Grinding equipment for aquatic feed pellets


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Aquatic animals have various feeding habits and feed intakes. For example, fish swallow feeds so they need about 40 minutes to intake feeds. However, shrimps nibble feeds so they need three to six hours to intake feeds.

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Grinding equipment for aquatic feed pellets

  1. 1. September | October 2013 Grinding equipment for aquatic feed pellets The International magazine for the aquaculture feed industry International Aquafeed is published six times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2013 Perendale Publishers Ltd.All rights reserved.No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058 INCORPORATING f ish farming technolog y
  2. 2. Innovations for a better world. Bühler AG, Feed & Biomass, CH-9240 Uzwil, Switzerland, T +41 71 955 11 11, F +41 71 955 28 96, Fatten up your bottom line. Bühler high-performance animal and aqua feed production systems are used by leading companies around the world. These producers know they can rely not just on the technology itself, but also on the support that accompanies it. A service combining local presence with global expertise both lowers feed mill operating costs and increases capacity utilization. To find out more, visit
  3. 3. A quatic animals have various feeding habits and feed intakes. For example, fish swallow feeds so they need about 40 minutes to intake feeds. However, shrimps nibble feeds so they need three to six hours to intake feeds. The digestive tract of aquatic animals is relatively short so they have poor digestive ability. For example, fish have no salivary glands in the oropharyngeal cavity which helps seek, intake and swallow feeds. So the func- tions of tearing and grinding feeds degenerate. Fish dissolve and digest feeds from the feed surface so aquatic feeds with small particles are convenient for digestion and absorption. These characteristics mean that aquatic feed pellets should have good stability and water resistance; be easy to digest; and be the fineness specific growth stages. In order to produce ideal aquatic feed pel- lets, feed ingredients, processing technology and equipment especially the grinding process, should be carefully considered. Nutrition sources for feed pellets Raw materials for pellets should con- sider not only the nutritional values but also the need for good stability in water. Protein, which ensures the growth and reproduction of aquatic animals, is an essential of aquatic feed pellets. It accounts for 25-50 percent of the feed formula with wheat and wheat by-products as the main sources of protein. If the viscosity of protein is increased when heated, then the pelletizing performance is improved and the stability is good. Starch is the most common carbohydrate used in aquatic feed pellets. To ensure the stability of feed pellets in water, the starch content of sinking feed pellets should be up to 10 percent and that of floating feed pellets should be about 20 percent. Coarse fat is a good source of high quality energy. The crude fat level includes the fat of feed ingredients and that of added fat. The added fat has great influence on the pelletizing effect but too much fat will make the feed pellet loose and influence the stability. For this reason, the content of added fat should not exceed 3 percent. Fishmeal is widely used in aquatic feed pellets. High quality fishmeal has good water resistance qualities. Similarly, rapeseed dregs contain high coarse fibre which is conducive to improving the water resistance of aquatic feed pellets. Among the commonly used feed ingredients cotton pulp, fishmeal and soybean meal, have good water resistance characteristics while the water tolerance of corn, bran and rice bran is poor. Adding moderate binders can improve water resistance. There are two kinds of binders: natural substances such as sodium lignin sulphonate and align, and chemical sub- stances such as carboxymethyl cellulose and sodium polyacrylate. So when designing feed formula the raw materials should be highly nutritious and have good water resistance properties. Why is grinding so important? The aquatic feed pellet has high require- ments in terms of particle size and viscosity so the processing technology is important. In general, feed ingredients for aquatic feed pellet should be ground to 40 meshes. For special aquatic animals such as shrimps, turtles, eels and other small animals, the raw materials should be super-finely ground so as to pass through a 100 mesh screen. The fine crushing granularity can improve the utilization rate of aquatic feed pellet. Aquatic animals have simple digestive sys- tem and the residence time of feed in the gut is short so pellets containing large particles are Grinding equipment for aquatic feed pellets by Joyce Li, customer service, Amisy Machinery, China Table 1 10 | InternatIOnal AquAFeed | September-October 2013 FEATURE
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  5. 5. not conducive to easy digestion. The finer the crushing granularity, the larger the surface area which contacts with the digestive enzyme thus the digestibility is increased. Raw materials come in different shapes and thicknesses. So if they are not ground before processing, the finished pellets can lack a balanced nutritional quality and have poor stability in water. Table 1 shows the relationship between the grinding fineness and stability in water. Feed pellets have little viscosity when ground to a large particle size. The crushing fineness also has an effect on the following processes such as mixing and steam modulat- ing and the fineness of pulverization has great influence on stability. When the grain fineness is perfect, the raw materials can be fully mixed and the swelling property of materials converge making for good stability. Finer particle sizes will have a larger surface area which can be fully modulated, making better-formed pellets. Although finer particle size is conducive to producing feed pellets with good stability, the grain size should not be too fine otherwise the pel- leted feeds are fragile. The proportions of coarse grain, medium grain and fine grain should be appropriate so that during the pelleting period the fine grain can fill the space between the coarse grains. This means that the contact area between particles is increased and the pelletizing performance is improved. Choosing the appropriate grinding equipment is crucial Controlling the grinding fineness has a direct influence on the stability of aquatic feed pellet and the production cost. The impor- tance of cost should not be underestimated; electricity consumption during the grinding process accounts for 50-70 percent of the total power consumption. Choosing the appropriate grinding equip- ment is also critical. Different aquatic animals have different requirements in terms of par- ticle size of feed ingredients which requires corresponding grinding equipment. Hammer mills are widely used in the feed industry and in aquatic feeds. The hammer mill consists of hammers, a rotor, the grinding surface and sieve. The hammer is the main working part whose shape, size, quantity and line speed has a great influence on the grinding efficiency and grinding fineness. When the linear velocity of hammer blade is slower, the grinding efficiency and production efficiency are low. A quicker line speed will improve grind- ing efficiency. However, too high a speed will make the material speed fast, reduce Figure 1 September-October 2013 | InternatIOnal AquAFeed | 11 FEATURE Extruder OEE for the Production of Fish FeedExtruder OEE for the Production of Fish Feed AMANDUS KAHL GmbH & Co. KG, Dieselstrasse 5-9, D-21465 Reinbek / Hamburg, Phone: +49 40 727 71 0, Fax: +49 40 727 71 100,
  6. 6. the grinding efficiency, increase the power consumption and increase the energy con- sumption of products. The optimal line speed should consider factors such as the power consumption, grinding fineness, noise and production efficiency. The number of hammers has a great effect on the grinding fineness and crushing efficiency. Out simply, more hammers means faster and finer grinding. Fewer hammers results in a coarser product. Mesh screen and sieves are related to the grinding fineness. Figure 1 shows the relationship between grinding fineness of corn, bean pulp and the mesh screen diameter. The smaller the diameter of mesh screen, the finer the grinding fineness and the lower the output. In turn, when the diameter is big, the grinding fineness is coarse and the output is high. The size of mesh screen diameter is determined by the required size of the final pellet so in the context of meeting the grinding fineness of feed pellets a sieve with big diameter should be adopted so as to improve the crushing efficiency and reduce energy con- sumption. Studies show that when the sieve area is increased by 9 percent, the grinding efficiency can be improved by 35 percent and the electricity consumption can be reduced by 13 percent. So choosing the appropriate sieve area can improve the output. In addition, the thickness of sieve influ- ences the sieving ability of materials. There is a corresponding and restrictive relationship between the sieve thickness and the diameter of mesh screen: sieve thickness is less than or equal to the diameter of mesh screen. The fineness requirement of ordinary aquatic feed pellet is 40-60 mesh. In order to achieve the ideal crushing fineness and avoid the super-fine grinding of materi- als, the grinding surface shape should be changed. A water drop grinding surface is widely adopted in producing the aquatic feed pellets. A water drop sieve shape can increase the effective sieve area, destroy the circulation layer of materials so as to change the material motor direction, increase the frequency of hammer grind- ing the materials and improve crushing efficiency. Grinding machine options Machine for fine grinding have a higher spindle speed, more hammers numbers and a wider grinding surface than models for coarse grinding. The Amisy series of AMS-ZW-29C, AMS-ZW-38C and AMS-ZW-50C hammer mills can be used for coarse grinding of feed ingredients. The main differences of the three models are the grinding room width, hammer blade quan- tity, power. The wider the grinding room, the higher the crushing effi- ciency. More hammers will produce finer prod- ucts though of course the higher power means the more output. The Amisy series of AMS-ZW- 60B and AMS-ZW- 80B ham- mer mills are mainly used for fine grind- ing. The out- put differenc- es between the two models are related to the power, grinding room width and hammer numbers. The AMS-ZW-80B model has more ham- mers, a wider grinding surface and greater- power than that of the AMS-ZW-60B. This means that the output of AMS-ZW-80B is greater than that of AMS-ZW-60B. Both the series use the water drop design to ensure a larger space for grind- ing and to improve crushing efficiency. The crushing fineness differences between the two models mainly lie in the spindle speed, hammer numbers and grinding sur- face width. Producing fine feeds As mentioned previously, aquatic animals such as shrimps, eels and turtles require fine feeds. For these animals, grinding fineness must be up to 80 mesh. Ordinary hammer mills cannot reach this fineness so ultra fine feed grinding equipment is necessary. To achieve the required small particle size, ingredients should be crushed twice. An initial coarsely grinding can be done by a hammer mill with a second grind on an ultra fine mill. Ultra fine grinding equipment uses the blade type. The grinding chamber and grading room of Amisy’s AMSSWFL42, AMSSWFL75, AMSSWFL102 and AMSSWFL128 models are located in the same machine body so that crushing, grad- ing and separation can be completed simul- taneously. The main differences between the three models lie in feeding motor power, sieving motor power, rotor diame- ter and rotor speed. When the rotor speed is faster the grinding fineness is finer but the grinding efficiency and output are accord- ingly reduced. Compared with other feed hammer mills, the ultra fine feed crushing mill has a lower output because the rotor speed is faster. The main index to evaluate the working efficiency of feed grinding equipment is the grinding fineness, output and power consump- tion. Grinding fineness has great influence on the feed utilization, production properties of aquatic animals, feed pellet quality and production cost. Considering factors such as the mesh screen, hammer quantity, spindle speed, grind- ing surface size and choosing the appropriate power based on the composite factors, grind- ing can produce homogenous pellets, improve output and reduce the electricity consump- tion and production costs. More InforMatIon: Email: Website: 12 | InternatIOnal AquAFeed | September-October 2013 FEATURE Die and roll re-working machines O&J Højtryk A/S Ørnevej 1, DK-6705 Esbjerg Ø CVR.: 73 66 86 11 Phone: +45 75 14 22 55 Fax: +45 82 28 91 41 mail: AD_o&j.indd 1 21/11/2012 15:08
  7. 7. September-October 2013 | InternatIOnal AquAFeed | 13 FEATURE THE BEST WAY TO PREDICT THE FUTURE IS TO CREATE IT. —Peter F. Drucker Turning ideas into opportunities. PROGRESSIVE AQUAFEED PROCESSING What will tomorrow bring BElGIUm TAIWAN BRASIl CHINA TURkEY INDIA Why retire a workhorse that’s still doing the job? Simply put, your old dryer may be costing you a bundle. In fact, today’s Wenger dryer could save you enough in operating efficiency alone to cover the replacement of your old dryer. Additionally, our new advanced dryer designs give you less potential for cross-contamination and bacteria build-up; feature new direct drive spreaders for level product bed and uniformity of final prod- uct moisture; and afford quicker, easier inspection and cleaning. Contact us now. With new concepts and fresh initiatives, we’re ready to help you develop the product possibilities of the future. Wenger12_AQ_210x147mm.indd 1 8/8/12 12:01 PM
  8. 8. LINKS • See the full issue • Visit the International Aquafeed website • Contact the International Aquafeed Team • Subscribe to International Aquafeed The potential of microalgae meals – in compound feeds for aquaculture Understanding ammonia in aquaculture ponds Volume 16 Issue 5 2013 - sePTemBeR | oCToBeR INCORPORATING fIsh fARmING TeChNOlOGy EXPERT TOPIC – Salmon AquaNor event review Thisdigitalre-printispartoftheSeptember|October2013editionofInternational Aquafeed magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on To purchase a paper copy of the magazine, or to subscribe to the paper edition please contact our Circulation and Subscriptions Manager on the link above. INFORMATION FOR ADVERTISERS - CLICK HERE