Wet electrostatic precipitator

Application

Wet electrostatic precipitator (WESP, wet ESP) is dust collection device widely used for thermal power plant, cement plant, sulfuric acid making plant, metallurgy furnace & smelter, chemical plant, etc. WESP could effectively collect and remove fine particles, aerosol, tar, resin, oil, mist suspended in flue gas or tail gas. Different with dry ESP, wet ESP performance is not influenced by moisture content of gases, it could be used to process saturated air stream.

Why we need wet electrostatic precipitator?

1. For wet flue gas desulfurization process without GGH, exhaust gas leaving scrubber is around 50℃ only. Dew point corrosion caused by SO3 to stack is serious, even stack is specially treated.
2. Flue gas after FGD contains lots of liquid droplets, aerosol, sulfuric acid mist, fine partciles. These wet gases would condensate and form plume after leaving stack.
3. For coal fired power plant, WESP could prevent so called “gypsum rain” phenomenon.

Working principle

Wet electrostatic precipitator has tubular design and poly-stage design. Both of them have the same principle. Collecting electrodes and discharge electrodes are charged with high voltage DC current. In the strong electric field, air molecules close to discharge electrodes are ionized by corona discharge and carry negative charge. When drity airstream enters WESP, the particulates will be electrically charged by catching some ions. Then these particulates will move towards grounded collecting electrodes oppositely charged. Particulates are collected on plates or rectangular tubes and washed off.

Plate configuration VS Tubular configuration

Plate precipitator consists of many parallel collecting plates usually made of carbon steel or stainless steel. The steel can’t stand the corrosion perfectly, so continous water washing is required to form water film on steel plates to protect against corrosion. An additional water treatment system is required.

Tubular precipitator has vertical honeycomb-alike collecting electrode made of FRP or PVC. These materials are featured with good electricity conductivity, low weight, excellent anti-corrosion performance, long service life. Intermittent water washing is enough. Dirty water could be discharged into WFGD water system. So compared with plate precipitator, it consumpes much less water and doesn’t require additional water treatment system.

Wet electrostatic precipitator could effectively remove SO3, fine particles (PM2.5), liquid droplet, sulfuric acid mist to control pullutant emission, furtherly, it can greatly relieve vapor plume, gypsum rain, stack corrosion. Now we have successfully supplied wet electrostatic precipitator for 300MW, 600MW, 1000MW thermal power plants.