Patent ID: 7288128

Claim:
A thermal mixing method for reducing overall temperature of flue gas supplied to a fabric having a maximum temperature tolerance, from at least two spray dry absorbers which are each operable to cool flue gas passing therein, the method comprising: providing a housing having a first inlet passage for flue gas from a first spray dry absorber, a second inlet passage for flue gas from a second spray dry absorber, an outlet passage for supplying flue gases from the first and second spray dry absorbers to a fabric filter, and a mixing passage between the inlet passages and the outlet passage, the mixing passage having an axis; providing a plurality of damper vanes extending at least partly across the mixing passage and having a mixing position for mixing together the flue gases from the first and second inlet passages to supply mixed gas to the outlet passage at relatively high pressure drop in the mixing passage, the vanes having a non-mixing position for passage of the flue gases from the first and second inlet passages without mixing to supply unmixed gas to the outlet passage at relatively low pressure drop, the vanes in the non-mixing position being parallel to, and spaced from each other, with each vane lying in a plane that is parallel to the axis of the mixing passage in the non-mixing position and each vane extending from a bottom to a top of the mixing passage and the vanes being spaced from each other horizontally across the mixing passage; moving the vanes to the mixing position when one of the spray dry absorbers is not operating to cool flue gas passing therein so that the temperature of the mixed flue gas is intermediate the temperature of the flue gas that has been cooled and the flue gas that had not been cooled; and moving the vanes to the non-mixing position when the first and second inlet passages both receive cooled flue gas.