The ultra-fine particle removal performance of a wet electrostatic precipitator for oxy-fuel combustion

Hak-Joon Kim(1), Bangwoo Han(1), Won-Suk Hong(1), Wan-Ho Shin(1), Sang-Hyun Jeong(1), Sung-Hoon Shim(1), Yong-Jin Kim(1)

(1) Korea Institute of Machinery and Materials (KIMM), Daejeon, South Korea

     Abstract Number: 313
     Last modified: May 6, 2010

Abstract
The removal of ultra-fine particles in CO2-enriched environments which are resulted from oxy-fuel combustion has been very important for CCS (Carbon Capture and Storage) because the tolerances of total concentration of particulates from the oxy-fuel combustion for CCS should be less than 10 mg/Nm3 or 0.1 mg/Nm3. In order to meet these limits, several research groups suggested the application of wet-type electrostatic precipitators (ESP) downstream of dry ESPs or a FGD (Flue Gas Desulfurization) system in gas clean-up systems for CCS.
In this study, the electrical and ultra-fine particle removal performance of a wet ESP with rigid discharge electrodes was evaluated in CO2 rich condition. The collection plates of the wet ESP using fabrics, smooth stainless steel plates, sand-blasted stainless steel plates, and the stainless steel plates coated with TiO2 nano particles were compared in order to find out the most efficient collection plates of the wet ESP which consume minimum water for the uniformly wetted film on the collection plates. 5 L/min/m2 of water was supplied onto the collection plates (200 mm x 200 mm) from two tubes with the length of 200 mm, the diameter of 6 mm, and the pin holes of 0.5 mm diameter and 1 mm gap. Negative high voltage (0~-30 kV) was applied to the electrodes of the wet ESP, and discharge current was measured with and without water supply, respectively. For the particle removal efficiency test, the potassium chloride (KCl) ultrafine submicron particles with a mean diameter of 100 nm were used as test aerosols, and the particle collection efficiency of the ESP was measured by comparing the downstream particle number concentration with the upstream number concentration, both measured using a scanning mobility particle sizer (SMPS, Model 3936, TSI). Face velocity through the ESP was 1 m/s and the gas composition was 70% CO2, 15% N2 and 5% O2.
The stainless steel plates with sand-blasted surface formed uniform water film, while smooth stainless steel plates and fabrics had dry area on the surface with the water supply of 5 L/min/m2. However, after coated with the nano particles, the stainless steel plates showed similar hydrophilic property, regardless of their surface conditions. The voltage-corona current curves of the ESP with and without the water film were almost the same due to the relatively thin thickness of the water film less than 0.5 mm. The removal efficiencies of the wet ESP for the particles ranged in submicron meter were more than 90 % at 1 m/s using approximately 11.8 W of power consumption, and kept continuously due to the self cleaning of the collection plates.
From the results, it can be concluded that surface treatment such as sand-blast and nano particle coating can reduce the amount of water waste from wet ESPs, and a water film can maintain electrical property and high removal efficiency of the ESP against ultra-fine particles from Oxy-fuel combustion.