SEALING OF NO COMPRESSOR AND RESIDUAL GAS EXPANDER IN NITRIC ACID PLANT Russian patent published in 2013 - IPC C01B21/28 

FIELD: chemistry.

SUBSTANCE: invention relates to a method and a corresponding apparatus for sealing a NO compressor and a residual gas expander using residual gas in a plant for production of nitric acid via a dual-pressure process. The plant has a low-pressure stage (1), an NO compressor (3), wherein the shafts (14, 15) of the NO compressor are sealed from components exposed to the gas by means of at least 2 sealing chambers, a high-pressure stage (5) with oxidation and absorption, a heat exchanger (7), a residual gas expander (11), wherein the shafts (12, 13) of the expander are sealed in the same manner as shafts (14, 15), and all sealing chambers have labyrinth seals. In the method, ammonia and compressed air are fed into stage (1), where ammonia is oxidised to NO and water by means of a catalyst. The resultant NO is partially oxidised to NO₂. The resultant NO- and NO₂-saturated gas is fed into the NO compressor (3). The compressed NO- and NO₂-saturated gas is fed into stage (5) where oxidation of the residual NO to NO₂ takes place, followed by an absorption of nitrogen dioxide to form nitric acid. The residual gas (6) from the stage (5) is fed via the heat exchanger (7) into the expander (11), wherein the first sealing chamber lies next to the rotor of the compressor (3) which is exposed to the gas and, respectively, the expander (11). A portion (10) of the residual gas (8) after the heat exchanger is taken off and divided into 2 substreams (17, 21). The first stream (21) is fed into the respective first sealing chambers of the NO compressor (3), and the second stream (17) is fed into the respective first sealing chambers of the expander (11). A large portion of the residual gas of the substreams, owing to a higher pressure level, passes through the labyrinth seal separating the rotor exposed to the gas from the first sealing chamber to the rotor exposed to the gas. The residual gas (18 or 19) passing from the respective first sealing chamber into the respective second sealing chamber through leaks in the labyrinth seal passes into the exhaust gas stream (20) of the expander (11). The result is reliable sealing of the apparatus, wherein there is no need to fed any additional gas for sealing.

EFFECT: more efficient operation of the apparatus.

7 cl, 2 dwg, 1 ex