EP3803118B1 - Device and method for compressing a low-pressure gas - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device and a method for compressing a gas at low pressure. It applies, in particular, to the compression of biogas.

STATE OF THE ART

Collecting available gas at low pressure to compress it at high pressure poses technical and economic difficulties. To achieve this compression, different compressor technologies exist. These different technologies are very energy-intensive.

To achieve the targeted compression ratio, the compressor may include several compression stages with intermediate cooling, which complicates the process.

• Compresseurs à déplacement positif qui fournissent un écoulement de puissance intermittent (compresseur alternatif ou à vis). Dans ces technologies, le gaz est comprimé dans un petit volume, ce qui a pour effet d'en augmenter la pression
• Compresseurs dynamiques qui fournissent un écoulement continu de puissance, ce qui existe dans l'écoulement axial ou centrifugeur. Dans les compresseurs centrifuges, l'énergie cinétique est convertie en énergie potentielle ce qui a pour effet d'augmenter la pression du fluide.

The compressors can be of different types with the chosen configurations:

• Positive displacement compressors that provide intermittent power flow (reciprocating or screw compressor). In these technologies, the gas is compressed into a small volume, which has the effect of increasing its pressure.
• Dynamic compressors that provide a continuous flow of power, which exists in axial or centrifugal flow. In centrifugal compressors, kinetic energy is converted into potential energy which has the effect of increasing the pressure of the fluid.

Positive displacement compressors require frequent maintenance, are only applied at low flow rates, have lower availability and are energy-intensive.

Dynamic compressors are sensitive to load composition, flow variation, have a limited compression ratio and are energy-intensive.

We know the patent application US 5,863,186 which discloses a device for compressing a gas at low pressure provided with a chamber for a gas and another for a liquid as well as a piston.

OBJECT OF THE INVENTION

The present invention aims to remedy all or part of these drawbacks.

• au moins une chambre de compression comportant :
  • une entrée pour gaz à basse pression,
  • une sortie pour gaz à haute pression,
  • une entrée pour liquide,
  • une sortie pour liquide et
  • un piston situé entre l'entrée et la sortie pour gaz d'une part et l'entrée et la sortie pour liquide d'autre part,
• un moyen de déplacement de liquide positionné sur un circuit de liquide reliant une sortie pour liquide et une entrée pour liquide d'une chambre de compression et
• un moyen de mesure de la pression du gaz à l'intérieur de la chambre de compression et un circuit de recirculation du gaz vers l'entrée d'une chambre de compression lorsque la pression mesurée est inférieure à une valeur limite déterminée.

To this end, according to a first aspect, the present invention relates to a device for compressing a gas at low pressure, which comprises:

• at least one compression chamber comprising:
  • an inlet for low pressure gas,
  • an outlet for high pressure gas,
  • an inlet for liquid,
  • an outlet for liquid and
  • a piston located between the inlet and the outlet for gas on the one hand and the inlet and the outlet for liquid on the other hand,
• a liquid moving means positioned on a liquid circuit connecting a liquid outlet and a liquid inlet of a compression chamber and
• a means for measuring the pressure of the gas inside the compression chamber and a gas recirculation circuit towards the inlet of a compression chamber when the pressure measured is lower than a determined limit value.

Thanks to these arrangements, the energy cost of gas compression is reduced. Indeed, under the action of the increase in the pressure of the liquid in the compression chamber, the piston is moved and compresses the gas. However, compressing a liquid consumes less energy than compressing a gas.

In some embodiments, the device that is the subject of the present invention comprises a non-return valve configured to prevent backflow of gas into a gas inlet.

These embodiments make it possible to avoid gas reflux towards the inlet of the compression chamber.

In embodiments, the device that is the subject of the present invention comprises a liquid retention valve configured to retain liquid in a compression chamber.

These embodiments make it possible to ensure improved compression of the gas by constraining the outlet of the liquid to a determined pressure.

In some embodiments, the displacement means is configured so that the liquid at the outlet has a pressure of between 30 and 70 bar.

In embodiments, the moving means is a pump.

In embodiments, the device that is the subject of the present invention comprises a plurality of compression chambers in series for the liquid circuit, an outlet for liquid from one compression chamber being connected to an inlet for liquid from another chamber compression.

These embodiments make it possible to pool the liquid circuit.

In some embodiments, the device which is the subject of the present invention comprises a plurality of compression chambers in parallel for the gas, each compression chamber comprising an inlet and an outlet for gas independent of another compression chamber.

These embodiments make it possible to simultaneously compress several quantities of gas.

In embodiments, the device that is the subject of the present invention comprises a means for measuring the pressure of the gas inside the compression chamber and a means for opening the outlet for gas from the compression chamber depending measured pressure.

• une étape d'entrée de gaz à basse pression dans une chambre de compression,
• une étape d'entrée de liquide dans la chambre de compression,
• une étape de déplacement d'un piston situé entre l'entrée et une sortie pour gaz d'une part et l'entrée et une sortie pour liquide d'autre part dans la chambre de compression,
• une étape de sortie de gaz à haute pression de la chambre de compression
• une étape de sortie de liquide de la chambre de compression,
• une étape de déplacement de liquide sur un circuit de liquide reliant une sortie pour liquide et une entrée pour liquide d'une chambre de compression et
• une étape de mesure de la pression du gaz à l'intérieur de la chambre de compression et un étape de recirculation du gaz vers l'entrée d'une chambre de compression lorsque la pression mesurée est inférieure à une valeur limite déterminée.

According to a second aspect, the present invention relates to a process for compressing a gas at low pressure, which comprises:

• a low-pressure gas entry step into a compression chamber,
• a liquid inlet step in the compression chamber,
• a step of moving a piston located between the inlet and an outlet for gas on the one hand and the inlet and an outlet for liquid on the other hand in the compression chamber,
• a high pressure gas outlet step from the compression chamber
• a liquid outlet step from the compression chamber,
• a liquid displacement step on a liquid circuit connecting an outlet for liquid and an inlet for liquid of a compression chamber and
• a step for measuring the pressure of the gas inside the compression chamber and a step for recirculating the gas towards the inlet of a chamber compression when the pressure measured is lower than a determined limit value.

The aims, advantages and particular characteristics of the method which is the subject of the present invention being similar to those of the device which is the subject of the present invention, they are not repeated here.

BRIEF DESCRIPTION OF FIGURES

• la figure 1 représente, schématiquement, un premier mode de réalisation particulier du dispositif objet de la présente invention,
• la figure 2 représente, schématiquement, un deuxième mode de réalisation particulier du dispositif objet de la présente invention et
• la figure 3 représente, schématiquement et sous forme d'un logigramme, une succession d'étapes particulière du procédé objet de la présente invention.

Other advantages, aims and particular characteristics of the invention will emerge from the non-limiting description which follows of at least one particular embodiment of the device and of the method which are the subject of the present invention, with reference to the appended drawings, in which:

• there figure 1 represents, schematically, a first particular embodiment of the device which is the subject of the present invention,
• there figure 2 represents, schematically, a second particular embodiment of the device which is the subject of the present invention and
• there picture 3 represents, schematically and in the form of a flowchart, a particular succession of steps of the method which is the subject of the present invention.

DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

This description is given on a non-limiting basis, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner.

Note that the figures are not to scale.

It is noted here that the term "gas" refers to both natural gas, biogas and syngas.

It is noted here that the term “liquid” refers to any liquid. Preferably, the use of a viscous and incompressible fluid is envisaged.

• au moins une chambre 105 de compression comportant :
  • une entrée 110 pour gaz à basse pression,
  • une sortie 115 pour gaz à haute pression,
  • une entrée 120 pour liquide,
  • une sortie 125 pour liquide et
  • un piston 130 situé entre l'entrée et la sortie pour gaz d'une part et l'entrée et la sortie pour liquide d'autre part et
• un moyen 135 de déplacement de liquide positionné sur un circuit de liquide reliant une sortie pour liquide et une entrée pour liquide d'une chambre de compression.

We observe, on the figure 1 , which is not to scale, a schematic view of an embodiment of the device 100 object of the present invention. This device 100 for compressing a gas at low pressure comprises:

• at least one compression chamber 105 comprising:
  • an inlet 110 for low pressure gas,
  • an outlet 115 for high pressure gas,
  • a 120 inlet for liquid,
  • a 125 outlet for liquid and
  • a piston 130 located between the inlet and the outlet for gas on the one hand and the inlet and the outlet for liquid on the other hand and
• a liquid displacement means 135 positioned on a liquid circuit connecting an outlet for liquid and an inlet for liquid of a compression chamber.

• l'entrée 110 pour gaz à basse pression,
• la sortie 115 pour gaz à haute pression,
• l'entrée 120 pour liquide et
• la sortie 125 pour liquide.

The compression chamber 105 is formed, for example, of a sealed wall surrounding a determined volume in which the piston 130 evolves. Preferably, the sealed wall comprises for only openings

• entry 110 for low pressure gas,
• outlet 115 for high pressure gas,
• inlet 120 for liquid and
• outlet 125 for liquid.

The compression chamber 105 may have an interior volume of cylindrical shape, for example. The term “cylindrical”, here, referring to a cylinder of revolution around an axis.

However, the interior volume of the compression chamber 105 can be of any type allowing the movement of a piston 130. This generally implies a constant cross section with respect to an axis of movement of the piston 130.

This piston 130 constitutes a tight separation between liquid and gas. The compression chamber 105 is configured to allow an increase in gas pressure to pressures greater than 50 bar, 100 bar or 200 bar, for example. Preferably, the pressure of the gas entering a compression chamber 105 is greater than 3 or 4 bar, and preferably greater than 7 bar.

Each element among the inlet 110 and the outlet 115 for gas and the inlet 120 and the outlet for liquid 125 is, for example, an opening made in the compression chamber 105. Each of these elements, 110, 115, 120 and 125, is preferably associated with a gas or liquid transport pipe depending on the nature of the element.

In preferred variants, at least one element among the inlet 110 and the outlet 115 for gas and the inlet 120 and the outlet 125 for liquid is provided with a non-return valve 140. This non-return valve 140 can be mounted directly on an opening of the compression chamber 105 or downstream of this opening, at the level of a pipe associated with the element considered, for example.

Such a check valve 140 is configured, for example, to prevent backflow of gas into a gas inlet 110.

In variants, at least one non-return valve 140 is replaced by a valve or any other type of device capable of blocking the passage of gas or liquid depending on the associated element.

In variants, the device 100 comprises a liquid retention valve 145 configured to retain the liquid in a chamber 105 of compression. This valve 145 can be of any type known to those skilled in the art and adapted to the operating pressure in the circuit 150 of liquid. This valve 145 can be mounted directly at the outlet of the compression chamber 105 or along the circuit 150.

It is noted that each element among the inlet 110 and the outlet 115 for gas and the inlet 120 and the outlet for liquid 125 can be formed of a multitude of sub-elements of the same type participating in the same function. For example, the gas inlet 110 may be formed by a multitude of openings in the compression chamber 105, each opening being supplied by a separate conduit or one common to other openings.

The piston 130 is, for example, a sealed surface or a membrane moving along an axis of the compression chamber 105. This piston 130 can be guided by an axis fixed to one or the other of the ends movement of said piston 130.

The displacement means 135 can be of any type allowing the displacement of a liquid in a liquid circuit. The choice of displacement means 135 depends on the size of circuit 150 and the total pressure drop of this circuit 150.

Preferably, the displacement means 135 is configured so that the liquid at the outlet has a pressure of between 30 and 70 bar. However, device 100 can achieve compression at any pressure value, preferably less than 300 bar.

Preferably, the displacement means 135 is a pump.

In preferred embodiments, the device 100 which is the subject of the present invention comprises a plurality of compression chambers 105 in series for the liquid circuit 150, an outlet 125 for liquid from a compression chamber being connected to an inlet 120 for liquid from another compression chamber.

In this variant, the filling of the chambers 105 is carried out sequentially, starting with the chamber closest to the discharge of the means 135 for moving the liquid. Once the operation is complete, the liquid is then sent to the second chamber 105, and so on.

In another variant, shown in figure 2 , the filling of the chambers 105 is carried out simultaneously. This filling is ensured, for example, by a main circuit which supplies the various compression chambers 105 .

In preferred embodiments, the device 100 which is the subject of the present invention comprises a plurality of compression chambers 105 in parallel for the gas, each compression chamber comprising an inlet 110 and an outlet 115 for gases independent of another compression chamber. compression.

In preferred embodiments, the device 100 which is the subject of the present invention comprises a means 165 for measuring the pressure of the gas inside the compression chamber 105 and a circuit 160 for recirculating the gas towards the inlet of a compression chamber when the measured pressure is below a determined limit value.

The pressure measuring means 165 is, for example, a pressure sensor positioned inside the compression chamber 105, on the gas side of the piston 130 or on the liquid side of the piston 130.

In variants, the pressure measuring means 165 is mechanical or electrical and operates by sensing the position of the piston 130 in the chamber. When this piston 130 reaches a determined position on its axis of movement, a gas pressure is deduced by the means 165 of measurement.

This determined limit value can be fixed during the design of the device 100 or variable and recorded from a central control circuit connected to the device 100 by means of a wired or wireless control link.

In preferred embodiments, the device 100 which is the subject of the present invention comprises a means 165 for measuring the pressure of the gas inside the compression chamber 105 and a means 170 for opening the outlet 115 for the compression chamber as a function of the measured pressure.

The opening means 170 is, for example, a discharge valve. In this example, the overflow device forms both the measuring means 165 and the opening means 170. This overflow device is calibrated at a set pressure.

In variants, the opening of a valve at the gas outlet as soon as the target pressure is reached is carried out, this valve closing at a threshold pressure. These pressure levels will be chosen by the operator depending on the use.

The operation of the device 100 as described with regard to the figure 1 is better understood with regard to the description, below, of the method 200 of operation of said device 100.

• une étape 205 d'entrée de gaz à basse pression dans une chambre de compression,
• une étape 210 d'entrée de liquide dans la chambre de compression,
• une étape 215 de déplacement d'un piston situé entre l'entrée et une sortie pour gaz d'une part et l'entrée et une sortie pour liquide d'autre part dans la chambre de compression,
• une étape 220 de sortie de gaz à haute pression de la chambre de compression
• une étape 225 de sortie de liquide de la chambre de compression et
• une étape 230 de déplacement de liquide sur un circuit de liquide reliant une sortie pour liquide et une entrée pour liquide d'une chambre de compression.

We observe, in picture 3 , schematically, a flowchart of particular steps of the method 200 object of the present invention. This method 200 for compressing a gas at low pressure comprises:

• a step 205 of entry of low pressure gas into a compression chamber,
• a step 210 of liquid entry into the compression chamber,
• a step 215 of moving a piston located between the inlet and an outlet for gas on the one hand and the inlet and an outlet for liquid on the other hand in the compression chamber,
• a step 220 for exiting high pressure gas from the compression chamber
• a stage 225 of liquid outlet from the compression chamber and
• a step 230 of liquid displacement on a liquid circuit connecting an outlet for liquid and an inlet for liquid of a compression chamber.

Preferably, initially, the pressure in the compression chamber is lower than the pressure in a gas supply line to a gas inlet of said compression chamber. This can be obtained by pressurizing the gas upstream or by reducing the pressure in the part dedicated to the liquid of the compression chamber.

To obtain such a reduction in pressure, a valve at the inlet of the liquid inlet is closed, for example, while the moving means is in operation. This causes the piston to move towards the liquid outlet, which reduces the pressure inside the gas part of the compression chamber, the gas outlet of which is also closed. Optionally, the gas inlet is also closed.

In cases where only the gas outlet is closed, a gas suction mechanism occurs through the gas inlet and gradually fills the gas part of the combustion chamber. This makes it possible to avoid the implementation of a displacement means specific to the gas supplied to the method 200 which is the subject of the present invention.

Whatever the solution for bringing the gas into the compression chamber, once entered, it finds itself captive to the variable volume dedicated to the gas in said compression chamber.

The displacement means 135 is activated, so as to fill the liquid part of the compression chamber with liquid, which gradually moves the piston towards the gas outlet, thereby compressing this gas.

Once the desired gas pressure is reached, the gas is released to the gas outlet of the compression chamber. To facilitate the exit of said gas, the circulation of liquid can continue, so as to further move the piston until the total, or almost total, evacuation of the gas towards the gas outlet.

To evacuate the liquid contained in the part dedicated to the liquid of the compression chamber, the outlet for liquid of the compression chamber is opened.

• fermeture de la sortie pour gaz,
• fermeture de l'entrée pour liquide,
• ouverture de l'entrée pour gaz,
• ouverture de la sortie pour liquide,
• mise en fonctionnement du moyen de déplacement du liquide,

ceci entraînant l'aspiration du gaz dans la chambre de compression, puis :

• fermeture de l'entrée pour gaz,
• ouverture de l'entrée pour liquide,
• fermeture de la sortie pour liquide,
• mise en fonctionnement du moyen de déplacement du liquide,

ceci entraînant la compression du gaz puis :

• ouverture de la sortie pour gaz,
• mise en fonctionnement du moyen de déplacement du liquide,

ceci entraînant l'expulsion du gaz.It is thus noted that it is possible to create a gas suction/compression/expulsion cycle by:

• closure of the gas outlet,
• closure of the liquid inlet,
• opening of the gas inlet,
• opening of the outlet for liquid,
• operation of the means for moving the liquid,

this causing gas to be drawn into the compression chamber, then:

• closure of the gas inlet,
• opening of the inlet for liquid,
• closure of the outlet for liquid,
• operation of the means for moving the liquid,

this leading to the compression of the gas then:

• opening of the gas outlet,
• operation of the means for moving the liquid,

this causing the gas to be expelled.

The method 200 object of the present invention is carried out, for example, by the implementation of one of the devices 100 or 300 objects of the present invention and described with regard to the figure 1 And 3 .

Claims (10)

1. Device (100, 300) for compressing a low-pressure gas, which comprises:

   - at least one compression chamber (105) comprising:

   - an inlet (110) for low-pressure gas,

   - an outlet (115) for high-pressure gas,

   - an inlet (120) for fluid,

   - an outlet (125) for fluid, and

   - a piston (130) located between the gas inlet and outlet, on the one hand, and the fluid inlet and outlet, on the other hand;

   - a fluid movement means (135) positioned on a fluid circuit connecting a fluid outlet and a fluid inlet of a compression chamber;

   - a means (165) for measuring the gas pressure inside the compression chamber; and

   characterized in that it comprises a circuit (160) to recirculate gas to the inlet of a compression chamber when the measured pressure is less than a predefined limit value.
2. Device (100, 300) according to claim 1, which comprises a check valve (140) configured to prevent a return of gas in a gas inlet (110).
3. Device (100, 300) according to one of claims 1 or 2, which comprises a fluid retention valve (145) configured to retain the fluid in a compression chamber (105).
4. Device (100, 300) according to one of claims 1 to 3, wherein the movement means (135) is configured such that the pressure of the exiting fluid is between 30 and 70 bar.
5. Device (100, 300) according to one of claims 1 to 4, wherein the movement means (135) is a pump.
6. Device (100, 300) according to one of claims 1 to 5, which comprises a plurality of compression chambers (105) in series for the fluid circuit (150), a fluid outlet (125) of one compression chamber being connected to a fluid inlet (120) of another compression chamber.
7. Device (100, 300) according to one of claims 1 to 6, which comprises a plurality of compression chambers (105) in parallel for the gas, each compression chamber comprising a gas inlet (110) and a gas outlet (115) independent of any other compression chamber.
8. Device (100, 300) according to one of claims 1 to 7, which comprises a means (165) for measuring the gas pressure inside the compression chamber (105) and a means (170) for opening the compression chamber gas outlet (115) as a function of the measured pressure.
9. Device (100, 300) according to one of claims 1 to 8, wherein the piston (130) of at least one compression chamber (105) comprises an impermeable surface or a membrane moving along an axis of the compression chamber (105).
10. Method (200) for compressing a low-pressure gas, which comprises:

    - a step (205) of inputting low-pressure gas into a compression chamber;

    - a step (210) of inputting fluid into the compression chamber;

    - a step (215) of moving a piston located between the gas inlet and a gas outlet, on the one hand, and the fluid inlet and a fluid outlet, on the other hand, in the compression chamber;

    - a step (220) of outputting high-pressure gas from the compression chamber;

    - a step (225) of outputting fluid from the compression chamber;

    - a step (230) of moving fluid over a fluid circuit connecting a fluid outlet and a fluid inlet of a compression chamber;

    - a step (235) of measuring the gas pressure inside the compression chamber; and

    characterized in that it comprises a step (240) of recirculating gas to the inlet of a compression chamber when the measured pressure is less than a predefined limit value.

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