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Show emissions in the context of ever more stringent laws. In the future, burners may be asked to do more than just mix the fuel and the oxidizer and act as an anchor for the flame. For example, they may carry solid or liquid particles for processing within the flame. The burner may be required to act as a catalytic reactor. Through some innovative combination, the combustion system may be able to provide both heat and process gas tailored for a specific purpose. Such heretofore unconceived arrangements will be the key to process technology breakthroughs. NEW APPLICATIONS The foregoing list of requirements may seem daunting. However, significant progress continues to be made everyday. The following discussion of GRI sponsored projects illustrates some of the advances made to date and the plans GRI has for future developments: ADVANCED GAS MELTER - The AGM processes raw batch or finely ground cullet (recycled glass) through a combustor to melt the material and initiate the fining reactions. This technology is derivative of a coal slagging combustor which has a high particulate loading capability. Its adaptation to glass melting has resulted in several major improvements. A 200 ton per day melting unit would be approximately 2.4m (8 ft.) in diameter and 6.1m (20 ft.) tall, which is a major reduction in size in comparison to a conventional glass tank. The fuel consumption will be in the order of 3721 kJ/kG (3.2 million BTU per ton), compared to today's average of between 4650 and 6975 kJ/kG (4 and 6 million BTU per ton). NOx and SOx will be cut by almost 90%. The technology has the potential to be applied for processing other materials. The possible applications include calcining, baghouse dust metal reclamation, and flame synthesis of commodity raw materials. OXY-GAS BURNERS FOR ELECTRIC ARC FURNACES - This recently developed burner was the first successful oxy-fuel burner to be permanently mounted in the sidewall of an EAF. The temperature of this steel scrap melting furnace is 1650-l760oC (3000-32000F), and the burner is subjected to splashing molten steel and slag. The burner design utilizes a film cooling technique, borrowed from rocket engine technology, to protect the metallic combustor. Although the benefits of these burners has long been recognized, they were not accepted because of the high level of maintenance associated with the need. to retract the burners when not in use. The next application planned by GRI for this type of burner is an all gas-fired steel scrap melter. This development will utilize some form of submerged combustion. The burners will have to withstand the extreme 324 heat and corrosiveness of the molten steel while effectively mixing and burning the fuel under the surface of the steel. IMMERSION TUBE ALUMINUM MELTING - Aluminum reverberatory furnaces must operate at 12000 (22000F) even though the melting point of aluminum is 6750 c (12500 F). This high temperature heat is required because the aluminum bath is a poor receptor of heat. The advances in structural ceramics have made possible the use of gas-fired tubes immersed directly into the bath. This greatly improves the heat transfer and thus the efficiency of the process. The biggest benefit of this approach to the user will be the reduction in the amount of metal lost to oxidation. This melting concept utilizes single ended radiant tubes and burners. The combustion system must be able to deliver the highest heat flux possible tominimize the number of tubes required. Heat fluxes achieved to date are about 91 kW/m2 (200 BTU/HR/IN2) of outside tube surface in 7600C (14000F) aluminum. Further development of these systems would be beneficial to increase the heat flux and the level of combustion air preheat. Immersion tube molten metal heating is in limited use in aluminum and zinc. As the state-of-the-art improves, GRI wants to apply this technology to iron and steel, copper and other non-ferrous melters. This approach may be one means for natural gas systems to compete with small capacity induction melters. DIRECT-FIRED MOLTEN METAL HEATING - Direct fired gas-fired systems are commonly applied to processes operating up to l4250C (26000 F). GRI is sponsoring a project to develop a l6500C (30000F) system to deliver heat to molten steel and iron holding vessels. This is a high temperature, corrosive and particulate laden application. The system will utilize the latest in ceramic heat exchangers (fixed boundary or compact regenerative type) to supply high temperature combustion preheated air. Due to the high temperature of the process, efficient and cost effective heat recovery systems are essential to make this technology attractive. HEAT TREATING - Approximately 80% of the heat treating furnace population is gas-fired. However, furnaces which operated above 11000C (20000 F), such as powder metal sintering or tool steel hardening, are all electrically heated because there is no gas option. The fastest growing segment of the heat treat market is in the llOOoC (20000 F)-plus range. These processes are indirect fired and often involve the use of vacuum chambers. Gas equipment is needed that, at a minimum, can mimic the performance of electrical heating elements. Two approaches to heating the work chamber may be considered. The first is the use of radiant tubes located within the chamber. The second would utilize a combustion system to |
