Each test was repeated five times, and the calculated average of the
five tests was used as the value of the properties.
After each compaction test, the length, diameter and mass of each
briquetteweremeasured using amicrometer and an electronic balance,
respectively. Briquette density represents the ratio between the sample
mass and its volume, including pore volume. The volume of the briquettes
was calculated as the volume of a cylinder with the dimensions
(length and diameter) measured.
According to the Technical Specification CEN/TS Standards [20], briquette
durability was estimated using a dustproof rotating drumprototype.
The drum had a 598 mm internal diameter and a 598 mm depth
(volume 168 l). It was equipped with a baffle (200 × 598 mm) perpendicular
to the wall surface of the cylinder. In the tests presented here,
the rotation speed was fixed at 21 rpm for 5 min. The total number of
revolutions during a test was 105. The durability was calculated as the
ratio of weight after tumbling over the weight before tumbling, multiplied
by 100. The compressive strength of the briquettes was determined
by a diametrical compression test. The sample was placed between two
parallel horizontal plates of the WAW-300universal testing machine and
compacted at a rate of 0.5 MPa/s until the briquette broke. The compressive
strength was calculated as the value of the maximum load during
deformation divided by the cross-sectional area (MPa). The impact resistance
was tested by adapting the ASTM method [21] of drop shatter for
coal. The briquettes were dropped 1.83 m onto a concrete floor twice,
and the retained weight as a percentage of the initial weight was taken
as the briquette impact resistance.