Abstract
The current paper presents the research results carried out at one of Polish power plants at a pulverized hard coal-fired 225 MW unit. The research was carried out at full load of the boiler (100% MCR) and focused on analysis of mercury content in the input fuel and limestone sorbent for wet flue gas desulfurization (FGD) system, as well as investigation of mercury content in the combustion products, i.e. fly ash, slag, FGD product (gypsum) and FGD effluents (waste). Within the framework of the present study the concentration of mercury vapor in the exhaust gas was also investigated. The analysis was performed using Lumex RA-915+ spectrometer with an attachment (RP-91C). The measurements were carried out at three locations, i.e. before the electrostatic precipitator (ESP), downstream the ESP, and downstream the wet FGD plant. Design of the measurement system allowed to determine both forms of mercury in the flue gas (Hg 0 and Hg 2+ ) at all measurement locations.Based on the measurement results the balance of mercury for a pulverized coal (PC) boiler was calculated and the amount of mercury was assessed both in the input solids (fuel and sorbent), as well as the gaseous and solids products (flue gas, slag, ash, gypsum and FGD waste).
Highlights
Getting rid of pollutants, such as sulfur dioxide, nitrogen oxides or particulate matter, that are emitted to the atmosphere due to the combustion processes associated with the production of electricity and/or heat has become an important issue
One of the system was equipped with wet flue gas desulphurization (FGD) facility and electrostatic precipitator (ESP).The mercury was introduced to the system with coal and limestone and the overall mercury load was estimated as 13.62 g/h
The measurements carried out downstream the ESP indicated that the amount of mercury in the flue gas decreased to roughly 8.5 mg/Nm3 and over 82% of the mercury was in the form of Hg2+
Summary
Getting rid of pollutants, such as sulfur dioxide, nitrogen oxides or particulate matter, that are emitted to the atmosphere due to the combustion processes associated with the production of electricity and/or heat has become an important issue. From the anthropogenic emission more than half of mercury compounds emitted to atmosphere is contributed by the combustion of fossil fuels since millions tons of hard coal and lignite are being burned every year to produce electricity and heat. The other boiler system investigated by Tang and Pan [8] was equipped with an SCR (selective catalytic reduction plant) to control the emission of NOx. The main source of Hg was again coal and sorbent and mercury input to that boiler system was estimated as 7 g/h. The power generating facilities were equipped with SCRs, ESPs and wet FGDs. The authors reported that the total amount of mercury was introduced with coal and its concentration in the flue gas in the furnace was about 27.3 mg/Nm3 and that the amount of Hg2+ in the flue gas downstream the SCR facility increased significantly from 3.7% to 14.7%. The intention of this paper is to provide some data on emission and balance of mercury in a 225 MW pulverized hard coal fired power generation plant in Poland
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