O_(2)/CO_(2)条件下半焦-生物质的混燃特性及动力学分析

Co-combustion characteristics and kinetics analysis of semi-coke and biomass in O_(2)/CO_(2)atmosphere

半焦与生物质在O_(2)/CO_(2)条件下混燃是实现碳基燃料清洁高效利用和碳减排的重要途径,准确掌握其混燃特性及动力学特性尤为关键。通过热重分析和正交实验研究了半焦与三种生物质(稻壳、松木、核桃壳)在O_(2)/N_(2)和N_(2)/CO_(2)气氛下混燃的燃烧特性、交互作用及反应动力学。结果表明:O_(2)/N_(2)气氛下掺混生物质可改善半焦的着火和燃尽特性,O_(2)/CO_(2)气氛下掺混生物质可改善半焦的着火特性,但会延迟半焦的燃尽。半焦和生物质在主燃区存在明显的交互作用,该作用显著提高了混燃反应性和燃烧强度,降低了着火活化能。生物质掺混比增大,燃烧特性指数提高,混合燃料低温区的活化能E_(1)和高温区的活化能E_(2)均逐渐降低;掺混生物质为松木时,混燃特性最好,掺混生物质为稻壳时,混燃特性次之,掺混生物质为核桃壳时,混燃特性再次之。与O_(2)/N_(2)气氛相比,O_(2)/CO_(2)气氛下的综合燃烧特性指数降低,E_(1)和E_(2)都提高,提高O_(2)/CO_(2)气氛中的O_(2)体积分数可小幅改善燃烧特性。燃烧气氛对燃烧特性和活化能的影响最显著,生物质掺混比的影响次之,掺混生物质的种类的影响最小,但若只考虑O_(2)/CO_(2)气氛的O_(2)体积分数变化,燃烧气氛对混燃特性的影响很小。

Co-combustion of semi-coke and biomass with oxy-fuel combustion technology is a significant method for clean and high-efficiency utilization of carbon-based fuel and CO_(2)emission reduction.It is particularly crucial to clarify the co-combustion characteristics and kinetics properties of semi-coke and biomass.Thermogravimetric analysis and orthogonal experiments were carried out to investigate the co-combustion characteristics,interactions and reaction kinetics of semi-coke(SC)and three types of biomass(rice husks,pine wood,walnut shells,denoted by dk,sm,htk respectively)in the atmospheres of O_(2)/N_(2) and O_(2)/CO_(2).The results show that in O_(2)/N_(2) atmosphere,the additive of biomass can improve both the ignition and burnout characteristics of semi-coke.However,in O_(2)/CO_(2)atmosphere,blending of biomass can enhance the ignition characteristics,but delay the burnout of semi-coke.There is a significant interaction between semi-coke and biomass in the main combustion zone,which plays a crucial role in enhancing the co-combustion reactivity and reducing the activation energy of the blends.As the blending ratio of biomass increases,the combustion characteristic index improves,and activation energies in both low-temperature(E_(1))and high-temperature zones(E_(2))gradually decrease.The order of blends based on combustion characteristics from good to second is SC-sm,SC-dk,SC-htk.Compared to those in O_(2)/N_(2) atmosphere,the comprehensive combustion characteristic index decreases in O_(2)/CO_(2)atmosphere with E_(1) and E_(2) increasing.A slight improvement in combustion characteristic index can be achieved by increasing O_(2)volume fraction in O_(2)/CO_(2)atmosphere also leading to the reduction of activation energy.The combustion atmosphere plays the most significant role in determining the co-combustion characteristics,followed by the blending ratio of biomass,while the type of blended biomass has the least impact.However,if only considering the O_(2)volume fraction variation in the O_(2)/CO_(2)atmosphere,the influence of the combustion atmosphere appears to be relatively weak.