Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Patent
1999-03-30
2000-05-16
Doerrler, William
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
62647, F25J 300
Patent
active
060620447
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for producing a gas, in particular oxygen, from air at a variable flow rate by air distillation.
The invention applies in particular to the production of oxygen under pressure at a variable flow rate.
The pressures referred to here are absolute pressures and the flow rates are molar flow rates.
BACKGROUND OF THE INVENTION
EP-A-0,422,974 in the name of the Applicant Company describes a process of this type, called a "swinging-type process", intended for the production of gaseous oxygen at a variable flow rate. The second fluid involved is air to be distilled, which is condensed at a variable flow rate.
In this known process, it is easy to show that, in order to keep the supply and delivery flow rates of the distillation unit constant, it is necessary to vary the incoming air flow rate in the same direction as the variations in oxygen demand. If the oxygen is produced under pressure, the air which is condensed in order to vaporize the liquid oxygen is overpressured by an additional booster and, when the oxygen demand varies, it is necessary to vary significantly both the overpressured flow and the flow compressed by the main compressor.
Consequently, in this known process, the compressor, and optionally the booster, are oversized significantly with respect to the nominal oxygen flow rate to be produced. In addition, they work most of the time at considerably lower flow rates compared to their capacities and therefore with downgraded efficiency.
It has also been proposed to store gas to be produced, in gaseous form, in an auxiliary tank or "buffer", at a pressure greater than the production pressure. However, this approach is not satisfactory since it requires very large buffers to be installed in order to satisfy peaks in demand of long duration. In addition, producing all the gas at the buffer pressure is expensive in terms of energy.
OBJECT OF THE INVENTION
The object of the invention is to allow production of a gas from air at a variable flow rate under particularly efficient and economical conditions.
To this end, the subject matter of the invention is a process of the aforementioned type, characterized by the characterizing part of the first independent claim.
This process may include one or more of the characteristics disclosed in the dependent claims.
The subject of the invention is also a plant for implementing such a process. This plant is disclosed in second dependent claim.
This plant may include one or more of the characteristics disclosed in the second set of dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
An example of how the invention is implemented will now be described with regard to the appended drawings, in which:
FIG. 1 shows diagrammatically a plant for producing oxygen under pressure at a variable flow rate according to the invention; and
FIG. 2 is a heat-exchange diagram illustrating the vaporization of liquid oxygen at the production pressure; and
FIGS. 3 and 4 represent diagrammatically two alternative embodiments of the plant.
DETAILED DESCRIPTION OF THE INVENTION
The plant shown in FIG. 1 essentially comprises a variable-flow main air compressor 1, for example of the moving-vane centrifugal type, an adsorption-type purification unit 2, a heat-exchanger 3, a cold-holding turbine 4, an air distillation unit 5 consisting of a double column, itself comprising a low-pressure column 7 and a vaporizer-condenser 8 on top of a medium-pressure column 6, a liquid-oxygen storage tank 10, a liquefied-air storage tank 11, two pumps 12 and 13, an air booster 14 and an auxiliary tank or "buffer" 15. This plant is intended to produce a variable flow rate of gaseous oxygen via a production line 16, at a pressure of approximately 15 bar.
In order to describe the operation of this plant, it will first of all be assumed that the gaseous oxygen demand in the line 16 is constant and equal to the nominal production rate, i.e. approximately 20% of the nominal flow rate of air compressed by the compressor 1.
The nominal flow
REFERENCES:
patent: 5082482 (1992-01-01), Darredeau
patent: 5526647 (1996-06-01), Grenier
patent: 5941098 (1999-08-01), Guillard et al.
Alain Guillard
Bernard Darredeau
Doerrler William
l'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation de
LandOfFree
Method and plant for producing an air gas with a variable flow r does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and plant for producing an air gas with a variable flow r, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and plant for producing an air gas with a variable flow r will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-249486