GB2574864A

GB2574864A - Method and apparatus for preparing animal feed

Info

Publication number: GB2574864A
Application number: GB201810179A
Authority: GB
Inventors: Mitchell Aidan
Original assignee: John Thompson and Sons Ltd
Current assignee: John Thompson and Sons Ltd
Priority date: 2018-06-21
Filing date: 2018-06-21
Publication date: 2019-12-25
Also published as: GB201810179D0; GB2574914B; IE20190094A2; GB201900473D0; IE87442B1; GB2574914A

Abstract

A method for preparing animal feed includes grinding one or more ingredients by splitting an incoming ingredient batch into at least first and second portions and feeding the portions to respective grinders 6, 8 arranged in parallel. The process time taken for the grinders to grind their respective portions is determined, and the relative sizes of first and second portions in a subsequent batch is adjusted as a function of the difference in process time taken for the grinders to grind their respective portions of a previous batch in order to minimise the difference in process times for the grinding of portions in subsequent batches. An adjustable splitter device 4 may be used to split incoming batches. The first and second portions may be recombined downstream of the grinders prior to a mixing step 10. The method preferably comprises additional steps downstream of the grinding step, including a blending step, liquid adding step, steam conditioning step 14, pelleting step 16, cooling step 18, and oil coating step. An apparatus is also claimed, comprising parallel grinders, incoming batch splitting means, and control means for determining subsequent batch portioning sizes based on prior batch process times.

Description

Method and Apparatus for Preparing Animal Feed

FIELD OF THE INVENTION

This invention relates to a method and apparatus for preparing animal feed and in particular to a method and apparatus for preparing animal feed including a grinding step for grinding one or more ingredients.

BACKGROUND OF THE INVENTION

Animal feed is typically prepared in a compounding mill, wherein weighed batches of ingredients are ground, mixed and blended together with binders and other additives before being pressed into pellets or meal for supply to farmers. The first three stages; weighing, grinding and mixing, are collectively described within the industry as a blending operation.

An important step in the blending operation is the grinding of feed materials, primarily vegetable matter such as grains, pollard, soya, sunflower, distillers grains and palm kernel, to pre-determined particle size in one or more grinders to ensure the homogeneity of the finished product and to produce the physical attributes required.

In order to increase the capacity of the mill it is known to provide two or more grinders arranged in parallel such that multiple batches of ground material can be produced simultaneously. The incoming feed batch of material may be split into separate portions to be fed to each grinder and then recombined into the next process, for example upstream of a mixer.

The efficiency of each grinder or set of grinders may vary over time due to wear. Grinding times through each grinder will vary over several days or weeks as various components of each grinder pass through their natural wear/maintenance periods and due to the air density changes effecting the air flow and suction of material through screens and the clogging of filters and dust bags which also effects the air flow and hence grinder throughput. The overall length of time for the grinding process will be limited by the slowest grinder or grinder set. Therefore there is a desire to optimise the relative sizes of the portions of the incoming batch of material supplied to each hopper so that the grinding time for each batch is substantially the same. An object of the present invention is to overcome this problem and to minimise the length of time of the grinding step.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method for preparing animal feed including a grinding step for grinding one or more ingredients, said grinding step comprising the steps of providing a first grinder arranged in parallel to one or more further grinders, splitting an incoming batch of material to be ground into at least first and second portions, said first portion being fed to said first grinder and said second portion being fed to at least one of said one or more further grinders, determining the process time taken for said first grinder to grind said first portion and determining the process time taken for said at least one of one or more further grinders to grind said second portion, and adjusting the ratio of said first and second portions in a subsequent batch as a function of the difference between the process time taken for said first grinder to grind said first portion and the process time taken for said at least one of one or more further grinders to grind said second portion of one more batches in order to minimise said difference in process times for the grinding of the first and second portions of subsequent batches.

The method may comprise using a mechanical device is used to split said incoming batch into said first and second portions at a selected ratio.

In one embodiment the method may comprise the step of configuring the first grinder such that said incoming batch is selectable from a feed batch of at least one of a plurality of grinders or sets of grinders of a compounding mill, such that said at least one of said plurality grinders or sets of grinders comprises said one or more further grinders.

Preferably the method comprises the step of recombining said first and second portions downstream of said first and one or more further grinders and upstream of a mixing step.

The method may comprise a blending step for blending ingredients to form said animal feed, said blending step comprising a weighing step, said grinding step and a mixing step.

The method may further comprise adding liquids to the ingredients in said mixing step downstream of said grinding step.

Preferably the method further comprises a conditioning step downstream of said mixing step, wherein the blended ingredients are conditioned by the application of heat. Said application of heat may be achieved by supplying steam to the ingredients.

The method may further comprise a pressing step downstream of said conditioning step, wherein the resulting animal feed is pressed into pellets. The pressing step may comprise extruding said animal feed through one or more dies or through a nip at a downstream end of a screw press. Preferably the animal feed is cooled downstream of said pressing step. The animal feed may be coated with an oil, such as vegetable oil, downstream of the pressing step.

According to a further aspect of the present invention there is provided an apparatus for preparing animal feed comprising a first grinder, one or more further grinders arranged parallel to said first grinder, means for splitting an incoming batch of material to be ground into at least first and second portions at a selected ratio, wherein said first portion is fed to said first grinder and said second portion is fed to at least one of said one or more further grinders, determining means for determining the process time taken for said first grinder to grind said first portion and determining the process time taken for said at least one of one or more further grinders to grind said second portion, and control means adapted to control the splitting means to adjust the ratio of said first and second portions in a subsequent batch as a function of the difference between the process time taken for said first grinder to grind said first portion and the process time taken for said at least one of one or more further grinders to grind said second portion of one more batches, thereby minimising said difference in process times for the grinding of the first and second portions of subsequent batches.

The splitting means may comprise a mechanical device configured to split said incoming batch into said first and second portions at a selected ratio. The mechanical device may comprise a moveable wall or diverter plate in a flow passage carrying said incoming batch.

The first and one or more further grinders may comprise rotating hammers or beater bars acting against a grinder screen or mesh.

In one embodiment there is provided a plurality of grinders or grinder sets, the first grinder being reconfigurable such that said incoming batch is selectable from a feed batch of at least one of said plurality of grinders or grinder sets, such that said at least one of said plurality of grinders or grinder sets comprises said one or more further grinders.

A blending process may be provided for blending ingredients to form said animal feed, said blending process comprising a weighing step, a grinding step and a mixing step, wherein said grinding step comprises said first grinder and said one or more further grinders.

Preferably means are provided for adding liquids to the ingredients in said mixing step downstream of said grinding step.

A conditioning process may be provided downstream of said blending process, wherein the blended ingredients are conditioned by the application of heat. For example, a boiler may be configured to add steam to the ingredients to heat the ingredients.

The apparatus may further comprise a pressing process downstream of said conditioning step, wherein the resulting animal feed is pressed into pellets by extruding said animal feed through one or more dies or through a nip at a downstream end of a screw press.

The apparatus may further comprise means for coating the animal feed with an oil, such as vegetable oil, downstream of the pressing step.

BRIEF DESCRIPTION OF THE DRAWINGS

A method and apparatus for preparing animal feed in accordance with embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which :Figure 1 is a schematic view of an apparatus for preparing animal feed in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

As schematically illustrated in Figure 1, a method and apparatus for preparing animal feed in accordance with an embodiment of the present invention comprises a weighing step 2, a grinding step 6,8 and a mixing step 10 for feed materials, typically comprising vegetable matter, followed by a conditioning step 14, a pressing step 16 and a cooling step 18.

In the weighing step 2, specified quantities of bulk solid raw materials may be dropped from bulk storage silos, preferably via screw conveyors with sufficient gradient to guarantee good emptying, into one or more load cell mounted hopper scales. The scales may be adapted to weight incoming batches between 1kg and 50kg or between 30kg to 3T to suit the amounts of each ingredient required. The weighed out raw materials may be transferred into dedicated pre-grinder bins.

Bulk liquid raw materials may be pumped from respective bulk storage tanks using dedicated pumps and process lines and added to the work in progress, or ‘mix’, as required.

Packed raw materials are either weighed out manually using weigh scales or prefilled into micro-ingredient bins and automatic weighing systems.

Medicinal additives may be automatically added, for example via a dedicated carousel unit, on a closed loop to mixers, enabling accurate additions to be made. Medicinal additives required in smaller quantities may be added manually. The manually weighed out raw materials may be added to the mix via a dedicated entry point.

The consumption of these licensed raw materials may be recorded in a register to facilitate subsequent verification of the materials and quantities consumed.

In order to ensure the homogeneity of the finished product and to produce the physical attributes required, the cereal raw material ingredients are ground in one or more grinders in a grinding step prior to being conveyed into a batch specific top hopper of a mixing plant in a mixing step.

Typically the batch grinding process is the slowest step in the animal feed production process. Therefore to avoid the creation of a bottle neck in the system two or more grinders 6,8 may be provided arranged in parallel, typically referred to as grinder sets, wherein an incoming batch of material to be ground is split to pass through each grinder of the set, the ground material being recombined downstream of the grinders of the grinder set. However, a problem with this arrangement is that the grinders may not all operate at the same efficiency as each other. Therefore simply splitting the incoming batch into equal portions may lead to one of the grinders in a grinder set taking longer to grind its portion of the batch that the others, causing delays in the system. It is also known to provide parallel arranged grinders sets, each comprising a plurality of parallel arranged grinders. Again, differences in overall process time between each grinder set can cause delays in the overall production process.

In accordance with an embodiment of the present invention there is provided a control system including an adjustable splitter device 4 upstream of a plurality of parallel grinders 6,8 (two shown in Figure 1), whereby the relative size of each portion of an incoming batch supplied to each grinder, or to two or more groups of grinders (grinder sets), may be adjusted, and means for determining the process time for each grinder or group of grinders to complete a grinding operation on a respective portion of the incoming batch, for example by sensing the arrival of material from each grinder or group of grinders at the subsequent mixing step, wherein the control system is programmed to compare the process time for each grinder or group of grinders and to adjust the splitter device 4 to adjust the relative size of each portion of a subsequent batch supplied to each grinder 4,6 or group of grinders to minimise the difference in the process time between the grinders.

By monitoring the process time of each grinder or group of grinders and, based thereon, adjusting the splitter device to adjust the proportion of material supplied to each grinder or group of grinders in subsequent batches, the effect of any fall off in performance of a particular grinder on the overall time required for the grinding process to be completed can be minimised.

In one embodiment an additional grinder may be provided arranged in parallel to one or more existing grinders or grinder sets, a portion of the incoming batch normally supplied to the one or more existing grinders or grinder sets being separated by said splitter device such that the additional grinder can reduce the overall process time of the mill by reducing the time required by the grinding step of the blending process. The process time of the additional grinder may be compared to the process time of the one or more existing grinders or grinder sets and the resulting time difference may be used by the control system to adjust the proportion of subsequent batches of material separated by the splitter device and supplied to the additional grinder to optimise the overall time of the grinding step.

It is envisaged that the additional grinder may be reconfigurable to be coupled in parallel to different sets of grinders (i.e. groups of grinders arranged in parallel to one another for grinding a common incoming batch of material) in the feed production plant, for example in parallel blending lines, where additional grinding capacity is required, to increase the adaptability of the mill.

Each grinder may comprise an electrically driven grinder, operating within a sealed enclosure, adapted to grind the material to a uniform particle size. In a preferred embodiment, rotating hammers within each grinder break down the raw materials and force them through a mesh. Variation in rotation speed and mesh size allow different products to be processed, as required (e.g. fast and fine for pellets and slow and coarse for meals).

Each grinder may be mounted above a respective collection hopper which may be vented via a reverse jet bag filter dust abatement unit which discharges to within the process buildings. Once ground, the batch of material in the collection hoppers is conveyed to the mixing step top hopper by means of enclosed conveyors.

From the top hopper the materials are gravity-fed into a batch mixer (schematically shown by reference number 10 in Figure 1). Mixers may be dedicated to specific product types (e.g. ruminant and monogastric formulations) to prevent cross contamination. At this stage of the process, the low inclusion ingredients (representing typically 5% of the product mass), such as vitamins, trace materials and medicinal additives, may be added directly into the mixer via feed lines 12. Depending upon the recipe, liquid additives, such as oils, can be weighed and added into the mix via dedicated lines at this stage.

The mixing may be performed within a horizontal enclosed continuous mixer. Two horizontal enclosed continuous mixers may be arranged sequence to improve process speed. The residence time for the mixing process is typically three to four minutes prior to despatch into a bottom hopper. When the mixing cycle is complete the homogeneous batch is conveyed for further processing in the conditioning and pressing steps. However, if a meal product is being produced, the batch may be either be transferred directly from the mixer to a finished product bin (if no heat treatment is required) or may be passed to the heat treatment line (conditioning step) for further processing.

The mixing step of the method is in an area in which tight controls and procedures are preferably employed, to prevent cross contamination, which can occur as a result of a batch of blended feed or raw material picking up traces of feed or raw material left behind by the previous batch. Production may be planned to sequence batches of medicated feed together, ensuring that the sequencing of production runs does not lead to cross contamination issues. When this is not practical, the processing system may be purged with a small batch of raw materials (such as non medicated cereal) known as a ‘flush batch’ or ‘clean-out batch’, to ensure that all traces of medicated additives are removed from the process lines and mixer. This flush batch may be incorporated in a finished batch of product in accordance with the relevant code of practice.

A conditioning step 14, comprising heat treatment of the feed product, may follow the mixing step 10. In the conditioning step steam may be directly added into the mix to raise its temperature so that any bacteria present (such as salmonella) are eradicated. The steam also improves the ‘workability’ of the mix in preparation for the subsequent pelleting process in the pressing step. Steam may be supplied from a boiler and passed into the mix through insulated lines. At this stage, further materials (such as molasses) may be added as required. Batches may undergo short term and long term conditioning, short term conditioning having a residence time of approximately 10 seconds and long term conditioning (LTC) having a residence time of approximately several minutes, dependant on LTC size and press throughput. During the conditioning step the mix may typically absorb between 1 and 4% by weight of moisture.

After conditioning the hot mix is preferably conveyed to a respective press line of the pressing step 16.

Two types of pressing may be carried out, namely standard pressing, where the pellets are produced by passing the mix into a press and extruding it through ring dies, or BOA compaction, where the pellets are produced by extruding the mix through a nip at the end of a screw conveyor prior to second pressing in a standard press. Varying the processing parameters, including nip and die dimensions and press rotation speeds facilitate the production of different pellet sizes, to meet specific product requirements.

After pelleting in the pressing step the hot product may then be passed through a counter flow air cooler 18 in a cooling step to reduce its temperature, causing it to harden and become durable. The cooling process preferably involves air at ambient temperature being passed directly over the pellets or nuts, either in vertical towers or over trays of feed in rotary coolers. Waste air generated throughout this part of the process may be ducted into a respective cyclone to remove dust and may then be vented to atmosphere. The dust collected may be recycled into production.

At least a portion of the resulting feed product may be crumbed to produce feeds for specific animals, such as piglets and chickens. Crumbing is the process of passing pelleted product through the nip between a set of counter rotating rollers within an enclosed system to produce a smaller product known as a crumb.

Approximately 95% of the processed pellets and crumb may be conveyed into an enclosed coater into which vegetable oils may be sprayed via meters onto the product.

Product despatch may be conducted in several outloading bays. Bulk vehicles may be positioned on a weighbridge below a conveyor discharge system.

Non-medicated products may be conveyed from finished product holding bins via a screen to remove extraneous dusty matter, to an appropriate discharge pipe and into the vehicle for delivery to the customer. Medicated products, however, may be conveyed from finished product holding bins to the vehicle without being screened and therefore are delivered to the customer with particulate matter, as a result of its associated medicinal additive content.

The invention is not limited to the embodiments described herein but can be amended or modified without departing from the scope of the present invention.

Claims

1. A method for preparing animal feed including a grinding step for grinding one or more ingredients, said grinding step comprising the steps of providing a first grinder arranged in parallel to one or more further grinders, splitting an incoming batch of material to be ground into at least first and second portions, said first portion being fed to said first grinder and said second portion being fed to at least one of said one or more further grinders, determining the process time taken for said first grinder to grind said first portion and determining the process time taken for said at least one of one or more further grinders to grind said second portion, and adjusting the ratio of said first and second portions in a subsequent batch as a function of the difference between the process time taken for said first grinder to grind said first portion and the process time taken for said at least one of one or more further grinders to grind said second portion of one more batches in order to minimise said difference in process times for the grinding of the first and second portions of subsequent batches.

2. A method as claimed in claim 1, wherein said method comprises using a mechanical device is used to split said incoming batch into said first and second portions at a selected ratio.

3. A method as claimed in any preceding claim, comprising the step of configuring the first grinder such that said incoming batch is selectable from a feed batch of at least one of a plurality of grinders or sets of grinders of a compounding mill, such that said at least one of said plurality grinders or sets of grinders comprises said one or more further grinders.

4. A method as claimed in any preceding claim, comprising the step of recombining said first and second portions downstream of said first and one or more further grinders and upstream of a mixing step.

5. A method as claimed in any preceding claim, including a blending step for blending ingredients to form said animal feed, said blending step comprising a weighing step, said grinding step of any of claims 1 to 4 and a mixing step.

6. A method as claimed in claim 5, further comprising adding liquids to the ingredients in said mixing step downstream of said grinding step.

7. A method as claimed in claim 5 or claim 6, said method further comprising a conditioning step downstream of said mixing step, wherein the blended ingredients are conditioned by the application of heat.

8. A method as claimed in claim 7, wherein said application of heat is achieved by supplying steam to the ingredients.

9. A method as claimed in claim 7 or claim 8, further comprising a pressing step downstream of said conditioning step, wherein the resulting animal feed is pressed into pellets

10. A method as claimed in claim 9, wherein said pressing step comprises extruding said animal feed through one or more dies or through a nip at a downstream end of a screw press.

11. A method as claimed in claim 9 or claim 10, wherein the animal feed is cooled downstream of said pressing step

12. A method as claimed in any of claims 9 to 11, wherein the animal feed is coated with an oil, such as vegetable oil, downstream of the pressing step.

13. An apparatus for preparing animal feed comprising a first grinder, one or more further grinders arranged parallel to said first grinder, means for splitting an incoming batch of material to be ground into at least first and second portions at a selected ratio, wherein said first portion is fed to said first grinder and said second portion is fed to at least one of said one or more further grinders, determining means for determining the process time taken for said first grinder to grind said first portion and determining the process time taken for said at least one of one or more further grinders to grind said second portion, and control means adapted to control the splitting means to adjust the ratio of said first and second portions in a subsequent batch as a function of the difference between the process time taken for said first grinder to grind said first portion and the process time taken for said at least one of one or more further grinders to grind said second portion of one more batches, thereby minimising said difference in process times for the grinding of the first and second portions of subsequent batches.

14. An apparatus as claimed in claim 13, wherein said splitting means comprises a mechanical device configured to split said incoming batch into said first and second portions at a selected ratio.

15. An apparatus as claimed in claim 14, wherein said mechanical device comprises a moveable wall or diverter plate in a flow passage carrying said incoming batch.

16. An apparatus as claimed in any of claims 13 to 15, wherein said first and one or more further grinders comprise rotating hammers or beater bars acting against a grinder screen or mesh.

17. An apparatus as claimed in any of claims 13 to 16, comprising a plurality of grinders or grinder sets, the first grinder being reconfigurable such that said incoming batch is selectable from a feed batch of at least one of said plurality of grinders or grinder sets, such that said at least one of said plurality of grinders or grinder sets comprises said one or more further grinders.

18. An apparatus as claimed in any of claims 13 to 17, comprising a blending process for blending ingredients to form said animal feed, said blending process comprising a weighing step, a grinding step and a mixing step, wherein said grinding step comprises said first grinder and said one or more further grinders.

19. An apparatus as claimed in claim 18, comprising means adapted to add liquids to the ingredients in said mixing step downstream of said grinding step.

20. An apparatus as claimed in claim 18 or claim 19, further comprising a conditioning process downstream of said blending process, wherein the blended ingredients are conditioned by the application of heat.

5

21. An apparatus as claimed in claim 20, further comprising a boiler configured to add steam to the ingredients to heat the ingredients.

22. An apparatus as claimed in claim 20 or claim 21, further comprising a pressing process downstream of said conditioning step, wherein the resulting animal feed is

10 pressed into pellets by extruding said animal feed through one or more dies or through a nip at a downstream end of a screw press.

23. An apparatus as claimed in claim 22, further comprising means for coating the animal feed with an oil, such as vegetable oil, downstream of the pressing step.