WO2002009880A1

WO2002009880A1 - Process and apparatus for the milling, drying and separation of raw material

Info

Publication number: WO2002009880A1
Application number: PCT/IT2000/000319
Authority: WO
Inventors: Stefano Barbetti
Original assignee: Stefano Barbetti
Priority date: 2000-07-27
Filing date: 2000-07-27
Publication date: 2002-02-07
Also published as: AU2000264698A1

Abstract

A process and an apparatus are described for carrying out a centrifugal grinding and, possibly, drying and separation of the ground material simultaneously with the grinding. The apparatus comprises a main body (1), a support structure (2), at least one exit pipe (3) for ground material, and is characterized in that it also comprises means of centrifugation (5) of the material to be ground; first means of grinding (8); means of actuating (10, 12) said means of centrifugation; and means of conveying (31) the ground material towards a collection area.

Description

PROCESS AND APPARTUS FOR THE MILLING, .DRYING AND SEPARATION OF RAW MATERIAL

DESCRIPTION The present invention relates to a process and an apparatus for the grinding and simultaneously the drying and separation of raw material and, in particular, to a process and apparatus for grinding, possible drying and separation which is performed by this process through centrifugation of the material. < Currently, apparatuses are known which perform the grinding of raw material through centrifugation of the same . According to a first type of such grinding apparatus, a rotating plate is provided which is enclosed inside a container and a collector body, with the material to be ground being conveyed onto this plate. When the material to be ground touches the rotating plate, it is conveyed, due to centrifugal force, towards the outside of the plate, thus progressively increasing its own kinetic energy. At the peripheral part of the plate a perimetrical partition is provided against which the material hits at high speed. The particles of the hitting material break and the grinding of the material is thus obtained. At this point the material stops and is then collected or conveyed to a successive phase of separation or drying if required.

There is, furthermore, a second type of improved centrifugal grinding apparatus wherein there is provided a rotating disc known as a rotor, with the latter being provided with partitions arranged in an intermediary position with respect to its diameter. These partitions produce a surface on which the material impinges during its centrifugation and breaks, whereafter it is successively centrifuged towards the outside of the rotor where the material again impinges against the outer partitions of the .body enclosing the rotor. According to a constructional solution such as this, a "double" grinding centrifugal effect is obtained. However, The types of apparatus as described above present certain disadvantages. An initial disadvantage is that of the transmission of kinetic energy to the material through dragging and hitting on a rotating surface which leads to very low yields and significant wear on the mechanical parts. As a result, this type of apparatus, during the intrinsic industrial process, requires large amounts of energy to process low quantities of material to be ground. A second disadvantage is that to date all types of apparatus such as the above described one are constructed in a way "dedicated" to the type of material to be processed and, as a result, they totally lack versatility. A third disadvantage is that during grinding, the material impinging against the partitions of the apparatus tends to form particles which bind together with the material which the apparatus is made of, even though this occurs only in microscopic quantities, thus resulting in a contamination of the material that is ground in this manner, as well as in significant wear of the apparatus .

A fourth disadvantage is that of such types of apparatus for grinding do not in anyway provide for the possibility of carrying out the drying and/or separation phases of the ground material, thereby requiring further different and separate apparatus to perform the above mentioned phase of drying and separation.

A fifth disadvantage is that until now all types of apparatus for grinding are cumbersome and heavy, of complex design requiring a high amount of maintenance, thus leading to an increase in running costs and the cost of the finished material.

It is therefore an object of the present invention to overcome the aforementioned disadvantages by providing an apparatus and a process for grinding wherein the material to be ground will not become contaminated by the grinding process, thus allowing the grinding of any type of material .

A further object of the present invention is that of supplying an apparatus and a process for grinding wherein it is possible to carry out simultaneously, if required, the phase of grinding, drying and/or separation.

Another object of the present invention is that of supplying an apparatus and a process for grinding with high efficiency and with reduced machine times, major versatility, of compact size and low weight and, last but not least, with reduced running costs.

Further advantages and objects of the present invention will be explained below in more detail wherein a detailed description of some preferred embodiments of the present invention will be provided making reference to the attached drawings, and given by way of example without limiting the invention in any way and, wherein:

Figure 1 shows a perspective and partially sectional view which illustrates the entirety of the apparatus according to a first embodiment of the present invention;

Figure 2 shows a diagrammatic view in elevation which partially illustrates the apparatus in Figure 1;

Figure 3 shows a diagrammatic plan view of the apparatus in Figure 1 ; Figures 4a, 4b and 4c show plan views which diagrammatically illustrate three different embodiments of the apparatus according to the present invention;

Figures 5a, 5b show plan views which diagrammatically illustrate a further two different embodiments of the apparatus according to the present invention;

Figure 6 shows a diagrammatic plan view which illustrates in detail a part of the apparatus according to a fourth embodiment of the present invention; Figure 7 shows an elevational and partially sectional view of the part of the apparatus in Figure 6;

Figure 8 shows a diagrammatic plan view of a part of the apparatus according to a fifth embodiment, and

Figure 9 shows an elevational view which partially illustrates the part of the apparatus in Figure 8.

Figure 1 shows a first form of embodiment of the apparatus according to the present invention.

According to the invention, the apparatus has a main body 1 mounted on a supporting structure 2 and connected underneath to a tapered pipe 3 for collecting the ground material . In addition, it is provided that the tapered pi e 3 is connected underneath to a control valve 30 connected to an Archimedian screw device 31 to convey the ground material in a way already known per se.

The main body 1 has a substantially cylindrical shape above which a movable closing partition 4 is provided. As will be better understood further on, the partition pneumatically closes off the inside of the main body 1. Inside the main body 1, there are 3 rotors 5 each one of which has, at the central area thereof, a distribution pipe 6 for the material which is pneumatically connected to an external pipe 7 for feeding the material by means of an appropriate connection member 70 (this will be explained in more detail below and in fig. 9) .

Each rotor 5 has on its inside a plurality of pipes 8 for grinding the material which are pneumatically connected to the inlet pipe 6 and communicate with the outer area of the rotor. The pipes 8 preferably have a circular section. In correspondence with the outer area of each rotor 5, there is a ring-shaped partition (or track) 9 which is an integral part of the main body 1 (explained below in further detail) .

In addition, each rotor 5 is attached to a respective transmission shaft 10 mounted in a swiveling manner on the support structure 2 and across the tapered pipe 3. Each shaft 10 is connected synchronously to an electric motor 12 by means of a transmission 11 for the simultaneous actuation of each rotor 5. The transmission 11 is of the tooth belt pulley type to ensure the synchronism of the rotors 5.

Further on, in correspondence with the upper part of each rotor 5, there is a plurality of partitions or blades 13 arranged in an integral way which as a whole constitute the separator for the ground material. The partitions or blades 13 can be mounted on the rotor 5 in a fixed, or, alternatively, swiveling way in relation to the radial direction of the rotor 5 (explained below in more detail) . On the movable partition 4 and at the area of the blades 13 there ^' is an outlet 14 provided for the suction of the material separated inside the main body 1.

Figure 2 explains the process of grinding the material by means of the apparatus according to the present invention. In principle, the material to be ground is conveyed by means of a distributor and rotating mixer 15 through the pipes 7 and towards the distribution pipes 6 in the rotors 5. From here the material is centrifuged inside the pipes 8 towards the outside, where, during the passage through the pipes 8, the first grinding of the material occurs due to reciprocal impact between the particles of the material per se.

Alternatively, the said distributor and rotating mixer can also be situated upstream the apparatus. At this point, when the material is discharged from the rotor 5, it is expelled with a velocity and direction equal to the vectorial sum of the radial and tangential velocities of the rotor 5 and thus goes and strikes against other material revolving around the rotor, thus performing a second grinding of the material . The striking of the expelled material against other expelled material which is circulating creates a disintegration of the material which is proportional to its kinetic energy.

This is carried out until it stops onto the ring- shaped partitions 9. Once the material has stopped, it starts to fall towards the bottom where it is collected by the pipe 3 underneath and conveyed to the collection area. At the same time, the smallest part of the thus ground material is sucked towards the top as a result of the suction applied to the suction outlets 14 where, passing across the blades 13, the coarser part is separated from the finer one by centrifugation of the former. Thus, only the lightest part can be sucked through the apertures 14, while the heavier part is removed from the blades 13 and tends to fall towards the bottom again where it is conveyed to the collection area. From here, the material can undergo a screening phase to be separated and thus its coarser part can be reintroduced into the grinding cycle as described above as recycled material with new material through the mixer and distributor 15. Figure 3 shows a diagrammatic view of the operation of the apparatus according to the present invention. More precisely, the material once conveyed inside the rotor 5 is first homogeneously distributed in the circular direction by means of the distributor pipe 6 which is also in rotation, which material is then pulled by centrifugal force to the inside of the pipes 8, where its velocity increases. The accelerated movement creates micro impacts between the various particles of material thus carrying out a first grinding of the material without having to physically strike parts of the apparatus . The material is given maximum energy in a single step. Thus, corresponding to the peripheral area between the rotor 5 and track 9, the material is expelled at a velocity which is the vectorial sum of its radial and tangential velocity (thus with a greater modulus than the single peripheral velocity of the rotor 5) , thus proceeding to strike the already expelled material which is revolving between the rotor 5 and track 9, disintegrating and thus effecting a second grinding of the same. Notice should be taken here that depending on the material or the diameter of the material which is to be obtained, an appropriate device can be provided by varying the diameter of the ring-shaped track 9 during the operation of the apparatus.

At this point, the coarsest portion of the material tends to fall towards the bottom while the semi-fine portion tends to be sucked towards the top by the suction outlets 14. The passage across the blades 13 is forced, where the physical separation of the finer particles occurs being immediately sucked into the outlets 14, whereas the heavier particles are centrifuged by the blades 13. It should be noted, that the blades 13 can be mounted on the rotor in a swiveling manner in order to enable a reduction of the passage way between each blade and thus perform a calibration of the size of the suctionable particles. Figures 4a, 4b e 4c show three different embodiments of the apparatus according to the present invention, wherein the apparatus has one, two or three rotors respectively arranged with their axis of rotation horizontally. In particular, from now on, for the sake of simplicity, parts will have identical numbers and their detailed description will be omitted as it has already been given previously.

According to these embodiments, it is provided that the apparatus has each rotor 5 arranged with its own axis of rotation along the horizontal direction. In addition, it is provided that the main body 1 and the collection pipe 3 coincide, presenting a cylindrical shape which encloses the rotor (s) 5. Under the main body 1 an outlet for collection and conveyance of the ground material is provided as described above. A constructional embodiment such as this has shorter shafts 10 and the two bearings outside the main body 1. Advantageously, a solution such as this is much more compact in terms of weight and size as compared with the previous embodiment .

Also according to the embodiments above described, the separator devices 13 can be provided as part of the rotors with the advantageous possibility of having rotors 5 with separator devices 13 on both of the vertical faces of the main body 1, thus providing perfect symmetry of the apparatus . Figures 5a and 5b now show two further forms of embodiment of the apparatus according to the present invention wherein, according to figure 5a, three rotors 5 are provided with axis of rotation thereof being horizontally arranged and three rotors 5 are provided with axis of rotation thereof being vertically arranged, while according to figure 5b two rotors 5 are provided whose axis of rotation is horizontal and 2 rotors are provided whose axis of rotation is vertical .

More precisely, it is provided according to these two forms of embodiment that the ring-shaped track 9 is interrupted corresponding to the barycentric area or central to the main body 1 above the collection pipe 3. By doing this a third grinding of the material is performed because the material is ejected by one rotor 5 against the material coming from another rotor 5, thus conveying the material coming from all the rotors 5 at the central area 100 of the main body 1. In this way, impacts are created exclusively between particles of the same material against other particles of material when they are thrown against each other, thus obtaining the disintegration of the material without contamination of the particles by other material of the apparatus, this due to the absence of impacts between material and apparatus . In addition, it is possible to expel the material at the open area of the ring-shaped track 9 by means of a synchronized expulsion device 16 mounted on each rotor 5 and as explained below in closer detail .

Furthermore, as can be understood from the figures where the rotors 5 are arranged in sets oriented orthogonally in relation to each other, it transpires that an arrangement such as this does not alter the grinding efficiency and at the same time there is a reduction in the bulkiness of the apparatus. The principle of open tracks at the area where they coincide is also valid in non-orthogonal embodiments. In the same way as described previously, it is also possible for this embodiment to provide for the separation of the material by means of the blades 13 mounted on the rotors 5.

Figures 6 and 7 show the expulsion device 16 of material from rotor 5. More exactly, according to this embodiment, the rotor 5 comprises, at the outlet of each pipe 8, a tilting valve 17 mounted in a hinged way on a supporting plate 170 which is an integral part of the rotor 5. The valve 17 is actuated by a cam follower 18 which is also mounted in a hinged way on a plate 180 in a sliding and blockable way on the bottom part of the rotor 5. The delivery cam 18 is maintained in its position by centrifugal force. The connection between valve 17 and delivery cam 18 is performed by a thin shaped member 19 or the like. On the other side a freely rotating cam 20 is provided mounted underneath the rotor 5 and in central position to the main body 1 in such a way so as to be capable of cooperating with two or more rotors 5 simultaneously (only one of these is shown in the figures) .

The arrangement of the rotating cam 20 is such that during the rotation of the rotor 5, the cam follower 18 strikes the track of the cam 20 and moves the thin shaped member 19, which in turn opens the valve 17 under the action of a spring or the like, the opening of the valve 17 enables the synchronized outlet of material from the rotor 5. Notice should be taken here that the arrangement of the members as described above is symmetrical for each pipe 8 of each group of rotors 5, thereby performing, during the operation of the apparatus, the synchronized opening of a pipe 8 of a respective rotor 5 in the same direction where the material coming from another adjacent rotor 5 is conveyed. Furthermore, the plate 180 being blockable in a sliding way allows adjusting the opening advance of the valve 17 during the rotation of the rotor 5. Figures 8 and 9 show a further embodiment of the apparatus according to the present invention.

According to this embodiment, each pipe 8 of a respective rotor is provided with an externally ending tubular connection member 21 with an inclined closing partition 22 and a lateral outlet 23 for the discharge of the material. The function of the member 21 is that of carrying out a further grinding of the material when the latter reaches the closing partition 22 and strikes against it. Furthermore, the existence of the inclined partition 22 creates an undercut region 24, which allows the creation of a layer of material which remains adhered to the latter by centrifugal force. The layer of material creates a bed of material where other material, coming from the pipe 8, will strike before being expelled, thus avoiding the contamination of the latter due to the absence of impacts between material and mechanical parts. An experimental example performed with the apparatus according to the present invention is provided below. EXAMPLE An apparatus with a vertical shaft was used which was provided with the following parameters :

Using the above apparatus, 47.5 kg of cement clinker having an initial size of 10.0 - 2.5 mm was subjected to a grinding cycle, with initial fineness as given in the following table (values expressed as % by weight in relation to the total weight) :

Thus, grinding of all the material for a time of 44 sec. was carried out, and the following fineness was obtained:

It should be noted that with the material of a size less than 63 μm being considered cement, the efficiency of the apparatus was 10.8 % x 47.5 kg = 5.13 kg of finished material.

The productive capacity of the apparatus with the rotor turning at 1200 rpm yielded the following results:

5.13 (kg) x 3600 (sec/h) / 44 (sec) = 420 kg/h

In addition, the motor's power consumption was measured which turned out to be 7.6 kWh. Therefore, the yield of the apparatus was :

7.6 (kWh) / 0.420 ton = 18.1 kW/ton

As it can be understood, this value is significantly lower than those obtained with apparatuses of the state of the art, which are generally around 45 kW/ton.

The present invention has numerous advantages .

A first advantage is the fact that it is possible to carry out the drying and the separation of the micronized parts from grinding simultaneously with a single piece of apparatus. In fact, due to the energy exchange during the impacts, the material is able to lose a considerable part of water vapor due to the disintegration and its rise in temperature, thus carrying out the drying and the grinding of the disintegrated particles at the same time. Another advantage is the fact that due to its constructional design the apparatus requires less power as compared to volumes treated by state of the art apparatuses .

A further advantage is that the working time of the material which provides for simultaneous grinding, drying and separation is consistently reduced.

In addition, according to another advantageous aspect of the present invention, a high re-cycling capability of the material is provided, therefore allowing the production of granules by means of screening separate from the apparatus. Thus it is advantageously possible to obtain simultaneously micronized particles between 5 ÷.15 μm and granulated between 1 or more mm, or in-between with fractions of millimeter sizes, the latter being especially relevant for the production of pre-mixes destined for building.

A third advantage is that all the available energy from the rotor is transmitted to the material and the grinding occurs by means of impacts and friction between the material to be ground and not between the material to be ground and mechanical parts, thus reducing the wear on and the maintenance of the apparatus .

Another advantage is the possibility of managing the grinding by means of control parameters during all the phases of the grinding process, which was not possible up until now, thus making the apparatus suitable for any type of material to be ground, ranging, for example, from foodstuffs to strongly abrasive material, and producing ground products of any type.

A further advantage is the fact that the volumes of air treated by the apparatus are significantly lower than state of the art apparatus, thus reducing external pollution.

Claims

1. A process for grinding raw material in a centrifugal apparatus, characterized in that it comprises the following phases: - conveying the raw material inside a pneumatically controlled part of apparatus (1) and in correspondence with means of centrifugation; centrifuging the material through a plurality of centrifuging pipes (8) ; - carrying out a first grinding of the material during its transfer to the inside of the said plurality of centrifuging pipes (8) by means of impacts between material/material and material/partitions; - carrying out a second grinding of the material by subjecting the same to impacts at the exit area (9) from said plurality of centrifuging pipes (8) ; and conveying by discharging the thus ground material to a collection area.

2. A process for the grinding of raw material according to claim 1, further comprising the following phases : centrifugally separating inside of the said pneumatically controlled apparatus (1) the microscopic particulates from the ground particles of the material, obtained after the said first and second phases of centrifugal grinding through means of separation (13) ; - sucking said microscopic particulates from inside of the said pneumatically controlled apparatus (1) ; and conveying said microscopic particulates towards a collection area (14) . 3. A process for the grinding of raw material according to claim 1 or 2 , further comprising the phase of drying the material during the said first and second phase of grinding through forced convection and heat exchange of the energy coming from the impacts of the material or possible additional heat exchange.

4. A process for the grinding of raw material according to claims 1 or 2 or 3 , wherein said second phase of grinding occurs through impacts between centrifuged material and material revolving around said means of grinding (5) at said exit area (9) inside of the said apparatus (1) . 5. A process for the grinding of raw material according to any one of the previous claims, comprising in addition a third phase of grinding by providing impacts between material and other material at an area (100) barycentric to the apparatus (1) . 6. A process for the grinding of raw material according to any one of the preceding claims, further comprising the following phases: screening of the material conveyed to the collection area; and - sending the screened material of predetermined dimensional size to the apparatus (1) to undergo a further grinding.

7. An apparatus for the grinding of raw material comprising a main body (1) , a supporting structure (2) , at least one inlet pipe (7) for material to be ground and at least one outlet pipe (3) for ground material, the apparatus being characterized in that it comprises in addition: means of centrifugation (5) of the material to be ground; first means of grinding (8) ; means of actuating (10,12) the said means of centrifugation; and means of conveying (31) the ground material towards a collection area.

8. An apparatus for the grinding of raw material according to claim 7, wherein the said means of centrifugation is at least one rotor (5) with a central inlet (6) for the admission of the material to be ground connected with said first means of grinding (8) .

9. An apparatus for the grinding of raw material according to claim 7 or 8 , wherein the said first means of grinding is a plurality of pipes (8) arranged radially in each of said at least one rotor (5) and pneumatically connected with the said central inlet (6) and with the peripheral partition of said rotor (5) . 10. An apparatus for the grinding of raw material according to claims from 7 to 9, further comprising means of separation (13) of the ground material arranged internally in the said main body (1) and being an integral part of the said at least one rotor (5) . 11. An apparatus for the grinding of raw material according to the previous claim, wherein said means of separation are a plurality of partitions (13) externally being integral to each of the said at least one rotor

(5) , with the partitions (13) being arranged along the radial direction of said rotor (5) and pneumatically connected to the outside of the apparatus through an outlet (14) for suction in the said main body (1) .

12. An apparatus for the grinding of raw material according to the previous claim, wherein the said plurality of partitions (13) are mounted in a hinged way onto said rotor (5) in such a way as to be capable of orientation in respect of the radial direction of said rotor (5) .

13. An apparatus for the grinding of raw material according to any one of claims 7 to 12, wherein the said means of actuation are at least an electric motor (12) with a transmission of motion (11) connected to the said at least one rotor (5) .

14. An apparatus for the grinding of raw material according to the preceding claim, wherein the said at least one electric motor (12) is a variable speed motor.

15. An apparatus (1) for the grinding of raw material according to anyone of claims from 7 to 14, further comprising an exit area for the material

' delimited between said rotor (5) and a ring-shaped track

(9) arranged externally and perimetrically corresponding with the peripheral area of the said at least one rotor

(5) .

16. An apparatus for the grinding of raw material according to the previous claim, wherein the said ring- shaped track (9) is suitable for varying its diameter during the operation of the apparatus.

17. An apparatus for the grinding of raw material according to claims 8 to 16, further comprising: a valve (17) arranged at the exit aperture of each pipe of the said plurality of pipes (8) ; - a rotatable cam (20) and arranged under said rotor (5) ; and a cam follower (18) arranged at each valve (17) operatively connected to the latter and for cooperating with the said cam (20) . 19. An apparatus for the grinding of raw material according to claims 8 to 16, further comprising an end pipe (21) mounted at each exit outlet of a respective pipe (8) of said plurality of pipes (8) and with an inclined end closing wall (22) and an exit outlet (23) for the ground material .

20. An apparatus for the grinding of raw material according to any one of claims 7 to 19 , wherein the said means of conveying of ground material are a pipe

(30) and an Archimedian screw arranged under the said apparatus .

21. The ground material obtained through the process and apparatus according to the preceding claims.