Method for expansion of sand grain-shaped raw material

A method for expansion of a sand grain-shaped raw material wherein the sand grain-shaped raw material is fed into one end of a heated vertical shaft, the heated vertical shaft comprising a plurality of heating elements for forming a temperature profile within the heated vertical shaft;

• wherein a shaft flow prevails in the heated vertical shaft;
• wherein as a result of a heat transfer in the heated vertical shaft the sand grain-shaped raw material expands to an expanded granulate;
• wherein the expanded granulate produced within the heated vertical shaft is received by a pneumatic conveying line on a second end of the heated vertical shaft;
• wherein a conveying flow prevails in the pneumatic conveying line for further transport of the expanded granulate;
• wherein the expanded granulate is transported via the conveying flow to a separating device which separates the expanded granulate from the conveying flow;
• wherein the separated expanded granulate is concentrated to form a granulate flow and said granulate flow is directed into a measuring container;
• wherein the measuring container comprises a base surface having openings through which openings at least one part of the granulate flow being directed into the measuring container is draining continuously;
• wherein the measuring container is connected to a weighing device;
• wherein a weight of the expanded granulate flowing through the measuring container is continuously measured by the weighing device in order to determine the bulk density of the expanded granulate flowing through the measuring container and to detect deviations from at least one desired bulk density of the expanded granulate;
• and wherein upon detection of a deviation of the determined bulk density from the at least one desired bulk density the temperature profile in the heated vertical shaft is adapted automatically or manually and/or the feeding of the sand grain-shaped raw material into the heated vertical shaft is adapted automatically or manually.