Patent Application
20220349526
The present disclosure relates generally to dispensing systems for cryogenic fluids and, more particularly, to a system for fueling an on-board vehicle tank or other use device with a cryogenic fuel.
Cryogenic fluids find use as fuels in a variety of industrial processes and vehicles. Natural gas is a cryogenic fluid useful as an alternative fuel source for powering vehicle engines. It is typically stored and transported as liquefied natural gas (LNG) because it occupies a much smaller volume (approximately 1/600th the gaseous state). Temperature and pressure regulation of liquefied natural gas during storage is extremely important. Liquefied natural gas is typically stored in insulated cryogenic tanks because of the low temperature requirements (˜−160° C.) and typically at lower pressures. Furthermore, in fueling station applications, the stored cryogenic liquid is typically saturated, so that the gas and liquid states simultaneously exist at a desired temperature and pressure.
Liquefied or liquid nitrogen (LIN) is often used in LNG fueling stations for maintaining low temperature within the LNG storage tanks. The LNG tanks often feature a condensing coil in the tank headspace. Liquid nitrogen boils inside the condensing coil, and this causes natural gas vapors to condense on the coil's surface. Prior art LNG tanks often vent the evaporated nitrogen to the atmosphere. Additionally, sometimes nitrogen vapors are taken from the top of a liquid nitrogen tank associated with the LNG tank, and warmed up in an ambient air heat exchanger to be utilized as instrument air for valve actuation, purging and inerting.
In such prior art LNG tanks, the liquid nitrogen tank is separated from the LNG tank which increases the equipment footprint and system costs. Additionally, nitrogen vapor (from the coil) is not utilized in the system and instead is directly vented into the atmosphere. At the same time, liquid nitrogen from the LIN tank is evaporated in a pressure building heat exchanger in order to build pressure in the LIN tank and to generate heated vapor to be used as instrument air. This results in unnecessary heat input into the system.
There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.
In one aspect, a cryogenic fluid fueling system includes a first container comprising a first inner vessel and a first outer shell wherein the first inner vessel defines a first interior configured to contain a first cryogenic liquid with a first headspace being positioned above the first cryogenic liquid. A heat exchanger is fluidically connected to the first container and is configured to vaporize a portion of the first cryogenic liquid, such that pressure within the first container is raised as vaporized cryogen moves from the heat exchanger into the first headspace. A second container includes a second inner vessel and a second outer shell wherein the second inner vessel defines a second interior. The second interior is configured to contain a second cryogenic liquid with a second headspace being positioned above the second cryogenic liquid. A condensing coil is positioned within the second headspace of the second container and is fluidically connected to the first interior of the first container such that a portion of the first cryogenic liquid is propelled into the condensing coil and is warmed to provide a first cryogenic vapor.
In a second aspect, a cryogenic fluid fueling system includes a first container having a first inner vessel and a first outer shell wherein the first inner vessel defines a first interior configured to contain a first cryogenic liquid with a first headspace being positioned above the first cryogenic liquid. A second container has a second inner vessel and a second outer shell wherein the second inner vessel defines a second interior. The second interior configured to contain a second cryogenic liquid with a second headspace being positioned above the second cryogenic liquid. A heat exchanger is positioned within the second container and is fluidically associated with the first container so as to vaporize a portion of the first cryogenic liquid such that pressure within the first container is raised as vaporized cryogen moves from the heat exchanger into the first headspace. A condensing coil is positioned within the second headspace of the second container. The condensing coil is fluidically connected to the first interior of the first container such that a portion of the first cryogenic liquid is propelled into the condensing coil and is warmed to provide a first cryogenic vapor.
A heat exchanger 114 is fluidically associated with the first container 102. More specifically, the heat exchanger 114 serves as a pressure building unit (PBU) and is configured, when valve 115 is opened, to vaporize a portion of the liquid nitrogen 110, such that pressure within the first container 102 is raised as the vaporized nitrogen moves from the heat exchanger 114 into the first headspace 112. The pressure increase in the first interior 108 drives liquid nitrogen out of the first container 102 via line 117 when valves 119 and 121 are opened.
The system 100 also includes a second container, indicated in general at 116, having a second inner vessel 118 and a second outer shell 120 with an insulation space defined therebetween. A vacuum is preferably drawn on, or air is at least partially evacuated from, the insulation space. The second inner vessel 118 defines a second interior 122 having a pump 124 positioned therein and configured to direct cryogenic liquid out of the tank to an on-board vehicle tank or other use device (not shown). The pump 124 may be any appropriate liquid pump known in the art. The second container interior, indicated in general at 122, is configured to contain a second cryogenic liquid 126, which is a cryogenic fuel, with a second headspace 128 being positioned above the second cryogenic liquid 126. In the present embodiment, and in the embodiments described below, the second cryogenic liquid 126 is liquid natural gas.
A condensing coil 130 having a surface 132 is positioned within the second headspace 128 of the second container 116. The condensing coil 130 may be any appropriate condensing coil known in the art. The condensing coil 130 is fluidically connected to the first interior 108 of the liquid nitrogen container. More specifically, as described above, after the pressure in the first interior 108 propels liquid nitrogen 110 out of the first container 102 via line 117, the liquid nitrogen 110 flows into the condensing coil 130. The liquid nitrogen 110 causes natural gas vapor within headspace 128 of the liquid natural gas container to condense on the surface 132 and return to the LNG 126 below. As a result, the pressure within the second container interior 122 is reduced as the headspace pressure is collapsed and the LNG 126 is cooled. The LNG 126 is pumped out of the second container 116 and system 100 to the vehicle fuel tank by the pump 124.
A heater 134 is fluidically connected to the outlet of the condensing coil 130, such that nitrogen vapor from the condensing coil is heated by the heater 134. The heater 134 may be any appropriate heater known in the art, including, but not limited to, a heat exchanger (ambient air or other warming fluid), an electric heater or a heater using another power source. The heated nitrogen vapor 138 is directed out of the system for use as instrument air. As non-limiting examples, use as instrument air may include using the warmed nitrogen vapor for valve actuation, purging and inerting. A portion (or all) of the nitrogen vapor from condensing coil 130 may optionally be vented to atmosphere via vent valve 139 instead of being directed to the heater 134.
Turning next to
Turning next to
As non-limiting examples, where the first container contains liquified nitrogen and the second container contains liquified natural gas, the design pressure for the first container and the second container may be 11 barg. An example pressure operating range for the first container is 6 to 10 barg. An example pressure operating range for the second container is 0 to 10 barg. Temperatures of the liquid nitrogen and the liquefied natural gas corresponding to these pressures are shown in the graph of
All fluidic connections described above may be made by any appropriate known gas and/or liquid piping. Each time an element is described above as fluidically connected to another element, one or more pipes may act as a conduit between the element and the other element. Additionally, all system valves may be controlled to provide the above functionality by a control system including a micro-processor, CPU or other computer device.
While the preferred embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the disclosure, the scope of which is defined by the following claims.
This application claims the benefit of U.S. Provisional Application No. 63/183,348, filed May 3, 2021, the contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63183348 | May 2021 | US |
