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Sample preparation for the analysis of secondary fuels - part two

World Cement,

Important analyses

Other important analyses are the determination of chlorine content according to DIN 51727 and the determination of Total Organic Carbon (TOC). Due to the inhomogeneous nature of the sample, proper sample preparation is essential to get correct values for the mentioned analysis. This preparation involves the size reduction of the sample with a laboratory cutting mill to between 0.5 mm to 1 mm.

Fritsch developed the cutting mill combination PULVERISETTE 25/19 with cyclone separator specially for this application. The entire sample, with a particle size of up to 30 mm, is pre-crushed by the PULVERISETTE 25, then falls automatically through a funnel into a sample divider with a variable division ratio up to 1:13. This allows the throughput of large sample quantities of up to several litres.

The smaller sample fraction is automatically ground with the PULVERISETTE 19 down to a final fineness of 0.5 mm to 1 mm. The air vortex within the Fritsch cyclone separator draws the ground sample into the attached sample bottle.

To avoid cross-contamination between samples, fast and easy cleaning of the mill is important. The Fritsch cutting mill allows the user to remove all grinding parts without tools, resulting in a completely open, empty grinding chamber for simple cleaning and protection against cross-contamination.

The sample preparation of tar paper is also possible, but due to the nature of the sample it is recommended that dry ice is added while milling. The dry ice cools the grinding chamber and avoids temperature effects such as the sticking of the sample to the rotor or the sieve.


To minimise the cost of the production of cement, and to reduce the use of fossil energy, an increasing number of cement plants are utilising secondary fuels.

Several chemical analyses are required for quality control, such as calorific value, TOC or determination of chlorine. For proper results, a reliable sample preparation of these inhomogeneous samples is essential. Fritsch offers a tool to help with sample preparation of secondary fuels.

This is part two of a two-part article written for World Cement’s March issue and abridged for the website. Subscribers can read the full issue by signing in, and can also catch up on-the-go via our new app for Apple and Android. Non-subscribers can access a preview of the December 2015 issue here.

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