Air Distributor Designs for Fluidized Bed Combustors: A Review

Abstract

Fluidized bed combustion (FBC) has been recognized as one of the suitable technologies for converting a wide variety of biomass fuels into energy. One of the key factors affecting the successful operation of fluidized bed combustion is its distributor plate design. Therefore, the main purpose of this article is to provide a critical overview of the published studies that are relevant to the characteristics of different fluidized bed air distributor designs. The review of available works display that the type of distributor design significantly affects the operation of the fluidized bed i.e., performance characteristics, fluidization quality, air flow dynamics, solid pattern and mixing caused by the direction of air flow through the distributors. Overall it is observed that high pressure drop across the distributor is one of the major draw backs of the current distributor designs. However, fluidization was stable in a fluidized bed operated at a low perforation ratio distributor due to the pressure drop across the distributor, adequate to provide uniform gas distribution. The swirling motion produced by the inclined injection of gas promotes lateral dispersion and significantly improves fluidization quality. Lastly, the research gaps are highlighted for future improvement consideration on the development of efficient distributor designs.

Image velocimetry and statistical analysis of a mesh-coupled axial blade distributor for mass transfer in a swirling bed

“…On comparison of the optimized values of air velocity at different blade angles, the highest bed velocity was achieved at an angle of 60 • . For this blade angle, the frictional effects on bed dynamics were more pronounced near the bed column wall as compared to the central cylinder (Shukrie et al, 2016). The centrifugal force led the tracer particles to follow the tangential paths.…”

Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

“…Superficial gas velocity, minimum fluidization velocity, gas-particle dispersion enhancement, bubble size and movement behavior, gas-solid contacting pattern, void fraction, residence time distribution of gas and solids, gas-solid movement, and mixing pattern are some of the aspects affected by the distributor plate design. Many distributor designs have been tested, and their impact on the hydrodynamics of the fluidized bed has been reported with various parameter variations (Shukrie et al, 2016). Many types of distributor designs are available in the literature, based on the direction of air entering the column, i.e., normal direction, a lateral direction, and inclined direction.…”

“…Normal direction includes sparger, perforated plates, and sintered metal. Lateral direction comprises bubble caps, multi-vortex, and nozzles, while inclined direction distributors are classified into annular and helical nozzles (Shukrie et al, 2016). Many researchers and scientists have studied the types mentioned above of distributors to investigate the effect of mixing and pressure drop characteristics of the various fluidized bed phenomena.…”

Air Distributor Pressure Drop Analysis in a Circulating Fluidized‐Bed Boiler for Non‐reference Operating Conditions

“…These parameters directly depend on the gas‐solid mixture flow structure in the boiler circulation contour, which over the last several decades has been the subject of intense studies by many researchers . Particularly important in this respect is a grid zone, which is a key element determining the quality of fluidization and conversion of reagents . As has been reported by Yates et al., as much as 50 % of this conversion occurs in the shallow area of a dense air distributor deciding not only about the level of exhaust gases emission but also the efficiency of heat and mass transfer processes , .…”