What does a pelleting system consist of?

Why pellet?

The most obvious reasons are:

•             Better digestibility;

•             Less waste during consumption and transportation & storage;

•             More assured intake of all elements;

•             Conversion of powdery / unpalatable ingredients to concentrated feed and ensuring separated mixed ingredients are all consumed;

•             Higher bulk density and therefore less storage & transportation space;

•             However, the most compelling reason for pelleting is that the gain per kilogram feed increases with pelleted feed vs mash.

•             It has been innumerable times proven that swine specifically gained on average 113 grams per day more weight being fed pellets than the same ration and amount of mash. Poultry, cattle and small stock likewise has similar gain advantages.

•             In the case of sheep and goats, which are notoriously picky eaters, the full ration and waste are also important reasons to pellet feed.

What is the cost of pelleting?

Pelleting should not add more than R103 (US$6-7)  per ton to your feed, which includes electricity, maintenance, wear and tear, and operator cost.

At one pig’s average consumption of 2.5kg feed per day, a ton of feed would last 400 days or would finish approximately 4 pigs to 80-90kg. With 113 grams additional weight per day on pelleted feed, the said pigs would gain 51 additional kilograms, being more than R1,200 higher income at slaughter at R24 per kg live weight.

Therefore a 1,165% gain over the additional operational cost.

Can cost be reduced & efficiency increased by adding steam?

Yes it can. Steam lubricates the product for faster production, the lubrication extends die life, it reduces energy costs and gelatinizes starch for higher nutritional value. Fines also bind better and less pellet breaking occurs.

Heating mash with steam to 75 degrees C will reduce friction heat no less than 30% and reduce motor amps by 20% while increasing capacity fourfold. The amount of roughage vs grain and protein, molasses content etc. would however play a role in these equations.

While steam addition at 50kg per hour or 5% on a 1,000kg/hour mill, an additional electricity cost on around 37kW can be expected. This however would be easily offset by the higher production and lower replacement cost of dies as well as lower electricity per kilogram produced on the pellet mill itself and a payback of less than 6 months.

An electric steam generator can be purchased from ABC Hansen for around R119,400 VAT Included. This steam generator will produce 50kg. of steam at working pressure of 101 PSIG (pounds per square inch guage) operating at 4 – 94 PSIG (or around 7 Bar) with 3 x 12kW = 36kW elements plus a 0.55kW pump and is a perfect match for our MPEL400  and one or two MPEL260 pellet mills.

What does a pelleting system consist of?

1. Supply bins and intake: With free flowing grain and other free flowing materials hopper bins are normally filled by elevator and conveyor from bulk trucks. Bagged free flowing materials may also be discharged into a reception bin and conveyed into a supply bin. Non-flowing items are normally offloaded in heaps and collected with front end loaders into reception bins on load cells prior to conveyance to the pre-blending bin. Should these non-free-flowing materials be loaded into a bin, a roto-flow vibrating device needs to be installed below the bin. The supply bins should have at least 5 times the capacity of the pre-blending bin.

2. A scalper fitted with magnets to screen out large particles and tramp steel should be part of the intake system in order to prevent damage to all equipment down-line.

3. Milling: It is preferable to grind down the raw materials to a size is at most equal to the pellet die aperture and preferably smaller. Particles any larger would imply that the pellet mill would be tasked to grinding these particles resulting in higher wear and tear, higher electricity use and lower capacity. A Hippo hammer mill should be selected in the correct capacity. This range of mills includes

4. Pre-blending bin: This is preferably located over the blender allowing the complete ration to be made up and dumped into the blender once the previous blend has been unloaded. This increases the number of batches to be mixed per hour.

5. The blender: The size of the blender together with the speed of conveyance into the pre-blending bin and the speed of unloading  determines the capacity of the mill. Blender capacity in liters would presume that the blender is filled only to the shaft and the density of the mix is then calculated to determine the kilogram capacity of the blender. A 3,000 liter blender filled to the shaft at around 1,500 liters, with a density of 0.6 would determine a mixing capacity of 900 kilograms per batch.

6.Post blending bin: Where the batch is immediately conveyed to subsequent to mixing, usually at the fastest capacity possible to ready the blender for the next mix and is at least two or three times the capacity of the blender and matching the capacity of the pellet mill times 3 to allow for the clearing of blockages, change of die and other non-scheduled and scheduled break in continuous production.

7. The conveyor feeding the pellet mil, allowing for minute speed selection to allow the mill to operate at most efficient capacity.

8. The steam generator with steam addition to the conveyor feeding the pellet mill or in a special conditioning chamber with feed, is normally in capacity of 5 – 7% of the normal production of the pellet mill without steam having been added. With 3 x the capacity of the pellet mill without steam, at least 2% moisture should be added to the mix containing a minimum of 12% moisture prior to steam addition. Wet molasses addition and further water addition may be used to bring the mix to +- 12% prior to steam addition. The pelleting process would remove around 2% moisture from the mix resulting in neither shrinkage nor gain. Higher moisture addition would result in higher gain but also in more pellet breakage – thus a 2% gain is generally accepted as optimal.

9. Pellet mill: The original pellet mills manufactured and patented in 1931 in California, had a stationary flat die. Today primarily cylindrical as well as flat revolving and stationary dies are used. Smaller mills up to +- 30 kw and 1 ton capacity per hour on dry basis are often flat dies due to its relatively simpler design, faster cleaning (when blockages occur), lower die-, roller- and maintenance cost and generally lower market entrance cost. Speed reduction may be either be V-belt with sprocket and chain and gearbox. Mills are generally driven by electric motors but diesel or petrol engines with gearboxes are often fitted. Ensure the supplier has sufficient dies and rollers and other spare parts in stock and is able to service the mill, before buying it. It is strongly advised not to try and import a pellet press yourself as end user as you will probably end up re-buying this machine several times over.

10 Pellet cooler and grader: Pellets need to be cooled with cold air to avoid sweating which produces cracking and disintegration. Broken pellets are screened out and may be used to either re-introduce into the pellet press or may be crumbled for small sized feed for poultry and birds. The preferred conveyance methods are bucket elevators and belt conveyors to avoid breaking of pellets

11. Crumbler: This is a roller mill through which pellets are run crumbled to the desired size for feeding chicks of various types.

12. Finished products bins are  filled with bucket elevators and  belt conveyors and unloaded the same way into bulk feeding trucks or bagged off for further distribution.

These and many more pelleting facts can be obtained by visiting www.abchansen.co.za.

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