ITRM20130313A1 - HYDRODYNAMIC COMPRESSOR FOR COMBUSTIBLE AND DETONING GASES - Google Patents

Description

HYDRODYNAMIC COMPRESSOR FOR COMBUSTIBLE AND DETONANT GASES

DESCRIPTION

Technical field of invention

The present invention relates to the field of operating machines. In particular, it relates to a compressor suitable for use with combustible or detonating gases.

Background

Many types of compressors, and in general of operating machines, capable of increasing the pressure of a gas, are known in the art. In known systems, a mechanical member, for example an impeller or a piston, interacts directly with the gas to increase its pressure.

The operating methods of known compressors become critical in the application to detonating or combustible (flammable) gases, such as for example methane, propane, butane, synthesis gas, volatile solvents or hydrogen, and this due to the risk of gas leaks and / or of explosions. A further risk is then associated with the possible alteration of the purity of the gas to be compressed.

Summary of the invention

The technical problem posed and solved by the present invention is therefore that of providing a compressor which allows to overcome the drawbacks mentioned above with reference to the known art.

This problem is solved by a hydrodynamic compressor according to claim 1 and by a method according to claim 10.

Preferred features of the present invention are the subject of the dependent claims.

The invention uses a liquid, preferably water, as a means of compressing the gas, which liquid is in direct contact with the gas inside a compression chamber that receives both of them, which chamber is preferably obtained in a cylinder.

In this way, the invention is able to solve the aforementioned problem of the compression of explosive or flammable gases, avoiding gas leaks, deflagrations and / or alterations in the purity of the compressed gas. In particular, the compressor and the method of the invention are also applicable to those gases, such as oxygen, in which the absolute purity of the compressed gas is essential.

Furthermore, as will become clearer also from the detailed description given below, the invention allows to:

∠’reduce the need for mechanical seals;

∠’reduce the risk of gas leaks;

∠’reduce the risk of compressed gas deflagration;

∠’cooling the compressed gas using the same compression liquid;

∠’arrange a motor group - hydraulic pump that pressures the aforementioned liquid in a remote position with respect to the gas compression area;

∠’to make the aforementioned motor unit - hydraulic pump work safely even outdoors with the presence of flammable gases;

∠'use almost exclusively mechanical components, particularly in gas compression cylinders, limiting the electrical power supply to the engine unit only - hydraulic pump (and thus eliminating the possibility of explosive triggers in the gas compression area) ;

∠’make said motor group - hydraulic pump in modular form;

∠’drastically reduce maintenance needs;

∠eliminate the risk of contamination of the gas to be compressed with impurities associated with the moving mechanical parts of the known art.

It should be noted that the compressor of the invention makes it possible to associate the safety of known hydraulic compressors for very high pressures (250 bar) with the large flow rates typical of current water-cooled mechanical compressors.

Other advantages, characteristics and methods of use of the present invention will become evident from the following detailed description of some embodiments, presented by way of non-limiting example.

Brief description of the figures

Reference will be made to the figures of the attached drawings, in which:

Figure 1 shows a block diagram of a preferred embodiment of the compressor of the invention;

- Figures 2A and 2B each show a schematic representation of a first variant embodiment of part of the compressor of Figure 1, in a specific operating phase;

- Figures 3A and 3B each show a schematic representation of a second variant embodiment of part of the compressor of Figure 1, in a specific operating phase, in which Figure 3B highlights some components omitted, for greater clarity, in Figure 3A;

- Figures 4A, 4B and 4C each show a schematic representation of some valves of the compressor of the previous figures, in specific operating configurations;

- Figure 5 shows a variant embodiment of the compressor of Figure 1; And

â– Figures 6 and 7 each show a respective exemplary graph of the operating modes of the compressor of Figure 1.

Detailed description of preferred embodiments

With reference initially to Figure 1, a compressor according to a preferred embodiment of the invention is generally denoted by 1. Figure 1 shows the compressor 1 as a whole and in absolutely schematic form. In particular, for the sake of simplicity, no accessory components have been shown such as filters, ventilation systems for cooling, pressure and temperature control instruments and so on.

The compressor 1 comprises a pumping system 2, typically formed by a hydraulic pump, by a relative driving motor and by two non-return valves, positioned respectively on a fluid inlet line 91 and on a fluid outlet line 101 .

The pumping system 2 is designed to pressurize a compression liquid which flows through lines 91 and 101.

The compressor 1 then comprises a system of valves 3, or equivalent flow control means, operatively connected to the pumping system 2 by means of fluid supply lines denoted by 9 and 10, so that the unit 2 and the system 3 are precisely in communication of fluid, and in particular of liquid. In the embodiment shown, line 10 carries liquid from system 2 to system 3 and line 9 carries fluid from system 3 to system 2.

The valve system 3 preferably comprises two flow reversal valves, generally denoted by 14 in Figure 1, and an optional by-pass valve 15.

The valve system 3 is then operationally connected - again by means of fluid supply lines that establish a communication of liquid - to a gas compression system, the latter overall denoted by 4. In particular, in Figure 1 are two hydraulic lines 11 and 12 are shown, both configured in such a way as to allow the fluid to flow in both directions, according to the specific operating phase.

The gas compression system 4 comprises a pair of cylinders, 16 and 17 respectively, each suitable for receiving inside the gas to be compressed and the compression liquid in such a way that they are in direct contact at respective interface surfaces. Variants of embodiment can provide a pair of compression chambers different from the cylinders 16 and 17 considered here.

Each cylinder 16, 17 therefore comprises respective inlet means - in particular a respective inlet port 200, 210 - for the gas to be compressed and respective outlet means - in particular a respective outlet port 220, 230 - for the compressed gas. In the present example, the aforesaid inlet and outlet doors are, for each cylinder 16, 17, distinct.

At said inlet and outlet ports, respective non-return valves are preferably provided, denoted by references from 20 to 23 in Figure 1.

Each cylinder 16, 17 then comprises respective inlet and outlet means for the compression liquid, which in the present example are realized as the same port 180, 190. Also in this case, in correspondence with the liquid inlet / outlet ports 180 and 190 Respective valves 18 and 19 are provided. Preferably, the latter are suitable for regulating the minimum-maximum level of liquid within the respective cylinder 16, 17, according to methods which will be illustrated hereinafter.

In the arrangement shown, the inlet and outlet of liquid are provided at a lower base of each cylinder 16, 17, while the gas supply and its outlet are provided at an upper portion of each cylinder 16, 17 longitudinally opposite the lower base.

Figure 1 also shows a gas supply line to be compressed within the cylinders 16 and 17, denoted by 7, and a line 8 which conveys the compressed gas that comes out of the cylinders 16 and 17 towards a condensate separator 5. The line 8 is a pressurized line in use, receiving the compressed gas from cylinders 16 and 17 through the respective non-return valves 22 and 23.

The gas leaving the condensate separator 5 flows in a gas outlet line 140 (generally connected to a tank and / or a distribution line), while the condensate flows in a condensate outlet line 141 which joins the line 10 already introduced above.

The condensate separator 5 separates precisely the part of vaporized compression liquid that has been dragged along with the compressed gas out of cylinders 16 and 17.

The condensate separator 5 can be of a per se known type, typically incorporating a condensate recirculation pump and a non-return valve. Preferably, the condensate recirculation pump is instrumented / configured in such a way as to stop the pump itself when, after the condensate, gas is present in the line 141 or in an associated duct. Preferably, however, the flow rate of the recirculation pump is regulated in such a way that the condensate is recirculated continuously.

The compressor 1 further comprises, or is associated with, a reservoir 6 for replenishing the compression liquid. The latter provides a supply line for make-up liquid, denoted by 13 and preferably associated with a non-return valve, and a line 131 for supplying liquid to the pumping system 2, which flows into the inlet line 9 / 91.

It will be understood that the various liquid and gas supply lines introduced up to now can be made in the form of ducts.

As will be clear from the operating modes of the compressor 1, the liquid supply lines form a hydraulic circuit suitable for supplying the cylinders 16 and 17 alternately.

Compressor 1 also includes a control unit, not shown and which can also be incorporated into any of the components described, as a single unit or divided into sub-units. The control unit is suitable for allowing coordinated operating methods between the various components introduced up to now, which methods will be described shortly. It is also integrated with a set of sensors, in particular pressure sensors, to allow the selective activation of the various components, again according to the operating modes that will be described later.

In a preferred embodiment, the compression liquid is water. Variants of construction can provide for the use of other fluids such as oil or glycol. The specific choice depends on the purity requirements and / or the chemical contents required in the gas to be compressed.

As far as gas is concerned, this can be air or any gas, even detonating or flammable, as already mentioned, for example methane.

As already mentioned in general terms, the arrangement described makes it possible to position the compression system 4, and in particular the cylinders 16 and 17, in a remote (and therefore safe) position with respect to the other components of the compressor, and in particular with respect to the system pumping pump 2 and valve system 3. Of course, you can choose the desired length and route for lines 11 and 12 for this purpose.

Precisely because it is located far from the compression system 4 and not in direct contact with the gas to be compressed, the pumping system 2 does not require any specific technical device. In particular, the use of magnetic couplings is not necessary for both the motor and the relative pump. This translates into the possibility of using substantially any motor both DC and AC, both synchronous and asynchronous and with every possibility of regulating the number of revolutions and torque. Similarly, the pump can be piston, lobe, vane, screw or other, volumetric or not, the specific choice depending of course on the range of flow rates and pressures to be obtained for the compressed gas.

As mentioned above, the various valves and necessary control devices are almost all located near the pumping system 2 and only the gas suction / expulsion valves 10-23 and the minimum / maximum liquid level 18 and 19 are located in the body of the compression system 4.

The operating modes of compressor 1 will now be described.

Figures 2A and 2B are schematic representations, in principle, of the cylinders 16 and 17, of the valve system 3 and of the pumping system 2 of the compressor 1. In the variant shown, the pumping system 2 is of the reciprocating piston type. Its engine, for simplicity, has not been shown.

Compressor 1 is configured in such a way that pumping system 2 sends the compression liquid, water in this example, alternately into cylinder 16 and cylinder 17.

Going more into the operational detail, Figure 2A shows a configuration in which the cylinder 17 is in the gas compression phase - this last one denoted by G and represented in a dark background as precisely under pressure - by means of the compression - the latter denoted by L and also represented in dark tones as it is under pressure. The gas inlet port 210 (shown in Figure 1) is closed by means of the valve 21 and the gas outlet port 230 is closed by the valve 23, while the liquid inlet / outlet port 190 is open for to allow the liquid itself to enter the cylinder 17.

In the configuration shown in Figure 2A, the pressure is rising in cylinder 17. This pressure increase continues until substantial equality with the pressure in line 8 is achieved (or when the pressure in cylinder 17 is not slightly higher than that of the line 8).

At this point the expulsion of the gas begins through the special valve 23.

The ducts 11 and 12 that connect the pumping system 2 to the cylinders 16 and 17 are also shown in light and dark shades respectively to represent the different pressure of the liquid (higher in line 12).

Simultaneously, the cylinder 16 is in the phase of aspiration of the gas through the inlet port 200 and the relative valve 20, shown open in Figure 2A (for this reason the gas has been represented with a less dense background). In this phase, the gas outlet port 220 and the relative valve 22 are closed and the liquid outlet port 180 is open to allow this to flow out of the cylinder 16.

With reference to Figure 2B, when the compressed gas has been completely expelled from the cylinder 17, a closing valve 231, by means of its own mechanical element, blocks the gas outlet port 230 and therefore closes the outlet flow, generating a peak pressure in the hydraulic connection line 12 (a similar shut-off valve 221 is present on the cylinder 16). A special sensor detects this pressure peak and determines the activation of the inversion valve 14, so that the flow of liquid is reversed, ie it flows out of cylinder 17 and into cylinder 16. In the latter, meanwhile à The gas suction phase is finished and is therefore ready to be compressed.

The â € œcrossedâ € connections shown at the level of the valve 14 are a graphic example of the exchange of the suction and delivery connections of liquid.

Also in Figure 2B the ducts 11 and 12 that connect the pumping system 2 to the cylinders 16 and 17 are shown in inverted shades with respect to Figure 2A, respectively dark and light to represent the different pressure of the liquid (higher in line 11).

The bypass valve 15 (schematized in Figure 1 and then in the following Figure 3A) assumes the role of short-circuiting the liquid suction pipe 9 and the liquid compression pipe 10, i.e. to exclude the pumping system 2 thus depressurizing the relative hydraulic pump and the cylinder compressed when the flows are reversed.

In the phase immediately following that shown, therefore, in the cylinder 16 the gas inlet port 200 is closed by means of the relative valve 20, while the gas outlet port 220 is also closed by means of the valve 22. As already illustrated in relation to compression in the cylinder 17, also in cylinder 16 the outlet valve 22 remains closed until the pressure in the cylinder 16 reaches and / or slightly exceeds the pressure in the outlet line 8. At this point, the valve 22 will be forced to open and allow the outlet of the compressed gas flow, while in the cylinder 17 the gas inlet port 210 is opened by means of the valve 21, while the gas outlet port 230 remains closed.

A special pressure switch (not shown) detects the pressure in the outlet line 140 (shown in Figure 1) and sends, when the desired level has been reached, a shutdown signal to the pump motor of the pumping system 2.

Figures 4A, 4B and 4C exemplify the different possible configurations for the reversing valve 14 and for the bypass valve 15.

In particular, Figure 4A refers to a normal operating phase, in particular that of Figure 2A, in which one cylinder (17) is in the gas compression phase and the other (16) in the gas suction phase . Bypass valve 15 is closed.

Figure 4B refers to the interlocutory phase of flow reversal, in which the bypass valve is open, causing a `` short circuit '' between the suction and compression lines 8 and 9, so that the pumping system 2 recirculate the liquid between the outlet and inlet of cylinders 16 and 17. This allows the position of the reverse flow valve 14 to be changed.

Finally, Figure 4C refers to a different normal operating phase, corresponding in particular to that of Figure 2B.

It will be better understood at this point that the valve system 3 is configured in such a way as to allow the fluid compressed by the hydraulic pump of the system 2 to flow alternately, through the appropriate flow inversion valve 14, from the intake cylinder. to compression and vice versa.

The hydrodynamic compressor just described is therefore conceptually alternative, even if the pumping system 2 can assume any possible configuration.

It will be better appreciated at this point that the valves and components of the regulation and control system of the hydrodynamic compressor 1 can be of the mechanical type, without requiring electronic systems powered by electricity. However, this does not exclude the possibility that an electronic adjustment system of the compression system 2 offers both great operational flexibility and a significant reduction in costs, without detracting from the total safety of the entire gas compression system. Therefore, both the by-pass valve 15 and the flow inversion valve 14 can also be made in the form of two-way (ON-OFF) and three-way electrically operated valves. As regards the realization of both valves in the form of three-way valves, it is good to remember that, in passing from the connection to one way to the connection to the other, there will be a period in which the three ways can all be connected among them. During this period there will be a decompression of the cylinder under pressure and a compression of the other. Subsequently, the pump of system 2 will continue to suck from one cylinder to compress in the other. In this case, the “task” of the two-way ON-OFF valve (by-pass), the role graphically separated from the attached diagrams, is inherent in a transitory moment in the functioning of the three-way valves.

With reference now to Figure 3A, according to a variant embodiment, the pumping system, denoted here with 52, is based on a volumetric lobe pump (schematized as a sort of gears). This type of pump can provide greater continuity and contextuality of the suction and compression phases, making the operation continuous and not very noisy.

For the rest, the compressor of this embodiment variant can be similar to the one already described with reference to the previous figures. In particular, Figure 3A also explicitly represents the condensate separator 5 (showing both a real separator body 500 and an associated pump 501) and the non-return valve.

In addition, Figure 3B also provides for the make-up tank 6. This last figure also provides an exemplary graphical representation of the valves 18 and 19 associated with the fluid inlet / outlet ports 180 and 190.

On the basis of a preferred embodiment variant, shown in Figure 3B and which can also be associated with the embodiments of the compressor described with reference to Figures 1 to 3A, the valves 18 and 19 are suitable for closing the flow of outgoing liquid if the respective cylinder is in the gas suction phase and the fluid level inside it is too low (cylinder 17 in Figure 3B). This closure causes a depression in the hydraulic circuit which, by mechanical effect only, allows the pump of the system 52 to suck the liquid from the tank 6, thus replenishing the leak. The same valve 18 or 19 (the 19 in the phase shown in Figure 3B) will, at the same time, open a smaller duct 55, 56 (56 in the example shown) connected to the pressure line (line 11 in the example shown), in order to bring the level back to the maximum position. In this way the fluid level inside each cylinder on the intake will be kept between two minimum and maximum positions.

Also in Figure 3B, for greater clarity, non-return valves have been shown arranged on lines 9, 10 and 141, on pipes 55 and 56 and at the outlet from tank 6.

With reference now to Figure 5, a variant embodiment is shown in which two compression systems 41, 42 are provided, connected in parallel to a single pumping system 52.

It will be appreciated that the compressor of the invention lends itself to being absolutely modular, allowing the addition of cylinders and other components according to specific power requirements.

A brief analysis of the energy savings associated with an embodiment of the invention is now carried out by way of example.

By briefly analyzing the compression device 4 of Figures 1 to 4C and assuming an adiabatic thermodynamic transformation for the compressed gas, we can apply the Poisson equation (considering Cpe Cv constant):

T p <(1-γ) / γ> = cost (1)

with γ = Cp / Cv.

In the case of methane (Cp = 35.877 J / (mol · k) and Cv = 27.467 J / (mol · k)), it results γ = 1.305.

The (1) then becomes

T p <-0.234> = cost (2).

If we now assume a final pressure of 9 absolute bars we will have:

T9bar = 293 1/9 <-0.234> = 490 K (217 ° C)

We consider that the transformation may not be totally adiabatic, on the contrary, by suitably finning the compression cylinders 16 and 17, we will have a transfer of heat to the outside.

For the sole purpose of providing an idea of the energy savings that the system offers, it is assumed that all the heat generated in the compressed gas evaporates part of the liquid interface which is in immediate contact with the compressed gas. Considering a latent heat of evaporation of water equal to about 2300 kJ / kg and that the energy needed to raise the temperature of 1 mole of methane, for example from 20 to 150 ° C, is about 4.7 kJ, a we will have the evaporation of about 4.7 / 2300 = 2 g of water for each mole of compressed methane.

Finally, considering an atomic weight of water equal to 18, we will have in volumetric terms:

2/18 â ‰ ˆ 0.11 moles / (moles of CH4) â ‰ ˆ 2.5 dm <3> of steam, again for each mole of compressed CH4.

The evaporation of the interface water brings the transformation towards an isotherm, rather than towards an adiabatic. The graph of the adiabatic follows the Poisson equation: p V <γ> = cost, while the isotherm follows the ideal gas equation (Boyle-Mariotte): p V = cost

The graph shown in Figure 6 provides the reason for the decrease in the work required, since a higher air flow rate can be brought to the same pressure, because it has a lower temperature (point B of the Isotherm).

In a volumetric compressor, to pass from a volume A to a volume B, we will find higher pressures in the adiabatic transformation (Badiab) than in the isothermal one (Bisot), as shown in the graph of Figure 7

This translates into substantial energy savings which, combined with the regulation and control systems of the motor unit, can easily lead to savings of around 30%.

The invention also relates to a method as defined in the following claims, preferably implemented by means of the structural and / or functional characteristics of the compressor as described up to now.

The present invention has been described heretofore with reference to preferred embodiments. It is to be understood that other embodiments may exist which refer to the same inventive core, as defined by the scope of protection of the claims reported below.

Claims (14)

CLAIMS 1. Compressor (1), particularly suitable for use with combustible or detonating gases, comprising: - a pumping system (2), adapted to pressurize a compression liquid; - a pair of compression chambers (16, 17), each having gas inlet (20, 21) and outlet (22, 23) means and inlet and outlet (18, 19) means for the compression liquid; And - a hydraulic circuit (11, 12) for connection between said chambers (16, 17) and said pumping system (3), the overall configuration being such that in each of said chambers (16, 17) the compression liquid and the gas are in direct contact, in each of said chambers (16, 17) a gas compression phase takes place alternatively by of the compression liquid and a phase of aspiration of gas to be compressed, and in which said hydraulic circuit (11, 12) is such that said chambers (16, 17) operate in a mutually alternating manner, said compression liquid flowing between the two chambers (16, 17) in such a way that when in a chamber a gas compression phase takes place in the other a gas suction phase takes place, and vice versa. Compressor (1) according to claim 1, comprising a pair of cylinders (16, 17) each of which has a respective compression chamber. Compressor (1) according to claim 1 or 2, wherein said pumping system (2) comprises a rotary pump, in particular a lobe pump. Compressor (1) according to claim 1 or 2, wherein said pumping system (2) comprises a reciprocating pump, in particular a plunger pump. 5. Compressor (1) according to any one of the preceding claims, comprising means for reversing the flow (14) from / to each of said chambers (16, 17), arranged in correspondence with said hydraulic circuit (11, 12). 6. Compressor (1) according to any one of the preceding claims, comprising bypass means (15) of said pumping system (2), arranged in correspondence with said hydraulic circuit (11, 12) and adapted to put in direct communication a Liquid outlet (180, 190) of one of said chambers (16, 17) with a liquid inlet (180, 190) of the other of said chambers (16, 17) and vice versa. Compressor (1) according to any one of the preceding claims, comprising a condensate separation device (5) of said compression liquid from the compressed gas, and preferably a condensate recirculation system within said hydraulic circuit (11, 12). Compressor (1) according to any one of the preceding claims, comprising a system (6), preferably automatic, for replenishing the compression liquid within said hydraulic circuit (11, 12). Compressor (1) according to any one of the preceding claims, comprising sensor means suitable for detecting a gas pressure in one or more selected points of a gas outlet line (8) and / or sensor means suitable for detecting a pressure of liquid in one or more selected points of said hydraulic circuit (11,12) and a control unit suitable for controlling the alternating operation of said compression chambers (16, 17) according to the pressure value or values detected by said sensor means. 10. Method of compression of a gas, particularly suitable for the compression of a combustible or detonating gas, in which two compression chambers (16, 17) are provided, in each of which a compression liquid is placed in direct contact with the gas to be compressed, in which in each of said chambers (16, 17) there is alternately a gas compression phase by the compression liquid and a gas suction phase to be compressed, and in which said chambers (16, 17) operate in a mutually alternating manner, said compression liquid flowing between the two chambers in such a way that when a compression phase takes place in one chamber, an aspiration phase takes place in the other, and viceversa. 11. Method according to the preceding claim, in which said chambers are formed in respective cylinders (16, 17). Method according to claim 10 or 11, which provides for a separation of the condensate of said compression liquid from the compressed gas, and preferably a recirculation of the condensate within said chambers (16, 17). 13. Method according to any one of claims 10 to 12, wherein the alternating operation of said compression chambers (16, 17) is controlled as a function of the gas pressure value detected at an outlet line ( 8) and / or the liquid pressure value detected in correspondence with a hydraulic circuit (11, 12) for feeding said chambers. Method according to any one of claims 10 to 13, which is used in a compressor (1), the latter preferably according to any of claims 1 to 8.