下行床反应器用于重油催化裂解制取低碳烯烃

建立了一套下行式循环流化床反应装置,利用此装置进行了重油催化裂解制取低碳烯烃的实验研究.以中间基丙烷脱沥青油(DAO)为原料、工业CHP-1分子筛平衡剂为催化剂,主要考察了下行床反应器中反应温度和剂油比对实验结果的影响.试验表明：当以丙烯、丁烯为目标产物时,反应温度存在最佳值,剂油比越大低碳烯烃收率越高.由于下行床具有短停留时间、气固流动更均匀和返混小的优点,能获得更高的产品收率,使干气收率受到抑制.试验结果说明下行床反应器是一种适合于石油烃类裂解工艺过程的反应器形式.     

重油生产低碳烯烃等化工品技术研究进展

当前国内炼油产能过剩,化工品如低碳烯烃及苯-甲苯-二甲苯混合物（BTX）等存在缺口,因此应推动炼油向石化的生产转变,化解过剩产能同时提高化工品供给。我国原油馏分偏重且原油重质化劣质化趋势不可逆转,因此利用重油生产低碳烯烃等化工品成为技术关键。本文介绍了重油生产低碳烯烃的催化裂解单项技术典型工艺,包括重油深度催化裂解（DCC）、催化热裂解（CPP）及重油裂解制烯烃（HCC）工艺,认为催化裂解技术的发展在于催化剂的改性与反应器型式的革新优化,下行床反应器前景更为广阔。同时,本文也介绍了从重油或原油通过加氢裂化联合催化裂解、蒸汽裂解及芳烃装置一体化生产化工品的几种国内外工艺技术及工程项目。在单项技术无法取得明显突破之前,炼化一体化生产化工品具有集约化、高效化、灵活性高及经济效益好等优势。一体化技术的重点在于重油（渣油）的深度转化,可通过渣油的加氢裂化工艺来实现。     

Effect of Feedstocks on High‐Severity Fluid Catalytic Cracking

A novel fluid catalytic cracking (FCC) process, that utilizes a downer reactor, has been developed to enhance the yield of light olefins under high‐severity reaction conditions. The effect of heavier feedstock on this high‐severity fluid catalytic cracking (HS‐FCC) process has been investigated using a small‐scale HS‐FCC pilot plant (0.1 b/d). Hydrotreated and virgin vacuum gas oils (VGO), hydrotreated and virgin atmospheric residues (AR) were used as test‐feeds in a previous study. The yield of desired products, such as gasoline and light olefins, produced from virgin VGO cracking was 79 wt.‐%, which is much higher than that obtained from a conventional FCC process. In the case of hydrotreated VGO, the yield of desired products decreased to 76%, however. On the other hand, AR feeds exhibited a performance similar to VGO with a slight increase in coke formation. In this study microactivity test (MAT) results are reported in which the activity and selectivity of the Y‐zeolite based catalyst is evaluated. Kinetic modeling was also done based on a four‐lump reaction model.     

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.     

热等离子体裂解煤制乙炔下行反应器的研究进展

从反应器的工艺开发角度探讨了热等离子体裂解煤制乙炔下行反应器的研发进程,分析了热等离子体裂解煤制乙炔的快速连串反应特点,对比了下行及上行两种不同类型反应器对能耗及乙炔收率的影响,评述了下行床传递性能的显著优点,进而从超短接触反应、高乙炔收率与流体动力学角度出发指出了热等离子体下行床的集成工艺是裂解煤制乙炔工艺的合理选择。最后提出了制约该工艺实际连续生产的严重结焦难点与解决的方法。     

A comparison of flow development in high density gas‐solids circulating fluidized bed downer and riser reactors

Comparison of flow development in high density downer and riser reactors is experimentally investigated using fluid catalytic cracking particles with very high solids circulation rate up to 700 kg/m²s for the first time. Results show that both axial and radial flow structures are more uniform in downers compared to riser reactors even at very high density conditions, although the solids distribution becomes less uniform in the high density downer. Solids acceleration is much faster in the downer compared to the riser reactor indicating a shorter length of flow development and residence time, which is beneficial to the chemical reactions requiring short contact time and high product selectivity. Slip velocity in risers and downers is also first compared at high density conditions. The slip velocity in the downer is much smaller than in the riser for the same solids holdup indicating less particle aggregation and better gas‐solids contacting in the downer reactors. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1172–1183, 2015     

下行床反应器热试装置设计与开发

气固并行向下流动的下行床反应器比提升管具有气固接触时间短、气固速度及浓度径向分布更为均匀、气固轴向返混大大减少、易实现高固气比操作等特点。在下行床反应器小型热试装置开发过程中,为发挥下行床的技术优势,重点研究和解决了反应器出入口结构、原料雾化、高温高流通量下固体循环量测量与控制等几个关键性的工程问题,为下行床反应器的热试研究和应用开发提供了基础。     

Measurement techniques to characterize the contact between injected liquid and circulating solids in a downer mixing chamber

Gas-solid fluidized-bed reactors operating in either conventional or circulating (riser or downer) modes are used in many applications such as fluid catalytic cracking and fluid coking. In such applications, uniform contact of the liquid feed droplets and entrained particles is essential for minimizing heat and mass transfer resistances and generating high yields of desirable products. This contact may be intensified in the mixing chamber of downer reactors. The objective of this study was to measure the quality of mixing between injected liquid feed and circulating solid particles in a downer mixing chamber.An efficient method was developed to determine the local quality of solid-liquid mixing on a short time scale. The measurement technique used two types of measurements in order to obtain the cross-sectional distribution of liquid-to-solid ratios. First, temperature measurements were used to characterize the solid/liquid distribution and, second, tribo-electric probes were used to obtain the local solids fluxes. The measurement technique has proven to be a very reliable and reproducible method to determine the extent of liquid and solid mixing resulting from a variety of injection configurations. Very good and rapid contact between sprayed droplets and particles can be achieved by using appropriate mixing chamber geometries where four or more liquid spray jets impact each other.     

Mass transfer and reaction performance of the downer and its hydrodynamic explanation

Catalytic decomposition of ozone was carried out in a 15‐m high, 90‐mm inner diameter downer reactor. Radial distributions of ozone concentration at different axial elevations under different operating conditions were measured. The results were explained from the flow structure experimental data and corresponding signal analysis in time domain and frequency domain. The aggregation status of solid particles, relative movement between the gas and solids, and the dynamic behaviour of clusters were considered to have a joint influence on the mass transfer and reaction process in the downer.     

甲苯和甲醇烷基化反应热力学分析与计算

甲苯甲醇烷基化制备对二甲苯是一条增产对二甲苯的新的工艺路线。文章对甲苯甲醇烷基化反应过程进行了较为详尽的热力学分析,并用Matlab语言计算得到不同温度下相关反应的Gibbs自由能、平衡常数以及产物之间的平衡关系等。结果表明,甲苯甲醇烷基化制备对二甲苯副产低碳烯烃在热力学上均能自发进行并能达到很高限度,但是对二甲苯和低碳烯烃的产率受热力学平衡限制。因此,开发高选择性的催化剂将具有广阔的应用前景。     

A Selective and Practical Synthesis of Nitroolefins

A straightforward and general synthesis of nitroolefins from nitric oxide (NO) and olefins is presented. The direct nitration of aromatic olefins, allyl compounds, and acrylic acid derivatives proceeds smoothly at room temperature with high regioselectivity and good yields. The advantages of this novel procedure compared to established nitration procedures are demonstrated.     

A Comparison of Flow Dynamics and Flow Structure in a Riser and a Downer

Flow development and flow dynamics were systematically investigated using local solids concentration measurements in a pair consisting of a downer (0.1 m I.D., 9.3 m high) and a riser of the same diameter (0.1 m I.D., 15.1 m high). Both statistical and chaos analysis were employed. Values for the Kolmogorov entropy (K), correlation dimension (D), and Hurst exponent (H) were estimated from time series of solids concentration measurements. Axial distributions of chaos parameters were more complex in the downer than those in the riser, especially in the entrance section. Flow in the downer was more uniform with a flatter core in all the radial profiles of chaos parameters. The radial profiles of K varied significantly with increasing axial levels due to different clustering behavior in the wall region of the downer. In both the riser and the downer, anti‐persistent flow in the core region and persistent flow behavior near the wall were identified from the profiles of H. Different flow behavior in the region close to the wall in the downer and riser was characterized from the combination of the three chaos parameters. Relationships between chaos parameters and local time‐averaged solids holdup in the core and wall regions of the developed sections in both the downer and riser were also analyzed.     

下行床反应器内催化裂化过程的CFD模拟

耦合湍流气粒多相流模型和催化裂化集总动力学模型,建立了描述下行床内多相流动和催化裂化过程的反应器数学模型,并利用计算流体力学单元模拟软件CFX4.3对下行床内的催化裂化过程进行了数值模拟及分析.模型能预测出在工业应用中反应器内最受关注的诸多参数,如固含率、相间滑移速度、压降、气固相的加速区以及各组分浓度的分布情况.预测结果表明,气相反应的进行将导致反应器内的气粒流动行为发生较大变化,充分考虑反应与流动行为的耦合十分重要;而反应器床径的增大将导致转化率和各产物收率的下降.     

下行式循环流化床用于催化裂化过程的数学模拟

采用十一集总动力学,结合气固流体力学行为和轴、径向扩散行为,建立了适合于提升管及下行式循环流化床催化裂化的数学模型,采用此模型对催化裂化过程计算的结果表明,下行床内目的产品选择性显著高于提升管,但在与工业提升管相同的操作条件下,下行床内原料转化率较低,优势不能发挥。适当增加下行床长度、增大床径、使物料循环反应、增加剂油比、提高反应温度或反应压力等可以改善下行床的反应效果。下行床用于催化裂化过程,与之较匹配的应该是具有更高活性的催化剂,研制新型高活性催化剂也是下行床推向工业的重要措施之一。     

CATALYTIC CONVERSION OF METHANOL TO LOW MOLECULAR WEIGHT OLEFINS

Methanol is converted by use of an ion exchanged Chabazite catalyst to ethylene, propylene and propane with yields of 35, 30 and 25%respectively. The presence of water in the feed increases the selectivity towards ethylene. An increase in pressure from one to 27 atmospheres decreases the yield of ethylene while increasing the yields of propylene and propane. Carbon disulfide in the feed at 6000 ppm changes the character of the catalyst from an olefin producing catalyst to a dehydrogenation catalyst. Carbon disulfide in the feed at 2000 ppm, increases the life of the catalyst in producing olefins. Dimethyl ether accelerates the deactivation process in conversion to olefins. The use of a chabazite catalyst as described herein offers an attractive alternative route for producing olefins from coal based methanol.     

Synthesis of epichlorohydrin from 1,3-dichloropropanol using solid base

In this work the synthesis of epichlorohydrin (ECH) from 1,3-dichloropropanol (DCP) by using solid sodium hydroxide (NaOH) is carefully investigated.Inert organic solvent,l-octanol,is introduced to ensure reaction intensity under control.The reaction performances with respect to apparent kinetics and selectivity are determined to explore optimized reaction conditions and confirm potentials for enhancing productivity in one batch.The dissolution and liquid phase reaction mechanism and instant reaction assumption are proposed and verified through process analysis.A process design towards free additional water is schematically figured out to manipulate solid NaOH,by-product,and unreacted starting materials to realize a nearly closed circuit.This process allows high selectivity over 97％ and complete DCP conversion at 323.2 K within a reaction time less than 20 min.Other advantages include near-zerowastewater emission,economically possible NaOH regeneration from NaCl,and robust operating condition window.     

Evaluation of an improved epichlorohydrin synthesis from dichloropropanol using a microchemical system

Synthesizing epichlorohydrin (ECH) from dichloropropanol (DCP) is a complicated reaction due to the partial decomposition of ECH under harsh conditions. A microchemical system can provide a feasible platform for improving this process by conducting a separation once full conversion has been achieved. In this work, referring to a common DCP feed used in industry, the reaction performance of mixed DCP isomers with NaOH in the microchemical system on various time scales was investigated. The operating window for achieving high conver-sion and selectivity was on a time scale of seconds, while the side reactions normal y occurred on a time scale of minutes. Plenty of Cl?ions together with a high temperature were proved to be critical factors for ECH hydrolysis. A kinetic study of alkaline mediated ECH hydrolysis was performed and the requirements for an improved ECH synthesis were proposed by combining quantitative analysis using a simplified reaction model with experimen-tal results on the time scale of minutes. Compared with the conventional distillation process, this new strategy for ECH synthesis exploited microchemical system and decoupled the reaction and separation with potentials of higher productivity and better reliability in scaling up.     

大型下行式循环流化床反应器颗粒浓度分布研究

采用双光路光纤密度探头研究了内径418mm,高18米大型下行式循环流化床（其中下行床部分长度6．5m)反应器中的颗粒浓度分布，结果表明大直径下行床中颗粒浓度沿径向呈现中心均匀，近壁处存在高浓环形区的分布，这类似于小直径反应器中的结果，随着反应器直径的增加，颗粒浓度分布最大值的径向位置向边壁方向移动，即：当下行床放大时，中心颗粒浓度均匀分布区的面积占整个床层截面积的比例增大，在一种特殊设计的下行床边壁结构中测量了颗粒浓度沿径向的分布，实验结果说明边壁效应对下行床近壁区颗粒浓环的形成起到了重要作用，研究结果将有助于了解下行床反应的放大特性。     

气固下行流化床反应器 Ⅲ气、固混合

与气固并流上行提升管反应器相比，气固并流下行管反应器的轴向气固返混明显降低，而径向气固混和仍然相当大，因而有利于提高气固快速反应的转化率及选择性。本文在分析下行流化床反应器内气、固混合机理的基础上，比较了有关气、固混合的研究方法及结果，并比较了提升管和下行管的不同混合现象，旨在促进对这一课题更加深入系统地研究，以适应循环床下行管反应器设计、放大和模型化的迫切要求。     

合成气直接制低碳烯烃技术进展与经济性分析

合成气直接制低碳烯烃是近年来研究较多的石油替代路线合成重要有机化学品的工艺之一。本文对该工艺的技术进展,包括催化剂和工艺的开发情况进行了综述,认为高催化活性、高选择性催化剂是打破产品分布受ASF规律限制的关键,而反应器和新工艺的开发也可提高低碳烯烃的收率,减少CO2排放,并通过与其它成熟技术的组合,推进该工艺的工业化进程。由初步的技术经济性分析可见,与传统蒸汽裂解和经甲醇制烯烃工艺相比,合成气直接制低碳烯烃工艺具有较强的经济竞争力。