The Thermal Screening Unit (TSU) from HEL has been developed for the first step in reaction hazards assessment.
It is designed to be a more comprehensive solution than traditional screening by DSC/DTA .
For effective reaction hazards screening, two critical pieces of data need to be determined: the 'onset' temperature for the reaction and the pressure generated by the runaway.
The TSU offers the user the simplicity of operation associated with DSC and DTA, while providing pressure data.
In addition, by utilising sample cells of up to 8ml, representative samples can be tested.
The standard procedure involves heating of the sample at a user-defined rate (typically 0.5 to 5C/min) while both the temperature and pressure are recorded.
Deviation from linearity (for example, a sharp rise) indicates the 'onset' of an exotherm.
The subsequent rise shows the severity of hazard directly without the need for any calculation.
Additional operating modes include isothermal, dual scan and soak-and-scan.
Operating Range: temperature from ambient to 400C, resolution of 0.01C.
Pressure transducers are available in several ranges, typically up to 200 bar.
Spherical test cells of approximately 8ml in stainless steel, hastelloy, and other alloys are available, as well as in glass.
This large volume allows for truly representative samples and the study of liquids, solids and reaction mixtures.
WinISO has been developed in-house to provide a logical and simple interface for development of multiple step processes.
It runs under Windows software.
During operation all conditions are displayed numerically and on a trend graph.
All steps can be modified during operation.
Modifications are fully documented in the output file.
Applications include: thermal stability of feeds, intermediates and products; testing liquids and solids; evaluating long-term exposure at elevated temperatures (isothermal or 'soak' test); and evaluation of safe operating and storage temperatures, as well as the consequences of a runaway reaction.
Key data produced includes: onset temperature of exotherm; rate of temperature rise; rate of pressure rise; maximum temperature and pressure; and time from exotherm initiation to maximum rate.
Several TSUs can be used in parallel, running from the same computer.
This is a cost-effective method of screening large numbers of samples.
The compact design of the instrument makes it easy to fit several units into a standard fume cupboard.
