OPERATION CHARACTERISTICS OF A NEW LIQUID-SOLID CIRCULATING MOVING BED REACTOR

The liquid-solid circulating moving bed reactor is a novel one, which consists of two or more reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through an upper conduit and to the particle transport system through a lower conduit, and then are conveyed into the upper reaction chamber through a riser. The circulating rate of particles and the flow of liquid in the two conduits are key factors to the continuous steady operation of the reactor; they can be controlled by varying operating conditions: the outlet liquid flow rate in the regeneration chamber, the outlet liquid flow rate in the reaction chamber, the inlet liquid flow rate of the reactants, and the flow rate of driving flow. A flow model has been proposed to quantify the operation characteristics of the reactor. The results predicted by the model show satisfactory agreement with the experimental data.     

液固循环移动床反应器操作规律和模拟

液固循环移动床反应 -再生系统由上下两个或两个以上的反应室、再生室、连通管和颗粒提升管组成 .颗粒经再生室、反应室向下移动 ,进入输送管后被向上输送返回至再生室 .颗粒循环能力和各流股间的窜液行为是循环移动床连续操作的关键 .通过实验对该液固循环移动床的颗粒循环、斜管窜液和连接段窜液的规律进行了研究 ,同时建立了循环移动床的液固流动模型 ,并进行了模拟计算     

Study on the stress distribution and modeling of the stand pipe in a circulating moving bed

The liquid-solid circulating moving bed reactor is a novel one, which consists of two reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through a coupling standpipe and to the particle transport system through a bottom standpipe, and are then conveyed into the upper reaction chamber through a riser. A stress distribution model based on the equations of continuity and momentum balance in the reactor is established and used for simulations which shows that the stress concentration regions are at the coupling standpipe and the bottom of the regeneration chamber. To reduce the largest stress in the stress concentration regions and to minimize catalyst consumption, the regeneration chamber should be designed to give a low ratio of height to diameter. Zoning diagrams of the flow patterns in the bottom standpipe are proposed and the flow patterns can be readily deduced from the pressure gradient.     

液固循环移动床反应-再生系统的颗粒循环量调节和输送

液固循环移动床反应－再生系统由上下两个或两个以上的反应室、再生室、连通管和颗粒提升管组成。颗粒经再生室、反应室向下移动,进入输送管后被向上输送返回至再生室。颗粒循环能力决定了反应室和再生室内的颗粒更新速率。是循环移动床操作的关键之一,对反应器的颗粒循环进行了实验研究,提出了一种射流输送和调节结构并对射流输送行为进行了模拟计算。     

耦合反应器提升管段颗粒速度分布及约束特性

A large-scale cold model experimental setup of a riser-fluidized bed coupled reactor was established according to the olefin reduction technology with an auxiliary reactor for FCC naphtha upgrading.Distributions of particle velocity in the riser section were experimentally investigated in the setup.Furthermore,the restriction index of particle velocity was defined to quantitatively show the restriction effects of the riser outlet lotus-shaped distributor and the upper fluidized bed on the particle flow behavior in the riser.The experimental results showed that the riser could be divided into two regions in the longitudinal direction,i.e.,lower traditional transport region and upper restriction region.In the longitudinal direction,the averaged cross-sectional particle velocity in the traditional transport region increased firstly,and then tended to be smooth,while decreased in the restriction region.With the increase of static bed height in the upper fluidized bed,the local particle velocity decreased,and the tendency of change in the core region is more than that in the wall region.Restriction effects of the lotus-shaped distributor and the upper fluidized bed on particle flow behavior enhanced with the increases of superficial gas velocity,solids flux and static bed height in the upper fluidized bed.In the same cross-section,outlet restriction effects enhanced with the increase of the dimensionless radial position r/R,and would not change when r/R≥0.5.     

提升管与气-固环流床层耦合反应器的流体力学特性及流动模型

针对催化汽油辅助反应器改质降烯烃技术,在一套提升管与气-固环流床层耦合反应器大型冷模实验装置上,研究了上部环流床层的流体力学特性。结果表明,在环流床层与提升管耦合操作的情况下,床层内颗粒环流存在两种推动力,分别为静压差推动力和颗粒喷射推动力;环隙与导流筒之间的整体平均固含率差随导流筒表观气速增加而增加,随颗粒外循环强度增加而降低;颗粒环流速度随导流筒表观气速和颗粒外循环强度增加而增加。通过对环流床层进行动量衡算,建立了提升管与环流床层耦合流动的数学模型,模型平均相对误差在15.95％以内。     

Phenomenological approach to interpret the effect of liquid flow modulation in trickle bed reactors at the particle scale

This work analyzes the influence of liquid flow modulation on the behavior of a reaction occurring in a spherical porous particle within a trickle bed reactor. A single first-order reaction between a gaseous reactant and a non-volatile liquid reactant is considered. Non-steady-state mass balances for gas and liquid reactants are formulated and solved under isothermal conditions in order to focus the analysis on the mass transport effects. Dynamic reactant profiles inside the catalytic particle are obtained for different cycling and system conditions. The enhancement factor (ε) due to periodic operation is defined to evaluate the impact of induced liquid flow modulation on reaction rate. Influence of cycling and system parameters on the enhancement factor is also reported for a wide range of conditions. Experimental trends observed by several authors can be explained with this approach.     

提升管-流化床耦合反应器颗粒约束返混区的流动特性及约束作用分析

针对催化汽油辅助反应器改质降烯烃工艺,在一套提升管-流化床耦合反应器大型冷态实验装置上,系统研究了提升管出口段的颗粒流动特性,通过定义约束指数R_i（R_i为颗粒约束返混区实际截面平均固含率与理论截面平均固含率之比）定量反映提升管出口分布器及流化床层的约束作用。结果表明,与常规提升管相比,耦合反应器提升管出口存在一个颗粒约束返混区,其长度主要受表观气速、颗粒循环强度及上部流化床内颗粒静床高度影响;由于出口设置了倒锥形分布器,使得颗粒约束返混区靠近提升管出口区域在表观气速较低和颗粒循环强度较大时,局部固含率最大值出现在量纲 1半径Φ＝0.7处;颗粒约束返混区的约束指数在靠近出口的过程中逐渐增大,气固流动受到分布器及上部流化床层的约束作用亦逐渐增强。     

STRUCTURE OPTIMIZATION OF A CIRCULATING MOVING BED REACTOR

A stress distribution model for a liquid-solid circulating moving bed reactor that consists of a bottom reaction chamber, a top regeneration chamber, a coupling standpipe, a particle transportation system, and a bottom standpipe is established based on the equations of continuity and momentum balance. Simulations show that the stress concentration regions are at the bottom of the regeneration chamber and the coupling standpipe. To reduce the maximal stress and increase the operation flexibility in a reactor for the 2000-ton-per-year production of linear alkylbenzene, the regeneration chamber should have a low height-to-radius ratio (about 9), a suitable half-conical angle between 28° and 35°, and standpipe radius of about 0.05 m.     

STRUCTURE OPTIMIZATION OF A CIRCULATING MOVING BED REACTOR

A stress distribution model for a liquid-solid circulating moving bed reactor that consists of a bottom reaction chamber, a top regeneration chamber, a coupling standpipe, a particle transportation system, and a bottom standpipe is established based on the equations of continuity and momentum balance. Simulations show that the stress concentration regions are at the bottom of the regeneration chamber and the coupling standpipe. To reduce the maximal stress and increase the operation flexibility in a reactor for the 2000-ton-per-year production of linear alkylbenzene, the regeneration chamber should have a low height-to-radius ratio (about 9), a suitable half-conical angle between 28° and 35°, and standpipe radius of about 0.05 m.     

含细长颗粒的洗涤冷却室内的多相分布特性

采用改进的直接取样法,在按几何尺寸缩小的工业气化炉洗涤冷却室冷模装置内,同时测量不同操作条件下的轴径向局部固含率和气含率,对细长颗粒在洗涤冷却室内的多相分布特性进行研究。结果表明：以下降管出口截面为界,洗涤冷却室可分为上部气液固混合区和下部固液流动区,其中上部区域由下降管出口区、破泡板作用区和气垫层区组成,下部区域由气相湍动作用区、回流区和二次流动区组成;在颗粒阻碍效应减速沉降和团聚效应加速沉降的共同作用下,轴向固含率呈现波动分布;环隙气速、固相体积分数和长径比的增加均会增强床层的湍动,促进气体的径向扩散;操作条件的改变使颗粒的漂移速度发生改变,径向固含率分布出现波动;在气相扰动和回流作用下,二次流动区呈现环状流动,流体和颗粒的"壁面效应"使该区域的固含率呈现中心高边壁低的特点。     

Wall-flow filters with wall-integrated oxidation catalyst: A simulation study

Diesel soot abatement via diesel particulate filters composed of so-called wall-flow monoliths is well established. Today, due to recent improvements in the production technology full-featured catalyst functionality can be implemented in the filter walls.

This work focuses on a comparison of the reactor performance of the wall-flow filter and the conventional flow-through monolith. To this end a two-dimensional numerical model is set up for each of the two reactor configurations.

Concentration profiles in the wall-flow filter systematically change as a function of flow velocity.

At high flow velocities transport from the inlet channel into the porous wall is nearly entirely dominated by convection. This leads to uniform axial concentration profiles in the inlet and outlet channel and a steep gradient in the porous wall.

At low velocities radial transport into the porous wall is dominated by diffusive transport. This leads to a negligible radial concentration gradient between the inlet and the outlet channel.

Under most operating conditions relevant for an automotive exhaust catalyst the flow velocity is in an intermediate range with contributions of diffusive and convective transport.

The transition from entirely convection dominated transport at high space velocities to increasingly diffusion dominated transport at lower flow velocities is similarly found for first order kinetics and a generalized Langmuir–Hinshelwood–Hougen–Watson (LHHW) rate law.

Wall-flow filters show systematic conversion advantages over the conventional monolith for a first order reaction. For a reaction with LHHW-type kinetics this effect is not generally observed. It is one major result of this work that the relative performance of the two reactor configurations depends on the kinetics of the catalyzed reaction.     

Phenylacetylene hydrogenation in a three-phase catalytic packed-bed reactor: experiments and model

A mathematical model was developed for the cocurrent operation of a three-phase catalytic packed-bed reactor under both trickling- and pulsing-flow regimes. The local fluctuations of liquid-solid mass transfer, liquid flow rate, and liquid holdup in unsteady pulsing-flow were simulated as periodic square-wave functions. The transport properties employed in the model were obtained using published correlations, while expressions for the intrinsic reaction kinetics were taken from our previous work. The model results were found to be in good agreement with experimental data obtained from a laboratory-scale reactor, and verified the advantage of pulsing-flow operation over trickling-flow.     

下行床煤拔头工艺的产品产率分布和液体组成

基于循环流化床锅炉燃烧技术和下行床技术相结合,在处理能力为8 kg/h的煤拔头工艺热态实验装置上,以内蒙古霍林河褐煤为原料,普通河砂为固体热载体,考察了反应温度和煤粉粒径对气液固产品产率分布和液体组成的影响规律. 结果表明,在实验温度范围内,随着温度的升高,气体和液体产品的产率增加;液体产率随粒径的增大而降低. 当反应温度为660℃、煤粉粒径小于0.28 mm、加料率为4.7 kg/h时,轻质焦油(焦油中的正己烷可溶物)的产率可达7.5%(干煤基,w),其中酚类占57.1%,粗汽油(脂肪烃类)占12.9%,芳香烃占21.4%,极性组分和其他组分占8.6%. 实验表明,下行床由于气固沿重力场并流向下流动的特点,是适合煤拔头工艺的比较理想的反应器.     

双出口分级气流床气化炉内颗粒速度和浓度分布

煤炭分级利用是煤炭高效低碳利用的主要途径之一,提出一种同时制备热解气和合成气的分级气流床气化炉,炉体上部为煤热解室,下部为煤焦气化室。采用PV6M颗粒测速仪对气化炉内固体颗粒的速度和浓度分布进行测量,并运用CFD软件对气化炉内气固两相流场进行模拟。结果表明,在射流发展区域与射流碰撞后的折射流发展区域,颗粒速度较高;边壁区域颗粒速度较低且出现回流现象。在惯性和气流曳力作用下,热解室内大部分颗粒自流进入气化室。热解室上部径向颗粒浓度中心高边壁低;气化室下部径向颗粒浓度中心低边壁高。热解室与气化室进气量比、喷嘴角度及颗粒直径等对气化炉出口颗粒流出量分配有重要的影响。热解室进气量增大,颗粒从热解室出口流出占比先减小后增大;热解喷嘴偏转角与颗粒Stokes数增大,颗粒从热解室出口流出占比减小。     

双出口分级气流床气化炉内颗粒速度和浓度分布

煤炭分级利用是煤炭高效低碳利用的主要途径之一,提出一种同时制备热解气和合成气的分级气流床气化炉,炉体上部为煤热解室,下部为煤焦气化室。采用PV6M颗粒测速仪对气化炉内固体颗粒的速度和浓度分布进行测量,并运用CFD软件对气化炉内气固两相流场进行模拟。结果表明,在射流发展区域与射流碰撞后的折射流发展区域,颗粒速度较高;边壁区域颗粒速度较低且出现回流现象。在惯性和气流曳力作用下,热解室内大部分颗粒自流进入气化室。热解室上部径向颗粒浓度中心高边壁低;气化室下部径向颗粒浓度中心低边壁高。热解室与气化室进气量比、喷嘴角度及颗粒直径等对气化炉出口颗粒流出量分配有重要的影响。热解室进气量增大,颗粒从热解室出口流出占比先减小后增大;热解喷嘴偏转角与颗粒Stokes数增大,颗粒从热解室出口流出占比减小。     

Calorimetric determination of polymerisation conversion in a large laboratory reactor

A calorimetric measuring system for continuous recording of rate of reaction and conversion in a 14 1 polymerisation reactor has been developed. The reactor was jacketed and thermostated with circulating water. The measuring signals to the calculating unit represented the temperature difference between inlet and outlet water, the water flow and the heat losse from reactor to the environment. The measuring system was constructed to calculate correctly the conversion even if the heat losses to the environment changes during the reaction. The applicability of the reactor system was demonstrated by its use in suspension polymerisation of vinyl chloride.     

氯铝酸盐离子液体催化苯与十二烯烷基化反应

针对酸性氯铝酸盐室温离子液体[BMIM][AlCl4]催化苯与1-十二烯烷基化合成十二烷基苯反应体系的物理化学特性,设计了一套可以分别进行间歇和连续操作的连续流动搅拌反应装置。间歇操作的反应结果表明．[BMIM][AlCl4]催化剂体系的总体结果优于传统催化剂无水AlCl3和氢氟酸,催化剂的用量和反应温度可以大大降低,2-苯基异构体的选择性较高。在连续操作条件下,一定的流量范围内实现了离子液体催化剂和反应料液的原位分离,催化剂被有效地局限在反应区域,并因在运转过程中始终未暴露从而得到了比间歇操作更加稳定和高效的反应结果。     

含内构件的循环流化床的动态压力特性

针对含内构件的循环流化床,以石英砂为物料,使用动态压力传感器测量了含内构件的流化床中气固两相流的动态压力,分析了床内的瞬时压力特性. 结果表明,在进出口总压降中,文丘里压降最大,占主床压降的60%以上. 表观气速和固体颗粒循环流率共同影响循环流化床内的压力特性. 压力瞬时波动功率谱分析表明,压力波动对应一个主频,表观气速越小、颗粒循环流率越大时,压力波动越大,且循环流化床底部压力波动比上部大. 加入内构件能有效引导气流,使流动更均匀.     

对撞流反应器甲醇合成实验研究

液相法甲醇合成由于有惰性液体介质的存在,气液相间传质对反应起到了一定的阻碍作用,对撞流反应器使用喷嘴将催化剂浆料雾化从而强化了气液相间传质。文中在对撞流反应器内对甲醇合成温度、合成气比例、气流量、浆料循环量以及喷嘴个数进行了考察,结果表明,温度控制在230℃左右操作比较适宜,二氧化碳参与反应对甲醇合成较为有利,合成气流量在22.4 L/min以后时空产率几乎不再增加,增加浆料循环量和采用对置式二喷嘴或四喷嘴比单喷嘴时空产率和出口甲醇体积分数都有所增加。由结果可知,利用喷嘴雾化和液体对撞可以显著地增强气液传质从而达到增加液相甲醇合成时空产率的目的。