石油焦燃烧过程中影响多环芳烃生成的因素分析

Influencing Factors of Polycyclic Aromatic Hydrocarbons Formation during Petroleum Coke Combustion

利用管式炉层燃方式研究了燃烧温度、气氛等不同条件对高硫石油焦燃烧过程中多环芳烃(PAHs)生成及其分布的影响,探讨了石油焦特性对生成PAHs种类的影响。研究结果表明,石油焦在空气中燃烧PAHs的生成总量随着实验温度(600～900℃)的升高先增加后降低,在700℃时达到最大值。石油焦在氮气中热解时,PAHs生成规律也是随温度升高先增加后降低,在800℃时达到最大释放值。不同反应温度和气氛下释放的PAHs均以低环芳烃为主。相同燃烧条件下,随着石油焦挥发分质量分数的增加,PAHs生成量总体呈现增加趋势;石油焦中硫元素质量分数的增加会使PAHs生成量减少;随着石油焦中碳元素质量分数的增加,PAHs生成量呈现先降低再增加的变化趋势。

Petroleum coke consumption is an important contributor to energy production in China and is regarded as one of the most important sources of air pollutants that have considerable impacts on human health.Particularly,hazardous organic pollutants such as polycyclic aromatic hydrocarbons(PAHs)generated during combustion process of petroleum coke are highly genotoxic,mutagenic and carcinogenic.The effects of combustion conditions on the formation of PAHs in petroleum coke combustion process were studied in a tube furnace by controlling combustion temperature and atmosphere.The influence of the composition of petroleum coke on the formation of PAHs was further investigated by burning six types of petroleum coke at 800℃.The experimental results show that,the release amount of PAHs increases up to a maximum value at 700℃as the combustion temperature(600-900℃)is increased in air,while above 700℃,the intensity of oxidation and thermal degradation cause a decrease of the PAHs emission.Similarly,the release of PAHs is initially increased and then decreased with the increasing of pyrolysis temperature in N 2,and the maximum release is reached at 800℃.2-ring and 3-ring PAHs are the main species at different temperatures and atmosphere conditions.PAHs are generated not only by thermal degradation of petroleum coke structure,but also by the combination of different small molecular free radicals with each other.The higher the volatile substance of petroleum coke is,the more small molecular free radicals are produced during the combustion.Therefore,the release of PAHs increases with of the amount of volatile substance during the petroleum coke combustion.Moreover,the release of PAHs decreases with mass fraction of sulfur element in petroleum coke.The release of PAHs decreases first and then increases with the mass fraction of carbon element in petroleum coke during the combustion.