Bindered anthracite briquettes as fuel alternative to metallurgical coke: Full scale performance in cupola furnaces

The authors have developed bindered anthracite briquettes that can replace conventional coke as a fuel in foundry cupolas. The anthracite briquettes included fine anthracite grains that were bindered together with collagen, lignin and silicon. These binders gave the briquettes high mechanical strength through the full spectrum of temperatures encountered in a foundry cupola furnace - from ambient temperature up to 1550 C. The bindered anthracite briquettes offered the same structural strength and fuel content as has conventional foundry grade coke. The conventional coking process involves pyrolyzing coal at 1000 C for a day; and this consumes about 15% of the raw coal's energy, while releasing volatile organic air pollutants. In contrast, the briquetting process consumes scant energy, without releasing pollutants. During two full-scale demonstrations that each employed 4 tons of these briquettes, the anthracite briquettes performed similarly to the foundry grade coke, while the briquettes replaced up to 25% of the coke. During briquette replacements, the cupola temperatures, off-gas CO/CO₂ proportions, tuyere back-pressures, and metal-to-fuel ratios were maintained or improved. The iron castings produced during this briquette replacement were of the same high quality and composition as when mere coke was used; and these iron castings were sold. Observations through the tuyere windows - where oxygen-enriched air was lanced into the bottom of the cupola - showed that these anthracite briquettes reached the cupola's melting zone while maintaining their physical integrity. Once these briquettes reached the level of the tuyere windows, they exhibited faster burning in the oxygen-enriched air than did conventional coke.