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Show Spent foundry sand containing 1% to 2% organic resins and binders was successfully processed at IGT in the 3-footdiameter pilot unit using natural gas as supplemental fuel.[8] Bench-scale fluidized-bed studies were first conducted to establish residence time and operating temperature to reduce the organic binder level in the spent foundry sand (measured as Loss on Ignition) to 0.2 weight percent. These tests established the basis for conducting a large-scale, continuous test with 40 tons of sand. The SGFB pilot plant was then operated at 1 ton/h for approximately 50 hours to incinerate used clay-bonded sand containing crushed resin-bonded core butts from a major automobile manufacturer. The processed sand was then mechanically scrubbed (by others) to remove trace quantities of clay and returned to the foundry for core rebonding and strength testing. The core strength data for the three resin-bonding systems tested were quite favorable. IGT also participated in the American Foundry Society 4S Committee's thermal reclamation study of clay-bonded sands in 1984. IGT's effort, financed in-house, included the incineration in the SGFB Process Development Unit (PDU) of 1 ton each of clay-bonded sand from a General Motors and a John Deere foundry. These sands were then scrubbed (by others) and samples were sent to the resin manufacturing companies. Each company used its own bond formulations and conducted rebond core strength tests. The reclaimed sand was found to be suitable for reuse, thus achieving the test objectives. Some of the results from the test are shown in Table 1. Table 1. SPENT SAND THERMAL RECLAMATION TEST RESULTS Loss on Ignition, % Clay, % Before After Before After Sand I 1.0 0.16 2.2 1.1 Sand II 5.6 0.4 12.3 1.6 Sand III 0.9 0.06 1.1 0.1 Incineration and Reclamation of Used Blast Grit Naval shipyards and other domestic port facilities generate thousands of tons of used blast grit annually and dispose of it in landfills. Also, there are thousands of steel bridges in the United States that are on a repaint maintenance schedule that requires grit blasting for surface preparation; this used grit also goes to landfills. Nevertheless, for environmental reasons it is becoming prohibitively expensive to landfill used blast grit containing paint residues. IGT has conducted test work to develop a process to clean blast grit to make possible its recycling for reuse. Essentially, IGT applied a transfer/adaptation of fluidized-bed incineration system developed for the reclamation of foundry sand. -10- INSTITUTE o F GAS TEe H N 0 LOG Y |
