微小液固流化床中硼氢化钠水解制氢反应特性的研究

发布时间：2018-07-06 17:37

本文选题：微小液固流化床 + 流化特性　；参考：《青岛科技大学》2016年硕士论文

【摘要】：近年来由于全球经济的迅猛发展,全球对于能源的需求急剧扩大。但受能源短缺、环境恶化等一系列问题的影响,人们对新能源的需求正逐渐增加。氢能作为一种热值极高的清洁能源,在其开发和利用的过程中,储存和运输等问题使其规模化应用受到了阻碍。硼氢化钠水解制氢技术由于具备诸多优势引起了研究者们的广泛关注。早期研究人员多将注意力集中在高效廉价的硼氢化钠水解制氢催化剂的开发上,却鲜有文献对制氢反应器进行详尽研究考察。反应器作为硼氢化钠水解制氢反应发生的场所,对于反应能否高效安全地进行起到了举足轻重的作用。因此,本文简要介绍了一套自行搭建的微小液固流化床制氢反应器,在考察了其流化特性的同时,还利用了核桃壳活性炭钴基催化剂,在装置中考察了硼氢化钠水解制氢反应特性。首先,本文使用石英砂和核桃壳活性炭等固体颗粒考察了微小液固流化床的流化特性。通过观察实验现象对流化过程中出现的流型进行了划分,并与常规尺寸液固流化床在流化过程中出现的流型进行了简要对比。实验结果表明填料高度对各流型操作流速的影响较小,但随着颗粒粒径及密度的减小,维持散式流化的流速范围减小;随着填料高度的增加,床层膨胀率会降低,但流化过程的均匀程度有所提高。另外,颗粒粒径和密度越小,床层膨胀率受液速的影响越明显,流化的均匀程度亦越高。当床层填料高度增加、颗粒粒径减小,床层压降均会有所增加,流化质量也会提高。除此之外,颗粒的最小流化速度随颗粒的粒径和密度的增大而增大。其次,本论文还考察了硼氢化钠水解制氢反应特性。实验结果表明随着硼氢化钠溶液浓度的降低,稳定制氢时间呈先增长后变短的趋势。当溶液浓度为2 wt.%时,稳定制氢时间最长,占总反应时间的58.46%。改变反应液的流速虽对总反应时间影响不大,但会影响反应过程中稳定制氢的时间长短。此外,随流速增加,稳定时间先增长后缩短,在流速为3.00×10-3 m·s-1时,稳定制氢时间最长。较高温度有利于反应快速进行,但不利于反应稳定进行。随温度的降低,反应速率逐渐降低,反应时间变长,当反应液温度为25°C时,稳定制氢时间最长。颗粒粒径对制氢稳定性影响不大,但催化剂粒径越小,反应越快,反应时间越短。
[Abstract]:In recent years, with the rapid development of the global economy, the global demand for energy has expanded rapidly. However, due to a series of problems, such as energy shortage and environmental deterioration, the demand for new energy is increasing gradually. Hydrogen energy is a kind of clean energy with high calorific value. In the process of its development and utilization, storage and transportation problems hinder its application on a large scale. The technology of hydrolysis of sodium borohydride to produce hydrogen has attracted extensive attention of researchers due to its many advantages. Early researchers focused their attention on the development of efficient and cheap catalysts for the hydrolysis of hydrogen by sodium borohydride, but there were few studies on hydrogen production reactors in detail. As a place where hydrolysis of sodium borohydride to produce hydrogen occurs, reactor plays an important role in efficient and safe reaction. Therefore, a set of micro liquid-solid fluidized bed hydrogen production reactors built by ourselves was introduced in this paper. The fluidization characteristics of the reactor were investigated, and the activated carbon cobalt based catalyst of walnut shell was also used. The characteristics of hydrolysis of sodium borohydride to produce hydrogen were investigated in the device. Firstly, the fluidization characteristics of micro liquid-solid fluidized bed were investigated by using solid particles such as quartz sand and walnut shell activated carbon. By observing the experimental phenomena, the flow patterns in fluidization process are divided and compared with those in conventional liquid-solid fluidized beds. The experimental results show that the packing height has little effect on the operating flow rate of each flow pattern, but with the decrease of particle size and density, the flow velocity range of maintaining the flow rate decreases, and the bed expansion rate decreases with the increase of the packing height. But the uniformity of fluidization process has been improved. In addition, the smaller the particle size and density, the more obvious the influence of liquid velocity on bed expansion rate and the higher the uniformity of fluidization. When the height of the bed is increased, the particle size decreases, the pressure drop of the bed increases and the fluidization quality increases. In addition, the minimum fluidization rate of particles increases with the increase of particle size and density. Secondly, the characteristics of hydrolysis of sodium borohydride to produce hydrogen were investigated. The experimental results show that with the decrease of the concentration of sodium borohydride solution, the stable hydrogen production time increases first and then shortens. When the concentration of the solution was 2 wt.%, the time of hydrogen production was the longest, accounting for 58.46% of the total reaction time. Changing the flow rate of the reaction liquid has little effect on the total reaction time, but it will affect the time of the stable hydrogen production during the reaction process. In addition, with the increase of the flow rate, the stabilization time increases first and then shortens. When the flow rate is 3.00 脳 10 ~ (-3) m 路s ~ (-1), the stabilization time is the longest. Higher temperature is conducive to rapid reaction, but is not conducive to the stability of the reaction. With the decrease of temperature, the reaction rate decreases gradually and the reaction time becomes longer. When the reaction temperature is 25 掳C, the time of stable hydrogen production is the longest. The particle size has little effect on the stability of hydrogen production, but the smaller the catalyst size is, the faster the reaction time is and the shorter the reaction time is.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ116.2

【相似文献】