合成碳酸二甲酯宏观动力学及反应器数值模拟

在固定床反应器中研究了PdCl_2-CuCl_2-KOAc/AC催化剂上甲醇气相氧化羰基化合成碳酸二甲酯(DMC)反应的宏观动力学,建立了以CO、O_2、甲醇分压表示的幂函数动力学模型,统计检验表明所得模型具有较高的可信度。依据动力学模型,建立了用于该反应过程的固定床反应器二维拟均相模型,借助Matlab软件,模拟分析了空速、原料组成、进口温度、操作压力和管外介质温度等因素对反应过程的影响。模拟计算结果显示,操作压力和空速对反应器的热点温度影响显著,而甲醇的转化率及DMC对CO的选择性受原料组成影响较大。优化确定了在PdCl_2-CuCl_2-KOAc/AC催化剂上甲醇气相氧化羰基化合成碳酸二甲酯适宜的条件为进料组成CH_3OH/CO/O_2的体积比为0.20:0.27:0.53,空速7 500 h~(-1),进口温度160℃,操作压力0.30 MPa。在该条件下,床层的热点温度为214.96℃,甲醇的转化率为51.69%,DMC对CO的选择性为65.92%。     

乙烯环氧化反应器操作参数敏感性分析

采用乙烯环氧化制取环氧乙烷单管一维数学模型计算和实验,研究乙烯环氧化反应操作参数如原料入口温度、冷却介质温度、总传热系数、空速以及入口乙烯、氧和二氧化碳体积分数对列管式反应器轴向热点温度分布和转化率、选择性的影响.结果表明:冷却介质温度、空速以及总传热系数对反应器热点温度有较大影响.在原料入口温度120-210℃、乙烯...     

合成气完全甲烷化固定床反应器数值模拟

以煤制天然气为背景,研究了反应器高径比、进料温度、操作压力、空速、原料气组成对高温甲烷化反应器内部温度和浓度分布的影响。通过建立固定床反应器拟均相二维模型,模拟合成气完全甲烷化过程,采用MATLAB进行数值求解,并与工业侧线试验数据进行对比。结果表明,高径比为2~3时有助于减小热损,可以控制床层热点温度在700℃以下;进料温度升高到400℃,加快了反应速率,导致热点温度过高,接近800℃;操作压力不适宜,直接影响CO的加氢效果;空速由4000提高到16000 h?1时,床层热点显著向反应器出口移动;原料气氢碳比(H2/(3CO+4CO2))增大到2,促进CO转化,而水气比由0.19增加到0.4,可以有效控制床层温升,热点温度在650℃左右。相关研究结果为反应器设计和工艺参数的优化提供了依据。     

两种煤气甲烷化反应器的模拟和比较

建立了耐硫甲烷化外冷列管式反应器的拟均相二维模型和外循环式反应器的拟均相一维模型,考察了设备参数和操作条件对反应床层的影响．从反应工程角度考虑,外冷列管式反应器优于外循环式：外冷列管式反应器在近于等温条件下进行;外循环式反应器存在大量产品气的返混,降低了有效气（CO和H2）含量．     

耦合传质的羰基化固定床反应器传热模拟分析

固定床反应器中进行强放热反应时, 反应器的热点温度对操作参数变化敏感,容易引起飞温,导致转化率下降,影响催化剂寿命。为强化羰基化固定床反应器内热质传递与化学反应的协同性,建立考虑颗粒内扩散影响的羰基化固定床反应器拟均相一维传热模型,考察操作参数对床层热点温度、反应转化率、床层温升的影响。不仅体现传热传质和反应的协同作用,而且影响关系明晰、求解方便。为保证反应转化率,本实验条件下确定催化剂颗粒直径小于等于1.5 mm。反应器入口温度/冷却剂油温既要满足床层热稳定性需求,又要使反应转化率和床层温升都在合理范围内。模拟结果表明在床层入口温度升高的同时,可通过降低冷却剂油温获得良好的反应转化率和较小的床层温升。在此基础上,考察入口环氧乙烷浓度对反应转化率和床层温升的影响。本研究可为固定床反应器满足转化率要求、床层合理温升而选择催化剂颗粒直径、床层入口温度、冷却剂油温和床层入口浓度等操作参数提供计算依据。     

合成气制二甲醚管壳型反应器的二维数学模型与分析

建立了合成气一步法制二甲醚管壳式固定床反应器二维拟均相模型,采用有限差分和Runge-Kutta相结合的方法(MOL法)求解催化床层内关键组分浓度与床层温度的轴向与径向分布,模拟分析了反应管直径和操作条件对反应器性能的影响. 结果表明,当反应管内径为38 mm时,标况下床层热点在距反应管入口2.1 m处,热点温度为262.76℃,最大径向温度差为4.1℃,CO单程转化率为64.12%,二甲醚选择性为89.86%. 反应管直径增大导致热点温度升高,沸腾水温度、入塔气量和CO含量都对CO单程转化率、二甲醚选择性和床层热点温度有较大影响.     

固定床丙烷脱氢反应影响因素分析

丙烷脱氢装置的核心是反应。为了提高反应阶段丙烯的收率,对丙烷脱氢反应机理、脱氢热力学进行理论分析;对反应温度、压力、空速影响转化率、选择性及生焦量进行实验分析;对进料杂质组分影响反应进行定量和定性分析。结果表明：反应温度、压力、空速以及进料杂质组分都会影响丙烯的收率。基于以上分析,对丙烷脱氢反应工艺参数进行优化实验,确定反应较佳的工艺条件为：反应器床层温度585—600℃,反应器绝对压力0.05 MPa,反应器空速0.6—0.7 h^-1。     

甲醇制氢反应器的一维模拟及工况分析

在温度220-280℃、液空速0．8-2．0h^-1、压力1．3-2．7MPa条件下，于无梯度反应器中测定了ALC-1A型双功能催化剂工业颗粒的宏观反应速率，得到了以速度表示的甲醇裂解重整多重反应的双速率宏观动力学方程。建立了甲醇裂解重整制氢工业管式反应器的一维拟均相数学模型，以工业反应器结构尺寸和操作数据为基准计算出计入壁效应及催化剂失活的活性校正因子。考察了不同的原料液配比、系统压力、液空速、壁温及进口温度下甲醇的转化率、氢气的时空产率和床层出口温度的变化。结果表明在一定范围内，降低甲醇在原料液中的含量，提高压力，选择适当的液空速和壁温，将有利于提高反应器的操作性能：单纯提高床层进口温度对反应几乎没有影响。     

固定床反应器甲醇制烯烃反应过程的CFD模拟

基于工业甲醇制烯烃反应过程,建立固定床反应器一维拟均相模型,采用集总动力学模型及FLUENT中的多孔介质传递模型、S-A单方程湍流模型进行反应过程的稳态模拟,在验证模型可靠性的基础上,考察操作参数(进料温度、操作压力、进料水醇比)对甲醇转化率、产物选择性和烯烃摩尔比的影响,得到温度、组成、选择性等参数沿反应管轴向分布的规律。结果表明:操作条件影响甲醇转化率和产物选择性,较合适的操作条件是进料温度723~773 K、操作压力0.3~0.4 MPa、水醇比低于0.5。该研究结果对于甲醇固定床反应过程的研究及工业操作有良好的指导意义。     

小型反应器内气相甲醇制二甲醚操作优化与分析

通过对小型反应器内气相甲醇催化制二甲醚反应进行高温热态实验,探究了反应温度与甲醇质量空速对催化剂床层轴向温度分布的变化规律,同时分析了不同的操作条件对甲醇转化率和二甲醚选择性的影响,从而优化小型反应器的操作参数。研究结果表明：当甲醇质量空速为1 h^-1时,在不同反应温度条件下,催化剂床层会出现约1.7～2.9℃的轴向绝热温升,且催化剂床层热点温度接近于催化剂床层轴向中部位置;当反应温度为250℃,甲醇质量空速为1 h^-1时,催化剂床层轴向温度分布曲线较为平缓,且甲醇转化率和二甲醚收率均较高,即反应温度为250℃及甲醇质量空速为1 h^-1可视为该小型反应较优的操作条件。     

鲁奇甲醇生产装置的数学模拟和工况分析——(Ⅱ)鲁奇管式变换炉

建立了鲁奇甲醇装置中管式变换炉催化床的一维数学模型,模拟计算了变换炉催化床气体浓度、床层温度、冷管内气体温度分布,讨论了不同操作条件对变换率及床层出口温度的影响。     

工艺条件对甲醇脱水制二甲醚反应的影响

以La改性氧化铝为催化剂,在模拟绝热固定床反应器中考察工艺条件对甲醇气相脱水制二甲醚反应的影响。结果表明,甲醇进料温度210℃时,甲醇脱水反应剧烈,绝热温升约130℃。催化剂床层热点温度低于380℃时,二甲醚选择性大于98%,过高温度产生大量副产物甲烷。反应压力对反应影响甚微。在甲醇进料温度240℃(热点温度370℃)、甲醇进料空速1.5 h-1和反应系统压力为50 k Pa条件下,甲醇转化率大于84%,二甲醚选择性大于98.5%,连续运转2 000 h,催化剂无明显失活迹象。     

能源化工与催化固定床一步法制二甲醚催化剂性能

采用固定床反应装置,以共沉淀法制备甲醇催化剂和一步法合成二甲醚催化剂,采用BET、XRD和SEM对催化剂进行表征。在反应压力2.5 MPa、反应温度260 ℃和空速(500~900) h^-1条件下,催化剂催化活性最好,其中,CO转化率≥90%,二甲醚收率≥60%,二甲醚选择性≥65%。     

Performance characteristics of fluidized bed syngas methanation over Ni-Mg/Al2O3 catalyst

The performance characteristics of isothermal fluidized bed syngas methanation for substitute natural gas are investigated over a self-made Ni–Mg/Al2O3 catalyst. Via atmospheric methanation in a laboratory fluidized bed reactor it was clarified that the CO conversion varied in 5% when changing the space velocity in 40–120 L·g?1·h?1 but the conversion increased obviously by raising the superficial gas velocity from 4 to 12.4 cm·s?1. The temperature at 823 K is suitable for syngas methanation while obvious deposition of uneasy-oxidizing Cγoccurs on the catalyst at temperatures around 873 K. From a kinetic aspect, the lowest reaction temperature is suggested to be 750 K when the space velocity is 60 L·g?1·h?1. Raising the H2/CO ratio of the syngas increased proportionally the CO conversion and CH4 selectivity, showing that at enough high H2/CO ratios the active sites on the catalyst are sufficient for CO adsorption and in turn the reaction with H2 for forming CH4. Introducing CO2 into the syngas feed suppresses the water gas shift and Boudouard reactions and thus increased H2 consumption. The ratio of CO2/CO in syngas should be better below 0.52 because varying the ratio from 0.52 to 0.92 resulted in negligible increases in the H2 conversion and CH4 selectivity but decreased the CH4 yield. Introducing steam into the feed gas affected little the CO conversion but decreased the selectivity to CH4. The tested Ni–Mg/Al2O3 catalyst manifested good stability in structure and activity even in syngas containing water vapor.     

Effects of system parameters on the performance of CO2-selective WGS membrane reactor for fuel cells

Performing water gas shift (WGS) reaction efficiently is critical to hydrogen purification for fuel cells. In our earlier work, we proposed a CO₂-selective WGS membrane reactor, developed a one-dimensional non-isothermal model to simulate the simultaneous reaction and transport process and verified the model experimentally under an isothermal condition. Further modeling investigations were made on the effects of several important system parameters, including inlet feed temperature, inlet sweep temperature, feed-side pressure, feed inlet CO concentration, and catalyst activity, on membrane reactor performance. The synthesis gases from both autothermal reforming and steam reforming were used as the feed gas. As the inlet feed temperature increased, the required membrane area reduced because of the higher WGS reaction rate. Increasing the inlet sweep temperature decreased the required membrane area more significantly, even though the required membrane area increased slightly when the inlet sweep temperature exceeded about 160 °C. Higher feed-side pressure decreased the required membrane area as a result of the higher permeation driving force and reaction rate. A potentially more active catalyst could make the membrane reactor more compact because of the enhanced reaction rate. The modeling results have shown that a CO concentration of less than 10 ppm is achievable from syngases containing up to 10% CO.     

Numerical simulation of fixed bed reactor for oxidative coupling of methane over monolithic catalyst

A three-dimensional geometric modelwas set up for the oxidative coupling of methane (OCM) fixed bed reactor loaded with Na₃PO₄-Mn/SiO₂/cordierite monolithic catalyst, and an improved Stansch kinetic model was established to calculate the OCMreactions using the computational fluid dynamicsmethod and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant is 80 ml·min^-1 under standard state, the CH₄/O₂ ratio is 3 and the temperature and pressure is 800 ℃ and 1 atm, respectively. The contour of the characteristic parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated valuesmatchedwell with the experimental values on the conversion of CH₄ and the selectivity of products (C₂H₆, C₂H₄, CO,CO₂ and H₂) in the reactor outlet with an error range of ±4%. The mass fractions of CH₄ and O₂ decreased from 0.600 and 0.400 at the catalyst bed inlet to 0.445 and 0.120 at the outlet, where the mass fractions of C₂H₆, C₂H₄, CO and CO₂ were 0.0245, 0.0460, 0.0537 and 0.116, respectively. Due to the existence of laminar boundary layer, the mass fraction contours of each species bent upwards in the vicinity of the boundary layer. The volume of OCM reaction was changing with the proceeding of reaction, and the total moles of products were greater than reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg·m^-3 at the inlet of the catalyst bed to 2.18 kg·m^-3 at the outlet of the catalyst bed, while the average velocity magnitude increased from 0.108 m·s^-1 to 0.120 m·s^-1.     

碳二前脱丙烷前加氢催化剂工艺条件试验

采用浸渍法制备Pd-Ag/α-Al2O3催化剂,采用碳二前脱丙烷前加氢工艺系统考察反应器入口温度、空速和反应压力对催化剂性能的影响。结果表明,随着反应器入口温度升高,乙炔和丙炔+丙二烯转化率提高,乙烯选择性提高至一定值后趋于稳定,丙烯选择性波动不大,正丁烯生成量增加,较为适宜的反应器入口温度为(60~70)℃;随着空速升高,乙炔和丙炔+丙二烯转化率降低,乙烯选择性提高,丙烯选择性变化不大,正丁烯生成量降低,较为适宜的空速为(12 000~14 000)h-1;随着反应压力升高,乙炔转化率和丙炔+丙二烯转化率略增,乙烯选择性降低,较为适宜的反应压力为3.6 MPa。     

AN EXPERIMENTAL STUDY OF METHANE OXIDATIVE COUPLING IN FIXED BED REACTORS WITH A DISTRIBUTED OXYGEN FEED

Methane oxidative coupling has been carried out in a reactor with a distributed oxygen feed. The system consists of a catalytic bed of Li/MgO in a quartz reactor with one inlet for methane and one or more inlets for oxygen. To enable the comparison between the co-fed mode and the distributed feed mode, an especial experimental design was used in order to maintain the same contact time in the co-fed and in the distributed feed modes, and in order to minimize the temperature gradients caused by the exothermic oxidation process. The results clearly show that a distributed oxygen feed may give rise to significant increases in the hydrocarbon selectivity obtained at a given methane conversion,     

DYNAMICS OF A RESIDUE HYDRODESULFURIZATION TRICKLE BED REACTOR SYSTEM

An adiabatic residue hydrodesulfurization trickle bed reactor packed with a porous catalyst undergoing deactivation is simulated numerically in order to examine the dynamic behavior of this specific reaction system. One dimensional pseudo-homogeneous model incorporating the effects of mass and heat dispersion is used in the mathematical derivation. The parameters used in the simulation are primarily based on the experimental data of Shoji Kodama and other correlations. The method of orthogonal collocation is used to obtain the solution of coupled mass and energy balance equations. The catalyst deactivation model adopted was proposed by Shoji Kodama to include the interaction of demetallization and coking reaction on a catalyst. The performance of the reactor during start-up period and that for long time operation are examined. Meanwhile, step-wise changes of feed composition, feed rate, inlet temperature on the dynamic behavior of the reactor @KEYWORDS: Residue hydrodesulfurization, Dynamics, Trickle bed reactor, Simulation Orthogonal collocation.