Patent ID: 6863875
Filing Date: 2005-03-08
Classification: B01D

Abstract:
1. A flue gas treating process for treating a flue gas comprising nitrogen oxides and sulfur oxides, the process comprising: denitrating the flue gas with a denitrator; injecting ammonia into the flue gas prior to introducing the gas into an absorption tower, wherein the amount of ammonia is injected in such a quantity that an excessive level of ammonia or an ammonium salt will remain in the flue gas when the flue gas is subsequently contacted with an absorbing fluid; introducing the flue gas into an absorption tower; and desulfurizing the flue gas in the absorption tower by contacting the flue gas with the absorbing fluid, wherein the absorbing fluid absorbs sulfur oxides, spraying the flue gas with a liquid having a higher acidity than the absorbing fluid, wherein the spraying is done downstream of the desulfurization step and in the absorption tower, whereby ammonia remaining in the flue gas is absorbed in the absorption tower, recovering heat from the flue gas, heating the flue gas leaving the absorption tower to a temperature favorable for emission into the atmosphere by using at least a part of the heat recovered in the heat exchanger; and pressurizing the flue gas with a fan, wherein pressure loss in the absorption tower or reheating section is counter acted, wherein the absorption tower, the reheating section and the fan are arranged together on a vertical axis in the form of a stack and wherein the amount of ammonia injected is at a concentration so that the amount of ammonia remaining in the flue gas after the injection step will be not less than 30 ppm.