Introduction of Design Points for Installation of Sand Mixer Dust Collector

In the sand mixing process of the foundry, especially the addition of old sand, the addition of white mud, expansion powder, and coal powder during the mixing and rolling process of the sand mixer, the local dust concentration is as high as thousands of milligrams. In order to enable the operator to clearly see the grinding of the sand mixer on site, a fan roller was added to the position where the operator stood in the past to prevent dust from escaping to the operator's side, resulting in a large dust source in the factory, causing dust to fly in a large area in the workshop, especially when a large amount of pulverized coal or graphite flies away, objects can hardly be seen clearly from a few steps away. In the technical transformation of the sand mixer, the station needs to be treated as a key point to meet environmental protection requirements.

Considering that the sand mixer operator is used to opening the hood door closed on one side to observe the sand mixer, the dust extraction system sets the exhaust air volume higher. The total resistance of dust removal includes the overall resistance of the exhaust hood, the frictional resistance and local resistance of the air duct and its components, and the resistance of the purification equipment. The total resistance loss of the air duct is obtained by adding the air duct resistance of the remote dust collection point or circuit with high resistance in the system. According to the air volume and selected wind speed of each pipe section, the local friction resistance can be obtained by determining the pipe diameter. According to the calculation in the figure below and the conditions given above, the total resistance loss of the air duct is approximately1kPa, the local resistance loss of the sealed housing is150 kPa. When the wind speed of bag filter is2 Meters/Minutes-2.5Meters/At minutes, the working resistance is1.1kPa-1.5kPa, when the resistance difference between the parallel branches of the dust removal system exceeds10%The balance can be achieved by adjusting the pipe diameter, increasing the length of the air duct and increasing the local resistance.

The total exhaust air volume of each section of the dust removal system of the sand mixer should generally be considered according to the simultaneous work of each exhaust point in this section. When some exhaust points are not working at the same time and the exhaust air volume is large, when calculating the total exhaust air volume of each section of air duct, the exhaust air volume can be calculated according to the exhaust points working at the same time. A butterfly valve is installed on the branch pipe of each intermittent exhaust point, and the air outlet of the intermittent equipment is adjusted to be closed at the same time of the equipment. The dust suction port of our sand mixer is located near the top of the airtight cover. In order to prevent the powder from being sucked away by the large exhaust volume, the sand mixing process is to add water and sand at the same time. In addition, the powder conveyed by the screw conveyor is connected to the grinding wheel of the sand mixer through the cloth bag.

Through the above measures, the dust removal effect of the sand mixer system has reached the ideal state. Compared with the use of a single plug-in pulse bag filter, choosing a bag filter in parallel with multiple mixers for dust removal has both advantages and disadvantages. The former one-time investment is small, installation and maintenance is simple. The disadvantage is that the dust removal air volume is large, which will absorb a certain amount of powder and cause waste. The above reasonable process methods and measures can reduce the waste of powder, which is relatively simple, cheap and economical.

The powder conveying and dust removal powder conveying of the sand mixer is a self-designed powder pressing device, which uses compressed air for pneumatic conveying to lift the powder. The system is designed with built-in unloading and unloading positions7.5The rice bag dust collector uses compressed air to blow back the dust to effectively control the dust in the conveying process.