Patent Grant
7497092
This application claims the benefit of U.S. Non Provisional application Ser. No. 11/023,003, filed Dec. 27, 2004, the entire contents of which are incorporated herein by reference.
The present invention relates to an integrated air compression, cooling and purification unit and air compression, cooling, and purification process. In particular, it relates to cryogenic air separation units and air separation processes using the air compression, cooling, and purification unit and process.
Certain markets, in particular for the conversion of natural gas, require large amounts of oxygen; therefore, increased sizes of air separation units. It is therefore necessary to increase the dimensions of the air compression systems for the air separation unit.
Generally, compressors with intercoolers are used to feed air separation units. For large plants, the cost of these compressors becomes prohibitive and their size makes them expensive to install.
To get around this problem, several compressors can be used in parallel but this is not very economical.
Usually these large compressors are powered by gas turbines or steam turbines, since the size of electric motors is limited. The steam turbines use the steam generated by the natural gas conversion processes. It is also known that gas turbines use axial compressors to treat air flows much larger than those used for air separation. However, these compressors are adiabatic and their energy consumption is disappointing, or even incompatible with air separation, since the heat of compression is not recycled.
It is known from U.S. Pat. No. 4,461,154 that air compressed in an adiabatic compressor may be used to preheat boiler feed water. U.S. Pat. No. 6,117,916 describes the use of heat from an adiabatic compressor to warm a working fluid before sending the air from the compressor. The air is then further cooled and sent to an air separation unit.
It is an object of the present invention to use the heat present in the compressed air efficiently so as to generate energy.
The invention provides an integrated process for the compression, cooling, and purification of air in which:
Additionally, the invention provides an integrated apparatus for the compression, cooling, and purification of air comprising:
The economic use of the heat generated by the adiabatic compression gives rise to a steam consumption equivalent to that of a multi stage compressor, as classically used in air separation.
For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:
The invention provides an integrated process for the compression, cooling, and purification of air in which:
The invention may also include one or more of the following aspects:
Additionally, the invention provides an integrated apparatus for the compression, cooling, and purification of air comprising:
The invention may additionally comprise one or more of the following features:
According to one embodiment of the invention, there is provided an air separation unit comprising an apparatus, as described above, a further heat exchanger for cooling the air cooled in the cooling unit and a distillation column system, a conduit for sending air to a column of the column system, and a conduit for removing a product from a column of the column system.
The unit may comprise a heat exchanger, a conduit for sending a nitrogen rich stream from the column system to the heat exchanger, and thence to the purification unit, and a conduit for sending at least part of the second warmed pressurized stream to the heat exchanger to warm the nitrogen rich stream upstream of the purification unit.
The economic use of the heat generated by the adiabatic compression gives rise to a steam consumption equivalent to that of a multi stage compressor, as classically used in air separation.
In
The air 4 cooled in exchanger 3 is sent to the bottom of a cooling tower 5 where it exchanges heat by direct contact with water 15, 17 introduced at two separate points. Stream 15 is cooled before entering the cooling tower in an adsorption type cooling unit 31 using at least part of stream 9 (here shown as partial stream 9C).
The air 17 cooled in the cooling tower 5 is then purified in purification unit 8 to produce air stream 47. This stream is then further cooled and sent to the columns of a cryogenic air separation unit, which may be of any known type.
The purification unit is periodically regenerated by a nitrogen rich stream 45 produced by the air separation unit fed by air stream 47. This nitrogen rich stream 45 is warmed, preferably to the regeneration temperature using at least part of stream 9 (here shown as partial stream 9B).
The turbine 11 is fed by first warmed pressurized stream 11 sent to the entrance of the turbine, preferably mixed with another stream of steam 13. At least part of stream 9 (here shown as partial stream 9A) is sent to an intermediate level of the turbine 11.
The expanded steam 23 is condensed and recycled, together with either or both of the partial condensed streams 9B, 9C to the inlet of exchanger 3, following pumping. The water stream 37, 39 may both be pumped to different pressures, or as shown both streams are pumped to a common pressure and one 39 is expanded. Obviously, it is also possible to pump both stream to a common pressure and to further pump stream 37 to a higher pressure.
According to a further embodiment as shown in
In the first compartment 5A, the water stream at the higher pressure 37 circulates in a coil 137 at the bottom of the compartment where the temperature is highest and the water stream at the lower pressure 39 circulates in another coil 139 above coil 137 where the temperature is lower. It will be appreciated that any number of streams of water and/or coils may be used.
The second compartment 5B contains trays, structured packing, random packing or any other packing allowing mass and heat transfer between air and water. The water stream 15 following cooling in adsorption type cooling unit 31 is introduced at the top of the tower and water stream 17 is introduced at an intermediate point of the second compartment 5B. The air rises up the second compartment 5B from the first compartment and is cooled therein by direct heat transfer with the water. The warmed water 41 is removed at the bottom of the second compartment and then recycled to the cooling tower (not shown) in a manner well known from the prior art.
An example of a process using the installation of
If only the low-pressure section of the compressor is kept, the compressor becomes suitable for feeding an air separation unit and could be powered by a 3,600 rpm steam turbine.
If the compressor output is 6 bars, a 91 MW steam turbine is required to power the compressor. The real steam consumption is equivalent to that of a 71 MW compressor.
An electric motor can be used in addition to the steam turbine to power the adiabatic air compressor.
The following table illustrates the advantages of the invention:
It will be appreciated that while one embodiment of the invention has been shown and described hereinbefore, many modifications may be made by the person skilled in the art without departing from the spirit and scope of this invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3950957 | Zakon | Apr 1976 | A |
| 4461154 | Allam | Jul 1984 | A |
| 5505050 | Arriulou et al. | Apr 1996 | A |
| 5921106 | Girault et al. | Jul 1999 | A |
| 6117916 | Allam et al. | Sep 2000 | A |
| 7225637 | Le Bot | Jun 2007 | B2 |
| Number | Date | Country |
|---|---|---|
| 3908505 | Sep 1989 | DE |
| 0532429 | Mar 1993 | EP |
| 1389672 | Feb 2004 | EP |
| 2313581 | Dec 1976 | FR |
| Number | Date | Country | |
|---|---|---|---|
| 20060137394 A1 | Jun 2006 | US |
