Takaji Akiya

Internally Heat-Integrated Distillation Columns: A Review

The heat-integrated distillation column to be addressed in this paper is a special distillation column that involves internal heat integration between the whole rectifying and the whole stripping sections. An overview of the research on this process is presented in this work. It covers from the thermodynamic development and evaluations to the practical design and operation investigations for the process. Comparative studies against conventional distillation columns are introduced and the results obtained show distinctively the substantial advantages in energy efficiency of the process over its conventional counterparts. Some relevant issues of process design and operation are to be stressed and the results of the first of its kind bench-scale plant experimentation are given in great detail. The application of internal heat integration principle to other distillation-related processes is also discussed in depth. These include heat integration within batch distillation columns, pressure-swing distillation columns that are used for the separation of pressure-sensitive binary azeotropes, and different distillation columns that have no connections at all. The prospects of the HIDiC and our future research work are then highlighted.

Parameter analysis and optimization of ideal heat integrated distillation columns

Abstract Parametric analysis is performed for ideal heat integrated distillation columns (HIDiC) and comparative studies are made with conventional distillation columns. Implications of process design and operation variables are clarified and heuristics are provided for the effective process design. A generalized process configuration is suggested, which is demonstrated to have both higher energy efficiency and higher flexibilities than its original configuration. Simulation studies are conducted and the obtained results confirm the conclusion.

Operating an ideal heat integrated distillation column with different control algorithms

The operation of an ideal heat integrated distillation column is addressed. Five control strategies, namely, single loop composition control system, multi-loop composition control system, multivariable internal model control (IMC) system, modified multivariable IMC control (MIMC) system and nonlinear process model based control (NPMC) system, are design and applied to the process. Simulation results demonstrate that all the control systems are capable of keeping both end products on their specifications. The NPMC is the best one in the operation of the ideal HIDiC. It can very smoothly realize setpoint transition and efficiently counteract external disturbances. The MIMC ranks the second for the regulatory responses to feed composition disturbances have relative longer setting time. The next comes to the multi-loop composition control system. Although it works well for the operation of the ideal HIDiC, it produces relative larger oscillations and longer setting time in the system responses. The IMC can not compete with the multi-loop composition control system because it is extremely sensitive to operating condition changes. The single-loop composition control system is the worst one for the responses of the uncontrolled product is extremely sluggish.

Simulation oriented development of a new heat integrated distillation column and its characteristics for energy saving

Abstract So far, Process Systems Engineering (PSE) has contributed to the creation and improvement of new chemical production systems, by effective and rational combination of existing elementary production units and related information treatment parts, from both design and operational view points. However, it should not be forgotten that the structure of production units or information treatment parts are already fixed and given in many cases, when such methodologies are going to be applied to practical production systems. In this paper, we show that such production units or information treatment parts themselves should be newly created and synthesized from the viewpoint of the production system as the total, in order to create more rational production systems in the coming century. Next, the development of a new heat integrated distillation column, based on the above general concept, is reported and its characteristics of energy saving are discussed from a thermodynamic viewpoint. t;**

A New Configuration of Ideal Heat Integrated Distillation Columns (HIDiC)

Abstract A new configuration for ideal heat integrated distillation columns (HIDiC) is proposed by further heat integration between its overhead product and feed. This modification makes the ideal HIDiC more self-support and imposes fewer constraints to the environment. The added heat integration is different in nature from the one between the rectifying and the stripping sections. The latter is self-regulating, while the former is not. Open-loop integrating process is produced by the added heat integration, which makes the process more difficult to control than before. It is therefore extremely important to explore the interaction and tradeoff between process design and operation. Simulation studies are conducted to evaluate the process operation feasibility and it is found that the process can be well controlled through manipulations of pressure difference between the rectifying and the stripping sections and feed thermal condition.

Remarkable Antiagglomeration Effect of a Yeast Biosurfactant, Diacylmannosylerythritol, on Ice-Water Slurry for Cold Thermal Storage

Antiagglomeration effects of different surfactants on ice slurry formation were examined to improve the efficiency of an ice‐water slurry system to be used for cold thermal storage. Among the chemical surfactants tested, a nonionic surfactant, poly(oxyethylene) sorbitan dioleate, was found to show a greater antiagglomeration effect on the slurry than anionic, cationic, or amphoteric surfactants. More interestingly, diacylmannosylerythritol, a glycolipid biosurfactant produced by a yeast strain of Candida antarctica, exhibited a remarkable effect on the slurry, attaining a high ice packing factor (35%) for 8 h at a biosurfactant concentration of 10 mg/L. These nonionic glycolipid surfactants are likely to effectively adsorb on the ice surface in a highly regulated manner to suppress the agglomeration or growth of the ice particles. This is the first report on the utilization of biosurfactant for thermal energy storage, which may significantly expand the commercial applications of the highly environmentally friendly slurry system.

Evaluation of pore size distribution in boundary region of micropore and mesopore using gas adsorption method

This paper discusses an accurate method of pore size distribution evaluation in boundary regions of micropores and mesopores using the gas adsorption process on the basis of the capillary condensation theory, which is liable to be underestimated with the existing BJH and DH methods. A typical nitrogen adsorption isotherm for highly ordered mesoporous silica, which has cylindrical pores with diameter smaller than 4 nm, is considered to be type IV and it is well known for the steep increase of the amount adsorbed through capillary condensation in the region of the relative pressure P/P0 smaller than 0.4. In calculating the distribution of the pore size from the change of the amount adsorbed due to capillary condensation, it is important to accurately predict both the multilayer thickness t of the adsorbed nitrogen molecules and the critical radius rc where capillary condensation occurs. It is necessary to consider the curvature of the adsorption layer-gas phase interface when predicting the multilayer thickness t of nitrogen adsorbed within the pore of highly ordered mesoporous silica. Revision of the Kelvin equation is also required when rc is to be predicted. While the predicted value of t based on the Broekhoff and de Boer theory is matched well with the value of t which is actually measured using highly ordered mesoporous silica, and the predicted value of rc based on the GTKB-Kelvin-cylindrical equation that has been revised considering the effect of the interfacial curvature on the interfacial tension of the adsorption layer-gas phase interface is matched with the value of rc which is actually measured using highly ordered mesoporous silica. A combination method of the Broekhoff and de Boer equation and the GTKB-Kelvin-cylindrical equation is proposed as a means of accurately evaluating, from the nitrogen adsorption isotherm, the pore size distribution in the highly ordered mesoporous silica in boundary region of micropore and mesopore. The proposed new method of pore size evaluation features high accuracy and offers the convenience of obtaining the pore size distribution without repeated calculations by employing the same algorithm as DH method. The pore size predicted by the Halsey equation and the Kelvin equation of the conventional DH method is about 20% smaller than the pore size predicted by the newly proposed evaluation method.

Bromomalonic acid as a source of photochemically produced Br− ion in the Ru(bpy)32+-catalyzed Belousov-Zhabotinsky reaction

Abstract Experimental observation shows that bromomalonic acid (BrMA) is one of the sources of photo-induced Br− ion in the photosensitive Belousov-Zhabotinsky reaction. The rate of Br− production by visible light was measured using a Br−-ion-selective electrode in a solution containing BrMA, H2SO4 and Ru(bpy)3SO4 but no oxybromine species. The order of reaction was 1 for [BrMA] and [H+], and about 1 2 for the light intensity and [Ru(bpy)32+]. Two types of probable photocyclic mechanisms are proposed.

Evaluating control structures for a general heat integrated distillation column (general HIDiC)

Abstract The assessment of control configurations for a general HIDiC (an ideal heat integrated distillation column incorporated with a overhead condenser and bottom reboiler structure) is addressed in this work. It is found that the double ratio control configuration, (L/D, V/B) is still the best one among all the possibilities. Moreover, the pressure difference between the rectifying and the stripping sections and the feed thermal condition are expected to be consistent manipulative variables for the control of the general HIDiC. The control configuration, (pr-ps, q), appears to be a feasible one for the process operation. The performances of the general HIDiC can be substantially improved by employing efficient multivarible control algorithms.

Phase equilibria of some alternative refrigerants hydrates and their mixtures using for cool storage materials

Electric power demand for residential air-conditioning has been increasing in Japan. Development of cool storage systems which shifts this demand to off-peak period and contributes to the load leveling of power generation is necessary. The hydrate cool storage system is the suitable cool storage system because its cool storage density is large and chiller efficiency is high. In this study, alternative refrigerants HFC-32(CH/sub 2/F/sub 2/), HFC-125(C/sub 3/CHF/sub 2/) gas hydrate and their mixture were selected for cool storage materials. The phase equilibria of these alternative refrigerants gas hydrates and its mixtures were obtained. From these phase equilibria, the critical decomposition temperature, the critical decomposition pressure and the heat of formation of these gas hydrates were determined.