CN-114787585-B - Method for operating a flow measurement point of a medium having at least one liquid phase

Abstract

The invention relates to a method for operating a flow measurement point of a medium having at least one liquid phase, comprising a coriolis measuring device for measuring a mass flow rate and a density of the medium flowing through a conduit, and a differential pressure measuring device for sensing a differential pressure between a flow region arranged upstream of the coriolis measuring device and a flow region arranged downstream of the coriolis measuring device, wherein a flow measurement based on the differential pressure measurement is corrected by means of a measurement value obtained using the coriolis measuring device.

Inventors

• ZHU HAO

Assignees

• 恩德斯+豪斯流量技术股份有限公司
• 恩德斯+豪斯流量技术股份有限公司

Dates

Publication Date

20260421

Application Date

20201120

Priority Date

20191216

Claims (18)

1. 1. A method (100) of operating a flow measurement point (1) of a medium having at least one liquid phase, the flow measurement point comprising: a coriolis measuring device (10), which coriolis measuring device (10) is used for measuring a mass flow rate and a density of a medium flowing through a pipeline (2), wherein the coriolis measuring device has at least one measuring tube (11), the at least one measuring tube (11) having in each case an inlet (11.1) and an outlet (11.2); wherein the differential pressure measuring device (20) is configured to detect a differential pressure between a flow region (3.1) arranged upstream of the flow barrier and a flow region (3.2) arranged downstream of the flow barrier, Wherein the method has the following steps: checking a medium state (101) by means of the coriolis measuring device; -upon detection of a pure liquid medium, Measuring a first density of the medium by means of the coriolis measuring device and storing a measured value (102.1) of the first density; measuring a first mass flow rate (102.2) by means of the coriolis measuring device; Determining a first viscosity of the medium based on the first density, the pressure differential, and the first mass flow rate, and storing a measurement of the first viscosity (102.3), Upon detection of a gaseous fraction in the medium, Determining a first Reynolds number (103.1) of the medium by means of -A first viscosity; -when the gaseous fraction is detected, a first density and/or a second density of the medium measured by means of the coriolis measuring device; when the gaseous fraction is detected, a second mass flow rate measured by means of the coriolis measuring device, A third mass flow rate (103.2) is determined based on the pressure differential and the first reynolds number.
2. 2. The method according to claim 1, Wherein the flow obstruction is the coriolis measurement device.
3. 3. The method according to claim 1, Wherein, when the gaseous fraction is detected, the following iterative method steps are performed: The second Reynolds number (104.1) is determined by means of -Said third mass flow rate; -said first viscosity; said first density and/or said second density, And storing a measurement of the second reynolds number, A third mass flow rate (104.2) is determined based on the pressure differential and the second reynolds number, and a measurement of the third mass flow rate is stored.
4. 4. A method according to claim 3, Wherein the iteration is terminated once the amount of difference between successive measurements of the third mass flow rate or the second Reynolds number is below a limit value, Wherein the limit value is 5% of the average of the measured values forming the difference or the limit value is 5% of one of the measured values forming the difference.
5. 5. The method according to claim 4, wherein the method comprises, Wherein the limit value is 2% of the average value of the measured values forming the difference.
6. 6. The method according to claim 5, Wherein the limit value is 1% of the average value of the measured values forming the difference.
7. 7. The method according to claim 4, wherein the method comprises, Wherein the limit value is 2% of one of the measured values forming the difference.
8. 8. The method according to claim 7, Wherein the limit value is 1% of one of the measured values forming the difference.
9. 9. The method according to any one of claim 1 to 8, Wherein the medium state is checked by means of the coriolis measuring device (10), wherein vibration damping of at least one measuring tube (11) of the coriolis measuring device and/or fluctuations in the resonance frequency are used during the check.
10. 10. The method according to any one of claim 1 to 8, Wherein the resonance frequency of at least one measuring tube (11) of the coriolis measuring device (10) is used in measuring the density.
11. 11. The method according to claim 10, Wherein when a gaseous fraction is detected, correcting the measurement of the second density based on a physical mathematical model, Wherein the model takes into account the movement of the gas bubbles relative to the measuring tube wall in the direction of vibration of the measuring tube.
12. 12. The method according to any one of claim 1 to 8, Wherein when a gaseous fraction is detected, a second density of the medium is measured by means of the Coriolis measuring device (10), Wherein the volume ratio of the gaseous fraction to the liquid fraction is determined based on the first density and the second density, Wherein the measured value of the differential pressure measurement is corrected by means of the volume ratio.
13. 13. The method according to any one of claim 1 to 8, Wherein the differential pressure measuring device (20) has a first pressure sensor (21.1) and a second pressure sensor (21.1), wherein the first pressure sensor is arranged upstream of the flow barrier, and wherein the second pressure sensor is arranged downstream of the flow barrier, and/or Wherein the differential pressure measurement device has a differential pressure sensor (22), the differential pressure sensor (22) detecting a differential pressure of an upstream side of the flow obstruction and a downstream side of the flow obstruction.
14. 14. The method according to any one of claim 1 to 8, Wherein an electronic measurement/control circuit (12) of the coriolis measuring device provides and outputs a measurement of the mass flow rate, Wherein when a pure liquid medium is detected, a measured value of the first mass flow rate detected by means of the coriolis measuring device is output, And wherein when a gaseous fraction is detected in said medium, outputting a measured value of said third mass flow rate detected by means of said pressure difference, Wherein the electronic measuring/control circuit is arranged in a housing (13) of the coriolis measuring device.
15. 15. The method according to any one of claim 1 to 8, Wherein the effect of the static pressure difference on the measured value of the pressure difference is corrected.
16. 16. The method according to any one of claim 1 to 8, Wherein the mass flow rate determined by means of the pressure difference is set to a zero value if the absolute value of the pressure difference is below a limit value, wherein the limit value is 20mbar.
17. 17. The method according to claim 16, Wherein the limit value is 10mbar.
18. 18. The method according to claim 17, Wherein the limit value is 5mbar.

Description

Method for operating a flow measurement point of a medium having at least one liquid phase Technical Field The invention relates to a method for operating a flow measurement point comprising a coriolis measurement device and a differential pressure measurement apparatus. Background Coriolis measuring devices for measuring the flow or density of a liquid medium flowing through a conduit have reduced measurement accuracy in terms of flow measurement under certain conditions, such as, for example, very low flow rates or bubbles in the medium. In this case, it has proven advantageous to detect the pressure drop across the medium of the coriolis measuring device by means of a differential pressure measuring device and to use the measured value of the differential pressure for flow measurement, see for example DE102005046319A1. However, in applications where the medium composition fluctuates in a relatively short time, flow measurements by means of differential pressure measurements are also subject to destructive uncertainties. The object of the present invention can therefore be seen as achieving or improving flow measurements under difficult conditions. Disclosure of Invention This object is achieved by the method according to the invention. In the method according to the invention for operating a flow measurement point of a medium having at least one liquid phase, The flow measurement point includes: A coriolis measuring device for measuring a mass flow rate and a density of a medium flowing through a conduit, wherein the coriolis measuring device has at least one measuring tube, which has in each case an inlet and an outlet; Wherein the differential pressure measuring device is configured to detect a differential pressure between a flow region arranged upstream of a flow obstacle, in particular a coriolis measuring device, and a flow region arranged downstream of the flow obstacle, The method comprises the following steps: Checking the medium state by means of a coriolis measuring device; -upon detection of a pure liquid medium, Measuring a first density of the medium by means of a coriolis measuring device and storing a measured value of the first density; measuring a first mass flow rate by means of a coriolis measuring device; A first viscosity of the medium is determined based on the first density, the pressure differential, and the first mass flow rate, and a measurement of the first viscosity is stored. Upon detection of the gaseous fraction in the medium, Determining a first Reynolds number of the medium by -A first viscosity; -when the gaseous fraction is detected, a first density and/or a second density of the medium measured by means of the coriolis measuring device; when a gaseous fraction is detected, a second mass flow rate measured by means of a coriolis measuring device, A third mass flow rate is determined based on the pressure differential and the first Reynolds number. In this way, the mass flow rate measurement can be corrected based on the differential pressure measurement so that a sufficiently accurate measurement is obtained even under difficult conditions. For example, the state of the medium can rapidly fluctuate when crude oil is produced from an oilfield. The gas dissolved in the medium under high pressure can form bubbles during depressurization, thereby affecting variables of the medium such as density or viscosity. For the start of the method, when a gaseous medium is initially present, the person skilled in the art can specify, for example, initial values of the measured values of the first density and of the first viscosity, which are obtained, for example, by estimation or by experience or by physical calculation. He can also let the flow measurement point wait at the beginning of the method until a pure liquid medium is present for the first time. When determining the first reynolds number by means of the first viscosity, the first density, the second density or the second mass flow rate, the corresponding measurement values are used. The same applies to the determination of other measured variables. In one embodiment, when a gaseous fraction is detected, the following iterative method steps are performed: the second reynolds number is determined by means of: -a third mass flow rate; -a first viscosity: A first density and/or a second density, A measured value of the second reynolds number is stored, A third mass flow rate is determined based on the pressure differential and the second Reynolds number, and a measurement of the third mass flow rate is stored. Such an iteration can further improve the measurement accuracy. In one embodiment, once the amount of difference between successive measurements of the third mass flow rate or the second reynolds number falls below a limit value, the iteration is terminated, Wherein the limit value is, for example, 5%, in particular 2%, preferably 1% of the average value of the measured values forming the difference or is, for example, 5