The principle of gypsum flash calcining by simultaneous grinding has proved to be the most accepted technology for producing stucco plaster suitable for the manufacture of plasterboard.Here two flash calcining technologies are compared-a roller mill system and a hammer mill system-taking into consideration the raw gypsum available,the total output,maintenance,thermal expansion and energy consumption.Twenty years ago,it was the general opinion of plasterboard producers that stucco had to be produced using an indirect calcining system.The preferred equipment for indirect systems is a kettle and a rotary tubular calciner.Stucco produced in an indirect calcining system has a low proportion of soluble anhydrite III.A greater quantity of stucco can be mixed with water to provide the same consistency and the setting time is longer than a stucco calcined in a flash calcining system.
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