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Cyclone dust collector

Author: admin Source: This station Time: 2015-08-01 13:19
Cyclone dust collector

Cyclone dust collector is a kind of dust removal device. The mechanism of dust removal is to make the dust laden air flow rotate, separate the dust particles from the air flow by centrifugal force and capture them on the wall of the filter, and then make the dust particles fall into the ash hopper with the help of gravity. Each part of cyclone dust collector has a certain size proportion, and the change of each proportion relationship can affect the efficiency and pressure loss of cyclone dust collector, among which the dust collector diameter, inlet size and exhaust pipe diameter are the main influencing factors. It should be noted that when a certain limit is exceeded, favorable factors can also be converted into unfavorable factors. In addition, some factors are beneficial to improve the dust removal efficiency, but they will increase the pressure loss, so the adjustment of each factor must be taken into account.

Cyclone dust collector is composed of inlet pipe, exhaust pipe, cylinder, cone and ash hopper. Cyclone dust collector has the advantages of simple structure, easy manufacture, installation, maintenance and management, low equipment investment and operation cost. It has been widely used to separate solid and liquid particles from gas flow or solid particles from liquid. Under normal operation conditions, the centrifugal force acting on particles is 5-2500 times of gravity, so the efficiency of cyclone dust collector is significantly higher than that of gravity settling chamber. Based on this principle, a cyclone dust removal device with a dust removal efficiency of more than 90% has been successfully developed. In the mechanical dust collector, the cyclone dust collector is the most efficient one. It is suitable for the removal of non viscous and non fibrous dust, mostly used to remove particles above 5 μ M. the parallel multi tube cyclone device also has 80-85% dust removal efficiency for 3 μ m particles. The cyclone dust collector is made of special metal or ceramic materials with high temperature resistance, wear resistance and corrosion resistance. It can operate under the conditions of temperature up to 1000 ℃ and pressure up to 500 × 105Pa. Considering the technical and economic aspects, the pressure loss control range of cyclone dust collector is generally 500 ~ 2000Pa. Therefore, it belongs to the medium efficiency dust collector, and can be used for the purification of high-temperature flue gas. It is widely used in boiler flue gas dust removal, multi-stage dust removal and pre dust removal. Its main disadvantage is that the removal efficiency of fine particles (< 5 μ m) is low.
According to the method of integrating the axial velocity with the flow area, the variation of the descending flow after installing different types of drag reducing rods in the conventional cyclone dust collector is calculated, and the percentage of the descending flow at different cross sections in the total flow rate of the dust collector is plotted under various conditions, so as to show the average value of the over flow in the up and down flow areas, that is, the difference between the actual flow rate and the flow rate in the down flow area The size of. It can be seen that the short-circuit flow rate and falling flow rate of each model change along the height of the dust collector. Compared with the conventional cyclone dust collector, the short-circuit flow rate increases when the full-length drag reduction rods 1 ? and 4 ? are installed, but the short-circuit flow is reduced after installing non full length drag reduction rods H1 and H2. After installing 1 ? and 4 ? and 4 ?, the variation law of the descending flow along the process is basically the same as that of the conventional cyclone dust collector, showing a linear distribution, and the three lines are parallel to each other. However, after installation of H1 and H2, the distribution is a broken line rather than a straight line, and its inflection point is exactly the section position where the drag reduction rod is inserted from bottom to top. It can also be seen that the non full length drag reducing rod increases the downward flow extending above the section, which is larger than that of the conventional dust remover. However, after contacting the drag reducing rod, the descending flow decreases rapidly, reaching or lower than the value of the conventional dust collector at the bottom of the cone.
The reduction of short-circuit flow can improve the dust removal efficiency, increase the falling flow of cross-section, and increase the residence time of dust containing air in the dust collector, which creates more separation opportunities for dust. Therefore, although the drag reduction effect of the non full length drag reducing rod is not as good as that of the full length drag reducing rod, it is more conducive to improve the dust removal efficiency of the cyclone dust collector. The short circuit near the entrance of the cyclone will seriously affect the overall effect of the cyclone. How to reduce the short-circuit flow will be a research direction to improve the efficiency. Although the drag reduction effect of the non full length drag reducing rod is not as good as that of the full length drag reducing rod, it will have more practical significance because it reduces the short-circuit flow of the conventional cyclone dust collector, increases the cross-section flow rate and improves the dust removal efficiency of the cyclone dust collector.
 Cyclone dust collector

Air inlet

The air inlet of cyclone dust collector is the key component to form the rotating air flow, which is the main factor affecting the dust removal efficiency and pressure loss. The inlet area of tangential inlet has a great influence on the dust collector. When the inlet area is small relative to the cylinder section, the tangential velocity of the airflow entering the dust collector is large, which is conducive to dust separation.

Cylinder diameter and height

The diameter of cylinder is the most basic size of cyclone. At the same tangential velocity, the smaller the cylinder diameter D, the smaller the rotating radius of the airflow, the greater the centrifugal force on the particles, and the easier the dust particles to be trapped. If the diameter of the cylinder is too small, it is easy to choose the diameter of the cylinder. When the treatment air volume is large, due to the small diameter of the cylinder and the limited air volume for dust treatment, the parallel operation method of several cyclones can be adopted. The air volume treated by parallel operation is the sum of the air volume processed by each precipitator, and the resistance is only the resistance of that part of the air volume borne by a single dust remover. However, the parallel operation is more complex and requires more materials, and the gas is easy to be blocked at the inlet, which will increase the resistance. Therefore, the number of parallel units should not be too much. The total height of the cylinder is the sum of the height of the cylinder and the cone of the dust collector. With the increase of the total height of the cylinder, the number of rotation circles of the airflow in the dust collector can be increased, and the chances of separating the dust from the air flow are increased. However, with the increase of the total height of the cylinder, the radial velocity of the centripetal force in the outer swirling flow increases the chances of some fine dust entering the inner swirling flow, thus reducing the dust removal efficiency. Generally, the total height of the cylinder is 4 times of the diameter of the cylinder. As the radius of the conical cylinder decreases, the tangential velocity of the air flow increases, and the distance from the dust to the outer wall decreases, so the dust removal effect is better than that of the cylinder part. Therefore, when the total height of the cylinder is fixed, properly increasing the height of the conical cylinder is beneficial to improve the dust removal efficiency. When the height of the cylinder is 1.5 times of its diameter and the height of the cone is 2.5 times of the cylinder diameter, the dust removal efficiency can be better.

Diameter and depth of exhaust pipe

The diameter and insertion depth of exhaust pipe have great influence on the dust removal efficiency of cyclone. A suitable value must be selected for the diameter of the exhaust pipe. The smaller the diameter of the exhaust pipe can reduce the rotation range of the inner swirling flow, and the dust is not easy to be discharged from the exhaust pipe, which is beneficial to improve the dust removal efficiency, but at the same time, the speed of the air outlet increases and the resistance loss increases; If the diameter of the exhaust pipe is increased, the resistance loss can be obviously reduced, but because the exhaust pipe is too close to the wall of the cylinder, it is easy to form the "short circuit" phenomenon of the inner and outer swirling flow, so that part of the dust in the outer swirling flow is directly mixed into the exhaust pipe and discharged, thus reducing the dust removal efficiency. It is generally considered that the exhaust pipe diameter is 0.5 ~ 0.6 times of the cylinder diameter. It is easy to insert dust into the bottom of the air duct and increase the friction between the dust containing pipe and the secondary air outlet, so as to increase the friction between the dust containing pipe and the secondary air outlet, and increase the air flow resistance between the dust exhaust pipe and the secondary air outlet, and increase the air flow resistance between the dust exhaust pipe and the air inlet cone, so as to increase the friction between the dust exhaust pipe and the secondary air outlet pipe, so as to increase the friction between the dust exhaust pipe and the secondary air outlet, so as to increase the dust mixing efficiency. The insertion depth of exhaust pipe should be slightly lower than the bottom of air inlet. As the unit steel consumption of cyclone dust collector is relatively large, the better method in the design scheme is to gradually decrease the material from thick to thin from the upper part of the cylinder!

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