[0001] The present invention relates to a gas compression system.
[0002] Oil-pressure systems for compressing a gas are known, wherein a gas is compressed
in order to reduce its volume for easier storage and easier distribution.
[0003] Fig. 1 shows a generic oil-pressure system for compressing a gas of the prior art,
which is generally indicated with reference numeral (100). The system (100) comprises
a hydraulic compressor (C) connected to a suction conduit (6) and to a delivery conduit
(7) suitable for letting in the gas to be compressed and for letting out the compressed
gas, respectively.
[0004] The hydraulic compressor (C) is provided with press means for compressing the gas
that are actuated by pressurized oil fed by a hydraulic circuit (I). Pressure adjusting
means (R) are connected to the hydraulic circuit (I) to adjust the pressure of the
oil to be fed to the hydraulic compressor (C) at a pressure value that is sufficient
to compress the gas at the desired pressure.
[0005] With reference to Fig. 2, the hydraulic compressor comprises a piston (1) disposed
in a cylinder (2) and the hydraulic circuit (I) comprises a pump (P) connected to
a motor (M) to pressurize the oil that pushes the piston (1). The piston (1) pushes
the gas in the cylinder (2) and compresses the gas at a desired pressure.
[0006] A cylinder with a partition (20) and a double piston with a stem (10) that passes
through the partition (20) and two plungers (11, 12) at the ends of the stem are generally
used to recover the forward and backward travels of the piston. In view of the above,
the cylinder (2) is divided into four chambers: a first oil chamber (A), a second
oil chamber (B), a first gas chamber (G1) and a second gas chamber (G2).
[0007] The first gas chamber (G1) and the second gas chamber (G2) respectively communicate
with a first fitting (3) and a second fitting (4) of three-way type. Each fitting
(3, 4) comprises:
- a suction inlet (30, 40) suitable for being connected to the suction conduit (6) that
provides the gas to be compressed,
- a delivery outlet (31, 41) suitable for being connected to the delivery conduit (7)
that transports the compressed gas, and
- a communication conduit (32, 42) in communication with the respective gas chamber
(G1, G2) of the cylinder.
[0008] Unidirectional valves are disposed in the suction inlets (30, 40) and in the delivery
outlets (31, 41) to guarantee the gas flow during suction and delivery.
[0009] In order to permit an alternate movement of the piston (1), the oil must alternately
go into the first oil chamber (A) firstly and then into the second oil chamber (B).
In order to permit such an alternate oil flow, a reversing valve (5) is normally provided
between the pump (P) and the partition (20) of the cylinder (2) to alternately send
the oil into the first oil chamber (A) and into the second oil chamber (B).
[0010] The pressure adjusting means (R) are embedded in the reversing valve (5) to adjust
the oil pressure.
[0011] The pressure adjusting means (R) of the reversing valves of the gas compression systems
according to the prior art are manually regulated. The reversing valve (5) has two
pressure regulators (5A, 5B) of manual type that adjust the pressure of the oil sent
into the first oil chamber (A) and into the second oil chamber (B), respectively.
The pressure regulators (5A, 5B) are controlled by means of adjusting screws (50A,
50B) that are operated manually by the operator.
[0012] The delivery conduit (7) has a pressure switch (70) that is adjusted by the operator
according to the delivery pressure, namely the desired gas compression pressure.
[0013] For illustrative purposes, if the suction pressure is 100 bar and the desired delivery
pressure is 220 bar, an oil pressure of 150 bar will be necessary, with a 18 kw absorption
of the motor of the pump, considering a residual thrust of 45 kN on the piston.
[0014] In order to do this, nowadays, the operator goes to the installation, adjusts the
pressure switch (70) at a pressure of 220 bar, lets the suction gas in the first gas
chamber (G1) and operates the reversing valve (5) manually. Otherwise said, the user
manually adjusts the adjusting screw (50A) of the first pressure regulator of the
reversing valve (5), increasing the oil pressure in the first oil chamber (A) until
the first plunger (11) of the piston reaches the end of the compression travel because
the oil has reached the pressure that is necessary to compress the gas at the pressure
of 220 bar and the gas flows in the delivery conduit through the pressure switch (70).
Now, the operator blocks the adjusting screw (50A), setting the adjustment of the
first pressure regulator (5A).
[0015] With reference to the example, the user has set the reversing valve in such a way
to have an oil pressure higher than 150 bar, with an approximation by excess.
[0016] The same procedure will be applied to adjust the oil pressure in the second oil chamber
(B), by means of the adjusting screw (50B) of the second pressure regulator (50B)
of the reversing valve that adjusts the oil pressure in the second oil chamber (B).
[0017] Considering that it is a manual operation, it will be extremely difficult for the
operator to set the pressure values in the first oil chamber (A) and in the second
oil chamber (B) in the same way.
[0018] Moreover, it must be considered that the gas suction pressure may vary.
[0019] For illustrative purposes, if the gas suction pressure drops from 100 bar to 90 bar,
an oil pressure higher than 150 bar and equal to approximately 163 bar will be necessary
to obtain a delivery pressure of 220 bar However, since the reversing valve is set
to have an oil pressure of approximately 150 bar, the installation would be stopped
because the oil pressure of 150 bar is not sufficient to obtain a gas compression
of 220 bar. In such a case, the operator must adjust the oil pressure again with the
adjusting screws (50A, 50B) of the reversing valve until an oil pressure of approximately
163 bar is reached.
[0020] On the contrary, for illustrative purposes, if the gas suction pressure increases
from 100 bar to 110 bar, an oil pressure lower than 150 bar and equal to approximately
138 bar will be sufficient to obtain a delivery pressure of 220 bar. However, since
the reversing valve is set to have an oil pressure of approximately 150 bar, the system
would continue to operate, it being regulated for an oil pressure higher than the
requested one, but it would be energetically inefficient because the motor (M) of
the pump would consume more energy than necessary. In fact, the motor would absorb
18 kw to maintain an oil pressure of approximately 150 bar, when it could absorb 16.6
kw to maintain an oil pressure of 138 bar that is sufficient to compress the gas at
the desired pressure of 220 bar.
[0021] Moreover, if the gas compression pressure changes, because of a request from the
customer, once again, the operator must set the pressure regulators (5A, 5B) based
on the desired compression pressure.
[0022] Furthermore, the travel of the piston (1) is fixed and adjusted in such a way that
the speed of the piston (1) is equal to the speed at the maximum flow rate of the
pump (M). Therefore, if the user intends to expand the gas compression system, using
two hydraulic compressors (C), it will be necessary to purchase a new pump with a
higher flow rate.
[0023] US5863186 discloses a gas compression system according to the preamble of claim 1.
US5863186 does not specify the fluid of the hydraulic circuit, the provision of a pressure
regulator embedded in a reversing valve connected to the hydraulic circuit and the
provision of a third pressure transducer.
[0025] US2016230786A1 discloses a hydraulic pressure generation unit with pneumatic actuation.
[0026] US5238372A discloses a cooled spool piston compressor.
[0027] The purpose of the present invention is to eliminate the drawbacks of the prior art
by disclosing a gas compression system that is accurate, reliable, versatile and efficient.
[0028] Another purpose of the present invention is to disclose such a gas compression system
that is automated and capable of eliminating the human action and capable of adjusting
to any pressure variations of the gas introduced in the compression system.
[0029] These purposes are achieved according to the invention with the characteristics of
the independent claim 1.
[0030] Advantageous embodiments of the invention appear from the dependent claims.
[0031] The gas compression system according to the invention is defined by claim 1.
[0032] Additional features of the invention will be manifest from the following detailed
description, which refers to a merely illustrative, not limiting embodiment, as shown
in the appended figures, wherein:
Fig. 1 is a block diagram that diagrammatically shows a generic compression gas system
according to the prior art;
Fig. 2 is a block diagram that diagrammatically shows a specific compression gas system
according to the prior art;
Fig. 3 is a block diagram that diagrammatically shows a gas compression system according
to the invention; and
Fig. 4 is a look-up table used in the PLC of the gas compression system according
to the invention.
[0033] In the following description, elements that are identical or corresponding to the
ones described above will be indicated with the same numerals, omitting their detailed
description.
[0034] With reference to Fig. 3, the gas compression system of the invention is disclosed,
which is generally indicated with reference numeral (200).
[0035] Instead of the manually controlled reversing valve (5), the gas compression system
(200) provides for a reversing valve (8) that is electronically controlled by means
of a programmable control logic (PLC) (9).
[0036] The electronic reversing valve (8) has a first way (8A) and a second way (8B) respectively
connected to the first oil chamber (A) and to the second oil chamber (B) of the cylinder
(2).
[0037] A shutter (80) is disposed inside the electronic reversing valve (8) and moves in
alternate motion to alternately open and close the first way (8A) and the second way
(8B) in such a way to alternately feed the first oil chamber (A) and the second oil
chamber (B) of the cylinder (2).
[0038] The movement of the shutter (80) is controlled by the PLC (9).
[0039] The electronic reversing valve (8) also comprises pressure adjusting means (R) that
consist in a pressure regulator (81) suitable for adjusting the oil pressure that
passes from the first way (8A) and from the second way (8B) and reaches the first
chamber (A) and the second chamber (B) of the cylinder. Unlike the reversing valves
of the prior art, the pressure regulator (81) of the reversing valve (8) is electronically
controlled by the PLC (9). The pressure regulator (81) has a mobile part that is moved
by the PLC (9) according to the desired oil pressure.
[0040] In particular, the pressure regulator (81) is controlled by a control signal (S4),
for example an electric signal of impulse type, from the PLC (9).
[0041] The gas compression system (200) comprises:
- a first pressure transducer (T1) disposed in the gas suction conduit (6) to measure
the suction pressure of the inlet gas;
- a second pressure transducer (T2) disposed in the gas delivery conduit (7) to measure
the delivery pressure of the outlet gas, and
- a third pressure transducer (T3) disposed in the reversing valve (8) to measure the
pressure of the oil fed in the first chamber and in the second chamber of the cylinder.
[0042] Obviously, the second pressure transducer (T2) can be a pressure transducer embedded
in the pressure switch (70) disposed in the delivery conduit (7).
[0043] The three pressure transducers (T1, T2, T3) are electrically connected to the PLC
(9), in such a way that the PLC (9) receives electrical signals (S1, S2, S3) indicative
of the pressure of the inlet gas, of the pressure of the outlet gas and of the pressure
of the oil.
[0044] A look-up table is stored in the PLC (9). The look-up table contains possible suction
pressure values, possible delivery pressure values, and corresponding oil pressure
values calculated based on the suction pressure values and the delivery pressure values.
In view of the above, a given oil pressure value uniquely corresponds to each pair
composed of a suction pressure value and of a delivery pressure value. For illustrative
purposes, the suction pressure values can vary from 0 to 250 bar and the delivery
pressure values can vary from 10 bar to 250 bar.
[0045] Fig. 4 shows a similar look-up table wherein:
the suction pressure values vary from a1 to an, wherein a1 = 0 and an = 250 bar;
the delivery pressure values vary from bi to bm, wherein b1 = 10 bar and bm = 250 bar;
[0046] The oil pressure values vary from c
11 to c
nm, based on the suction pressure values and on the delivery pressure values.
[0047] For illustrative purposes, if the first transducer (T1) measures a suction pressure
of 100 bar and the second transducer (T2) measures a delivery pressure of 220 bar,
the look-up table gives an oil pressure value of 150 bar. Consequently, the PLC (9)
controls the pressure regulator (81) of the reversing valve in such a way to obtain
an oil pressure of 150 bar. When the third pressure transducer (T3) measures an oil
pressure of 150 bar, the PLC (9) will control the shutter (80) of the reversing valve
in such a way to move in alternate motion in order to alternately send the oil into
the first oil chamber (A) and into the second oil chamber (B).
[0048] Since the look-up table of the PLC contains all possible suction pressure values
and all possible delivery pressure values, in case of a variation of the suction pressure
and of the delivery pressure, the gas compression system (200) will be self-adjusted,
making gas compression possible with the maximum energy efficiency.
[0049] If the gas suction pressure drops to 90 bar, the gas compression system (200) will
automatically adjust the oil pressure at 162 bar, permitting the standard operation
of the installation.
[0050] On the contrary, if the gas suction pressure increases to 110 bar, the gas compression
system (200) will automatically adjust the oil pressure at 138 bar, with an energy
saving from 18 kw to 16.6 kw.
[0051] Moreover, the gas compression system (200) can adjust the quantity of oil to be sent
to the first chamber (A) and to the second chamber (B) in order to reach the desired
gas compression pressure. Otherwise said, the movement of the piston (1) is adjusted
in such a way that the plungers (11, 12) do not reach the end of their travel (as
in the prior art). In view of the above, the speed of the piston (1) is adjusted,
and is not necessarily equal to the speed at the maximum flow rate of the pump (P).
Therefore, if the user intends to expand the gas compression system, using two cylinder-piston
assemblies, it will not be necessary to purchase a new pump with a higher flow rate,
and it will be possible to use the same pump, by simply adjusting the travel of the
pistons.
[0052] Although the present description refers to a hydraulic compressor (C) with a piston
with two plungers (11, 12) and to a cylinder (2) with four chambers, the invention
refers to any type of hydraulic compressor, such as a compressor with a piston with
only one plunger disposed in a cylinder in such a way to generate two chambers: an
oil chamber and a gas chamber. In any case, the hydraulic circuit (I) is suitably
configured to fill and empty the oil chamber for the movement of the piston. The peculiarity
of the invention consists in the fact that the pressure adjusting means (R) are electronically
controlled by the PLC (9) to adjust the oil pressure based on the suction pressure
values and on the delivery pressure values.
[0053] If an electronically controlled reversing valve (8) is used in the hydraulic circuit
(I), the pressure adjusting means (R) consist in the pressure regulator (81) of the
reversing valve.
[0054] Considering that the gas compression system (200) generally operates with explosive/flammable
gases, advantageously the reversing valve (8) must be suitable for operating in zones
with explosion/fire risks; for instance, the reversing valve (8) must be ATEX classified.
1. Gas compression system (200) comprising:
- a hydraulic compressor (C) suitable for compressing a gas; said hydraulic compressor
(C) comprising a cylinder (2) and a piston (1) with at least one plunger (11, 12)
disposed in the cylinder in such a way to generate at least one fluid chamber (A,
B) and at least one gas chamber (G1, G2),
- a gas suction conduit (6) connected to said hydraulic compressor (C) for the inlet
of gas to be compressed,
- a gas delivery conduit (7) connected to said hydraulic compressor (C) for the outlet
of compressed gas,
- a hydraulic circuit (I) connected to said hydraulic compressor (C) in order to hydraulically
actuate said hydraulic compressor (C) by means of a pressurized fluid; and
- pressure adjusting means (R) connected to said hydraulic circuit (I) in order to
adjust the pressure of the fluid fed in said hydraulic compressor (C),
- a reversing valve (8) connected to said hydraulic circuit (I); said reversing valve
(8) comprising a shutter (80) that is moved with alternate motion to permit an alternate
flow of fluid in the hydraulic circuit (I) in order to move the piston (1) alternately,
- a programmable logic circuit (PLC) (9),
- a first pressure transducer (T1) electrically connected to said PLC (9); said first
pressure transducer (T1) being disposed in the gas suction conduit (6) to measure
the suction pressure of the inlet gas, and
- a second pressure transducer (T2) electrically connected to said PLC (9); said second
pressure transducer (T2) being disposed in the gas delivery conduit (7) to measure
the delivery pressure of the outlet gas,
wherein said pressure adjusting means (R) are electronically controlled and electrically
connected to said PLC (9); and
said PLC (9) is configured in such a way to electronically control the pressure adjusting
means (R) in order to adjust the fluid pressure at a pressure value that is calculated
based on the pressure values measured by said first pressure transducer (T1) and by
said second pressure transducer (T2);
characterized in that
said hydraulic circuit (I) comprises a pump (P) actuated by a motor (M);
said fluid of the hydraulic circuit (I) is oil;
said reversing valve (8) comprises said pressure adjusting means (R) consisting in
a pressure regulator (81) connected to said PLC;
said system (200) further comprises a third pressure transducer (T3) electrically
connected to said PLC; said third pressure transducer (T3) being disposed in the reversing
valve (8) to measure the pressure of the oil that is fed in said at least one oil
chamber; and
said PLC (9) being suitably configured to actuate said shutter (80) of the reversing
valve in alternate motion when the oil pressure measured by said third pressure transducer
(T3) reaches said pressure value calculated based on the pressure values measured
by said first pressure transducer (T1) and by said second pressure transducer (T2).
2. The system (200) of any one of the preceding claims, wherein said PLC (9) comprises
a look-up table that contains possible suction pressure vales, possible delivery pressure
values, and corresponding oil pressure values that are calculated based on the suction
pressure values and on the delivery pressure values.
3. The system (200) of claim 2, wherein said possible suction pressure values of the
look-up table vary from 0 to 250 bars and said possible delivery pressure values of
the look-up values vary from 10 to 250 bars.
4. The system (200) of any one of the preceding claims, comprising a pressure switch
(70) disposed in said delivery conduit (7) and configured in such a way to let the
gas pass when the gas pressure reaches the desired compression pressure, said second
pressure transducer (T2) being embedded in said pressure switch (70).
5. The system (200) of any one of the preceding claims, wherein said piston (1) of the
hydraulic compressor has two plungers (11, 12) and one stem (10) passing through a
partition wall (20) disposed in the cylinder (2) in such a way to generate two oil
chambers (A, B) and two gas chambers (G1, G2).