Local Distributions of Bubble Velocity and Interfacial Area in the Slender Particle-Containing Scrubbing–Cooling Chamber of an Entrained-Flow Gasifier

Abstract

Radial bubble velocities, chord lengths, and local gas holdups were measured by a dual-tip conductivity probe in a slender particle-containing scrubbing–cooling chamber. The annulus region of the bubbling bed was divided into three regions according to the radial distributions of bubble velocity, bubble size, and local gas holdup. Bubble velocity distributions were obtained by the kernel density estimation, and the relationships between mean bubble velocity and diameter were discussed. The interfacial area was calculated by the size distribution of total bubbles in the bed which was transformed from that of total bubbles touching the probe by an analytical transformation method. Effects of superficial gas velocity, fiber volume fraction, and aspect ratio on the distributions of bubble velocity and interfacial area were discussed. The experimental interfacial area values were in good agreement with the calculated ones obtained by the modified Besagni and Inzoli correlation.

Prediction of Bubble Size Distribution above the Bubble-Breaking Plate

“…Tap water as the liquid phase is added from the water inlet, and the initial static liquid-level height is 680 mm. To simplify the experimental operation, the air ( T = 293.15 K and P = 101.325 K Pa) under normal temperature and pressure is used to replace the crude gas, which is widely used in the study of fluid flow characteristics in the scrubbing–cooling chamber. , The air is compressed by the Roots blower, measured by the rotor flowmeter, and then enters through the top inlet and goes down the descending pipe into the liquid pool. The conductivity probe was fixed at 525 and 675 mm.…”

Time Domain, Frequency Domain, and Time–Frequency Domain Analysis of Axial Liquid Velocity Signals under the Influence of Internal Components

“…6 The bubblebreaking effect of the plates can be precisely characterized by the characteristic parameters of the fluids: higher gas holdup and smaller bubble size imply a good bubble-breaking effect, which contributes to the increase of the gas−liquid interfacial area and the heat−mass transfer efficiency. 5 Good interphase contact relies on bubble motion processes, and bubble-scale interbubble interactions and bubble swarm effects favor the generation of high-frequency fluctuations in fluid systems. 27 The increase in high-frequency fluctuations is conducive to interphase contact and heat-mass transfer.…”

“…Current studies of the complex fluid dynamics within scrubbing-cooling chambers are mainly based on the nature of the mean flow behavior, ,, and the analysis of time-series parameters can yield more meaningful information about the fluid dynamics characteristics. The instantaneous liquid velocity fluctuation signal, usually derived from the differential pressure signal utilizing an equation, reflects the turbulence and bubble dynamics of the bubble bed system and is a crucial time-series parameter for characterizing the dynamic behavior within the system. − The liquid velocity time-series data can be used to reveal more detailed information about the behavior of transient oscillations through time–frequency domain analysis .…”

“…Their serrated structure increases the probability of bubble breakage in the vicinity, reducing the bubble size, increasing the interphase contact area, and enhancing the interphase heat–mass transfer . The bubble-breaking effect of the plates can be precisely characterized by the characteristic parameters of the fluids: higher gas holdup and smaller bubble size imply a good bubble-breaking effect, which contributes to the increase of the gas–liquid interfacial area and the heat–mass transfer efficiency . Good interphase contact relies on bubble motion processes, and bubble-scale interbubble interactions and bubble swarm effects favor the generation of high-frequency fluctuations in fluid systems .…”