Research On Preparation And Mechanism Of Sludge Ceramisite

The sludge of city sewage treatment plant is a main by-product in the wastewater treatment process, which not only contains a variety of bacteria,eggs and parasites, butalso has many kinds of concentratedheavy metals and other harmful substances. If not properly dealed with, it may cause great harm to the environment, soil,animal and plant and human health. It has become one of the hot topics in our country and abroad that how to dispose of sludge with large output and complex components scientifically to realize harmlessness and resource utilization in sludge disposal process.This topic is to solve the problem of resource utilization of sewage sludge, with loess and bentonite as ingredients, carrying out the research on preparation of sludge ceramsite.The aspects of main research work are as follows:Firstly, the thermal kinetics characteristicsof sludge, loess, bentonite and ceramic blank are analyzed with DSC-TG-DTG method, the kinetic parameters are determined and then the decomposition rate constantsat different temperature are obtained to infer process conditions of burning ceramsite through researching the relationship between time and the decomposition of ceramic blankunder the different temperature. Secondly, the sludge, bentonite and loess are used as raw materials for sludge ceramsite firing.Through extreme difference analysisof the experimental results, the primary and secondary orderof the influences of various factors on the properties of ceramsite is investigated and the accuracy of speculation on the firing process of the anterior part is verified. Thirdly, it is studied that the effect of the sintering temperature and the organic content of ceramsite raw materials on the main properties and microstructure. Furthermore, sintering mechanism of ceramsite is exploredand basic data for the industrial production of ceramsite are provided.Through the researches above, the following conclusions can be drawn:The thermal weight loss rate of sludge ceramsite blank ball improves monotonically with the increase of the heating rate and the maximum value of total weight loss rate reach 24.36%in the experiment. By analyzing weight loss conditions of TG curve of blank ball during the firing process, it can be inferred that the temperature range suitable for ceramic preheating is 300 to 500℃. According to the thermal decomposition kinetics of ceramic ball blank, sludge ceramsite is sintered over 1000℃;The primary and secondary order of the influence of the five factors selected in the experiment on the ceramisite properties is as follows:sintering temperature, sludge ratio, bentonite ratio, preheating temperature and sintering time. And it is confirmed that to a certain extent inferring process conditions of ceramic firing by researching relationship between decomposition and time of ceramic blank under different temperature is reliable.If the sintering temperature is too high, it will make the ceramic blank excessive melting and produce a large number of liquid phase. Besides, it may result in the decrease of viscosity of ceramicbody, the grown-up of the internal pore and the reduction of ceramisite strength. Appropriate content of organic matter in the blank ball can improve the strength of ceramic products. The experimental results show that when the organic matter content in the blank reach 14.69%, the strength of ceramsite will run up to the peak value, in the preparation of high strength ceramsite, the organic matter content of ceramic blank should be controlled in 14%～ 17%; Acertain range of organic matter content in ceramic material actually corresponds to a most suitable sintering temperature. The ceramic blank which has high organic content needs lower sintering temperature, generally controlled below 1140℃ while the ceramic blank which has low organic content needs relatively higher sintering temperature so that it can achieve good performance.