Methods for the recovery of sulfur components from flue gas and recycle sodium sulfite by reduction-smelting and carbonating to strip hydrogen sulfide

摘要

An improved method for recovering sulfur from flue gas which contains sulfur dioxide formed from burning sulfur containing fuels. The method first involves the reduction burning of auxilary fuel in the presence of sodium sulfite to convert it to smelt containing sodium sulfide and sodium carbonate. The smelt is dissolved, and the solution reacted with carbon dioxide, hydrogen sulfide and water vapor forming sodium hydrosulfide. The sodium hydrosulfide is reacted with a high concentration of recycled sodium bicarbonate and stripped with carbon dioxide to form sodium carbonate and release the sulfides as hydrogen sulfide from the stripper. The hydrogen sulfide released is then converted to sulfur dioxide, sulfuric acid or elemental sulfur. Pressurized carbon dioxide is used for pressure carbonation of recycled solution from the stripper to convert the sodium carbonate to the high concentration of recycled sodium bicarbonate used for stripping. The sodium carbonate and sodium bicarbonate from the stripper are reacted under pressure with sodium bisulfite in a decarbonator to form sodium sulfite and release carbon dioxide under pressure for use in the pressure carbonation. A portion of the sodium sulfite formed by decarbonation is then reduced in the smelter. The balance of the sodium sulfite is then used for absorption of the sulfur dioxide from the flue gas forming the sodium bisulfite used for decarbonation.