Steel making Slag Converter and Iron Sinter

We started our first trial with the converter slag sample. Because elemental silicon was present, we don’t recommend using cyclohexane or 2-propanol. With elemental silicon and those solvents, we often observed a formation of static pressure.

So far, we found good grinding results and no significant formation of pressure with silicon oil, octodecene or PEG.

We checked the present start size of the converter slag by static light scattering. A small amount was dispersed in 0,1 % Na4P2O7 water with our ultrasonic bath LABORETTE 17 for a minute. Afterwards, sample was transferred into our Laser Particle Sizer ANALYSETTE 22 NeXT Nano (d90 < 250 µm). We used one of the prepared sample batches of 5 grams and added the sample into a bowl 45ml made of hardmetal tungsten carbide which was equipped with 200 g of 1 mm Ø WC grinding balls. Further 9 grams of PEG 400 were added to moisten all present particles.

The mill was programmed to grind in cycles of 1 minute at 1100 rpm, followed by a programmed pausing time of 3 minutes to avoid over pressure. After a total grinding time of 5 minutes, we checked the bowl. No static pressure was formed during these first minutes of grinding. Longer grinding times could be applied. We also checked the present particle size distribution and found a d90 < 2 µm (Fraunhofer theory). With this level of fineness, proper Mie parameters are required for a more precise particle size distribution.

We proceeded grinding until a total grinding time of 15 minutes was applied. Afterwards, we checked for Mie parameters which showed a low RMS error. With 0,16, the determined particle size distribution with d50 < 240 nm and d90 < 480 nm, the result was very accurate. The required 80 % < 1 µm results was achieved and the sample was packed.

We flushed the bowl with fresh PEG several times to regain a maximum of sample amount. For an intensive cleaning afterwards, we ground a typical amount of fine sand and water for 2 minutes. Afterwards, the complete equipment was flushed with fresh water and dried off to prevent corrosion.

The Iron-sinter sample was ground similar to result 01. We checked the particle size distribution of the original sample material by static light scattering and determined a d90 < 75 µm with a maximum about 200 µm.

The 4,9 grams were placed into the 45 ml bowl which was equipped with 1 mm Ø WC grinding balls. We added 12 grams of PEG 400 and started our grinding trial. After one minute, no static pressure was present and we proceeded grinding. If elemental silicon is present and 2-propanol would be required, we would recommend to release static pressure in short intervals (minute wise), to avoid a leakage of the gasket.

We ground the sample for a total grinding time of 5 minutes and checked present level of fineness afterwards. By static light scattering, we determined a d50 < 1,2 µm and d90 < 2,6 µm. We proceeded grinding and checked the particle size distribution after finally 15 minutes.

Already d90 < 1 µm was reached at this point. The sample was packed best possible (it also would be possible using desired 2-propanol, to flush the equipment). Finally, we cleaned the equipment by comminution of fine sand and water for 2 minutes.