氨合成塔内催化剂床层同平面温差处理方法探讨

文章分析了产生氨合成塔内催化剂床层同平面温差的各种原因，并探讨了处理氨合成催化剂床层同平面温差的方法。     

浅谈φ600XF－ⅢJ型氨合成塔内件的冷管效应及径向温差的控制

本文以本厂和几个使用φ６００ＸＦ－ⅢＪ型内件的小氮肥厂的实际生产情况为依据，分析了ⅢＪ型内件存在“冷管效应”及产生同平面温差的机理和操作控制方法。     

一次GC型氨合成塔触媒温差过大事故处理过程

通过兖矿鲁南化肥厂GC型氨合成塔使用过程中出现的轴向层触媒同平面温差过大问题,技术人员根据问题现象,结合工艺流程特点和设备结构特点,综合分析了可能产生GC型氨合成塔内触媒床层同平面温差过大问题的各种原因,采用排除法缩小原因范围,并最终确定问题原因。文章介绍了问题的处理过程及改进措施,吸取了事故教训,总结了经验。     

合成塔同平面温差的分析

通过对氨合成塔使用过程中出现的同平面温差现象的分析，找出了温差产生的原因，提出了修改方法及意见。     

Ø1 400 mm ZFJ冷管型甲醇合成塔内件的设计与应用

通过对甲醇合成反应最适宜温度的计算,确定1 400 mm ZFJ冷管型甲醇合成塔内件的结构和移热方式.工厂实际应用表明,该内件具有平面温差小、产量大、结构牢靠、操作方便等特点,适合化肥企业的联醇生产.     

(φ)1 400 mm ZFJ冷管型甲醇合成塔内件的设计与应用

通过对甲醇合成反应最适宜温度的计算，确定φ1400mm ZFJ冷管型甲醇合成塔内件的结构和移热方式。工厂实际应用表明，该内件具有平面温差小、产量大、结构牢靠、操作方便等特点，适合化肥企业的联醇生产。     

冷激型氨合成塔内件故障原因分析及材料选用浅议

氨合成塔内件使用环境严苛,其设计制作及运行维护尤为重要。简介合成氨生产特点及氨合成塔的基本结构,结合某180 kt/a合成氨装置氨合成塔冷激型内件(采用三轴一径冷激结构,内件材质为0Cr18Ni9)运行至第10年时的故障案例——第二层、第三层氨合成催化剂床层同平面温差日益加大(加负荷过程中尤为明显),检修发现冷激气分布器丝网损坏致催化剂进入了分布器内,基于氢对碳钢的腐蚀、对比几种不锈钢材料(304、30408、321)的性质以及铁素体不锈钢/304奥氏体不锈钢之475℃脆性进行原因分析,认为造成氨合成塔内件冷激气分布器丝网破裂的原因为304奥氏体不锈钢中含有较多的铁素体以及铁素体不锈钢之475℃脆性。并提出冷激型氨合成塔内件选材注意事项及相应的预防措施。     

轴径向合成塔运行中的问题探讨

对轴径向氨合成塔运行中出现的同平面温差大和径向层入口温度偏低等问题进行了分析探讨，提出了稳定操作、净化气体成份、改进触煤装填方案、提高内件组装质量等建议。     

温差变化工况下接管螺纹接头密封形式的改造

分析了温差变化工况下设备内部接管密封失效的原因,通过将传统平面密封形式改为函式的O形圈密封,将螺纹接头接管改为内外双套管等方式及将原普通螺纹接头改为O形圈函式密封和迷宫密封结合的特殊结构,解决了在温差变化工况下接头松动导致平面密封压力不足而产生泄漏的问题。     

锅炉汽包热应力的产生及控制研究

就锅炉汽包壁温度变化引起的热应力进行讨论,详细分析了汽包上下壁、内外壁温差的产生原因、温差引起的热应力的产生过程和热应力对汽包寿命的各种影响因素,提出了控制汽包壁温差的措施,以保证汽包安全运行。     

废热锅炉(TLE)泄漏原因及维修方案

列举了废热锅炉（TLE）出现换热管泄漏的原因，并根据不同的泄漏情况，检修时间和现场条件提出了封堵内管，更换内管，更换外管和更换中间体等维修方案，同时给出了参考焊接工艺，对维修实践有一定的指导作用。     

Residual stresses in polymers I: The effect of thermal history

The distribution of residual stresses in quenched modified poly(phenylene oxide) (PPO) specimens was investigated. Quenching was carried out from temperature level above T_g to various temperatures below T_g. As expected, compressive stresses were measured at the surface layers while tensile stresses were in the inner layers. The ratio between the tensile and compressive stresses varied, depending on the thermal history. The level of residual surface stresses was found to depend on both the total temperature difference during cooling and the initial specimen temperature. At constant initial temperature the surface stresses are proportional to the total temperature difference, whereas, at constant final temperature the surface stresses are inversely proportional to the total temperature difference. An empirical correlation describing the surface stresses as a function of thermal history has been suggested. The differences between present theories and experimental data are discussed. emphasizing the apparent discrepancy regarding the influence of initial temperature above T_g on the level of residual stresses.     

直硝高压釜损坏原因分析及改进设想

介质内氧化性物质的腐蚀性及釜内外压差与外压失稳等是造成直硝高压釜损坏的直接原因 ,提出了相应改进方案     

硫化机硫化外胎露线原因剖析和改进措施

叙述硫化外胎胎冠花纹沟露线、胎冠中心线露线、胎肩露线、胎圈露线以及胎里露线等问题的特征和弊端，提出结构设计、生产工艺和设备条件各方面的预防和改进措施：同一规格、不同花纹的轮胎要用不同的胎面挤出口型，胎肩曲线、内衬层厚度等设计要合理；压延、挤出、成型和定型、硫化各工序要严格执行工艺规程；要经常检查硫化设备运行状况，对磨损和老化部件及时更换。     

硝酸装置低压反应水冷器的优化改造

介绍了双加压法硝酸装置低压反应水冷器的运行工况及特性,分析了水冷器腐蚀的原因主要为温差应力腐蚀、高温冷凝稀硝酸冲刷和Cl-聚集的应力腐蚀。针对腐蚀原因,提出了采用内孔焊先进制造工艺、改变设备布置形式等优化改造措施,能够有效解决目前存在易腐蚀的问题。     

What causes differences of C-S-H gel grey levels in backscattered electron images?

Backscattered electron (BSE) images of heat-cured concretes show alite grains surrounded by inner C-S-H gel of two distinct grey levels (referred to as two-tone inner C-S-H gel). The lighter rim forms at elevated temperature whereas the darker rim develops during subsequent exposure to moisture at 20 °C. This microstructural feature can potentially be used as an indicator to assess the curing history of a concrete. However, microstructural examinations of room-temperature concretes containing silica fume or which have been exposed to severe conditions (external sulfate, carbonation) also show distinct rims of two-tone inner C-S-H gel.The chemical compositions of the rims were determined by EDX microanalysis in the scanning electron microscope (SEM). Our results show that for heat-cured samples, the different grey levels of the two-tone inner C-S-H are caused by relative differences in microporosity and water content and not by ones in chemical composition. However, in silica-fume blended concrete, sulfate attacked or carbonated specimens the different grey levels of the two-tone inner C-S-H gel were associated with significant differences in chemical composition. This difference allows two-tone inner C-S-H gel arising from heat curing to be distinguished from that arising from these other causes.     

工艺参数对水辅助注塑弯曲圆管内径的影响

采用聚丙烯(PP)材料,研究了工艺参数对水辅助注塑弯曲圆管制品内径的影响.结果表明:缩短注水延迟时间、提高注水压力,制品内径增大.提高模具温度,由水辅助填充的弯曲段和平直段内径有所减小.熔体温度越高,内径沿水道方向的变化幅度越大.提高水温,内径总体上呈减小趋势.提高熔体注射压力,由短射熔体填充的弯曲段和平直段内径呈增大趋势.     

Numerical Simulation for Injection Molding with a Rapidly Heated Mold,Part II: Birefringence Prediction

In the accompanying paper, Part I, the advantages of the rapid thermal response (RTR) molding process were investigated for thin-wall-mold filling by employing coupled analysis of flow and heat transfer. Besides the complete filling of the cavity, frozen-in molecular orientation is another major quality issue in thin wall molding. The frozen-in orientation causes residual stress and birefringence, and potential part distortion. The present work focuses on the prediction and visualization of birefringence in RTR-molded parts. To calculate birefringence, flow-induced residual stress is computed first and the stress-optical law is then applied. The simulation results show that the amount of molecular orientation, residual stress, and birefringence level considerably decrease in the RTR-molding process. The effect of the mold temperature on the level of birefringence was also studied and predicted birefringence patterns were compared with experimental results for a thin-walled rectangular strip. Both predicted and experimental patterns of birefringence are in agreement on the observation that the birefringence level diminishes significantly when the mold temperature is raised to above the glass transition temperature.     

Circulation of particles in a vibrated bed with an inner tube

The particle motion in a vibrated bed with an inner tube was simulated by the discrete element method (DEM). A height difference is observed in the vibrated particle bed between the interior and annulus of the inner tube. The bed height difference is strongly affected by the ratio of the cross section at the interior to that at the annulus of the inner tube. When the inner tube is immersed in the particle bed, the bed height difference causes the circulation of particles in the bed. The direction and velocity of particle circulation can be controlled by changing the inner tube diameter and the circulation velocity is also controlled with vibration conditions.     

Numerical simulation on residual thickness of pipes with curved sections in water‐assisted co‐injection molding

The residual thicknesses of the skin and the inner layers are important quality indicators of water‐assisted co‐injection molding (WACIM) process or overflow WACIM (O‐WACIM) parts. At the curved section, the residual thicknesses change significantly. A numerical simulation program based on the computational fluid dynamics method was developed to simulate the O‐WACIM process. After the numerical simulation program was validated with the experimental results, it was used to study the effects of the bending radii and bending angles on the residual thicknesses of the skin and inner layers of O‐WACIM parts. The results showed that the penetration of the inner melt and water was always close to the inner concave side due to the higher local pressure gradient and temperature. The effects of processing parameters on the residual thicknesses of the skin and inner layers were investigated using the orthogonal simulation method. It was found that the residual thicknesses of the skin/inner layer at the inner concave/outer convex side are mainly influenced by different parameters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42468.