A Comprehensive Review of the Influence of Heat Exchange Tubes on Hydrodynamic,Heat,and Mass Transfer in Bubble and Slurry Bubble

Bubble and slurry bubble column reactors(BCRs/SBCRs)are used for various chemical,biochemical,and petro-chemical applications.They have several operational and maintenance advantages,including excellent heat and mass transfer rates,simplicity,and low operating and maintenance cost.Typically,a catalyst is present in addition to biochemical processes where microorganisms are used to produce industrially valuable bio-products.Since most applications involve complicated gas-liquid,gas-liquid-solid,and exothermic processes,the BCR/SBCR must be equipped with heat-exchanging tubes to dissipate heat and control the reactor’s overall performance.In this review,past and very recent experimental and numerical investigations on such systems are critically dis-cussed.Furthermore,gaps to befilled and critical aspects still requiring investigation are identified.

Simultaneous production and utilization of methanol for methyl formate synthesis in a looped heat exchanger reactor configuration

In this investigation, a novel thermally coupled reactor （TCR） containing methyl formate （MF） production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting feature of this TCR is that productive methanol in the exothermic side could be recycled and used as feed of endothermic side for MF synthesis. Other important advantages of the proposed system are high production rates of hydrogen and MF. The configuration consists of two thermally coupled concentric tubular reactors. In these coupled reactors, autothermal system is obtained within the reactor. A steady-state heterogeneous model is used for simulation of the coupled reactor. The proposed model has been utilized to compare the performance of TCR with the conventional methanol reactor （CMR）. Noticeable enhancement can be obtained in the performance of the reactors. The influence of operational parameters is studied on reactor performance. The results show that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is required to validate the operation of the novel reactor.

Review on the effect of heat exchanger tubes on flow behavior and heat/mass transfer of the bubble/slurry reactors

Bubble/Slurry bubble column reactors(BCR/SBCR)are intensively used as multiphase reactors for a wide range of application in the chemical,biochemical and petrochemical industries.Most of these applications involve complicate gas–liquid/gas–liquid–solid flow behavior and exothermic process,thus it is necessary to equip the BCR/SBCR with heat exchanger tubes to remove the heat and govern the performance of the reactor.Amounts of experimental and numerical studies have been carried out to describe the phenomena taking place in BCR/SBCRs with heat exchanger tubes.Unfortunately,little effort has been put on reviewing the experiments and simulations for examining the effect of internals on the performance and hydrodynamics of BCR/SBCR.The objective of this work is to give a state-of-the-art review of the literature on the effects of heat exchanger tubes with different types and configurations on flow behavior and heat/mass transfer,then provide adequate information and scientific basis for the design and the development of heat exchanger tubes in BCR/SBCR,ultimately provide reasonable suggestions for better comprehend the performance of different heat exchanger tubes on hydrodynamics.

Macroscopic Structural Analysis on a 10 kW Class Lab-Scale Process Heat Exchanger Prototype under a High-Temperature Gas Loop Condition

A PHE (Process Heat Exchanger) is a key component in transferring high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for the massive production of hydrogen. Last year, a 10 kW class lab-scale PHE prototype made of Hastelloy-X was manufactured at the Korea Atomic Energy Research Institute (KAERI), and a performance test of the PHE prototype is currently underway in a small-scale nitrogen gas loop at KAERI. The PHE prototype is composed of two kinds of flow plates: grooves 1.0 mm in diameter machined into the flow plate for the primary coolant, and waved channels bent into the flow plate for the secondary coolant. Inside the 10 kW class lab-scale PHE prototype, twenty flow plates for the primary and secondary coolants are stacked in turn. In this study, to understand the macroscopic structural behavior of the PHE prototype under the steady-state operating condition of the gas loop, high-temperature structural analyses on the 10 kW class lab-scale PHE prototype were performed for two extreme cases: in the event of contacting the flow plates together, and when not contacting them. The analysis results for the extreme cases were also compared.

核电站蒸汽发生器传热管电磁超声导波自动化检测系统设计

蒸汽发生器传热管作为高温气冷堆核电站一回路压力边界的关键部件,承担着热交换及辐射屏障的重要作用,其结构完整性严重影响核电安全运行。针对该类特殊结构传热管的在役检查难题,设计了专用的电磁超声导波自动化检测系统,研制了内置单点检测式的磁场增强型电磁超声导波探头,开发了采用模块化组件的五轴联动多自由度自动运载装置,提出了基于机器视觉的管孔动态定位方法,建立了蒸汽发生器全尺寸模拟体试验平台并开展了定位精度测试与缺陷检测试验。试验结果表明所设计的自动化检测系统可实现任意位置目标管孔的高精度定位及自动行走,可识别模拟体上异种钢焊缝处与距离检测端约60 m处的刻槽缺陷,有效检测范围覆盖传热管全长,有望为高温气冷堆核电站蒸汽发生器特殊结构传热管的质量健康评价提供技术支撑。

示范快堆中间热交换器材料316H钢钠中老化行为研究

316H钢是中国示范快堆中间热交换器的主要材料,随着运行时间的增加,其老化效应不断累积。为探索316H钢在示范快堆中间热交换器运行工况下的老化行为,此研究分别在353℃和535℃静态钠条件下对316H钢管材和板材试样进行了1000~8000 h的相容性试验,并对试验后的样品开展微观表征、腐蚀速率测量以及力学性能测试等分析。结果显示:353℃条件下试样几乎不发生腐蚀现象,而在535℃条件下,高温加速了扩散使得材料的老化行为显著,随着试验时间的增加,材料在钠中的腐蚀转为稳态阶段。研究表明:316H钢在钠中的老化行为受到钠的温度、浸泡时间以及材料制造工艺等因素影响,在低氧低碳的低温钠环境中有较好的抗老化能力,在温度相对较高、时间较长的钠环境中存在老化迹象。

Experimental Studies of Heat Transfer Characteristics and Properties of the Cross-Flow Pipe Flow Melt Lead

The process of heat transfer in a HLMC cross-flow around heat-transfer tubes is not yet thoroughly studied. Therefore, it is of great interest to carry out experimental studies for determining the heat transfer characteristics in a lead coolant cross-flow around tubes. It is also interesting to explore the velocity and temperature fields in a HLMC flow. To achieve this goal, experts of the NNSTU performed the work aimed at the experimental determination of the temperature and velocity fields in high-temperature lead coolant cross-flows around a tube bundle. The experimental studies were carried out in a specially designed high-temperature liquid-metal facility. The experimental facility is a combination of two high-temperature liquid-metal setups, i.e., FT-2 with a lead coolant and FT-1 with a lead-bismuth coolant, united by an experimental site. The experimental site is a model of the steam generator of the BREST-300 reactor facility. The heat-transfer surface is an in-line tube bank of a diameter of 17 × 3.5 mm, which is made of 10H9NSMFB ferritic-martensitic steel. The temperature of the heat-transfer surface is measured with thermocouples of a diameter of 1 mm being installed in the walls of heat-transfer tubes. The velocity and temperature fields in a high-temperature HLMC flow are measured with special sensors installed in the flow cross section between the rows of heat-transfer tubes. The characteristics of heat transfer and velocity fields in a lead coolant flow were studied in different directions of the coolant flow: The vertical (“top-down” and “bottom-up”) and the horizontal ones. The studies were conducted under the following operating conditions: The temperature of lead was t = 450°C - 5000°C, the thermodynamic activity of oxygen was a = 10-5 - 100, and the lead flow through the experimental site was Q = 3 - 6 m3/h, which corresponds to coolant velocities of V = 0.4 - 0.8 m/s. Comprehensive experimental studies of the characteristics of heat transfer in a lead coolant cross-flow around tubes have been carried out for the first time and the dependences for a controlled and regulated content of the thermodynamically active oxygen impurity and sediments of impurities have been obtained. The effect of the oxygen impurity content in the coolant and characteristics of protective oxide coatings on the temperature and velocity fields in a lead coolant flow is revealed. This is because the presence of oxygen in the coolant and oxide coatings on the surface, which restrict the liquid-metal flow, leads to a change in the characteristics of the wall-adjacent region. The obtained experimental data on the distribution of the velocity and temperature fields in a HLMC flow permit studying the heat-transfer processes and, on this basis, creating program codes for engineering calculations of HLMC flows around heat-transfer surfaces.

基于反应器-换热网络耦合的C4+烯烃裂解装置催化剂再生周期优化

为了研究烯烃催化裂解装置催化剂失活对系统的影响,优化催化剂再生周期,构建了考虑催化剂失活的反应与换热网络通用集成模型。基于反应和催化剂失活动力学、换热网络集成原理和公用工程迁移规律,构建了反应器-换热网络耦合集成模型,可确定反应器参数和换热网络目标能耗随催化剂失活的变化规律,以单位产品的平均能耗为评价指标优化催化剂再生周期。据此模型探讨了烯烃催化裂解装置催化剂活性变化对反应器出料组成、温度、换热网络最小公用工程用量以及单位产品平均能耗的影响规律,确定了催化剂的最佳再生活性为0.8,最佳再生周期约为4.5天。优化后,单位产品平均生产能耗可降低41.5%。

铅铋反应堆新型双层换热管式主热交换器设计与优化分析

双层换热管的设计可以有效降低换热管破裂事故的发生概率,但管间接触热阻会导致换热管传热效率降低,不利于铅铋反应堆一回路系统热量的顺利导出,因此需要优化双层换热管的设计。本文以铅铋反应堆双层换热管式主热交换器为研究对象,提出在双层换热管间隙中填充镓基石墨烯纳米流体作为热界面材料,分析换热管长度、壁厚、外径和间距对传热性能的影响规律,并与未填充热界面材料的双层换热管式主热交换器传热性能进行对比分析;分别以JF因子和成本效率比(Cost-effectiveness Ratio,CER)为优化目标,以上述4种参数为优化变量,采用遗传算法对主换热器传热性能进行优化和综合评估,得到一种铅铋反应堆新型双层换热管式主热交换器设计方案。优化后的主换热器总传热系数增加5.79%,一回路压降提升2.32%,JF因子提升5%,CER因子提升24.62%。结果表明:在双层换热管间隙中填充镓基石墨烯纳米流体可以在降低蒸汽发生器管破裂事故概率的前提下,有效提高双层管换交换器的传热性能。

内嵌SiC-He螺旋管热交换器的三氯化铝反应炉散热特性研究

为解决三氯化铝反应炉炉内高温及余热积累问题,提出一种新型内嵌式SiC-He螺旋管热交换器结构,利用Fluent软件在恒定热源下对换热管中流动换热进行数值模拟,采用正交试验和极差分析的方法研究管径、螺距及横向管间距等对管内流动换热特性和反应炉散热特性的影响。试验结果表明,管径对管内流动换热特性影响最大,螺距影响最小,随着横向管间距的增大,炉内温度分布由对称逐渐趋向均匀。最优参数组合为管径70 mm、螺距100 mm、横向管间距1600 mm。

高温气冷堆蒸汽发生器换热管电磁超声导波检测方法研究

高温气冷堆蒸汽发生器螺旋换热管是压力边界相对薄弱的部分,若出现降质破损,可能引起放射性介质泄漏并造成堆芯损伤。针对该类换热管由于管路复杂缺乏无损检测方法的现状,提出了适用于高温气冷堆蒸汽发生器复杂结构换热管的电磁超声导波检测方法,开发了专用电磁超声导波检测仪及检测探头,建立了1∶1的高温气冷堆蒸汽发生器换热管全尺寸模拟体试验平台,开展了灵敏度测试优化试验及换热管全长缺陷检测试验。试验结果表明,该电磁超声导波检测方法能够有效解决高温气冷堆蒸汽发生器换热管在役无损检测难题,所开发的电磁超声导波检测仪和检测探头能够在单点位置实现换热管长距离全覆盖检测,可有效识别模拟体上换热管异种钢焊缝薄弱处与远端约60.2 m处截面损伤率为16.8%的刻槽缺陷,验证了高温气冷堆蒸汽发生器换热管电磁超声导波在役检测的可行性。

催化裂化汽油烯烃含量对S Zorb装置长周期运行影响分析

介绍了某公司催化裂化汽油中烯烃含量的上升对S Zorb装置进料换热器(E101)、反应器过滤器(ME101)等设备以及装置工艺参数调整的影响。该公司S Zorb装置中原料烯烃的质量分数在短时间内从21.5%上升到28.0%,不仅造成装置中反应进料换热器(E101)管程结焦严重,换热能力大幅下降,换热器偏流现象加剧,而且使得反应器过滤器(ME101)压差短时间内明显上涨,严重影响了装置的安全运行,同时还造成装置的辛烷值损失加剧。为保证装置长周期安全运行,针对烯烃结焦现象,提出了加强原料和关键设备监控、及时调整反吹系统和反应器温升以及严格控制醚后碳四回炼流程等优化建议。

加氢装置循环氢流量波动原因分析

某炼油厂2.2 Mt/a渣油加氢装置循环氢压缩机出口流量出现了较大幅度的异常波动,且循环氢流量较低,反应器催化剂床层压力降波动大,装置处理量提升困难。对引起波动的原因进行了分析,确定根本原因为混合氢与热高分气螺纹锁紧环换热器内漏,装置正常生产过程中,应确保平稳操作,并密切关注螺纹锁紧环换热器螺栓预紧力的变化情况,为解决同类装置生产过程中遇见的类似问题提供借鉴。

Selection of organic Rankine cycle working fluids in the low-temperature waste heat utilization

In the current study, simulations based on the engineering equation solver （EES） software are performed to determine the suitable working fluid for the simple organic Rankine cYcle system in different temperature ranges. Under the condition of various temperatures and a constant thermal power of the flue gas, the influence of different organic working fluids on the efficiency of the subcritical organic Rankine cycle power generation system is studied, and its efficiency and other parameters are compared with those of the regenerator system. It is shown that the efficiency of the subcritical organic Rankine cycle system is the best when the parameters of the working fluid in the expander inlet are in the saturation state. And for the organic Rankine cycle, the R245fa is better than other working fluids and the efficiency of the system reaches up to 10.2% when the flammability, the toxicity, the ozone depletion, the greenhouse effect and other factors of the working fluids are considered. The R60 l a working fluid can be used for the high-temperature heat source, however, because of its high flammability, new working fluid should be investigated. Under the same condition, the efficiency of the organic Rankine cycle power generation system with an internal heat exchanger is higher than that of the simple system without the internal heat exchanger, but the efficiency is related to the properties of the working fluid and the temperature of the heat source.

甲醇反应器的CFD模拟与换热优化

混合气制备甲醇是目前较为常用的工业生产甲醇方法,利用CFD软件模拟甲醇的固定床反应器,在Fluent中输入主副反应的动力学,得到模拟结果并针对该强放热反应提出设备换热上的优化方案,在提高甲醇产量的同时,保证反应器内部有较高的正向反应速率。

不同结构控温变换反应器的技术特点分析

控温变换技术凭借着自身能够从根本上克服“双高”粗煤气变换反应催化剂床层超温难题的优势,获得很多企业及科研单位的青睐,是近些年来发展势头极为强劲的控温技术。国内具有代表性的几大公司都开发了自己的控温变换技术,每种技术的控温变换反应器结构都有所不同。详细介绍了每种结构的控温变换反应器的技术特点,并进行对比,对控温变换反应技术及反应器的选择具有指导意义。

可变换热面积等温变换炉及其工艺流程开发

常规等温变换炉在应对催化剂末期升温工况时表现并不理想,因此在消化吸收其技术优势的基础上,开发出了可变换热面积等温变换炉,完成了配套粉煤气化造气合成甲醇的可变换热面积等温变换工艺流程开发,阐述了该工艺技术的特点和优势,为相应工程设计及工艺选择提供参考。

开式自然循环回路流动不稳定性及其抑制措施研究

为了研究开式自然循环回路运行过程中的流动不稳定现象,并对可能的抑制措施进行验证,本文采用RELAP5程序建立了详细的实验回路分析模型,通过该模型计算结果与实验数据进行比较,验证了该模型在模拟开式自然循环回路流动及其不稳定现象的准确性。在该模型基础上,对自然循环回路运行过程中的流动不稳定现象进行了分析,对采用不可凝气体注入以抑制流动不稳定性现象的措施进行了验证。结果表明,通过在回路上升段注入一定速率的不可凝气体,能够较好地抑制回路运行过程中的流动不稳定现象,并且能够提高回路的循环流速,有利于提高回路排热能力。

催化裂化汽油吸附脱硫装置高负荷长周期运行总结

针对中国石油化工股份有限公司广州分公司的1.5 Mt/a S Zorb装置,考察了影响装置长周期平稳运行的因素。采取使用国产高通量滤芯及在转剂线上使用耐磨管件,对再生取热盘管进行改造,对闭锁料斗程控阀进行预防性维修等措施解决了装置长周期运行瓶颈,实现了在95.06%设计负荷工况下连续平稳运行超过49个月的目标,关键设备反应器过滤器运行超过4 a,期间压差未超过30 kPa。