Two-dimensional Simulation for Hydrogen/Air Combustion in a Monolith Reactor

Recent studies on hydrogen combustion were reviewed briefly. The laminar flow and combustion of premixed hydrogen/air mixture in a cylindrical channel of a monolith reactor with and without catalytic wall was numerically modeled by solving two-dimensional (2-D) Navier Stokes (N S) equations, energy equation, and species equations. Eight gas species and twenty reversible gas reactions were considered. The control volume technique and the SIMPLE algorithm were used to solve the partial differential equations. The streamlines of the flow field, temperature contours, the entrance length, and the concentration fields were computed. It is found that the entrance zone plays an important role on flow and temperature as well as species distribution. Therefore, the flow cannot be assumed either as fully developed or as plug flow. There is a small but strong thermal expansion zone between the wall and the entrance. Both diffusion and convection affect the heat and mass transfer processes in the expansion zone. Thus the equations of momentum, energy and species conservations should be used to describe hydrogen/air combustion in the monolith reactor. The hot-spot location and concentration field of the homogeneous combustion is strongly influenced by the inlet velocity and temperature, and the equivalence ratio. The catalytic combustion of premixed hydrogen/air mixture over platinum catalyst-coated wall in a cylindrical channel was also simulated.     

微量有机化合物催化燃烧反应器数学模拟

建立了甲苯、二甲苯、环己烷催化燃烧反应器的一维拟均相数学模型 ,在MnCuOx/Al2 O3 催化剂上催化燃烧反应动力学采用Langmuir双曲型动力学方程。模拟计算了废气处理量、废气中有机化合物的浓度、床层入口温度对净化率的影响     

甲烷高温催化燃烧研究进展

甲烷催化燃烧具有环保、高效、节能等诸多优点,引起人们广泛的关注。综述了甲烷高温催化燃烧的研究现状,对甲烷燃烧催化剂材料的研究进展作了介绍,阐述了甲烷高温催化燃烧反应器的概况。     

甲烷高温燃烧催化剂研究进展

催化燃烧具有环保、高效、节能等诸多优点.综述了甲烷高温催化燃烧的研究现状,对甲烷燃烧催化剂材料的研究进展做了较详细的介绍,并阐述了甲烷高温催化燃烧反应器的研究进展.     

Catalytic Combustion of Methane over Rare Earth Stannate Pyrochlore

Well-defined Ln₂Sn₂O₇ powders (Ln = La, Sm and Gd) with a phase-pure pyrochlore structure were synthesized by hydrothermal reaction. The catalytic activities of Ln₂Sn₂O₇ powders for methane combustion were measured. Methane oxidation started at 500 °C and increased with oxidation temperature. Catalytic methane combustion is strongly influenced by the presence of oxygen vacancies that form by breaking Sn–O lattice bonds as the temperature increases. Addition of manganese to the rare earth pyrochlores improved methane oxidation activity. Manganese-doped samarium stannate pyrochlore (Sm₂Sn_1.8Mn_0.2O₇) shows highest the catalytic activity. Light-off and complete oxidation temperatures were measured at about 400 and 650 °C, respectively.     

Simulation of a Reverse Flow Reactor for the Catalytic Combustion of Lean Methane Emissions

This work is focused on the performance prediction of pilot scale catalytic reverse flow reactors used for combustion of lean methane-air mixtures. An unsteady one-dimensional heterogeneous model for t...     

丙烯腈尾气流向变换催化燃烧的实验研究

在固定床反应器中利用HPA型催化剂进行了丙烯腈尾气流向变换催化燃烧实验。考察了在不同尾气组成、不同空速及不同换向周期下流向变换催化燃烧反应系统的热波特性、可燃物的转化率等特性。结果表明,在广泛的操作条件变化范围内,可燃物的转化率均能维持在96％以上,即使空速、气体组成在一定范围内短期波动,流向变换催化燃烧反应系统仍然能够维持正常操作,但在可燃物浓度较低且空速、换向周期与可燃物浓度匹配不合理时反应系统将熄火,浓度较高时将飞温。     

The Effect of Catalytic Washcoat Geometry on Light-off in Monolith Reactors

This paper presents the results of a series of simulations of the light-off of carbon monoxide in excess oxygen in a single channel monolith reactor. The catalytic washcoat geometry is tested for its effect on the light-off position and shape. The simulations used a combination of two and three-dimensional modelling with non-linear oxidation kinetics. Different temperature ramp rates were employed. It is seen that the shape of the washcoat has an influence on the shape of the light-off curve, especially for high values of gas hourly space velocity and larger temperature ramp rates. The washcoat geometry that gives the fastest rise to complete conversion is the one that is the most non-uniform in shape; that is, the one that has thin sections.     

Catalytic Combustion Kinetics: Using a Direct Search Algorithm to Evaluate Kinetic Parameters from Light‐Off Curves

This paper describes a method for evaluating the kinetic constants in a rate expression for catalytic combustion applications using experimental light‐off curves. The method uses a transient one‐dimensional single channel monolith finite element reactor model to simulate reactor performance. The heat and mass transfer models used account for developing flow in the entrance region. A parameter global optimization routine based on a generalized pattern Search algorithm is used to determine the best fit parameters in the rate expression for the oxidation of CO and mixtures of CO and CH4. The algorithm is compared to a more classical gradient method, the Fletcher‐Reeves method.     

不同金属取代LaMAl11O19-δ催化剂的制备及甲烷催化燃烧的性能

采用溶胶-凝胶法制备了系列的LaMAl11019(M=Fe,Co,Ni,Mn,Cu)催化剂,并且用XRD、BET、TEM等技术对其进行表征.进一步研究了M对六铝酸盐催化剂的形成.比表面积、燃烧活性的影响.结果表明M促进了六铝酸盐催化剂的形成,其中Mn取代的六铝酸盐催化剂的热稳定性高,而且具有更高的甲烷催化活性.     

热法磷酸塔内流动与燃烧过程的数值模拟

在全面考虑燃磷塔内燃的燃烧、湍流流动及辐射传热等物理机制的基础上,给出了燃烧塔内磷燃烧过程的数学模型和数值模拟方法。针对云南省磷化工中试基地所提供的燃磷塔的设计结构,进行了磷燃烧过程的数值模拟;模拟结果给出了燃磷塔内的速度场、温度场和各组分浓度场,所预报的壁面热流值与现场试验结果符合较好。     

超细In2O3-SnO2复合催化剂的制备及其催化性能的研究

以InCl3·4H2O及SnCl4·5H2O为原料,用共沉淀法制备超细In2O3SnO2复合催化剂,用XRD、TEM、TPD等对所制备的样品催化剂进行表征.XRD、TEM测定结果表明,所制备的样品粒径20～30 nm,分布窄,用TPD测定了样品对O2及CH4的脱附情况.CH4的催化燃烧试验表明,所制备的In2O3-SnO2复合催化剂具有良好的催化反应活性.     

Catalytic combustion of methane in a monolith washcoat: Effect of water inhibition on the effectiveness factor

This paper reports the results of a numerical investigation of the diffusion and reaction of methane in the washcoat of a catalytic monolith reactor. The kinetic rate expression used is an empirical equation determined experimentally for a palladium oxide catalyst. The effect of water inhibition on the reaction rate is included in the model. A multi-species diffusion and reaction model is used to simulate the process. The model is solved in a 2-D space using a finite element method. It is observed that the inhibiting effect of water tends to lower the observed reaction rate and that a higher surface water concentration results in an increase in the observed effectiveness factor. The effectiveness factor depends on three dimensionless parameters. Strong diffusion limitation can lead to high water concentrations at the interior of the catalytic washcoat.     

甲烷空气部分氧化制合成气喷动床反应器的研究

On the basis of hydrodynamic and scaling-up studies, a pilot-plant-scale thermal spouted bed reactor (50 mm in ID and 1500 mm in height) was designed and fabricated by scaling-down cold simulators. It was tested for making syngas via catalytic partial oxidation (CPO) of methane by air. The effects of various operating conditions such as operating pressure and temperature, feed composition, and gas flowrate etc. on the CPO process were investigated. CH4 conversion of 92.20％ and selectivity of 92.3% and 83.30/0 to CO and H2, respectively, were achieved at the pressure of 2.1 MPa. It was found that when the spouted bed reactor was operated within the stable spouting flow regime, the temperature profiles along the bed axis were much more uniform than those operated within the fixed-bed regime. The CH4 conversion and syngas selectivity were found to be close to thermodynamic equilibrium limits. The results of the present investigation showed that spouted bed could be considered as a potential type of chemical reactor for the CPO process of methane.     

甲烷催化部分氧化制合成气的研究进展

文章叙述了甲烷催化部分氧化制合成气研究的进展情况。介绍了两种主要的反应机理：间接反应机理和直接反应机理;对负载型镍系催化剂的研究现状进行了叙述,并简单介绍了非负载型催化剂;另外还对固定床、流化床、膜反应器以及一些新开发的反应器的特点进行了讨论。     

Rh负载的泡沫独石上甲烷部分氧化的基元反应动力学模拟

Rh负载的泡沫独石催化剂上进行的甲烷催化部分氧化反应,能够在自热、毫秒级接触的条件下达到接近平衡的转化率和选择性.采用CH4在Rh催化剂上发生部分氧化反应的基元反应动力学网络结合平推流模型,进行了一维的反应流模拟,揭示了毫秒级催化反应的反应历程.CH4/O2摩尔比在1.7～2.3,外界温度550～800℃的范围内,模拟结果和实验结果能够很好地吻合.模拟不仅给出了催化剂床层内气相和表面物种的变化情况,还揭示了催化剂有效内表面积和甲烷吸附能力对反应的影响,发现一定程度下有效内表面积的增加和甲烷吸附能力的增强,能够大幅度地提高反应的转化率和选择性.     

多重射流燃烧反应器制备纳米二氧化硅颗粒的数值模拟

建立了不同长径比的千吨级工业多重高速射流燃烧反应器三维物理模型,结合可实现k-ε湍流模型、有限速率/涡耗散模型、涡耗散概念化学反应模型、Discrete Ordinate辐射模型、欧拉-拉格朗日离散相模型、氢气19步详细反应机理与空气龄自定义函数对燃烧反应器内燃烧情况进行了多尺度数值模拟.结果表明,随着燃烧反应器长径比...     

甲烷催化燃烧催化剂催化理论与应用研究进展

概述了甲烷催化燃烧催化剂的研究现状,从组成甲烷燃烧催化剂的3个部分（基体、活性组分、氧化物载体）分别加以论述。通过掺杂一些金属和金属氧化物,不但可以提高高活性贵金属催化剂的热分解温度,还可以提高高温催化剂（如钙钛矿和六铝酸盐材料等）的催化活性。最后简要综述了甲烷催化燃烧反应机理。     

整体型催化剂在天然气部分氧化中的研究进展

由于热量散失和均相反应使直接部分氧化甲烷很难控制,本文介绍了整体型催化剂在天然气部分氧化中的应用,使用整体型催化剂反应可在大空速下自热进行,基本实现干氧化。     

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

Activation phenomena of a Pd/γ-Al₂O₃ catalyst under methane combustion reaction conditions were studied. The activation of the catalyst with time-on-stream is not due to Cl removal from the surface but seems to be related to sintering of the palladium particles. This could induce structural changes in the palladium particle, which would favor the activation of O₂ on the surface of PdO.