dry sludge in the volatile phase is higher,and the pulverized coal is mainly driven by the combustion of fixed carbon.In this study,the types and contents of heavy metals in residual ash after combustion were measured and compared with the coal ash after combustion of traditional fuels.The results show that the content of heavy metals in the remaining material is not significantly different from that of coal ash after calcination of the dry sludge by the cement kiln system,and the heavy metal limit of the cement clinker specified in GB50295-2008 "Cement Plant Design Code" is met.Comparing the heat of the sludge in different moisture content and drying to different moisture content to absorb the heat and drying time,considering the economic,practical and other factors,to determine the sludge for the cement industry alternative fuels reasonable moisture content range of 10%-30%.The different kinds of sludge were mixed with pulverized coal in different proportions,and the combustion process of mixed samples was studied by synchronous thermal analysis.Analysis of the quality of mixed samples and the heat absorption and desorption situation,it was concluded that the addition of sludge in coal should not exceed 40%.