下吸式生物质气化炉热力学平衡模型研究

建立下吸式生物质气化炉热力学平衡模型,该模型包括焦炭、焦油和气体,并用已公布的实验数据对模型进行验证,均方根（RMS）在1.304~3.814之间,结果表明该模型的预测值与实验数据吻合较好,可认为模型可靠。然后模拟棉秆在下吸式生物质气化炉中以空气和富氧气体2种气化氛围下,不同操作参数(当量比、预热温度和气化炉反应温度)下对棉秆气化的气体组分、热值和产率的影响。模拟结果表明：富氧气体为气化剂时,当量比从0.20增至0.35时,气体中N₂含量比空气显著下降,达10%以上,同时发现能提高气体中H₂和CO的含量和热值,热值比空气提高约20%。预热温度对气化成分变化影响有限,随预热温度从30 ℃变化到130 ℃,气体的平均热值从空气的5.2 MJ/m³提高到富氧气体的7.0 MJ/m³。随气化炉内反应温度从750 ℃升至1250 ℃,空气和富氧气体2种气化剂下的H₂和CO分别从20.94%、26.84%和21.77%、28.67%下降到4.06%、9.12%和10.49%、21.60%,导致气体的热值降低。

STUDY ON THERMODYNAMIC EQUILIBRIUM MODEL OF DOWNDRAFT BIOMASS GASIFIER

The thermodynamic equilibrium model of downdraft biomass gasifier was established, which includes coke, tar and gas. The model was verified with published experimental data, and its root mean square（RMS） was between 1.304 and 3.814. The results show that the predicted value of the model is in good agreement with the experimental data, and the model could be considered reliable. Then, the effects of different operating parameters （equivalent ratio, preheating temperature and reaction temperature of gasifier） on gas composition, calorific value and yield of cotton stalk gasification in two gasification atmospheres of cotton stalk downdraft biomass gasifier with air and oxygen-rich gas were simulated. The simulation results show that when the oxygen-enriched gas is used as the gasification agent, with the equivalent ratio from 0.20 to 0.35, the N₂ content in the gas is significantly lower than that in the air, decreasing more than 10%. While it was found that the content of H₂ and CO and the calorific value in the gas can be increased, and the calorific value is about 20% higher than that with air. The preheating temperature had a limited effect on the change of gasification composition. As the preheating temperature changed from 30 ℃ to 130 ℃, the average calorific value of the gas increased from 5.2 MJ/m³ of air to 7.0 MJ/m³ of oxygen-enriched gas. As the reaction temperature of the gasifier increased from 750 ℃ to 1250 ℃, H₂ and CO under the two gasification agents of air and oxygen-enriched gas decreased from 20.94%、26.84% and 21.77%、28.67% to 4.06%、9.12% and 10.49%、21.60%,leading to a decrease in the calorific value of the gas.