Patent ID: 7776305
Filing Date: 2010-08-17
Classification: C01B

Abstract:
1. A method of purifying nitrogen oxides, comprising: an initial absorption step for applying a first absorption solution containing liquefied dinitrogen tetraoxide to a source gas containing nitrogen monoxide, to cause the first absorption solution to absorb nitrogen monoxide; an additional absorption step performed in parallel with the initial absorption step, the additional absorption step including applying a second absorption solution containing liquefied dinitrogen tetraoxide to an unabsorbed gas remaining unabsorbed in the first absorption solution through the initial absorption step, to cause the second absorption solution to absorb nitrogen monoxide in the unabsorbed gas; a revaporization step for heating and/or depressurizing the first and second absorption solutions after the additional absorption step, to generate an intermediate gas from the first and second absorption solutions, the intermediate gas containing a larger amount of nitrogen monoxide and a smaller amount of nitrogen dioxide; and a condensation-separation step for cooling and/or pressurizing the intermediate gas to convert nitrogen monoxide and nitrogen dioxide into condensed dinitrogen trioxide and/or condensed dinitrogen tetraoxide, the conversion of nitrogen monoxide including a reaction of nitrogen monoxide with nitrogen dioxide for conversion into the condensed dinitrogen trioxide, a non-condensed portion of the intermediate gas being separated from the condensed dinitrogen trioxide and/or the condensed dinitrogen tetraoxide for recovery.