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 μm and briquetting at 40°C enabled to prepare cokes with tensile strength (σ) over 10 MPa from 4 coals with f_C of 82-85 or 67 wt%-daf. Then, by introducing fine pulverization to sizes of < 10 μm before the briquetting, 7 coals were converted successfully into cokes with σ = 11-25 MPa. Increasing the briquetting temperature to 240°C further increased σ 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 σ 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°C. Characteristics of bonding/ coalescence among particles of different types of coals were responsible for such synergies.