| With the development of science and technology, pneumatic conveying systems are more and more widely applied in industries, e.g. power generation, steel making, chemical and food processing etc. Accurate measurement of the mass flow rate of solids plays a key role in pneumatic conveying systems. Successful on-line measurement of pulverized fuel concentration would lead to an improvement in combustion efficiency and stability, and a reduction in atmospheric pollution and corrosion of the combusting chamber in power stations. In recent years, applications of process tomography as a robust non-invasive tool for direct analysis of the characteristics of multiphase flows have increased in number. Electrical capacitance tomography (ECT) is considered to be the most powerful tool among all available tomographic techniques because of its advantage such as, high-speed capability, low construction cost, high safety and adaptability for small or large vessels.Practical difficulties of the gas-solid concentration measurement using ECT are the soft-field characteristic and the inhomogeneous sensitivity, therefore it is difficult to make a quantitative analysis using ECT. Materials closer to the electrodes, i.e. the wall of the sensor, will be easier to detect than materials away from the electrodes, e.g. in the central areas of the cross-section. So local measurement accuracy for the dynamic parameters appears to be dependent greatly on the measuring location. In this dissertation a cyclone condensation apparatus is employed to compensate the inhomogeneity of the sensor sensitivity. The research in this dissertation is very important, as it doesn't only supply an online measurement technology for pneumatic conveying systems, but also will promote the application of ECT technology.The main contributions of this dissertation are as follows:(1) The image reconstruction algorithms of ECT are reviewed in this dissertation and analyzed. The reconstruction must be fast as well as high quality for online mass flow rate measurement, so a new image reconstruction algorithm ETRM is introduced according to this requirement. Compared to the algorithms used practically like linear back projection (LBP), the Tikhonov regularization method and the OIOR algorithm, the image quality has been improved and reconstruction time has been reduced using this new algorithm; (2) In order to investigate the condensation effect of the cyclone condensation apparatus, numerical simulations have been carried out using the commercial CFD software-FLUENT. Established numerical simulation methods that are most suitable for the gas filed in the cyclone separator-RSM model for turbulent flow, QUICK scheme for difference scheme, PRESTO scheme for pressure discretization and SIMPLEC for pressure-velocity coupling. The velocity field and pressure field in the apparatus have been simulated and analyzed. The volume concentration distribution of solids has been simulated using the Eulerian two-fluid model. It is found that solids can be condensed to the wall region well through the simulation results;(3) Experimental studies are carried out on the subtle mass flow measurement in a pneumatic conveying pipeline using ECT. In this system a cyclone condensation apparatus is employed where the sensors are placed. The volume concentration is altered through changing the screw feeder speed and the suction amount on the top of the apparatus. The distribution of volume concentration in radial direction, the average volume concentration and the fluctuating characteristics have been analyzed. The feasibility and reliability of the concentration effect are validated by experimental results;(4) The volume concentration and solid velocity in the cyclone condensation apparatus are measured simultaneously using twin-layer ECT sensors. For the objective of saving the data acquisition time, the two sensors are selected with different number of electrodes. The up-stream sensor with 8 electrodes is used to determine the volume concentration. The down-stream sensor has 4 electrodes, and determines the solids velocity with the up-stream sensor using cross-correlation method. The data acquisition time is 0.00425 second for every frame. With the concentration and velocity measurement results, mass flow rate can be calculated through relative equations. In order to validate the accuracy and reliability of this capacitance measurement method, the results are compared to that of load cell. The results error is in a controllable way, mainly below 5%, so the reliability and feasibility of this method are validated.
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