The main factors affecting the mixing uniformity of the compound feed are: the main physical characteristics of the mixer, the mixture, the filling amount of the mixer, the mixing time and the specific operating conditions.
First, the impact of the mixer on the mix
In general, the performance of the mixer:
1, high mixing uniformity, no dead angle, less material residue;
2, short mixing time, high production efficiency, and supporting the entire unit (including connection and power matching);
3, the structure is simple and sturdy, the door switch is flexible, easy to operate, easy to detect sampling and cleaning and cleaning;
4, have the right power package, can work normally under full load;
5. Under the premise of ensuring the quality of mixing, the energy consumption is low.
The models of the mixer can be divided into many types according to different classification methods, mainly horizontal, vertical, horizontal paddle, drum type, left and right type, planetary type, rotary container type, V type, double cone type, etc. Intermittent working (batch type) and continuous working two states. The production level of different mixer manufacturers will definitely have advantages and disadvantages. When purchasing the mixer, the mixer with higher manufacturing level should be selected according to the production needs.
Different types of mixers have different mixing methods, and practice has proved that some mixed objects (materials) have the best mixing effect in a certain way, so according to the mixing target of different mixing objects and producers themselves ( Effect) to choose different types of mixers.
The paddle mixer is more difficult to mix the powder evenly, but when the feed needs to add molasses and the addition amount is as high as 30%-40%, it is quite suitable to mix with this mixer; Type mixers and V-type mixers are suitable for mixing materials with better fluidity and poor fluidity. If the particle size (thickness) between the mixture materials is close to the vertical mixer, and the difference in particle size between the mixture materials is larger, the horizontal mixer is used (and the rotary container mixer cannot be used); Horizontal or rotary vessel mixers should be used if less residue is required.
In addition, if the mixing requirements are higher, the rotary container mixer should be used, but the production capacity is generally low; and if the mixing effect is general, the vertical, horizontal or continuous mixer can be selected. The production capacity is relatively high.
The mixing efficiency, the length of the mixing time, and the speed of the mixing speed are mainly determined by the type of the mixer and the manufacturing accuracy of the equipment itself. In general, the time required for the horizontal mixer to mix uniformly is relatively short, and the vertical mixer takes longer. Of course, the length of the mixing time depends on other factors such as the type of raw materials and their physical properties.
Second, the impact of the main physical properties of the mixture on the mixing of
The closer the main physical enthalpy between the materials to be mixed is, the smaller the separation tendency is, the easier it is to be uniformly mixed, the better the mixing effect, and the shorter the time required to achieve uniform mixing. Physical properties mainly include material size, shape, bulk density, surface roughness, flow characteristics, adhesion, moisture content, fat content, pH and so on. The particles with high moisture content tend to agglomerate or agglomerate, are not easy to be uniformly dispersed, and the mixing effect is unsatisfactory. Therefore , it is generally required to control the moisture content of the mixed materials to not exceed 12%, and the mixing of the materials with strong hygroscopicity is When the effect of the formulation is not affected, if necessary, silica or precipitated calcium carbonate may be added in an appropriate amount to improve the mixing effect.
Some additives in the feed are pre-mixed with a carrier (or diluent) before being added to the mixer to form an additive premix, which is then added to the mixer in a certain order for mixing with other components. The particle size of the additive to be diluted is generally fine, so a carrier having a similar particle size and density is selected. Suitable carriers include commonly used feed components, such as soybean, wheat bran, defatted rice bran, etc., generally choose a material with fine particle size, no dust, and affinity for the active ingredient in the additive as a diluent (or carrier), preferably The choice of neutral materials helps maintain the stability of vitamins and other active ingredients.
Third, the impact of mixer filling on mixing
The mixer mainly relies on three mixing modes of convection mixing, diffusion mixing and shear mixing to make the material move in the machine to achieve uniform mixing of materials. Regardless of the type of mixer, the suitable loading amount is that the mixer works normally and An important prerequisite for achieving the desired results. If the loading is too much, the mixer will be overloaded. More importantly, too much loading will affect the cyclic movement of the materials in the machine, resulting in a decrease in the mixing quality. If the charging is too small, it will not be sufficient. Taking advantage of the efficiency of the mixer, wasting energy, is also not conducive to the flow of materials in the mixer, and affects the quality of the mixture.
Various types of feed mixers have their own reasonable filling factors, and their respective reasonable filling factors have been obtained in the laboratory and practice. Among them, the batch (intermittent) horizontal ribbon mixer has a filling coefficient. Generally, 0.6-0.8 is suitable, the material position should not exceed the plane of the top of the rotor; the filling coefficient of the batch vertical spiral mixer is generally controlled at about 0.6-0.85; the drum mixer is about 0.4; the planetary mixer 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; and the double-cone mixer is about 0.5-0.6. The filling coefficients of various continuous mixers are not the same, generally controlled at around 0.25-0.5, not exceeding 0.5.
Fourth, the appropriate mixing time
In most compound feed lines, the most commonly used mixers are basically batch-type, while for batch (batch) mixers, there is also an optimum mixing time. If the mixing time is too short, the material will not be fully mixed in the mixer and will be discharged, and the mixing quality will not be guaranteed. However, it is not the longer the mixing time, the better the mixing effect. The experiment proves that any material with good fluidity and uneven particle size has a tendency to separate. If the mixing time is too long, the material is over-mixed in the mixer. It will cause separation, which also affects quality and increases energy consumption. Because the mixing and separation are carried out simultaneously during the mixing of the materials, once the mixing and separation have reached a certain equilibrium state, the degree of mixing is determined, and even if the mixing is continued, the mixing effect cannot be improved, but the mixing is excessive. And the separation occurs. The mixing time is determined according to the combination of the model of the mixer, its manufacturing level, the physical properties of the material, and the actual test results. The length of time required for the simple model itself is not the same concept. The mixer will be used for a period of time, and various parameters may change, so check the inspection regularly and adjust the time required for mixing according to the inspection results.
Fifth, the correct operation
For the preparation of the additive premix, the method of stirring from a small amount of mixing to a small amount mixing to a medium amount mixing to a large amount of mixing stepwise expansion is carried out. The correct order of material addition should be: after the components with large proportion are added first or most of them are added to the machine, a small amount and a small amount of components are added to it; in various materials, generally the group with large particle size It is added to the mixer first, and then the particle size is small. When the difference in specific gravity between the materials is large, the material with a small specific gravity is generally added first, and then the material with a larger specific gravity is added.
For fixed-container mixers, the mixer should be started before feeding to prevent full-load start-up, and the machine must be unloaded before it can be shut down; while the rotating container mixer should be started after feeding, first stop, then unload For V-type mixers, the feed should be fed separately from the two feed ports. Measures should be taken to minimize the influence of other factors on the mixing uniformity of the finished mixture: the mixed material is preferably pressed into granules immediately, so that the various components of the material are fixed in the granules or directly packaged; avoid or minimize Conveying and falling of mixed materials; minimizing the loading and unloading work after mixing; minimizing the falling, rolling or sliding of materials; the storage bin after mixing should be as small as possible, and the mixing equipment after mixing is preferably Belt conveyors.
In order to ensure the mixing quality, the running performance of the mixer should be checked regularly. The bearings and the connecting shafts of the moving shafts are often lubricated. The worn parts are repaired and replaced in time, and the optimum mixing time is correctly determined according to the sampling result of the uniformity. Frequently check the operation of each switch, clean the debris in the machine, remove the residual material around the door switch, make the door switch flexible, and prevent the leakage.
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