Feed water retention and moisture control during production
At present, the competition of feed enterprises is becoming increasingly fierce, and feed production has entered a period of low profit, and its production cost has become one of the important factors affecting the efficiency of feed enterprises. Production energy consumption, material loss during production, production efficiency, mechanical wear and other factors directly affect production costs. Feed enterprises must be in an invincible position in the competition, and must minimize production costs. In addition to the management factors and mechanical equipment factors in feed production, feed moisture is the most important factor affecting production costs. Scientific use of water can reduce production energy consumption, mechanical wear and process loss without reducing feed quality. Increasing production efficiency and reducing production costs while maintaining normal moisture in feed can improve the palatability of feed and improve animal performance.
1 The content of water in feed products and its impact on economic benefits
1.1 The content of moisture in feed products
In the autumn and winter seasons, due to lower temperatures, manufacturers use more newly-produced corn and other raw materials. These newly-listed feed ingredients generally have high moisture content. After the corn-soybean-type diet is granulated in feed production, the water content is generally below 13%, which can basically meet the quality control requirements, but with the agricultural and sideline products such as rice bran and DDGS (the moisture content is low, about 9%-12%). The large amount of use has reduced the moisture content of the finished product to within 12%. In summer and autumn, the feed ingredient moisture is generally around 11%-13%. In addition to the high temperature in summer, the feed material moisture loses part of the crushing and granulation process, so that the feed product moisture is very low, generally around 9%-11%, low. The standard required by the state. If the feed moisture is too low, there will be adverse factors such as increased dust during feed processing, increased loss rate of finished products, increased energy consumption of granulation, unsatisfactory corn gelatinization, wear of granule ring mold, and decreased palatability of feed, which will directly affect feed enterprises. Economic benefits.
1.2 The effect of feed product moisture content on the economic benefits of feed production enterprises
The moisture content of the feed product not only affects the internal and external product quality of the feed, but also has a direct impact on the product yield and economic benefits. A pellet feed enterprise with an annual output of 30,000 tons can have an annual economic benefit of up to 750,000 yuan. According to the production season and the changes of raw materials, the production process parameters are adjusted, especially the adjustment of the tempering process parameters during granulation, which can significantly improve the economic benefits of the enterprise and the quality of the feed products.
1.3 The effect of feed water retention on animal production performance
Liu Chunxue et al. (2004) studied the effects of adding 0%, 0.5%, 1.5%, 2.5% moisture on the growth performance of pigs. The results showed that by adding 0.5% and 1.5% water to the powder, the daily weight gain of pigs was increased by 2% and 9%, respectively, and the feed conversion efficiency was also improved. The reason is that the degree of gelatinization and the durability of the starch during the granulation process are increased after the addition of water. Adding 2.5% moisture does not improve the growth performance of pigs because adding too much water before quenching will reduce the ability of the material to absorb steam, thereby reducing the quenching and tempering temperature, which is not conducive to starch gelatinization.
2 Methods and measures to improve feed moisture in the feed processing process
2.1 Moisture control in the feed crushing stage
By comparing the moisture content of the pulverizer sieves with different pore sizes before and after pulverization, it was found that the water loss increased significantly with the decrease of the pulverization particle size of the material. Similarly, for the materials with different gradient moisture content, the moisture content of the materials before and after pulverization was compared. The detection and analysis showed that as the moisture content of the material increased, the water loss of the pulverized powder increased, and the maximum loss of moisture was close to 1%. As the moisture content of the material increases, the pulverization efficiency also decreases significantly, and the energy consumption increases significantly. For the pulverizer equipped with a vacuum suction and a damper adjustment device, as the air volume increases, the water loss still increases. After the corn was crushed, the water loss by mechanical transportation was 0.22%, and the pneumatic transportation loss was 0.95%.
2.2 Moisture control during feed mixing
When the moisture content of the powder after mixing is less than 12.5%, it may be considered to spray atomized water when the materials are mixed. However, there are many problems in this aspect. It should be noted that the water spray during mixing should not exceed 2% of the material. Otherwise, the moisture uniformity of the material is not good, and the feed is prone to mildew. In addition, the atomized water is sprayed directly into the material, and the water retention performance is poor. The water retention rate of adding 2% water is only 40%-50%. Spraying atomized water in the mixing process, 1 should consider the mixing time and the water addition time consistent; 2 to ensure the uniformity of the water spray, adjust the position of the nozzle and the size of the water spout; 3 pay attention to timely clean the inner wall of the mixer Residue of materials; 4 need to add anti-mold agent.
To add moisture to the material, the moisture in the incoming material, the mixed powder and the final product must be monitored in real time. Only when the mixed powder and the final product have a moisture content of less than 13% can the moisture addition be considered. 1 Strictly measure the moisture of the purchased single raw materials, and enter the cost accounting table in time; 2 Carry out the first test on the processed feed, that is, the initial moisture (steam) of the first batch of mixed powder (mixed powder in the mixer) Before the treatment, the determination is carried out; 3 according to the proportion of the moisture of various raw materials in the diet, the theoretical value of the initial moisture of the powder is calculated (calculated value may be higher than the measured value due to the pulverization and transportation of the raw materials), for example, the moisture value is lower than 13%. When mixing, apply a proper amount of water. The amount of water added is set manually according to the test or calculation result. The target moisture should be set at 2% higher than the initial moisture, but the maximum moisture should not exceed 13%.
2.3 Moisture control during feed granulation process
The source of raw materials used in feed processing and the variety of varieties have brought about differences in the moisture distribution of feed processing intermediate products and final products and the variability of water content. Studies have shown that the moisture content of the semi-finished powder after mixing is generally between 9% and 14%, and the moisture content of the mold material after quenching and tempering is relatively reasonable between 15% and 17%. The pellet feed produced at this time has good processing quality, uniform smoothness, low powdering rate, and low energy consumption, and the moisture content of the final product is also easy to meet the standard requirements. Generally, the moisture content of the pellet feed should not be higher than 12.5%, and it should be no higher than 13.5% in the north. If the pellet feed is processed in the summer, the optimum moisture of the finished pellet is preferably not higher than 12.5% ​​due to the higher ambient temperature. Otherwise it is easy to mold and deteriorate.
2.3.1 Reduce the steam supply pressure of the boiler when the pellet feed is produced, and increase the water content of the steam supply steam.
Usually, the feed production boiler has a steam supply pressure of 7-9 kg/cm2 and a production pressure of 3-4 kg/cm2. The higher the pressure, the lower the humidity; conversely, the lower the pressure, the higher the humidity and the higher the moisture content of the steam. Therefore, as long as the production needs are met, the lower the pressure, the better. It is recommended that the boiler steam supply pressure be adjusted to 4-6 kg/cm2 and the production use pressure adjusted to 2-2.5 kg/cm2.
2.3.2 increase the quenching and tempering time of materials in the conditioner.
Increasing the residence time of the material in the conditioner, so that the material and steam are fully mixed, is conducive to starch gelatinization, improve the digestion and absorption rate of livestock and poultry, and also enables the material to fully absorb the moisture in the steam, thereby increasing the moisture of the product. Increasing the quenching and tempering time can be solved by reducing the speed of the conditioner or adjusting the blades of the conditioner.
2.3.3 Closing or adjusting the steam trap in the steam supply pipe
Usually, a lot of steam traps are installed in the steam drum and the steam supply pipe, the purpose of which is to remove the condensed water in the steam pipe, prevent the steam from introducing too much water, and cause the granulator to block the machine, but in summer, due to the raw materials The water content is lower, the water content of the steam is also lower, and the moisture content of the tempered material is difficult to reach 16%. Therefore, adjusting or closing the trap will not cause the machine to block, but will help to increase the moisture of the product.
2.3.4 Select the appropriate size of the material ring mold
The pore size and thickness of the feed ring mold are not only the main factors affecting the capacity of the granulator, but also affect the moisture of the pellet feed product. The die with a small aperture has a small diameter of the particles, and the cooling air volume of the cooler easily penetrates the feed particles, so that the moisture carried away during cooling is high, and the moisture of the feed product is low. On the other hand, the material ring mold with a large pore diameter has a large particle diameter, the cold wind does not easily penetrate the particles, and the water taken away during cooling is less, and the moisture of the feed product is increased. For the ring mold with larger thickness, the friction resistance is larger during the granulation process, the material does not easily pass through the pore diameter, and when the granulation is performed, the friction temperature is high, the water dispersion is large, and the moisture of the feed pellet is lowered, so it is recommended to use When making a ring mold, the hole diameter and thickness of the stamper should be suitable.
2.3.5 When the feed pellets are cooled, choose the appropriate cooling air volume.
The purpose of the cooling process is to reduce the temperature of the pellet feed to a temperature of 3-5 ° C; on the other hand, it can also take away the moisture in the feed, so that the moisture of the feed product meets the specified requirements, according to the moisture of the finished product before cooling. Set the cooling parameters of the corresponding finished product to avoid excessive water loss.
3 methods and measures to improve the moisture of feed ingredients or semi-finished products
Ways to increase the moisture content of feed ingredients include: directly adding water to the feed (adding a liquid with a high moisture content); using high-moisture raw materials, such as corn with a higher moisture content. Properly improving the moisture content of feed ingredients or semi-finished products can improve product quality and reduce production costs.
3.1 The problem of directly adding water to the feed or using high-moisture raw materials
The possibility of directly increasing the water or using high-moisture raw materials can increase the chance of using the mildew of the feed, which may cause problems such as blockage during granulation and pulverization, large variations in feed moisture, and low feed water retention rate in the feed production process.
There are three necessary conditions for mold growth: moisture (water activity Aw), temperature and oxygen. Only the feed moisture can not accurately evaluate the effect of microorganisms on the mildew of the feed. At present, water activity has become an important indicator for evaluating the development of feed mold and mycotoxin. The feed water activity is not only related to the moisture content of the feed, but also related to the temperature and humidity of the environment.
The moisture in the feed is divided into free water and combined water. The amount of free water in the feed is determined by the amount of vapor pressure on the product. If the feed is stored in a sealed place, the moisture in the feed will soon be equalized by the evaporation of free water. Therefore, the vapor pressure (P) measured in the equilibrium state can be used to determine the amount of free water therein. The vapor pressure of pure water measured in the same place is called Po. Water activity refers to the equilibrium relative humidity, which can be expressed by the Aw value, which is equal to P/Po. Whether mold spores and other microorganisms have a chance to grow is determined by the Aw value, not by the water content. Mold and other microorganisms can utilize the free water of the material. Most of the way to increase moisture in the feed in summer is to spray water before quenching, but the water is easily used by microorganisms to make the feed moldy. Under different water activity conditions, the microorganisms that are easy to grow are also different. When the Aw value is in the interval of 0.91-0.95, the bacteria grow most easily. When the Aw value is 0.88, the yeast grows most easily. When the Aw value is 0.80, the mold is most likely to grow.
3.2 Methods and measures for hydrating feed ingredients or semi-finished products
Xiong Yiqiang (2008) pointed out that the basic model of feed moisture control is to pay attention to the initial moisture of the mixer powder and determine the target temperature after steam treatment, and control the moisture of the finished product. When the initial moisture content of the powder is less than 13%, part of the moisture can be added. The moisture content of the finished product should not exceed 13%, otherwise there is a danger of mold. Liu Chunxue et al. (2004) studied the effect of adding 0%, 0.5%, 1.5%, 2.5% moisture on the pellet quality in the mixer powder. The results showed that the moisture of the finished product was 11.02%, 11.33%, 12.01%, respectively. 12.32%, adding 0.5%, 1.5% water has a water retention rate of 65% in the finished product, and adding 2.5% water has a water retention rate of only 50%.
The main manifestation of the mildew of the feed is the local mold in the package, the surface of the feed pellets is mildewed, and there is little overall mildew. The root cause is that the temperature difference changes and the water migrates and accumulates, resulting in an increase in the moisture content on the surface of the particles and the sealing portion of the package, causing mildew. In order to control the water activity of the feed, a surfactant and a water binder may be added to the sprayed water. The water-binding agent and the surfactant usually contain various organic acids such as propionic acid, propionic acid amine, formic acid, sorbic acid, lactic acid, and citric acid. Organic acid molecules such as formic acid, propionic acid, and sorbic acid have strong inhibitory effects on molds, etc.; a strong buffer system formed by propionic acid and ammonium propionate can reduce the corrosiveness of equipment. Therefore, the presence of water binder and surfactant avoids the movement of moisture to the surface of the feed pellets, combined with free water, thereby reducing the loss of moisture, ensuring uniform distribution of moisture inside and outside the feed pellets, and maintaining water retention for the feed. effect.
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