Stirred tank used for process intensification of gas-liquid bioreactors. Photo by: Thorkild Christensen

Chemical and biochemical sustainable process synthesis - Intensification

Abstract

As per most experts, the global market of chemicals is expected to grow to 5.6 trillion Euros by 2035. In recent times, chemical and biochemical process industry has faced enormous pressure in terms of process efficiency, resource availability, regulatory and environmental fronts. On the other hand, bio-resources remain un-economical to be incorporated in large scale biochemical industrial processes. Also, the global rise in temperature has been directly associated with carbon dioxide (CO2) emissions. The development of sustainable process synthesis intensification methods is expected to yield a net zero or net negative CO2 emission. These problems can be overcome by Process Intensification methods i.e. an integrated approach for process and product innovation and development of new technologies. Such approaches are often sustainable, efficient and lead to significantly reduced energy and resource consumption. During the last decade, process intensification (PI) has become a major potential method in the bulk and fine chemicals and pharmaceutical industries by which the overall improvement of a process can be achieved sustainably while improving its overall efficiency (e.g. energy efficiency, waste reduction etc.). Initially, PI existed at the unit operations level [1] which has further been developed to a process level [2]. The industry is limited to those intensified unit operations which have been implemented and deemed successful from an industrial perspective e.g. reactive distillation, dividing wall columns, membrane reactor etc. A systematic synthesis and design methodology for the selection of intensified unit operations for a given process has been developed further at the process level by Deenesh et al. [2]. Still, the PI database needs to be expanded to yield better results. Therefore, the need arises for the further development of a systematic phenomena-based synthesis and design methodology which not only goes beyond the existing methodology but also provides the opportunity for the expanded database for the generation of novel intensified equipment’s and sustainable processes. This methodology by Deenesh et al [2] has been developed by proceeding one fundamental step lower than the unit operations level, this being the phenomena level. Thus, the major task of this work is to find the integrated solutions and further expand the PI database and enhance the methodology resulting in the creation of a computer-aided tool to automatize the steps involved when applying the methodology for the intensification of a given process.

Introduction

Process intensification (PI) has been receiving increased attention and importance because of its potential to obtain innovative and more sustainable process design alternatives. PI has been defined as the improvement of an entire process through the enhancement of the involved phenomena in terms of the integration of unit operations, functions, phenomena’s and the targeted enhancements of phenomena for a given operation. PI aims to improve processes without sacrificing product quality, by increasing efficiency, reducing energy consumption, costs, volume and waste as well as the overall improvement of plant safety. Recently, Deenesh et al. [2] built on the work done by Lutze et al [1] which reported the development of a systematic phenomenon based synthesis and design methodology incorporating PI at the process level. It was initially limited to the unit operation level. Here in this methodology the phenomena have been combined to form simultaneous building blocks (SPB’s). To be novel by design that is going beyond the existing PI unit operations one must proceed at a lower level of aggregation, namely the phenomenon level and investigate the underlying driving forces associated with the unit operations. Then these phenomenon’s can be combined to generate new alternatives. This is exactly the approach followed by Deenesh et al [2]. Using the analysis of the underlying phenomena of the flowsheet, the synthesis and designmethodology process options has been generated and reduced the number systematically through several screening steps until to find the optimal flowsheet solution.

Objective

The research conducted in this field is majorly within the field of process systems engineering (PSE). This work seeks to further develop Process Intensification database, extend the phenomenon based synthesis and design methodology and develop a computer-aided software tool for the intensification of processes via a systematic approach. Within the framework all possible flowsheet options should be generated even for bio processes and reduce systematically via logical and structural constraints and performance metrics to find the optimal intensified flowsheet option.

Methodology

The synthesis, design and intensification methodology is presented in Figure 1. This methodology is a built on previous work done by Lutze et al. [1] and Deenesh et al. [2]. It is operated at two scales on a bigger picture. These scales are Unit operation level and phenomenon level. The required information for the application of the methodology is either the base case flowsheet design of an existing or conceptual process or the input/output specifications of the existing/conceptual process. To start with the problem must be defined i.e. the process which needs to be intensified is defined and then the base case is designed. Here the base case can also be taken from the literature and then the analysis is performed to find the bottlenecks and design hotspots that can be improved. The whole methodology followed until this point is under the unit operation level. Thought the thermodynamic data would still be required to have the base case design. These steps can also be achieved quickly by using Computer aided flowsheet design tool (CAFD) by Anjan et al. [4]. Now, the second scale of the methodology comes in the picture. The unit operations are used to identify the tasks and further broken into the phenomenon’s. here as strengthen the PI database is, more detailed will be the phenomenon validity. This is the major objective which will be worked upon during the PhD work. After this the next step is to combine the phenomenon’s to SPB’s and generate new alternatives or may be novel unit operations which combine to make alternative flowsheets. These alternatives are then verified and then screened based on the operational constraints and performance metrics to find the final intensified flowsheet. This methodology has been applied to various case studies by Deenesh et al. [2] including one bio process.

Conclusion

In conclusion, an overview of the systematic approach based on phenomena’s and design methodology has been shown for the intensification of processes [1,2]. The phenomena based approach has been extended from unit operation level [1] to the process level [2]. Further work is intended to be done for the extension of the database and a general methodology has been defined. Here, phenomena can then be combined to form stages which can be combined to form flowsheets. The concept of phenomena based PI is promising because it is believed that all intensified flowsheet options can be generated if one operates at this level of aggregation. These flowsheets can then be screened to find those flowsheets which provide the highest benefit with respect to operational constraints and performance metrics and these are then further optimized to find the optimal intensified flowsheet.

Future Work

Currently, a systematic methodology for the Process Intensification has been developed by Deenesh et al. [2]. The future work related to this work is as follows:

  • An enhancement of PI database and an existing
    methodology.
  • Further application of the methodology to other
    case studies including bio processes.
  • Development of a computer aided tool for the
    automation of the methodology.

Supervisors

Prof. John M. Woodley (Principal supervisor) 
Prof. Georgios Kontogeorgis

PhD Study Started: October 2016 To be completed: October 2019

To see figures and references for this text, please find the original in the Graduate School Yearbook 2017

Kontakt

Nipun Garg
Ph.d.-studerende
DTU Kemiteknik
91 85 86 04

To see figures and references for this PhD study, please download the Graduate School Yearbook.

The yearbook provides an overview of most of the PhD theses currently being written at DTU Chemical Engineering and is updated every year in February.