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题名	铁基化学链制氢工艺基础研究
作者	苏玉琰
学位类别	硕士
答辩日期	2011-05-24
授予单位	中国科学院研究生院
导师	宋文立 ; 李松庚
关键词	化学链 氢气 载氧体 失活 积碳
其他题名	A Fundamental Investigation of Iron-based Chemical Looping Hydrogen Generation Process
学位专业	化学工程
中文摘要	氢气是一种清洁，可持续的能量载体，是解决目前化石燃料清洁利用的重要途径。目前的制氢工艺采用水煤气变换，变压吸附等高耗能单元提纯氢气的流程大大降低了氢气的经济性，限制了氢气作为能量载体的发展。化学链是近年来发展起来的一种具有产物自分离效果的新型技术，将化学链技术应用到制氢上，可以代替目前制氢工艺中的水煤气变换，变压吸附等高耗能单元，大大降低制氢的成本。本文针对目前化学链制氢工艺中的主要的技术问题进行了一系列的研究。首先在固定床反应器上对铁基化学链法制氢进行了工艺研究，考察了温度、颗粒粒径、还原时间等的影响。温度对反应的影响较大，在500～800℃的范围内，反应开始时，温度越高，还原反应的转化率越高，在反应后期，温度越低，转化率越高。同时，温度越低，氧化阶段的产氢量越大，但氢气纯度越低。在所考察的时间范围内（10～40min），还原反应持续时间越长，产氢量越大。本文还考察了利用铁基化学链法同时调节合成气中的H2/CO的比例来作为其他合成工艺的原料的可能性。得出温度越低，经过反应后合成气的H2/CO越高。压力对于还原阶段的平衡组成影响不大。加入适量的水蒸汽能够有效的增强工艺调节合成气H2/CO的能力，但是在实际过程中应选择适当的水蒸汽的量来同时满足调节合成气氢碳比和保持较高的氢气产率。其次，本文利用固定床，XRD，SEM，BET等手段研究了颗粒的失活现象，发现颗粒的失活在第一个循环比较严重，之后活性逐渐趋于稳定。还原阶段的积碳和氧化阶段的烧结是颗粒失活的主要原因。加入Al2O3载体能够有效的减弱颗粒的失活，在前四个循环，利用混合法制备的加入Al2O3载体的载氧体颗粒活性减弱较轻。在载氧体颗粒中加入石墨作为扩孔剂，可增强颗粒反应活性和稳定性，经过6 个循环后，实际产氢量仍保持在理论产氢量的40%以上(不加石墨仅为20%)且仍保持一定的孔结构，而未加石墨的颗粒几乎完全烧结。积碳是影响氢气纯度的主要因素，本文利用XRD，SEM，TG等对颗粒的积碳现象进行了研究。温度对积碳影响非常大，在800℃以上时，积碳反应基本可以忽略。反应的氧化阶段能够消除一部分积碳，但是相比生成的积碳量，消除的积碳的量只占很小的一部分。在还原阶段加入适量的水蒸汽能够有效的抑制积碳的发生，在本实验条件下，加入H2O的量与CO之比大于0.33时，制得的H2的浓度接近100 %。
英文摘要	Hydrogen is a clean and reliable energy carrier, and provides a promising pathway for efficient and clean utilization of fossil fuels. A two-stage water gas shift (WGS) reaction followed by a pressure swing unit is a traditional way for fossil fuels to produce pure hydrogen, which is complicated. Chemical looping technology has received much attention due to its inherent separation of greenhouse gas CO2, which has been applied to the production of pure hydrogen recently. In this work, fundamentals on iron-based chemical looping hydrogen generation process have been performed. Firstly, parametric study was carried out in a fixed bed reactor including temperature, particle size, and reduction reaction time. At temperatures of 500-800℃, syngas conversion increases with an increase of temperature in the beginning of the reaction. Subsequently, it increases with a decrease of temperature. In the oxidation stage, the yield of hydrogen decreases with an increase of temperature while the purity of hydrogen exhibits an inverse trend. Hydrogen yield is also related to the reduction reaction time. The longer the reduction reaction time, the higher the yield of hydrogen is under the experimental conditions. Feasibility of adjustment of H2/CO ratio in the syngas with chemical looping hydrogen generation process was also investigated. The ratio of H2 to CO decreases with an increase of temperature. No obvious effect of pressure is found on H2/CO ratio. Appropriate amount of steam added in the reduction stage can enhance the ability of adjusting H2/CO ratio. However, the amount of steam added in the reduction stage should be carefully chosen to fulfill both the adjusting ability and high purity hydrogen production. Secondly, the deactivation of the oxygen carriers was investigated with XRD, BET and SEM. It is found that the deactivation in the first cycle is serious. It becomes relatively stable in the following cycles. Carbon deposition in the reduction stage and the sintering of oxygen carriers in the oxidation stage are main causes of deactivation of the oxygen carriers. Al2O3 support can alleviate the deactivation to some degree. Cyclic property of the oxygen carriers can be enhanced by adding graphite as pore-forming additive. After the sixth cycle, hydrogen yield can still reach 40% of the theoretical value while the yield of hydrogen for the oxygen carrier without the pore-forming additive is only 20%. Thirdly, carbon deposition in the reduction stage was investigated since it has a strong effect on the purity of hydrogen produced in the oxidation stage. It is found that the carbon deposition can be ignored at temperatures above 800 C. At low temperatures, carbon deposition becomes serious. Carbon deposited on the surface of oxygen carriers can partially be removed in the oxidation stage. Appropriate amount of steam added in the reduction stage can effectively suppress the carbon formation. The purity of hydrogen approaches 100% with steam/ CO ratio higher than 0.33 under the experimental conditions.
语种	中文
公开日期	2013-09-24
页码	96
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1725]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	苏玉琰. 铁基化学链制氢工艺基础研究[D]. 中国科学院研究生院. 2011.

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