生物甘油自热重整制氢强化手段的研究

发布时间：2018-05-21 02:14

本文选题：甘油 + 重整　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：生物柴油具有绿色环保可再生等优势,生物柴油的大量制备导致其副产物甘油大多被浪费,甘油重整制氢为甘油利用提供了一种有效途径。为了能够提高甘油利用率和氢气产率,重整强化手段的研究成为了近年来的研究热点。流化床反应器具有更好的流动性以及传热传质性,在甘油重整制氢中具有广阔的前景。因此,以甘油水蒸气重整制氢为研究对象,针对流化床内甘油重整过程及其强化手段进行热力学模拟以及流体动力学模拟研究。考虑到甘油重整制氢为吸热反应,为了减少能量投入,利用氧化反应释放热量从而达到自热的状态,构建出甘油水蒸气自热重整反应体系,对不同操作条件下的重整体系进行热力学分析。研究表明,自热状态虽然能够有效地减少外界能量的投入,但氢气产量却会明显减少。考虑体系内加入吸收剂,通过反应发生平衡移动,促进反应进行,同时可以通过吸收反应放热使体系达到自热状态。通过对氧化钙作为二氧化碳吸收剂的甘油重整反应体系进行热力学模拟,结果表明,氧化钙的加入使氢气产量增加,最大氢气产量所对应的操作温度降低,起到了明显的强化作用。同时由于碳酸钙高温分解等因素,反应器温度不能高于850K,氧化钙-甘油投料比在3~4之间比较适合于强化重整反应的进行。考虑到半透膜可以有效地将反应体系内部的氢气分离,促使反应平衡发生移动,对甘油重整制氢过程起到强化作用,对甘油自热除氢体系进行了热力学分析。结果表明,半透膜的除氢强化手段能够使氢气产率增加,抵消氧气的引入所带来的负面影响,并且氢的分离系数越大,效果越明显。但氢气分离的同时会促进反应体系内部的甲烷化反应,增加积碳的产量。为了探究粗甘油重整的可行性,反应体系内引入乙醇杂质。结果表明,乙醇的引入会对氢气产量产生负面影响,并且这种负面影响会随着氢气分离系数的增大而增强。应用本文建立的气固多相流体模型,模拟计算了流化床反应器内甘油水蒸气重整制氢过程。结果表明,流化床内颗粒呈现出明显的流化状态。床层内部有明显的稀相区和密相区,伴随着颗粒聚团行为以及气泡生成和运动现象,并且反应器内部存在着颗粒回流现象。反应器中颗粒拟温度表现出随着颗粒浓度的逐渐增加而减小的分布趋势。通过对流化床内反应特性进行研究发现,在流化床反应器内部,甘油和水蒸气作为反应物,在反应器底部快速分解,生成一系列生成物气体,其中氢气是甘油重整的主要生成物。将有吸收强化和未吸收强化的甘油重整制氢过程进行对比,证明体系内部加入氧化钙吸收二氧化碳作为吸收强化手段,不但能够使反应体系达到自热状态,还能够有效地提高甘油的转化率以及氢气的产率。吸收强化后,反应器出口处氢气份额由47%提升到了55%,一氧化碳和甲烷的份额都相对的降低。
[Abstract]:Biodiesel has the advantages of green environment protection and renewable. The production of biodiesel leads to the waste of glycerol. Glycerol reforming to produce hydrogen provides an effective way for the utilization of glycerol. In order to improve glycerol utilization and hydrogen yield, reforming enhancement has become a hot research topic in recent years. Fluidized bed reactor has better fluidity, heat and mass transfer, and has a broad prospect in glycerol reforming hydrogen production. Therefore, the hydrodynamic simulation and thermodynamic simulation of glycerol reforming in fluidized bed were carried out. Considering that the hydrogen production of glycerol reforming is an endothermic reaction, in order to reduce the energy input, the oxidation reaction is used to release heat so as to reach the state of self-heating, and a self-heating reforming system of glycerol water vapor is constructed. Thermodynamic analysis of reforming system under different operating conditions was carried out. The results show that although the self-heating state can effectively reduce the external energy input, the hydrogen production will be significantly reduced. Considering the addition of absorbent in the system, the equilibrium shift of the reaction occurs and the reaction can be promoted. At the same time, the self-heating state of the system can be achieved by the absorption reaction exothermic. The thermodynamic simulation of glycerol reforming reaction system with calcium oxide as carbon dioxide absorbent was carried out. The results showed that the addition of calcium oxide increased the hydrogen production and reduced the operating temperature corresponding to the maximum hydrogen production. Has played the obvious enhancement function. At the same time, because of the decomposition of calcium carbonate at high temperature, the reactor temperature can not be higher than 850K, and the ratio of calcium oxide to glycerol is more suitable for the enhanced reforming reaction. Considering that the semi-permeable membrane can effectively separate the hydrogen in the reaction system and promote the shift of the reaction equilibrium, the hydrogen production process of glycerol reforming is strengthened, and the thermodynamics analysis of the self-heating dehydrogenation system of glycerol is carried out. The results show that the enhancement of hydrogen removal by semi-permeable membrane can increase the hydrogen yield and counteract the negative effect brought by the introduction of oxygen, and the higher the separation coefficient of hydrogen is, the more obvious the effect is. However, hydrogen separation can promote the methanation reaction in the reaction system and increase the yield of carbon deposition. In order to explore the feasibility of crude glycerol reforming, ethanol impurities were introduced into the reaction system. The results showed that the introduction of ethanol had a negative effect on hydrogen production, and the negative effect would increase with the increase of hydrogen separation coefficient. Based on the gas-solid multiphase fluid model established in this paper, the hydrogen production process of glycerol steam reforming in a fluidized bed reactor was simulated and calculated. The results show that the fluidized bed particles show an obvious fluidization state. There are obvious dilute and dense phase regions in the bed, accompanied by particle agglomeration, bubble formation and movement, and particle reflux in the reactor. The particle pseudo temperature in the reactor decreases with the increase of particle concentration. By studying the reaction characteristics in the fluidized bed, it is found that in the fluidized bed reactor, glycerol and water vapor are used as reactants, which decompose rapidly at the bottom of the reactor and produce a series of resultant gases. Hydrogen is the main product of glycerol reforming. By comparing the hydrogen production process of glycerol reforming with and without absorption enhancement, it is proved that adding calcium oxide to absorb carbon dioxide as a means of absorption enhancement can not only make the reaction system self-heated. The conversion of glycerol and the yield of hydrogen can also be increased effectively. After absorption enhancement, the hydrogen share at the outlet of the reactor increased from 47% to 55%, and the carbon monoxide and methane share decreased relatively.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ116.2

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