RU2336434C2 - Gas compression system - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: device relates to natural gas and/or hydrogen compression units and is designed to be used in vehicles operating on gaseous fuel. Compressor unit incorporates one layer of gas desiccant and condenser idle in gas compression cycle, introduced into the gas flow channel in compression cycle. In the case of multi-stage compressor the aforesaid gas desiccant layer is introduced primarily in between the first and the second compressor stages. Moisture absorbed by the said layer is removed periodically by regeneration cycle based on the compressor and desiccant layer gas closed-loop recirculation. The other gases present in the said recirculation cycle when the compressor unit terminates feeding the compressed gas are also removed. The moisture removed from the desiccant layer is condensed and mainly, evaporated into ambient medium through a semi-transparent membrane. The engine and its control circuit is arranged in the body shared with the compressor allows reducing electromagnetic radiation to minimum.

EFFECT: removal of separated moisture along with reduction of electromagnetic radiation.

13 cl, 10 dwg

Description

The scope of the invention

The present invention generally relates to gas compression. More specifically, the present invention relates to the compression of natural gas and / or hydrogen for use in gaseous fuel vehicles. In particular, it relates to the creation of a device and methods for removing vaporous moisture as part of a compression procedure and separating the removed moisture from the contaminants contained therein. The present invention also relates to minimizing the excitation of electromagnetic radiation.

BACKGROUND OF THE INVENTION

It is known to remove moisture from a gas in order to store such gas for use in a car (as fuel). Moisture is also removed from compressed gases in various other applications. Typically, during a gas compression cycle, compressible gas is passed over a layer of desiccant, which removes moisture from the gas. Ultimately, the desiccant layer will be saturated. A moisture sensor can be used to measure the amount of moisture present in the gas leaving the compressor to determine when the measured moisture content at the compressor output exceeds the allowable upper threshold value. Alternatively, a drainage layer may be used for a predetermined period of time. In any case, a regeneration step is necessary to recharge the desiccant layer.

Technologies for drying gas flows are well developed. They include the use of absorption and condensation processes and membrane separation systems. Examples of such technologies, used in isolation or in conjunction, are shown in US patent N 5034025; 5071451 and 5240472, as well as in the well-known publications cited therein.

Existing compressors of this type use gas dehumidifiers that operate continuously, using a system with two desiccant layers. Examples of this type of technology are given in US Pat. No. 6,117,211.

The present invention is directed to compressing natural gas with a limited amount of moisture, using a gas dehumidifier that works intermittently using a single desiccant system, the gas compression being interrupted from time to time to regenerate the system.

When processing gas streams due to moisture removal processes, extracted water is obtained, which may contain traces of pollutants contained in the main stream. In the case of natural gas, these pollutants contain hydrogen sulfide, sulfur dioxide and mercaptans. The removal (discharge into wastewater) of water containing pollutants of this type may be due to restrictions related to the fight against environmental pollution.

The resulting water cannot be discharged into local wastewater, as it contains pollutants. Except in unforeseen circumstances, even the smell of organic or sulfur compounds from a natural gas stream can tell the consumer that there is a leak in the compressor system.

The first objective of the present invention is the proper removal of the separated water, taking into account the above circumstances.

Another objective of the present invention is to minimize electromagnetic radiation from a running compressor system.

Next, a brief description of the invention will first be given, and then its detailed implementation in the form of specific options given with reference to the accompanying drawings. These options serve to explain the principles of the present invention and how to implement them.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a compressor for compressing a gas that normally operates in a gas compression cycle equipped with a gas dehumidification step that contains a single desiccant layer located on the gas flow path (sequentially) passing through the compressor during the gas compression cycle. The specified compressor contains a condenser, which is also located along the path of gas flow through the compressor during the gas compression cycle, and the specified condenser during the gas compression cycle does not work. The temperature of the desiccant layer and the condenser is controlled mainly by electrical means. During the compression cycle, such temperature control devices mainly do not work. However, upon entering the regeneration cycle, the desiccant layer is heated, and the condenser is cooled.

During the regeneration cycle that begins after the corresponding valve has been activated, the gas trapped in the compressor, the desiccant layer and in the condenser is sent from the compressor outlet for circulation in a closed loop, as a recycle gas stream through the compressor, with at least a portion of such recirculation gas passes through a desiccant layer and capacitor. This makes it possible to transfer the moisture released from the desiccant layer by means of a recirculation gas to the condenser, where it condenses due to the low temperature maintained in the condenser by means of temperature control.

More specifically, in a preferred embodiment, the compressor outlet is connected, via an electronically controlled valve, to a discharge pipe through which compressed gas enters the storage tank during the compression cycle. When the compressor stops operating in the compression cycle, the electronically controlled valve switches the gas flow instead of the discharge pipe to the internal volume of the compressor housing. In this case, the compressor input is connected to the suction from the body cavity.

The resulting pressure drop in the discharge pipe closes the control valve in the external reservoir, which contains high pressure gas. Then, the compressed gas trapped in the discharge pipe enters the internal volume of the housing and creates a slightly higher pressure compared to the pressure in the supply line, for example 30-60 psi. At the same time, the control valve of the supply line leading to the internal volume is closed, since the pressure of the gas source is approximately only from 0.2 to 0.5 psi.

When the compressor output is connected to the body cavity, then the trapped gas can be circulated in a closed loop through the compressor, the desiccant layer, the condenser and the body volume, and the trapped gas serves as a sweep gas to regenerate the desiccant layer. The gas is circulated through this closed loop at a low gas flow rate, so that the circulating gas passing through the condenser is predominantly completely cooled at the outlet of the condenser. This allows in a preferred mode of operation to maximize the efficiency of moisture transfer from the desiccant layer to the condenser.

Circulation at a low gas flow rate can be achieved by reducing the speed of the compressor motor. Alternatively, one or more valve-controlled bypass lines may deflect a portion of the circulating gas from passing through the desiccant layer and / or condenser, allowing only a limited amount of gas to flow through these components. The permissible flow rate through the desiccant layer, which is set by means of a valve or other means of flow restriction, is set (set) in such a way that it meets the condition for condensation of water vapor from such a gas. Such a construction allows the system to work with a constant speed engine.

During the regeneration process, the moisture that is released from the desiccant layer increases the moisture content in the circulating gas. The desiccant layer is heated at this stage in order to enhance the separation of moisture. The released moisture, in the form of water vapor, is then transferred by a gas stream to the condenser, where it condenses due to the low temperature maintained in the condenser. The circulating gas leaving the condenser is in a cooled state and contains saturated water vapor. However, by the time the circulating gas reaches the heated desiccant layer, its temperature rises and it no longer contains saturated water vapor. Therefore, the heated circulating gas can absorb additional moisture from the desiccant layer as it passes by this layer.

To remove condensed water from the condenser, such water can simply be accumulated. However, to ensure long-term autonomous operation, condensed water is directed, mainly by gravity, into contact with a semipermeable membrane, which allows water to evaporate. At this time, aromatic compounds present in the condensate are retained by the membrane in the condenser. To increase the rate of evaporation and water flow through a semipermeable membrane, an external fan and, possibly, a heating element can be used, which allows the circulation of warm air past the membrane surface.

It is important to note that the condenser, in accordance with the present invention, is located in the path of the gas flow (sequentially) during the compression cycle. This allows you to act on the capacitor and semipermeable membrane high pressure. According to a preferred embodiment of the present invention, the compressor is a multi-stage compressor, wherein the desiccant layer and the condenser are arranged in series between successive stages of the compressor, and preferably between the first and second stages of the compressor. Thus, despite the fact that the condenser is subjected to high pressure, this pressure is not the final, maximum pressure created by the compressor. Rather, it is an intermediate pressure that occurs after only one compression stage.

This limitation of the pressure acting on the condenser is particularly significant in the preferred embodiment of the invention, in which the condenser is directly connected to a semipermeable membrane through which condensed water can evaporate into the environment. Such membranes can withstand only a moderate pressure difference. In the case of a multi-stage compressor, the pressure developed between the first and second stages is not so high as to prevent the use of such a semi-permeable membrane as a means of removing water condensate. A preferred membrane form is a tube-shaped hygroscopic ion-exchange membrane.

Thus, in accordance with this preferred embodiment, the condensed water that accumulates in the condenser, directly (immediately) or finally (over time), is removed into the environment, mainly through a semi-permeable membrane. The use of such a membrane ensures the separation and retention of complex molecules that have an odor, so that only pure water is released into the environment.

After recharging the desiccant layer, the heating of the layer is stopped. In addition, cooling of the condenser and heating of the semipermeable membrane, if used, are also stopped. Then turn on the valve to connect the output stage of the compressor to the discharge pipe. Then increase the speed of the compressor motor to resume the compression cycle if this speed has been previously reduced, and the inlet of the discharge pipe automatically opens. Alternatively, if a constant speed motor is used, the bypass lines are closed, allowing a normal compression cycle to resume.

In another preferred embodiment, the compressor is enclosed in a sealed metal housing. The supply gas enters the internal volume of this housing through a control valve and is sucked into the compressor from the crankshaft portion of this internal volume. This housing also contains a motor, and preferably a variable speed motor, and also contains a control circuit for supplying current to the motor. According to this preferred embodiment, the motor is an AC induction motor, in which case the control circuit generates an alternating current signal with an adjustable frequency, as a result of which the rotational speed of the motor is changed in accordance with the requirements of the system.

According to another preferred embodiment of the invention, not only the electric motor driving the compressor mechanism is contained in the same housing as the compressor, but also the motor control circuit is enclosed in the same housing. The advantage of this construction is that the electromagnetic radiation arising from the flow of current from the engine control circuit to the engine does not extend beyond the metal casing.

The control unit can create a direct current voltage of 360 V, supplied through a sealed input in the wall of the housing. The motor control circuit can create alternating current with a frequency of about 60 Hz, which has many harmonics. In a typical case, a current of 8 to 10 A is supplied to the motor. In the wires going from the control circuit to the motor, when such a current flows at such a frequency, electromagnetic radiation occurs. When these wires are placed in a metal casing, electromagnetic radiation is shielded and does not enter the environment.

The low speed when starting the engine reduces the high inrush current drawn from the power supply system. This allows the unit to work from a standard household electrical network, for example, with a voltage of 110-120 V, with fuses designed for moderate current. After starting, the initial gas compression can be carried out at a high engine speed. After a high pressure is obtained in the fuel tank of the car or in another receiving device, the engine speed is reduced in order to reduce wear of the rings (compressor) and to limit energy consumption. This procedure is particularly suitable for compressors without oil lubrication, since the wear rate of the compressor cylinder o-rings in these units increases when the compressor system is operating at high speed and with high back pressure.

In addition, in the case of using a continuously adjustable engine with a variable rotational speed, the engine speed can be controlled so as to avoid the natural resonant frequencies of the mechanical components resulting from vibrations of the mechanical components of the engine, which otherwise increase the noise and vibration generated by the unit.

Above were summarized the main characteristics of the invention and described some of its possible aspects. Next, preferred embodiments will be described with reference to the drawings.

Brief Description of the Drawings

Figure 1 shows a gaseous fuel vehicle parked in a garage having a domestic fueling device in accordance with the present invention mounted on an inner wall of the garage.

Figure 2 schematically shows the main components of a household device, where you can see, in addition to the engine and compressor, a layer of desiccant, the main logic controller, the engine control circuit and various sensors.

Figure 3 schematically shows a variant of figure 2, where you can see the gas flow during the compression cycle.

Figure 4 schematically shows the household device of figure 2 during a regeneration cycle in which the desiccant layer is recharged and the engine speed is regulated.

Figure 5 shows a side cross-sectional view of the compressor / engine unit in its inner housing and with dryer components. An engine, a purge volume and an engine control circuit are enclosed in a compressor housing. Also shown is an additional outer casing or ventilation cap restricting the flow of cooling air.

Figure 6 schematically shows in detail a front view in section of sections of the dryer, condenser, and semipermeable membrane of Fig. 2, the semipermeable membrane having the shape of a tube through which water condensate flows by gravity.

On figa shows a front view in section of sections of the dryer, condenser and semipermeable membrane of Fig.6, where you can see the semipermeable membrane in the form of a tube through which the water condensate evaporates in the presence of a heated air stream created by the fan.

Figure 7 shows in detail a side sectional view in close-up of the semipermeable membrane of figures 5 and 6a, where air flow around a twisted tube can be seen.

FIGS. 8A and 8B schematically show the household devices of FIG. 2 during a regeneration cycle in which the engine speed is constant and the dryer-condenser unit has a bypass line that can divert the flow from flowing through the dryer-condenser unit by switching the flow to the loop circulation either into the cavity of the housing, or in both of these places, so that the gas flow at a reduced speed flows through the condenser.

Description of Preferred Option

Figure 1 shows a household fueling device 1 mounted on a garage wall and equipped with a high pressure discharge hose 2 connected to the car, an intake hose 3 connected to a gas source 6, and an electric cord 4 with a plug inserted in standard household outlet.

Figure 2 schematically shows a block operating in compression mode. Figure 2 shows the gas line 6, which may contain pollutants 8, which is included in the internal volume 14 of the housing 26, from where the gas enters the first of four sequential compression stages 28, 32, 33, 34 of the compressor 5. The gas in the line 6, which usually has a pressure of 0.2 to 0.5 psi, is sucked into the internal volume 14 due to the suction created by the first compression stage 28. The pressure sensor 21 analyzes the pressure in the gas line and sends a signal to the main logic controller 46.

From the exit of the first stage 28, gas 6 passes through a layer of desiccant 7, which is contained in the absorption chamber 29. A layer of desiccant 7, which consists of a material such as activated alumina or neolite, absorbs moisture from gas 6, including at least some pollutants 8. From the exit of the absorption chamber 29, the dried gas enters the volume of the condenser 30, which, at this stage of operation, is passive. After exiting the condenser 30 through the pipeline 55, the gas 6 enters the next, second stage 32 of the compressor 5. The gas flow in this compression cycle is shown in FIG. 3.

As shown in Fig. 4, and in more detail in Figs. 6 and 6A, desiccant 7 is regenerated due to the influence of purification gas 13 originating from the gas stream captured by compressor 5, engine 27, desiccant layer 7 and capacitor 30, when the compression cycle ends. As shown in FIG. 4, the purification gas 13 is sucked in at a reduced flow rate through the absorbent layer 7, possibly at a low speed of the engine 27. Conditions are maintained for the evaporation of moisture from the absorbent layer 7 into the purification gas 13 due to its dry state, which is discussed further in more detail, due to the pressure in the layer of absorbent 7 and an additional supply of heat to it.

From the output of layer 7, gas flows into the capacitor 30, which contains a heat exchange surface. This heat exchange surface is predominantly cooled by a cooling unit 53 operating on the electrothermal Peltier effect.

The cooled circulating purification gas 13, which has been dried in the condenser 30, then enters the return line 55, which leads to the second stage 32 of the compressor. The slow operation of the engine 27 and compressor 5 leads to the fact that the cleaning gas 13 can circulate indefinitely until the regeneration cycle is completed.

To accelerate the regeneration process and facilitate subsequent water withdrawal, a thermostatically controlled electric element 52 is used, which heats the desiccant 7. The heated, humidified cleaning gas more effectively releases moisture when it passes through the condenser 30.

As shown in FIGS. 2 and 6, water 54 generated from steam accumulates at the bottom of the condenser 30 in the form of condensate, below the level of the return pipe 55 in the condenser. Condensed water 54 contains some residual pollutants 8a. This water condensate 54, containing residual contaminants 8a, can simply accumulate or can be directed to a separation chamber, preferably made in the form of a tube 31, the walls of which are formed from a semi-permeable membrane 61. The semi-permeable membrane 61 only allows the penetration of water in the form of permeate. On the other side of the membrane 61, water diffusing through it evaporates. This process can be accelerated by the air flow created by the fan 42. In this case, the hood (casing) 43 serves as a duct creating a constant air flow over the membrane 61. If necessary, the air flow in the immediate vicinity of the membrane can be heated using heater 56 membranes.

The circulating air stream 60 from the fan 42 can also be used to cool the condenser 30, mainly using a separate duct (not shown).

As water diffuses through the membrane 61, some contaminants 8a may accumulate on the inner surface of the membrane 61. Over time, the diffusion rate may decrease to the level at which it is necessary to clean or replace the membrane 61.

In the description, we are talking about a semi-permeable membrane 61, which may be in the form of a plate forming part of the wall of the separation chamber. Figures 6 and 7 show a preferred embodiment in which the semipermeable membrane is in the form of a tube 31. This tube 31 has a wall primarily formed of a semipermeable hygroscopic ion-exchange membrane material. It has been found that tube-shaped membranes made of modified Teflon (TM) are suitable for this application and have a sufficient service life for practical use.

It should be borne in mind that the absorption chamber 29 and the condenser 30 are located in the high pressure zone of the compressor 5, between the first stage 28 and the second stage 32. The pressure in this zone is only about 200 psi during the compression cycle. It should be borne in mind that such a pressure level increases the efficiency of gas drainage. It was found that at such pressure levels, the semipermeable membrane 61 in the form of a tube can be brought out from the pressure zone if reliable connection elements 57 are used, which provide a tight connection between the tube 31 and the condenser chamber 30. Such a construction is especially simple when using a multi-stage compressor .

Other components shown in FIG. 2 include an inlet filter 22, a high pressure sensor 24, a pressure relief valve 25 connected to the ventilation hole 50, a burst disk 35 in the fourth stage 34 to relieve excessive overpressure, a serial detachable connector 36, a connecting neck motor vehicles 38, gas leakage sensor 39, airflow sensor 40 and ambient temperature sensor 41.

On figa and 8B shows a variant with a constant speed motor, in which the bypass line 60 or 60A opens when the valve 61 is activated, upon receipt of a signal from the main logic controller 46, during regeneration. Due to this bypass line, the purification gas 13 can pass through the desiccant material 7 and the condenser 30 at a preferred flow rate. The amount of purification gas 13 passed by the valve 61 through this regeneration branch depends on the flow restriction means, which is set in such a way as to ensure maximum efficiency of the vaporization and condensation process. The recycle gas 13 is discharged into the second stage 32 through the bypass line 60, or is discharged into the body 14 through the bypass line 60A, or passes through both of these bypass lines.

Referring again to FIG. 2, it is shown that the compressor 5, the engine 27, and the engine control circuit 45 are all located in the housing 26 (if we consider the compressor unit as part of the housing), which, in turn, is surrounded by an outer shell 43. In accordance with with the first embodiment of the present invention, an electronic motor control circuit 45 that supplies current to an electric motor 27 is advantageously located entirely in the volume of the engine / compressor unit. Such a sealed volume is created using the same metal casing 26, which surrounds the parts of the engine and compressor. The engine control circuit 45 is located, in particular, in the purge volume 14, which is completely sealed inside the housing 26. The metal wall of the housing 26 acts as a radiator to remove the heat generated by the engine control circuit 45, and as a shield for the emitted electromagnetic radiation from the connection circuit between engine 27 and engine control circuit 45.

As shown in figure 2, the main logic controller 46, powered by a power source 47, allows you to turn on the engine 27 and to control its speed in a variant of the engine with a variable speed through the engine control circuit 45. The signals between the main logic controller 46 and the engine control circuit 45 pass through the sealed input 44 of the housing 26. The control logic of the controller 46 sends commands and receives data using digitally encoded signals transmitted over optical fibers. This allows to minimize the flow of electric current into the inner space 14 of the cavity of the metal housing 26, which contains natural gas at a slight increased pressure.

Despite the fact that specific embodiments of the invention have been described, it is clear that they are given by way of example only and changes and additions may be made to the invention by experts in the field, which do not, however, go beyond the scope of the claims.

Claims (15)

1. A compressor system for compressing gas, which includes: an engine-driven compressor having at least a first stage and a gas supply inlet through which a stream of compressible gas flows to the compressor inlet from a gas source; compressor output for supplying gas from the compressor to the discharge pipe; a gas dehumidification step that comprises a desiccant layer located along the gas flow path through the compressor during the gas compression cycle; a condenser which is located below the desiccant layer along the gas flow path through the compressor during the gas compression cycle, said condenser separating water from the gas during the regeneration cycle and does not work during the gas compression cycle, a temperature control means for controlling the temperature of the desiccant layer and the condenser which during the gas compression cycle does not work, and when it enters the regeneration cycle it is turned on in order to heat the desiccant layer and cool the condenser; and a valve for switching the gas flow from the compressor outlet for recirculation through the compressor, whereby during the regeneration cycle that occurs when the valve is activated, the gas trapped in the compressor, the desiccant layer and the condenser is sent from the compressor outlet for circulation in a closed loop as a stream recirculation gas through the compressor, and at least a portion of such a recirculation gas stream passes through the desiccant layer and the condenser, which allows you to remove the released moisture from the desiccant layer using gas p circulation to the condenser, where it condenses due to the low temperature maintained in the condenser by means of temperature control. 2. The compressor system according to claim 1, in which the compressor is a multi-stage compressor having at least first and second stages, the desiccant layer and the condenser installed in series between the compressor stages. 3. The compressor system according to claim 2, characterized in that the desiccant and the condenser are installed between the first and second stages of the compressor. 4. The compressor system according to claims 1 to 3, in which the condenser produces water in the form of condensate and which further comprises a semipermeable membrane through which condensed water can evaporate into the environment. 5. The compressor system according to claim 4, in which the membrane is made in the form of a tube filled by gravity with condensed water. 6. The compressor system according to claim 1, in which the compressor has a sealed metal casing with an internal volume connected to the specified gas supply inlet and to the first stage of the compressor, the internal volume additionally comprising a motor for driving said compressor and a supply valve at the gas supply inlet, which closes when the valve switches the gas flow to recirculation through the compressor, and opens when the compressed gas is passed into the discharge pipe, due to which, in accordance with the state of inclusion of the valve Pan, gas can be sucked into the internal volume of the casing using the first stage of the compressor either from the specified gas supply inlet or from the specified compressor output. 7. The compressor system according to claim 6, which further comprises a main logic controller connected to an engine control circuit for controlling the engine speed so that the engine and compressor operate at a reduced speed, said speed being regulated during regeneration so that flow is limited recirculation gas passing through the condenser, which allows you to cool the gas stream when it leaves the condenser, due to which moisture is transferred from the desiccant layer capacitor. 8. The compressor system according to claim 7, in which the motor is an asynchronous AC motor, and the motor control circuit generates an AC signal with a varying frequency, due to which the speed of the engine changes in accordance with the indicated changing frequency. 9. The compressor system according to claims 6-8, which comprises an engine control circuit installed in the housing for supplying current to the engine, said circuit being connected to the engine using wires that are shielded by said housing, resulting in electromagnetic radiation, that occurs when current flows from the engine control circuit to the engine, is not transmitted to the outside of the metal casing. 10. The compressor system according to claim 1, which contains a main logic controller connected to a bypass valve in the bypass line, which passes recirculation gas, so that it deviates and does not pass through the specified desiccant layer and capacitor, as a result of which the flow is limited during regeneration recirculation gas passing through the condenser, which allows cooling the gas stream when it leaves the condenser, due to which moisture is transferred from the desiccant layer to the condenser. 11. The compressor system of claim 10, in which the first stage of the compressor has an input of the first stage of the compressor, the desiccant layer and the condenser are located along the gas flow path after the first stage of the compressor and the bypass line diverts recirculation gas to the inlet of the first stage of the compressor. 12. The compressor system according to claim 10 or 11, characterized by the presence of a sealed metal casing with an internal volume connected to the specified gas supply inlet and with the input of the first stage of the compressor, and the bypass line discharges recirculation gas into the internal volume of the sealed metal casing. 13. The compressor system according to claim 1, characterized in that the compressor is a multi-stage compressor having at least first and second stages, and the desiccant layer and condenser are located along the path of gas flow from the first stage to the second stage during the cycle gas compression, and the compressor system includes a sealed metal casing with an internal volume connected to the specified input of the first stage of the compressor and to the specified gas supply inlet, the first bypass line, which exhausts the gas accumulation into the internal volume of the sealed metal casing, a second bypass line that discharges the recirculation gas to the second stage, and valves designed to divert gas to the first and second bypass lines, due to which during the regeneration cycle the valves can operate to divert recirculation gas from passing through the indicated desiccant layer and the condenser in both the first and second bypass lines, so that during regeneration to restrict the flow of recirculation gas passing through the capacitor, allowing the gas flow is cooled inside the condenser, due to which moisture is transferred from the desiccant layer to the condenser. Priority on points: 10/04/2002 according to claim 9; 09.09.2003 according to claims 1-8.

Images