Abstract: A continuously operable apparatus including a rotatably positioned container having an open upper end and with a stack of annular discs in the container where the discs are of uniform inner and outer diameters for a major portion of the height of the stack but being of progressively smaller inner diameters approaching the upper end of the stack to form a conically shaped inner surface. A helical scraper means is positioned within the stack of discs and has an outer peripheral surface complementary to the inner surfaces of the stacked discs. Brake means are operatively associated with a top member that has the scraper means secured thereto to produce relative rotation of the helical scraper re the stack of discs for scraping solid particles therefrom to deliver them to the upper end of the apparatus.