GB2294943A

GB2294943A - Process and plant for separating husks from malt.

Info

Publication number: GB2294943A
Application number: GB9520420A
Authority: GB
Inventors: Manfred Gottschalk; Jochen Kribbe
Original assignee: Buehler GmbH
Current assignee: Buehler GmbH
Priority date: 1994-11-12
Filing date: 1995-10-06
Publication date: 1996-05-15
Anticipated expiration: 2015-10-06
Also published as: KR100366054B1; GB2294943B; JP4031063B2; JPH08205848A; GB9520420D0; DE4440481A1; KR960017838A; HK1001541A1

Description

1 2294943 PROCESS AND PLANT FOR SEPARATING HUSKS FROM MALT This invention

relates to a process and to a plant for separating husks from malt. During brewing it is necessary to effect a separation of solid and liquid components of the so-called mash. This process is effected within the conventional brewing room equipped with settling vats by sedimentation. During this procedure, the insoluble hulls of malt, also called husks, in particular sink to the double bottom of the settling vat, thus forming a natural filtering layer through which the liquid is withdrawn. It would be desirable to be able to provide a more homogeneous filter bed and to increase the specific load of the settling vat, in this way keeping the dimensions of the settling vat small and, thus, making it economical; in order to 2. filter through said filter bed in a particular efficient manner in terms of clearness and throughput per time unit; in order to obtain the chance to remove part of the husks before the brewing process, thus reducing the emission of undesirable substances, such as of polyphenolene and anthocyanogene, from the husks, but to obtain, nevertheless, a well structured settling bed. The applicants have recognised that the quality of the husks constitutes the decisive criterion for the improvement of the 3.

1 filter properties.

According to the present invention there is provided a method for separating husks from malt, characterised by the following combination:

a) that the malt having husks adhering thereto is first moistened, b) that then the malt having husks adhering thereto is subjected to a pressure treatment between hard surfaces, c) that subsequently a first separation of husks from malt is effected, and d) that the husks separated in step c) are then subjected in a second separation step to an impact treatment.

Individual ones of this combination of process steps have already been suggested for other purposes. For example, DE-C972592 discloses moistening of barley germinated for removing grain tips and subsequent comminution. This is done in order to achieve pore swelling of high- molecular components which are difficult to attack per se, and has nothing to do with recovering pure husks.

DE-C-1 068 202 discloses wet removal of germs of green malt and mentions also removal of germs by impact centrifuging. Thus, also this reference has nothing to do with obtaining pure husks.

DD-A-13 778 describes the production of an additive to unmalted grain from residues of barley of a particle size below 2mm. The material is centrifuged and dehusked, but it is clear that with such a particle size the husks are already removed, and 3 there are merely parts of husks remaining.

In the combination of characteristics according to the present invention the procedure of impacting relatively gently serves to purify the husks. This could be done by any mill exerting an impact onto the material to be treated. However, sieving or sifting means in particular a sieve drum and an inner rotor, is preferred for this purpose, especially such a sieve drum whose number of revolutions per time unit can be set in order to adjust the power of the impact action. Certainly, the husks are already separated from malt in step c), but they still contain small malt particles adhering thereto which results in losses of extract, particularly in connection with removal of part of the husks from the process mentioned under point 3.above. This means that the separation procedure, according to the invention, is effected in two steps, and one could say in form of a coarse separation (in most cases by a sieve) and a fine separation (by impacting). In this way, an additional amount of malt, thus recovered, will be obtained as a side-effect.

Step b) may be carried out in different ways, such as by means of jaws to be pressed against each other. According to the invention it is preferred, however, that step b) is effected within a roller mill by means of the hard surfaces of at least one, and preferably at least two, rolls, where it is even possible to use a roll, eg. a fluted roll, cooperating with a stator (eg. like in cone crushers) or with another rotor.

4 Preferably step c) is carried out using a grist mill comprising at least one sieve incorporated as a roller mill.

In certain impact centrifuging machines, eg. in those where air flows upwards and separates the light-weighted husks from malt particles falling down, it is, in fact, possible to obtain residual malt and husks separated at the outlet so that it has proven to be useful to additionally carry out a sieving or sifting step after step d).

A plant for carrying out the method of the invention is characterised by a damper, a mill including at least two milling surfaces moveable relatively to each other, a separation device for separating husks and ground malt, and an impact device for impacting the husks and knocking off any malt particles adhering thereto, said impact device having an inlet and an outlet.

Further details and advantages of the invention will become apparent from the following description of embodiments schematically illustrated in the drawings given by way of example only, and of which:

Fig. 1 shows a scheme of a plant according to the invention, and Fig. 2 illustrates a modification of a detail thereof.

In a plant for processing malt, there is a plurality of bins 1 for different sorts of malt, only two bins being shown. At this outlet of the bins, there is suitably a weighing device 2 to be able to supply weighed amounts of different sorts of malt to a mixing device 3.

Subsequently, the mixed malt is supplied via an elevator 4 to a purifying step which in the embodiment shown comprises at least a sieve 5 operating under aspiration (for dust removal) as well as a gravity separator (or lldestonerll) 6, but may include alternatively or in addition other purifying machines. After this first purifying step, control weighing by means of a weigher 7 may be carried out. However, it is also possible to effect this weighing after the purifying steps described below or to do this latter weighing procedure in addition.

After lifting anew by means of an elevator 4a, any metallic parts which may then be still present are removed by a magnetic separator after which the usual precleaning step is finished.

In order to gain a maximum yield of malt, on the one hand, and to obtain, above all, a pure fraction of husks, the malt is slightly moistened within a damper 8, i.e. the addition of water remains below 10% by weight, and is, in general, between It and 5%; depending on the sort of malt. Good result were attained with an addition of water of about 2%. By this only slight moistening, the husks, being brittle when dry, become elastic so that they can stand a pressure treatment without breaking to pieces.

This pressure treatment takes suitably place within a malt grist mill 9 which has at least a pair, preferably, however, at least two pairs of rolls 9a as well as subsequent sieves 9b, as is known per se. A preferred embodiment of such a mill is disclosed in EP-B-0 357 762, the rolls 9a and the sieves 9b being advantageously arranged in a common frame.

6 By the pressure treatment between the hard surfaces of the rolls 9a (in contrast to a pressure treatment by means of a pressure fluid which allows for yielding) malt is not only broken, but is also detached to a wide extent from the hsks which remained elastic and entire due to such elasticity. Thus, they will have such a size that they can easily be separated by means of the sieves 9b. Therefore, it may be seen that the malt fraction falling through the opening of the sieves will have a higher degree of purity and a smaller amount of comminuted husks.

On the other hand, the husks which remained complete will form the overtails and may be conveyed, subsequently to a valve 10a, to a further elevator 4b via an output conduit 11. Of course, any other conveying means could be used instead of the conduit 11.

At the same time, the malt fraction freed from husks is received in an explosion-proof storage bin 13 comprising an associated dust filter 12 via a valve 10b, the malt from this bin 13 being supplied, when desired, to a bin 14 or the like by means of a discharge screw 13a.

Although the measures described will already result in a relatively pure malt fraction and of relatively pure entire husks, this is not sufficient for the intended purposes. This means that malt particles and residues of germs may still adhere to the husks undesirably affecting colour, taste, extract contents and quality of the wort to be obtained when they are used as a filtering means during settling.

Therefore, these husks are subsequently subjected, according to the invention, to an impact treatment within an impact mill 15 where the residues of malt adhering to the husks are separated. Depending on the construction of such an impact mill which, for example, comprises a rotor surrounded by a sieve, an additional yield of malt, which is otherwise lost, will be 7 obtained at a conduit 16, if separated outlets are provided for the fines and the coarse material whereas the husks are collected for later use as a filtering aid in a storage bin 13? analogous to the storage bin 13. In so far, this apparatus operates as an impact centrifuging sifter. Since the transitions from an impact mill, where impacting is rather effected for comminuting purposes, and an impact centrifuging sifter are fluid, the term "centrifuging impact mill" shall encompass both constructions within the framework of this disclosure.

In other constructions of impact mills, a sieve and/or a sifting device for separating malt and husks could be provided following the outlet. However, an centrifugal impact mill is preferred where a sieve is integrated in such a manner that the impacting surface surrounding the usual centrifuging dish is formed as a sieve surface. Such a construction has proved itself best.

Thus, a very pure husk of large volume will be obtained which is an excellent filtering aid. As an advantageous side-effect, an increased yield of malt will result in addition.

Since a centrifuging impact mill comprises, in general, a centrifuging dish concentric to an impact wall, this centrifuging dish can also be used to act as the centrifuging rotor of a wind sifter in a manner known per se, as is schematically indicated in Fig. 2. While the husk material with adhering malt supplied from the outlet of the roller mill (e.g. 9) is fed into the centrifuging impact mill 15a by any feeder 20, an air inlet conduit 17 is arranged in the place indicated or in a region below.

In the present arrangement, the conduit 17 is about at the level of the centrifuging rotor 15b, merely schematically indicated, and air is drawn in by a fan 18 suitably connected to a cyclone separator (not shown). Thus, air flowing upwards entrains the light husks which are then collected via the 8 cyclone separator and are supplied, for example, to the storage bin 131. In contrast, the malt particles knocked off will fall to the bottom of the centrifugal impact mill 15a, are discharged via a conduit 19, and may then be bagged or may optionally be admixed to the fraction already existing in the storage bin 13.

The method according to the present invention shall be illustrated with reference to a non-limiting example.

In order to separate appropriately the husks from malt flour and grits and to prevent broken husks from remaining, subsequent to the precleaning procedure described above in two steps moistening in damper 8 is carried out first directly before milling. It should be noted that residual husks can be, in cases, disadvantageous during brewing, because they contain components which affect the taste of beer, such as polyphenoles and anthocyanogenes. Thus, when a betterseparation of husks is achieved, the taste of beer will be improved.

Moistening of malt is suitably effected just before milling, as mentioned above, because this ensures the desired elasticity of husks during processing. It is convenient, if the damper 8 is constructed to ensure a certain time of dwell after the supply of liquid, in particular water. From Fig. 1 it is seen that addition of H20 is already effected in the first third of the damper 8 so that, for example, water has a period of about 1 to 2 minutes up to the discharge from the damper 8 for influencing the husks. Alternatively, a container for continuously passing malt through may be postponed after the damper 8 in order to ensure the necessary period of influence.

After conditioning the malt by means of the damper 8, milling is carried out within the mill 9 in the usual manner. After milling, the husks may be weighed. In the present example, there was an amount of 3 tons per hour of husks with an inlet 9 capacity of 12 tons per hour at the inlet of mill 9. These husks now being in their entire state had a relatively large volume, i.e. there were about 23 m3/H which has to be considered in dimensioning the storage bin.

Therefore, two centrifugal impact mills were connected in parallel at the discharge end of the conduit 11 in this example to cope with this large volume.

While the proportion of husks initially (i.e. before the mill 9) amounted approximately to 12,6%, there were husks after the sieves 9b which still had an amount of 25,2% of malt particles, the volume of those husks being 750 ml per 100 9 of material. This volume could be increased up to 1100 ml/100 g after a centrifugal impact mill 15 (having a basket-like sieve around the centrifugal dish and an adjustable number of revolutions) which means an increase of 32% as compared with the volume after the mill 9, simultaneously resulting in a corresponding gain in malt particles.

The centrifugal impact mill 15 was operated for tests with different numbers of revolutions, i.e. with 450 to 800 revolutions of the centrifugal dish per minute, resulting in radial velocities of the husks of 12 to 23 m/s. Best results were obtained with 16 to 19 m/s. In another test with larger particles, velocities of 12 to 16 m/s, and preferably of 13 to 15 m/s, have been used.

The husks, thus recovered, were successfully used as a filtering aid in an economical and easy to dispose way at the end of the brewing procedure. In doing so, it was found that it was possible to add a smaller amount of husks by weight to the mash or settling process due to their large volume, thus reducing possible introduction of polyphenoles and obtaining a beer which was "softer" in taste without any risk of losses of extract which would be due to a too high residual extract in the husks disposed. In comparison, husks without the treatment according to the invention would result in a reduced volume so that a larger amount of husks would be necessary for forming a filter bed of the same height (as compared with the filter bed established with husks treated according to the invention) which would lead to a higher extraction of tanning substances and, therefore, to a negative effect onto the taste of the beer produced.

11 C L A 1 M S 1. A method for separating husks from malt, characterized by the following combination:

2. Method according to claim 1, characterized in that step b) is effected within a roller mill by means of the hard surfaces of at least one roll preferably of at least two rolls.

3. method according to claim 2, characterized in that a grist mill comprising at least one sieve incorporated is used as a roller mill for carrying out step c).

4. Method according to any of the preceding claims, characterized in that at least one sieving or sifting step is additionally carried out after step d).

5. Method according to any of the preceding claims, characterized in that the impact treatment is effected by centrifuging the husks having adhering malt particles against a radially outer impact surface.

6. Method according to any of the preceding claims, characterized in that step a) is carried out immediately before step b).

7. Method according to any of the preceding claims, characterized in that the husks having adhering malt particles are 12 centrifuged with a velocity of 12 to 23 m/s, preferably of 16 to 19 m/s, or even of 12 to 16 m/s, preferably of 13 to 15 m/s, against an impact surface of the centrifugal impact mill.

8. A plant for carrying out the method according to any of the preceding claims, characterized by the succession of the following means:

a) a damper b) a mill including at least two milling surfaces moveable relatively to each other, c) a separation device for separating husks and ground malt, and d) an impact device for impacting the husks and knocking off any malt particles adhering thereto, said impact device having an inlet and an outlet.

9. Plant according to claim 8, characterized in that the separation device comprises at least one sieve having at least two outlets for overtails and for fines.

10. Plant according to claim 9, characterized in that the outlet for overtails is connected to the inlet of the post poned impact device via a conveying means.

11. Plant according to claim 9 or 10, characterized in that the at least one sieve is accommodated conjointly with at least two rolls in a common frame.

12. Plant according to any of claimes 8 to 11, characterized in that a sieving and/or a sifting means is assigned to the impact device 13. Plant according to any of claimes 8 to 12, characterized in that the impact device is formed as a centrifuging device comprising a rotor driven by a drive means for centrifuging the husks against a radially outer impact surface.

13 14. Plant according to claim 13, characterized in that the outer impact surface is formed as a sieving surface for separating the malt particles knocked off.

15. Plant according to claim 13 or 14, characterized in that the centrifuging device is driven by said drive means with a rotary speed as to centrifuge the husks having adhering malt particles with a velocity of 12 to 23 m/s, preferably of 16 to 19 m/s, or of 12 to 16 m/s, preferably of 13 to 15 m/s.

16. Plant according to claim 13 or 14, characterized in that the damper is directly preponed to the mill 17. A method of separating husks from malt substantially as described with reference to the accompanying drawings.

18. A plant for carrying out the method of claim 17 substantially as described with reference to and as illustrated by the accompanying drawings.