Change in composition and properties of fuel shales during heat treatment

The chemical composition and properties of fuel-shale briquets produced from tailings at the Leningradsk shale field are studied. The main problem in the processing and use of fuel shale in the electrode industry is copious ash production. At the same time, the composition of the shale’s mineral component changes. The change in fuel-shale mass on heat treatment at 25–950°C is determined. The shale mass declines in five stages, with changes in the structure and physicochemical properties. Analysis of the liberation of volatile components condensed in aqueous solution during heat treatment shows that the pH of the solution declines from 6.72 to 6.31 with increase in temperature and that P2O5 and SO3 are liberated. The oxides Al2O3, SiO2, CuO, ZnO, and MgO are also present as a suspension in the solution. Investigation of the briquets’ structure and physicochemical properties during heat treatment permits the determination of the optimal duration of semicoking and coking.