Gaseous preconditioning

CRECEP, WRC and Kiwa have performed experiments with liquid preeonditioning. Kiwa, LHRSP and TZW have performed experiments with gaseous preconditioning. Reference, unpreconditioned, samples have been tested in the five laboratories. 

Gaseous preconditioning appears to be less practicable and also less representative of the service condition than is liquid preconditioning. 

This preconditioning of the catalyst is necessary to separate the chemical reactions from the catalytic ones (7). In the first few minutes, the iron surface transforms to catalytically active pyrrhotite, as shown (7) by the gradual increase in carbon monoxide consumption and corresponding increase in carbon dioxide production. The initial gaseous sulfide by-products react with the iron in the catalyst to form iron sulfides. In a previous publication (8), it was shown that lattice sulfur is a more versatile and useful carbon monoxide-sufurizing agent than molecular sulfur. The hypothesis tested was that metal sulfides with relatively weak metal-to-sulfur bonds are more effective in forming the active intermediate (9) carbonyl sulfide. 

In the conormative research project, preconditioning with liquid and gaseous carbonation of the cement materials was tested. The preconditioning consists of wet contact with several water types (soft and moderate hardness) or dry contact with CO2 imder several conditions (C02-pressure, time). The effect of preconditioning is compared with unpreconditioned cement mortar specimens. 

Gaseous foam emissions were compared in the standard fogging test procedure outlined in SAE J1756 [9]. A standard 7.6 cm thick piece of foam was preconditioned for 48 hours, then tested in the Hart fogging apparatus at 100 °C for 3 hours. Glossmeter readings of the foam were taken after 60 minutes at room temperature. 

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