I had a tour of a pigment factory (SunChemical)....they use ice for the reaction somehow...there was a 20ft tall cylinder about 15ft dia. with scrapers on the outside to knock the ice off. The cylinder was about 1/2 thick but hollow. It had ammonia circulated inside and water sprayed on the outside. It turned very slowly but made crapload of ice.
Supported top and bottom by mounted bearings that were quite small (I thought). Seemed like an amazingly simple system.
Not sure of the science behind ammonia for heat transfer but must be cost effective, they had been using it for years.
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