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《化工学报》2017,(2)
通过计算流体力学(CFD)的方法,将丙烷裂解反应动力学与流动方程、能量方程耦合,考察了在普通裂解炉管中加装中空立交盘(hollow cross-disk,HCD)内构件对管内流动及裂解反应的影响。结果发现,HCD内构件通过壁面几何形状变化重布了流场结构,以合理的压力损失为代价产生径向速度,并诱导产生纵向涡剪切破坏边界层,强化了流体的湍动程度,降低热阻,提高了温度分布均匀性。相比于普通炉管,加入中空立交盘后,裂解管丙烷转化率提高7.24%,烯烃选择性提高3.67%,乙烯收率降低0.87%,但丙烯收率大幅上升16.50%,烯烃总收率上升6.94%。此外发现,纵向涡产生的径向流动促进了近壁区高温流体和管中心区相对低温流体的换位,流体温度最高下降了0.7℃;与普通炉管相比,新型裂解管出口处重组分浓度下降了28.33%,说明加入中空立交盘可防止近壁面高温区域过度裂解,有助于抑制结焦。在此基础上,结合模拟所得的场分布数据,定量分析了HCD强化传热和传质的机理,并就阻力损失和强化效果做出综合评价。 相似文献
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利用计算流体动力学(computational fluid dynamic,CFD)方法对含新型内插件强化传热辐射炉管(fortified induced turbulence,FIT)进行了流体流动与传热特性的研究,采用RNG双方程模型求解了动量方程和能量方程,给出了FIT炉管内的流体流动和传热特性,包括速度场、湍动强度和温度场的分布;计算了FIT炉管的强化传热因子和压降。研究结果表明,FIT炉管内插件迫使流体流动由活塞流转变为旋转流,增强了流动湍流程度,符合流动-能量场协同理论,同时流体边界层由于FIT炉管的特殊结构而减薄。FIT炉管具有增强辐射传热、减薄边界层、增加比表面积和旋流增强等强化传热特性。相比于普通当量圆炉管,FIT强化传热炉管的整体传热能力提高了20%左右,证明该新型炉管强化传热效果显著,可以在工程实际中应用。 相似文献
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介绍裂解炉出口热电偶结构形式的设计改进,新结构形式热电偶密封材料的选择及生产运行,新结构形式特点,密封性好,方便维修。 相似文献
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乙烯装置裂解炉,因炉管内壁处于渗碳气氛之中,故要求炉管除具有高温强度外,还要求具备优越的耐渗碳性。以前,通常使用内径为3~4英寸的大直径离心铸造管。近年来, 相似文献
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计算流体力学在裂解炉设计上的应用 总被引:3,自引:0,他引:3
阐述了计算流体力学(CFD)在石油化工领域,特别是在裂解炉技术上的应用。内容共分两部分:1.国外公司在裂解炉设计及故障诊断中CFD软件的应用简介。2.应用CFX软件对裂解炉中的关键技术的模拟、分析及计算情况的综述。 相似文献
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通过对乙烯裂解炉管运行工况的分析 ,在金属扩散理论与渗碳失效机理的基础上提出了渗碳产生的应力计算方法。对HP Nb材料制成的乙烯裂解炉管在 832~ 90 2℃下的应力场进行了模拟 ,分析了炉管在温度、内压、渗碳和蠕变等交互作用下炉管管壁应力的分布情况。结果表明 ,渗碳是引起炉管失效的主要因素。 相似文献
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Carl M. Schietekat David J. Van Cauwenberge Kevin M. Van Geem Guy B. Marin 《American Institute of Chemical Engineers》2014,60(2):794-808
The use of one‐dimensional reactor models to simulate industrial steam cracking reactors has been one of the main limiting factors for the development of new reactor designs and the evaluation of existing three‐dimensional (3‐D) reactor configurations. Therefore, a 3‐D computational fluid dynamics approach is proposed in which the detailed free‐radical chemistry is for the first time accounted for. As a demonstration case, the application of longitudinally and helicoidally finned tubes as steam cracking reactors was investigated under industrially relevant conditions. After experimental validation of the modeling approach, a comprehensive parametric study allowed to identify optimal values of the fin parameters, that is, fin height, number of fins, and helix angle to maximize heat transfer. Reactive simulations of an industrial Millisecond propane cracker were performed for four distinct finned reactors using a reaction network of 26 species and 203 elementary reactions. The start‐of‐run tube metal skin temperatures could be reduced by up to 50 K compared to conventionally applied tubular reactors when applying optimal fin parameters. Implementation of a validated coking model for light feedstocks shows that coking rates are reduced up to 50%. However, the increased friction and inner surface area lead to pressure drops higher by a factor from 1.22 to 1.66 causing minor but significant shifts in light olefin selectivity. For the optimized helicoidally finned reactor the ethene selectivity dropped, whereas propene and 1,3‐butadiene selectivity increased with a similar amount. The presented methodology can be applied in a straightforward way to other 3‐D reactor designs and can be extended to more complex feedstocks such as naphtha. © 2013 American Institute of Chemical Engineers AIChE J 60: 794–808, 2014 相似文献
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Computational fluid dynamics‐based steam cracking furnace optimization using feedstock flow distribution
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Yu Zhang Pieter A. Reyniers Carl M. Schietekat Kevin M. Van Geem Guy B. Marin Wenli Du Feng Qian 《American Institute of Chemical Engineers》2017,63(7):3199-3213
Nonuniform temperature fields in steam cracking furnaces caused by geometry factors such as burner positions, shadow effects, and asymmetry of the reactor coil layout are detrimental for product yields and run lengths. The techniques of adjusting burner firing (zone firing) and feedstock mass flow rate (pass balancing) have been practiced industrially to mitigate these effects but could only reduce the nonuniformities between the so‐called modules (a group of many coils). An extension of the pass balancing methodology is presented to further minimize the intra‐module nonuniformities, that is, variation between the coils within a module, in floor fired furnaces. Coupled furnace‐reactor computational fluid dynamics‐based simulations of an industrial ultraselective conversion (USC) furnace were performed to evaluate four different feedstock flow distribution schemes, realizing equal values for coil outlet temperature, propene/ethene mass ratio, maximum coking rate and maximum tube metal temperature (TMT), respectively, over all the reactor coils. It is shown that feedstock flow distribution creates a larger operating window and extends the run length. Out of the four cases, the coking rate as criterion leads to the highest yearly production capacity for ethene and propene. Uniform maximum coking rates boost the annual production capacity of the USC furnace with a nameplate ethene capacity of 130 103 metric tons per year with 1000 metric tons for ethene and 730 metric tons for propene. For industrial application, achieving uniform maximum TMT is more practical due to its measurability by advanced laser‐based techniques. Most steam cracking furnaces can be retrofitted by optimizing the dimensions of venturi nozzles that regulate the feedstock flow to the coils. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3199–3213, 2017 相似文献
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M. W. Collins M. Ciofalo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,52(1):5-47
Fluid transport behaviour is of great importance within the chemical process industry and in biotechnology. The complexity of this behaviour, reflected in the nature of the fundamental partial differential equations which describe it analytically, means that it has to be treated by numerical methods. In this paper the basic equations are given, and the approaches necessary to treat laminar and turbulent flows are carefully explained. As digital computers have increased in size, so has the comprehensiveness of the problems which can be treated, and the development of typical computer programs is described. Problems of accuracy and experimental validation are also surveyed, and it is shown that recent developments in whole-field optical measurement methods, and image and data processing are all involved here. Then, a review of work at City University is shown to comprise typical examples of applications to engineering situations and biotechnology problems. Chosen instances of the former are flow and heat transfer behaviour for convective enhancement caused by roughness elements, and the design balancing of a thermosyphon. The latter include such diverse studies as blood flows in arterial bifurcations, and heat and mass transport in grain storage. They involve the three-dimensional and transient capabilities of current codes, and their applicability to non-standard geometries. 相似文献
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催化裂化(FCC)工艺在重质油轻质化过程中发挥着重要作用, 而FCC提升管反应器的模型化是催化裂化新工艺与新装备的开发、催化裂化装置稳定操作与生产调优等常需做的工作。本文首先根据流动模型与反应模型不同的集成方式对提升管反应器流动-反应耦合模型进行了归纳与分类, 并回顾了国内外流动-反应耦合模型的研究历程, 指出了耦合模型的发展趋势;随后对当前研究较多的计算流体力学(CFD)流动-反应耦合模型进行了较为全面的阐述, 包括对耦合模型的应用场合、模型求解解耦方法的研究情况等均作了介绍, 同时还分析了该类耦合模型所存在的不足之处, 并指出工业提升管反应器在线采样技术的开发在耦合模型的验证工作上的必要性;最后, 对FCC提升管反应器流动-反应耦合模型研究进行了总结与展望, 以期能够为FCC提升管反应器模型化新方法的提出以及耦合模型的验证工作等研究给予借鉴和指导。 相似文献
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填料塔内气体分布器对进料气流的分布作用和填料塔的分离效率,特别是对低压降、高效填料有重大影响。文中运用计算流体力学(简称CFD),采用欧拉-拉格朗日二相流模型建立了填料塔内双切向气体分布器内三维瞬态气液二相流模型,气体的湍流运动采用k-ε湍流模型计算。模型中考虑了二相之间的作用力,包括液滴所受的曳力和虚拟质量力。求解时时间项采用隐式格式,时间步长取1×10-4s,对流项采用二阶迎风格式,压力-速度耦合方程的求解采用了S imp lec方法。在不同操作条件下,模型计算得到的压降、夹带、气体分布不均匀度和文献报道的实验值吻合较好。从而可以看出,CFD模型可以较为准确地描述双切向环流式气体分布器内瞬时气液二相流场。 相似文献
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Guozhao JI Guoxiong WANG Kamel HOOMAN Suresh BHATIA Jo?o C. DINIZ da COSTA 《Frontiers of Chemical Science and Engineering》2012,6(1):3
This work reviews the development of computational fluid dynamics (CFD) modeling for hydrogen separation, with a focus on high temperature membranes to address industrial requirements in terms of membrane systems as contactors, or in membrane reactor arrangements. CFD modeling of membranes attracts interesting challenges as the membrane provides a discontinuity of flow, and therefore cannot be solved by the Navier-Stokes equations. To address this problem, the concept of source has been introduced to understand gas flows on both sides or domains (feed and permeate) of the membrane. This is an important solution, as the gas flow and concentrations in the permeate domain are intrinsically affected by the gas flow and concentrations in the feed domain and vice-versa. In turn, the source term will depend on the membrane used, as different membrane materials comply with different transport mechanisms, in addition to varying gas selectivity and fluxes. This work also addresses concentration polarization, a common effect in membrane systems, though its significance is dependent upon the performance of the membrane coupled with the operating conditions. Finally, CFD modeling is shifting from simplified single gas simulation to industrial gas mixtures, when the mathematical treatment becomes more complex. 相似文献
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José Sierra‐Pallares Daniele L. Marchisio María Teresa Parra‐Santos Juan García‐Serna Francisco Castro María José Cocero 《American Institute of Chemical Engineers》2012,58(2):385-398
Supercritical fluids have been extensively used for particle production of many natural and pharmaceutical substances providing useful alternatives for pharmaceutical and nutraceutical particulate system formulation. Among the different methods, the gas or supercritical antisolvent (GAS or SAS) process and its variants, have received a considerable interest due to the wide range of materials that can be micronized. Controlling particle formation in order to nucleate small particles is a key issue in GAS and SAS processes and this is directly related to mixing at all scales. In this work, we focus on numerical simulation of the process, emphasizing mixing modeling. Different mixing devices characterized by different nozzles are analyzed, to get an insight into mixing dynamics and its influence on the final particle size distribution. Results show that mixing is determinant in obtaining small particles, and that mixing at the microscale is a significant parameter to account for in the proper design of precipitators. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
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Olumayowa T. Kajero Rex B. Thorpe Tao Chen Bo Wang Yuan Yao 《American Institute of Chemical Engineers》2016,62(12):4308-4320
Computational fluid dynamics (CFD) is a simulation technique widely used in chemical and process engineering applications. However, computation has become a bottleneck when calibration of CFD models with experimental data (also known as model parameter estimation) is needed. In this research, the kriging meta‐modeling approach (also termed Gaussian process) was coupled with expected improvement (EI) to address this challenge. A new EI measure was developed for the sum of squared errors (SSE) which conforms to a generalized chi‐square distribution and hence existing normal distribution‐based EI measures are not applicable. The new EI measure is to suggest the CFD model parameter to simulate with, hence minimizing SSE and improving match between simulation and experiments. The usefulness of the developed method was demonstrated through a case study of a single‐phase flow in both a straight‐type and a convergent‐divergent‐type annular jet pump, where a single model parameter was calibrated with experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4308–4320, 2016 相似文献