WO2018011429A2

WO2018011429A2 - An environmentally friendly gas supply and storage system

Info

Publication number: WO2018011429A2
Application number: PCT/EP2017/067948
Authority: WO
Inventors: Christopher Maltin
Original assignee: Christopher Maltin
Priority date: 2016-07-14
Filing date: 2017-07-14
Publication date: 2018-01-18
Also published as: DE212017000182U1; GB201901846D0; GB2567368B; GB2567368A; WO2018011429A3; GB2567368A8; GB201612227D0

Abstract

A swappable LNG tank is provided and comprises a tank suitable for both transport from a source and storage at a point of use, whereby LNG can be delivered in, and accessed directly from, the tank without transfer of material.

Description

AN ENVIRONMENTALLY FRIENDLY GAS SUPPLY AND STORAGE SYSTEM

All over the world natural gas is increasingly being used to replace oil as a fuel for heating, generating electricity and for transport. Not only does gas have better long-term availability than oil, but gas is always likely to be cheaper as it is more plentiful than oil. Also, because gas is cleaner and its use produces less C0₂ and less pollution in terms of its effect on air quality, it will remain likely to be taxed less throughout the world. In the UK, for example, this increasing trend towards the use of gas for transport is being supported by the British Government, specifically to encourage the replacement of diesel oil by natural gas as a vehicle fuel.

Gas is methane (CH ) and it can be either fossil fuel natural gas or it can be biomethane made from renewable sources such as organic wastes. Whether natural gas or biomethane, it can be stored as a compressed gas (CNG) or in liquid form (LNG). In the absence of the availability of a suitable pipeline, the vast majority of gas is shipped and stored as LNG.

Presently LNG is transported on land in cryogenic road tankers. The capital and operating costs of these tankers is high and in the UK there is presently only one facility (at the Isle of Grain) for them to be refilled. Additionally the transfer of LNG from these tankers to the storage tanks at the point of use is a complicated and potentially dangerous process as it involves pumping liquid gas at temperatures of around minus 163°Centigrade.

According to an aspect of the present invention there is provided a swappable LNG tank comprising a tank suitable for both transport from a source and storage at a point of use, whereby LNG can be delivered in, and accessed directly from, the tank without transfer of material.

According to an aspect of the present invention there is provided a swappable tank comprising a tank suitable for both transport from a source and for storage at a point of use, whereby product can be delivered in, and accessed directly from, the tank without transfer of material.

In some embodiments the present relates to an innovative solution to allow the efficient transfer of natural gas, particularly to include renewable natural gas, from liquefaction at the point of supply, landfill site or anaerobic digestion plant; to the point of use in a gas vehicle, marine or rail refuelling station, industrial heating or processing plant. Instead of conventionally transferring the liquid gas from a cryogenic tanker to the storage tank where the gas is required for use, the new system involves merely exchanging the empty tank for a full one. This system has a worldwide market and its use results in capital and operational savings in excess of 80% with much of the conventional handling and pumping involved being rendered unnecessary.

I In some aspects and embodiments the present invention also provides a lightweight composite tank, for example to enable Liquid Natural Gas (LNG) to be transported in standard shipping containers from places like Qatar to conventional container ports such as those in the UK, rather than having to be unloaded at a marine port specifically designed for bulk LNG handling. The composite tanks replace the transport of LNG using conventional stainless steel tanks or using bulk LNG carriers.

The LNG, having been, for example, produced or imported into the UK in these smaller than usual composite tanks, then needs to be converted to gas to allow it to be used as a source of energy or compressed to form Compressed Natural Gas (CNG) when it can be used as a transport fuel. This process normally requires a great deal of energy and expensive equipment. The present invention also provides a methodology for conversion from LNG to CNG by using the energy which is released when the LNG warms up from about minus 165 degrees Celsius to ambient temperature and expands (by about 400 times). The tank may comprise an internal storage chamber and an external tote.

In some embodiments the dimensions of the tank are important. For example, if the tank is to fit onto a particular type of transport vehicle and/or fit into a standard container (such as an ISO container). The tank, or external tote where provided, may have the following dimensions: length in the range 3000mm to 3600mm; height in the range 2250mm to 2750mm; width in the range 2000mm to 2500mm.

For example the dimensions may be approximately: length of 3300mm; height of 2490mm; width of 2265mm.

The internal storage chamber comprises a plurality of storage elements. Each element may be generally tubular and has a generally hexagonal section. The present inventor has found that this arrangement is useful for providing a lightweight tank structure to enable it to be easily transportable and also have the required dimensions to fit into standard ISO containers.

A further aspect provides a storage tank comprising a plurality of storage cells, each cell being generally tubular and having a generally hexagonal section.

A further aspect provides a storage tank for LNG comprising a plurality of storage cells, each cell being generally tubular and having a generally hexagonal section.

The tank may be formed with a plurality of outer cells defining the periphery of the tank and surrounding (in plan) a plurality of inner cells. In some embodiments the wall thickness of the outer cells is greater than the wall thickness of the inner cells.

The present invention also provides an LNG fuelling station comprising a plurality of LNG tank bays for receiving swappable LNG storage tanks.

Tanks may be received by a stillage.

The present invention also provides a methodology for conversion from LNG to CNG by using the energy which is released when the LNG warms up from about minus 165 degrees Celsius to ambient temperature and expands (by about 400 times).

A further aspect provides a method of converting LNG to CNG comprising the steps of: releasing a measured slug of LNG from a storage tank into a compression cylinder having a piston and including CNG on a downstream side of the piston in the cylinder; allowing the LNG to warm so as to cause the piston to displace CNG under pressure from the compression cylinder into a CNG cylinder, and at the same time causing displacement of a linked piston in an expansion cylinder so as to cause pressurising of CNG and formation of a vacuum in the expansion cylinder; evacuating CNG from the expansion cylinder into the CNG cylinder; using the vacuum in the expansion cylinder to evacuate CNG from the downstream side of the compression cylinder piston; drawing a measured slug of LNG into the downstream side of the compression cylinder piston so that the expansion-compression-evacuation cycle can begin again.

A further aspect provides a locking mechanism is provided for fixing a storage tank in position during transport or storage, the mechanism comprising an enclosed tubular volume which can be inflated and deflated, the volume can be placed against the tank in a deflated state during loading and unloading, and inflated when the tank is in a required position so that the volume presses against an adjacent surface to hold the tank in position. Amongst the innovative points of some aspects and embodiments of the system may be the following:

- Principle of tanks going from source (anaerobic digestion plant, gas field, landfill site) to the point of use, without transfer of material

- Multiple use of the tanks: hence no one way empty travel:

e.g. export of seaweed, potable water

Swap for "fluid" such as LNG, petrol, diesel

- Principle of using swappable tanks with multi, for example three, slot stillages

- Swappable tanks of a size and weight which can be transported on "Light Commercial" class C I category vehicles (i.e. standard van class vehicles) with ADR certificates

Capital equipment cost of £40,000 for vehicle to carry 4 tonnes of LNG

Cost c50 per mile to operate Driver licences required for vehicles of this category:

Car with trailer Category B + E Up to C I 3.500 to 7.5 tonnes

or

Goods vehicle Category C I Between 3.5 tonnes and under 7.5 tonnes Goods vehicle Category C or CE (ex Class II) Over 7.5 tonnes)

- Requiring drivers to have valid:

ADR licence plus

(a) ordinary car licence issues before 1997

or

(b) C I licence (goods vehicle licence)

Compared with a conventional cryogenic tanker:

CE class vehicles (i.e. cryogenic tankers with GVW up to 44 tonnes) with ADR certificates

Capital equipment cost of £400,000 for vehicle (tractor and cryogenic trailer) to carry 12 tonnes of

LNG

Cost c2.20 per mile to operate

Requires ADR testing and recertification every three months

Requires driver with valid:

ADR licence plus

Dangerous Goods Tanker Driving Licence plus

Class I HGV licence

Lightweight tanks:

Composite material

Bonded hexagonal construction for pressure vessel reduces outer wall thickness

Hexagons morphed into cylinders at one end or both ends for fitting end caps, or inserted and bonded end caps

Variable wall thicknesses of the hexagons, depending on position in the stack which makes up the rectangular tank

Variable wall thickness within each hexagon (outer faces are thicker)

- Tanks no longer needs to be circular:

Can make tanks in ANY shape

- Level transfer from transport to stillage:

No cranes or materials handling

Control

Further aspects and embodiments, or features of aspects and embodiments, of the present invention may be as follows:

I ) A mechanism (for example a captive screw) for effecting and controlling the transfer of the full tank from the transport to the stillage, then fixing and locking the tank in position; and vice versa for unlocking the fixed position of the empty tank on the stillage and transferring it back on to the transport in a completely controlled manner, then locking it to the flatbed on the transport.

2) A removable flatbed with sides and ends which can be fixed (using standard twistlocks) to the chassis of a vehicle or to the existing flatbed of a vehicle, to carry the tanks and to facilitate their transfer to and from the stillage.

3) A locking mechanism for fixing the tanks in position (in a shipping container, on the flatbed of the vehicle, or in the stillage) which relies on atmospheric air pressure to maintain the size of a flexible cell based packing tube. The air is evacuated from this sealed tube containing open cells, causing the shaped tube to collapse during loading and unloading of the tank. When the tank is in position the valves to the vacuum pipe are opened to atmospheric pressure, causing the shaped tube to expand and lock the tank in position in a fail safe manner. An aspect of the present invention relates to a lightweight composite tank to enable Liquid Natural Gas (LNG) to be transported in standard shipping containers from places like Qatar to conventional container ports such as those around the UK rather than having to be unloaded at a marine port specifically designed for bulk LNG carriers. This is to replace the conventional stainless tanks. The LNG, having been, for example, produced or imported into the UK, in these smaller than usual composite tanks, needs to be converted to gas to allow it to be used as a source of energy or compressed to form Compressed Natural Gas (CNG) when it can be used as a transport fuel. This process normally requires a great deal of energy and expensive equipment. Another aspect relates to how conversion from LNG to CNG can be achieved by using the energy which is released when the LNG warms up from about minus 163 degrees Celsius to ambient temperature and expands (by about 400 times).

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

The present invention is more particularly shown and described, by way of example, in the accompanying drawings.

The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternative forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

In the description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention.

Dimensions are shown in mm. The dimensions are show as examples and may or may not be limiting on the scope of the present invention.

Referring first to Figure I there is shown isometric, top, front and side views of a transporter generally indicated 10. In this embodiment the transporter comprises a flatbed truck or van 15 which carries a tank tote 20 that houses a tank (not shown).

The tank tote 20 is shown in more detail in Figure 2, which illustrate the stages in its construction.

In stage I a frame 25 is provided and comprises six spaced base cross members 26 which extend between two parallel inner struts 27a, 27b. Six generally U-shape upstand members 28 are joined to the outside of the structs 27 and extend parallel to the cross members 26. Each member 28 comprises a pair of spaced legs 28a, 28b joined by a bight portion 28c having rounded corners at each end. On both side, four lateral cross members 29 extend between the legs 28a and 28c of the six upstand members 28. Two outer struts 30a, 30b attach to the outside of the members 28 and bolts 3 I pass through the struts 29, members 28 and struts 27, and also extend into the members 26 to form a rigid structure.

In stage 2 a tank 35 is introduced and sits on the members 26.

In stage 3 side panels 40 are attached to the outside of the upstand member legs 28a, 28b. In stage 4 a roof or top panel 45 is attached across the bight portions 28c of the upstand members. In stage 5 a pair of end panels 50 are attached to close the two ends off.

A locking mechanism is provided for fixing the tanks in position (in a shipping container, on the flatbed of the vehicle, or in a stillage) which relies on atmospheric air pressure to maintain the size of a flexible cell based packing tube. The air is evacuated from this sealed tube containing open cells, causing the shaped tube to collapse during loading and unloading of the tank. When the tank is in position the valves to the vacuum pipe are opened to atmospheric pressure, causing the shaped tube to expand and lock the tank in position.

In stage 6 an atmospheric packing band 55 is added in form of two hollow flexible sections 56, 57 the air from which is evacuated by way of a valve 58 during loading and unloading of the lightweight tanks. When the lightweight tank is in position on the transport truck the valve 58 is opened to allow air to return into the hollow section which expands and locks the tank into position.

This securing system also works when the lightweight tanks are in position in a stillage or in a shipping container (see below).

In some embodiments the tote structure may be provided with wheels or other rolling support means so that it can be moved onto and off the transport vehicle. For example in this embodiment six wheels 32 are provided; three wheels being fixed between the pairs of struts 27a, 30a and 27b, 30b.

A pair of rails 60 is provided and could, for example, be fitted to stillages (see Figure 7; reference 260)or to the flat bed of a transport truck (or such rails 160 could be fitted to the base of a shipping container - see below). The rails 60 include a longitudinal groove 61 in which can run the wheels 32 connected to their respective struts 27, 30. The rails 60 guide the tote to be slid on and off the bed of the truck or into a stillage or into a shipping container.

Figure 3 shows top, isometric, front and side views of the tank 35.

In this embodiment the tank 35 comprises a regular array of tank elements each having a generally hexagonal section and being arranged in a generally rectangular honeycomb formation. There are sixty seven elements in total, with the perimeter defined by thirty outer hexagonal elements 36a and within that thirty seven inner hexagonal elements 36b being provided. This "honeycomb" configuration can be used to build a chamber with any required size and shape.

The wall thickness of the outer elements 36a is greater than that of the inner elements 36b; in this embodiment the outer element wall thickness is approximately 12mm and the inner element wall thickness is approximately 2mm. The total volume provided by the tank (excluding end caps - see below) is approximately 7554 litres.

In this embodiment the elements are formed from a composite material. For example braided carbon PEEK material (e.g. 30% Carbon and 70% PEEK) may be used to form the LNG tank elements. In other embodiments phenolic-based FRP material may be used.

Composite material may also be used to form pipework used to fill, empty and to connect up the hexagons which form the tanks and also for the piping to carry the liquid nitrogen (at minus 200 degrees Celsius) which is used to keep the LNG cold (at minus 162 degrees Celsius).

Figure 4 shows top, isometric, front and side views of an end cap 65 formed in accordance with the present invention and suitable for closing either/both ends of the tank elements 36a, 36b. The cap is generally hexagonal so as to match the wall of the element, and internally has a domed end 66 for pressure tolerance.

Figure 5 shows top, isometric, front and side views of a flatbed 70 forming part of the truck shown in Figures l a to I d.

In Figure 6 an alternative transportation method is shown. In this embodiment a plurality (in this case, four) of tanks 135 are transported together in a standard ISO container 175 (such as a 40' high cube ISO container). The container floor is provided with rails 160 on which the wheeled tanks can be rolled.

Figure 7 shows a refuelling station 280.

The station 280 comprises a stillage 285 which, in this embodiment, has slots for up to three tanks (two are shown - 235a, 235b) in respective bays 290a, 290b, and 290c (shown empty). Each of the bays 290a, 290b, 290c may or may not have a roof 295a, 295b, 295c. By providing three slots in the stillage continuity of supply can be maintained. Normally there are two tanks in position in the three slot stillage i.e. only two of the slots in the stillage are used at any one time, except during the exchange operation.

When one tank is empty supply can be switched to one of the other tank. Meanwhile a transporter can be used to bring a new, full tank. The full tank is fitted from the transporter in to the empty slot. The empty tank is removed and then taken away on the transporter for refilling.

Underneath the bays the necessary pipework, pumping equipment, CNG cylinders, evaporators etc. can be located. Figures 8a to 8e illustrate a method for conversion from LNG to CNG.

This sequence starts during the cycle where the High Pressure CNG cylinder H has been filled to capacity (250bar) and the filling of the intermediate capacity CNG cylinder 2 has already started. The next stroke is about to start so valves 6 and 9 have been opened to connect the high vacuum in G to the trapped CNG at 250 bar pressure in B, such that the pressure in B and G are now equal and only just below atmospheric pressure.

PHASE I - charging the compression cylinder

Valves I and 2 are opened and a measured slug of LNG is drawn into Volume B.

PHASE 2 - vapourisation of the LNG Valve I is closed and the LNG starts to worm up which causes a pressure rise in Volume B, forcing the linked pistons to move. This displaces CNG under pressure from Volume D into CNG cylinder 2. The pressure rises in Volume G, which contains a small quantity of CNG. The pressure falls in Volume F.

PHASE 3 - end of compression stroke

The small quantity of CNG in Volume G is pumped into CNG cylinder 2. A high vacuum level has been formed in Volume F.

PHASE 4 - evacuation of remaining compressed CNG into expansion cylinder

Valves 3 and 4 are opened to allow the high vacuum in Volume F to evacuate Volume D, resulting in a moderate vacuum in the joint Volumes.

PHASE 5 - charging of compression cylinder for return stroke

A new measured slug of LNG is drawn into Volume D, which is under moderate vacuum and then the expansion-compression-evacuation cycle begins again.

Figures 9a to 9c illustrate an LNG-CNG slug pump suitable for use in the method of Figures 8a to 8e.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A swappable LNG tank comprising a tank suitable for both transport from a source and storage at a point of use, whereby LNG can be delivered in, and accessed directly from, the tank without transfer of material.

2. A tank as claimed in claim I , in which the tank comprises an internal storage chamber and an external tote. 3. A tank as claimed in claim 2, in which the external tote has the following dimensions: length in the range 3000mm to 3600mm; height in the range 2250mm to 2750mm; width in the range 2000mm to 2500mm.

4. A tank as claimed in claim 3, in which the dimensions are approximately: length of 3300mm; height of 2490mm; width of 2265mm.

5. A tank as claimed in any of claims 2 to 4, in which the internal storage chamber comprises a plurality of storage elements. 6. A tank as claimed in claim 5, in which each element is generally tubular and has a generally hexagonal section.

7. A storage tank for LNG comprising a plurality of storage cells, each cell being generally tubular and having a generally hexagonal section.

8. A storage tank as claimed in claim 7, in which a plurality of outer cells define the periphery of the tank and surround a plurality of inner cells

9. A storage tank as claimed in claim 8, in which the walls thickness of the outer cells is greater than the wall thickness of the inner cells.

10. An LNG fuelling station comprising a plurality of LNG tank bays for receiving swappable LNG storage tanks. I I . A station as claimed in claim I I , in which tanks are received by a stillage.

12. A station as claimed in claim 10 or claim I I in combination with one or more tanks as claimed in any of claims I to 9. 13. A method of transporting LNG as described herein.

14. A method of converting LNG to CNG comprising the steps of:

releasing a measured slug of LNG from a storage tank into a compression cylinder having a piston and including CNG on a downstream side of the piston in the cylinder;

- allowing the LNG to warm so as to cause the piston to displace CNG under pressure from the compression cylinder into a CNG cylinder, and at the same time causing displacement of a linked piston in an expansion cylinder so as to cause pressurising of CNG and formation of a vacuum in the expansion cylinder;

evacuating CNG from the expansion cylinder into the CNG cylinder;

- using the vacuum in the expansion cylinder to evacuate CNG from the downstream side of the compression cylinder piston;

drawing a measured slug of LNG into the downstream side of the compression cylinder piston so that the expansion-compression-evacuation cycle can begin again. 15. A locking mechanism is provided for fixing a storage tank in position during transport or storage, the mechanism comprising an enclosed tubular volume which can be inflated and deflated, the volume can be placed against the tank in a deflated state during loading and unloading, and inflated when the tank is in a required position so that the volume presses against an adjacent surface to hold the tank in position.