JPS6157065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cyclone used for removing dust floating in a gas or separating particulate matter in a gas in a chemical process.

Referring to FIGS. 1 and 2, a conventional cyclone includes a cylindrical portion 1 having an inverted conical portion 1a at the bottom and a vertical axis, and an exhaust pipe 4 provided concentrically within the cylindrical portion 1. A gas containing powder to be collected is introduced from an introduction duct 3 tangentially connected to the upper part of the cylindrical part 1 . The gas flowing into the cylindrical part 1 descends while swirling along the inner wall of the cylindrical part 1, as shown by the broken line in FIG. . During this time, the powder contained in the gas is drawn to the inner wall of the cylindrical portion 1 by centrifugal force as shown by the solid line in FIG. The dust is collected in the dust box via the chute.

Considering the movement of gas inside this cyclone,
The gas flow is a three-dimensional spiral flow having minute velocities in the radial, axial and circumferential directions of the cylindrical portion 1. Of these, the minute velocity in the circumferential direction is, as shown in Figure 2, a free vortex 6 with constant rotational momentum (actually, due to friction with the wall, it is not a pure free vortex but a quasi-free vortex). A so-called Rankine vortex is a combination of a free vortex 6 and a forced vortex 7 whose rotational speed is proportional to the radius.
When considering the pressure loss of the cyclone, the pressure loss in the axial direction from the inlet 4a to the outlet of the exhaust pipe 4 can be ignored because the minute velocity in the axial direction is small.
Moreover, it has been known from the past that the exit pressure of the cyclone is equal to the pressure near the boundary 8 between the free vortex 6 and the forced vortex 7, and that the cyclone entrance pressure is equal to the pressure at a position close to the inner wall surface of the cylindrical portion 1. It is being Therefore, the pressure loss of the cyclone can be considered to be approximately equal to the pressure difference from the boundary 8 to the inner wall surface of the cylindrical portion 1. At this time, since the exhaust pipe 4 is concentric with the cylindrical part 1 as shown in FIGS. ), its maximum velocity u ₀ is extremely large. Therefore, a strong forced vortex is formed inside the free vortex, resulting in a large pressure loss. Further, near the gas inlet 5, there is a large pressure loss due to collision between the gas swirling within the cylindrical portion 1 and the gas flowing in from the introduction duct 3.
Further, due to this collision, the velocity of the inflowing gas from the introduction duct 3 increases locally, and the pressure loss increases accordingly.

The collection efficiency of this cyclone (the weight ratio of the collected powder to the incoming powder) is determined by the size of the cyclone, the inflow and
Although it varies depending on the exhaust gas velocity and the properties of the gas and powder, it generally reaches 90-100%. Therefore, although cyclones have a relatively large pressure loss, they are widely used due to their simple structure. For example, in a suspension preheater in which cement raw material powder is thrown into hot gas and suspended in hot gas to exchange heat with the hot gas before firing, multiple cyclones are combined to collect high-temperature powder. It is used as In this suspension preheater, the cyclones are arranged in multiple stages above and below to improve heat exchange performance, but in order to reduce the power of the blower and save energy, it is possible to reduce the pressure loss of each cyclone. requested. However, the collection efficiency in each cyclone is a factor that has a significant effect on the heat exchange performance of the suspension preheater, and it is essential to maintain high collection efficiency in each cyclone. Furthermore, recently, in order to improve productivity, baking equipment 1
The capacity of each unit is increasing to 3,000 to 10,000 tons/day, and the amount of exhaust gas from a 350℃ suspension preheater is 6,000 to 20,000 m ³ /min, so the diameter of the cyclone is increasing to 5 to 10 m. In order to suppress the increase in equipment costs due to the increase in the size of the entire suspension preheater, there is a strong demand for miniaturization of the cyclone.

Therefore, an object of the present invention is to provide a cyclone that can significantly reduce pressure loss without reducing collection efficiency and that is also miniaturized.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a horizontal sectional view of one embodiment of the present invention. This cyclone 10 has an inner cylinder 4b extending vertically arranged in a cylindrical part 11 which has an inverted conical part (not shown) at the lower part and extends vertically, like a conventional cyclone. 11 and the center 14 of the inner cylinder 4b are misaligned. An inlet 15 is formed in the upper part of the cylindrical part 11, and an introduction duct 16 is connected to the inlet 15.
1 are connected in the tangential direction. For comparison, the cylindrical portion 1 of a conventional cyclone is shown with a phantom line.

The center 14 of the inner cylinder 4b is parallel to the tangential introduction direction 23 of the introduction duct 16 and the center 13 of the cylindrical part 11
The inlet 1 is located on the imaginary diameter line 24 and the diameter line 26 passing through the
5 and is provided offset to the opposite side. Further, the inner surface of the cylindrical portion 11 is inscribed in the cylindrical portion 1 shown by the virtual line of the conventional cyclone on the inlet 15 side, and the center 13
The position of the center 13 of the cylindrical part 11 and the inner radius r3 are selected so that the center 13 of the cylindrical part 11 passes through the center position on the diameter line 26 between the inner surface of the cylindrical part 1 and the outer surface of the inner cylinder 4b on the opposite side from the inlet 15. It can be done. Therefore, the cylindrical part 11
The horizontal annular gap 17 between the inner surface of the inlet 15 and the outer surface of the inner cylinder 4b gradually narrows from the inlet 15 along the gas swirling direction 18 to reach the narrowest position 19, and gradually expands from the narrowest position 19. is formed so as to reach the inlet 15. Therefore, the gas flowing in from the inlet 15 swirls along the gap 17 and tries to flow down in the axial direction of the cylindrical part 11, so the gas near the inner cylinder 4b sequentially flows into the inner cylinder 4b and the swirling gas The amount decreases sequentially. Therefore, the free vortex generated by the swirling of the gas does not become large and u ₀ is suppressed. This prevents the generation of strong forced vortices and thus reduces pressure losses for the reasons mentioned above in connection with the prior art. Also gap 1
7 is expanded from the narrowest position 19 toward the inlet 15 along the swirling direction 18, the swirling energy of the gas that has passed the narrowest position 19 is reduced,
Correspondingly, the pressure loss caused by the collision between the inflow gas and the swirling gas near the inlet 15 and the local speed increase of the collided inflow gas is also reduced.

Referring again to FIG. 2, assume the case of a conventional cyclone in which the inner cylinder 4b and the cylindrical portion 1 are provided concentrically. If we closely observe the flow of gas and powder inside the cyclone in this case, we can see that the powder in the gas swirls along the inner surface of the cylindrical part 1, as shown by the stippled lines, and the radial width of the flow narrows. , almost the entire amount of powder is transferred to the cylindrical part 1 in less than one turn from the inlet 5.
It has been found through experiments by the present inventor that the other region 21 that reaches the inner surface and is not stippled is a region that does not contribute to the separation of the powder and gradually increases in width. Therefore, it can be seen that even if the gap 17 is gradually narrowed along the powder swirling direction 18 as shown in FIG. 3, the powder collection efficiency does not decrease.

The powder that is most difficult to collect is the powder located at the innermost position 22a of the stippled region 22 in FIG. Focusing on this powder, at the narrowest position 19 of the gap 17, the cylindrical part 11 and the inner cylinder 4b are biased so that the powder at the innermost position 22a is outside the outer surface of the inner cylinder 4b. If carefully placed, the collection efficiency can be comparable to traditional cyclones. Therefore, so that the innermost powder is located outside the outer surface of the inner cylinder 4b,
By selecting the position of the center 13 of the cylindrical portion 11 and the inner radius r3 of the cylindrical portion 11, it is possible to prevent the collection efficiency from decreasing. As in the present cyclone 10, at the narrowest position 19, the inner surface of the cylindrical portion 11 is at the center position between the outer surface of the inner cylinder 4b and the inner surface of the cylindrical portion 1 shown by the imaginary line in FIG. 3 of the conventional cyclone. As can be seen from the experimental results shown in FIGS. 5 and 6, which will be described later, the collection efficiency does not decrease even if the particles pass through the air.

Next, it will be explained that by having the above-mentioned configuration, the cyclone of the present invention is made smaller than a conventional cyclone. In a conventional cyclone in which the inner cylinder 4b and the cylindrical part 1 are arranged concentrically, the ratio of the inner radius r1 of the cylindrical part 1 to the outer radius r2 of the inner cylinder 4b is r1/r2.
is generally selected around 2. It is (1)
If r1/r2 is too small, the inlet width becomes small and the inlet cross-sectional area cannot be increased, which increases the gas inflow velocity and increases the pressure loss. This is based on the fact that if the cross section of the inlet is made vertically elongated in order to suppress an increase in the gas inflow velocity, the vertical length of the cylindrical portion 1 will increase, leading to an increase in the cyclone volume. So r1/r2
A conventional cyclone having a ratio of 2 and the present cyclone 10 having the above-described configuration will be compared. The width d of the gap 17 at the narrowest position 19 of the cyclone 10 is as follows: d=r1-r2/2=(r1-r1/2)/2=1/4
r1…(1) becomes. Further, the amount of deviation δ between the center 13 of the cylindrical portion 11 and the center 14 of the inner cylinder 4b is as follows: δ=1/2×1/4r1=1/8r1 (2). Therefore, the inner radius r3 of the cylindrical portion 11
is r3=r1-1/4r1+1/8r1=7/8r1...(3), and the cylindrical part 11 can be made smaller in diameter than the cylindrical part 1 of the conventional cyclone, and the present cyclone 10 can be adjusted accordingly. It is understood that it can be made smaller than conventional cyclones.

According to the experiments conducted by the present inventor, the axis 14 of the inner cylinder 4b is deviated to the side opposite to the inlet 15 on the diameter line 26 of the cylindrical portion 11 perpendicular to the imaginary diameter line 24, as shown in FIG. In the case where the width d of the gap 17 at the narrowest position 19 is approximately 1/3 of the difference between the inner radius r3 of the cylindrical portion 11 and the outer radius r2 of the inner cylinder 4b, that is, 1/3 (r3-r2). If it was above, no decrease in collection efficiency was observed.

The present invention is applicable not only to the case where the center 14 of the inner cylinder 4b is on the diameter line 26 of the cylindrical portion 11 perpendicular to the imaginary diameter line 24 as in the embodiment shown in FIG. The center 14 of the inner cylinder 4b is (a) virtual diameter line 2
(b) a straight line 28 connecting the center 13 of the cylindrical portion 11 and the inner end of the introduction duct 16; and (c) a hatched portion 25 surrounded by the inner wall of the cylindrical portion 11. It was confirmed that almost the same effect can be obtained when the area is located within the same area.

Further, the present invention provides an inner cylinder 4b within the cylindrical portion 11, as described in connection with the embodiments of FIGS. 3 and 4.
Not only the cyclone that entered the cylinder, but also the cylindrical part 11
It should be added that this can also be carried out when the exhaust pipe 4 is not inserted into the interior.

Next, the experimental results conducted using the cyclone 10 of the embodiment shown in FIG. 3 are shown in FIGS. 5, 6, and 7.
As shown in the figure. In each figure, the solid line indicates the cyclone, and the broken line indicates the conventional cyclone. In this experiment, cement raw material powder with an average particle size of 30 microns was used as the powder, and the gas inflow speed was 15 m/sec. The 〇 mark is the current result, and the △ mark is the conventional result.

Generally, the pressure loss ΔP of a cyclone is expressed by the following equation.

ΔP=ζ・γ・v ² /2g …(4) Here, ζ is the pressure loss coefficient, γ is the specific weight of the gas,
v is the gas inflow velocity, and g is the gravitational acceleration. No.
From equation (4), under conditions where the specific weight γ of the gas and the inflow velocity v of the gas are equal, the pressure loss ΔP increases as the pressure loss coefficient ζ increases. From FIG. 5, it can be seen that the pressure loss coefficient ζ of the cyclone of this invention exhibits a significantly lower value than that of conventional cyclones. Further, as shown in FIG. 6, it can be seen that when the amount of deviation δ of the inner cylinder 4b becomes larger than about 1/10 of the outer circumferential radius r2 of the inner cylinder 4b, the pressure loss coefficient ζ decreases significantly. Note that the radius of the cylindrical portion is the radius of the inner cylinder 4b.
Since it depends on r2, only the radius r2 is displayed. From this, the pressure loss Δ of the cyclone is
We were able to confirm that P was smaller than that of conventional cyclones. Moreover, from FIG. 7, it can be seen that the present cyclone exhibits a collection efficiency equivalent to that of a conventional cyclone.

As described above, according to the present invention, the center of the exhaust stack is connected to the radial line on the opposite side of the introduction duct, which is the virtual diameter line passing through the center of the cylindrical part parallel to the tangential introduction direction of gas.
A straight line connecting the center of the cylindrical part and the inner end of the inlet duct, and an annular gap between the exhaust pipe and the cylindrical part, which is offset within the area surrounded by the inner periphery of the cylindrical part and from the inlet along the swirling direction of the gas. Since the gap is gradually narrowed, gas near the exhaust stack is gradually sucked into the exhaust stack, and the maximum velocity of the free vortex in the gap becomes smaller. Therefore, generation of strong forced vortices is suppressed, and pressure loss is reduced accordingly. Further, since the gap is expanded along the swirling direction from the narrowest position, the swirling energy of the gas after the narrowest position is weakened. Therefore, pressure loss due to collision between the inflow gas and the swirling gas near the gas inlet and a local speed increase of the collided inflow gas is also reduced. On the other hand, in the cyclone, the powder in the gas swirls along the inner surface of the cylindrical part, and the radial width of the flow narrows, and it is confirmed that almost all the powder reaches the inner wall of the cylindrical part in less than one revolution. has been
Even if the gap between the exhaust pipe and the cylindrical portion is narrowed from the gas inflow port along the swirling direction as in the present cyclone, the collection efficiency does not decrease. Furthermore, by making the exhaust pipe and the cylindrical part eccentric, it is possible to eliminate a region within the cyclone that does not contribute to the separation of powder, and the cyclone can be made smaller by that amount.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional cyclone, FIG. 2 is a horizontal sectional view thereof, FIG. 3 is a horizontal sectional view of an embodiment of the present invention, and FIG. 5, 6 and 7 are graphs showing experimental results. 4... Exhaust pipe, 4b... Inner cylinder, 10... Cyclone, 11... Cylindrical part, 13... Center of cylindrical part 11, 14... Center of inner cylinder 4b, 15... Inflow port,
16...Introduction duct, 23...Tangential introduction direction, 2
4, 26...Virtual diameter line.

Claims (1)

[Claims] 1. A cyclone in which an exhaust pipe is arranged at the top of a cylindrical part having a gas inlet, and an introduction duct is connected to the inlet in a tangential direction of the cylindrical part,
The center of the exhaust pipe is a virtual diameter line passing through the center of the cylindrical part parallel to the tangential direction, a radial line on the opposite side of the introduction duct, a straight line connecting the center of the cylindrical part and the inner end of the introduction duct, and the inner periphery of the cylindrical part. A cyclone characterized in that it is provided offset within an area surrounded by.