流化催化裂化提升管进料段混合研究进展

流化催化裂化是最重要的重油加工工艺之一,提升管反应器是催化裂化装置的关键部分,提升管反应器的进料混合段存在返混严重;油剂两相在提升管截面上浓度分布不均匀等问题。进料段内油滴和催化剂的混合状况对产品的收率与分布有着极为重要的影响。从喷嘴和进料段结构对改善提升管进料段的混合效果进行了分析,同时介绍了近年来研究的新成果,以及设备应用的新进展。     

两段提升管反应器技术在重油催化裂化装置中的应用

论述了两段提升管反应器技术在前郭石化分公司重油催化裂化装置中的应用。通过对单段和两段提升管反应器催化裂化装置运行和标定数据分析对比,说明了两段提升管反应器技术的优越性。应用后装置的产品分布和液体产品收率均明显好转,处理量的加大和液体收率的提高,使装置的经济效益明显提高。     

两段提升管重油催化裂化(Ⅰ型)新工艺的初步研究

针对目前催化裂化提升管反应器后半段催化剂性能严重下降以及产品分布不太合理的状况,提出了采用两段提升管催化裂化新工艺技术取代常规的单段提升管催化裂化工艺技术.该工艺的突出特征是催化剂接力、分段反应、大剂油比和短反应时间. 在对新工艺进行理论分析的基础上,以大庆蜡油掺兑65%渣油为原料,采用ZC-7300催化剂,在小型提升管催化裂化装置上进行了一系列实验,考察两段提升管催化裂化（Ⅰ型）新工艺的可行性和先进性. 实验结果表明：与常规单段工艺相比,在相近转化率下,两段柴油产率提高6～8个百分点,轻油产率提高1～2个百分点;汽油烯烃含量减少,辛烷值提高,产品质量提高. 新工艺在提高柴油收率及改善产品分布和产品质量方面具有明显优势.     

重油催化裂化工艺的新进展

介绍了重油催化裂化工艺的新进展,如毫秒催化裂化工艺、下行床反应器催化裂化工艺、两段提升管催化裂化工艺、多产轻质烯烃的催化裂化新工艺、催化裂化汽油改质降烯烃新工艺等,并对重油催化裂化工艺的发展趋势进行了展望。     

渣油催化裂化反应技术新进展

重油催化裂化技术作为主要的重质油轻质化手段得到了迅速的发展,国内外围绕重油催化裂化的提升管反应器开发了许多新技术。概括介绍了渣油催化裂化提升管反应系统的最新进展,如新型进料喷嘴、轻烃预提升技术、两段提升管催化裂化、提升管末端快分技术、MTC等,并对目前工业提升管存在的问题和有待开发的技术领域进行了讨论。     

提升管-下行床耦合反应器模拟

采用轴径向二维扩散模型对提升管-下行床耦合反应器催化裂化反应进行了数学模拟,并与提升管及下行床进行了对比.结果表明,在下行床之前耦合一段适当长度的提升管不仅可以保证原料具有较高的转化率,而且可以保证目的产品的选择性较高,缩短达到相同产品收率所需的下行床长度.这种耦合反应器充分利用了提升管与下行床各自的优势,并可以根据具体的原料及产品需求调整进料的位置以改变提升段与下行段的长度比例,实现柔性操作.     

浅谈催化裂化技术进展

介绍了国内外催化裂化工艺及反应器技术进展。从满足清洁燃料生产要求、生产低碳烯烃的催化裂化技术进展、重油催化裂化、重油加氢与催化裂化双向组合技术(RICP)几个角度阐述工艺进展。从传统的单提升管反应器、改造后的单提升管反应器、双提升管反应器、下行式催化裂化反应器几个方面阐述了催化裂化反应器的进展。最后展望了未来催化裂化工艺和反应器的发展趋势。     

湍流气固两相流动状况的数值模拟

应用已建立的提升管反应器固两相流动反应模型,对工业催化裂化提升管反应器内在有传热及裂化反应时的湍流气固两相流动进行了数值模拟,得到了气固两相湍充动状况的详细信息,揭示了提升管内部有反应和传热时气固两相湍流流动的基本特征。模拟结果表明,在轴向,径向和圆周方向都存在着流动,湍能与率剂颗粒浓度的不均匀分布,进料段内的流动是整个反应器最复杂的部分。工业提升管反应器内这一复杂的气固两相湍流流动必将对传热和裂     

催化裂化提升管进料混合段研究进展

催化裂化是炼油工业中重要的二次加工过程,提升管反应器是催化裂化装置的核心部分,其中的进料混合段是原料油与催化剂的初始接触阶段,该区域油、剂间的接触与混合效果将对裂化反应的产品分布产生直接影响。在传统的提升管进料段结构中,存在着催化剂分布不均匀、颗粒返混严重等问题,不利于实现油、剂间快速而均匀的混合与反应。针对提升管进料混合段内存在的缺点与不足,国内外研究者提出了诸多改进方法,其中改变进气方式、增加内构件、提升管变径等方案的效果较为显著。     

催化裂化提升管反应器模型的建立

工业催化裂化提升管反应器内既存在着气固两相的湍流流动,又存在着传热和裂化反应,而且这些过程是相互影响,高度耦合在一起的。本文全面系统地考虑湍流气因两相流动,传质,传热及反应等复杂因素及其相互影响,建立了催化裂化提升管反应器三维气固两相流动反应模型,形成了相应的数值解法,编制了大型的模拟计算程序。由此可对工业催化裂化提升管反应器内湍流气固两相流动进行系统的数值模拟研究。     

Kinetic modeling of FCC process

Catalytic cracking of petroleum fractions a process termed as FCC is usually carried out in a reactor block with somewhat complicated hydrodynamic regime. The reactor block is considered as a combination of two different reactors. The riser is a near ideal plug-flow displacement of the catalyst and reaction mixture, while the main reactor vessel (separator) is considered as an ideal mixing CSTR. Temperature gradient along the plug-flow riser can vary on a linear and non-linear dependence. This is reflected by the thermal effect on the cracking products, along the altitude of the riser. Moreover, it can exert a considerable influence on the selectivity of the process in general, as characterized by the diversity of different hydrocarbon groups both in the gaseous and liquid products. The fluid catalytic cracking (FCC) is a process of conversion of a heavy oil fraction into lighter products in a catalytic fluidized reactor. The chemical composition and the structure of the feed are reflected on the catalyst's selectivity and the amount of coke deposited. It is, therefore, necessary to consider the feed type on modeling the process. Cracking reaction in the model was represented as a five-stage process. Reaction rates for the plug-flow riser and the ideal mixing separator are described mathematically in differential and algebraic forms. The model takes into account, exponential dependence of the specific reaction rate on temperature, as well as reflects the influence of the real and bulk catalyst densities, circulation rate, equilibrium and fresh catalyst's activities, reactor pressure, feed rate and unit construction. The model was developed based on a data taken from an industrial FCC unit, that were used to compute the kinetic constants and other parameters. Concrete computed kinetic parameters were compared with corresponding experimental data for adequacy. FCC process is in constant technological development with modernization of especially the riser reactor. Kinetic modeling of the catalytic FCC reactor will give a further understanding of the process and explain the complicated mechanism involved for an efficient and optimal conversion of the feed stock.     

Numerical Simulation on Gas-Solid Two-Phase Turbulent Flow in FCC Riser Reactors(Ⅱ) Numerical Simulation on the Gas-Solid Two-Phase Turbulent Flow

Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.     

Downer reactor: From fundamental study to industrial application

Downer reactor, in which gas and solids move downward co-currently, has unique features such as the plug-flow reactor performance and relatively uniform flow structure compared to other gas-solids fluidized bed reactors, e.g., bubbling bed, turbulent bed and riser. Downer is therefore acknowledged as a novel multiphase flow reactor with great potential in high-severity operated processes, such as the high temperature, ultra-short contact time reactions with the intermediates as the desired products. Typical process developments in industry have directed to (1) the new-generation refinery process for cracking of heavier feedstock to gasoline and light olefins (e.g., propylene) as by-products; and (2) coal pyrolysis in hydrogen plasma which opens up a direct means for producing acetylene, i.e., a new route to synthesize chemicals from a clean coal utilization process. This paper is to give a comprehensive review on the development of fundamental researches on downer reactors as well as the particular industrial demonstrations for the fluid catalytic cracking (FCC) of heavy oils and coal pyrolysis in thermal plasma.     

催化裂化提升管反应器流动反应耦合模型研究进展

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。     

Numerical Simulation on Gas-Solid Two-Phase Turbulent Flow in FCC Riser Reactors(Ⅰ) Turbulent Gas-Solid Flow-Reaction Model

Gas-solid two-phase turbulent flows,mass transfer,heat transfer and catalytic cracking reactions areknown to exert interrelated influences in commercial fluid catalytic cracking(FCC)riser reactors.In the presentpaper,a three-dimensional turbulent gas-solid two-phase flow-reaction model for FCC riser reactors was devel-oped.The model took into account the gas-solid two-phase turbulent flows,inter-phase heat transfer,masstransfer,catalytic cracking reactions and their interrelated influence.The k-V-k_P two-phase turbulence modelwas employed and modified for the two-phase turbulent flow patterns with relatively high particle concentration.Boundary conditions for the flow-reaction model were given.Related numerical algorithm was formed and a nu-merical code was drawn up.Numerical modeling for commercial FCC riser reactors could be carried out with thepresented model.     

小型提升管反应器流动-反应耦合模拟

在提升管气固两相湍流流动模型和重油反应动力学集总模型的基础上,利用Fluent软件建立了催化裂化提升管反应器气固两相流动与反应耦合模型,对实验室小型提升管反应器进行了数值模拟,考察了气固两相的流动、传热、传质与反应过程。结果表明,提升管反应器内气固两相在轴向和径向的流动、传热与反应的分布不均匀。在入口附近。原料和催化剂温度变化显著,各组分的浓度变化剧烈,在提升管上部,变化平缓。反应器出口各组分质量分数的模拟值和实验值基本吻合。说明该模型对提升管反应器出口参数和反应结果具有较好的预测性。     

提升管和下行床在催化裂化过程中的比较

在综合考虑流动、反应、传质的基础上,建立了适用于模拟提升管和下行床反应器中催化裂化过程的二维返混模型,并利用正交配置法进行数值求解,得到了各产物在两种反应器内的不同浓度分布规律。这处结果源于两者流动结构和混合状况的差异。和提升管相比,由于下行床内的气固两相流动更接近平推流,气固速度和颗粒浓度径向分布均匀,气固轴向返混小,因而可得到更高的汽油收率。     

Modeling of vaporization and cracking of liquid oil injected in a gas-solid riser

Vaporization and cracking of liquid oil injected in a gas-solid riser (fluid catalytic cracking riser reactor) was computationally studied in this work. Evaporation of a single drop injected in a stream of gas-solid mixture was analyzed first. A model for simulating evaporation of a drop considering heat transfer from the gas phase as well as from the solid particles was developed. The model relates the evaporation rate of droplet with rate of collisions of solid particles, specific heat capacities of solid and liquid, latent heat of vaporization, relative velocity of gas and liquid and temperatures of three phases. The understanding gained from such a model was then extended to simulate evaporation of liquid drops injected in FCC risers. The Eulerian-Lagrangian approach was used to simulate simultaneous evaporation and cracking reactions occurring in FCC riser reactors. A commercial CFD code, FLUENT (of Fluent Inc., USA) was used. Four and ten lump models were used for simulating cracking reactions. Appropriate user defined functions were developed to implement heterogeneous kinetics and heat transfer models in FLUENT. A special algorithm was developed to calculate accumulated coke on catalyst particles. A boiling point range was considered for simulating realistic oil feedstock. The model was first evaluated by comparing predicted results with published industrial data. The simulations were then carried out to understand influence of key design and operating parameters on performance of FCC riser reactors. The parameters studied included; initial oil droplet distribution, catalyst inlet temperature, catalyst to oil ratio and thermal cracking. The approach, model and results presented here would be useful for optimization of FCC operation, cost to benefit analysis of new FCC nozzles and related decision-making.