Evaluation of membrane reactor with hydrogen-selective membrane in methane steam reforming

A comparative analysis of a conventional industrial process and a membrane reactor plant for hydrogen production via natural gas steam reforming is proposed by calculating two sustainability metrics: mass and energy intensities. The analysis takes into account membrane reactors equipped with hydrogen-selective membranes (Pd-based) which can operate at milder temperature (500 °C) and pressure (1.0 MPa) conditions and at higher CH₄ conversion levels (90–100%) than that achieved in conventional industrial systems.The use of the MR retentate stream to produce the steam required as feed for the reforming section is proposed and for this option a reduced mass intensity is calculated (reduced amount of fuel to the process) with respect to the conventional plant. The reduction is in the range 25–32% for the MRs operated at m=3 and 44–50% for the MRs operated at m=2. A more important saving concerns the energy use.     

Theoretical and experimental analysis of methane steam reforming in a membrane reactor

Thermal effects on methane steam reforming process were analyzed, in a Pd-Ag (23wt%) membrane reactor as a function of several parameters, such as temperature, reactant and sweep-gas flow rate, and reactant molar ratio. Heat transfer from the oven was very important for the outlet methane conversion, which also depends on the temperature profile along the reactor. In particular, when the reactant flow rate was high the conversion degree decreased because the energy supplied was not sufficient to maintain the temperature in the reactor. A non-isothermal mathematical model was presented which reproduced the experimental data.     

Catalytic combustion assisted methane steam reforming in a catalytic plate reactor

A theoretical study of methane steam reforming coupled with methane catalytic combustion in a catalytic plate reactor (CPR) based on a two-dimensional model is presented. Plates with coated catalyst layers of order of micrometers at distances of order of millimetres offer a high degree of compactness and minimise heat and mass transport resistances. Choosing similar operating conditions in terms of inlet composition and temperature as in industrial reformer allows a direct comparison of CPRs with the latter. It is shown that short distance between heat source and heat sink increases the efficiency of heat exchange. Transverse temperature gradients do not exceed across the wall and across the gas-phase, in contrast to difference in temperature of outside wall and mean gas phase temperature inside the tube usually observed in conventional reformers. The effectiveness factors for the reforming chemical reactions are about one order of magnitude higher than in conventional processes. Minimisation of heat and mass transfer resistances results in reduction of reactor volume and catalyst weight by two orders of magnitude as compared to industrial reformer. Alteration of distance between plates in the range 1- does not result in significant difference in reactor performance, if made at constant inlet flowrates. However, if such modifications are made at constant inlet velocities, conversion and temperature profiles are considerably affected. Similar effects are observed when catalyst layer thicknesses are increased.     

A fluidized bed membrane reactor for the steam reforming of methane

In the present investigation a realistic two-phase model accounting for the change in the total number of moles accompanying the reaction is utilized to explore a novel reactor configuration suggested for the methane steam reforming process. The suggested design is basically a fluidized bed reactor equipped with a bundle of membrane tubes. These tubes remove the main product, hydrogen, from the reacting gas mixture and drive the reaction beyond its thermodynamic equilibrium. The proposed novel design is also equipped with sodium heat pipes which act as a thermal flux transformer to provide the large amount of heat needed by the endothermic reaction through a relatively small heat transfer surface, assuring better reactor compactness. Two options for fluid routing through the membrane tubes are proposed; each is suitable for a certain industrial application. The performance of this novel configuration is compared with that of an industrial fixed bed steam reformer and the comparison shows the potential advantages of the suggested configuration.     

Preliminary design and simulation of a microstructured reactor for production of synthesis gas by steam methane reforming

The present study considers the potentials of the well-known production of syngas by steam methane reforming (SMR), by operation within microstructured reactors. The model of a microchannel reactor is developed, including very fast kinetic reaction rates on the coated catalytic walls of the reactor module. By varying the characteristic dimensions of the channels, and considering technical constraints on the design and operating conditions, the results demonstrate that the SMR reactor can be drastically miniaturized while maintaining its productivity without any additional pressure drop. Furthermore, by reducing the channel characteristic dimensions, it is possible to suppress heat and mass-transfer limitations enabling SMR reactor operation at thermodynamic equilibrium. A fast method for preliminary design of microstructured heat-exchanger reactors is developed, that enables to identify the optimal channels number and heat power needed to reach process specifications.     

Pure hydrogen production by methane steam reforming with hydrogen-permeable membrane reactor

Low temperature steam reforming of methane mainly to hydrogen and carbon dioxide (CH₄ + 2H₂O → 4H₂ + CO₂) has been performed at 773 and 823 K over a commercial nickel catalyst in an equilibrium-shift reactor with an 11-μm thick palladium membrane (Mem-L) on a stainless steel porous metal filter. The methane conversion with the reactor is significantly higher than its equilibrium value without membrane due to the equilibrium-shift combined with separation of pure hydrogen through the membrane. The methane conversion in a reactor with an 8-μm membrane (Mem-H) is similar to that with Mem-L, although the hydrogen permeance through Mem-H is almost double of that through Mem-L. The amount of hydrogen separated in the reaction with Mem-H is significantly large, showing that the hydrogen separation overwhelms the hydrogen production because of the insufficient catalytic activity.     

催化剂颗粒形状对甲烷水蒸气重整反应的影响及工业反应器模拟

甲烷水蒸气重整工艺是现阶段最主要的工业制氢技术,催化剂颗粒形状和反应器操作条件是影响重整反应器性能和产物组成的重要因素。首先从颗粒尺度研究催化剂形状对甲烷水蒸气重整反应的影响,在不同的反应温度和压力下,计算并比较了球形、柱形和环形催化剂的效率因子,其大小顺序为:柱形 < 球形 < 环形。其次,将反应器床层的质量、热量和动量传递与环形催化剂颗粒的扩散-反应方程相结合,建立了用于描述甲烷水蒸气重整工业反应器的一维轴向数学模型。计算并分析了反应器进口温度和压力对反应器床层的温度和压力分布、催化剂效率因子以及甲烷转化率和各组分浓度分布的影响,确定了适宜的工业反应器进口温度和压力,分别为773 K和3 MPa。     

Analysis of a novel reverse-flow reactor concept for autothermal methane steam reforming

One of the main shortcomings of existing multifunctional reactor concepts for the autothermal coupling of endothermic and exothermic reactions is inefficient heat integration leading to excessive maximum temperatures or poor reactor performance. For the asymmetric operation of a reverse-flow steam reforming reactor, conditions under which these shortcomings can be overcome are proposed. The asymmetric process is based on the formation of travelling reaction zones. The features of these transient phenomena are analysed by means of a simplified model.During the endothermic semicycle, the heat consumption forms a temperature wave with an expansive low-temperature and a compressive high-temperature part. During the exothermic semicycle a proper axial distribution of the heat supply is necessary in order to maintain a favourable temperature profile in the cyclic operation mode.The results obtained with the simplified model are verified by direct dynamic simulation.     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

板翅式反应器中甲醇水蒸气重整制氢

研制了一种高效板翅式反应器,其特点是体积相对较小,便于放置,便于扩大规模;集预热、气化、重整、催化燃烧于一体;板翅式反应器内部热量利用合理,放热反应与吸热反应、气化与冷却之间实现了较好的热量耦合;可实现完全自供热.在反应器中进行了一系列甲醇水蒸气重整的实验,考察了不同条件对甲醇重整制氢过程的影响、对反应器床层温度分布的影响,及反应器的稳定性.另外,由于板翅式结构的良好传热性,甲醇水蒸气重整在获得较高转化率的同时重整气中CO浓度较低,且反应器的稳定性良好.     

On a possible mechanism of the methane steam reforming in a gliding arc reactor

This work is dedicated to the study of methane steam reforming (SR) using a rotating discharge reactor. The process efficiency is described in terms of methane conversion, SR selectivity, energy input and hydrogen production cost. The experiments clearly demonstrated the ability of glidarc to accelerate chemical reactions at low temperatures and with very low energetic costs. A good approximation model describing the chemical processes on the basis of classical thermodynamics is also proposed. The analysis gives information on reactor design in order to improve its chemical performances.     

Performance of microchannel reactor combined with combustor for methanol steam reforming

The microchannel reactor with combustor for methanol steam reforming was fabricated to produce hydrogen for onboard proton exchange membrane (PEM) fuel cell device. A commercial copper-containing catalyst (Cu/ZnO/Al₂O₃) and Pt/ZrO₂ were used as a catalyst for methanol steam reforming and combustion reaction, respectively. It was found that catalyst layer with zirconia sol solution in microchannel showed no crack on the surface of catalyst layer and an excellent adherence to stainless steel microchannel even after reaction. The temperature of combustor could be controlled between 200 and 300 °C depending on the methanol feed rate. The hydrogen flow of 3.9 l h⁻¹ hydrogen was obtained with the reforming feed flow rate of 3.65 ml h⁻¹ at 270 °C.     

Innovative steam methane reforming for coproducing CO-free hydrogen and syngas in proton conducting membrane reactor

Steam methane reforming (SMR) is a commercial process to produce syngas. Normally, the as-produced syngas is characterized by a H₂/CO ratio of 3. However, such H₂/CO ratio is unsuitable for Fischer–Tropsch synthesis. The hydrogen obtained by subsequent upgrading of syngas usually contains residual CO, which readily deactivates Pt electrocatalysts in fuel cells. Here we report an innovative route by coupling SMR with H₂ removal in a proton conducting membrane reactor to coproduce syngas with a preferable H₂/CO ratio of 2 and CO-free H₂ on opposite sides of the membrane, which can be directly used for Fischer–Tropsch synthesis and fuel cells, respectively. Notably, H₂ is in-situ extracted by the membrane that only allows the permeation of H₂ as protons through the oxide lattice with infinite selectivity, and thus the obtained H₂ is CO-free. This work could provide an alternative option in one-step conversion of methane into two inherently separated valuable chemicals.     

Modeling of membrane reactor for steam methane reforming: From granular to structured catalysts

Different types and operating modes of a tubular membrane reactor for steam methane reforming with a production rate of 0.6 m3/h are compared using the results of mathematical modeling. It is shown that, for a cylindrical membrane, the use of a catalytic bed based on waved bands of porous nickel instead of a granular bed of a commercial catalyst (NIAP-18) can theoretically increase the yield of hydrogen by 15–18%.     

Micro-channel reactor for steam reforming of methanol

Micro-channel reactor for steam reforming of methanol seems to be attractive for portable application as one part of fuel processor in fuel cell. In the present study, steam reforming of methanol was performed in one stainless steel micro-channel reactor coated with commercial catalyst. The different sols (alumina, zirconia and mixed sol of alumina and zirconia) as a binder for the catalyst were applied to compare the stability and performance. Among the different sols, mixed sol of alumina and zirconia comparatively produced better stability and performance.     

FT合成反应器的研究进展

费托（FT）合成反应是强放热反应,为了有效移热,反应器的研制开发是这一方案有效实施的关键。本文较系统地分析了FT合成工业化主流反应器的发展和使用状况,同时对近几年新近出现的几种新型FT合成反应器,如微通道反应器、径向反应器、新型流化床反应器、带扩径段的浆态床反应器和环流浆态床反应器进行了分类和介绍。通过对这些介绍,对反应器的特点和发展状况进行了分析和展望。     

On the reported attempts to radically improve the performance of the steam methane reforming reactor

Steam reforming of light hydrocarbons is a key step for producing hydrogen and syngas for important processes in the petroleum and petrochemical industries. Since the establishment of the SMR process in 1930, research and development have led to improved catalyst performance and improved reactor tube materials. Since about 1970, new reactor configurations have been considered. The authors critically review recent attempts to radically improve the SMR reactor performance, analyze the areas of improvement and the suitability of proposed configurations for different reforming applications.     

Steam reforming of methane in a membrane reactor

Methane reforming in a Pd/Ag membrane reactor was carried out. The operational limits for the steam-to-methane ratio are discussed. To avoid carbon formation, this ratio has to be higher in a Pd/Ag membrane reactor than in a conventional steam reforming tubular reactor.     

Hydrogen from steam methane reforming by catalytic nonthermal plasma using a dielectric barrier discharge reactor

A scaled-up dielectric barrier discharge (DBD) reactor has been developed and demonstrated for the production of hydrogen from steam methane reforming (SMR) by catalytic nonthermal plasma (CNTP) technology. Compared to SMR, CNTP offers conversion at ambient pressure (101.325 kPa), low temperature with better efficiency, making it suitable for distributed hydrogen production with small footprint. There have been several lab-scale DBD reactors reported in the literature. Dimension of the scaled-up DBD reactor is about six times the lab-scale version and can produce 0.9 kg H₂/day. The scale-up is, however, nonlinear; several technical innovations were required including spray nozzle for homogeneous introduction of steam, perforated tube central electrodes for generation of homogeneous plasma. Conversion efficiency of the scaled-up DBD reactor is 70–80% at 550°C and 500 W. A continuous run of 8 hr was demonstrated with typical product gas composition of 69% H₂, 6% CO₂, 15% CO, 10% CH₄.