进气管内气体分布对塔内气体分布影响探究

在填料塔大型化、薄层化的趋势下,塔内气体初始分布显得尤为重要.因此气体分布器结构以及流场研究也成为人们研究的热点.针对某些大型塔塔径过大,气体分布器结构设计安装均困难的问题,利用计算流体力学(CFD)软件模拟的方法,探索性地对进气管内气体分布对塔内气体分布影响作了初步研究.结果表明:比较合理的进气管内构件对塔内气体分布...     

微型流化床内气体返混

微型流化床基础和应用在近几年受到越来越多的关注。针对微型流化床对气固反应分析的应用要求,利用脉冲示踪法研究了内径10 mm和21 mm两种尺寸微型流化床中的气体返混特性,具体考察了管内径、颗粒静床高度、床料颗粒粒径和气体表观流速对气体返混程度的影响。结果表明:随着床内径、颗粒静床高度和表观气速的减小和床料颗粒粒径的增大,气体在床内的返混程度减小。使用粒径约270 μm粗颗粒时,两种床径的浅层微型流化床中的气体返混程度都较小,对应的Peclet数在27以上,证明了床内气体流动接近平推流,从而为利用微型流化床最小化气体返混对反应测试的影响,获得近本征反应动力学参数提供了流动特性的保障。     

流化床反应器颗粒结块原因与对策分析

流化床反应器在现代工业中的早期应用于粉煤气化的温克勒炉,随着现代流化反应技术的开拓,流化床反应器已在化工、石油、冶金、核工业等部门得到广泛应用。但是流化床反应器的物料结块故障不仅影响产品质量,严重的还会影响生产。本文针对全密度聚乙烯低压气相法流化床层结块的现象,分析了结块的原因,并提出了生产中防止和减少聚乙烯流化床结块的措施。     

流化床反应器研究现状

系统介绍了流化床的研究现状、流化床反应器特点、工业应用、分类以及对流化现象作了具体阐述;对有关流化床计算方面作了具体的介绍;展望今后流化床反应器研究发展方向。     

大型流化床反应器的结构设计

本文主要讲述我公司生产的直径4．2米,总高度284米的流化床反应器的结构设计,对流化床反应器的结构制造,具有一定的参考价值。     

填料塔的气体分布装置

介绍了填料塔的进气结构、几种新型气体分布装置及其多腔分布结构的形式。     

填料塔进料气体分布研究

在６００ｍｍ精馏塔中,对几种进料气体分布器进行了分布均匀性、液沫夹带量和气体阻力的实验测定和分析对比。开发与改进了双切向流线式气体分布器,该气体分布器综合性能较好,结构较简单,操作可靠,已在大型润滑油减压蒸馏塔中应用成功。     

固定床反应器内气体预分布器研究

研究了直径1 000 mm,高3 000 mm的固定床冷模装置中气体预分布器对反应器内气流分布的影响。结果表明:气体分布器可改变床层内气流流形并使径向气流的速度分布趋于均匀;随着表观气速的增加,反应器内气流的不均匀程度增加;分布器的环隙高度在一定的范围可使反应器内气流的不均匀程度相对较好。应用计算流体力学软件CFX对固定床反应器内的流场进行模拟计算,并与大型冷模试验测试结果进行比较,模型计算值和冷模试验测量值吻合较好。     

串行流化床内气固流动控制

针对化学链燃烧分离CO₂技术特点,在一串行流化床（循环床+喷动床）冷态实验装置上,以CaSO₄载氧体为实验原料（d_p= 0.6 mm）,研究串行流化床气固流动特性。基于床内压力分布特征,提出将循环床（空气反应器）沿床高方向划分为鼓泡段和快速流化段2个流型区域,将喷动床（燃料反应器）沿床高方向划分为喷动段、鼓泡段和悬浮段3个流型区域,得出串行流化床内气固流动控制机理。研究并考察了循环床流化风速度、喷动床喷动风速度对串行流化床内反应器间（空气反应器和燃料反应器）气体串混、颗粒循环速率以及床层压降的影响。研究结果表明,流化风是床内颗粒循环的驱动力,流化风速度应控制在 3.77～4.05 m·s^-1;喷动风速度对床内颗粒循环以及系统稳定运行起着关键作用,建议将喷动风速度控制在0.42～0.56 m·s^-1。     

Two-phase modeling of a gas phase polyethylene fluidized bed reactor

A two-phase model is proposed for describing the behavior of a fluidized bed reactor used for polyethylene production. In the proposed model, the bed is divided into several sequential sections where flow of the gas is considered to be plug flow through the bubbles and perfectly mixed through the emulsion phase. Polymerization reactions occur not only in the emulsion phase but also in the bubble phase. Voidages of the emulsion and bubble phases are estimated from the dynamic two phase structure hydrodynamic model. The kinetic model employed in this study is based on the moment equations. The hydrodynamic and kinetic models are combined in order to develop a comprehensive model for gas-phase polyethylene reactor. The results of the model are compared with the experimental data in terms of molecular weight distribution and polydispersity of the produced polymer. A good agreement is observed between the model predictions and actual plant data. It has been shown that about 20% of the polymer is produced inside the bubble phase and as such cannot be neglected in modeling such reactors.     

甲醇制汽油固定流化床试验装置的设计

根据甲醇制汽油反应的工艺要求和影响流化床反应器性能的主要特性参数,设计研制了固定流化床反应器,使其作为前期催化剂实验室研发的一个评价装置,并取得了较佳的效果。     

Flue gas desulfurization in an internally circulating fluidized bed reactor

An internally circulating fluidized bed reactor (ICFBR) was used as a desulfurization apparatus in this study. The height of the bed was 2.5 m, and the inner diameter was 9 cm. The bed materials were calcium sorbent and silica sand. The effects of the operating parameters of the flue gas desulfurization including relative humidity, particle size of the calcium sorbent, inlet concentration of SO₂, difference between the superficial gas velocities in the draft tube and the annulus, and superficial gas velocity in the draft tube on SO₂ removal efficiency (RE) were investigated. It was found that when the relative humidity (RH) was varied from 40% to 80%, the steady state RE had a largest value of approximately 15% when the relative humidity was 60%. When RH = 50%, 60% and 70%, RE decreased initially and then increased. After that RE decreased again until a steady state was reached. In addition, RE decreased with increasing calcium particle size or inlet SO₂ concentration. A larger difference between the superficial gas velocities in the draft tube and the annulus had a higher RE resulting from increasing reactivity of the calcium sorbent caused by a higher attrition rate. Moreover, a higher attrition rate had a higher total volume of the flue gas treated. Finally, a model to predict the steady state RE in ICFBR was proposed. It assumed that the draft tube section was a bubbling fluidized bed while the annulus section was a moving bed. In addition, the effects of the calcium sorbent conversion, attrition rate and gas-bypassing fractions on RE were also taken into account in this model. It was found that the values of RE predicted by this model agreed with the experimental results.     

Propenoxide isomerization in a fluidized bed reactor

Propenoxide isomerization, over lithium orthophosphate as a catalyst, was investigated in a fluidized bed reactor. A mathematical model of the process was developed and its kinetic parameters identified. There is a high degree of selectivity for allyl alcohol.     

Synthesis gas production from natural gas in a fixed bed reactor with reversed flow

The feasibility of producing synthesis gas by partial oxidation of natural gas on a Ni-catalyst in a fixed bed reactor with reversed flow was investigated by means of simulation. A one dimensional reactor model of the non-steady state heterogeneous type, accounting for internal diffusional limitations, was applied. A double temperature peak is observed just after flow reversal, influencing the selectivities at the exit through enhanced steam reforming reactions. The second peak gradually decreases in importance with time during the semi-cycle. The influence of several operating conditions on the reactor performance was studied. Most of the coke deposited in a semi-cycle can be removed after flow reversal. This observation opens new perspectives for the reversed flow operation.     

Electrostatics and gas phase fluidized bed polymerization reactor wall sheeting

Reduction of electrostatic charge accumulation in fluidized bed polymerization reactors can reduce the frequency of reactor wall sheeting incidents and decrease the cost of operating fluidized bed polymerization reactors. The accumulation of excess electrostatic charge in fluidized bed polymerization reactors causes the fluidized polymer particles to adhere to the reactor wall and form wall sheets. Reactor wall sheets are described in order to characterize the problem. Electrostatic forces are compared to other forces influencing fluidization, such as drag forces and van der Waals forces. Literature values of measured particle electrostatic charges are compared to the maximum theoretical values predicted by Gauss’ law applied to the particles and to the entire fluidized bed. Electrostatic charge mitigation techniques are reviewed and future research areas are suggested based on the theoretical analysis and identified knowledge gaps.     

Gas mixing in a turbulent fluidized bed reactor

A series of experiments has been conducted to study mixing and hydrodynamic behaviour of a downward facing sparger in a turbulent fluidized bed reactor. Using pressure measurement techniques, two flow discharge modes were identified around the sparger by injecting a gas tracer into the bed. These are bubbling and jetting conditions. Experimental results show that, under bubbling conditions, bubbles tend to keep their identity, while under jetting conditions a highly turbulent heterogeneous area is formed around the injection point. Due to attrition and erosion of internal heating or cooling surfaces in industrial reactors, the dominant discharge mode is the bubbling pattern. Therefore, in this investigation, the bubbling pattern is studied by measuring the radial and axial dispersion of gas tracer injected to a hot fluidized bed reactor of 20 cm diameter of FCC and sand particles. A three‐phase model is also proposed in order to predict the mixing length. In addition, the effect of sparger configuration on tracer gas mixing was examined for FCC particles.