Processing Technology and Equipment for Fish Feed
With the development of fish farming business, projecting reasonable and proper fish feed processing equipment to produce high-quality feed to help fishes growing, is the key to promoting the sustainable development of fish farming industry.
Fish Feed Crushing Technology and Equipment
According to fishes’ physiological features and their requests for living environment, to ensure the optimal feed conversion rate and reduce the aquatic environment pollution that is caused by fish feed, the fish feed should be easy for digestion and absorption by fishes. For the same feed material, small particle size means a large surface area contacting with the digestive enzyme, which improves the digestibility of nutrients. So, making the digestible feed with small particle size is one of the effective methods to improve the feed utilization rate. Different fishes in different growing stages have different demands for feed particle size, therefore, choosing the right crushing technology and equipment is very important.
The crushing technology includes methods of crushing before dosing which is pre-grinding, or crushing after dosing which is post-grinding, or an integrated use of these two methods. The method of crushing before dosing is mainly for the adult freshwater fish feed production, and the crusher machine can be deployed based on the quality of the raw material to get economical validity.
However, pre-grinding also comes with some insufficient:
1)The exchange of raw materials will expend some time and impact the unit-time crushing capacity.
2)Small particle size increases the surface area of raw materials, making materials moist and less-mobility, causing materials caking, and then impacting the proper operation of dosing.
3)In the fish feed formula, there are many kinds of raw materials consisting of high protein and high fat, and the fat will block the crusher machine.
The post-grinding technology can solve the problems that pre-grinding has. Grinding means a good mixing of raw materials, eliminating feed materials caking. And the grinding machine for crushing after dosing has to be capable of crushing the hardest feed materials.
The integrated use of pre-grinding and post-grinding is especially working well for materials that need micro-grinding. Coarse grinding is the first-step processing; mixing the powder raw materials is the second-step processing, which benefits even mixing of raw materials and micro-grinding; and the third-step processing is to deliver the well-mixed materials into the micro-crushing machine to complete further crushing. Because a lot of heat will be produced during the micro-grinding process, the heat-sensitive material should be added when doing mixing after grinding; and different density and suspension velocity of materials will cause materials grading and unevenness, so, a second mixing is necessary after regrinding.
There are several crushing equipment for fish feed grinding, including hammer mill, vertical hammer mill, water-drop crushing machine, disk mill, micro-grinding machine and ultrafine grinder. Hammer mill has high efficiency when using the 2, 4mm sieve pore to process feed materials into particles with a size of 1200 µm; its 1 mm sieve pore can process materials into particles with a size of 500-600 µm which is the right particle size for the adult freshwater fish. But, hammer mill is not working well for fine grinding and processing raw materials of high moisture.
Vertical hammer mill has a higher working efficiency than hammer mill, because it has a rotor working as a fan, but it is not good at fine grinding, either.
Water-drop crushing machine has a crushing chamber employing double-grinding design. It can complete coarse, fine and micro grinding with 15% rise in capacity and particle size of 100-500µm. It is the first-choice machine for general fish feed crushing.
To get a particle size that is less than 500µm, a hammer mill and a grading screen can be combined to use; 60-100 µm particle size can be reached by air-grading micro-grinder; the required particle size for fishes’ first-feed is 10-20 µm processed by colloid grinder.
Fish Feed Mixing Technology and Equipment
To make fishes get full nutrition, especially the young fishes, feed materials need to be mixed well. And right mixing technology and equipment is of great importance.
1.Horizontal-type helical blade mixer and double-shaft paddle mixer are used in all-around feed mills for their compatibility.
2.In the post-grinding system, there should be 2 sets of mixing machines. One is used before crushing, and the other is used after crushing, to ensure an even mixing effect of finished powder materials.
3.Powder materials moisture content has significant impact on pellet feed process, capacity, quality and stability in the water, so, the water adding device is needed in the mixing process to add water into feed materials uniformly in atomazation form.
4.Affected by the friction motion in mixing process, feed materials will carry electrostatic charge that will influence the mixing uniformity, and ground connection and anti-static agent can solve this problem effectively.
Fish Feed Conditioning Technology and Equipment
Fish feed conditioning is to gelatinize the starch, denature the protein and soften the raw material by heat-moisture treatment to keep high-quality pellet fish feed with high stability and digestibility. There are two kinds of conditioning techniques: conditioning before fish feed pelleting and conditioning after fish feed pelleting, and the conditioning equipment has multiplex conditioner, curing tank, extruding conditioner (conditioning before pelleting) and stabilizer (conditioning after pelleting), etc.
1.Multiplex conditioner: it employs the organized assembly of two or three double-jacketed conditioners to prolong the time of conditioning powder material to improve conditioning result, but a certain amount of water in powder materials should be given. The curing tank has the same working principle with the multiplex conditioner, and they all take up too much space and the finished product can not realize the performance of first-in last-out.
2.Extruding conditioner: it uses high temperature and high pressure to make an increase in water resistance of pellet fish feed. This conditioning method has no high demand for feed particle size and formula, at the same time, it can make full use of cheap raw materials and reduce cost. Itt is an ideal conditioning method for fish feed mills with good prospect.
3.Stabilizer conditioning: after fish feed pelletization, the pellet is hot and it enters into the thermal insulation container to use its own heat and moisture and the heat produced by the steam in the jacket to better fish feed pellet digestibility and stability in the water.
Fish Feed Pelletizing Technology and Equipment
Pelletizing technology and equipment is an important factor affecting fish feed quality.
1.Fish feed pellet mill
The performance of fish feed pellet mill is critical for fish feed pellet quality. In terms of die thickness and compression ratio, the fish feed pellet mill needs to be equipped with a die of great thickness and high compression rate.
2.Fish pellet feed extruding machine
Extruded feed is a standard of high-quality fish feed. And fish pellet extruding machine can be used to produce floating fish feed pellet, sinking fish pellet feed, and floating-sinking fish feed pellet to meet different feeding requirements of various fishes.
3.Fish feed pellet cooler
Cooling the finished feed pellets with high temperature and humidity is for well pellet packing and storage. But the quick cooling is not available, because it will cause cracks in pellets surface, thus weakening the water resisting property of pellet feed. Counter-flow pellet cooler and horizontal pellet cooler are the two types of commonly-used cooling equipment with ideal cooling effect.
Fish Feed Liquid Coating Technology and Equipment
Except the existed fat in the feed, the extra fat needs to be added into the fish feed pellet to supply sufficient fat acid to facility fishes growing and production. The fat coating for fish feed pellet can be done before pelleting or after pelleting. But the heat-sensitive nutrients, such as vitamins, amino acid, enzyme, etc. should be added into fish feed pellets by liquid coating equipment after pelleting to ensure their effectiveness.
The coating technology has been improved a lot to guarantee fish pellet feed quality and avoid water pollution. According to the working principle, the liquid coating equipment is divided into vacuum infusion coater, spraying atomization coater and centrifugal atomization coating machine.
1.Vacuum infusion coater: there is a vacuum in the coater, and when the dry material is rolling-over and moving, the fat and heat-sensitive nutrients that are sprayed into the coater is absorbed by loose structure of the dry material.
2.Spraying atomization coater: the fat and nutrients are micro-granulated by the sprayer and then sprayed to the fish feed surface.
3.Centrifugal atomization coating machine: this kind of machine employs centrifugal motion to micro-granulate additives to coat the fish feed pellet.
4.Electrostatic coating is another feed pellet coating technology introduced from food processing technologies. It makes the atomized liquid to complete pellet feed coating efficiently.
All in all, choosing proper fish feed processing technology and equipment should be based on fish species, fish feed raw materials and processing efficiency to meet the fish feed production demands and reduce production cost as well.