The invention relates to a method of cooling and comminuting particulate material and an apparatus for practicing the method. This invention relates to a method of and apparatus for breaking and cooling the coarse portion of a hot material having a substantial range of particle size. The invention can be used in any minerals application in which rocks are first burned and then cooled, such as for example, in treating the clinker of mixed size frequently produced during the manufacture of Portland cement.

The present method of cooling and comminuting particulate material is utilized in conjunction with cooling material which has been burnt in a kiln or heated by some other process. The cooling apparatus used in the present method can comprise stationary or movable grate coolers and other coolers. The method of operation of the above and other coolers is well known in the art.

Background Of The Invention

Typically kilns in a cement making operation produce clinker product having different sizes. When cooling such material, large clinker particles do not cool as efficiently as smaller particles due to the ratio of particle surface area to particle volume. When such large particles are discharged from a clinker cooler they may still contain large quantities of heat, necessitating additional and frequently costly processing steps in subsequent cement plant operations.

It is known to use roll breakers downstream from such clinker cooler installations. The roll breaker's function is to reduce the size of large clinker agglomerations as they leave the clinker cooler. In some cases it is known to employ roll breakers at the front of the cooler, wherein all the cooler function is after the roll breaker, or in mid-cooler, that is, any location where there is cooler function both before and after the roll breaker, to break up the larger pieces of clinker in an attempt to avoid the problems specified above. From a clinker-cooler process standpoint the front cooler or mid-cooler roller breakers would appear to be desired solutions because either situation allows the cooler to operate on smaller clinker, which is easier to properly cool. However, a front or mid cooler roller breaker is not a good option economically because of a high operating temperature (exceeding approximately 55O ⁰ C) and thus the roller breaker faces a multitude of complications required for high-temperature service (refractory, shaft and frame cooling systems, etc).

It would be advantageous, therefore, and it is an object of the present invention to have a clinker processing system that utilizes a clinker cooler in conjunction with a roll breaker in which there is achieved the advantages of utilizing a front or mid-cooler breaker in that the cooler will thereby treat smaller sized particles to thereby raise the efficiencies of the cooler without the inherent disadvantages of a front or mid-cooler breaker that involve operating a roll breaker in an extreme temperature environment.

Summary Of The Invention The above and other objects are achieved by using a crushing means located at the discharge end of and in the same environment as the clinker cooler, in conjunction with a screening means located intermediate the discharge end of the cooler and the crushing means to first remove fully cooled smaller sized clinker for transportation to the next step in the process. The larger size material that are not removed are comminuted in the crushing means and then transported via a mechanical transportation system (for example, a pan conveyor used in conjunction with a screw feeder) and re-introduced in the mid- cooler area. Most preferably the screening means and the crushing means are embodied in the same device, a roll breaker.

Description Of The Drawings

FIG 1 is a sectional, side view of one embodiment of the invention in which the roll breaker utilized in the method of the invention is a four roll breaker having transport/screening shafts and crushing shafts. FIG 2 is a sectional, side view of another embodiment of the invention in which a two roll breaker is utilized as a crushing means in conjunction with a separate dynamic screening device.

FIG 3 is a sectional, side view of another embodiment of the invention in which a two roll breaker is utilized as a crushing means in conjunction with a separate static screening device.

Detailed Description Of The Invention Referring to FIG. 1, there is depicted one embodiment of the system and method of the present invention in which there is a clinker cooler 10 having a clinker discharge end 11 remote from clinker inlet end 12. It should also be noted that cooler 10 can be of any design and no particular specific type of clinker cooler is especially preferred for use in the present invention. Roll breaker 20 is positioned immediately after clinker discharge end 11.

Clinker material is transported through the cooler from inlet 12 to outlet 11 in the direction of Arrow C. It is a feature of the present invention that roll breaker 20 is located within the same enclosed environment as cooler 10, in that they both share a common housing which is, for example, comprised in part of enclosing roof 13 and end wall 14. No external transportation devices are required to transport material from the cooler to the roll breaker, and most preferably material will fall by gravity from clinker discharge end 11 to roll breaker 20.

A roll breaker suitable for use in the invention will contain at least two rolls in series, and generally between two to six rolls, and the top of each of the rolls may or may not be on the same horizontal plane. Roll breaker 20 consists of, in the depicted embodiment, four rolls in series designated by the numbers 21, 22, 23 and 24. Rolls 21 and 22 comprise screening and transport section 1. As such rolls 21 and 22 serve to screen out the smaller particles (which will pass through the gap 26 between rolls 21 and 22) and also to transport material to crushing rolls 23 and 24. The material falling between rolls 21 and 22 will be transported to the next step in the process, such as via conveyor 33.

In typical clinker cooling operations, the screening rolls will be placed relative to each other and the crusher rolls to screen out particles having a maximum size of about 20mm, although this invention is not to limited to any specific size for the screened particles, and it is further understood that the size of both the particle being filtered and the preferred size to which the larger material is comminuted are industry dependant, as mineral operations other than cement may have different size requirements, hi any event, particles larger than a specified size will be directed to crusher rolls 23 and 24 between which the particles will be comminuted to a desired size of less than about 20 mm in cement operations.

In one embodiment of the invention as set forth in Fig. 1, the rolls are not located on a straight horizontal line, but the uppermost point, i.e., the top, of the transport rolls 21 and

22 is located at a higher level than the top of the first crushing roll 23 that is immediately adjacent to the transport rolls so that material will naturally move to the first crushing roll by action of gravity, and, furthermore, the top of the last crushing roll 24, i.e., the roll furthest removed from the transport rolls, is located higher than the top of the crushing roll 23 to aid in preventing material from moving over crushing roll 24 and therefore not being crushed.

As depicted hi FIG. 1, the rotation of the transport rolls 21 and 22 and first crushing roll

23 are as specified by arrow A, which, in the perspective of FIG. 1, are rotating in a clockwise direction. Crushing roll 24 rotates in the direction specified by arrow B, which is the opposite direction from first crushing roll 23 to thereby draw the material into gap 27 located between the crushing rolls 23 and 24, whereupon the material will be broken down.

After the crushing step the still hot clinker is transported to a secondary material inlet 15 located between the cooler clinker inlet 12 and outlet 11 for further cooling. As depicted the clinker is transported by conveyor 34 to a transport device, which can be, for example, a mechanical transport device such as pan-conveyor 31, that feeds the material into a screw conveyor 32 which inserts the material to a cooler via inlet 15. Other forms of transport mechanisms suitable for use in the invention include other mechanical conveyors such as a drag chain conveyor or a non-mechanical conveyance means such as a hot fluidized bed conveying device. Preferably an air-lock feeder mechanism, such as screw conveyor 32, is used to insert the material into to cooler. Other feeder devices such as a rotary feeder or a flap valve can also be employed.

As indicated, material moves through cooler 10 in the direction of arrow C. In zone (1) material beneath a certain desired fineness is screened out of the cooled material and is sent to the next stage of the process, in the case of a cement process, finish grinding. This is material that is small enough to be effectively cooled by the cooler. Material above the desired fineness is transported to zone 2, in which such material is subject to crushing. This crushed material is still too hot for downstream operations and therefore is recycled back to the cooler.

Fig. 2 shows the use of a two roll breaker 120 in conjunction with a separate screening device 121 which takes the place of the initial transport and screening rolls 21 and 22 in a four roll breaker. The screening device is a "dynamic" screening device having at least one movable part. The specific device shown utilizes rotating discs, although other dynamic screening designs such as a reciprocating bar screener are contemplated for use in the invention.

Fig. 3 shows the use of a two roll breaker 120 in conjunction with an alternative separate screening device 221 which also takes the place of the initial transport and screening rolls 21 and 22 in a four roll breaker. The screening device depicted is a "static" screening device having only stationary parts. The device shown is a bar gizzly which is deployed at an angle so that material will move over it by gravity. Other static designs such as a screening grate are contemplated for use in the invention. It is also considered to be understood that other embodiments and modifications of the described embodiments are possible within the scope of the invention which is limited only by the attached claims.

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