Synthesis of Heat Integrated Complex Distillation Systems via Stochastic Optimization Approaches

This paper addresses the application of stochastic optimization approaches to the synthesis of heat integrated complex distillation system, which is characterized by large-scale combinatorial feature. Conventional and complex columns, thermally coupled (linked) side strippers and side rectifiers as well as heat integration between the different columns are simultaneously considered. The problem is formulated as an MINLP (mixed-integer nonlinear programming) problem. A simulated annealing algorithm is proposed to deal with the MINLP problem and a shortcut method is applied to evaluate all required design parameters as well as the total cost function. Two illustrating examples are presented.     

A systematic approach for synthesizing a low-temperature distillation system

In this paper, by combining a stochastic optimization method with a refrigeration shaft work targeting method, an approach for the synthesis of a heat integrated complex distillation system in a low-temperature process is presented. The synthesis problem is formulated as a mixed-integer nonlinear programming (MINLP) problem, which is solved by simulated annealing algorithm under a random procedure to explore the optimal operating parameters and the distillation sequence structure. The shaft work targeting method is used to evaluate the minimum energy cost of the corresponding separation system during the optimization without any need for a detailed design for the heat exchanger network (HEN) and the refrigeration system (RS). The method presented in the paper can dramatical y reduce the scale and complexity of the problem. A case study of ethylene cold-end separation is used to il ustrate the application of the approach. Compared with the original industrial scheme, the result is encouraging.     

考虑操作分解的热集成用水网络设计

This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an important parameter of the problem. By treating the direct and indirect heat transfers separately, target freshwater and energy consumption as well as the operation split conditions are first obtained. Subsequently, a mixed integer non-linear programming （MINLP） model is established for the design of water network and the heat exchanger network （HEN）. The proposed systematic approach is limited to a single contaminant. Example from literature is used to illustrate the applicability of the approach.     

Closed-loop scheduling optimization strategy based on particle swarm optimization with niche technology and soft sensor method of attributes-applied to gasoline blending process

Gasoline blending scheduling optimization can bring significant economic and efficient benefits to refineries.However,the optimization model is complex and difficult to build,which is a typical mixed integer nonlinear programming(MINLP) problem.Considering the large scale of the MINLP model,in order to improve the efficiency of the solution,the mixed integer linear programming-nonlinear programming(MILP-NLP) strategy is used to solve the problem.This paper uses the linear blending rules plus the...     

模拟退火方法用于带有中间换热器精馏塔的优化综合

This article presents a simulated annealing-based approach to the optimal synthesis of distillation column considering intermediate heat exchangers arrangements. T-he number of intermediate condensers and/or intermediate reboilers, the placement locations, the.operating pressure of column, and the heat duties of intermediate heat exchangers are treated as optimization variables. A novel coding procedure making use of an integer number series is proposed to represent and manipulate the structure of system and a stage-to-stage method is used for column design and cost calculation. With the representation procedure, the synthesis problem is formulated as a mixed integer nonlinear programming （MINLP） problem, which can then be solved with an improved simulated annealing algorithm. Two examples are illustrated to show the effectiveness of the suggested approach.     

等温或非等温颗粒吸附动力学模型:应用于吸附热泵(英文)

Understanding the interaction between a fluid and a solid phase is of fundamental importance to the design of an adsorption process.Because the heat effects associated with adsorption are comparatively large,the as-sumption of isothermal behavior is a valid approximation only when uptake rates are relatively slow.In this article,we propose to determine when it is needed to choose the isothermal or non-isothermal assumption according to two physical parametersα(ratio convection/capacity) andβ(quantity of energy/capacity) .The proposed problem is solved by a mathematical method in the Laplace domain.Whenα→∞(infinitely high heat transfer coefficient) or β→0(infinitely large heat capacity) ,the limiting case is isothermal.When the diffusion is rapid(α10) the kinetics of sorption is controlled entirely by heat transfer.If the adsorption process is to be used as a heat pump,it shall be represented by an isotherm model withαandβas high as possible.     

ON THE MINLP APPROACH FOR OPTIMAL DESIGN OF CHEMICAL ENGINEERING SYSTEMS (I) A GLOBAL OPTIMIZATION METHOD FOR NONCONVEX MINLP PROBLEMS

An algorithm for global optimization of a class of nonconvex MINLP problems is devel-oped and presented in this paper.By partitioning the variables,dual representation of the primal ofsubproblems and outer-approximation strategy are used to develop a representative relaxed iterativeproblem.Then the original MINLP problem is replaced by a series of subproblems and relaxediterative problems.By exploiting the particular form of the nonconvex MINLP problem,the feasibleregion of this problem is explicitly included in the representative problem,thus the inconvenienceencountered with the GBD method can be avoided.The proposed method is illustrated andinterpreted geometrically with an example problem.     

INFLUENCE OF INITIAL LIQUID DISTRIBUTION ON MASS TRANSFER IN PACKED BEDS

1 INTRODUCTIONA major problem in the design of packed columns is dimensioning the liquid distributor.Thenumber of outlets is an important factor,because it governs the quality of the liquiddistribution at the inlet cross-section and thus the extent to which the packing is Wetted.Thehigher the degree of wetting and thus the greater the area of phase contact,the more efficientthe mass and heat transfer within the bed of packing.     

用伪并行遗传/模拟退火算法进行多流股换热器网络综合的研究

The multi-stream heat exchanger network synthesis (HENS) problem can be formulated as a mixed integer nonlinear programming model according to Yee et al. Its nonconvexity nature leads to existence of more than one optimum and computational difficulty for traditional algorithms to find the global optimum. Compared with deterministic algorithms, evolutionary computation provides a promising approach to tackle this problem. In this paper, a mathematical model of multi-stream heat exchangers network synthesis problem is setup. Different from the assumption of isothermal mixing of stream splits and thus linearity constraints of Yee et al., non-isothermal mixing is supported. As a consequence, nonlinear constraints are resulted and nonconvexity of the objective function is added. To solve the mathematical model, an algorithm named GA/SA (parallel genetic/simulated annealing algorithm) is detailed for application to the multi-stream heat exchanger network synthesis problem. The performance of the proposed approach is demonstrated with three examples and the obtained solutions indicate the presented approach is effective for multi-stream HENS.     

ON THE MINLP APPROACH FOR OPTIMAL DESIGN OF CHEMICAL ENGINEERING SYSTEMS(Ⅱ)SYNTHESIS OF DISTILLATION SEQUENCES

In this paper the MINLP method proposed in Part(Ⅰ)is illustrated by applying it tothe synthesis problem of non-sharp distillation sequences.A MINLP formulation for the synthesis ofdistillation sequences with non-sharp separation is proposed.In this formulation the recoveries of thekey components are introduced as optimization variables and this makes it possible to synthesize adistillation sequence with specified component recoveries,and at the same time,renders the MINLPproblem nonconvex.The solution procedure is illustrated with three example problems.     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

Analyse Expérimentale et Numérique du Comportement de Membranes Thermoplastiques en ABS et en HIPS dans le Procédé de Thermoformage

In this work, we are interested, on the one hand in the characterization of circular polymeric ABS and HIPS membrane under biaxial deformation using the bubble inflation technique, on the other hand in modelling and numerical simulation of the thermoforming of ABS and HIPS materials using the dynamic finite element method. Hyperelastic models (Mooney‐Rivlin, Ogden) are considered. First, the governing equations for the inflation of a flat circular membrane are solved using a variable‐step‐size‐finite difference method and a modified Levenberg‐Marquardt algorithm to minimize the difference between the calculated and measured inflation pressure. This will determine the material constants embedded within the models used. For numerical simulation, the lagrangian formulation together with the assumption of the membrane theory is used. Moreover, the influence of the hyperalastic model on the thickness and on the stress distribution in the thermoforming sheet are analysed for ABS and HIPS materials.     

ACR对PVC加工性能的影响

详细研究了丙烯酸酯类PVC加工助剂———ACR的特性黏度、组成对PVC共混物加工性能的影响。结果表明,随着甲基丙烯酸甲酯用量的下降和丙烯酸丁酯用量的提高,其塑化速度增大,但熔体强度降低,在组成相同的情况下,特性黏度越大,塑化越慢,熔体强度越大;丙烯酸酯类加工助剂对PVC制品的拉伸强度和维卡软化点无明显影响,高黏度的加工助剂有提高PVC制品拉伸强度和维卡软化点的趋势。     

Kinetics of organic solvent-soluble and native lipase

Organic solvent-soluble lipase was prepared with a synthetic detergent. The solvent-soluble lipase was presumed to be a complex of the enzyme and the detergent. To investigate the effect of the detergent attachment to the enzyme on the reaction properties, the kinetics of the solvent-soluble lipase and of the native lipase were estimated by using glycerides in a homogeneous solution of buffer and tetrahydrofuran. Analysis of the direct interaction between the enzyme and the substrate could serve to characterize the steric structure around the active site of the lipase. The K_m values also differentiated the solvent-soluble lipase from the native lipase. These findings show for the first time that the detergent surrounding the enzyme molecule may affect not only the solubility of the enzyme, but its kinetics as well.     

液滴撞击微结构疏水表面的动态特性

对去离子水滴撞击不同几何尺寸显微结构方柱和方孔状疏水表面的动态特性进行了研究。结果表明：当液滴以不同速度撞击微方柱疏水表面时,液滴展现铺展和回缩过程,且随着韦伯数（We数）增大,最大铺展直径增大,并伴随卫星液滴出现,但到达最大铺展直径的时间一致;而当液滴以相同的速度（We数相同）撞击间距不同的微方柱疏水表面时,液滴的最大铺展直径随着间距的增大而减小,且铺展过程会液滴浸润状态变得不稳定,发生由Cassie向Wenzel状态的浸润转变。当微方柱间距较小时,液滴受到的黏附功越小,越易发生向Cassie状态的转变;液滴撞击微方孔疏水表面时,液滴以规则的圆环状向外铺展和回缩,最后呈现近似规则的椭球状,不会发生向Wenzel状态的浸润转变,利用建立的物理模型对前述现象进行了分析。     

一种自适应柱状密封气膜特性分析

提出一种自适应柱状气膜密封,构建气膜-密封环为研究对象,考虑了偏心间隙发散问题,并定义Rayleigh台阶对气膜周期的突变性,建立了气膜雷诺方程和膜厚变化函数关系式的动力润滑数值模型,获得了摩擦副气膜润滑特性,研究结果表明：气膜力随转速和压力升高而增加,泄漏量随压力升高而增加但是随转速增加而下降,说明密封内部压力流占主导地位。随后,利用曲面槽型雕刻技术,结合高速试验台对密封进行测试,结果表明：理论计算模型与试验结果吻合度较高,斜槽区域存在更多擦痕与磨损,说明斜槽浮动性弱于直列槽;但斜槽的切向流动小于直列槽,导致斜槽泄漏量小于直列槽。该研究成果为自适应柱状气膜密封的气体流动规律和应用提供了理论基础。     

水平及竖直基底上微小固着液滴的蒸发特性分析

为揭示非水平表面上微小蒸发液滴的传热传质特性,本文在准稳态模型的假设下构造三维液滴模型,综合考虑了蒸气扩散、蒸发冷却以及气相域中的自然对流这3种传输机理,对水平以及竖直基底上液滴的蒸发过程进行数值研究。通过分析气液界面上温度分布、蒸发通量分布及总蒸发率的变化,重点探究了基底过热度以及重力的改变对液滴蒸发特性的影响。结果表明：与水平基底上温度的对称分布不同,竖直基底上气液界面温度分布表现出明显的非对称性,且非对称性随基底过热度的升高而增强,最低温度点不再位于液滴顶点,而向一侧偏移。此外,水平基底上气液界面局部蒸发通量呈对称分布,各截面分布相似,而竖直基底上局部蒸发通量分布则呈现出显著的非对称性以及各截面异性,非对称性随着基底过热度的升高而增强,这是重力改变后气相域自然对流发生改变的结果。与水平基底相比,竖直基底上蒸发率更高,总蒸发时间更少。最后,基底由水平变为竖直时,液滴内部流场由对称双涡转变为非对称单涡,单涡流速显著大于双涡流速,液滴内流速随基底过热度的上升而增大,单涡环流造成了气液界面温度分布的改变以及最低温度点的偏移。     

Lipid distribution on textiles in relation to washing with lipases

Effectiveness of lipase in detergency was studied using three test soils (lard, artificial sebum, and olive oil) on a woven cotton fabric. Distribution of oily soil on fabrics was determined for three different treatments (unwashed, washed with detergent without lipase, and washed with detergent plus lipase). Osmium tetroxide was used to label lipid soil for analysis in the scanning electron microscope. Both longitudinal and cross-sectional backscattered electron images for unwashed samples showed that soil was present on surfaces of the cotton fibers and in interfiber spaces of the yarn bundle. Lard soiled samples had large deposits on the fabric surfaces, while artificial sebum and olive oil appeared more uniformly distributed throughout the textile. Oil was deposited in the interfiber capillaries of the yarn bundle and in the crenulation, secondary walls, and lumen of the fibers. Energy dispersive X-ray microanalysis was used to determine relative concentrations of oil at selected morphological locations within the fiber structure and at the fiber surface. Soil distributions within the fibrous structures differed with type of soil and laundry treatment. Backscattered electron images dramatically demonstrated the effect of lipase on cleaning. After washing with detergent plus lipase, yarn surfaces had much less residual soil; residual soil that remained was in the irregularities of the cotton fiber surfaces. Concentrations of oil in the secondary walls, crenulations, lumen, and the fiber surfaces were lower after lipase treatment for all three soils. While washing with detergent removed soil from the yarn and fiber surfaces and the crenulation of the cotton fiber, only the samples washed with detergent plus lipase had lower concentrations of soils within the secondary wall and lumen of the cotton fibers. Fabrics soiled with olive oil and washed with detergent plus lipase had the lowest concentrations of residual soil across the textile structure; the residual soil observed was mainly in the irregularities on the fiber surfaces.     

二氧化钛改性α-氧化铝载体对银催化剂催化乙烯环氧化反应性能的影响

为了排除载体孔结构变化对催化性能的影响,研究了二氧化钛改性α-氧化铝载体对银催化剂催化乙烯环氧化反应性能的影响。研究结果表明,二氧化钛表面改性α-氧化铝载体对载体的比表面积、孔结构无明显影响;载体表面改性导致催化活性组分银在载体表面均匀分散,分散状况明显改善;经二氧化钛改性后载体表面与银的相互作用增强;对单负载银催化剂,由改性载体制备的银催化剂的活性和选择性均下降,改性对催化性能明显不利;对于共浸渍法制备的多组分银催化剂,低温焙烧对催化性能不利,而由经1000℃高温焙烧的二氧化钛改性载体制备的银催化剂的催化活性明显提高。研究表明,载体表面等电点降低及其与银的强相互作用是造成催化剂上金属银良好分散的主要原因;此外,银催化剂助剂的存在减弱了二氧化钛改性载体与银之间的强相互作用、抑制了环氧乙烷（EO）深度反应的活性,两者协同作用提升了多组分银催化剂的催化反应性能。     

煤油贮箱冷氦鼓泡增压过程数值研究

火箭飞行过程中,约90 K的低温氦气用以加压室温下的煤油贮箱使煤油流出,保障发动机燃料供应。为尽可能减少氦气用量,设计低温氦气从液相中喷入,使得氦气在贮箱内上升过程先和液态煤油充分换热升温,再进入气相空间增压。但该过程可能引起两个不利的结果,首先浸没在煤油中的低温氦气管路表面可能结冰,结冰沉底或可能堵塞发动机滤网;其次氦气可能被煤油携带,从而排出口位置可能出现气液两相流。这两种情况都对火箭发动机稳定运行造成负面影响,因此是不允许的。对低温氦气在贮箱中心喷入和环向多孔喷入两种结构的气液两相流过程进行了数值研究,构建了基于Euler-Euler模型的两相传热非稳态模型,数值结果与地面实验观察到的现象进行了定性对比,定性验证了模型的准确性。重点考察了煤油排出过程两种喷入结构的气液两相流分布以及煤油结冰可能性。研究结果从机理上解释了实验现象,并为煤油贮箱增压排出方案设计提供了参考。