The invention relates to a burner for a rotary tubular furnace for the production of cement clinker, with a duct, arranged annularly within a burner carrier tube, for the discharge of primary fuels, for example coal dust, with at least one annular primary-air duct and with at least one tube, integrated in the burner, for the pneumatic transport of particulate secondary fuels and for the blowing these out at the burner mouth.
In a cement clinker production line, calcined raw cement meal is burnt in the sintering zone of a rotary tubular furnace into cement clinker. To heat the rotary tubular furnace, a long burner lance is introduced into the furnace outflow end through the stationary furnace outflow housing, at the mouth of which burner lance the fuels introduced into the lance burn so as to form a burner flame. The correct temperature, the length and the other configuration of the burner flame are important in the formation of clinker minerals in the rotary tubular furnace. Development tends to give the rotary tubular furnace itself as short a build as possible by virtue of high-quality calcination of the raw cement meal outside the rotary tubular furnace, so that, in reaction to this, the burner flame is, as a rule, to be as short and as hot as possible. Increasingly often, instead of liquid and gaseous fuels, the fuels used are solid fuels, in particular coal dust, but, recently, also pneumatically transportable particulate waste fuels, such as, for example, waste plastic granulates, etc., as secondary fuels.
Known rotary-furnace burners are often designed as what are known as three-duct burners (for example DE 43 19 363 A1), with at least three ducts concentric to one another, that is to say the pneumatically transported coal dust flows as fuel through the middle burner duct and emerges through an annular gap nozzle, the outflowing coal dust being surrounded by radially inner and by radially outer primary air as combustion air. The radially outer air, also called jet air, is subdivided, by means of a multiplicity of individual nozzles arranged in the annular jet-air duct, into a large number of individual high-velocity primary-air jets which generate a vacuum zone in their surroundings, that is to say the many high-velocity primary-air jets serve as propulsive jets on the injector principle, by virtue of which the large mass of the virtually stationary hot secondary air of, for example, about 1000° C., which surrounds the rotary-furnace burner, is sucked inwards in the direction of the core of the burner flame, where an intensive intermixing of the hot secondary air with the coal dust emerging through the annular gap nozzle takes place, the intention being that the coal dust should bum quickly and completely so as to form a short hot flame.
In the known three-duct burner, it would not be possible to inject particulate secondary fuel through the coal dust duct by means of its annular gap nozzle, since this secondary fuel would block the annular gap nozzle. Attempts have therefore already been made to blow through the central tube of the burner, into which a central ignition burner can be inserted, particulate secondary fuel which then emerges, however, as a compact jet, in which the particular fuel fans out a little, flies too far in the rotary tubular furnace, forms too long a flame and does not bum out or bums out too late. Furthermore, attempts have been made to set the injected secondary fuels in rotation at the mouth of the burner lance, the result of this being that, in particular, the large secondary fuel particles of high specific gravity are thrown onto the periphery, in any event are thrown out of the flame cone, instead of burning in the flame.