wood chips (dry)

To show several results with different cutting mills (and various benefits for each model) , we split the limited amount of sample into 1/3. With the desired amount of 500 g of sample, we are guessing the particles can become slightly warmer.

Because particles can pass the openings of the sieve insert longitudinal, few particles with a length up to ~ 6 mm can be found. Also sieve inserts with smaller openings can be used to comminute the sample.

The complete sample amount of 150 g got ground within 30 seconds. Temperature of ground particles had been checked directly. With a room temperature of ~ 22,5 °C, the particles temperature rose to 31,4 °C after grinding (a warming of ~ + 8,9 °C).

The handing of the oldest cutting mill in our portfolio uses to be a bit more complicated. Especially the rotor is not removable without using an Allen key. For this, cleaning will take higher effort compared to Power Cutting Mill PULVERISETTE 25 or Universal Cutting Mill PULVERISETTE 19.

It is possible that a lower feed rate of sample will be beneficial for the temperature of ground goods.

The Power Cutting Mill PULVERISETTE 25 with a rotor speed of only ~ 330 rpm instead of ~ 2800 rpm might induce less heat to the sample (see result 2).

The Power Cutting Mill PULVERISETTE 25 use to have a much lower rotor speed, with 300-360 rpm, less heat will be induced to the sample during the grinding.

With a Power Cutting Mill PULVERISETTE 25, sieve cassettes with < 2 mm openings will become less efficient with its lower speed, the output uses to be much lower compared to e.g. Universal Cutting Mill PULVERISETTE 19 with 2800 rpm.

The complete sample amount of 150 g got ground within 30 seconds too. Temperature of ground particles had been checked directly. With a room temperature of ~ 22,5 °C, the particles temperature rose to 29,6 °C after grinding (a warming of ~ + 7,1 °C).

With the lower rotor speed, more loose particles will be found on top of the sieve cassette after grinding. Cleaning can be performed rapidly by vacuuming with a soft brush.

It is also possible to use the optional sample exhauster system with cyclone separator to chill sample during grinding (see result 3).

With the optional cyclone separator, an air flow of ~ 2800 liter / min, sample will be cooled additionally. Also fine ground particles will be removed directly out of the grinding chamber when they are able to pass the openings of the used sieve cassette.

With this accessory, even a high speed spinning rotor of a Universal Cutting Mill PULVERISETTE 19 (~ 2800 rpm like PULVERISETTE 15 too) will not heat up sample that much during the grinding process.

It is also possible to combine the cyclone separator with a Power Cutting Mill PULVERISETTE 25.

The complete sample got ground within 20 seconds. The grinding chamber uses to be almost free of residues. Rotor, lid and sieve cassette can be removed quickly without using tools. Cleaning can be performed rapidly by vacuuming with a soft brush. Also sieve cassettes with smaller openings can be used to comminute the sample.

We checked the temperature of ground particles directly after grinding and found ~ 25,1 °C with a room temperature of 22,9 °C in this laboratory. For this, the sample got heated up by only ~ 2,2 °C.

For all three trials we performed, also a previous chilling of sample will be beneficial to keep sample chilled. If tolerable for your sample, also dry ice can be added during the grinding process for additional chilling.

As requested, one sample has been previously chilled inside a fridge before grinding with Cutting Mill PULVERISETTE 15.

We placed the sample overnight into a fridge with – 18°C. Next day, sample has been taken out and brought into our laboratory. With a standard contact thermometer, a sample temperature of – 9,4 °C has been detected inside the heap of wood chips.

The ~ 250 grams of wood chips got ground within 40 seconds. Afterwards, temperature of resulting particles has been checked again. Our thermometer has shown a maximum temperature of 18,7 °C which was -1,9 °C below actual room temperature.

As expected, the openings of the sieve insert remain free, a grinding of higher amounts is still possible.