Application Research On Fine Particle Matters Control And Emission Characteristics Of ESP And WFGD With Coal-fired Boilers

Implementation of the new emission standard of environmental protection required particle matters ?PM? emission <20 mg/m3 with coal-fired boilers of key region, and the vast majority of industrial electrostatic precipitators ?ESP? in exiting pants need to be upgraded. In order to promote and enhance the development of PM control technologies and equipment with coal-fired boilers, supported by national high-tech research and development program of China ?863 Program? named the technology and equipment of PM_2.5 process control and emission reduction in key industries. At this background, PM emission measurement and original data collection are achieved on more than 60 coal-fired boilers in this thesis, and has a systematic analysis and study of PM emission characteristic with ESP and wet flue gas desulfuration ?WFGD?.Ultra-low emission technical route of Low-temperature economizer + ESP + WFGD is adopted for PM emission characteristic research of coal-fired boilers, and the method is to analyze the effects of the single parameters on the PM emission with ESP and WFGD via experimental measurement at the same and/or similar operating condition, the research on ESP index equation is basic on mathematical fit of experimental data, and based on electrical low-pressure impactor?ELPI? with heating and dilution is mainly used for experimental measurement. The main contents of this thesis conclude that at the research beginning, based on experimental ESP platform the relationship between the collection efficiency and specific collection area & electric field strength of ESP is studied, and ESP index equation is acquired at experimental condition, at the subsequent of this thesis, based on industrial coal-fired boilers the applicability of ESP index equation in industrial ESP is first studied as well as the effects of the ESP operating single condition on PM emission, at the last the PM₁₀ diameter distribution changes at inlet and outlet of WFGD and the effects of WFGD on PM₁₀ collection are studied. The significance of this research is to supply guidance and/or reference for the sizing design of industrial ESP, and a more scientific method of process optimization for ESP operating, meanwhile can be reference of ultra-low emission with coal-fired boilers for the ultra-low emission technical route of the synergistic effect of ESP and WFGD. The main conclusions of this thesis are as follows:1) It is a sufficient capacity of ESP sizing and a scientific process control of ESP operating that are the necessary conditions for ESP with a standardized emission. On the basis of scientific process control, the relation between PMio emission and/or its collection efficiency of ESP and operating power and specific collection area of ESP can be satisfied with the ESP index equation:Inm/?pM=-apPS and/or lg1-?/?E=-?EEaEpS.2) It is flue gas temperature, current density of the last electric field and rapping that have a greater effects on ESP emission of PMio with coal-fired boilers as the process factors. With the condition of flue gas temperature higher than 110 ? it is obvious for ESP emission of PMio decrease by reducing flue gas temperature; with less than 110?C, which has little relation of temperature changing, but ESP collection efficiency for PMo.1?1 is decreased. The last electric field should be operated at the limitation of current density ranged from 0.1 mA/m2?0.3 mA/m2 according to the different PM concentration,and a higher current density operating can increase ESP emission. The effects of rapping on ESP emission are mainly about the reentrainment and the back corona result of an unreasonable rapping,which all can increase ESP emission.3) Based on the statistic analysis of experimental data from ESP samples selected, the average collection efficiency of WFGD for PMio & PM_2.5 is about 51.39 % & 16.88 %,respectively. With the same type demister, it is flue gas temperature and PM concentration at WFGD inlet that are the main factors which affect WFGD collection efficiency of PM₁₀.4) Based on the statistic analysis of experimental data from ESP samples selected, at ESP outlet, the same to WFGD inlet, PM_2.5 mass concentration average percentage in PMio is about 17.38 %,ranged from 6.5 % ?28.74 %; at WFGD outlet, this average percentage is about 28.74 %,ranged from 17.38 % ?64 %.5) The mass concentration distribution of PMi all presents a single peak at ESP outlet and WFGD outlet. For ESP emission distribution the peak diameter is mainly ranged from 0.2 ?m?0.5 ?m, however, for WFGD emission distribution the peak diameter has a wider range from 0.2?m?1 ?m.