Flue gas is a by-product of many energy and industrial plants and is typically emitted through a
chimney stack. If the
flue gas temperature in the
chimney stack drops below the
flue gas
dew point, condensation of
water vapor and acid gases ensues. These gases are very corrosive for
chimney stacks designed to operate in a dry condition. The
Flue Gas Reheat
System of the present invention continuously and proactively manages
flue gas chimney stack temperatures above the
dew point in order to optimize emission control and effectuate energy efficiency improvements in industrial plants.
Waste heat is harvested from the exterior surfaces of existing steam and
pollution control equipment through conduction,
convection and
radiation. This heat is transferred to a
working fluid. The
working fluid is then directly mixed with the
flue gas prior to the
flue gas entering the chimney stack to raise the temperature of (or re-heat) the
flue gas above its
dew point to maintain a dry chimney stack condition. The use of residual or
waste heat from throughout the
plant and the minimal equipment required to harvest the
waste heat reduces the
operating cost and improves the overall reliability of the
system. This method is useful in many industries, including
electric power generation plants and other energy intensive process industries that seek emission control and various boiler and fuel energy efficiency improvements, many of which improvements result in a reduction in normal chimney stack temperature.