DEVICE AND METHOD FOR PRODUCING SUPPLEMENTARY CEMENTITIOUS MATERIALS

The present invention relates to device for heat-treating solid material, in particular in granular form, wherein the device comprises a kiln and an external heat source, wherein said device comprises at least two steps arranged above each other, wherein each step comprises a gas permeable sloped sliding surface on which a bed of said solid material slides down within said device due to gravity and wherein said sloped sliding surfaces of said steps directly consecutive to each other slope in opposite directions, wherein the kiln comprises at least one, preferably at least two, of said steps and the kiln is configured such that a hot gas generated by the external heat source is led through said solid material inside the kiln to heat said solid material to a desired temperature in order to change the substance properties of said solid material. According to the invention, said device comprises at least one gas temperature adjustment system comprising a gas outlet in a second step of said steps, a temperature adjustment zone and a gas inlet in a first step of said steps, preferably the first step being arranged directly consecutive and above the second step, wherein at least the first step is one of said at least one step inside the kiln and wherein said gas temperature adjustment system is adapted such that hot gas is extracted from said second step through the gas outlet, directed into the temperature adjustment zone where a hot gas temperature is adjusted to an adjusted temperature by the external heat source and reintroduced into said first step at said adjusted temperature. The invention further relates to a method for producing supplementary cementitious materials.