Three stream purification of flue gas - using dry wet and by=pass streams in combination according to sulphur content

摘要

In the Parent patent (describes a method of flue gas purification in which) 50% of the flow is dry purified after the electrostatic filters and 50% is wet purified; absorption agent is added in excess of the stoichiometric quantity in the dry stage and is utilised in the wet stage. The dry purified is mixed with the wet purified gas to discharge into the chimney at above the dew point of SO2. In this addition, the hot, dry flue gas purification stream is tapped from the boiler at above 350 deg.C, the wet gas purification stream is tapped behind the normal boiler outlet, i.e. behind an air preheater, pref. behind an electrostatic filter; a bypass leads upstream of the inlet to the wet gas purification stream but downstream of the electrostatic filter to conduct untreated gas directly to the gas mixing chamber; here it is mixed with the hot gas from the dry side and the cooler gas from the wet side. Desulphurisation in accordance with modern regulations can be achieved. The tapping of gas to form an additional, third stream as well as the dry and wet purification streams can be varied according to the amount of sulphur to ensure the correct temp. at discharge into the chimney.