Control method for ultralow emission of NOx in cement kiln

Abstract

The invention provides a control method for ultralow NOx emission of a cement kiln, and belongs to the technical field of industrial environmental protection. The air volume, the air pressure and the internal and external air opening degree in the low-nitrogen burner are controlled according to the heat value and volatile components of the pulverized coal, and the flame peak temperature is stabilized; the temperature of the reduction area of the decomposing furnace and the CO content of an outlet of the decomposing furnace are controlled by controlling the raw material ratio and the coal injection ratio of the reduction area of the decomposing furnace and the main furnace area; gas is treated by spraying ammonia water to the cyclone cylinder, NOx is controlled within 50 mg / Nm < 3 >, and the requirement for ultralow emission of NOx is met. The low-nitrogen combustor, the low-nitrogen decomposing furnace and the SNCR efficient denitration technology are jointly used, the production quality is guaranteed, meanwhile, the use amount of ammonia water is reduced, the production and operation cost is reduced, and ultralow emission that the concentration of NOx at the kiln tail is smaller than or equal to 50 mg / Nm < 3 > is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of industrial environmental protection, and in particular to a method for controlling ultra-low NOx emissions from a cement kiln. Background Art

[0002] During the normal operation of the rotary kiln, the calcination temperature in the kiln will reach 1400-1480 ℃, under which a large amount of NOx will be produced. In addition, although the combustion temperature of the pulverized coal in the decomposition furnace is only 850-950 ℃, a small amount of NOx will also be produced, which will be directly discharged into the atmosphere through the chimney, causing environmental pollution.

[0003] As the country's requirements for environmental governance become increasingly stringent, the requirements for cement plant exhaust emissions are also getting higher and higher. Some companies use SNCR (non-selective catalytic reduction technology) to control NOx emissions, but the SNCR denitrification efficiency is only 80%. Not only is the ammonia consumption high, but NOx is also difficult to control within 50 mg, making it difficult to meet ultra-low emission requirements.

[0004] Although the SNCR (non-selective catalytic reduction technology) + SCR (selective catalytic reduction technology) technology can control NOx within 50 mg, the operating cost is relatively high. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a low-cost and effective control method for ultra-low NOx emissions in cement kilns. By jointly using a low-nitrogen burner, a low-nitrogen decomposition furnace and SNCR high-efficiency denitrification technology, and by controlling the ratio of raw materials in the reduction zone of the decomposition furnace and the ratio of coal injection in the main furnace area, the temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace are controlled, the amount of ammonia water used is reduced, and the emission of NOx at the kiln tail is ≤50 mg / Nm 3 .

[0006] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0007] A method for controlling ultra-low NOx emissions from a cement kiln comprises the following steps:

[0008] (1) Control the air volume, air pressure, and internal and external air openings in the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal to stabilize the peak flame temperature;

[0009] (2) The gas generated in the low-nitrogen burner enters the decomposition furnace through the smoke chamber. The raw material ratio of the decomposition furnace reduction zone and the main furnace area is controlled to (1-3): (7-9), that is, the raw material ratio of the decomposition furnace reduction zone is 10%~30%, and the raw material ratio of the decomposition furnace main furnace area is 70%~90%; the coal injection ratio of the decomposition furnace reduction zone and the main furnace area is controlled to (8-9): (1-2), that is, the coal injection ratio of the decomposition furnace reduction zone is 80%~90%, and the coal injection ratio of the decomposition furnace main furnace area is 10%~20%, so as to control the temperature of the decomposition furnace reduction zone and the CO content at the outlet of the decomposition furnace;

[0010] (3) The gas in the decomposition furnace enters a cyclone at a certain temperature, and the gas is treated by spraying ammonia water into the cyclone to control NOx at 50 mg / Nm 3 Within.

[0011] The present invention controls the temperature of the reduction zone of the decomposition furnace to 900-1000°C by controlling the ratio of raw materials added to the reduction zone and the main furnace area of ​​the decomposition furnace and the amount of coal injection. In the reduction zone of the decomposition furnace, NOx generated in the kiln and H generated by coal powder decomposition under high temperature and low oxygen environment are 2 , CH 4 , CO and other reducing gases to reduce NOx to N 2 If the temperature in the reduction zone is too high, crusting will occur or aggravate the erosion of refractory materials. If the temperature is too low, insufficient reducing gas will be generated, the denitration reaction efficiency will be low, and the denitration effect will be poor. In the main furnace area of ​​the decomposition furnace, most of the carbonate decomposition is completed. At the same time, the reducing gases such as CO generated in the reduction zone must be completely burned in the main furnace to avoid affecting the effect of subsequent ammonia denitration. At the same time, the heat loss caused by incomplete combustion of coal powder and the occurrence of increased coal consumption must be avoided. The present invention reasonably arranges the feed port and the coal injection port in the decomposition furnace so that the material in the decomposition furnace will not fall directly into the smoke chamber, so that the NOx generated in the kiln and the reducing gas generated in the reduction zone have sufficient reaction time, space and temperature, thereby improving the reduction effect of the low-nitrogen decomposition furnace and reducing the NOx concentration at the outlet of the decomposition furnace.

[0012] The operating conditions of cement kilns are complex and changeable. The present invention can enhance the stability of the entire denitrification system by arranging multiple ammonia spray guns at multiple locations and automatically adjusting the flow rate. The temperature, airflow velocity and flue gas composition at different locations of the cyclone are different. The multi-point arrangement and automatic adjustment method can fully utilize the characteristics of each location, so that the denitrification reaction can be effectively carried out under different working conditions; the temperature at the location of the cyclone is usually in the range of 830~880℃, which is conducive to the reduction reaction of ammonia produced by the decomposition of ammonia with NOx to generate nitrogen and water; in the cone, due to the rotation of the airflow and the aggregation of materials, ammonia can be better mixed with flue gas, increasing the reaction contact area and improving the denitrification efficiency; at the inlet of the cyclone, the airflow velocity is faster, and ammonia can be quickly mixed with flue gas; at the outlet, the flue gas after the initial reaction can be further denitrified, thereby improving the adaptability of the entire system to complex working conditions. By real-time monitoring of NOx concentration, temperature, air volume and other parameters, the automatic adjustment system can adjust the ammonia flow in time. When the NOx concentration increases, the ammonia flow is automatically increased to ensure that there is enough ammonia to react with NOx, so that the NOx emission concentration is always controlled at a low level. Automatic adjustment of the ammonia flow also helps to reduce ammonia escape. Through real-time monitoring and precise adjustment, the ammonia flow is just enough to meet the needs of the reaction with NOx, so that the ammonia escape is controlled within a reasonable range. When the temperature or NOx concentration drops, the ammonia flow is automatically reduced to avoid ammonia escape caused by excessive injection of ammonia.

[0013] Furthermore, the raw material inlet of the reduction zone of the decomposition furnace is arranged in the middle of the reduction zone of the decomposition furnace; and the raw material inlet of the main furnace area of ​​the decomposition furnace is arranged above the tertiary tuyere.

[0014] The present invention controls the raw material ratio between the reduction zone and the main furnace zone of the decomposition furnace by dividing a feed discharge pipe into two parts, wherein one feed discharge port is arranged in the middle of the reduction zone of the decomposition furnace, so that a small amount of raw material is allowed to enter the reduction zone to adjust the temperature of the reduction zone, and then the raw material entering the reduction zone is brought to the main furnace zone for decomposition under the action of kiln wind; the other feed discharge port is arranged above the tertiary air port, so that most of the raw material is allowed to enter the main furnace zone of the decomposition furnace to complete carbonate decomposition, and the tertiary air and the hot air from the grate cooler (used to cool the hot air of the kiln clinker) can support the raw material to prevent the raw material from falling into the smoke chamber, and at the same time prevent the coal powder from falling into the smoke chamber, thereby ensuring the production quality.

[0015] Furthermore, the coal injection point in the reduction zone of the decomposition furnace is arranged at the lowest part of the cone of the reduction zone of the decomposition furnace; the coal injection point in the main furnace area of ​​the decomposition furnace is at the same height as the tertiary tuyere.

[0016] The present invention controls the coal injection ratio between the reduction zone and the main furnace area of ​​the decomposition furnace by arranging two groups of coal injection points at the tail coal of the decomposition furnace, wherein the coal injection pipe in the reduction zone of the decomposition furnace is arranged at the lowest part of the cone of the reduction zone of the decomposition furnace, which can ensure that the reduction zone of the decomposition furnace is as large as possible while preventing the tail coal from falling into the smoke chamber to form high temperature or crust in the smoke chamber; the coal injection pipe in the main furnace area of ​​the decomposition furnace is arranged at the tertiary air inlet, so that the air, coal and materials can be evenly mixed to ensure combustion efficiency.

[0017] Furthermore, the flame peak temperature is 1450-1480°C, the temperature of the reduction zone of the decomposition furnace is 900-1000°C, and the temperature of the cyclone is 830-880°C.

[0018] Furthermore, the temperature of the main furnace area of ​​the decomposition furnace is 860-890°C.

[0019] Furthermore, the CO content at the outlet of the decomposition furnace is 0.25% to 0.4%. The NOx generated in the burner reaches the reduction zone of the decomposition furnace through the smoke chamber, and part of the NOx can be reduced to N by the reducing gas CO. 2 In a non-confined space, NOx cannot be completely converted into N 2 , the unreduced NOx passes through the main furnace area and enters the cyclone. When the temperature of the reduction zone of the decomposition furnace is too high and the amount of coal injection is too large, more CO is generated. The excessive CO cannot be burned in time, which will cause the CO content at the outlet of the decomposition furnace to be too high, resulting in the inhibition of ammonia denitrification in the cyclone. At this time, it is necessary to appropriately increase the amount of raw materials or reduce the amount of coal injection in the reduction zone; when the temperature of the reduction zone of the decomposition furnace is too low and the amount of coal injection is too small, the CO content generated is insufficient, the amount of reduced NOx is also reduced accordingly, the CO content at the outlet of the decomposition furnace is too low, and the NOx concentration entering the cyclone increases, resulting in an increase in ammonia consumption and even excessive NOx emissions. At this time, it is necessary to appropriately reduce the amount of raw materials or increase the amount of coal injection in the reduction zone.

[0020] Furthermore, the air volume in the low nitrogen burner is 45-55 m 3 / min, wind pressure is 70~80 kPa.

[0021] Furthermore, the control of the air volume and the opening of the internal and external air in the low nitrogen burner according to the calorific value and volatile matter of the pulverized coal comprises the following steps:

[0022] When the calorific value of the pulverized coal is ≥6300 kcal / kg, the internal air opening is controlled to be 50%-75% and the external air opening is 100% to lengthen the flame and reduce the peak flame temperature;

[0023] When the calorific value of the pulverized coal is 5500-6300 kcal / kg, the internal air opening is controlled to be 75%-100%, and the external air opening is controlled to be 50%-75%, the flame is shortened, the flame temperature is increased, and the normal calcination temperature of the clinker is ensured;

[0024] When the volatile matter of the pulverized coal is ≥28%, the air volume is controlled to be 50~55 m 3 / min;

[0025] When the volatile matter of the pulverized coal is ≤28%, the air volume is controlled to be 45~50 m 3 / min;

[0026] The air volume in the low-nitrogen burner is mainly used to assist the combustion of volatile matter. Therefore, the burner air volume is adjusted according to the size of the volatile matter to ensure the combustion speed of the pulverized coal.

[0027] Furthermore, a plurality of ammonia spray guns are arranged at the cone portion of the cyclone, the cyclone outlet and the cyclone inlet.

[0028] Furthermore, a total of 14 ammonia spray guns are arranged at the cone of the cyclone, the cyclone outlet and the cyclone inlet, including 8 at the cone of the cyclone, 4 at the cyclone outlet and 2 at the cyclone inlet.

[0029] Furthermore, the total flow rate of the ammonia water is 11.7~12.3 L / min; when the gas passes through the low-nitrogen burner and the low-nitrogen decomposition furnace to the cyclone inlet, the NOx concentration drops to about 350 ppm, and the ammonia water flow rate at the cyclone inlet is 1.8~2 L / min; the gas dust concentration in the cone of the cyclone is the lowest, and the denitrification efficiency is high, and the ammonia water flow rate in the cone of the cyclone is 7~7.2 L / min; the ammonia water flow rate at the cyclone outlet is 2.9~3.1 L / min.

[0030] Compared with the prior art, the present invention is beneficial in that:

[0031] The present invention stabilizes the peak flame temperature of the low-nitrogen burner by adjusting the air volume, air pressure and internal and external air openings, controls the raw material ratio and coal injection ratio of the reduction zone and the main furnace area of ​​the decomposition furnace to control the temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace, and arranges ammonia spray guns at the inlet, cone and outlet of the cyclone to treat the gas. Under the premise of ensuring production, the amount of ammonia water can be reduced, the production and operation costs can be reduced, and the denitration efficiency of the reduction zone can be improved, so that the NOx concentration at the kiln tail is ≤50 mg / Nm 3 Ultra-low emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the process flow diagram of the cement kiln. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides a method for controlling ultra-low NOx emissions from a cement kiln (see process flow chart for details). Figure 1 ), including the following steps:

[0035] A method for controlling ultra-low NOx emissions from a cement kiln comprises the following steps:

[0036] 1. Control the air volume, air pressure, and internal and external air openings in the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal to stabilize the peak flame temperature;

[0037] 2. The gas generated in the low-nitrogen burner enters the decomposition furnace through the smoke chamber. The raw material ratio of the decomposition furnace reduction zone and the main furnace area is controlled to (1-3): (7-9), that is, the raw material ratio of the decomposition furnace reduction zone is 10%~30%, and the raw material ratio of the decomposition furnace main furnace area is 70%~90%; the coal injection ratio of the decomposition furnace reduction zone and the main furnace area is controlled to (8-9): (1-2), that is, the coal injection ratio of the decomposition furnace reduction zone is 80%~90%, and the coal injection ratio of the decomposition furnace main furnace area is 10%~20%, so as to control the temperature of the decomposition furnace reduction zone and the CO content at the outlet of the decomposition furnace;

[0038] 3. The gas in the decomposition furnace enters a cyclone at a certain temperature and is treated by spraying ammonia water into the cyclone.

[0039] In some examples, the flame peak temperature is 1450-1480°C, the temperature of the reduction zone of the decomposition furnace is 900-1000°C, and the temperature of the cyclone is 830-880°C.

[0040] In some examples, the CO content at the outlet of the decomposition furnace is 0.25%~0.4%.

[0041] In some examples, the air volume in the low nitrogen burner is 45-55 m 3 / min, wind pressure is 70~80 kPa.

[0042] In some examples, the specific operation of controlling the air volume, air pressure, and internal and external air opening of the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal is as follows: when the calorific value of the pulverized coal is ≥6300 kcal / kg, the internal air opening is controlled to be 50%~75%, and the external air opening is 100%, the flame is elongated, and the peak flame temperature is reduced; when the calorific value of the pulverized coal is 5500~6300 kcal / kg, the internal air opening is controlled to be 75%~100%, and the external air opening is 50%~75%, the flame is shortened, the flame temperature is increased, and the normal calcination temperature of the clinker is ensured; when the volatile matter of the pulverized coal is ≥28%, the air volume is controlled to be 50~55 m 3 / min; when the volatile matter of the pulverized coal is ≤28%, the air volume is controlled to be 45~50 m 3 / min, the air volume in the low-nitrogen burner is mainly used to assist the combustion of volatile matter. Therefore, the burner air volume is adjusted according to the size of the volatile matter to ensure the combustion speed of the pulverized coal.

[0043] In some examples, the total flow rate of the ammonia solution is 11.6~12.6 L / min; wherein, the flow rate of the ammonia solution at the inlet of the cyclone is 1.8~2 L / min; the flow rate of the ammonia solution at the cone of the cyclone is 7~7.4 L / min; and the flow rate of the ammonia solution at the outlet of the cyclone is 2.8~3.2 L / min.

[0044] In the following specific embodiments, unless otherwise specified, the raw material inlet of the reduction zone of the decomposition furnace is arranged in the middle of the reduction zone of the decomposition furnace; the raw material inlet of the main furnace area of ​​the decomposition furnace is arranged above the tertiary air inlet; the coal injection point of the reduction zone of the decomposition furnace is arranged at the lowest part of the cone of the reduction zone of the decomposition furnace; the coal injection point of the main furnace area of ​​the decomposition furnace is at the same height as the tertiary air inlet; a total of 14 ammonia spray guns are arranged at the cone of the cyclone, the cyclone outlet and the cyclone inlet, including 8 at the cone of the cyclone, 4 at the cyclone outlet and 2 at the cyclone inlet.

[0045] Example 1

[0046] A method for controlling ultra-low NOx emissions from a cement kiln comprises the following steps:

[0047] (1) Control the air volume, air pressure, and internal and external air openings in the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal to stabilize the peak flame temperature:

[0048] The current calorific value of coal powder is detected to be 6453 kcal / kg, and the volatile matter is 29%. The air volume in the low nitrogen burner is adjusted to 53%, the air pressure to 80%, the internal air opening to 60%, the external air opening to 100%, and the stable flame peak temperature at 1465±5 ℃.

[0049] (2) By controlling the raw material ratio and coal injection ratio between the reduction zone and the main furnace area of ​​the decomposition furnace, the temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace can be controlled:

[0050] Before adjustment: the upper, middle and lower temperatures of the reduction zone of the decomposition furnace were 1135 ℃, 1015 ℃ and 1052 ℃ respectively. The CO content at the outlet of the decomposition furnace was as high as 0.52%. The opening of the C4 material distribution valve was 26%. 95% of the tail coal was distributed to the reduction zone. At this time, the total flow rate of ammonia water in the cyclone was 18 L / min, and the NOx concentration at the kiln tail was 73 mg / Nm 3 about.

[0051] After adjustment: the material distribution valve remains unchanged, the coal consumption in the reduction zone is adjusted from 95% to 82%, the upper, middle and lower temperatures in the reduction zone are reduced to 955°C, 998°C and 964°C, the CO content at the outlet of the decomposition furnace is reduced from 0.52% to 0.4%, the total flow rate of ammonia water in the cyclone is reduced to 13 L / min, and the NOx concentration at the kiln tail is stabilized at 42 mg / Nm 3 Too much CO will affect the denitrification reaction. After reducing the coal in the reduction zone, the temperature of the reduction zone drops, the denitrification efficiency increases, and the amount of ammonia water used decreases.

[0052] Example 2

[0053] A method for controlling ultra-low NOx emissions from a cement kiln comprises the following steps:

[0054] (1) Control the air volume, air pressure, and internal and external air openings in the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal to stabilize the peak flame temperature:

[0055] The current calorific value of coal powder is detected to be 6275 kcal / kg, and the volatile matter is 21%. The air volume in the low nitrogen burner is adjusted to 47%, the air pressure to 78%, the internal air opening to 81%, the external air opening to 60%, and the stable flame peak temperature at 1455±5 ℃.

[0056] (2) By controlling the raw material ratio and coal injection ratio between the reduction zone and the main furnace area of ​​the decomposition furnace, the temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace can be controlled:

[0057] Before adjustment: the upper, middle and lower temperatures of the reduction zone of the decomposition furnace were 860 ℃, 908 ℃ and 875 ℃ respectively. The CO content at the outlet of the decomposition furnace was as low as 0.09%. The opening of the C4 material distribution valve was 32%. 83% of the tail coal was distributed to the reduction zone. At this time, the total flow rate of ammonia water in the cyclone was 16 L / min, and the NOx concentration at the kiln tail was 77 mg / Nm 3 about.

[0058] After adjustment: the coal distributor valve remains unchanged, the C4 distributor valve in the reduction zone is adjusted from 32% to 15%, the upper, middle and lower temperatures in the reduction zone rise to 965°C, 1015°C and 948°C, the CO content at the outlet of the decomposition furnace rises from 0.09% to 0.25%, the total flow of ammonia water in the cyclone drops to 13L / min, and the NOx concentration at the kiln tail is stabilized at 45 mg / Nm 3 , that is, the reduction effect of the decomposition furnace is enhanced and the amount of ammonia water used is reduced.

[0059] Example 3

[0060] A method for controlling ultra-low NOx emissions from a cement kiln comprises the following steps:

[0061] (1) Control the air volume, air pressure, and internal and external air openings in the low-nitrogen burner according to the calorific value and volatile matter of the pulverized coal to stabilize the peak flame temperature:

[0062] The current calorific value of coal powder is detected to be 6763 kcal / kg, and the volatile matter is 31%. The air volume in the low nitrogen burner is adjusted to 55%, the air pressure to 80%, the internal air opening to 75%, the external air opening to 100%, and the stable flame peak temperature at 1460±5 ℃.

[0063] (2) By controlling the raw material ratio and coal injection ratio between the reduction zone and the main furnace area of ​​the decomposition furnace, the temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace can be controlled:

[0064] Before adjustment: the upper, middle and lower temperatures of the reduction zone of the decomposition furnace were 855°C, 876°C and 922°C respectively, the CO content at the outlet of the decomposition furnace was 0.1%, the C4 material distribution valve opening was 17%, and 70% of the tail coal was distributed to the reduction zone. At this time, the total flow rate of ammonia water in the cyclone was 15.5 L / min, and the NOx concentration at the kiln tail was 69 mg / Nm 3 about.

[0065] After adjustment: the feed valve remains unchanged, the coal consumption in the reduction zone is adjusted from 70% to 85%, the temperature in the reduction zone rises to 972°C, 958°C, and 987°C, the CO content at the outlet of the decomposition furnace increases from 0.1% to 0.32%, the total flow of ammonia water in the cyclone drops to 12.8 L / min, and the NOx concentration at the kiln tail is stabilized at 41 mg / Nm 3 The effect of the reduction zone of the decomposition furnace is not good. The amount of pulverized coal in the reduction zone is appropriately increased to improve the denitrification efficiency of the reduction zone, reduce the amount of ammonia water, and stabilize NOx emissions.

[0066] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A method for controlling ultra-low NOx emissions from a cement kiln, characterized in that: The following steps are involved: According to the calorific value and volatile matter of the pulverized coal, the air volume, air pressure, and internal and external air openings in the low-nitrogen burner are controlled to stabilize the peak flame temperature; The gas generated in the low-nitrogen burner enters the decomposition furnace through the smoke chamber. The temperature of the reduction zone of the decomposition furnace and the CO content at the outlet of the decomposition furnace are controlled by controlling the raw material ratio between the reduction zone of the decomposition furnace and the main furnace area to (1-3): (7-9) and the coal injection ratio between the reduction zone of the decomposition furnace and the main furnace area to (8-9): (1-2). The gas in the decomposition furnace enters a cyclone at a certain temperature, and is treated by spraying ammonia water into the cyclone to achieve ultra-low NOx emissions from the cement kiln.

2. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The raw material inlet of the reduction zone of the decomposition furnace is arranged in the middle of the reduction zone of the decomposition furnace; the raw material inlet of the main furnace area of ​​the decomposition furnace is arranged above the tertiary tuyere.

3. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The coal injection point in the reduction zone of the decomposition furnace is arranged at the lowest part of the cone of the reduction zone of the decomposition furnace; the coal injection point in the main furnace area of ​​the decomposition furnace is at the same height as the tertiary tuyere.

4. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The peak temperature of the flame is 1450-1480°C, the temperature of the reduction zone of the decomposition furnace is 900-1000°C, and the temperature of the cyclone is 830-880°C.

5. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The CO content at the outlet of the decomposition furnace is 0.25%~0.4%.

6. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The air volume in the low nitrogen burner is 45~55 m 3 / min, wind pressure is 70~80 kPa.

7. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: The method of controlling the air volume and the opening of internal and external air in the low nitrogen burner according to the calorific value and volatile matter of the pulverized coal comprises the following steps: When the calorific value of the pulverized coal is ≥6300 kcal / kg, the internal air opening is controlled to be 50%-75% and the external air opening is controlled to be 100% to lengthen the flame and reduce the peak flame temperature; When the calorific value of the pulverized coal is 5500-6300 kcal / kg, the internal air opening is controlled to be 75%-100%, and the external air opening is controlled to be 50%-75%, the flame is shortened, the flame temperature is increased, and the normal calcination temperature of the clinker is ensured; When the volatile matter of the pulverized coal is ≥28%, the air volume is controlled to be 50~55 m 3 / min; When the volatile matter of the pulverized coal is ≤28%, the air volume is controlled to be 45~50 m 3 / min.

8. The method for controlling ultra-low NOx emissions from a cement kiln according to claim 1, characterized in that: A plurality of ammonia spray guns are arranged at the cone portion of the cyclone, the cyclone outlet and the cyclone inlet.

9. A cement kiln NOx ultra-low emission control method according to claim 8, characterized in that: The total flow rate of the ammonia water is 11.6~12.6 L / min; among them, the ammonia water flow rate at the cyclone inlet is 1.8~2 L / min; the ammonia water flow rate at the cyclone cone is 7~7.4 L / min; and the ammonia water flow rate at the cyclone outlet is 2.8~3.2 L / min.

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