Rotary scraper and method for discharging foreign matter having high specific gravity in gypsum slurry

:

• A rotary scraper comprising at least three plates of an upper plate;
• a lower plate;
• and an intermediate plate between the upper plate and the lower plate;
• said at least three plates overlapping with each other in a plan view,
• wherein said at least three plates have openings passing through the plates in a vertical direction respectively, and
• a means for rotating the intermediate plate;
• wherein said openings are arranged to switch, by rotation of the intermediate plate, between a state where the opening of the upper plate and the opening of the intermediate plate are overlapped and the opening of the intermediate plate is not overlapped with the opening of the lower plate and
• a state where the opening of the intermediate plate and the opening of the lower plate are overlapped and the opening of the intermediate plate is not overlapped with the opening of the upper plate;
• the rotary scraper further comprising at least two resin films between the upper plate and the intermediate plate and between the intermediate plate and the lower plate;
• wherein the resin films are fixed to one of the plates respectively and are provided with openings respectively passing through the resin films and overlapping the openings of the plates to which the films are fixed to;
• wherein the upper plate and the lower plate are larger in diameter than the intermediate plate;
• an elastic ring surrounding annually the intermediate plate;
• and
• a fastener mechanism compressing the elastic ring and fastening the upper plate and the lower plate with adjusting the gap between the upper plate and the lower plate.