Using hot-vapor bypass for pressure control in distillation columns

Distillation column control is widely explored in literature due to its complexity and importance in chemical and petrochemical industries. In this process, pressure represents one of the most important variables to be controlled. However, there are few studies about how pressure affects the dynamic behavior of distillation columns and most research on distillation column control involve direct manipulation of cooling fluid through the condenser. Nevertheless, such an approach demands constant changes in cooling fluid flowrates that are commonly by the order of tons per hour, which can be difficult to work or even unfeasible in a real plant. Furthermore, this strategy is usually avoided, as it can cause fouling and corrosion acceleration. The hot-vapor bypass strategy fits well as a solution for these issues, eliminating the need to dynamically manipulate cooling fluid flowrates in the condensation unit. This work presents the modeling and simulation of a conventional distillation column for the separation of water and ethanol, in which a comparative study between a conventional pressure control and a control using hot-vapor bypass was performed. The main results were obtained through dynamic simulations which considered various disturbances in the feed stream, and demonstrated superior performance by the hot-vapor bypass system over the usual scheme proposed in literature, while evaluating the lntegral Absolute Error （IAE） norm as the control performance index.

Challenges Associated with the Bypass Valves of Control Valves in a Seawater Service

Modern processing plants use a variety of control loop networks to deliver a finished product to the market.Such control loops,like control valves,are designed to keep process variables such as pressure,temperature,speed,flow,etc.within the appropriate operating range and to ensure a quality product is produced.All control valves have a bypass so that production can proceed if maintenance is needed for the control valve as part of the control loop.The important point is that in both operation and maintenance situations,the bypass valve and the control valve should have approximately the same flow capacity to provide nearly the same amount of pressure.This paper presents a case study in seawater service on the selection of manual bypass valves for a 16″control valve in class 150 and titanium material.A 16″butterfly valve of class 150 was chosen for the control valve bypass,which provided a much higher flow capacity than the control valve.In this paper,four solutions are recommended to achieve the same coefficient value(Cv)for the control and bypass valve.Using the reduced size butterfly valve could be the cheapest and best solution.On the other hand,selecting the same control valve for bypass line is the most expensive but maybe the most reliable solution.Using a flow orifice for throttling could be ranked as the second expensive option and the second reliable one.Selection of butterfly valve for throttling is the second cheapest option,but it has the least reliability.Different parameters such as space and weight saving,cost as well as reliability have been considered in evaluation of different solutions.

Bypass Selection for Control of Heat Exchanger Network

Considering the flexibility and controllability of heat exchanger networks (HENs), bypasses are widely used for effective control of process stream target temperatures. However, the optimal location for the bypass is generally difficult to design with the trade-off between controllability and capital investments. In this paper, based on the steady-state model of heat exchanger networks the optimal bypass location was firstly selected by iteratively calculating the non-square Relative Gain Array (ns-RGA). To simplify the calculation process, rules of bypass selection were also proposed. In order to evaluate this method, then, the structural controllability of heat exchanger networks was analyzed. With both the consideration of the controllability and capital investments, the bypasses locations were finally selected. A case study on the HEN in Crude Distillation Unit was presented in which the ns-RGA and structural controllability were used to select bypasses and also to evaluate the results.

Efficacy of Xuebijing Injection(血必净注射液)on Cardiopulmonary Bypass-Associated Pulmonary Injury:A Prospective,Single-center,Double Blinded,Randomized Controlled Trial

Objective： To evaluate the efficacy of Xuebijing Injection（血必净注射液, XBJ） on the lung injury induced by cardiopulmonary bypass（CPB）. Methods： Fifty patients undergoing CPB were randomized to either the saline group or XBJ group according to a random number table（25 cases in each group）. The patients in the saline group received saline and patients in XBJ group received XBJ at 12 h prior to the operation, at the beginning of the operation, and at 12 h after the second injection. The PaO_2/Fi O2 at extubation 3 days post-operation, duration of ventilation in the intensive care unit（ICU）, and lengths of stay in the ICU and hospital were recorded. The levels of inflammatory mediators including interleukin（IL）-1β, IL-8, IL-10, and C-reactive protein（CRP） in bronchoalveolar lavage fluid（BALF） and plasma were measured. The neutrophil count and elastase neutrophil elastase in BALF were also measured. In addition, adverse events were monitored. Results： The PaO-2/FiO_2 in the XBJ group was higher than that in the saline group from 12 to 72 h post-operation（all P〈0.05）. The blood levels of IL-1β, IL-8, and CRP in the XBJ group from 12 to 72 h were all significantly lower than those in the saline group（all P〈0.05）. In contrast, the level of the anti-inflammatory cytokine IL-10 was significantly higher in the XBJ group than in the saline group（P〈0.05）. In addition, 4 patients presented with atelectasis in the saline group and none in the XBJ group. Ten patients experienced mild acute respiratory distress syndrome（ARDS） during hospitalization, and 5 patients with mild ARDS were in the XBJ group（P〈0.05）. Conclusion： XBJ shows protective potential against lung injury in patients who undergo CPB surgery, possibly through the downregulation of inflammatory mediators, reduction in neutrophil infiltration, and upregulation of IL-10（Trial registry： Chi CTR-TRC-14004628）.

Key details of the duodenal-jejunal bypass in type 2 diabetes mellitus rats

AIM: To investigate which surgical techniques and perioperative regimens yielded the best survival rates for diabetic rats undergoing gastric bypass. METHODS: We performed Roux-en-Y gastric bypass with reserved gastric volume, a procedure in which gastrointestinal continuity was reestablished while excluding the entire duodenum and proximal jejunal loop. We observed the procedural success rate, long-term survival, and histopathological sequelae associated with a number of technical modifications. These included: use of anatomical markers to precisely identify Treitz's ligament; careful dissection along surgical planes; careful attention to the choice of regional transection sites; reconstruction using full-thickness anastomoses; use of a minimally invasive procedure with prohemostatic pretreatment and hemorrhage control; prevention of hypo-thermic damage; reduction in the length of the procedure; and accelerated surgical recovery using fast-track surgical modalities such as perioperative permissive underfeeding and goal-directed volume therapy. RESULTS: The series of modif ications we adopted reduced operation time from 110.02 ± 12.34 min to 78.39 ± 7.26 min (P < 0.01), and the procedural success rate increased from 43.3% (13/30) to 90% (18/20) (P < 0.01), with a long-term survival of 83.3% (15/18) (P < 0.01). CONCLUSION: Using a number of fast-track and damage control surgical techniques, we have successfully established a stable model of gastric bypass in diabetic rats.

Efficacy of Valerian Extract on Sleep Quality after Coronary Artery bypass Graft Surgery: A Triple-Blind Randomized Controlled Trial

Objective:To assess the effect of valerian root extract on the sleep quality of patients after coronary artery bypass graft(CABG)surgery.Methods:The patients who participated in this triple-blind clinical trial were selected by permuted block randomization.The participants were assigned to the valerian(n=36)and placebo(n=36)groups.The valerian group received 530 mg of valerian capsules for 30 nights after CABG surgery,and the placebo group received 530 mg of the placebo capsules containing wheat flour.The Pittsburgh Sleep Quality Index(PSQI),the prothrombin time(PT)and partial thromboplastin time(PTT)were assessed on four occasions,including the baseline,the 3 rd,14 th and 30 th days following intervention.Results:The odds ratio of worsened sleep quality significantly varied over time(the interaction of time and group)in the valerian group compared to the placebo group in various dimensions including total sleep quality(P=0.001),sleep latency(P<0.01),sleep duration(P=0.020),sleep efficiency(P=0.001)and daytime dysfunction(P=0.025).No significant difference was observed in the alterations of the odds ratio of PT in the two groups over time.(P=0.371).Conclusion:The consumption of oral valerian root extract over 30 nights could significantly improve the patients'sleep quality safely after CABG surgery.

Graft Quality Control with the Traditional Roller Pump Flow Measurement in Comparison to the Transit-Time Flow Measurement

Objective: Vein graft quality control had been traditionally done for more than 20 years with a roller-pump flow measurement (RPFM) in our institute until off-pump coronary artery bypass grafting was introduced as the standard technique of myocardial revascularization in the year 2009 in our institute. In this study, the RPFM method was compared with the Transit-time flow measurement (TTFM). Patients and Methods: From February to September 2005, 31 patients (5 females) undergoing CABG in our institute were included into the study. All the patients were operated with cardiopulmonary bypass. In those patients, 27 distal anastomoses were done with the left internal thoracic artery and 99 anastomoses were done with vein grafts. Those 99 vein graft were assessed both, with the RPFM method and TTFM method. Results: CABG could be safely performed in all cases. In all target vessels, the RPFM method overestimated bypass flow compared to the TTFM method, and simple linear regression revealed no correlation between the TTFM measurement and the RPFM measurement (r = 0.08, p = 0.21). There were two cases in which a graft problem could be detected only with TTFM method, even in our small patient cohort. Conclusion: The present study suggests that the TTFM method is clearly superior to the traditional RPFM method and we believe now that TTFM should be performed routinely in all CABG to improve patient care and quality of surgical results.

Efficacy of electroacupuncture on myocardial protection and postoperative rehabilitation in patients undergoing cardiac surgery with cardiopulmonary bypass:a systematic review and Meta-analysis

OBJECTIVE:To evaluate the efficacy of electroacupuncture(EA)intervention on myocardial protection and postoperative rehabilitation in patients undergoing cardiac surgery with cardiopulmonary bypass(CPB).METHODS:Eight databases,including Pub Med,Embase,the Cochrane Library,Web of Science,Chinese Bio Medical Literature Database,China National Knowledge Infrastructure Database,Wanfang Data,China Science and Technology Journal Database,and two clinical trial registries,were searched.All randomized controlled trials(RCTs)related to EA intervention in cardiac surgery with CPB were collected.Based on the inclusion and exclusion criteria,two researchers independently screened articles and extracted data.After the quality evaluation,RevMan 5.3 software was used for analysis.RESULTS:Fourteen RCTs involving 836 patients were included.Compared with the control treatment,EA significantly increased the incidence of cardiac automatic rebeat after aortic unclamping[relative risk(RR)=1.15,95%confidence interval(CI)(1.01,1.31),P<0.05;moderate].Twenty-four hours after aortic unclamping,EA significantly increased the superoxide dismutase[standardized mean difference(SMD)=0.96,95%CI(0.32,1.61),P<0.05;low],and interleukin(IL)-2[SMD=1.33,95%CI(0.19,2.47),P<0.05;very low]expression levels and decreased the malondialdehyde[SMD=-1.62,95%CI(-2.15,-1.09),P<0.05;moderate],tumour necrosis factor-α[SMD=-1.28,95%CI(-2.37,-0.19),P<0.05;moderate],and cardiac troponin I[SMD=-1.09,95%CI(-1.85,-0.32),P<0.05;low]expression levels as well as the inotrope scores[SMD=-0.77,95%CI(-1.22,-0.31),P<0.05;high].There was no difference in IL-6 and IL-10 expression levels.The amount of intraoperative sedative[SMD=-0.31,95%CI(-0.54,-0.09),P<0.05;moderate]and opioid analgesic[SMD=-0.96,95%CI(-1.53,-0.38),P<0.05;low]medication was significantly lower in the EA group than in the control group.Moreover,the postoperative tracheal intubation time[SMD=-0.92,95%CI(-1.40,-0.45),P<0.05;low]and intensive care unit stay[SMD=-1.71,95%CI(-3.06,-0.36),P<0.05;low]were significantly shorter in the EA group than in the control group.There were no differences in the time to get out of bed for the first time,total days of antibiotic use after surgery,or postoperative hospital stay.No adverse reactions related to EA were reported in any of the included studies.CONCLUSIONS:In cardiac surgery with CPB,EA may be a safe and effective strategy to reduce myocardial ischaemia-reperfusion injury and speed up the recovery of patients after surgery.These findings must be interpreted with caution,as most of the evidence was of low or moderate quality.More RCTs with larger sample sizes and higher quality are needed to provide more convincing evidence.

营商环境法治化三维论

市场秩序稳定公平、规则透明公开、法治公正、投资可预期的营商环境,是投资主体实现投资自由便利制度的核心价值所现。推进政府职能新定位,强化“放管服”,放宽市场主体准入等,是优化营商环境的基本环节。自由度是主体最活跃的动力源和策源地,政府确保“中立地位”,促进主体公平竞争和实施反垄断,维护所有市场主体都享有平等、自由、公平竞争机制。便利度是彰显政府向市场主体提供快速实现自由度的便捷化、快捷化和效率化的社会效应程度,核心在于强化市场主体获得从商活动权利能力的快捷、简便、高效行为状态等。创新度是市场主体实现自由度与便利度融合发展处于动态的追求状态,显现了优化营商环境持续创新的法治动力。政府干预与市场调节有机协同调控,做大主体自由度,提升主体更多便利度,促进营商环境的持续创新优化。自由、便利与创新,已成为优化营商环境的路径选择,创新成为优化营商环境的否定之否定规律。自由度、便利度与创新度的辩证关系价值,成为引导探寻优化营商环境的立足点、突破点和发力点。

Efficient Handling of Lock Hand-off in DSM Multiprocessors with Buffering Coherence Controllers

Synchronization in parallel programs is a major performance bottleneck in multiprocessor systems. Shared data is protected by locks and a lot of time is spent on the competition arising at the lock hand-off. In order to be serialized, requests to the same cache line can either be bounced （NACKed） or buffered in the coherence controller. In this paper, we focus mainly on systems whose coherence controllers buffer requests. In a lock hand-off, a burst of requests to the same line arrive at the coherence controller. During lock hand-off only the requests from the winning processor contribute to progress of the computation, since the winning processor is the only one that will advance the work. This key observation leads us to propose a hardware mechanism we call request bypassing, which allows requests from the winning processor to bypass the requests buffered in the coherence controller keeping the lock line. We present an inexpensive implementation of request bypassing that reduces the time spent on all the execution phases of a critical section （acquiring the lock, accessing shared data, and releasing the lock） and which, as a consequence, speeds up the whole parallel computation. This mechanism requires neither compiler or programmer support nor ISA or coherence protocol changes. By simulating a 32-processor system, we show that using request bypassing does not degrade but rather improves performance in three applications with low synchronization rates, while in those having a large amount of synchronization activity （the remaining four）, we see reductions in execution time and in lock stall time ranging from 14% to 39% and from 52% to 7170, respectively. We compare request bypassing with a previously proposed technique called read combining and with a system that bounces requests, observing a significantly lower execution time with the bypassing scheme. Finally, we analyze the sensitivity of our results to some key hardware and software parameters.

旁通阀结构对燃料电池系统阴极压力控制效果的分析

为减小压力波动对燃料电池寿命的不利影响,通过仿真及对比试验,探究增加旁通阀对阴极供给系统压力波动的改善效果。根据对燃料电池输出特性与各组件工作原理的分析,建立机理与控制模型;采用基于自抗扰的反向解耦方法实现流量与压力的解耦控制;运用模糊PI方法实现压力波动控制。通过Matlab/Simulink仿真验证了解耦方法在该系统结构下的控制效果,在对比试验中,压力波动峰值分别为无旁通阀1.82kPa与有旁通阀1.09kPa,旁通阀的增加减小了压力波动,使阴极流道压力的稳定性得到了更有效的控制,对提升燃料电池寿命有重要意义。

Comparison of the Birds Point-New Madrid Floodway, Mississippi River and the Yolo Bypass, Sacramento River

The Birds Point-New Madrid Floodway（BP-NMF） and the Yolo Bypass, located on the Mississippi and Sacramento rivers, respectively, are agriculture areas that were once each part of vast wetlands but are now intermittently used for flood control. Here the similarity stops, the BP-NMF has been used to convey floodwaters only twice in nearly 80 years, while the Yolo Bypass is used for this purpose on average every other year. The consequences are greatly different. In 2011, the BP-NMF was activated through the explosive detonation of the ＇fuse plug＂ portion of its levees, resulting in elevated property and economic damages, crop losses, and litigation. High-energy flows following the opening of the BP-NMF scour coarse sediment in the vicinity of the opening of the BP-NMF and deposit this material within the floodway, including on agricultural fields. In general the environment of much of the BP-NMF provides poor wildlife habitat. In contrast, the routine operation of Yolo Bypass is expected, avoids damage and litigation, supplies organic-rich sediment to fields, and provides good wildlife habitat. The difference between the two systems is attributed to a better approximation of natural conditions on the Yolo Bypass.

Nacelle intake flow separation reduction at cruise condition using active flow control

Turbofan engine intakes are designed to provide separation-free flow at the fan faceover a wide range of operating conditions. But at some off-design conditions, like at high flightspeeds and high angles of attack (AoA), the aero engine intake may encounter flow separation.This boundary layer separation inside the nacelle inlet of an aircraft engine can lead to a largenumber of undesirable outcomes like reduction in fan efficiency, engine stall and high levels ofstress on the fan blades. Active flow control is a promising solution to reduce inlet boundarylayer separation and the associated fan-face flow distortion at such off-design conditions. Byblowing pressurized air into the intake near the separation point, the boundary layer is ener-gized and separation can be controlled. This study investigates the applicability of lip blowing,an active flow control technique, to control intake separation and flow distortion at the fan-face.First, intake separation was triggered in a 3D CFD model based on the NASA CommonResearch Model (CRM) using high AoA cases at cruise condition (Mach number 0.85, Massflow capture ratio w0.7) and the features of separated flow were analyzed. Thereafter, activeflow control was introduce to the intake in the form of two types of lip blowing, direct andpitched blowing. The efficacy of lip blowing at achieving separation control in an ultra highbypass ratio turbofan engine intake has been established through this study. The present paperalso examines the significance of blowing parameters like the type of blowing, blowing pres-sure ratio, and blowing slot dimension, at different angles of attack to identify the critical con-trol parameters. Our research successfully establishes proof of concept by demonstrating the feasibility of using lip blowing for separation control in aero-intakes, via numerical modelling.Furthermore, this study also provides crucial insights regarding the important variables to beconsidered for future experimental studies, and also for detailed studies covering a wider rangeof operating and blowing conditions.

控制性低中心静脉压对心肺转流心脏手术中静脉淤血和术后急性肾损伤的影响

目的探讨控制性低中心静脉压(CLCVP)对心肺转流(CPB)心脏手术中静脉淤血和术后急性肾损伤(AKI)的影响。方法选择择期拟于全麻CPB下行心脏手术的患者137例,男73例,女64例,年龄18~70岁,BMI 20~28 kg/m^(2),ASAⅡ或Ⅲ级。采用随机数字表法将患者分为两组:控制性低中心静脉压组(CL组,n=68)和对照组(C组,n=69)。CL组在CPB停机后20 min,通过泵注硝酸甘油应用CLCVP将CVP降低至10 mmHg以下,直至手术结束,必要时应用去甲肾上腺素维持MAP≥65 mmHg。C组采用标准化麻醉管理。分别在麻醉诱导前、术后12 h采集尿液标本检测肾损伤分子-1(KIM-1)浓度。分别在麻醉诱导前、术后2 h采集尿液标本检测中性粒细胞明胶酶相关脂质运载蛋白(NGAL)浓度。使用CVP高于10、12、16、20 mmHg的累计时间和时间加权平均CVP评估静脉淤血。记录术后AKI发生情况、2期及以上AKI发生情况、肾脏替代治疗(CRRT)、术后低心排综合征(LCOS)发生情况、到达ICU时心脏术后急性肾功能不全(AKICS)评分、住院死亡情况、ICU停留时间和术后住院时间。结果与C组比较,CPB后CL组CVP高于10、12、16、20 mmHg的累计时间明显缩短,时间加权平均CVP明显降低(P<0.05)。术后CL组发生AKI 9例(13.2%),C组15例(21.7%),两组差异无统计学意义。CL组发生2期及以上的AKI 1例(1.5%),C组2例(2.9%),C组有1例需行CRRT。与C组比较,CL组术后12 h KIM-1浓度和术后2 h NGAL浓度明显降低(P<0.05)。两组LCOS、AKICS评分、住院死亡率、ICU住院时间和术后住院时间差异无统计学意义。结论在心肺转流心脏手术中应用控制性低中心静脉压通过减轻静脉淤血,减少术后肾损伤的发生,具有一定的肾脏保护作用。

疥疮感染患者行冠状动脉旁路移植术的围手术期护理

总结1例疥疮感染患者行冠状动脉旁路移植术的围手术期护理体会。针对患者疥疮传染期行手术治疗,医护人员防护经验欠缺、重症患者普遍易感、感染防控难度大等问题,采取组建多学科防控组及护理专项组,提升疥疮防控能力;严格把控疥疮传染三大环节,预防院内感染发生;做好疥疮用药及皮肤管理等措施。经过17 d积极治疗与精心护理,患者症状及体征改善,局部刮片虫卵检测阴性,未发生院内感染,隔离解除后转普通病房继续治疗,术后第28天顺利出院。

常规岛汽机旁路调节阀抗震性能研究

为防止常规岛汽机旁路调节阀在地震期间发生共振,致使调节阀与连接管道受到破坏,使用ANSYS软件中Modal模块,对DN 300 Class900汽机旁路调节阀进行模态分析,得到调节阀各阶自振频率。当调节阀的基频高于33 Hz时,使用等效静力法。对调节阀进行抗震分析,得到阀门整体及各部件的等效应力和变形。根据ASME BPVC-Ⅲ中对核级设备抗震的规定,对调节阀在承受地震载荷时的应力强度进行评定,结果表明:阀体、阀盖、阀杆、支架最大应力分别为133.63、77.52、29.46、71.54 MPa,中法兰螺栓最大拉应力为183.23 MPa,最大剪应力为15.36 MPa,均满足抗震强度要求。

加料泵旁通阀PID自动控制系统

作为烟丝生产工艺中的重要环节,添加香糖料可对烟丝质量起到关键性作用。为了保证生产中香糖料的流量控制精度,在加料管路中使用旁通阀PID自动控制。通过实际生产跟踪,加料泵旁通阀PID自动控制系统与电动调节针形阀的配合调控,使料液流量具有更快速、灵敏的调控反应,提高了对加料环节的流量控制。

基于红外热成像的精馏塔冷凝器液位识别装置及算法研发

在传统原油精馏热旁路法控制塔压过程中,当塔顶不凝气含量较高时,塔压控制存在一定滞后,极端情况下存在回流泵抽空损伤、压力失控等风险,严重影响装置安全生产。为了解决上述问题,提出一种热旁路红外液位识别装置设计方案,在热旁路法塔压调节工艺中加入红外液位识别控制流程,当不凝气大量集聚造成操作大幅波动时,自动触发冷凝液位识别控制回路,精准调节液位,从而降低热旁路塔压控制风险,提升装置安全水平。建立的基于数字图像处理算法的液位识别模型,经验证综合准确率达97.63%,能够满足工业需要。

特高压分级式可控高抗的集约化设计与应用

特高压分级式可控高抗(HCSR)解决了固定高抗在限制过电压和无功补偿方面无法兼顾的矛盾,其系统调控的灵活性高,为特高压交流电网的安全、稳定运行提供了保障。HCSR各个分设备不仅具有特高压设备重量重、体积大、结构复杂等特点,分设备之间的集成设计、绝缘配合均会导致建设用地需求大幅增加,这与国家严控建设用地增量的政策存在偏差。为此,本文充分考虑户外环境因素的影响,合理利用立体化空间设计理念,创新性提出了取能电抗器区域转接母线垂直设计,以及成套装置局部GIS设计的集约化设计方案。在合理控制设备和工程建设成本的前提下,优化解决了其粗放型使用建设用地的问题。采用集约化设计后,HCSR占地可节约25%左右,效果显著。

1030MW机组高压旁路调节阀失效分析及技术对策

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