JPH1087355A - Cement raw material preheating apparatus and its modification method - Google Patents

Abstract

(57) [Problem] To improve the efficiency of a cement raw material preheating apparatus using a cyclone in multiple stages. SOLUTION: Among suspension preheaters 10 constituted by multi-stage cyclones 11 to 14, a lowermost cyclone 11 is formed in a top shape to improve dust collection efficiency. As a result, the raw material charging efficiency and the thermal efficiency of the entire suspension preheater 10 can be improved, and the operation can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preheating a cement raw material such as a suspension preheater for firing a granular cement raw material or a suspension preheater with a calciner, and a method for modifying the same.

[0002]

2. Description of the Related Art Conventionally, a cyclone 1 as shown in FIG.
However, a plurality of stages are used for a suspension preheater (abbreviated as “SP”) of a cement raw material preheating device, a suspension preheater with a calciner (abbreviated as “NSP”), and the like. The body of the cyclone 1 includes a cylindrical body 2 and an inverted conical body 3. An inner cylinder 4 is inserted into the center of the cylindrical body 2 from above. An inlet duct 5 for introducing exhaust gas from a firing device such as a rotary kiln in a tangential direction is connected to the outer periphery of the cylindrical body 2. The exhaust gas introduced from the inlet duct 5 descends while turning along the inner peripheral surfaces of the cylindrical body 2 and the inverted conical body 3. Exhaust gas that has descended along the inner wall at the lower portion of the inverted conical body 3 reverses and rises, and separates from the particulate cement raw material mixed with the exhaust gas. Exhaust gas from which the granular material is separated and purified is sucked into the inner cylinder 4 and discharged through the outlet pipe 6. Outlet pipe 6
The connection between the inner cylinder 4 and the inner cylinder 4 is sealed with a bellows 7.

[0003] The flow velocity vi of the exhaust gas into the cyclone 1 is, for example, 15 to 20 m / s, and the exit velocity vo to the inner cylinder 4 is usually 18 to 20 m / s. Assuming that the height of the inlet duct 5 is A, the inner cylinder 4 projecting into the cylindrical body 2
Is about 0.3 to 0.5A.

Even if the suspension preheater is configured by arranging a plurality of cyclones 1 as shown in FIG. 7, it is difficult to sufficiently recover the cement raw material contained in the exhaust gas in a dust state. Japanese Patent Application Laid-Open Nos. 54-77721 and 55-27061 disclose an electric precipitator in place of the uppermost cyclone on the lowest temperature side to improve the efficiency of recovering heat and raw materials. Is disclosed. In Japanese Utility Model Laid-Open Publication No. 4-50149, a cyclone having a shape in which the diameter temporarily increases near a portion where the gas flow reverses and rises in the middle of the inverted cone body 3 of the cyclone 1 as shown in FIG. Prior art on this is disclosed. In the present specification, such a cyclone having an inverted conical body whose inner diameter once increases will be referred to as a "coma cyclone".

[0005]

In the prior art in which an electric precipitator is provided in place of the uppermost cyclone in order to improve the efficiency of recovering the heat and raw materials of the suspension preheater, the scattering dust is reduced, and the dust to the fan is reduced. Although effective against dust adhesion and abrasion due to dust, the electric precipitator is very expensive and increases equipment costs.
Since the collection efficiency of the electrostatic precipitator is good, the amount of raw materials charged is reduced, the temperature of the exhaust gas is increased, and the effect of improving the heat recovery rate is reduced. Furthermore, the fine powder in the raw material collected by the electrostatic precipitator cannot be collected in the lower high-temperature cyclone, and such fine powder circulates in the system of the suspension preheater. The required power also increases, which can lead to poor thermal efficiency.

Conventionally, each cyclone constituting the suspension preheater is designed to have substantially the same inlet / outlet flow rate with respect to exhaust gas. Since the temperature of the exhaust gas is higher in the lower stage, the cyclone is larger in the lower stage and the gas viscosity is high, so that the dust collection efficiency as the cyclone is low. Therefore, the fine powder collected on the low temperature side and sent to the high temperature side cannot be collected on the high temperature side, and the fine powder circulates in the suspension preheater system, causing problems such as an increase in pressure loss, a decrease in thermal efficiency, and a hindrance to safe operation. Furthermore, the conventional lower-stage cyclone has a high exhaust gas temperature of 850 to 900 ° C., so the inner cylinder of the cyclone is severely burnt, and the insertion length of the inner cylinder has to be shortened from the viewpoint of life and replacement cost. Efficiency is getting worse.

An object of the present invention is to provide a cement raw material preheating apparatus and a method for modifying an existing cement raw material preheating apparatus, which can easily improve dust collection efficiency and heat efficiency as a whole apparatus.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a powdery or granular cement raw material is preheated by using the exhaust gas of a firing furnace, and the cement raw material mixed in the exhaust gas is separated and collected by cyclones arranged in multiple stages. In the cement raw material preheating apparatus, the cyclone arranged on the highest temperature side among the cyclones arranged in multiple stages is a cement raw material preheating apparatus characterized in that it has a higher dust collection efficiency than the remaining cyclones. According to the present invention, among the cyclones arranged in multiple stages constituting the cement raw material preheating apparatus, a high dust collection efficiency type is used for the cyclone arranged on the highest temperature side, so that the raw material powder is circulated in the system. Is minimized, so that power can be reduced by reducing pressure loss, thermal efficiency can be improved, stable operation can be performed, production can be increased, and product quality can be stably improved. In particular, when modifying an existing suspension preheater, the overall efficiency can be increased by modifying the lowermost highest-temperature cyclone to a high dust collection efficiency type. Modification effect of the middle stage cyclone is small.

Further, in the present invention, among the cyclones arranged in multiple stages, the cyclone arranged on the lowest temperature side together with the cyclone arranged on the highest temperature side has a higher dust collection efficiency than the remaining cyclones. There is a feature. According to the present invention, among the cyclones arranged in multiple stages,
Since a high dust collection efficiency type cyclone is used for the cyclone arranged on the lowest temperature side as well as on the highest temperature side, it is possible to reduce the amount of cement material discharged out of the system and improve the efficiency of collecting the material.

In the present invention, the high dust collection efficiency type cyclone has an inner cylinder outlet speed of exhaust gas of 25 m / s or more,
The insertion length of the inner cylinder is at least 0.7 times the height of the inlet duct. According to the present invention, the outlet speed in the exhaust gas inner cylinder is 25 m / s
As described above, the speed is faster than that of the conventional cyclone, and the insertion length of the inner cylinder is 0.7 times or more the diameter of the inlet pipe. Therefore, the exhaust gas sucked into the inner cylinder is sufficiently separated from the cement raw material, and Recovery efficiency can be improved.

Further, the present invention is characterized in that the inner cylinder of the high dust collection efficiency type cyclone has a double structure, and is cooled by air collected as combustion air. According to the present invention, the inner cylinder of the high dust collection efficiency type cyclone is
Since it is cooled by air collected as combustion air in a double structure, even if a high dust collection efficiency type cyclone is used on the high temperature side, damage to the inner cylinder can be prevented. Since the air used for cooling the inner cylinder is recovered as combustion air, heat loss due to cooling can be compensated comprehensively.

Further, in the present invention, the high dust collection efficiency type cyclone is characterized in that an inlet cross section is reduced as compared with the remaining cyclone, and an exhaust gas inlet speed is 25 m / s or more. According to the present invention, in the cyclone of the high dust collection efficiency type, the inlet cross section is reduced as compared with the remaining cyclone, and the inlet speed of the exhaust gas increases to 25 m / s or more, so that the cyclone turns along the inner wall of the cyclone. Separation of the cement raw material from the gas stream can be performed efficiently.

In the present invention, the high dust collection efficiency type cyclone is connected to a lower portion of a cylindrical body having a constant inner diameter, and has an inverted conical body whose inner diameter decreases as it goes down, and has an inner diameter near a reversal rising portion of the exhaust gas. Has a shape such that it temporarily expands. According to the present invention, the cyclone of the high dust collection efficiency type has a shape such that the exhaust gas flow swirls and descends along the inner wall of the inverted conical fuselage, and the inner diameter temporarily increases near the portion where the exhaust gas reverses and rises. Therefore, re-dispersion of the cement raw material separated from the exhaust gas flow can be reliably prevented.

In the present invention, the outer peripheral surface of the inverted conical body may be
It is characterized by being inclined at an angle of 65 ° or more with respect to a horizontal plane, and having a diameter expanding 1.5 to 1.8 times near the reversal rising portion of the gas. According to the present invention, the total height of the lowermost cyclone of the suspension preheater made of a cement raw material can be made as small as possible to obtain a high dust collection efficiency type.

Further, in the present invention, the inverted conical body is characterized in that an axis is inclined at an angle of 15 ° or less with respect to a vertical line below the enlarged portion of the inner diameter. According to the present invention, since the cement raw material has little adhesion,
The axis of the inverted cone can be inclined to reduce the overall height of the cyclone.

Further, the present invention provides a cement raw material preheating apparatus for preheating a particulate cement raw material by using exhaust gas from a firing furnace and separating and collecting the cement raw material mixed in the exhaust gas by cyclones arranged in multiple stages. A remodeling method characterized by improving the dust collection efficiency of cyclones arranged on the highest temperature side and / or the lowest temperature side among the cyclones arranged in multiple stages. According to the present invention, of the existing multi-stage cyclone cement raw material preheating apparatus, by improving the dust collection efficiency of the cyclone arranged on the highest temperature side and / or the lowest temperature side, the overall heat efficiency and raw material input efficiency are improved. Can be easily improved.

[0017]

FIG. 1 shows a schematic structure of a suspension preheater 10 as a cement raw material preheating apparatus according to an embodiment of the present invention. The suspension preheater 10 has a multi-stage cyclone 1 indicated by C1 to C4.
1, 12, 13, and 14. A raw material input section 15 is provided between the third stage cyclone 13 and the fourth stage cyclone 14. First stage cyclone 11
Is a top type and is about 1100 from the rotary kiln 16.
Exhaust gas at a temperature of approx. 8 ° C.
The temperature drops to 50 ° C. The exhaust gas whose temperature has dropped to about 850 ° C. is led to the second-stage cyclone 12, and
The temperature drops to 00 ° C. Exhaust gas at about 700 ° C is the third
The temperature is reduced to about 550 ° C. by the cyclone 13 at the stage. The exhaust gas at about 550 ° C. is guided to the fourth stage cyclone 14, and on the way, a powdery cement material is supplied from a raw material supply unit 15. 4th with cement raw materials
Exhaust gas introduced into the cyclone 14 at the stage is about 350
The temperature drops to ° C and is discharged out of the system.

The cement raw material collected by the fourth stage cyclone 14 is mixed into the exhaust gas guided from the second stage cyclone 12 to the third stage cyclone 13,
Separated by the third stage cyclone 13. The separated cement raw material is mixed in the process of guiding the exhaust gas from the first stage cyclone 11 to the second stage cyclone 12,
It is separated from the exhaust gas in the second stage cyclone 12. The separated cement raw material is supplied from the rotary kiln 16 to the first
It is mixed into the exhaust gas introduced into the cyclone 11 of the first stage, separated by the cyclone 11 of the first stage, and introduced into the rotary kiln 16.

FIG. 2 shows the first stage cyclone 11 of FIG.
Is shown. The cyclone 11 has a top shape in order to achieve high dust collection efficiency, and an inverted conical body 21 is interposed between a cylindrical body 22 and an inverted conical body 23 below. An inner cylinder 24 is inserted into the cylindrical body 22 from above near the center. An inlet duct 25 is connected to an outer peripheral surface of the cylindrical body 22, and introduces exhaust gas in a tangential direction of an inner circumference of the cylindrical body 22. The introduced exhaust gas descends while turning along the inner peripheral surface of the inverted conical body 21 from the inner peripheral surface of the cylindrical body 22,
It is reversed and rises near the reversal rising portion 26 and is sucked into the inner cylinder 24. The inverted conical body 21 is temporarily stopped at the reversal rising portion 26, the inner diameter is enlarged at the enlarged wall portion 27, and the inverted conical body 23 is connected again downward from the enlarged diameter portion 28. Here, the inner diameter of the cylindrical body 22 is D, the inner diameter of the inner cylinder 24 is d,
6, the inside diameter of the inverted conical body 21 is D1,
, The maximum inner diameter of the inverted conical body 21 is D2, the inner diameter of the lower end of the inverted conical body 23 is d1, the height of the inlet duct 25 is A,
The height of the cylindrical body 22 is H1, and the height from the upper part of the cylindrical body 22 to the lower end of the inverted conical body 23 is H. In addition, the inclination angle of the outer peripheral surface of the upper inverted conical body 21 with respect to the horizontal plane is θ.
1. The inclination angle of the inner wall surface of the diameter enlarged portion 28 with respect to the horizontal plane is θ.
2. The inclination angle of the outer wall of the lower inverted conical body 23 with respect to the horizontal plane is θ3. d1 is set to 0.1D.

FIG. 3 shows a structure of a main part of a top cyclone 31 according to another embodiment of the present invention. This embodiment is similar to the top cyclone of FIG. 2 and shows only different parts. The enlarged wall portion 37 and the enlarged diameter portion 38 below the reversing rising portion 26 are connected to an inverted conical body 40 whose axis 39 is inclined by an angle α with respect to a vertical line. Since the cement raw material has less adhesion than, for example, lime, the inverted cone body 40 can be inclined to reduce the overall height.

The following Table 1 shows a comparison between the cyclone 31 shown in FIG. 3 and the top cyclone constituting the lime fluidized bed firing apparatus disclosed in Japanese Utility Model Laid-Open No. 50149/1992.

[0022]

[Table 1]

The following Table 2 shows the effect of the height H reduction according to the embodiment of FIG. 3 on the top cyclone constituting the lime fluidized bed baking apparatus.

[0024]

[Table 2]

FIGS. 4 and 5 show a process of a high dust collection efficiency cyclone according to still another embodiment of the present invention.
FIG. 4 is a longitudinal sectional view, and FIG. 5 is an enlarged sectional view taken along the line VV of FIG. In the cyclone 41 according to the present embodiment, an inverted conical body 43 is connected below the cylindrical body 42, an inner cylinder 44 is inserted from above into the cylindrical body 42, and a tangent line is formed from the side of the cylindrical body 42 by an inlet duct 45. Exhaust gas is blown in the direction. An outlet pipe 46 is connected above the inner cylinder 44 and is sealed by a bellows 47. The refractory 48 is inserted into the inner peripheral surface of the inlet duct 45, the height A of the inlet duct 45 decreases, and the inlet speed vi increases to 25 m / s or more. Further, the inner diameter of the inner cylinder 44 is reduced so that the outlet speed vo of the inner cylinder 44 becomes 25 m / s or more. The inner cylinder 44 is provided with an inner cylinder cover 49 on the outer periphery, and has a double pipe structure. For the double pipe structure, an air inlet 50 and an air outlet 51 are provided, and the gap between the double pipe structures is divided by a plurality of partition plates 52. A communication section 53 is provided below each partition plate 52.
Is formed, and the air flowing in from the air inlet 50 can pass to the air outlet 51 side.

When modified to increase the entrance / exit flow velocity,
The critical particle diameter δmax is proportional to the reciprocal of the square root of the inlet velocity vi, and is proportional to the temperature T raised to the 乗 power. The logarithm of the efficiency η is proportional to the exit speed vo. However, as the flow velocity increases, re-scattering increases and efficiency decreases. Inner cylinder 4
4 has a length L larger than 0.7 A, so that the efficiency decrease due to an increase in re-dispersion is alleviated, and the inner cylinder 44 is cooled by air cooling.
Life can be extended. The heat lost by air cooling recovers the cooling air as hot air for combustion and does not reduce the overall thermal efficiency.

FIG. 6 shows a schematic configuration of a suspension preheater with a calciner as a cement raw material preheating apparatus according to still another embodiment of the present invention. Parts corresponding to the configuration in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
The suspension preheater 60 uses a top cyclone as the first stage cyclone 61, and further cools the inner cylinder by air. The first stage cyclone 61 includes a calciner 62
Exhaust gas from is introduced. First stage cyclone 61
The air cooled in the inner cylinder is used for burning the burner 63 of the calciner 62. The cement clinker fired in the rotary kiln 16 is supplied to an air quenching cooler (abbreviation “A”).
QC ") 64. The air heated to a high temperature by cooling the cement clinker by the air quenching cooler 64 is returned to the calciner 62 as combustion air. In the present embodiment, the cyclone 65 at the uppermost stage of the suspension preheater 60 is also of a top shape and achieves high dust collection efficiency.

The following Table 3 shows the simulation results for the modified apparatus of FIG.

[0029]

[Table 3]

As a method of improving the dust collection efficiency of the cyclone as described above, it is generally known that the outlet flow velocity vo is increased by reducing the diameter, and the inlet flow velocity vi is increased by reducing the inlet cross section. It is also known that the longer the L is within the height H1 of the cylindrical body, the better the efficiency is. By making the inner cylinder of the lowermost cyclone of the conventional suspension preheater elongated, the outlet flow velocity vo = 20 m / s and L
= 0.3-0.5A to vo = 25m / s and L =
0.7A, and the dust collection efficiency was improved from 80% to 85%. Further, the inlet flow velocity vi is increased from 20 m / s to 25 m / s.
When increased to s, the efficiency increases to over 87%. vi
= Vo = 30 m / s, the re-scatter increased and the efficiency decreased.

Even if the inner cylinder of the lowermost cyclone is elongated,
By forcibly cooling the air and collecting the cooling air, the life of the inner cylinder could be extended without heat loss. If the bottom cyclone is remodeled into a top type, re-dispersion is reduced and the efficiency is 8
0% to 87%, and vo = vi = 25 m /
s increased to 93%.

Although the pressure loss in the cyclone increases as the flow velocity increases, the top type is about 20% less than the conventional type.
Since the pressure loss is small, it is possible to sufficiently cover. In addition, even if the flow rate of the entrance / exit is further increased,
Even if = vi = 30 m / s, re-dispersion does not increase and efficiency is improved, but pressure loss increases, which is not preferable.

Based on a prior art in which a top cyclone is applied to a suspension preheater of a lime fluidized bed firing apparatus,
In order to apply the top cyclone to the cement raw material preheating device, the results of various experiments show that the specific gravity, particle size, adhesion, powder concentration, etc., of the powder will cause the cement to have the shape shown in Table 1 above. And high dust collection efficiency could be obtained. That is, the angles θ1 and θ3 of the inverted conical body outer wall are 6 in the case of cement.
If it is 5 ° or more, the powder does not adhere and the efficiency does not change. Even if the diameter D2 of the enlarged portion is slightly smaller than that in the case of lime, the efficiency does not change. Even if the axis of the lower inverted conical part is inclined within α = 15 °, the powder can be discharged smoothly, and the efficiency does not change.

When the lowermost cyclone of the existing suspension preheater or suspension preheater with a calciner is to be converted into a top-type cyclone, the height H should be minimized due to the arrangement.
Needs to be smaller. In the calculation example of Table 2 above, in the case of lime, the total height H is 3.173D, whereas in the case of cement raw material, H is 2.009D, which is almost close to the total height H of the conventional cyclone of 1.972D. Therefore, it is possible to improve the performance of the suspension preheater with a simple modification.

[0035]

As described above, according to the present invention, among the multi-stage cyclones, the highest-temperature cyclone disposed at the lowermost stage has a higher dust collection efficiency than the remaining cyclones. In addition, the circulation of the raw material in the system is minimized, and many effects such as a reduction in power, an improvement in thermal efficiency, a stable operation, an increase in production, and a stable and improved product quality can be obtained. Cyclone efficiency changes with changes in operating conditions, such as particle size distribution, cohesion, concentration, and amount of circulation in the system, and it is impossible to theoretically elucidate due to the problem of re-scattering. However, in an actual machine test, a desired effect of improving the efficiency as a whole was obtained by improving the efficiency of the lowermost cyclone.

According to the present invention, among the multi-stage cyclones, the one having the highest dust collection efficiency is also used for the lowest temperature side cyclone disposed at the uppermost stage, so that the cement raw material discharged outside the system is used. And the efficiency of material input can be improved.

Further, according to the present invention, since the outlet speed of the exhaust gas in the inner cylinder of the cyclone is set to 25 m / s or more and higher than that of the normal cyclone, and the insertion length of the inner cylinder is made longer than that of the normal cyclone. It is possible to improve the dust collection efficiency in the inside.

According to the present invention, the inner cylinder of the cyclone has a double-pipe structure, and is cooled by air recovered as combustion air. Can be extended.

Further, according to the present invention, since the inlet cross section is reduced and the inlet speed of the exhaust gas is made 25 m / s or more, the efficiency of separation of the cement raw material in the cyclone can be improved.

Further, according to the present invention, since the inverted conical body has such a shape that the inner diameter temporarily increases near the reversal rising portion of the exhaust gas, re-dispersion of the cement raw material can be prevented, and the dust collection efficiency can be improved. .

According to the present invention, the angle of inclination of the outer peripheral surface of the inverted conical body with respect to the horizontal plane is 65 ° or more, and the expansion of the inner diameter near the reversal rising portion becomes 1.5 to 1.8 times,
The height of the cyclone can be reduced according to the properties of the cement raw material.

Further, according to the present invention, the inverted conical body at the lower portion of the enlarged wall has a shaft inclined at an angle of 15 ° or less with respect to the vertical line below the enlarged inner diameter portion, so that it can be used as a cyclone. The overall height can be reduced.

Further, according to the present invention, of the existing cement raw material preheating apparatus, it is sufficient to modify the cyclone arranged at the highest temperature side and / or the lowest temperature side so as to improve the dust collection efficiency. Can easily improve the overall thermal efficiency and raw material recovery efficiency.
As a result of various simulations, it has been found that when retrofitting an existing suspension preheater, it is most effective to increase the efficiency of the lowermost cyclone, and that the retrofit of the intermediate cyclone is less effective. In addition, since the effect of improving the efficiency of the uppermost cyclone is also recognized, it is desirable to remodel the uppermost cyclone to be a high-efficiency type.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a schematic configuration of a suspension preheater according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a first-stage cyclone of FIG. 1;

FIG. 3 is a partial cross-sectional view of a cyclone according to another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a configuration of a cyclone according to still another embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view of the cyclone of FIG. 4 as viewed from a section line VV.

FIG. 6 is a system diagram showing a configuration of a suspension preheater according to still another embodiment of the present invention.

FIG. 7 is a longitudinal sectional view showing a configuration of a conventional cyclone.

[Explanation of symbols]

10, 60 Suspension preheater 11, 12, 13, 14, 31, 41, 61 Cyclone 15 Raw material charging section 16 Rotary kiln 21, 23, 40, 43 Inverted conical body 22, 42 Cylindrical body 24, 44 Inner cylinder 25, 45 Inlet Duct 26 Reversing rising part 27, 37 Enlarged wall part 28, 38 Diameter enlarged part 39 Shaft core 48 Refractory 49 Inner cylinder cover 50 Air inlet 51 Air outlet 62 Pre-calcination furnace

Claims (9)

[Claims] 1. A cement raw material preheating apparatus for preheating a particulate cement raw material using exhaust gas from a firing furnace and separating and collecting the cement raw material mixed in the exhaust gas by cyclones arranged in multiple stages. A preheater for cement raw material, wherein a cyclone arranged on the highest temperature side among the arranged cyclones has a higher dust collection efficiency than the remaining cyclones. 2. The cyclone arranged on the lowest temperature side among the cyclones arranged in the multi-stage, together with the cyclone arranged on the highest temperature side, has a higher dust collection efficiency than the remaining cyclones. The cement raw material preheating apparatus according to claim 1, characterized in that: 3. The cyclone of the high dust collection efficiency type is characterized in that the exhaust speed of the inner cylinder of the exhaust gas is 25 m / s or more, and the insertion length of the inner cylinder is 0.7 times or more the height of the inlet duct. The cement raw material preheating apparatus according to claim 1 or 2, wherein 4. The preheating cement raw material according to claim 3, wherein the inner cylinder of the high dust collection efficiency type cyclone has a double structure, and is cooled by air collected as combustion air. apparatus. 5. The high-density collection type cyclone according to claim 1, wherein an inlet cross section is reduced as compared with the remaining cyclone, and an exhaust gas inlet speed is 25 m / s or more. The cement raw material preheating apparatus according to any one of the above. 6. The high dust collection efficiency type cyclone is connected to a lower part of a cylindrical body having a constant inner diameter, and the inverted conical body whose inner diameter decreases as it goes down, has an inner diameter once near a reversal rising portion of exhaust gas. The cement raw material preheating apparatus according to any one of claims 1 to 5, wherein the apparatus has an expanding shape. 7. An outer peripheral surface of the inverted conical body is inclined at an angle of not less than 65 ° with respect to a horizontal plane, and a diameter thereof is increased by 1.5 to 1.8 times near a reversal rising portion of the gas. The cement raw material preheating apparatus according to claim 6, wherein 8. The inverted conical body, wherein a shaft core is inclined at an angle of 15 ° or less with respect to a vertical line below the enlarged portion of the inner diameter. Cement raw material preheating equipment. 9. A method of modifying a cement raw material preheating apparatus for preheating a powdery cement raw material using exhaust gas from a firing furnace and separating and collecting the cement raw material mixed in the exhaust gas by cyclones arranged in multiple stages. The highest temperature side and / or
Alternatively, a method for remodeling a raw material preheating apparatus for cement, wherein the dust collection efficiency of a cyclone arranged on the lowest temperature side is improved.