Small scale pellet boiler gas treatment in fog unit
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ORIGINAL RESEARCH
Small scale pellet boiler gas treatment in fog unit Dagnija Blumberga1 · Vivita Priedniece1 · Elvis Kalniņš1 · Vladimirs Kirsanovs1 · Ivars Veidenbergs1 Received: 10 June 2020 / Accepted: 5 September 2020 © Islamic Azad University 2020
Abstract The current research is aimed at experimentally finding out characteristic parameters of the operation of the fog unit and their effect on the efficiency of particulate matter capture. To conduct the experiment, a laboratory equipment—fog unit— was designed and prepared. The fog unit is suitable for 10, 20 and 30 kW pellet boilers. The impact of the parameters on essential changes of indicators important for PM capture is described: sprayed water and gas contact surface; droplets and gas contact time in the unit; droplets holdup in the unit. In the process, a regression equation for predicting the effectiveness of PM capture in a direct contact fog unit is obtained. A good experimental and calculated data correlation is observed (adjusted R squared statistics is 85.32%). Keywords Air pollution · Wet scrubber · Performance evaluation · Particulate matter · Droplet · Pellet boiler Abbreviations ω1, ω2 Inlet and outlet moisture content, kg/kg dry gas Cp1, Cp2 Inlet and outlet PM concentration in flue gas, mg/Nm3 ΔCp PM reduction, % dd Diameter of a droplet, m dd0 Initial diameter of a droplet, m Fd Total droplets surface area, m2 g Water volumetric flow rate, l/s Gb Boiler water flow rate, m3/h Gw Water volumetric flow rate, l/h H Height of the unit, m Hd Droplets holdup of the unit Mf Fuel consumption, kg//h O2 Oxygen concentration in flue gas, % Of Fuel lower heating value, MJ/kg Ofu Fog unit capacity, kW Ob Boiler capacity, kW tb1, tb2 Boiler water input and output temperature, °C tg1, tg2 Gas inlet and outlet temperature, °C tw Water temperature, °C tw1, tw2 Inlet and outlet water temperature, °C ud Droplet velocity, m/s ug Gas velocity, m/s * Vladimirs Kirsanovs [email protected] 1
Institute of Energy Systems and Environment, Riga Technical University, Azenes iela 12/1, Riga 1048, Latvia
ug2 Outlet gas velocity, m/s ur Settling velocity of a droplet in relation to gas, m/s Vw Water volumetric flowrate, m3/s Vg Gas volumetric flowrate, m3/s S Cross-sectional area of the unit, m2
Introduction Biomass combustion has been used as energy source since prehistoric times, nowadays it is coming “back in style” as a climate neutral alternative to fossil fuels. However, there are several issues that cannot be overlooked. One of them is emissions in the air. While biomass is considered C O2 neutral in comparison with fossil energy sources, its combustion results in higher particulate matter (PM) emissions than other fuels. Flue gas from biomass combustion contains or can contain particles of ash, tar, soot, char and possibly other residues depending on specific conditions such as fuel, combustion conditions and other. It also contains various gaseous substances: sulphur oxides (SOx), nitrogen oxides (NOx), carbo
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