Progress Variables to Resolve the Steady State Period in a Batch-Type Fixed Bed Combustor

Junejo, Awais; Al-Abdeli, Yasir M.; İkhlaq, Muhammad

doi:10.1080/00102202.2022.2150969

Cited by 2 publications

(1 citation statement)

References 43 publications

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“…9 The role of secondary air in biomass combustion becomes very important due to high volatile matter content of biomass, which requires a further supply of air at the second stage above the fuel bed. 10 Whilst a number of work have already been published on biomass combustion in a fixed bed on the current configuration recently, 9,[11][12][13] there remains ambiguity on the exact flow dynamics induced through the use of secondary air.…”

Section: Introductionmentioning

confidence: 99%

Secondary air induced flow structures and mixing in a fixed bed combustor

Junejo

Chapela

Porteiro

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part A:

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Air staging features widely in biomass combustion from small space heaters to industrial-scale moving grate systems. Whilst studies have been conducted into the impact of air staging on emissions and combustion performance, there is little or no insight into the exact flow dynamic and physical mechanisms that are induced by secondary air under such conditions. This paper uses experimental data to validate numerical predictions before investigating the flow field structures and mixing characteristics in a fixed bed air staged combustor. The study utilizes Constant Temperature Anemometry (CTA) experiments to establish boundary conditions for a lab-scale fixed bed combustor. Results from numerical simulations obtained using [Formula: see text] l- 𝜔 model were in good agreement with experimental data. Conditions tested cover five different secondary to total air ratios (Qs/Qt) and two different locations of secondary air injection. Results show that at Qs/Qt = 0.50, 0.25 and 0.18 one strong recirculation zone is induced upstream of the secondary air injection and one downstream. Varying the point of injection of secondary air from h/D = 0.64 to h/D = 0.40 also had an effect on the size of the upstream recirculation zone. Qs/Qt = 0.50 had the highest values of mixing index among all spatially located planes at the upstream of secondary air injection. The overall findings shed light on the possible flow interactions between secondary air and the top layers of fuel bed. They also highlight the significance of secondary air on inducing both upstream and downstream flow structures.

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Section: Introductionmentioning

confidence: 99%

Secondary air induced flow structures and mixing in a fixed bed combustor

Junejo

Chapela

Porteiro

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part A:

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Role of Air Staging in a Batch-Type Fixed Bed Biomass Combustor under Constant Primary Air

Junejo,

Al-Abdeli,

Porteiro

2023

J. Therm. Sci.

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Staged combustion of biomass is the most suitable thermo-chemical conversion for achieving lower gaseous emissions and higher fuel conversion rates. In a staged fixed bed combustion of biomass, combustion air is supplied in two stages. In the first stage, primary air is provided below the fuel, whereas in the later stage, secondary air is supplied in the freeboard region. The available literature on the effects of air staging (secondary air location) at a constant primary air flow rate on combustion characteristics in a batch-type fixed bed combustor is limited and hence warrants further investigations. This study resolves the effect of air staging, by varying the location of secondary air in the freeboard at five secondary to total air ratios in a batch-type fixed bed combustor. Results are reported for the effects of these controlled parameters on fuel conversion rate, overall gaseous emissions (CO2, CO and NOx) and temperature distributions. The fuel used throughout was densified hardwood pellets.Results show that a primary freeboard length (distance between fuel bed top and secondary air injection) of 200 mm has higher fuel conversion rates and temperatures as well as lower CO emissions, at a secondary to total air ratio of 0.75 as compared to primary freeboard length of 300 mm. However, NOx emissions were found to be lower for a primary freeboard length of 300 mm as compared to 200 mm. An increase in secondary to total air ratio from 0.33 to 0.75 resulted in higher freeboard temperatures and lower CO as well as NOx emissions. The outcomes of this study will be helpful in the effective design of commercial scale biomass combustors for more efficient and environmentally friendly combustion.

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Progress Variables to Resolve the Steady State Period in a Batch-Type Fixed Bed Combustor

Cited by 2 publications

References 43 publications

Secondary air induced flow structures and mixing in a fixed bed combustor

Secondary air induced flow structures and mixing in a fixed bed combustor

Role of Air Staging in a Batch-Type Fixed Bed Biomass Combustor under Constant Primary Air

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