Preparation of High-Strength Coke by Carbonization of Hot-Briquetted Victorian Brown Coal

Abstract

Cokes with tensile strengths of 6À37 MPa were prepared by binderless briquetting and subsequent carbonization up to 900 °C of pulverized Victorian brown coal that had little fluidity and very low reflectance. Application of mechanical pressures of 64À128 MPa at temperatures of 130À200 °C caused softening of the coal because of mobilization of both low-and high-molecularmass components, deformation of the coal matrix, and then coalescence/bonding of particles. The resulting coke had a density as high as 1.1À1.3 g/cm 3 and tensile strength of 28À37 MPa, which was 5À6 times that of conventional metallurgical coke.

Preparation of Coke from Hydrothermally Treated Biomass in Sequence of Hot Briquetting and Carbonization

“…The briquette undergoes carbonization with no or insignificant softening/fusion, but transforms into coke that has tensile strength of 5-40 MPa. 5,6) It was also found for every type of lignite that the tensile strength of coke was correlated linearly with its bulk density, and this trend was consistent with general knowledge of mechanical strength of coke.…”

“…The gross coke yields from the HT solids with HTT ≥ 250-260°C are well above 50 wt%, and are as high as those from hot-briquetted lignites. 5,6) As seen in Fig. 8(b), HT at 240°C and higher temperatures give net coke yield that is equivalent to or even higher than that without HT in spite of substantial mass release during HT.…”

“…Details of the procedure are reported elsewhere. 5,6) In brief, 0.9-1.0 g of solid was placed in a 14.1 mm diameter mold and heated to 130 or 200°C. A mechanical pressure (PB) of 12, 25, 55 or 114 MPa was then loaded for 8 min.…”

“…25) Details of the tests and the method of determining the tensile strength (TS) are reported elsewhere. 5,6) Compression strength was not employed because it depends on the shape (i.e., aspect ratio of cylindrical specimen). Fractured surface of the coke was observed by scanning electron microscopy (SEM) on a micrograph (Keyence, model VE-9800).…”

“…3,4) The present authors 5,6) proposed sequences of hot briquetting and carbonization 5) or hydrothermal treatment, hot briquetting and carbonization 6) for production of coke from lignite. The briquetting of pulverized lignite at 100-200°C causes its thermomechanical plasticization while macromolecular relaxation occurs due to breakage of non-covalent bonds such as hydrogen ones.…”