Roller press for thermal compaction and thermal briquetting of loose materials

A roller press, for the thermal compaction and briquetting of loose material, having rollers each comprising a core having a cylindrical outer surface and a shell carried on the core, the shell being formed from a plurality of adjacent segments each extending longitudinally of the roller and having longitudinal edges parallel to the axis of the roller and detachably secured at their ends to the roller core, circumferentially-spaced cooling ducts parallel to the axis of rotation of the roller being provided in the roller core at positions inwardly of the outer surface of the core and interconnected to form at least one cooling circuit provided with an inlet and an outlet for the passage therethrough of a coolant. The cooling ducts in the roller core can be connected in series or in parallel.

The invention relates to a roller press for thermal compaction and thermal 
briquetting of loose materials, in which each of the rollers comprises a 
core having a cylindrical outer surface and a shell carried on the core, 
the shell being formed from a plurality of adjacent segments each 
extending longitudinally of the roller and having longitudinal edges 
parallel to the axis of the roller and detachably secured at their ends to 
the roller core. 
In the case of thermal compaction and briquetting of pre-reduced iron ores 
or spongy iron especially, the loose material has to be treated at 
temperatures above 900.degree. C. At these high temperatures, the segments 
suffer considerable wear, especially where moulding depressions for the 
production of shaped briquettes are provided in them. In order to provide 
an adequate service life for the segments, segments are used that are made 
of materials that are usually very resistant to wear and very hard. The 
hardness may, for example, reach 60 HRc. However with increasing hardness 
of the materials, their toughness decreases and the brittleness increases 
and thus the risk of tearing and fracture of the material arises. In spite 
of this the service lives of the segments remain comparatively short. 
An object of the invention is to provide means whereby it is possible to 
realise substantially longer service lives for the segments. 
This problem is solved according to the invention in that 
circumferentially-spaced cooling ducts parallel to the axis of rotation of 
the roller are provided for the segments at positions inwardly of the 
outer surface of the core, the ducts being connected to form at least one 
coolant circuit provided with an inlet and an outlet for the passage 
therethrough of a coolant, one or each pair of inlets and outlets 
communicating with common inlet and outlet connections co-axial with the 
roller core. 
In a preferred embodiment annular plate may be provided on end faces of the 
roller core, each annular plate containing circumferentially-extending 
internal ducts communicating with the internal cooling ducts in the roller 
core, thereby to interconnect cooling ducts in the roller core to produce 
at least one said cooling circuit therein. 
Alternatively, flow paths interconnecting internal cooling ducts in the 
roller core may be formed in one or each end face of the roller core, said 
end face or end faces carrying annular cover plates secured over said flow 
paths. 
Two or more of said internal cooling ducts may be connected in series or in 
parallel to form one or more of said coolant circuits. 
The invention also provides a roller for use in a roller press as set out 
in any one of the preceding four paragraphs. 
With a roller press designed according to the invention, the segment 
temperature during operation can be considerably reduced, whereby in turn 
the wear is reduced. By the cooling, a constant temperature gradient is 
set up over the radial thickness of the segment, which thereby owing to 
the cooling, is subjected to only slight internal stresses. Further in the 
roller press according to the invention, the heat flow to the shaft of the 
roller core and therefore to the bearings of the roller core is 
substantially reduced. 
It is known to cool the surface of the press rollers during thermal 
briquetting by currents of air or by spraying with water or wet steam. 
This type of cooling leads to considerable thermal stresses and therefore 
to increased risk of cracking especially with brittle materials (British 
Pat. No. 295,910). 
In rollers for roller presses for briquetting coal having a shaping ring 
into the outer surface of which the briquette moulds are inserted, it is 
known to cool or heat the shaping rings and therewith the moulding 
depressions. For this purpose it is known to provide outward-opening ducts 
in the surface of the roller core, the said ducts being provided with 
inlet or outlet ducts for a cooling or heating medium, led through the 
roller shaft. Here the ducts are hermetically sealed at their outer ends 
by the shaping ring which is shrunk on to the roller core (German patent 
application No. 1,029,723 and German Pat. No. 809,546). It is also known, 
in a cylinder press for producing ice briquettes, to provide a duct for 
liquid opening inwards, in a shaping ring, the duct here being closed by 
the cylindrical surface of the roller core (German Pat. No. 601,426).

FIG. 1 shows a longitudinal section through approximately half of a press 
roller 2 designed according to the invention. Two such press rollers 
arranged with their axes of rotation parallel are disposed side-by-side in 
a substantially horizontal plane in a roller press. The press roller 2 has 
a generally cylindrical core 4 which is made in one piece with axial 
extensions 6 by which the roller can be rotated over ball bearings in 
bearing blocks which are situated in lateral openings of the press 
housing. Normally the axis of rotation of one of the press rollers is 
fixed while the other press roller is movable horizontally relative to the 
fixed roller, usually against a hydraulic support. 
The press roller core 4 is provided on its circumference with a shell 8 
which consists of a plurality of longitudinal segments 10 having 
longitudinal edges parallel to the axis of the roller and adjacent one 
another at the circumference of the roller core. The segments 10 are 
provided at their ends with extensions 12 which are engaged by fastenings 
14 by which the segments are fixed to the roller core 4. The fastenings 14 
shown in the drawing are hinged clamp straps 16 mounted on the roller core 
4 and are pressed against the segments 10 through tension bolts 18 of 
which only one is shown. Alternative fasteners can be provided, for 
example cooled shrunk rings, radially disposed bolts, or equivalent means. 
The external surfaces 20 of the segments 10 can be plain cylindrical 
surfaces. However moulding depressions can alternatively be provided in 
known manner in the segment surfaces. The roller core 4 is provided with a 
smooth cylindrical surface 22 at its circumference. The radially inner 
supporting surfaces of the segments 10 are correspondingly of smooth 
part-cylindrical shape. 
At a distance x from the surface 22 of the roller core 4 cooling ducts 26 
each parallel with the axis of the roller 2 are provided on a pitch circle 
indicated at 24. As can be seen from FIGS. 2a and 2b, these ducts extend 
between the end faces 28 of the roller core 4. In front of the outlets 30 
of the cooling ducts 26, annular plates or rings 32 are fixed on the end 
faces 28 of the roller core 4. The rings 32 have 
circumferentially-extending ducts 34 formed thereon. The ducts 34, as can 
be seen from FIGS. 2a and 2b, can be designed in such a way that they 
respectively form a flow path between the ends of two neighbouring cooling 
ducts 26. In this way a meandering duct having an inlet 36 and an outlet 
38 for the cooling medium, especially water, is formed. The inlets 36 and 
the outlets 38 may be connected to duct sections 40, 42 parallel to the 
other cooling ducts 26 and extending to a limited extent into the core 4. 
However it is also possible to provide a through drilling and to separate 
the latter into two sections by a plug in the middle. From the respective 
duct sections 40 and 42, the inlet and outlet 36, 38 are preferably formed 
by radial drillings leading to axial ducts 44 and 46, which are led 
through one or both of the shaft extensions and are connected to 
attachments for introducing and removing the coolant. The drillings are 
closed by plugs at the circumference 22 of the roller core. 
In order to achieve a uniform cooling effect, a plurality of cooling 
circuits can be provided, distributed over the circumference of the pitch 
circle. In FIGS. 2 and 2a three such cooling circuits I, II and III are 
shown, each being connected by respective radial drillings 36 and 38 with 
the inlet and outlet 44 and 46 in the shaft. 
In the embodiment in FIGS. 2 and 2a, the coolant circuit I is connected in 
parallel and consists of a plurality of cooling ducts 26 one behind the 
other. It is also possible to connect all of the cooling ducts 26 in 
parallel. In this case the ring would have to be provided with a circular 
groove open towards the end face of the roller core 4; for uniform loading 
of the cooling ducts it is expedient to provide a plurality of radial 
inlet and outlet drillings here too. In the embodiment shown in FIG. 2b, 
the cooling circuit I is connected in series. 
It is also possible to provide a plurality of coolant circuits with cooling 
ducts passed through in parallel in each case. In such an embodiment shown 
as the cooling circuit I in FIG. 2a , the flow channel 34 inside the ring 
32 would have to be divided over the circumference into a corresponding 
number of sections, each section then being connected to a plurality of 
cooling ducts 26. It is further possible to provide a plurality of cooling 
circuits with cooling ducts passed through in series in each circuit, as 
shown in cooling circuit I in FIG. 2b. 
In any case, the connecting of the cooling ducts 26 is chosen from the 
point of view of producing a heat sink which operates as uniformly as 
possible over the whole circumference 22 of the roller core 4. 
The flow paths interconnecting the flow ducts 26 can also be inserted into 
the two end faces of the roller core 4; a ring smooth on the inside can be 
used as a seal for covering the said flow paths. 
The rings 32 are respectively secured by bolts to the roller core. For flow 
circuits such as those represented in FIG. 2, the bolts indicated at 48 
can be screwed into the roller core 4, on the pitch circle 24, through 
massive lands between neighbouring flow paths 34. Also as shown by 
reference numeral 34a, the flow path may be directly formed in the end 
face of the roller core. 
Finally it is possible to connect two adjacent cooling ducts 26 via 
external flow paths to an annular duct, there being connected a first 
radial drilling for the admission of the cooling medium and a second 
radial drilling for the discharge of the cooling medium. The flow paths 
between these two radial drillings should preferably be of equal length 
and in that case, the annular flow path thus formed is traversed by two 
opposing streams from the inlet to the outlet drilling.