Study On Sampling Method Of Low Concentration Particulate Matter In Coal-fired Power Plant

With the gradual strict emission limit of particulate matter in coal-fired power plants and the increasing improvement of dust removal and desulfurization technology and its equipment,the accurate determination of the mass concentration of particles in the flue gas of the power plant has become a hot spot in the field of fixed source pollution control in recent years.In this paper,single factor method is applied to carry out experiments on constant weight conditions and influencing factors for different manufacturers of filter media.Using selected filter media at the ESP(electrostatic precipitator)outlet of 4 typical coal-fired power plants in Xinjiang,the multi-point isokinetic and single-point constant-speed sampling synchronous test is carried out,and the conditions for the single-point constant-speed sampling of the particles in the flue gas of the ESP and WFGD(wet desulphurization)flue gas of the coal-fired power plant are analyzed.The feasibility of single-point constant-speed sampling is verified theoretically and practically.According to the sampling problems encountered in the sampling pipe and the fastening device is improved.The results show that:(1)The optimum constant weight of the filter is as follows: the drying temperature is 110 ?,the drying time is 2h,the cooling time is 1h.For the high temperature flue gas(>110 ?),the drying temperature is not less than the measured gas temperature.The dust film is used for the flue gas with temperature less than180 ?.The optimum constant weight conditions are T=110 ? and t=1h;the filter membrane can be weighed with the acid solution,and the other factors have no effect on the two kinds of films.(2)After the simultaneous use of multi-point isokinetic and single-point constant-speed sampling at the ESP exit of 4 coal-fired power plants,the results were verified by RSD analysis,F test and t test,which proved that the consistency was better and no significant difference.By analyzing the single particles in the flue,the conditions for the constant-speed sampling of the single-point of the ESP and WFGD exit flue gas in 4 coal-fired power plants are as follows: the particle flow is laminar flow and the particle size is less than 4 ?m.Through the field comparison test,the theoretical condition and the literature analysis,it is concluded that the ESP and WFGD exits of most power plants can adopt simple and fast single-point andconstant-speed sampling in the actual sampling instead of the multi-point isokinetic sampling of time consuming force.(3)For the vertical sampling before the initial dust and the dust removal,the water vapor condensate carried the impurities in the flue gas into the filter tube,which affects the accuracy of the measurement results.When the sampling gun is clamped,it is not easy to keep vertical with the wall of the flue.It affects the normal sampling of the device,and improves the upper and lower arm of the fastening forceps and the clamp tsui.