A Method of Post-compensation on Disperse Phase Volume Fraction due to Variation of Salinity
Yiwei Xiang1, Mi Wang1
1 School of Chemical and Process Engineering, University of Leeds, UK
*Email: firstname.lastname@example.org, email@example.com
Linear back-projection algorithms (LBP) have extensively been used in process tomography for online mapping of disperse phase volume fraction distribution in multiphase processes, which are based on relative change of conductivity distribution to conductivity of continuous phase in processes. However, the conductivity of continuous phase may vary due to the change of salinity or temperature in process, which may cause conductivity differences from those at the time of taking reference voltages. Correction to the variation is necessary if it may cause a considerable shift from true volume fraction distribution derived with relative change of conductivity. Generally, the correction to raw data can be carried out by either taking new reference voltages from continuous phase only fluid or compensating the shifts from original reference voltages based on ohm law. However, it demonstrates a practical challenge from either taking a new reference voltages or conducting the compensation before image reconstruction. This paper reports a method of post-compensation on disperse phase volume fraction distribution derived with Maxwell relationship from electrical impedance tomogram. The method takes the linear property of LBP and the feature of Maxwell relationship, introduces a h-factor to present the ratio between conductivities of continuous phase at the times before and after a process change and then compensates the shift of disperse phase volume fraction directly without correction to reference voltages. The paper presents details of the theoretical derivation and reports effects of the compensation on disperse volume fractions under different salinity variations with and without an object, providing a simple and practical approach for correcting measurement error caused by change of salinity in process.
Keywords: continuous phase conductivity, volume fraction distribution, electrical impedance tomography, post-compensation
Industrial Application: Oil and gas, dredging and mineral process
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