Process and apparatus for cooling of fired or sintered material

Abstract

Fired or sintered material supported on a continuously travelling grate composed of successive individual plates is cooled by passing air between the plates and through the material. At periodic intervals the speed of movement of adjacent plates is accelerated and decelerated with respect to the rate of travel of the grate.

Description

This invention relates to methods and apparatus for the cooling of fired or sintered material resting as a layer on a continuously moved air-permeable support surface. Cooling of the material is effected by the passing of cooling air through the support surface and the layer of material.

It is known to cool fired or sintered material on a travelling grate by repeatedly passing cooling air through the layer of material. The main problem with this cooling is to prevent the cooling air seeking preferred flow channels through the layer of material, which leads to non-uniform cooling of the material and the occurrence of hot lumps of material at the end of the cooler. The difficulty of achieving uniform cooling of all the material is usually still further increased by the material having been fed onto the travelling grate with a very irregular distribution. Measures using mechanical or pneumatic means to achieve uniformity of feed of the material have not been found satisfactory in practice.

The object of this invention is to avoid these disadvantages by providing methods and apparatus which achieve good distribution of the material on the continuously moved air-permeable support surface, uniform passage of air through the layer of material, and hence an excellent cooling effect.

According to the invention this objective is achieved by the provision of individual areas of the support surface which are intermittently given an extra positive or negative movement superimposed on the continuous movement, so that adjacent areas of the support surface have a periodically varying different resultant rate of movement.

In this way, in addition to the actual continuous conveying movement, the individual particles of material are given a periodic and locally varying further movement which causes the layer of material to be made uniform, but prevents the cooling air only passing through preferred flow channels, and hence ensures that the cooling air has a uniform cooling effect on all the material. The method provided by the invention is thus marked by high cooling efficiency and particularly uniform cooling of all the material.

If the air-permeable support surface is formed by at least one grate band which includes a plurality of grate plates which are driven by continuously moved chain members, then in accordance with a preferred embodiment of the invention at least some grate plates are movable to a limited extent relative to the chain members, by means of additional drive elements.

The areas of the grate band with periodically variable rates of movement, with different resultants (i.e., the grate plates with limited mobility relative to the chain members) can extend over the entire width or over part of the width, and also over the entire length or over part of the length of the grate band.

Numerous variations are also possible within the scope of the invention with regard to the other features of the travelling grate (e.g. inclination of conveyor device, number of grate bands), to the type of air feed (e.g. single or double air feed), and to the provision of intermediate or subsequent crushers etc.

One embodiment of the invention is shown schematically in the drawings wherein:

FIG. 1 is a side elevational view of a typical portion of the grate band; and

FIG. 2 is an enlarged, isometric view of a pair of adjacent grate plates of the band.

The travelling grate used for the cooling of fired or sintered material comprises a grate band 1 consisting of a number of grate plates (e.g. 2, 3, 4, 2', 3', 4' etc) in overlapping relation with gaps therebetween to form an air-permeable, straight support surface. The plates can be driven continuously by chain links 5 through driving bolts 6.

For this purpose the grate plates (e.g. 2) are provided with coupling means comprising a driver holder 7 and a guide 8 which embrace succeeding driving bolts 6 in the manner shown in the drawing. The arrangement is such that the individual grate plates (e.g. 2) are capable of lost motion longitudinally of the grate band to a limited degree relative to the chain links 5, to the extent that the inner length of the driver holder 7 is greater than the diameter of the driving bolt 6.

In order to impart a positive (acceleration) or negative (deceleration) additional movement to the grate plates driven at constant speed by the chain links 5, extra drive elements are provided in the form of chain drums 10, 10' which rest on support track shafts 11, 11', said shafts deriving their drive from the chain links 5 by means of driving drums (not shown). The dimensions of these driving drums and of the chain drums 10, 10' are so chosen that in the area of their forward engaging surfaces 13, 13' the teeth 12, 12' of the chain drums 10, 10' impart to the grate plates a slightly higher speed V.sub.1 than the speed of movement V.sub.3 of the chain links 5, while the backs 14, 14' of the teeth 12, 12' give the following grate plate (insofar as this was advanced, e.g. 4 or 4') a somewhat lower speed V.sub.2 than the speed of movement V.sub.3.

Consequently, the grate plates of the straight section of the support, when they have reached about the position of plate 3, are pushed forward by the chain drum 10, so that they assume the position of the grate plate 4, wherein the corresponding driving bolt 6 lies almost at the rear end of the driver holder 7. In this position the grate plate 4 is being driven neither by the chain link 5 through the driving bolt 6 nor by the chain drum 10. It drops its speed below the chain speed to V.sub.2 by engagement with the rear of the chain drum 10', so that in the position of the grate plate 2' the corresponding driving bolt 6 again lies against the front inner edge of the driver holder 7. The grate plate is now conveyed at the speed of the chain into the position of the grate plate 3', wherein through this additional drive movement of the chain drum 10' the speed of movement of the grate plate is again increased above the chain speed.

FIG. 2 shows the engaging of adjacent grate plates 3, 4. Driver holder 7 provided with a web 21 is secured with an arm 20 by means of rivets 22. Spaced guides 8 are secured with a member 24 by means of legs 23 and rivets 25. Driver holder 7 fits between both guides of the adjacent grate plate and is guided by these means.

In the section of the straight travelling grate represented, the grate plates are given intermittently -- i.e., as long as they are within the operating range of the chain drums 10 or 10' -- extra movements which are superimposed on the continuous conveyor movements of the chain links 5 to reduce or enlarge their speed relative to the chain speed for a specific period of time, and are finally conveyed a further length of route at the chain speed, before the described cycle recommences.

It will be apparent that succeeding grate plates undergo movement relative to each other, by which the layer of material lying on the grate plates (and not shown in the drawing) is additionally conveyed, loosened and made uniform due to the shape of the grate plates, so ensuring optimum cooling effect from the air passing through the grate band and the layer of material. The source of the cooling air is not shown in the drawings, but any conventional source may be utilized to direct air upwardly through the gaps between adjacent grate plates.

Claims

What is claimed is:

1. In a method of cooling a layer of fired or sintered material supported on a straight portion of an air permeable support movable at a substantially constantly speed in one direction and composed of a plurality of relatively movable plates coupled to one another, the improvement comprising periodically varying the speed of movement of adjacent plates in said straight portion of said support whereby adjacent plates of said straight portion have a periodically varying resultant rate of movement in said direction.

2. The method according to claim 1 wherein the speed of movement of adjacent plates is accelerated relative to the speed of movement of said support.

3. The method according to claim 1 wherein the speed of movement of adjacent plates is decelerated relative to the speed of movement of said support.

4. The method according to claim 1 wherein the speed of movement of said portion of said support first is accelerated and subsequently decelerated relative to the speed of movement of said support.

5. Apparatus adapted for use in the cooling of fired or sintered material comprising a plurality of grate plates fitted to one another and together forming a grate band having an air permeable support surface on which a layer of such material may rest; drive means movable in one direction; lost motion means coupling said grate plates to said drive means whereby said grate plates and said drive means are capable of relative movement; and additional driving means engageable with selected ones of said grate plates during their movement by said drive means for varying the rate of speed of said selected ones of said grate plates relative to the rate of speed of said drive means.

6. Apparatus according to claim 5 wherein said coupling means comprises a holder carried by each of said plates and a driver member extending through said holder, said driver member being movable relatively to said holder in the direction of movement of said band.

7. Apparatus according to claim 5 wherein said additional driving means comprises a rotary driving drum having teeth engageable with said selected plates.

8. Apparatus according to claim 7 wherein each of said teeth extends radially from said drum for insertion between adjacent ones of said plates.

9. Apparatus according to claim 8 wherein each of said teeth has first and second surfaces engageable with leading and trailing plates, respectively, at different radial distances from the axis of rotation of said drum.

10. Apparatus according to claim 5 wherein a plurality of said plates define a straight section of said band and wherein said additional driving means is engageable with plates of said straight section.