【作者】 阚涛；

【导师】 李全新；

【作者基本信息】 中国科学技术大学 ， 物理化学， 2009， 博士

【摘要】 能源是人类生存和社会经济可持续发展的重要物质基础。随着能源需求和环境保护的压力迅速增长,利用可再生的生物质能受到人们极大的关注。氢气是目前最理想的高热值清洁能源之一,生物质以其资源丰富、环境友好、可再生等优点而成为一种很有前途的氢源。生物质制氢尚处于研发阶段,提高氢气产率、降低制氢成本以及减少催化剂失活等是生物质制氢研发过程中尚需解决的关键问题。本论文针对上述生物质制氢仍存在的问题,提出一种以生物质为原料制取氢气的新方法以及一种以生物质快速热裂解油为原料制取氢气的新方法。本论文研究内容如下:1.串联流化床装置系统中以生物质为原料制取氢气实验室在以前相关工作的基础上,独立研制出用于生物质制氢的串联流化床装置系统。该系统主要由四部分组成,即上游生物质热裂解流化床系统,中间产物收集和分析系统,下游有机物蒸汽催化重整流化床系统以及尾气分析与净化系统。利用该系统进行生物质制氢的过程中,高温水蒸气作为整个反应系统的载气以及下游重整流化床的反应物。生物质首先进入热裂解流化床进行热裂解反应,生成的有机物蒸汽在不经过冷凝和保温的条件下直接进入重整流化床进行水蒸气重整反应和水煤气变换反应生成富氢气体。实验研究了上游生物质裂解温度(Tp)和气相滞留时间(τ)对各种裂解产物(生物油,裂解气和生物质焦炭)的产率和的影响以及Tp对各种产物性质的影响,并研究了下游有机物蒸汽重整温度(Tr),水蒸气/有机物碳(S/C)摩尔比率对有机物蒸汽制氢性能的影响。结果表明,在Tp = 430 ~ 630 oC的温度范围内,生物油产率随温度的升高先升高后降低。裂解气产率随温度的升高而升高,生物质焦炭的趋势则与之相反。气相滞留时间对各种裂解产物产率的影响不显著。在Tp = 480 oC,τ= 0.62 s的生物质裂解条件下,可以得到最高的生物油产率(45.1%)。同时,在研究的范围内,尾端氢气产率随Tr和S/C的升高而增加。利用该串联流化床装置系统,氢气产率可达79.1 g H2/kg dry-biomass,产物气的主要组成为H2 (68.4%),CO2 (25.8%), CO (7.2%), CH4 (0.1%)等。通过生物质焦炭的气化,可进一步提高氢气产率。2.双固定床系统中以生物质快速热裂解油为原料制取氢气以粗生物油为原料进行高效产氢的过程在双固定系统中进行。双固定系统主要包括上游的生物油气化床和下游的催化重整床。实验室近期发明的电催化重整(ECR)制氢方法被应用于下游的NiCuZn-Al2O3催化剂重整床以提高氢产率。实验分别研究了粗生物油的单独气化过程和集成的气化-电催化重整过程中的整体产氢性能。结果表明,单独气化过程的产氢率很低(< 30 %);集成的气化-电催化重整过程中,在气化温度为800 oC,生物油进量为14.4 g/h,S/C为10.6,空速为7810 h-1,重整温度为700 oC以及电流为3.0 A的条件下,氢气产率可达81.4 %,生物油的碳转化率为87.6 %。最终的产物气主要包括H2 (~ 73 vol%)和CO2 (~ 26 vol%),以及极少含量的CO和CH4 (< 1 vol%)。此外,通过XRD、XPS、TGA等表征手段对催化剂的结构性能以及在反应前后和有无电流的情况下的变化进行了初步分析。与生物油在催化剂上的直接水蒸气重整制氢相比,集成的气化-电催化重整制氢方法极大降低了催化剂的失活速率,并显著提高了氢产率。更多还原

【Abstract】 Energy is an important material basis for the survival and continuable development of the human beings. With the rapid increases in the energy demand and the pressure from the environment protection, the application of renewable bio-energy is receiving great attention globally. Hydrogen is recognized as a clean fuel and energy carrier with very high heating value and will play an important role in the future global economy. Biomass is rich and friendly environmentally renewable resource, hydrogen production from biomass is one of the most promising options and it is still in development. The improvement of hydrogen yield and energy efficiency as well as the decrease in hydrogen production cost and the catalyst deactivation, etc., are the key problems existing in the investigation of hydrogen production from biomass. In view of these problems, novel approaches for hydrogen production from biomass and biomas pyrolysis oil (i.e., bio-oil) were proposed in our research. The main content of present thesis was focused on the items as follows.1. Hydrogen Production from Biomass through the Integrative Tandem Fluidized Beds Reaction SystemBasing on the previous work, an integrative tandem fluidized beds reaction system for hydrogen production from biomas was firstly designed and manufactured. This reaction system was mainly made of four main units, i.e., the unit of the biomass pyrolysis, the unit of the intermediate products’collection and sampling, the unit of the steam reforming of bio-oil vapor, and the unit of final product purification and measuring. In this work, hydrogen was produced from biomass by a three stepwise process. In the first step, the biomass was converted into the oxygenated organic compounds vapor (i.e., the bio-oil vapor) by the fast pyrolysis of biomass in the pyrolysis reactor with a capacity of 2-20 kg moisture-free biomass/h. In the second step, the bio-oil vapor without cooling was then fed into the reforming rector and converted the oxygenated organic compounds into the rich-hydrogen mixture gas (i.e, H2, CO2, CO, etc.) via the catalytic steam reforming of the bio-oil vapor. Finally, the mixture gas was purified to produce pure hydrogen with a lower impurity by removing ash and CO2, etc. The most important parameters, such as biomass pyrolysis temperature (Tp), vapor residence time (τ) in the pyrolysis reactor and reforming temperature (Tr) in the reforming reactor, steam/bio-oil carbon molar ratio (S/C) was investigated. The results indicated that, in the pyrolysis temperature range of 430 ~ 630 oC, the bio-oil yield initially increased with temperature and then decreased. The yield of pyrolysis gas increased with temperature, accompanied by the opposite trend of the char yield. The effect of vapor residence time on the products’yields was not so obvious. Meanwhile, in the reforming reactor, the final hydrogen yield increased with incresing the reforming temperature and S/C. A hydrogen yield of 79.1 gH2/kg moisture-free biomass was obtained under the conditions of Tp = 480 oC,τ= 0.62 s and Tr =700 oC, S/C= 4.8, GHSV= 47,000 h-1 with the product gas’s composition of H2 (68.4%),CO2 (25.8%), CO (7.2%) and CH4 (0.1%). The hydrogen yield can be further improved through the steam gasification of the biomass char.2. Hydrogen Production from Crude Bio-oil through the Integrative Dual Fixed Beds Reaction SystemHigh efficient production of hydrogen from the crude bio-oil was performed in the gasification-reforming dual beds. A recently developed electrochemical catalytic reforming method was applied in the downstream reforming bed using NiCuZnAl catalyst. Production of hydrogen from the crude bio-oil through both the single gasification and integrative gasification-reforming processes was investigated. Results showed that the hydrogen yield in the single gasification was very low (< 30 %).The maximum hydrogen yield of 81.4 % with carbon conversion of 87.6 % was obtained through the integrative process under the conditions of Tg = 800 oC, f (bio-oil fed rate) = 14.4 g/h, S/C = 10.6, GHSV = 7810 h-1 and Tr = 700 oC. Hydrogen is a major product (~ 73 vol%) together with by-products of CO2 (~ 26 vol%) as well as very low content of CO (< 1 %) and a trace amount of CH4 through the integrative route. In particular, the deactivation of the catalyst was significantly depressed by using the integrative gasification-reforming method, comparing to the direct reforming of the crude bio-oil. XRD, XPS and TGA, etc., were employed to characterize the catalysts before and after reaction.更多还原