Moisture index is one of the key indicators of pellet feed quality, and its economic benefits for feed mills are self-evident. Imagine a pellet feed processing plant with an annual output of 40,000 tons. If the water index is lower than the control target by 1%, the direct economic benefit loss of the whole year can reach more than 1 million. At the same time, it will bring some other negative effects, such as increased dust during feed processing, increased powder content of granules, increased energy consumption of granulation, unsatisfactory gelatinization of corn, wear of granule ring mold, and decreased palatability of feed.
There are many reasons for the “water damage†of feed mills. Such as:
(1) “micro-breathing effect of food crops during storage;
(2) Impact friction and suction effect during pulverization;
(3) Selection of process parameters in the process of quenching and tempering;
(4) Parameter selection of the cooling section.
Therefore, the control of the moisture of the finished product is a complicated and systematic work. This article summarizes several common hydration methods for reference only.
(1) Using high-moisture raw materials to adjust the theoretical moisture of the finished product
The theoretical moisture of the finished product can be estimated based on the moisture detected by the raw materials used before the formulation is put into production. If the theoretical moisture of the finished product itself is very low (<12%), it will often result in the product's moisture not reaching the standard, and the subsequent process parameter adjustment has little effect. At this time, it is preferable to adjust by adding a raw material having a high moisture content.
Disadvantages : By adjusting the formula, it is often more economical than the adjustment of the process parameters.
(2) Mixing machine with water
When the moisture content of the powder after mixing is less than 12.5%, it is considered to add water to the mixer. The following points should be noted when adding water to the mixer:
1. It is necessary to add atomized water, and the added amount should not exceed 2% of the material (the actual water retention rate is estimated to be no more than 50%), otherwise it is easy to mold;
2, adding liquid anti-mold agent, but has a certain impact on palatability;
3. Pay attention to the residual conditions in the equipment such as mixers and finished sieves, and clean them regularly (accordingly, small particles are screened out at the finished powder screen).
Disadvantages : mixing uniformity problems, equipment residue problems, mildew problems, palatability problems.
Note: The picture is quoted from the network
(3) Conditioner adding water
It has been reported that the water content of the finished product can be increased by 0.4 to 0.6% by spraying hot water of 95 to 100 ° C at the inlet of the conditioner at 1% to 1.5%. At present, there are similar molding products on the market: hydration flasher, this method should have an advantage in controlling mildew compared to mixing water.
A company's installed hydration flasher
(4) Steam pressure control
For livestock and poultry feed, the commonly used boiler steam supply pressure is 6-9kg/cm 2 , and the pressure before quenching and tempering is 2-4kg/cm 2 . The higher the pressure, the higher the steam saturation and the lower the humidity. Conversely, the lower the pressure, the higher the humidity and the higher the moisture content of the steam. When the production needs are met, the lower boiler supply pressure (5-6kg/cm 2 ) can be selected, and the control can be controlled at 2-3kg/cm 2 before quenching, and it is better to install the pressure reducing valve after the steam drum in the workshop. Perform voltage regulation control.
Disadvantages : In the process of formula switching, it may be necessary to repeatedly adjust the steam pressure in order to achieve different quenching and tempering conditions.
(5) Increase the quenching and tempering temperature
After quenching and tempering, the suitable moisture is controlled at 15-17%. If the moisture is low before quenching, the moisture can be increased by moderately increasing the temperature. Studies have shown that under certain conditions, for every 10-15 °C increase in temperature, water can be increased by 1%.
Disadvantages : Randomly changing the quenching and tempering temperature required by the formula may result in an increase in the nutritional loss of the formula.
(6) Increase the quenching and tempering time
There are two ways to increase the quenching and tempering time: 1. Reduce the quenching and tempering speed; 2. Adjust the modulator blade angle: by adjusting the blade angle, the contact area between the material and the steam can be affected, and the fullness of the modulator affects the moisture of the material. .
(7) Closing or adjusting the steam trap in the steam supply pipe
The purpose of installing the trap is to remove condensate from the steam line and improve the quality of the steam. In the case of low moisture in the semi-finished product, it can often be reversed: adjusting or closing the trap will not cause blockage, but will help increase product moisture.
(8) Reduce the compression ratio of the ring mold
The thickness of the ring mold affects the resistance of the material as it passes through the ring die. For a ring mold with a certain aperture, in the process of granulation, generally the greater the thickness, the greater the friction resistance, the higher the friction temperature, the more the water dispersion is lost. Therefore, in the case of ensuring the appearance quality and powder content of the product, moderately reducing the compression ratio of the ring mold also contributes to the increase of moisture.
(9) Regulation of cooling air volume
Under the premise of ensuring the cooling effect of the product, the following aspects can be adjusted: 1 moderately reduce the height of the leveler; 2. adjust the size of the damper; 3. control the speed of the fan through the frequency conversion technology.
The regulation of finished product moisture is a complex and systematic project. From raw material procurement, storage, production and processing to finished product storage, it is necessary to establish moisture control points in all aspects. In order to obtain the desired moisture content of the finished product, the key is to effectively monitor the various control points of the water and select effective improvement methods.
This article was written by a special contributor to the China Feed Industry Information Network, contributor: Zhou Xiaoquan. Reprint, please indicate the source ~
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