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Show 1. The closure of plant before the end of its economic life is a wa ste of re s ourc e s. 2 . The d ismantl i ng of a plant is itself a cause of pollution even if mo s t of the materials are recycled. 3. The construction of new plant uses considerable energy and causes pollution. 4 . We simply do not have sufficient engineering and manufacturing resources to completely replace most existing plant. 5. Wholesale closure of existing plant and replacement would cause shortages and economic upheaval even in recessionary times. 6. Industry simply does not have the money available. Given these constraints, much depends on keeping existing plant running and improving its performance using cost effective techniques. To achieve this objective requires a much better understanding of how the plant operates than was the case when it was designed and built. Most existing process plant have been built using empirical design methods and simplistic scale up from previous plant with scant regard for some of the more important parameters, especially combustion aerodynamics, heat release patterns and fuel air · mixing regimes. This paper describes how various modelling techniques have been used to improve the energy efficiency and reduce the emissions of several existing plants, and its contribution to the design of a new plant to minimize energy consumption. 2. THE CONTRIBUTION OF MODELLING The first step in reducing the energy consumption of a plant or lessening its emissions, is to establish how the plant is currently operating, \~hat the potential for energy savings are, and where the emissions arise. Whilst this is stating the obvious, it is surprising just how many energy saving programmes and emission reduction exercises are implemented, without this first step being fully explored. This is a consequence of combustion and the heat transfer from flames being such a complex subject, that it is generally not well understood, and no analytical solutions exist to assist with the design of flames, furnaces and the associated burners. Most furnaces have therefore been designed using empirical methods and their associated burners designed as a result of long hours of trial and error testing, often in a totally different environment from the final application. Indeed, one standard burner design may be selected by furnace designers for a wide range of applications, many for which it is entirely suited, but a minority for which it is quite unsuitable. Unfortunately, the burner ~esigner is often unaware of how the burner and furnace aerodynamics interact, and it is in this area that modelling can contribute a great deal to the understanding of furnace design and operation. In the absence of analytical solutions to the problems of burner and furnace design, modelling allows us to build an understanding of the process. Generally, it is necessary at present to use a number of modelling techniques simultaneously to study a real industrial problem. |