| 摘要 |
A process is described for separating SO2 from a moist current of gas containing the same, at least intermittently, in a concentration which is impermissibly high for discharge into the ambient atmosphere, with attendant production of a strong sulfuric acid by the nitrogen oxide process in a system of reaction zones, in which system the SO2-containing gas flows successively through a denitration zone, thereafter through the SO2-processing zone, and subsequently through a nitrogen oxide absorption zone, in the course of which flow it is brought into contact, at least in the SO2-processing zone, with dilute acid having an H2SO4-concentration of less than 70% by weight and flowing in a cycle through the latter zone, and wherein said nitrose containing acid is indirectly heated, prior to its introduction into said denitration zone to a sufficient temperature for freeing the latter acid substantially completely from nitrogen-oxygen compound, whereby the acid leaving said denitration zone has an H2SO4-content of at least about 75% by weight, thus being withdrawable as product acid; wherein the nitrogen oxides withdrawn from the said nitrose-containing acid into the current of gas are absorbed by nitrose-free or nitrose-poor sulfuric acid having an H2SO4-concentration between 70 and 85% by weight, from said denitration zone; and bringing a moist current of said SO2-containing gas in a pretreatment zone upstream of said denitration zone into contact with a portion of said dilute sulfuric acid removed from the circulation through said SO2-processing zone and passed into the pretreatment zone, the resulting acid more diluted by moisture from said gas being reintroduced into said circulation, thereby diluting the sulfuric acid formed in the SO2-processing zone, this portion of the moisture content of the SO2-containing gas thus bypassing the gas flowpath leading to the denitration zone.
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