subject: Vermiculite machine used in processing plant [print this page] The term vermiculite applies to a group of minerals characterized by their ability to expand into long, worm-like strands when heated. This expansion process is called exfoliation. The name vermiculite is derived from a combination of the Latin word vermiculare meaning "to breed worms," and the English suffix-ite, meaning mineral or rock. In its expanded form, vermiculite has a very low density and thermal conductivity, which makes it attractive for use as a soil amendment, lightweight construction aggregate, and thermal insulation filler. Expanded vermiculite also has a very large chemically active surface area, which makes it useful as an absorbent in some chemical processes. When vermiculite is ground into a fine powder, it is used as a filler in inks, paints, plastics, and other materials.
The manufacturing process used to produce commercial expanded vermiculite consists of two separate operations. The mining and concentrating operations that produce raw vermiculite flakes are conducted at one location. The exfoliation and classifying operations that produce various sizes of lightweight, expanded vermiculite granules for use in other products are conducted in another location. Sometimes these two locations can be half a world apart.
The rocks are fed through a series of crushers and screens to reduce their size. The vermiculite is separated from the surrounding rocks and dirt using various wet or dry techniques depending on the particular mining operation and local environmental regulations. These techniques may include froth flotation, gravity separations, winnowing, or electrostatic separation. In each of these techniques, either the vermiculite itself or the other materials are trapped and separated from each other until the resulting vermiculite flakes are about 90% pure by weight.
The vermiculite flakes extracted from various sections of the mine may be blended together before further processing to ensure uniformity of the product.
The separated vermiculite flakes are sorted by size. This may be done with a series of screens or it may be done in a long enclosed wind tunnel . In the wind tunnel, the flakes are fed into the upstream end of the tunnel and are carried along the length of the tunnel by the flow of air. The larger flakes, being heavier, fall out of the air stream first and are caught in a hopper at the bottom of the tunnel. This separation by weight continues down the length of the tunnel until all the flakes are caught in hoppers. By controlling the length of each hopper opening and the velocity of the air, the flakes can be sorted into various sizes, or grades, ranging from about 0.63 in (16 mm) down to about 0.02 in (0.8 mm) in diameter. If the particular vermiculite being mined tends to form a high percentage of large flakes, the flakes may be slightly crushed to delaminate them and reduce their size. This process is called debooking and allows the flakes to be quickly heated during the exfoliation process.
The graded vermiculite flakes are dumped into large plastic bags or other containers for shipping to various exfoliation
There are Exfoliating, Classifying process after concentrating.
