Proper mixing time
For fractional mixers, it is critical that the mixing time is clearly targeted at the quality of the mixing. If the mixing time is too short, the material cannot be sufficiently mixed in the mixer and is discharged. The mixing quality cannot be ensured. If the mixing time is too long, the material is separated by excessive mixing in the mixer, which also harms the quality, and Increased energy consumption.
The definite mixing time lies in the mixing rate of the mixer, which is mainly determined by the model of the mixer. Such as a vertical ribbon mixer, generally 3 to 5 minutes each time, the length of which depends on the type and characteristics of raw materials, such as moisture content, particle size, fat rate, etc .; the mixing time of the two-shaft paddle mixer is low each time In 2min; for the drum mixer, because of its slower mixing efficiency, a longer mixing cycle time is required.
No matter what kind of mixer is targeted, the proper charging is a necessary condition for the mixer to work normally and achieve the expected goals. If there is too much charging, on the one hand, the mixer will be overloaded. What's more critical is that too much charging will endanger the entire process of mixing the materials in the machine, resulting in a reduction in the quality of the mixing. Using the high efficiency of the mixer will also endanger the quality of the mix. Therefore, no matter what kind of mixer, the loading level of the material should be properly controlled, so that all normal operations of the mixer can be ensured, and the quality requirements of the concentrated concentrate after mixing can be considered.
The filling index of the split vertical screw accumulation mixer is generally 0.6-0.9, and the maximum material level cannot exceed the top plan of the motor rotor. The filling index of the two-shaft paddle mixer is generally controlled at 0.6- — 0.85.
All powders with good liquidity tend to develop separately. There are three reasons for separation: ① When the material falls into a pile, large particles fall into the pile because of a large inertial force, and small particles with small inertia may be embedded in the gap in the pile; ② When the material is When shaking, smaller particles tend to move to the bottom, while large particles tend to move to the top; ③ When the mixture is blown away or dusted, the particle size and relative density are different, and the relative To produce separation.
In order to prevent separation, the following types of methods are often used: ① Make sure that the particle sizes of the various components of the mixture are close; or use liquid to prevent separation. ② Grasp the mixing time without having to mix too much. It is generally felt that the material should be discharged before the mixing is well-proportioned and mixed during the whole process of transportation or transfer. ③ Reduce the mixed loading and unloading work to the minimum level. The lower the material drops, flips or drags, the better. The storage bin after mixing should be as small as possible. The conveying equipment after mixing is a belt conveyor. As far as possible, no screw conveyor, bucket elevator and pneumatic conveying system equipment are needed. ④ Add antistatic agent to the grounding device of the mixer and concentrated feed to reduce the separation of the mixture caused by the electrostatic induction effect.
Effective practical sequence
In the order of feeding, generally, the large amount of ingredients are added first or most of them are added to the machine, and then the small and trace analysis ingredients are placed on the material. In a variety of materials, the mixer with a larger particle size is generally added first, and the mixer with a smaller particle size is added later. There is also a difference in the relative density of the materials. When there is a large difference, the materials with a relatively low density are generally put first, and then the materials with a high density are placed.