浅谈催化裂化轴流压缩机的防喘振和逆流保护

轴流压缩机防喘振控制系统的作用是:当压缩机由于管网阻力的变化,而将要进入喘振边界线运行时,能够迅速地实现压缩机出口旁通管道中一部分气体的放空,从而有效地杜绝了喘振现象的发生。接下来,本文将对催化裂化轴流压缩机进行分析,从而对其防喘振和逆流保护进行探讨。     

基于CCV的轴流压缩系统失稳主动控制

压缩机工作时,当负荷降低到一定程度时,会产生剧烈的失稳现象。旋转失速和喘振为轴流压缩系统的两类失稳现象,为其固有特性,传统的防喘振控制虽然能确保压缩机的安全运行,但却缩小了压缩机工作范围,使压缩机不能工作在高性能区域。为了改善防失稳现象的控制效果,首先选取结构简单、控制效果明显的紧连控制阀（CCV）作为主动控制执行机构,并基于轴流压缩系统经典MG模型和非定常理论,建立了包含CCV的动态响应数学模型;然后运用反步递推法(backstepping)设计推导了恒转速和变转速情况下抑制压缩系统失稳现象相应的主动控制律;最后针对压缩机恒转速和变转速下的旋转失速和喘振失稳现象在不同时间施加主动控制以及B参数变化的影响等多种情况进行了仿真实验,验证了CCV主动控制律的有效性以及CCV的执行高效性。     

叶轮压缩机喘振的机理及防喘振策略研究

分析比较压缩机的旋转失速现象和喘振现象的区别和联系，并着重分析压缩机旋转失速和喘振的产生机理，以及防喘振的主动与被动控制策略，介绍轴流压缩机和离心压缩机防止不稳定现象侧重点的不同。     

浅谈硝铵厂轴流压缩机和氧化氮离心压缩机的喘振试验

通过对氧化氮压缩机（R45—3离心压缩机）和空气压缩机（AV40—14轴流压缩机）进行防喘振试验．来研究确定最佳、经济、安全、可靠的试验方法和获取最可信的试验数据,以指导日常生产。     

浅谈轴流压缩机和离心压缩机的喘振试验

通过对AV-15型轴流压缩机(空气压缩机)和R-45型离心压缩机(氧化氮压缩机)进行工厂性能试验(喘振试验)来讨论最佳、最经济、安全、可靠的试验方法和获取最可信的试验数据,以指导日后生产。     

离心式压缩机防喘振流量确定及防喘振阀选择原则

介绍了如何确定离心式压缩机防喘振流量和ITCC控制厂家关于防喘振阀的选择和计算原则,并以某新建百万吨级乙烯装置的裂解气压缩机为例,就如何确定该压缩机的防喘振流量和选择防喘振阀以及计算防喘振阀门系数做了说明,并指出工艺设计中的注意事项。     

多级离心式压缩机防喘振系统模拟研究

针对多级离心式压缩机停车工况波动大、易喘振的问题,使用HYSYS建立动态仿真模型,研究各种情况下多级离心式压缩机停车的具体机组响应,并研究了防喘振阀Cv值和行程时间对多级离心式压缩机系统喘振的影响,为多级离心式压缩机防喘振阀选型提供理论支持.     

离心式压缩机的防喘振控制

针时离心压缩机的喘振影响其正常工作的问题,分析喘振发生的原因,运用折线函数确定防喘振线、动态干预防喘振曲线工作点及比例增益的自整定运算,用CS3000 DCS的HY1054模块控制循环阀的快开慢关,实现了离心式压缩机在线运行防喘振控制.投运结果表明,防喘振功能在CS3000系统中能够实现,并且运行效果良好.     

离心式压缩机喘振控制分析

离心式压缩机具有长输输气污染少、供气稳定、经济效益高等优点,深受石油、化工等行业的青睐。但在实际工作中,易出现喘振现象,影响压缩机正常运行,一不小心则可能造成严重事故。因此了解离心式压缩机喘振影响因素,采取针对性的喘振控制措施具有十分重要的意义。本文在分析影响离心式压缩机喘振主要因素的基础上,重点探讨了喘振控制的主要措施。     

离心式压缩机流量及喘振控制

概述了离心式压缩机的3种喘振控制方式，并对进口节流恒速操作、变转速操作、进口导叶恒速操作等三种控制方式分别作了介绍和分析。     

Globally stable control systems for processes with input multiplicities

A nonlinear process with input multiplicity has two or more input values for a given output at the steady state, and the process steady state gain changes its sign as the operating point changes. A control system with integral action will be unstable when both signs of the process gain and the controller integral gain are different, and its stability region will be limited to the boundary where the process steady state gain is zero. Unlike processes with output multiplicities, feedback controllers cannot be used to correct the sign changes of process gain. To remove such stability limitation, a simple control system with parallel compensator is proposed. The parallel compensator can be easily designed based on the process steady state gain information and tuned in the field. Using the two time scale method, the stability of proposed control systems for processes with input multiplicities can be checked.     

OPTIMAL TUNING OF PID CONTROLLERS FOR SINGLE AND CASCADE CONTROL LOOPS

Design of one parameter tuning of three-mode PID controller was developed in this present study. The integral time and the derivative time of the controller were expressed in terms of the time constant and dead time of the process. Only the proportional gain was observed to be dependent on the implemented tunable parameter in which the stable region could be predetermined by the Routh test. Extension of the concept towards designing cascade PID controllers was straightforward such that only two parameters for the inner and outer PID controllers required to be tuned, respectively. The optimal tuning correlative formulas of the proportional gain for single and cascade control systems were obtained by the least square regression method.     

Tuning digital PI controllers for minimal variance in manipulated input moves applied to imbalanced systems with delay

Determining the discrete-time proportional plus integral (PI) controller tuning parameters to achieve the smallest possible variance in the manipulated input moves, for a given variance in the controlled output, is the subject of this article. Previous researchers have developed tuning rules for PI and PI permutated nonlinear controllers to achieve what is commonly referred to as “level-flow smoothing”, or “averaging level control”, on imbalanced or integrating processes with delay, such as liquid level and gas pressure systems. The intent of this note is to demonstrate a new and simple technique of tuning digital PI controllers which utilizes either open or closed-loop historical data to estimate the process gain, dead-time and expected flow disturbance magnitude from which the digital PI tuning constants can be easily derived. By parameterizing the closed-loop system as a function of the PI tuning constants, we can simultaneously minimize the expected variation in the process input move and output responses while at the same time ensuring nominal stability of the overall system. In order to demonstrate the technique, an illustrative example is included which highlights the new procedure on an oil refinery liquid surge drum level process.     

A Simple Data Processing Approach for Drying Kinetics Experiments

A simple mathematical approach is proposed to be applied to drying kinetics raw data processing. The data collected in a drying experiment of powder cork under constant air drying conditions served as case study to present the methodology. Two functions (linear and third-degree polynomial) were used to fit solid moisture content in the constant drying rate and the falling rate periods. The drying rate curve was obtained by differentiation and the time at which the drying rate period's transition occurs was determined iteratively until virtually continuous functions were achieved. The critical moisture content was easily identified and two falling drying rate periods were detected.

The powder cork moisture decrease was also used to test several semiempirical models available in the literature. The Logarithmic, Midilli, and Page Modified I models were the ones that revealed the best correlations performance. When the methodology proposed was applied using these models, the critical moisture content was underpredicted.

The effective moisture diffusivity and the activation energy were also obtained for powder cork after the proposed mathematical approach has been applied on the raw data obtained in experiments performed at different air drying temperatures.     

压缩机出口缓冲罐接管失效分析及修复

压缩机出口缓冲罐接管不可避免会有振动特征,是裂纹较易形成的地方.对某公司氢压机出口缓冲罐接管泄漏进行了分析,结果表明泄漏是由于接管振动引起的疲劳裂纹所致.对修复方案进行了探讨,提出了有效的筋板修复方案.     

NATURAL CONVECTION IN A SHALLOW POROUS CAVITY HEATED FROM THE SIDE WITH A UNIFORM HEAT FLUX

Thermally driven flow in a thin rectangular cavity filled with a fluid saturated porous layer is studied analytically and numerically. A constant heat flux heating and cooling is applied on both vertical walls while the horizontal ones are assumed to be insulated. On the basis of the Darcy-Oberbeck-Boussinesq equations, the problem can be solved analytically, in the limit of a thin layer, using asymptotic expansions and an integral form of the energy equation. The flow field and temperature distributions are obtained explicitly in terms of the Rayleigh number in the conduction as well as intermediate regimes. A numerical study of the same phenomenon, obtained by solving the complete system of governing equations, is also presented. A very good agreement is found between the numerical simulations and the analytical predictions. The various physical processes in this type of flow are discussed based on the findings of the analytical and numerical studies.     

压缩机控制系统中喘振线的计算方法

介绍裂解气压缩机组的性能曲线,给出喘振线的参数说明。以裂解气压缩机一段防喘振为例探讨了喘振线的计算方法,并对计算过程中存在的问题进行了修正。修正后控制效果更佳,操作点更加远离了喘振线,提高了压缩机组的运行性能。     

Batch distillation: Better at constant or variable reflux?

Due to its outstanding flexibility, batch distillation is still widely used in many separation processes. In the present work, a comparison between constant and variable reflux operations is studied. Firstly, a mathematical model is developed and then validated through comparison between predicted and experimental results accomplished in a lab-scale apparatus. Therefore, case studies are performed through mathematical simulations. It is noted that the most economical form of batch distillation is at constant overhead product composition, keeping the flow rate of vapor from the top of the column constant.     

Native, denatured and reduced BSA: Enhancement of chronopotentiometric peak H by guanidinium chloride

In proteomics and biomedicine fast techniques applicable for preliminary tests of the protein properties and structural changes are sought. Methods of electrochemical analysis have been little utilized in these fields. We show that using constant current chronopotentiometric stripping peak H, minute amounts of denatured and reduced bovine serum albumin (BSA) can be easily discriminated from native BSA. Peak H, which is due to catalytic hydrogen evolution, is greatly enhanced in the presence of non-denaturing concentrations of guanidinium chloride. The course of BSA reduction and denaturation can be followed and traces of the damaged protein can be detected in native BSA samples.     

Dielectric Properties of Explosively Compacted BaTiO3

Polycrystalline BaTiO₃ was explosively compacted to nearly theoretical density, and its dielectric and piezoelectric properties were investigated. The compacted bodies did not exhibit dielectric hysteresis, a Curie point, or piezoelectric properties; their dielectric constant and dissipation factor increased linearly with temperature. The dielectric constant was much lower than those of similar dense bodies obtained by conventional sintering. These results may be interpreted in terms of weak intergranular bonding and increased numbers of defects generated in the shocked material. When explosively compacted bodies were sintered, normal ferroelectric and piezoelectric properties and improved microstructures were obtained.