循环气冷却器的设计

循环气冷却器是聚丙烯装置中的核心换热器,利用壳程侧冷却水吸收管程侧循环气中夹带的聚合反应热,控制循环气温度,保障反应器平稳操作。循环气冷却器为固定管板式结构,管、壳程壳体均采用碳钢,换热管材质根据冷却水的不同可选用碳钢或双相钢;通过折流板缺口区不布管和壳程入口设置防冲杆等结构能有效降低管束振动发生的概率;管箱采用锥形结构,通过在管箱内设置导流板限制循环气流通区域避免粉料堆积。本文对循环气冷却器的整体结构、折流板形式、防冲杆设置和管箱结构等进行了介绍,就该设备的材料选择、结构设计等问题进行了探讨。     

EDR软件在管壳式换热器设计中振动分析的运用

管壳式换热器的振动设计在工程设计中经常被忽略,造成换热管破裂并给生产带来不利影响。通过分析诱发换热管振动的机理,换热器壳程横流速度的增加,将引起换热管较大振动甚至共振。由此带来不同程度的磨损甚至断裂。理论参数组成的用于检测换热管振动的振动判据是考量换热器是否承载振动的基础。利用Aspen EDR软件的振动分析功能,有目的地对管壳式换热器设备结构中最可能遭受振动破坏的区段进行分析,解读报告,是一种在设计之初有效避免和消除振动影响的方法。并且可以给出防治换热器振动的多项措施,包括确定多种工况,开停车分析,U型管设计,进料管尺寸,入口环形分布器设置,入口速度限制,压应力检测等等。     

一段蒸发加热器振动原因分析及处理

针对尿素装置50%扩能改造后一段蒸发加热器振动的原因进行分析,结果表明振动原因是管、壳程的负荷加大,介质流速增加,设备产生异常振动。通过将设备壳侧固定板式折流板改为螺旋折流板、入口增加防涡挡杆等措施,减小振动,效果明显。     

管壳式换热器壳程传热强化研究进展

对比分析了管壳式换热器壳程传热强化的主要方式和壳程管束支撑结构的研究进展。大多数管壳式换热器壳程强化结构兼具管束支撑的功能,主要以不同形式的折流杆、整圆形孔板、空心环、管束自支撑和螺旋折流板等代替传统的弓形折流档板,结构的优化提高了换热器壳程传热系数,且有效降低了壳程的流动阻力,缓减了换热器壳侧管束的振动和结垢,从而提高了换热器的传热性能。     

石脑油加氢装置反应换热器内漏原因分析与解决措施

对石脑油加氢装置原料与反应产物换热器管束泄漏的发现经过和设备状况进行了描述。对管束泄漏的原因进行分析,认为主要是换热器壳程流体诱发的振动导致管束的破坏。对泄漏的管束提出了修复方案,并提出了生产实践中可以采取的防止换热器流体诱发振动的措施。     

核电常规岛高低压加热器流动阻力计算问题讨论

针对高低压加热器流动阻力计算,对换热管摩擦阻力系数相关经验式进行了对比分析,并对U形管弯曲管道摩擦阻力系数计算及进出口局部阻力系数计算提出了新的建议。针对加热器壳程饱和蒸汽冷凝工况,阐明了壳程压降的主要影响是使壳程冷凝换热推动力下降,而壳程压降的主要构成则是进口局部阻力压降和防冲板阻力压降。基于蒸汽冲击防冲板的流动特征,提出了防冲板压降计算模型,该模型既反映了压降随防冲板距离管口远近而变化的特点,又与现有阻力系数经验取值有一致性,对设计应用有参考价值。     

螺旋折流板换热器在石油化工行业中的应用

通过实验对比分析弓形折流板和螺旋折流板换热器的壳程传热与流动特性,得出单位压降条件下螺旋折流板换热器壳程对流传热系数均高于弓形折流板换热器;当壳程流量相同时螺旋折流板换热器壳程压降远低于弓形折流板换热器,随着流量的增加二者相差越大.结果表明螺旋折流板具有单位压降条件传热系教高,流动阻力小,能有效防止管束振动和适用范围广的优点,在石油化工领域是冷换设备较为理想的选择.     

换热器腐蚀类型分析及防腐对策研究

针对某乙烯厂裂解车间换热器腐蚀情况进行调查,采集腐蚀样品,通过宏观与能谱分析、水质分析得出该车间换热器腐蚀类型主要有三种:处于H2O-H2S-CO2-HCl腐蚀环境引起的点蚀;壳程入口高速流体冲击管束引起的冲刷腐蚀;管束表面沉积物引起的垢下腐蚀等。根据腐蚀产生的相关原因,通过操作工艺控制、水处理工艺控制、设计制造工艺控制三方面提出相应防腐措施,控制并降低系统腐蚀。     

折流板换热器壳程流场数值模拟与结构优化

基于多孔介质与分布阻力的概念,采用FLUENT软件对单弓形折流板换热器的壳侧流场进行了三维数值模拟,模拟结果与实验结果吻合较好。在此基础上针对折流板换热器壳程压降大、能耗高、存在传热死区等的缺点提出了壳程流场的改进方案,通过数值模拟可以看到壳程流场改进后不仅具有压降低、场协同性能好、基本无传热死区等特点,而且在一定程度还提高了管束抗流体诱导振动的性能。     

精馏塔顶冷凝器的节能改造

简要介绍某精馏塔顶冷凝器开车过程中因管束和壳体的温差太大,换热器壳程气体进口没有设防冲板,造成换热管振动,导致塔顶冷凝器气体进口处的换热管断裂,经采取措施后加以解决。同时将塔顶冷凝器原采用循环水冷却改造为加软水副产0.2MPa(G)蒸汽,既节约了水资源,副产蒸汽还可外用。     

Design of multiple shell and tube heat exchangers in series: E shell and F shell

Multiple shell and tube heat exchangers in the series are employed to handle the temperature cross in the chemical process industries. Depending on the degree of temperature cross, certain number of heat exchangers (either E or F shell type) need to be connected in series such that the temperature cross in each exchanger is within allowable limit. Determination of the number of exchangers for the given terminal temperatures is essential during heat exchanger design phase. In this paper, using finite difference calculus, modeling has been done to calculate the number of shells required for both E and F shell cases. In addition, equations are developed to determine hot and cold fluid temperature profiles across all heat exchangers. Design procedure is illustrated with the help of a case study and the capital cost of both cases is compared. Issues related to E shell and F shells are also discussed.     

椰壳、椰壳渣与脱灰椰壳渣热解及热解动力学

用热重技术分析了椰壳类活性炭原料的热解过程,采用Coats-Redfern积分法求解了热解反应动力学模型。椰壳渣及脱灰椰壳渣热解失重过程主要集中在280~370℃之间,在热失重速率曲线上呈单峰,而椰壳热解失重主要集中在230~300℃和300~350℃两个温度范围,在热失重速率曲线上呈双峰。在低温段三者热解反应表观活化能差别较大,高温段差别较小,且最大反应速率均出现高温段。     

Core–shell latex containing fluorinated polymer rich in shell

Core–shell latex with polyacrylate rich in core and fluoropolymer rich in shell was prepared by semicontinuous emulsion polymerization in the presence of mixed emulsifiers. The solids content of the latex was about 25 wt %. The polymerization conditions for the latex were discussed. The morphology of latex particles was characterized by transmission electron microscopy and the surface properties were determined by the Wilhelmy method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1147–1153, 2002     

Characterization of activated carbon produced from almond shell and hazelnut shell

Ammonium chloride-impregnated and untreated almond shell and hazelnut shell samples were carbonized in a flow of nitrogen at relatively low temperatures. Pore structure characterization and sorption capacities of activated carbons prepared from shells of almond and hazelnut indicated that treatment with NH₄Cl increased the total surface area and improved sorption characteristics. Chemical activation carried out at 350°C gave products with surface area values above 500 m² g^?1. On the other hand, the surface area values observed for the products obtained from untreated raw materials were about half of this value. The surface area of products obtained from NH₄Cl-impregnated samples reached values of over 700 m² g^?1 when the carbonization temperature was increased 700°C.     

窑筒体裂纹的处理

河南省七里岗水泥厂2号窑是1000t/d新型干法生产线,采用三档支撑的φ3.2m×46m回转窑,于1994年12月份投产,1998年分解炉改造后,1999年实现了年度达产,由烧优质烟煤改为烧本地的低挥发分煤,大窑运转率达到92％,2001年10月系统检修时,托轮岗位工发现烧成带筒体在中档轮带附近18mm与25mm过渡钢板焊缝处有一微小环向裂纹,经过超声波探伤,裂纹长140mm,最深处达15mm。我们采用焊接方法进行修复,收到了较好的效果。l 简体裂纹产生原因分析     

山竹壳合成贝壳粉负载纳米铁催化降解铬黑T

以山竹壳提取液和贝壳粉制备了贝壳粉负载的纳米零价铁（MS-NZVI/SP），探究其催化铬黑T的类芬顿降解效果。采用SEM、XRD、FTIR等手段对制备的材料进行表征。结果表明，MS-NZVI/SP被成功制备，且呈均匀球状颗粒，表面覆盖了有机物多酚，具有较好的稳定性和重复使用性。通过单因素实验优化了MS-NZVI/S对铬黑T降解性能，得到优化条件为：贝壳粉与纳米零价铁负载质量比1∶1，温度35℃，溶液pH为3，投加4 mL过氧化氢，100 mg合成的材料。在优化条件下，铬黑T的降解效率可达到93.01%，其降解过程符合准二级动力学模型。     

Effect of the core‐shell impact modifier shell thickness on toughening PVC

The shell thickness of a core/shell impact modifier is found to be the single most important factor in the toughening of rigid polyvinyl chloride (PVC). When the shell thickness is greater than a critical value of 15.8 nm, these core‐shell elastomeric particles are able to remain structurally intact and well dispersed within the PVC matrix after melt blending. However, too thick a shell thickness results in a hard core (high modulus) of these core/shell particles and loss of the rubbery nature required of an efficient impact modifier. Therefore, these over‐thick particles can act only as rigid fillers, not as efficient rubbery modifiers. On the other hand, when the shell thickness is less than the critical value of 4.9 nm, too thin a shell layer is simply unable to fully protect and cover the inner rubbery core during vigorous processing conditions, and these core‐shell particles tend to connect with one another through the partially exposed core to form a cellular‐like structure, thus resulting in poor toughening efficiency. Regardless of the particle size, as long as the shell thickness of these core/shell elastomers is between these two critical values (15.8 nm and 4.9 nm), they all display high efficiency in toughening rigid PVC. Polym. Eng. Sci. 44:1885–1889, 2004. © 2004 Society of Plastics Engineers.     

核壳PBA/PMMA乳液粒径分布规律与壳层聚合研究

通过半连续饥饿态法合成了核壳型PBA/PMMA乳液,并利用激光粒度仪时实监控壳层聚合阶段粒子粒径变化,结合理论数学计算模型,研究了壳层单体加料速度与补加乳化剂的量对平均数均粒径及其分布与总粒子数的影响.理论计算乳液中的总粒子数的变化规律和对比反应前后粒径大小,并通过傅立叶红外光谱证实了核壳结构的存在.核壳聚合中壳层聚合机理为单体在加入种子核乳液过程中大部分先在水相中均相成核形成PMMA低聚物,随后由于表面吸附作用而迁移到PBA核表面成为活性中心继续聚合成为壳层.