U.S. patent application number 11/575956 was filed with the patent office on 2007-11-08 for method and device for compressing a gaseous medium.
This patent application is currently assigned to Linde Aktiengesellschaft. Invention is credited to Robert Adler, Georg Siebert.
Application Number | 20070258828 11/575956 |
Document ID | / |
Family ID | 34978927 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070258828 |
Kind Code |
A1 |
Adler; Robert ; et
al. |
November 8, 2007 |
Method and Device for Compressing a Gaseous Medium
Abstract
A method and device for compressing a gaseous medium,
specifically hydrogen, is disclosed. Compression of the gaseous
medium takes place by way of a fluid, where a fluid is used in
which the gaseous medium is not soluble and/or can be separated
residue-free from the gaseous medium. An ionic fluid, a
high-boiling hydraulic oil, or a fluid which has a very low vapor
pressure is used as the fluid.
Inventors: |
Adler; Robert; (Gerasdorf,
AT) ; Siebert; Georg; (Wien, AT) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Linde Aktiengesellschaft
Wiesbaden
DE
65189
|
Family ID: |
34978927 |
Appl. No.: |
11/575956 |
Filed: |
August 2, 2005 |
PCT Filed: |
August 2, 2005 |
PCT NO: |
PCT/EP05/08370 |
371 Date: |
March 23, 2007 |
Current U.S.
Class: |
417/46 |
Current CPC
Class: |
C10N 2020/077 20200501;
F04F 1/10 20130101; F04F 1/06 20130101 |
Class at
Publication: |
417/046 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2004 |
DE |
10 2004 046 316.6 |
Claims
1-16. (canceled)
17. A method for compressing a gaseous medium, wherein a
compression of the gaseous medium is carried out by a fluid,
wherein the gaseous medium is not soluble in the fluid and/or the
fluid is separable residue-free from the gaseous medium.
18. The method according to claim 17, wherein the gaseous medium is
hydrogen.
19. The method according to claim 17, wherein an ionic fluid, a
high-boiling hydraulic oil, a fluid which has very low vapor
pressure, or a fluid which has a gas solubility of less than
10.sup.-4 mol/l bar, is used as the fluid.
20. The method according to claim 17, wherein compression heat is
at least partially removed by means of the fluid.
21. The method according to claim 17, wherein a portion of the
fluid, entrained by the gaseous medium when compressed, is
separated from the compressed gaseous medium.
22. The method according to claim 21, wherein the portion of the
fluid separated from the compressed gaseous medium is returned
again for the compression, wherein the separated fluid is storable
before it is returned.
23. The method according to claim 17, wherein the compression
allows compression of the gaseous medium by a factor of 1000.
24. The method according to claim 17, wherein a replenishment of
fluid required for compression takes place during a suction
stroke.
25. The method according to claim 17, wherein the fluid is exposed
to an electrical field.
26. A device for compressing a gaseous medium, comprising: one or
more cylinders; supply and discharge lines which supply the gaseous
medium to be compressed to, and discharge a compressed gaseous
medium from, the cylinder or cylinders, respectively; at least one
fluid line per cylinder which supplies and discharges a fluid
compressing the gaseous medium in the cylinder or cylinders; and
means for changing a volume of the fluid in the cylinder or
cylinders; wherein the gaseous medium is not soluble in the fluid
and/or the fluid is separable residue-free from the gaseous
medium.
27. The device according to claim 26, wherein the gaseous medium is
hydrogen.
28. The device according to claim 26, wherein the means for
changing the volume of the fluid in the cylinder or cylinders is a
fluid pump, a hydraulic pump, an axial piston pump, a slide pump,
or a gear pump.
29. The device according to claim 26, wherein a heat exchanger
which removes compression heat is assigned to the fluid line
provided per cylinder.
30. The device according to claim 26, wherein at least one
separation device is located in the discharge line for the
compressed gaseous medium, wherein the separation device separates
a portion of the fluid, entrained with the compressed gaseous
medium, from the compressed gaseous medium.
31. The device according to claim 30, wherein the separation device
is connected in a circulation loop to at least one of the
cylinders.
32. The device according to claim 30, wherein a fluid storage
device is allocated to the separation device.
33. The device according to claim 26, wherein a heat exchanger is
located within the cylinder or cylinders.
34. The device according to claim 26, wherein means to generate an
electrical field in the cylinder or cylinders is provided.
35. A method for compressing a gaseous medium, comprising the steps
of: supplying the gaseous medium to a cylinder; supplying a fluid
to the cylinder; and compressing the gaseous medium in the cylinder
by the fluid in the cylinder.
36. A device for compressing a gaseous medium, comprising: a
cylinder; a gaseous medium supply line coupled to the cylinder,
wherein the gaseous medium supply line supplies the gaseous medium
to the cylinder; a fluid supply line coupled to the cylinder,
wherein the fluid supply line supplies a fluid to the cylinder;
wherein the gaseous medium supplied to the cylinder is compressed
by the fluid supplied to the cylinder; and a compressed gaseous
medium discharge line coupled to the cylinder, wherein the
compressed gaseous medium discharge line discharges the compressed
gaseous medium from the cylinder.
Description
[0001] This application claims the priority of International
Application No. PCT/EP2005/008370, filed Aug. 2, 2005, and German
Patent Document No. 10 2004 046 316.6, filed Sep. 24, 2004, the
disclosures of which are expressly incorporated by reference
herein.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] The invention relates to a method for compressing a gaseous
medium, specifically hydrogen.
[0003] The invention further relates to a device for compressing a
gaseous medium, specifically hydrogen.
[0004] In methods and devices of a generic kind for compressing a
gaseous medium, reciprocating piston compressors or reciprocating
piston compressor systems are normally used at the present time.
Reciprocating piston compressors require appropriate sealing
systems in order to keep the medium to be compressed separate from
the medium driving the piston, for example hydraulic oil.
[0005] Particularly in the compression of hydrogen, natural gas and
high purity media, or if contamination of the medium to be
compressed by the drive medium must be prevented and/or is
undesirable for specific reasons, precisely fitting cylinders with
pistons and correspondingly effective dynamic sealing systems are
required; as a rule, these systems result in high production and
maintenance costs. Often, even more cost-intensive compression
variants, such as diaphragm compressors, oil-free reciprocating
piston compressors, etc., are brought in for such applications.
[0006] Generic methods and devices of a generic kind are used, for
example, in natural gas compressor stations such as are found in
natural gas filling stations.
[0007] The object of the present invention is to specify a method
and a device of a generic kind for compressing a gaseous medium,
specifically hydrogen, which avoid the aforementioned
disadvantages.
[0008] Concerning the method, this object is achieved through the
compression of the gaseous medium by a fluid, wherein a fluid is
used in which the gaseous medium is not soluble and/or which can be
separated residue-free.
[0009] The characteristics of the device in accordance with the
invention for compressing a gaseous medium are that it
comprises
[0010] a) one or more cylinders,
[0011] b) supply and discharge lines which serve to supply the
gaseous medium to be compressed to or remove it from the cylinder
or cylinders,
[0012] c) at least one fluid line per cylinder which serves to
supply and remove the fluid compressing the gaseous medium in the
cylinders, and
[0013] d) means to change the quantity of fluid in the cylinder or
cylinders,
[0014] e) wherein the fluid is a fluid in which the gaseous medium
to be compressed is not soluble and/or which can be separated
residue-free from the gaseous medium.
[0015] The invention makes it possible to dispense with a piston
and any (piston) sealing systems in the compression of a gaseous
medium. This is managed by achieving compression of the gaseous
medium to be compressed by way of a variable column of fluid inside
a cylinder. The pistons used previously, which consist of a solid
material, are replaced by a incompressible fluid, or column of
fluid. Through an upward and downward movement of the column of
fluid--similar to the upward and downward motion of a piston--the
gaseous medium to be compressed is drawn in and compressed.
[0016] In order to achieve optimal compression even of high purity
media which must not be contaminated by the fluid being used, a
fluid is preferably selected in which the gaseous medium to be
compressed is not soluble and which can be separated residue-free
from the gaseous medium.
[0017] In an advantageous way, an ionic fluid, a high-boiling
hydraulic oil or fluids which have a very low vapor pressure, as
for example, vacuum pump oils, molten salts and metals with a low
melting point, or fluids which have a gas solubility of less than
10.sup.-4 mol/l bar are used as fluid.
[0018] Ionic fluids are low-boiling, organic salts with melting
points between 100 and -90.degree. C., where most of the known
ionic fluids are already present in liquid form at room
temperature. In contrast to conventional molecular fluids, ionic
fluids are completely ionic and thus reveal new and unusual
properties. Ionic fluids are comparatively easily adaptable in
their properties to given technical problems as a result of the
variation in the structure of anion and/or cation and the variation
in their combinations. For this reason they are frequently also
described as "designer solvents." With conventional molecular
fluids on the other hand, only a variation in the structure is
possible.
[0019] In contrast to conventional molecular fluids, ionic fluids
have the additional advantage that they possess no measurable vapor
pressure. This means that--as long as their decomposition
temperature is not reached--they do not boil off to the slightest
degree, even in a total vacuum. From this result their properties
of non-flammability and environmental friendliness since, as a
result, ionic fluids cannot reach the atmosphere.
[0020] As already mentioned, the melting points of known ionic
fluids are by definition below 100.degree. C. The liquidus
range--the range between melting point and thermal
decomposition--is usually 400.degree. C. or higher.
[0021] In addition, ionic fluids have very high thermal stability.
Their decomposition points are frequently above 400.degree. C. In
the case of ionic fluids, their density and mixing characteristics
with other fluids can be affected, or adjusted, through the choice
of ions. Ionic fluids have the additional advantage that they are
electrically conductive and as a result can prevent static
electrical charges--which represent a potential hazard.
[0022] Ionic fluids have the advantage that it is possible to
separate them completely from the compressed medium with a
comparatively small expenditure for equipment.
[0023] Entertainment of the ionic fluid by the compressed medium is
henceforth not possible since ionic fluids--as mentioned
previously--have no vapor pressure.
[0024] In the case of fluids with high gas solubility, there is
firstly undesirable cavitation of the drive pump(s) and secondly
undesirable entrainment of gas into the (interim) fluid storage
tank which is normally provided. Through the use of a fluid which
has a gas solubility of less than 10.sup.-4 mol/l bar, these
problems can be avoided. As a result, the life of the drive pump
used is extended; further, the safety-related problems accompanying
the gas formation, or entrainment, are avoided.
[0025] The method in accordance with the invention, the device in
accordance with the invention and further embodiments of same are
explained in more detail using the embodiment shown in the
drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0026] The drawing shows a potential embodiment of the invention in
which compression takes place in two separate cylinders Z1 and Z2.
Alternatively, compression can be carried out in only one or also
in more than two cylinders.
DETAILED DESCRIPTION OF THE DRAWING
[0027] The gaseous medium to be compressed is brought to cylinders
Z1 and Z2 through the lines 1, 1' and 1''. Inlet valves a and b are
located in the aforementioned lines. After compression has taken
place, the compressed gaseous medium is drawn off from cylinders Z1
and Z2 through the discharge lines 2' and 2'' in which valves c and
d are similarly located.
[0028] The compressed gaseous medium is freed in a separating
device A of any fluid which may have been entrained from cylinders
Z1 and Z2, and which will be looked at more closely in what
follows, and is then taken by way of line 2 to be used further
and/or to interim storage.
[0029] A suitable fluid D is provided inside cylinders Z1 and Z2
which serves to compress the gaseous medium. Cylinders Z1 and Z2
are connected by way of lines 3 to 6 and hydraulic pump X which is
driven by an electric motor M.
[0030] The fluid levels D in the cylinders Z1 and Z2 are varied by
means of the hydraulic pump X such that one of the cylinders draws
in the medium to be compressed while simultaneously, or essentially
simultaneously, the gaseous medium is compressed in the other
cylinder. Preferably an axial piston pump with swash plate drive is
used for this, where transfer volume and/or direction can be
changed through a simple adjustment of the swash plate.
[0031] Compared with the prior art, the invention has the further
advantage that the (compression) heat created during compression
can be removed at least partially by way of the fluid D. For this,
as shown in the drawing, heat exchangers, or radiators, K1 and K2,
are provided through which the heat created in the cylinders during
compression can be discharged to the environment and/or another
suitable medium. In the case of complete removal of compression
heat through the fluid D and the heat exchangers, or radiators, K1
and K2, isothermal, single-stage compression can be realized.
[0032] Valves e or g are located between the radiators K1 and K2
and the hydraulic pump X; the effect of these so-called stationary
valves is that no system pressure is present at the hydraulic pump
X when it is not running.
[0033] In accordance with an advantageous embodiment of the device
in accordance with the invention, heat exchangers E1 or E2 can be
located in the cylinders Z1 and Z2.
[0034] In the compressor or cylinder designs reckoned among the
prior art, cooling of the cylinder chamber can only be implemented
from outside since the moving piston inside the cylinder does not
permit the provision of a heat exchanger. Until now, the heat
generated during compression has therefore been given off by the
compressor or cylinder outer jacket to the cooling medium (air,
water, coolant, etc.). Because of this fact, compression cannot
normally be carried out isothermally, which results in
corresponding high compression energy.
[0035] By means of the aforementioned advantageous embodiment of
the device in accordance with the invention, internal cooling can
now be implemented, the consequence of which is that the
disadvantages of the prior art can be avoided.
[0036] The term "heat exchanger" is understood to mean any designs
for heat exchangers--designated as "active heat exchanger" in what
follows--and thermal reservoirs--designated as "passive heat
exchanger" in what follows.
[0037] While the heat arising during compression is removed by
means of a suitable cooling medium in the case of an active heat
exchanger, this heat remains inside the compressor or cylinder
chamber in the case of a passive heat exchanger. In the latter
case, the compression heat is in fact extracted from the medium to
be compressed, but is then given off to the fluid D which carries
away the compression heat--as explained above. Cooling ribs, fins,
etc., and/or fillers such as metal spheres, plates, etc., can be
used as passive heat exchangers, or thermal reservoirs
respectively.
[0038] The aforementioned advantageous embodiment of the device in
accordance with the invention allows a substantial reduction in the
required compression energy and thereby approximately isothermal
compression. Furthermore, lower gas exit temperatures can be
realized, and a reduction in the thermal load on the compressor
valves can be achieved.
[0039] The fluid coming from the cylinders Z1 and Z2 and separated
from the compressed medium in the separating device A is taken by
way of line 9, in which a shutoff valve i is located, to an
optionally provided interim storage tank S. From here, the fluid
can be taken according to need by way of the lines 7 and 8 and the
two shutoff valves f and h to the cylinders Z1 and/or Z2.
[0040] In accordance with a further advantageous embodiment of the
method in accordance with the invention for compressing a gaseous
medium, the replenishing of fluid required for compression takes
place during a suction stroke.
[0041] There is a loss of fluid D particularly at the drive, or
hydraulic, pump needed for compression. In order to compensate for
these losses, it is therefore necessary to replenish or fill the
system with new fluid when fluid falls below a minimum level. Care
must be taken that there is no interaction between the pressure and
suction sides while fluid is being filled. Furthermore, care must
be taken that the desired or maximum energy requirement of the
system, which must be defined by the compression process, is not
(unnecessarily) increased.
[0042] The embodiment of the method for compressing a gaseous
medium described previously creates an opportunity for filling
fluid in which the requirements described previously can be
satisfied.
[0043] As a matter of course, the time for replenishing fluid
required for compression should be guided by the current power
consumption of the system; preferably fluid replenishment should
take place during or close to a power minimum. At this time, the
system, or the drive pump, has sufficient power reserves available
which can be used for replenishing the fluid.
[0044] Preferably the fluid D to be replenished is fed into the
appropriate cylinder, Z1 or Z2 respectively, by way of line 10,
which has a feed pump P, during a suction stroke. However, care
must be taken that replenishment does not take place in the
immediate proximity of the reversal point since then the danger
exists that fluid D might possibly escape from the corresponding
cylinder Z1 or Z2 by way of the pressure line 2' or 2''. The
consequence would be that the separation device A which serves to
separate fluid entrained from the cylinders Z1 and Z2 would have to
be dimensioned correspondingly larger. Adding fluid during the
suction stroke also minimizes the energy requirements of the feed
pump P.
[0045] Fluid loss is detected by measuring the deviations of the
fluid levels in cylinders Z1 and Z2 from a reference value which is
usually determined at the beginning of the compression process.
[0046] In accordance with a further advantageous embodiment of the
method for compressing a gaseous medium in accordance with the
invention, the fluid is exposed to an electrical field. For this
purpose, means for generating an electrical field in the cylinder
or cylinders are to be provided on the device side.
[0047] Particularly when ionic fluids come into direct contact with
other media (gases, fluids, etc.), the result can be intermixing at
the interface and formation of a two-phase mixture. In the present
case, such a two-phase mixture can arise, for example, inside the
cylinder or cylinders at the interface between ionic fluids and the
medium to be compressed.
[0048] For a clean and reliable separation of ionic fluid and the
medium to be compressed, an adequate difference in density and a
matching gravitational field--which in the present case is
generated by the acceleration of gravity--are required. The maximum
reversal acceleration inside the cylinder is defined thereby. In
the Earth's gravitational field, the consequence is that a maximum
acceleration of 7 m/s.sup.2 can be realized. Acceleration of this
nature is, however, frequently not sufficient to reseparate
completely the two-phase mixture that has resulted.
[0049] By means of the embodiments of the method in accordance with
the invention described previously, or the device in accordance
with the invention, natural force fields such as gravitation,
Coreolis force, etc., can be intensified by an electrical
field.
[0050] These embodiments can be realized with all ionic fluids
which have a corresponding dipole moment and/or corresponding
electrical conductivity.
[0051] Influencing ionic fluids by means of an electrical field
allows an increase in acceleration at the reversal points of the
pistonless compressor without increased risk of phase intermixing.
Furthermore, a clean and reliable separation of ionic fluids from a
two-phase mixture is also possible when the differences in density
between the ionic fluid and the medium to be compressed are
comparatively minor. In addition to the embodiment of the invention
explained using the drawing, embodiments of the method in
accordance with the invention and the device in accordance with the
invention are realizable for which only one cylinder or three or
more cylinders are provided. While continuous delivery of the
compressed medium with respect to compression pressure is not
possible with only one cylinder, such often desirable delivery of
the compressed medium with two or more cylinders is possible.
[0052] Considerable savings in investment costs are achieved by
dispensing with solid pistons and dynamic sealing systems. In
addition, maintenance costs are reduced since the maintenance
intervals, compared with those of conventional compressors, are
extended.
[0053] The invention is suitable for compressing gaseous media up
to currently attainable pressures of 1000 bar. It should be
emphasized that in principle higher pressures of any type are
attainable. The invention further makes possible compression to
maximum pressure with only a single compression stage. Furthermore,
the transfer volume can be varied as desired. Particularly with
respect to the compression of high purity media, the invention
creates an economical opportunity for compressing such media as
well to very high pressures.
* * * * *