The Bureau of Mines investigated several western bituminous coals, chars, coke breeze, and combinations of these for their briquetting potential in bench-scale experiments. Calcined briquets made from Sunnyside high-volatile b coal had the highest compressive strength, 1,380 psi. These briquets were formed at 15,000 psi and 710 deg. F and calcined at 1,750 deg. F using a heating rate of 7 deg. Per minute. Strongest raw briquets made at comparable conditions had a compressive strength of about 2,100 psi and were formed from equal parts of Hiawatha high-volatile B and coal basin medium-volatile bituminous coals and from equal parts of Sunnyside and coal basin coals; however, the latter combination crumbled during calcination. Briquets made from Sunnyside char mixed with 24 percent coal-tar pitch binder, formed at 3,000 psi and 275 deg. F, and calcined for 55 minutes at 1,750 deg. (Heating rate of 9.5 Deg. Per minute) had ASTM coke stability factors (plus 1 inch) ranging from about 9 to 56 percent, but no plus 2-inch material remained after the test. The average compressive strength of the calcined briquets, which was 1,220 psi when calcined at a hearing rate of 9.5 Deg. Per minute, was increased to 1,340 psi when the heating rate was 5 deg. Per minute, and breakage was less marked. Neither calcination of the char at 1,650 deg. Before briquetting nor preheating of the briquets before calcination improved the strength or appearance of the product.
Proc. 11th Biennial Conf., Inst. for Briquetting and Agglomeration, Feb., 1971, PP. 115-124