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Show The recuperator is designed to preheat the combustion air to a temperature of about 575 °F. The recuperator is of the "basket" type and the majority of the heat transferred to the tubes from the exhaust gases is by radiation. Software for calculation of the recuperator parameters has been developed for use on PC's. The melt is discharged from the melting bath using a special tapping device. Different designs are used depending on the operating mode of the melter: periodic or continuous. For mineral wool products, the tapping device is designed to ensure melt discharged in a continuous stable stream. The melt is then transported along an inclined heated channel to the fiber forming device (centrifuge). Currently, two melters based on the above designed are operating at two separate plants - in Kiev (Ukraine) and in Bereza (Belarus') - both producing thermo-insulation mats from mineral fiber. Both have an area of 18 ft by 13 ft, and their height (up to the top of the recuperator) is 30ft. The production rate from this melter is about 17500 to 19500 ft3 of mats per day, with a density of 6.2 lb/ft^. The waste is negligible since all of the 12 to 18 % rejects are fed back into the melter. The melt contains small gas bubbles which have not been found to have any adverse impact on the quality of the mineral fiber. The exhaust gases leaving the melter contain only negligible amounts of carbon monoxide and only 70 to 100 vppm of N O x (corrected to 0 % O2). The N O x levels are less than one-quarter of those generated in the best conventional tank melters. The heat balance for the commercial melters shows the heat losses through the frozen melt lining are relatively high. Their impact can be reduced, however, by using larger melters, by utilizing the transferred heat, and/or by utilizing industrial oxygen. The thermal efficiency of the commercial melters is 19%. Increasing recuperator temperature to 800 °F and preheating the batch would raise thermal efficiency to 2 8 % . Efficiency can be raised to 4 5 % by increasing production rate from 80 to 105 ton/day and increasing fuel preheat to 1650 °F. Using industrial oxygen will allow production rate to be doubled and provide a high thermal efficiency of 6 5 % . The thermal performance of the melter improves with capacity because with an increase in the size of the melting bath, the water-cooled surface area, and consequently, the specific heat losses through the lining, per unit of manufactured product decrease. The heat transferred through the lining to the cooling water is a reserve which, if properly utilized, can further improve the thermal characteristics of the melter. For example, if an evaporating system of cooling is used, and if the generated steam is used for process heating, energy generation, and/or for other useful purposes, then the thermal efficiency of the overall system can be further increased by a substantial amount. Pilot-Scale Testing The pilot-scale SCM unit was designed and fabricated by GI and assembled at IGT to allow production and study of a variety of melts. The highly flexible system was shipped from Kiev, Ukraine to Chicago, Illinois and assembled at IGT's Energy Development Center. The melter is capable of producing up to 500 lb/h of melt using either oxy-gas or air-gas burners. The first shake-down tests with the pilot-scale melter involved batch and continuous melting of basalt and basalt-dolomite mixtures. This represented the first operation of stable oxy-gas submerged combustion melting in a working furnace. 5 |