DD300844A5 - Arrangement for the separation of fines for a fluidized bed opposed jet mill - Google Patents

Abstract

The invention relates to an arrangement for fine material separation for a fluidized bed counter-jet mill, which is used in ultrafine comminution of highly pure, highly abrasive, temperature-sensitive and / or difficult feinstzerkleinerbarer substances in Feinstkornbereich <100 Mym application. The technical object of the invention is to develop an arrangement for fines separation of the fine material contained in the feed material for a fluidized bed counter-jet mill, in which overmilling of this fine material is reliably prevented. According to the invention the technical object is achieved in that in the known fluidized bed counter-jet mill, which consists of a grinding chamber, arranged above the grinding chamber feed and a sifter, additional air jet nozzles are arranged between the feed and grinding chamber whose axes are inclined in the direction of viewers and cut before feeding in the middle of the process space.

Description

Ausführungsbelsplol

The invention will be explained in more detail with reference to an embodiment. For clarity, an arrangement according to the invention is shown in FIG.

The plant for ultrafine comminution, as shown in Figure 1, consists of a grinding chamber 1, the jet nozzles 2, the air jet nozzles 3, the feed 4, in the form of a metering screw, driven by the motor M1, the reservoir 5, the separator 6, driven by the motor M2, the filter 7, the discharge lock 8, the carrier gas finished product outlet 9, the discharge lock 10 and the process chamber 11. The feed from the reservoir 5 is fed via the feed 4 of the grinding chamber 1. The feed material and the already used material are transported to the separator 6 as a solid-gas fountain. The sieved fines pass through the carrier gas Fertiggut-Austriu to the filter 7, in which the ground material is separated from the carrier gas. The rejected by the classifier 6, coarse particles get back into the process chamber 11 and there are subjected to a further grinding process.

From Figure 1 it can be seen that the fines are first transported in the feed to the separator 6 and sighted so that it leaves the grinding chamber 1, before it is claimed. This process is supported by the two air jet nozzles 3, by the fine material is transported by superimposition of air flow and Mahlluftvolumenstrom targeted toward classifier 6 and the coarse material is acted upon only with the Mahlluftvolumenstrom. In this way, only the coarse material in the feed material are claimed and overmilling of the fines safely avoided, whereby the crushing intensity increases and thus the specific energy consumption is reduced.

About the discharge lock 8, the finished material mass flow m _F and on the discharge lock 10, the coarse material mass flow m _{G can be} deducted. The jet nozzles 2 are expediently charged with the same grinding air volume flow V _M. The same applies to the air jet nozzles 3, which are acted upon by the same air volume flow Vk. It is expedient if the air volume flow V _{K is} smaller than the Mahlluftvolumenstrom Vm, in order to prevent premature comminution and thus over-grinding of the fine material.

Claims (2)

1. Arrangement for fines separation for a fluidized bed counter-jet mill, consisting of a grinding chamber with grinding nozzles, a sifter and arranged between sifter and grinding chamber feed for the feed material, characterized in that between the grinding chamber (1) and the feed (4) within the Process chamber (11) air jet nozzles (3) are arranged, whose axes are inclined in the direction of the separator (6) and intersect in front of the feed (4) in the middle of the process space (11). 2. Arrangement according to claim 1, characterized in that the air jet nozzles (3) are acted upon by an air jet volume flow Vk, which is smaller than the Mahlluftvolumenstrom Vm. For this 1 page drawing Field of application of the invention The invention relates to an arrangement for fines separation for a fluidized bed counter-jet mill, which finds in Feinstzerkleinerung high purity, high-abrasive, temperature-sensitive and / or difficult feinstzerkleinerbarer substances in Feinstkornbereich <100μηι application. Characteristic of the known state of the art The known arrangements for fines separation consist of a separator which is arranged above the grinding chamber of the fluidized bed counter-jet mill and over which the fines are discharged via an air volume flow from the fluidized bed with a fineness determined by the visual parameters. The feeding of the feed takes place in known fluidized bed counter-jet mills in two different embodiments. In the first embodiment, the supply via a horizontally arranged metering screw, which is positioned at the bottom of the grinding chamber. This solution has the disadvantage that the fines in the feed before the classification is already claimed. From DE-OS 3338138 a fluidized bed counter-jet mill is known in which the supply also takes place via a metering screw, which, however, is arranged in the middle part above the grinding chamber. In both cases, the milled material is offered to the classifier exclusively with the grinding air and the fine particles are discharged. The disadvantage of this solution is that the fine material contained in the feed material is not removed in its entirety from the feedstock before comminution, which leads to a partial over-grinding of the remaining fine material. The oversize causes the specific energy consumption and agglomeration risk to increase. Object of the invention The object of the invention is to improve the comminution intensity while improving the quality of the final product and lowering the specific energy consumption with simple means. Explanation of the essence of the invention The technical object of the invention is to develop an arrangement for fines separation of the fine material contained in the feed material for a fluidized bed counter-jet mill, in which an over-grinding of this fine material is reliably prevented. According to the invention the technical object is achieved in that in the known fluidized bed counter-jet mill, which consists of a grinding chamber, arranged above the grinding chamber feed and a sifter, additional air jet nozzles are arranged between the feed and grinding chamber whose axes are inclined in the direction of viewers and cut before feeding in the middle of the process space. This additional air jet nozzles causes the fine grain fraction located in the feed material is transported directly to the classifier by the air volume flows exiting from the air jet nozzles and their superposition with the Mahlluftvolumenstrom and classified there, whereby the fine material contained in the feed material, the grinding chamber in full before a possible Stress in the grinding zone leaves. The air pressure of the air jet nozzles for fines separation is lower than the Mahlluftdruck, d. H. the air volume flow Vk is smaller than the Mahlluftvolumenstrom Vm- In this way, only the coarse material are claimed and thus prevents over-grinding of the fine material contained in the feedstock. The crushing intensity can thus be easily improved and the specific energy consumption can be reduced. The inventive arrangement also offers the further advantage that the fluidized bed counter-jet mill with abgeschalter.en grinding nozzles can be used as Sichteraniage. As a result of the low air volume flow, this machine variant makes it possible to create such flow conditions in the classifier, which permits a smaller separation grain size compared with the size-reduction variant. The coarse fraction is in this case withdrawn continuously at the bottom of the fluidized bed opposed jet mill through a rotary valve.