| 摘要 |
The present invention provides a method for purifying exhaust gas, in which nitrogen oxides (NOx) are removed from the combustion exhaust gas of, e.g., a marine diesel engine or other internal combustion engine, wherein: the denitrification performance of a denitrification catalyst can be expected to be improved not only by using the water content of the exhaust gas, but also by a further addition of moisture when an alcohol is used as a reducing agent; the durability of the NOx-removal catalyst can be sufficiently improved; and using a low-concentration alcohol aqueous solution that does not require handling as a hazardous substance by reducing the concentration of the alcohol aqueous solution and using the reduced-concentration alcohol aqueous solution, when, for example, the alcohol is loaded on a ship, whereby the method for purifying exhaust gas does not require an increase in the cost of the denitrification equipment and has excellent practical utility. The method for purifying exhaust gas according to the present invention is characterized in that water vapor is further added to the raw exhaust gas to be processed, and a moisture-adjusted exhaust gas in which the concentration of water vapor in the exhaust gas has been increased is introduced into a denitrification catalyst layer. The concentration of water vapor in the moisture-adjusted exhaust gas is preferably 22.0 vol% or less relative to the total of the water vapor already contained in the raw gas, and the added water vapor. |
