Table 4 shows that the oil contents of oil shale ball and particle are quite similar.
Figure 10 demonstrates that the strength of shale balls was first increased and then decreased with increasing temperature, according to the percentage of complete for oil shale ball.
The oil shale ball with a bentonite content of 6% was found to be optimal.
So, 38 mm x 29 mm oil shale balls were obtained (Fig.
A previous study  investigated the retorting of Haishiwan oil shale balls (29 mm x 38 mm) made of fine oil shale, bentonite and water.
Fisher assay results for coarse oil shale particles and oil shale balls (after ) Sample Oil, % Water, % Gas, % Coarse oil shale particles 12.23 2.84 3.74 Oil shale balls 12.06 2.94 3.85 Table 8.