Analysis of the volatility of solids is important in various industrial sectors. Determining the flash point measurement is necessary for the storage, transport, and disposal of materials, as well as for product quality specifications.
Flash point measurement for co-processing in cement plants.
The applications were developed in the cement industry, which uses the practice of co-processing solids and liquids in kilns and waste burners. The samples tested show a wide variation, ranging from solvents, solids, and fuels for burners to waste. In most cases, the expected flash point of these samples is unknown.
Fuel for burners
Cement manufacturers often use a special type of wood pulp mixed with refinery waste to heat their burners. The flash point can help determine fuel quality if the sample is properly homogenized before testing. If differences are observed in flash point tests, this is a good indication that the burner fuel quality is not homogeneous.
Solid samples
In the cement industry, it is also necessary to test various solid samples. The example below shows solid and powdery oil foam.
In this example, the expected flash point was unknown, so a rapid screening procedure was used:
- Sample volume: 2 mL
- Heating rate: 12 °C/min.
- Air: 0,6 s
- Ignition stage: every 3 °C, starting from 120 °C
- Expected flash point: 189 °C
The expected flash point of 189 °C was used to perform a standard D7094 measurement, starting at 170 °C, resulting in a flash point of 187 °C.
Solvents containing water
For solvents and oils containing a large amount of water, it is highly recommended to separate the water before performing the measurement, as the water boils during the test and can alter the flash point. Some methods for handling the water are centrifugation, drying, distillation, water separation with silica gel, addition of calcium sulfate or calcium carbonate before the test, or freezing the sample.
Given the differences between the samples to be tested, the “right” method for separation may vary from sample to sample. Distillation, for example, can evaporate highly volatile substances, in addition to water. Separating water with silica gel only works for some oils. And if there is diesel in the sample, freezing can also transform some components of the diesel into waxes.
Alternatively, it is possible to measure the flash point only up to 100 °C to avoid boiling the sample. The ADR limits for Class 3 liquids are normally below 100 °C. The limits are typically 23 °C, 60 °C, or above 60 °C and below 100 °C (e.g., diesel).
For samples known to contain water, two tests should be performed below 100 °C.
Step 1: Test from the top
Samples with a density lower than that of water will be separated at the top of the sample container.
- Let the substance being tested stand until, for example, the oil separates, or freeze it.
- Take a sample from the top of the sample container.
- Perform a flash point test. Set the Tf (final test temperature) of the analyzer to stop the procedure at 100 °C.
Step 2: Test from the mixture
Samples with a density greater than that of water will separate at the bottom of the sample container.
- Shake the sample container vigorously until the sample is homogeneous.
- Take a sample from the center of the container.
- Perform a flash point test. Set the Tf (final test temperature) of the analyzer to end the procedure at 100 °C.
From these two tests, the lowest flash point should be reported. If no flash point is reached, a flash point >100 °C may be reported.
Samples with a very low flash point
Since the flash point is not always known, it is best to place the sample and the measuring cup in the freezer. The "manual" measurement mode allows you to cool the oven to its initial temperature before removing the sample from the refrigerator and placing it in the instrument.
Rapid screening procedure with the MINIFLASH FP Vision
- Use 1 mL samples for solvents and 2 mL samples for viscous solids and liquids.
- Select the following methods:
- Solvents: select the ASTM D6450 screening method
- Viscous solids/liquids: select ASTM D7094 screening method
Note 1: A slower heating rate (5 °C/min) may be necessary for solid and viscous samples in order to allow sufficient time for sample degassing.
Note 2: Use a magnetic stirrer for non-homogeneous samples.
- Select the expected flash point. If the expected flash point is not known, program a very low initial temperature for liquids or a temperature > 100 °C for solid samples.
- Proper homogenization of the sample is very important: ALWAYS shake solvents and fuels vigorously before collecting a sample.
- The sample taken must be cooled at least 18 °C below the expected flash point.
- Place the cooled sample in the FP Vision sample cup and start the measurement.
- Clean the sample cup and electrodes after measurement.
Proper cleaning of the sample cup and electrode is recommended after each test. Sticky residues can best be removed by running a high-temperature cleaning program.
Technical criteria for determining the flash point in industrial waste.
By following the recommended procedure, it will be possible to obtain a quick and reliable method for measuring the flash point of both liquid and solid samples.
Do you have any challenging samples? Contact us Partner with Alutal, and we will help with your development!
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