A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

The invention is concerned with a method for producing a cement comprising milled cement clinker and a supplementary cementitious material, wherein the method comprises the steps of: producing the milled cement clinker by a clinkerization process, comprising the steps of calcining and subsequently milling a limestone-based raw material; producing the supplementary cementitious material by calcining a raw material of the supplementary cementitious material at a temperature of less than 980° C. and subsequently milling the calcined raw material of the supplementary cementitious material, wherein the raw material of the supplementary cementitious material has an average particle size of 1 to 300 mm; and blending the milled cement clinker and the supplementary cementitious material; wherein the method is a continuous process comprising the step of calcining the raw material of the supplementary cementitious material in a kiln with a separate heating unit and/or combustion unit. Further, the invention is concerned with a method for producing a cement comprising milled cement clinker and a supplementary cementitious material, wherein the method comprises the steps of: producing the milled cement clinker by a clinkerization process, comprising the steps of calcining and subsequently milling a limestone-based raw material; producing the supplementary cementitious material by calcining a raw material of the supplementary cementitious material at a temperature of less than 980° C. and subsequently milling the calcined raw material of the supplementary cementitious material, wherein the raw material of the supplementary cementitious material has an average particle size of 1 to 300 mm, wherein at least 5 wt % of the particles have a particle size of above 4.75 mm; and blending the milled cement clinker and the supplementary cementitious material. The invention is also concerns a cement comprising milled cement clinker and a supplementary cementitious material, wherein the supplementary cementitious material comprises an amorphous constituent of more than 30 wt % as measured by XRD, wherein the supplementary cementitious material comprises less than 70 wt % of inert components selected from the group comprising mullite, spinel, feldspar, diopside, mica, or combinations thereof, and wherein the color of the cement in the range of 130-160, 130-160, 120-160, wherein the measurement of the cement color is conducted by a RGB2 colorimeter, wherein the colors are referenced to a RGB scale of 0 to 255.

The present invention relates to a device for heat-treating solid material, in particular in granular form, wherein the device comprises a kiln and an external heat generator, wherein said kiln comprises at least one sloped sliding surface on which a bed of said solid material slides down within said kiln due to gravity while a hot gas generated by the external heat generator is led through said solid material 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 external heat generator for generating said hot gas is external to said kiln, wherein said kiln further comprises at least one kiln gas inlet through which said hot gas enters said kiln, such that the necessary temperature of said hot gas can be controlled precisely in that said hot gas is generated in said external heat generator, ensuring that the solid material does not experience temperatures above an allowed maximum temperature, and further such that the solid material is not exposed to radiation from a burner.

The present invention relates to a device for heat-treating solid material, in particular in granular form, wherein the device comprises a kiln and an external heat generator, wherein said kiln comprises at least one sloped sliding surface on which a bed of said solid material slides down within said kiln due to gravity while a hot gas generated by the external heat generator is led through said solid material 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 external heat generator for generating said hot gas is external to said kiln, wherein said kiln further comprises at least one kiln gas inlet through which said hot gas enters said kiln, such that the necessary temperature of said hot gas can be controlled precisely in that said hot gas is generated in said external heat generator, ensuring that the solid material does not experience temperatures above an allowed maximum temperature, and further such that the solid material is not exposed to radiation from a burner.

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.

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.

A furnace having a convection section with convection tubes in a convection compartment is disclosed. The convection tubes receive and preheat hydrocarbon feed primarily by convection of heat from hot flue gas that flows into in the convection section. The convection section additionally includes a perforated distributor plate that prevents flow channeling of the hot flue gas as it flows into the convection section. The furnace also includes a radiant section having radiant tubes in a radiant compartment. The radiant tubes are in fluid communication with the convection tubes so that preheated hydrocarbon feed flows from the convection section to the radiant section. The radiant section burns fuel and heats the preheated hydrocarbon feed primarily by radiation and from the hot flue gas, which flows from the radiant section into the convection section.

A furnace having a convection section with convection tubes in a convection compartment is disclosed. The convection tubes receive and preheat hydrocarbon feed primarily by convection of heat from hot flue gas that flows into in the convection section. The convection section additionally includes a perforated distributor plate that prevents flow channeling of the hot flue gas as it flows into the convection section. The furnace also includes a radiant section having radiant tubes in a radiant compartment. The radiant tubes are in fluid communication with the convection tubes so that preheated hydrocarbon feed flows from the convection section to the radiant section. The radiant section burns fuel and heats the preheated hydrocarbon feed primarily by radiation and from the hot flue gas, which flows from the radiant section into the convection section.

The present disclosure relates to a process for the decarbonation of limestone, dolomite or other carbonated materials. The process may include heating particles of carbonated materials in a reactor of a first circuit to obtain decarbonated particles. Particles of carbonated materials are conveyed by a first entraining gas in the first circuit for preheating. The gas includes the carbon dioxide, the gas composition being substantially free of nitrogen. The carbonated particles are separated from a first entraining gas flow. The decarbonated particles are transferred to a cooling section of a second circuit having a second entraining gas in which the conveyed decarbonated particles release a portion of their thermal energy. The decarbonated particles are separated from a second entraining gas flow. The second entraining gas is substantially free of carbon dioxide.