A rotary kiln includes: a heating tube; a material feeding unit disposed on a first end of the heating tube; a material collection unit disposed on a second end of the heating tube; an inner cylinder supported at the second end of the heating tube with the inner cylinder being inserted in a central portion of the heating tube; a plurality of branch tubes disposed circumferentially on an outer circumferential surface of the inner cylinder, each of the branch tubes branching from the inner cylinder and extending in an axial direction along an inner circumferential surface of the heating tube; a hot air supply tube supported to be relatively rotatable with respect to the inner cylinder with the hot air supply tube being inserted in one end of the inner cylinder that extends outside the heating tube; and a drive mechanism that rotates the heating tube.

Method of operating a long direct-fired inclined counterflow rotary kiln for the thermal treatment of material and counterflow rotary kiln adapted for same, whereby material to be treated is introduced into the kiln at the inlet end and treated material is evacuated from the kiln at the outlet end, whereby a main combustion zone extends inside the kiln over a distance of ¼ to ⅓ of the internal length L.sub.int of the kiln, whereby a supplementary combustion zone in which supplementary combustion takes place with an oxygen-rich oxidant extends inside the kiln over a distance from the inlet end of at most ¼ of the internal length L.sub.int, and whereby no combustion takes place in a heat exchange zone located between the main combustion zone and the supplementary combustion zone.

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.

An installation for thermal treatment of free-floating raw material, in particular cement raw meal and/or mineral products, may include a riser line through which hot gases can flow. The riser line has at least one fuel inlet for introducing fuel into the riser line. The riser line has at least one raw meal inlet for introducing raw meal into the riser line, which raw meal inlet is arranged upstream of the fuel inlet in a flow direction of gas inside the riser line. Further, a method for thermal treatment of free-floating raw material may involve introducing fuel via a fuel inlet into a riser line for guiding hot gases and introducing raw meal into the riser line. The raw meal is introduced into the riser line upstream of the fuel inlet in the flow direction.

An installation for thermal treatment of free-floating raw material, in particular cement raw meal and/or mineral products, may include a riser line through which hot gases can flow. The riser line has at least one fuel inlet for introducing fuel into the riser line. The riser line has at least one raw meal inlet for introducing raw meal into the riser line, which raw meal inlet is arranged upstream of the fuel inlet in a flow direction of gas inside the riser line. Further, a method for thermal treatment of free-floating raw material may involve introducing fuel via a fuel inlet into a riser line for guiding hot gases and introducing raw meal into the riser line. The raw meal is introduced into the riser line upstream of the fuel inlet in the flow direction.

The present invention relates to a method and apparatus for producing reduced iron from ironmaking dust which contains iron oxide which is generated at an ironmaking plant, takes note of the rotary kiln reduction method which does not require pretreatment of the dust, and has as its problem the pursuit of facilities which achieve further improvement of heat efficiency and stable operation.

To solve this problem, the present invention is characterized by heating and reducing carbon-containing shaped materials in a single closed space in which an internal heat type rotary kiln and an external heat type rotary kiln are arranged in series and including at least the insides of the two rotary kilns during which making the reduced exhaust gas which is generated at the external heat type rotary kiln burn inside of the internal heat type rotary kiln.

The present invention relates to a method and apparatus for producing reduced iron from ironmaking dust which contains iron oxide which is generated at an ironmaking plant, takes note of the rotary kiln reduction method which does not require pretreatment of the dust, and has as its problem the pursuit of facilities which achieve further improvement of heat efficiency and stable operation.

To solve this problem, the present invention is characterized by heating and reducing carbon-containing shaped materials in a single closed space in which an internal heat type rotary kiln and an external heat type rotary kiln are arranged in series and including at least the insides of the two rotary kilns during which making the reduced exhaust gas which is generated at the external heat type rotary kiln burn inside of the internal heat type rotary kiln.

Provided is a system for enhancing combustion in a kiln, including a kiln combustion chamber disposed within the kiln, the kiln combustion chamber having an atmosphere therein; a main burner for heating the atmosphere; a calciner assembly for providing a substance to be heated into the kiln combustion chamber; a precalciner including a precalciner combustion chamber disposed within the precalciner for receiving a biomass fuel for combustion in the precalciner combustion chamber, the precalciner combustion chamber in communication with the kiln combustion chamber; and a precalciner oxygen injector in fluid communication with the precalciner combustion chamber for providing a first oxygen stream into the biomass fuel for the combustion. A related apparatus and method for enhancing combustion with oxygen and biomass fuel are also provided.

Disclosed is a combustion heat generator with a recirculation region for forming uniform temperature distribution in a combustion chamber by forming a gas recirculation region around a central part of a combustion space in a housing and injecting fuel into the gas recirculation region to generate space combustion based on the recirculation region.