Toward Multiphase Flow Decomposition Based on Electrical Capacitance Tomography Sensors

We describe an approach, based on electrical capacitance tomography (ECT) sensors, to decompose and continuously monitor multiphase flow components (fractional areas or volumes) in mixtures containing conducting phases. The proposed approach exploits the Maxwell-Wagner-Sillars effect at distinct frequencies to reconstruct each phase of a multiphase flow and is also utilized to estimate the fractional volume of the various phases of the mixture. The approach is illustrated for a three-phase mixture composed of air, water, and oil. This approach utilizes the very same ECT measurement apparatus used for flow imaging and, as such, inherits its high speed of acquisition and suitability for real-time operation.

I. Introduction

Gas-liquid-solid reactor systems have been applied extensively to commercial operations for physical, chemical, petrochemical, electrochemical, and biochemical processing [1]. There are a variety of operational modes for such three-phase systems based on the behavior of the hydrodynamics of the gas-liquid-solid flows. For example, depending on the gas and liquid flow rates relative to the minimum fluidization velocity or the terminal velocity of the particle, various fluidization schemes are possible. The solids can be in the fixed bed regime, the expanded bed regime, or the transport regime. Both the liquid and solids can either be in a continuous flow condition or batch condition while the gas can either be a continuous phase or a discrete bubble phase. The flow of gas and liquid can be concurrent upward, concurrent downward, or countercurrent. Specific examples of applications include slurry bubble column reactors that are used for direct coal liquefaction or coal hydrogenation to directly produce liquid fuels or indirect coal liquefaction in which coal is first gasified and then followed by the Fischer-Tropsch synthesis to produce liquid fuels or chemicals [2]. Slurry bubble columns can also be used for hydro-treating tar sand and petroleum resins, and hydrogenation reactions for catalytic production of organic chemicals such as glucose to sorbitol, benzene to cyclohexane, and ethylene polymerization. Gas-liquid-solid fluidized beds can also be used for hydrotreating petroleum resins as in the H-Oil process and LC-Fining process, or for direct coal liquefaction as in H-Coal process. A three-phase fluidized bed wet scrubbing system such as the turbulent bed contactor was previously commercially used to remove sulfur dioxide and particulates from coal combustion flue gas [1]. With the advance of biochemical technologies, gas-liquid-solid fluidization systems have also found important applications in bioprocessing as bioreactors to produce high valued bioproducts such as enzymes, proteins and antibiotics. Three-phase fixed bed operation is also of considerable industrial interest. The operating capacity for the hydrodesulphurization and hydrodenitrogenation reactions in clean liquid fuel production from crude oil is significant and they are mostly carried out in the trickle bed reactors in industry. In the environmental industry, toxic chemicals in waste-water are also removed by oxidation in trickle beds, slurry bubble columns, and three-phase fluidized beds [3].