| 摘要 |
<p>The invention relates to a method for producing an expanded granulate from sand grain-shaped mineral material (1) with a propellant, wherein the material (1) is fed into a vertically upright furnace (2) from above and said material (1) falls along a drop section (4) through multiple heating zones (5) in a furnace shaft (3) of the furnace (2), wherein each heating zone (5) is heatable using at least one independently controllable heating element (6), and the material (1) is heated to a critical temperature at which the surfaces (7) of the sand grains (15) plasticize and the sand grains (15) are expanded by the propellant. In order to enable setting a closed surface of the expanded granulate in a purposeful fashion, it is provided in accordance with the invention that upon detection of a first reduction in the temperature of the material (1) between two successive positions (9) along the drop section (4) the heating elements (6) are controlled along the remaining drop section (4) depending on the critical temperature.</p> |
