Mass flow rate measurement of bulk solids based on microwave tomography and microwave Doppler methods
Graphical abstract
Introduction
Pneumatic transportation of bulk solids has been widely used in many applications, such as energy, food, medicine and chemistry, due to its advantages of nonintrusive, convenience, high-speed and automation [1]. As the most important evaluated parameter of the transportation, the mass flow rate of bulk solid flows plays an important role in measurement and control systems, which is determined by accurate flow velocity and concentration measurement of solids.
Tomography is imaging by sectioning, through the use of a penetrating wave or field. In broad terms, it is a technology to get target features, such as concentration and distribution by a non-contact or non-invasive means. Currently electrical capacitance tomography (ECT) [[2], [3]] and electric resistance tomography (ERT) [[4], [5]] are the common methods for industrial tomographic imaging. However, ERT is not suitable for the imaging of pneumatic transportation. Besides, both ERT and ECT have low image resolution. On the other hand, microwave tomography (MWT) which has a wide range of frequency can produce images of higher resolution than ECT and ERT. MWT can also be used to measure materials with high permittivity and conductivity, making it attractive for a range of industrial imaging applications, including industrial process monitoring and concentration measurements [[6], [7], [8], [9], [10], [11]], the comparisons of ERT, ECT and MWT are shown in Table 1.
To meet the needs of industrial production, a large number of velocity meters such as spatial filtering method, cross correlation method, laser Doppler method [12] have been introduced over the past decades [13,14]. Among them, the spatial filtering method is very complex. The cross correlation method has a poor spatial sensitivity with restricted signal processing and laser Doppler equipment is expensive. Therefore, it is urgent to develop a new method for the velocity measurement and analysis of bulk solid flows. In recent years, with the rapid development of microwave technology, remarkable progresses with diversified microwave sensors have been made for industrial applications [15,16]. Besides, Doppler method offers non-intrusive point velocity measurement with fine temporal resolution and high accuracy. With microwave Doppler sensors, consistent real-time velocity measurements can be achieved. The comparison between laser Doppler and MWD is shown in Table 2. Based on analysis and comparison above, a microwave Doppler (MWD) sensor is adopted to measure the flow velocity of solids in this investigation as a part of the mass flow rate measurement system [17].
The paper is organized into 5 sections. Following the introduction in Section 1, the test facility, MWT sensor and MWD sensor used in the study are described in Section 2. In Section 3, tomography measurements of bulk solids are presented, including the analysis of solid concentration and different flow regimes from the images obtained. Besides, average velocity measurement of bulk solids is described. In Section 4, the measured results of mass flow rate of bulk solids using MWT sensor and MWD sensor are presented and the errors are analyzed. Conclusions are given in Section 5.
Section snippets
The method of approach
The mass flow rate is the mass of a substance which passes per unit of time. The mass flow rate M for the bulk solid flows can be estimated using the “velocity-concentration” method, i.e.,where A is a system's constant, υ is the velocity of bulk solid flows, β is the solid concentration value, S is the cross sectional area of pipe, and ρ is the density of bulk solids.
Thus, the measurement of mass flow rate is converted to the measurement of velocity and concentration of bulk solid flows.
Measurement and results
In this section, the applicability of the proposed MWT sensor for imaging of bulk solids is investigated by conducting measurements and reconstructing the relative permittivity distribution. Images of solid particle flow with different types of flow regimes can be reconstructed quantitatively. Besides, MWD sensor is used to measure the velocity of bulk flows.
Mass flow rate measurement and error analysis
To show that microwave sensors can be applied to bulk industrial transportation, a MWD sensor is used to measure the average flow velocity of bulk solids and a MWT sensor is used to measure the concentration of bulk solids in the flow with the measurement facility shown in Fig. 1.
The wind speed is set at 20 m/s. Fig. 9 shows the average velocity υ(t), concentration values β(t) and the product of υ(t), β(t), S and ρ against time over a period of 40 s. At first, there is no solid flowing in pipe,
Conclusions
A new mass flow rate measurement and analysis method for bulk solids based on a MWT sensor and MWD sensor has been presented. The experiments carried out show that MWT can be used to measure concentration of bulk solids and particle distribution can be observed visually over the cross section. Besides, the average velocities of bulk solids can be measured with the MWD principle and short-time FFT. At last, the mass flow rate and the total mass of bulk solids can be calculated using the proposed
Acknowledgments
The authors would like to thank the National Natural Science Foundation of China (No. 61320106004) and CAS Interdisciplinary Innovation Team for their supports. The authors thank all the staff of the RF & Microwave Technology Research Center, WUT for their support throughout the experiment and for their comments.
References (23)
- et al.
Phase-shift detection for capacitance sensor measuring void fraction in two-phase flow
Sens. Actuators
(2010) - et al.
Application of electrical resistance tomography system to monitor gas/liquid two-phase flow in a horizontal pipe
Flow Meas. Instrum.
(2001) - et al.
2D microwave tomography system for imaging of multiphase flows in metal pipes
Flow Meas. Instrum.
(2017) - et al.
Measurement of velocity of gas/solid swirl flow using Electrical Capacitance Tomography and cross correlation technique
Flow Meas. Instrum.
(2017) - et al.
Two-point correlation estimation of turbulent shear flows using a novel laser Doppler velocity profile sensor
Flow Meas. Instrum.
(2009) - et al.
Rheology of complex fluids with vibrating fiber-optic sensors
Sens. Actuators A Phys.
(2017) - et al.
Comparative study of ultrafast X-ray tomography and wire-mesh sensors for vertical gas–liquid pipe flows
Flow Meas. Instrum.
(2017) - et al.
Image reconstruction for ECT based on extended sensitivity matrix
IEEE Sens. J.
(2016) - et al.
Investigation of gas-solid bubbling fluidized beds using ECT with a modified Tikhonov regularization technique
AIChE J.
(2018) - et al.
Resistivity imaging of binary mixture using weighted Landweber method in electrical impedance tomography
Flow Meas. Instrum.
(2017)
Microwave tomography: review of the progress towards clinical applications
Philos, Trans. A. Math. Phys. Eng. Sci.
Cited by (13)
Development and evaluation of a slurry density measurement system based on Applied Current-Magnetic Induction Tomography (AC-MIT)
2023, Flow Measurement and InstrumentationFlow monitoring by microwave imaging inside a cuboid cavity: Theory and numerical feasibility analysis
2021, Flow Measurement and InstrumentationCitation Excerpt :Flow monitoring as an essential part of production requires non-intrusive, safe, and accurate technologies for a diverse set of industries such as in-line monitoring of food [1,2] and multiphase oil/gas flow imaging [3–5].
Study on online detection method of particulate matter in natural gas pipeline based on microwave technology
2023, Huagong Xuebao/CIESC JournalParticle Fertilizer Mass Flow Measurement Based on Microwave Method
2023, Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural MachineryMass Flow Rate Measurement of Pneumatically Conveyed Solids in a Square-Shaped Pipe Through Multisensor Fusion and Data-Driven Modeling
2023, IEEE Transactions on Instrumentation and Measurement