The moisture content of pellet feed is a very important quality index, which directly affects the quality of pellet feed and the economic benefits of feed enterprises. Effective control of it is one of the key technologies to ensure the quality and safety of feed products. When the moisture content exceeds the prescribed standard, the pellet feed is prone to mildew and deterioration, which is not conducive to preservation, and also reduces the content of nutrients. However, if the moisture content of the product is too low, it will cause unnecessary loss to the enterprise, and the unevenness is uneven. The moisture content also causes instability of product quality and affects the brand reputation of the product. In the feed processing process, the appropriate moisture content is beneficial to granulation, reducing energy consumption and increasing production. Therefore, in the production process of compound feed, the production should be carried out more smoothly, the energy consumption is lower, the particles are smoother and more uniform, and the final product meets the specified moisture content standard, and moisture control must be carried out throughout the production process.
Moisture control is to comprehensively control various factors according to different situations in the whole process of production, so that the final moisture content of the product reaches the expected target of the producer. The main factors affecting the final moisture content of the feed product are: the moisture content of the feed material itself, the moisture change during the crushing stage, the liquid addition amount in the mixing stage, the moisture content of the steam, the level of quenching and tempering, the pore size of the stamper and its thickness, The air volume and air drying time of the cooler, the quality management of the packaging, and the influence of different climatic and environmental factors.
First, the moisture control of feed ingredients
1. The key to moisture control during raw material receiving process is to accurately detect the moisture content in raw material samples.
The sampling must represent the comprehensive situation of the whole batch of raw materials, samples should be taken according to the sampling standard to prevent leakage, and the moisture content of the raw materials should be sensed during the sampling process. In the raw material moisture detection process, it is necessary to ensure accuracy. To reduce the error, two to three parallel samples can be detected, and the average value is taken as the detection value.
2, do a good job of water-absorbing raw materials (rice bran, wheat bran, etc.) management and storage
Easy to absorb raw materials, do not need too much, and avoid stacking yards, pay attention to warehouse management, moisture, and wet weather to prevent moisture from entering the warehouse. It should be fed according to the amount of raw materials under normal production conditions, and the raw materials out of the warehouse should follow the principle of “first in, first out†to minimize the inventory period of raw materials. After testing, the cotton sorghum with a moisture content of 10% or more was found to have a moisture loss of about 1% after six months of stocking.
Second, the moisture control in the crushing stage
The pulverization process is the key link in the processing of feed products, and the loss of moisture in the pulverization process cannot be ignored. Through the comparison of 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. Similarly, the comparison of moisture content of materials with different gradient moisture content before and after pulverization found that with the increase of moisture content of the material, the water loss of the powder after pulverization increased, the maximum loss of moisture was close to 1%, and the pulverization efficiency was significantly reduced. The energy consumption has increased significantly. After the ultrafine pulverization of the shrimp material, the particle size of 98% can exceed 80 mesh. At present, the fish material is mostly used in a water droplet type hammer mill, and the sieve has a particle diameter of 1.0 to 1.5 mm. The size of the air volume can be adjusted for a pulverizer equipped with a vacuum suction and a damper adjustment device. Compared with the moisture loss of the material before and after crushing, it is found that the air volume has a significant impact on the production efficiency, while the water loss has no significant effect, but with the increase of the air volume, the water loss still has an increasing trend. After the corn was crushed, the water loss by mechanical transportation was 0.22%, and the pneumatic transportation loss was 0.95%. Most of the shrimp materials are ultra-fine pulverization without nets. They are transported by pneumatics using suction. Most of the fish materials are pulverized and transported by auger.
Third, the moisture control in the mixing process
When the moisture content of the powder after mixing is much lower than 12.5%, it is considered to spray atomized water during mixing. However, there are many problems in this aspect: no more than 2%; poor water retention performance, only 2 to 40% water retention is added; it is best to use hot water, mildew; consider mixing time and moisture addition time Consistently (spray together); to ensure uniformity, adjust the position of the nozzle and the size of the spout; need to add anti-mold agent; pay attention to clean the inner wall of the mixer. A number of factors limit the addition of water to the mixer, and the addition of free water increases the potential for mildew of the finished product.
Fourth, the moisture control in the process of
The quenching and tempering process is the most important process in the processing of feed products. Quenching and tempering moisture, quenching and tempering temperature and quenching and tempering time are the key factors controlling the quenching effect of the final material. In the process of steam quenching and tempering, water is the carrier of heat energy. The amount of quenching and tempering water affects the level of quenching and tempering temperature. The quenching and tempering water is regulated by controlling the amount of steam added, and the quenching and tempering time determines steam. Utilization of water and heat.
By analyzing the correlation of various factors in the quenching and tempering process, some of these factors can be adjusted to control some other factor. For example, the tempering moisture can be controlled by adjusting the amount of steam added and adjusting the length of the tempering time. The length of tempering can be adjusted by changing the filling factor of the material in the temper. This change can increase or decrease the tempering moisture by 0.5 to 1% with the same amount of steam added.
1. Under normal steam quality, the steam pressure of the boiler used in the feed mill is 6-9 kg/cm2, and the production pressure is 3~4 kg/cm2. The higher the pressure, the lower the water content of the steam; conversely, the lower the pressure, the higher the humidity and the higher the moisture content of the steam. If the gas distribution package and the steam supply pipeline are installed effectively and reasonably, the condensed water in the steam delivery pipeline can be completely eliminated, and the steam moisture content entering the conditioner is low. In the production process, it should be adjusted according to the actual situation, so that the mold material can reach the ideal moisture content. In the dry season of summer and autumn or when the moisture content of the raw materials used in the formula is low, it is necessary to find ways to increase the moisture content of the material. In this case, as long as the production needs are met, the lower the pressure, the better, the boiler steam pressure can be Adjusted to 3 ~ 5 kg / cm2, the production pressure can be adjusted to 2 kg / cm2, close all or part of the steam trap to increase the moisture content of the steam, so as to increase the moisture content of the material after quenching and tempering. Due to the lower moisture content of the raw materials, the water content of the steam is also lower, and the moisture content of the tempered material is difficult to reach 16% (the shrimp material is not easy to reach 14%), so closing the steam trap does not cause the machine to be blocked.
2. When the quenching and tempering time is normal, the longer the residence time of the material in the conditioner, the more sufficient it is to mix with the steam, and the moisture absorbed from the steam is correspondingly increased, and the moisture content of the material is higher. In the production process, if the moisture content of the material is low, it is necessary to absorb more moisture by increasing the quenching and tempering time. Increasing the quenching and tempering time can increase the effective length of the conditioner, reduce the speed of the conditioner, and adjust the angle of the conditioner blade. In addition, try to make the material full of the conditioner, it is also conducive to the material to absorb more water, but can not blindly pursue the improvement of the full factor and ignore the main function of the conditioner.
Fifth, the die hole size and thickness of the
1. The pore size of the pressure die of the stamper is different, and the moisture of the produced pellet feed product is also different. The die with a small aperture has a smaller diameter of the feed pellets, and the cooling wind easily penetrates the particles, so that the moisture carried away during cooling is high, and the moisture of the product is low. On the other hand, a large diameter die has a larger diameter of the feed pellets, and the cold wind does not easily penetrate the particles, and the moisture carried away during cooling is less, and the product moisture is higher.
2. The effective thickness of the stamper is a stamper with a large effective thickness. When the frictional resistance is large during the granulation process, the material is difficult to pass through the die hole, the friction temperature is high, the water dispersion is lost, and the water content of the granule product is low. In contrast, a thinner stamper has a higher moisture content.
Sixth, the moisture control of the cooling link
Cooling is the last step in controlling the moisture of the product during the processing. In this process, the first is to ensure that the moisture of the product does not exceed the product quality control index, and secondly, the temperature of the control product is within the appropriate range to ensure that the product will not be adversely affected by the excessive temperature. At present, most of the counterflow coolers are used, and the effect is very good. When cooling, the decrease in moisture is related to the decrease in temperature. As in the modulator, the increase in moisture corresponds to an increase in temperature. Generally, for every 10°C increase (or decrease) in temperature, the moisture content of the material will increase (or decrease) by 0.6%.
Cooling is to reduce the temperature of the pellet feed so that it does not exceed 3 to 5 ° C at room temperature, taking away the moisture in the pellets, so that the moisture content of the pellet feed product meets the prescribed standards. According to the yield, temperature, moisture, particle size and composition of pellet feed just released or from the post-maturing equipment, the cooling air volume and cooling time should be adjusted in time. The cooling air volume for the dry and smaller pellet feed should be smaller. The cooling time should be shorter; on the contrary, the wet and larger pellet feed should increase the air volume and extend the cooling time.
Seven, finished product management
Finished product management is also very important. The pellets after granulation (or after post-curing) should be fully cooled by the cooler before they can be packaged. Under normal circumstances, the temperature of the finished feed should not be higher than room temperature by 3 ° C, and the touch can not be warm by hand to reach the standard. After packaging, it is best to avoid sun exposure, otherwise the residual moisture in the product will migrate to the place where the packaging and storage temperature are low, so that the humidity in these places will increase and the feed product will be more susceptible to mildew.
Eight, the impact of environmental temperature and humidity on the moisture content of feed products
For every 11.1 °C increase in air temperature, the hydraulic power of the air can be doubled. It is because of this air heating process that the pellet feed can be dried in the cooler even in high humidity weather. The hot particles raise the temperature of the air, allowing the air to carry more water. In the summer, the moisture content of the raw materials is low and the moisture content of the finished materials is lower, so some processing parameters may need to be changed. Ambient humidity will increase water slightly.
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