Generally, the process flow of a small and medium-sized livestock and poultry feed factory consists of raw material receiving, crushing, batching, mixing, granulation, cooling and screening, and finished product packaging sections; the core production equipment is a pulverizer, mixer, granulator, etc. The selection of these equipment plays a vital role in feed production and ensuring the quality of feed. The following will briefly discuss the role and selection of the three types of equipment in production.
1 The function and selection of the pulverizer
Crushing is an operation method that mechanically overcomes the cohesive force of solid materials and breaks them. It is one of the most important processes in the feed processing process and is an important factor affecting feed quality, output, power consumption and processing costs. Effects of crushed feed: a. Increase the surface area and particle size of the feed, which is beneficial to the digestion and absorption of animals. Animal nutrition experiments have proved that reducing the particle size improves the digestion and absorption of dry matter, protein and energy, and reduces the feed-to-meat ratio; b. Improve and enhance the processing performance of materials. Through crushing, the particle size of the material can be basically the same, reducing the material classification after mixing evenly; for trace elements and some small component materials, only by crushing to a certain extent to ensure that there are sufficient particle numbers can the mixing uniformity requirements be met; and For example, for the granulation process, the particle size of the crushed material must consider the interaction between the crushed particle size and the pellet feed, and the crushed particle size will affect the durability of the pellets and the stability of the aquatic feed in water; c. The particle size of the crushed feed can be significantly improved The conversion rate of feed can reduce the excretion of animal feces, improve the utilization rate of animal feed, and improve the efficiency and quality of subsequent feed mixing, tempering, granulating, and extruding.
The power equipment of the pulverizer generally accounts for about 1/3 of the total power equipment of the feed factory. How to reasonably select advanced pulverizing equipment, design the best process route, and use the pulverizing equipment correctly is very important for feed production enterprises. Livestock and poultry feed generally use SFSP series hammer mills, which are widely used because of their high efficiency, good crushing performance, and wide adaptability. They can crush feed materials to 40-60 meshes, and are suitable for various pig feeds and chicken feeds. , the production of cattle and sheep materials, this model has the following characteristics: a. It adopts a large-diameter low-speed structure, low noise and reduced vibration; Positive and negative conversion work ensures that the tangential feeding of the material is compatible with the rotation of the rotor, and there is also an emergency stop function; c. The screen is directly inserted and then pressed by the operation door to facilitate loading and unloading; d. Tungsten carbide is used The wear-resistant hammer with surfacing welding can increase the service life by 7~8 times compared with ordinary hammer; e. The additional safety device can make the pulverizer unable to start after the operation door is opened, ensuring safety.
In addition, the purchase of a centrifugal fan for a pulverizer can do more with less to improve the pulverization efficiency. After the material passes through the friction between the hammer and the sieve, it should be discharged out of the crushing chamber immediately, so as not to cause blockage, increase the temperature in the crushing chamber, or even cause a dust explosion. How is the crushed material quickly discharged from the crushing chamber? After the centrifugal fan is started, a continuous negative pressure environment will be formed in the crushing chamber and settling chamber, and qualified materials will quickly pass through the sieve under the action of negative pressure to complete the crushing of materials. The centrifugal fan can absorb the moisture of the finished product, reduce the humidity in the finished product, facilitate storage, increase the crushing efficiency by 10%~15%, and reduce the dust in the crushing room. Therefore, it is very important to choose a centrifugal fan with a suitable wind pressure to improve the crushing efficiency.
2 The function and selection of the mixer
Mixing is an operation in which various feed materials are mixed with each other under the action of external force after metering and batching of various feed materials to make them evenly distributed. In order to ensure that livestock and poultry can eat rations containing various nutrients in each meal, it is necessary to ensure that each component material is evenly distributed in the whole batch of feed, especially some additives that are added in a very small amount and affect the growth of livestock and poultry. Large "active ingredients", such as vitamins, trace elements, pharmaceuticals and other trace ingredients, require even distribution. Therefore, in feed production, the working condition of the main mixer not only determines the quality of the product, but also plays a decisive role in the productivity of the production line and the quality of the feed, so it is known as the "heart" of the feed factory.
The main technical indicators of the mixer are: mixing amount per batch, mixing uniformity, mixing speed and material residual rate in the machine. a. High requirements for mixing uniformity: According to the feed standard, the coefficient of variation of the mixing uniformity of the compound feed is ≤10%, and the coefficient of variation of the mixing uniformity of the premixed feed is ≤5%; b. The mixing time should be short: the mixing time is determined The length of the mixing cycle and mixing time can affect the productivity of the production line; c. The residual rate in the machine should be low: in order to avoid cross-contamination and ensure the product quality of each batch, the residual rate in the compound feed mixer is ≤1%, pre-mixed Feed mixer ≤0.8%. The current advanced models can reach less than 0.01%; d. The mixer should meet the mechanical performance requirements such as reasonable structure, simple structure, no material leakage, and easy inspection, sampling and cleaning. At present, the most widely used in the market is the twin-shaft paddle mixer. The mixing is light and gentle, and the mixture has no segregation phenomenon. Especially when the particulate material (trace additive) is in a fluid state, the diffusion mixing effect is better; the material is in the mixer. A fluidized area is formed inside, coupled with convective mixing and shear mixing, the twin-shaft paddle mixer has faster mixing speed and higher mixing uniformity than ordinary mixers. During the use of the mixer, the sealing strip needs to be replaced regularly to prevent material leakage, so as to ensure that all materials remain uniform during the mixing process; at the same time, the mixer should be cleaned regularly to prevent materials sticking to the inner wall of the mixer in a humid environment. Bacteria and mildew will affect the quality of livestock and poultry feed.
3 The function and selection of pellet machine
Granulation refers to the process of compacting a single raw material or a compound mixture through mechanical action and extruding it out of the die hole to form a granular feed. The purpose of pelleting is to make finely divided, dusty, poorly palatable and difficult-to-ship feeds into pellets by using the heat, moisture and pressure in the pelleting process.
Compared with powdered feed, pelleted feed has the following advantages: a. Improve feed digestibility: During the pelleting process, due to the combined effects of water, temperature and pressure, some physical and chemical reactions will occur in the feed to gelatinize the starch and activate enzymes. The enhanced activity enables the fed animals to digest feed more quickly, which translates into weight gain. b. Reduce animal picky eating: compound feed is made of various raw materials according to the nutritional needs of animals. Through granulation, various powdery raw materials are integrated into a whole, which can prevent animals from picking what they like to eat from the powder and refuse to eat. The phenomenon of adding other ingredients, because the pellet feed can maintain uniformity during storage, transportation and feeding, can reduce feed loss by 8% to 10%. c. Make storage and transportation more economical. Granulation generally increases the bulk density of the powder by 40% to 100%. d. Avoid automatic grading of feed ingredients and reduce environmental pollution. In the process of powder storage and transportation, due to the different bulk density of various powders, it is easy to produce grading, and there is no grading of feed ingredients after being made into granules, and the granules are not easy to dust. During the feeding process, the granules are harmful to air and water quality. The pollution is much less than that of powder. e. Eliminate Salmonella in animal feed: Salmonella will remain in animal tissues when ingested by animals. People will get a Salmonella gastrointestinal disease after eating animal products infected with this bacteria. The method of high-temperature steam conditioning and granulation can kill Salmonella existing in animal feed and reduce the spread of pathogens.
3 The function and selection of pellet machine
Granulation refers to the process of compacting a single raw material or a compound mixture through mechanical action and extruding it out of the die hole to form a granular feed. The purpose of pelleting is to make finely divided, dusty, poorly palatable and difficult-to-ship feeds into pellets by using the heat, moisture and pressure in the pelleting process.
Compared with powdered feed, pelleted feed has the following advantages: a. Improve feed digestibility: During the pelleting process, due to the combined effects of water, temperature and pressure, some physical and chemical reactions will occur in the feed to gelatinize the starch and activate enzymes. The enhanced activity enables the fed animals to digest feed more quickly, which translates into weight gain. b. Reduce animal picky eating: compound feed is made of various raw materials according to the nutritional needs of animals. Through granulation, various powdery raw materials are integrated into a whole, which can prevent animals from picking what they like to eat from the powder and refuse to eat. The phenomenon of adding other ingredients, because the pellet feed can maintain uniformity during storage, transportation and feeding, can reduce feed loss by 8% to 10%. c. Make storage and transportation more economical. Granulation generally increases the bulk density of the powder by 40% to 100%. d. Avoid automatic grading of feed ingredients and reduce environmental pollution. In the process of powder storage and transportation, due to the different bulk density of various powders, it is easy to produce grading, and there is no grading of feed ingredients after being made into granules, and the granules are not easy to dust. During the feeding process, the granules are harmful to air and water quality. The pollution is much less than that of powder. e. Eliminate Salmonella in animal feed: Salmonella will remain in animal tissues when ingested by animals. People will get a Salmonella gastrointestinal disease after eating animal products infected with this bacteria. The method of high-temperature steam conditioning and granulation can kill Salmonella existing in animal feed and reduce the spread of pathogens.
The pellet mill is the key equipment for producing pellet feed, and it is also one of the equipment with the largest power consumption in the feed factory. Its energy consumption accounts for more than 40% of the total energy consumption of the feed factory. Therefore, it is necessary to comprehensively consider. At present, ring die pellet mills are mainly used in the market, which are characterized by large output, uniform discharge, good shape and stable quality. According to different driving methods, ring die pellet mills can be divided into gear type and belt type. Generally, small and medium-sized feed mills use belt type pellet mills. Due to the characteristics of flexible transmission, the finished products have smooth surfaces and beautiful shapes. It is accepted by the majority of feed mills, and its cost is relatively low.
When the granulator is in use, the material must be strictly tempered: the material must be tempered before granulation, the pressure of the steam must be stable (4~8bar), and the steam must be dehydrated before conditioning , if the steam contains a lot of water, it will cause blockage of granulation. After the material has been tempered, it has been matured to a certain extent, which can significantly improve the utilization rate of nutrients in the feed, and at the same time, reduce energy consumption by 10% to 20%, and improve production efficiency. During the granulation process, the humidity and temperature of the material should be checked frequently. The method of checking the humidity is: after gently kneading by hand, the material can form a block as well. It depends on the variety of granulation, and the temperature should be stably controlled at 75~95℃ and the moisture content should be 15.5%~17%. The cooling of the granules after granulation must not be too fast or not cooled enough. If the cooling is too fast, the surface of the material granules will crack. If the cooling is not enough, the temperature is too high, which will make the material absorb moisture and cause mildew. The cooled material should be consistent with room temperature .
4 Case studies
When a feed factory in Xinjiang selected equipment at the initial stage of construction, due to the limited budget and equipment layout space, the dust collector, centrifugal fan and other equipment supporting the pulverizer were removed from the process. Although this simplified the process and saved installation space and investment costs, But it brought many problems to the later production.
After the official operation of the project, the customer's production management personnel found that even if the pulverizer was turned on 24 hours a day, it was difficult to meet the feeding volume requirements of the mixer and granulator in time, which greatly affected the production efficiency. After the technicians of the feed production equipment arrived at the site, they proposed two solutions. One was to replace the pulverizer with a larger output without adding supporting equipment to save space, but it would increase the total power of the equipment; the other was to increase the supporting equipment of the pulverizer Advanced dust collectors, centrifugal fans, material sealing augers and other equipment can improve the efficiency of the pulverizer, but more installation space is required. After careful consideration, the feed mill finally chose the second option, which is more cost-effective. After on-site installation and commissioning, the output of the pulverizer has been significantly increased, which can fully meet the needs of the back-end mixer and granulator.
Practice has proved that the selection of feed factory equipment must be scientifically screened, and the supply and demand output between each section must be strictly matched. According to practical experience, the output of front-end equipment generally needs to be 20% to 30% higher than the output of back-end equipment in order to ensure the entire system. efficient operation. Moreover, there must be a certain degree of foresight when building a factory.
5 Conclusion
Good selection of core equipment can achieve twice the result with half the effort for a continuous production feed factory, can effectively reduce equipment maintenance time, and improve feed production efficiency. In addition to the above three core equipment, the feed factory also has some supporting equipment, such as scraper conveyor, bucket elevator, feeding auger, rotary vibrating screen, distributor, etc., because it has little impact on the quality of the finished feed , and most of them are general-purpose devices, so this article will not introduce them in detail here.