Improving form coke briquette strength

Abstract

Formcoke technology, which involves briquetting of char, coke and/or raw coals with a binder material, permits the use of a wide range of coals as the feedstock. This technology aims to produce a fuel that possesses properties similar to those of conventional coke. In addition to a high calorific value and fixed carbon content, the major physical requirement is that the formcoke must retain its shape and form during shipping and storage, as well as exposure to heat in a furnace. The major objective of this study was to determine the conditions that could provide high compressive strengths [in excess of 2.8×10 7 Pa (4000 psi)] for piston formcoke briquettes prepared without air-curing green briquettes in the FMCoke process. The effect of the thermal pretreatment of the binder on compressive strength of briquettes was examined. In addition, novel methods to promote stronger bonds at the binder/ calcinate interface were explored. The addition of liquid phase oxidants (for example, hydrogen peroxide, among others) to coal tar binders was examined to promote in situ release of oxygen during curing under an inert environment. This release of oxygen, simulating the presence of air in the curing environment, was expected to promote stronger interfacial bonds between the binder and the calcinate. Modification of the binder/ calcinate interface was also examined through use of minor quantities of other types of additives. In particular, the addition of phosphoric acid to the calcinate delivered piston briquettes with compressive strength readily exceeding 2.8×10 7 Pa without recourse to air-curing. Curing in air, in fact, led to compressive strengths exceeding 5.5×10 7 Pa.