WO1994022616A1

WO1994022616A1 - Method and device for the mechanical regeneration of used sand

Info

Publication number: WO1994022616A1
Application number: PCT/NL1994/000071
Authority: WO
Inventors: Johannes Gerardus Van Gemert
Original assignee: Gemco Engineers B.V.
Priority date: 1993-04-07
Filing date: 1994-04-07
Publication date: 1994-10-13
Also published as: AU6545194A; NL9300606A

Abstract

In a method for the mechanical regeneration of, for example, clay-bonded and chemically-bonded sand, after first drying and cooling (if and when this is necessary) the used sand is ground with the aid of a grinding organ (3), whereupon the ground away foreign matter is separated from the thereby regenerated sand. To this end, the device for the execution of the method contains, in addition to the grinding organ (3), sand displacement means placed in its proximity, which sand displacement means (4) can move preferably concentrically around the grinding organ (3), and which sand displacement means (4) keep the sand moving at a relatively slow pace in order to ensure a uniform contact between the sand which is used and/or intended for grinding.

Description

Title: Method and device for the mechanical regeneration of used sand

Description

The invention pertains to a method for the mechanical regeneration of used sand, whereby, for example, one can think o sand attached to clay, but also chemically bonded sand or sand granules. Very particularly, one can think of formed sand or core san which is generally used in foundry processes, or of sand for othe industries, such as the filter sand used by water-utility companies and which, after single or multiple usage, becomes unusable. Because of the increasing costs of dumping such sand, the foundries (among others) are being forced to look for alternative solutions for the disposal of this old sand. In addition to the search for alternative applications for the sand in the road-building and the brick-making industries, for example for the longer term, because of the consequences it has for the environment, re-use is seen as the only acceptable and economically manageable solution to this problem.

A method for the regeneration-processing of largely clay- bonded used casting sand is known from NL-A-9002597, which known mechanical regeneration-processing is not suitable in practice fo the processing of sufficient quantities of other types of used sand. .,-

Accordingly, it is the aim of the current invention to provide a universal method and device suitable for multiple types of sand (which may or may not be 'used') , which method and device can be operated^' at minimal^",operational, maintenance and energy- costs.

To that end, the method for the mechanical regeneration of used sand in accordance with the invention comprises the measures that, subsequent to drying and cooling of the used sand (if and when this is necessary) , a grinding organ with which the sand is brought into contact is used for grinding purposes, subsequent to which the ground material is separated from the thereby regenerated sand. The method according to the invention thereby creates possibilities in the processing of, in principle, all kinds of used sand or granulate where the sand grains are enveloped with foreign matter. A good regeneration and a high yield are guaranteed as a result of the sand grains' being ground while being in direct contact with the grinding organ, but also because the grains exert a scouring action on each other, whereby an additional processing at the soiled outer surface of each sand grain occurs. Moreover, it is of advantage that the form of the sand grain in the case of so-called 'old' sand or 'new' sand will become more rounded as a result of the application of the method according to the invention; a fact which improves the qualities of the regenerated sand.

In a further embodiment of the method according to the invention, the sand, before being brought into contact with the moving grinding organ, is brought into a circulating motion around the grinding organ.

Of advantage hereby is the fact that the circulating motion leads to a homogenous distribution of the sand alongside the generally rotating grinding organ, whereby all of the sand comes into contact with the grinding organ to the best degree possible.

In a further refinement of the method according to the invention, the foreign matter separated off by the grinding process is dusted down, whereby the usable components are

>»_ extracted from the material.

It'is of advantage hereby that, in particular in the case of the use of e.g. used "clay-bonded" casting sand, the usable components, which in that case consist of bentonite and carbon powder, can be reclaimed and re-used. The device for application of the method for the mechanical regeneration of soiled sand is constructed from a largely cabinet- shaped body, within which body one or more grinding organs are located, in whose proximity sand displacement means are set up in a manner such that they are movable. In a further refinement of the device according to the invention, the grinding device is rotatable, whereby the sand displacement means are preferably (concentrically) movable around the grinding organ; this is a topology which enjoys preference from the point of view of construction. In a special embodiment of the device according to the invention, the grinding organ and the sand displacement means are located to one side of dust-separation means fitted to the cabinet-shaped body, and a dust exhaust is located at the other side.

The advantage of this embodiment of the device according to the invention is that lubricating effects, which have a negative influence on the grinding of the sand and are largely accounted for by the presence of dust lying between the sand grains which are to be regenerated, occur to an extremely diminished degree.

In a further preferential embodiment of the device according to the invention, the sand displacement means have preferably curved shovelling organs, whereby the capacity of the total amount of sand which can be moved around the grinding organ with the aid of the displacement means is increased even further.

The current invention and the thereby related advantages shall now be further elucidated on the basis of the attached drawing, within which:

Figure 1 depicts a preferential embodiment of the device for the mechanical regeneration of used sand; and

Figures 2 and 3 depict preferential embodiments of dust extraction means for application in the device shown in figure 1.

Figure 1 shows a possible embodiment of a device for the implementation of the method for the mechanical regeneration of used sand. The used sand or granulate is generally, subsequent to prior drying and cooling if and when this is necessary, directed to the device 1 shown in figure 1. The used sand is directed to the largely cabinet-shaped device 1 via a feeder 2 placed therein. In the depicted embodiment of the device 1, a grinding organ 3 is located at the undermost side of the device 1, which grinding organ 3 is schematically depicted as a generally rotatable grinding organ. Movable sand displacement means 4 are located in the proximity of the grinding organ 3. It is shown that the sand displacement means 4 can be moved concentrically around the grinding organ 3. In the depicted embodiment, an exhaust 5 is located on the undermost side of the device 1, from which exhaust 5 the contents of the device 1 can be extracted if desired.

Subsequent to the loading of the device 1, the used sand particles come into contact with the grinding organ 3, which grinding organ 3 normally rotates at a high speed. The rate of revolution of the grinding organ 3 will often lie in the order of several hundred to even thousands of revolutions per minute. The sand particles which are thereby vigorously excited into motion are ground at their outermost surface, whereby the foreign materials located in and on that outermost surface of the sand particles are ground away. The sand grains move not only against the grinding organ 3, but a grinding action is also achieved by means of mutual frictional rubbing of the particles during their circulation, whereby the surrounding foreign particles are also ground off the sand grains. During this process, the total quantity of the used sand which is located in the device 1 is kept in a circulating motion around the grinding organ 3 by the motion of the sand displacement means 4. The sand displacement means 4, however, move with a much lower speed which will usually lie in the range of several tens of revolutions per minute. The direction of motion of the sand displacement means 4 can be either opposite to, or in harmony with, the direction of motion of the grinding organ 3. After the contents thereof have been ground for a certain period of time, the exhaust 5 can be opened and, if desired, the contents can be directed to an extra dust-off installation in order to free the clean sand from foreign particles which exist in the form of dust; the sand can otherwise be directly used without first undergoing suc -h<*_ a suppl_'emental cleaning. Dust separation means 6 are included in the embodiment of the device 1 as depicted in figure 1. A dust exhaust 7 is located at the uppermost end of the cabinet-shaped body,-^* while an air intake 8 has been fitted in the proximity of the undermost end. During the grinding process, air is injected via the air intake 8, which air, together with the dust separated from the sa d grains, is sucked out at the dust exhaust 7.

Figures 2 and 3 depict some preferential embodiments of profiles 9, which profiles 9 are placed at regular distances from each other and, in particular, are V-shaped. The depiction shows isosceles V-shaped profiles 9 turned over at an angle of approximately 90 degrees, which V-shaped profiles 9, in the embodiment of figure 2, are placed with their respective tops 10 in opposite directions to each other, while in the embodiment of figure 3, the tops consistently point upwards. It goes without saying that other embodiments of the dust separation means 6 are possible. If desired, subsequent to the collection of the dust from the dust exhaust 7, the usable components of the dust can be further extracted, although it is also possible to extract these useful components during the grinding process by means of an optimal tuning of the grinding and the dust-off processes..

The embodiment of the sand displacement means 4 with shovelling organs, as depicted in figure 1, can, in order to increase the total capacity in respect of the amount of sand displaced thereby in the device 1, be equipped with extremes 11 indicated by dotted lines, which extremes 11, in the case of a direction of rotation of the sand displacement means 4 in the direction of the arrow, are curved in the indicated manner. In this way, the sand dislodged by the curved extremes 11 when the sand displacement means 4 are to all intents and purposes vertica shall be forced to come into contact with the rapidly rotating grinding organ 3.

The grinding process itself is in general governed by a number of process parameters, including the grinding time, the quality of the grinding organ, the rate of revolution of the grinding organ 3, the degree of loading of the device 1, the grinding-resistance of the soiled sand, the degree of dust-off, and the like. The magnitude of these process parameters will ofte be determined on the basis of practical experience. The currently described method and device are applicable for use in burst modes or for continuous operation. Within the scope of what has been described up to this point, -it is possible to apply several grinding organs 3 and sand displacement means 4 in one and the same housing.

Claims

C A I M S

1. Method for the mechanical regeneration of used sand, whi sand, subsequent to a possibly necessitated prior drying and cooling, is ground with a grinding organ (3) with which it is brought in contact, subsequent to which the ground away foreign material is separated from the sand which is regenerated in this manner.

2. Method in accordance with claim 1, whereby the sand, before being brought into contact with the moving grinding organ (3), is brought into a circulating motion around the grinding organ (3) .

3. Method in accordance with claim 1 or 2, whereby the grou away foreign material is dusted off, whereupon the usable components of the material are reclaimed.

4. Device for the application of the method according to one of the claims 1-3, constructed from a largely cabinet-shaped body within which body a grinding organ (3) is situated, in the proximity of which grinding organ (3) sand displacement means (4) are set up in a manner such that they can be moved.

5. Device in accordance with claim 4, whereby the grinding organ (3) can be rotated.

6. Device in accordance with claim 4 or 5, whereby the sand displacement means (4) are set up in a manner such that they can be moved around the grinding organ (3) .

7. Device in accordance with one of the claims 4-6, whereby the sand displacement means (4) can be moved-concentrically aroun the grinding organ (3) .

8. Device in accordance with one of the claims 4-7, whereby the sand displacement means (4) Hkve extremes (11) embodied as shovelling organs.

9. Device in accordance with claim 8, whereby the shovelling organs are curved in such a manner that, upon movement of the san displacement means (4) , the sand is moved in a direction towards the grinding organ (3) .

10. Device in accordance with one of the claims 4-9, whereby the grinding organ (3) and the sand displacement means (4) are located to one side of dust-separation means (6) fitted to the device (1) , and a dust exhaust (7) is located at the other side.

11. Device in accordance with claim 10, whereby the dust- separation means (6) are embodied as profiles (9) placed at regular intervals from each other.

12. Device in accordance with claim 11, whereby the profiles (9) are largely V-shaped in form.

13. Device in accordance with claim 11 or 12, whereby the profiles (9) are embodied in an isosceles manner.

14. Device in accordance with claim 12 or 13, whereby the V- shaped profiles (9) are turned over at an angle of approximately 90 degrees.