WO1989012497A1

WO1989012497A1 - A granulating method

Info

Publication number: WO1989012497A1
Application number: PCT/DK1989/000150
Authority: WO
Inventors: Peter Lip
Original assignee: F.L. Smidth & Co. A/S
Priority date: 1988-06-20
Filing date: 1989-06-19
Publication date: 1989-12-28
Also published as: PT90917A; DK335888D0; DK159643C; ES2016142A6; DK335888A; PT90917B; DK159643B

Abstract

A method of granulating material, such as lime powder or the like, wherein the material is subjected to mechanical working in a container. To obtain an improved granulate material, use is made of a working container with a horizontal or inclined axis of rotation about which the container and/or mixing means contained therein are rotatable. The container contains loosely situated working bodies, and the material is added with or is given such a degree of moisture that after treatment for some time in the container it sticks to the working bodies and peels off after a certain additional treatment period and is discharged from the container through a grate.

Description

A granulating method

The invention concerns a method of the type defined in the introductory portion of claim 1 „ Known granu¬ lating methods using rotary discs or screw conveyors are vitiated by various drawbacks, partly in the form of high costs, partly in the form of defects in the granulate produced, such as a too great size or layered structure which might result in a tendency to breaking or disintegration.

Methods of granulating are known in which either rotary discs or a screw conveyor system (an edge mill prin¬ ciple) is used. These known methods have several draw¬ backs. Thus, the rotary disc principle usually entails expensive plants, and furthermore the granulating method is inexpedient as the granulates proper obtain a layered structure causing the granulates to tend to break or disintegrate, when dried at high temperatures.

According to the edge mill principle the raw material is subjected to moistening in a screw conveyor,"grinding in a moistening edge mill, and typically passes through a vibrating screen or, via a so-called "mincing machine" principle, through a plate with holes adapted for that purpose, whereby the kneaded material is discharged in a number of lengths and is chopped into suitable pieces. This manufacturing process also entails rather heavy costs, and additionally it necessitates extensive pre- and aftertreatment of the raw material in view of the requisite moistening and kneading prior to chop¬ ping off. This manufacturing process provides granulates of a non ball-shaped nature, which is inexpedient when exposing the granulates to loads, e.g. by storage or transportation, which easily entails a certain waste of material . Thus, there has been developed a granulating system which uses a rotary mixing machine known per se, which, in combination with a new method, has been found to be advantageous for making granulates. The mixing vessel is here filled with a layer of ball-shaped objects, such as stones or the like. Using such objects in a rotary mixing container is known in connection with so-called ball mills, but the object here, in contrast to the object of the present invention, is to obtain comminution of materials.

The applicants' patent application 1026/87 filed on February 27, 1987 describes a method of the present type, wherein a vessel, which rotates about a vertical axis and is equipped with scraper means, is used as a working container. The bottom of the vessel is covered with a layer of substantially ball-shaped working bodies, and the moisture degree of the added material is regu¬ lated before or after adding, so that, after a certain time of working, the material settles as peels on the working bodies and peels off after additional working for some time and is finally discharged through a grate in the bottom of the vessel.

With this method it has been found possible to manu¬ facture stable granulates at low costs, e.g. with a greatest dimension of the order of 0.5-6 mm.

The present invention is based on the finding that correspondingly good results can be obtained in a work¬ ing container having a horizontal axis of rotation, and the characteristic features of the method of the invention are accordingly defined in the characteriz¬ ing portion in claim 1.

In this embodiment of the method, the speed of rotation is preferably kept at a low value, as stated in claim 2, such that the material will substantially be worked by pressure and rubbing.

Other expedient details are stated in claims 3-6.

Claims

P a t e n t C l a i m s

1. A method of granulating material, such as lime powder or the like, wherein the material is subjected to mechanical working in a container, c h a r a c - t e r i z e d by using a working container having a horizontal or inclined axis of rotation about which the container and/or mixing means contained therein are rotatable, said container containing loosely situated working bodies, said material being added with or being given such a degree of moisture that after treatment for some time in the container it sticks to the working bodies and peels off after a certain additional treat¬ ment period and is discharged from the container through a grate.

2. A method according to claim 1, c h a r a c t e r ¬ i z e d by keeping the speed of rotation of the con¬ tainer and/or the mixing means at such a low value that the working bodies remain in contact with one another.

3. A method according to claim 1, c h a r a c t e r ¬ i z e d in that the working bodies are made of metal, e.g. steel or aluminium, ceramic material, quartzite, densite or stone, e.g. flint nodules, and that their diameter is in the range 10 - 200 mm.

4. A method according to claim 1, 2 or 3, c h a r a c ¬ t e r i z e d by adjusting the moisture content of the added material to between 5 and 50%, preferably between 5 and 15%.

5. A method according any of the preceding claims, c h a r a c t e r i z e d by adding a binder, e.g. bentonite, lime hydrate, burnt clay, cement, carboxy- methyl cellulose, tar substances, glue or peridur, for binding the material in the individual granulates.

6. A method according to any of the preceding claims, c h a r a c t e r i z e d in that the treatment time is 2-60 minutes, preferably 5-10 minutes.