Method for expanding open-bore perlite by gas indirect heating

The invention discloses a method for expanding open-bore perlite by gas indirect heating, which heats the open-bore perlite in a gas indirect heating mode. The method comprises the following step: a.a gas indirect heating expansion furnace comprising an expansion cylinder (3) with a small upper cylinder and a big lower cylinder is used; b. the open-bore perlite expands in a high temperature area(5) of the small expansion cylinder in the furnace chamber, so that the perlite micropowder loses crystal water, quickly expands and increases the volume; c. the expanded perlite quickly enters in a low temperature area (8) in the big cylinder to gradually drop temperature without sticking to the wall; d. a draft fan absorbs high temperature waste gas in the furnace chamber through a high temperature flue (6), so that the temperature of the low temperature area in the big cylinder drops, and the form of the perlite is defined; and the discharge end uses a graded closed-loop separating system to ensure no pollution on the environment. The method solves the problem of difficulty in the expansion of the perlite micropowder with 100-250 meshes, has the advantages of short expansion range of balls, quick product discharge, high efficiency, no sticking to the furnace, and low equipment investment, and is suitable for the expansion and the separation of large granules and micro granules.