Case Number 095021 - Heat-Exchanger/Wet-Film Electrostatic Precipitator for Flue Gas Cleaning

Contact: Geoffrey Pinski
Phone: 513-558-5696

Description:  This process involves two sections of electrostatic precipitator (ESP): the collection plates of the first section act as heat exchanger plates where simultaneous cooling and particle collection are taking place, and the collection plates of the second section are covered with wet film of water flowing downward where simultaneous condensation and collection of acid neutralization products are taking place.

The purpose of the first section is to simultaneously remove particles (mostly flyash) and recover heat, and yet to maintain a dry condition preventing corrosion in the system. The temperature of the first section is maintained at between 5 and 300F above saturation. To prevent collection of sulfur trioxide and other acidic compounds on the collection plate, a small amount of calcium hydroxide or equivalent caustic material(s) (e.g., ammonia gas) up to a 10% of acid molar amount is injected upstream of the first section. It is expected to achieve almost a complete removal of flyash and solid particles at this section.

An equimolar amount of gaseous ammonia and/or fine powders of other alkaline materials is injected between the first and second sections. The alkaline compounds quickly react with sulfur dioxide, sulfur trioxide and various forms of nitric oxides, and the reaction products in the form of fine particles are electrostatically charged by high voltage wires and effectively collected by the wet collection plates of the second section. The collected reaction products on the collection plates are carried down and dissolved by the water flowing down from the top of the plates. Up to a 98% removal of acidic gas components is expected. The bottom pool of product solution is pumped out for further treatment and water recycling. The advantages of this invention over the established art are as follows:
  1. Low gas-phase pressure drop.
  2. Low liquid pumping cost.
  3. High removal efficiency of sulfur oxides and nitric oxides.
  4. High removal efficiency of particles.
  5. Heat recovery.
  6. Water recovery from flue gas.

US Patent # 7,022,296 - Method for treating flue gas, issued on April 4, 2006