Cement kiln flue gas denitration system and cement kiln production system

Abstract

The utility model discloses a cement kiln flue gas denitration system and a cement kiln production system. The system comprises a rotary denitration device and a penetrating denitration device which are arranged on a flue between a rotary cement kiln and a decomposing furnace. The penetrating type denitration device is mainly used for removing nitrogen oxides (including a thermal type and a fuel type) generated by combustion of head coal in the rotary cement kiln; the rotary denitration device is used for further denitrating the flue gas generated in the rotary kiln, and meanwhile, the generation of tail coal fuel type nitric oxide is strongly inhibited, and the concentration of tail coal fuel type NOX is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas treatment, in particular to a system for denitrifying cement kiln flue gas and a cement kiln production system. Background Art

[0002] The cement production industry is an important basic material industry in my country. Currently, my country's cement production has reached an annual output of more than 2 billion tons, and the number of cement clinker production lines is about 1,700, covering all provinces in my country.

[0003] In the cement production process, the thermal decomposition reaction of cement raw materials and the mineralization reaction of cement clinker are completed by the high temperature (about >825℃ and >1450℃ respectively) obtained after the combustion of coal powder. In this process, the nitrogen-containing substances in the coal powder will produce nitrogen oxides NO when burned. x (fuel type); in addition, if the high temperature condition exceeds 1200℃ (such as the mineralization reaction condition of cement clinker), the N2 in the combustion air will also be oxidized to NO x (Thermal type). Therefore, the rotary kiln (equipment that completes the mineralization reaction of cement clinker) and decomposition furnace (equipment that completes the reaction of CaCO3 in cement raw materials decomposing into CaO) used in cement production will produce a large amount of NO during the combustion process. x (nitrogen oxides), sulfur dioxide, particulate matter and other atmospheric pollutants.

[0004] In 2013, the state issued and implemented the mandatory national standard GB4915-2013 "Cement Industry Air Pollutant Emission Standard" for pollutant emissions from the cement production industry, which stipulates that NO x The emission limit is 320mg / Nm 3 (Calculated based on 10% baseline oxygen content). In January 2024, the Ministry of Ecology and Environment and five other ministries and commissions jointly issued the "Opinions on Promoting the Implementation of Ultra-low Emissions in the Cement Industry" (hereinafter referred to as the "Opinions"), gradually promoting the implementation of the emission limit of nitrogen oxides in cement clinker production of ≤50mg / Nm 3 (calculated according to 10% baseline oxygen content), while the amount of denitrification ammonia water is ≤3.5 kg / ton clinker (based on 20% ammonia water concentration), ammonia escape is ≤8 mg / Nm 3 Therefore, the flue gas generated in the cement production process needs to be treated to meet the above indicators before it can be discharged into the atmosphere.

[0005] In order to meet the requirements of various standards and opinions, the cement production industry currently mainly adopts two types of denitrification methods:

[0006] The first category is the chemical denitrification technology of kiln tail gas represented by "selective non-catalytic reduction (SNCR)" and "selective catalytic reduction (SCR)". "Selective non-catalytic reduction (SNCR)" denitrification technology usually uses ammonia water as a reducing agent to chemically reduce and denitrify nitrogen oxides in the flue gas. However, this technology cannot simultaneously meet the requirements of the three indicators of "nitrogen oxide emission limits", "desnitrification ammonia water usage" and "ammonia escape" in the above-mentioned "Opinion". Although the "selective catalytic reduction (SCR)" denitrification technology can meet the regulatory requirements for ultra-low emissions, its construction cost is about RMB 20 million, and the catalyst components need to be replaced regularly. The operation and maintenance costs are high, which increases the production cost of cement clinker. At the same time, the discarded catalyst components have the risk of secondary pollution.

[0007] The second category: Process denitrification technology represented by "staged combustion" of pulverized coal, that is, in the decomposition furnace, the reducing gas (mainly CO gas, etc.) produced during the oxygen-poor combustion of pulverized coal is used to reduce the nitrogen oxides produced by combustion into harmless nitrogen, thereby reducing the nitrogen oxide content in the flue gas discharged from the cement kiln system and achieving the purpose of denitrification. However, the denitrification efficiency of this denitrification technology is low, and it is easily affected by the cement clinker production process. Even if used in conjunction with SNCR, it cannot stably meet the requirements of the above-mentioned "Opinion" for the emission limit of nitrogen oxides. Utility Model Content

[0008] The utility model aims to address the technical defects existing in the prior art. In a first aspect, a system for denitrifying flue gas from a cement kiln is provided, comprising a rotary denitrifying device (01) arranged at the position of an ascending flue (15) of the cement kiln, wherein the rotary denitrifying device (01) comprises a hollow and funnel-shaped cylinder (16), wherein a plurality of first nozzles (03-1) for spraying tail coal and water vapor into the inner cavity of the cylinder (16) are arranged on the cylinder wall, and all the first nozzles (03-1) are deflected to the same side at the same angle.

[0009] The angle at which the first nozzle (03-1) is deflected to the same side is the angle between the nozzle axis and the tangent line of the cylinder circumference at the nozzle location, and the angle does not exceed 75°.

[0010] The first nozzle (03-1) is an integrated nozzle capable of simultaneously and separately spraying coal powder and water vapor, or comprises a first coal powder nozzle (03-2) and a first water vapor nozzle (03-3) which are independently arranged.

[0011] It also includes a penetrating denitrification device (02) disposed on the ascending flue and connected to the rotary denitrification device (01), wherein the penetrating denitrification device (02) includes a pipe body (17) and a plurality of second nozzles (04-1) installed on the side wall of the pipe body (17) for spraying tail coal and water vapor into the inner cavity of the pipe body (17).

[0012] The second nozzle (04-1) faces the central axis of the tube body (17).

[0013] The first nozzle (03-1) and the second nozzle (04-1) are respectively arranged in the horizontal direction, or at an angle with the horizontal direction; the first pulverized coal nozzle (03-2) and the first water vapor nozzle (03-3) are arranged at intervals on the same horizontal plane, or are arranged symmetrically in the vertical direction of the cylinder (16); the second pulverized coal nozzle (04-2) and the second water vapor nozzle (04-3) are arranged at intervals on the same horizontal plane, or are arranged symmetrically in the vertical direction of the tube (17).

[0014] The rotary denitrification device (01) and the penetrating denitrification device (02) are arranged from bottom to top or from top to bottom at the position of the ascending flue (15); the cylinder (16) of the rotary denitrification device (01) and the tube (17) of the penetrating denitrification device (02) are arranged coaxially or non-coaxially; the cylinder (16) and the tube (17) are arranged coaxially or non-coaxially with the ascending flue (15).

[0015] The water vapor inlet of the first nozzle (03-1) is connected to a steam generator, or to an exhaust steam pipeline of a waste heat power generation device of a cement kiln; the water vapor inlet of the second nozzle (04-1) is connected to a steam generator, or to an exhaust steam pipeline of a waste heat power generation device of a cement kiln.

[0016] A temperature detection device (05) is provided in the cylinder (16) of the rotary denitration device (01).

[0017] In a second aspect, the utility model provides a cement kiln production system, comprising a rotary kiln (11), a decomposition furnace (12), and an ascending flue (15) connecting the rotary kiln (11) and the decomposition furnace (12), characterized in that it also includes the above-mentioned system arranged at the position of the ascending flue (15), and no tail coal inlet (08) is provided on the decomposition furnace (12).

[0018] The utility model system adds two different types of denitrification devices to the original flue between the rotary kiln and the decomposition furnace: ① a rotary denitrification device; ② a penetrating denitrification device. The utility model can significantly improve the flue gas denitrification efficiency by simply changing the equipment structure of the original cement clinker production line. It has a clever design, low implementation cost, and good acceptance of application and promotion.

[0019] The above system is used to denitrate the flue gas in the cement clinker production process. A unique denitrification device is set up on the basis of fully considering the cement clinker production process conditions and process equipment. The denitrification device takes into account the cement clinker production process associated with denitrification, realizes close integration with the cement clinker production process, and makes full use of the material composition and heat transfer in the cement production process; and the denitrification process of the system does not basically change the original cement clinker production process, the denitrification process does not interfere with the original cement clinker production process, and can also be used in conjunction with SNCR denitrification technology. The denitrification of the flue gas in the cement clinker production process by the utility model system can fully meet the requirements of the aforementioned "Opinion" on NOx emissions in the cement clinker production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown is a schematic structural diagram of an existing cement clinker production system.

[0021] Figure 2 Shown is a schematic diagram of the structure of the utility model system.

[0022] Figure 3 Shown is a schematic cross-sectional view of the rotary denitrification device along AA in the system of the utility model.

[0023] Figure 4 Shown is a schematic cross-sectional view along BB of the penetration-type denitrification device in the system of the utility model.

[0024] Figure 5 Shown is a schematic diagram of the layout of a rotary denitrification device in another embodiment of the system of the utility model.

[0025] Figure 6 Shown is a schematic diagram of the layout of a rotary denitration device in another embodiment of the system of the utility model.

[0026] Figure 7 Shown is a schematic structural diagram of a first nozzle in another embodiment of the system of the utility model.

[0027] Figure 8 Shown is a schematic structural diagram of a second nozzle in another embodiment of the system of the utility model.

[0028] Figures 9A-9C Shown are schematic structural diagrams of the first nozzle and / or the second nozzle in several implementation modes of the system of the utility model.

[0029] Figures 10A-10B Shown are schematic structural diagrams of coal powder nozzles and water vapor nozzles in several implementation modes of the system of the utility model.

[0030] In the figure:

[0031] 01: Rotary denitrification device, 02: Penetrating denitrification device, 03-1: First nozzle, 03-2: First pulverized coal nozzle, 03-3: First water vapor nozzle, 04-1: Second nozzle, 04-2: Second pulverized coal nozzle, 04-3: Second water vapor nozzle, 05: Temperature detection device, 06: Secondary air, 07: Tertiary air inlet, 08: Tail coal inlet, 09: Fourth-stage tube discharge pipe, 10: Fifth-stage tube discharge pipe, 11: Rotary kiln, 12: Decomposition furnace, 13: Decomposition furnace cone, 14: Smoke chamber, 15: Rising flue, 16: Cylinder body, 17: Pipe body, 31: Main conveying pipe, 311: Coal powder conveying pipe, 312: Water vapor conveying pipe. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, the existing production process of cement clinker is:

[0033] The high temperature (1450℃~1600℃) generated by the combustion of the first coal in the cement rotary kiln completes the mineralization reaction of the materials in the kiln and produces four main minerals C3S, C2S, C3A, C4AF, i.e. clinker. The high-temperature secondary air flue gas (including thermal and fuel NO X ) passes through the rotary kiln 11, along the direction indicated by the secondary air 06 arrow, from bottom to top, through the smoke chamber 14, the rising flue 15 at the end of the kiln, the decomposition furnace cone 13, and enters the decomposition furnace 12.

[0034] Tail coal powder along the tail coal inlet 08( Figure 1 The high-temperature air (tertiary air) required for the combustion of tail coal flows into the decomposition furnace 12 along the tertiary air inlet 07 ( Figure 1 The tertiary air (in the direction indicated by the middle arrow) also enters the decomposition furnace 12. The tertiary air comes from the high-temperature air generated when the cement clinker is cooled, and the temperature is usually around 950°C. The cement raw material enters the decomposition furnace 12 along the four-stage tube discharge pipe 09. The high temperature (about 850°C to 1000°C) generated by the combustion of the tail coal completes the chemical reaction of decomposing the calcium carbonate in the raw material in the decomposition furnace 12 into calcium oxide.

[0035] All the reactants in the decomposition furnace 12, the high-temperature flue gas generated during the combustion of tail coal (including NO X The solid powder (hot raw material) separated by the five-stage drum enters the rotary kiln along the five-stage drum feed pipe 10, and when it reaches the burning zone in the rotary kiln, it completes the mineralization reaction under the high temperature (1450℃~1600℃) generated by the combustion of the head coal to produce clinker.

[0036] The "staged combustion" denitrification technology mentioned in the background technology usually involves introducing some tail coal into the cone 13 of the decomposition furnace. Since this is an oxygen-deficient environment, the fixed carbon and volatile matter in the tail coal generate reducing gases such as CO with reducing properties in the oxygen-deficient and high-temperature environment, thereby reducing the nitrogen oxides in the secondary air flue gas from the ascending flue 15 to nitrogen.

[0037] However, since the wind speed of the secondary flue gas is as high as 20 to 30 m / s, the nitrogen oxides entering the cone section 13 of the decomposition furnace do not have enough time to undergo a reduction reaction, and the presence of raw materials in the cone section 13 of the decomposition furnace usually interferes with the progress of the reduction reaction. Therefore, the efficiency of denitrification using this technology is relatively low, and even if used in conjunction with SNCR, it cannot simultaneously meet the requirements for all indicators in the aforementioned "Opinion".

[0038] In combination with the existing cement clinker production process and considering the shortcomings of the denitrification technology commonly used in the industry, the utility model proposes a new denitrification system for cement kiln flue gas.

[0039] The following is a more detailed description of the present invention in conjunction with specific embodiments, and further elaboration of the present invention, but these embodiments are by no means intended to limit the present invention.

[0040] As mentioned above, in the production of cement clinker, the flue gas temperature entering the ascending flue 15 is 1000℃~1100℃, and the volume concentration of oxygen content is usually ≤3.5%, which belongs to high temperature and oxygen-deficient conditions. The concentration of nitrogen oxides can even be as high as 1000mg / Nm 3 The utility model creatively proposes to modify the existing flue system and add a denitrification device in the original ascending flue. For example, see Figure 2 As shown, at least a rotary denitrification device 01 is added, or a rotary denitrification device 01 and a penetrating denitrification device 02 connected in sequence are added at the same time, and the tail coal inlet 08 originally provided on the decomposition furnace 12 is cancelled (see Figure 1 ), the tail coal is introduced into the denitration device of the utility model instead of the decomposition furnace 12 or the decomposition furnace cone 13 (the way of introducing the tail coal into the denitration device will be described later), thus forming the denitration system for cement kiln flue gas of the utility model. Among them,

[0041] like Figure 2 and Figure 3As shown, the rotary denitration device 01 includes a hollow and funnel-shaped cylinder 16, and a temperature detection device 05 is provided at a convenient position in the cylinder 16, which is generally located near the top surface of the cylinder 16. A plurality of first nozzles 03-1 are installed on the cylinder wall of the cylinder 16 to spray coal powder and water vapor. These first nozzles 03-1 can be evenly distributed on the inner wall of the cylinder 16, and the nozzle outlets face and extend into the inner cavity of the cylinder. All first nozzles 03-1 are deflected to the same side at the same angle (for example, not more than 75°), which is the angle between the nozzle axis and the tangent of the cylinder circumference at the position of the nozzle, so that it enters the cylinder 16 along the approximate tangent direction of the cylinder 16 (the local enlarged structure is shown in FIG. Figure 3 As shown in FIG. 1 , the coal powder and water vapor sprayed from the first nozzle 03-1 can form a swirl flow along the inner wall of the cylinder 16 when sprayed into the inner cavity of the cylinder 16 through the first nozzle 03-1. The first nozzle 03-1 can be arranged in the horizontal direction (see FIG. 1 ). Fig.9A ), and may also have an angle with the horizontal direction. For example, when it is necessary to prolong the time that the smoke stays in the cylinder 16, the first nozzle 03-1 may be introduced in a downward direction, see Fig. 9B On the contrary, when it is necessary to shorten the time that the smoke stays in the cylinder 16, the first nozzle 03-1 can be introduced in an upward direction, see Fig. 9C In the present invention, the first nozzle 03-1 is preferably designed as an integrated nozzle capable of simultaneously and separately injecting coal powder and water vapor, for example, formed by a set of coal powder delivery pipe 311 and water vapor delivery pipe 312, see Fig. 10A The package can be that the pulverized coal conveying pipe 311 is outside / inside, and the steam conveying pipe 312 is inside / outside, and the two conveying pipes are coaxially packaged; or Fig. 10B The two delivery pipes shown are each independently mounted in a main delivery pipe 31. Here, the water vapor delivery pipe 312 can be connected to an independent steam generator device, or it can be connected to the exhaust steam pipeline of the original kiln tail waste heat power generation of the cement kiln system to reuse the exhaust steam; the coal powder delivery pipe 311 inputs the tail coal. The first nozzle 03-1 can also be a first coal powder nozzle 03-2 and a first water vapor nozzle 03-3 (such as a first coal powder nozzle 03-2 and a first water vapor nozzle 03-3) that are independently set. Figure 7 The pulverized coal nozzle and the steam nozzle can be arranged at intervals on the same horizontal plane (not shown in the figure), or the two can be paired up and down and arranged at intervals in the horizontal direction (see Figure 7 ), or symmetrically distributed on the cylinder wall of the cylinder 16 along a certain length in the axial direction (such as axisymmetric, center symmetric). The first steam nozzle 03-3 can be connected to an independent steam generator device, or can be connected to the exhaust steam pipeline of the original kiln tail waste heat power generation of the cement kiln system to reuse the exhaust steam; the first pulverized coal nozzle 03-2 inputs tail coal.

[0042] The specific arrangement of the first nozzle 03-1 of the utility model is not limited to Figure 3Alternatively, two nozzles may be arranged at an angle of 90 degrees to each other along a substantially tangential direction of the cylinder 16 to introduce coal powder and water vapor into the cylinder 16 and generate a rotating airflow therein.

[0043] The approximate tangent direction mentioned here is the cross-sectional view cut along the horizontal direction (such as Figure 3 ,along Figure 2 In the AA line in the figure, a direction range near the tangent direction of the cylinder 16 (or understood as the deflection angle range between the nozzle axis and the tangent), when the first nozzle 03-1 is arranged along any direction within the range, the coal powder and water vapor can form a swirl when they pass through the first nozzle 03-1 into the cylinder 16. For example, the range can be a direction range in which the nozzle deviates by no more than 75 degrees relative to the tangent direction.

[0044] In the above-mentioned rotary denitrification device, a mixture of pulverized coal and water vapor passes through a nozzle and enters the cylinder at a high speed along the tangent off-center direction of the inner wall of the rotary denitrification device to form a gas-solid two-phase rotating airflow bed; in this rotating flow field, the residence time of pulverized coal and water vapor is prolonged, and the edge area of ​​the rising flue gas flow field, pulverized coal, and water vapor are mixed more fully; at the same time, under the oxygen-poor and high-temperature environment conditions inside the cylinder of the rotary denitrification device, the following physical and chemical reactions occur simultaneously: ① The volatile matter in the pulverized coal is pyrolyzed and gasified to produce reducing gases such as CO gas, which converts NO in the secondary air flue gas into X ② The water vapor reacts with the fixed carbon in the coal powder to produce H2 (strongly reducing) gas and CO gas, which reduces the NO in the secondary air flue gas. X ③ During the pyrolysis and gasification process of coal powder, most of the volatile nitrogen and part of the coke nitrogen in the coal powder are released into the gas phase, and most of them are converted into harmless nitrogen in a strong reducing atmosphere; that is, most of the fuel-type NO generated during the pyrolysis and gasification process of coal powder X , and is also reduced to harmless nitrogen by reducing gases such as H2 and CO. Based on these reactions, the rotary denitrification device can not only effectively remove nitrogen oxides in secondary air flue gas, strongly inhibit and remove fuel-type nitrogen oxides generated by coal powder itself, but also significantly improve the combustion characteristics of coal powder, which is conducive to the rapid and stable subsequent aerobic combustion process, thereby reducing the production system's requirements for coal powder quality and reducing the production cost of cement clinker.

[0045] As an optimized implementation method, the utility model also provides a penetration type denitrification device 02, such as Figure 2 and Figure 4 As shown, the penetration type denitrification device 02 includes the original ascending flue (see Figure 1The second nozzle 04-1 is an integrated nozzle capable of simultaneously injecting pulverized coal and water vapor, and its structure is completely the same as that of the first nozzle 03-1, which will not be described in detail here. The second nozzle 04-1 can also be a second pulverized coal nozzle 04-2 and a second water vapor nozzle 04-3 (such as a second pulverized coal nozzle 04-3) that are independently arranged. Figure 8 The pulverized coal nozzle and the steam nozzle can be arranged at intervals on the same horizontal plane (not shown in the figure), or the two can be paired up and down and arranged at intervals in the horizontal direction (see Figure 8 ), or symmetrically distributed on the tube wall of the tube body 17 along a certain length of the axial direction (such as axisymmetry, center symmetry). The second nozzle 04-1 can be set in the horizontal direction, or at an angle to the horizontal direction (for example, when it is necessary to extend the time that the smoke stays in the tube body 17, the second nozzle 04-1 can be inserted in a downward direction; conversely, when it is necessary to shorten the time that the smoke stays in the tube body 17, the second nozzle 04-1 can be inserted in an upward direction; refer to Figures 9A-9C The second water vapor nozzle 04-3 can be connected to an independent steam generator device, or it can be connected to the exhaust steam pipeline of the original kiln tail waste heat power generation of the cement kiln system to reuse the exhaust steam. The second nozzle 04-1 has the same structure and form as the first nozzle 03-1, and different forms can be used alone or in combination.

[0046] In the above-mentioned penetrating denitrification device, the mixture of coal powder and water vapor that enters radially inward along the pipe body (flue gas channel) at high speed through the nozzle penetrates the flue gas flow field of the rising flue and reaches the central area of ​​the flue gas channel cross section; the mixture of coal powder and water vapor that enters from different radial directions collides in the radial central area of ​​the flue gas channel, forming strong turbulence and mixing with the flue gas. At the same time, under the oxygen-poor and high-temperature environment conditions inside the pipe body of the above-mentioned penetrating denitrification device, the following three main physical and chemical reactions occur simultaneously: ① The volatile matter in the coal powder is pyrolyzed and gasified to produce reducing gases such as CO gas, which converts NO in the flue gas into X ② The water vapor reacts with the fixed carbon in the coal powder to produce H2 (strong reducing gas) and CO gas, which reduces the NO in the flue gas. X ③ During the pyrolysis and gasification process of coal powder, most of the volatile nitrogen and part of the coke nitrogen in the coal powder are released into the gas phase, and most of them are converted into harmless nitrogen in a strong reducing atmosphere; that is, most of the fuel-type NO generated during the pyrolysis and gasification process of coal powder X, and is also reduced to harmless nitrogen by reducing gases such as H2 and CO. Based on these reactions, the penetrating denitrification device can not only effectively remove nitrogen oxides in the secondary air flue gas, strongly inhibit and remove the fuel-type nitrogen oxides produced by the coal powder itself, but also consume the high oxygen in the secondary air flue gas when the cement clinker process is in an abnormal state, thereby improving the adaptability of this denitrification system to the process fluctuations of the clinker production system and ensuring the denitrification efficiency of this denitrification system.

[0047] In the system of the utility model, the rotary denitrification device 01 and the penetrating denitrification device 02 are preferably arranged in combination, and their relative positions in the flow direction of the secondary air flue gas can be interchanged when they are arranged in combination. For example, the penetrating denitrification device 02 and the rotary denitrification device 01 are arranged from bottom to top along the flow direction of the secondary air flue gas, or Figure 2 The exemplary rotary denitrification device 01 and the penetrating denitrification device 02 are arranged from bottom to top along the flow direction of the secondary air flue gas.

[0048] One implementation method is to only set up the rotary denitrification device 01 without setting up the penetrating denitrification device 02. Compared with the penetrating denitrification device, the pulverized coal and water vapor stay longer in the rotary denitrification device. Therefore, even if the amount of pulverized coal is large, the above three reactions can be basically completed; compared with the penetrating denitrification device, the rotary denitrification device can achieve a large amount of fuel-type NO generated by pulverized coal. X of removal.

[0049] In the utility model, the geometric shapes of the inner walls of the cylinder 16 of the rotary denitrification device 01 and the tube 17 of the penetrating denitrification device 02 can be cylindrical, elliptical, square, polygonal, or a combination of these shapes. When it is a square cylinder or a polygonal cylinder, the deflection angle of the first nozzle 03-1 is the angle between the nozzle axis and the inner wall of the cylinder.

[0050] In the utility model, Figure 5 , Figure 6 As shown, the cylinder 16 of the rotary denitration device 01 and the tube 17 of the penetrating denitration device 02 can be coaxially arranged or non-coaxially arranged; the two can be coaxially arranged with the flue and the smoke chamber or non-coaxially arranged.

[0051] Through the above settings, the tail coal originally fed into the decomposition furnace is no longer fed into the decomposition furnace, but is sprayed into the rotary denitration device 01 and the penetrating denitration device 02 by the first nozzle 03-1 and the second nozzle 04-1 respectively. The amount of pulverized coal sprayed into the penetrating denitration device 02 by the second nozzle 04-1 accounts for 0-50% of the total amount of tail coal ("0" means that the penetrating denitration device is not provided), and the remaining tail coal is sprayed into the rotary denitration device 01 by the first nozzle 03-1. Preferably, the amount of pulverized coal sprayed by the second nozzle 04-1 accounts for 20-30% of the total amount of tail coal, and the amount of pulverized coal sprayed by the first nozzle 03-1 accounts for 70-80% of the total amount of tail coal.

[0052] The denitration system of the present utility model is further described below in conjunction with specific embodiments.

[0053] In this embodiment, the penetrating denitrification device 02 and the rotary denitrification device 01 are arranged from bottom to top along the direction (i.e., flow direction) of the secondary air flue gas. That is, the rotary denitrification device 01 is located at the upper position of the original flue (closer to the decomposition furnace than the penetrating denitrification device 02), the top surface of the cylinder 16 is the top surface of the rotary denitrification device 01, and is connected to the cone 13 of the decomposition furnace; the bottom surface of the cylinder 16 is connected to the top of the penetrating denitrification device 02. The penetrating denitrification device 02 is located at the lower position of the original flue (closer to the smoke chamber than the rotary denitrification device 01), the top surface of the tube 17 is connected to the bottom surface of the rotary denitrification device 01; the bottom surface of the tube 17 is connected to the top of the smoke chamber 14.

[0054] When the system of this embodiment is used to perform denitration, the following steps are specifically included:

[0055] (1) When the secondary air flue gas 06 with a temperature of about 1050°C (O2 concentration of about <3.5%) enters the penetrating denitrification device 02 through the smoke chamber 14, the mixture of tail coal pulverized coal and water vapor (the pulverized coal accounts for about 30% of the total tail coal pulverized coal) enters the penetrating denitrification device 02 through the four second nozzles 04-1, penetrates the flue gas flow field to reach the central area of ​​the flue gas channel cross section, and collides in the radial central area of ​​the flue gas channel, forming strong turbulence and mixing with the flue gas, such as Figure 2 and Figure 4 At the same time, under the oxygen-poor high-temperature environment conditions inside the penetrating denitrification device 02, the following three main physical and chemical reactions occur simultaneously: ① The volatile matter in the coal powder is pyrolyzed and gasified to produce reducing gases such as CO gas, which converts NO in the flue gas 06 X ② The water vapor reacts with the fixed carbon in the pulverized coal to generate H2 gas and CO gas, which reduces the NO in the flue gas to XReduced to harmless nitrogen; ③ During the pyrolysis and gasification process of coal powder, most of the volatile nitrogen and part of the coke nitrogen in the coal powder are released into the gas phase, and most of them are converted into harmless nitrogen in a strong reducing atmosphere. Furthermore, all the final products of the above reactions enter the rotary denitrification device 01 through the connected common flue.

[0056] The main chemical reactions occurring in the penetration type denitrification device 02 are as follows:

[0057] C+O2→CO2+Q (exothermic reaction)

[0058] 2C+O2→2CO+Q (exothermic reaction)

[0059] C+H2O(g)→CO+H2-Q (water gas reaction, endothermic reaction)

[0060] 2CO+2NO→N2+2CO2 (denitrification reaction)

[0061] 2H2+2NO→N2+2H2O (denitrification reaction).

[0062] (2) When the flue gas from the penetrating denitrification device 02 (temperature of about 900°C to 1200°C, O2 concentration of about <1.5%) enters the rotary denitrification device 01, the mixture of tail coal powder and water vapor (wherein the tail coal powder accounts for about 70% of the total tail coal powder) enters the rotary denitrification device 01 through two first nozzles 03-1 to form a gas-solid two-phase rotating fluidized bed, such as Figure 2 and Figure 3 In this rotating flow field, the residence time of coal powder and water vapor is extended, and the mixing of coal powder and water vapor in the edge area of ​​the rising flue gas is more complete; at the same time, under the oxygen-poor high-temperature environment conditions inside the rotary denitrification device 01, the following physical and chemical reactions occur simultaneously: ① The volatile matter in the coal powder is pyrolyzed and gasified to produce reducing gases such as CO gas, which reduces the NO in the flue gas in the device 01. X ② The water vapor reacts with the fixed carbon in the coal powder to produce H2 gas and CO gas, which reduces the NO in the flue gas in the device 01. X ③ In the process of pyrolysis and gasification of coal powder, most of the volatile nitrogen and part of the coke nitrogen in the coal powder are released into the gas phase, and most of them are converted into harmless nitrogen in a strong reducing atmosphere; that is to say, most of the fuel-type NO generated in the pyrolysis and gasification process of coal powder, which accounts for about 70% of the total amount of tail coal powder, is converted into harmless nitrogen. X , is reduced to harmless nitrogen by reducing gases such as H2 and CO. Further, all the final products of the above reactions enter the decomposition furnace 12 through the connected common flue and the decomposition furnace cone 13.

[0063] The main chemical reactions occurring in the rotary denitration device 01 are as follows:

[0064] 2C+O2→2CO+Q (exothermic reaction)

[0065] C+H2O(G)→CO+H2-Q (water gas reaction, endothermic reaction)

[0066] 2CO+2NO→N2+2CO2 (denitrification reaction)

[0067] 2H2+2NO→N2+2H2O (denitrification reaction).

[0068] (3) The rising flue gas (the temperature of which is usually controlled within the range of 900°C to 1200°C) from the rotary denitrification device 01 enters the decomposition furnace 12. The rising flue gas contains H2 gas, CO gas, CO2 gas, N2 gas, coal coke, semi-coke, ash, and a small amount of unreacted coal powder, which re-burns after encountering the tertiary wind in the decomposition furnace 12 to complete the decomposition of calcium carbonate.

[0069] Taking a clinker production line with a designed output of 5,000 tons / day as an example, the denitrification system of this embodiment is fully adopted, and the NO X The concentration level is about 150 mg / Nm when no other denitrification technology is used. 3 The NO content of other denitrification technologies is much lower than that of other denitrification technologies. X Content level (in most cases ≥400mg / Nm 3 , usually 400mg / Nm 3 ~600mg / Nm 3 ). X When the SNCR denitrification technology is used in combination with NO X Emissions <50mg / Nm 3 Under the premise of the requirements, the theoretical dosage of SNCR denitrification ammonia water (20% concentration) is about <1 kg / ton of clinker.

[0070] The utility model denitrification system is used. Under the temperature condition of about 1000℃, the H2 gas and CO gas with the same concentration have a higher denitrification rate than H2 gas. X The reduction efficiency is CO to NO X The efficiency is 3 to 4 times higher; therefore, a water vapor nozzle is added to the nozzle of the utility model system, so that the water vapor sprayed from the nozzle and the fixed carbon in the coal powder establish a water-gas chemical reaction system. The reaction product of this reaction system not only increases the concentration of CO gas, but more importantly, greatly increases the concentration of H2 gas at the same time, thereby improving the denitrification efficiency of the system.

[0071] Furthermore, in the above-mentioned rotary denitration device and the above-mentioned penetration denitration device, the pyrolysis and gasification of pulverized coal volatiles, water-gas reaction, denitration reaction and other physical and chemical processes all require additional heat to be continuously completed. In the utility model, the continuous, stable and sufficient heat carried by the secondary air flue gas and generated by the full combustion of the rotary kiln head coal is cleverly used as the heat source for the above-mentioned physical and chemical reactions, thereby fully ensuring the progress of the above-mentioned physical and chemical reactions.

[0072] Furthermore, by adjusting the amount of water vapor sprayed into the rotary denitrification device and the penetrating denitrification device, the reaction intensity of the water-gas reaction in the above-mentioned devices can be regulated, thereby achieving the control of the temperature inside the rotary denitrification device and the penetrating denitrification device to always be within a reasonable range.

[0073] Furthermore, if other denitrification technologies have been used in the original clinker production system, or the nitrogen content of pulverized coal is low, the original system NO X When the overall emission level is low, a rotary denitrification device or a penetrating denitrification device can be installed separately to obtain the most cost-effective NO X Emission-compliant denitrification methods.

[0074] Furthermore, the spatial position of the rotary denitrification device and the penetrating denitrification device can be exchanged in the upper and lower order according to the spatial conditions of the original clinker production equipment, and the denitrification effect after the exchange is not significantly different from that before the exchange.

[0075] In addition to generating reducing H2 gas and CO gas, the water vapor injected into the system of the utility model also plays an important role in regulating the temperature in the system within a reasonable range. By adjusting the amount of water vapor injected from the first nozzle of the rotary denitrification device 01 and the second nozzle of the penetrating denitrification device 02, the temperature in the rotary denitrification device 01 and the penetrating denitrification device 02 can be regulated. The principle is as follows: in the chemical reaction occurring in the rotary denitrification device 01 and the penetrating denitrification device 02, the water-gas reaction C+H2O(G)→CO+H2 is a strong endothermic reaction; by adjusting the amount of water vapor (or molar equivalent), the probability of the water-gas reaction is adjusted, so that the temperature in the rotary denitrification device 01 and the penetrating denitrification device 02 is within a reasonable range, which enables the coal powder to form tiny char or semi-char particles after gasification, and then can be carried by the flue gas to smoothly enter the decomposition furnace for re-combustion, avoiding the situation where the coal powder ash melts due to excessive local temperature in the system (mainly the rotary denitrification device 01) and forms a crust and agglomerates and adheres to the inner wall of the equipment, affecting the normal operation of the equipment. Specifically, when the amount of water vapor is increased, the probability of the water-gas reaction increases, more heat is consumed by the endothermic reaction, and the temperature inside the rotary denitrification device 01 and the penetrating denitrification device 02 will decrease; otherwise, the temperature will increase. This temperature range needs to be set according to the ash melting temperature of the coal powder used, and is usually about 900°C to 1200°C.

[0076] The utility model cleverly sets a denitration device at the original flue location, where there is less cement material, which has less interference with the denitration reaction, resulting in a good denitration effect. The denitration system of the utility model is used in conjunction with the SNCR denitration technology to meet the environmental protection requirements for ultra-low emissions in the cement production industry in the aforementioned "Opinion".

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the content of the present invention.

Claims

1. A system for denitrification of cement kiln flue gas, characterized in that: The invention comprises a rotary denitrification device (01) arranged at the rising flue (15) of a cement kiln, wherein the rotary denitrification device (01) comprises a hollow and funnel-shaped cylinder (16), wherein a plurality of first nozzles (03-1) for spraying tail coal and water vapor into the inner cavity of the cylinder (16) are arranged on the cylinder wall, and all the first nozzles (03-1) are deflected to the same side at the same angle.

2. The system according to claim 1, characterized in that: The angle at which the first nozzle (03-1) is deflected to the same side is the angle between the nozzle axis and the tangent line of the cylinder circumference at the nozzle location, and the angle does not exceed 75°.

3. The system according to claim 1, characterized in that: The first nozzle (03-1) is an integrated nozzle capable of simultaneously and separately spraying coal powder and water vapor, or comprises a first coal powder nozzle (03-2) and a first water vapor nozzle (03-3) which are independently arranged.

4. The system according to any one of claims 1 to 3, characterized in that: It also includes a penetrating denitrification device (02) disposed on the ascending flue and connected to the rotary denitrification device (01), wherein the penetrating denitrification device (02) includes a pipe body (17) and a plurality of second nozzles (04-1) installed on the side wall of the pipe body (17) for spraying tail coal and water vapor into the inner cavity of the pipe body (17).

5. The system according to claim 4, characterized in that: The second nozzle (04-1) faces the central axis of the tube body (17).

6. The system according to claim 5, characterized in that: The first nozzle (03-1) and the second nozzle (04-1) are respectively arranged in the horizontal direction, or at an angle with the horizontal direction; the first pulverized coal nozzle (03-2) and the first water vapor nozzle (03-3) are arranged at intervals on the same horizontal plane, or are arranged symmetrically in the vertical direction of the cylinder (16); the second pulverized coal nozzle (04-2) and the second water vapor nozzle (04-3) are arranged at intervals on the same horizontal plane, or are arranged symmetrically in the vertical direction of the tube (17).

7. The system according to claim 6, characterized in that: The rotary denitrification device (01) and the penetrating denitrification device (02) are arranged from bottom to top or from top to bottom at the position of the ascending flue (15); the cylinder (16) of the rotary denitrification device (01) and the tube (17) of the penetrating denitrification device (02) are arranged coaxially or non-coaxially; the cylinder (16) and the tube (17) are arranged coaxially or non-coaxially with the ascending flue (15).

8. The system according to claim 4, characterized in that: The water vapor inlet of the first nozzle (03-1) is connected to a steam generator, or to an exhaust steam pipeline of a waste heat power generation device of a cement kiln; the water vapor inlet of the second nozzle (04-1) is connected to a steam generator, or to an exhaust steam pipeline of a waste heat power generation device of a cement kiln.

9. The system according to claim 1, characterized in that: A temperature detection device (05) is provided in the cylinder (16) of the rotary denitration device (01).

10. A cement kiln production system, comprising a rotary kiln (11), a decomposition furnace (12), and an ascending flue (15) connecting the rotary kiln (11) and the decomposition furnace (12), characterized in that: It also includes a system for denitrifying cement kiln flue gas as described in any one of claims 1 to 9, which is arranged at the position of the ascending flue (15), and no tail coal inlet (08) is provided on the decomposition furnace (12).

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