Mass flow monitoring using electrical resistance tomography
The ERT system with dual sensing modules efficiently measures mass flow rate by generating tomograms for density and correlating raw signals for velocity, addressing complexity and cost issues in multiphase flow measurement.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PROCESS FLOW INTELLIGENCE LTD
- Filing Date
- 2025-12-08
- Publication Date
- 2026-06-18
AI Technical Summary
Existing ERT systems for measuring mass flow rate in multiphase flows require additional complex and costly modalities to measure both product density and velocity, increasing system complexity and cost.
An ERT system with two sensing modules, each with electrode arrays, where the first module generates tomograms for density and the second module correlates raw signals to calculate flow velocity, minimizing processing power by comparing data from corresponding electrodes.
Enables accurate measurement of mass flow rate using a single technology, reducing complexity and cost by integrating density and velocity measurement within a single ERT system.
Smart Images
Figure GB2025052664_18062026_PF_FP_ABST
Abstract
Description
[0001] Mass Flow Monitoring using Electrical Resistance Tomography Field of the invention
[0002] The invention relates to measurement of mass flow rate using electrical resistance tomography and is particularly intended to monitor the flow of a solid product in an electrically conductive slurry during mining operations.
[0003] Background of the invention
[0004] Electrical resistance (or impedance) tomography, herein termed ERT, is a low-energy, high-speed technique that can be used to derive in-line, real-time process information regarding the nature and distribution of electrically conductive components in a multiphase flow within a process space.
[0005] An ERT system comprises three modules, namely a sensor module, a data acquisition module, and an image reconstruction module.
[0006] The sensor module comprises an array of electrodes placed around the internal periphery of a process space, such as a pipeline. The electrodes can serve both as transmitting electrodes, to cause an a.c. current to flow and thereby create an electric field within the process space, and as receiving electrodes, to sense the resultant field at different locations around the periphery of process space. Electrically conductive regions distributed within the process space will modify the electric field and therefore affect the output signals of the electrodes acting as sensing electrodes.
[0007] The data acquisition module causes different electrodes about the periphery of the process space to operate sequentially as transmitting electrodes. While an a.c. current is applied via different transmitting electrodes, the data acquisition module records the resultant voltages at the receiving electrodes
[0008] The image reconstruction module, by analysing the measured voltages created when a.c. current is applied using different electrodes around the periphery of the process space, calculates an image of the cross-section of the process space, showing the distribution of the electrically conducting regions within the process space.
[0009] In this way. an ERT system can monitor a flow of an electrically conductive product being transported within a process fluid, to determine the density of the product.
[0010] ERT systems are known and have been used previously in a variety of applications. It is not therefore believed necessary, within the present context, to provide a more detailed explanation of the data acquisition module nor of the image construction module. Instead, reference is made, for example, to W02023 / 026045 which describes in more detail an ERT system used to monitor a chemical process in a column apparatus, and to
[0011] EP 2992364 in which an ERT system forms part of an apparatus for monitoring the flow of mixtures of a fluid in a pipeline.
[0012] In order to measure mass flow rate of a product, it is not sufficient to measure the density of the product in the flow, but it is also necessary to measure the velocity of the product. As explained in EP 2992364, measurement of velocity is a multiphase flow is complicated because the different phases may not travel at the same velocity. The latter reference provides a solution requiring multiple monitoring modules to measure, electrical permittivity, electrical conductivity and the velocity of at least one of the phases.
[0013] In W02020 / 104761, the present Applicant disclosed a mass flow monitoring system comprising one or more processors, a magnetic source operable to selectively provide a magnetic field through a section of flow conduit to be monitored and an electric source comprising a plurality of electrodes arranged around the circumference of the section of said flow conduit to provide conductive paths therein. The one or more processor is operable to select an electrode-pair, from the plurality of electrodes. In a flow density mode, the processor is operable to apply an electrical signal across the electrode-pair and measure the responsive electrical signal across one or more other electrode-pairs. In a flow rate mode, the processor is operable to cause the magnetic field and the plurality of conductor paths to be angularly displaceable relative to each other, and to measure the responsive electrical signal of a selected electrode-pair. The measured flow density mode responsive electric signals and the measured flow rate mode responsive electric signals are computed to determine the mass flow through said section of conduit.
[0014] Other systems have previously been proposed for oil and gas applications that aim to measure the flow rate of the product using different modalities, such as acoustic, optical or differential pressure measurements. The need for such additional different systems increases complexity and therefore cost.
[0015] Object of the invention
[0016] The aim of the present invention is to provide a measurement system which using only ERT equipment can measure both product density and flow rate, so as to arrive at a measurement of mass flow rate, and that minimises the processing power required to perform the measurement. Summary of the invention
[0017] The present invention provides an ERT system for measuring mass flow rate of a solid product carried within a multiphase electrically conductive flow in a pipeline, comprising first and second sensing modules to be placed on an interior surface of the pipeline, one downstream of the other, each sensing module comprising an array of electrodes that intersect a common cross-sectional plane and are circumferentially spaced from one another to act as signal transmitting and signal receiving electrodes, wherein only the first sensing module is associated with a data acquisition module and with an image construction module that serve to determine the distribution of the product within the cross-sectional plane of the first module, and wherein a processor is provided for correlating raw signals generated at different times at corresponding receiving electrodes in the two sensor modules to determine the flow velocity of the product and thereby enable calculation of the mass flow rate of the product.
[0018] The acquisition and image construction module associated with the first sensing module generate a series of tomograms showing the distribution of the product over the crosssection of the pipeline as the flow passes the first sensing module. The distribution will change from one tomogram to the next, each being representative of a different “slice” of the flow through the pipeline. Processing of the signals from the first sensing module alone will, in this way, provide an indication of the density of the product within each slice.
[0019] To calculate the product flow rate, it is also necessary to obtain a measure of the flow rate of the product, which is not necessarily the same as the velocity of the flow. To achieve this with a minimum of additional processing, the present invention provides a second sensing module, but in this case its signals are not processed to obtain tomograms. Instead, the raw data of only some of the receiving electrodes, and optimally only a single pair of receiving electrodes, are correlated with the raw data from the corresponding pair(s) of the first sensing module. From a knowledge of the time difference between the signals at which the correlation coefficient is maximised and the distance between the two sensing modules, it is possible to compute the product mass flow rate.
[0020] As it is only necessary to compare signals from a subset of the signals generated at the receiving electrodes of the first sensing modules, the second sensing module may have fewer electrodes that the first sensing module. In some embodiments, the processor configured to correlate signals from the two sensing modules may additionally be configured to perform the data acquisition and image construction of the first sensing module.
[0021] Brief description of the drawings
[0022] The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:
[0023] Figure 1 shows schematically the sensor module of an ERT system for monitoring mass flow of a product along a pipeline,
[0024] Figure 2 depicts method steps employed by the ERT system of Figure 1,
[0025] Figure 3 shows the current flow paths and the lines of equipotential within a cross¬ section of the pipeline when current is applied to two adjacent electrodes, Figure 4 is a schematic diagram of the hardware of the ERT system of Figure 1, and Figure 5 shows calculated density images through the cross-section of a pipeline taken at different times.
[0026] Detailed description of the drawings.
[0027] The measurement system in Figure 1 comprises an electrical resistance tomography sensor which comprises two sensing modules, formed by arrays of electrodes 5 and 5’. The electrode arrays 5 and 5’ are arranged around the interior of a pipeline 3 at locations that are axially spaced from one another along the length of the pipeline. The electrodes 5 and 5’ within each array are centred at a plane of the pipeline 3 which is perpendicular to the flow axis.
[0028] Whereas a plane has zero depth, each sensing location does have depth in the flow direction, on account of the elongate nature of the electrodes 5 and 5’. The electrical stimulation applied to the electrodes permeates in all directions into the material adjacent the electrodes 5. As such, each sensing location may be considered as a volume which is defined by (e.g. centred about) the plane.
[0029] Each of the electrodes 5 and 5’ is formed from a conductive material, allowing electrical contact to be made between the electrodes 5 and the material within the pipeline 3. The electrodes 5 may be made from a material resistant to erosion and corrosion, such as stainless steel. The electrodes 5 may be inlaid into the pipeline 3 such that the inner wall of the pipeline 3 which is not covered by an electrode is formed from the same material as the pipeline 3. Alternatively, the electrodes 5 may be mounted on a collar which is fitted to the inner wall of the pipeline 3. The internal surface of the collar (e.g. the surface which would be in contact with the material in the pipeline 3) which is not covered by the electrodes may be formed from an erosion and corrosion resistant material. For example, the internal surface of the collar may be formed from a poly ether ether ketone (PEEK) or another polyurethane material that has a sufficient chemical resistivity
[0030] Each electrode array is shown in Figure I as being associated with a respective current source 6 or 6’ operable to apply an electrical stimulation to a pair of (or multiple pairs of) electrodes 5 or 5’, a voltage monitor 7 or 7’ operable to receive an electrical signal from a pair of (or multiple pairs of) electrodes 5 or 5’ following the permeati on of the electrical signal through the material 2, and a controller 8 or 8’. While this diagrammatic representation helps in explaining that the apparatus comprises two ERT systems located one downstream of the other, it will be appreciated that a single current source, a single voltage monitor may be connected to both sensing module and the apparatus requires but a single controller.
[0031] The controller 8 may be a programmable logic controller (PLC), such as, for example, a PLC manufactured by Bachmann electronic GmbH, Feldkirch, Austria. The controller 8 controls the current source 6 and the voltage monitor 7. The controller 8 also performs processing as described further below' in more detail.
[0032] The first ERT system is intended to a produce a series of tomograms, such as shown in Figure 5, of the density distribution of a product within the pipeline at the sensing location, the tomograms in a series varying with the times when they were generated.
[0033] Figure 3, which is a schematic cross-section of one of the first sensor module, show's the current line I and the lines of equipotential V which occur when an a.c. current is applied through the electrodes labelled 5a and 5b, these being in this case the transmitting electrodes. These lines I and V will however be modified if the electrical resistance of the medium through which the current flows is not homogeneous. The voltages measured using the sensing or receiving electrodes labelled 5c to 5p will therefore depend not only on the current flowing through electrodes 5a and 5b, but also on the distribution of the conductive paths defined by the medium. By stimulating a current flow' sequentially from different directions using different electrode pairs and measuring the voltages at the other electrodes, one can obtain data which when fed into an inverse algorithm will reconstruct tomograms, such as shown in Figure 5, that represent the density distribution of the conductive regions within the sensing location.
[0034] Thus, as represented schematically in Figure 2, the steps carried by the ERT system at each sensing module are:
[0035] S1 Apply electrical stimulation, i.e. connect an a.c. current source to a pair of electrodes of the array,
[0036] S2 Receive electrical signal, i.e. measure the voltages at the other electrodes of the same array, and
[0037] after repeating steps S1 and S2 using different pairs of electrodes in step S1
[0038] S3 Determine the characteristic(s), i.e. calculate using an inverse algorithm an image of the conductivity distribution within the sensing location.
[0039] The physical apparatus that may be used to perform the stimulation, voltage measurement and image calculation for the first sensing module is shown diagrammatically in Figure 4. The controller 8 in this embodiment is essentially a micro-computer. The computer has a monitor screen 8e, with a keyboard 8f and a mouse 8g as input devices. The computer also includes a central processing unit (CPU) 8a, random access memory (RAM) 8b, non¬ volatile memory in the form of a hard disk drive 8c, all communicating with one another via a data bus 8i. The computer also includes a network interface 8h.
[0040] The computer is programmed to control two peripheral units, namely the current source(s) 6 and the voltage monitor(s) 7 by way of an Input / Output (I / O) interface 8d. The program to be run on the CPU instructs the current source 6 to energise different pairs of electrodes in the two sensor modules and to gather data from the other electrodes using the voltage monitor 7. This data is store in RAM for processing to arrive at tomograms at the different sensing times.
[0041] As so far described, the steps performed at the first sensing location are conventional and have been used to produce tomograms as shown in Figure 5 indicative of density / distribution of conductive material within a pipeline.
[0042] Hitherto, to measure mass flow rate, as described previously, separate equipment, often using a different modality, was required to obtain a measurement of the flow velocity of the product. In the present invention, such a measurement is achieved by providing a second ERT systems and comparing the data from the two systems.
[0043] However, in the present invention, the signals from the second sensing module are not used to generate tomograms, in order to simplify processing.
[0044] As material flows through the pipeline, the raw (i.e. yet to be processed) signals generated at the receiving electrodes of first sensing module will change with time, to enable different tomograms to be calculated. The raw signals generated at the receiving electrodes of the second sensing module will change in the same manner with time as the flow sections analysed by the first sensing module arrive at the second module. By correlating the raw data from corresponding electrodes of the first and second sensing modules, it is possible to compute the flow velocity of the product.
[0045] While it is necessary, in order to be able to correlate like with like, that the positions of the transmitting electrodes and receiving electrodes be the same on the two sensing modules, it is not essential for the two sensing modules to be identical. Indeed, the correlation need only be between a subset of the receiving electrodes of the first sensing module and possible only a single pair of receiving electrodes. Consequently, the second sensing module may be formed with fewer electrodes.
[0046] The precision of the velocity measurement will in practice depend on the time between generated tomograms at the first sensing module and the distance between the sensing modules. Increasing the distance between the sensing modules, will increase the precision of velocity measurement but, because the distribution of the product with the measurement cross-section may change as slices travel along the pipeline, the correlation coefficient will be decreased. Increasing the rate of generation of tomograms would of course increase the measurement precision but require higher processing power. In practice, the optimum separation of the sensing modules is determined in dependence on the available processing power.
[0047] The invention enables production measurement to be achieved using a single technology (ERT) and permits ERT to be used in assessment of multi-phase flow, such as hydrotransportation of slurry in dredging and mining industries.
Claims
CLAIMS1. An ERT system for measuring mass flow rate of a solid product carried within a multiphase electrically conductive flow in a pipeline, comprising first and second sensing modules to be placed on an interior surface of the pipeline, one downstream of the other, each sensing module comprising an array of electrodes that intersect a common cross-sectional plane and are circumferentially spaced from one another to act as signal transmitting and signal receiving electrodes, wherein only the first sensing module is associated with a data acquisition module and with an image construction module that serve to determine the distribution of the product within the cross-sectional plane of the first module, and wherein a processor is provided for correlating raw signals generated at different times at corresponding receiving electrodes in the two sensor modules to determine the flow velocity of the product and thereby enable calculation of the mass flow rate of the product.
2. An ERT system as claimed in claim 1, wherein the second sensing module has fewer electrodes that the first sensing module.
3. An ERT system as claimed in claim 1 or 2, wherein the processor is configured to correlate signals derived from a single pair of receiving electrodes of the first sensing module with signals derived from a corresponding single pair of receiving electrodes of the second sensing module.
4. An ERT system as claimed in any preceding claim, wherein the processor that is configured to perform the correlation of the data derived from the two sensing modules, is additionally configured to perform the data acquisition and image construction of the first sensing module.