Device for producing expanded mineral granulated material

An apparatus for producing a mineral granulate, said apparatus comprising:

• a heated processing channel for mineral granulate fed to a conveying flow;
• said processing channel having an inflow opening therein forming a granulate-free laminar flow running along an inner wall of the processing channel;
• wherein the processing channel comprises two channel sections with cross-sections, one of said cross-sections being larger than the other of said cross-sections;
• wherein the channel section with the smaller cross-section projects into the channel section with the larger cross-section so as to form the inflow opening between an inside wall of the channel section with the larger cross-section and a portion of the channel section with the smaller cross-section that is located inside said inside wall;
• and
• wherein the channel section with the smaller cross-section is enclosed by the channel section with the larger cross-section so that the inflow opening extends completely around the portion of the channel section with the smaller cross-section that is inside said inside wall of the channel section with the larger cross-section and provides the granulate-free laminar flow along the inner wall of the processing channel.