Application of process tomography in gas–solid fluidised beds in different scales and structures

Abstract

Gas-solids fluidised beds are commonly used in particle-related processes, e.g. for coal combustion and gasification in the power industry, and coating and granulation process in the pharmaceutical industry. Because the operation efficiency depends on the gas-solids flow characteristics, it is necessary to investigate the flow behaviour. This paper is about application of process tomography, including electrical capacitance tomography (ECT) and microwave tomography (MWT), in multi-scale gas-solids fluidisation processes in the pharmaceutical and power industries. This is the first time that both ECT and MWT are applied for this purpose with multi-scales and complex structure. To evaluate the sensor design and image reconstruction and to investigate the effects of sensor structure and dimension on the image quality, a normalised sensitivity coefficient is introduced. In the meanwhile, computational fluid dynamic (CFD) analysis based on a computational particle fluid dynamic (CPFD) model and a two-phase fluid model (TFM) is used. Part of the CPFD-TFM simulation results are compared and validated by experimental results from ECT and/or MWT. By both simulation and experiment, the complex flow hydrodynamic behaviour in different scales is analysed. Time-series capacitance data are analysed both in time and frequency domains to reveal the flow characteristics.

Numerical investigation of the particle circulation characteristics in a tapered fluidized bed

“…Moreover, u mf can be calculated theoretically, according to Kunii et al (1991), where w s is the sphericity, ε mf is the void fraction of under the minimal fluidization state, it is expressed as TFBs with three different inclination angles are considered. The prototype of the fluidized bed is a dryer which has been introduced in the previous publication (Wang et al, 2018;Ge et al, 2016), and the particle properties (shown in Table 2 and Table 4) are determined based on the cellulose particles in previous studies (Che et al, 2018(Che et al, , 2020.…”

Investigation of the riser cross-sectional aspect ratio effect on the flow dynamics in circulating fluidized beds by electrical capacitance tomography

“…The data acquisition rate is 120 frames/s for each sensor and 1000 sets of data are acquired for each case. Wang et al (2018) gives a detailed description of the ECT image reconstruction, and concludes that the Landweber iteration algorithm is suitable to reconstruct solids distribution and identify the flow regime in gas-solids fluidized beds.…”

“…Normally, the riser shape of a CFB can be circular, square and rectangular (Wang et al, 2018), which has been studied a lot by the researchers, especially the circular CFB. For example, Rao et al (2010) studied the effect of the column diameter and the bed height on the minimum fluidization velocity, and found that the minimum fluidization velocity insignificantly increases as the diameter of the fluidization column is reduced, or if the height of the bed is increased.…”

“…It can provide additional information on the gas-solids flow hydrodynamics, that is, flow regime transition (Qiu et al, 2015), which can be used for process monitoring and fault diagnosis of gas-solids fluidized beds. Wang et al (2018) already demonstrated that ECT has been successfully applied in gas-solid fluidised beds with different scales and structures. However, to study the meso-scale and mirco-scale details, measurement is not a good option; computational fluid dynamics (CFD) simulation is a better choice, and drag model is a determinant factor for its accuracy.…”

Teaching Approach and Materials for Enhancing Student Learning Experience in Tomography Engineering: Soft-Field Tomography

“…PT (Process Tomography) (Gladden, 1997;Wang et al, 2018) Mastering this subject requires students to gain a deep understanding in a number of relevant areas, in particular, two major concepts, i.e. the forward problem and the inverse problem (Munck, Faes, & Heethaar, 2000).…”