Method for separation of sulfur dioxide from gases

Abstract

To prevent the formation of encrustations on a pH sensor in a combustion exhaust or flue gas washing apparatus, alkaline additives are added to the wash water which, upon contacting SO.sub.2 in the gases, form sulfite particles. The sulfite particles are prevented from depositing at the bottom of a collection vessel (11) in form of a mud, and, in accordance with the invention, rather are continuously stirred and recirculated in a closed recirculation loop to a spray device (25). The particles, upon being recirculated, will grow to form a granulate which, eventually, will deposit, the granulate, however, being constituted by granules substantially in excess of those which form a mud; the larger granules also prevent deposition of encrustations along the walls, and, for example, a pH sensor (47). The washing liquid within the tank or vessel 11 can be held in continuous turbulence or agitated form by a stirrer (53) coupled for example to the shaft of an immersion pump (21), an additional stirrer, by a recirculating fluid injection nozzle (57) or by directing run-off sprayed water into the tank by a direction and collection vane (28). Preferably, oxygen is excluded from the gases to prevent the formation of sulfates, and the washing liquid is held at a temperature below 40.degree. C. by a suitable heat exchanger which can supply hot utility water. A preferred pH is between 6 to 6.5.

Dependencies are inferred from the claim text.