Removal of ammonia from a reformed fuel gas stream and replenishing acid electrolyte in a phosphoric acid fuel cell

摘要

Ammonia which is found in fuel cell fuel gases and is produced in the reformer (4) in concentrations which can adversely affect operation of a phosphoric acid fuel cell power plant is removed therefrom by passing the fuel gas stream (18) through a scrubber bed (20) of porous carbon pellets containing phosphoric acid. The ammonia reacts with the phosphoric acid in the scrubber bed to form ammonium phosphate compounds which remain in the scrubber bed. The ammonia content of the fuel gas stream is thus lowered to a concentration of about one ppm or less. By maintaining the temperature of the fuel gas stream passing through the scrubber bed in a range of about 400 DEG F to about 450 DEG F sufficient phosphoric acid will also be evaporated from the scrubber bed to replace acid electrolyte lost during operation of the power plant. Adjustments in the temperature of the fuel gas flowing through the scrubber may be made in order to match electrolyte losses which occur during different operating phases of the power plant. The scrubber (20) formed in accordance with this invention thus serves two functions, one being to remove ammonia from the fuel gas stream, and the other being to replenish electrolyte lost in the power plant during normal operation thereof.