| 摘要 |
Exhaust gases are fed into a first gas-solid separator (12), where most of the HCl and SOx are trapped. The partially purified gas is mixed with a denitrification reactant and sent to a catalytic reactor. The denitrified gases are cooled and fed to a second gas-solid reactor also fed with a neutralization reactant. The solids collected here are recycled to upstream of the first separator. The exhaust gases to be purified (1, 2) are fed at between 180 and 300[deg]C, preferably between 200 and 250[deg]C, into a first gas-solid separator (12) of filter or electrofilter type in which at least 70% of the HCl, at least 50% of the SO2 and at least 60% of the SO3 are captured. The partially purified gases (3) are mixed with a denitrification reactant (4) and the mixture is fed to a selective catalytic denitrification reactor (13). The denitrified gases (6a) are cooled (14) to bring them to a temperature between 90 and 180[deg]C, preferably between 120 and 150[deg]C. The cooled gases (6) are fed into a second gas-solid separator (15) which is also supplied with a neutralization reactant (7), such as chalk, magnesium, sodium carbonate or sodium bicarbonate. At least a major part of the solids collected in the second separator are recycled (9) to upstream of the first gas-solid separator. The exhaust gases to be purified (1) are sent to a device protecting against incandescence (11) such as an anti-spark drum or cyclone, before feeding them to the first separator, and the solids from the second separator are recycled to upstream of this protection device. A small fraction (less than 30%, preferably less than 20%) of the solids collected by the second separator are removed (by 9') upstream of the first separator. The denitrified gases are cooled by water evaporation (5). Some of the solids collected in the first separator are recycled to upstream of the first separator. A small amount (7') of neutralization reactant is admitted into the first separator at the same time as the exhaust gases to be purified. An independent claim is made for an installation to carry out the above process. |
