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气固逆流下行床煤热解实验研究
Alternative TitleExperimental investigation on coal pyrolysis in gas-solid countercurrent downer reactor
董鹏飞
Subtype博士
Thesis Advisor宋文立
2013-06-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword煤热解   逆流下行床   二次反应   气固两相流
Abstract气固逆流下行床的概念最早源自郭慕孙院士的广义流态化理论。在煤热解过程中,气固逆流接触不仅可以强化气固两相间的传质和传热、提高颗粒停留时间和系统的热效率,还可以促进重质焦油在冷煤颗粒表面冷凝及其轻质化。相对其它煤热解工艺,气固逆流下行床可以获取轻质组分含量较高的焦油。目前关于气固逆流下行床的相关研究较少。 本文分别从颗粒流动和煤热解反应两个方面对气固逆流下行床煤热解过程进行实验研究,主要研究工作如下: 1)采用光纤探头测量了测试主体长度7m,内径90mm的逆流下行床9个截面位置的颗粒浓度和速度的径向分布,并且计算出了不同径向位置的颗粒轴向流率,考察了操作条件对颗粒浓度、速度的影响,给出了逆流下行床轴、径向宏观整体流动图像。 2)基于实验数据,发现颗粒速度分布存在过渡面,并给出过渡面与颗粒入口距离Zc与操作条件ug、Gs的关系式。 3)采用固定床反应器,分别考察了温度、气相停留时间对挥发分二次反应产物分布的影响以及对甲酚和苯酚在700°C下的裂解反应,探讨挥发分二次反应过程。 4)以府谷烟煤为原料,在气固逆流下行床热态装置上考察了热解温度、加料速率和煤粒径等工艺参数对热解产物产率和组成的影响,获得了气固逆流下行床得到高焦油产率,高轻质油品含量的规律和最优工艺条件。通过传热和流动模型数值计算,提出了适合本文气固逆流下行床煤热解的粒度范围:<0.75mm。 5)沿轴向取样,对比研究了气固逆流和气固并流两种不同的流动形式的煤热解过程。气相停留时间短、重质组分冷凝及低温二次反应是气固逆流下行床煤热解制得的焦油轻质组分高于气固并流下行床的主要原因。 6)提出了逆流下行床煤热解工艺与鼓泡床半焦燃烧耦合工艺,实现了气固逆流下行床自热运行。为气固逆流下行床工业化开发提供基础数据。
Other AbstractGas-solid countercurrent downer was first proposed by Mooson Kwauk, which is a branch of generalized fluidization. In coal pyrolysis process, gas-solid countercurrent contact not only improves the mass transfer and heat transfer, increases particles’ residence time and enhances the thermal efficiency of system, but also promotes the heavy tar condensation on the surface of cool coal particles, thus improves the quality of tar. Compared with other coal pyrolysis processes, tar obtained in gas-solid countercurrent downer reactors contains more light components. At present, few reseaches about the gas-solid countercurrent downer reactor have been pubulished. The present work focuses on two aspects: experimental study on the gas-solid two-phase flow in gas-solid countercurrent downer reactor, and the reaction of coal pyrolysis in it. 1) The local solid concentration and velocity of solid particle were measured at 9 axial positions in a 7 m and 90 mm i.d. gas-solid countercurrent downer to characterize the overall flow structure by using a fiber optical probe. The effect of operating conditions on the flow structure was discussed. 2) Based on the experimental data, the transition axial distrance of particle volicity radial distribution was found, and an expression for the distrance (Zc) with ug and Gs was given. 3) The influences of temperature and residence time of volatiles on the secondary reactions were also investigated with a fixed bed reactor , and the cracking reactions of cresol and phenol at 700 °C were investigated, respectively.The final products of cracking reaction are CH4, CO and H2. 4) Experiments on pyrolysis of Chinese Fugu coal were carried out in a downer reactor, and the effects of temperature, feeding rate and particle size on product distribution were investigated. The optimal operation conditions for light components and tar yield were obtained. The suitable particle size (<0.75mm) for coal pyrolysis in gas-solid countercurrent downer was presented by mathematical model of heat transfer and gas-solid two-phase flow. 5) The influences of gas-solid countercurrent and gas-solid co-current flow on coal pyrolysis were studied via sampling along six axial sampling positions. The reasons for the light component in tar obtained from CCDR is higher than that of Co-CDR include the shorter resident time of gas in reactor, the condensation of heavy tar on coal particles and the condensed tar creacking at the lower section of the downer. 6)The process of coal pyrolysis in countercurrent downer reactor coupling with bubbling bed combustor is proposed. It provided fundamental data for the industrialization of coal pyrolysis in gas-solid countercurrent downer.
Pages196
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8237
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
董鹏飞. 气固逆流下行床煤热解实验研究[D]. 中国科学院研究生院,2013.
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