Optimization on 200 t / d garbage co⁃utilization in a coal⁃fired power plant through air⁃free pyrolysis process

With the gradual growth of urban garbage amount in China，the reduction and harmless treatment of gar⁃ bage has become more and more urgent. Compared with the traditional waste treatment methods such as landfill and incineration，the pyrolysis treatment of garbage has the advantages of less dioxin emission and less secondary pollution，and has received more and more attention from researchers in recent years. A new process route of co⁃utilization of gar⁃ bage coupled with coal⁃fired power plants was proposed for the needs of waste treatment at the county and township level in China. Combined with the field experimental data，aiming at the actual case of a 55 MW coal⁃fired unit cou⁃ pled with 200 t / d garbage，the process was verified and simulated by Aspen plus software. The experimental and simu⁃ lation results show that without extracting flue gas from coal⁃fired boilers，the tar and gas produced by the anaerobic pyrolysis of garbage can be burned as a heat source for drying and pyrolysis. And part of the surplus high calorific val⁃ ue pyrolysis oil and gas can be sent to coal⁃fired units for combustion. When part of the middle and high temperature coal⁃fired flue gas is extracted for the garbage drying and pyrolysis process，the anaerobic pyrolysis of gar⁃ bage can spare more high⁃calorific value oil and gas for combustion⁃supporting and peak shaving. At the same time，the high⁃chlorine garbage charcoal produced by garbage pyrolysis can be directly sent to the boiler for combus⁃ tion. The on⁃site detection of dioxins produced by 55 MW coal⁃fired units coupled with garbage charcoal was carried out. When the garbage charcoal was not mixed，the total dioxin content in the flue gas was 0.006 1 ng TEQ/ m3 . When the garbage charcoal mixing ratio was 1%，the total dioxin content in the flue gas was 0.005 3 ng TEQ / m3 . The dioxin content did not change significantly before and after mixing，and was far below the local emission standard. The high⁃humidity flue gas in the drying process was recirculated into the oil and gas combustion hot blast stove，which is beneficial to improve the surplus pyrolysis oil and gas of the coupling system. Considering the safety of flue gas transportation，the actual extracted boiler flue gas temperature is lower than the combustion temperature of pyrolysis oil and gas， so the actual maximum extracted boiler flue gas volume in this case ( 55 MW unit coupled with 200 t / d garbage) is no more than 2% of the total boiler flue gas volume，which has no significant impact on the overall performance of the boiler.