Gas separation: processes – Solid sorption – Including reduction of pressure
Patent
1993-07-26
1995-02-28
Spitzer, Robert H.
Gas separation: processes
Solid sorption
Including reduction of pressure
95130, B01D 5304
Patent
active
053933265
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the production of a gas with a substantial oxygen content by adsorption of nitrogen from the air and more particularly a process of the type in which, on a plurality "n" of adsorbers, there is successively and cyclically assured according to a period T, in each of the adsorbers, with offset of a time T
from one adsorber to the next: withdrawing gas in a so-called co-current direction at high pressure, with admission of air; counter-current under a sub-atmospheric pressure to the minimum pressure of the cycle, of the order of 0.2.times.10.sup.5 Pa absolute; repressurization with gas enriched in oxygen; being such that at any time at least two adsorbers will be in the pumping phase of the depressurization stage, at different pressure levels.
BACKGROUND OF THE INVENTION
In this process, to ensure pumping which extends, in the course of a depressurization from atmospheric pressure, or slightly less if an equilibrium is assured between an adsorber at the beginning of repressurization, to a pressure as low as about 0.2.times.10.sup.5 Pa absolute, with rejection of a residue to the atmosphere, one utilizes generally volumetric compressors of the "Roots" type, which, if they are suitable to handle high flow rates, accept, at these pressure levels, only relatively small pressure differences between the inlet and the outlet, of the order of 0.5.times.10.sup.5 Pa. For higher compression loads, the output of the compressor falls, because one must use two stage volumetric compressors, the second stage being operated in series with the first stage when the pressure has fallen thanks to the first single stage, to a value of the order of 0.5.times.10.sup.5 Pa absolute, and one sometimes uses, when the pumped flow rate is great, a multi-stage compressor.
This procedure is therefore burdensome particularly as to energy consumption and has difficulties of embodiment for production units with high flow rates.
SUMMARY OF THE INVENTION
The present invention provides certain arrangements which permit achieving such a depressurization under vacuum in a rapid manner, which is indispensable in this type of use, with the least cost of investment and of energy consumption, and the subject of the invention is achieved, in a process characterized by points a) to d) above, by the combination of the following measures:
e) the pumping phase is subdivided into a plurality of pumping sub-stages, all of the same duration equal to T
, or to a sub-multiple of T
, and each pumping sub-stage is associated with a pumping means specific to the conditions of flow rate and pressure variation of said sub-stage;
f) each pumping means is immediately switched with an adsorber at the end of the sub-stage associated with said means, toward an adsorber at the beginning of said sub-stage;
and more particularly, there is provided one or the other of the following arrangements:
1. One pumping means is of the volumetric compressor type for values of pressures higher than a lower limit of the order of 0.5.times.10.sup.5 Pa absolute, of the centrifugal compressor type for pressure values comprised between said upper limit and a lower limit of the order of 0.2.times.10.sup.5 Pa absolute.
This arrangement permits combining the flexibility of the volumetric compressor as to the inlet pressure level and the excellent output of the centrifugal compressor for higher compression loads.
2. The different pumping means are all of the volumetric compressor type, the pumping means corresponding to any pumping sub-stage except the first sub-stage, comprising an elementary pumping means combined in series and downstream (according to the direction of circulation of the gas) of the pumping means of a pumping sub-stage which immediately precedes it, the number of elemental pumping means corresponding to one pumping sub-stage at a given initial depression being greater by one unit than the number of elemental pumping means associated with the pumping sub-stage which immediately precedes it, and more particu
REFERENCES:
patent: 3226913 (1966-01-01), Avery
patent: 3498025 (1970-03-01), Bednarski
patent: 3720042 (1973-03-01), Simonet
patent: 4070164 (1978-01-01), Miwa et al.
patent: 4614525 (1986-09-01), Reiss
patent: 4813977 (1989-03-01), Schmidt et al.
patent: 4892565 (1990-01-01), Schmidt et al.
patent: 5084075 (1992-01-01), Sircar
Engler Yves
Monereau Christian
Petrie Wilfrid
L'Air Liquide Societe Anonyme pour l'Etude et, l'Exploitation de
Spitzer Robert H.
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