组合约束型提升管出口气固分布器的压降

在一套组合约束型提升管冷态实验装置上,通过实验研究了不同操作条件下提升管出口气固分布器的压降,并与常规气体分布器压降进行了对比。实验结果表明,在零床层及有床层的操作模式下,气固分布器压降均随提升管内表观气速和颗粒循环强度的增加而增大,在颗粒循环强度较低时,气固分布器压降曲线变化的斜率随着表观气速的增加而增大,在颗粒循环强度较高时,气固分布器压降曲线变化的斜率随着表观气速的增加而减小;随着开孔率及上部流化床层压降增加,气固分布器压降呈降低趋势,当流化床层压降达到一定程度后,分布器各孔方可实现有效布气,此后气固分布器压降趋于近似不变;在相同表观气速及开孔率下,气固分布器压降大于常规气体分布器压降。     

不同流型下组合约束型提升管出口段固含率分布

在一套组合约束型提升管冷态实验装置上,研究了气力输送和快速流态化两种流型下,出口段局部固含率分布规律及不同操作条件对固含率的影响。结果表明:局部固含率径向分布整体上呈中心小、边壁大的分布特征,并随分布器开孔率和表观气速的降低而增大,随上部流化床层压降和颗粒循环强度的降低而减小;在快速流态化操作下,局部固含率曲线分布形式与常规提升管类似,而在气力输送状态下,临近出口区域局部固含率最大值通常不出现在边壁处,其位置随表观气速和分布器开孔率增加以及颗粒循环强度和上部流化床层压降降低而远离边壁;两种流型下局部固含率径向分布的均匀性均随表观气速及分布器开孔率的增加而升高,随颗粒循环强度及流化床层压降的增加而降低。     

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。     

垂直筛板流化床中FCC催化剂的流化性能

以FCC催化剂颗粒研究垂直筛板流化床内构件对气固两相流化性能的影响,考察了板孔气速、颗粒循环量和帽罩开孔比等筛板结构对流化床压降和提升量强度的影响. 结果表明,气固两相总体逆流流动条件下,帽罩内气速达4 m/s,气固高速并流喷射无气泡,两相接触好、返混小,属快速流态化. 由于没有气泡,床层压力波动小,在塔板上颗粒返混小. 垂直筛板压降随板孔气速、帽罩底隙高度增大而增大,随帽罩开孔比、板孔径增大而减小,颗粒提升量大,床层压降大. 提升量强度随板孔气速、帽罩底隙高度、颗粒循环量增加而增大,随帽罩高度与塔节高度比增大而减少,随帽罩筛孔孔径变化存在最大值. 当帽罩开孔比为1.2~2.5、板孔面积与帽罩截面积比为0.42、帽罩底隙高与板孔孔径比为0.36~0.64时帽罩流化性能较好.     

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。     

多段分级转化流化床提升管速度场的研究

针对流化床煤气化过程中需要长气固接触时间和高固体浓度,开发了耦合灰熔聚流化床和提升管的多段分级转化流化床。为了研究多段分级转化流化床提升管中局部颗粒速度的径向、轴向分布,在不同的操作条件下,采用PV-6型颗粒速度测量仪在冷态实验装置中系统测定提升管内局部颗粒速度。实验结果表明:提升管中任何径向、轴向位置的颗粒速度随着操作气速的增大而增大,随循环量的增加而减小。操作条件对中心区颗粒速度变化的影响明显高于边壁区。颗粒的加速首先发生在提升管中心区域,然后向边壁区域扩展。颗粒速度径向分布的不均匀性沿轴向逐渐增大,并且受操作气速影响比较大。     

提升管加床层反应器不同操作模式下的压力脉动特性

在提升管加床层反应器冷模实验装置上,分别采取零床层和有床层的操作模式,测量并分析了提升管内的压力脉动行为. 结果表明,有床层操作模式下的提升管内压力脉动标准偏差明显高于零床层操作模式;压力脉动主频零床层操作模式下主要集中于1.56?3.13和0?0.391 Hz,主要源于提升管内颗粒的脉动,有床层操作模式下为12.5?25.0和0?0.391 Hz,12.5?25.0 Hz频段主要源于提升管出口上方设置的气固分布器加流化床层对提升管内气固流动的约束及其影响下的气体脉动行为,0?0.391 Hz频段主要源于提升管段进料的不连续性及其与进料口下方提升气体的相互作用.     

新型液固循环移动床流动特性的实验研究

在新型液-固循环移动床反应-再生冷模装置中,以水-玻璃珠为液-固体系,对300 mm×3 000 mm的液-固循环移动床再生器内的操作域和流动特性进行了研究.实验结果表明,下料管出口和料位高度的相对位置对床层流动状态有较大影响,当料位高度高于下料管出口高度时,床层流动可以分为局部流化床区和移动床区两个区域.随着表观再生液速的增大,移动床区先后经历了移动床流动和散式流化床流动,移动床流动的操作液速为0～6.5 mm/s,散式流化床流动的操作液速为6.5～20.5 mm/s.随着表观再生液速的增大,移动床层各轴向高度颗粒平均速率均增大;表观再生液速超过一定值后,颗粒平均速率基本不变.在各轴向高度床层上,随着表观再生液速的增大,局部流化床区周向影响区中心夹角不断增大.     

耦合流化床提升管流动结构及边壁层厚度的研究

在射流流化床与提升管耦合的多段分级转化流化床冷态实验装置上,采用压力传感器和PV-6型颗粒速度测量仪,对提升管流动结构和边壁层厚度进行了系统研究。结果表明,一定的操作气速下,固体循环量增加使提升管中气固流动状态从稀相气力输送过渡到快速流态化区域。当提升管处于快速流态化区域时,一定固体循环量下,表观气速增加使提升管轴向各个位置的边壁层厚度减小;一定气速下,固体循环量增加使提升管各个截面的边壁层厚度增加,且低气速时提升管各个截面的边壁层厚度随固体循环量增加的程度明显高于高气速时。拟合得到了边壁层厚度与截面平均固体浓度的关系式,较好地预测了快速流态化区域内边壁层厚度随截面平均固体浓度的变化关系,该表达式的计算值和实验值吻合较好。     

16m高气固提升管中的压力梯度与流动行为研究

在较宽操作条件范围对16m高提升管中气－固两相流（空气－FCC颗粒）的压力梯度进行了实验测试,进一步揭示了快速流态化和密相气力输送这两种流动形态的动力学特征及其与操作参数的关系。结果表明,在表观气速增大的过程中气固提升管中的轴向压力梯度并非总是不断趋于均匀分布;提升管高度对快速流态化到密相气力输送状态的过渡有重要影响,对于给定的表观气速,提升管高度增加将使过渡点所应的颗粒循环量和床层颗粒浓度都减小。本实验条件下所有过滤点对应的床层颗粒浓度较为一致,平均为0．0104,并由此得到过渡点操作参数Ug与Gs的关联式。本文研究表明,在以往工作基础上进一步研究提升管高度对流动行为的影响极有必要。     

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.     

提升管出口T型弯头压降特性的实验分析

在大型循环流化床装置上,以FCC催化剂颗粒为实验物料,针对提升管出口T型弯头用动态压力传感器测量了操作参数和结构尺寸变化对其压降的影响,系统地分析了T型弯头的压降特性。实验结果表明T型弯头的压降与颗粒浓度呈线性关系,与入口速度（提升表观气速）呈二次方关系;T型弯头出口管截面积的减小使得压降显著增大;T型弯头盲管高度的增加可使T型弯头的压降降低,但是当盲管高度增加到一定值时,压降减小不明显。盲管高度对压降的影响是由于盲管高度的增加改变了提升管上部压力的分布,使T型弯头入口压力减小,导致T型弯头的压降降低;同时盲管高度的增加也使提升管出口区域的负压约束区长度增加。盲管所形成的负压约束区构成了对提升管出口的约束作用,T型弯头的盲管高度越大负压约束区越长,约束作用越强。     

A study of the pressure balance around the loop of a circulating fluidized bed

Pressure measurements around the loop of a circulating fluidized bed with 152 mm ID riser and L-valve fecuer were analysed to determine the effect of operating parameters (superficial gas velocity in the range 2.2 - 4.0 m/s, solids circulation flux in the range 5 - 50 kg/m² · s and solids inventory, in the range 80 - 180 kg) on the components of the pressure balance. The riser pressure drop, and hence, riser solids holdup were not affected by changes in the inventory of solids in the system, provided riser superficial gas velocity and solid circulation flux were held constant. The mean suspension concentration in the riser was found to be directly proportional to the ratio of solids flux to superficial gas velocity (G / U) in the riser.     

Solids Holdup of High Flux Circulating Fluidized Bed at Elevated Pressure

Experimental studies on the solids holdup of a high‐flux circulating fluidized bed (HFCFB) at an operating pressure up to 0.5 MPa were carried out. The effects of operating pressure, solids mass flux and superficial gas velocity on the solids holdup distribution were systematically tested. It was found that the solids holdup at elevated pressure increases with increasing solids mass flux but decreases with increasing superficial gas velocity, which is similar to the trends at atmospheric condition. As a result, the condition of a high‐density circulating fluidized bed (HDCFB), i.e., solids holdup in everywhere of the riser is larger than 10 %) is easier to be achieved at elevated pressure than in a HDCFB operated at atmospheric pressure. In the current work, the condition of a full HDCFB with Geldart group B particles has been achieved successfully at 0.5 MPa.     

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.     

Fluid mechanics of circulating fluidized beds

A fluid mechanical model of segregated vertical gas-solids flow has been developed. Mass and force balances were set up with the aid of this model and, finally, a dimensionless state and pressure drop diagram was calculated. In this diagram, the pressure gradient caused by the solids transport is plotted in dimensionaless form versus the superficial gas velocity in the form of a particle Froude number. Parameter is the ratio of the solids volumetric flow rate at minimum fluidization to the gas volumetric flow rate. The state and pressure drop diagram is valid for a given gas-solids system, i.e. for a given Archimedes number and given minimum fluidization porosity. The fluid mechanical behaviour of different types of circulating fluidized beds can be explained with the aid of the state and pressure drop diagram for segregated vertical gas-solids flow. As an example, the operating behaviour of circulating fluidized bed with a syphon in the solids downcomer is discussed. Measurements of the circulating solids mass flow rates are compared with calculation results.     

提升管与气-固环流床层耦合反应器颗粒相循环比的模型及预测

引言Geldart A类颗粒气-固环流技术是一种利用气-液环流原理,并结合气-固聚式流化体系特点而开发的一种新型流态化技术[1],具有气固接触效率高、传质传热性能好等优点,被广泛用于石油炼制领域中的催化裂化汽提器、提升管出口粗旋快分的预汽提器、外取热器、石油焦燃烧器和降烯烃反应器等装备中[2]。     

Axial pressure profile in circulating fluidized beds

Design and operation of a circulating fluidized bed requires the knowledge of fluid mechanics. According to heat and mass transfer as well as chemical reactions, the effect of the set superficial gas velocity on the axial pressure profile is of particular interest. The axial pressure profile was measured for a variety of solids, as a function of the superficial gas velocity, in a cylindrical circulating fluidized bed with an inner diameter of 0.19 m and an overall height of 11.5 m. Depending on the solids content and superficial gas velocity, two or one sections can be observed in the plant where the pressure gradient is constant. A pressure profile with one pressure gradient exists only at high gas velocities, so long as the acceleration pressure drop immediately above the gas distributor is negligible. Comparison of measured pressure drops in circulating fluidized beds with those measured in vertical pneumatic conveying led to a state diagram for vertical gas-solid flows. The operation behaviour of different types of circulating fluidized bed plants can be explained with the aid of this diagram.