Patent ID: 7381389

Claim:
A wet gas purification method for removing ammonia from a coal or heavy oil gasification gas, the method comprising: a water-washing step comprising a gas cleaning step and a gas cooling step which is carried out upstream of the gas cleaning step in a gasification gas flow direction, wherein an amount of absorbent make-up water for absorbing ammonia is charged into the coal or heavy oil gasification gas in the gas cleaning step, part of the absorbent used in the gas cleaning step is sent to the gas cooling step such that ammonia is absorbed into the absorbent to be removed from the gasification gas in both the gas cooling and the gas cleaning step, and at least a portion of the absorbent make-up water is discharged from the washing step; and an ammonia treating step for stripping ammonia from the absorbent make-up water discharged after the water-washing step to separate the discharged absorbent make-up water into an off-gas containing ammonia and an effluent, wherein the amount of absorbent makeup water charged in the gas cleaning step is controlled so that the concentration of ammonia in the gasification gas after the gas cleaning step is 10 ppm or lower.