Device for expansion of sand grain-shaped raw material

A system for producing expanded granulate comprising:

• a vertical heated shaft comprising a plurality of heating elements, wherein the plurality of heating elements are designed to expand sand-grain-shaped raw material being fed into a first end of the vertical heated shaft to create expanded granulate;
• a conveying line being connected to a second end of the vertical heated shaft configured for receiving the expanded granulate and conveying it via a conveying flow;
• and
• a device for measuring a bulk density of expanded granulate comprising:
• a separating device connected to a pneumatic conveying line to receive the conveying flow containing the expanded granulate from the conveying line in order to separate the expanded granulate from the conveying flow into a granulate flow;
• at least one measuring container disposed underneath the separating device to receive at least a part of the granulate flow from the separating device, wherein the at least one measuring container has a base surface comprising openings configured to allow at least a part of the granulate flow that is received to drain continuously from the at least one measuring container;
• and
• a weighing device connected to the at least one measuring container configured to continuously measure weight of the expanded granulate flowing through the at least one measuring container in order to determine the bulk density of expanded granulate flowing through the at least one measuring container and to detect deviations from a desired bulk density of expanded granulate.