Development And Production Of Sludge Ceramisite

Sludge (including sewage sludge, industrial sludge and Lake Creek) contains large amounts of heavy metals, pathogens, toxic organic matter. It has become an important factor affecting the water quality and aquatic ecology. At present, the main treatment methods of sludge reclamation, including land reclamation, piling and landfill. But these methods have not solve the potential hazards of sludge fundamentally. Sintering ceramsite by using sludge, not only realize the harmless sludge treatment, also has great economic benefit.Due to the high content of silicon, loess is beneficial to improve the strength of ceramisite; High content of oxygen and calcium, bentonite is good for ceramic expansion with high temperature; Loess and bentonite have extensive sources. Therefore, we determine use the loess, bentonite and sludge as raw materials. Considering the main chemical composition of sludge, loess and bentonite were SiO2, Al2O3, Fe2O3and CaO, so we lead to three elements phase diagram like SiO2-Al2O3-FeO, SiO2-Al2O3-solvent and so on. Use the three elements phase diagram as a guidance to design the constitute of sludge ceramisite, in order to get low energy consumption, excellent pore structure, mechanical properties and bulk density of it, to meet the requirements of high quality ceramic.In this paper, through the analysis of sludge, loess and bentonite chemical composition, microstructure, thermal properties, burn expansion mechanism and physical and chemical change in ceramic firing process, clear the sludge ceramisite sintering process is divided into the stage of drying stage, preheating stage, oxidation decomposition stage and high temperature firing stage, in which the oxidation decomposing process and the high temperature phase is a key phase of sludge sintering ceramsite.Research shows that the bulk density and strength of the cylinder pressure of sludge ceramisite decreased with the increase of the percentage of sludge, increases with the sintering temperature increasing. The effect of sintering temperature on the ceramisite cylinder compressive strength is significantly, sintering temperature reaches or exceeds the melting glaze state of ceramisite, the higher the temperature, the more fully vitrify of ceramic. The proportion of sewage sludge and ceramic sintering temperature is the key to high quality ceramic firing. With the increase of percentage of sludge ceramsite, the porosity of ceramic decreases, the average pore diameter increases, the unicom pore ratio increases, the specific surface area decreases, the influence of sludge percentage change the ceramsite pore significantly.Under laboratory conditions, the best scheme of the preparation of sludge ceramsite:sludge20%, bentonite16%, loess64%, the preheating temperature is300℃and the sintering temperature is1150℃.In the sludge ceramisite production, through the method of preheating temperature and sintering temperature fast conversion, we can adjust the expansibility of ceramsite. Add the percentage of sludge appropriately, we can reduce the ceramisite calcination temperature, so as to achieve the purpose of reducing energy consumption. In the actual production, the optimal scheme of sludge sintering ceramsite:sludge6%, bentonite24%, Ioess70%, the preheating temperature is350℃and the sintering temperature is1135℃.