The design scheme of environmental dust removal system for sand and gravel plant is as follows (for reference only):

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I. General Principles

1.1 Environmental dust collection facilities need to be "three-in-one" with engineering design, construction and commissioning.

1.2 It is necessary to ensure that dust emission indicators meet the national or key regional standards.

1.3 The dust collection design air volume needs to be determined by calculation, with the principle that dust does not escape outside the workshop. When conditions permit, the dust collection air volume can also use measured data.

1.4 The dust collected by the dust collection facilities should be properly transported and stored to avoid secondary dust caused by improper transportation or collection.

II. Composition of dust collection system

A complete dust collection system should include dust collection hood, air duct, dust collector, dust unloading device, fan, air compressor, etc.

2.1 The dust hood controls the dust source by sucking air;

2.2 The air duct conveys gas;

2.3 The dust collector purifies the dust-containing gas, separates the dust in the dust-containing gas and recycles it;

2.4 The dust unloading device includes a spiral reamer (or air conveying chute) and a rotary air lock valve (weighted flap valve), which mainly discharges the dust separated by the dust collector and stored in the ash hopper, and then conveys it to downstream equipment;

2.5 The fan is the power equipment in the dust collection system, which sucks the dust-containing gas into the dust collection hood, conveys it into the dust collector through the air duct, and then discharges it into the atmosphere after purification;

2.6 The air compressor mainly provides compressed air and is the power source for dust collector cleaning.

3. Design of dust hood and dust collecting air duct

1) Design of dust hood

a) It can effectively control the dust-containing gas from escaping from the sealing hood to avoid sucking away the material being transported;

b) The wind speed at the suction port of the dust hood is generally ≤1.4~2m/s. The finer the material, the lower the wind speed;

c) The dust hood should not be close to open holes to avoid sucking out irrelevant gases;

d) Keep it as far away from the drop point as possible to avoid the material being sucked away before it falls.

2) Dust collection duct design

a) The dust collection duct should be straight and short, and the inner surface of the duct should be smooth to reduce resistance;

b) In principle, the dust collection duct should avoid horizontal ducts. The angles between the upward and downward inclined ducts (viewed along the airflow direction) and the horizontal direction are generally 60° and 45°. In certain cases, when the inclination angle is less than 60° and less than 45°, a well-sealed cleaning hole should be provided on the duct;

c) The dust collection branch pipe should be connected from the top or side of the main pipe, and the angle of the tee pipe is generally not less than 30° and not more than 45°;

d) The radius of curvature of the dust collection duct elbow is 1.5 to 2 times the pipe diameter, and can be equal to the pipe diameter in special cases;

e) The pipeline layout of the dust collection system should be as simple as possible, the dust collection points should generally not exceed 10, and the duct should not be too long, and the number of dust collection duct elbows should be minimized;

f) The wind speed control of dust-containing air ducts in sand and gravel plants is as follows: generally 12-16m/s for inclined ducts, 18-22m/s for horizontal ducts, and 8-12m/s for vertical ducts;

g) The dust collecting air duct should adopt a circular cross-section;

h) A manual butterfly valve should be installed on the dust collecting air duct to adjust the air volume balance of the dust collecting system;

i) The wind speed of the dust collector outlet duct is generally 12-15m/s;

j) The dust collector unloading point should be designed after the exhaust point to avoid secondary dust.