Apparatus and method for determining the quantity of compressed gas

Abstract

The present invention relates to a measurement device (20) for determining the amount of compressed gas when gas is drawn from a compressed gas reservoir (4) including multiple sub-reservoirs (6a-6d) from which gas can be drawn independently. The measurement device (20) includes a gas pressure sensor (22) pressure-connected to each of the sub-reservoirs (6a-6d) via a measurement pipe (24). The measurement device (20) further includes a switching device (26) inserted into the measurement pipe (24) for alternately connecting the gas pressure sensor (22) to each of the sub-reservoirs (6a-6d) for selectively measuring the gas pressures (P1-P4) of each of the sub-reservoirs (6a-6d) via the switching device (26). The measurement device (20) further includes at least one temperature sensor (28a-28d) located at the compressed gas reservoir (4) for measuring the gas temperatures (T1-T4).

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for determining the quantity of compressed gas, particularly hydrogen gas. [Background technology]

[0002] Industrial or technical gases are usually stored under pressure in appropriate compressed gas containers and transported from the production site to the use site. To transport the relatively large gas quantities required for industrial purposes or gas tank stations, such compressed gas containers are usually permanently mounted on tank vehicles or tank trailers. For transporting hydrogen in particular, tank trailers with multiple gas cylinders are used. In this case, such gas cylinders are often grouped together to form a cylinder bundle (cascade), and the gas can be removed from each cylinder bundle independently. Such tank vehicles or tank trailers are usually driven filled to the use site and then emptied and returned to the supply source, in particular the production site or intermediate storage facility, for refilling.

[0003] However, reliably and accurately determining such large gas volumes is technically complex under real-world conditions in use, based on the physical and chemical properties of the compressed gas being transported.

[0004] In many cases, the gas consumption (i.e., the amount of gas extracted) is offset by measuring the pressure difference between the initial (gas) pressure in a filled compressed gas container before the start of gas extraction and the final (gas) pressure in a fully or partially emptied compressed gas container after the end of gas extraction. The amount of gas extracted is calculated from the determined pressure difference using gas equations, taking into account the container volume (i.e., the volume of the compressed gas container from which gas extraction took place) and the assumed average reference temperature. A drawback of such a measurement method is the high inaccuracy caused by the temperature dependence of the gas pressure. If the final pressure is measured at a higher temperature than the initial pressure, the actual amount of gas consumed will be underestimated. Conversely, if the final pressure is measured at a lower temperature than the initial pressure, the actual amount of gas consumed will be overestimated.

[0005] To enable a more accurate determination of gas consumption, mass flow measuring devices based on the Coriolis principle are sometimes used (Coriolis flowmeters). However, Coriolis flowmeters with sufficient measurement accuracy are associated with high procurement costs, which often makes their use uneconomical.

[0006] Korean Patent No. 10-1222874 discloses a system and method for measuring the amount of compressed gas replenished in a tank by referring to pressure and temperature as parameters. These values ​​are detected by pressure and temperature sensors in a reference vessel inserted between the gas storage vessel and the pressure vessel to be replenished. To indirectly determine the pressure and temperature of the pressure vessel before the tank replenishment process, the reference vessel is first filled with compressed gas up to the maximum achievable filling pressure. The pressure vessel to be replenished is then filled from the reference vessel until an isothermal hydrostatic pressure is reached. This pressure is measured in the reference vessel and transferred to a control unit. After the pressure vessel is filled from the gas storage vessel, the pressure and temperature are measured again in the reference vessel and transmitted to the control unit. From these pressure and temperature values, the control unit calculates the amount of gas replenished in the tank and the corresponding payment due at the end of the tank replenishment process.

[0007] EP 3 271 636 B1 describes a method for filling pressure vessels with compressed gas, particularly hydrogen. The method is carried out by a filling station including multiple storage tanks for compressed gas and a piping system for transporting gas from the storage tanks to the pressure vessels via a single or multiple pressure equalization processes. The piping system has a first end to which the storage tanks are connected in parallel. At a second end of the piping system, a transport piping is movably connected to one or more pressure vessels to be filled. A first shut-off valve, a flow or pressure control device, and a second shut-off valve are connected in series between the first and second ends of the piping system. In this method, both shut-off valves are closed at the end of filling the first pressure vessel and before filling the second pressure vessel, thereby trapping a compressed gas reserve in the piping system between the shut-off valves. This gas reserve is then used to refill at least one of the pressure vessels.

[0008] DE 10 2019 120 242 A1 describes a method for determining the fill mass of a pressure vessel having a vessel volume enclosed by a vessel wall, the fill mass being determined using dimensional data of the pressure vessel measured on the pressure vessel.

[0009] US Patent No. 7,647,194 B1 describes a method for calculating the hydrogen temperature during vehicle tank refueling. The calculation basis is data on the ambient temperature, the initial static pressure, the final static pressure of the pressure gauge, the added mass, and the filling time.

[0010] EP 3 299 775 B1 describes a system for mobile calibration of gas-filling devices. In this case, a filling container housed in a measuring housing is filled by the gas-filling device with high-pressure combustible gas, and the weight of the supplied combustible gas is determined by a balance. For the measurement process, dry gas is introduced into the measuring housing to prevent moisture condensation on the filling container, which would distort the measurement. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent No. 10-1222874 [Patent Document 2] European Patent No. EP 3 271 636 B1 [Patent Document 3] German Patent Application Publication No. 10 2019 120 242 A1 [Patent Document 4] U.S. Patent No. 7 647 194 B1 [Patent Document 5] European Patent No. 3 299 775 B1 Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to make it possible to determine the exact amount of compressed gas, in particular hydrogen gas, at the time of withdrawal at low cost. [Means for solving the problem]

[0013] With regard to a measuring device for determining the amount of compressed gas when the gas is withdrawn from a compressed gas reservoir, this problem is solved according to the invention by the features of claim 1. With regard to a method for determining the amount of compressed gas withdrawn from a compressed gas reservoir, this problem is solved according to the invention by the features of claim 9. Further embodiments of the invention are a device for storing and / or transporting compressed gas as defined in claim 6 and a method for calibrating this device as defined in claim 12 or 13. Preferred embodiments and developments of the invention are set out in the dependent claims and the following description.

[0014] The present invention is based on an apparatus for storing and / or transporting compressed gas, commonly referred to as a "tank system," which may be, for example, a tank vehicle, a tank trailer, or a pressure reservoir at a tank station. Such a tank system includes a compressed gas reservoir for storing compressed gas, which includes multiple sub-reservoirs that are independently "removable," i.e., accessible for the removal of compressed gas. Such sub-reservoirs are hereinafter also referred to as "cascades." Within the scope of the present invention, each cascade may be comprised of an individual compressed gas container. However, preferably, particularly for the transport of gases such as hydrogen gas that are stored and transported under high pressure, each cascade is comprised of a bundle of compressed gas containers that are fluidly connected to one another.

[0015] Here and in the following, what is understood as a pressure or fluid "connection" between two bodies is generally a connection, for example by a pipe, that allows gas movement and therefore pressure equilibrium between these bodies. In contrast, a terminological distinction is made between what is called a pressure or fluid "coupling" and what means are provided for establishing such a pressure or fluid "connection" (especially reversibly). For example, in the sense of this terminology, a pipe line laid between two bodies and equipped with a shut-off valve is a pressure / fluid connection regardless of the position of the shut-off valve, but only when the shut-off valve is open is a pressure or fluid connection. The verbs "to connect" (anschliesen) and "to connect" (verbinden) are also used in the corresponding sense.

[0016] The measuring device according to the invention includes a gas pressure sensor that is hydraulically (fluidically) connected to each cascade via a measuring pipe. Furthermore, the measuring device includes a switching device inserted into the measuring pipe, by which the gas pressure sensor can be alternately connected to each cascade in order to selectively measure the gas pressure of each cascade. This switching device (hereinafter also referred to as a "multiplexer") operates in particular such that no more than one cascade is hydraulically connected to the gas pressure sensor at any one time. Furthermore, the measuring device includes at least one temperature sensor located at the compressed gas reservoir in order to measure the gas temperature of the compressed gas reservoir.

[0017] In principle, embodiments in which the measuring device has only one temperature sensor measuring the temperature in the compressed gas reservoir or its spatial surroundings as a reference value for the gas temperature are also within the scope of the present invention. However, it is preferable for the measuring device to include a number of temperature sensors corresponding to the number of cascades, with each temperature sensor being arranged at the location of the cascade assigned to it in order to measure the gas temperature of that cascade. In this case, the temperature sensor or each temperature sensor is arranged, in particular, directly in the pressure space of the cascade or in a branch pipe connecting this cascade to the collective gas outlet pipe of the tank system. In another embodiment of the present invention, the measuring device includes multiple temperature sensors per cascade, for example, one temperature sensor for each of the pressure vessels of the cascade. In this case, a (simple or weighted) average value is formed from the values ​​of the multiple temperature sensors of each cascade, thereby obtaining an averaged temperature value for each cascade.

[0018] In operation, the measuring device calculates the amount of gas extracted from at least one of the cascades at the beginning (i.e., immediately before the start) and end (i.e., immediately after the end) of gas extraction from the cascades, taking into account the provided measured values ​​of the gas pressure and gas temperature. The state equation is preferably derived from a gas equation, i.e., from the thermal equation of state for an ideal gas or, preferably, for a real gas. In principle, this calculation of the gas amount can be performed manually within the scope of the present invention. However, in a preferred embodiment, the measuring device includes an electronic control unit that is signal-technically connected to a pressure sensor and a temperature sensor or to each temperature sensor for receiving the measured values ​​of the gas pressure and gas temperature of each of the subreservoirs. The electronic control unit is set up to automatically calculate the amount of gas extracted from the cascade, taking into account the assigned measured values ​​of the gas pressure and gas temperature of at least one of the cascades at the beginning and end of gas extraction.

[0019] The terms "immediately before the start of gas removal" and "immediately after the end of gas removal" mean that no change in the amount of gas in the cascade before gas removal occurs between the first pressure and temperature measurement and the start of gas removal, or between the end of gas removal and the second pressure and temperature measurement. (Furthermore, this does not matter what the time span is between the first pressure and temperature measurement and the start of gas removal, or between the end of gas removal and the second pressure and temperature measurement; in particular, a settling phase is preferably inserted between the end of gas removal and the second pressure and temperature measurement, during which the pressure situation in each cascade is stabilized.) The above-described terms "immediately before" and "immediately after" also apply—in one preferred embodiment of the invention—if several cascades are emptied, fully or partially, one after the other, between the first pressure and temperature measurement in all cascades and the second pressure and temperature measurement in all cascades. Gas removal from at least one of the cascades can then be carried out at several time-separated intervals.

[0020] Preferably, the electronic control unit is also controllably (especially electrically) connected to a multiplexer. The electronic control unit is then set up to selectively connect the gas pressure sensor to each of the cascades by controlling the multiplexer in order to measure the gas pressure in one of the cascades. Alternatively, in another embodiment of the invention, the switching device has a manually operable switching mechanism by which the gas pressure sensor can be manually connected to each of the sub-reservoirs in order to measure the gas pressure in one of the sub-reservoirs. The switching mechanism then comprises a sensor mechanism that supplies the electronic control unit with information about the sub-reservoir that is respectively connected to the gas pressure sensor.

[0021] The electronic control of the measuring device preferably comprises programmable components, such as a microprocessor or a single-board computer, on which software (firmware) that implements the functions of the electronic control is operatively installed. Alternatively, the electronic control may comprise non-programmable hardware circuitry (e.g., in the form of an ASIC) within the scope of the present invention. Still alternatively, the electronic control may comprise a combination of programmable and / or non-programmable components within the scope of the present invention.

[0022] The electronic control unit is preferably integrated together with the gas pressure sensor and the multiplexer into one module, also called a state variable transducer (abbreviated as ZMU).

[0023] The device (tank device) according to the invention comprises a compressed gas reservoir formed from a number of sub-reservoirs (cascade) and a measuring device according to the invention as described above, in particular in one of the embodiments described above.

[0024] In an advantageous embodiment, the device comprises a collective gas outlet pipe to which each cascade is fluidly connected via an assigned branch pipe, in which an automatic shut-off valve (especially in the form of a solenoid valve) is preferably inserted, by means of which each cascade can be reversibly fluidly connected to and fluidly isolated from the collective gas outlet pipe.

[0025] The above-described method according to the invention for determining the amount of compressed gas extracted from a compressed gas reservoir is carried out by the above-described measuring device according to the invention, and therefore the embodiments of the measuring device correspond to the corresponding embodiments of the method, so that the descriptions of the embodiments of the measuring device can be transferred to the embodiments of the method and vice versa.

[0026] During the quantity determination method, when gas is removed from one of the cascades, an initial measured value of the gas pressure and an initial measured value of the gas temperature are measured in the cascade immediately before the start of the gas removal. Furthermore, immediately after the end of the gas removal, a final measured value of the gas pressure and a final measured value of the gas temperature are measured in the cascade. Taking into account the initial and final measured values ​​of the gas pressure and the initial and final measured values ​​of the gas temperature, the quantity of gas removed from the cascade is calculated. In this case, a gas pressure sensor of the measuring device is selectively connected to the cascade by a multiplexer to measure the initial and final measured values ​​of the gas pressure.

[0027] When calculating the amount of gas extracted from each cascade, the pressure-dependent and / or temperature-dependent changes in the volume of each cascade are preferably taken into account, for example by reference to characteristic data or formulas stored in the electronic control unit.

[0028] In one embodiment of the method, the gas withdrawal from each different cascade is staggered in time so that no gas is withdrawn from more than one cascade at the same time. Alternatively, compressed gas is withdrawn simultaneously from multiple cascades. In both cases, the amounts of gas withdrawn determined for each individual cascade are added together.

[0029] In the course of a first embodiment of the method according to the invention for calibrating an apparatus, an external reference tank, which is empty in particular at the start of the calibration, is filled with reference gas from a sub-reservoir (cascade) of the tank system. The reference tank is then mounted on a balance, whereby the injected gas quantity of reference gas (reference gas quantity) is measured by weighing (i.e., by determining the weight). The detected weight of the reference gas quantity replenished in the tank is then compared with a calculated gas quantity, in particular automatically by the measuring device, with reference to the measured gas pressure and gas temperature and the measured geometric volume of the cascade.

[0030] A second, equally advantageous embodiment of the method for calibrating a device is the reverse of the above. In this alternative method embodiment, the device is calibrated by filling the sub-reservoir rather than emptying it. To this end, the device is filled from a reference tank, which is also attached to a balance. The amount of gas refilled is then determined by weight and compared with the calculated gas amount.

[0031] In either case, the state equations applied to the calculation of the gas quantity are adapted so that the calculated gas quantity corresponds to the gas quantity of a reference gas determined by weighing.

[0032] Both aspects of the calibration method described above can be implemented as components of the method described above for determining the amount of compressed gas extracted, or can be implemented independently of each other. If the volume and volume change of the cascade consumed in the tank system are not specified in the tank system's accompanying container documentation, they can be volume-determined by the calibration method to determine the actual volume and volume change under pressure.

[0033] In the above-described calibration method embodiment, nitrogen gas can be used as the reference gas, for example, because this gas is relatively heavy and therefore measurement errors of the balance have a relatively small effect on the gas amount measurement. Furthermore, nitrogen is inert and easy to handle, which is advantageous. Alternatively, within the scope of the present invention, the same gas species that will later be replenished as compressed gas, such as hydrogen gas, can also be used as the reference gas.

[0034] In addition to a reliable and accurate determination of the quantity of compressed gas, taking into account the factors listed above and government regulations regarding calibratability, embodiments of the present invention also solve the problem of cost-intensive measuring equipment. In particular, Coriolis mass flow meters, which are one of the main cost drivers in conventional tank systems, are not required in the tank system according to the present invention and are therefore preferably not provided. [Effects of the Invention]

[0035] As the conventionally used Coriolis flowmeter is replaced by a gas pressure sensor and at least one temperature sensor, the energy consumption of the measuring device is also significantly reduced compared to conventional systems.

[0036] A further advantage of the measurement device of the present invention is that it overcomes the problems of prior systems related to measurement accuracy that are based on the use of multiple individual sensors.

[0037] The preferred automation of the measurement process reduces the risk of an erroneous determination of the amount of extracted gas as a result of human error or misuse. The measuring device according to the invention and the method according to the invention for determining the amount of gas have the advantage that they can be calibrated, resulting in high accuracy and tamper resistance.

[0038] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0039] [Figure 1] 1 shows a schematic block diagram of an apparatus for storing and / or transporting compressed gas, in particular hydrogen gas, having a compressed gas reservoir including a plurality of sub-reservoirs (cascade) that can be opened independently of one another, and a measuring device for determining the amount of compressed gas upon withdrawal of gas from the compressed gas reservoir. [Figure 2] 1 shows a schematic diagram of a first of two embodiments of a method for calibrating a measurement device. [Figure 3] 1 shows a schematic diagram of a second of two embodiments of a method for calibrating a measurement device. DETAILED DESCRIPTION OF THE INVENTION

[0040] Corresponding parts and quantities are always given the same reference numerals in all the drawings.

[0041] In the exemplary embodiment shown in Fig. 1, the device (tank device) according to the invention consists of a tank truck 2, i.e., a (self-propelled) tank vehicle or tank trailer, on which a plurality of, in the illustrated example, four sub-reservoirs (cascades 6a, 6b, 6c, 6d) each containing a plurality of compressed gas containers 8 are fixedly mounted as compressed gas reservoirs 4. The compressed gas containers 8 belonging to the same cascade 6a-6d are fixedly piped to each other, i.e., are fixedly fluidly connected to each other by pipelines 10. Each cascade 6a-6d is fluidly connected to a collective gas withdrawal pipe 14 via an assigned branch pipe 12a-12b-12c-12d. In each branch pipe 12, a shut-off valve 16a, 16b, 16c, 16d (especially in the form of an electrically controllable solenoid valve or a manual valve, respectively) is arranged, by means of which the associated cascades 6a-6d can be reversibly fluidly connected to and fluidly isolated from the collective gas take-off pipe 14. The tank truck 2 is particularly configured and used for transporting and storing hydrogen gas.

[0042] The tank truck 2 is assigned a measuring device 20 for determining the gas volume of the compressed gas taken from the compressed gas reservoir 4. The measuring device 20 comprises a gas pressure sensor 22 which is pressure-coupled with each of the cascades 6a-6d via a measuring line 24.

[0043] The measuring device 20 further includes a switching device (multiplexer 26) inserted in the measuring pipe 24, which allows the gas pressure sensor 22 to be pressure-connected to each of the cascades 6a-6d, thereby selectively measuring the gas pressures P1, P2, P3, and P4 of each of the sub-reservoirs 6a-6d. Here, by way of example, the cascade 6a is assigned to the gas pressure P1, the gas pressure P2 to the cascade 6b, the gas pressure P3 to the cascade 6c, and the gas pressure P4 to the cascade 6d. Preferably, apart from the multiplexer 26, the measuring pipe 24 does not include any other interrupting means that could interrupt or limit the fluid connection between each of the cascades 6a-6d and the gas pressure sensors 22.

[0044] Furthermore, the measuring device 20 includes a temperature sensor 28a, 28b, 28c, 28d for each cascade 6a-6d, where each temperature sensor 28a-28d is preferably arranged either directly in one of the compressed gas containers 8 of the respective assigned cascade 6a-6d or outside the compressed gas container 8 in good thermal contact with the container wall in order to measure the gas temperatures T1, T2, T3, T4 in the respective cascade 6a-6d. Here, gas temperature T1 is assigned to cascade 6a, gas temperature T2 to cascade 6b, gas temperature T3 to cascade 6c, and gas temperature T4 to cascade 6d.

[0045] Finally, the measuring device 20 includes an electronic control unit 30, which is formed, for example, by a microcontroller, which is signal-technically (in particular electrically) connected to the gas pressure sensor 22 and to each of the temperature sensors 28a-28d and receives the measured values ​​of the gas pressures P1-P4 and the gas temperatures T1-T4 from these sensors as input quantities.

[0046] Furthermore, the electronic control unit 30 is controllably (in particular electrically) connected to the multiplexer 26, so that by correspondingly controlling the multiplexer 26, the electronic control unit 30 can alternately and in each case selectively connect the gas pressure sensor 22 to each of the cascades 6a-6d in a pressure-sensitive manner and perform measurements of the gas pressures P1-P4 in the respectively connected cascades 6a-6d. Alternatively, the multiplexer 26 can be provided with a manually operable switching mechanism (manual switch), by means of which the user can manually (but also alternately and in each case selectively) connect the individual cascades to the gas pressure sensor 22. Such a manual switch preferably has a sensor mechanism (switching position sensor) that transmits information about the respectively connected cascades 6a-6d to the electronic control unit 30.

[0047] The gas pressure sensor 22, the multiplexer 26 and the electronic control unit 30 are integrated into a module called a state converter 32. The state converter 32 is preferably mounted in a closable control cabinet 34, also on the tank truck 2.

[0048] For tank refueling, i.e., for the withdrawal of compressed gas from the compressed gas reservoir 4, the cascades 6a-6d are preferably emptied one after the other. That is, one of the cascades 6a-6d is preferably first nearly empty before being closed again and replaced by another cascade 6a-6d that is still full. The tank refueling process, i.e., the connection and disconnection of the cascades 6a-6d to and from the collective gas withdrawal line 14, as well as the switching between the different cascades 6a-6d, are, in a preferred embodiment of the method, manually directed by the user by operating the shut-off valves 16a-16d. In this case, only the measurement of the amount of gas withdrawn during the tank refueling process is automatic.

[0049] To this end, the electronic control unit 30 has a computer program (firmware) operatively installed therein, which automatically executes, as it proceeds, the following exemplary method for determining the amount of gas extracted from the cascades 6a-6d:

[0050] Immediately before and immediately after the start and end of gas withdrawal from at least one of the cascades 6a-6d, the respective gas pressures P1-P4 and the respective gas temperatures T1-T4 are measured for each cascade 6a-6d. For the pressure measurements, the electronic control unit 30 accordingly controls the multiplexer 26 to sequentially connect each cascade 6a-6d to the gas pressure sensor 22. In the case of gas withdrawal from several cascades 6a-6d, a first measurement of the temperatures T1-T4 and pressures P1-P4 is preferably performed before the start of gas withdrawal from the first cascade 6a-6d, whereas a second measurement of the temperatures T1-T4 and pressures P1-P4 is preferably performed after the end of gas withdrawal from the last cascade 6a-6d.

[0051] From the corresponding measured values ​​of the gas pressures P1-P4 and gas temperatures T1-T4 of each cascade 6a-6d, the electronic control unit 30 calculates the gas amounts contained in the cascades 6a-6d before and after gas withdrawal using stored equations of state, preferably equations of state for real gases. Then, from the difference between the calculated gas amounts (also called "equations of state"), the electronic control unit 30 calculates the gas amount withdrawn from each cascade 6a-6d. In the case of gas withdrawal from several cascades 6a-6d, the electronic control unit 30 sums the gas amounts withdrawn from each individual cascade 6a-6d.

[0052] As a parameter for this calculation, the electronic control unit 30 takes into account the volume of each cascade 6a-6d. Information about the volume of each cascade 6a-6d and, preferably, about the change in this volume depending on the gas pressures P1-P4 and / or gas temperatures T1-T4, is provided, for example, in the container documentation assigned to the tank truck 2. Such volume data is entered into the electronic control unit 30 when the measuring device 20 is put into use and saved. The volume data is, for example, in the form of a characteristic curve or a characteristic data table of the volume of each individual compressed gas container 8 depending on the temperature and / or gas pressure. Alternatively, a reference volume defined for a predetermined reference temperature and a predetermined reference pressure is entered as volume data for each compressed gas container 8 or cascade 6a-6d. In the latter case, the electronic control unit 30 preferably calculates the temperature- and / or pressure-dependent volume change from the saved reference volume and the measured values ​​of the gas pressures P1-P4 and the gas temperatures T1-T4, with reference to a predetermined correction formula.

[0053] All measurements taken into the calculations and all calculations are recorded (irrevocably) and consecutively numbered in an electronic logbook by the electronic control unit 30 to make the measurement method tamper-proof. Optionally, the calculated amount of compressed gas replenished in the tank is subsequently used to generate a delivery note (manually or automatically).

[0054] The measurements necessary to determine the amount of gas extracted are preferably directed fully automatically (without user intervention).

[0055] To this end, in an advantageous embodiment, the measuring device 20 includes a connection sensor, e.g., an inductive sensor (not explicitly shown), which detects the connection of the hose lines to the collective gas offtake line 14. The electronic control unit 30 is then set up to automatically start a first measurement process for determining the gas pressures P1-P4 and the gas temperatures T1-T4 before gas offtake when the connection sensor signals the connection of the hose lines. Furthermore, the electronic control unit 30 is set up to automatically start a second measurement process for determining the gas pressures P1-P4 and the gas temperatures T1-T4 after gas offtake when the connection sensor signals the disconnection of the hose lines.

[0056] In an alternative embodiment, the measurement device 20 includes a door open sensor (also not explicitly shown) that detects the opening of a door of the control cabinet 34. The electronic control unit 30 is set up in this embodiment to automatically start a first measurement process when the door open sensor signals the opening of the control cabinet 34. The electronic control unit 30 is further set up to automatically start a second measurement process when the door open sensor signals the closure of the control cabinet 34. To prevent misuse, the electronic control unit 30 preferably blocks the closure of the control cabinet 34 as long as at least one of the shut-off valves 16a-16d is open.

[0057] In another embodiment of the measuring device 20, both measuring processes are carried out by the electronic control unit 30 when the user releases or terminates the tank refilling process by operating a corresponding command input.

[0058] In another embodiment of the invention, the electronic control unit 30 is not only responsible for determining the amount of gas extracted, but also for automatically controlling the tank replenishment process. In this embodiment, the electronic control unit 30 is controllably (especially electrically) connected to each of the shut-off valves 16 a-16 d, so that the electronic control unit 30 can automatically fluidly connect and disconnect the associated cascade 6 a-6 d to and from the collective gas extraction line 14 by correspondingly controlling one of the shut-off valves 16 a-16 d. In particular, the electronic control unit 30 automatically switches over to another (still filled) cascade 6 a-6 d as needed after one cascade 6 a-6 d has been emptied. The electronic control unit 30 automatically measures the gas pressures P1-P4 and gas temperatures T1-T4 in each of the corresponding cascades 6a-6d before automatically switching one of the cascades 6a-6d to the collective gas extraction pipe 14 and after automatically separating the cascades 6a-6d from the collective gas extraction pipe 6a-6d.

[0059] In particular, in cases where the (vessel) volume of the individual cascades 6a-6d required for calculating the amount of gas extracted cannot be determined from the available vessel documentation or cannot be determined with sufficient accuracy, this volume can be determined by a calibration method, as shown in two embodiments in Figures 2 and 3.

[0060] In a first embodiment of the calibration method shown in Fig. 2, an external reference tank 36, which is empty at the start of the calibration, is filled with reference gas from the cascades 6a-6d to be calibrated, and the gas pressures P1-P4 and gas temperatures T1-T4 are determined before and after gas withdrawal in each cascade 6a-6d according to the measurement method described above, from which a value for the amount of gas withdrawn is calculated. The reference tank 36 is then mounted on a balance 38, by means of which the injected amount of reference gas (reference gas amount G) is determined weighing.

[0061] 3, the cascades 6a-6d to be calibrated are filled with reference gas from an external reference tank 36, and the gas pressures P1-P4 and gas temperatures T1-T4 are determined in each cascade 6a-6d before and after gas supply, again according to the measurement method described above, from which values ​​for the amount of gas supplied to the cascades 6a-6d are calculated. The reference tank 36 is then likewise mounted on a balance 38, with the aid of which the amount of reference gas G removed from the reference tank 36 is determined.

[0062] In both of these calibration method variants, the gas quantity calculated by the measuring device 20 is checked against the reference gas quantity G. If necessary, the volumetric indication stored in the electronic control unit 30 is corrected, thereby adapting the calculated gas quantity to the reference gas quantity G determined by weighing. This adaptation is preferably performed automatically by the electronic control unit 30, which is provided, either manually or automatically, with a measurement value of the reference gas quantity G determined by the balance 38. In an alternative embodiment of the calibration method, the balance 38 provides the electronic control unit 30 with the measured weight of the reference tank 36 before and after the supply or removal of the reference gas. In this case, the reference gas quantity G is determined by the electronic control unit 30 with reference to the provided weight measurement value.

[0063] The calibration method described above can also be used for periodic checks (recalibration) of the measurement device 20. Nitrogen gas is particularly used as the reference gas.

[0064] The above-described embodiment of the present invention has the following particular features. The determination of the amount of gas when the compressed gas is withdrawn is carried out using a temperature sensor and a gas pressure sensor. No flow rate measuring device is required and is therefore preferably not used within the scope of the method and device. The gas volume is preferably calculated as a function of the gas pressure and / or gas temperature, taking into account the volume changes in the sub-reservoirs of the tank system (i.e. individual compressed gas containers or cascades). Only one gas pressure sensor and preferably at least one temperature sensor per cascade is used, reducing measurement errors. If one of the cascades itself consists of several compressed gas containers, it is preferable that the compressed gas containers associated with the cascade are fixedly piped to one another. Each individual cascade can be pressure-coupled individually to a gas pressure sensor via a switching unit (multiplexer) using automatic valves (especially solenoid valves), so that the pressure for each cascade can be determined sequentially using this one gas pressure sensor.Pressure recording is preferably carried out in a measuring line that cannot be closed off—except by the multiplexer—so that the measurement results cannot be manipulated.In particular, the use of a single gas pressure sensor in the measuring line ensures that the same measurement accuracy is always achieved, which simplifies the consideration of this measurement accuracy. With regard to the calibratability, it should be noted that each sensor must be calibrated at regular intervals. In this way, the cost of the measuring device of the present invention is low, since it has a relatively small number of sensors (i.e., overall, only one gas pressure sensor is used for the measurement regardless of the number of cascades, and preferably only one temperature sensor per cascade). The cylinder bundles and their piping, which are preferably fixedly assembled in the individual cascades, facilitate the realization of the accuracy of the measurement results up to the extent that they are calibratable, by first checking the weight of the tank system or functional parts of the tank system (tank vehicle / individual cylinder bundle / individual cascade) and the measurement results in the empty and full state. The temperature is preferably measured directly in at least one compressed gas cylinder per cascade. For this purpose, the corresponding compressed gas cylinder is preferably fitted with a thermowell equipped with a temperature sensor. The volume displaced in this case can be neglected. The gas volume of the extracted compressed gas is determined, in particular with reference to the given volume of the cascade from which the gas extraction took place and with reference to the measured gas pressure and gas temperature in that cascade. Only one gas pressure sensor is used. The gas pressures in each of the different cascades are measured sequentially using a switching valve (multiplexer). At the same time, the gas temperature is measured in each cascade. The gas volume is preferably calculated with the aid of the real gas equations, with correction factors taken into account, in particular, for pressure- and / or temperature-dependent volume changes.

[0065] The measurement method and corresponding apparatus (tank apparatus), in at least some embodiments of the present invention, have the following advantages: High measurement accuracy: The measurement of compressed gases in terms of pressure and temperature is based on calculations using the real gas equations, a given volume, and corrections for volume change, providing a good basis for accurate measurements. Measurement accuracy is enhanced by using only one pressure measuring device, so that only the measurement error of this single pressure measuring device needs to be considered, rather than the measurement errors of multiple devices. High cost-effectiveness: The cost-effectiveness of the measuring method and the corresponding tank system is realized, in particular, by the reduced procurement costs due to the number and type of sensors compared to conventional systems (especially systems with Coriolis flowmeters). At the same time, the low energy consumption of the measuring system (especially compared to measuring systems with Coriolis flowmeters) contributes to further cost savings. If sensors have to be recalibrated, the low number of sensors supports a fast and therefore convenient process. Due to its simplicity, the measuring system according to the invention also allows for problem-free retrofitting into existing tank systems, which significantly reduces procurement costs. Avoidance of human-induced measurement errors: The above-described measurement of the amount of extracted gas can be easily automated and preferably carried out fully automatically without human interaction, thereby reducing the risk of measurement errors as a result of misoperation or misuse. Accuracy and calibratable with tamper-proofing: The measurement accuracy described above leads to a system that can be calibrated in the context of tamper-proofing. High measurement security and data security guarantee tamper-proofing. Measurement security is provided in particular by the fixed piping of the pressure vessels inside the cascade, by measurement piping that can only be shut off at the state transducers, and by the avoidance of artificial measurement errors by automated measurements. Data security is provided by the fact that data and measurements are stored in a logbook with consecutive numbers, so that the data cannot be altered later. Simple and compact measurement device: The measurement method and the corresponding device (tank device) can be implemented in a space- and weight-saving manner. Furthermore, the measurement method and the corresponding device are easily scalable, can be retrofitted quickly and cost-effectively, and are independent of measurement dynamics (unlike Coriolis measurements, which only function accurately over a limited range of flow velocities).

[0066] The present invention will be particularly elucidated with reference to the examples described above, but is not limited to these examples alone, rather further and further embodiments of the invention can be derived from the claims and the above description. [Explanation of symbols]

[0067] 2 tanker trucks 4 Compressed Gas Reservoirs 6a-6d Cascade 8 Compressed gas cylinders 10 conduit 12a-12d Branch piping 14 Collective gas extraction piping 16a-16d Shut-off valve 20 Measuring Equipment 22 Gas pressure sensor 24 Measurement piping 26 Multiplexer 28a-28d Temperature sensors 30 Electronic control unit 32 State converter 34 Control Cabinet 36 Reference Tank 38 Scales P1-P4 gas pressure T1-T4 gas temperatures G Reference gas amount

Claims

1. A measuring device (20) for determining the amount of compressed gas when it is drawn from a compressed gas reservoir (4) comprising a plurality of sub-reservoirs (6a-6d) from which gas can be drawn independently of one another, comprising: a gas pressure sensor (22) pressure-connected to each of the sub-reservoirs (6a-6d) via a measurement pipe (24); a switching device (26) inserted in the measuring pipe (24), by which the gas pressure sensor (22) can be alternately connected to each of the sub-reservoirs (6a-6d) for selectively measuring the gas pressures (P1-P4) of each of the sub-reservoirs (6a-6d); at least one temperature sensor (28a-28d) located at the compressed gas reservoir (4) for measuring gas temperatures (T1-T4); A measuring device (20).

2. the system has temperature sensors (28a-28d) the number of which corresponds to the number of the sub-reservoirs (6a-6d), and each of the temperature sensors (28a-28d) is disposed at a location of the sub-reservoirs (6a-6d) assigned to it for measuring the gas temperatures (T1-T4) of the respective sub-reservoirs (6a-6d); The measuring device (20) of claim 1.

3. Each of the temperature sensors (28a-28d) is disposed in a gas chamber of each of the sub-reservoirs (6a-6d) or in a branch pipe (12a-12d) that fluidly connects each of the assigned sub-reservoirs (6a-6d) to a collective gas extraction pipe (14).

3. The measuring device (20) of claim 2.

4. an electronic control unit (30) in signal connection with the gas pressure sensor (22) and the temperature sensor or each temperature sensor (28a-28d) to receive measurements of the gas pressure (P1-P4) and the gas temperature (T1-T4) of each of the sub-reservoirs (6a-6d), the electronic control unit (30) being set up to calculate the amount of gas extracted from at least one of the sub-reservoirs (6a-6d) taking into account the supplied measurements of the gas pressure (P1-P4) and the gas temperature (T1-T4) immediately before the start and immediately after the end of gas extraction, A measuring device (20) according to any one of claims 1 to 3.

5. the electronic control unit (30) is in control-engineering connection with the switching device (26) inserted in the measuring pipe (24), and the electronic control unit (30) is set up to selectively pressure-connect the gas pressure sensor (22) to each of the sub-reservoirs (6a-6d) by controlling the switching device (26) for measuring the gas pressure (P1-P4) of one of the sub-reservoirs (6a-6d); 5. The measuring device (20) of claim 4.

6. The switching device (26) has a manually operable switching mechanism by which the gas pressure sensor (22) can be manually connected to each of the sub-reservoirs (6a-6d) for measuring the gas pressure (P1-P4) in one of the sub-reservoirs (6a-6d), the switching mechanism comprising a sensor mechanism for supplying the electronic control unit (30) with information regarding the sub-reservoir (6a-6d) which is respectively connected to the gas pressure sensor (22).

5. The measuring device (20) of claim 4.

7. 1. An apparatus (2) for storing and / or transporting compressed gas, in particular in a tank car or tank trailer, comprising a compressed gas reservoir (4) including a plurality of sub-reservoirs (6a-6d) from which gas can be drawn independently of one another, and a measuring device (20) according to any one of claims 1 to 6.

8. An apparatus (2) for storing and / or transporting compressed gas, in particular a pressure vessel of a tank car, a tank trailer or a tank station, comprising a compressed gas reservoir (4) including a plurality of sub-reservoirs (6a-6d) that can be opened independently of one another, a collective gas outlet pipe (14) to which each of the sub-reservoirs (6a-6d) is fluidly connected via assigned branch pipes (12a-12d), and a measuring device (20) according to any one of claims 4 to 6, an automatic shut-off valve (16a-16d) is assigned to each of the sub-reservoirs (6a-6d), and the shut-off valve (16a-16d) is inserted in the branch pipe (12a-12d) assigned to each of the sub-reservoirs (6a-6d), and each of the sub-reservoirs (6a-6d) can be reversibly fluidly connected to the collective gas outlet pipe (14) and fluidly separated from the collective gas outlet pipe (14) by the shut-off valve (16a-16d).

9. Each of the sub-reservoirs (6a-6d) comprises a plurality of pressure vessels (8) fixedly connected to one another in a fluidic manner; 9. Apparatus (2) according to claim 7 or 8.

10. 6. A method for determining the amount of compressed gas extracted from a compressed gas reservoir (4) comprising a plurality of independently reservoirs (6a-6d) that can be opened independently of one another, by means of a measuring device (20) according to any one of claims 1 to 5, comprising the steps of: initial measurements of gas pressures (P1-P4) and gas temperatures (T1-T4) are taken in the sub-reservoirs (6a-6d) immediately before the start of gas extraction; Immediately after the gas extraction is completed, final measurements of the gas pressures (P1-P4) and the gas temperatures (T1-T4) are taken in the sub-reservoirs (6a-6d); calculating the amount of gas extracted from the sub-reservoir (6a-6d) taking into account the initial and final measured gas pressures (P1-P4) and the initial and final measured gas temperatures (T1-T4); wherein the gas pressure sensor (22) of the measuring device (20) is selectively connected to the sub-reservoirs (6a-6d) by the switching device (26) for measuring initial and final gas pressure measurements (P1-P4).

11. the pressure-dependent and / or temperature-dependent changes in the volume of each of the sub-reservoirs (6a-6d) are taken into account when calculating the amount of gas extracted from each of the sub-reservoirs (6a-6d); The method of claim 10.

12. The gas is taken out from each of the different sub-reservoirs (6a-6d) at different times.

12. The method according to claim 10 or 11.

13. A method for calibrating a device (2) according to any one of claims 7 to 9, comprising: a reference tank (36) is filled with a reference gas quantity of a reference gas from one of said sub-reservoirs (6a-6d); the amount of reference gas is determined by weighing the reference tank (36) before and after filling the reference tank (36) with a reference gas; at least one of the temperature sensors (28a-28d) of the measuring device (20) detects measured values ​​of the gas temperatures (T1-T4) of the sub-reservoirs (6a-6d) before and after filling the reference tank (36) with a reference gas; the gas pressure sensor (22) of the measuring device (20) detects measured values ​​of the gas pressures (P1-P4) in the sub-reservoirs (6a-6d) before and after filling the reference tank (36) with a reference gas; Taking into account the detected measured values ​​of the gas temperatures (T1-T4) and the gas pressures (P1-P4), the extracted gas volume is calculated using the stored state equations and compared with the reference gas volume of the reference gas determined by weighing, and The state equation is adapted so that the calculated gas amount corresponds to a reference gas amount of a reference gas determined by weighing. method.

14. 10. A method for calibrating a device according to any one of claims 7 to 9, comprising: A reference gas amount of a reference gas is injected from a reference tank (36) into one of the sub-reservoirs (6a-6d); the quantity of reference gas is determined by weighing said reference tank (36) before and after filling the sub-reservoir (6a-6d) in question with reference gas; said at least one temperature sensor (28a-28d) of said measuring device (20) detects measured values ​​of the gas temperatures (T1-T4) of said sub-reservoirs (6a-6d) before and after filling said sub-reservoirs (6a-6d) with a reference gas; the gas pressure sensors (22) of the measuring device (20) detect measured values ​​of the gas pressures (P1-P4) in the sub-reservoirs (6a-6d) before and after filling the sub-reservoirs (6a-6d) with a reference gas; Taking into account the detected measured values ​​of the gas temperatures (T1-T4) and the gas pressures (P1-P4), the quantity of gas supplied is calculated using the stored state equations and compared with the reference gas quantity of the reference gas determined by weighing, and The state equation is adapted so that the calculated gas amount corresponds to a reference gas amount of a reference gas determined by weighing. method.

15. Nitrogen gas is used as the reference gas.

15. The method of claim 13 or 14.

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