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Show THE USE OF MODELLING TECHNIQUES IN THE REDUCTION OF EMISSIONS AND ENERGY CONSERVATION Peter J. Mullinger & Gary Broadley Fuel and Combustion Technology ABSTRACT The use of modelling to study combustion systems dates from the 1940's. Water/bead modelling was used, initially by research laboratories, and later in the 1960's by at least two commercial burner companies. Acid/alkali modelling and zone heat transfer modelling came into the commercial field in the 1980's and more recently computational fluid dynamics (CFO) is making its contribution. Thi~ paper reviews the current status of these various modelling techniques and their application to industrial furnaces. A selection of example case histories are reviewed, where these techniques have been used for the reduction of pollutant emissions and energy conservation. The case histories include:- 1. The design of a flash calciner using water/bead, acid/alkali and CFO modelling. 2. The upgrading of kiln combustion systems, to allow a fuel change from oil to gas with minimal efficiency derating using acid/alkali and mathematical zone modelling. 3. The upgrading of furnace firing systems to increase efficiency and minimize the emission of pollutants using water/bead and mathematical zone modelling. 1. INTRODUCTION The emphasis of this paper is on energy conservation and emission reductions as a consequence of improved combustion performance on existing process plants. The energy consumption of many plants such as cement and lime kilns, flash calciners for limestone and alumina, and smelting furnaces for metals are dependent on the efficiency of the heat transfer between the flame and the product. These are processes where the flame is in direct contact with the product and hence the flame characteristics are critical to product quality, energy consumption and emissions. The flame characteristics can also affect processes where the flame is not in direct contact such as steam raising or petr~chemical heaters but generally to a lesser extent. Most process plants designed and built today, have a lower energy consumption and produce less pollution than plant built twenty years ago. In some cases, the improvements are spectacular, but in others the differences are quite small. Whilst it may seem to many observers that large reductions in energy and emissions can be achieved by building a new plant, this is not always the case. Even when it is, this ideal may not be achievable and may even be undesirable for a number of reasons:- |