The main factors affecting the mixing uniformity of compound feed are: the mixer, the main physical properties of the material to be mixed, the filling amount of the mixer, the mixing time and the specific operating conditions.
1. The influence of mixer on mixing
In general, the mixer performance:
1. High mixing uniformity, no dead angle, less material residue;
2. The mixing time is short, the production efficiency is high, and it is matched with the whole unit (including connection and power matching);
3. The structure is simple and sturdy, the door switch is flexible, the operation is convenient, and it is convenient for testing, sampling and cleaning;
4. With suitable power matching, it can work normally under full load;
5. On the premise of ensuring the mixing quality, the energy consumption is low.
The models of mixers can be divided into many types according to different classification methods, mainly including horizontal, vertical, horizontal paddle, drum, left and right, planetary, rotating container, V, double cone, etc. There are two types of intermittent working type (batch type) and continuous working type. The product manufacturing level of different mixer manufacturers will definitely have advantages and disadvantages. When purchasing a mixer, you should choose a mixer with a higher manufacturing level according to your own production needs.
Different types of mixers have different mixing methods, and practice has proved that some mixing objects (materials) have the best mixing effect in a certain way, so it should be achieved according to different mixing objects and the mixing goals required by the producer itself ( effect) to choose different types of mixers.
It is difficult for the paddle mixer to mix the powder evenly, but when the feed needs to be added with molasses, and the addition amount is as high as 30%-40%, it is quite suitable to use this mixer for mixing; while the double cone The V-type mixer and the V-type mixer are more suitable for mixing materials with good fluidity and poor fluidity, respectively. If the particle size (thickness) between the mixed materials is close, a vertical mixer should be used, and when the particle size difference between the mixed materials is large, a horizontal mixer (and a rotary container mixer cannot be used) should be used; if If the residual amount is less, a horizontal or rotating container mixer should be used.
In addition, if the mixing requirements are high, the rotary container mixer should be used, but its production capacity is generally low; while the mixing effect is generally required, vertical, horizontal or continuous mixers can be used. production capacity is relatively high.
The level of mixing efficiency, the length of mixing time, and the speed of mixing are mainly determined by the model of the mixer and the manufacturing accuracy of the equipment itself. Generally speaking, the time required for uniform mixing in a horizontal mixer is relatively short, while that in a vertical mixer is longer. Of course, the length of the mixing time also depends on other factors such as the type of raw materials and their physical properties.
2. The influence of the main physical properties of the mixed materials on the mixing
The closer the main physical properties of the mixed materials, the smaller the separation tendency, the easier it is to be mixed uniformly, the better the mixing effect, and the shorter the time required to achieve uniform mixing. Physical properties mainly include particle size, shape, bulk density, surface roughness, flow characteristics, adhesion, moisture content, fat content, pH, etc. of the material. The material particles with high moisture content are easy to agglomerate or form agglomerates, and it is not easy to disperse uniformly, and the mixing effect is not satisfactory. Without affecting the required effect of the formula, if necessary, an appropriate amount of silica, precipitated calcium carbonate, etc. can be added, which is beneficial to improve the mixing effect.
Some additives in the feed need to be premixed with a carrier (or diluent) before being added to the mixer to make an additive premix, and then added to the mixer in a certain order to mix with other components. The particle size of the additives that need to be diluted is generally finer, so a carrier with a particle size and density close to it should be selected. Suitable carriers include commonly used feed ingredients, such as soybeans, wheat bran, defatted rice bran, etc. Generally, materials with fine particle size, no dust, and affinity for the active ingredients in the additive are selected as diluents (or carriers), which are suitable. The choice of neutral materials is conducive to maintaining the stability of vitamins and other active components.
3. The influence of the filling amount of the mixer on the mixing
The mixer mainly relies on three mixing methods of convection mixing, diffusion mixing and shear mixing to make the material move in the machine to achieve the purpose of mixing the material evenly. Important prerequisites for obtaining the desired effect. If the material is loaded too much, the mixer will be overloaded, and more importantly, the excessive amount of material will affect the circulation process of the material in the machine, resulting in a decrease in the mixing quality; if the material is too small, it will not be sufficient The efficiency of the mixer is used, energy is wasted, and it is not conducive to the flow of materials in the mixer, which affects the mixing quality.
Various types of feed mixers have their own reasonable filling coefficients. Their respective reasonable filling coefficients have been obtained in the laboratory and practice. Among them, the batch (intermittent) horizontal ribbon mixer has its filling coefficient Generally, 0.6-0.8 is appropriate, and the highest material position should not exceed the plane of the top of the rotor; the filling coefficient of batch vertical screw mixers is generally controlled at about 0.6-0.85; drum mixers are about 0.4; planetary mixers It is about 0.4-0.5; the rotary container mixer is about 0.3-0.5; the V-type mixer is about 0.1-0.3; the double-cone mixer is about 0.5-0.6. The filling coefficient of various continuous mixers is not the same, generally controlled at about 0.25-0.5, not more than 0.5.
4. Appropriate mixing time
In most compound feed production lines, the most commonly used mixers are basically batch type, and for batch type (batch type) mixers, there is also a problem of optimal mixing time. If the mixing time is too short, the material will be discharged without being fully mixed in the mixer, and the mixing quality will definitely not be guaranteed. However, it is not that the longer the mixing time, the better the mixing effect. Experiments have shown that any material with good fluidity and uneven particle size has a tendency to separate. If the mixing time is too long, the material will be excessively mixed in the mixer. It will cause separation, which also affects quality and increases energy consumption. Because in the mixing process of materials, mixing and separation are carried out at the same time. Once the mixing and separation reach a certain equilibrium state, the degree of mixing is already determined. Even if the mixing continues, the mixing effect cannot be improved. resulting in separation. The mixing time should be determined according to the combination of factors such as the model of the mixer and its manufacturing level, the physical properties of the material and the actual test results, which is not the same concept as the length of time required for the simple model itself. The mixer is used for a period of time, and various parameters may change, so it is necessary to check and test regularly, and adjust the time required for mixing correctly according to the inspection results.
5. Correct operation
For the production of additive premix, the stirring method should be gradually expanded from micro-mixing to small-volume mixing to medium-volume mixing and then to large-volume mixing. The correct order of adding materials should be: the components with large proportions are added first or most of them are added to the machine, and then a small amount and a small amount of components are added on top of it; among various materials, generally the components with large particle size are added. Add the mixer first, and then add the small particle size; when the specific gravity difference between the materials is large, generally add the material with a small specific gravity first, and then add the material with a large specific gravity.
For fixed container mixers, the mixer should be started first and then added to prevent the phenomenon of full load start-up, and it should be stopped after unloading; while the rotary container mixer should be started after feeding, first stopped, and then unloaded. For the V-type mixer, the materials should be fed from two feed ports respectively. Measures should be taken to minimize the influence of other factors on the mixing uniformity of the completed mixed materials: the mixed materials should be pressed into granules immediately, so that the various components of the materials can be fixed in the granules or directly packed in bags; avoid or minimize The transportation and drop of the mixed materials; the loading and unloading work after mixing should be minimized; the falling, rolling or sliding of the materials should be minimized; the storage bin after mixing should be as small as possible, and the conveying equipment after mixing should preferably be Belt conveyors.
In order to ensure the mixing quality, the running performance of the mixer should be checked regularly, lubricating oil is often added to the bearings and the joints of each movable shaft, and the wear parts should be repaired and replaced in time, and the optimal mixing time should be correctly determined according to the sampling inspection results of uniformity. Regularly check the operation of each switch, clean the sundries in the machine, remove the residual materials around the door switch, make the door switch flexible, and prevent the phenomenon of material leakage.
The mixer machine is important in the production line, and you can also go to see the feed drying machine .
