GB2053726A - Method and apparatus for crushing agglomerated mass - Google Patents

Abstract

A method for crushing agglomerated mass consists essentially in that the agglomerated mass is subjected to a dynamic impact directed upon a hot side 2 of said agglomerated mass. The apparatus comprises a housing 5 which accommodates a rotor 6 formed by impact members 8 having teeth 9, set rigidly on a shaft 7. The apparatus also comprises a feed and discharging de vices. The impact members 8 are mounted on said shaft 7 in series, the teeth 9 being of a crescent shape and each having a concave surface 21 thereof arranged radially with respect to said rotor 6. Each said tooth 9 is formed as a tee in cross section with a web located at right angle to the axis of said rotor 6 and a flange parallel to the axis 20 of said rotor 6. <IMAGE>

Description

SPECIFICATION Method and apparatus for crushing agglomerated mass The invention relates to mining and metallurgy, and more particularly, to methods and apparatus for crushing agglomerated mass.

The invention can effectively be used for crushing hot agglomerated mass and stabilizing sinter lumps in terms of shape and mechanical strength.

The invention can also be employed for crushing large coal lumps, slag skulls (particularly when hot), flagstone blocks, frozen materials and others.

The terminology used in the description is as follows.

Agglomerated mass is used to denote a sintered agglomeration burden comprising iron ore concentrate, sintered iron ore, limestone, solid fuel (such as coke fines, coal and others) and other components.

As the fuel burns, said components melt, then solidify turning into a strong agglomerated mass.

By sintered cake (agglomerated mass slab) we mean an agglomerated mass of a given geometric shape, as, for example, a rectangular slab.

Sinter is understood to be an agglomerated mass slab crushed to lumps of a specified size.

Standard sinter is understood to be a lump iron ore material obtained by crushing agglomerated mass and suitable, after fines (0 to 5 mm) are screened for blast-furnace smelting.

The principal object of this invention is to provide an improved method and apparatus for crushing agglomerated mass which would make it possible to obtain a blast-furnace sinter of optimum size composition by a single-stage crushing process.

Another object of the present invention is to provide said method and apparatus which would make it possible to obtain a blast-furnace sinter a stable shape and mechanical strength by a singlestage crushing process.

The invention resides essentially in that an agglomerated mass is crushed by means of a dynamic impact method directed upon the hot side of the agglomerated mass.

The impact method of agglomerated mass crushing, effected on the hot side thereof, makes possible a selective crushing against a least consumption of electric power per ton of standard product (sinter). Impacts applied to the hot side prevent an over-crushing of the sinter through compression of the cold solidified mass of the sintered cake and make it possible to concentrate the impact loads upon the strongest, most elastic and partly plastic portion of the sintered cake.

The invention provides an apparatus for crushing agglomerated mass which comprises a feed and discharging devices and a housing which accommodates a rotor with sprockets which are set rigidly in series on a shaft and having crescent-shaped teeth with a concave surface thereof being positioned radially with respect to the rotor and a tee cross section thereof having a web arranged at right angle to the axis of the rotor and a flange set in parallel to the axis of the rotor.

The series arrangements of the toothed sprockets, set on a single line parallel to the axis of the rotor, makes it possible to effect simultaneously a splitting blow by a group of teeth upon a section of an agglomerated mass slab which has entered the work zone of the rotor. This ensures a translational, directional, ordered motion of the slab, preventing random falling of lumps and enabling blows to be applied by a most active part of teeth, i.e., by their work edges.The crescent shape of the tooth, with the apex thereof having a minimum surface area for support, provides for an unhindered discharge of agglomerated mass slab as a section of the slab, which has entered the work zone of the rotor, and which is sheared therefrom as the tooth apex cuts through the body of the slab, said crescent shape of the teeth providing a maximum concentration of impact loads at points where the blows are applied.

This prevents practically a non-central application of the load by a tooth upon the agglomerated mass slab and a random projection of the turning noncrushed lumps of the mass from the work zone of the rotor, thereby improving the crushing effect in terms of breakage of the whole of the agglomerated mass slab against a minimum of electric power consumption.

In addition, the concave surface of the teeth allows for more effective concentration of the impact load in terms of time, whereas its work surface arranged radially with respect to the axis of the rotor and at the edges ensures the application of an impact approximating substantially a normal blow, this enhancing the concentration of the impact loads and providing a greater crushing efficiency.

An enlarged base makes the crescent-shaped teeth very strong mechanically.

The most advantageous height of sprocket teeth from the viewpoint of sintered cake crushing effectiveness is one where the ratio of tooth height to maximum thickness of the sintered cake is (1 to 1.5):1, i.e., one which ensures a complete cutting of the sintered cake by the sprocket teeth.

Transversally, the teeth have a tee cross section with a web which is arranged at right angle to the axis of the rotor and fulfils initially the function of a stress concentrator -- a splitter -- as a blow is applied.

The tee web also splits the strong incandescent part of the sintered cake into large lumps and initiates an impact wave which ensures a selective breakage along the weakened inter-block sections of the solidified part of the agglomerated mass slab and prevents the penetration of the cold, more solid mass into a hot, less solid plastic mass. This enhances the effectiveness of crushing from the viewpoint of agglomerated mass slab breakage and optimum size composition of the standard sinter.

The tee flange makes possible the gripping of large incandescent agglomerated mass lumps (resulting from initial breakage) whose size exceeds the dimensions of the slot formed between teeth of adjacent sprockets in a single row and imparting said lumps sufficient kinetic energy for subsequent final crushing and stabilization of the size and of the mechanical properties of sinter lumps.

This ensures, in the final analysis, the production of sinter lumps of a specified top size limit and of a maximum mechanical strength, which is due to the fact that the teeth of the rotor rotating at a high speed (up to 420 rpm) in the direction of sinter lump motion create a directional flow of air which intensifies the extraction of heat from the surface of incandescent sinter lumps and thus promotes the solidification of the non-solidified agglomerated mass slab and the formation of a stronger iron oxide structure in the form of a dendrite framework.

It is advantageous to secure to the tee section web at least one stiffening rib, this providing, for the same dynamic impact value, a lesser top size limit, i.e., a greater effectiveness of agglomerated mass slab crushing.

It is good practice to locate a shield, having a curvilinear surface, inside the apparatus housing at a distance from the rotor generatrix substantially equal to the rotor diameter.

The shield of this type contributes to further crushing of larger agglomerated mass lumps and stabilizes effectively their size as various projecting of lumps are knocked off while the lumps roll over the curvilinear surface of the shield. This, in the final analysis, results in all of the standard product (sinter) having a specified top limit size and in a maximum stabilization of sinter size composition.

Roughly 50 to 25 % of all the standard product are broken to final size on the shield, it being more advantageous to handle a hotter, thoughout its height, sintered cake.

The size of the gap between the rotor generatrix and the shield along the horizontal axis is such as to prevent the wedging of sintered cake lumps when the rotor stops and to utilize more effectively the kinetic energy of the lumps which are projected by the teeth flanges upon the guard shield.

Lump size is stabilized more effectively if the curvilinear surface of the shield is shaped as a parabola with its apex located level with the axis of the rotor and has a length sufficient to ensure a maximum stabilization of sinter lump size.

The proposed construction is highly reliable and safe in operation; it is readily adapted for automatic performance in sinter production, being not larger in size than the existing sinter crushing plants; also, it is easy to service and replace; requires minimum consumption of electric power per ton of standard sinter and minimal capital investments; its throughput capacity is many times greater than that of a sintering machine on which it may be mounted.

The invention will now be explained in greater detail with reference to embodiments thereof which are represented in the accompanying drawings, wherein: Figure 1 illustrates schematically successive steps in the breakage of an agglomerated mass slab until lumps of optimum size for blast furnace smelting are obtained, according to the invention; Figure 2 is a schematic cross section of an apparatus for crushing agglomerated mass, accord ing to the invention; Figure 3 is a schematic longitudinal section of a crushing chamber, view along arrow A on Figure 2, of an apparatus for crushing agglomerated mass, according to the invention; Figure 4 is a cross section along line IV-IV on Figure 2 of a rotor sprocket tooth, according to the invention;; Figure 5 is a schematic view along arrow B on Figure 2 of web of tee with a stiffening rib, according to the invention.

The method according to the invention for crushing agglomerated mass is illustrated in Figure 1 and is characterized by that agglomerated mass is crushed through the agency of a dynamic impact directed along arrow C upon a slab 1 of agglomerated mass moving at a velocity V1. The slab 1 of agglomerated mass has a hot side 2 and a cold side 3. The dynamic impact along arrow C is effected at an angle of 90" to the surface of the slab 1 upon its hot side 2.

The force of the impact is concentrated in the hot, the strongest plastic part of the agglomerated mass, then a portion of the impact energy effects a direct mechanical breakage of the hot side 2 of the slab 1 of the agglomerated mass of the pattern of glass breakage, whilst another part of the impact energy in the form of an impact wave (which spreads the same as in an elastic medium at a speed of more than 2000 m/sec) breaks the solidified (cold) portion of agglomerated mass along the weakest inter-block cross sections and areas, leaving unbroken only the strongest sinter lumps which are crushed subsequently. This is the procedure for selective crushing of agglomerated mass.

However, the largest broken lumps of hot plastic agglomerated mass, which have not been broken to optimum size and which have acquired a sufficient amount of kinetic energy, move in directions along arrows D at a velocity V2, impinge for a second time upon a solid obstacle 4 (guard shield) at an angle less than 90 , break up to a specified size and, having acquired a rotary motion, roll in directions along arrows 4 over the curvilinear concave smooth surface of the solid obstacle 4, the result being stabilized both shape and mechanical properties of sinter lumps.

With a view of improving the quality (crushing to constant size with the time) of crushing, the slab 1 of the agglomerated mass is fed at a constant specified velocity V1 and directed strictly along the motion of the sintered cake so as to prevent a disordered fall thereof into the crushing zone.

It thus proves possible, as a result of the dynamic impact on the hot side 2 of the agglomerated mass, selective crushing of the agglomerated mass, ard the elimination of the overcrushing of the cold agglomerated mass through mechanical squeezing and mixing with hot plastic sintered cake, to obtain a standard product of optimum, with respect to blastfurnace smelting requirements, top limit size and size composition.

There is proposed an apparatus for crushing agglomerated mass illustrated in Figure 2.

The apparatus comprises a housing 5 which accommodates a rotor 6 formed with sprockets 8 with teeth 9, the sprockets 8 being set rigidly on a shaft 7 of the rotor 6.

The apparatus also comprises a feed and discharg ing devices. The feed device is basically a chute 10 with a working surface 11 of wear plates, which is set radially with respect to the shaft 7 of the rotor 6.

The housing 5 of the apparatus is a metal construction welded of sheet and sections and made airtight in the zone surrounding the rotor 6.

The discharging device is basically outlet hole 12 formed with side 13 (Figure 3) and a front walls 14 of the housing 5 and defined at the underside by a work surface 15 of a device 16 for screening crushed sinter.

The apparatus has a guard shield 17, previously termed as a solid obstacle 4, of curvilinear shape approximating a parabola with the apex thereof lying level with the axis of the rotor 6, the guard shield being of a wear-resistant material. The internal concave smooth surface 18 of the shield 17 goes around the rotor 6 by an angle ensuring reception and discharge of sinter lumps in the work zone of the rotor 6 and their maximum size stabilization. The shield 17 is a welded metal construction lined on the inside with wear plates and secured to the housing 5 with the aid of a hinge 19 so that its position can be adjusted in space as required. The inside surface 18 of the shield 17 is set along the horizontal axis 20 (Figure 3) of the rotor 6 at a distance L (Figure 2) from the generatrix of the rotor 6 substantially equal to diameter (ZI of the rotor 6.The distance Lisa function of a maximum utilization of the kinetic energy of lumps as they impinge upon the shield 17 and should additionally be such as to prevent wedging of agglomerated mass lumps in emergency stoppages of the apparatus.

According to the invention, the sprockets 8 with teeth 9 are set on the internally water-cooled shaft 7 of the rotor 6 in series and in such a manner as to locate work edges 21 (Figure 3) of the teeth 9 of a single row along a same line parallel to the axis 20 of the rotor 6, whereas the length of arc f (Figure 2) of the gripping sector (distance between edges of adjacent teeth in the sprocket) should be governed by the ratio of the inlet velocity V1 of the slab 1 of the agglomerated mass into the work zone of the rotor 6 to the optimum peripheral velocity V3 of rotation of the teeth 9 of the rotor 6, its value being substantially equal to 1:5.

The teeth 9 are crescent shaped, their forward concave surfaces 22 being located radially with respect to the rotor 6. The teeth 9 are, in cross section, a tee, such as shown in Figure 4, with a web 23 arranged at right angle to the axis of the rotor 6, and with a flange 24 positioned in parallel to the axis 20 of the rotor 6. The tee has a cross section variable with the height and a variable height of the web 23.

To provide a maximum load at the point of impact where the tooth 9 bears by its end face (front) the web 22 of the tee, it is imperative to stagger in time the penetration of said web 22 into the slab 1.

The crescent shape of the tooth 9 is the one which provides for a minimum contact area when the edge 21 of the tooth 9 cuts through a given section of the agglomerated mass slab 1 and so avoids the slowing down of said slab 1 as it bears upon the edge 21 of the tooth 9. In addition, the subsequent motion of the tooth 9 through the body of the slab 1 should tend to lower its edge 21 in the direction of motion of the slab 1, at least by a value equal to its descent during the time it takes for the tooth 9 to cut through the slab 1, i.e. by a ratio of more than 1:1.In this case, there will occur no shift of the agglomerated mass along the edge 21 of the tooth 9 if the angle of contact of the tooth 9 with the surface of the agglomerated mass slab 1 approximates 90 , this substantially lessening the abrasive action of the agglomerated mass upon the material of the tooth.

In addition, the contact of the work areas of the tooth 9 and of the surface 18 of the shield 17 with plastic hot agglomerated mass lumps sharply reduces abrasive action thereon, hence is a high wear-resistance of work members of the proposed apparatus for crushing agglomerated mass.

The web 20 of the tee of the tooth 9 may be with or without stiffening ribs, such as shown in Figure 5.

Such construction ensures a more effective crushing of the agglomerated mass, all other things being equal, and yeilds a lesser top limit size of lumps, as a section of sintered cake sheared on initial contact with the edge 21 of the tooth 9 is then split additionally by a "false" edge 25 (Figure 5) provided in the work zone of the tooth 9 at a distance e from the edge 21.

The height h of the tooth 9 is substantially equal to (1 to 1.5):1 times the thickness H of the sintered cake.

The distance S (Figure 3) between the edges 21 of the flanges 24 of the teeth 9 of the adjacent sprockets 8 must be substantially equal to the specified top limit size of the sinter lumps, whereas the thickness 5 (Figure 3) of the tooth 9 of the sprocket 8 should be substantially equal to S, but it is also correlated with the structural strength of the tooth 9.

Bearings 26 of the rotor 6 should be designed for service in dust-laden atmosphere at t = 1 50"C.

It is very convenient to have an electric drive 27 operating on direct current in orderto make possible a smooth adjustment of rotor speed as a function of sintering techniques.

Agglomerated mass in the form of a slab 1, having a hot 2 and a cold 3 sides, slides off the sintering pallet 28 (Figure 2) of the sintering machine, rolls freely over the work surface 11 of the chute 10 of the feed device to enter the work zone of the rotor 6 rotating in the direction of motion of the slab 1 of the agglomerated at a specified speed. The teeth 9 of the sprockets 8 of the rotor 6 impinge at right angle on the hot side 2 of the slab 1 of the agglomerated mass, shearing by the edge 21 of the tooth 9 a section of agglomerated mass along the length of the slab 1 and splitting said section into separate large lumps in the direction of motion of agglomerated mass. Fine crushed, mainly cold, sinterfalls through the gaps between the teeth 9 of the adjacent sprockets 8 upon the work surface 15 of the device 16 for screening sinter, whereas the larger lumps, which have not been broken up to top limit size, mainly of hot agglomerated mass, are gripped by the flanges 24 of the tee of the tooth 9 which then project said lumps against the guard shield 17.

Having acquired a sufficient amount of kinetic energy, the lumps move through inertia, attain the surface 18 of the shield 17 at an angle of not less than 90" and break up into lumps with top limit size close to a specified value. As a result of the tangential motion along a curvilinear surface, broken sinter lumps are given a rotary motion and tumbled.

All the projections and weak formations are broken off, the surface of the lumps is strengthened, acquiring a round shape on rolling through a predetermined length of path along the surface 18 of the shield 17, and the lumps are stabilized in the process.

Both the rotor 6 rotating at a speed of more than 20 m/s and the shield 17 create a considerable air flow directed along arrows N (Figure 1) toward the screening device 16. The fully open blocks (most dense lumps) of sinter are intensively cooled, this being particularly true of the sinter lumps broken to optimum size. Due to a rapid solidification of the remaining part of the melt, dendrites of iron oxide form in the centre (core) of sinter lumps and strengthen them.

Thus, sinter lumps, subjected to an impact crushing (2 impacts), stabilized in shape and mechanical strength and partly cooled, are then screened and further treated.

Therefore, one-stage impact crushing and stabilization on the apparatus according to the invention yield a sinter of optimum (for blast furnace smelting) size composition, of most suitable shape for interaction with gases and of high mechanical properties, which, in terms of abrasion resistance and of impact strength, surpasses by respectively 2-3 times (in abs.

%) and 10 % those of sintertreated in known apparatus.

The efficiency of the apparatus of the invention exceeds that of sintering machines by a factor of more than 6, the yield of standard sinter being equal to or greater than that of existing two or three-step sinter crushing methods.

While the invention has been described herein in terms of the preferred embodiments, numerous variations may be made in the method and in the apparatus illustrated in the drawings and herein described without departing from the invention as set forth in the appended claims.

Claims (8)

1. A method for crushing agglomerated mass consisting in that crushing is effected by a dynamic impact directed upon a hot side of an agglomerated mass.

2. An apparatus for crushing agglomerated mass comprising a feed and discharging devices and a housing receiving a rotor formed with toothed sprockets set rigidly on a shaft, said sprockets being mounted in series on said shaft and their teeth having a crescent shape with a concave surface of said teeth located radially with respect to said rotor and having a cross section shaped substantially as a tee with a web of said tee arranged at right angle to the axis of said rotor and with a flange of said tee set parallellyto the axis of said rotor.

3. An apparatus as claimed in claim 2, wherein the height of the tooth is in a ratio to the thickness of agglomerated mass subjected to crushing of (1 to 1.5):1.

4. An apparatus as claimed in claim 2, wherein said tee web carries at least one stiffening rib.

5. An apparatus as claimed in claim 2, wherein said housing accommodates a guard screen with a curvilinear surface surrounding said rotor and located from the generatrix of said rotor at a distance substantially equal to the diameter of said rotor.

6. An apparatus as claimed in claim 5, wherein the curvilinear surface of the guard shield is shaped as a parabola with the apex thereof located on the axis of said rotor.

7. A method for crushing agglomerated mass substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

8. An apparatus for crushing agglomerated mass substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.