Experimental Studv On Sludge Gasification In Fixed Bed

The rapid economic development and the acceleration of urbanization process have brought the growing generation of municipal sewage, and the municipal sludge also has increased dramatically as the processing byproducts. Sludge treatment has become an urgent problem needed to be solved in the field of modern environmental protection. Owing to the secondary pollution on the environment brought by the traditional sludge treatment technologies. People are trying to find methods be more environment-friendly. The thermal treatment of sludge has great advantages in reducing pollution and resource recycling, which can also produce carbon monoxide and hydrogen-rich combustible gas while fixes heavy metals in the residue. It is meaningful both in energy ultilizition and environmental protection to study the gasification characteristics and improve the gasification technology of sludge.Taking from the source of sludge, as well as its harm and status,this article analyses and discusses the treatment methods of sludge at home and abroad, and also the technology to make resource from sludge. The better way to process the municipal sewage sludge is sludge gasification and pyrolysis. Sludge gasification and pyrolysis at home and abroad have been reviewed. On the basis of these,sludge gasification characteristics in different temperatures, different gasification agents and different gasification agent proportions have been researched.Then some sludge gasification experiments have been performed using a small-scale fixed bed reactor.Sludge, which were Pre-dried and crushed, the moisture content of3.68%, gasified respectively in air, carbon dioxide and water vapor. The test temperatures were controlled between500℃and800℃. Some results have been obtained, such as how the gas composition and the gas heat values change with the variation of temperature, air equivalence ratio, CO2/C molar ratio and H2O/C molar ratio. The char characteristics and the tar characteristics from sludge air gasification were also investigated. The experimental analyses show that, hydrogen, carbon monoxide and methane are the main components of the gas products. The gas contribution and heat values are greatly affected by temperatures. Hydrogen and carbon monoxide content increase with the rise of temperature obviously. The influence on gas products by gasifying agents is more complicated, The content and the heat value of the gas products is not simply increased or decreased with the change of the gasifying agent level. Therefore, an optimal ratio of sludge on gasification agent exists. In addition, the experimental analyses show that, temperature increase reduces the carbon content and the bulk density of the char. The main components of the tar from sludge air gasification are composed of benzene and its compounds, polycyclic aromatic hydrocarbons, olefins and nitrogen-containing compounds, etc. Among the tar components, phenol and naphthalene are of the highest concentrations, about half of the total content.