Abstract: The invention relates to a method for producing an expanded granulate (29) made of a sand grain-shaped mineral material (1) using a propellant; wherein the material (1) is fed to a substantially upright furnace (2); wherein the material (1) is conveyed along a conveying path (4) through a plurality of vertically separated healing zones (5) in a furnace shaft (3) of the furnace (2), wherein each heating zone (5) can be heated by at least one independently controllable heating element (6); wherein the material (1) is heated to a critical temperature at which the surfaces (7) of the sand grains (1) become plastic and the sand grains (1) are expanded through the propellant.

Abstract: A method for producing an expanded granulate made of a sand grain-shaped mineral material uses a propellant. The material is transported along a transport path through multiple heating zones in a furnace shaft, heated to a critical temperature at which the surfaces of the sand grains plasticize, and the sand grains are expanded based on the propellant. The material is fed from the bottom together with an amount of air; the material is transported from the bottom to the top along the transport path by the air quantity which flows from the bottom to the top in the furnace shaft and the sand grains are expanded in the upper half of the transport path. The material is heated such that the material immediately prior to entering into the furnace shaft is at a material entry temperature lower than the critical temperature and higher than the ambient temperature.

Abstract: The invention relates to a method for producing an expanded granulate (29) made of a sand grain-shaped mineral material (1) using a propellant; wherein the material (1) is fed to a substantially upright furnace (2); wherein the material (1) is conveyed along a conveying path (4) through a plurality of vertically separated healing zones (5) in a furnace shaft (3) of the furnace (2), wherein each heating zone (5) can be heated by at least one independently controllable heating element (6); wherein the material (1) is heated to a critical temperature at which the surfaces (7) of the sand grains (1) become plastic and the sand grains (1) are expanded through the propellant.