Biomass combustion in fixed-bed reactors generates significant emissions, including carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${SO}_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi mathvariant="italic">SO</mi> </mrow> <mi>x</mi> </msub> </math></EquationSource> </InlineEquation>), and carbon dioxide (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">${CO}_{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi mathvariant="italic">CO</mi> </mrow> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>), which contribute to air pollution and climate change. Conventional combustion methods struggle to balance combustion efficiency with emissions control, often resulting in pollutant levels exceeding permissible exposure limits for safe domestic and industrial applications. This study investigates the potential of oxy-fuel combustion as a strategy to mitigate these emissions while improving combustion efficiency in carbonized rice husk briquettes. Combustion experiments were conducted in a fixed-bed reactor, with emissions of NOx, CO, CO2 and SOx measured using a Testo 350 analyzer. A response surface methodology (RSM) was employed to assess the statistical significance of the measured emissions and to provide a visual representation of their relationship with oxy-fuel mass flux (0.1–0.15 kg/m2s), oxygen-to-carbon dioxide ratio (20–40%), and binder content (3.5–9.7 wt.%). The results indicate that NOx emissions peak near stoichiometric conditions and decrease in fuel-rich and fuel-lean environments, while CO emissions are highest under fuel-rich conditions due to incomplete combustion but decline with improved combustion efficiency. CO2 emissions increase with mass flux, peaking at stoichiometric conditions, while SOx emissions depend on sulfur content and combustion conditions, rising near stoichiometric levels. A comparison with regulatory limits suggests that NOx and SOx emissions are within permissible industrial limits but may require additional control measures for domestic use. Furthermore, the study compares emissions with those reported in previous literature, demonstrating that oxy-fuel combustion reduces NOx emissions more effectively than conventional air combustion. These findings confirm that oxy-fuel combustion of rice husk briquettes can optimize biomass energy utilization while maintaining emissions within acceptable limits.

Effect of oxy-fuel environment on emission characteristics of carbonized rice husk briquettes in fixed bed reactor

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发表日期：

2025年9月24日

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J. Akema,
R. Kiplimo,
P. O. Oketch,
J. K. Tanui

摘要

Biomass combustion in fixed-bed reactors generates significant emissions, including carbon monoxide (CO), nitrogen oxides (NO_x), sulfur oxides ( ${SO}_{x}$ ${SO}_{x}$ ), and carbon dioxide ( ${CO}_{2}$ ${CO}_{2}$ ), which contribute to air pollution and climate change. Conventional combustion methods struggle to balance combustion efficiency with emissions control, often resulting in pollutant levels exceeding permissible exposure limits for safe domestic and industrial applications. This study investigates the potential of oxy-fuel combustion as a strategy to mitigate these emissions while improving combustion efficiency in carbonized rice husk briquettes. Combustion experiments were conducted in a fixed-bed reactor, with emissions of NO_x, CO, CO₂ and SO_x measured using a Testo 350 analyzer. A response surface methodology (RSM) was employed to assess the statistical significance of the measured emissions and to provide a visual representation of their relationship with oxy-fuel mass flux (0.1–0.15 kg/m²s), oxygen-to-carbon dioxide ratio (20–40%), and binder content (3.5–9.7 wt.%). The results indicate that NO_x emissions peak near stoichiometric conditions and decrease in fuel-rich and fuel-lean environments, while CO emissions are highest under fuel-rich conditions due to incomplete combustion but decline with improved combustion efficiency. CO₂ emissions increase with mass flux, peaking at stoichiometric conditions, while SO_x emissions depend on sulfur content and combustion conditions, rising near stoichiometric levels. A comparison with regulatory limits suggests that NO_x and SO_x emissions are within permissible industrial limits but may require additional control measures for domestic use. Furthermore, the study compares emissions with those reported in previous literature, demonstrating that oxy-fuel combustion reduces NO_x emissions more effectively than conventional air combustion. These findings confirm that oxy-fuel combustion of rice husk briquettes can optimize biomass energy utilization while maintaining emissions within acceptable limits.