Abstract
Fluidized bed gasification has proven to be an appropriate technique for converting various biomass feedstocks into helpful energy. Air distributor plate design is one of the critical factors affecting the thermochemical conversion performance of fluidized bed gasifiers. The present study is proposed to investigate the mixing pattern and pressure drop across different configurations of air distributors using a two-fluid model (TFM) of finite volume method-based solver ANSYS FLUENT. The pressure drop across the bed and mixing pattern have been investigated through qualitative and quantitative analysis of CFD results using three diverse distributor plate designs: perforated plate, 90° slotted plate, and 45° swirling slotted plate. The pressure drop by employing the perforated distributor plate reveals the highest pressure drop due to the smallest open area ratio. However, the pressure drop in the case of 90° slotted plate is found to be 7% and 4% lesser than perforated and 45° slotted plate respectively due to a smaller velocity head developed through the wider open area of the straight slotted plates. The distributor design configuration having a 45° slotted plate exhibits considerable pressure drop compared to the 90° slotted plate due to the longer path length of the slot. Numerical pressure drop results across the bed with different types of distributor plates prove reasonable agreement with the experimental results available in the literature. Mixing behavior in perforated distributor plates exhibits lower portion solid volume fraction of around 0.58. However, it falls rapidly as go up the riser (7.7% of column height); 90° slotted plate shows bottom region solid volume fraction of around 0.5. In addition, it exhibits an even broader range of sand volume fraction and column height (13.46% of column height). Finally, the 45° distributor plate reveals the highest range of volume fraction through the riser height (17.3% of column height), indicating the better mixing characteristics of the fluidized zone.
Highlights
Fluidized bed combustion (FBC) has been renowned as a suitable technology for converting a wide variety of feed, i.e., coal and biomass, into energy due to its superior heat and mass transfer characteristics
The results have revealed that if a smaller aperture was applied for the same open area ratio (OAR), fluidization quality was enhanced
Pressure drop predicted by Computational fluid dynamics (CFD) simulation was compared with experimental findings using different plate designs
Summary
Fluidized bed combustion (FBC) has been renowned as a suitable technology for converting a wide variety of feed, i.e., coal and biomass, into energy due to its superior heat and mass transfer characteristics. A fluidized bed combustor usually consists of the reaction zone, air distributor plate, combustion chamber for flue gases to preheat the bed material, cyclone separator, and fuel inlet device. When the air velocity reaches a particular value on which its drag force balances the bed particles’ weight, the bed is fluidized. The velocity at this specific point is called the minimum fluidization velocity (Rao and Bheemarasetti, 2001). Many designs and operating parameters influence the performance of fluidized bed reactor/gasifier, including the type of feedstocks, residence time of gas and fuel particles within the reaction zone, superficial gas velocity, minimum fluidization velocity, particle size distribution, operating and maximum temperature, operating pressure, equivalence ratio (ER), appropriate mixing/contacting of gas-solid phases, pressure drop across the air distributor and throughout the bed, bed height, and temperature and heat transfer coefficients (Armstrong et al, 2011; Baruah and Baruah, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
