A process for reforming the fly ash by heating a raw fly ash powder that contains the unburned carbon and thereby decreasing the content of the unburned carbon, characterized in that (a) as means for heating the raw fly ash powder, use is made of a heating unit that heats the raw fly ash powder by passing it through a heated medium-fluidized bed, (b) a high-temperature gas stream is passed through the heating unit to form the heated medium-fluidized bed and to fluidize and convey the raw fly ash powder that is thrown into the medium-fluidized bed, (c) the flow rate of the high-temperature gas stream is so set that the raw fly ash powder thrown into the heating unit is all heated in the medium-fluidized bed and is taken out from a take-out port provided at an upper part of the heating unit but that the particulate medium forming the medium-fluidized bed is not discharged from the take-out port, (d) the fly ash powder after heated and discharged from the take-out port of the heating unit is introduced into an air classifier where it is separated into a fine powder and a coarse powder, (e) the fine powder separated by the air classifier is recovered as the reformed fly ash, and (f) the coarse powder separated by the air classifier is measured for its content of the unburned carbon and when the measured value is larger than a predetermined threshold value, the coarse powder is introduced again into the heating unit so as to be heated again and when the measured value is smaller than the threshold value, the powder is recovered as the reformed fly ash.

A process for activating clays having high residual moisture by: feeding wet clay into a device for drying, comminuting the previously dried clay in a device for comminuting, thermally activating the comminuted clay in an entrained flow reactor or in a fluidized bed reactor in which the comminuted clay is in suspension in a hot gas, removing the gas from the entrained flow reactor or the fluidized bed reactor in a device for removing, and cooling the thermally activated clay in a device for cooling with a cooling gas, and to a corresponding plant. The cooling gas, heated after cooling the thermally activated clay, is combined with the gas from the reactor, and the combined gases are introduced into the drying device. The drying air is filtered after drying, and clay removed by filtration is unified with the dried clay.

A process for activating clays having high residual moisture by: feeding wet clay into a device for drying, comminuting the previously dried clay in a device for comminuting, thermally activating the comminuted clay in an entrained flow reactor or in a fluidized bed reactor in which the comminuted clay is in suspension in a hot gas, removing the gas from the entrained flow reactor or the fluidized bed reactor in a device for removing, and cooling the thermally activated clay in a device for cooling with a cooling gas, and to a corresponding plant. The cooling gas, heated after cooling the thermally activated clay, is combined with the gas from the reactor, and the combined gases are introduced into the drying device. The drying air is filtered after drying, and clay removed by filtration is unified with the dried clay.

A method for manufacturing cement clinker includes the steps: preheating a raw meal in a first preheater using kiln off-gas to provide a partially preheated raw meal, preheating the partially preheated raw meal in a second preheater to provide preheated raw meal, precalcination of the pre-heated raw meal in a calciner being a circulating fluidized bed reactor by burning fuel with oxygen and recirculated calciner exhaust gas instead of air to provide a precalcined raw meal wherein at least 2 mbar overpressure are adjusted in the calciner, transferring the precalcined raw meal to a rotary kiln for sintering to provide the cement clinker, cooling the cement clinker, and capturing carbon dioxide from a calciner exhaust gas in a carbon dioxide purification unit.

A method for manufacturing cement clinker includes the steps: preheating a raw meal in a first preheater using kiln off-gas to provide a partially preheated raw meal, preheating the partially preheated raw meal in a second preheater to provide preheated raw meal, precalcination of the pre-heated raw meal in a calciner being a circulating fluidized bed reactor by burning fuel with oxygen and recirculated calciner exhaust gas instead of air to provide a precalcined raw meal wherein at least 2 mbar overpressure are adjusted in the calciner, transferring the precalcined raw meal to a rotary kiln for sintering to provide the cement clinker, cooling the cement clinker, and capturing carbon dioxide from a calciner exhaust gas in a carbon dioxide purification unit.