What Is a Cyclone Separator?

Cyclone separator is a kind of equipment for gas-solid or liquid-solid separation. The working principle is that the solid particles or liquid droplets with large inertial centrifugal force are separated from the outer wall surface by the rotational movement caused by the tangential introduction of the air flow. The main features of the cyclone separator are simple structure, high flexibility, high efficiency, convenient management and maintenance, and low price. It is used to capture dust with a diameter of 5-10 m. It is widely used in the pharmaceutical industry, and is particularly suitable for coarse dust particles Under the condition of high dust concentration, under high temperature and high pressure conditions, it is also often used as an internal separation device of a fluidized bed reactor or as a pre-separator. It is a widely used separation equipment in industry.

Cyclone separator is a kind of equipment for gas-solid or liquid-solid separation. The working principle is to rely on the rotational motion caused by the tangential introduction of the airflow, which has a large inertia.

The main characteristics of the cyclone separator are simple structure, large operation flexibility, high efficiency, and management.

The main function of cyclone separator equipment is to remove as much solid particles and liquid droplets as possible from the conveying gas to achieve gas-solid-liquid separation to ensure the normal operation of pipelines and equipment. In the West-to-East Gas Transmission Project, the cyclone separator is More important equipment. ^[1]

The cyclone separator adopts a vertical cylindrical structure, and the interior is divided into a liquid collection area, a cyclone separation area, and a purification room area in the axial direction. The built-in cyclone sub-members are evenly arranged in the circumferential direction and fixed by upper and lower tube plates; the equipment is supported by a skirt seat, and the head adopts a high pressure resistant oval head.

Device nozzles provide paired

Changes in the overall structure

In the swirling airflow inside the cyclone, the particles are moved radially outward (toward the cone wall) by the centrifugal force. The speed of movement can be obtained from the centrifugal force and the motion equation of the airflow resistance. Obviously, the purpose of separation of the cyclone dust collector is to make the particles reach the side wall of the cone as soon as possible. Therefore, prolonging the movement time of the particulate matter in the cyclone dust collector, increasing the probability that the particulate matter collides with the cone wall of the cylinder under the action of the airflow, and improving the dust removal efficiency of the cyclone dust collector.

Y.Zhu (2001) proposed adding a cylinder wall to the ordinary cyclone dust collector. This cylinder wall divides the internal space of the cyclone dust removal equipment into two annular areas. At the same time, the exhaust core pipe is moved to the lower side and the exhaust core The updraft in the tube has also become a downdraft, and the particulate matter has been separated in the outer and inner annular regions. In fact, this cyclone separator is equivalent to bringing two cyclones together. In theory, this improvement increases the probability of particulate matter being collected. The test results of Y.Zhu cyclone dust collector (air flow rate range 10L / min 40L / min, particle size range 0.6m 8.8m) were compared with Stairmand cyclone dust collector: improved cyclone dust collector The dust removal efficiency of the filter is improved, and it increases with the increase of the air flow. At the same time, for the same dimensionless cyclone dust collector, the resistance of the former is smaller than that of the latter. Y.Zhu considers various factors and gives the corresponding optimized comprehensive index to conclude that the improved cyclone dust collector performance is better than the traditional cyclone dust collector. This modified cyclone dust collector has a slightly more complicated structure than the original traditional cyclone dust collector.

Adding additional parts to the original cyclone structure

The systems in practical applications are relatively large. The use of new cyclones to replace the original cyclones will inevitably lead to a relatively large amount of engineering and cost. Based on this idea, many researchers have sought to improve the cyclone performance by adding additional components without changing the original cyclone structure.

Because of the low efficiency of the cyclone dust collector for fine particles, especially the dust removal efficiency of PM10 (particles with a particle diameter of less than 10 m) gradually decreases as the particle diameter decreases. In other words, during the operation of the cyclone dust collector, most of the fine dust penetrated the separation area, resulting in a decrease in the efficiency of the fine dust. A. Plomp et al. (1996) proposed a cyclone dust collector equipped with a secondary separation attachment, as shown in Figure 3. The secondary separation accessory is located on the top of the cyclone body and is called POC (post cyclone).

The secondary separation of POC is to use the strong swirling action of the exhaust core tube to make the fine dust move to the side wall by centrifugal force, and collide with the baffle, and then fall into the shell of the lower part of the baffle through the gap 1. In the beginning, it did not collide with the side wall, but because it is always subject to centrifugal force, when it reaches the top of the POC, a large part of it also enters the space between the baffle and the shell through the gap 2. Then, due to the main About 10% of the airflow forms an osmotic flow through the gap, and the particles are blown out of the shell by the osmotic push.

The research results show that under specific structural dimensions and operating conditions, the total efficiency is improved by 2% to 20% compared with that before improvement; the resistance of the POC is about 10% of the cyclone dust collector body, and the resistance has nothing to do with the permeate gas flow (at the given parameters Within the scope); For cyclone dust collectors with large diameters, especially when the performance of the original cyclone dust collector is not very high, the method of installing POC is effective to improve the performance of cyclone separation. The POC device is effective for the separation of dust above 3m, and has no significant effect on the dust below 3m; the permeate flow and the centrifugal force of the POC device have a significant impact on the performance of the POC; the use of a perforated (smaller) inner baffle can improve the separation efficiency.

Local structural improvement

Many researchers have studied the airflow flow inside the cyclone dust collectors and concluded that the airflow velocity distribution of the cyclone dusters is axially asymmetric or eccentric. Especially near the lower part of the cone near the dust outlet, there is obvious "eccentricity"; near the lower mouth of the exhaust pipe, the radial air velocity is large and there is a "short circuit" phenomenon. Eccentric airflow or short circuit is not conducive to dust separation.

(1) Change of import structure

Penghe Environmental Protection Co., Ltd. aimed at the asymmetry of the airflow axis in the cyclone dust collector, and changed its inlet from single inlet to double inlet (as shown in Figure 4). The experimental study of the flow field in the cyclone dust collector showed that the flow field of the double inlet cyclone dust collector Axial symmetry is better than single inlet cyclone dust collector, dual inlet cyclone dust collector vortex core deformation is small; tangential speed of double inlet cyclone dust collector is higher than single inlet about 6%, and attenuation is also slow in quasi-free vortex area; double inlet The short-circuit flow of the cyclone dust exhaust pipe is less than the single inlet. Double inlet cyclone dust collector is more conducive to improving dust removal efficiency and reducing equipment resistance than single inlet cyclone dust collector.

In order to reduce the dust removal efficiency due to the short-circuit flow of dust, Penghe Environmental Protection has adopted a rotary channel in the inlet structure (see Figure 5), in order to reduce the centripetal dust concentration gradient entering the cyclone dust collector space. Gas-solid two-phase separation of two channels with variable cross-section was analyzed. It is pointed out that the use of an inlet slewing channel with a reasonable slewing angle can improve the dust removal efficiency of the cyclone dust collector. This method separates the two sections of the barrel and cone of the cyclone from the structure into three sections of the inlet channel, the tube and the cone.

(2) Change in cone structure

Rongbiao Xiang et al. Studied the effect of cone size on small cyclones used for atmospheric sampling. Using particle size and airflow velocity as parameters, the efficiency of three cyclones with different lower diameter cones was measured. The measurement results show that the diameter of the lower part of the cone has a significant effect on the efficiency of the cyclone sampler, but does not significantly affect the degree of change between the efficiency of particles with different particle sizes. When the diameter of the lower part of the cone is larger than the diameter of the exhaust core tube, the cone parameter is reduced, and the sampling efficiency will be improved without significantly increasing the resistance; however, the cone can be seen from the resistance test results The diameter of the weapon part should not be smaller than the diameter of the exhaust core pipe. In theory, a decrease in the diameter of the lower part of the cone can cause an increase in tangential velocity and thus increase the centrifugal force. For cyclones with the same cylinder diameter, if the cone opening is small, the maximum tangential velocity is close to the cone wall. This allows the particles to be better separated. At the same time, if the cone opening is small, the vortex will touch the cone wall, making it possible for the particles to re-enter the outlet airflow, but the latter has a smaller impact on the cyclone sampler than the former. In short, appropriately reducing the diameter of the lower part of the cone is conducive to improving efficiency. In order to facilitate the design of the new cyclone sampler, it is also pointed out that the Barth theory and Leith-Licht theory, which have a good prediction effect on the efficiency of the high-efficiency Stairmand cyclone dust collector, also have a good prediction effect on the collection efficiency of the cone change cyclone sampler.

Cyclone separator is suitable for purifying non-sticky, non-fiber dry dust larger than 1-3 microns. It is a purification equipment with simple structure, convenient operation, high temperature resistance, high equipment cost and high resistance (80-160 mm water column). Cyclone dust collector is most widely used in purification equipment. The improved cyclone separator can replace the exhaust gas filtering equipment in some units.

Cyclone separator is a device that uses the principle of centrifugal sedimentation to separate particles from the air stream. The velocity of gas passing through the air inlet is 10-25m / s, generally 15-20m / s. The centrifugal force generated can separate particles and mist as small as 5m. Therefore, it is a widely used equipment in the production of mines and cement. Especially in the chemical production process, cyclone separators are used in many places, and they are also common in the ventilation and dust removal systems of factory buildings. Its extensive use can not only improve the environment, but also turn waste into treasure to reduce the economic loss of the factory. For example, in a synthetic detergent factory, in the exhaust gas recovery system that handles dusting, cyclone separator dust removal measures are adopted, which not only improves the operating environment and reduces air pollution, but also recovers considerable tail powder, which greatly reduces the factory cost. ^[2]