JP3250758B2 - Baking equipment for cement clinker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for firing a cement clinker, and more particularly to an improvement in denitration efficiency.

[0002]

2. Description of the Related Art Conventionally, in a cement clinker firing apparatus, a calcareous material and a clay material are mixed,
Heated until partially melted in a kiln called a rotary kiln. The heating temperature is, for example, about 1400 ° C.,
Large rotary kilns have a maximum flame temperature of 2000 ° C
It can reach up to. When combustion is performed at such a high temperature, nitrogen in the air is oxidized and nitrogen oxides (NOx)
Occurs. Since nitrogen oxides are air pollutants, their emission must be minimized. Prior art for removing nitrogen oxides from a cement clinker firing apparatus is disclosed in, for example, JP-A-53-6267, JP-A-55-33510, JP-A-58-40411, and JP-A-58-40411. It is disclosed in, for example, JP-A-62-18510. FIG. 3 shows an example of the prior art disclosed in JP-A-53-6267. A rising duct 2 is connected to the top of the kiln 1 for firing the cement clinker. Above the rising duct 2, a calciner 4 is connected via a throttle 3. The raw material preheated to 550 to 650 ° C. is supplied to the calciner 4 via a raw material supply chute 5. A burner 6 is provided near the upper side of the stop 3. The burner 6 is supplied with fuel. Above the burner 6, a secondary air inlet 7 is provided, and air or oxygen gas is supplied. The top of the calciner 4 is connected to the cyclone 8 to collect the cement raw material contained in the exhaust gas from the calciner 4.

In the calciner 4, a spouted bed (I) is formed near the throttle 3, and a floating layer (II) is formed above the spouted bed (I). In the spouted bed (I), the cement raw material, which is an endothermic decomposition reaction, is calcined, and is maintained at a temperature of 820 to 950 ° C. Since the combustion is performed using the oxygen in the exhaust gas from the kiln 1, the oxygen is insufficient, and the combustion is performed in a reducing atmosphere. This reducing atmosphere has a denitration effect and reduces the content of nitrogen oxides. In the floating layer (II), the remaining fuel is completely burned. If combustion is insufficient,
Combustion continues even in the cyclone 8 following the calciner 4,
Poor thermal efficiency.

Japanese Patent Application Laid-Open No. 55-33510 discloses a configuration in which exhaust gas from a fluidized bed is recirculated to suppress generation of nitrogen oxides. JP-A-58-40
No. 411 discloses a configuration for reducing nitrogen oxides and sulfur oxides using a two-stage fluidized bed.
Japanese Utility Model Laid-Open Publication No. Sho 62-18510 discloses a configuration for reducing nitrogen oxides by a plurality of stages of combustion.

[0005]

In the prior art of JP-A-53-6267 as shown in FIG. 3, fresh air or oxygen gas is introduced from the secondary air inlet 7 and burned. High temperature locally. Therefore, the nitrogen oxides reduced in the fluidized bed (I) may be formed again in the floating bed (II). In the spouted bed (I),
Since it is difficult to sufficiently mix the fuel, oxygen gas and raw material powder, the denitration reaction is insufficient. Further, since fresh air or oxygen gas is introduced from the secondary air inlet 7, the range of the reducing atmosphere is narrow. Although a configuration in which a plurality of diaphragms are stacked is also disclosed, the lower part of the intermediate diaphragm also becomes an oxidizing atmosphere and the denitration effect is low.

[0006] In the prior art in which a two-stage combustion or exhaust gas recirculation is performed in a fluidized bed, 1300 combustion such as cement clinker firing is required.
The denitration effect hardly occurs for a fluidized bed at a temperature of not less than ° C.

An object of the present invention is to provide an apparatus for firing a cement clinker capable of increasing the reduction rate of nitrogen oxides.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a cement clinker in which a cement raw material powder is preheated by a preheating means and then charged into a spouted bed or a fluidized bed granulating furnace, and the granulated material is fired in the fluidized bed furnace. In the sintering apparatus, the exhaust gas from the granulation furnace is supplied to the bottom part extending upward from immediately above the granulation furnace, and includes a calciner in which a throttle is formed at an intermediate height position. Is a cement clinker baking apparatus characterized in that the cement raw material powder and the fuel preheated by the preheating means are charged, and a part of the exhaust gas from the granulation furnace is introduced so as to form a swirling flow. .

Further, the present invention is characterized in that a part of the exhaust gas from the granulating furnace is introduced above the throttle of the calcining furnace so as to form a swirling flow.

[0010]

According to the present invention, the cement raw material powder is preheated, then granulated in a spouted bed or fluidized bed granulation furnace, and fired in a fluidized bed furnace. Immediately above the granulation furnace, an upwardly extending calciner is provided. Exhaust gas from the granulation furnace is supplied to the bottom of the calciner. A throttle is formed at an intermediate height position of the calciner. Preheated cement raw material powder and fuel are introduced into the lower part of the throttle of the calciner, and a part of the exhaust gas from the granulating furnace is introduced so as to form a swirling flow. Due to the swirling flow, the raw material, the fuel and the exhaust gas are rapidly mixed, and the combustion and the decomposition reaction of the raw material are performed very quickly. Since the combustion is performed by the residual oxygen (O ₂ ) contained in the combustion exhaust gas from the granulating furnace, the combustion is performed in a reducing atmosphere, and the nitrogen oxide reduction rate is high. In addition, the reaction is performed uniformly, and the temperature is maintained at about 850 to 900 ° C. by the endothermic reaction due to the decomposition of the raw material, thereby increasing the denitration rate.

Further, according to the present invention, the exhaust gas from the granulating furnace is introduced so as to form a swirling flow also above the throttle.
Since the exhaust gas is at a high temperature, the secondary combustion at the upper part of the throttle can be reliably and efficiently performed.

[0012]

FIG. 1 shows the construction of a cement clinker firing apparatus according to one embodiment of the present invention. The preheating device 10 has 4
Stage cyclones (C1 to C4) 11 to 14 and calciner 1
5 is included. Exhaust gas from the fourth-stage cyclone 14 is discharged through the suction fan 16. The raw material is supplied to the raw material supply port 17 in a powder state. Raw material supply port 17
Is the third cyclone 13 to the fourth cyclone 1
4 in the exhaust gas channel. The supplied raw material is transported by air to the cyclone 14. Within cyclone 14,
Exhaust gas and raw materials are separated. The collected raw material is introduced into a conduit for guiding exhaust gas from the cyclone 12 to the cyclone 13. The raw material powder is supplied to a calciner (PC) 15 through the cyclone 13 and the cyclone 12.

The calciner 15 is provided immediately above a spouted bed or fluidized bed granulator 21 (SBK). In the spouted bed or fluidized bed granulation furnace 21, the raw material powder is heated to about 1300 ° C,
Granulation is performed. Immediately below the spouted bed or fluidized bed granulation furnace 21, a fluidized bed firing furnace (FBK) 22 is provided. In the fluidized bed firing furnace 22, the granulated raw material powder is heated to about 1400 ° C. and fired. After being calcined, it is quenched by a fluidized bed cooler (FBQ) 23 and further packed with a packed bed cooler (P
BC) 24.

The exhaust gas from the calciner 15 is cyclone 1
1 and the exhaust gas and the raw material powder are separated. The separated raw material powder is guided to an ejector 26 via a supply chute 25. The ejector 26 is supplied with air from a pushing blower 27, and the raw material is supplied into the spouted bed or fluidized-bed granulation furnace 21 through a supply line 28 by air flow.
In the spouted bed or fluidized bed granulation furnace 21, the fluidized bed baking furnace 2
The exhaust gas from 2 forms a spouted bed or a fluidized bed and is heated by a burner. The granulated powder is stored in the L-valve 30 via the discharge chute 29. L-
The valve 30 supplies the stored granules to the fluidized-bed firing furnace 22 via the charging chute 31 as necessary while performing airtight sealing with a material seal.

In the fluidized bed sintering furnace 22, sintering by burner heating is performed while forming a fluidized bed. The calcined powder is guided to the fluidized bed cooler 23 by the supply chute 32, and is rapidly cooled to improve the quality as cement. The exhaust gas from the fluidized-bed cooler 23 is supplied to the fluidized-bed baking furnace 2
2 and supplied into the spouted bed or fluidized bed granulation furnace 21. The fluidized-bed cooler 23 has a pushing blower 34.
Is supplied through the air supply line 35 for cooling. The quenched powder is discharged through a discharge chute 36.

The discharge chute 36 is connected to the packed bed cooler 24. The packed-bed cooler 24 has a push-in blower 37.
Supplies cooling air. The exhaust gas from the packed bed cooler 24 is supplied to the wind box of the fluidized bed firing furnace 22 via the exhaust duct 38. From the packed bed cooler 24, the discharge device 3
The cement clinker of the product is discharged via 9.

Exhaust gas from the spouted bed or fluidized bed granulation furnace 21 is divided into an exhaust gas 40 introduced to the bottom of the calciner 15 and an exhaust gas 41 introduced from the middle of the calciner 15. The divided exhaust gas 41 is a part of the whole,
It is desirable to be in the range of 30%.

FIG. 2 shows the configuration of the calciner 15 in an enlarged manner. The lower part of the calciner 15 has a cone shape.
The burner 42 and the nozzle 43
Is provided. The burner 42 is supplied with fuel for combustion. The separated exhaust gas 41 is supplied to the nozzle 43 via a valve 43a. Exhaust gas is ejected from the nozzle 43 so as to form a swirling flow inside the calciner 15.
A nozzle 44 is also provided in the upper part of the calciner 15 and the valve 4
The separated exhaust gas 41 is supplied via 4a. The nozzle 44 also blows exhaust gas into the calciner 15 so as to form a swirling flow. An aperture 45 is formed at an intermediate height position below the nozzle 44 of the calciner 15. A raw material supply chute 46 is provided below the throttle 45, and raw material powder from the second-stage cyclone 12 is supplied.

In the space below the throttle 45 of the calciner 15, the raw material powder supplied through the raw material supply chute 46, the fuel supplied from the burner 42, and the exhaust gas 40 are mixed. Through 43, a part of the exhaust gas 41 is supplied so as to form a swirling flow. This results in rapid mixing, with 5-10% in the exhaust gas 40,41.
Combustion occurs due to the residual oxygen (O ₂ ) and the high temperature of the exhaust gases 40 and 41. However, since the oxygen concentration is low, combustion in a reducing atmosphere occurs. Further, since the calcining reaction of the raw material is an endothermic reaction, the temperature is 850 to 900 ° C.
Is kept uniform. Therefore, the nitrogen oxides are reduced, and the denitration effect is high.

Above the throttle 45, a part of the exhaust gas 41 is supplied from a nozzle 44. Since the temperature of the exhaust gas 41 is high, unburned fuel is reliably burned. Thereby, the thermal efficiency can be improved.

As described above, according to the present embodiment, the calciner 1
By using the reducing atmosphere of No. 5, the denitration effect can be enhanced. Further, since the firing is efficiently performed using the fluidized bed firing furnace 22 and the heating temperature is about 1400 ° C., the amount of generated nitrogen oxides should be smaller than that of a large rotary kiln or the like whose flame temperature reaches about 2000 ° C. Can be. In addition, since the denitration effect can be enhanced in the calcination step and the combustion conditions are stable, the generation of nitrogen oxides can be sufficiently suppressed.

[0022]

As described above, according to the present invention, the combustion in the calcination furnace and the decomposition reaction of the raw materials can be performed quickly and at a uniform temperature in a reducing atmosphere, so that the denitration rate and the thermal efficiency can be improved. be able to.

According to the present invention, the secondary combustion can be performed reliably and efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of an embodiment of the present invention.

FIG. 2 is a simplified sectional view of the calciner 15 shown in FIG.

FIG. 3 is a simplified sectional view showing a configuration for denitration in a conventional cement clinker firing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Preheating apparatus 11-14 Cyclone 15 Calcination furnace 21 Spouted bed or fluidized-bed granulation furnace 22 Fluidized-bed sintering furnace 23 Fluidized-bed cooler 24 Packed-bed cooler 40,41 Exhaust gas 42 Burner 43,44 Nozzle 43a, 44a Valve 45 Throttle 46 Raw material supply chute

Continuing from the front page (72) Inventor Toshiyuki Ishibachi 1 Sumitomo Cement Co., Ltd., Kanda-Midshiro-cho, Chiyoda-ku, Tokyo (72) Inventor Isao Hashimoto 1-1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. (72) Inventor Mikio Murao 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe, Hyogo Prefecture Inside the Kobe Plant of Kawasaki Heavy Industries, Ltd. (72) Inventor Shozo Kanamori 3 Higashikawasakicho, Chuo-ku, Kobe, Hyogo Prefecture No. 1-1 Kawasaki Heavy Industries, Ltd. Kobe Plant (56) References JP-A-2-293357 (JP, A) JP-A-55-42254 (JP, A) JP-A-55-27884 (JP, A) JP-A-53-118423 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B ^7/ 00-7/60

Claims (2)

(57) [Claims] 1. A cement clinker baking apparatus for preheating a cement raw material powder by a preheating means and then charging the powder into a spouted bed or a fluidized bed granulating furnace, and firing the granulated material in the fluidized bed furnace. Exhaust gas from the granulation furnace is supplied to the bottom extending upward from immediately above, and includes a calciner in which a throttle is formed at an intermediate height position.The lower part of the throttle of the calciner is preheated by preheating means. A cement clinker firing apparatus, wherein a cement raw material powder and a fuel are charged, and a part of exhaust gas from a granulation furnace is introduced so as to form a swirling flow. 2. A cement clinker firing apparatus according to claim 1, wherein a part of the exhaust gas from the granulating furnace is introduced into the upper part of the throttle of the calciner so as to form a swirling flow. .