Abatement of Fine Particle Emissions from a Coal-Fired Power Plant Based on the Condensation of SO₃ and Water Vapor

Abstract

A new process was proposed to reduce fine particle emissions in coal-fired flue gases via the condensation of SO3 and water vapor. In this new process, hot atomized water was sprayed before the electrostatic precipitator (ESP) system to decrease the flue gas temperature and increase the flue gas humidity, causing the flue gas temperature to drop below the acid dew point; thus, SO3 would condense on the particle surfaces ahead of the ESP, which would enhance the fine particle removal efficiency of the ESP. Then, a fluoroplastic heat exchanger was located between the ESP and the wet flue gas desulfurization (WFGD) system to make the WFGD inlet flue gas temperature decrease further at a high humidity, leading to the condensation of water vapor on the particle surfaces in the desulfurization scrubber, which would improve the removal efficiency of the WFGD. The feasibility of this new process was analyzed by numerical calculation, and the results showed that the new process was feasible for the original flue gas with high SO3 concentrations, high temperature, and high humidity. The effectiveness of this new process under typical operating conditions was also presented. Furthermore, the influence of several main parameters, such as the SO3 concentration of original flue gas, the temperature drop of flue gas before the ESP, and the temperature of flue gas at the WFGD inlet, were also investigated. The results indicated that the fine particle emissions in the final exhausted flue gas would be reduced by 50–70% with this new process.

Removal Characteristics of Sulfuric Acid Aerosols in the Wet Electrostatic Precipitator System

“…After the slurry scrubbing in the spray scrubber, the relative humidity of the flue gas could reach 100%. With the decrease of the gas temperature, the water vapor turned to be supersaturated and condensed onto the sulfuric acid aerosols, which made these aerosols grow larger . The removal efficiency of the WESP system was relevant to the particle/droplet sizes, and the larger size was beneficial for the removal process.…”

Formation and Emission Characteristics of Ammonium Sulfate Aerosols in Flue Gas Downstream of Selective Catalytic Reduction

“…The SO 4 2– concentrations of the condensate were analyzed with an ion chromatograph analyzer (ICS-2100, Dionex Ltd., U.S.A.). Using the sampling volume of the flue gas and the concentration of SO 4 2– in solution, the concentrations of SO 3 were calculated. , …”

Validation and Accuracy Study of SO₃ Detection Using the Controlled Condensation Method

“…The sampling system of CCM consists of three main components, namely sampling gun with heating and filtering unit, condenser tube and water bath unit, and flue gas sampling device [26], as shown in Fig. 1.…”

“…CCM mainly uses the principle of physical adsorption. After the flue gas temperature decreases, SO 3 condenses into acid mist, which is then collected by centrifugal force [26]. The applied range of the CCM is relatively wide.…”