Feed Forage Industry and Drying Technology

After years of efforts, China has become a relatively complete industrial system that includes cross departmental and interdisciplinary industries such as feed processing industry, feed raw material industry, feed additive industry, and feed machinery industry.

The commonly used feed in industrial production refers to formulated feed (including concentrate supplements), concentrated feed, and additives. The production of feed, feed raw materials, and feed additives has far exceeded the production scope of feed processing plants, involving many departments such as grain, food, light industry, chemical industry, medicine, geology and mining, etc. Therefore, the processing technology and equipment used in the production engineering of feed industrial products mainly come from these departments. Drying technology is applied to varying degrees in the production process of feed, feed raw materials, and feed additives, which means that drying technology is widely used in the feed industry.

                                                                               1、 Forage production

During the production of feed processing plants, the raw materials used, such as corn, soybean meal, fish meal, and other raw materials, may have excessive moisture due to improper storage, rain or dampness, or the purchased raw materials may have excessive moisture upon entry. Therefore, in the production of mixed feed or concentrated feed, it is often necessary to dry the raw materials, such as using tower dryers, airflow dryers, or vibrating fluidized bed dryers.

The main raw materials used in the production of additive premixes include feed additives, which belong to the light industry, chemical, and pharmaceutical sectors and have low moisture content; Except for special circumstances, there is generally no need for further drying treatment in feed processing plants; It is mainly carrier or diluent used in premix production, such as stone powder, bran, corn flour or corncob powder. When its moisture content is high, it needs to be dried by airflow dryer, fluidized bed dryer, rotary dryer, etc.

When producing pellet feed, the temperature of the pellet feed that just comes out of the granulator reaches about 80 ℃ and the moisture content is about 17%. Therefore, ventilation and cooling are required to reduce the temperature to near room temperature (slightly higher than room temperature) and the moisture content to below 13%. The dried feed is easy to store and not easily moldy.

2、 Production of forage raw materials

Due to limited grain production in China, the raw materials used in feed production far exceed conventional feed materials such as corn, soybean meal (cake), and fish meal. Many by-products in industrial and agricultural production become valuable feed materials after processing, such as: leather protein powder is processed from the leftovers of the leather factory, bone meal, Meat and bone meal, intestinal feather meal, feather meal, blood meal is processed from the leftovers of the slaughterhouse, DDGS (fully dried alcohol grains) or DDG is processed from the waste liquid of the alcohol factory, brewer's grains and waste liquid are used to produce feed brewer's grains, beer feed yeast, and grass is processed into grass powder, grass grains, grass pieces, etc.

In the production of feed raw materials, especially when using animal and plant by-products or waste (wastewater, waste residue) from industrial and agricultural production to produce (recover) feed raw materials, the vast majority of materials need to be dried. In terms of animal and plant feed Recycling, although the properties of various materials are different, the processing technology can generally include 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 operation can be selected from the above universally applicable processes to form a complete process flow suitable for such raw materials or products.

In the operation of material moisture removal, drying is an operation with high energy consumption and 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 appropriate drying methods and equipment according to the material properties and product requirements can we obtain efficient returns.

(1) The leather protein powder is produced by spray dryer or vacuum dryer after the waste leather of the tannery is treated by alkali hydrolysis.

(2) The raw blood powder of high protein feed can be produced by spray drying after the animal blood in slaughterhouse is treated.

(3) The bone, meat, hoof, horn, intestines, feathers, blood and other leftovers of pigs, chickens, ducks, cattle, etc. in the slaughterhouse can be smelted (digested) to produce bone meal, Meat and bone meal, feather meal, intestinal feather meal, mixed protein feed of intestinal feather and blood and other feed raw materials according to the raw materials. Some of them are smelted (digested) and dried during the production process, and the primary treatment is completed; Some adopt a combined drying process of first level melting (steaming) drying (when the material humidity and viscosity are high) and second level airflow drying.

(4) The waste liquid (yellow syrup) of corn flour mill is generally dried by airflow after mechanical dehydration to produce corn gluten powder.

(5) When alcohol factories use corn as raw material to produce alcohol, their waste liquid is mechanically dehydrated (using a horizontal screw centrifuge or a plate frame filter press) and then dried using a disc dryer or tube bundle dryer to obtain DDG protein feed. Alternatively, the soluble components in the mechanically separated waste liquid are concentrated in a multi effect evaporator (usually 4-6 levels) and mixed with the solid obtained from mechanical dehydration to dry to obtain DDGS protein feed.

(6) After pretreatment, the solid dregs of breweries and Baijiu factories are dried in fluidized beds or airflow, and the products can be used as feed raw materials. Beer feed yeast can be produced by drying the yeast waste liquid from a brewery through a drum dryer. Yeast is a high-quality feed protein raw material.

(7) When chemical, fermentation, or thermal spraying methods are used for detoxification treatment of cottonseed meal, rapeseed meal, and other oil seed meal containing toxins, the processing process generally requires drying operations, such as airflow drying, spouted bed drying, fluidized bed drying, etc.

3、 Hay drying

According to their different uses, some grasses are directly ventilated and dried, while others are heated and dried to quickly reduce the moisture content of grass powder, grains, and clumps.

(1) Grass ventilation and drying: Grass is stored in a simple storage bin, mainly ventilated (cold air or low-temperature heated air) to dry the grass, which is called ventilation drying or storage drying. Some use cylindrical tower silos, which allow air or forced hot air to dry the grass.

(2) According to production needs, high-temperature air is used for hay thermal drying to accelerate hay drying, usually divided into continuous and intermittent types. Fuel is used to heat the air to achieve rapid hay drying. Continuous operation drying equipment includes conveyor chain type, airflow pipeline type, airflow rotary drum type, etc.

                                                                        4、 Trace Elements and Bacitracin Zinc

(1) Mineral trace elements are important additives for animal feed. Some products need to be dried in the production process, especially sulfate products, such as CuSO 4 · 5H 2O, FeSO 4 · 7H 2O, ZnSO 4 · 7H 2O, etc. Because they contain 5 or 7 Water of crystallization, they have high hygroscopicity, are prone to deliquescence and caking, It is often pre-treated, such as crushing the sulfate (agglomerate) and feeding it into a rotary dryer, where the material undergoes a downstream heat exchange with the hot air to complete the drying process.

(2) Bacitracin zinc is a kind of medicated feed additive which is widely used in feed production. In the production process, after the Bacitracin fermentation broth and Zn 2+ions become salt, the stability of Bacitracin is enhanced, and the final product is obtained by spray drying.

                                                                5、 Production of feed additive vitamin A

Vitamin A is an essential vitamin for animal growth, and therefore an important nutritional additive in feed products. Due to vitamin A being a fat soluble vitamin that cannot be directly diluted with water, it can be damaged when exposed to oxygen and light in the air. Therefore, vitamin A must be made into a powder that is isolated from the air and has good fluidity in order to be easily added to feed. The commonly used dry powder preparation includes complex coagulation microcapsule industry and spray granulation process.

The spray granulation process is to make the aqueous solution of vitamin A oil and gelatin into an oil in water emulsion. After making micro drops through the spray system, it meets the starch suspended in the cold air to form starch coated particles; The wet VA particles formed in the whole spray granulation project are continuously sent to the fluidized bed dryer for drying.

There are many types of feed additives besides vitamin A. Currently, 191 types of nutritional and general feed additives have been announced for use, such as amino acids, vitamins, mineral elements, enzyme preparations, antioxidants, preservatives, etc., and 9 types are within the protection period; There are 33 types of drug feed additives allowed to be used in commercial feed. Many products of these additives cannot be separated from the drying process in the production process.

6、 Summary

In summary, it can be seen from the specific application of drying technology in the feed industry that many aspects of the feed industry need to apply drying technology. In the process of feed processing, whether it is formula feed, concentrated feed, or pre mixed feed, the production of their products or the treatment of their raw materials and carriers will adopt different drying processes depending on the situation of their products or raw materials. Drying technology is an indispensable component in the production process of feed industry.

With the continuous development of the feed industry, more and more industries will be involved, and new products will continue to be developed. The drying processing techniques and equipment used in their production process are becoming more and more widespread