| 摘要 |
Process for sealing the NO compressor (3) and the residual gas expander (11) in a plant for the production of nitric acid by the dual-pressure process, including a low-pressure section (1), a NO compressor (3), a high-pressure section with oxidation and absorption (5), at least one heat exchanger (7), a residual gas expander(11), in which ammonia and compressed air are passed into the low-pressure section (1) of the nitric acid plant, where ammonia is oxidised via a catalyst to yield NO and water, the obtained NO is partly oxidised to yield NO2, the NO- and NO2-saturated gas (2) is passed into the NO compressor (3), the compressed NO- and NO2-saturated gas (4) is passed into the high-pressure section (5) of the nitric acid plant where the residual NO is oxidised to yield NO2, followed by absorption of nitrogen dioxide to nitric acid, the residual gas from the high-pressure section (6) is routed to the residual gas expander (11) via at least one heat exchanger (7), the shafts of the NO compressor (14, 15) are sealed by at least two sealing chambers (22, 23) against the gas-fed components, the shafts of the residual gas expander (12,13) are sealed by means of at least two sealing chambers against the gas-fed components, all sealing chambers are provided with labyrinth seals (25), part (10) of the residual gas (8) is withdrawn downstream of the heat exchanger (7) and subdivided into two partial flows (17, 21), the first partial flow (21) being passed into the respective first sealing chambers (14, 15) of the NO compressor (3), and the second partial flow (17) being passed into the respective first sealing chambers (12, 13) of the residual gas expander (11), and the major part of the residual gas of the two partial flows reaches the gas-fed impeller through the labyrinth seal (25) separating the gas-fed impeller (27) from the first sealing chamber (22) owing to the higher pressure level, and the residual gas (18 or 19) escaping from the respective first sealing chamber (22) into the respective second sealing chamber (23) due to leaks in the labyrinth seals is passed into the off-gas flow (20) of the residual gas expander (11). |
