Lignin that had been extracted from Kraft black liquor was investigated as a fusing binder in briquetted anthracite fines for a foundry coke substitute. Cupola "heat zone" pyrolytic temperatures of 300-1550°C were appraised, with the focus on 900°C. Briquettes with favorable strength were made with 86-92% anthracite fines, 2.3-8.6% lignin, 4.5% silicon metal powder, and 0.9% hydrolyzed collagen (denatured collagen) by mass. Briquettes were pyrolyzed under a nitrogen atmosphere or a starved air condition to simulate a cupola pyrolytic heat zone, and then crushed after this pyrolysis so as to discern their unconfined compressive (UC) strength. These tests mimicked key features of the crushing load that coke endures in a cupola. After 30 min of 900°C pyrolysis, UC strength reached 2200-3000 kPa (320-440 psi), when these briquettes contained 4.5% softwood lignin or 2.3% hardwood lignin. With ≥6.5% hardwood lignin, the UC strength after 900°C pyrolysis reached 6000-6500 kPa. When no lignin was incorporated into the briquette, the UC strength after 900°C pyrolysis was a mere 200 kPa. Denatured collagen quantity affected lignin heat zone strength, despite by itself losing strength around 300°C: with 4.5% lignin present, 1.8% denatured collagen doubled the strength of 0.45% denatured collagen briquettes. Adding tannic acid to the briquettes greatly increased the UC strength as well. Lignin provided strength up to 1400°C. Moreover above 1100°C, silicon carbide nanowires greatly enhanced UC strength relative to lignin alone. Briquettes with lignin gained UC strength very quickly when flash pyrolyzed to 900°C, which is important in the cupola. The results herein showed that the bindered briquettes burned at an equal rate as did coke when these were burned at 1100°C in air. The briquettes also contained an energy density that was 38% higher by volume than that of coke. Harnessing these high temperature pyrolytic lignin fusing reactions creates a valuable foundry coke substitute for the future, as well as large scale applications for otherwise underutilized industrial streams of lignin.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology
- Organic Chemistry