甲烷重整制氢用催化剂的研究进展

氢气作为高效、洁净的二次能源将成为未来社会的主要能源之一.甲烷重整是一种被广泛使用的经济、高效的制氢工艺.催化剂是重整工艺中的重要组成部分,其种类、活性和寿命对氢气的产率、纯度和制氢成本具有重要影响.详细论述了甲烷水蒸气重整、二氧化碳重整、部分氧化重整用催化剂的种类、制备方法和催化机理等.     

混合导体透氧膜反应器中焦炉煤气重整制合成气的实验研究

研究了以焦炉煤气为原料在BaCo0.7Fe0.2Nb0.1O3-δ(BCFNO)透氧膜反应器中制合成气。实验结果表明,BCFNO膜反应器的自催化性能差。加入催化剂后,膜反应器的重整性能得到明显提高,在875℃,焦炉煤气中甲烷转化率为87.0%,产物中氢气和一氧化碳选择性分别为78.3%、105.6%,透氧量达到15.8ml/(cm2.min)。焦炉煤气中的甲烷在膜反应器中反应路径为首先焦炉煤气中的氢气与膜片透过去的氧反应生成水,然后甲烷再与水重整生成氢气和一氧化碳。实验过程中,透氧膜没有出现破裂,BCFNO透氧膜反应器在富氢的焦炉煤气下显示出很好的稳定性。     

基于3D打印技术的甲烷水蒸气重整研究

天然气(主要成分为甲烷)重整是天然气高效清洁利用的重要途径,重整获得富含氢气的重整气,可供固体氧化物燃料电池进行高效发电。甲烷水蒸气重整需要反应器以及负载其上的重整催化剂,基于3D打印技术的多孔结构具有良好的耐高温、抗氧化和结构稳定性等特点,负载Ni基催化剂用于甲烷催化重整可有效提升反应器稳定性,但相关研究较少。采用浸渍法将Ni-CeO₂/γ-Al₂O₃催化剂负载于3D打印制备的多孔结构和金属泡沫反应器,通过催化剂形貌、分布规律、相结构以及热稳定性的表征,研究了重整反应温度、浆料配比、反应器结构等因素对甲烷水蒸气重整效果的影响。结果显示,催化剂的最佳配比是PVA含量为3.5%(若无特殊说明,均为质量分数),Ni含量为19%,CeO₂和γ-Al₂O₃的含量分别为16%和2.5%。重整测试结果表明,负载催化剂前,重整反应温度低于700℃时,Inconel625和泡沫Ni多孔反应器重整得到的氢气浓度均低于13%(体积分数),而重整反应温度高于800℃时,Inco...     

专利信息

镍催化裂解甲烷制备碳纳米管的方法公告号1266018申请人 天津大学文 摘 本发明公开了一种镍催化裂解甲烷制备碳纳米管的方法。该方法是以氧化镍为催化剂母体,将定量的氧化镍置于反应器内,加热至一定温度后,用氢气还原反应一定时间,然后通入反应气体,使其裂解制备碳纳米管。本发明的特征在于,反应气体是含有甲烷的混合气体,混合气体是指甲烷与氢气混合,或者是甲烷与氢气及包括氩气的不活泼气体的混合。本发明具有收率高,工艺过程简单,反应稳定,     

法液空星氧公司在新加坡拓展氢气业务

法液空公司旗下的新加坡星氧有限公司,日前与耐斯特石油公司签署了长期合约,向其在新加坡的可再生柴油厂供应氢气。为了满足耐斯特石油公司对工业气体的需求,星氧公司将投资1·25亿欧元,在裕廊岛兴建一套世界规模的甲烷蒸汽重整器。这套装置预计在2010年启动,氢气产能为10 000     

熔融盐相变储热材料的研究现状及发展趋势

熔融盐相变储热材料具有潜热大、储能密度高、过冷度小、热稳定性好、成本低等优点,广泛应用于太阳能热利用的储热介质.在对熔融盐相变储热材料进行分类的基础上,综述了国内外对碳酸盐、氯化盐和硝酸盐等储热材料在热物性和腐蚀性方面的研究现状.针对熔融盐储热材料导热率低的问题,详述了以膨胀石墨、金属、陶瓷、陶土等为基体材料、熔融盐为附体材料的高导热率复合材料制备方面的研究进展.最后展望了熔融盐相变储热材料的研究趋势.     

硝酸熔盐储热材料在太阳能利用中的研究进展

随着全球经济的快速发展,能源危机日渐凸显,太阳能作为可再生能源的一种,越来越受到人们的重视.因此,如何高效利用太阳能资源值得深究.熔盐具有良好的蓄热特性,在石化、电池及冶金行业中发挥着很大的作用,尤其可以作为传热蓄热介质应用于太阳能热发电和太阳能制氢中.其中硝酸盐的特性较为适合用于熔盐储热材料.主要针对硝酸熔融盐体系,一是介绍了硝酸熔融盐体系在太阳能方面的应用,二是介绍了国内外学者对此体系的物化性质研究,如工作温度范围、热力学性质及热稳定性等.通过对比,总结了不同混合熔融盐各项性能的异同.指出了硝酸熔融盐性能深入研究的方向,为硝酸熔盐在能源开发利用和环境保护等方面发挥更重要的作用提供了重要参考.     

甲烷水蒸气重整反应研究进展

甲烷水蒸气重整(SMR)作为可与多种高温发电系统耦合的燃料供应过程,目前受到相当普遍的重视。本文从SMR的过程和反应机理、甲烷重整催化剂材料和性能评价、传统反应器和微反应器的SMR性能比较,以及耦合SMR系统的匹配等方面,对SMR反应的研究进展进行了归纳和分析。分析结果表明,目前与固体氧化物燃料电池(SOFC)耦合的SMR反应,尤其是与非传统的微小型反应器匹配的催化剂材料、反应器结构设计、结构与材料一体化的研究都有待深入。     

模型孔中化学气相渗透过程的热解碳沉积模拟

研究耦合均气相反应机理和总括反应机理, 以模拟甲烷在模型孔中的热解碳沉积过程。在平推流反应器模型中, 利用均气相反应机理对甲烷裂解的气相组分的变化进行模拟, 并将平推流反应器相应位置的气体组分浓度作为模型孔入口初始浓度。运用包含总括反应机理及氢气抑制模型的热解碳沉积模型, 对甲烷在模型孔中的化学气相渗透过程进行模拟。在温度1373和1398 K, 甲烷压强10~20 kPa, 停留时间0.08和0.2 s下, 沿模型孔深度方向的热解碳平均沉积速率的模拟结果与文献报道的实验结果有较好的吻合。模拟结果表明: 热解碳平均沉积速率随甲烷压强和模型孔深度的增加而增大, 且通孔的沉积速率要低于相应实验条件下一端闭孔的模型孔沉积速率。     

用于水煤气变换的透氢膜反应器研究现状

综述了以Pd膜和微孔SiO2膜透氢膜材料为膜反应器核心部件在水煤气变换制氢气中的应用研究.由于Pd膜和微孔SiO2膜对氢气有很好的选择性渗透,能够有效地提高膜反应器中的水煤气变换反应时CO的转化率.通过调整反应条件使得反应能够超过平衡转化率,在一定条件下CO甚至能够完全转化.     

Optimization of an experimental membrane reactor for low-temperature methane steam reforming

The systematic and rigorous model-based optimization of the configuration and operating conditions of a methane membrane steam reforming reactor for hydrogen production is performed. A permeable membrane with Pd–Ru deposited on a ceramic dense support is used to selectively remove the produced hydrogen from the reaction zone. The shifted chemical equilibrium towards hydrogen production enables the achievement of high methane conversion at relatively low reactor temperature levels. Steam reforming takes place over a Ni–Pt/CeZnLa ceramic foam-supported catalyst that ensures better thermal distribution, at an operating temperature of 773 K and a pressure of 10⁶ Pa. A nonlinear, two-dimensional, and pseudo-homogeneous mathematical model of the membrane fixed-bed reactor is developed and subsequently validated using experimental data. For model validation purposes, two sets of experiments have been performed at the experimental reactor installed at CPERI/CERTH. The first set of experiments aims to investigate membrane permeability in order to estimate the parameters involved in the applied Sieverts law. The second set of experiments explores the performance of the membrane reactor at different steam to carbon ratios and total inlet volumetric flowrates. The derived mathematical model, consisted of mass, energy, and momentum balances that consider both axial and radial gradients of temperature and concentration, is then utilized within a model-based optimization framework that calculates the optimal operating conditions for the highly interactive reactor system. The optimal steam to carbon ratio and sweep gas flow rate that minimize the overall methane utilization (i.e., reformed methane and equivalent methane for heating purposes) are calculated for a range of hydrogen production rates. Τhe optimal reactor design configuration described by the length of the catalyst zone is also obtained for a given pure hydrogen production rate.     

Numerical study of hydrogen production by the sorption-enhanced steam methane reforming process with online CO<Subscript>2</Subscript> capture as operated in fluidized bed reactors

A three-dimensional (3D) Eulerian two-fluid model with an in-house code was developed to simulate the gas-particle two-phase flow in the fluidized bed reactors. The CO₂ capture with Ca-based sorbents in the steam methane reforming (SMR) process was studied with such model combined with the reaction kinetics. The sorption-enhanced steam methane reforming (SE-SMR) process, i.e., the integration of the process of SMR and the adsorption of CO₂, was carried out in a bubbling fluidized bed reactor. The very high production of hydrogen in SE-SMR was obtained compared with the standard SMR process. The hydrogen molar fraction in gas phase was near the equilibrium. The breakthrough of the sorbent and the variation of the composition in the breakthrough period were studied. The effects of inlet gas superficial velocity and steam-to-carbon ratio (mass ratio of steam to methane in the inlet gas phase) on the reactions were studied. The simulated results are in agreement with the experimental results presented by Johnsen et al. (2006a, Chem Eng Sci 61:1195–1202).     

Modeling of the carbon nanotube chemical vapor deposition process using methane and acetylene precursor gases

Chemical vapor deposition of carbon nanotubes (CNTs) in a horizontal tube-flow reactor has been investigated with a fully coupled reactor-scale computational model. The model combined conservation of mass, momentum, and energy equations with gas-phase and surface chemical reactions to describe the evolution of a hydrogen and hydrocarbon feed-stream as it underwent heating and reactions throughout the reactor. Investigation was directed toward steady state deposition onto iron nanoparticles via methane and hydrogen as well as feed-streams consisting of acetylene and hydrogen. The model determines gas-phase velocity, temperature, and concentration profiles as well as surface concentrations of adsorbed species and CNT growth rate along the entire length of the reactor. The results of this work determine deposition limiting regimes for growth via methane and acetylene, demonstrate the need to tune reactor wall temperature to specific inlet molar ratios to achieve optimal CNT growth, and demonstrate the large effect that active site specification can have on calculated growth rate.     

Using biomass as an energy source with low CO2 emissions

This work deals with the carbon dioxide cycle and emissions from biomass incineration under a hydrogen production context. It is proposed to use the thermal energy obtained by biomass combustion to produce water steam, which afterwards would be converted into hydrogen by high temperature electrolysis (HTE). In France, the thermal energy potential from nonvalorised biomass reaches almost 6.5 Mtep. In this study, the potential avoided carbon emissions are quantified as well as the feasible hydrogen production capacity based on the steam supplied by the incineration units. Results show that carbon consumption in hydrogen production by steam methane reforming (SMR) or biomass incineration–HTE process is almost equivalent between both processes. However, the hydrogen produced by the biomass incineration–HTE process used to fuel vehicles, would lead to a decrease of 135 Mt of carbon from fossil origins yearly, in contrast to SMR.     

Modeling of high-temperature reforming reactor based on interactive thermal control with a tail gas combustor

This paper proposes a method to model hydrocarbon reforming by coupling detailed chemical kinetics with complex computational fluid dynamics. The entire chemistry of catalyzed reactions was confined within the geometrically simple channels and modeled using the low-dimensional plug model, into which the interactive thermal control of the multi-channel reforming reactor has been implemented with a tail-gas combustor around the external surface of these catalytic channels. The geometrically complex flow in the tail gas combustor was simulated using FLUENT without involving any chemical reactions. The influences of the conditions at the reactor inlet such as the inlet gas velocity, the inlet gas composition and the variety of hydrocarbons of each channel on gas conversions were investigated numerically. The impact of the tail gas combustor setup on the efficiency of the reforming reactor was also analyzed. Methane catalytic partial oxidation (CPO_x) and propane steam reforming (SR) were used to illustrate the approach reported in the present work.     

Numerical simulation of gas-solid flows in fluidized bed gasification reactor

A numerical model for simulating a fluidized bed gasifier should include appropriate parameters to capture the dynamics of gas-solid flows, gasification kinetics and the interaction between these two. The focus of the present study is to analyze the effects of coal gasification chemistry models reported in literature on the prediction of product gas composition in a fluidized bed gasification reactor. Numerical results are validated against the experimental data available in literature. The validated model is used to examine the available chemical kinetics schemes for water gas shift reaction, steam methane reforming reaction and char heterogeneous reactions. It is also used to assess the effects of hydrodynamic models parameters such as drag model, particle-particle restitution coefficient and specularity coefficient on exit gas composition. Results show that the predictions of product gas composition are notably affected by the choices of the kinetics schemes for water gas shift and steam methane reforming reactions. Systematic analysis using the available choices to simulate initial processes such as moisture removal, volatile and tar cracking is reported. Drag models and the value of specularity coefficient are shown to have no effect on product gas composition, and the particle-particle restitution coefficient slightly influences the predicted gas composition.     

Hydrogen production from methane steam reforming: parametric and gradient based optimization of a Pd-based membrane reactor

In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics available, as well as, the influence of five important parameters on methane conversion (X_CH4_{\mathrm{CH}_{4}}) and hydrogen recovery (Y_H2_{\mathrm{H}_{2}}) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response surface technique. This meta-model was included into a constrained optimization problem solved using NPSOL. The third model, referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane conversions and hydrogen recoveries were reached through these methodologies.     

Using a membrane reactor for the oxidative coupling of methane: simulation and optimization

An oxidative coupling of methane (OCM) is a promising process to convert methane into ethylene and ethane; however, it suffers from the relatively low selectivity and yield of ethylene at high methane conversion. In this study, a membrane reactor is applied to the OCM process in order to prevent the deep oxidation of a desirable ethylene product. The mathematical model of OCM process based on mass and energy balances coupled with detailed OCM kinetic model is employed to examine the performance of OCM membrane reactor in terms of CH₄ conversion, C₂ selectivity, and C₂ yield. The influences of key operating parameters (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) on the OCM reactor performance are further analyzed. The simulation results indicate that the OCM membrane reactor operated at higher operating temperature and lower methane-to-oxygen feed ratio can improve C₂ production. An optimization of the OCM membrane reactor using a surface response methodology is proposed in this work to determine its optimal operating conditions. The central composite design is used to study the interaction of process variables (i.e., temperature, methane-to-oxygen feed ratio, and methane flow rate) and to find the optimum process operation to maximize the C₂ products yield.     

Conversion of hydrocarbon fuel in elements of thermal protection of a hypersonic flight vehicle

The problems of increasing the cooling capacity of hydrocarbon fuel by its thermochemical transformation in elements of thermal protection of a hypersonic flight vehicle and hydrogen production on board for providing stable burning in a scramjet are considered. A comparison of the chemical reactions of cracking and steam conversion of hydrocarbons, as regards the cooling capacity and amount of hydrogen in reaction products, is made. The process of steam conversion of methane in a thermochemical reactor and the factors influencing the conversion level of hydrocarbons are studied experimentally.