王淼, 卫俊涛, 张涛, 丁宽, 徐德良, 李斌, 王焦飞, 张红, 张书. 干/湿法烘焙预处理对稻壳燃烧反应特性的影响[J]. 农业工程学报, 2022, 38(6): 236-243. DOI: 10.11975/j.issn.1002-6819.2022.06.027
    引用本文: 王淼, 卫俊涛, 张涛, 丁宽, 徐德良, 李斌, 王焦飞, 张红, 张书. 干/湿法烘焙预处理对稻壳燃烧反应特性的影响[J]. 农业工程学报, 2022, 38(6): 236-243. DOI: 10.11975/j.issn.1002-6819.2022.06.027
    Wang Miao, Wei Juntao, Zhang Tao, Ding Kuan, Xu Deliang, Li Bin, Wang Jiaofei, Zhang Hong, Zhang Shu. Effects of dry/wet torrefaction pretreatments on the combustion reaction characteristics of rice husk[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 236-243. DOI: 10.11975/j.issn.1002-6819.2022.06.027
    Citation: Wang Miao, Wei Juntao, Zhang Tao, Ding Kuan, Xu Deliang, Li Bin, Wang Jiaofei, Zhang Hong, Zhang Shu. Effects of dry/wet torrefaction pretreatments on the combustion reaction characteristics of rice husk[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2022, 38(6): 236-243. DOI: 10.11975/j.issn.1002-6819.2022.06.027

    干/湿法烘焙预处理对稻壳燃烧反应特性的影响

    Effects of dry/wet torrefaction pretreatments on the combustion reaction characteristics of rice husk

    • 摘要: 烘焙是提高生物质燃料性质的重要技术手段,探究干/湿法烘焙对稻壳热解燃烧反应特性的影响具有重要意义。该研究利用固定床与高压反应釜对稻壳进行了不同温度下的干法烘焙和湿法烘焙(水热碳化)预处理,并利用热重分析仪对稻壳、稻壳烘焙炭和稻壳水热炭开展了非等温燃烧反应特性分析,并且利用Coats?Redfern法与三种常见的气-固反应机理模型对样品的燃烧反应特性进行了动力学分析。最后,该研究对干法与湿法烘焙两种预处理方式对稻壳的热解燃烧反应特性的影响进行了比较。结果表明两种预处理方式对稻壳的热解与燃烧反应参数存在影响:均导致热解反应性降低,干烘焙提高稻壳燃烧反应性,且反应性随着干烘焙温度的提高而升高。但湿烘焙使稻壳燃烧反应性略有降低。在相同的预处理温度条件下,稻壳烘焙炭较稻壳水热炭具有更高的热解起始失重温度、更低的热解最大失重速率及其对应温度和热解反应性。对于稻壳、稻壳烘焙炭及稻壳水热炭的热解燃烧反应性,模型O1较其他两个模型的线性回归指数更高。干/湿法烘焙使稻壳热解活化能升高,而湿烘焙使燃烧活化能降低。此外,两个阶段样品的指前因子(A)均随活化能的增大而增大,二者间存在明显的线性关系(R2均大于0.95),表明反应过程具有动力学补偿效应。

       

      Abstract: Abstract: Torrefaction has been one of the most significant steps to improve the biomass-based fuel quality. Rice husk has been widely used as typical agricultural biomass, due to a large annual yield in China. It is of great significance to explore the effect of dry/wet torrefaction on biomass pyrolysis and combustion reaction characteristics. In this study, the dry/wet torrefaction pretreatment of rice husk was carried out at various temperatures (200, 250, and 300 ℃; 180, 200, and 220 ℃) in the fixed bed and high-pressure reactor, where the starting temperature was room temperature, and the heating rate was 10 ℃/min. The proximate and ultimate analysis of samples was then conducted by the infrared fast coal quality analyzer (5E-MAG6700) and element analyzer (Vario MACRO), respectively. The Thermogravimetric Analyzer (TGA) was selected for the non-isothermal (room temperature to 800 ℃, 20 ℃/min) combustion of rice husk, rice husk torrefied char, and rice husk hydrochar. Moreover, the kinetics analysis of pyrolysis and combustion of samples were also conducted with the Coats?Redfern method and three common gas-solid reaction mechanism models (first-order model O1, phase boundary controlled reaction model R2 and R3). An evaluation was made on the effects of dry/wet torrefaction on the pyrolysis and combustion characteristics of rice husk. The results show that the dry/wet torrefaction increased the ash, fixed carbon, and carbon content of raw materials, while decreasing the volatile, hydrogen, and oxygen content. van Krevelen diagram displayed that the dry/wet torrefaction pretreatment behaved essentially like the process of dehydration and decarboxylation of raw materials, where the rice husk torrefied char at 300 ℃ (RT-300) was the most significant. Both pretreatments dominated the pyrolysis and combustion reaction parameters of rice husk, leading to the reduction in the pyrolysis reactivity. Dry torrefaction improved the combustion reactivity of rice husk, particularly with the temperature (200-300 ℃) rising. But the wet torrefaction slightly reduced the combustion reactivity of rice husk. The rice husk torrefied char presented a higher temperature of initial weight loss, a lower maximum rate of weight loss, the corresponding temperature and reactivity than the rice husk hydrochar during pyrolysis at 200 ℃. Moreover, the rice husk torrefied char behaved with the lower final temperature of combustion and the maximum rate of weight loss corresponding to temperature, while the higher maximum rate of weight loss and reactivity, compared with the rice husk hydrochar. Interestingly, the linear regression index of model O1 was higher than that of the other two models for the pyrolysis and combustion reactivity of rice husk, rice husk torrefied char and rice husk hydrochar (the regression indexes were all above 0.95). The dry/wet torrefaction increased the pyrolysis activation energy of rice husk, whereas, the wet torrefaction decreased the combustion activation energy. Moreover, the pre-exponential factor of the samples in the two stages increased with an outstanding linear relationship, as the activation energy increased, indicating the kinetic compensation effect between pre-exponential factor and activation energy during combustion. The rice husk torrefied char had a lower pyrolysis activation energy and a higher pre-exponential factor than the rice husk hydrochar at the pretreatment temperature of 200 ℃. In addition, the higher activation energy of combustion and the lower pre-exponential factor were achieved in the rice husk torrefied char, compared with the rice husk hydrochar.

       

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