Chapter 3
A Structuring Regime to Control
Bubbling Beds
This chapter discusses the characteristics and regularity of structured flows in quasi2D pulsed fluidised beds. A model-based pattern recognition approach is proposed
and implemented to compute the degree-of-order of patterned flows, considering
cross-correlation of bubbles. Impacts of flow conditions and static bed depths on the
flow patterns are investigated and associated with bubble characteristics and level
of structuring. Guided by the degree-of-order, the full operating regime for pulsed
fluidisation in quasi-2D beds of Geldart B particle is divided into two areas: unstructured and structured fluidisation regimes. Flow patterns in the structured regime
become predictable and exhibit highly precise control over bubbles, regulating both
solid mixing and particle-bubble contact time. Nevertheless, the level of structuring
also varies significantly with the applied oscillatory flows. The controllability over
size and separation distribution of bubbles is strongly proportional to the level of
structuring. In the unstructured regimes, bubble motions remain largely chaotic, and
size and spatial distribution of bubbles are in resemblance of those in fluidised beds
operated under a constant flow rate.
3.1 Introduction
Gas-solid bubbling fluidised beds provide good mixing and transport rates for a
broad range of gas-solid operations, such as gasification, drying and combustion.
The overall performance of a bubbling bed relies significantly on the macroscopic
flow of bubbles. In typical bubbling beds, bubble motion is often irregular, and
solids circulate in complex, scale-dependent patterns. For such complicated hydrodynamics, bubble growth, interphase contact time, and transport rate are troublesome
to predict and control. Without accurate manipulation and control of these critical
design parameters, operation and scale-up remain as largely empirical exercises.
Allowing for more degrees of freedom at the design stage is a promising way to
structure gas-solid flows. One may overcome some of the disadvantages associated
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_3
61
A Structuring Regime to Control
Bubbling Beds
This chapter discusses the characteristics and regularity of structured flows in quasi2D pulsed fluidised beds. A model-based pattern recognition approach is proposed
and implemented to compute the degree-of-order of patterned flows, considering
cross-correlation of bubbles. Impacts of flow conditions and static bed depths on the
flow patterns are investigated and associated with bubble characteristics and level
of structuring. Guided by the degree-of-order, the full operating regime for pulsed
fluidisation in quasi-2D beds of Geldart B particle is divided into two areas: unstructured and structured fluidisation regimes. Flow patterns in the structured regime
become predictable and exhibit highly precise control over bubbles, regulating both
solid mixing and particle-bubble contact time. Nevertheless, the level of structuring
also varies significantly with the applied oscillatory flows. The controllability over
size and separation distribution of bubbles is strongly proportional to the level of
structuring. In the unstructured regimes, bubble motions remain largely chaotic, and
size and spatial distribution of bubbles are in resemblance of those in fluidised beds
operated under a constant flow rate.
3.1 Introduction
Gas-solid bubbling fluidised beds provide good mixing and transport rates for a
broad range of gas-solid operations, such as gasification, drying and combustion.
The overall performance of a bubbling bed relies significantly on the macroscopic
flow of bubbles. In typical bubbling beds, bubble motion is often irregular, and
solids circulate in complex, scale-dependent patterns. For such complicated hydrodynamics, bubble growth, interphase contact time, and transport rate are troublesome
to predict and control. Without accurate manipulation and control of these critical
design parameters, operation and scale-up remain as largely empirical exercises.
Allowing for more degrees of freedom at the design stage is a promising way to
structure gas-solid flows. One may overcome some of the disadvantages associated
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_3
61