Patent ID: 7691349

Claim:
A method of treating exhaust gas in an exhaust gas processing device comprising: preheating air for combustion in a combustion device by using exhaust gas emitted from the combustion device; recovering heat of the exhaust gas at an outlet of an air preheater to a heat medium; collecting dust in the exhaust gas at an outlet of a gas-gas heater heat recovery device using a dust collector; removing sulfur oxide in the exhaust gas at an outlet of the dust collector; heating the exhaust gas at the outlet of a wet-type desulfurization device by using the heat medium supplied from the gas-gas heater heat recovery device; connecting heat transfer tubes provided in each of the gas-gas heater heat recovery device and the gas-gas heater re-heater; and circulating the heat medium through the heat transfer tubes; squarely arranging the heat transfer tube of the gas-gas heater heat recovery device in the gas flow direction in such a manner that the inter-tube flow rate, which is the flow rate of the exhaust gas between the heat transfer tubes adjacent in the direction orthogonal to the gas flow direction, can be less than or equal to approximately 10 m/s, wherein at least some of the heat transfer tubes of the gas-gas heater are fin-equipped heat transfer tubes, and the fin pitch of the heat transfer tubes of the gas-gas heater heat recovery device is set at approximately 7.25 to approximately 10.16 mm, and the fin pitch of the heat transfer tubes of the gas-gas heater re-heater is set at approximately 6.35 to approximately 8.47 mm.