Apparatus for charging a shaft furnace

Apparatus for charging a shaft furnace for calcining and sintering material in lump form, such as limestone, dolomite, magnesite or the like, with granular bulk material, with a charging silo arranged above the furnace shaft having a substantially circular cross-section with a substantially homogeneously mixed bulk material and a charging bunker outlet for supplying the bulk material onto the surface of the bulk material column to be covered in the furnace shaft in a distribution controllable over the shaft diameter, characterized by a substantially circular plate arranged in spaced manner below the charging bunker outlet and whose diameter is smaller than the internal diameter of the furnace shaft and larger than the diameter of the opening of the charging bunker outlet and a rotary ring box or the like concentric to the plate and to which is fitted a plurality of strippers which penetrate the sloping bulk material in the plate and with each of the strippers is associated in fixed manner one of the guide chutes or the like terminating at different distances from the median longitudinal axis of the furnace shaft.

The invention relates to an apparatus for charging a shaft furnace for 
calcining and sintering material in lump form, such as limestone, 
dolomite, magnesite or the like, with a granular bulk material, with a 
charging bunker positioned above the furnace shaft having a substantially 
circular cross-section with a substantially homogeneously mixed bulk 
material and a charging bunker outlet for feeding the bulk material onto 
the surface to be covered of the bulk material column located in the 
furnace shaft with a distribution controllable over the shaft diameter. 
The feeding of bulk material in the above-described manner into a shaft 
furnace for the heat treatment of lump material, such as limestone, 
dolomite, magnesite or the like, particularly limestone or the like to be 
calcined, onto the surface of the material column in the furnace shaft and 
which is to be covered, leads to problems because it is difficult to bring 
about a uniform distribution of the bulk material already homogeneously 
mixed in the upper part of the furnace and which is constantly provided 
from the charging bunker over the furnace over the entire shaft diameter, 
as a result of the unavoidable slope of the bulk material. Relatively 
complicated arrangements are known for this purpose, e.g. in the form of 
charging bells with a different diameter. It is in particular difficult to 
uniformly cover with sliding bulk material in the desired manner the 
circular surface of the bulk material or material column in the furnace 
end to be covered. In such known arrangements, the surface to be covered 
is subdivided into several circular rings with in each case the same 
cross-sectional area, i.e. into annular surfaces and a necessarily 
resulting centrally arranged residual surface with a circular 
cross-section, to each of which is allocated an identical material 
quantity. 
The problem of the present invention is to provide an apparatus of the 
aforementioned type making it possible in a simple manner to supply the 
bulk material to be fed in with a desired distribution over the furnace 
shaft diameter. 
According to the invention, this problem is solved in an apparatus of the 
aforementioned type by a substantially circular plate arranged in spaced 
manner below the charging bunker outlet and whose diameter is smaller than 
the internal diameter of the furnace shaft and larger than the diameter of 
the charging bunker outlet port, as well as a rotary ring box or the like 
arranged concentrically to the plate and on which is provided a plurality 
of strippers projecting into the bulk material sloping on the plate and 
with each of said strippers is associated a guide chute or the like, whose 
outlet terminates at a different distance from the median longitudinal 
axis of the furnace shaft. 
According to a particularly preferred embodiment of the invention, the 
plate is arranged in a preferably horizontally oriented position. The ring 
box can also be driven in controlled manner by an electric motor or the 
like. 
Another embodiment of the invention is characterized in that the immersion 
depth of at least one of the strippers into the bulk material located on 
the plate is adjustable. 
The invention optionally proposes that at least one of the guide chutes 
passes from the plate or ring box in downwardly sloping manner towards the 
inner wall of the furnace shaft and at least one of the guide chutes runs 
in the direction of the remaining surface to be covered. According to the 
invention, the chutes can also terminate in spaced manner above the upper 
edge of the furnace shaft. 
According to another embodiment of the invention, the outlets of the guide 
chutes are essentially located in a horizontal plane. According to the 
invention, the strippers can comprise substantially vertically arranged 
plates, preferably made from sheet metal or the like. 
The invention also optionally proposes that the strippers project from a 
circumferential point of the ring box located behind the particular guide 
chute in the rotation direction of said box under an angle deviating from 
the radial direction to a position in the bulk material which is 
circumferentially located within the area of the particular chute. 
Due to the fact that in the apparatus according to the invention, the 
substantially horizontally arranged circular plate is provided in spaced 
manner below the charging bunker outlet and whose spacing can be adapted 
to the particle size of the complete bulk material, in the case of a 
corresponding plate dimensioning, any undesired bulk material outflow from 
the charging bunker can be prevented. The strippers uniformly distributed 
around the circumference of the rotary ring box and which project into the 
loose material of the bulk material slope on the plate and whose number 
coincides with the number of the circular rings described hereinbefore, 
together with the residual surface, during the rotation of the ring box, 
whose rotation speed is adjustable, take up equal material quantities from 
the plate and the pocket formed by it and pass the particular bulk 
material onto the associated guide chute. The guide chutes, like the 
strippers are fixed to the ring box and rotate therewith. Naturally the 
number of chutes and strippers is the same, a chute being associated in 
fixed manner in each case with one stripper. The number of strippers and 
chutes is the same as the number of circular rings to be covered and the 
residual surface of the bulk material in the furnace end. As a function of 
requirements, the number of circular rings can e.g. be four, but can also 
be more or less. Each chute is constructed in such a way that its outlet 
passes over its associated circular ring or residual surface of the bulk 
material in the furnace end. 
As a result of the rigid, mechanical connection of the strippers fixed to 
the rotary ring box to the guide chute, bulk material can only flow over 
the outer edge of the plate when the rotation of the ring box has started, 
so that there can be no superimposing or non-movement of the circular 
rings during starting or stopping. As necessarily all the strippers and 
the associated chutes deliver material at the same time, all the circular 
rings and the residual surface are covered at the same time, so that it is 
not possible for a disadvantage slope to form, as could be the case when 
only one circular ring was covered. This prevents undesired separation of 
the bulk material in the furnace. Any correction which may be needed to 
the individual delivered quantities, such as e.g. for producing a 
trough-like material surface in the furnace shaft, can be brought about by 
merely adjusting the immersion depths of the strippers, without it being 
necessary for an operator to climb into the furnace end.

As can be gathered from the drawings, the already homogeneously mixed bulk 
material 2 continuously made available by the charging bunker 1 above the 
shaft furnace is uniformly distributed in the upper part of the furnace on 
a surface 3 having a circular cross-section. The circular surface 3 of the 
bulk material in the furnace end to be covered is subdivided into several 
circular rings 4, 5, 6, 7, with in each case the same cross-sectional 
area, i.e. into ring areas and a necessarily resulting, centrally located 
residual area 8 with a circular cross-section, each of the ring areas 4, 
5, 6, 7, and the residual area 8 being allocated the same bulk material 
quantities. 
In spaced manner below a charging bunker outlet 9 is provided a circular 
plate 10. Strippers 11, which project into the sloping bulk material 2 
loosely placed on plate 10, are mounted in fixed manner on a rotary ring 
box 12. The strippers 11 comprise vertically located metal plates which, 
in the manner shown in FIG. 2, project into the bulk material 2 under an 
angle differing from the radial direction in such a way that their ends 
projecting furthest in the direction of the median longitudinal axis of 
the shaft furnace are located within the circumferential area of the ring 
box 12 over which the guide chutes 14 associated with each of the 
strippers 11 slope downwards from the circumferential edge of plate 10. 
The strippers 11 are uniformly distributed around the circumference of 
ring box 12, their number coinciding with the number of the circular rings 
4, 5, 6, 7, and the residual surface 8. The outlets of guide chutes 14 
terminate above the surface 3 to be covered at different distances from 
the median longitudinal axis of the furnace, one of the chutes 14 in each 
case running out above each of the circular rings 4, 5, 6, 7, or residual 
surface 8. Guide chutes 14 are naturally also fixed to the ring box 12, 
the number of chutes 14 and strippers 11 coinciding. 
On rotating the ring box 12, the strippers 11 take up equal material 
quantities from plate 10 and carry said bulk material onto the associated 
guide chute 14, which then supplies the material to the particular 
circular ring 4, 5, 6, 7, or residual surface 8. 
The features of the invention disclosed in the description, drawings and 
claims can be essential to the realization of the different embodiments of 
the invention, either singly or in random combinations.