Cyclone

Abstract

[Problem] To improve dust collecting efficiency while reducing the pressure loss of a cyclone. [Solution] This cyclone 1 comprises: an outer cylinder 3 provided at the upper part of a revolving cylinder 2 and expanded in diameter downward; an inner cylinder 4 concentrically provided in the outer cylinder 3; a conical part 9 provided at the lower end of the outer cylinder 3 and contracted in diameter downward; a flow straightening member 5 which is provided in the space directly below the inner cylinder 4 and in which a plurality of planar flow straightening plates, each having a curved surface formed in at least the lower half thereof, is provided at equal angular intervals around the axis of the inner cylinder 4, the curved surface of each planar flow straightening plate being oriented in a direction opposite to the swirling flow flowing around the inner periphery of the inner cylinder 4; an inflow cylinder 6 provided in the tangential direction to the outer periphery of the outer cylinder 3; and a drop port 8 provided at the lower part of the revolving cylinder 2. An inner diameter D2 of the lower end of the outer cylinder 3 can be 1.1-2.2 times an inner diameter D1 of the upper end of the outer cylinder 3. The height of the outer cylinder 3 can be 0.8-1.6 times the inner diameter D1 of the upper end of the outer cylinder 3.

Description

Cyclone

[0001] The present invention relates to a cyclone that separates dust by centrifugal force by creating a swirling flow of dust-containing gas.

[0002] A cyclone is a dust collection device that uses centrifugal force. It has a simple structure with no internal drive unit and can be used regardless of the temperature of the dust-containing gas, so it is used in various fields of the chemical industry. In recent years, there has been an increasing demand for low-pressure drop cyclones from the perspective of energy conservation.

[0003] For example, in cement calciners, cyclones are used in suspension preheaters used to preheat raw materials, and the cyclones account for most of the pressure loss in the preheaters of cement calciners. Reducing the pressure loss in the cyclones increases production volume and reduces the power consumption of the fans, leading to reduced cement production costs.

[0004] Patent Document 1 discloses a low pressure loss cyclone in which pressure loss is significantly reduced by a straightening member in which the outer and inner swirl cylinders are arranged concentrically, and a plurality of inverted triangular planar straightening plates, each with a curved surface in the lower half, are arranged at the lower end of the inner cylinder at equal angular intervals around the axis of a conical straightening member, with the curved surface of each planar straightening plate facing the swirling flow flowing around the outer periphery of the conical straightening member.

[0005] Japanese Patent No. 2609168 Japanese Patent No. 3336440

[0006] When evaluating cyclone performance, dust collection efficiency is an important factor along with pressure loss, and a decrease in dust collection efficiency is undesirable because it increases the load on downstream exhaust gas treatment equipment (such as bag filters). Furthermore, in cement firing equipment, a decrease in the cyclone's dust collection efficiency increases the amount of heat carried out outside the preheater system and the amount of dust circulating within the preheater, causing problems such as an increase in heat consumption.

[0007] Generally, there is a trade-off between the pressure loss and dust collection efficiency of a cyclone, and it is not easy to meet the requirement of low pressure loss while maintaining dust collection efficiency.

[0008] The low-pressure-loss cyclone in Patent Document 1 can reduce pressure loss, but it also has the problem of reducing dust collection efficiency. Furthermore, the invention in Patent Document 2 aims to improve dust collection efficiency compared to the low-pressure-loss cyclone in Patent Document 1, but the straightening member is installed in a space close to the conical portion. As a result, re-entrained dust is sucked into the inner cylinder, and there have been cases in which dust collection efficiency has deteriorated in actual equipment.

[0009] The present invention has been made in view of the above circumstances, and has as its object to improve the dust collection efficiency while reducing the pressure loss of a cyclone.

[0010] In order to achieve the above object, the present invention provides a cyclone comprising: an outer cylinder arranged at the top of a swirling cylinder and expanding in diameter downward; an inner cylinder arranged concentrically within the outer cylinder; a conical section arranged at the lower end of the outer cylinder and contracting in diameter downward; a straightening member arranged in the space directly below the inner cylinder, in which a plurality of planar straightening plates each forming a curved surface in at least the lower half are arranged at equal angular intervals around the axis of the inner cylinder, with the curved surface of each planar straightening plate oriented in the same direction as the swirling flow flowing around the inner circumference of the inner cylinder; an inlet cylinder arranged tangentially to the outer circumference of the outer cylinder; and a drop outlet arranged at the bottom of the swirling cylinder.

[0011] Dust-laden gas that flows into the cyclone is separated into gas and dust by centrifugal force in the outer cylinder, and the dust passes through the wall of the cone and is discharged from the outlet at the bottom of the cyclone. Meanwhile, the gas reverses direction midway through the cone and is discharged from the inner cylinder while rotating upward.

[0012] At this time, the gas that reverses and rises flows into the inner cylinder while swirling at high speed, causing a very large pressure loss inside the inner cylinder. By using the flow straightener to straighten the swirling gas, the pressure loss can be significantly reduced.

[0013] According to the present invention, by installing a straightening member in the inner cylinder and expanding the diameter of the outer cylinder downward, the flow velocity of the swirling flow near the straightening member is slowed, thereby increasing the relative settling velocity of the dust.In addition, by increasing the distance between the straightening member and the cyclone wall surface, the amount of dust flowing into the inner cylinder is reduced, and the dust collection efficiency can be improved while reducing pressure loss in the cyclone.

[0014] The inner diameter of the lower end of the outer cylinder may be 1.1 to 2.2 times the inner diameter of the upper end of the outer cylinder.

[0015] The height of the outer cylinder may be set to 0.8 to 1.6 times the inner diameter of the upper end of the outer cylinder.

[0016] 1 is a schematic cross-sectional view showing an embodiment of a cyclone according to the present invention, and FIG. 2 is a schematic cross-sectional view showing an example of a conventional cyclone.

[0017] Next, an embodiment of the present invention will be described. To facilitate understanding of the configuration and operation of the cyclone according to the present invention, a conventional cyclone will first be described.

[0018] FIG. 2 shows an example of a conventional cyclone. This cyclone 11 constitutes, for example, a suspension preheater for a cement burning apparatus, and comprises an outer cylinder 13 of diameter D1 provided at the top of the swirling cylinder 2, an inner cylinder 4 provided concentrically within the outer cylinder 13, a flow straightening member 5 provided in the space directly below the inner cylinder 4, an inlet cylinder 6 provided tangentially to the outer periphery of the outer cylinder 13, a drop port 8 provided at the bottom of the swirling cylinder 2, and a conical section 19 provided at the lower end of the outer cylinder 13.

[0019] The flow straightening member 5 is a flow straightening plate (spiral cone) described in Patent Documents 1 and 2, which is made up of a plurality of planar flow straightening plates, each of which has a curved surface formed in at least the lower half thereof, mounted on the inner cylinder 4 at equal angular intervals around the axis of the inner cylinder 4 and such that the curved surface of each planar flow straightening plate faces in the same direction as the swirling flow flowing around the inner circumference of the inner cylinder 4. As for the flow straightening member 5, in addition to the planar flow straightening plate directly mounted on the inner cylinder 4 as described above, there are also flow straightening members 5 which are mounted on the inner cylinder 4 via a conical flow straightening plate. The shape of each planar flow straightening plate also varies, for example, to a vertically elongated rectangular shape or an inverted triangular shape.

[0020] In the cyclone 11 having the above-described configuration, a dust-containing gas G is supplied tangentially from the inlet tube 6 into the outer tube 13, generating a swirling flow inside the outer tube 13. The swirling flow moves from the top to the bottom of the outer tube 13, and dust D suspended in the gas is thrown out toward the wall of the outer tube 13 by centrifugal force, falls along the inner wall surface, and is discharged to the outside through the drop port 8.

[0021] Dust particles smaller in particle size than the dust separated by the swirling flow near the inner wall surface of the outer cylinder 13 form a swirling flow together with the gas and move to the space directly below the inner cylinder 4. This dust-laden gas is then guided by the surface of the curved planar straightening plate of the straightening member 5, where it gradually changes from a swirling flow to an upward flow, converting the tangential velocity of the swirling flow into a velocity in the axial direction only, and moves through the inner cylinder 4 to the next process.

[0022] In the conventional cyclone 11, the flow straightening member 5 straightens the reverse gas and weakens the swirl, thereby reducing pressure loss. However, by installing the flow straightening member 5 directly below the inner cylinder 4, the gas vector in the vicinity of the flow straightening member 5 changes from the tangential direction to an upward direction toward the inner cylinder 4, and the dust-containing gas is more likely to be sucked into the inner cylinder 4, resulting in a decrease in dust collection efficiency.

[0023] Therefore, in one embodiment of the cyclone according to the present invention, as shown in Fig. 1, the outer cylinder 3 is gradually expanded downward so that the inner diameter D2 at the lower end of the outer cylinder 3 and the upper end of the conical portion 9 is approximately 1.1 to 2.2 times the inner diameter D1 at the upper end of the outer cylinder 3. The height H of the outer cylinder 3 is approximately 0.8 to 1.6 times the inner diameter D1 at the upper end. Since the other components are the same as those of the cyclone 11 shown in Fig. 2, the same reference numerals as those in Fig. 2 are used for the other components, and their description will be omitted.

[0024] In the present invention, the outer cylinder 3 is gradually expanded downward so that the lower end of the outer cylinder 3 has an inner diameter D2, thereby slowing the flow rate of the swirling flow near the straightening member 5 and increasing the relative settling rate of the dust. In addition, by increasing the distance between the straightening member 5 and the outer cylinder 3, the amount of dust flowing into the inner cylinder 4 is reduced, thereby improving dust collection efficiency.

[0025] A comparative test was conducted on pressure loss and dust collection efficiency between cyclone 1 according to the present invention and a conventional cyclone. The pressure loss and dust collection efficiency of the cyclones were compared using cyclone 1 according to the present invention as Example, a cyclone with the same shape as cyclone 1 according to the present invention (the shape shown in FIG. 1) but without the flow straightening member 5 as Comparative Example 1, cyclone 11 (the cyclone shown in FIG. 2) with the flow straightening member 5 at the lower end of the inner cylinder 4 as Comparative Example 2, and a cyclone with the same shape as cyclone 11 shown in FIG. 2 but without the flow straightening member 5 as Comparative Example 3. The results are shown in Table 1.

[0026]

[0027] As shown in Table 1, the cyclone 1 according to the present invention has a slightly lower dust collection efficiency than Comparative Example 1, but has significantly lower pressure loss, and has improved dust collection efficiency with lower pressure loss than Comparative Examples 2 and 3.

[0028] The present invention is not limited to the above-described embodiment, and can be carried out by partially changing the configuration or partially adding other configurations within the scope of the gist. Furthermore, the illustrated embodiment is merely an example, and is not intended to limit the technical scope of the present invention.

[0029] REFERENCE SIGNS LIST 1 cyclone 2 swirl cylinder 3 outer cylinder 4 inner cylinder 5 flow straightening member 6 inlet cylinder 8 drop port 9 conical portion

Claims

1. A cyclone comprising: an outer cylinder arranged above a swirling cylinder and expanding in diameter downward; an inner cylinder arranged concentrically within the outer cylinder; a conical section arranged at the lower end of the outer cylinder and contracting in diameter downward; a straightening member arranged in the space directly below the inner cylinder, with a plurality of planar straightening plates each forming a curved surface in at least the lower half thereof at equal angular intervals around the axis of the inner cylinder, with the curved surface of each planar straightening plate oriented in the same direction as the swirling flow flowing around the inner circumference of the inner cylinder; an inlet cylinder arranged tangentially to the outer periphery of the outer cylinder; and a drop outlet arranged at the bottom of the swirling cylinder.

2. A cyclone according to claim 1, wherein the inner diameter of the lower end of said outer cylinder is between 1.1 and 2.2 times the inner diameter of the upper end of said outer cylinder.

3. A cyclone according to claim 1 or 2, characterized in that the height of the outer cylinder is between 0.8 and 1.6 times the inner diameter of the upper end of the outer cylinder.

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