What are the water replenishment measures for pelleted feed
Moisture content is one of the key indicators of pelleted feed quality, and its impact on the economic benefits of a feed mill is self-evident. Imagine a pelleted feed processing plant with an annual output of 40,000 tons: if its moisture content is 1% below the control target, the direct economic loss for the whole year can reach more than 1 million yuan. At the same time, it also brings some other negative effects, such as increased dust during feed processing, more fines in the pellets, higher pelleting energy consumption, unsatisfactory corn gelatinization, wear on the pellet mill ring die, and reduced feed palatability.
There are many reasons for "water loss" in feed mills. Such as:
(1) During storage, the "micro-respiration" of grain crops;
(2) Impact friction and suction effects during the grinding process;
(3) Selection of process parameters during the conditioning and pelleting process;
(4) Selection of parameters in the cooling section.
Therefore, controlling the moisture content of the finished product is a complex and systematic task. This article summarizes several common water replenishment methods, for reference and learning only.
>>>>(1) Using high-moisture raw materials to adjust the theoretical moisture content of the finished product
Before a formula is put into production, the theoretical moisture content of the finished product can be estimated based on the tested moisture content of the raw materials used. If the theoretical moisture content of the finished product itself is already very low (<12%)，往往会造成成品水分的不达标，而且后续的工艺参数调整影响效果也不大。此时最好能通过加入高水分的原料进行调整。
Disadvantage: Adjusting the formula often causes greater economic losses than adjusting process parameters.
>>>>(2) Adding water in the mixer
When the moisture content of the mixed mash feed is lower than 12.5%, adding water in the mixer can be considered. The following points should be noted when adding water in the mixer:
1. Atomized water must be added, and the amount added should preferably not exceed 2% of the material (the actual water retention rate is estimated not to exceed 50%), otherwise it is prone to mold;
2. Add a liquid mold inhibitor, but it has a certain impact on palatability;
3. Pay attention to residues in equipment such as the mixer and finished product sieve, and clean them regularly (according to reports, small particles are screened out at the mash finished product sieve).
Disadvantages: mixing uniformity problems, equipment residue problems, mold problems, palatability problems.
>>>>(3) Adding water in the conditioner
It has been reported that by spraying 95-100°C hot water at 1%-1.5% at the inlet of the conditioner, the moisture content of the finished product can be increased by 0.4-0.6%. There are currently similar commercial products on the market: water replenishment flash evaporators. Compared with adding water in the mixer, this method should have more advantages in controlling mold.
>>>>(4) Steam pressure control
For livestock and poultry feed, the commonly used boiler steam supply pressure is currently 6-9 kg/cm2, and the pressure before conditioning is 2-4 kg/cm2. The higher the pressure, the higher the steam saturation is often, and the lower the humidity; conversely, the lower the pressure, the higher the humidity, and the higher the water content of the steam. When production needs are met, a lower boiler steam supply pressure (5-6 kg/cm2) can be selected, and it is sufficient to control it at 2-3 kg/cm2 before conditioning, and it is best to install a pressure reducing valve after the workshop steam header for pressure stabilization control.
Disadvantage: When switching formulas, steam pressure may need to be adjusted repeatedly to achieve different conditioning conditions.
>>>>(5) Increasing the conditioning temperature
After conditioning, the more suitable moisture content is controlled at 15-17%. If the moisture content before conditioning is relatively low, the moisture content can be increased by appropriately raising the conditioning temperature. Some studies have pointed out that under certain conditions, for every 10-15°C increase in temperature, the moisture content can increase by 1%.
Disadvantage: Arbitrarily changing the conditioning temperature required by the formula may increase the loss of nutrients in the formula.
>>>>(6) Increasing the conditioning time
There are two ways to increase the conditioning time: 1. Reduce the conditioning speed; 2. Adjust the paddle angle of the conditioner: by adjusting the paddle angle, the contact area between the material and steam can be affected, and the fill degree of the conditioner can thereby affect the moisture content of the material.
>>>>(7) Closing or adjusting the steam trap in the steam supply pipeline
The purpose of installing a steam trap is to remove condensate water from the steam pipeline and improve steam quality. When the moisture content of the semi-finished product is relatively low, the opposite can often be done: adjusting or closing the steam trap will not cause machine blockage, but instead helps increase the moisture content of the product.
>>>>(8) Reducing the compression ratio of the ring die
The thickness of the ring die affects the resistance when the material passes through the ring die. For a ring die with a certain aperture, during the pelleting process, generally speaking, the greater the thickness, the greater the frictional resistance, the higher the friction temperature, and the more moisture is lost. Therefore, while ensuring the appearance quality and fines rate of the product, appropriately reducing the compression ratio of the ring die also helps increase moisture content.
>>>>(9) Adjustment of cooling air volume
On the premise of ensuring the cooling effect of the product, adjustment can be carried out through the following aspects: 1. Appropriately lower the height of the level sensor; 2. Adjust the size of the air damper; 3. Control the fan speed through variable frequency technology.
The adjustment of finished product moisture content is a complex and systematic project. From raw material procurement, storage, production and processing to finished product preservation, moisture control points need to be established at every stage. To obtain ideal finished product moisture content, the key is to effectively monitor each moisture control point and choose effective improvement methods. Zhou Xiaoquan