X-ray measurements on the influence of optical probes on gas–solid fluidized beds

Maurer, Simon; Wagner, Evert C.; Schildhauer, Tilman J.; Ommen, J. Ruud van; Biollaz, Serge M.A.; Mudde, Robert F.

doi:10.1016/j.ijmultiphaseflow.2015.04.002

Cited by 16 publications

(17 citation statements)

References 15 publications

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“…Various measurement devices can be used to measure gas holdup in bubble/slurry bubble columns, such as fiber optical probes, conductivity probes, differential pressure probes, ultrasonic techniques, electrical capacitance tomography, X‐ray tomography, gamma‐ray densitometry, and gamma‐ray computed tomography (CT) . However, gamma‐ray computed tomography is superior to other techniques due to its capability to visualize and measure gas holdup over the entire cross‐sectional area of the column in dense and opaque flows that are not visible to other measurement devices due to their limitation to measure in single points (such as probe‐based measurement) or their low penetration capability to pass through the high attenuating material (such as X‐ray tomography) …”

Section: Introductionmentioning

confidence: 99%

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

et al. 2018

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This study identifies and addresses some major pitfalls that are involved in the visualization and quantification of the gas‐liquid distributions and their profiles in a bubble column with internals using the gamma‐ray computed tomography (CT) technique. Some of these pitfalls encountered in the scanning of bubble columns with internals are using an improper reference scan, and applying the same experimental scanning procedure and mathematical relationships for estimating the gas holdup in the column without internals to the column with internals. The experimental results revealed that the selection of the inappropriate reference scan for CT experiments would significantly affect the reconstructed linear attenuation coefficient values and consequently the gas holdup results. Additionally, the reconstructed linear attenuation values showed good agreement with theoretical values when considering air as reference scans. However, disagreement is observed when using the empty column with internals as a reference scan. Moreover, it was found that using the proper reference scan eliminated the errors not only for the reconstructed linear attenuation coefficients but also for the gas holdup values near the wall region. Furthermore, the CT technique was capable of capturing the small thickness (5 mm) of the wall for phantom and bubble columns as well as the internals when the air was used as the reference scan. Finally, a new methodology has been implemented to exclude the internals from the cross‐sectional images, and the azimuthally averaged gas holdup profiles to provide accurate and reliable results for comparison and validation purposes for the bubble column with internals.

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Section: Introductionmentioning

confidence: 99%

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

et al. 2018

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“…Rowe et al [10,20,21] clearly showed that probes have an effect on bed hydrodynamics, while Maurer et al [22] indicated there in no effect. In these studies, however, they only focused on individual bubbles.…”

Section: Rowe and Everettmentioning

confidence: 99%

“…Maurer et al [22] used a fast X-ray system to noninvasively image bubble dynamics below and above horizontally oriented optical robes. The bed was operated at the minimum fluidization velocity while single bubbles were centrally injected into the bed.…”

Section: Rowe and Everettmentioning

confidence: 99%

Probe effects on the local gas holdup conditions in a fluidized bed

2016

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Fluidized beds are found in the energy production industry, and knowing their hydrodynamic conditions, such as local gas holdup or volumetric gas fraction, is important for effective operation. Local measurement probes are commonly used to measure local gas holdup. Although the probes are typically as small as possible to mitigate their influence on the local conditions, the invasive nature of this measurement technique has the potential to alter the fluidized bed behavior. This study used a noninvasive measurement technique, X-ray computed tomography (CT) imaging, to determine the local time-average gas holdup everywhere within a 10.2 cm diameter fluidized bed filled with 500-600 m glass beads in which simulated probes were inserted. Three different simulated probe tips (pointed, rounded, and flat) and two different orientations (horizontal and vertical) were investigated at four different bed heights and two different fluidization velocities. The results show increases in local time-average gas holdup when the probes were present, but the scale of the effects was dependent upon the height at which the probes were placed; the lower the probe within the fluidized bed, the larger the local effects. The shape of the probe tip did not show any differences in the local gas holdup. On the

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“…Due to their intrusive character, it cannot be excluded that the flow pattern gets disturbed by the sensor. To deal with this issue, the influence of intrusive probes on the flow structure in fluidized bed systems is investigated in Bai et al (2010) , Maurer et al (2015a) , Tebianian et al (2015Tebianian et al ( ,2016 , Whitemarsh et al (2016) . The possibility to design an optical sensor in a way that the flow structure is almost not influenced by the intrusive character of the sensor is shown in Maurer (2015) , Maurer et al (2015a) , and Whitemarsh et al (2016) .…”

Section: Introductionmentioning

confidence: 99%

“…idization state over the entire cross section and gather the bubble diameter, the hydraulic bubble diameter and the position of the center of gravity ( Maurer et al, 2015a ). However, these measurement methods cannot be easily implemented at industrial scale ( Liu et al, 2010 ).…”

Section: Introductionmentioning

confidence: 99%

Generation and evaluation of an artificial optical signal based on X-ray measurements for bubble characterization in fluidized beds with vertical internals

Schillinger

Schildhauer

Maurer

et al. 2018

International Journal of Multiphase Flow

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X-ray measurements on the influence of optical probes on gas–solid fluidized beds

Cited by 16 publications

References 15 publications

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

Overcoming the gamma‐ray computed tomography data processing pitfalls for bubble column equipped with vertical internal tubes

Probe effects on the local gas holdup conditions in a fluidized bed

Generation and evaluation of an artificial optical signal based on X-ray measurements for bubble characterization in fluidized beds with vertical internals

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