JP2008291872A - Low-temperature liquefied gas flow rate measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow rate measuring system easy in maintenance or correction of its instruments while keeping a heat insulation performance necessary for flow measuring equipment. <P>SOLUTION: The flow rate measuring system is interposed in a low-temperature liquified gas transfer path (2) for transferring low-temperature liquified gas in a liquid status from a supply storage tank (1) of the low-temperature liquified gas into a liquid-receiving reservoir. The system is stored in a cold chamber (7) of a vacuum heat insulation structure composed of a supercooling processing device (4) for performing supercooling processing the low-temperature liquified gas during transfer, a flow meter (5), and a flow control unit (6) together with pipes to be able to open/close. The supercooling processing device (4) is composed of an immersion vessel (8) and a heat-exchanging part (9) housed inside the immersion vessel (8). A branching path (10) branching from the low-temperature liquified gas transfer path (2) in the cold chamber (7) is communicated inside the immersion vessel (8) of the supercooling processing device (4). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a low-temperature liquefied gas flow measurement technique, and more particularly to a technique for measuring a flow rate with high accuracy during a discharge flow of a liquefied gas under pressure and low-temperature holding discharged from a liquefied gas storage section such as a pressure vessel.

  When measuring the flow rate of the liquefied gas held at a low temperature, measurement by weight is common. This is because there was no flow measurement method that could measure with high accuracy in the case of liquefied gas, and for that reason, it relied on weight measurement, but the weight measurement equipment was large in terms of equipment, and there were many cases where flow measurement was not performed. . For this reason, it is desired to measure liquefied gas with a highly accurate flow meter. However, the measurement of the flow rate of the liquefied gas held at a low temperature has not been put into practical use because a large measurement error occurs due to the influence of the gas-liquid mixed phase flow caused by vaporization while flowing in the liquefied gas supply path.

  In other words, the liquefied gas that is required to be kept at a low temperature simply flows through the supply pipe from the outlet of the storage container to the place of use, and bubbles are generated due to heat input or pressure drop from the outside. When the flow rate is measured in a liquid mixed phase flow, a large measurement error occurs due to the measurement mechanism. In addition, a means to prevent the generation of bubbles by rapidly pressurizing the liquefied gas using a pump or gas can be considered, but even in that case, the problem of the driving energy of the pump and the internal pressure in the storage tank are adjusted. There were some aspects that were not suitable for the actual situation, and it was not put to practical use.

Therefore, the present applicant has a structure that suppresses the heat input of the flow rate measurement unit and the supercooling effect by heat exchange using the difference in physical properties due to pressure, and supercools the liquefied gas to be measured with the liquefied gas kept at atmospheric pressure. In addition, we have proposed a system that measures the flow rate by suppressing the generation of bubbles in the measuring device by protecting the measuring unit from heat input. (Patent Document 1)
JP 2006-200553 A

  However, in the conventional proposal, the heat exchange part of the liquid discharge path and the flow meter are arranged in the heat-insulated dip container, and the liquefied gas immediately after being discharged from the liquefied gas storage container is kept at a low temperature while the dip container is kept at a low temperature. The inside of the immersion container is maintained at atmospheric pressure, and the liquefied gas flowing in the liquid discharge path and the flowmeter is cooled by supercooling accompanying the vaporization of the liquefied gas in the immersion container, thereby I try to suppress the occurrence. In such equipment, vacuum insulation is applied to suppress heat intrusion from the outside air, but vacuum insulation in such equipment is generally performed by a vacuum double pipe with a welded fixing structure. . For this reason, it becomes a structure difficult to remove after construction.

  However, when using the flow meter, maintenance and calibration at regular intervals are necessary. However, the previously proposed one has a welded fixed structure as described above, so the flow meter is maintained and calibrated. There was a problem that it was difficult, and the modification of the piping structure was troublesome.

  The present invention has been made paying attention to such points, and it is intended to provide a flow measurement system that facilitates maintenance and calibration of instruments while maintaining necessary heat insulation performance for each device for flow measurement. Objective.

  In order to achieve the above object, the present invention described in claim 1 is provided in a low-temperature liquefied gas transfer path for transferring low-temperature liquefied gas from a storage tank for supplying low-temperature liquefied gas to a liquid receiving container in a liquid state. The flow measurement system is configured to be able to open and close the supercooling processing device that supercools the low-temperature liquefied gas being transferred, the flow meter, and the flow control unit together with the piping that connects these devices in communication. Stored in a cold chamber having a vacuum insulation structure, and a low temperature liquefied gas transfer path from the low temperature liquefied gas supply storage tank to the cold chamber and a low temperature liquefied gas transfer path from the cold chamber to the liquid receiving container are insulated. The supercooling treatment device is composed of an immersion container and a heat exchange unit accommodated in the immersion container, and the branch path branched from the low-temperature liquefied gas transfer path in the cold chamber is supercooled. It is characterized by communicating with the immersion container processing apparatus.

  Further, in the present invention described in claim 2, the low-temperature liquefied gas of the invention described in claim 1 is liquid hydrogen, and in the present invention described in claim 3, the liquid receiver of the invention described in claim 2 is used. The container is a fuel gas storage container mounted on an automobile.

  In the present invention, a supercooling processing device for supercooling the low-temperature liquefied gas being transferred, a flow meter and a flow rate control unit are housed in a cold chamber, and a part of the liquefied gas to be transferred is boiled in the supercooling processing device. The flow rate of the low-temperature liquefied gas flowing through the transfer path is measured by a flow meter that is placed in the cold chamber and maintained in a low-temperature state in a supercooled state using the difference and in a liquid phase flow. Therefore, the flow rate in the liquid phase state can be measured, and the flow rate can be detected with high accuracy.

  In addition, the devices such as the supercooling processing device, the flow meter and the flow control unit are accommodated in the cold chamber, and the cold chamber can be opened and closed, so the devices such as the flow meter accommodated in the cold chamber. It is not necessary to have a heat insulating structure, and maintenance work and calibration work for equipment such as a flow meter can be easily performed, and piping can be easily changed.

  FIG. 1 is a schematic configuration diagram of a low-temperature liquefied gas flow measurement system showing an embodiment of the present invention. This low-temperature liquefied gas flow measurement system includes a low-temperature liquefied gas supply storage tank (1) and a low-temperature liquefied gas supply system. A liquid receiving container (not shown) is connected in communication with a low-temperature liquefied gas transfer path (2) having an adiabatic specification, and a liquefied gas dispenser (3) is disposed in the middle of the low-temperature liquefied gas transfer path (2).

  The liquefied gas dispenser (3) has a supercooling treatment device (4) for supercooling the low-temperature liquefied gas being transferred, a flow meter (5), a flow control unit (6), and these devices together with a group of vacuum insulation. It is comprised by accommodating in the cold chamber (7) of a structure.

  The supercooling treatment device (4) is composed of an immersion vessel (8) and a heat exchange part (9) piped in the immersion vessel (8), and both ends of the heat exchange part (9). Is connected to the low temperature liquefied gas transfer path (2), and the branch path (10) branched from the low temperature liquefied gas transfer path (2) in the cold chamber (7) is opened in the immersion container (8). ing. For this reason, the liquid phase part and the gas phase part of the liquefied gas are formed in the immersion container (8), the heat exchange part (9) is immersed in the liquid phase part, and the gas phase part is communicated with the communication path (11). It communicates outside the cold chamber. Further, the cold chamber inner space (12) is maintained in a vacuum state.

  Therefore, since the internal pressure of the immersion container (8) is maintained at atmospheric pressure, the liquid temperature in the immersion container (8) is the boiling point temperature under atmospheric pressure. On the other hand, the temperature of the low-temperature liquefied gas flowing in the heat exchange section (9) is a temperature corresponding to the vapor-liquid equilibrium pressure in the low-temperature liquefied gas storage tank (1), and therefore flows in the heat exchange section (9). In the meantime, the low-temperature liquefied gas is supercooled by exchanging heat with the liquid phase in the immersion container, and the liquid-phase flow is measured in the low-temperature liquefied gas transfer path (2) in the cold chamber. The flow meter (5) can detect the flow rate with high accuracy.

  This eliminates the need for these devices and pipes housed in the cold chamber (7) to have a heat insulating structure, and sufficiently suppresses heat input from the outside to the devices and pipes. Because it will be possible, the liquefied gas can be circulated in the supercooled state inside equipment and piping, and it can be measured as a single liquid flow with a flow meter, so the flow rate must be measured with high accuracy. Can do.

  At the beginning of the low-temperature liquefied gas flow, the temperature of the piping, flow meter, and flow rate control unit is high, and the liquefied gas vaporizes and becomes a gas-liquid mixed phase flow. Return to the immersion container (8) through the return path (14). The flow rate control unit (6) monitors the temperature and pressure, and when the temperature of the low-temperature liquefied gas falls below the boiling point corresponding to the pressure of the low-temperature liquefied gas, the return to the immersion vessel (8) is stopped.

  The cold chamber (7) is composed of a body (7a) and a lid (7b), and the cold chamber (7a) is released by releasing the connection between the lid (7b) and the body (7a). ) Is configured to open. With this configuration, maintenance, calibration work, or pipe replacement work of the flow meter (5) can be easily performed.

  The flow rate measurement system having the above-described configuration can be used for a liquid hydrogen supply piping system that supplies liquid hydrogen in a liquid state, and in particular, the flow rate measurement in a fuel supply facility of a hydrogen engine automobile that uses liquid hydrogen as a fuel source. It is suitable as a system.

  INDUSTRIAL APPLICABILITY The present invention can be used for measuring the flow rate of a liquefied gas as a single liquid flow, and in particular, can be used as a flow rate measurement system in a station that supplies liquid hydrogen as an automobile fuel.

It is a schematic block diagram of the flow measurement system of the low-temperature liquefied gas which shows one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Storage tank for low temperature liquefied gas supply, 2 ... Low temperature liquefied gas transfer path, 4 ... Supercooling processing device, 5 ... Flow meter, 6 ... Flow control unit, 7 ... Cold chamber (7a ... trunk | drum, 7b ... Lid ), 8 ... immersion container, 9 ... heat exchange part, 10 ... branching path.

Claims (3)

A flow rate measurement system interposed in a low-temperature liquefied gas transfer path (2) for transferring low-temperature liquefied gas in a liquid state from a storage tank (1) for supplying low-temperature liquefied gas to a liquid receiving container,
The supercooling treatment device (4) that supercools the low-temperature liquefied gas being transferred, the flow meter (5), and the flow control unit (6) can be opened and closed together with the pipes that connect these devices. The low-temperature liquefied gas transfer path (2) from the storage tank (1) for supplying the low-temperature liquefied gas to the cold chamber (7) and the cold chamber (7) ) To the receiver vessel, the low-temperature liquefied gas transfer path (2) is insulated, and the supercooling device (4) is accommodated in the immersion vessel (8) and the immersion vessel (8). (9), and the branch passage (10) branched from the low-temperature liquefied gas transfer passage (2) in the cold chamber (7) is communicated with the immersion container (8) of the supercooling treatment device (4). Low temperature liquefied gas flow measurement system characterized by   The low-temperature liquefied gas flow rate measuring system according to claim 1, wherein the low-temperature liquefied gas is liquid hydrogen.   The low-temperature liquefied gas flow measurement system according to claim 2, wherein the liquid receiving container is a fuel gas storage container mounted on an automobile.

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