ANALYTICAL AND LABORATORY EQUIPMENT 17
Te main benefit of extending the range of operation is the increase in the number of applications to which DVS can be applied. Two examples are the analysis of water sorption by microporous materials for gas and air drying, which requires low RH studies, and the study of new materials for water sorption- based thermochemical energy storage, which requires high temperatures.
Water sorption by microporous materials such as zeolites occurs at low RH due to its increased interaction with small pores compared to mesopores or macropores. Once the pores of a hydrophilic material are filled, as required for gas drying, the sorption isotherm saturates, i.e. reaches a plateau – see Fig. 1. Te information contained below this, in the Henry’s Law region, is inaccessible without low RH measurement capability. Full in-situ drying of the sample must also be possible to reliably
measure reproducible isotherms or sorption kinetics.
Termochemical energy storage systems typically operate at high temperatures. Current demonstration and pilot plants use silica gels and zeolites as sorbents, and characterisation of their moisture sorption properties under operational conditions is clearly critical, which is a key benefit of DVS. Te alternative is to measure sorption with respect to vacuum but the measurement of water sorption at ambient pressure in a dynamic system more closely resembles the situation in real sorption systems.
Tese examples illustrate the need to expand the operational range of DVS analysers beyond standard (near-ambient) conditions; however, the characterisation of materials for a range of other applications will also benefit from such increased functionality, which is subject to
the practical restrictions outlined above. Further expansion through improved instrument design will lead to yet more applications for the already widely applied DVS technique.
For more information ✔ at
www.scientistlive.com/eurolab
Fig. 2. Example of an IGAsorp DVS analyser from Hiden Isochema.
Darren Broom is with Hiden Isochema.
www.hidenisochema.com
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MOTION | POSITIONING For more information ✔ at
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