A device and method for reducing NO by using active gas to temper pulverized coal for reburning x ​

Abstract

The present invention discloses a method for reducing NO by reburning pulverized coal conditioned with active gas x The method includes the following steps: medium and high volatile coal fuel is carried by primary air and injected into the main burner on one side of the pulverized coal combustion chamber, and hot air enters the main combustion zone through the main burner in sequence; the medium and high volatile coal fuel is carried by recirculating flue gas and enters the reburner above the main burner through the reburn pulverized coal pipeline and the reburn pulverized coal nozzle, and the conditioning gas enters the reburner through the conditioning gas pipeline, the conditioning gas nozzle and the reburn pulverized coal nozzle in sequence. The medium and high volatile coal fuel and the conditioning gas are mixed in the reburner and then enter the reburn zone; hot air enters the burnout zone through the separated overfire air pipeline, the separated overfire air nozzle and the burnout burner above the reburner to burn out the combustion products. By adopting the above steps, the present invention uses the conditioning gas to condition the solid fuel, which not only ensures the effect of reducing NO x emissions, but also alleviates problems such as poor burnout caused by using a high proportion of reburn pulverized coal.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler combustion, and particularly to a device and method for reducing NO by using active gas-conditioned pulverized coal reburning x . Background Art

[0002] Thermal power is the main source of electricity in China. The state has been increasing its efforts in controlling air pollution, and all coal-fired power plants in the country that are eligible for transformation have achieved ultra-low emissions, with the nitrogen oxide emission concentration not exceeding 50 mg / m 3 (at a reference oxygen content of 6%).

[0003] Currently, measures for controlling NO x emissions in boilers include post-combustion flue gas purification and low-NO x combustion technologies. The post-combustion flue gas purification technology (SCR technology) can significantly reduce NO x emissions, but its initial investment is huge and the operating cost is expensive. The low-NO x combustion technology is an in-furnace combustion technology that adopts measures such as low-NO x burners, fuel staging, and air staging. It is widely used because of its small initial investment and zero or very low operating cost.

[0004] When using the low-NO x combustion technology, the NO x emission level is 130 - 400 mg / m 3 , achieving the effect of controlling NO x emissions at the source. The traditional pulverized coal reburning technology uses air to transport the reburning pulverized coal to the reburning zone, and the reburning pulverized coal burns to produce nitrogen-based active substances, which react with the NO x produced by the combustion of pulverized coal in the main combustion zone, so as to achieve the purpose of reducing NO x emissions.

[0005] However, traditional coal-fired power plants use air to transport the reburning pulverized coal, and the oxygen contained in the powder-transporting air consumes a large amount of the reburning pulverized coal at the initial stage of reburning. In order to ensure the amount of pulverized coal that can participate in reducing NO x after the air is basically exhausted, it is necessary to increase the proportion of the reburning pulverized coal to about 30%. Due to the short burnout time of the reburning pulverized coal, a high proportion of the reburning pulverized coal will lead to a series of problems such as poor burnout of the boiler and limited operation and adjustment methods. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for reducing NO by using active gas-conditioned pulverized coal reburning x , which can ensure the effect of reducing NO x emissions and relieve problems such as poor burnout caused by the use of a high proportion of reburning pulverized coal.

[0007] To achieve the above object, the present invention provides a method for reducing NO by reburning pulverized coal conditioned with active gas, x which comprises the following steps:

[0008] S1. 75-90% of medium and high volatile coal fuel is carried by primary air and sequentially passes through the primary air duct, the primary air nozzle and the main burner on one side of the pulverized coal combustion chamber, and hot air sequentially passes through the secondary air duct, the secondary air nozzle and the main burner to enter the main combustion zone;

[0009] The primary air ratio accounts for 10-50%, and the secondary air ratio accounts for 50-90%.

[0010] S2. 10-25% of medium and high volatile coal fuel is carried by recirculating flue gas and enters the reburner above the main burner through the reburned pulverized coal duct and the recirculating flue gas nozzle. At the same time, 0-6% of the conditioning gas sequentially passes through the conditioning gas duct, the conditioning gas nozzle and the recirculating flue gas nozzle to enter the reburner. The medium and high volatile coal fuel and the conditioning gas are mixed in the reburner and then enter the reburn zone. As soon as the medium and high volatile coal fuel is sprayed into the reburn zone, it is quickly activated by the conditioning gas into gaseous CH i , CO, OH and H and highly reactive coke;

[0011] S3. Hot air sequentially passes through the separated overfire air duct, the separated overfire air nozzle and the overfire burner above the reburner to enter the burnout zone and burn out the combustion products.

[0012] Preferably, the excess air coefficient in the main combustion zone is controlled at 0.65-1.05, and the residence time of the flue gas is controlled at 0.2-1.4 s.

[0013] Preferably, the excess air coefficient in the reburn zone is 0.6-0.95, and the residence time of the flue gas is controlled at 0.2-1.3 s.

[0014] Preferably, the excess air coefficient in the burnout zone is 1.05-1.4, and the residence time of the flue gas is controlled at 0.2-1.8 s.

[0015] Preferably, the recirculating flue gas includes CO2 = 10-18%, O2 = 4-10%, N2 = 66-80%, H2O = 0-16%.

[0016] Preferably, the conditioning gas includes one or more of natural gas, carbon monoxide, hydrogen, methane, coal gas and unsaturated hydrocarbon gases.

[0017] The above method for reducing NO by reburning pulverized coal conditioned with active gas xThe method uses a device, including a pulverized coal combustion chamber with a main combustion zone, a reburning zone, and a burnout zone arranged in sequence from bottom to top. The main burner connected to the main combustion zone is provided with a primary air nozzle and a secondary air nozzle. The reburning burner connected to the reburning zone is provided with a reburning pulverized coal nozzle, and the reburning pulverized coal nozzle is connected to a conditioning gas nozzle. The burnout burner connected to the burnout zone is provided with a separated burnout air nozzle.

[0018] Preferably, one end of the primary air nozzle far from the main burner is connected to the primary air duct, and one end of the secondary air nozzle far from the main burner is connected to the secondary air duct.

[0019] Preferably, one end of the reburning pulverized coal nozzle far from the reburning burner is respectively connected to the reburning pulverized coal duct and the conditioning gas nozzle, and one end of the conditioning gas nozzle far from the reburning burner is connected to the conditioning gas duct.

[0020] Preferably, one end of the separated burnout air nozzle far from the burnout burner is connected to the separated burnout air duct.

[0021] Therefore, the beneficial effects of the present invention adopting the above technical solutions are as follows:

[0022] 1. The present invention arranges the conditioning gas nozzle at the reburning burner, and uses the principle of intensified combustion to make the conditioning gas fully react with oxygen, consuming the excess oxygen in the recirculated flue gas through the combustion reaction, that is, a stable conditioning zone with a strong reducing property and appropriate temperature can be obtained by using a smaller amount of combustible gas volume, and then the fuel is conditioned, which not only ensures the effect of reducing NO x emissions, but also reduces the proportion of reburning pulverized coal;

[0023] 2. The present invention cleverly uses the active gas as the conditioning gas to condition the reburning pulverized coal, which can not only ensure the effect of reducing NO x emissions, but also minimize the usage amount of expensive conditioning gas to ensure the economy of the device investment and operation;

[0024] 3. The present invention uses the conditioning gas to condition the reburning pulverized coal. The conditioning gas reacts rapidly with the oxygen in the recirculated flue gas, releasing a large amount of reducing free radicals, protecting the active sites on the surface of the char, enhancing the ability of the char to reduce NO, improving the removal efficiency of NO x , and increasing the specific surface area of the char after the conditioning gas activation;

[0025] 4. The device provided by the present invention is convenient to arrange and has strong coal type adaptability.

[0026] The following further describes the technical solutions of the present invention in detail through the drawings and embodiments. Brief Description of the Drawings

[0027] Figure 1 It is a method for using active gas to condition pulverized coal reburning to reduce NOx Schematic diagram of the device;

[0028] Figure 2 It is a combined graph of NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 of the present invention,

[0029] wherein, Figure 2 in (a), it is a graph of the change trend of NO concentration when Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 reduce NO,

[0030] Figure 2 in (b), it is a comparison graph of the NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1;

[0031] Figure 3 It is a combined graph of the specific surface areas of char in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 of the present invention,

[0032] wherein, Figure 3 in (a), it is a comparison graph of the specific surface areas of activated char in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1,

[0033] Figure 3 in (b), it is a comparison graph of the pore volumes of different activated chars in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1;

[0034] Figure 4 It is the NO x removal efficiency curve graph in Example 8 and Comparative Example 1 and Comparative Example 2 of the present invention.

[0035] Reference numerals

[0036] 1, main burner; 2, reburn burner; 3, conditioning gas nozzle; 4, overfire burner; 5, pulverized coal combustion chamber. Detailed implementation manners

[0037] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0038] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0039] Example 1

[0040] A method and apparatus for reducing NO by reburning pulverized coal conditioned with active gas x The apparatus for the method includes a pulverized coal combustion chamber 5 having a main combustion zone, a reburning zone, and an overfire zone sequentially arranged from bottom to top. The main burner 1 communicating with the main combustion zone is provided with a primary air nozzle and a secondary air nozzle. The reburning burner 2 communicating with the reburning zone is provided with a reburning pulverized coal nozzle, and the reburning pulverized coal nozzle is communicated with a conditioning gas nozzle 3. The overfire burner 4 communicating with the overfire zone is provided with a separated overfire air nozzle.

[0041] One end of the primary air nozzle away from the main burner 1 is communicated with the primary air duct, and one end of the secondary air nozzle away from the main burner 1 is communicated with the secondary air duct. Hot air A enters the main combustion zone through the secondary air duct and the secondary air nozzle of the main burner 1 in sequence, and the mixed gas flow B of primary air and pulverized coal enters the main combustion zone through the primary air duct and the primary air nozzle of the main burner 1 in sequence.

[0042] One end of the reburning pulverized coal nozzle away from the reburning burner 2 is respectively communicated with the reburning pulverized coal duct and the conditioning gas nozzle, and one end of the conditioning gas nozzle 3 away from the reburning burner is communicated with the conditioning gas duct. The recirculated flue gas, hot air and the mixed gas flow C of reburning pulverized coal enter the reburning zone through the reburning pulverized coal duct and the reburning burner 2 in sequence. The conditioning gas D enters the reburning zone through the conditioning gas duct, the conditioning gas nozzle 3 and the reburning burner 2 in sequence.

[0043] The conditioning gas nozzle 3 is arranged at the outlet of the reburning pulverized coal nozzle. By using the principle of intensified combustion, the conditioning gas can fully react with oxygen, and can quickly react with the oxygen in the carrier gas to form a conditioning zone at the front end of the nozzle of the reburning burner 2. The excess oxygen in the recirculated flue gas is consumed through the combustion reaction, that is, a stable conditioning zone with strong reducibility and appropriate temperature can be obtained with a smaller amount of combustible gas, and then the fuel is conditioned. Gaseous reducing molecules (CHi such as CO, OH, and H) and NO x A homogeneous reduction reaction occurs. This not only ensures the effect of reducing NO x emissions but also reduces the proportion of reburned pulverized coal.

[0044] One end of the separated overfire air nozzle far from the overfire burner 4 is connected to the separated overfire air duct, and hot air A enters the overfire zone successively through the separated overfire air duct and the separated overfire air nozzle.

[0045] Example 2

[0046] A combustion method for a device that uses active gas to condition pulverized coal for reburning to reduce NO x is as follows. As shown in Figure 1 the figure, it includes the following steps: S1. 75% of the high-volatile coal fuel is carried by the primary air and enters the main combustion zone successively through the primary air duct, the primary air nozzle, and the main burner on one side of the pulverized coal combustion chamber. The primary air rate accounts for 35%. The hot air enters the main combustion zone successively through the secondary air duct, the secondary air nozzle, and the main burner. The secondary air rate accounts for 65%. The excess air coefficient in the main combustion zone is controlled at 0.65, and the residence time in the main combustion zone is controlled at about 1.2 s.

[0047] S2. 25% of the medium-high-volatile coal fuel is carried by the recirculating flue gas and enters the reburn burner above the main burner through the reburned pulverized coal duct. The composition of the recirculating flue gas is N2:CO2:O2 = 80:16:4. At the same time, 2% of the conditioning gas methane CH4 enters the reburn burner successively through the conditioning gas duct, the conditioning gas nozzle, and the recirculating flue gas nozzle. The medium-high-volatile coal fuel and the conditioning gas are mixed in the reburn burner and then enter the reburn zone. The excess air coefficient in the reburn zone is 0.6, and the residence time in the reburn zone is controlled at 1.1 s.

[0048] S3. The hot air enters the overfire zone successively through the separated overfire air duct, the separated overfire air nozzle, and the overfire burner above the reburn burner to burn out the combustion products. The excess air coefficient in the overfire zone is 1.4, and the residence time is controlled at 1.0 s to burn out the residual carbon.

[0049] Example 3

[0050] A combustion method for a device that uses active gas to condition pulverized coal for reburning to reduce NO x includes the following steps: S1. 80% of the high-volatile coal fuel is carried by the primary air and sprayed into the main combustion zone successively through the primary air duct and the primary air nozzle. The primary air rate accounts for 30%. The hot air enters the main combustion zone successively through the secondary air duct and the secondary air nozzle. The secondary air rate accounts for 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0051] S2. 20% of the high-volatile coal fuel is carried by the recirculating flue gas through the reclaimed pulverized coal pipeline and enters the reburning burner. The composition of the recirculating flue gas is N2:CO2:O2 = 80:16:4. Meanwhile, 3% of the conditioning gas methane CH4 enters the reburning burner through the conditioning gas pipeline, the conditioning gas nozzle, and the recirculating flue gas nozzle in sequence. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0052] S3. The hot air passes through the separated overfire air pipeline and the separated overfire air nozzle in sequence and enters the burnout burner to burn out the combustion products. The excess air coefficient in the burnout zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0053] Example 4

[0054] A combustion method for a device using active gas to condition pulverized coal reburning to reduce NO x When the coal type is Shenhua bituminous coal, 85% of the fuel is carried by the primary air and sprayed into the main combustion zone through the primary air pipeline and the primary air nozzle in sequence. The primary air rate accounts for 20%. The hot air enters the main combustion zone through the secondary air pipeline and the secondary air nozzle in sequence. The secondary air rate accounts for 80%. The excess air coefficient in the main combustion zone is controlled at 0.9, and the residence time in the main combustion zone is controlled at about 0.8 s.

[0055] S2. 15% of the high-volatile coal fuel is carried by the recirculating flue gas through the reclaimed pulverized coal pipeline and enters the reburning burner. The composition of the recirculating flue gas is N2:CO2:O2 = 80:12:8. Meanwhile, 4% of the conditioning gas CH4 enters the reburning burner through the conditioning gas pipeline, the conditioning gas nozzle, and the recirculating flue gas nozzle in sequence. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.8, and the residence time in the reburning zone is controlled at 0.8 s.

[0056] S3. The hot air passes through the separated overfire air pipeline and the separated overfire air nozzle in sequence and enters the burnout burner to burn out the combustion products. The excess air coefficient in the burnout zone is 1.2, and the residence time is controlled at 1.2 s to burn out the residual carbon.

[0057] Example 5

[0058] A combustion method for a device using active gas to condition pulverized coal reburning to reduce NO xCombustion method of the device, comprising the following steps: S1. 90% of the high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through the primary air duct and the primary air nozzle in sequence. The primary air rate accounts for 10%. Hot air enters the main combustion zone through the secondary air duct and the secondary air nozzle in sequence. The secondary air rate accounts for 90%. The excess air coefficient in the main combustion zone is controlled at 1.05, and the residence time in the main combustion zone is controlled at about 0.6 s.

[0059] S2. 15% of the high-volatile coal fuel is carried by recycled flue gas and enters the reburning burner through the reburning pulverized coal duct. The composition of the recycled flue gas is N2:CO2:O2 = 80:10:10. At the same time, 5% of the conditioning gas CH4 enters the reburning burner through the conditioning gas duct, the conditioning gas nozzle and the recycled flue gas nozzle in sequence. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.9, and the residence time in the reburning zone is controlled at 0.6 s.

[0060] S3. Hot air enters the burnout burner through the separated overfire air duct and the separated overfire air nozzle in sequence to burn out the combustion products. The excess air coefficient in the burnout zone is 1.1, and the residence time is controlled at 1.3 s to burn out the residual carbon.

[0061] Example 6

[0062] A combustion method for reducing NO by reburning pulverized coal with active gas conditioning x Combustion method of the device, comprising the following steps: S1. 80% of the high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through the primary air duct and the primary air nozzle in sequence. The primary air rate accounts for 30%. Hot air enters the main combustion zone through the secondary air duct and the secondary air nozzle in sequence. The secondary air rate accounts for 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0063] S2. 20% of the high-volatile coal fuel is carried by recycled flue gas and enters the reburning burner through the reburning pulverized coal duct. The composition of the recycled flue gas is N2:CO2:O2 = 80:14:6. At the same time, 3% of the coal gas enters the reburning burner through the conditioning gas duct, the conditioning gas nozzle and the recycled flue gas nozzle in sequence. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0064] The composition of the coal gas is CH4 = 10%, CO = 60%, H2 = 30%.

[0065] S3. Hot air enters the burnout burner through the separated overfire air duct and the separated overfire air nozzle in sequence to burn out the combustion products. The excess air coefficient in the burnout zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0066] Example 7

[0067] A combustion method for a device that uses active gas to condition pulverized coal for reburning to reduce NO x comprises the following steps: S1. 80% of the high-volatile coal fuel is carried by primary air and sequentially sprayed into the main combustion zone through the primary air duct and the primary air nozzle. The primary air ratio is 30%. Hot air sequentially enters the main combustion zone through the secondary air duct and the secondary air nozzle. The secondary air ratio is 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0068] S2. 20% of the high-volatile coal fuel is carried by recirculating flue gas and enters the reburning burner through the reburning pulverized coal duct. The composition of the recirculating flue gas is N2:CO2:O2 = 80:14:6. Meanwhile, 3% of hydrogen gas H2 sequentially enters the reburning burner through the conditioning gas duct, the conditioning gas nozzle, and the recirculating flue gas nozzle. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0069] S3. Hot air sequentially enters the burnout burner through the separated overfire air duct and the separated overfire air nozzle to burn out the combustion products. The excess air coefficient in the burnout zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0070] Example 8

[0071] A combustion method for a device that uses active gas to condition pulverized coal for reburning to reduce NO x comprises the following steps: S1. 90% of the high-volatile coal fuel is carried by primary air and sequentially sprayed into the main combustion zone through the primary air duct and the primary air nozzle. The primary air ratio is 30%. Hot air sequentially enters the main combustion zone through the secondary air duct and the secondary air nozzle. The secondary air ratio is 70%. The excess air coefficient in the main combustion zone is controlled at 0.8, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0072] S2. 15% of the high-volatile coal fuel is carried by recirculating flue gas and enters the reburning burner through the reburning pulverized coal duct. The composition of the recirculating flue gas is N2:CO2:O2 = 80:10:10. Meanwhile, 5% of the conditioning gas CH4 sequentially enters the reburning burner through the conditioning gas duct, the conditioning gas nozzle, and the recirculating flue gas nozzle. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.85, and the residence time in the reburning zone is controlled at 0.8 s.

[0073] S3. Hot air passes through the separated overfire air duct and the separated overfire air nozzle in sequence and enters the burnout burner to burn out the combustion products. The excess air coefficient in the burnout zone is 1.15, and the residence time is controlled at 1.0 s to burn out the residual carbon.

[0074] Example 9

[0075] A combustion method for a device using active gas to condition pulverized coal reburning to reduce NO x includes the following steps. S1. 80% of the high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through the primary air duct and the primary air nozzle in sequence. The primary air rate accounts for 30%. Hot air passes through the secondary air duct and the secondary air nozzle in sequence and enters the main combustion zone. The secondary air rate accounts for 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0076] S2. 20% of the high-volatile coal fuel is carried by recirculating flue gas and enters the reburning burner through the reburning pulverized coal duct. The composition of the recirculating flue gas is N2:CO2:O2 = 80:16:4. At the same time, 3% of the conditioning gas carbon monoxide CO passes through the conditioning gas duct, the conditioning gas nozzle and the recirculating flue gas nozzle in sequence and enters the reburning burner. The high-volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0077] S3. Hot air passes through the separated overfire air duct and the separated overfire air nozzle in sequence and enters the burnout burner to burn out the combustion products. The excess air coefficient in the burnout zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0078] Comparative Example 1

[0079] S1. 80% of the high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through the primary air duct and the primary air nozzle in sequence. The primary air rate accounts for 30%. Hot air passes through the secondary air duct and the secondary air nozzle in sequence and enters the main combustion zone. The secondary air rate accounts for 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0080] S2. 20% of the high-volatile coal fuel is carried by circulating flue gas and enters the reburning burner through the reburning pulverized coal duct and then enters the reburning zone. The composition of the circulating flue gas is N2:CO2:O2 = 80:14:6. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0081] S3. Hot air passes through the separated overfire air duct and the separated overfire air nozzle in sequence and enters the burnout burner to burn out the combustion products. The excess air coefficient in the burnout zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0082] Comparative Example 2

[0083] S1. 80% of the high-volatile coal fuel is carried by primary air and sequentially enters the main combustion zone through the primary air duct and the primary air nozzle. The primary air ratio accounts for 30%. Hot air sequentially enters the main combustion zone through the secondary air duct and the secondary air nozzle, and the secondary air ratio accounts for 70%. The excess air coefficient in the main combustion zone is controlled at 0.75, and the residence time in the main combustion zone is controlled at about 1.0 s.

[0084] S2. 20% of the high-volatile coal fuel is carried by hot air and enters the reburning zone through the reburning pulverized coal duct and then enters the reburning burner. The excess air coefficient in the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

[0085] S3. Hot air sequentially passes through the separated overfire air duct and the separated overfire air nozzle and enters the overfire burner to burn out the combustion products. The excess air coefficient in the overfire zone is 1.3, and the residence time is controlled at 1.1 s to burn out the residual carbon.

[0086] Test Example 1

[0087] a. Use a micro-fluidized bed reactor analyzer (MFBRA) to test the NO reduction ability

[0088] The MFBRA system quickly heats the sample and uses a mass spectrometer to monitor the gaseous products after combustion, so as to obtain the actual conversion process of char. The test temperature is 1073 K, and the test atmosphere is the reburning zone atmosphere simulating pulverized coal (4% O2, 20% CO2, 500 ppm NO, and the rest is Ar). Each experiment uses a 3 ± 0.01 mg sample.

[0089] In the data processing process, in order to facilitate the comparison of the NO reduction abilities of Example 3 (methane), Example 6 (coal gas), Example 7 (hydrogen), Example 9 (carbon monoxide) and Comparative Example 1 (recirculated flue gas), all NO reduction ability data are normalized to 1 mg. Through preliminary experiments, it is proved that all samples have completed the reaction within 10 s. In the case of trace samples, it is assumed that the NO reduction amount is proportional to the mass of the measured sample in the reactor. The instantaneous NO concentration is integrated with respect to the reaction time, and the absolute value of the area under the line of NO concentration of 500 ppm is A1. The absolute value of the area above the line of NO concentration of 500 ppm is A2. The difference between A1 and A2 represents the ability of the char to reduce NO.

[0090] As Figure 2 shown, Figure 2 in (a) is the NO concentration change trend when Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 reduce NO; Figure 2Among them, (b) is the comparison chart of NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1. From Figure 2 it can be seen that compared with the separate circulating flue gas for transporting pulverized coal in Comparative Example 1, the NO reduction ability of coke after activation by CH4 in Example 3 increased by nearly 75%, the NO reduction ability of coke after activation by CO in Example 9 increased by nearly 5%, and the NO reduction ability of coke after activation by H2 in Example 7 increased by nearly 19%.

[0091] b. Specific surface area test

[0092] As Figure 3 shown, Figure 3 among them, (a) is the comparison chart of specific surface areas of activated coal cokes in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1, Figure 3 among them, (b) is the comparison chart of pore volumes of different activated coal cokes in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1. In Example 3 (methane), Example 6 (coal gas), Example 7 (hydrogen), Example 9 (carbon monoxide) and Comparative Example 1 (circulating flue gas), compared with the separate circulating flue gas for transporting pulverized coal in Comparative Example 1, the specific surface area of coke after activation by CH4 in Example 3 increased by nearly 54.2%, the specific surface area of coke after activation by CO in Example 9 increased by nearly 3%, and the specific surface area of coke after activation by H2 in Example 7 increased by nearly 12.3%. It can be seen that the combustion method of the present invention utilizes the heat instantaneously released by the combustion of the conditioning gas and oxygen to promote the release of volatile matter, thereby enriching the pore structure of the coal coke.

[0093] c. NO x removal efficiency

[0094] As Figure 4 shown, compared with Comparative Example 2, the NO x removal efficiency in Example 8 increased by 36.9%, and compared with Comparative Example 1, the NO x removal efficiency in Example 8 increased by 22.2% (at the level of 6% oxygen content in the flue gas after conversion).

[0095] Therefore, the present invention adopts a device and method for using an active gas to condition pulverized coal for reburning to reduce NO x . By using the conditioning gas to condition the solid fuel, it not only ensures the effect of reducing NO x emissions, but also alleviates problems such as poor burnout caused by using a high proportion of reburning pulverized coal.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements do not cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for reducing NO by reburning pulverized coal tempered with active gas x is characterized in that: It includes the following steps: S1. 75-90% of medium and high volatile coal fuel is carried by primary air and sprayed into the main burner on one side of the pulverized coal combustion chamber successively through the primary air pipeline and the primary air nozzle. Hot air enters the main combustion zone through the secondary air pipeline, the secondary air nozzle and the main burner successively. S2. 10 - 25% of the medium and high volatile coal fuel is carried by the recycled flue gas through the recycled pulverized coal pipeline and the recycled pulverized coal nozzle and enters the reburning burner above the main burner. At the same time, 0 - 6% of the conditioning gas sequentially passes through the conditioning gas pipeline, the conditioning gas nozzle and the recycled pulverized coal nozzle and enters the reburning burner. The medium and high volatile coal fuel and the conditioning gas are mixed in the reburning burner and then enter the reburning zone. As soon as the medium and high volatile coal fuel is injected into the reburning zone, it is quickly activated by the conditioning gas into gaseous CH i , CO, OH and H and highly reactive coke; S3. Hot air enters the burnout zone through the separated overfire air pipeline, the separated overfire air nozzle and the burnout burner above the reburning burner successively to burn out the combustion products.

2. A method for reducing NO by reburning pulverized coal tempered with active gas according to claim 1 x , characterized in that: The excess air coefficient in the main combustion zone is controlled at 0.65-1.05, and the residence time of the flue gas is controlled at 0.2-1.4 s.

3. A method for reducing NO by reburning pulverized coal conditioned with active gas according to claim 1 x , characterized in that: The excess air coefficient in the reburning zone is 0.6-0.95, and the residence time of the flue gas is controlled at 0.2-1.3 s.

4. A method for reducing NO by reburning pulverized coal tempered with active gas according to claim 1 x , characterized in that: The excess air coefficient in the burnout zone is 1.05-1.4, and the residence time of the flue gas is controlled at 0.2-1.8 s.

5. A method for reducing NO by reburning pulverized coal tempered with active gas according to claim 1 x , characterized in that: The recycled flue gas includes CO2 = 10-18%, O2 = 4-10%, N2 = 66-80%, H2O = 0-16%.

6. A method for reducing NO by reburning pulverized coal tempered with active gas according to claim 1 x , characterized in that: The conditioning gas includes one or more of natural gas, carbon monoxide, hydrogen, methane, coal gas and unsaturated hydrocarbon gases.

7. A device for the method of using active gas to temper pulverized coal for reburning to reduce NO according to any one of claims 1-6, characterized in that: x It includes a pulverized coal combustion chamber with a main combustion zone, a reburning zone and a burnout zone arranged successively from bottom to top. The main burner connected to the main combustion zone is provided with a primary air nozzle and a secondary air nozzle. The reburning burner connected to the reburning zone is provided with a reburning pulverized coal nozzle. The reburning pulverized coal nozzle is connected to a conditioning gas nozzle. The burnout burner connected to the burnout zone is provided with a separated overfire air nozzle.

8. A device for the method of using activated gas to temper pulverized coal for reburning to reduce NO x is characterized in that: One end of the primary air nozzle far from the main burner is connected to the primary air pipeline, and one end of the secondary air nozzle far from the main burner is connected to the secondary air pipeline.

9. A device for the method of reducing NO by reburning pulverized coal tempered with active gas according to claim 7, characterized in that: x One end of the reburning pulverized coal nozzle far from the reburning burner is respectively connected to the reburning pulverized coal pipeline and the conditioning gas nozzle, and one end of the conditioning gas nozzle far from the reburning burner is connected to the conditioning gas pipeline. ​ 10. A device for the method of using active gas to temper pulverized coal for reburning to reduce NO x is characterized in that: One end of the separated overfire air nozzle far from the burnout burner is connected to the separated overfire air pipeline.

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