DE1219779B - Mill drying process and installation for carrying out the process - Google Patents

Description

Mill drying process and equipment for carrying out the process The invention relates to a grinding drying process for moist material, the initially only dried and then essentially in a drying stage is ground, whereby the semolina that occurs during a layering of the ground material is re-ground and at least one grinding stage of the drying stage spatially is immediately downstream.

In a known Mahltrocknunas method, the moist grinding stock is first fed to a hammer or Prallmi.ihle and then sent to the sifter, the grits of which are fed to a Kucyelmühle, whose products are fed to the sifter in the case of a pond. The individual units of this known system are heated to dry the goods. With this known Maliltrocknun2sverfahren with very moist, sticky sound in the hammer or impact mill, easily disruptive clogging and caking, which cannot be completely avoided even by additional heating of the impact or impact surfaces. A disadvantage of this known mill drying method further that anspruchung in the separator with respect to the high mechanical and thermal loading results in a considerable wear.

There is also a hfahltrocknungsverfahren known in which the Mahlnut in an air-flow tube mill at the same time as the grinding process through drying Qas dried and then conveyed to the classifier in an air stream. This procedure is conditional Considerable energy consumption due to the high flow resistance.

To get the grist before you enter the actual grinding room To dry as much as possible with better grindability, one still has a Mahltrocknunasverfahren developed using a tube mill with a separate drying chamber finds. In this known mill-drying method, the drying gas is sequentially through the drying chamber and the INlahlkaminer -efi.ihrt. However, there is now for the drying in the drying chamber of a tube mill has an optimal speed des Trockiluil, -saases, which, however, when the material is moist, far exceeds the Gcacli @ viiidi, keit lic'tit as she for the Mahlvornan ;! L11'e (: knl; lßia is. The meal, ut is at too high G @ S! @ eSCh @ 'ilndl' @ klat in tinerwünSChter lNlen (, e with the gas flow # itis #; ctri ## cn, \ vas the llahlvor; aiig affecti`, it and leads to a minutely ener-ic expenditure.

One especially from @@ cprä @ atc discrepancy between stage on the other hand optimal gas volumes result from the use of drying gases at a low temperature, as they have recently been used to an increasing extent for grinding drying. The lower the temperature of the drying gas is, the higher it is for the drying stage required gas volume. Uni is so harder to do with the well-known Maliltrynunas process, in which the drying gas then flows through the grinding stage, in the latter achieve reasonably favorable operating conditions.

The invention is therefore based on the object of a mill-drying process of the type mentioned in such a way that even when using gases low temperature both in the drying stage and in the grinding stage Relationships result.

This object is achieved according to the invention in that that of the drying stage supplied drying gas is removed immediately after flowing through it and the or a separate gas stream is fed to the grinding stages immediately downstream will.

In this way one can do the two processes of drying and grinding perform unaffected by each other without interdependence and both in the drying stage as well as in the grinding stage the optimal conditions with regard to Set the gas volume, gas speed and gas temperature.

Details of the invention can be found in the description of some of the the drawing of illustrated embodiments. It shows F i n. 1 up to @ 3 schematic sections through three tube mills to carry out the invention F. i @. -1 an overall scheme of a 1 \ lahltrocknunasanlaae according to the invention.

In the case of the in FIG. 1 shown tube mill is the wet Malilaut introduced into drying chamber 2 by task 1. Lifting shovels 3 ensure for a very intensive contact of the goods with the via a nozzle 4 in controllable Amount of drying gas entering. The gas is after flowing through the drying chamber 2 sucked through openings 5 and a line 6V. The grist falls through the openings z into an Austra-s- @ iiehäuse 7 and is withdrawn through a connector 8.

The tube mill also contains a grinding chamber 9, from which the material passes through a slit wall 10 into the discharge housing 7. The total flow of goods goes to a sifter. whose grits are introduced into the grinding chamber 9 via the receptacle 11 will. The grinding chamber is through a nozzle 12 with a separate gas flow provided.

In the case of the in FIG. 2 the tube mill shown is the moist grist also supplied via the task 1, dried in the drying chamber 2 and discharged through the openings 5. The drying gas is after flowing through the Sucked off drying chamber 2 without passing through grinding chamber 9. The grist from the grinding chamber 9 is not brought together with the material from the drying chamber 2; the two streams of material are rather separated via the two discharge housings 7 ' and 7 ". Here the material emerges from the grinding chamber 9 through the slit wall 10 and openings 5 'in the discharge housing 7 ".

When the material discharged from the drying chamber 2 is for fine grinding is still too coarse in the grinding chamber 9, the dried material can be or impact mill are pre-crushed (and, if necessary, post-dried here), before the sifting and fine grinding takes place. The material from the grinding chamber 9 is expediently together with the goods from the hammer mill or impact mill the sifted coarse fraction is fed to the grinding chamber 9 via the feed 11.

The mill-drying process according to the invention can also be used with the in Fig. 3 perform the tube mill shown. The one from the drying chamber 2 Incoming goods migrate here over a screen cylinder 13. That goes through this screen cylinder Fine material that passes through reaches the Atistra @ (Ysgeliäuse 7, while the sieve residue is passed from a lifting wall 14 into a pre-grinding chamber 15 will. From this, the material becomes together with that coming from the fine grinding chamber 9 Well discharged through the slot walls 16 or 10 and openings 17 in the housing 7. The entire flow of material withdrawn through the nozzle 8 is fed to a sifter, whose coarse fraction reaches the fine grinding chamber 9 via the task 11.

In this exemplary embodiment, too, this is the drying stage supplied drying gas discharged immediately after flowing through it, during a separate gas stream is fed to the Nfahlstufe. In the suction line 6 an additional control element 18 is provided to control the gas velocities in the the individual chambers to the desired values.

In the case of the in FIG. -1 shown Maliltrocknunasani; ige will that Moist Nlalil # -, ut via the feeder 1 and a feeder 19 of the drying chamber 2 fed to the tube mill 20. That in the drying chamber 2 intensively the drying gases exposed and thereby pre-dried material reaches a bucket elevator 21 heated hammer mill 22. A screw conveyor 23 transports the finished or at least Almost completely dried material to the fine grinding chamber 9 of the tube mill 20. That from this Material emerging from the fine malil chamber is fed to a sifter 25 via a Beclierwerk 2-1. Whose semolina go with the property from the hammer mill 22 to the fine grinding chamber 9, while the finished flour is discharged in the gas stream from the classifier 25 and in a Zvklon 26 or in a dedusting device 27 is deposited.

The drying oasis. which are formed, for example, by the exhaust gases of a rotary kiln system, reach the drying chamber 2 of the tube mill 20 via a line 28 and a branch 4. Another branch 29 of the pipeline 28 also supplies the hammer mill 22 with drying gas, while via the lower branch 30 also the fine malil chamber 9 of the tube mill 20 can be fed with hot gases. The gas flows passed through the two chambers 2 and 9 of the tube mill 20 are drawn off via the discharge housing 7. The Abcyase from the tube mill 20 and the hammer mill 22 flow through the classifier and are sucked into the open air via the cyclone 26 and the dedusting device 27.

The crushed material can be screened off under the hammer mill 22 take place, the coarse portion being given up via the screw 23 of the fine malil chamber 9 is, while the fine fraction is fed to the bucket elevator 24 and first the sifter 25 happened. In this way, the fine material portion of the hammer mill 22 becomes the finished product Excreted flour that no longer loads the fine grinding chamber 9 @.

Instead of the one shown in FIG. 4. provided separately ventilated classifier 25 can a turbo sifter with its own ventilation can also be used. In this case it must A grit separator is built into the suction line for the exhaust gases from the tube mill 20 so that the fines occurring in the dedusting device are not over-sized contains. The grits from the grit separator are fed to the fine grinding chamber 9.

You can also use that from the drying chamber 2 of the tube mill 20 subject the emerging material to a screening process and the resulting fine fraction the bucket elevator 24 leading to the classifier 25 at @ 17eben, while the coarse fraction is above the bucket elevator 21 reaches the hammer mill 22.

Is a particularly moist one that tends to stick or stick To process regrind, a partial flow of the already in the drying chamber 2 dried and crushed by the hammer mill 22 together with the fresh Good to be fed to the drying chamber 2 again. This results in a powdering of the fresh grist, which prevents caking with even greater security will.

Claims (1)

Claims: 1. N-faliltrockntings @ -crfaliren for moist goods, which initially essentially only dries and then in a drying stage is ground, whereby the portion of semolina resulting from a sifting of the gcmalilenen good ground again and at least one grinding stage of the drying stage is spatially immediately downstream, characterized in that the drying stage supplied drying gas is removed immediately after it has flowed through and the or a separate gas stream is fed to the grinding stages immediately downstream will. ?. Nifahl drying process according to claim 1, characterized. that the product dried in the drying stage is more beating in a pre-shredding stage and bouncing processing is subjected and then together with the off The material discharged from the grinding stage is subjected to a classification, with the semolina content is fed back to the grinding stage. 3. Mill-drying method according to claim 1, characterized in that the material dried in the drying stage together with the material discharged from the grinding stage is subjected to a classification and the semolina content is returned to the grinding stage. "4. Mill-drying process according to claim 1, characterized in that the product which has been dried in the drying process is followed by a further AusSSleburig of the fine fraction is fed to a first grinding stage and then subjected to a classification together with the material discharged from a second grinding stage will. 5. Malile drying method according to claim 1, characterized in that the Drying level, in addition to the moist load, a partial flow of pre-dried items Well fed. 6. Mill drying system for carrying out the in the claims 1 and 3 to 5, consisting of a tube mill through which gas flows with a drying chamber forming the drying stage and at least one grinding chamber, characterized in that the drying chamber (2) provided with lifting blades and the grinding chamber (9) of the tube mill equipped with grinding media on its outer side End faces each have a feed line (4, 12) for the drying gas and in the area of their common end face a common outlet housing (7) for the gas and the grist have, wherein the outer end face of the drying chamber with a Roligutaufgabe (1) is provided and the discharge nozzle (8) of the common outlet 'housing with a sifter (25) is connected, the grit return line (11) in the outer forehead. wall of the pale chamber opens. 7. Mill-drying system according to claim 6 in particular for the method: according to claim 4, characterized in that! between the drying chamber (2) and de grinding chamber (9) of the tube mill a pre-grinding chamber (15) is switched on, the ground material coming from the drying chamber is fed via a sieve chamber (13) and the material and gas outlet openings (17) that are common to the grinding chamber, the together with the fine material discharge openings (5) of the sieve chamber into the common Outlet housing (7 open. S. Malile drying system according to claims 6 and 7, characterized in that i the common outlet housing (7) of the Rohi mill sub-chambers (T, 7 ") lead to the separated aluminum from the drying, Tskammjr (2) and from the grinding chamber (9) the tube mill au; worn in, lalilgutes are present. 9. - Nlaliltrocknuiinsanla2c according to claim 1, in particular for implementing the method according to claim 2, characterized marked, since the discharge nozzle (8 ') for the coming from the Trocl nunmkammer 1.1 grist with a mill (22) serving for pre-shredding and the nozzle (8 ") for the ground material carried out of the grinding chamber is connected to the classifier (25). Considered publications: German Patent Specifications No. 680 969, 577 537.