System and method for metering of liquid or gaseous media

Abstract

A system (1) for metering a liquid or gaseous medium comprises a pressure control valve (4) and a flow sensor, the pressure control valve (4) and the flow sensor forming a closed control loop (6). The required metering quantity can be adjusted by controlling the metering pressure (p2) by means of the pressure control valve (4).

Description

Technical Field

[0001] This invention relates to systems and methods for measuring liquid or gaseous media. The liquid or gaseous media are, in particular, low-viscosity fluids or gases such as butane, pentane, CO2, ethanol, methanol, nitrogen, and argon. Background Technology

[0002] In conventional metering systems for low-viscosity liquids, pumps operating on the displacement principle, such as piston pumps or diaphragm pumps, are frequently used. The metering volume (i.e., the delivery rate per piston stroke) depends on the pump's rotational speed and the volume of the piston or diaphragm chamber. Control valves are required to operate these pumps, such as check valves to ensure the intake or pumping of the medium. These pumps are configured for a limited flow range, which is limited by the maximum pump speed and the volume of the piston or diaphragm chamber. If only a small metering volume is to be pumped using a piston or diaphragm pump—that is, if the pumped volume is in the lower metering range—the metering volume is very small compared to the volume of the piston chamber. Therefore, in the lower metering range, the delivery rate cannot be precisely controlled because the piston or diaphragm is very large relative to the metering volume. This results in pulsating flow in the lower metering range. Furthermore, such metering systems are prone to failure due to the control valves.

[0003] For example, according to EP0486957A1, a needle valve can also be used for metering low-viscosity liquids and gases, by means of which the metering quantity can be set depending on the position of the needle. In a closed-loop control loop, a mass flow sensor can be used to control the defined metering quantity via an adjustable throttle valve function. In this needle valve, the metering quantity depends on the position of the needle in the valve seat and the pressure difference across the metering valve, causing metering quantity fluctuations to occur even when the pressure upstream or downstream of the needle valve is not constant. Therefore, this pressure difference is the pressure difference between the pre-pressure (p1) and the metering pressure (p2). Furthermore, even with a given pressure difference due to the position of the needle, the adjustable metering quantity can vary within a very limited range, so the needle valve is typically used only within the maximum metering quantity range of 1:10 to 1:20. For a metering quantity range of 1:10, the minimum metering quantity corresponds to 1 / 10 of the maximum metering quantity. For a metering quantity range of 1:20, the minimum metering quantity is equal to 1 / 20 of the maximum metering quantity. Under large pressure differences, the required small metering quantity leads to pulsating metering behavior. Under small pressure differentials, it is impossible to adjust large measurement volumes because even with the needle fully raised, the pressure differential is insufficient to precisely adjust the measurement volume. Therefore, known measuring devices can only cover a very limited measurement range. Summary of the Invention

[0004] The object of the present invention is to create a system and method for metering liquid or gaseous media, the system and method having a large metering spectrum, that is, covering a large metering range, and delivering the medium constantly and reliably via a valve regardless of the pressure difference between the pre-pressure (p1) and the metering pressure (p2).

[0005] The potential problems of the invention are solved by the system for metering liquid or gaseous media according to claim 1 and by means of the method according to claim 12. According to claim 15, the system and method are preferably used for metering CO2. Advantageous embodiments of the system are the subject matter of claims 2 to 11. Advantageous variations of the method are the subject matter of claims 13 and 14.

[0006] If the term "for example" is used in the following description, it refers to exemplary embodiments and / or variations, and should not be construed as a preferred application of the teachings of the present invention. The terms "preferred" and "ideal" should be understood in a similar manner by referring to embodiments from a group of exemplary embodiments and / or variations, and should not be construed as a preferred application of the teachings of the present invention. Therefore, the terms "for example," "preferred," or "ideal" may refer to multiple exemplary embodiments and / or variations.

[0007] The following detailed description includes various exemplary embodiments for the systems and corresponding methods according to the present invention. The description of a particular system should be considered exemplary only. In the specification and claims, the terms "comprising," "including," and "having" are interpreted as "including but not limited to."

[0008] A system for metering a liquid or gaseous medium entering a fluid flow through a closed channel and having a process pressure (p3) includes a supply line for the liquid or gaseous medium. The supply line is fluid-guidedly connected to the closed channel. A pressure control valve and a flow sensor are arranged in the supply line. The pressure control valve and the flow sensor are configured as a closed-loop control circuit. A measured flow rate value can be generated by the flow sensor. The measured flow rate value can be supplied as an input value to a controller. An output value can be attributed to the input value by the controller, wherein the output value corresponds to a desired metering pressure. The desired metering pressure can be adjusted by the pressure control valve, wherein the metering quantity is determined by the pressure difference between the metering pressure (p2) and the process pressure (p3). Therefore, the metering quantity in the system according to the invention is controlled only by setting the metering pressure (p2). The process pressure (p3) is constant or set to a constant value by an upstream valve.

[0009] According to an embodiment, the flow sensor is configured as a mass flow sensor. According to an embodiment, the controller is configured as a mass flow controller. According to an embodiment, the flow sensor and the mass flow controller may form a unit.

[0010] A flow sensor is positioned upstream of a pressure control valve in the supply line. In one embodiment, a pressure reducing valve is positioned upstream of the flow sensor. This pressure reducing valve reduces pressure fluctuations caused by the compressor to a constant value. The compressor can fill the accumulator discontinuously.

[0011] According to an embodiment, the pressure control valve is configured as a solenoid valve. The pressure control valve can therefore control the metering pressure based on an analog input signal. As an example, the analog input signal may include a voltage. In particular, the voltage can be up to 10V. The range of 0 to 10V may correspond to, for example, a pressure range of 0 to 400 bar. This means that, for example, an input signal of 10V corresponds to a metering pressure of 400 bar. In particular, the correlation between the voltage value of the input signal and the associated metering pressure can be linear; for example, an input signal of 1V corresponds to a metering pressure of 40 bar, an input signal of 2V corresponds to a metering pressure of 80 bar, and so on. The input signal can be determined by a mass flow controller.

[0012] Alternatively, the input signal may include a current in the range of, for example, 0 to up to 20mA and including 20mA, particularly in the range of 4mA to up to 20mA and including 20mA.

[0013] Alternatively, digital control with discrete signals can be provided, for example, via a BUS system.

[0014] The mass flow controller includes a processor unit by means of which the associated input signal can be determined from the measured flow value transmitted by the flow sensor.

[0015] According to an embodiment, the measurement range between the minimum and maximum measurement quantities is at least 1:50. Specifically, the measurement range between the minimum and maximum measurement quantities can be at least 1:100. Specifically, the measurement range between the minimum and maximum measurement quantities can be at least 1:500. Specifically, the measurement range between the minimum and maximum measurement quantities can be at least 1:1000.

[0016] According to one embodiment, a compressor generates a pre-pressure acting on the upstream side of the pressure control valve. The compressor is advantageously used when the medium is gaseous. This compressor can be configured as a rotary compressor. According to another embodiment, a pump generates a pre-pressure acting on the inflow side of the pressure control valve. A pump can be provided for conveying liquid media.

[0017] According to an embodiment, a first pressure measuring device for measuring the pre-pressure present on the input side of the pressure control valve is formed between the flow sensor and the pressure control valve.

[0018] According to an embodiment, a second pressure measuring device for measuring the metering pressure in the supply line is arranged downstream of the pressure control valve.

[0019] According to an embodiment, the pre-pressure controller is arranged between the pressure control valve and the discharge opening of the fluid flow into the supply line of the closed channel.

[0020] According to an embodiment, the accumulator is positioned upstream of the flow sensor.

[0021] According to an embodiment, the controller is configured as a PID controller.

[0022] A method for metering a liquid or gaseous medium entering a fluid flow through a closed channel (where the fluid flow has a process pressure) includes filling the closed channel with the liquid or gaseous medium via a supply line. A pressure control valve and a flow sensor are arranged in the supply line. The pressure control valve and the flow sensor are arranged in a closed-loop control loop. A measured flow rate value is generated by the flow sensor and supplied as an input value to a controller, wherein the controller attributes an output value to the input value, wherein the output value corresponds to a desired metering pressure. The desired metering pressure is regulated by the pressure control valve, wherein the metered quantity is determined by the pressure difference between the metering pressure and the process pressure.

[0023] Specifically, if the measurement changes, the new actual value for the measurement is reached in less than 60 seconds.

[0024] In particular, when the setpoint used to measure pressure is changed, the actual value of the measured quantity is approximately 30% different from the setpoint of the measured quantity.

[0025] For example, the system and method according to one of the foregoing embodiments can be used to control the amount of CO2 measured.

[0026] The pressure control valve sets the metering pressure required for accurate measurement, where the final measurement is obtained from the pressure difference between the metering pressure and the process pressure. At a given process pressure (e.g., specified by a fluid flow into which the liquid or gaseous medium to be measured is introduced), the metering pressure must always be higher than the process pressure to allow the liquid or gaseous medium to flow and enter the fluid flow. The measurement depends on the pressure difference between the metering pressure and the process pressure. This relationship can be used for quantity control: the metering pressure is increased until the desired measurement is achieved. If the measured measurement is greater than the target value, the metering pressure is reduced. If the measurement is too small, the metering pressure is increased accordingly by means of the pressure control valve. This results in pressure-based control of the measurement at a given process pressure. If the controller operates quickly enough, the desired measurement can be set accurately and over a wide range. Because the metering pressure is insensitive to fluctuations in, for example, the inlet pressure from the compressor, the measurement remains constant even with pressure difference fluctuations. Preferably, the flow sensor is a mass flow sensor because, compared to a volumetric flow sensor, it is independent of the medium's temperature.

[0027] As demonstrated, using a pressure control system, both very small and very large metering volumes can be metered using the same pressure control valve. Metering ranges of up to 1:1000 can be repeatedly set; that is, with the aid of pressure control, metering volumes of 10 g / h to 10000 g / h of liquid or gaseous media can be added to the fluid flow. Metering volumes can also be set very precisely, and the time elapsed between setting a new metering pressure and reaching it is very short. Furthermore, no significant overshoot or misalignment is observed when changing the metering volume, which is crucial for the metering process.

[0028] It will be apparent that the system and associated methods according to the invention have the advantage that, as the flow rate increases, the effective metering amount delivered will not exceed 30% of the set metering amount. According to an embodiment, as the flow rate increases, the actual metering amount delivered will not exceed 20% of the set metering amount. According to an embodiment, as the flow rate increases, the actual metering amount delivered will not exceed 10% of the set metering amount. Attached Figure Description

[0029] The system according to the present invention is illustrated below with the aid of some exemplary embodiments. Wherein, it is shown that:

[0030] Figure 1 This is a schematic diagram of a first embodiment of the system according to the present invention.

[0031] Figure 2 This is a schematic diagram of a second embodiment of the system according to the present invention.

[0032] Figure 3 It is for the basis Figure 1 or Figure 2 An example of comparing the target and actual values ​​of different measurement quantities in a system.

[0033] Figure 4 This is a graphical representation of the correlation between the metering quantity of a known needle valve and the pressure difference p1-p2.

[0034] Figure 5 This is an example of comparing the set point and actual value of different measurement quantities of the system according to a further embodiment. Detailed Implementation

[0035] Figure 1 A system 1 for metering a liquid or gaseous medium entering a fluid flow through a closed channel 11, the fluid flow having a process pressure p3, is shown. The system includes a supply line 10 for the liquid or gaseous medium, which is fluid-guidedly connected to the closed channel 11. A pressure control valve 4 and a flow sensor 3 are arranged in the supply line 10, wherein the pressure control valve 4 and the flow sensor 3 are configured as a closed-loop control loop 6. The pressure control valve 4 may be configured, for example, as a solenoid valve. The measured flow rate value can be determined by means of the flow sensor 3, wherein the measured flow rate value can be supplied as an input value to a controller 7. This input value can be attributed to an output value by the controller 7, wherein the output value corresponds to a desired metering pressure p2. The desired metering pressure p2 can be regulated by means of the pressure control valve 4, wherein the metering quantity is determined by the pressure difference between the metering pressure p2 and the process pressure p3.

[0036] According to an embodiment, the flow sensor 3 is configured as a mass flow sensor and / or the controller 7 is configured as a mass flow controller. Specifically, the flow sensor 3 and the controller 7 may form a unit that, in Figure 2 As shown in the diagram. Controller 7 can be configured as, for example, a PID controller.

[0037] Flow sensor 3 is positioned upstream of pressure control valve 4 in supply line 10. According to... Figure 1 A first pressure measuring device 8 is arranged between the flow sensor 3 and the pressure control valve 4. This first pressure measuring device 8 detects the pre-pressure p1. Therefore, the first pressure measuring device 8 is configured to measure the pre-pressure p1 present on the inlet side or upstream side of the pressure control valve 4. The pre-pressure p1 acting on the upstream side of the pressure control valve 4 can be measured by means of... Figure 1 The compressor 2 generates the gas. A sufficiently high prepressure p1 is required so that the gaseous or liquid medium can flow through the supply line 10 in the direction of the fluid flow flowing in the closed channel 11.

[0038] like Figure 1As shown, a second pressure measuring device 9 for measuring the metering pressure p2 in the supply line 10 can be arranged downstream of the pressure control valve 4.

[0039] Figure 2 A system 1 for metering a liquid or gaseous medium entering a fluid flow through a closed channel 11, according to a second embodiment, is shown. The same or similarly functional elements are equipped with... Figure 1 The same reference numerals are used, and reference should be made to... Figure 1 The description. According to Figure 2 System 1 and according to Figure 1 The difference in System 1 is that the flow sensor 3 and controller 7 are configured as a single unit. The flow sensor 3 measures the amount of liquid or gaseous medium flowing from the compressor 2 through the supply line 10 in the direction of the closed channel 11. The closed-loop control loop 6 for controlling the metered quantity includes the flow sensor 3, controller 7, and pressure control valve 4. As per [reference to a previous sentence]... Figure 1 As in the system described above, controller 7 determines the setpoint for measuring pressure p2. For example, the setpoint for measuring pressure p2 can be converted into an analog voltage signal. The voltage signal is supplied to pressure control valve 4 via a signal line, which can be part of the closed-loop control circuit 6. If pressure control valve 4 is configured as a solenoid valve, it can be adjusted to the measuring pressure p2 by means of the voltage signal.

[0040] As in the preceding exemplary embodiment, the fluid flow flowing in the closed channel 11 has a process pressure p3.

[0041] However, if the process pressure p3 fluctuates, the pressure difference p2-p3 changes, resulting in a change in the metering quantity. If the pressure difference p2-p3 decreases, a smaller metering quantity is supplied to the fluid flow; if the pressure difference p2-p3 increases, a larger metering quantity is supplied to the fluid flow accordingly. A pre-pressure regulator 5 can be provided so that fluctuations in the process pressure p3 do not affect the metering quantity. Figure 2 The pre-pressure regulator 5 is shown positioned between the pressure regulating valve 4 and the opening of the supply line 10 in the closed passage 11 for fluid flow. The simulated process pressure p3' can be set by means of the pre-pressure regulator 5, such that the metering quantity is determined by the pressure difference p2-p3'.

[0042] According to an embodiment not shown, the accumulator is arranged upstream of the flow sensor 3.

[0043] Figure 3 It shows that according to Figure 1 or Figure 2An example of comparing the setpoint and actual value of different metering quantities in System 1, wherein the method described below can be performed. A method for metering a liquid or gaseous medium entering a fluid flow through a closed channel 11 and having a process pressure p3 includes, for example, according to... Figure 1 or Figure 2 System 1, one of the embodiments shown. A liquid or gaseous medium is supplied to a closed channel 11 via a supply line 10. A process pressure p3 exists in the closed channel 11. A pressure control valve 4 and a flow sensor 3 are arranged in the supply line 10 such that a closed-loop control loop 6 is configured by the pressure control valve 4 and the flow sensor 3. The measured flow rate is determined by means of the flow sensor 3. The measured flow rate is supplied as an input variable to a controller 7, which assigns an output value to the input value, which corresponds to the desired metering pressure p2. The desired metering pressure p2 is regulated by the pressure control valve 4, wherein the metering quantity is set by the pressure difference between the metering pressure p2 and the process pressure p3.

[0044] When the measured quantity changes, the new setpoint value for measuring pressure is reached within less than 60 seconds. Figure 3 The example shown is an embodiment.

[0045] If the setpoint for the metering pressure is changed, for example, if the setpoint is increased or decreased, the actual metering amount will be approximately 30% different from the setpoint for the metering amount.

[0046] exist Figure 3 In the example shown, CO2 is metered into the fluid flow using the method described above. In this example, the pre-pressure p1 is 200 bar and the process pressure p3 is 170 bar. Figure 3 This shows the time progression of the setpoint compared to the actual value for different measurement parameters. The setpoint is shown as a solid line, and the actual value as a dashed line. Therefore, time is plotted on... Figure 3 The graph shown is plotted on the horizontal axis, and the relative quantity as a percentage of the maximum possible quantity is plotted on the vertical axis. According to this example, the maximum possible quantity corresponds to 2000 g / h or 100%.

[0047] Figure 3 The following metering values ​​are set: (31) 100g / h, (32) 200g / h, (33) 400g / h, (34) 1000g / h, (35) 2000g / h, (36) 1000g / h, (37) 400g / h, (38) 100g / h, and (39) 20g / h. Each metering value is set within a time period of less than one minute by transmitting the metering pressure p2 corresponding to the corresponding metering value as a voltage signal to the pressure control valve 4 via the controller 7.

[0048] Figure 3 The system demonstrates that the deviation between the target and actual quantities occurs only within a maximum of 30 seconds, after which the target quantity precisely corresponds to the actual quantity. The initial deviation between the target and actual quantities is substantially the same for both large and small quantities. Therefore, this system and its associated processes are suitable for both small and large quantities. In particular, the system can be used reliably when the measured quantities or fluctuations in measured quantities are significantly different.

[0049] For a known needle valve, if the pressure difference Δp between the pre-pressure (p1) and the metering pressure (p2) changes, then Figure 4 This is a graphical representation of the permissible measurement range 41. The measurement quantity D is plotted on the vertical axis, and the pressure difference Δp(p1-p2) is plotted on the horizontal axis. If the pressure difference Δp(p1-p2) changes, the permissible measurement range changes. Figure 4 In the diagram, four permissible metering ranges 42, 43, 44, and 45 with four different pressure differences (Δp1, Δp2, Δp3, Δp4) are shown as examples. For needle valves, the maximum possible metering range 46 is plotted on the vertical axis, and this maximum possible metering range is derived from the difference between the maximum and minimum metering values.

[0050] Therefore, for this type of needle valve, the metering quantity depends on the pressure difference between the pre-pressure (p1) and the metering pressure (p2) and the needle position. Specifically, the permissible metering range depends on the pressure difference between the pre-pressure (p1) and the metering pressure (p2) and the needle position. Because the needle seat, due to its design, only allows a limited range of needle position changes, the permissible metering range achievable at a given pressure difference is smaller than the maximum metering range. Therefore, in order to use the needle valve's maximum metering range 46, the pressure difference between the pre-pressure (p1) and the metering pressure (p2) must also be changed to alter the permissible metering range 46.

[0051] For this reason, fluctuations in the pre-pressure (p1) or metering pressure (p2) at a constant needle position result in changes in the metering quantity.

[0052] exist Figure 5 In the example shown, one of the aforementioned fluids entering the fluid flow is measured using the method described above. In this example, the prepressure p1 is 100 bar and the process pressure p3 is 40 bar. Figure 5 This shows the time progression of target and actual quantities for different measurements. Target quantities are shown as solid lines, and actual quantities as dashed lines. Therefore, time is plotted on... Figure 5 The graph shown is plotted on the horizontal axis, and the relative quantity as a percentage of the maximum possible quantity is plotted on the vertical axis. According to this example, the maximum possible quantity corresponds to 5000 g / h or 100%.

[0053] Figure 5 The following quantities are set: (51) 5000 g / h, (52) 4000 g / h, (53) 1000 g / h, (54) 50 g / h, (55) and 2500 g / h. Each quantity is set within a time period of less than two minutes by transmitting a voltage signal corresponding to the pressure p2 from the controller 7 to the pressure control valve 4.

[0054] Moreover, for this embodiment, Figure 5 The system demonstrates that the deviation between the target and actual quantities occurs within a maximum of 30 seconds, after which the target quantity precisely corresponds to the actual quantity. The initial deviation between the target and actual quantities is substantially the same for both large and small quantities. Therefore, this system and its associated processes are suitable for both small and large quantities. Consequently, this system can be used reliably in cases of highly biased or fluctuating quantities.

[0055] It will be apparent to those skilled in the art that many further variations are possible beyond the described embodiments without departing from the inventive concept. Therefore, the subject matter of the invention is not limited to the foregoing description, but is determined by the scope of protection defined by the claims. A comprehensive understanding of the claims is authoritative in interpreting the claims or the specification. In particular, the terms "comprising" or "including" are to be interpreted in such a way that they refer to elements, components, or steps in a non-exclusive sense, intended to indicate the presence of elements, components, or steps or their use in combination with other elements, components, or steps not explicitly mentioned. When a claim relates to an element or component from a group that may consist of elements or components A, B, C through N, the statement should be interpreted in such a way that only a single element from that group is required, rather than combinations of A and N, B and N, or any other combination of two or more elements or components from that group.

Claims

1. A system (1) for metering a liquid or gaseous medium entering a fluid flow through a closed channel (11) and having a process pressure (p3), comprising a supply line (10) for the liquid or gaseous medium, wherein the supply line (10) is fluid-guidedly connected to the closed channel (11), wherein a pressure control valve (4) and a flow sensor (3) are arranged in the supply line (10), wherein the pressure control valve (4) and the flow sensor (3) are configured as a closed-loop control loop (6), wherein a measured flow value can be generated by the flow sensor (3), wherein the measured flow value can be supplied as an input value to a controller (7), wherein an output value can be attributed to the input value by the controller (7), wherein the output value corresponds to a desired metering pressure (p2), characterized in that, The desired metering pressure (p2) can be regulated by the pressure control valve (4), wherein the metering quantity is determined by the pressure difference between the metering pressure (p2) and the process pressure (p3), wherein the flow sensor (3) is arranged upstream of the pressure control valve (4) in the supply line (10).

2. The system according to claim 1, characterized in that, The flow sensor (3) is configured as a mass flow sensor.

3. The system according to claim 1 or 2, characterized in that, The controller (7) is configured as a mass flow controller and / or the flow sensor (3) and the controller (7) form a unit.

4. The system according to claim 1 or 2, characterized in that, The pressure control valve (4) is configured as a solenoid valve.

5. The system according to claim 1 or 2, characterized in that, The maximum measurement is up to 50 times larger than the minimum measurement, and includes 50 times.

6. The system according to claim 1 or 2, characterized in that, The pump is positioned upstream of the pressure control valve (4) to generate a pre-pressure (p1) on the upstream side of the pressure control valve (4).

7. The system according to claim 6, characterized in that, A first pressure measuring device (8) is arranged between the flow sensor (3) and the pressure control valve (4) to measure the pre-pressure (p1) on the input side of the pressure control valve (4).

8. The system according to claim 1 or 2, characterized in that, A second pressure measuring device (9) for measuring the metering pressure in the supply line (10) is arranged downstream of the pressure control valve (4).

9. The system according to claim 1 or 2, characterized in that, The pre-pressure controller (5) is arranged between the pressure control valve (4) and the discharge opening of the fluid flow into the supply line of the closed channel (11).

10. The system according to claim 1 or 2, characterized in that, An accumulator or pressure reducing valve is located upstream of the flow sensor (3).

11. The system according to claim 1 or 2, characterized in that, The controller (7) is configured as a PID controller.

12. A method for metering a liquid or gaseous medium entering a fluid flow through a closed channel (11), wherein the fluid flow has a process pressure (p3), wherein the liquid or gaseous medium is supplied to the closed channel by a supply line (10), wherein a pressure control valve (4) and a flow sensor (3) are arranged in the supply line (10), wherein the pressure control valve (4) and the flow sensor (3) are configured as a closed-loop control loop (6), wherein a measured flow rate value is generated by the flow sensor (3), wherein the measured flow rate value is supplied as an input value to a controller (7), wherein an output value is attributed by the controller (7) to the input value, wherein the output value corresponds to a desired metering pressure (p2), characterized in that, The desired metering pressure (p2) is regulated by the pressure control valve (4), wherein the metering quantity is determined by the pressure difference between the metering pressure (p2) and the process pressure (p3), wherein the flow sensor (3) is arranged upstream of the pressure control valve (4) in the supply line (10).

13. The method according to claim 12, characterized in that, When the measured quantity changes, a new actual value for the measured quantity is obtained within less than 60 seconds.

14. The method according to claim 12 or any one of claim 13, characterized in that, If the set point of the metering pressure is changed, the actual value of the metered quantity will be approximately 30% different from the set point of the metered quantity.

15. Use of the system according to any one of claims 1-11 for controlling the metering of CO2.

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