DE2122452A1 - METHOD AND DEVICE FOR GRIND DRYING - Google Patents

Description

P 1770

Polysius AG., Neubeckum

Method and device for grinding drying

The invention relates to a method and a device for grinding drying using a means a hot gas flow heated multi-chamber mill with central discharge.

For the mill-drying of moist material, single-chamber mills with a final discharge are available in various designs, in particular known as air flow mills or mills with a bucket elevator. Their main disadvantage is that that in a single grinding chamber there is generally no optimal comminution from gravel size to flour fineness can be achieved.

It is also known to use multi-chamber mills with a central discharge for grinding and drying, which in terms of grinding technology is a enables optimal shredding. However, this causes difficulties with relatively low-temperature Exhaust gases to achieve adequate drying of moist material, since the gas volume to be drawn through the system is limited is.

The invention is therefore based on the object of creating a method and a device for grinding drying, when using a two-chamber mill with central discharge the advantage of optimal grinding with that of a large one Connect drying performance.

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The object is achieved according to the invention in that part of the hot gas flow is fed directly to the center discharge by bypassing the pre-grinding chamber and to the pneumatic conveyance of the material is used to a part of the plant downstream of the mill.

In this way it is achieved that the material discharged from the pre-grinding chamber during its pneumatic Conveyance to a system part downstream of the mill, in particular a sifter, for intensive post-drying is subjected to by the hot gas stream. Since a substantial part of this conveying gas flow bypassing the pre-grinding chamber is fed directly to the center discharge, this gas stream has a low temperature even when used Exhaust gases still have a high heat content «The bypass-like routing of this hot gas flow also avoids this the high energy loss associated with leading the entire flow of conveying air through the pre-grinding chamber were.

These and other details of the invention are based the following description of an embodiment illustrated in the drawing. Show it

Fig.l is a diagram of a mill-drying system according to the invention;

FIG. 2 shows a longitudinal section through the multi-chamber mill provided in the system according to FIG.

3 shows a section along the line III-III of Fig. 2.

The system shown in. Fig.l contains a feed hopper 1 for the ground material, a take-off device 2 and a Multi-chamber mill 3 with a pre-drying chamber 4, a pre-

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grinding chamber 5, a central discharge housing 6 and a fine grinding chamber 7

The system also includes a static classifier 8, a cyclone 9, a fan 10, a filter 11 and another fan 12.

The ground material arrives from the bunker 1 via the extraction device 2 in the pre-drying chamber 4 of the mill 3 »the just like the pre-grinding chamber 5 by a stream of hot gas (Arrow 33) is heated. The material entering the pre-grinding chamber 5 with a certain residual moisture is allowed in this Grinding chamber 5 are only comminuted to the extent that this is essential for further drying.

The material then reaches the discharge housing 6 and is conveyed to the separator 8 by a gas stream (arrow 14). This The gas flow is composed of that through the chambers * i and 5 drawn gas flow, a circulating air flow returned by the fan 10 (arrow 15) and, according to the invention, another Hot gas stream (arrow 16), which is fed directly to the center discharge 6, bypassing the pre-grinding chamber. To this During the pneumatic conveyance of the material from the mill 3 to the classifier 8, intensive post-drying takes place of the still moist material.

The separation into coarse and fine material takes place in the classifier 8. The coarse material is conveyed back to the mill 3, to be precise predominantly into the fine grinding chamber 7 · However, there is also the option of feeding a small portion of the coarse material the pre-drying chamber. The fine material passing through the static sifter 8 is carried to the cyclone 9 and left there. The filter removes dust from the exhaust gases.

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It goes without saying that the material discharged pneumatically from the mill can also be fed immediately to a cyclone can, in which its separation takes place, the separated material then a turbo windsifter for separation is abandoned in coarse and peing goods.

Figures 2 and 3 illustrate details of the mill 3 and the gas supply and discharge.

As can be seen in particular from FIG. 3, the housing 13 of the center discharge 6 surrounds the mill 3 off-center, so that the clear cross section between the mill and discharge housing 13 widens in the direction of rotation (arrow 17) of the mill from top to bottom. The consequence of this is that in this zone the main amount of air flows from the mill tube into the discharge housing, the rotation of the mill promoting the downward precipitation of the material. The discharge housing is provided with a connection 18 for supplying the gas flow and with a connection 19 for discharging the gas material flow.

The mill discharge housing branches off from the gas supply line Immediate by-pass Leitting 20 from that into a bend the conveying line 21 opens via Lei & Leche 22. Through this Good deposits are avoided in this elbow. The amount of additional air introduced through the by-wet line 20 leaves regulate by means of a throttle valve 23.

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Claims (4)

Claims lj) Method of mill drying using a multi-chamber mill heated by means of a stream of hot gas with central discharge, characterized in that part of the hot gas flow while bypassing the pre-grinding chamber, it is fed directly to the center discharge and for pneumatic conveying of the goods is used to a part of the plant downstream of the mill. 2.) Method according to claim 1, characterized in that that the center discharge also part of the circulating air flow is fed. 3.) Device for performing the method according to claim 1 with a multi-chamber mill with central discharge, characterized in that the one with a connection (18) for supplying the gas flow and a connection (19) Discharge housing (6, 13) provided for discharging the gas / material flow surrounds the mill (3) eccentrically in such a way that that the clear cross-section between the mill and discharge housing in the direction of rotation of the mill from above expanded below. 4.) Device according to claim 3, characterized in that one of the gas supply line (18) is the mill discharge housing (6,13) bypass line (20) branches off into a bend in the delivery line (21) for the gas-good mixture opens. 309808/0331