MOBILE GAS FILLING STATION
DESCRIPTION FIELD OF INVENTION This invention provides a simple, inexpensive, reliable method and design solution for combustible gases (natural gas, hydrogen, etc.) dispersion from compressed gas road tankers (trucks, trailers, semi-trailers, trains, ships and other carriers) to consumer's tanks
(NGV on-board tanks, stationary consumer's tanks, etc.) requiring final high gas pressure, comparable with gas pressure in road tankers, to provide big stored gas quantity. The present invention will enable gas-fueled motor vehicle and stationary storage tanks to be refueled quickly and efficiently over a wide range of suction pressures (i.e., changeable gas pressure inside a gas carrier's tank).
BACKGROUND OF THE INVENTION
Natural gas off-pipeline transportation in compressed form (CNG) by surface vehicles (trailers, semitrailers, tracks, railroad trains, ships) is getting more popular in the areas where there are no gas regular pipelines. In principle, there are two distinct applications for off-pipeline CNG transportation and delivery: one is for industrial, commercial and residential direct gas usage by transferring gas from the high pressure mobile carrier into low pressure consumer's devices (burners, etc.); the second is transferring gas from one high pressure tank (tanks) into anotlier high pressure tank (tanks), for example, in the case of natural gas vehicles (NGV), when gas is supplied from any gas earner to the vehicle on-board tank.
In the last case we face the problem of filling the NGV on-board tanks with high pressure (200- 250 bars usually), whereas gas carriers store gas at a pressure of 200-250 bars also. The gas compressed at high pressure in the carrier's tanks begins to lose pressure as soon as it passes the outlet valve and enters into the high pressure line leading to next tank (on-board NGV tanks or any consumer stationary tank). Without recompression, or some other method of maintaining gas pressure in the gas carrier's tank, the gas transfer from one vessel to another vessel results in a balancing of the pressure between the above two vessels. In order to connect the two earners and consumer tanks directly, the consumer gas tanks cannot be filled to the maximum required pressure. Currently, in order to overcome the above problem with gas pressure drop at the consumer tanks refilling from mobile pressured gas stations mechanical or/and hydraulic compressors at the consumer place or on-board mobile filling station are used.
In this case, the problem is the following. Conventional reciprocating compressors cannot operate over a wide range of inlet pressures (such as about 10-250 bars) that is generally required for mobile gas compression at delivery mobile systems. Inlet pressures for conventional compressors are generally limited to narrow ranges, based upon the working pressures of the equipment and the ratio of the outlet pressure to the inlet pressure for each stage (usually a ratio of 3 - 4 for each stage is the maximum operable ratio for conventional compressors). In addition, conventional compressors typically often have a low maximum inlet pressure capability (such as 20-30 bars) due to the pressure limitations of the compressor case and crankshaft seals. The above limitation inherent to conventional compressors limits these compressors usage for mobile gas delivery. Compressors providing wide range suction pressure (10-250 bars) are very cumbersome and expensive.
Other previously disclosed CNG refueling systems utilize adsorbent-filled cylinders to reduce the tank pressure needed to store a predetermined amount of natural gas. Such
systems are disclosed, for example, in U.S. Pat. Nos. 4,522,159; 4,531,558; and 4,749,384.
However, now really only several firms propose HPU on the market, therewith all proposed systems are applicable to tube trailers equipped with 4-12 gas tubes only, whereas majority of the existing mobile fueling station (based on trucks, trailers and semi-trailers mainly) are equipped with big number of relatively small cylindrical tanks
(150 - 300 cylinders). Among these firms is NEOgas (USA), ENK (Korea), Enric (China).
Along with possibility to be used in tube trailers only, existing HPU have the following disadvantages:
- it requires large volume of hydraulic fluid from a large hydraulic fluid reservoir (for example in the ENK system 5 000 1, Neo Gas system about 3 000 1). The large quantity
of hydraulic fluid requires significant power handling capabilities; it must be preheated in colder climates, etc.
- once the vessels are filled with hydraulic fluid, a significant amount of time is required to drain the vessels THE DISCLOSED TECHNOLOGY
The first four embodiments of the proposed mobile filling station is shown on FIG.l .
In all cases the system comprises the following elements:
1) Rigid truck or auto combination that is tractor - semi-trailer, or tractor - full trailer.
2) Vehicle (tractor) conventional mechanical power take off (PTO) device (2) connected to the transmission of the tractor or rigid truck, which includes a secondary drive shaft and a second control system for engaging and disengaging the power take off.
3) Air driven gas booster.
3) Compressed air source.
Depending on compressed air source our invention has four embodiments, In the first embodiment air source is mechanical PTO - driven air compressor (3). In the second embodiment air source is towed air compressor driven by any ICE (internal combustion engine) or electric motor powered by main or any generator. In the third embodiment compressed air supply is provided by any stationary compressor driven by any ICE (internal combustion engine) or electric motor powered by main or any generator. In the fourth embodiment high pressure air cylinder-accumulator serves as compressed air source.
4) Air driven gas booster connected with air source. It is good alternative to high pressure stationary type compressors. These boosters have a compact, lightweight design.
The booster has two sections. The first - for compressed air, in which air is supplied at pressure 6-10 bars from any air source and after working cycle is exhausted to atmosphere at pressure close to one bar. The second - for compressed gas, in which gas is sucked at any pressure, compressed to required pressure and supplied to consumer.
5) Two groups of high-pressure cylinders (A, B), mounted on the deck or frame of the rigid truck or semitrailer/trailer.
6) Piping, valving, instrumentation Associated components are: gas filling station (9) placed near gas pipeline and consumer gas storage tank (8).
Although consumer's storage tank (8), gas booster-compressor BR, buffer tank (4), compressed air tank-accumulator (7) are shown in FIG. 1 as single components, it will be appreciated by those of ordinary skill in the art upon reading this disclosure that a
plurality of intercomiected components can be substituted.
All compressed air sources are designed and constructed so as to operate at drive air pressures ranging about 6-12 bars and gas input pressure ranging about 10-200/ 250 bars (depending on the country). Maximum output pressure is 250 - 300 bars.
These data corresponds in Europe (200 bars) and USA since in USA the working pressure in CNG system 250 bars is accepted. It is, of course, possible to connect two or more air sources in parallel as required to provide an increased refueling capability or capability during times when one source is shut down for maintenance or repair.
The semitrailer or trailer or rigid truck or any other vehicle (ship, railway car, etc.) carry
set of the cylinders including supply cylinders (group A) and charging cylinders (group B). The supply cylinders (A) have one inlet/outlet port only, whereas charging cylinders are equipped with two ports from both sides. The upper side of die cylinders (A) is connected alternatively with the booster suction line (d) and supply line from gas filling station (cl). Charging cylinders (B) upper side is connected alternatively with supply line (b) from gas filling station and the booster suction line (c2).
The system according to the first four embodiment operates in seven modes by the following manner. First Mode: Empty mobile filling station arrives to stationary gas station (9) and is joined to outlet line from gas compressor through quick connector 10. All on-board cylinders are filled from stationary gas filling station (9).This time valves II, III, VIII are opened (all other valves are closed) and gas flows throw pipe (a), (b) and (c) to the cylinders of both groups A and B. When the preset pressure in the cylinders is reached the valves II and III are closed and the mobile station moves to the first consumer area.
If the invention is realized in USA market, the tanks are filled up to pressure 250 bars (3625 psi) or 310 bars (4500 psi) at standard temperature. The matter is that according to
NGV-2 Standard established by the Natural Gas Vehicle Coalition CNG tanks can be overfilled by 25% of their rated pressure. Correspondingly, in Europe tank max pressure
is 200 bar (3000 psig) or tank could be filled up to 259 bars (3750 psig).
Second Mode: Boosters BR pumps gas from the cylinders groups A and B simultaneously to consumer tank (8). That time valves II, III, VI, VII, IX are opened whereas all other valves are closed. Gas flows from cylinders groups A and B through pipes (b), (cl), (d), (e), (f), (g) and pressure regulator (12) to tank (8).
Third mode: Boosters BR pumps gas from cylinder group B to consumer tank (8). That time valves I, III, VII, IX are opened and booster BR takes gas from the cylinders group B and supplies to consumer tank (8) through pipes (c2), (d), (e), (f), (g).
Forth mode: Booster BR pumps gas from cylinders group A to cylinders group B. That time valves V, III, VI, IX are opened and booster BR pumps gas from the cylinders group A through pipe (cl), (d) and (h) to the cylinders group B.
Fifth mode: Decanting from both cylinders groups A and B. That time valves II, II, IV are opened and gas flows from the cylinders groups A and B through pipes (cl), (b), (i), (g) to consumer tank ( 8) .
Sixth mode: Gas decanting from cylinders groups B. That time valves IV, III, are opened and gas flows from the cylinders group B through pipes (b), (i), (g) to consumer tank (8).
Seven mode: The system is used as stationary gas compression station and gas is pumping directly from gas pipeline or gas storage reservoir to consumer's tank bypassing on-board gas storage cylinders A and B. That time valves III, VII, IX, X, XI are opened and gas flows from pipeline 11 through pipes (a) and (c3) booster BR and from the booster through pipe (e), (f), (g) to consumer's tank (8).
The above modes are used alternatively to provide effective operation algorithm of the proposed system depending on characteristics of used boosters, sort of consumer ( GV or stationary consumer compliances), phases of working cycle (moving on road, discharge), phase of discharge (initial phase with pressure in tanker tank close to maximum or minimum, etc.). For example, forth mode can be used in the course of the tanker moving from one customer to other or in the case when booster operates effectively at relatively high suction pressure, etc.
The both fifth and sixth embodiments are shown on FIG. 2.
The fifth embodiment differs from the first four embodiments by application of two boosters: the first booster operates in high pressure zone of gas suction; the second booster operates in low pressure zone of gas suction. Such arrangement enables to provide required constant capacity at wide range of gas suction pressure.
The system operates in seven modes by the following manner.
First Mode: On-board cylinders are filling from stationary gas filling station.
Second Mode: Both boosters BR1 and BR2 pump gas from the cylinders groups A and B simultaneously to consumer tank (6). Operation is similar to the first four embodiments, valve IX is opened. Third Mode: Both boosters BR1 and BR2 pump gas from the cylinders groups A to cylinders group B. Operation is similar to the first four embodiments, valve IX is opened.
Forth mode: Booster BRlpumps gas from cylinders group A to cylinders group B whereas booster BR2 supplies consumer tank (5) from cylinders group B. That time valves V, VI, VIII, X are opened and booster BR1 pumps gas from the cylinders group A through pipe (cl), (dl) and (h) to the cylinders group B. At the same time valves I, VII and XI are opened and booster BR2 takes gas from the cylinders group B and supplies gas to consumer tank 5 through pipes (e2), (f), (g). Thus, the booster BR1 receives inlet high pressure due to gas pumping from to inlet line by booster BR2. Fifth mode: Booster BR1 pumps gas from both cylinders groups A and B to consumer tank. That time valves II, VI, VII, VIII, XI 1 are opened and gas flows through pipes (c), (dl), (el), (f), (g) from both cylinders groups to consumer tank (6).
Sixth mode: Decanting from both cylinders groups A and B. That time valves II, IV, VIII are opened and gas flows from the cylinders groups A and B through pipes (b), (i), (g) to consumer tank (8). Seventh mode: Decanting from cylinders groups B. That time valves IV, VIII are opened and gas flows from the cylinders group B through pipes (b), (i), (g) to consumer tank (8).
It gives wide possibility to apply different algorithms depending on booster parameters and filled facility (NGV, stationary consumer's appliances, etc.). In sixth embodiment instead of direct mechanical drive hydraulic or electric drive (to provide air on-board compressor operation) is used. In this case it is possible to use remote power supply and install the booster in any remote place. Hydraulic motor or generator (2) is driven by PTO directly, whereas hydraulic or electric motor (3) is mounted on air compressor (4) with remote location.
Seventh embodiment is shown in FIG. 3. According this embodiment any vehicle equipped with compressor or compressed air accumulator can make self-fueling with gas from gas road tanker equipped with gas tanks and gas booster or along with this make fueling of any other stationary consumer or NGV.
The system comprises the following elements:
1) Road gas tanker that is rigid truck or auto combination that is tractor - semi-trailer, or tractor - full trailer equipped with air driven gas booster) and gas storage cylinders mounted on the deck or frame of the road gas tanker
2) NGV equipped with PTO driven air compressor.
4) Vehicle's conventional mechanical, hydraulic or electric Power Take Off (PTO) or compressed gas on-board or outside accumulator
5) On-board vehicle fueling gas tank (tanks) .
6) Piping, valving, instrumentation.
Associated components are: gas filling point joined to magisterial or distribution gas pipeline or outside gas storage tank.
The system operates by analogy of previous embodiment for all above modes.
BRIF DESCRIPTION OF THE DRAVINGS
FIG. 1 illustrates the invented system according to first four embodiments that is system comprising on-board air compressor or towed air compressor or stationary compressor or on- board/stationary air accumulator.
FIG. 2 illustrates the invented system according to fifth and sixth embodiments. Fifth embodiment is system comprising two gas boosters wherein the first operates in high pressure zone of gas suction, the second operates in low pressure zone of gas suction. Sixth embodiment is system where instead of direct mechanical drive from PTO hydraulic or electric drive to provide air on-board compressor operation is used.
FIG.3 illustrates the invented system according to seventh embodiments where any vehicle equipped with compressor or compressed air accumulator makes self-fueling with gas from gas road tanker or any stationary gas storage tank