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Show from one or two weeks to one or more months. The limit was about 4 months. In all that time only one drum was found to be unusable; it settled within a week or two and could not be redispersed by any means we could use. With all the other samples some lesser or greater degree of settling was observed after several weeks but there was no problem of redispersion using either a propellor-mixer or an air lance, or both, and subsequent pumping was always satisfactory. It is a question, of course, whether this procedure alters the slurry properties. We have been informed by some investigators that it is their practice to discard samples used in test pumpings because of changes in the slurry properties. This approach, of course, would present problems with the two-stage, overpumping system used in our experiments. 4. RESULTS 4.1 General Performance Characteristics. As might be expected from other reports (1 - 10), stabilization of the CWS flames depended rather critically on the degree of atomization, the nature of the atomizing fluid (air or gas/air), the degree of air swirl, and the matching between the air and atomizing pattern. A detailed decomposition of the effects of the various factors is not possible at this time because usually several factors were changed at the same time in a search for acceptable operating conditions, particularly in the initial experiments. With a proper balance of the different factors, however, very bright (yellow) stable flames were obtained that were then relatively tolerant to upsel conditions and apparently at high combustion efficiency. With a poor balance ol the different factors, the flames were less tolerant to upset conditions, were generally redder, and the striations of paths of groups of particles were very much more evident. Good combustion conditions required high air swirl with a roughly matching atomizing pattern. When gas atomization was used, no advantage was |