Research On Total Flue Gas Mercury Online Monitoring Technology Based On High Temperature Reduction And UV Differential Optical Absorption Spectroscopy

China is a coal-fired country which coal-fired power plant consumption accounted for the majority.The situation supply power based on coal will stay for a period of time.Coal-fired power plants bring economic benefits to people at the same time,also brought serious environmental pollution.Flue gas mercury which get more and more attention in recent years has great harm to environment and human body.In 2012,the most recent implementation of the "thermal power plant air pollution emission standards",coal-fired boiler atmospheric pollution emission concentration limits: mercury and mercury compounds emission concentration limit of 0.03 3mmg,which become more stringent for mercury emissions.Mercury emissions from flue gas is mainly 0Hg and2(10)Hg,however,the on-line monitoring method based on optics can only be aimed at atomic mercury.So 2(10)Hg needs to change 0Hg to realize on-line monitoring.This paper achieve monitoring of total mercury in flue gas on line by high temperature reduction combined with UV Differential spectroscopy method.The high temperature heating system was prepared and built mercury standard gas generating system,two mercury standard gas generation system and simulation of mercury in flue gas monitoring system.Part of each system,including high temperature heating system,standard gas preparation system,data acquisition and processing system and optical system are analyzed in this article.This article used low pressure mercury lamp as the light source and combined with the measurement of the mercury monochromator determine the spectral range of mercury was 253.4-253.9nm.We compared the condition of high temperature and normal temperature based on elemental mercury and the error of mercury in the high temperature condition is 8.7%,which verifies the feasibility of the high temperature system.By processing the spectrum of elemental mercury and oxidized mercury of genetic algorithm,FFT and the integral area method on the concentration of mercury in flue gas based on the traditional DOAS algorithm,the error of the inversion results of the integral area method is minimum,which is-1.3%.Moreover,the error level is more stable than the other three algorithms.Comparing the mixed sequence of elemental mercury and oxidized mercury in online monitoring simulation experiment of total mercury,the results show that the order does not affect the measurement of total mercury concentration inversion and the genetic algorithm is both close to the actual value.However,the volatility of method of integral area is smaller and the error is controlled within 5% and fourier transform and traditional DOAS method are not suitable for low concentration of mercury inversion with a large error.Analyzing the influence on monitoring mercury in different condensing temperatures in the condition of laboratory system,we found that inversion error is the smallest at the condensation temperature of 22-25℃ and mercury concentration will be lower than the true value with the high or small condensation temperature.