Study On Pollutants Emission From Sludge Combustion And Physico-chemical Proper Ties Of Ash And Slag

Sludge is a kind of solid wastes, which has large amounts and harmful to human and environment. It widely comes from wastewater treatment in municipal wastewater, industrial wastewater and water bodies dredging. At present landfill, agricultural utilization and combustion are the main sludge treatment methods. Because sludge landfill and agricultural utilization will result in second pollution to the environment, the sludge treatment method of combustion combined drying is regarded as the most effective method to achieve the sludge reduction, harmlessly treatment and utilization. However, pollutants emission during the sludge combustion process and heavy metals in the fly ash and bottom slag after sludge combustion will easily damaged environment. Based on this background, this paper has conducted researches on pollutants emission during sludge combustion process. And establish a theoretical system to guide the industrial applications.In this paper, it has introduced the sludge definition, various sorts of sludge and sludge damage firstly. And put more emphasis on the introduction of sludge treatment and disposal technologies available in the world, as well as pollutants emission status during sludge combustion. Based on this, we selected Shanghai Zhuyuan sludge as combustion fuel to study the characteristics of pollutants emission during sludge combustion process in a lab scale fluidized bed boiler. The emission characteristics of dioxins, NOx and heavy metals from the flue gas at different water contents and different combustion temperatures were obtained. And the physic-chemical properties of ash and slag after sludge combustion has been comprehensively analyzed, and we obtained the morphological characteristics, element composition and mineral component, as well as toxicity characteristic of leaching procedure of heavy metals.The last part of this paper, a sludge drying and co-combustion with coal system in Haining Metropolitan Thermal-Electric Power Plant was studied. The characteristics of pollutants emission during the process of Haining tannery sludge drying and combustion in this sludge drying and co-combustion system was obtained by engineering sampling. It has been found that activated carbon adsorption-plasma desorption apparatus has a better reduction for pollutants during the sludge drying process, the pollutants degradation efficiency has reached more than90%. Meanwhile, SO2, NOx, dust and some other common pollutants all were reduced by a four-electric-field electrostatic precipitator and a dual-alkali wet flue gas de-acid system during sludge combustion in the CFB boiler. More than99%of flue dust was reduced, and SO2was reduced to less than100ppm. Pollutants emission of the whole system were well controlled and met the state standard.