| abstract |
In flue gas purification, SO2, HCl and HF are separated by a circulating washing fluid which contains calcium ions, consumed calcium ions being replaced by addition of lime, so that calcium sulphate is formed as the end product. The process is less suitable for separating nitrogen oxides likewise contained in the flue gas. For this purpose, the gas is passed, after the desulphurisation, through a droplet separation device, to the first stage of which is supplied an oxidising agent, for example sodium hypochlorite solution, while an alkaline washing water, for example weak ammonia water, is supplied to a second stage. Both liquids are trapped together and conducted into a circulation tank and from there into a stripper column, in which the chemically bound ammonia is released, so that the liquid can be reused as washing water. |