Abstract: A system for processing hot flue gas to remove both gaseous contaminants such as sulfur dioxide and particulate matter such as flyash integrates spray scrubbing apparatus and wet electrostatic precipitation apparatus and provides for the advantageous extraction and utilization of heat present in the flue gas. The integrated system utilizes a spray scrubbing tower and a wet electrostatic precipitator which includes a portion constructed as a cross flow heat exchanger with flue gas saturated with water vapor moving vertically upwards inside tubes arranged in a staggered pattern and ambient air being pulled horizontally across the outside of those tubes to cool the tube walls and thereby remove heat from the flue gas and cause condensation of water vapor on the inside wall surfaces. The condensate washes the electrostatically collected flyash particles down from the inside tube walls.