Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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Combining the vapor recompression (VRC) with an intermediate reboiler (VRCIR) and an internally heat integrated distillation column (HIDiC) has emerged as a promising technology. The present work aims at advancing this hybrid HIDiC-VRCIR configuration by introducing multiple intermediate reboilers (IRs). Increasing the number of IR leads to provide a better distribution of internal heat along the column, thereby increasing the energy efficiency. In designing a sample double IR (DIR) based HIDiC-VRC, the location of IRs and their coupling with stripper trays play a crucial role. The optimal position of DIR system is proposed to identify based on two criteria: lowest total annualized cost (TAC) and highest energy savings. Further, aiming to enhance the energetic and economic potential of the HIDiC-VRCDIR structure, it is proposed to choose either the series or parallel mode of compressor applying the same two criteria stated above. By simulating a ternary wide-boiling hydrocarbon system, the promising performance of the sample HIDiC-VRCDIR configuration is evaluated with a couple of unique features. Extending this proposed thermal integration mechanism, one can configure the hybrid HIDiC-VRCIR column with any suitable number of IRs. © 2016 Institution of Chemical Engineers

Department of Chemical Engineering

School of Chemical Engineering

Vellore Campus

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Chemical Engineering Research and Design

Thermal integration of vapor recompression in a heat-integrated distillation: Impact of multiple intermediate reboilers

Declining petroleum reserves, increasing fuel demands and environmental problems have attracted increasing research attention in improving the energetic potential of separation processes dominated by distillation. In this contribution, we develop an intensified thermal integration scheme for a pressure-swing distillation (PSD) by combining the internally heat integrated distillation column (HIDiC) and the vapor recompression column (VRC), thereby acquiring the benefit of both of them. Since the PSD process typically combines a low-pressure (LP) and a high-pressure (HP) distillation unit, the possibility of thermal coupling arises between the HP column (heat source) and the LP column (heat sink) within the framework of HIDiC scheme. Aiming to further reduce the consumption of external energy in the PSD system, the overhead vapor of HP column is proposed to act as a heat source for bottom liquid reboiling in the LP column by the application of VRC mechanism. By this way, the HIDiC-VRC combination gets the shape of an intensified structure and it is capable of providing an enhanced energy efficiency potential. For a reactive pressure-swing distillation (reactive PSD), the proposed HIDiC-VRC configuration is shown to be more energy efficient and cost-effective compared to the HIDiC-alone scheme. © 2014 Elsevier Ltd.

Applied Thermal Engineering

Assessing the performance improvement of an intensified heat integration scheme: Reactive pressure-swing distillation

A novel combination of internally heat-integrated distillation column (HIDiC) and vapor recompression column (VRC) with intermediate reboiler (IR) is proposed. Supplying heat at the highest temperature point (i.e., column bottom) of the VRC scheme is not thermodynamically favorable and, therefore, we aim to install the IR for better distribution of heat along the column length, thereby reducing the compressor work. Introducing IR in the combined HIDiC-VRC system formulates an open-loop variable manipulation policy to evaluate the comparative impact of internal and external heat sources on bottom liquid reboiling. With internal energy driven bottom reboiler, we further investigate the hybrid HIDiC-VRCIR column with proposing the two modes of compressor arrangement, namely parallel and series. Finally, a multicomponent distillation system is exampled to show the promising potential of the proposed HIDiC-VRCIR configurations in improving the energetic and economic performance over the HIDiC-alone and HIDiC-VRC schemes with reference to a conventional standalone column. © 2014 American Institute of Chemical Engineers.

AIChE Journal

Introducing vapor recompression mechanism in heat-integrated distillation column: Impact of internal energy driven intermediate and bottom reboiler

In this contribution, a hybrid thermal integration scheme is proposed for a pressure-swing distillation (PSD) column by combining an internally heat integrated distillation column (HIDiC) with vapor recompression column (VRC). The purpose of this article is three fold: first, it designs a HIDiC for a PSD system with a reduced number of internal heat exchangers. Second, it develops a hybrid column configuration by integrating that HIDiC, which is devised based on the thermal driving force existed between the two diabatic columns, and VRC that is devised based on the thermal driving force existed between the top and bottom of the same high pressure column, yielding an ideal HIDiC-VRC configuration. Third, it provides a comprehensive comparison between the HIDiC-alone and its hybrid HIDiC-VRC structure with reference to a conventional standalone PSD column. To evaluate the performance of all these configurations, we estimate the two performance indexes, namely energy consumption and total annual cost, for an example of a bioethanol dehydration system. © 2015 Elsevier B.V.

Separation and Purification Technology

A hybrid heat integration scheme for bioethanol separation through pressure-swing distillation route

Most of the published studies have focused on the thermal integration of nonreactive distillation columns. The key limitation of reactive distillation (RD) technology is that the necessary conditions (such as pressure and temperature) for the reaction must match those of distillation. Owing to this constraint, the reaction conversion may be adversely affected at the elevated pressure in the reactive section of an internally heat integrated distillation column (HIDiC). This fact forces us to adopt an external heat integration approach for an industrial heterogeneously catalyzed ethyl tert-butyl ether (ETBE) RD column. The direct vapor recompression column (VRC) is an external heat integration scheme that is successfully used as an energy efficient scheme for separating a close-boiling mixture. Interestingly, there exists a large temperature difference between the two ends of the representative ETBE column, and it makes the external heat integration more challenging. Aiming to improve the thermal efficiency of the ETBE column under the VRC framework, various heat pump arrangements with intermediate reboiler(s) (IR(s)) are explored and analyzed with performing a comparative study in terms of energy consumption and economics. To improve further the thermal efficiency, in this contribution, a novel multistage vapor recompression RD column with IRs is introduced addressing a number of practical concerns. An algorithm for the proposed column is formulated showing the sequential steps involved in heat integration. It is inspected that the proposed multistage vapor recompression RD system appears overwhelmingly superior to the classical vapor recompression RD and its conventional stand alone column providing a significant savings in energy as well as cost. © 2012 American Institute of Chemical Engineers (AIChE).

A novel multistage vapor recompression reactive distillation system with intermediate reboilers

In this contribution, a novel intensified heat integrated ternary distillation column (int-HITDiC) is introduced. The objective is to show the superiority of the int-HITDiC over its general form, namely the HITDiC and the conventional standalone column on the basis of two criteria: energy consumption and economics. The concept of pinch technology has been applied to identify the feasibility region for internal thermal coupling between two diabatic sections, namely the rectifying section and stripping section. In this study, the influence of system parameters on the behavior of HITDiC is examined. The optimum compression ratio is arrived at by taking into account the energetic and economic aspects. Performing a detailed analysis, it is observed that the general HITDiC scheme shows lower energy consumption and better economic figure compared to its conventional counterpart. Aiming to improve the overall efficiency further, the int-HITDiC scheme has been explored. The proposed intensified strategy gets the advantage of both HIDiC and direct vapor recompression column (VRC). © 2012 Elsevier Ltd.