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Show Striving for High Efficiency Early research and development activities at B G Technology focused on the efficient use of natural gas, whilst improving product quality and increasing production. This was driven by cost, particularly when natural gas was significantly more expensive than other fuels, e.g. oil. By improving the energy efficiency of a furnace, the amount of gas consumed would fall, making this cost effective compared to alternatives. The Heat Transfer Process Conventional high temperature furnaces operate generally with thermal efficiencies of between 5% and 50%. The major loss is in the flue gas, but other losses also occur because of radiation through openings in the furnace structure, from the casing and because of frequent temperature cycling of the structure. Changes to furnace construction have already been shown to improve the latter two losses. The other obvious routes to improve efficiency are to minimise the avoidable losses, by recovering some of the high grade heat which leave the furnace in the flue gases and by the incorporation of better air/fuel ratio and furnace control. The later two options will n o w be discussed in more detail. Heat Recovery From Flue Gases A considerable amount of the energy input into a furnace can end-up in the flue gases. This gives the furnace operator a great incentive to recover this heat either for secondary applications, such as a waste heat boiler or to reintroduce back into the furnace. The heat in the flue gases can be either transferred to the incoming natural gas or the combustion air. Although both can be carried out, air preheating is by far the most practical option: Figure 1. B G Technology working with a number of U K burner manufacturers, has developed several techniques based on preheating the incoming air up to temperatures > 1300°C. 0 200 400 600 800 1000 1200 1400 Air preheat temperature, *C Figure 1 : Effect of Air Preheating on Fuel Saving |