In a method for reducing the NOx emissions of a rotary kiln of a clinker production plant, fuel supplied through a burner of the rotary kiln is burned along with primary air fed through the burner, wherein the primary air has a lower oxygen content and the primary air has an oxygen content reduced relative to that of the ambient air and a temperature increased relative to that of the ambient air, and the primary air is obtained by mixing ambient air with exhaust gas from the rotary kiln or from a heat exchanger connected to the rotary kiln and used for preheating raw meal. The primary air is further obtained by mixing with hot air, in particular waste air from a clinker cooler.

A biomass solid fuel manufacturing device (100) includes: a rotary kiln (2) that carbonizes a biomass molded body molded from raw material biomass. The rotary kiln (2) includes a kiln body (20), a raw material supply unit (30) that supplies the biomass molded body to an upstream end portion of the kiln body (20), and an inert gas supply unit (50) that supplies inert gas to an upstream end portion inside the kiln body (20).

A biomass solid fuel manufacturing device (100) includes: a rotary kiln (2) that carbonizes a biomass molded body molded from raw material biomass. The rotary kiln (2) includes a kiln body (20), a raw material supply unit (30) that supplies the biomass molded body to an upstream end portion of the kiln body (20), and an inert gas supply unit (50) that supplies inert gas to an upstream end portion inside the kiln body (20).

In a known method for treating pourable, inorganic grain, a heated rotary tube is used that rotates about an axis of rotation and surrounds a treatment chamber that is divided into a plurality of treatment zones by means of separating elements. The grain is supplied to the treatment chamber at a grain inlet side and is transported, in a grain transport direction, to a grain outlet side and is exposed to a treatment gas in the process. In order, proceeding herefrom, to allow for reliable and reproducible thermal treatment of pourable inorganic grain, in particular SiO.sub.2 grain in the rotary kiln, in a manner having low and effective consumption of treatment gas, it is proposed for spent treatment gas to be suctioned out of a reaction zone of the treatment chamber, by a gas manifold that rotates about the longitudinal axis thereof.

In a known method for treating pourable, inorganic grain, a heated rotary tube is used that rotates about an axis of rotation and surrounds a treatment chamber that is divided into a plurality of treatment zones by means of separating elements. The grain is supplied to the treatment chamber at a grain inlet side and is transported, in a grain transport direction, to a grain outlet side and is exposed to a treatment gas in the process. In order, proceeding herefrom, to allow for reliable and reproducible thermal treatment of pourable inorganic grain, in particular SiO.sub.2 grain in the rotary kiln, in a manner having low and effective consumption of treatment gas, it is proposed for spent treatment gas to be suctioned out of a reaction zone of the treatment chamber, by a gas manifold that rotates about the longitudinal axis thereof.

A porous and easy water soluble amorphous silica which does not contain tar, crystal, residual agrichemicals, and carcinogens, and method and apparatus to produce same, by using only one burning treatment from a plant including abundant silica, including a method of manufacturing the amorphous silica wherein rice family plants are burned while stirring and introducing into the furnace an atmospheric gas having a mass of 6.7 or more and 20 or less of the weight of the rice family plants, or oxygen gas having a weight of 1.4 or more and 4 or less with respect to the weight of the rice family plants, and at the same time as burning, combustion gas generated at the time of combustion is discharged.

A porous and easy water soluble amorphous silica which does not contain tar, crystal, residual agrichemicals, and carcinogens, and method and apparatus to produce same, by using only one burning treatment from a plant including abundant silica, including a method of manufacturing the amorphous silica wherein rice family plants are burned while stirring and introducing into the furnace an atmospheric gas having a mass of 6.7 or more and 20 or less of the weight of the rice family plants, or oxygen gas having a weight of 1.4 or more and 4 or less with respect to the weight of the rice family plants, and at the same time as burning, combustion gas generated at the time of combustion is discharged.

In the disclosed solution sand to be cleaned is thermally cleaned by rotating the sand being cleaned in a large oven (1) by rotating the oven (1). Before cleaning, the sand may be pre-processed by crushing any lumps and cleaning the sand fraction by magnetic separation. Preprocessed sand to be cleaned and heat energy are fed (5) into the rotating oven. The oven (1) is set slightly inclined so that a second end of the oven (1) is lower than a first end. The inclination and rotating speed of the oven (1) as well as the feed amount of sand are adjusted, whereby the advancing speed of the sand may be adjusted, as well as the ratio of the sand being cleaned to the volume of the oven (1) kept as desired. The temperature of the oven (1) is monitored at the coldest area of the oven, which is substantially at the second end of the oven. The temperature of the oven (1) is adjusted by adjusting the amount of heat energy fed in. By means of temperature monitoring and knowing the advancing speed of the sand, it is also possible to determine the average temperature of the sand and adjust it as desired by adjusting the supplied heat energy. Finally, the cleaned sand is let run (12) from the second end of the oven (1).

In the disclosed solution sand to be cleaned is thermally cleaned by rotating the sand being cleaned in a large oven (1) by rotating the oven (1). Before cleaning, the sand may be pre-processed by crushing any lumps and cleaning the sand fraction by magnetic separation. Preprocessed sand to be cleaned and heat energy are fed (5) into the rotating oven. The oven (1) is set slightly inclined so that a second end of the oven (1) is lower than a first end. The inclination and rotating speed of the oven (1) as well as the feed amount of sand are adjusted, whereby the advancing speed of the sand may be adjusted, as well as the ratio of the sand being cleaned to the volume of the oven (1) kept as desired. The temperature of the oven (1) is monitored at the coldest area of the oven, which is substantially at the second end of the oven. The temperature of the oven (1) is adjusted by adjusting the amount of heat energy fed in. By means of temperature monitoring and knowing the advancing speed of the sand, it is also possible to determine the average temperature of the sand and adjust it as desired by adjusting the supplied heat energy. Finally, the cleaned sand is let run (12) from the second end of the oven (1).

An arrangement for burning lime mud into lime in a lime kiln. The lime mud flows counter-currently to flue gases from a feed end to a firing end and the fuel used is flue gas that is produced by gasifying a fuel in the presence of combustion air in a gasifier. The combustion air for gasification is preheated with heat generated in lime mud combustion. The arrangement is provided with a conduit between the lime kiln and the gasifier for leading air from the lime kiln into the gasifier as combustion air. At least a portion of the combustion air for gasification is preheated with heat generated in the lime mud combustion so that air is led into cooling of lime obtained in the combustion and further into the kiln, from or through the firing end of which air is taken into the gasification.