Gas-solid flow behaviors in a multi-stage circulating fluidized bed under elevated pressure

Ren, Feng; Li, Junguo; Dong, Libo; Hao, Zhenhua; Ba, Zhongren; Zhan, Haijuan; Fang, Yitian

doi:10.1016/j.ces.2018.11.057

Cited by 19 publications

(7 citation statements)

References 28 publications

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“…[ 3,6,7 ] The reported calibration curves for solids concentration OFPs have mostly displayed nonlinear behaviours, while the degree of nonlinearity was discernibly higher in dilute conditions than the dense state. [ 6,8–19 ] Linear calibration curves were also reported in the literature. [ 20–24 ] The refractive index of the medium, as well as the size, shape, and chromaticity of particles can alter the output signal intensity and/or nonlinearity.…”

Section: Introductionmentioning

confidence: 94%

“…Free falling in a longnarrow downer with a solid entrapping system [5,13,15,16,18,19,33] Gas Calibration is accomplished in a (the target) gaseous environment. Adopting an improved solids feeding system.…”

Section: Solids Droppingmentioning

confidence: 99%

“…This is in accordance with our observations in Figure 1 and the experimental results reported in the literature for the calibration of solids concentration OFPs by other methods. [3,6,13,15] The overall nonlinearity of calibration curves could be partially attributed to the presence of blind zones for the adopted probes, which can be inferred from their reflective curves. Examples of the reflective curves of Probe A (with no GW) when employing FCC-PS and FCC-PMMA blocks are presented in Figure 4.…”

Section: Effect Of the Medium Refractive Index On The Calibration Curvementioning

confidence: 99%

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Calibration of solids concentration optical fibre probes with solids‐polymer blocks

2021

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Owing to the determinant effects of the local distribution of solids concentration on transport phenomena, particularly in gas‐solids flows in such processing units as gas‐solid fluidized beds and pneumatic conveying lines, its accurate measurement has received considerable attention. Despite the widespread applications of optical fibre probes for the measurement of local solids concentration, these instruments may create measurement uncertainties due to their structural designs and challenges in their accurate calibrations. Several calibration methods have been proposed in the literature, while they need to be further improved. In the present study, we calibrated in‐house, fabricated, solids concentration mixed parallel optical fibre probes by two sets of solids‐polymer blocks covering solids volume fractions in the range of 0‐0.30. The uniform blocks were produced by a twin‐screw extruder and an injection moulding machine. FCC particles, 86 μm in diameter, formed the dispersed solids in the blocks, while poly styrene and poly methyl methacrylate were separately acting as the transparent medium. They helped us investigate the effects of the refractive index of the medium and the probe tip design on the calibration curve. The blind distance (zone) in front of the adopted probes was determined, at about 0.70 mm, upon measuring their reflective curves. Two glass windows with 1.00 and 1.60 mm thicknesses were separately installed at the tip of a probe to study their effects on the calibration curve. Experimental results indicated that in the absence of a glass window, the probes' voltage readings varied nonlinearly with solids concentration, the voltage readings were higher for blocks with a higher refractive index of the transparent medium, while the normalized calibration curves were similar for both sets of solids‐polymer blocks. In addition, the extent of the uniform distribution of illuminating and reflecting fibre strands at the tip of a mixed parallel optical fibre probe can change the degree of nonlinearity of its calibration curve. The application of glass windows thicker than the blind distance decreased the degree of nonlinearity of the calibration curve, yet did not completely eliminate it.

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Section: Introductionmentioning

confidence: 94%

Section: Solids Droppingmentioning

confidence: 99%

Section: Effect Of the Medium Refractive Index On The Calibration Curvementioning

confidence: 99%

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Calibration of solids concentration optical fibre probes with solids‐polymer blocks

2021

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“…The reason is that the pressure mainly affects the gas density. When the gas phase density increases, it will correspondingly increase the powder motion drag and reduce the collision frequency between powders, thus making it more diffi cult for the powder to aggregate and a relatively uniform fl ow structure to be formed 35, 36 . Combined with the spatial distribution of the powder layer, the variation of instantaneous area, and the standard deviation distribution, it shows that the powder motion behavior is less affected by gas perturbation under high operating pressure conditions.…”

Section: Distribution Of the Powder Layermentioning

confidence: 99%

Effect of elevated pressure on gas-solid flow properties in a powder feeding system

Ren

Sun

et al. 2022

Polish Journal of Chemical Technology

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In view of the powder feeding system, a multi-physical coupling model of the gas-powder-piston was established based on the Euler-Euler two-fluid model. The numerical simulation method was applied to explore the effects of dense gas-solid flow characteristics under different operating pressures. The results show that gas-solid pulsations at different operating pressures are mainly concentrated in the upper part of the powder tank. An elevated operating pressure efficiently decreases the powder layer area (εp = 0.1) fluctuation. As the operating pressure increases from 0.5 MPa to 3.0 MPa, the rising time and fluctuation rate of pressure are reduced by 71.4% and 62.3%, respectively, and the pressure in the tank has a long stabilization period. Meanwhile, the variation of the instantaneous powder flow rate is more stable and its average value is closer to the theoretical. A high-pressure environment is more conducive to the stable transportation of powder.

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“…Qi et al 16 and Zhu et al 17 concentration was obtained. Rongtao et al 19 also studied the gas−solid flow state in a multistage CFB under elevated pressure. They found that the good gas−solids contacting and mixing by the uniform radial and axial distributions occurred with the elevated pressure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Inner Solid Circulation Pattern in the Multistage Riser

Zhang

2021

Ind. Eng. Chem. Res.

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A multistage riser reactor with the enlarged section plays an increasingly important role in industries such as energy conversion. However, gas−solid complex flow in the multistage riser needs to be further explored. Inner solid circulation occurred in the enlarged section exerts essential effects on flow behavior. In this work, inner circulation mechanisms of solids in the multistage riser are investigated experimentally by correlating the bed geometry. Solid streamline and velocity profiles show that the inner circulation in the enlarged section involves the vortex core part in the upstream region and the expansion part in the downstream region. For the vortex core part, single and dual circulations of solids occur in different enlarged sections. The results also indicate that vortex core motions tend to strengthen with the increase of the diameter ratio and height−diameter ratio but weaken with the increase of the angle. Moreover, the effects of the expansion part on gas−solid flow increase as the angle increases.

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Gas-solid flow behaviors in a multi-stage circulating fluidized bed under elevated pressure

Cited by 19 publications

References 28 publications

Calibration of solids concentration optical fibre probes with solids‐polymer blocks

Calibration of solids concentration optical fibre probes with solids‐polymer blocks

Effect of elevated pressure on gas-solid flow properties in a powder feeding system

Experimental Study of the Inner Solid Circulation Pattern in the Multistage Riser

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