内部热耦合对理想反应蒸馏塔动态特性的影响

基于理想型强放热反应蒸馏塔研究了3项内部热耦合策略对系统动态特性及可控性的影响.其中,实现反应段与提馏段间正耦合作用的措施能够有效提高系统热力学效率,但同时减弱了提馏段的传质推动力,不利于系统动态操作.为改善系统的动态特性及可控性,需要在提馏段补充一定量的分离塔板.下移上进料位置提高了系统热力学效率,但也引入了逆耦合作用,严重影响系统动态操作,故在过程强化中应该回避.     

过量进料反应隔离壁蒸馏塔的设计与比较

采用反应物过量技术克服反应蒸馏塔在分离具有较不利动力学特性的反应混合物时的缺陷,提出针对此类反应精馏的最优蒸馏塔结构设计策略。针对具有较不利相对挥发度排序的四元理想可逆放热反应,分别设计常规反应蒸馏塔(RDC)与采用反应物进料过量技术的反应隔离壁蒸馏塔(ER-DWDC),并对其稳态性能进行评价。结果显示,反应物中轻组分进料过量的反应隔离壁蒸馏塔能够最大程度强化蒸馏塔内部物质和能量耦合,具有优越的稳态性能,能够显著降低工业分离过程中的设备投资成本和操作能耗。     

基于粒子群算法的隔离壁精馏塔的综合与设计

隔离壁精馏塔（dividing-wall distillation column,DWDC）是提高两个或者多个传统精馏塔热力学效率的有效手段。由于隔离壁精馏塔内部结构复杂、相互作用强,传统的序贯优化方法计算时间长,很难达到全局最优解。标准粒子群算法应用广泛、易于实现,但易于早熟、易于陷入局部极值点。因此,本工作采用改进的元胞粒子群算法对Kaibel隔离壁精馏塔进行综合与设计研究。元胞粒子群算法通过改进粒子的学习策略,采用元胞邻域的方法可有效地将粒子分散在多个子空间。对比标准粒子群优化和元胞粒子群优化两种方法的50次优化效果,结果表明,两种粒子群算法能够对内部结构复杂、相互作用强的四组分Kaibel隔离壁精馏塔这一复杂分离系统进行优化,优化效果显著。     

简化外部热耦合双精馏塔的控制与优化

针对具有3个换热器结构的外部热耦合双精馏塔(S-EHIDDiC),提出了一种新型的控制与优化策略。顶部与底部换热器的热负荷能够改变高压精馏塔的回流量和低压精馏塔的上升汽量,因而可以用来控制高压精馏塔塔顶和低压精馏塔塔底的产品质量。这种控制方法与常规精馏塔的LV控制结构相似。S-EHIDDiC还有多余的决策变量(如进料分流比,高压精馏塔塔压和中间换热器的热负荷),可以对稳态操作进行优化。闭环仿真证明了这种控制结构的可行性,稳态优化也提高了系统的热力学效率。     

Modeling and Analysis of Internal Heat Integrated Distillation Columns

A generalized steady-state model is being developed for an internal heat integrated distillation column (IHIDiC). A procedure incorporating the Newton-Rapheon method is devised for solving the model equations. Separation of an ethanol-water binary mixture is simulated and analyzed with the model, Two pinch points are found within the process, making the separation ex-tremely difllcult and expensive. Two sharp fronts in the temp-erature and the composition profiles are being observed. With the introduction of heat integration, satisfactory separation may be obtained in a limited number of stages with lower reflux ratios. Increasing the pressure difference between the rectifylng and the strlpping sectlons, however, would bring about a reduced relative volatility between the two components involved, creating adverse separation performances. It is obvious that optimigation of the IHIDiC is of prime importance.     

Control of Ideal Heat Integrated Distillation Columns

The operation of an ideal heat integrated dlstillation columan (HIDiC) is addressed .Five Kinds of control configurations, i.e. single-loop control, multi-loop control, multivariable internal model control (IMC), modified multlvariable internal model control (MIMC) and nonlinear process model-based control (NPMC), are designed and applied to the process. Simulation results demonstrate that all of the above control confaguratloam ere valid for product quality control. NPMC control configuration is found to be the best one among all the alternatives. It can readily realize setpoint transitions and conduct effectively against external disturbance. MIMC control configuration ranks second in the row for its regulatory responses to feed composition disturbances with relatively extended setting time, Next comes from the multi-loop control configuration, which is moee or lees handicapped by its greater deviations and overshootings. IMC control configuration can not compete with the multi-loop control configuration because it is extremely sensitive to operating condition changes. Single-ioop control configuration is the worst one among all the mentioned control configurations. Its responses for the uncoutrolled end products are extremely sluggish.     

分段集结法建立多元精馏塔简化动态模型

本文用分段集结(compartment)方法,给出了一种新颖的多元精馏塔简化动态模型。其原理简单,推导方便,不受分离物系及精馏塔操作状态的限制,可根据需要将精馏塔任意分段,具有较强的灵活性,不仅可使得精馏塔逐板机理模型维数大为降低,而且简化模型的结构和参数均能保持原来的物理意义。用该简化模型对某一丙烯腈萃取塔进行仿真,所得过渡过程能够较好地拟合精确机理模型的动态响应,而且稳态值能够准确地契合精确模型的输出,同时耗机时间明显减少。仿真证明,分段集结建模方法是行之有效的。     

用于红外气体检测的多通池温度、压强控制系统研制

为了实现CO₂气体同位素的高性能检测,研制了高精度、高稳定性的多通池温度、压强控制系统。采用柔性PCB作为加热片包覆圆柱形多通池。考虑到温度控制系统的加热速率,外层包覆保温棉作为隔热装置,使得整个温度控制系统能实现快速加热,且能够保持温度的长时间稳定。采用铂电阻PT1000温度传感器对多通池温度进行精确采集,主控制器通过PWM信号,调控柔性PCB加热膜的发热功率,从而实现温度的闭环控制。压强控制系统方面,采用压强传感器连接于多通池前、后端,检测多通池内部气压,主控制器通过PWM信号,调控多通池前、后端比例阀导通状态,从而实现压强的闭环控制。结果表明,温度控制范围为18.48~42 ℃,温度控制精度为±0.08 ℃。多通池压强为60 Torr(1 Torr ≈ 133.322 Pa)时,控制精度为±0.04 Torr。该系统为红外CO₂气体同位素的高性能检测提供可靠保障。     

MODIFIED METHODOLOGY FOR DISTILLATION MODELLING BY ORTHOGONAL COLLOCATION

A major shortcoming of polynomial approximation in the medelling of distillation columns isthe difficulty encountered while choosing the number and location of collocation points,which are usually doneby rule of the thumb,inevitably giving rise to high dimensionality and longer computation time for the resultingmodel.In order to take full advantage of polynomial approximation in the modelling of complicatedmulticomponent distillation columns,modifications must be made to the model reduction procedure originallyproposed by Cho.This is achieved by putting in special polynomials to each of the variable profiles.Furthermore,the number and location of the collocation points can be determined by the optimization of anappropriate objective function.This would bring about less dimensionality and less computation time for theresulting reduced--order model as compared with Cho's procedure while its accuracy is still kept excellent.Theeffectiveness of such modifications is illustrated by two simulation examples.Bot