ES2368107T3 - HIGH ENERGY EFFICIENCY EQUIPMENT FOR METHANE COMPRESSION FOR AUTOMOTIVES. - Google Patents

Abstract

A gas compression plant (1) including at least a gas compressor (2) and at least a cylinder casing (3) is disclosed. The compressor (2) completely compresses the gas via at least two consecutive compression stages. The cylinder casing (3) contains as many cylinders (4) as the compression stages, the compressed gas being stored in the cylinders (4) substantially at the maximum pressure achieved in each compression stage. The gas compression plant (1) comprises means to feed the compressor (2), prior to the execution of each consecutive stage, with gas from the previous compression stage, stored in the respective cylinder (4).

Description

High energy efficiency equipment for methane compression for motor vehicles.

Technical Sector

The present invention relates to the natural gas compression process for use in automobiles and more particularly to a high energy efficient equipment for methane compression for automobiles.

State of the Art

The current technique in the sector of automotive methane compression systems contemplates an increase in the pressure in the pipeline (in a range between 4 bar and approximately 40 bar) up to 280 bar, necessary for filling operations, using a Multi-stage multi-stage compressor with intermediate heat exchanger.

The system involves the construction of a compressor with adequate capacity for the equipment requirements, correlated to the supply capacity normally required once in operation. Between the different stages there must be one of cooling on the one hand to lower the initial temperature of the compressed gas at each stage, thus reducing energy consumption, and on the other hand to protect the compressor's sealing parts.

Therefore, such systems require single-acting or double-acting multi-cylinder compressors designed so that the respective volumes are appropriate for density variations of a capacity that must be identical in each of the stages.

The known technique already included such multi-cylinder compressors, disclosed, for example, through FR 2,503,279, which is considered the closest known technique, where a compressor group provided with a plurality of compression stage compressors is illustrated , installed in a single tree. Said compressors are provided with bypass lines that can be closed to obtain that the power in the non-operational state is as low as possible and to obtain as quickly as possible at the time of start-up or when it goes into the non-operational mode.

Another example of such compressors is disclosed in EP 0.757.179 where a compressor apparatus for cooling circuits is displayed, which is provided with a turbocharger with a plurality of compression stages installed in a single shaft. Such apparatus comprises mixing devices, interspersed between two successive stages of the compressor, into which the feed and main gas flows are introduced. The two flows are mixed in the mixing device so that the flow leaves the mixing device with a homogeneous temperature distribution and speed distribution before operating in the next stage of said turbocharger having a plurality of compression stages.

In the known technique, and more particularly in the automotive methane compression equipment sector, cooling requires large and, consequently, expensive systems, which significantly influence the final cost of the equipment. In fact, they must cool the gas predominantly with air or water circuits. Also, every time the compressor is used to extract gas, it is subjected to permanent starts and stops. This is one of the main factors that affect its reliability, therefore imposes, at the time of the project, having to oversize it.

The problems of operation of such equipment increase in the case of high ambient temperatures (for example, in tropical countries), which damages the intermediate heat exchanger system.

A traditional equipment of the type described above is schematically shown in Figure 1.

Disclosure of the Invention

A main objective of the present invention is to eliminate the disadvantages of known equipment by providing equipment whose operation exhibits significantly higher energy efficiency.

A second objective of the present invention is to provide equipment capable of obtaining the pressure changes obtained by known equipment using a much simpler and therefore less expensive design and one that is more reliable compared to similar known designs.

A further objective of the present invention is to provide equipment with a smaller compressor.

Another objective is to provide equipment with compressors designed to operate constantly, which are more reliable than traditional intermittently operated compressors.

In accordance with the present invention said objectives are achieved by means of a device (according to claim 1 and / or any of the claims directly or indirectly dependent on it) using a single stage compressor and suitable intermediate storage systems at different pressures, located In a refrigerated environment. Through a single compression stage the gas is brought from its pipe pressure to a low pressure, it is stored, then it is brought to a medium pressure and ultimately to its final pressure.

Pressure changes are obtained by the same compressor through a supply switching with suction. The compressor achieves different pressures through different delivery periods in accordance with the amount of gas stored in the cylinders.

At the filling station, the customer's vehicle will be fed first with low pressure methane, then with medium pressure methane and finally with maximum pressure gas. This will allow to inject into the tanks or cylinders of the vehicle the total mass of gas required at its maximum pressure, thus saving the energy that could be necessary to bring the total mass to said maximum pressure.

Brief Description of the Drawings

The advantages of an equipment manufactured according to the present invention are illustrated below by a detailed description of a preferred embodiment given purely by way of example and, therefore, without restriction of the same equipment, where:

-

Figure 1 is a basic drawing of a conventional compression equipment;

-

Figure 2 is a functional diagram of the equipment fed with a pressure of approximately 20 bar, where the different pressure levels are displayed;

-

Figure 3a is a functional diagram of the stage in which the low pressure cylinder is fed with gas from the pipe;

-

Figure 3b is a functional diagram of the stage in which the medium pressure cylinder is fed with gas from the low pressure cylinder;

-

Figure 3c is a functional diagram of the stage in which the high pressure cylinder is fed with gas from the medium pressure cylinder;

-

Figure 4 is a functional diagram of the distribution stage to customers, with multiple successive fillings from the three different cylinders;

-

Figure 5 is a basic drawing of an equipment manufactured according to the present invention, provided with a stage of adaptation to the suction pressure of the pipe.

Detailed Description of the Preferred Executions of the Invention

In the figures of the attached drawings, the number 1 indicates a gas compression equipment of the type provided with a gas compressor (2) and a cylinder liner (3).

The compressor (2) is a one-stage apparatus fed with natural gas from the pipeline through a suction conduit (9) that channels the compressed gas into a supply conduit (10). Pipeline gas enters the suction line (9) of the compressor (2) at an initial pressure of approximately 20 bar and exits the supply line (10) at a maximum pressure of approximately 290 bar.

The pressure change from an initial pressure to an end pressure is obtained through the compressor (2) in three successive stages of compression, among which the total pressure difference is appropriately divided.

The cylinder wrap (3) includes as many cylinders (4) as steps or compression stages, each cylinder

(4) storing compressed gas substantially at the maximum pressure obtained in each of the stages in which the total pressure difference has been subdivided.

Likewise, the equipment (1) includes means for feeding the compressor (2), before the execution of each of said consecutive stages, with gas coming from the cylinder (4) that has been filled last. The above is shown in greater detail in Figures 3a, 3b and 3c, where you can see the functional diagrams of the three phases of compression and storage.

As can be seen in figure 3a, the gas coming from the supply line (14) is compressed from the initial pipe pressure [for example 20 bar] to a low pressure (LP) of approximately 49 bar.

This is achieved by aspirating natural gas from the supply line (14), while an inlet valve (11) located in said line is open, a valve (12) located before a first low pressure cylinder (4) ( LP), and a valve (13) located on a first branch (15) that connects the supply line (10) to the first low pressure cylinder (4) (LP).

As can be seen in Figure 3b, the gas is compressed at the average pressure (MP) of approximately 120 bar. Compression of natural gas in the compressor (2) is obtained by aspirating gas from the low pressure cylinder (4), keeping the valve (12) and a valve (17) located in a section (20) of the conduit that is open Connect the low pressure cylinder (LP) to the suction line (9) of the compressor (2). An inlet valve (18) is also open to the medium pressure cylinder (4) (MP), and a valve (19) located in a second branch (21), which connects the supply line (10) to the cylinder ( 4) medium pressure (MP).

As can be seen in Figure 3c, the gas is compressed at the maximum pressure [approximately 290 bar]. Compression is obtained by aspirating gas from the medium pressure cylinder (4), keeping open the valves denoted with 17 and 18. A valve (22) located in a section (23) of the conduit connecting the medium pressure cylinder (4) to the suction duct (9) of the compressor (2) through the section denoted with 20 and an inlet valve (24) to the high pressure cylinder (4) located at a third branch (25) of the feed duct (10).

Figure 4 shows the filling of a storage cylinder of a vehicle. Operations begin with the filling of the vehicle storage cylinder with gas at a pressure just greater than the pressure in the same cylinder of the vehicle, keeping the interception valve open

(26) of a distribution hose (28) and an outlet valve (27) of the low pressure cylinder (4) (LP).

Once the low pressure is reached, the vehicle cylinder is filled from the medium pressure cylinder (4) (MP), keeping the valve denoted with 26 and an outlet valve (29) of the medium pressure cylinder (4) open ( MP).

Once this step is completed, the vehicle cylinder is finally filled with gas from the high pressure cylinder (4) (HP), keeping said valve denoted with 26 and an outlet valve (30) of the cylinder (4) open high pressure (HP).

In the description of the operation of the equipment (1), the storage and supply of natural gas have been described as if they were independent of each other. Obviously, storage and supply can be performed simultaneously.

The equipment (1) comprises cooling means (5) of the gas stored in the cylinders (4). The system can be carried out in the form of a conventional cooling system with a compressor (31), whose function can be carried out by the same compressor (2) that compresses natural gas.

The cooling system may be provided with motors to propel the compressor (31). Such engines may be separated or be the same as the natural gas compressor (2) propulsion engine (6).

The motors can be indifferently electric or thermal.

Alternatively, the cooling can be carried out by a high thermal capacity fluid spray system associated with the cylinders (4) in the liner (3) of the cylinders.

In particular, the cylinders, stacked on shelves, can be sprayed from above with a chilled solution of water and ethyl alcohol by means of a nozzle system; said solution, collected in a tank, can then be aspirated by means of a pump that takes it back to the cooling system for its new cooling. The system requires a coating for the shelves and the tank.

An alternative embodiment is one where the cooling is provided by a tank containing a high thermal capacity fluid in which the cylinders (4) are submerged.

More particularly, the cylinders (4), regardless of the way they have been packaged, must be placed in large water-impermeable steel containers filled with a solution of water and ethyl alcohol from the cooling system; As in the case mentioned above, the fluid is taken back to the refrigerator to be cooled again. When available, as an alternative to the cooling system, well filtered water made periodically recirculated could be used.

In any case, the cylinders function as heat exchangers. Therefore, if necessary it is possible to use devices that increase heat exchange, for example fins.

In accordance with the present invention, the equipment (1) is provided with sensor means (8), operatively associated with the compressor (2) and with the cylinders (4). Once it has been detected that the maximum pressure in each cylinder (4) has been achieved, said sensor means (8) disconnect the gas inlet into the compressor (2), activating its connection to the next cylinder (4) and connect the compressor suction (2) activating its connection to the previous filled cylinder (4) during the preceding compression stage.

The pressure of the individual stages is defined based on what is customary. The minimum pressure in the storage cylinder of a vehicle when it is presented to a filling station is approximately 30 bar. This determines the low pressure value, which will reasonably exceed 30 bar; a value of approximately 50 bar is considered appropriate.

Since the maximum allowable filling pressure is normally about 300 bar, the average pressure is approximately 120 bar.

Since a single compressor is used, starting from a pipe pressure of 20 bar, an appropriate progression of 49-120-294 is obtained by a constant compression ratio, equal to 2.45. In the case of higher pipe pressures an adequate compression ratio is calculated and, therefore, the pressure progression is adapted. On the other hand, in the case of lower pipe pressures, to reach 20 bar it is imperative to place a pressure adaptation stage, with its corresponding storage and cooling stage.

A basic drawing of such equipment is shown in Figure 5; In the same figure you can see a pipe pressure of 4 bar, common in Italy, and which requires an additional compressor with a compression ratio equal to 5.

The invention disclosed fully satisfies these requirements and also achieves other advantages.

An additional advantage is that, acting only on the pressure difference between the stages and only on a reduced amount of gas, that is to say the amount of gas supplied to the cylinder casing (3), they are subject to gas storage at intermediate pressures. a single compressor (2) and a single compression stage.

From the above derives considerable energy savings.

In addition, the lower total compression ratio required to the compressor (2) allows the use of smaller compressors (2), which implies lower equipment and exercise costs.

The continuous operation design of the compressor (2) carries the additional advantage of greater equipment reliability (1).

On the other hand, another advantage is that the cylinders (4) can function as coolers.

The present invention can be modified and adapted in different ways by experts in the sector, who can choose the most appropriate dimension and the most suitable construction materials depending on the type of application. Such changes, therefore, should be considered inherent in the invention and as such included within the scope of the subject of the following claims.

Claims (13)

1.-Gas compression equipment, of the type comprising at least one gas compressor (2) and at least one cylinder envelope (3), characterized by the fact that said compressor (2) is a one-stage compressor that the complete compression of the gas is obtained through at least two consecutive compression steps, said consecutive compression steps obtained by means of successive compression steps through said one-stage compressor (2), said cylinder wrap (3) including as many cylinders (4) as compression steps, said cylinders (4) storing compressed gas substantially at the maximum pressure obtained in each of said steps, and supply means (7) for distributing compressed gas to fill the cylinder of storage of a vehicle; said equipment being provided with means for feeding said compressor (2), before the execution of each of the successive steps, with gas from the previous compression step, stored in the respective cylinder (4). 2. Equipment according to claim 1, characterized in that it comprises cooling means (5) of the gas stored in said cylinders (4). 3. Equipment according to claim 2, characterized in that said cooling means (5) comprise a cooling system. 4. Equipment according to claim 2, characterized in that said cooling means (5) comprise a high thermal capacity fluid spray system associated with the cylinders (4) arranged in said cylinder wrap (3). 5. Equipment according to claim 2, characterized in that said cooling means (5) comprise a tank containing a high thermal capacity fluid into which said cylinders (4) are submerged. 6. Equipment according to claim 3, characterized in that said cooling system comprises a compressor (2), said gas compressor (2) being the propulsion compressor (2) of the cooling system. 7. Equipment according to claim 3, characterized in that said cooling system comprises engines (6), said gas compressor (2) being propelled by engines (6) which are also propulsion of the cooling system. 8. Equipment according to claim 1, characterized in that said compressor (2) is propelled by electric motors (6). 9. Equipment according to claim 1, characterized in that said compressor (2) is propelled by thermal motors (6). 10. Equipment according to claim 1, characterized in that said cylinders (4) can store and supply compressed gas simultaneously. 11. Equipment according to claim 1, characterized in that said complete compression is obtained through three consecutive compression steps. 12. Equipment according to claim 1, characterized in that it comprises sensor means (8) operatively associated with said compressor (2) and with said cylinders (4), which after having detected that the maximum pressure has been reached in the different cylinders (4) disconnect the gas inlet into the compressor (2) activating its connection to the next cylinder (4) and connect the compressor suction (2) by activating its connection to the last filled cylinder (4) arranged upstream. 13. Equipment according to claim 1, characterized in that said compressed gas is natural gas for motor vehicles.