Control of reactive distillation production of high-purity isopropanol

The process characteristics and control strategy of a high-purity IPA reactive distillation column were investigated. A robust nominal operation was found by maintaining an excess of propylene feed to the column and recycling the unreacted propylene to the feed instead of the top stage. Stage temperature and propylene composition with one-to-one relationship with reboiler duty and propylene feed are selected as controlled variables for maintaining bottom purity and feed ratio in the presence of possible measurement bias respectively. High nonlinearity between selected input–output pair was reduced by using variable transformation. Dynamic simulations demonstrated that such a control scheme with nonlinear transformed variable was capable of providing much superior control performance than the one using natural variable.     

ON THE DYNAMICS OF THE COMBUSTION OF SINGLE CHAR PARTICLES

Diffusion and reaction models of varying complexity are used to study the stability of the combustion of single char particles. In contrast to past studies which have considered only the reaction of carbon with oxygen, both the heterogeneous reactions of carbon with oxygen and carbon dioxide and the homogeneous oxidation of carbon monoxide are taken into account in the formulation of the mathematical models. Emphasis is placed on the investigation of the feasibility of occurrence of oscillatory combustion. Our results show that high rates of the C-O₂ reaction and high concentration of O₂ in the ambient favor the occurrence of multiple steady states and oscillatory solutions, but the appearance of oscillatory instability is suppressed by the homogeneous reaction in the gas phase and the presence of CO and CO₂ in the ambient. The parametric investigation of the problem reveals, in agreement with the results of past studies, that the heat capacity of the porous solid, the Lewis number, and the thickness of the stagnant film are three key parameters for the occurrence of the oscillatory response of the system. Reasonably large values of solid heat capacity practically eliminate the possibility of oscillatory combustion, but an appropriate combination of large values of stagnant film thickness and small Lewis numbers may offset the effect of solid heat capacity     

THE DYNAMIC BEHAVIOR AND CHAOS FOR TWO PARALLEL REACTIONS IN A CONTINUOUS STIRRED TANK REACTOR

The dynamical behavior for two parallel reactions in a continuous stirred tank reactor (CSTR) is considered. The global maximum number of steady states is five. Stability conditions are obtained. When the steady state is unique and unstable, a circulating attractor is proven to exist. The orbit structure is numerically found to consist of periodic orbits and chaotic behavior.     

丁烯氧化脱氢反应器开发中的工程问题

在丁烯氧化脱氢反应过程的开发放大中,发现实验室反应器和工业规模反应器通过反应器壁的热反馈存在不同的影响。实验室反应器壁的热反馈能够引起反应器的多态,但在同样的操作条件下,由于壁热反馈影响很小,工业反应器内多态现象不会出现。本文从模型研究和实验测定证实了器壁不同的导热作用以及线速的影响。     

建筑复杂性与建构的创造性表达——RUR事务所的建筑思想及其作品

作为赋有创新意识的建筑事务所,RUR通过对建筑复杂性的研究和实践,提出或强调了诸如＂整体大于部分之和＂、重视建筑设计中的不可见过程、突出普遍存在的差异性等设计思想,并对复杂性所影响下的几何形体操作进行了一定的理论总结。同时,通过对物质材料的研究,揭示建筑结构和形式的新可能性,以创造性地表达建筑的基本建构属性。本文还对其近期作品作了简要介绍。     

MULTIPLICITY AND STABILITY ANALYSIS OF AGGLOMERATION CONTROLLED PRECIPITATION

The possibility of multiplicity in continuous isothermal MSMPR precipitators has been explored for agglomeration controlled conditions and general criteria, independent of nucleation kinetics, are developed for stability and multiplicity of the steady states. For the Volmer model of primary nucleation and the magma dependent power law model of secondary nucleation, parameter regions are determined in which multiple steady states exist, and their linear stability is analyzed. The analysis holds in general for all types of agglomeration kernel. For the Volmer nucleation kinetics three steady states exist in the region of multiplicity with the “middle” one always being unstable. The analysis for magma dependent power law model showed multiplicity regions having as many as four steady states, the number depending on magma and kinetic order. Unlike the case of molecular growth control, limit cycle behaviour is not possible, and the approach to the steady state is always asymptotic     

DEPENDENCE OF THE MULTIPLICITY FEATURES OF AN ISOTHERMAL CATALYTIC REACTION ON EXTERNAL AND INTERNAL TRANSPORT RESISTANCES

A mathematical model (Robin) which accounts for both internal and external transport resistances is used to determine the multiplicity features of a porous catalytic pellet in which an isothermal Langmuir-Hinshelwood reaction occurs. At most three solutions exist for a slab, but an arbitrarily large number of solutions can be found for an infinite cylinder or a spherical pellet. The maximal number of solutions for any finite external mass transfer resistance is bounded between that existing for a model which ignores the external mass transfer resistance and one which ignores intra-particle concentration gradients. The approximate shape of the cross section of the bifurcation set and of the uniqueness boundary of the Robin model can be estimated from the knowledge of the multiplicity features of three simplified (lumped, Dirichlet and Neumann) models, each containing one less parameter.     

一类半线性Nicholson果蝇方程的精确解的个数

在Rn（n≥1）的单位球B^n上研究带有第一类边值条件的果蝇模型：Δu＋λf（u）=0for x∈B^nu=0 for x∈B^n（其中λ〉0,f=u（-1＋be-au））的精确解的个数,并得到了精确的全局分支结构.利用Rabinowitz从单特征值出发的分支定理,得到该方程的解的结构,特别地,得到了方程的正解的存在性及正解的个数等结果.这些结果将在生物经济中有广泛的应用.     

高能碰撞中的多重数分布与动力学涨落

通过多重数分布研究EMU01国际实验组中高能重核束流与微乳胶相互作用中的动力学起伏的规律。引入多重数分布动力学因子dq及其比值Dq两个物理量来定量量度动力学涨落,得到了Dq与D2的幂次标度律,并且给出标度律中指数与q-1的标度关系,所得出的标度指数γ的值在各种碰撞体系中大致相同。