空分过程变量预测的多变量时间序列分析方法

氮塞是空分过程的常见故障,粗氩塔冷凝器出口氩气含氩量是工业现场中指示氮塞是否发生的关键变量,对该变量进行准确的预测可以使氮塞故障的报警时间提前.本文采用多变量时间序列相空间重构的方法,建立了粗氩塔冷凝器出口氩气含氩量和其它过程变量之间的一步线性回归预测模型,以迭代方式获得多步预测的结果,并利用滑动窗口实现了模型参数的在线修正.通过某钢铁公司空分装置实际数据的建模与仿真,分析了相空间重构时嵌入维数以及预测步数的选取对最终预测结果的影响,即预测均方误差与嵌入维数成反比,与预测步数成正比.仿真结果同时表明,本文建立的模型能够较为准确地对空分过程关键变量进行预测,预测提前时间在4～5分钟之间.     

分布式MIMO 系统的迭代空时检测算法

针对未来无线通信系统中广义分布式天线阵的架构,提出了一种适用于分布式多输入多输出（MIMO） 系统的LST-STBC 空时编码方案．该方案通过具有差错控制编码的分层空时（LST）结构与基于正交设计的分组空 时码（STBC）的有效结合,同时获得了分集和复用增益．针对提出的空时编码结构,接收端采用基于软干扰抵消和 最小均方误差（MMSE）的迭代检测算法,通过检测和译码软信息的迭代,有效降低了系统的误码率．仿真结果表 明,文中提出的基于接收端迭代检测的空时编码方案能有效提高分布式MIMO 系统的传输速率和传输质量．     

拉绳塔的非线性分析

本文采用有限元法解拉绳塔非线性问题。拉绳塔非线性分析问题包括在静力和地震力作用下的内力和位移、整体稳定、自振周期和振型的计算。文中推导了拉绳塔在大位移下的精确刚度矩阵,采用矩阵迭代法求解非线性方程组,在每次迭代过程中用分块直接法求解非对称方程组,并给出某一拉绳塔的部分计算结果。     

用分隔壁精馏塔分离松节油中蒎烯的模拟

提出采用分隔壁精馏塔代替常规精馏塔序列分离松节油以得到α-蒎烯和β-蒎烯的新工艺。为了选择适合松节油体系的分隔壁塔结构,采用Aspen软件分别模拟计算了DWC、DWC-SS和DWC-SR三种塔型,结果表明,与常规工艺相比DWC塔可节能26%,DWC-SS塔可节能16.6%,DWC-SR塔可节能12.5%。在此基础上考察了DWC塔进料位置、回流比、隔板位置、气液相分配比和中间产品出料位置对分离效果和热负荷的影响,得出气液相分配比是影响分隔壁塔操作稳定性的主要因素。     

空分行业控制系统解决方案

众所周知,空分装置的稳定,是提高氧提取率和氩提取率的保证。通常在分子筛纯化器的切换过程中,压力和流量波动较大,造成空分主塔工况的不稳定,从而直接影响氧和氩的提取。所以我们设计以下针对制氧机分子筛纯化系统的措施。     

汉诺塔问题的层次迭代算法

汉诺(Hanoi)塔是程序算法设计的一个比较经典问题,目前已有大量的相关文献对其进行了研究。为进一步加快汉诺塔问题的求解速度,通过对汉诺塔问题抽象解树的分析,发现其可以划分为不同层次相同结构的子树,通过对子树层次化控制即可迭代出整个问题的解。基于此,提出了一种用已知子树分层次迭代汉诺塔问题的非递归算法。运行时间测试表明,该算法进一步提高了求解的速度。     

两种级联空时格码方案的EXIT分析

级联空时格码方案可以有效地提高空时格码系统的性能。研究了两种级联空时格码方案:PC-STTC和ST-Turbo-TC。由于两种级联方案都使用了迭代译码方法,而外信息转移(EXIT)图是分析迭代译码性能的有利工具,主要分析比较了PC-STTC和ST-Turbo-TC的EXIT性能,比较了不同信噪比和编码多项式对于译码外信息转移特性的影响。研究结果显示,PC-STTC方案比ST-Turbo-TC方案有着更好的迭代收敛性能,同时给出了BER仿真图证明了EXIT图的分析结论。     

一种大规模MIMO系统中STBC迭代接收机算法

针对大规模MIMO中的空时分组编码(STBC)系统的接收机复杂度随天线数指数增长的问题,提出一种基于EM算法的低计算复杂度的最大似然(ML)接收机。利用STBC和OFMD调制的正交性,避免了矩阵求逆运算;采用步骤E与步骤M迭代处理的方式,极大降低接收机复杂度。基于信道特性提出EM算法初始化方法,达到减少迭代次数进而降低接收机复杂度和提升性能的目的。与之前的决策反馈的非迭代接收机相比,该迭代接收机性能显著提高,在具有快衰落的典型无线信道中,其计算复杂度接近ML接收机,适合实时实现。     

CENTUM CS1000在空分装置中的应用

简述了空分工艺流程和特点,介绍了日本横河电机的CENTUM CS1000 DCS控制系统配置结构、系统硬件、系统软件总体设计组态,包括控制站组态和操作站组态.通过对空分工艺过程精馏系统控制回路的下塔液位控制回路的详细组态分析,和对相关功能模块的介绍,加深了对DCS模块控制的理解,总结了涮试工作,对提升DCS应用的水平很有帮助,对控制系统的长期稳定运行也大有裨益.     

35000Nm3/h空分装置先进控制技术的开发和应用

针对空分工艺流程的过程检测控制具有过程响应迟缓、多参数耦合的缺点,在传统偏差控制的基础上,采用APC先进优化控制技术,开发设计了空分装置先进控制系统.基于装置的物料平衡、能量平衡和组分平衡,采用工艺计算方法,实时协调多变量预测控制器,实现了对装置的优化操作.实践证明,该系统提高了生产过程的自动化水平,在保证产品质量的同时也降低了能耗.     

A wave propagation approach for reduced dynamic modeling of distillation columns: Optimization and control

Reduced models enable real-time optimization of large-scale processes. We propose a reduced model of distillation columns based on multicomponent nonlinear wave propagation (Kienle 2000). We use a nonlinear wave equation in dynamic mass and energy balances. We thus combine the ideas of compartment modeling and wave propagation. In contrast to existing reduced column models based on nonlinear wave propagation, our model deploys a hydraulic correlation. This enables the column holdup to change as load varies. The model parameters can be estimated solely based on steady-state data. The new transient wave propagation model can be used as a controller model for flexible process operation including load changes. To demonstrate this, we implement full-order and reduced dynamic models of an air separation process and multi-component distillation column in Modelica. We use the open-source framework DyOS for the dynamic optimizations and an Extended Kalman Filter for state estimation. We apply the reduced model in-silico in open-loop forward simulations as well as in several open- and closed-loop optimization and control case studies, and analyze the resulting computational speed-up compared to using full-order stage-by-stage column models. The first case study deals with tracking control of a single air separation distillation column, whereas the second one addresses economic model predictive control of an entire air separation process. The reduced model is able to adequately capture the transient column behavior. Compared to the full-order model, the reduced model achieves highly accurate profiles for the manipulated variables, while the optimizations with the reduced model are significantly faster, achieving more than 95% CPU time reduction in the closed-loop simulation and more than 96% in the open-loop optimizations. This enables the real-time capability of the reduced model in process optimization and control.     

Control of a two-pressure distillation column

A recent paper explored the separation of the close-boiling mixture 1,2 propanediol (PDO) and ethylene glycol (EG). The optimum operating pressure using a traditional single vessel was 282 kPa with a reboiler duty of 399 kW. However, the vapor–liquid equilibrium shifts with pressure such that higher pressure is favorable in the PDO-rich region. An interesting steady-state design was developed that splits the column into a high-pressure rectifier (4.9 bar) and a low-pressure stripper (2.38 bar). A compressor (32 kW) moves vapor from the top of the stripper into the bottom of the rectifier. The hot vapor leaving the top of the rectifier at 244 °C provides all the heat required in the reboiler at the base of the stripper (234 °C). This novel design reduces energy cost by 85%.An effective control structure for this complex process is developed in this paper. A small auxiliary reboiler and condenser are used to stabilize the system and to handle large disturbances in throughput and feed composition.     

Physiologically acceptable resistance of an air purifying respirator

Physiologically acceptable limits of inspiratory impediment for air purifying respirators (APRs) were sought.Measurements on 30 subjects included pressure in, and flow through, an APR, and respiratory and cardiovascular variables. Exercise with and without APR included ladder climbing, load lift and transfer, incremental running and endurance running, with endurance at 85% peak oxygen uptake. Resistance that did not alter minute ventilation (VE) was judged acceptable long-term. Acceptable short-term impediments were deduced from end exercise conditions. Proposed long-term limits are inspiratory work of breathing per tidal volume (WOBi/VT) ≤ 0.9 kPa and peak inspiratory pressure (P (i) peak) ≤1.2 kPa. Proposed short-term limits are: for VE ≤110 L min(-1), WOBi/VT ≤1.3 kPa and P (i) peak ≤ 1.8 kPa; and for VE >130 L min(-1), WOBi/VT ≤1.6 kPa. A design relation among VE, pressure–flow coefficients of an APR, and WOBi/VT is proposed. STATEMENT OF RELEVANCE: This work generalises results from one APR by considering the altered physiological parameters related to factors inhibiting exercise. Simple expressions are proposed to connect bench-test parameters to the relation between ventilation and work of breathing. Population-based recommendations recognise that those who need more air flow can also generate higher pressures.     

Dynamic modeling and linear model predictive control of gas pipeline networks

A linear model predictive control (LMPC) strategy is developed for large-scale gas pipeline networks. A nonlinear dynamic model of a representative pipeline is derived from mass balances and the Virial equation of state. Because the full-order model is ill-conditioned, reduced-order models are constructed using time-scale decomposition arguments. The first reduced-order model is used to represent the plant in closed-loop simulations. The dimension of this model is reduced further to obtain the linear model used for LMPC design. The LMPC controller is formulated to regulate certain pipeline pressures by manipulating production setpoints of cryogenic air separation plants. Both input and output variables are subject to operational constraints. Three methods for handling output constraint infeasibilities are investigated.     

液体空气汽液平衡计算模型

汽液平衡计算是精馏塔模拟计算中重要的组成部分。以液体空气汽液平衡计算为研究对象,利用神经网络技术,建立了总压（P）和各组分液相组成（X1、X2、X3）为输入节点,3种不同参数作为输出节点。（1）平衡温度（T）、各组分汽相组成（Y1、Y2、Y3）;(2)平衡温度（T）、各组分平衡常数（K1、K2、K3);（3）平衡温度（T）、汽相氮组成（Y1）及氩、氧平衡常数（K2、3））的BP神经网络模型。通过计算比较,第三种参数作为输出节点的液体空气汽液平衡计算模型,不仅具有良好的学习能力,而且预测结果也比较满意。对进一步研究并应用于空分塔模拟计算具有一定的指导意义。     

Microsieve supporting palladium-silver alloy membrane and application to hydrogen separation

A submicron thick and defect-free palladium-silver (Pd-Ag) alloy membrane is fabricated on a supporting microsieve by using microfabrication techniques. The microfabrication process also creates a robust wafer-scale membrane module, which can easily be inserted into a membrane holder to have gas-tight connections to the outer world. The microfabricated membrane demonstrated high separation fluxes of up to 4 mol H/sub 2//m/sup 2//spl middot/s with a minimal selectivity of 1500 for hydrogen over helium (H/sub 2//He) at 450/spl deg/C and 83 kPa H/sub 2/ retentate pressure. The present membrane has great potential for hydrogen purification and in applications like dehydrogenation chemistry. In addition, the presented technology can be used to fabricate other kinds of ultrathin but strong and defect-free membranes to set up new applications.     

基于双截面ERT对鼓泡床气含率分布的可视化测量

鼓泡床以其结构简单、效率高,广泛应用于化工、制药等领域。鼓泡床中气/液分布受诸多因素影响,如筛板构型、气/液混合比、温度等,而气/液分布直接影响反应效率。因此,气含率分布的实时检测成为过程控制及鼓泡床优化的重要依据。通常,传统检测手段,如压差法及电导探针法,仅能测得集总或局部信息。将电阻层析成像(ERT)技术引入鼓泡床测量,可获得2D/3D电导率分布及流速分布图像。通过对数据/图像后处理,可提取整体和局部流动参数。试验结果显示,ERT结果与传统方法符合,测量误差≤5%。     

Control of a recuperative vapor- recompression air separation process

The use of oxy-combustion for producing furnace stack gases with low nitrogen and high carbon dioxide concentrations is a potential method for economical sequestration of green house gases. A conventional air separation unit to provide oxygen compresses all the air feed and operates with one of the two cryogenic distillation columns at elevated pressure so heat integration can be employed.The use of recuperative vapor recompression has been recently proposed in which only a portion of a nitrogen stream is compressed to provide liquid reflux to two columns, which both operate at low pressure where the separation is easier. Steady-state designs have been developed and economically optimized.The purpose of this paper is to explore the dynamic controllability of this type of vapor recompression system for air separation.     

Controlled equilibrium mounts for aircraft engine isolation

Softer than usual engine mounts for aircraft engine isolation can be used by adding control of the equilibrium position of the mount. The control power comes from bypass air from the engine. This isolation concept is called a controlled equilibrium mount or CEM. A model of the CEM has been developed which includes a front and rear mount with proper loading for each. These mounts possess passive stiffness and damping properties, and they can be pressurized or exhausted through control valves. The thermodynamics of the air is also modeled. A control strategy is proposed that keeps the mounts at their equilibrium positions. The simulation results show that the supply pressure and temperature of the bypass air varied with flight conditions. However, the variations are acceptable, and equilibrium can be maintained with acceptable flow rates from the bypass air for most flight conditions.     

MEMS光纤法珀压力传感器的设计及解调方法实现

基于外界压力引起敏感膜片形变导致腔长变化来实现压力信号传感的原理,提出了一种MEMS光纤法珀压力传感器的设计,建立了传感器敏感膜片的挠度变化与膜厚、半径及施加压力的关系理论模型,并在此基础上进行了膜片的MATLAB二维数值仿真和Comsol Multiphysics三维数值仿真,并完成了FP压力敏感头的制作,进而设计了能够应用于光纤传感的解调方法,搭建了光纤传感的压力测试系统并进行了相关实验,利用所设计的解调方法对实验数据进行处理,进而对压力传感器的性能及特性进行了测试和验证。实验结果表明,传感器测试曲线线性度良好,与数值仿真结果基本一致,在100 kPa的量程范围内其灵敏度可达62.3 nm/kPa,温度敏感系数为0.023μm/℃,测量精度3.93%,且最小压强分辨率为1.29 kPa,证实了该MEMS光纤法珀压力传感系统具有一定的可行性。