GB2175221A - Production of animal feed materials - Google Patents

Abstract

In the production of animal feedstuffs, a plurality of ingredients, at least some of which are in oversized particulate form, are mixed together in predetermined quantities in a mixer (30). This mixture is introduced into a vibratory sieve (48) which acts to separate the oversized particles from the mixture. The oversized particles are ground down in a grinder (52) and the ground particles are re-introduced to the inlet of the vibratory sieve (48) the material passing through the sieve constituting the required output feed which can be bagged or pelleted, as desired. At the beginning of a production run, the output of the sieve (48) during an initial predetermined period is arranged to be stored until the end of that production run when it is added to the final output of the grinder (52) to ensure that the ingredients in the resulting output of the sieve (48) remain in the correct proportions. <IMAGE>

Description

SPECIFICATION Method and system for the production of animal feed materials The present invention is concerned with systems for the production of animal feed materials, such systems being of the type which involve the grinding down and mixing of constituent materials during formation of the final product.

Animal feed products such as poultry meal, pig meal and cattle meal are produced conventionally by forming a mixture of a plurality of constituent materials, such as bean meal, sunflower, wheatfeed meal, rocksalt, maize, vitamin premix, calcium magnasite etc., the amounts of such constituents being in accordance with predetermined controlled limits.

In order to achieve a uniform end product (which in practice is usually pelleted), it is necessary for the constituent materials to be subjected to a grinding operation in order to reduce the dimensions of over-sized particles to a suitable level. It is in this grinding operation that a major part of the energy requirement of the total process is generated.

Atypically known system uses a grinder driven by a 200 HP electric motor. A batch of raw materials in predetermined quantities is pre-mixed in a live bin and passed to a two stage sieve disposed upstream of the grinder. Fines from the sieve bypass the grinder and are led via a holding pin to a main mixer whilst coarse materials separated in the sieve are ground down in the grinder before being passed to the mixer. The resulting mix is passed to a further holding bin before being pelleted to product a final product.

A principal problem with this known system is that, because it operates on a batch basis, the grinder is for part of the time working under a load considerably above its mean operating level during the batch and for part of the time working under a load considerably less than its mean operating level.

Naturally, the grinder must have a operational rating capable of satisfying this higher load level and must therefore be relatively large and correspondingly expensive. Since the grinder is operating at a continuously varying load, it is also subject to relative high wear and tear which tends to reduce its operational life expectancy.

It is a principal object of the present invention to provide a system for the production of animal feed having a grinder which is able to be run continuously at a substantially constant operational load whereby a smaller rating for the grinder motor can be tolerated and a greater life expectancy and power saving can be anticipated.

In accordance with a first aspect of the present invention, there is provided a method for the production of animal feedstuffs comprising the steps of: (a) mixing together in predetermined quantities a plurality of ingredients, at least some of which are in oversized particulate form; (b) introducing this mixture into a separator which acts to separate the oversized particles from the mixture; (c) grinding down the oversized particles in a grinder; and (d) re-introducing the ground particles to the inlet of the separator.

Preferably, the separator is in the form of a vibratory sieve, the material passing through the sieve constituting the required output feed which can be bagged or pelleted, as desired.

Advantageously, the output of the sieve during an initial predetermined period at the beginning of a production run is arranged to be stored until the end of that production run when it is added to the final output of the grinder to ensure that the ingredients in the resulting output of the sieve remain in the correct proportions.

In accordance with a second aspect of the invention there is provided an apparatus for the production of animal feed comprising: (a) means for continuously supplying a mixture of ingredients from a mixer to an oversized particle separator; (b) a grinder for receiving oversized particles from the separator; (c) means for returning ground particles from the grinder to the separator; and (d) means for outputting particles through the separator.

Preferably, the system includes a mixer for receiving and mixing together the ingredients supplied thereto in their correct proportions, a storage hopper for receiving mixture from the mixer, and a control system which ensures that the storage hopper is periodically or continuously supplied with mixture from the mixer so that the storage hopper always contains a supply of mixture throughout a production run.

Advantageously, material passing through the separator (what is preferably in the form of a vibratory sieve) is received on a conveyor which normally transports the material to an output region of the apparatus. However, for use at the start of a production run, the conveyor can selectively transport the mixture from the sieve to a storage bin where it can be held until the end of the production run when it can be arranged to be added to the sieve together with the final output of the grinder.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a known system for producing animal feedstuffs; and Figure2 is a diagrammatic representation of one embodiment of a system in accordance with the present invention for producing animal feedstuffs.

Referring first to Figure 1, the known system includes a scale 10 which receives raw material ingredients from a plurality offeed bins 12, of which four are shown in the drawing. The particle sizes of the ingredients supplied to the scale 10 range from fine dust to large granules. These ingredients are passed into the top of a first stage mixer 14, usually called a live bin, which contains a worm gear for achieving coarse mixing of the ingredients. The resulting mix is passed onto a separator 16, for example in the form of a Bu hler vibratory sieve. The fine materials passing through the sieve 16 are led to a main mixer 21 via a holding bin 18whereasthe materials separated by the sieve are passed into a grinder 20.The grinder 20 is driven by a relatively large electric motor (not shown), typically having a power rating of 200 HP. Ground materials leaving the grinder 20 are joined with the fines from the sieve 16 in the holding bin 18.

After thorough mixing in the mixer 21, the mixture is raised by an elevator 22 and fed to a holding bin 24, prior to being pelleted in a pelleting machine 26.

The final product may be in bulk forum or bagged, as required.

As explained hereinbefore, the problem in practice with this known system is that it is essentially a batch operating system, that is a batch is prepared in the scale 10 of the relevant ingredients in their predetermined quantities and this is then fed through the system. When the batch is started, the grinder is initially working at substantially zero load.

When the batch arrives at the grinder, the grinder motor suddenly experiences a very heavy load. This load is controlled by a grinder feeder 19 which speeds up or slows down according to the power load on the grinder motor. The purpose of this feeder is to obtain a constant correct load on the grinder. However, with this system, the grinder has to run empty at the end of the batch until the holding bin 18 has been emptied into the mixer 21. This cycle is repeated for each batch so that the grinder is in fact repeatedly subjected to variable load which ranges from a very high level to a relatively low level.

Referring now to Figure 2, the illustrated system in accordance with the present invention employs a first mixer 30 to which the ingredients are supplied from feed bins (not shown) in their appropriate quantities and wherein they are then mixed. The mixer 30 lies above a hopper 32 and is connected thereto by feed pipes or chutes 34 containing controllable valves 36. The arrangement is such that the hopper 32 is never allowed to empty during a production run but is continuously or periodically topped up by the mixer 30 by way of the feed pipes 34. When the mixer 30 itself becomes empty a further supply of ingredients in the appropriate quantities is supplied thereto from the feed bins (not shown).An automatic control system monitors continuously the levels in the mixer 30 and/or the hopper 32 for determining suitable timing of the mixture flow through the valves 36.

Mixture is led off continuously from the bottom of the hopper 32 by means of an adjustable speed taper worm conveyor at a throughput slightly in excess of the output of downstream pettet mill or mixed meal plant, and is raised by an elevator 38 to a higher level 40 from where it is first subjected to the magnetic field of a magnet 42 to remove any unwanted ferro magnetic particles and then led to the foot of a second elevator 44 by way of ducting 47,49. The elevator 44 raises the mixture two a higher level at 46 at which it enters a separator 48, such as a Buhler vibratory sieve where fines are separated from larger particles in the mixture. The fines pass downwards onto an inclined conveyor 50. The larger particles separated by the sieve 48 are passed into a grinder 52 by way of a hopper 54 and feeder 56.

Ground material leaving the bottom end of the grinder 52 is passed back to the lower end of the elevator 44to join the mixture supplied from the hopper 32 by way of feed pipes 47 and 49. On its second pass over the sieve 48, at least the bulk of the previously rejected material is now sufficiently ground down to be passed by the sieve to the conveyor 50. Any material still rejected by the sieve is returned to the grinder for one or more further passes therethrough.

The upper end of the conveyor 50 communicates with a discharge chute 58 containing a controllable valve 60. When the valve is shut to close the discharge chute 58, material on the conveyor 50 is carried back by the downward run of the latter conveyor and discharges back to the hopper 32 by way of ducting 64 and 66 which can, where necessary, include conveying means. Any excess material which does not pass out of the discharge chute 58 is likewise carried back by the downward run of the conveyor 50 and, provided that a valve 78 is closed, is discharged to the hopper 32 via the ducts 64 and 66.

It is therefore possible to recirculate material back to the hopper 32 from the downward run of the conveyor 50 by way of ducts 64 and 66. Material can be discharged from this path to an output hopper 68 by way of a controllable valve 70.

Material leaving the conveyor 50 via the chute 58 and valve 60 is fed to a pelleting mill 72 via a kettle 74.

Finally, it will be noted that a small holding bin 76 is connected to the conveyor duct 66 by way of the valve 78 and a duct 80. The bin 76 can selectively discharge its contents to the bottom end of the elevator 44 by means of a controllable valve 82.

The operation of the abovedescribed system is as follows.

As described above, mixture in the relevant proportions is passed continuously to the elevator 38 and, from there, via the magnetic field of the magnet 42 and the ducts 47 and 49 to the foot of the elevator 44. The material is then raised by the elevator 44 to the sieve 48 where the smaller particles are passed through to the conveyor 50 and the larger particles are passed to the continuously operating grinder 52.

Material leaving the grinder is passed back to the lower end of the elevator so as to be reintroduced to the sieve. This time around at least the bulk ofthe previously rejected particles are small enough to pass through the sieve to the conveyor 50 which carries them upwards towards the discharge chute 58.

It has been found that, once the system has been operating for a short time and recirculation of ground particles is taking place, the mixture travelling up the conveyor 50 to the outlet chute 58 is sufficiently uniformly mixed to be discharged for pelleting. However, at the very beginning of a production run, it will be appreciated that when the unground material from the hopper 32 first reaches the sieve from the elevator 44, the material passing onto the conveyor 50 is entirely fines and contains very little of the components which need to be ground down. Similarly, at the very end of the run the last material to be discharged onto the conveyor 50 will be that which has had to go through the grinder and be recirculated to the sieve 48. This material will therefore be almost entirely deficient in fines since these will have already passed through the sieve on the previous pass.

This problem is solved by initially keeping the valve 60 closed for a predetermined period at the beginning of the run. During this period the fines fed to the conveyor 50 by the sieve 48 are arranged to be passed via the ducts 64 and 66, the valve 78 and the duct 80 to the holding bin 76 where they are then held. The predetermined time, which typically might be about 20 seconds, corresponds approximately to the time it takes for material to circulate between the sieve 48, the grinder 52 and back to the conveyor 44 to join with incoming material from the hopper 32.

At the end of the run, the bin 76 is arranged to be opened at an appropriate time to discharge its contents to the bottom of the elevator 44 in such a manner as to mix with the final output of the grinder 52, thereby ensuring that the constituents of the final material passing through the sieve to the conveyor 50 are still in the correct proportions for the required mix.

An important advantage of this system is that the grinder operates continuously throughout the production run at a substantially constant load. It has been found that, compared with the known apparatus described initially, a much smaller grinder motor can be used which uses correspondingly less power to drive it. It will also be noted that the necessity of the live bin 14 of the known system (an expensive item of equipment) has been dispensed with, so enabling the present system to achieve a cost saving in this area.

Claims (9)

1. A method for the production of animal feedstuffs comprising the steps of: (a) Mixing together in predetermined quantities a plurality of ingredients, at least some of which are in oversized particulate form; (b) introducing this mixture into a separator which acts to separate the oversized particles from the mixture; (c) grinding down the oversized particles in a grinder; and (d) re-introducing the ground particles to the inlet of the separator.

2. A method as claimed in claim 1, wherein the output of the sieve during an initial predetermined period at the beginning of a production run is arranged to be stored until the end of that production run when it is added to the final output of the grinder to ensure that the ingredients in the resulting output of the sieve remain in the correct proportions.

3. An apparatus for the production of animal feed comprising: (a) means for continuously supplying a mixture of ingredients from a mixer to an oversized particle separator; (b) a grinder for receiving oversized particles from the separator; (c)means for returning ground particles from the grinder to the separator; and (d) means for outputting particles through the separator.

4. Apparatus as claimed in claim 3, including a mixer for receiving and mixing together the ingredients supplied thereto in their correct proportions, a storage hopper for receiving mixture from the mixer and a control system which is arranged to ensure that the storage hopper is periodically or continuously supplied with mixture from the mixer so that the storage hopper always contains a supply of mixture throughout a production run.

5. Apparatus as claimed in claim 3 or 4, wherein material passing through the separator is arranged to be received on a conveyor which normally transports the material to an output region of the apparatus.

6. Apparatus as claimed in claim 5 wherein, for use at the start of a production run, the conveyor can selectively transport the mixture from the sieve to a storage bin where it can be held until the end of the production run when it can be arranged to be added to the sieve together with the final output of the grinder.

7. Apparatus as claimed in claim 3,4 or 5, wherein the separator is in the form of a vibratory sieve, the material passing through the sieve constituting the required output feed which can be bagged or pelleted, as desired.

8. A method for the production of animal feedstuffs substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

9. Apparatus for the production of animal feedstuffs, substantially as hereinbefore particularly described with reference to and is illustrated in Figure 2 of the accompanying drawings.