Abstract:

Biogas is a kind of gas transformed by biomass fermentation. At present, the biogas burners are mainly diffused burners and atmospheric burners, which generally have low thermal strength and are easy to blow out. Based on fully premixed water-cooled combustion technology, a kind of water-cooled biogas burner was designed. Then, the effects of CO₂ content, excess air coefficient, heat load and cooling water temperature in simulated biogas on combustion characteristics of burners were explored. The results showed that the designed burner had good adaptability for biogas with methane concentration from 55%—80%. As the CO₂ content increased, the combustion temperature decreased, the NO _x and CO content at the outlet decreased, but the flame length increased. As the excess air coefficient decreased, the combustion heat intensity improved, however, the NO _x and CO content in the flue gas increased. The result showed that the heat load of burner had a great influence on the maximum combustion temperature. The burner could still operate stably under the minimum load of 35%.

Key words: water cooled, fully premixed, low NO _x, combustion characteristics

摘要：

沼气是由生物质发酵转化而来的燃气。目前，常见沼气燃烧器主要是扩散式和大气式燃烧器，普遍存在热强度较低、易吹熄等问题。本文基于全预混水冷燃烧技术发明了一种可更换燃烧头的全预混低氮水冷沼气燃烧器，探究沼气中CO₂含量、过量空气系数、热负荷和水冷温度对燃烧器燃烧特性的影响，结果表明所设计的燃烧器对于甲烷浓度在55%~80%的沼气有良好的适应性。随着CO₂含量的增加，燃烧温度降低，出口NO _x 和CO含量降低，但是火焰长度增长；随着过量空气系数降低，燃烧热强度得到改善，但是烟气中NO _x 和CO含量增加；燃烧器热负荷对燃烧温度有较大影响，研究结果表明燃烧器在35%低负荷工况下仍可以稳定运行。

关键词: 水冷, 全预混, 低氮, 燃烧特性