To decrease the volume of sewage sludge and convert it to the resources, a unique compact sludge-melting furnace was developed. A dehydrated sludge was fed directly in the furnace by snake pump and oxygen enriched air by PSA unit was used for melting the sludge at a temperature of approximately 1350°C. Incinerated exhaust gas was discharged from the top of the furnace, and was cooled down after secondary combustor. Due to achieving a mild combustion, the amount of generating of particulates and NOx in the exhaust gas decreased extremely. On the other hand, the melt slag discharged from the bottom of the fur-nace was crystallized on a crystallizing conveyer. In this paper, simulation model for combustion of dehydra-tion sludge in the furnace was developed. The experimental results of SO2 and CO2 concentrations in the exhaust gas and height of the sludge cone in combustion tests were in close agreement with those of the simulation.
The thermal recycling of waste materials is a vital technology for both the effective utilization of energy and the long-term use of disposal sites. The blended combustion of waste materials in coal-fired power stations is one of the practical and economical means of the thermal recycling. The characteristics of the blended combustion of dried sludge pellets of municipal sewage sludge, produced using the Indirect Multi-Stage Tray Sludge Dryer Pelletier, with bituminous coal are investigated at a pulverized coal combustion test facility (thermal input of fuel: 760kW) in this study. Two combustion tests with bituminous coal and a blend of dried pellets and bituminous coal are carried out. The grindability, unburned carbon concentration in fly ash and NOx concentration in exhaust gas are analyzed. The distributions of temperature and gas composi-tions in the test furnace are also investigated, and compared for these two tests. The results indicate the applicability of the dried sludge pellets in coal-fired power stations from the aspects of the characteristics of combustion and NOx formation.
In Part II of this paper, regional (provincial) variations in energy consumption of urban households in China are analyzed using fuel expenditure data from the China Family Income and Expenditure Survey in 1999. A three dimensional matrix data of energy consumption by fuel type (including electricity), thermal-use type, and provinces is estimated using the methodology developed in Part I. In addition, the relationship with the underlying factors that affect the energy consumption structure such as, energy supply conditions, heating or cooling load, and income level are analyzed. The maximum energy consumption per household in 1999 was 36.99GJ/year·household in Heilongjiang and the minimum was 8.56GJ/year·household in Sichuan province. The average for this year was 18.81GJ/year·household. The regional variations are due primarily to differences in: space heating load, coal supply conditions and life styles, from variations in levels of income and urbanization.