甲烷化反应工艺流程和反应器模拟

通过分析绝热反应曲线和反应过程CO转化率曲线,设计可行的多级绝热固定床甲烷化工艺流程,得到了一个第一甲烷化反应器循环比为3.0,反应器个数为3的甲烷化反应系统。建立绝热固定床反应器的一维拟均相数学模型,在工业操作条件下,分析了该流程中3个甲烷化反应器内的温度和摩尔分数分布规律。在合成气的进料速度800 kmol/h,进料温度553 K,操作压力为3.0 MPa,氢碳物质的量比约为3.0,循环比为3.0的条件下,模拟结果表明:物料在3个反应器出口的温度分别为879,725,611 K;甲烷干基摩尔分数分别为53.48%,79.24%和95.49%;CO在3个反应器出口的转化率分别为82.18%,99.41%和100%。第3反应器出口CH4干基摩尔分数为95.49%,满足了工业生产要求。     

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。     

半连续碳纳米管反应器中试开发及流态化模拟

在间歇过程的碳纳米管制备实验基础上结合经验公式,开发设计了制备碳纳米管的半连续中试流化床反应器,结果表明:催化剂100 g、反应温度650℃时,甲烷平均转化率23.2%,碳纳米管产率为177.5 g/h,操作周期为间歇反应器的1/3,反应器可较好地实现碳纳米管制备功能。用计算流体力学方法对此反应器内的气固两相流化行为进行数值模拟,得到在工况条件下,最佳的催化剂用量为100 g、操作气速为0.15 m/s等工艺参数。     

流化床中甲烷芳构化过程

在石英流化床反应器中研究了无氧条件下甲烷直接催化转化制备芳烃的过程.发现催化剂的诱导期长短、甲烷的总转化率与温度、甲烷分压及甲烷空速相关.在973 K下,液体产品中苯的选择性与萘的选择性随着催化剂的失活呈现不同的变化趋势.所得主要技术指标（甲烷转化率、苯的收率与选择性等）与固定床微型反应器中的结果相近.还研究了催化剂上的积炭对甲烷转化率、催化剂失活的影响,为将来的进一步研究提供了基础.     

绝热多段甲烷化工艺研究

利用净化后的焦炉煤气在500℃的温度下进行甲烷化反应,通过分股的方式将原料气分别通入2个甲烷化反应器,从1~#反应器反应后的气体与其中一股原料混合后通入2~#反应器中;从2~#反应器反应后的部分气体循环至1~#反应器内,其他的气体通入3~#反应器内将剩余的一氧化碳、二氧化碳进行反应。利用Aspen Plus流程模拟软件对绝热多段甲烷化工艺进行了流程模拟,并优化相关参数。最终操作参数的运行结果显示,一氧化碳转化率为100%,二氧化碳转化率为99.67%,甲烷的含量由35.87%变为63.36%,为后续分离制LNG和氢气创造了条件。     

碱催化法制备生物柴油工艺研究

在250m l间歇式高压反应器中,以大豆油为原料,研究KOH催化甲醇酯交换反应制备生物柴油的工艺条件。主要考察了醇油摩尔比、反应温度、反应时间、催化剂用量等操作条件对脂肪酸甲酯转化率的影响。结果表明,当KOH用量为1%(wt),醇油摩尔比为5∶1,反应温度为65℃时,反应时间为15m in,脂肪酸甲酯的转化率可以达到92%。     

水合法制丙二醇的CSTR开车模拟及反应器稳定性分析

以水合法制丙二醇为例,对连续搅拌釜式反应器(CSTR)的开车过程进行了动态模拟研究,分析了开车过程中温度、浓度、转化率随时间的变化曲线,确定了影响反应器开车能否成功的主要因素,并对反应器的抗干扰能力进行了分析.研究结果表明,在反应器进料温度(T0)297.15K的条件下,反应器开车失败;而将反应器的进料温度升至300.00K,可使反应器开车成功:影响反应器开车成功与否的主要因素是反应器的进料温度是否高于其点火温度,而该反应体系的点火温度为297.70 K.借助多态理论指导使反应器成功开车后,在T0为297.15 K的条件下稳态操作,当反应器的进料温度升高时,对反应器的操作稳定性影响不大;当进料温度降温幅度低于 3.00 K时,反应器仍能维持在高转化率的状态下操作:但当反应器的进料温度降温幅度大于或等于 4.00 K时,反应器的操作状态将从高转化率跌落至低转化率,导致反应器的白动停车.山此可知,该反应器虽具有一定的抗扰动能力,但其稳定性较差.     

低浓度甲烷在微小燃烧器中的催化燃烧实验

选用泡沫金属(Fe-Ni)作为催化剂载体, 通过浸渍法制备了整体式催化剂(Pd/Al₂O₃/Fe-Ni)。然后使用该泡沫金属载体整体式催化剂在微小燃烧器中对低浓度甲烷进行催化燃烧实验, 分析了燃烧器温度、甲烷浓度以及流量对甲烷转化率的影响。结果表明, 随着燃烧反应器内温度的升高, 混合气体总流量的降低和甲烷浓度的增大, 甲烷的转化率增大;进一步分析表明温度是影响转化率最关键的因素, 当燃烧反应器内温度为550℃, 甲烷浓度为5%, 总流量为50 ml·min^-1时, 甲烷的转化率可以达到98.7%。     

300 kg/a规模流化床制碳纳米管中试研究

采用Ni-Mg-O复合氧化物催化剂进行了流化床甲烷催化裂解法制碳纳米管的中试实验,研究了主要操作变量对甲烷转化率、催化剂产碳率、产品团聚率及催化剂损失率的影响,得到了适宜的操作条件为：甲烷进气流速16~19 cm/s、催化剂粒径150~220 μm、催化剂加入量50~60 g、反应温度650~700 ℃、反应时间120~140 min。多批次重复性实验表明,在选定的操作条件下,甲烷转化率约为30 %,催化剂产碳率约为10 gCNTs/gCAT。对纯化后的产品进行SEM及TEM形貌表征显示,制得的碳纳米管管径均匀,中空结构明显,碳纳米管的外径为10~30 nm,内径为2~5 nm。     

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。     

Multi-period design of heat exchanger networks

Heat exchanger networks are an integral part of chemical processes as they recover available heat and reduce utility consumption, thereby improving the overall economics of an industrial plant. This paper focuses on heat exchanger network design for multi-period operation wherein the operating conditions of a process may vary with time. A typical example is the hydrotreating process in petroleum refineries where the operators increase reactor temperature to compensate for catalyst deactivation. Superstructure based multi-period models for heat exchanger network design have been proposed previously employing deterministic optimisation algorithms, e.g. (0005 and 0180). Stochastic optimisation algorithms have also been applied for the design of flexible heat exchanger networks recently (0110 and 0115). The present work develops an optimisation approach using simulated annealing for design of heat exchanger networks for multi-period operation. A comparison of the new optimisation approach with previous deterministic optimisation based design approaches is presented to illustrate the utilisation of simulated annealing in design of optimal heat exchanger network configurations for multi-period operation.     

操作参数对余热回收甲醇水蒸气重整制氢过程的影响

以模拟汽车尾气供热的甲醇水蒸气重整（MSR）制氢反应为研究对象,设计了集余热加热与MSR制氢反应于一体的肋式微反应器,考察了反应器进口热风速度、温度,反应物进口速度、温度、水醇比及顺逆流情况对MSR制氢过程的影响。计算结果表明,逆流、水醇比1.3、热风进口速度1.1 m/s、温度773 K、反应物进口速度0.1 m/s、温度493 K为该反应过程的最佳工况参数,此时甲醇转化率为99.4%,模拟汽车尾气余热的热效率为28%,反应器出口氢气的体积分数为69.6%。研究结果对开展余热综合利用及发动机尾气重整制氢掺氢燃烧的研究有借鉴意义。     

Energy efficient and controlled flow processing under microwave heating by using a millireactor–heat exchanger

A continuously operated microwave heated millireactor setup has been developed for performing reactions of highly microwave absorbing media in a controlled and energy efficient manner. The setup consists of a tubular reactor integrated with a heat exchanger. A microwave transparent liquid was used as coolant to extract the excess heat from the reaction mixture, thus controlling the temperature of the reaction mixture by avoiding overshoots and subsequent boiling. A reactor‐heat exchanger shell and tube unit with a diameter of the inner tube of 3·10^?3 m and a shell of 7·10^?3 m inner diameter has been manufactured in quartz. The unit size was defined based on simulation with a heat‐transfer model for the microwave cavity part. Microwave heating was incorporated as a volumetric heating source term using the temperature‐dependent dielectric properties of the liquid. Model predictions were validated with measurements for a range of 0.167·10^?6 to 1.67·10^?6 m³/s flow rates of coolant. The outlet temperature of both the reaction mixture and the coolant, were predicted accurately (tolerance of 3 K), and the process window was determined. The model for the reactor part provided the required length of the reactor for a hetero‐geneously catalyzed esterification reaction. The predicted conversions, based on the obtained temperature profile in the reactor packed with the catalyst bed, known residence times and kinetics of the esterification reaction, were found to be in good agreement with the experimental results. Efficient utilization of microwave energy with heat recovery up to 20% of the total absorbed microwave power and heating efficiencies up to 96% were achieved. It has been demonstrated that the microwave heating combined with millireactor flow processing provides controlled and energy efficient operation thus making it a viable option for a fine chemical production scale of 1 kg/day (24 h period). © 2011 American Institute of Chemical Engineers AIChE J, 58: 3144–3155, 2012     

具有不同操作工况的装置的热集成

针对具有不同操作工况的连续过程,为了使装置在任一工况下均能达到最大节能潜力,基于夹点技术,根据各工况所对应的夹点位置,扩展了夹点设计原则,提出了一个具有不同操作工况的装置的热集成方法,该方法可以使装置中固定不变部分换热网络结构相同,并且在不同工况下装置的换热网络始终是最大能量回收网络.     

CFB air-blown flash pyrolysis. Part I: Engineering design and cold model performance

The objective of this work was to design, construct and test a novel circulating fluid bed fast pyrolysis reactor system for production of liquids from biomass. The novelty lies in incorporating an integral char combustor to provide autothermal operation of the reactor. A reactor design methodology was devised which correlated input parameters to process variables, namely temperature, heat transfer and gas/vapor residence time, for both the char combustor and biomass pyrolyser. From this methodology, a CFB reactor was designed with integral char combustion for 10 kg/h biomass throughput. A full-scale cold model of the CFB unit was developed and tested to derive suitable hydrodynamic relationships and performance constraints. The hot CFB reactor was constructed, its operability was tested and appropriate modifications were accomplished prior to the commissioning.A major requirement for the desired dual-mode operation of the reactor system conceived was the close coupling of the two reactor subsystems, namely the pyrolysis riser (medium temperature) and char combustor (high temperature). The basic CFB reactor design was proven effective in providing the high heat transfer rates – expressed as low voidage values in the riser and high solid circulation rates – to biomass particles in the very short vapor residence times (VRTs) required. The understanding of the complicated aspects related to two-phase gas–solids flow in the standpipe resulted in a smooth, stable transfer of solids over a wide range of operating parameters during cold CFB reactor operation. In the hot CFB unit testing, the use of two and three cyclones in series was proved insufficient to capture char and unconverted wood particles, especially during the reactor start-up phase. These problems were partially faced by adopting a configuration of a primary cyclone and inertia impinger in series, but further development is still required. A variety of configurations for the product collection system were built and tested, the most efficient being a combination of a shell-and-tube heat exchanger (condenser) and a cotton wool filter. However, the liquid recovery configuration gave rise to a number of problems, the most important being gradual plugging of the heat exchanger due to the formation of sticky solid–liquid agglomerates.     

气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为

气相法聚乙烯工艺冷凝态操作模式由于显著提高了循环气移热能力和反应器时空产率,已成为流化床乙烯聚合工艺的主流操作模式。建立了气相法聚乙烯工艺冷凝态操作模式的数学模型,包括流化床反应器模型,多级换热器模型和反应温度、压力以及循环气组成的控制模型。基于此,采用流程模拟方法,计算了系统在反应器温度采用闭环控制时的稳态解;根据系统对小扰动的动态响应特点,定性判断了反应器温度采用开环控制和闭环控制时聚合反应系统的稳定性;考察了系统对1-己烯分压和催化剂进料速率的阶跃响应特性。结果表明,反应器温度采用闭环控制时,聚合反应系统在所考察操作条件下均是稳定的,而采用开环控制时,解曲线被分叉点分割为稳定区域和不稳定区域。反应器温度对1-己烯分压阶跃变化的动态响应表明聚合反应系统存在长、短周期两类振荡,表明冷凝态操作模式下乙烯聚合反应过程是一个多控制回路耦合的复杂过程。     

Bifurcation Analysis of the Fluidized Bed Polyethylene Reactor with Internal Cooler

A mathematical model has been developed to simulate a gas‐phase ethylene polymerization reactor with internal cooler. The model was analyzed to determine the effects of reactor operating conditions on dynamics and stability. The reactor model employed assumed that both the gas and polymer phase in the reactor are well mixed. Comparing the present model to one with external heat exchanger confirms that, in either form, gas‐phase polyethylene reactors are prone to show unstable steady states, limit cycles and excursions toward unacceptably high temperature steady states. It was also observed that, with internal cooler, minor design changes in the cooler area available for heat transfer and in the inlet temperature of the coolant have a significant effect on the low stable steady state range of catalyst feed rates. With internal cooler, the suitable operating range increased with the increase in the area available for heat transfer. This effect is insignificant in the case of a reactor with external heat exchanger. Manipulating the reactor coolant inlet temperature and/or gas velocity can increase the stability range in the reactor with internal cooler as against one with external heat exchanger.     

吹风气余热回收系统中尾部受热面管壁温度的控制

结合实践讨论了吹风气余热回收系统中酸露点对换热器的低温腐蚀和积灰的影响，强调了在换热器的设计和运行中应严格控制管壁温度。     

Stady‐state and Dynamical Simulation of an Autothermal Gasoline Reformer

Detailed numerical simulation is an important tool for the analysis, development and optimization of new reactor systems. In this contribution results of steady‐state and dynamic simulations of a hydrogen production system for mobile applications based on gasoline are presented. The system consists of an autothermal reformer, a high temperature shift reactor and a countercurrent heat exchanger for heat integration. The simulations are based on 1‐D, multiphase, dynamic models, which are solved with the simulation tool PDEX‐Pack. Firstly steady‐state and dynamic simulations of the autothermal reformer alone are presented. Concentration and temperature profiles in the reformer under different operation conditions are discussed and possibilities to improve the performance are assessed. Dynamic simulations of load change and cold start show the fast dynamic response of the reformer due to its low thermal mass. Simulations of the coupled system underline the impact of the heat exchanger design for the system performance, especially under dynamic conditions. Finally dynamic simulations of a possible cold start strategy for the system are discussed.     

DME synthesis and cyclohexane dehydrogenation reaction in an optimized thermally coupled reactor

This paper presents a study on optimization of DME synthesis and cyclohexane dehydrogenation in a thermally coupled reactor. A steady-state heterogeneous model has been performed in order to evaluate the optimal operating conditions and enhancement of DME and benzene production. In this work, the catalytic methanol dehydration to DME is coupled with the catalytic dehydrogenation of cyclohexane to benzene in a heat exchanger reactor formed of two fixed beds separated by a wall, where heat is transferred across the surface of tube. The optimization results are compared with corresponding predictions for a conventional (industrial) methanol dehydration adiabatic reactor operated at the same feed conditions. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize thermally recuperative coupled reactor considering DME and benzene mole fractions as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate and inlet temperature of exothermic and endothermic sides to maximize the objective function. The results suggest that optimal coupling of these reactions could be feasible and beneficial and improves the thermal efficiency of process. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.