Feed industry and drying

China Feed Industry Association Mou Yongyi

After years of hard work, China has become a relatively complete industrial system which includes feed processing industry, feed raw material industry, feed additive industry and feed machinery industry.

Feed in industrial production usually refers to compound feed (including Concentrate Supplement), concentrated feed and additive. The production of feed, feed raw materials and feed additives has been far beyond the production scope of feed processing plants, involving many departments such as grain, food, light industry, chemical industry, medicine, geology and mineral resources, so the processing technology and equipment used in the production engineering of feed industrial products are basically from the above departments. In the production of feed, feed raw materials and feed additives, drying technology is widely used in feed industry.

1、 Feed production

Some of the raw materials used in feed processing plants, such as corn, soybean meal, fish meal and other raw materials, have excessive moisture due to improper storage, rain or dampness, or the moisture content of the purchased raw materials exceeds the standard when entering the factory. Therefore, in the production of compound feed or concentrated feed, it is often necessary to dry the raw materials, such as tower dryer, air dryer or vibrating fluidized bed dryer.

The main raw materials used in the production of additive premix are the products of light industry, chemical industry and medicine departments, and their moisture content is very low. Except for special circumstances, drying treatment is not required in the feed processing plant. It is mainly the carrier or diluent used in the production of premix, such as stone powder, bran, corn flour or corncob powder. When the moisture content is high, it is necessary Air dryer, fluidized bed dryer and rotary dryer are used for drying.



During the production of pellet feed, the temperature of pellet feed just out of the granulator is about 80 ℃ and the moisture content is about 17%. Therefore, it is necessary to ventilate and cool the pellet feed to reduce the temperature to close to the room temperature (slightly higher than the room temperature) and the moisture content to below 13%. The dried feed is easy to store and not easy to mildew.



2、 Feed material production



Due to the limited grain production in China, the raw materials used in feed production have far exceeded the conventional feed materials such as corn, soybean meal (cake), fish meal, etc. Many by-products in industrial and agricultural production have become valuable feed raw materials after processing, such as: Leather protein powder processed by the leftovers of leather factory; bone meal, meat and bone meal, intestinal feather powder, feather powder, blood powder from slaughterhouse; DDGS or DDG processed by waste liquor of alcohol factory In addition, brewery's dregs and waste liquid are used to produce feed brewer's grains and beer feed yeast, as well as grass powder, grass grain and grass block processed from forage.



In the production of feed raw materials, especially the utilization of animal and plant by-products or wastes (waste water, waste residue) in industrial and agricultural production to produce (recycle) feed raw materials, most of them have to be dried. In the aspect of animal and plant feed resource recovery, although the properties of various materials are different, the processing technology generally includes ① material pretreatment. ② Sterilization and decomposition. ③ Dehydration, degreasing, concentration, liquid-solid separation. ④ Dry. ⑤ Crushing and packaging. For any specific product, several suitable unit operations can be selected from the above general applicable processes to form a complete process flow suitable for this raw material or product.



In the operation of material moisture removal, drying is an operation with high energy consumption, and also an important unit operation for the development and utilization of feed resources. It is one of the main factors to control product quality, production cost and production efficiency. There are many drying methods and equipment. Only by selecting the appropriate drying method and equipment according to the material properties and product requirements can the high-efficiency return be obtained.



(1) the waste dandruff of tannery is processed by alkali hydrolysis, and then spray dried or vacuum dryer is used to produce leather protein powder.

(2) animal blood in slaughterhouse is processed by spray drying to produce high protein feed raw material blood meal.

（ 3 ）The bone, meat, hoof, horn, intestines, feathers and blood of pigs, chickens, ducks and cattle in slaughterhouses can be smelted (boiled) to produce feed materials such as bone meal, meat and bone meal, feather powder, intestinal feather powder, mixed protein feed of intestinal feather blood, etc. some of them are smelted (boiled) and dried, and some are melted It is a drying process of combination of refining (cooking) drying (when the humidity and viscosity of materials are high) and two-stage air drying.



(4) The waste liquid (yellow pulp) of corn flour mill is usually produced by air drying after mechanical dehydration.



(5) In alcohol plant, when corn is used as raw material to produce alcohol, the waste liquid is dehydrated mechanically (horizontal screw centrifuge or plate and frame filter press), and then the DDG protein feed is dried by disc dryer or tube bundle dryer, or the soluble components in the mechanically separated waste liquid are passed through multi effect evaporator (generally 4-6) The DDGS protein feed was prepared by mixing the concentrated and mechanically dehydrated solids.



(6) After pretreatment, the solid dregs of breweries and distilleries are dried by fluidized bed or air flow, and the products can be used as feed materials. Beer feed yeast can be produced by drying yeast waste liquor in brewery by drum dryer. Yeast is high quality feed protein raw material.



(7) When cottonseed meal, rapeseed meal and other oil seed cake containing toxins are detoxified by chemical method, fermentation method or thermal spray method, drying operation is generally adopted in the processing process, such as air drying, spouting bed drying, fluidized bed drying, etc.



3、 Hay drying



According to the different uses of forage, some of them are directly ventilated and dried, and others are dried by heat to reduce the moisture content of grass powder, grass grain and grass block.



(1) The forage is stored in the storehouse with simple structure, and the main drying method is ventilation (cold air or low temperature heating air), which is called ventilation drying or storage drying. In some cases, a cylindrical tower is used to dry forage with air or forced hot air.



(2) According to the needs of production, high temperature air is used to speed up the drying of forage. It is usually divided into continuous type and intermittent type. Continuous operation drying equipment has conveying chain type, air flow pipe type, air flow rotary drum type, etc.



4、 Trace elements and bacitracin zinc



(1) Mineral and trace elements are important additives in animal feed. Some products need to be dried during the production process, especially sulfate products, such as CuSO 4 · 5h 2O, FeSO 4 · 7h 2O, ZnSO 4 · 7h 2O, etc., which contain 5 or 7 elements In order to facilitate the use of feed processing, it is often pretreated: for example, the sulfate (caking) is crushed and sent to the rotary drum dryer, and the material and hot air conduct a forward flow heat exchange until the drying is completed.
(2) Bacitracin zinc is a kind of drug feed additive which is widely used in feed production. During the production process, the stability of bacicin was enhanced after the bacilli fermentation broth was added to Zn 2 + ions, and the final product was prepared by spray drying.



5、 Production of feed additive vitamin A



Vitamin A is an indispensable vitamin for animal growth, so it is an important nutritional additive in feed products. Because vitamin A is a kind of fat soluble vitamin, it can not be directly dissolved in water for dilution, and it will be damaged when exposed to oxygen and light when placed in the air. Therefore, vitamin A must be made into powder which is isolated from air and has good fluidity, so it can be easily added to feed. Commonly used dry powder is prepared by complex coagulation microcapsule industry and spray granulation process.



Spray granulation technology is to make vitamin A oil and gelatin aqueous solution into oil in water emulsion. After spraying through the spray system, the droplet will encounter starch suspended in cold air and form starch coated particles. The wet VA particles formed in the whole spray granulation engineering are continuously and continuously sent into the fluidized bed dryer for drying.



In addition to vitamin A, there are many kinds of feed additives. At present, there are 191 kinds of nutritional feed additives and general feed additives, such as amino acids, vitamins, mineral elements, enzyme preparations, antioxidants, preservatives, etc., and 9 kinds are in the protection period; 33 kinds of pharmaceutical feed additives are allowed to be used in commercial feed. These additives in the production process, many products are inseparable from the drying process.



6、 Summary



To sum up, from the specific application of drying technology in feed industry, it can be seen that drying technology should be applied in many aspects of feed industry. In the process of feed processing, no matter compound feed, concentrated feed or premixed feed, the drying process will be adopted according to the different conditions of the products or raw materials. Drying technology is an indispensable part of feed industry.



With the continuous development of feed industry, more and more industries are involved. New products are constantly developed, and the drying process and equipment used in the production process are more and more extensive.