Refrigeration – Processes – Circulating external gas
Patent
1993-06-11
1995-06-06
Capossela, Ronald C.
Refrigeration
Processes
Circulating external gas
62 21, 62 37, F25J 300
Patent
active
054211638
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
(a) Field of the Invention
The present invention concerns the combined production of nitrogen and oxygen with adjustable flows, of the type utilizing an initial separation of air to produce a substantially pure flow of nitrogen and a flow of oxygen enriched residual gases, with subsequent purification treatment.
(b) Description of Prior Art
This production which is generally carried out by cryogenic distillation necessarily leads to the production of nitrogen and oxygen flows which are within well determined relative proportions, the flow of nitrogen being of the order of 2, 5 times the flow of oxygen except, of course, that two separation units which are independent from one another must be provided, which is very costly.
SUMMARY OF INVENTION
The aim of the present invention is to ensure the combined production of nitrogen and oxygen with adjustable flows starting from an initial separation of air, with addition of supplementary separation means representing moderate investment and maintenance costs, and this object of the invention is achieved by treating said residual gases, to which a complementary flow of air is possibly added, by adsorption to give an adjustable flow of substantially pure oxygen. It will be understood that this arrangement, which treats residual gases that have already been enriched in oxygen is less costly than a supplementary treatment of atmospheric air, while presenting an important flexibility of control of the respective flows of nitrogen and oxygen.
According to an embodiment, the treatment by adsorption is carried out at the pressure of the residual gases which are derived from the initial separation of air, while the regeneration of the adsorber is carried out at a truly inferior pressure, possibly under vacuum if the pressure of the residual gases from the initial separation is not much higher than atmospheric pressure. According to a variant, the residual gases from the initial separation of air are compressed again before treating them by adsorption.
Generally, the initial separation of air is a cryogenic distillation which is preceded by a drying-decarbonizing step, and in such a case: remainder being used as regeneration gas carrier in the drying-decarbonizing of the air to be treated by cryogenic distillation; cryogenic distillation is used to regenerate the drying-decarbonizing before being treated by adsorption and, advantageously by drying-decarbonizing; cryogenic distillation is directly treated by adsorption, the oxygen produced by adsorption being used as regeneration gas carrier for drying-decarbonizing the air intended to be treated by cryogenic distillation.
The invention also concerns an apparatus for carrying out the above process .
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be illustrated with reference to the annexed drawings in which:
FIGS. 1 to 3 are three variant embodiments of a production apparatus according to the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to FIG. 1, an apparatus comprises a unit for production by cryogenic distillation 1 including an inlet for air to be separated 2 which is connected via a double dryer-decarbonizer, 3, 4 to a cooler 5 downstream of an atmospheric air compressor 6. In usual manner, when a dryer-decarbonizer 3, (4) is in operation, the other 4, (3) is being regenerated by means of a hot carrier gas.
The distillation unit 1 includes an outlet for pure nitrogen produced 7 and an outlet for residual gases 8, having an oxygen content, between 30 and 60%, for example of the order of 42%. The outlet for residual gases 8 is connected on the one hand via a heater 9 to an "outlet" 10 of a dryer-decarbonizer 3 or 4 in the process of being regenerated, in which an "inlet" 11 constitutes the outlet of the regeneration gas carrier loaded with water and carbon dioxide, on the other hand via a duct 12 including possibly a compressor 13 to either inlet 14, 15 of a unit for separation by adsorption 16 including two adsorpers 17, 18 with molecular sieves which preferably a
REFERENCES:
patent: 3267645 (1966-08-01), Simonet
patent: 3421984 (1969-01-01), Jensen et al.
patent: 3912476 (1975-10-01), Mikawa et al.
patent: 4367082 (1983-01-01), Tomisaka et al.
patent: 4459143 (1984-07-01), Nawata et al.
Engler Yves
Monereau Christian
Petrie Wilfrid
Capossela Ronald C.
Frommer William S.
L'Air Liquide Societe Anonyme pour l'Etude et, l'Exploitation de
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