Cyclone

Abstract

[Problem] To improve dust collection efficiency while also reducing cyclone pressure loss. [Solution] A cyclone 1 comprises: an outer cylinder 3 provided to an upper part of a vortex cylinder 2; an inner cylinder 4 provided in a concentric manner inside the outer cylinder 3; a conical section 9 provided to a lower end of the outer cylinder 3; a flow-rectifying member 5 in which, near an upper end of the conical section 9 and in a space directly below the inner cylinder 4, a plurality of sheet-shaped flow-rectifying plates having a curved surface at least in the lower half are provided around the axis of the inner cylinder at equiangular intervals, with the curved surfaces of the sheet-shaped flow-rectifying plates being in the same direction as a swirling flow flowing along the inner periphery of the inner cylinder 4; an inflow cylinder 6 provided in a tangential direction to the outer periphery of the outer cylinder 3; and a discharge opening 8 provided to a lower section of the vortex cylinder. A lower end of the flow-rectifying member 5 can be supported at a bonded portion of the outer cylinder 3 and the conical section 9.

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 provided on top of a swirling cylinder, an inner cylinder provided concentrically within the outer cylinder, a conical section provided at the lower end of the outer cylinder, a straightening member provided in the space directly below the inner cylinder near the upper end of the conical section, in which a plurality of planar straightening plates having a curved surface in at least the lower half are arranged at equal angular intervals around the axis of the inner cylinder, and the curved surface of each planar straightening plate is arranged in the same direction as the swirling flow flowing around the inner circumference of the inner cylinder, an inlet cylinder provided tangentially to the outer circumference of the outer cylinder, and a drop outlet provided 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 providing a straightening member near the upper end of the conical section of the cyclone, it is possible to straighten the swirling flow of the dust-containing gas earlier than when the straightening member is provided directly below the inner cylinder, thereby reducing pressure loss. Furthermore, when the straightening member is provided directly below the inner cylinder, some of the gas and dust that flow in from the inlet tube are drawn directly into the inner cylinder with almost no swirling, leading to a deterioration in dust collection efficiency. However, when the straightening member is provided near the upper end of the conical section of the cyclone, separation of the gas and dust is promoted by swirling, so dust collection efficiency does not deteriorate, and it is possible to improve dust collection efficiency while reducing pressure loss in the cyclone.

[0014] In the cyclone, by supporting the lower end of the straightening member at the joint between the outer cylinder and the conical portion, the straightening member can be supported without impeding the straightening action of the straightening member.

[0015] It is a schematic cross-sectional view showing an embodiment of the cyclone according to the present invention, taken along line AA in Fig. 1. It is a schematic cross-sectional view showing an example of a conventional cyclone.

[0016] 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.

[0017] FIG. 3 shows an example of a conventional cyclone. This cyclone 11 constitutes, for example, a suspension preheater for a cement burning apparatus, and is equipped with an outer cylinder 3 provided on top of a swirling cylinder 2, an inner cylinder 4 provided concentrically within the outer cylinder 3, 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 3, a drop port 8 provided at the bottom of the swirling cylinder 1, and a conical section 9 provided at the lower end of the outer cylinder 3.

[0018] 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 in such a way 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. In addition to the planar flow straightening plates that are directly mounted on the inner cylinder 4 as described above, there are also those that are mounted on the inner cylinder 4 via a conical flow straightening plate. The shape of each planar flow straightening plate also comes in a vertically elongated rectangular shape or an inverted triangular shape.

[0019] In the cyclone 11 having the above-described configuration, dust-containing gas G is supplied tangentially from the inlet tube 6 into the outer tube 3, generating a swirling flow inside the outer tube 3. The swirling flow moves from the top to the bottom of the outer tube 3, and dust D suspended in the gas is thrown out toward the wall surface of the outer tube 3 by centrifugal force, falls along the inner wall surface, and is discharged to the outside through the drop port 8.

[0020] Dust particles smaller in particle size than the dust separated by the swirling flow near the inner wall surface of the outer cylinder 3 form a swirling flow together with the gas and move to the space directly below the inner cylinder 4. This dust-laden gas G is then guided by the surface of the curved planar straightening plate of the straightening member 5, and gradually changes from a swirling flow to an upward flow, during which the tangential velocity of the swirling flow is converted into a velocity in the axial direction only, and moves through the inner cylinder 4 to the next process.

[0021] 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.

[0022] Therefore, in an embodiment of the cyclone according to the present invention, as shown in FIG. 1 , the flow straightening member 5 is provided directly below the inner cylinder 4 near the upper end of the conical portion 9, separate from the inner cylinder 4, so as to be supported by the flow straightening member support portion 7. The provision of the flow straightening member 5 in this position is a feature of the present invention. The flow straightening member support portion 7 is composed of four rod-shaped members arranged in a cross shape when viewed from above, and supports the lower end of the flow straightening member 5 at the joint between the outer cylinder 3 and the conical portion 9. The number of flow straightening member support portions 7 extending from the upper part of the cone is not necessarily four. Furthermore, the flow straightening member support portion 7 does not necessarily have to be connected to the upper part of the cone. For example, the flow straightening member support portion 7 may be connected to a pipe below the drop opening 8, or the flow straightening member support portion 7 may be connected to the inside of the inner cylinder 4 and the flow straightening member 5 may be suspended from there. Other components are similar to those of the cyclone 11 shown in FIG. 3 , and therefore the same reference numerals as those in FIG. 3 are used for the other components, and their description will be omitted.

[0023] By providing a straightening member 5 near the upper end of the conical section 9 of the outer cylinder 3, the swirling flow of the dust-containing gas G is straightened early, reducing pressure loss, and the dust-containing gas G is effectively separated into gas and dust near the upper end of the conical section 9 of the outer cylinder 3 by the centrifugal force associated with the swirling flow, making it possible to improve the dust collection efficiency while reducing pressure loss in the cyclone.

[0024] A comparative test was conducted on the pressure loss and dust collection efficiency of the cyclone 1 according to the present invention and a conventional cyclone. The cyclone 1 according to the present invention was used as an example, a conventional cyclone without the flow straightening member 5 was used as comparative example 1, and the cyclone 11 having the flow straightening member 5 at the lower end of the inner cylinder 4 was used as comparative example 2, and the pressure loss and dust collection efficiency of the cyclones were compared. The results are as follows.

[0025] Example: Pressure loss 280 Pa, dust collection efficiency 98.6% Comparative Example 1: Pressure loss 490 Pa, dust collection efficiency 97.5% Comparative Example 2: Pressure loss 300 Pa, dust collection efficiency 96.7%

[0026] As described above, it can be seen that the present invention achieves a significantly lower pressure loss than Comparative Example 1, and also achieves a lower pressure loss than Comparative Example 2 and an improved dust collection efficiency.

[0027] The present invention is not limited to the above-described embodiment, and can be practiced by partially changing the configuration or partially adding other configurations within the scope of the present invention. For example, the flow straightening member support portion 7 can be arranged in any manner and can have any shape as long as it can stably support the flow straightening member 5 and does not interfere with the flow straightening action of the flow straightening member 5.

[0028] The illustrated embodiments are merely examples and are not intended to limit the technical scope of the present invention.

[0029] REFERENCE SIGNS LIST 1 Cyclone 2 Swirling cylinder 3 Outer cylinder 4 Inner cylinder 5 Flow straightening member 6 Inlet cylinder 7 Flow straightening member support portion 8 Drop opening 9 Conical portion

Claims

1. A cyclone comprising: an outer cylinder provided on top of a swirling cylinder; an inner cylinder provided concentrically within the outer cylinder; a conical section provided at the lower end of the outer cylinder; a straightening member provided in the space directly below the inner cylinder near the upper end of the conical section, the straightening member comprising 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 provided tangentially to the outer circumference of the outer cylinder; and a drop outlet provided at the bottom of the swirling cylinder.

2. The cyclone according to claim 1, wherein the lower end of the straightening member is supported at the joint between the outer cylinder and the conical portion.

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