DD290317A7 - DEVICE FOR CONTINUOUS WET FINE REMOVAL OF SOLIDS - Google Patents

Abstract

The invention relates to a device for the wet ultrafine comminution of solids, preferably of mineral hard materials, which can be used anywhere where disperse systems must be produced with grain sizes 5 mm. The object of the invention is to achieve effective wear reduction and, without additional effort, wear protection on the moving parts with little design effort. The invention is characterized in that on the inner surface of the rotating at high speed Auszenzylinders a deposit of Mahlkoerpern and particles of the ground material is, depending on radial acceleration, Mahlkoerperanteil; Throughput and training of Mahlraumwaende before or during the grinding process is formed and forms a ringfoermigen effective Mahlspalt with the inner cylinder. The advantage of the invention is u. a. in achieving high levels of fineness at high power densities, in the gap adjustment enabled by the process and in the wear protection by the buildup of the layer. {Finely chopped, nasz; Solids; Verschleiszschutz; Inner cylinder; Auszenzylinder, rotating; Speed, high; Deposit; Grinding gap, effective; Subtleties, high}

Description

For this 1 page drawings

Field of application of the invention

The invention relates to a device for continuous wet comminution of solids, preferably of mineral ureas. It can be used wherever disperse systems mitteilchengrößen <5μιη must be generated.

Characteristic of the known state of the art

Up to now, predominantly high-speed stirred mills have been used for wet superfine grinding. The demands for highest subtleties with narrow grain size distributions e.g. in the production of structural ceramics powder (Mohs hardness> 5) led to the development of agitator mills with annular Mahlraumquerschnitt. In the so-called Ringspaltrnühlen (DE-AS 1184188, DE-OS 2811899, DE-OS 3106062) moves in a fixed outer grinding vessel, a rotor which is designed so that an annular gap results as a grinding chamber. The devices are distinguished by the outer shape (cylindrical, conical, biconical), by the type of Mahlkörperabtrennung or by various linings. The disadvantage of dioser devices is that the energy densities in the usual gap widths of & -10mm for a hard material shredding <1 μηι not sufficient. Furthermore, cost-intensive material-specific linings of the stress organs are required for the fulfillment of the high purity requirements. There are also devices in which rotates in addition to the rotor and the grinding vessel. The additional drive of the Mahlgetäßes a stirred mill (DE-AS 1223236) is to improve the grinding with smaller grinding media or autogenous grinding by additional centrifugal forces increase the grinding capacity of smaller grinding media. In the conical annular gap ball mill in DE-OS 3536454, the additionally driven grinding vessel should also serve to increase the grinding performance of the grinding beads by intensifying their movement.

The grinding beads are kept in motion on the inside of the grinding gap by the rotor and additionally on the outside of the gap by the grinding container. In both cases, the additionally driven grinding vessel serves only as an aid for the acceleration of smaller grinding media or for intensifying the grinding media movement. The required high shear gradients are to be achieved by the counter-rotating drive of rotor and grinding vessel, as well as a horizontal or vertical adjustment of the center axes of rotor and grinding vessel. The disadvantage here is the high design effort for the

Column setting or gap change. A Spaltvaränderung during grinding at the usual grinding grain filling degrees of 90% in the mill is not possible without causing Mahlkörperbruch. The positional losses of the inner rotor, which lead to an asymmetrical gap, have the disadvantage that thereby the advantageously narrow stress spectrum of an annular gap mill widened again. A type of wear protection in annular gap mills, which is achieved on the moving grinding vessel by the operation of the mill and at the same time leads to increase the grinding performance by a gap narrowing, is not known.

Object of the invention

The aim of the invention is a device for wet fine grinding of solids, preferably of mineral hard materials, achieved in comparison to the prior art with low design cost effective Feinstzerkleinerung and wear protection is achieved on the moving parts without additional effort.

Explanation of the essence of the invention The invention is based on the object, a device for wet fine crushing of solids, preferably

mineral hard materials to develop, in which the power density in the grinding chamber compared to the prior art is substantially increased, the necessary for the grinding gap adjustment is not realized by additional design measures, but by the process control and highest subtleties have been achieved. According to the invention, this object is based on a device consisting of an outer cylinder (2), which constitutes the grinding vessel, and a concentrically arranged inner cylinder (1) between which an annular grinding gap (4) is formed, the one from

Mahlgutteilchen, grinding media and liquid existing suspension is flowed through, solved in that the Inner cylinder (1) is arranged stationary and the outer cylinder (2) rotates at a speed, the radial accelerations

greater than 740 m / s * ² guaranteed and that an annular effective grinding gap (9) between the outer cylinder (2) and

Inner cylinder (1) by deposition (8) of grinding media and particles of the material to be ground on the rotating outer cylinder (2)

is formed.

Essential to the invention is that the effective grinding gap (9) by changing the radial acceleration and / or the Mahlkörperanteils and / or the throughput and / or the formation of Mahlraumwände is varied. It is essential to the invention that the inner cylinder (1) can be cooled and that the outer wall of the inner cylinder (1) and / or the Inner wall of the outer cylinder (2) have a profiled or feinrauhe surface. Furthermore, it is essential to the invention that the annular grinding gap (4) is filled with 50 to 100% grinding media, the grinding body

Preferably, the grinding media diameter is in the range of 0.1 to 0.6 mm and the inner wall of the outer cylinder has autogenous wear protection by the deposition (8) of meal bodies and particles of the ground material.

It is furthermore essential to the invention that the width of the effective grinding gap (9) is 3 to 5 times the diameter of the grinding media

is.

At different dimensions of the annular grinding gap (4) of the mill is with a constant effective Mahlspalt

worked.

Thus, with an annular grinding gap (4), the mill can be from 2 to 5 mm with a constant effective grinding gap (9) of 1.5

to 2 mm, which is 3 to 5 times the diameter of the grinding media, when the suspension batch for the

Grinding contains at least as much grinding media as a 100% filling of the respective grinding gap with grinding media

equivalent. In the effective grinding gap (9) highest shear gradients are generated, which are the prerequisite for an intensive

Represent fine crushing. Part of the grinding media is always in the solid deposit (8), the rest is free in the gap

mobile and runs with the millbase suspension. Since no Mahlkörper-Mahlgut-separation takes place in the mill, the

Size of usable grinding media not determined by a separator in the mill, and it is advantageously possible

to work with very small grinding media and thus a favorable size ratio of grinding media to Mahlgutteilchen.

By the variation of the Mahlkörperanteils in the suspension batch and an addition of Mahlkörpern during the grinding can

the width of the annular effective Mahlspaltes (9) are selected and changed during the grinding.

The structure of the solid deposit (8) on the inner wall (1) of the rotating grinding vessel is connected to a cylindrical shape of the Grinding vessel bound because over the entire height of the outer cylinder (2) constant centrifugal forces act and the structure

a rotationally symmetrical deposition (8) with a nearly constant layer thickness over the height of the grinding vessel is possible.

A profiled or feinrauhe surface of the inner wall of the outer cylinder (2) supports the structure of the deposit (8)

a grinding media Mahlgutschicht. Compared with the prior art, the invention has the following advantages:

- Achieving higher subtleties

- Achieving a high power density

- Column adjustment not by additional design means, but by the process control

- Gap change during grinding

- Wear protection of the moving parts by the building up layer; also species-specific possible and thus easy adaptation to any substance possible

- Use of very small grinding media possible

- easy material feed over the stationary inner cylinder

- Simplification of the procedural process by the ability to perform in a crushing stage Feinstzerkleinerung

- easy cooling of the inner cylinder.

The invention will be explained in more detail with reference to an embodiment.

FIG. 1 and FIG. 2 show an exemplary embodiment of the device according to the invention for fine comminution. The device essentially consists of a fixed, profiled inner cylinder 1 (outer diameter: 129 mm) and a driven outer cylinder 2 (inner diameter 135 mm), which is provided with 0.6 mm deep longitudinal grooves and a special removable cover 3. Between the inner surface of the outer cylinder 2 and the outer surface of the inner cylinder 1, an annular grinding gap 4 of 3 mm width is formed, which is connected via the intermediate space between the cylinder bottoms with the suspension feed 5 ending at the bottom of the inner cylinder 1. On the outer edge of Innepzylinders 1 is a take-off device 6 for the ground suspension.

The inner cylinder 1 is flowed through by cooling water (Kühlwasserzu- and -ablauf 7) and used for the suspension supply. The surface of the inner cylinder 1 is designed wear-resistant.

During operation of the annular gap mill, the suspension (600 cm ³ ), which consists of the solid SiC <20 pm with a specific starting surface of 4mVg and a liquid (water) with a Feststoffmassoanteil of 0.5, over the inner cylinder by means of a pump or self-priming annular grinding gap 4 supplied. The suspension also contains 380g specially prepared SiC grinding media of size 0.2-0.4 mm. This amount of grinding media corresponds to a 100% gap filling. At a speed of 2000min ^-1 and a throughput of 50l / h, a deposit 8 (consisting of SiC grinding media and SiC grinding stock) is constructed on the outer cylinder 2, which is the annular Mahlspalt 4 of 3mm width to an effective grinding gap 9 of 1, 5mm width (shown in Figure 2) narrows. Part of the grinding media (about 10%) circulates with the suspension. Due to the gap narrowing, the power density in the effective grinding gap 9 is doubled. This brings SiC products with an initial surface area of 4 m '/ g to a BET specific surface area of 20 m' / g. In quasi-continuous operation, the particle size x _{i7 is} reduced from 16μηι to 1.6 \ itr \ with average residence times in the mill of 6-8min. If the grinding process is started with a smaller amount of grinding media, then the addition of further grinding media makes it possible to change the width of the effective grinding gap 9 during grinding. In addition, the proportion of worn grinding media can be easily replaced during grinding.

Claims (9)

1. Apparatus for continuous wet comminution of solids, comprising an outer cylinder (2), which constitutes the grinding vessel, and a concentrically arranged inner cylinder (1), wherein between outer cylinder (2) and inner cylinder (your annular grinding gap (4) is formed, which is flowed through by a Mahlgutteilchen, grinding media and liquid suspension, characterized in that the inner cylinder (1) is fixed and the outer cylinder (2) rotates at a speed that ensures radial acceleration greater than 740m / s ^f2 and that an annular effective grinding gap (9) between outer cylinder (2) and inner cylinder (1) by deposition (8) of grinding media and particles of the material to be ground on the rotating outer cylinder (2) is formed, 2. Apparatus according to claim 1, characterized in that i'aß the effective grinding gap (9) is varied by changing the radial acceleration and / or the Mahlkörperanteils and / or the throughput and / or the formation of Mahlraumwände. 3. Apparatus according to claim 1, characterized in that the inner cylinder (1) is coolable. 4. Apparatus according to claim!, Characterized in that the outer wall of the inner cylinder (1) and / or the inner wall of the outer cylinder (2) have a profiled or feinrauhe surface. 5. Apparatus according to claim 1, characterized in that the annular grinding gap (4) is filled with up to 100% grinding media. 6. Apparatus according to claim 1, characterized in that the inner wall of the outer cylinder (2) has an autogenous wear protection by the deposition (8) of the grinding media Mahlgut layer. 7. Apparatus according to claim 1, characterized in that the grinding media diameter is preferably in the range of 0.1 to 0.6 mm. 8. The device according to claim 1, characterized in that the grinding bodies consist of species-specific material. 9. Apparatus according to claim 1, characterized in that the width of the effective grinding gap (9) is 3 to 5 times the diameter of the grinding media.