Powder Bulk Solids - December 2007

In 2001, the company took delivery of the first Insitec on-line laser-diffraction particle sizer, which was installed on parallel lines 3 and 4. When it was clear that this system functioned successfully, a second instrument was installed in 2004 on line 1. Future planned plant improvements include the purchase of another unit for a new line known as TLC 1. A key part of accepting the new technology involved ensuring that the different Insitec systems produced identical data and that the data were consistent with those from the analytical techniques used previously.

quires to perform measurements. The Insitec system does not cause such errors because it measures much larger sample volumes that are statistically representative of the process. Furthermore, the system incorporates a multiple-scattering software correction that makes it less sensitive to variations in sample concentration. Accurate measurements can be obtained when the unit operates at obscurations ranging from 50 to 90%.

D50 Insitec 2 = 0.9985 × Insitec 1 R² = 0.9953

It was important for Toshiba to correlate laser-diffraction analysis with the historical measurement techniques used in the toner industry. When the Insitec laser-diffraction system was compared with the particle counter already in use, most discrepancies were attributed to the counter’s dispersion problems.

Sample preparation of stickier products is a lengthy process because these materials are difficult to disperse using the particle counter’s wet method. As the fineness of toner particles has increased, the particles have become more cohesive and more difficult to disperse. In order to overcome increasingly challenging dispersion problems, Toshiba Japan first invested in an ultrasonic tank in 2000 and then shifted to a tank in 2002 that is twice as powerful. Currently, the company is considering purchasing a tank that is 10 times more powerful than the current one.

In addition to dispersion problems, some
statistical error was attributable to the small
quantities of sample material that the particle
counter’s electrosensing zone technique re-

Figure 3: D50 correlation between the two Insitec systems at the Dieppe plant

Correlations

To establish a good correlation between the
Insitec system and the counter, a correlation
(not dependent on individual products) was

developed over a relatively broad particle size range of 8 to 12 μm. The refractive index and the absorption coefficient were especially important parameters to determine because they can affect the percentage of fines. The Insitec system provides a volume result that has to be

100.00

20.00

Transmission (%)

75.00

50.00

25.00

15.00

10.00

Diameter (μm)

5.00

0.00

02: 15

02:50

03: 25

04:00

04:35

Figure 4: Time history log

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