JPH0146466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for calcining cement raw materials.

Conventionally proposed calcining equipment for cement raw materials employs a method of incomplete combustion in a calcining furnace in order to reduce and remove nitrogen oxides contained in kiln exhaust gas. As a result, they were faced with the dilemma of increasing fuel consumption.

In view of the above-mentioned circumstances, the present invention seeks to provide a method and apparatus that improve the reduction performance of nitrogen oxides in kiln exhaust gas without increasing the fuel consumption rate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram of an apparatus for carrying out the method of the present invention incorporated into a cement firing kiln system.

In the figure, 1, 2, 3, and 4 are the respective cyclones, 5 is the calcining device of the present invention, 6, 7, 8, and 9 are the raw material discharge chutes from the cyclones 1, 2, 3, and 4, and 10 is the respective raw material discharge chute. The duct 10 connects the cyclone 1 and the exhaust fan 16. 11,12,1
3 is a duct connecting each of the cyclones, 14
15 is a raw material feeder, 17 is a kiln, 18 is a kiln burner, 19 is a cooler, 20, 21, 22 is a duct that connects the calcining device 5 and the cooler 19. ,2
3, 24, and 25 are dampers for adjusting air volume.

FIG. 2 is a longitudinal cross-sectional view of the calciner 5, in which the broken line arrows indicate the flow of supplied air, the solid line arrows indicate the flow of exhaust gas, and the area indicated by the dotted line in the center indicates the incomplete combustion part. , the area marked with an x on its outer periphery indicates the complete combustion part. This calcining device 5 includes an incomplete combustion chamber 50 (incomplete combustion area) and a main combustion chamber 60.
(main combustion area) and reburning chamber 70 (reburning area)
and a swirling mixing combustion chamber 80 (reburning area). 26 is a re-combustion chamber 70 and a swirling mixing combustion chamber 8
28 is a main burner, 29 and 30 are denitrification burners, and 31 and 32 are throttle parts. Air is introduced tangentially from the duct 21 to the top of the swirling mixing combustion chamber 80 (or to the upper side of the chamber). Moreover, the air can be supplied from the duct 22 to the lower part of the main combustion chamber 60 either in a tangential direction or in a right angle direction.
Note that the aperture portion 32 may not be particularly provided.

First, high-temperature exhaust gas containing nitrogen oxides discharged from the kiln 17 rises from the throttle section 31 to the incomplete combustion chamber 50 as shown by the arrow. At the same time, fuel is supplied from the denitrification burner 30 or 29, and a reduction reaction of nitrogen oxides is carried out. From here, the exhaust gas further rises to the complete combustion chamber 60, and fuel is further injected from the main burner 28, which is then passed through the duct 2.
Hot air is supplied at an air ratio of 1.02 to 1.10, preferably 1.05. Complete combustion occurs in the periphery of the chamber to maintain the temperature inside the furnace. On the other hand, in the center of the furnace, the incompletely combusted gas rises in the form of a jet while further reducing nitrogen oxides. On the other hand, from the top of the swirling mixing combustion chamber 80, the air ratio
1.08 to 1.20, preferably about 1.1, hot air is introduced in a swirling flow, guided to the partition wall 16, and rapidly mixed with the rising incompletely combusted gas in the swirling mixing combustion chamber 80 to be reburned and completely burnt. Promote combustion. After combustion, the exhaust gas passes through the duct 14,
It is processed by each cyclone 4, 3, 2, 1 and discharged by an exhaust fan 16.

Here, in the main combustion chamber 60, in order to burn the fuel from the main burner 28, the air ratio is 1.02~1.02.
The reason for supplying hot air of 1.10 is to suppress conversion to nitrogen oxides in the fuel by operating the air ratio for combustion in the main combustion chamber 60 at a value close to the theoretical value. This is because if it is less than 1.02, combustibility will deteriorate, and if it is more than 1.10, the nitrogen content in the fuel will be converted to nitrogen oxides. Furthermore, the reason why the air ratio of the hot air supplied from the top of the swirling mixing combustion chamber 80 is set to 1.08 to 1.20 is because if the re-combustion air is not introduced, the air ratio of the main combustion chamber 60 will be reduced.
Therefore, even if the nitrogen oxides in the incomplete combustion gas are reduced, the main combustion chamber 6
This is because nitrogen oxides will be generated again if the temperature is zero.

As described above, the present invention sequentially guides the kiln exhaust gas containing nitrogen oxides to the incomplete combustion zone, the main combustion zone, and the afterburning zone, and in the main combustion zone, while burning separately supplied fuel and air, the furnace The exhaust gas from the incompletely burnt part that occurs in the center of the furnace is raised by reaction, and swirling air is supplied from above the reburning area to promote the rise of the exhaust gas from the incompletely burnt part in the center of the furnace. The present invention relates to a method for calcining cement raw materials, which is characterized by performing re-combustion by rapidly mixing air with a swirling flow, and an apparatus for carrying out the method.

FIG. 3 shows the case where heavy oil is sprayed from the denitrification burner 30 of the apparatus according to the present invention shown in FIG.
It is a graph showing the relationship between the CO concentration and the denitrification rate at points B and C of the device. Curve X shows the denitrification rate at point B of the device. Curve Y shows the denitrification rate at point C of the device when hot air from the duct 21 is not sent to the swirling mixing combustion chamber 80, and curve Z shows the denitration rate when hot air is sent from the same duct 21 to the swirling mixing combustion chamber 80. The denitrification rates at the same point C are shown respectively. According to curve Y, even if the denitrification burner 30 denitrates the kiln exhaust gas at point B, the combustion air ratio of the main burner 28 increases, so nitrogen oxides are generated again, and the equipment This indicates that the overall denitrification function is reduced.
However, in the present invention, the fuel injected from the main burner 28 is mixed with hot air from the duct 22 at an air ratio of about
1.05, and hot air for re-combustion is supplied from the top of the swirling mixing combustion chamber 80 through the duct 21 in a swirling flow so that the air ratio is approximately 1.1. was further improved compared to curve X. In addition, denitrification rate (%) = {1-amount of nitrogen oxides passing through point B or point C (Nm ³ /h)/amount of nitrogen oxides passing through point A (Nm ³ /h)}×100 did.

In addition, the fuel consumption in the above example is per clinker.
81t/t・cl, and there was no change whether the denitrification burner was used or not.

According to the present invention, when the fuel is heavy oil, approximately 80
%, and in the case of coal, it has become possible to remove about 50%.

In addition, the conventional cement clinker firing apparatus, JP-A No. 54-8622, lacks the structure of the present invention, so it is difficult to completely burn the exhaust gas by feeding secondary air in a planned manner. Therefore, it is estimated that there is an amount of fuel loss corresponding to the secondary air shortage of 10 to 20% of the fuel supplied to the apparatus compared to the apparatus of the present invention.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the apparatus incorporated into a cement firing kiln system for carrying out the method according to the present invention, Figure 2 is a longitudinal cross-sectional explanatory diagram of the apparatus according to the present invention, and Figure 3 is CO concentration and denitrification rate. It is a graph showing the relationship between 1-4...Cyclone, 5...Calcination device, 17
...Kiln, 20, 21, 22...Duct, 2
3, 24, 25...Damper for adjusting air volume, 28...
...Main burner, 29,30...Denitration burner,
50...Incomplete combustion chamber, 60...Main combustion chamber, 70
... Re-combustion chamber, 80 ... swirling mixing combustion chamber.

Claims (1)

[Scope of Claims] 1 Kiln exhaust gas containing nitrogen oxides is sequentially introduced into an incomplete combustion zone, a main combustion zone, and a reburning zone, and in the main combustion zone, while separately supplied fuel and air are being combusted, The exhaust gas is caused to react and rise in the incomplete combustion area that occurs in the middle of the furnace, and swirling air is supplied from above the reburning area to promote the rise of exhaust gas in the incomplete combustion area in the center of the furnace. A method for calcination of cement raw materials, characterized by rapidly mixing the mixture with air in a swirling flow to perform re-combustion. 2 Incomplete combustion chamber 50 containing kiln exhaust gas
, a main combustion chamber 60 continuous to the upper part of the incomplete combustion chamber 50, and a re-combustion chamber 70 continuous to the upper part of the main combustion chamber 60. Funnel-shaped bulkhead 2
6, a swirling mixing combustion chamber 80 is provided above the partition wall 26, and a means for supplying combustion air that generates a swirling flow is provided above the swirling mixing combustion chamber 80. Fire firing device.