Effects Of Ultra-low Emission And Electric Energy Substitution On The Atmospheric Particulate Matter

With the frequent occurrence of haze events,fine particulate pollution has become a significant environmental pollution problem in China.China’s coal consumption ranks first in the world.Particulate emissions from coal combustion are one of the principal sources of particulate matter.With the completion of ultra-low emission transformation,the contribution ratio of atmospheric particulate emissions and smoke characteristics of coal-fired power plants have changed significantly.After the implementation of electricity substitution work,the contribution value of particulate coal to PM2.5 remains to be studied.Therefore,exploring the emission characteristics of particulate matter from coal-fired power plants under the new situation,evaluating the effect of ’coal to electricity’ on PM2.5 emission reduction,and analyzing the change in the proportion of coal-burning in the source of atmospheric particulate matter are important for future air pollution control.In this paper,three ultra-low emission units in Anhui province after the transformation of wet flue gas desulfurization device(WFGD),wet electrostatic precipitator(WESP)inlet and outlet particulates were collected and a variety of indicators were analyzed.The experimental research showed that the mass concentrations of PM1,PM2.5 and PM10 emitted by the three units were 0.25～0.38,0.31～0.42 and 0.42～0.57 mg·m-3 respectively.The elements in the particles mainly include as,Zn,Cr and Pb,which are enriched in the particles with particle size less than 1 μm.Inorganic water soluble ions are mainly composed of Ca2+,NH4+,SO42-and NO3-.There was no significant difference in the mass concentration of water-soluble ions among the three particle sizes.The removal efficiency of PM10 in WFGD process is higher than 80%.The removal rate of 1-2.5 μm particles is the highest.WFGD decreased the element concentration in coarse particles,but increased the element concentration in fine particles.WFGD reduces the element concentration in coarse particles and increases the element concentrations in fine particles.At the same time,the concentrations of Ca2+ and SO42-in PM10 are also increased.The entrained slurry from WFGD is the main reason why WFGD process increases the concentrations of water-soluble ions.WESP can effectively remove PM10,but it will increase the proportion of PM2.5 in PM10.It shows that the existing environmental protection equipment has low efficiency in removing fine particles and the concentration of elements and ions in WFGD particles.Therefore,the emission of fine particulate matter from coal-fired power plants is still the focus of attention.It is suggested that WESP be installed after WFGD for power plants to reduce particulate matter emissions.The atmospheric particulate pollution in Hefei is at a medium level in China.The sub-micron aerosol pollution is the main pollution in autumn and winter.During the sampling period,the average concentrations of PM1,PM2.5 and PM10 were 43.22,58.51 and 73.82 μg·m-3,respectively.The proportion of inorganic water-soluble ions in each particle size segment was higher,mainly SO42-,NO3-,Na+,Ca2+and NH4+,and the contents of NO3-,SO42-and NH4+ were higher,indicating that the secondary source was one of the main pollution sources.The preliminary source apportionment of enrichment factors and correlation analysis showed that the anthropogenic sources of atmospheric particulates in Hefei mainly included coal burning,metallurgical industry and vehicle exhaust.Source analysis results show that the sources of PM2.5 in Hefei are secondary particles(5.5%),coal-fired sources(19.6%),industrial mixed sources(21.2%),vehicle emission sources(27.2%),and dust sources(26.5%).The PM1 sources accounted for 15.5%of secondary particulate matter,15.2%of coal-fired sources,19.8%of industrial mixed sources,25.2%of motor vehicle emission sources,and 24.4%of dust sources.Combined with coal,coal powder in coal quantity in Hefei,the proportion of coal powder of PM2.5 emissions intensity and large proportion of coal in air parsing,the coal powder’s contribution to the PM2.5 emissions was calculated,compared with 2014,the contribution of bulk coal to PM2.5 emissions decreased from 11.4%to 9.0%,and the contribution of PM2.5 emissions from motor vehicles increased from 9.9%to 27.2%in 2018.The electric energy replacement plays an important role in reducing PM2.5 emissions from loose coal,and the ’coal to electricity’ project in Hefei and surrounding areas is an important way to improve PM2.5 pollution,while the implementation of electric energy replacement in the transportation sector will be an important action direction in Hefei to reduce air pollution.