Sludge generated by wastewater treatment has a high water content, due to the combination of water and sludge characteristics, mechanical removal methods have certain limits, sludge in the content of organic matter, ash, especially addition of flocculants for the final solid content plays an important role. In General, mechanical dewatering can get solid content of 20%-30%, also known as mud cake sludge formed by. High moisture content of sludge cake, a fluid nature, disposed of the difficulty and high cost, it is necessary to further reductions. At this time, in addition to dry only by heat forming evaporation, can achieve large-scale reductions. Dry process using heat is hot and dry.