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Show Melter designs are employed which minimize fluidization of the melt so droplet formation is minimized. These droplets, especially small ones formed when bubbles split, could be thrown well clear of the melt bath with considerable force. Designers of these types of furnaces have focused on controlling droplets and preventing excessive coating of the exhaust duct with an ever-thickening layer of frozen melt. In the present furnace, the issue is successfully resolved by maintaining the melt depth at the minimum acceptable level and by removing the combustion off-gases through a special separation zone. This approach also reduces the supply pressure needed for the gas and oxidant and reduces the amount of melt bath water-cooled wall surface area . A key factor in submerged combustion melter design is optimization of the geometry and configuration of the melting/combustion zone. Based on research data, the Gas Institute has developed a procedure for specifying the dimensions of the melting bath, including the optimum melt depth, for uniform distribution of the combustion gases. This procedure allows a furnace to be designed with the highest possible ratio of heat absorbed by the melt to heat transferred to the cooling water. For example, the optimum melt depth for mineral wool production in an air-fired melter has been determined to be 2.5 to 5 feet. Optimum melter geometry and melt depth are strong functions of the thermal and physical properties of the melt, the production rate of the melter, and the momentum of the jets from the submerged combustion burners. STATUS Submerged combustion melting technology has progressed through developmental stages at the Gas Institute and is now commercial for the production of mineral wool. The commercial mineral wool melter and proposed improvements are described. The Institute of Gas Technology has licensed the S C M technology and has built a 6-ton/day pilot-scale S C M unit for demonstration and development of new applications. The pilot-scale melter is the first in the world to use oxygen-natural gas fired burners. The pilot-scale melter and results of the initial oxy-gas testing in the pilot-scale unit are described. Commercial Operation The first commercial submerged combustion melter design is the result of extensive research efforts at GI. The main components of the system are: melt bath, separation zone, recuperator, feeding unit, melt tap, submerged burners, and stack. In addition, to ensure reliable and steady operation, systems are included for tank cooling, natural gas and combustion air supply, and process control, measurement, and safety (3). The melt bath is assembled from separate carbon-steel water-cooled panels lined with 1.2 in. thick layer of refractory on the surface exposed to the melt. The panels are divided into groups and each group is connected to the bottom of the floor panel. Material is fed through port in the crown panel by a loading and proportioning device. This device is designed to not only feed the batch in proportion to the production rate, but also to protect the feed nozzle from closing in the presence of the fluidized melt droplets. The exhaust gases from the melting bath are passed through a separation zone, where the melt droplets and solid particles are separated as a result of the centrifugal forces created by the turning exhaust gas flow. The exhaust gases go into the recuperator and then into the stack while the droplets and the solid particles remain in the furnace. 4 |