Sulphur di:oxide removal from exhaust gas streams - having scrubbing liquor in which pH is controlled by use of mineral and organic acid(s) and to which calcium carbonate is added

摘要

Exhaust gases are purified by a crubbing operating which involves contacting the gases with a circulating liquor. This liquor contains Ca ions, a mineral acid e.g. HCl and a buffer in the form of an organic acid e.g. formic or acetic acid. This causes SO2 to be absorbed as sibulphite which is later oxidised to SO4. Solic Ca(CO3)2 as crushed limestone slurry, is added to the liquor and the pH is controlled in the range 2.5 to 6. Used to remove gases such as SO2, NOx and HF from exhaust gas streams. The process and plant complexity and also the vol. of liquor needed, is reduced.