Abstract

The synthesis of chemical processes is a design process which can be achieved through a number of different synthesis techniques. There are however inherent requirements that need to be satisfied for any given industrial process if it is to be viable in economic and ‘process' terms, and these include the supply of ‘cheap' raw material, ease of access to the market place or hassle free transportation of the end product thereof, and so forth.

The area of focus in this instance is on the process development phase, where the intention is to use a specific process design method to develop a process flowsheet. However issues related to the determination of reaction kinetics and the outcomes thereof are of no consequence to the analysis process to be performed in the synthesis of a desired process since in this situation, the chosen method is based on thermodynamics. Thus, the focus here is on the latter technique i.e. on process synthesis methods based on thermodynamic principles. Given below is a brief outlook on how thermodynamics plays a role in aiding with the synthesis of chemical processes.

Thermodynamics is used as a process synthesis tool, usually in the design of heat exchanger networks, and in aiding with the design of other sections of a given process plant as well as in putting together those individual sections to form a complete process flowsheet. A method commonly referred to as pinch analysis is the technique employed in the design of heat exchanger networks, whereas exergy analysis is the synthesis tool used in both analyzing existing processes and in the design of new ones. Given below is an overview of these two process synthesis methods

In simple terms the objective of the thermodynamic analysis will be to identify major inputs and outputs of energy across defined system boundaries, the primary aim being to establish where the major losses of energy (heat and work) occur. But in order to analyse and characterize any given process, there are three basic principles that can be employed, and these are: the mass balance, the energy balance, and the Gibbs free energy balance (alternatively an exergy balance).

The process will then be rated in terms of mass/mole and energy efficiency but the ultimate goal of the analysis carried out will culminate in its use in the development of a graphical synthesis technique based on the outcome of this very analysis.

The primary aim of this paper is to develop a technique (graphical) which will allow and afford one an opportunity to have a look at a given chemical process in a holistic way and be able to identify areas that require in depth scrutiny. This technique will allow one to present, view and thus interpret the benefits of heat and work integration, the difference here being that the presentation and the point of view is unlike work that has been carried out before. Thus this is virtually a new way of looking at heat and work integration, the question of reversibility and related issues.

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