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RR710 - Assessment of the applicability of Dewar tests for screening hazardous waste treatment

In the waste treatment industry, the exothermic reaction incompatibility of mixtures is often determined by recording the temperature rise after mixing samples in a beaker. Instead, the use of non-pressurised Dewar vessels has been proposed by some parts of the industry as an improvement, because their cooling rates and heat losses are closer to bulk containers. Temperature rises of between 6-10°C in the Dewar vessel over a period of 10 minutes have been suggested by the industry to indicate an exothermic reaction of concern, with gas bubblers being used to indicate any gas generation.

Specialist inspectors in HSE have questioned the validity of these test methods for scale-up to large volumes. The objective of this work is, therefore, to investigate the range of applicability of the proposed technique. It was found, in particular, that the proposed ten-minute timescale could be insufficient to detect a runaway reaction. A number of other limitations to scale-up are discussed.

This report and the work it describes were funded by the Health and Safety Executive (HSE) with support from the Environment Agency. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE or Environment Agency policy.

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Updated 2019-09-03