Process development will culminate with a 1000 pph prototype SSCC firing a 40,000 lb capacity open hearth melting furnace at the Alcoa Laboratories. Phase I has begun with the design and construction of a 350 lb/h (coal) staged slagging cyclone combustor (SSCC) attached to a 7-ft dia aluminum melting ladle furnace. To achieve this goal, the program has been divided into two phases. The ultimate objective of this program is the commercial demonstration of an efficient, environmentally acceptable coal firing process suitable for implementation on melting furnaces throughout the aluminum industry. The amount of lime required, however, is about 50% more than that for the lime slurry process. This process does not require a scrubbing plant and therefore, has much lower equipment cost as compared to the lime slurry process. The experimental results also show that the flue gas can effectively be desulfurized by mixing lime with pulverized coal prior to combustion. No change in the sulfur content of slab material is observed. But the depth of decarburization is limited to within one half of a millimeter of the surface for 1 inch thick slabs. The experimental results from the more ยป operation of a small scale laboratory furnace indicate loss of carbon content in steel slabs preheated with pulverized coal. The effect of coal burning environment on the chemistry of slabs is also included in the evaluation. Savings in fuel energy cost easily compensate for higher equipment and operating costs of pulverized coal fired slab preheating systems. However, coal is cheaper than natural gas on a unit heat energy cost basis. Pulverized coal firing is more complex than natural gas firing and requires higher equipment and operating costs including the cost of flue gas cleaning. Pulverized coal instead of natural gas as a fuel for slab preheating furnaces is evaluated for economic and technical feasibility.
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