Method for delivering a fluid stored in liquefied form to an end user in gaseous form

Abstract

A system and method is disclosed for storing a fluid in a storage vessel in liquefied form and delivering it in gaseous form to an end user through a supply line. The system comprises a pressure relief circuit for returning the fluid from the supply line to the vessel when predetermined conditions are met. The pressure relief circuit comprises a return line connected to the supply line and the storage vessel, a diversion line to divert the fluid elsewhere and a switching device operable to direct the fluid to either one of the lines, as a function of predetermined conditions.

Claims

1. A method, comprising: storing a fluid in a vessel in liquefied form; delivering said fluid in gaseous form through a supply line to an end user; upon meeting a predetermined condition, reducing a fluid pressure in said supply line by directing fluid through a switching device to return said fluid in gaseous form from said supply line to said vessel; and upon not meeting said predetermined condition, directing said fluid through said switching device to divert said fluid from returning to said vessel and from being delivered to said end user through said supply line by directing said fluid elsewhere through a diversion line.

2. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid elsewhere when said fluid pressure is determined to be higher than a predetermined high pressure threshold.

3. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid elsewhere when said fluid pressure is determined to be lower than a predetermined low pressure threshold.

4. The method of claim 1, wherein said predetermined condition correlates to keeping a pressure inside said vessel below a threshold safety pressure of said vessel.

5. The method of claim 2, wherein said predetermined condition correlates to keeping a pressure inside said vessel below a threshold safety pressure of said vessel.

6. The method of claim 3, wherein said predetermined condition correlates to keeping a pressure inside said vessel below a threshold safety pressure of said vessel.

7. The method of claim 1, wherein said predetermined condition correlates to a pressure inside said vessel being less than a preset vessel relief pressure by a predetermined margin.

8. The method of claim 2, wherein said predetermined condition correlates to a pressure inside said vessel being less than a preset vessel relief pressure by a predetermined margin.

9. The method of claim 3, wherein said predetermined condition correlates to a pressure inside said vessel being less than a preset vessel relief pressure by a predetermined margin.

10. The method of claim 1, further comprising diagnosing whether said fluid contains contaminants and diverting said fluid elsewhere when contaminants are detected.

11. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through the diversion line includes diverting said fluid to a burner when at least one of the following is determined: said fluid pressure is determined to be higher than a predetermined high pressure threshold; and said fluid pressure is determined to be lower than a predetermined low pressure threshold.

12. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid to a catalytic converter when at least one of the following is determined: said fluid pressure is determined to be higher than a predetermined high pressure threshold; and said fluid pressure is determined to be lower than a predetermined low pressure threshold.

13. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid to a secondary user or another tank when at least one of the following is determined: said fluid pressure is determined to be higher than a predetermined high pressure threshold; and said fluid pressure is determined to be lower than a predetermined low pressure threshold.

14. The method of claim 1, further comprising determining said fluid pressure in said supply line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid to a re-liquefication device when at least one of the following is determined: said fluid pressure is determined to be higher than a predetermined high pressure threshold; and said fluid pressure is determined to be lower than a predetermined low pressure threshold.

15. The method of claim 1, wherein said end user is an internal combustion engine and said method further comprises delaying to return said fluid to said vessel until a predetermined time has elapsed.

16. The method of claim 3, wherein said end user is an internal combustion engine and said method further comprises delaying to return said fluid to said vessel until a predetermined time has elapsed since said engine has stopped running.

17. A method, comprising: containing a fluid in a vessel in liquefied form; delivering the fluid in gaseous form through a supply line to an end user; positioning a switching device to a first opened position when a predetermined condition is met, the positioning of the switching device to the first opened position causing the fluid in gaseous form from the supply line to return to the vessel, the returning of the fluid in gaseous form thereby reducing fluid pressure in the supply line; and positioning the switching device to a second opened position when the predetermined condition is not met, the positioning of the switching device to the second opened position causing the fluid in gaseous form from the supply line to divert the fluid in gaseous form from returning to said vessel and from being delivered to said end user through said supply line by directing said fluid elsewhere through a diversion line.

18. The method of claim 17, further comprising at least one of the following: determining the fluid pressure in the line, and wherein directing said fluid elsewhere through said diversion line includes diverting the fluid elsewhere when the fluid pressure is determined to be higher than a predetermined high pressure threshold; and determining the fluid pressure in the line, and wherein directing said fluid elsewhere through said diversion line includes diverting said fluid elsewhere when said pressure is determined to be lower than a predetermined low pressure threshold.

19. The method of claim 17, further comprising: detecting contaminants in the fluid; and removing the contaminants from the fluid by filtering the fluid with a filter.

20. The method of claim 17, further comprising separating the fluid in gaseous form from fluid in liquid form.

21. The method of claim 17, wherein the predetermined condition correlates to keeping a pressure inside the vessel below a threshold safety pressure of the vessel.

22. The method of claim 17, wherein directing said fluid elsewhere through the diversion line includes diverting said fluid in gaseous form to one of a burner, a catalytic converter, another tank, a secondary user or a re-liquefication device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a preferred embodiment of a system for delivering a gas stored in a vessel in liquefied form to an end user.

(2) FIG. 2 is a schematic diagram of an alternate embodiment of a system for delivering a gas stored in a vessel in liquefied form to an end user.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

(3) With reference to the schematic diagram of FIG. 1, system 100 comprises storage vessel 101 for storing a fluid in liquefied form and supply line 103 for delivering fluid in gaseous form to an end user 105. The fluid may be taken from the vapor space of storage vessel 101, already in gaseous form, or it can be warmed and vaporized in optional vaporizer 107, shown in dashed lines, or it can be delivered to the supply line as a supercritical fluid. End user 105 can be an internal combustion engine fueled with a gaseous fuel as further described in a preferred embodiment or it can be for example a second storage vessel which is filled with gaseous fuel supplied from storage vessel 101. Pressure relief circuit 110 comprises relief line 112 which is fluidly connected to supply line 103 and to switching device 114, which, in the embodiment illustrated in FIG. 1, is a three-way valve. Pressure relief circuit 110 further comprises return line 120 and diversion line 130, which are each fluidly connected to switching device 114. Switching device 114 is controlled by commands sent from controller 116, which, in typical embodiments, is an electronic control unit. When the end user 105 is receiving fluid from storage vessel 101 or at times when fluid pressure is wanted or required in supply line 103 and when the pressure in supply line 103 is below a predetermined pressure limit determined for example as a function of the current operating conditions of the end user 105, controller 116 commands switching device 114 to a position that prevents any fluid from flowing through relief line 112 to either return line 120 or diversion line 130. When the end user is supplied with fluid through supply line 103, but the pressure in supply line 103 is higher than a desired pressure determined for example as a function of the current operating conditions for that end user 105 or, alternatively, when fluid is to be discharged from supply line 103, for example when the end user 105 is shut down or when fluid is otherwise no longer required by the end user, controller 116 commands switching device 114 to a position that allows fluid to flow through relief line 112 and switching device 114 to return line 120 or to diversion line 130. Controller 116 commands switching device 114 to a position that directs fluid through return line 120 and back to storage vessel 101, or diverted elsewhere through diversion line 130 as a function of whether controller 116 determines that predetermined conditions have been met for returning the fluid to storage vessel 101. Contrary to conventional systems which avoid returning any fluid in gaseous form from a supply line back to the storage vessel (where the fluid is stored in liquefied form), if the mass of fluid to be returned to the storage vessel is relatively small compared to the mass of fluid already stored in the storage vessel, and if the fluid can be returned to the storage vessel without causing fluid to be vented therefrom, the disclosed system and method can be beneficial in recovering some of the fluid that might otherwise be wasted.

(4) Return line 120 can further comprise filter 122 for removing contaminants from the fluid before it is returned to storage vessel 101. Contaminants such as lubricants or other impurities can be introduced into the fluid as it flows through the supply line and through the components disposed therein, such as pumps, filters, pressure reducers and other components included in the delivery system through which the fluid flows. If such contaminants include ones that can freeze when subjected to the colder temperatures inside the storage vessel, such frozen contaminants in solid form can cause damage to the system components. For example, if end user 105 is a dual fuel engine fueled with a gaseous fuel and a liquid fuel, filter 122 can remove any liquid fuel in vapor form which has contaminated the gaseous fuel that is returned to storage vessel 101, by way of example, filter 122 can be a carbon-activated hydrocarbon vapor filter.

(5) Return line 120 passes through check valve 124, which prevents fluid backflow from storage vessel 101 through return line 120.

(6) FIG. 1 shows an embodiment of the system in which diversion line 130 vents the fluid to the atmosphere. This arrangement can work for example, when the system is a fuel delivery system for an engine that is fueled with natural gas and there is only a small amount of natural gas in supply line 103. For example, when the engine is shut down, it is preferred to discharge fuel from the fuel supply line and reduce the pressure of the gaseous fuel within the supply line so that it is not filled with natural gas with a pressure above atmospheric pressure when the engine is not running. In some conventional engines described in the prior art, since the volume of the fuel supply line is very small, all of the fuel is vented to atmosphere. In the present system illustrated in FIG. 1, to improve the efficiency of the system and to reduce waste, when predetermined conditions are met, at least some fluid is returned to storage vessel 101. As shown in the embodiments of FIG. 1, before even a reduced amount of gaseous fuel is vented to the atmosphere the gaseous fuel passes through gas separator 132 which separates gaseous fuel from any liquid fuel, lubricants or other contaminants that might have leaked into the stream of gaseous fuel, which is sometimes possible for example in the case of dual fuel or bi-fuel engines. In such systems, the liquid fuel collected by gas separator 132 can thereby be recovered and returned to liquid fuel tank 134. In some embodiments, for example in dual fuel engine systems fueled with natural gas and diesel, a carbon-activated hydrocarbon vapor filter can be used between gas separator 132 and liquid fuel tank 134.

(7) In some embodiments, diversion line 130 can direct the vented fluid through a treatment device 136, which can be a catalytic converter or any other type of burner to convert the fluid into another form before being vented to atmosphere. In other embodiments (not shown), instead of being vented to atmosphere the fluid can be directed instead to a secondary user or to a re-liquefication device, such as a cryocooler, to re-liquefy the fluid so that it can be returned to storage vessel 101. Devices for re-liquefying a gas can be expensive and can consume energy so an advantage of returning some or most of the fluid to the storage vessel in gaseous form is that it enables the use of a re-liquefying device with a smaller flow-through capacity and reduced energy consumption.

(8) In preferred embodiments of the disclosed system, when applied to a fuel delivery system for an engine, when controller 116 determines that the fluid should be discharged from supply line 103, tank shut off valve 102 is closed and controller 116 commands switching device 114 to open to either return the fluid to storage vessel 101 or direct it to diversion line 130. The fluid pressure in the supply line, depending upon the engine design and the operating conditions, generally is between 180 and 300 bar (at about 2610 to 4351 psi), which is much greater than the pressure in the storage vessel 101 , which is typically between 0 and 16 bar (between 0 to about 232 psi). In preferred embodiments, the pressure of the fluid in the supply line is a fluid parameter that forms the basis for one of the predetermined conditions that must be met for controller 116 to command switching device 114 to a position that returns the fluid to storage vessel 101. The pressure in fluid supply line 103 is measured by a pressure sensor 119 that can be placed in supply line 103 or in relief line 112 (as illustrated). If the fluid pressure is too high, returning the fluid to the storage vessel could result in immediate venting from the storage. However, controller 116 can be programmed to determine or approximate whether returning the fluid to the storage vessel 101 will result in triggering the storage vessel's pressure relief system. For example, the pressure of the fluid in the supply line could be higher than the normal pressure in the storage vessel 101 and still be returned thereto if the amount fluid to be returned is sufficiently small relative to the amount of fluid stored in the storage vessel, and to the volume of the storage vessel and if the fluid returning to the storage vessel 101 can be received without raising the pressure in the storage vessel 101 above the predetermined pressure relief limit. Accordingly, depending on the pressure ratings for a particular system and other system parameters considered by controller 116, switching device 114 can be commanded to direct fluid to diversion line 130 or to storage vessel 101 when the predetermined conditions are met. That is, controller 116 controls whether fluid is returned to storage vessel 101 or diverted to diversion line 130 depending on the predetermined conditions associated with a particular system.

(9) If the fluid can be received into storage vessel 101 without causing any immediate venting from storage vessel 101, then the fluid can be initially returned to storage vessel 101. If the controller determines that the pressure in the supply line is too high then the fluid might be initially directed to diversion line 130. As fluid is discharged from supply line 103, fluid pressure in supply line 103 starts to drop and when it reaches a lower range at which fluid can be received into the storage vessel, controller 116 can command switching device 114 to a position in which fluid is returned to storage vessel 101. When fluid pressure in supply line 103 drops below a predetermined threshold and it becomes substantially equal to or lower than the pressure in storage vessel 101 or when the pressure differential between the fluid pressure in supply line 103 and the fluid pressure in storage vessel 101 drops below a predetermined amount within an acceptable time frame, controller 116 can be programmed to command switching device 114 back to a position that directs the fluid to diversion line 130.

(10) In other embodiments, the fluid is always returned to storage vessel when fluid pressure in the supply line is greater than the fluid pressure in the storage tank by a predetermined margin. That is, for systems where the volume of the supply line is so much smaller than the volume of the storage vessel that the amount of fluid being returned to the storage vessel is so small relative to the amount of fluid stored inside the storage vessel, it can be presumed that the increase in pressure caused by the high pressure fluid will not cause venting from the storage vessel even if the returning fluid has a much higher pressure, such as, for example, 300 bar. That is, if the system is designed to be able to absorb the returned fluid without causing more fluid to be vented from the storage vessel than the amount that is returned, the system can be simplified by being designed to control switching device 114 to allow fluid to be returned through return line 120 to storage vessel 101.

(11) Other than the pressure of the fluid in supply line 103, the pressure of the fluid in storage vessel 101, and the design parameters associated with the storage vessel, such as the preset relief pressure, the size of the storage vessel and its ability to absorb a small amount of high pressure fluid in gaseous form, some embodiments can be designed to consider other parameters that can be measured and made part of the predetermined conditions that controller 116 considers in determining whether to return the fluid to storage vessel 101 or direct it to diversion line 130.

(12) An example of the disclosed system and method is now disclosed with reference to certain parameter values associated with a preferred embodiment for a gaseous fuel system for an internal combustion engine where gaseous fuel is directly injected into the combustion chamber. In such a system, during engine operation, the pressure of the fluid in the supply line is maintained at about 180-300 bar (at about 2600 to 4350 psi). The pressure in the storage vessel is generally about 0-16 bar (between 0 to about 230 psi). The fluid should not be returned from the supply line to the storage vessel if it will result in raising the pressure in the storage vessel above the preset relief pressure, which is generally about 16 bar (about 230 psi), but could be higher depending on the system design. In some embodiments, the pressure inside the vapor space of storage vessel 101 is monitored and fluid is returned to the storage vessel only when the storage vessel pressure is below a predetermined fixed limit which equals to the safety relief pressure for that particular vessel minus a predetermined margin.

(13) An additional predetermined condition includes returning the fluid to the storage vessel when diagnostics from the electronic control unit indicate that the drained fluid does not contain any contaminants. Contaminants are defined herein to mean any fluids that can take a solid form in a cryogenic environment. For example, with fuel systems for a dual fuel engine which is fueled for example with natural gas and diesel, it can be possible for the fluid to be contaminated with diesel or other heavy hydrocarbons and if this is the case then the fluid is not returned to the storage vessel unless the system includes a gas separator. In such embodiments the controller receives data from sensors and is programmed to determine if diesel or other heavy hydrocarbons are present in the fluid. For dual-fuel engine systems that run mainly on gaseous fuels but can also run in a liquid-fueled only mode, the system can be programmed with a predetermined time-delay after the engine has switched off to a gaseous-fuel mode before controller 116 can direct the fluid through return line 120, to ensure that liquid fuel is not passed into storage vessel 101. Alternatively, a liquid sensing device could be placed in relief line 112, in return line 120 or in filter 122 and controller 116 commands switching device 114 to divert the fluid elsewhere when the sensing device indicates that there is liquid present in fluid and to return of gaseous fuel to storage vessel 101 only when the sensing device indicates that the gaseous fuel in return line 120 is free of any liquid fuel.

(14) With reference now to the schematic diagram of FIG. 2 an alternate embodiment of the disclosed system is shown. This alternative embodiment has many components that are the same or equivalent to components of the embodiment shown in FIG. 1. Such like components are identified by like reference numbers increased by an increment of 100, and their function and what they are, may not be repeated in the description of the embodiment shown in FIG. 2.

(15) One difference between the two illustrated embodiments is that the embodiment illustrated in FIG. 2 has a gas separator 232 disposed on relief line 212 upstream from switching device 214. This allows liquid and other non-gaseous impurities to be separated from the gaseous fluid before the pressure relief circuit branches to return line 220 or diversion line 230, and in some systems this obviates the need for a filter 222 in return line 220, which is illustrated here as an optional component.

(16) The embodiment in FIG. 2 also illustrates an alternative form for switching device 214. Instead of a three-way valve, switching device 214 comprises a line with two branches with control valve 215 on one branch and control valve 217 on the other branch. Controller 216 commands first control valve 215 to open when fluid is to be directed to diversion line 230 and/or it commands second control valve 217 to open when fluid is to be directed to return line 220. When second control valve 217 is open, fluid flows through check valve 224 to storage vessel 201. When fluid pressure in return line 220 is lower than the pressure needed to open check valve 224 and to overcome the pressure inside storage vessel 201 and the end user 205 is shut down and fluid has to be discharged from supply line 203, controller 216 opens first control valve 215 and fluid will flow only to diversion line 230. When fluid pressure in supply line 203 is higher than a predetermined level as determined by the operating condition of the end user 205 or when the end user 205 is shut down and fluid pressure in supply line 203 has to be reduced, it is possible to open either first control valve 215 or second control valve 217 to direct fluid to either diversion line 230 or return line 220. First control valve 215 and second control valve 217 can be either fully or partially open. In some embodiments, controller 216 can command both first control valve 215 and second control valve 217 to an open position so that fluid flows through both diversion line 230 and return line 220 at the same time.

(17) In some embodiments, when the end user 205 is shut down and fluid has to be discharged from supply line 203, initially the pressure in relief line 212 is higher than the pressure in storage vessel 201 by a predetermined threshold and second control valve 217 is open so that fluid is returned to storage vessel 201. When the pressure in relief line 212 becomes equal to the pressure in storage vessel 201 controller 216 commands first control valve 215 to open and fluid is diverted elsewhere.

(18) The operation of this embodiment illustrated in FIG. 2 is generally similar to the operation of the embodiment shown in FIG. 1.

(19) While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.