engleski

Numerical investigation of co-firing biomass under oxy-MILD combustion

Oxy-fuel combustion is an attractive technology for the mitigation of CO2 emission from utility boiler. Nowadays, negative CO2 emission concept attracts increasing concern. Biomass is considered to be CO2-neutral. In this work, co- firing of biomass and coal was applied to achieve below-zero CO2 emission. MILD (moderate and intense low-oxygen dilution) combustion, which has high thermal efficiency and the advantage of NOx reduction, has become a hot point in recent years. In this paper, FLUENT 17.0 was used to simulate the co-firing of coal (Guasare coal) and biomass (olive waste) under traditional and oxy-fuel conditions respectively. EDC model with J-L four-step reaction was adopted to consider the turbulent chemistry interaction behavior. First, the model validation was conducted in the IFRF furnace NO.1 under traditional condition, and the results fitted well with experiments. Then combined with the characteristics of oxy-MILD combustion and co-firing biomass, the further research was carried out under the conditions of 10%, 20% and 30% biomass fraction respectively. The effect of working conditions on temperature distribution, rate of entrainment, burnout rate as well as NOx emission were discussed. Results show that for MILD case, oxy-combustion and biomass co-firing generate a more moderate temperature field and wall heat flux. MILD combustion in traditional air-mode has a higher peak temperature, reaching 1788 K. While under oxy-fuel conditions, it has a milder temperature field with a lower peak temperature, only 1702 K. The peak temperatures at 10%, 20%, and 30% biomass mixing ratios are 1690K, 1683 K, 1674 K respectively. The NOx emission is also significantly reduced when oxy-combustion and biomass co-firing are employed in MILD case.

MILD combustion ; oxy-fuel combustion ; co-firing biomass ; NOx emission

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