Abstract: Apparatus for producing mineral fibres from silicate raw materials such as basalt by blast drawing.When blast drawing is used to produce mineral fibres from basalt, there is arranged between the entry zone (26) of the chute (16) and the exit zone of the nozzle slot (10) of the blast nozzle unit (8), this slot forming the fiberization duct, a guide cell (13). The relative position of the side walls (29) of the guide cell is freely adjustable, so that desired flow conditions can be set and also the exit direction of the exit flow bundle (31) and hence the web formation can be controlled. As a consequence of a lateral distance (a) of the exit orifice (28) of the guide cell (13) relative to the entry flow bundle (27) additional secondary air is sucked in, which has a further cooling effect on the fibres.

Abstract: To produce basalt wool having a large fibre diameter of if desired 10 .mu.m with high output and low bead formation, the exit cross-section of the exit orifices (6) of the distributor tank (5), the vertical distance (vA) between the exit orifices (6) and the blow-in slits (29) for propellant gas, the horizontal width (hB) of the nozzle slot (10) and the vertical length (vL) of the nozzle slot (10) downstream of the blow-in slits (29) are dimensioned to be unusually large for an apparatus for producing rock fibres by blast drawing. As a result, it is possible to operate at a low melt temperature and a high propellant gas rate combined with a low propellant gas pressure in order, surprisingly, to obtain a coarse-fibered product with low bead formation and high output.