C/CO_(2)摩尔比对CO_(2)气氛流态化预热活化半焦特性的影响

Effect of C/CO_(2)molar ratio on CO_(2)atmosphere fluidized preheating activation characteristics of semi-char

我国工业领域涉及的行业多,碳减排压力大。富氧燃烧是燃烧中碳捕集的核心工艺,将流态化富氧预热活化与工业窑炉富氧燃烧过程耦合是拓宽燃料适应性、实现工业领域燃烧中碳捕集的新途径。利用小型流化床连续给料实验系统,在1050℃、CO_(2)流化速度为0.17 m/s条件下,通过调整给料速度,考察C/CO_(2)摩尔比(CC比)对半焦原料(RC)流态化预热活化的影响,分析煤气组分及低位热值,计算CO_(2)还原率,表征粗颗粒活化半焦(LC)和细颗粒活化半焦(FC)的比表面积、孔隙结构和碳架结构,并利用高温管式炉热天平实验系统评价了RC和FC在1300℃条件下的反应活性。结果表明:采用流态化预热活化技术实现了CO_(2)的资源化利用,制备出富CO煤气,CC比由1增至4时,煤气中CO+H_(2)体积分数由69.24%增至79.08%,CO体积分数最高为68.96%,CO_(2)体积分数由29.48%降至20.13%,CO_(2)还原率由50.37%提升至57.56%,煤气低位热值由8.69 MJ/m^(3)增至9.83 MJ/m^(3),是参考文献所述工程产出煤气低位热值的1.55~1.88倍,有利于窑炉系统的着火及稳定燃烧。随CC比增加,FC和LC的比表面积先增加后减小,FC和LC的最高比表面积分别为291.21 m^(2)/g和477.15 m^(2)/g,分别为半焦原料的48倍和78倍;FC和LC具有丰富的微孔结构,且石墨化程度比RC降低、活性点位增加;FC和LC的微孔面积占比表面积的54.93%~68.42%;相比较而言,LC具有更高的比表面积和增量孔容积,主要是由于LC在反应器内的停留时间较长,促进了孔隙的发展,形成了大量微孔。不同CC比条件下所得FC的反应活性指数R0.5、质量平均反应速率均高于RC,表明FC具有较高的反应活性,可预测在高温气固活化态热燃料燃烧过程中,FC将实现高效转化。提出了碳基燃料流态化富氧预热活化-高温气固活化态热燃料富氧燃烧的新思路,获得了CC比对CO_(2)气氛流态化预热活化半焦特性的影响规律,揭示了CO_(2)作为碳和氧载体的积极作用,研究结果为流态化预热活化技术在工业窑炉富氧燃烧行业的应用提供了数据支持。

There are many fields involved in China’s industry,and the carbon reduction is urgent.Oxy-fuel combustion is the core process of carbon capture in combustion.Coupling fluidized preheating activation with industrial kilns oxy-fuel combustion is a new way to expand fuel adaptability and achieve carbon capture during combustion.This study uses a small-scale fluidized bed continuous feeding experimental platform to investigate the effect of C/CO_(2)molar ratio(CC ratio)on the fluidized preheating activation characteristics of raw semi-char(RC)by adjusting the feeding rate at a temperat-ure of 1050℃and CO_(2)fluidized rate of 0.17 m/s.The gas composition and low calorific value are analyzed,and the CO_(2)reduction ratio is calculated.The specific surface area,pore structure and carbon frame structure of fine particle activated semi-char(FC)and large particle activated semi-char(LC)are characterized.The reactivity of RC and FC is evaluated using a high-temperature tubular furnace thermobalance at 1300℃.The results show that the use of fluidized preheating activation technology has achieved the resource utilization of CO_(2)and produced rich-CO fuel gas.When the CC ratio in-creases from 1 to 4,the CO+H_(2)volume fraction in the gas increases from 69.24%to 79.08%,and the highest CO volume fraction of 68.96%,the CO_(2)volume fraction decreases from 29.48%to 20.13%,and the CO_(2)reduction rate increases from 50.37%to 57.56%.The low calorific value of fuel gas increases from 8.69 MJ/m^(3)to 9.83 MJ/m^(3),which is 1.55-1.88 times higher than the low calorific value of the fuel gas produced by the project as described in the reference.The produced fuel gas in this study is conducive to the ignition and stable combustion of the kiln system.As the CC ratio increases,the specific surface area of FC and LC first increases and then decreases.The highest specific surface areas of FC and LC are 291.21 m^(2)/g and 477.15 m^(2)/g,respectively,which are 48 and 78 times higher than the RC.FC and LC have rich micropor-ous structures,and the degree of graphitization decreases while the active sites increase.The microporous area accounts for 54.93%-68.42%of the specific surface area.In comparison,LC has a higher specific surface area and incremental pore volume mainly due to its longer residence time in the reactor,which promotes the development of pores and forms a large number of micropores.The reactivity index R0.5 and the average mass reaction rate of FC obtained under different CC ratios are higher than the RC,which reveals the good reaction characteristics of FC.It can be predicted that FC will achieve an efficient conversion during the high-temperature gas-solid activated thermal fuel combustion process.This research proposes a new route of fluidized oxy-fuel preheating activation for carbon-based fuels coupled with oxy-fuel combustion of gas-solid activated fuel with high-temperature.The influence of CC ratio on the characteristics of semi-char at CO_(2)at-mosphere with fluidized preheating activation technology is obtained.The positive role of CO_(2)as a carbon and oxygen carrier is revealed.The research results provide a data support for the application of fluidized preheating activation techno-logy in the industrial kiln oxy-fuel combustion industry.