Two stage downflow flue gas treatment condensing heat exchanger

A two stage downflow flue gas treatment system for treating a flue gas, comprising:

• a housing having an inlet in an upper end and an outlet in a lower end, the flue gas entering the inlet and traveling downwardly through the housing and exiting through the outlet, the housing having a first portion which is larger than a second portion, the first portion being adjacent the upper end of the housing and the second portion being adjacent the lower end of the housing;
• first tubular heat exchanger means positioned in the first portion of the housing for cooling the flue gas, the first tubular heat exchanger means including corrosion resistant tubes positioned horizontally in the housing;
• second tubular heat exchanger means positioned in the housing beneath the first tubular heat exchanger means for further cooling the flue gas, the first and second tubular heat exchanger means being mounted vertically in series in the housing, the second tubular heat exchanger means including corrosion resistant tubes positioned horizontally in the housing, the second tubular heat exchanger means being smaller than the first tubular heat exchanger means;
• alkali reagent spray means positioned above the second tubular heat exchanger means for cleaning pollutants from the flue gas;
• spray wash means located above the first tubular heat exchanger means for washing the first and second tubular heat exchanger means;
• and
• collection means in the lower end of the housing below the second tubular heat exchanger means for collecting liquids and particulate.