Compressed natural gas refueling system

Abstract

 The present invention is referred to a transportable compressed natural gas supply system. This system is an integral solution for supplying compressed natural gas (CNG) to remote places that can not have access to the gas pipelines. It consists of storage modules (3), loading and unloading platform (4-32), a transport vehicle and a sequence of use of said modules (3). The modules (3) are formed by a protection cage with fibreglass lids having cylinders inside for the compressed natural gas. These cylinders are interconnected with pipes, and they also have lock, relief, excess and pressure gauge valves. Besides, these cylinders are separated from each other by rubber separators. The system is formed by loading and unloading platforms of the modules (3), a transport vehicle to help in replacing them and a sequence of use.

Description

FIELD OF THE INVENTION:

[0001] The present invention relates generally to a system for transporting compressed natural gas between a natural gas pipeline and a compressed natural gas (CNG) for the purpose of re-fuelling vehicles of any type, industries, residential gas pipelines, or any other type of natural gas customers located in remote places. More particularly, it relates to such a system especially adapted to the economies involved with re-fueling stations that are remote from a pipeline where the cost of constructing a conventional pipeline extension to a re-fuel station site is excessive, or impossible due to regulations or other factors, including geographical problems. These remote gas station sites must rely upon trucks and transport vessels to bring natural gas to the station site in steel tubes.

[0002] The purposed system comprises storage modules, loading and un-loading platforms, its transportation and sequence of use. This system defines an integral solution for delivering compressed natural gas (CNG) to remote places that can not access to the gas pipeline supply.

BACKGROUND OF THE INVENTION:

[0003] The use of compressed natural gas (CNG) as fuel for vehicles, automobiles, industries, etc., has been known for many years, and is in use in many areas of the world. For example, in Argentina, Brazil, and India between others are millions of automobiles using CNG. In big cities, there are gas pipelines that feed the gas stations and each gas station has a compressor for increasing the service pressure from the line pressure (1 bar) to service pressure (200 bar). For remote places located far away from big cities and consequently far away from gas pipelines, the conventional manner for handling the natural gas is to transport the gas, by high-pressure vessels, from a pipeline to re-fueling stations. Moreover, in some remote places the high-pressure vessels are not available, and the customers need to buy compressed natural gas in carafes.

[0004] In recent years, environmental-pollution concerns in several countries around the world have focused attention on the use of alternative fuels, i.e., fuels that emit fewer pollutants to the air than regular liquid fuel currently in use. It is scientifically proven that one of the least-polluting fuels is natural gas, which consumption is growing very fast in several countries, backed by governments and industries due to its easy access and long term availability. The most important problem to a massive conversion from liquid fuels to compressed natural gas (CNG) is the cost to deliver CNG to a re-fueling station from the nearest natural gas pipeline.

[0005] There are several examples in the prior art that illustrates how the industry is currently utilizing high-pressure vessels to deliver CNG. For example, United States Patent Nr. 4,139,019 of Bresie, et al. is referred to a method and system for transporting natural gas to a pipeline. Natural gas from one or more wells is gathered, dehydrated, compressed to a relatively high pressure, and loaded into pressure vessel means mounted for transporting at ambient temperatures by a transport vehicle. The pressure vessel means is then driven to a transmission pipeline terminal, or other end user, and the natural gas is off-loaded while being heated to prevent the formation of harmful hydrates, the gas being metered before flowing into the pipeline.

[0006] Another example is the United States Patent Nr. 4,213,476 of Bresie, et al., referred to a method and system for producing and transporting natural gas. Natural gas taken from a gas well is loaded continuously and at a pre-selected, generally uniform rate into a movable separate pressure vessel means until such is filled with a discrete batch of natural gas at a pressure in excess of 800 psi, whereupon it is replaced with another separate pressure vessel means, with no interruption of gas flow. The filled, movable vessel means is then transported to an off-loading terminal. Well shock is thus controlled, and maximum natural gas recovery obtained. A generally uniform flow rate is obtained by a regulating valve, when well head pressure exceeds about 800 psi, and by a compressor when the well head pressure is below such value.

[0007] The same inventor has the United States Patent Nr. 4,380,242 for a method and system for distributing natural gas. In this case, a user terminal is provided with two off-loading stations, and at least two separate pressure vessel means are employed to supply natural gas to the user terminal. At least one of the separate pressure vessels is movable to a supply terminal. The off-loading stations are preferably provided with an automatic switchover arrangement to change from one pressure vessel means to another, and the resulting method and system for distributing natural gas assures a continuous supply of natural gas at varying demand rates to the user terminal.

[0008] These solutions are expensive to operate and have limited availability. One of the higher costs in using the high-pressure tube-trailers is that they must utilize an expensive compressor to un-load the gas when it arrives at the re-fueling station.

[0009] These restrictions not only affect negatively the installation of new gas re-fueling stations but also increasing the number of vehicles and customers using CNG. Vehicles have certain autonomy, and they need to be refilled periodically, therefore CNG re-fueling stations should be spread out all over the country to obtain a real total autonomy of the system, including remote places and towns.

[0010] Moreover, the lack of natural gas in some zones results in an important restriction for locating industries that requires this fuel to work.

[0011] To solve this problem, a compressed natural gas re-fueling system has been developed. This system allows the installation of CNG stations almost everywhere, generating a unique, easy-to-install, operate and maintain gas re-fueling system.

[0012] Another background of this invention is the United States Patent Nr. 5,454,408 of DiBella, et al. referred to a variable-volume storage and dispensing apparatus for compressed natural gas. A variable-volume compressed natural gas ("CNG") storage vessel connected to a line supplying pressurized natural gas is described. The vessel connects to a dispensing station having a connection head--a fitting that allows a vehicle tank quickly and easily to be interconnected with and disconnected from the dispensing station. When a vehicle tank is being filled, or alternatively when a storage vessel is being replenished from the gas supply line, a controller responds to the pressure within the storage vessel to vary the volume of that vessel

[0013] The United States Patent Nr. 5,603,360 of Teel is referred to a method and system for transporting natural gas from a pipeline to a compressed natural gas automotive re-fueling station. This system for delivering natural gas, from a pipeline, is loaded onto a movable transport by flowing the gas into multiple pressure vessels equipped with internal flexible bladders which will contain the gas until the pressure in the vessels equalize with the pressure in the pipeline. At that time, the transport will be moved to a compressed natural gas (CNG) re-fueling station. At the re-fueling station, the multiple pressure vessels will be connected to an un-loading conduit leading to the storage facilities. The natural gas will be un-loaded by pressure differential until pressures equalize, then pressurized hydraulic fluid will be pumped into the annulus between the bladder and the steel walls of the pressure vessel which will deflate the bladder and squeeze the remaining gas out of the bladder to storage. The transport is then disconnected from the un-loading facilities and returned to the pipeline for re-filling with natural gas.

SUMMARY OF THE INVENTION:

[0014] It is the principal object of the present invention to provide a transportable compressed natural gas feeding system comprising a storing module, a charging and discharging platform, its transportation and sequence of use, comprising:

• A module containing storage vessels and the corresponding joint thereto, said module also contains:

• Vessels (cylinders) where gas is stored,
• A frame lodging said vessels, and
• Interconnection pipes useful for connecting and disconnecting said modules from its location and use,
• A charging platform,
• A discharging platform; and
• A transportation vehicle.

[0015] Another object is to provide a transport vehicle especially adapted to carry the gas vessels and help with the rotating vessels system explained below.

[0016] Another object is to provide a sequence of use for optimizing the usage of the gas in the vessels.

[0017] Another object is to provide a method and system for transporting natural gas from a pipeline to a re-fuel station, or other end-user facility.

[0018] Another object is to provide a system for transporting natural gas between a pipeline and a re-fuel station by use of a motor vehicle, designed to insure delivery of the natural gas in a condition satisfactory for use as a motor fuel.

[0019] The purposed invention is especially useful for different types of customers like branches of residential gas pipelines, gas stations, industries, etc.

[0020] In order to be able to carry out this invention, its components must comply with strict security requirements ruled by the local industrial security regulations and rules in force.

[0021] In order to have a better understanding of the concepts stated below, the following definitions are added:

"Upstream/Downstream": location of a predetermined object installed before or after a reference location, taking into account the fluid circulation direction.

"Flame arrester": an element installed to prevent the propagation of fire.

"Compression equipment": equipment installed at the central gas pipe of the secondary branch which increases the feeding gas pressure (1 bar) to storage and transport pressure (200 bar).

"Storage": composed by groups of tube racks receiving the compressed natural gas in the module.

"Charge": action of fueling the modules to certain pressure (200 bar).

"Discharge": action of un-fuel the modules.

"Transportation Units": is the motion unit for its distribution to different consumption locations.

[0022] Summing up, the present invention is referred to a transportable compressed natural gas supply system consisting of storage modules, loading platform, unloading platform, transport and use sequence, wherein the module comprises compressed natural gas cylinders, a frame containing the cylinders, interconnection tubes used to disconnect and connect the mentioned module in its place of allocation and use; cylinder separators, protection cage with fibreglass lids, locking valves, relief valves, excess fluid valves, pressure gauge and fast couplings.

BRIEF DESCRIPTION OF DRAWINGS:

[0023] 

Figure 1 is a general perspective view of the purposed module.

Figure 2 is a general perspective view of the module's frame.

Figure 3 illustrates how the cylinders are located in said frame, and the interconnection pipes connecting them.

Figure 4 is a perspective view of the charging platform.

Figure 5 is a perspective view of the discharging platform.

Figure 6 is a perspective view of the discharging platform.

Figure 7 is a perspective view of the modules transport vehicle.

Figure 8 shows in detail the machine mounted on the vehicle used to unload the modules from the transport vehicles.

DETAILED DESCRIPTION OF THE INVENTION:

[0024] Figure 1 illustrates the general form of the purposed module of the present invention, where the compressed natural gas (or any other fuel) may be transported and stored to different end-user location. It basically comprises a frame or chassis (3) where vessels (2) are lodged. Said frame (3) comprises a tubular structure, reinforced to be able to support the group of vessels on it. Even when in the illustrated case said vessels are defined by cylinders, and the frame has a hexagonal shape, this should not be understood as a limitation of the present invention.

[0025] Those cylinders (2) are grouped to form a single unit, interconnected between each other with the interconnection tubes (4), and separated between each other with separators (5). These separators (5) may be rubber triangular pieces, located between cylinders, to avoid the movements between each other, or strip-like aluminum piece surrounding each cylinder, to avoid the friction between them and thus a premature wearing.

[0026] Figure 2 illustrates said module in detail, designed as a self-contained structure, made of steel, and resistant to outdoor conditions due to an anticorrosion treatment. It is formed by a main structure (3) and a protection cage (7) on each side. The cylinders are fixed to the module's structure by fixing collars. The protection cage (7) is fixed by screws (8) to the chassis (3).

[0027] Considering this module (3) is loaded and unloaded from a transport vehicle, there are a couple of sensitive pieces, including valves and accessories, located inside the structure to avoid protruding from the frame's perimeter. Thus they are protected against impacts that may occur during the loading and unloading operations.

[0028] Figure 3 shows a lateral view of chassis (3) that includes on its base a set of sliding skates (6) for helping on its transportation. The interconnection between cylinders comprises seamless steel pipes, connectors and valves disposed to conveniently resist forces and vibrations.

[0029] Each cylinder includes a snap-action cutoff valve (9) provided with a pressure relief means of the combined type, metal fuse and blowout disc. Each module is provided with an over-pressure relief valve (10), installed downstream of the above mentioned cutoff valves, venting outward and upward.

[0030] There is also an over-flow valve (11) that prevents gas counter flow from the cylinders in the event of a gas refueling interruption or pipe breakage, and a line pressure gauge (12) and fast-coupling valve (13) where the hoses are connected.

[0031] Figure 4 illustrates the loading platform where the modules are going to be loaded and refuel at a maximum pressure of 250 bar. These platforms comprise a couple of parallel arms (22-23) over which the module rests, feet (15), capable of adjusting their height in accordance with the surface on which it will be laid on. It also has an interconnection pipe (16) between platforms, provided with specifications for each type of consumption capacity, crossbars (17), bringing rigidity, two couplings means (18) and manual relief valves (19) for venting the remaining gas in the lockout valves and venting gas of the hoses connecting the platforms to the modules, to be able to disconnect them. It also has an over-flow valve (20) for avoiding a charge drop if a failure occurs, and a manual lockout ball valve (21) which must be operated once the module is refueled.

[0032] In the loading station, there are as many platforms (4) as modules (3), plus a free loading platform. The total number of platforms (4) may vary depending on the system needs, and the transport vehicle used, but may be from one to five, going this number up if the system requires so. In the present case, five platforms per line are used, enabling the upload of four modules (3) at the same time, leaving one platform (4) free. The free platform should not always be the same; it must rotate to avoid the extreme wearing of a particular one.

[0033] Depending on the end-user needs, the loading station may have two or three lines of loading platforms (4). In this case, an actuated valve in the interconnection pipe (16) must be installed, commanded from a compressing station by means of a computer.

[0034] The platform (4) structure is self-contained and made of steel, resistant to atmospheric conditions by means of an anti-corrosion treatment. Valves and accessories of said platform (4), located so as to avoid projecting from the platform's perimeter, are fixed thereto by means of bolts, giving them mechanical protection.

[0035] Figure 5 illustrates an unloading platform (32) where modules (3) are unloaded. It has a couple of supporting arms (39) over which the module rests, feet (24) capable of adjusting their height in accordance with the surface on which it will be laid on, a couple of reinforcement crossbars (25), an interconnection pipe (26), two couplings means (27), a lockout valve (28), an over-flow valve (29), electro valves (30), and retention valves (31). As in the loading platform of Figure 4, in this unloading platform (32) there are as many platforms (32) as modules (3), plus a free unloading platform (32). The total number platforms may vary depending on the systems needs, and may be from 1 to 9. If this number is surpassed, another line with the same number of platforms is recommended, reminding that one of them should always be free. The quantity of modules (3) in the unloading stations is related to the system needs and may be increased if the system requires so.

[0036] The unloading platform is also a self-contained structure, made of steel resistant to the atmospheric conditions by means of an anti-corrosion treatment.

[0037] Valves and accessories are also located in the structure to avoid projecting from the platform perimeter, and fixed thereto by means of bolts that give them some mechanical protection.

[0038] The unloading platform (4) has a manual venting valve (33) whose function is venting the remaining gas charge in the pipe between the lockout valve (28) and the module (1) to disconnect it. There is also a manual-driven lockout valve (36) to be operated only before a failure of the actuator of an actuated valve (not shown).

[0039] Figure 6 illustrates an example of an un-loading platform (32) of compressed natural gas in a gas station where the modules (3) are unloaded. It has a base (40) capable of adjusting its height in accordance with the surface on which it will be laid on, and a couple of resting arms (45-46) over which the module will be placed. The upper crossbar (41) reinforces the whole structure, and the interconnection pipe (42) is similar to above cited (16) in Figure 4. This platform (32) also includes joins (43), a manual relief valve (44) and a blocking valve (47).

[0040] Figure 7 illustrates a vehicle for transporting modules (3) comprising a trailer (48) for transporting from one to four modules (3), four loading-unloading machines (49) (illustrated in detail in Figure 8 and described below), and stabilization feet (50).

[0041] Figure 8 illustrates in detail a machine (49) in charge of loading the modules (3) from the platform (4) in the trailer or from the trailer to the unloading platform (32). It comprises a metal U-shape frame (56) over which a winch (51), a lifting piston (52), an anchoring system (53), a couple of vertical arms (54) and a fixing means of the trailer machine (55) are located.

[0042] A secondary object of the present invention is the sequence of use of those means already described below. By using this sequence is possible to reload a gas station optimizing the usage of gas in the modules.

[0043] The sequence is based on the fact that there will always be an empty platform (4-32) and that the modules are unloaded sequentially. The position of the empty platform (4-32) will rotate while the modules (3) are being replaced.

[0044] This system has a sequence starting the first day with platform number one, being verified that the platform (4) has a module (3) with enough gas pressure to feed the system. To do that, information about the module's pressure is sent by a pressure transmitter to a platform commuter (not pressure). So, the platform is connected to the fueling system by opening the actuated valve of said platform, allowing a CNG flow from said module to the end-user installation, immediately after the valve is opened. The system verifies that the pressure reading is equal to the pressure indicated in the pressure transmitter. A difference between both readings will mean that the system valve is not properly opened or that the operator left a valve closed.

[0045] Once the valve is opened, the module starts refueling gas contained therein, and once the unloading operation is completed, the system will automatically open the valve of platform number 2 till the pressure indicates the correct termination of the sequence. After that, the system will proceed to close the valve operated from platform number 1.

[0046] To replace modules (3), once the CNG contained therein is finished; it must be commuted to another platform (4).

[0047] The following parameters must be taken into account:

• Normal commutation pressure PN
• Minimum system pressure PM that guarantees a pressure that satisfies the end-user consumption.
• Last pressure chosen to replace the modules PU
• Output regulated pressure PR

[0048] All these parameters can be are programmed when the system is installed and their function is to guarantee the service under the best possible conditions.

[0049] Since the system has a variable flow based on the inlet and outlet pressure and the flow demand also varies depending on the season of the year, the system verifies constantly that the module's pressure does not reach a point lesser than pressure PN, so the system demand can be kept inside predetermined parameters.

[0050] The PN pressure is the pressure used for dimensioning the system under conditions of maximum demand, but since this demand conditions are reached only some days of the year, the system uses the monitoring pressure PR as a decision variable. In that case, the system determines at which PM pressure is necessary to perform the module replacement procedure.

[0051] In case of minimum levels of consumption, the module will continue reducing the pressure till the PU pressure is reached, being said pressure a minimum pressure chosen to replace the modules (3).

[0052] Finally, an example of the rotating cascade: in this case three storing modules (3) were used, said three modules (3) are full and the priority system sequentially connects one to the other following a pattern depending on the pressure of each module and the pressure of the vehicle to be refueled.

Step 1

[0053] The modules (3) are full; the managing unloading system selects module number 1 as a lower bank, the second module 2 as medium bank, and the third module 3 as an upper bank.

[0054] When the vehicle to be refueled arrives to the end-user station, the system will start loading it from the lower bank. Once the pressures are equalized, it will be replaced by the medium bank. Once the pressures are equalized, the unloading system will commute again but this time for the upper bank to finalize the loading process, leaving the modules (3) after several loading processes in the following situation: the low pressure module will keep a pressure of 100 bar; the medium pressure module will keep a pressure equal to 150 bar and the high pressure module will have 200 bar, approximately.

Step 2

[0055] Under these conditions, module 1 and 2 have a lesser pressure than module 3, this is due to the charges preformed. This process goes on to Step 3.

Step 3

[0056] During Step 3, once the system has performed several fueling operations, pressure of module 1 will decrease until the internal pressure will not suffice to perform a new fueling operation. Therefore, the unloading managing system is turned on to reinforce the pressure in the line, thus reaching the desired pressure level.

Step 4

[0057] When there is no consumption at the gas pumps, the un-loading managing unit drives the recirculation of the module's gas. The first action will be to take gas from the low pressure module and put this gas in the medium pressure module.

Step 5

[0058] Once the pressure differential defined between the low and medium pressure storage is reached, the discharge managing unit will recirculate the gas again, but increasing the high-pressure storage module's pressure, taking gas from the medium pressure module.

Step 6

[0059] Once the recirculation of gas ends, the low pressure module has a 10% of gas and is replaced by a full one, becoming the high pressure module. Module 3, which was the high pressure module, becomes the medium pressure module, and the medium pressure module becomes the low pressure module.

Claims

1. A transportable compressed natural gas supply system, wherein the system includes a storage module, unloading and loading platforms, a transport vehicle and a sequence of use of said modules.

2. A transportable compressed natural gas supply system, in accordance to claim 1, wherein said modules comprise compressed natural gas cylinders, a frame containing the cylinders, interconnection tubes used capable of disconnecting and connecting said module to the system, cylinder separators, a protection cage with fibreglass lids, locking, relief, and over-fluid valves, a pressure gauge and fast couplings.

3. A transportable compressed natural gas supply system, in accordance to claim 1, wherein the loading platform consists of a U-shape frame, regulating feet, interconnection pipes, two reinforcement crossbars, couplings means, manually-operated relief valve, an over-flow valve, manually-block ball valve, and two upper crossbars.

4. A transportable compressed natural gas supply system, in accordance to claim 1, wherein the unloading platform includes a U-shape frame, regulating feet, interconnection pipes, two reinforcement crossbars, couplings means, manually-operated relief valve, an over-flow valve, a manually-block ball valve, and two upper crossbars.

5. A transportable compressed natural gas supply system, in accordance to claim 1, wherein the transport vehicle comprises a trailer, four loading-unloading machines to raise modules, and stabilization feet.

6. A transportable compressed natural gas supply system, in accordance to claim 5, wherein said machines to raise modules have a hoist, raising pistons, anchorage system, machine arms and fittings to the trailer.

7. A use sequence of the compressed natural gas supply system in accordance to claim 1, wherein the replacement of empty modules by full ones will be carried out through a rotating cascade method, starting from the module having the less gas pressure, following by a sequence based on priority, depending on the pressure of each module and the pressure of the vehicle to be refuelled.

8. A use sequence of the compressed natural gas supply system in accordance to claim 1, wherein said sequence comprise the following steps: Step 1 : the modules are full; the managing unloading system selects module number 1 as a lower bank, the second module 2 as medium bank, and the third module 3 as an upper bank; when the vehicle to be refueled arrives to the end-user station, the system will start loading it from the lower bank, once the pressures are equalized, it will be replaced by the medium bank, once the pressures are equalized, the unloading system will commute again for the upper bank to finalize the loading process, leaving the modules after several loading processes in the following situation: the low pressure module will keep a pressure of 100 bar; the medium pressure module will keep a pressure equal to 150 bar and the high pressure module will have 200 bar, approximately; Step 2: under these conditions, module 1 and 2 have a lesser pressure than module 3, this is due to the charges preformed; Step 3: the pressure of module 1 will decrease until the internal pressure will not suffice to perform a new fueling operation, then the unloading managing system is turned on to reinforce the pressure in the line, thus reaching the desired pressure level; Step 4: when there is no consumption at the gas pumps, the un-loading managing unit drives the recirculation of the module's gas and gas from the low pressure module will be taken and put this gas in the medium pressure module; Step 5: once the pressure differential defined between the low and medium pressure storage is reached, the discharge managing unit will recirculate the gas again, but increasing the high-pressure storage module's pressure, taking gas from the medium pressure module, finally Step 6: once the recirculation of gas ends, the low pressure module has a 10% of gas and is replaced by a full one, becoming the high pressure module, module 3, which was the high pressure module, becomes the medium pressure module, and the medium pressure module becomes the low pressure module.

Drawing