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. It is provided according to the invention that the material (1) is fed together with an amount of air from below, wherein the material (1) is conveyed from bottom to top along the conveying path (4) by means of the amount of air which flows from bottom to top within the furnace shaft (3) and forms an air flow (14), and wherein the expanding of the sand grains (1) occurs in the upper half, preferably in the uppermost third, of the conveying path (4).

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. It is provided according to the invention that the material (1) is fed together with an amount of air from below, wherein the material (1) is conveyed from bottom to top along the conveying path (4) by means of the amount of air which flows from bottom to top within the furnace shaft (3) and forms an air flow (14), and wherein the expanding of the sand grains (1) occurs in the upper half, preferably in the uppermost third, of the conveying path (4).

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.

A method for heat treatment of a grain-shaped feed material using a calcination device to remove carbonate or water of crystallization from the feed material are provided. To continuously check the quality of the heat treatment process, the bulk density of the heat-treated material is measured continuously, wherein upon detection of a deviation of the determined bulk density from the at least one desired bulk density at least one heat treatment parameter of the heat treatment is adapted automatically or manually.

A method for heat treatment of a grain-shaped feed material using a calcination device to remove carbonate or water of crystallization from the feed material are provided. To continuously check the quality of the heat treatment process, the bulk density of the heat-treated material is measured continuously, wherein upon detection of a deviation of the determined bulk density from the at least one desired bulk density at least one heat treatment parameter of the heat treatment is adapted automatically or manually.

An arrangement for producing a bulk material consisting substantially of foamed or blown mineral or oxide particles by thermal treatment of a bulk material of basic particles. The arrangement includes NIR halogen radiators for generating a NIR radiation field of radiation with an active component in a near infrared, NIR, range having a wavelength in a range between 0.8 m and 1.5 m and which has a power density of at least 50 kW/m.sup.2 for thermally treating the basic particles, a conveying device for transporting a layer or stream of the bed of basic particles through the radiation field, and a controller that controls heating of the bed of basic particles such that a maximum temperature in the layer or stream is in a temperature range between 600 and 1500 C.

The invention relates to a method for the expansion of sand grain-shaped raw material (1) in which the raw material (1) drops downwards through a substantially vertical heated shaft (4) provided with means (2) for forming a temperature profile (3), in which a shaft flow (5) prevails wherein the raw material (1) expands as a result of heat transfer in the shaft (4) to form expanded granulate (6) and the granulate formed (6) is passed into a pneumatic conveying line (7) with a conveying flow (8) for further transport. In order to continuously check the quality of the expansion process, the bulk density of the expanded granulate (6) is measured continuously, wherein upon detecting a deviation from at least one defined bulk density, the temperature profile (3) in the shaft (4) is adapted automatically or manually and/or the feeding of raw material (1) into the shaft (4) is reduced automatically or manually.

The invention relates to a method for the expansion of sand grain-shaped raw material (1) in which the raw material (1) drops downwards through a substantially vertical heated shaft (4) provided with means (2) for forming a temperature profile (3), in which a shaft flow (5) prevails wherein the raw material (1) expands as a result of heat transfer in the shaft (4) to form expanded granulate (6) and the granulate formed (6) is passed into a pneumatic conveying line (7) with a conveying flow (8) for further transport. In order to continuously check the quality of the expansion process, the bulk density of the expanded granulate (6) is measured continuously, wherein upon detecting a deviation from at least one defined bulk density, the temperature profile (3) in the shaft (4) is adapted automatically or manually and/or the feeding of raw material (1) into the shaft (4) is reduced automatically or manually.

The present disclosure concerns expandable silica particles having a coating comprising talc powder and kaolin powder provided on the outer surface of the expandable silica particle and expandable and expanded silica particles comprising silica fume and/or ultrafine quartz silica sand beneath the surface of the particles. Methods for producing expandable and expanded silica particles are disclosed, including a method using a vibration plate and a furnace having a vibration plate for carrying out that method. The expanded silica particles have high compressive strength, substantially uniform cell size and distribution, low water absorption, and low porosity on the outer surface. They are useful as a filler in matrix materials, like concrete or epoxy, as insulation material with various binder materials, and as water filtration medium.

The present disclosure concerns expandable silica particles having a coating comprising talc powder and kaolin powder provided on the outer surface of the expandable silica particle and expandable and expanded silica particles comprising silica fume and/or ultrafine quartz silica sand beneath the surface of the particles. Methods for producing expandable and expanded silica particles are disclosed, including a method using a vibration plate and a furnace having a vibration plate for carrying out that method. The expanded silica particles have high compressive strength, substantially uniform cell size and distribution, low water absorption, and low porosity on the outer surface. They are useful as a filler in matrix materials, like concrete or epoxy, as insulation material with various binder materials, and as water filtration medium.