基于PLIF检测的生物质挥发分燃烧多环芳烃生成特性

Generation Characteristics of Polycyclic Aromatic Hydrocarbons During Biomass Volatile Combustion Based on PLIF Detection

针对生物质挥发分燃烧过程,采用平面激光诱导荧光技术对火焰中1~2环、3~5环多环芳烃(PAHs)的二维分布进行了研究,分析对比了升温速率(1 000 K/min和1 500 K/min)、O_(2)体积分数(21%~50%)等关键因素对木屑、核桃壳颗粒挥发分燃烧过程中PAHs生成与转化特性的影响.结果表明:提高升温速率,生物质挥发分燃烧过程中1~2环和3~5环PAHs信号强度峰值显著增加,同时升温速率提高促进了1~2环和3~5环PAHs向小分子碳氢化合物转化;1~2环和3~5环PAHs信号强度峰值随O_(2)体积分数提高而增加,这是由于增加的O_(2)体积分数促进了PAHs的释放.但是由于O_(2)体积分数的提高同样增加了OH自由基浓度,导致PAHs消耗加快,使得1~2环和3~5环PAHs信号强度持续时间随O_(2)体积分数提高先增加后减少.木屑和核桃壳颗粒挥发分燃烧过程中生成的3~5环PAHs信号强度峰值和信号强度持续时间较为一致,但木屑颗粒生成的1~2环PAHs信号强度峰值更高,这可能是由于木屑颗粒脂肪烃和芳香环含量更高,同时燃烧过程中生成的OH自由基较多,有利于多环PAHs向1~2环PAHs的转化.

The two-dimensional distribution of 1—2 ring and 3—5 ring polycyclic aromatic hydrocar-the volatile combustion of biomass was studied by planar laser-induced fluorescence.The ef-fects of temperature rise rate(1000 and 1500 K/min),O_(2) concentration(21%—50%)and other key factors on the formation and conversion characteristics of PAHs during the volatile combustion of sawdust and walnut shell parti-cles were analyzed and compared.The results showed that with the increase of heating rate,the peak value of PAHs signal intensity of 1—2 ring and 3—5 ring increased significantly during the biomass volatile combustion.Meanwhile,the increase of heating rate promoted the conversion of 1—2 ring and 3—5 ring PAHs into small mo-lecular hydrocarbons,leading to more rapid conversion and consumption of PAHs.The peak signal intensity of 1—2 ring and 3—5 ring PAHs increased with the increase of O_(2) concentration,which was due to the release of PAHs promoted by the increased O_(2) concentration.However,the increase of O_(2) concentration also increased the concentration of OH radical,which led to the consumption of PAHs.Furthermore,with the increase of O_(2) con-centration,the duration of signal intensity of 1—2 ring and 3—5 ring PAHs increased first and then decreased.The 3—5 ring PAHs signal intensity peak and the duration of the signal intensity were consistent for wood chips and walnut shell particles,but the 1—2 ring PAHs signal intensity peak of wood chips was higher,which was likely due to the higher content of aliphatic hydrocarbons and aromatic rings in wood chips and the generation of more OH radicals in the combustion process.This is conducive to the conversion of multi-ring PAHs into 1—2 ring PAHs.