Numerical Simulation Of Airflow Distribution In Ultra-high Plate ESP Of Thermal Power Plant

"Emission standard of air pollutants for thermal power plants" GB13223-2011, which is implemented in January 1st,2012, has stipulated that the dust emission concentration of coal-fired boiler in thermal power plant shall not exceed 30mg/Nm3 and the dust emission concentration of some exceptional key areas be limited to be under 20mg/Nm3. The introduction of this standard leads to a higher technical requirements for the modification of old thermal power plant electrostatic precipitator equipment. During the modification process of the old thermal power plant the ESP equipment, being subject to the constraints of the original dust collection site, the dust collector body can not be lengthen or broaden. Therefore, the application of heightening the electrostatic precipitator body and installing high plate or ultra-high plate, in order to increase the effective collecting area, has gradually become effective measures to improve the dust collection efficiency of the old-fashioned ESP. The increase of ESP plate’ height will produce complex influence on airflow distribution of dusty gas inside the electric field, while the airflow distribution of dusty gas has a great impact on the dust collection efficiency of ESP.This paper is aiming to conduct a numerical simulation on airflow and temperature distribution inside the ultra-high plate ESP by using the software Fluent. The distribution plate setting schemes, under the best circumstance of airflow distribution in ESP with different plate height, have been achieved by changing holing layout and holing rate in the air distribution plate and setting the modular air distribution plate etc. The numerical simulation result of the airflow distribution shows that:with the increase of the plate’ height, the airflow distribution inside the electric field tends to be uneven; the plate height is in direct proportion linear relationship with relative root mean square value of airflow velocity; in installing a single-layer air distribution plate, the distribution plate in the shape of "回" is more conducive to improving the uniformity of the air distribution than in the shape of "目"; in installing double-layer air distribution plate, combining the shape of "目&回" is more conducive to improving the uniformity of the air distribution; in installing triple-layer air distribution plate, the shape of "目&目&回" is more conducive to improving the uniformity of the air distribution; This paper has established the plate height in 18m,20m and 24m, in which the airflow distribution of ESP-model is able to meet the engineering and technical requirements, through changing different holing layouts and holing rate and setting the modular air distribution plate etc. Therefore, It is technically feasible to apply ultra-high plate into improving the dust collection efficiency during the modification process of the old-fashioned ESP equipments. The numerical simulation result of the temperature distribution shows that:when high-temperature dusty gas enters the ESP, the temperature will be in a downward trend with the dusty gas flowing from front to back in the horizontal plane, from up to down in the vertical plane; with the increase of the plate’height, the downward trend of the dusty gas temperature is becoming increasingly obvious. The numerical simulation result of this subject can provide a reference for the design and modification of ultra-high plate ESP.