plane rotary screen or vibration grading screen. After crushed, materials on the meshes by screener will be conveyed into hammer mill to be crushed again. The method of enlarging the meshes can increase the material flow and reduce the energy consumption. The power saving is 26% ~ 40% than that of common crushing process, and the output is increased by 34% ~ 50%.

1.2 Secondary crushing process. The process uses two hammer mills or combination of roller mill and hammer mill. Materials are usually coarsely crushed by the first hammer mill, then the thick materials will be crushed by the second hammer mill or roller mill. This process can eliminate the effect of material reflux on the efficiency of hammer mill in a single cycle process. Roller mill can play an important role in combination with hammer mill. It not only saves electricity consumption, but also reduces noise and is easy to adjust product fineness.

2. The convey of the materials after crushing uses mechanical convey (plus suction air).

After the secondary crushing process, the output of hammer mill is increased, the lifting equipment and the horizontal conveying equipment after crushing section must have the corresponding transport capacity.

3. Use automatic feeder. In order to achieve the best effect, we must ensure feeding uniform under the maximum workload, to make the hammer mill work efficiently and steadily. Using automatic feeder can regulate feeding speed according to the moisture content, characteristics and fiber of materials. Because the feeder has achieved the best load control for hammer mill, it reduces the power consumption of the feed plant and increases the output.

4. Use a new type of hammer mill. The vertical hammer mill has been used in European feed mills in recent years and has shown its obvious advantages compared with the horizontal hammer mill. The vertical hammer mill eliminates the auxiliary air suction system, which solves the problem of inefficiency caused by improper suction system and air suction system fault in traditional process, and reduces water loss. The machine is equipped with screen changing system, fast loading and unloading mechanism. The temperature sensor and vibration sensor are also installed in the machine to monitor the working condition. Using vertical hammer mill can increase the output by more than 25% and save energy over 30%. There are many factors affecting the crushing efficiency. Taking full consideration of the selection of equipment and process layout is an important way to improve the quality and efficiency of crushing.