In the feed factory at FôrTek (Centre for Feed technology) at NMBU, an inventor of the Gyro Gearloose persuasion is hard at work. Through creative thinking, simple means and a passion for his trade, senior engineer and technical section leader Ismet Nikqi has altered the paddles of a mixing machine used in the feed production chain, in a way that may give new innards to these machines throughout the feed industry. The improved machine reduces the risk of pellets being crushed or breaking to bits.
More feed for the fish
The invention presents several advantages. Especially during feeding time at the fish farms. When farmed fish are fed in the netpens, compressed air “shoots” feed pellets through hoses that lead from a large container to the pen. The pellets travel at good speed over the fish in the pen.
However, at production in the factories, the pellets undergo some pitted treatment, which leads to crazing – tiny breaks or cracks – in the pellets. These cracks do not show on the surface, but during transport to the farm and during feeding, some of the pellets break.
─These smaller pieces are carried along through the feeding hoses. Since they have a relatively large surface and are sticky, they stick in lumps to the inside of the hoses – rather like the hardening of human arteries – says FôrTek Centre leader Olav Fjeld Kraugerud.
Out of 100 kg of produced feed, not all will reach the fish, due to dust etc., as mentioned above. If, however, the pellets get there without breakage, almost all the produced feedwill be available for the fish to actually feed on.
Not only do the fish farmers lose feed in this way, but the entire feeding installation must be cleaned regularly, and with hoses up to 2 kilometres in length, there is great potential for savings on the need for maintenance and cleaning.
Less wheat glue and less dust
When all the pellets are of even size and weight, they will sink at the same rate, and besides, the fish prefer the larger pieces, not the small dusty particles.
Wheat starch is added to the feed mix as a sort of glue to hold an individual pellet together. The fish are able to digest a limited amount of starch
─Not that it is a goal to reduce the amount of wheat starch in the feed itself, but the possibility will be there with this new and gentler production method, says Kraugerud.
Added bonuses to the method are reduced energy consumption during feed production, less dust at production, and the portion of feed dust and broken pellets that must be sifted and put through the process in the factory for a second time is reduced.
Quick intro to feed production
Producing feed pellets is a three stage process. First, all the dry ingredients are mixed together, then the mix is fed through to an extruder, where water is added. An extruder is basically a long screw inside a cylinder which is wide at one end and narrow at the other. The screw kneads and works the feed mix through the narrowing cylinder. When it reaches the end of the screw and cylinder, the feed is pushed through a perforated panel. The feed would look like spaghetti if not for the chopping mechanism which now cuts the feed spaghetti to the required length.
The final stage of the process, the adding of oil, takes place in a vacuum coater. This is where the innovation comes into its own. The pellets are poured into a large round container which rotates on its own axis. Oil is added, and inside the container there are structures that beat and throw the pellets about to distribute the oil evenly and coat each individual pellet. Next, all the air is sucked out of the container to create a vacuum, before air is let in again. Since there are tiny empty spaces inside the pellets, the oil is sucked into each pellet.
The crazing, breaks and cracks in the pellets originate largely while the paddles inside the coater are throwing the pellets around. This is where Nikqi had his idea for a gentler approach.
Started in a bucket
Inspired by experience from others who have attempted the same thing, and by reading an article saying how Brazilian authorities had set a maximum limit on the amount of crushed pellets to 5%, Nikqi got out a bucket and some left-over feed. He got hold of an inexpensive vacuum pump that fit the bucket, and started his testing.
To begin with, his hands did the job of the structures inside the coater.
─When I used my hands as paddles to distribute the oil around the pellets, I could see that the finished pellets had much less cracking than they have after a normal bout in the coater, Nikqi says.
Encouraged by the results from the bucket, Nikqi applied for and received support from the NMBU Technology Transfer Office to develop his idea.
The prototype rolls along
Step two was a prototype. The bucket was left behind, and in rolled a small cement mixer. A vacuum pump was mounted on to the mixer. And now for working out the details of the innovation.
─The goal was to design, fashion and make it in such a way that they treated the pellets as gently as my hands did in the bucket, says Nikqi.
Just like Gyro Gearloose, Nikqi used what he had at hand.
─In our back room, I found some bits of metal and some shelving that we had lying around.
After drawing, fashioning and fitting the metal pieces, after getting help with the mounting, some trial and error and testing, Nikqi was content. The construction of the new paddles inside the cement mixer gave the pellets a more gentle treatment and still distributed the oil evenly. The pellets were now treated gentle instead of being beaten and thrown around.
─There were more intact pellets and less crazing and cracks in the pellets that came out of the cement mixer than what comes out of the ordinary vacuum coater. Sink tests showed that the pellets sunk more evenly in water than ordinary pellets do, says Nikqi.
Selling the idea
Selling an idea isn’t necessarily easy, even when the idea is brilliant. But a visiting representative from the machine producer Amandus Kahl of Germany was intrigued.
Among other things, Kahl produces machines for the feed industry – machines with a capacity to process several tons of feed per hour.
Even though Nikqi had complete faith in his invention, he was a little anxious when a delegation from Kahl some time later came to NMBU and FôrTek to look at it. He wondered what they would think about the little 16 kg capacity cement mixer.
─I thought they might laugh when they saw it – and they did, says Nikqi.
But interest in the performance of the cement mixer soon caught everyone’s attention. The interest was so great that Kahl has now made their own prototype, and will eventually start producing vacuum coaters equipped with Nikqi’s know how installed.
Why hasn’t anyone thought of this earlier?
─We’ve wondered, too. Most likely because today’s vacuum coaters and the feed made in them sell well as it is. Perhaps no one has seen the need or the advantages to doing something about it.
─There are no drawbacks, only advantages, to the new coater, and it is technically simple. The Nikqi coater will surely become standard in all feed factories, says Kraugerud.