Production of High-strength Cokes from Non-and Slightly Caking Coals. Part II: Application of Sequence of Fine Pulverization of Coal, Briquetting and Carbonization to Single Coals and Binary Blends

Sequential coal briquetting and carbonization was applied to preparation of cokes from 9 non- or slightly caking coals with carbon contents (f(c)) of 67-85 wt%-daf. Coal pulverization to sizes of < 106 mu m and briquetting at 40 degrees C enabled to prepare cokes with tensile strength (sigma) over 10 MPa from 4 coals with fc of 82-85 or 67 wt%-daf. Then, by introducing fine pulverization to sizes of < 10 mu m before the briquetting, 7 coals were converted successfully into cokes with sigma = 11-25 MPa. Increasing the briquetting temperature to 240 degrees C further increased sigma to 19-35 MPa for all the 9 coals. It was thus demonstrated that the hot briquetting of finely pulverized coal was a method to prepare high strength coke regardless of the rank of parent coal. Cokes were also prepared from 14 binary coal blends. All the cokes prepared by applying the fine pulverization and hot briquetting had sigma of 20-35 MPa, which agreed well with that calculated by weighted average of those from the component coals. On the other hand, positive and also negative synergistic effects of blending occurred when blends were briquetted at 40 degrees C. Characteristics of bonding/coalescence among particles of different types of coals were responsible for such synergies.