Why it is Important to Determine the Flashpoint of Cement for Material Storage and Transportation

Within the cement sector, flashpoint determination is necessary for transportation, material storage, disposal, as well as for product quality specifications. The samples tested reveal a significant variation, ranging from burner fuel to waste, from solvents to solids. In most cases, the expected flashpoint of these samples is not identified.

Burner Fuel

Cement manufacturers often use a particular kind of wood grinding blended with refinery residue to heat their burners. The flashpoint can help to establish the fuel’s quality, if the sample is correctly homogenized before the test. If differences in flashpoint tests are noticed, this is a good sign that the burner fuel’s quality is not homogenous.          

Burner Fuel used by Titan cement, Greece

Solids

In the cement sector, several solid samples have to be tested as well. The example below illustrates solid dusty oil foam, tested at BAUMIT cement in Austria.

In this instance, the anticipated flashpoint was not known, so a fast screening process was used:

• Sample size: 2 mL
• Air: 0.6 second
• Heat rate: 12 °C/minute
• Ignition step: every 3 °C, starting from 120 °C
• Expected flashpoint: 189 °C

The expected flashpoint of 189 °C was used to conduct a typical D7094 measurement, beginning at 170 °C, resulting in a flashpoint of 187 °C.

Solvents Containing Water

For oil and solvents having a large quantity of water, it is suggested that the water is separated prior to performing a measurement. Water boiling during the test can alter the flashpoint. A few techniques to deal with water are centrifugation, distillation, drying, incorporating calcium sulfate or calcium carbonate before the test, separation of water using silica-gel, or freezing of the sample.

Oil separation by sample freezing.

Given the variances in samples to be tested, the “right” technique for separation can vary from sample to sample. Distillation, for instance, can evaporate extremely volatile substances besides water. Water separation using silica-gel works only for certain oils. If Summer-Diesel is in the sample, freezing can convert some diesel components into waxes.

As a substitute, it is feasible to measure the flashpoint merely up to 100 °C to stop boiling of the sample. ADR limits for class 3 liquids are normally below 100 °C. Limits are usually 23 °C, 60 °C, or above 60 °C and below 100 °C (for example, diesel fuels).

For samples known to contain water, two tests should be performed below 100 °C.

Step 1. Test from the Top

Samples having a lower density than water tend to separate to the top of the sample container.

• Allow the test substance to rest, until for example, the oil is separated, or alternatively freeze it
• Take a sample from the top of the sample container
• Conduct a flashpoint test. Terminate at 100 °C

Step 2. Test from the Mixture

Samples having a higher density than water tend to separate to the bottom of the sample container.

• Shake the sample container vigorously, until the sample is homogenized
• Take a sample from the middle of the container
• Conduct a flashpoint test. Terminate at 100 °C

From these two tests, the lower flashpoint will be conveyed. If a flashpoint is not reached, a flashpoint >100 °C can be stated.

Samples with a Very Low Flashpoint

Since the flashpoint is not frequently known, it is the best to place the sample and the cup into a deep-freeze. The “manual” measuring mode enables the cooling of the oven to the start temperature, before the sample is removed from the refrigerator and placed into the instrument.

MINIFLASH TOUCH Rapid Screening Procedure for the Cement Industry

1. A 1 mL sample size can be used for solvents and a 2 mL sample size for viscous liquids and solids
2. Choose the following “custom” settings:

• Heat rate: 12 °C/minute (NOTE: a slower heat rate (5 °C/minute) may be necessary for viscous and solid samples, to allow sufficient time for sample outgassing).
• Ignition step: every 3 °C
• Air: 0.6 second
• Place the stirrer in the cup, as it may be needed for certain type of samples

3. Choose the expected flashpoint. If the expected flashpoint is not identified, begin with a very low start temperature for liquid samples or a temperature of >100 °C for solid samples.
4. Correct homogenization of the sample is very crucial: Shake solvents and fuels briskly each time a sample is taken.
5. The drawn sample has to be cooled to at least 18 °C below the expected flashpoint.
6. The cooled sample should be transferred to the MINIFLASH sample cup and then the measurement can be started.
7. The sample cup and the electrodes have to be cleaned after the measurement.

NOTE:

Correct cleaning of the sample cup and the electrode is advised following each test. Sticky residuals can ideally be removed by running a high-temperature cleaning program.

Conclusion

Following the above-stated procedure will help users achieve a fast and reliable technique for measuring the flashpoint of solids and liquids.

This information has been sourced, reviewed and adapted from materials provided by Grabner Instruments.

For more information on this source, please visit Grabner Instruments.