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.

Internally Heat-Integrated Distillation Columns: A Review

Heat integrated distillation operation

Internal Thermally Coupled Distillation Columns (ITCDIC) are the frontier of energy saving distillation research. In this paper, the ideal ITCDIC is considered. A novel mathematical model and a related simulation algorithm are proposed. The dynamic responses of open-loop, PID controllers and the responses of closed-loops are carried out. The results show that the ITCDIC is a self-balance process and could be operated smoothly with two PID controllers; the steady-state optimization met the need of ITCDIC optimization. Furthermore, a steady-state optimization model of the operation parameters is presented, which can be used to directly obtain the optimal operation parameters simultaneously guaranteeing not only the product quality and the maximum energy savings but also the dynamic operability and controllability. The benzene-toluene system is studied as an illustrative example.

Modeling, Control, and Optimization of Ideal Internal Thermally Coupled Distillation Columns

Distillation is a unit operation in which two main processes are involved: heat transfer for vaporizing and condensing and mass transfer for the separation of the mixture. A distillation unit can be described as an exergy converter: that is a unit which converts thermal exergy into chemical exergy. To obtain a complete graphical representation of mass, enthalpy and exergy balances in a fractional distillation, we propose the use of a diagram: the specific enthalpy (in KJ/ Kg of mixture) is plotted against the Carnot factor θ to show the heat and mass transfer effects simultaneously. The application of the methodology to the distillation of an ammonia-water mixture is presented. Conventional fractional distillation consumes a lot of exergy. We propose a new type of distillation in which the reboiler and the condenser normally located at the bottom and at the top of distillation column, are replaced by two heat exchangers integrated in the column itself. The exchanger integrated in the bottom of the column inputs heat to the column, and the other exchanger located in the upper part of the column removes heat. This arrangement minimizes the creation of entropy in the column and therefore maximizes the exegetic effectiveness. This new process, called:“diabatic” or “quasi-reversible” distillation should bring important improvement to conventional distillation, not only from the point of view of energy use (large reduction in the consumption of heat carriers fluids for heating and cooling), but also in terms of capital investment as the cost of fitting a heat exchanger in the destillation column will probably be less than the cost of reboiler or condenser and reflux head.

Exergy analysis of distillation processes

Although reactive distillation columns allow direct utilization of heat of reaction to separation operation, the effectiveness of internal heat integration appears generally to be unsatisfactory and their thermodynamic efficiency could quite often be improved substantially through seeking further internal heat integration between the reaction and separation operations. Prudent arrangement of reactive section, effective determination of feed location, and deliberate distribution of catalyst constitute the three methods that can complement internal heat integration within a reactive distillation column. The reactive section is suggested to superimpose properly onto the stripping section for exothermic reactions and onto the rectifying section for endothermic reactions. Feed location and distribution of catalyst should be determined so that the effect of internal heat integration can be maximized to its fullest extent. A sequential procedure is proposed to determine an appropriate process configuration for internal heat integration within a reactive distillation column. Five reactive distillation systems, involving not only equilibrium-limited but also kinetically controlled reactions, are used to evaluate the design philosophy proposed. It has been found that a substantial improvement in system performance can be achieved even for some reaction systems with side reactions and/or unfavorable thermodynamic properties. Seeking further internal heat integration has been demonstrated to be an effective method for refining process design of a reactive distillation column involving reactions with highly thermal effect. These conclusions are of great significance and can provide process designers with additional latitude to elaborate their process designs. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Reactive distillation design with considerations of heats of reaction

A mathematic model for an internal heat-integrated packed distillation column (IHIPAC) is developed on the basis of interphase mass transfer theory. A new method for design of an IHIPAC is proposed using the newly developed model. The binary system of methanol-water is adopted for the simulation work. The results show that an IHIPAC can be operated at a reflux ratio smaller than the minimum reflux ratio of a conventional distillation column, and that an energy saving of approximate 30% can be achieved under various operating conditions.

https://www.jstage.jst.go.jp/article/jcej1968/21/6/21_6_595/_pdf

Modeling and design method for internal heat-integrated packed distillation column

This paper reports simulation and experimental studies of the energy efficiency and the separation performance of a wetted-wall distillation column with internal heat transfer from the rectifying section to the stripping section.In the simulation, a mathematical model was established on the basis of the interface mass transfer theory, and an operation-type simulator for a differential distillation column with internal heat integration was developed. in the experiments, a vertical concentric double-tube wetted-wall distillation column was used, and the separation of a binary system of ethanol–water was carried out.The close agreement between the simulation results and the experimental results suggests the applicability of the proposed model. Both the simulation and experimental results show extensive improvement of the energy efficiency and the separation performance of the wetted-wall distillation column when it is operated with internal heat integration.

Study of Energy Efficiency of a Wetted-Wall Distillation Column with Internal Heat Integration

本研究では, 十分にエネルギーを節減することが可能である段間熱交換蒸留塔に, その設計と性能を解析するために, マッケーブシール法を拡張する.この方法によれば, 全段数, 熱交換段数, 熱交換段における伝熱面積が, 原料および製品の仕様が与えられ, 2つの還流比と, 濃縮部回収部それぞれの操作圧が設定されたときに計算できる.圧縮動力を含む全エネルギー消費量もその結果として得られる.計算例としてベンゼン/トルエン系2成分蒸留にこの方法を適用し, 設計問題に対しどのように有効であるかを示す.

Design procedure for a plate-to-plate heat-integrated distillation column.

Distillation with internal heat integration, in which energy is recovered by heat transfer from the rectifying section to the stripping section, is an effective method for energy saving in distillation columns This paper analyzes the effects of distillation parameters such as relative volatility, column height and product specification on the energy reducibility of a packed distillation column with internal heat integration To make the effectiveness of internal heat integration clearer, the stripping section, the rectifying section and the integrated column (consisting of both sections) were analyzed separatelyIt was found that: 1) energy saving due to internal heat integration of the stripping section is more sensitive than that of the rectifying section; 2) especially for the stripping section, the reduction of the heat duty at the reboiler is greater than the quantity of heat added to the side of the column, provided that the column is short enough; and 3) for the integrated column, the effectiveness of the internal heat integration is comparatively greater when the relative volatility is large and the specification of the product purity is loose

Analyses of the Characteristics of a Binary Packed Distillation Column with Internal Heat Integration

本研究では段間熱交換蒸留塔の操作圧力に関する考察を行い, 濃縮部と回収部の間の操作圧力差を最小とする条件および, その決定法を示した. この操作圧力差の最小値により, 与えられた分離条件を段間熱交換蒸留塔で達成するために必要な圧縮機所要動力の最小値が計算できる. さらにここで提案した方法の有効性をベンゼン/トルエン二成分系の分離を例として示した.

https://www.jstage.jst.go.jp/article/kakoronbunshu1975/14/1/14_1_63/_pdf

Veerapot Lueprasitsakul

Papers

Modeling and design method for internal heat-integrated packed distillation column

Study of Energy Efficiency of a Wetted-Wall Distillation Column with Internal Heat Integration

Design procedure for a plate-to-plate heat-integrated distillation column.

Analyses of the Characteristics of a Binary Packed Distillation Column with Internal Heat Integration

Operating pressure of a plate-to-plate heat-integrated distillation column.