Secondary Fuels

The sample was very lightweight and contains a lot of fine plastic foils. To comminute such types of samples, a moderate feeding speed might be required to provide enough of air that the particles will become blown out into the collecting vessel.

Because such types of samples can contain metal fragments, we picked the rotor with V-cutting edges and fixed knives made of hardmetal tungsten carbide. Surely it would have a much longer durability than our standard rotor.

We used the about the half of provided sample amount for this first test and checked with a standard magnet (folded into a sheet of paper) if metal particles are present. Only small fragments < 1 mm were found on the bottom of the sample bag (see second photo).

With a 4 mm square perforated sieve cassette and a speed setting of 2000 rpm, we fed the sample into the grinding chamber. Feeding was finished after ~ 10 seconds. The major grinding sound vanished after 20 seconds. The mill was stopped after finally 40 seconds of total grinding time.

Only a few loose particles remained on the first fixed knife of the standard funnel or electrostatic charged on rotor and sieve cassette. Cleaning was performed rapidly by vacuuming with a soft brush. There was no significant smearing of sample on the rotor, or clogging of the sample on the used sieve cassette. Surely higher amounts of sample could be ground this way, too.

When higher amounts should be ground, the optional high-performance cyclone separator with dust exhauster might come into question (see result 2).

If higher amounts should be ground to a max. length of ~ 4 mm, it could be beneficial to use the optional high-performance cyclone separator with dust exhauster and a sieve cassette with 2,0 mm square perforations. The cyclone-exhauster system provides an air flow up to ~ 2800 liters / minute and chills temperature sensitive samples and grinding parts; also ground sample particles will be removed within the moment, they can pass the used sieve cassette perforations.

With our second trial, we used the rest of sample material (~ 29 grams) and fed the sample within ~ 5 seconds into the mill. Feeding was easier because the air flow of the dust exhauster was pulling the sample into the funnel.

The grinding sound started to vanish rapidly and no further grinding sound was recognized after 10 seconds. We switched off the mill after a total grinding time of 20 seconds.

The opened grinding chamber also contained some slightly attached particles on the surface of the 2 mm sieve cassette. Cleaning was performed rapidly by vacuuming with a soft brush. There was no smearing of sample, nor a significant clogging of the sieve cassette.

Surely higher amounts of sample can be ground this way, too.