Study On Controlled Pyrolysis And Fume Purification Process Of Rural Domestic Waste

The level of domestic waste treatment in rural areas of China has been improving year by year,but there is still a problem of low overall harmless levels.Pyrolysis technology can realize the treatment of rural domestic waste in the vicinity,with a high degree of harmlessness,which is an efficient and environmentally friendly treatment technology.The composition of domestic waste is complex,the pyrolysis process is not easy to control,and the flue gas is difficult to be effectively treated.In this paper,a low-temperature controlled-oxygen pyrolysis furnace with a treatment capacity of 3 t/d is used as the basic furnace model.Based on the principle of controlled-oxygen pyrolysis and layered dioxin control,the furnace is divided into a combustion layer,a pyrolysis layer,and a drying layer to improve the mineralization of domestic waste and suppress the dioxin generation based on maintaining a stable pyrolysis atmosphere in the furnace.The pyrolysis process was systematically analyzed using a combination of field tests and numerical analysis;on this basis,the performance of the pyrolysis furnace and flue gas purification devices for each pollutant was analyzed by numerical simulation,and the performance of the purification system was predicted to maintain the pyrolysis atmosphere in the furnace while giving the equipment operating parameters for achieving the standard emission of pyrolysis flue gas.The following main conclusions were drawn:（1）To address the problem of large changes in the seasonal generation of domestic waste,a low-temperature controlled oxygen pyrolysis furnace with a treatment capacity of 6 t/d domestic waste is designed,which can treat 4000-6000 persons daily domestic waste;based on uniform fabric,the temperature difference between different sections along the height direction of the optimized furnace model is less than 50℃,which can meet the demand of stable pyrolysis;numerical simulation is used to analyze the flue gas components in the process of controlled oxygen pyrolysis The changes of flue gas components during oxygen-controlled pyrolysis were analyzed by numerical simulation.The concentrations of SO₂,Hg,NO_X,HCl,Cd,Pb,and dioxins in the pyrolysis flue gas are lower than the emission limits specified in the"Pollution Control Standard for Domestic Waste Incineration";the particulate matter can be purified by the flue gas purification system to achieve the emission standards.（2）Based on the pollutant emission characteristics of pyrolysis flue gas,a low-temperature oxygen-controlled pyrolysis and flue gas purification control system consisting of"3 t/d domestic waste oxygen-controlled pyrolysis furnace-spray tower-wet cyclone dust collector-spray water circulation tank-fan"is constructed.The temperature difference between different sections of the oxygen-controlled pyrolysis furnace along the height direction is less than 50℃,which can realize stable pyrolysis.After the flue gas from the pyrolysis furnace enters the spray cooling tower,the temperature drops to below 50℃,the acidic gas is dissolved in water and removed,the liquid droplets combine with the larger particles in the flue gas and settle,and the aerosol particles in the flue gas are cooled to form condensed aerosol particles.The uniform distribution of the liquid film in the wet cyclone dust collector promotes the improvement of purification efficiency.The inlet air speed is 15 m/s,the pressure drop is 425 Pa,the cutting particle size is 1.2μm,the purification efficiency is more than 95%for particles above 5μm,and the effect is optimal.（3）Numerical simulation combined with field measurement is used to analyze the whole process control system of controlled oxygen pyrolysis and flue gas purification with a treatment capacity of 3 t/d domestic waste.In the process of flue gas purification,the air velocity of the empty tower at 2 m of spray tower is 0.8 m/s,the velocity of the wet cyclone dust collector inlet is 14.5 m/s,and the velocity of the pyrolysis furnace inlet is 2.3 m/s.The system airflow is evenly distributed and the flue gas purification equipment is in good operating condition.The deviation of the temperature at points A,B,and D inside the pyrolysis furnace from the numerical analysis results is less than5%;after pyrolysis,the capacity reduction rate of domestic waste reaches 95%,and the leaching concentration of heavy metals in the ash residue is lower than the standard value specified in the"Hazardous Waste Identification Standard-Leaching Toxicity Identification"and the"Surface Water Environmental Quality Standard"for Class V surface water,which realizes the capacity reduction and reduction of domestic waste.Harmless.