WO2025137993A1 - Device and method for nox reduction using reburning of active gas-conditioned pulverized coal - Google Patents

Abstract

Disclosed in the present invention is a method for NO_x reduction using reburning of active gas-conditioned pulverized coal, comprising the following steps: medium-to-high volatile coal fuel is carried by primary air and injected into a main burner on one side of a pulverized coal combustion chamber, and hot air sequentially passes through the main burner to enter a main combustion zone; the medium-to-high volatile coal fuel is carried by recirculated flue gas to pass through a reburning pulverized coal pipe and a reburning pulverized coal nozzle and enter a reburning burner above the main burner, a conditioning gas sequentially passes through a conditioning gas pipe, a conditioning gas nozzle and the reburning pulverized coal nozzle and enters the reburning burner, and the medium-to-high volatile coal fuel and the conditioning gas are mixed inside the reburning burner and then enter a reburning zone; and the hot air sequentially passes through a separated overfire air pipe, a separated overfire air nozzle and a burnout burner above the reburning burner and enters a burnout zone, so as to achieve burnout of a combustion product. The present invention uses the described steps where a conditioning gas is used for conditioning solid fuel, thus ensuring the effect of reducing NO_x emissions while ameliorating the problem of poor burnout performance caused by using a high proportion of reburning pulverized coal.

Description

A device and method for reducing NOx by reburning coal powder using active gas conditioning Technical Field

The invention relates to the technical field of boiler combustion, and in particular to a device and method for reducing _NOx by reburning pulverized coal tempered by active gas.

Background Art

Thermal power is the main source of electricity in China. The country has continuously increased its efforts to control air pollution, and all coal-fired power plants in the country that are eligible for transformation have achieved ultra-low emissions, with nitrogen oxide emission concentrations not exceeding 50 mg/m ³ (baseline oxygen content 6%).

At present, the measures to control boiler _NOx emissions include post-combustion flue gas purification and low _NOx combustion technologies. Post-combustion flue gas purification technology (SCR technology) can significantly reduce _NOx emissions, but its initial investment is huge and its operating costs are expensive. Low _NOx combustion technology is an in-furnace combustion technology that uses low _NOx burners, fuel staging, air staging and other measures. It is widely used because of its small initial investment and zero or very low operating costs.

When low NO _x combustion technology is used, the NO _x emission level is 130~400 mg/m ³ , achieving the effect of controlling NO _x emissions at the source. Traditional pulverized coal reburning technology uses air to transport reburned pulverized coal to the reburning zone. The reburned pulverized coal burns to produce nitrogen-based active substances, which react with NO _x generated by the combustion of pulverized coal in the main combustion zone to reduce NO x emissions, thereby achieving the purpose of reducing NO _x emissions.

However, traditional coal-fired power plants use air to transport reburned coal powder, and the oxygen contained in the transported air consumes a large amount of reburned coal powder in the early stage of reburning. In order to ensure that the amount of coal powder can participate in the reduction of _NOx after the air is basically exhausted, the proportion of reburned coal powder needs to be increased to about 30%. Since the burnout time of reburned coal powder is short, a high proportion of reburned coal powder will cause a series of problems such as poor burnout of the boiler, limited operation and adjustment methods, etc.

Summary of the invention

The object of the present invention is to provide a device and method for reducing _NOx by reburning pulverized coal using active gas to ensure the effect of reducing _NOx emissions and alleviate the problems of poor burnout caused by using a high proportion of reburned pulverized coal.

To achieve the above object, the present invention provides a method for reducing NO _x by reburning pulverized coal tempered by active gas, comprising the following steps:

S1. The 75-90% medium-high volatile coal fuel is carried by the primary air through the primary air duct, the primary air nozzle and the main burner on one side of the pulverized coal combustion chamber, and the hot air enters the main combustion zone through the secondary air duct, the secondary air nozzle and the main burner in turn;

The primary air rate accounts for 10-50%, and the secondary air rate accounts for 50-90%.

S2, 10-25% of medium-high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe and the recirculating flue gas nozzle into the reburning burner above the main burner, and at the same time, 0-6% of the tempering gas enters the reburning burner through the tempering gas pipe, the tempering gas nozzle and the recirculating flue gas nozzle in sequence, and the medium-high volatile coal fuel and the tempering gas are mixed in the reburning burner and enter the reburning zone. Once the medium-high volatile coal fuel is sprayed into the reburning zone, it is quickly activated by the tempering gas into gaseous CH _i , CO, OH and H and highly reactive coke;

S3. The hot air passes through the separation burnout air duct, the separation burnout air nozzle and the burnout burner above the reburning burner in sequence and enters the burnout zone to burn out the combustion products.

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 about 0.2~1.4 s.

Preferably, the excess air coefficient in the reburning zone is 0.6~0.95, and the flue gas residence time is controlled at 0.2~1.3 s.

Preferably, the excess air coefficient in the burnout zone is 1.05~1.4, and the flue gas residence time is controlled at 0.2~1.8 s.

Preferably, the recirculated flue gas includes CO ₂ =10-18%, O ₂ =4-10%, N ₂ =66-80%, and H ₂ O =0-16%.

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

The above-mentioned method and device for reducing _NOx by tempering pulverized coal with active gas and then burning it comprises a pulverized coal combustion chamber which is provided with a main combustion zone, a reburning zone and a burnout zone 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, the reburning pulverized coal nozzle is connected with a tempering gas nozzle, and the burnout burner connected to the burnout zone is provided with a separation burnout air nozzle.

Preferably, one end of the primary air nozzle away from the main burner is connected to the primary air duct, and one end of the secondary air nozzle away from the main burner is connected to the secondary air duct.

Preferably, one end of the reburning pulverized coal nozzle away from the reburning burner is respectively connected to the reburning pulverized coal pipeline and the tempering gas nozzle, and one end of the tempering gas nozzle away from the reburning burner is connected to the tempering gas pipeline.

Preferably, one end of the separation overburnt air nozzle away from the overburnt burner is connected to the separation overburnt air duct.

Therefore, the beneficial effects of the present invention using the above technical solution are:

1. The present invention arranges the tempering gas nozzle at the reburning burner, and utilizes the principle of enhanced combustion to make the tempering gas fully react with oxygen, and consumes the excess oxygen in the recirculated flue gas through the combustion reaction, that is, a stable tempering zone with strong reducing property and suitable temperature can be obtained with a small amount of combustible gas, thereby tempering the fuel, which not only ensures the effect of reducing _NOx emissions, but also reduces the proportion of reburned coal powder;

2. The present invention ingeniously uses active gas as conditioning gas to condition the reburned coal powder, which can not only ensure the effect of reducing NO _x emissions, but also minimize the use of expensive conditioning gas, ensuring the economic efficiency of device investment and operation;

3. The present invention uses conditioning gas to condition the reburned coal powder. The conditioning gas reacts rapidly with oxygen in the circulating flue gas to release a large number of reducing free radicals, protect the active sites on the surface of coal coke, enhance the ability of coke to reduce NO, improve the removal efficiency of NO _x , and increase the specific surface area of coke after activation by the conditioning gas;

4. The device provided by the present invention is easy to arrange and has strong adaptability to coal types.

The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a device for reducing NO _x by reburning pulverized coal tempered by active gas according to the present invention;

FIG2 is a combined diagram of NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 of the present invention,

Among them, (a) in FIG2 is a trend diagram of NO concentration change when reducing NO in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1,

(b) in FIG2 is a comparison chart of the NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1;

FIG3 is a combined graph of the specific surface area of coal char in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1 of the present invention,

Among them, (a) in FIG3 is a comparison chart of the specific surface areas of activated coal char in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1,

(b) in FIG3 is a comparison diagram of different activated coal coke pore volumes in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1;

FIG. 4 is a graph showing the removal efficiency of NO _x in Example 8 of the present invention and Comparative Examples 1 and 2.

Reference numerals

1. Main burner; 2. Afterburner burner; 3. Tempering gas nozzle; 4. Burnout burner; 5. Pulverized coal combustion chamber.

DETAILED DESCRIPTION

The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

Example 1

A method and device for reducing _NOx by reburning pulverized coal tempered by active gas, comprising a pulverized coal combustion chamber 5 having a main combustion zone, a reburning zone and a burnout zone arranged in sequence from bottom to top. A main burner 1 connected to the main combustion zone is provided with a primary air nozzle and a secondary air nozzle, a reburning burner 2 connected to the reburning zone is provided with a reburning pulverized coal nozzle, the reburning pulverized coal nozzle is connected with a tempering gas nozzle 3, and a burnout burner 4 connected to the burnout zone is provided with a separation burnout air nozzle.

The end of the primary air nozzle away from the main burner 1 is connected to the primary air duct, and the end of the secondary air nozzle away from the main burner 1 is connected to 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 air flow B of the primary air and coal powder enters the main combustion zone through the primary air duct and the primary air nozzle of the main burner 1 in sequence.

The end of the reburning pulverized coal nozzle away from the reburning burner 2 is connected to the reburning pulverized coal pipeline and the tempering gas nozzle, respectively, and the end of the tempering gas nozzle 3 away from the reburning burner is connected to the tempering gas pipeline. The mixed air flow C of the recycled flue gas, hot air and reburning pulverized coal enters the reburning zone through the reburning pulverized coal pipeline and the reburning burner 2 in sequence. The tempered gas D enters the reburning zone through the tempering gas pipeline, the tempering gas nozzle 3 and the reburning burner 2 in sequence.

The tempering gas nozzle 3 is arranged at the outlet of the reburning coal powder nozzle, and the tempering gas is fully reacted with oxygen by using the principle of enhanced combustion. The tempering gas can react quickly with the oxygen in the carrier gas to form a tempering zone at the front end of the nozzle of the reburning burner 2. The excess oxygen in the recycled flue gas is consumed by the combustion reaction, that is, a stable tempering zone with strong reducing property and suitable temperature can be obtained by using a small amount of combustible gas, and then the fuel is tempered, and the gaseous reducing molecules ( _CHi , CO, OH and H, etc.) generated instantly in the tempering zone and _NOx undergo a homogeneous reduction reaction. It not only ensures the effect of reducing _NOx emissions, but also reduces the proportion of reburning coal powder.

One end of the separation overburnt air nozzle away from the overburnt burner 4 is connected to the separation overburnt air duct, and the hot air A enters the burnt-out zone through the separation overburnt air duct and the separation overburnt air nozzle in sequence.

Example 2

A combustion method of a device for reducing NO _x by reburning coal powder with active gas conditioning, as shown in FIG1, comprises the following steps: S1, 75% high-volatile coal fuel is carried by primary air and sequentially passes through the primary air duct, primary air nozzle and the main burner on one side of the coal powder combustion chamber into the main combustion zone, and the primary air rate accounts for 35%. Hot air sequentially enters the main combustion zone through the secondary air duct, secondary air nozzle and main burner, and the secondary air rate accounts for 65%. The excess air coefficient of the main combustion zone is controlled at 0.65, and the residence time of the main combustion zone is controlled at about 1.2 s.

S2, 25% of medium and high volatile coal fuel is carried by the recirculated flue gas through the reburning coal pulverized pipe into the reburning burner above the main burner. The composition of the recirculated flue gas is N ₂ :CO ₂ :O ₂ =80:16:4. At the same time, 2% of the tempered gas methane CH ₄ enters the reburning burner through the tempered gas pipe, the tempered gas nozzle and the recirculated flue gas nozzle in turn. The medium and high volatile coal fuel and the tempered gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient of the reburning zone is 0.6, and the residence time in the reburning zone is controlled at 1.1 s.

S3, hot air passes through the separation burnout air duct, the separation burnout air nozzle and the burnout burner above the reburning burner in turn to enter the burnout zone and burn out the combustion products. The excess air coefficient in the burnout zone is 1.4, and the residence time is controlled at 1.0 s to burn out the residual charcoal.

Example 3

A combustion method of a device for reducing NO _x by reburning coal powder with active gas conditioning, comprising the following steps: S1, 80% 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, and 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, and the secondary air rate accounts for 70%. The excess air coefficient of the main combustion zone is controlled at 0.75, and the residence time of the main combustion zone is controlled at about 1.0 s.

S2, 20% high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe into the reburning burner, and the composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 16: 4. At the same time, 3% of the tempered gas methane _CH4 enters the reburning burner through the tempered gas pipe, the tempered gas nozzle and the recirculating flue gas nozzle in turn. The high volatile coal fuel and the tempered gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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, and the residual charcoal is burned out.

Example 4

A combustion method of a device for reducing _NOx by reburning coal powder with active gas conditioning, comprising the following steps: S1. 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 duct and the primary air nozzle in sequence, and the primary air rate accounts for 20%. Hot air enters the main combustion zone through the secondary air duct and the secondary air nozzle in sequence, and the secondary air rate accounts for 80%. The excess air coefficient of the main combustion zone is controlled at 0.9, and the residence time of the main combustion zone is controlled at about 0.8 s.

S2, 15% high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe into the reburning burner, and the composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 12: 8. At the same time, 4% tempered gas _CH4 enters the reburning burner through the tempered gas pipe, tempered gas nozzle and recirculating flue gas nozzle in turn. The high volatile coal fuel and tempered gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.8, and the residence time in the reburning zone is controlled at 0.8 s.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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 charcoal.

Example 5

A combustion method of a device for reducing _NOx by reburning coal powder with active gas conditioning, comprising the following steps: S1, 90% of 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, and 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, and the secondary air rate accounts for 90%. The excess air coefficient of the main combustion zone is controlled at 1.05, and the residence time of the main combustion zone is controlled at about 0.6 s.

S2, 15% high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe and enters the reburning burner. The composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 10: 10. At the same time, 5% tempered gas _CH4 enters the reburning burner through the tempered gas pipe, tempered gas nozzle and recirculating flue gas nozzle in turn. The high volatile coal fuel and tempered gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.9, and the residence time in the reburning zone is controlled at 0.6 s.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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 charcoal.

Example 6

A combustion method of a device for reducing _NOx by reburning coal powder with active gas conditioning, comprising the following steps: S1, 80% of 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, and 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, and the secondary air rate accounts for 70%. The excess air coefficient of the main combustion zone is controlled at 0.75, and the residence time of the main combustion zone is controlled at about 1.0 s.

S2, 20% of high volatile coal fuel is carried by the recirculating flue gas through the reburning coal powder pipeline into the reburning burner, and the composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 14: 6. At the same time, 3% of coal gas enters the reburning burner through the tempering gas pipeline, tempering gas nozzle and recirculating flue gas nozzle in sequence, and the high volatile coal fuel and tempering gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

The composition of coal-to-gas is CH ₄ =10%, CO=60%, H ₂ =30%.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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, and the residual charcoal is burned out.

Example 7

A combustion method of a device for reducing _NOx by reburning coal powder with active gas conditioning, comprising the following steps: S1, 80% of 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, and 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, and the secondary air rate accounts for 70%. The excess air coefficient of the main combustion zone is controlled at 0.75, and the residence time of the main combustion zone is controlled at about 1.0 s.

S2, 20% of high volatile coal fuel is carried by the recirculating flue gas through the reburning coal powder pipeline into the reburning burner, and the composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 14: 6. At the same time, 3% of hydrogen _H2 enters the reburning burner through the tempering gas pipeline, the tempering gas nozzle and the recirculating flue gas nozzle in sequence, and the high volatile coal fuel and the tempering gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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, and the residual charcoal is burned out.

Example 8

A combustion method of a device for reducing NO _x by reburning coal powder with active gas conditioning, comprising the following steps: S1, 90% of 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, with the primary air rate of 30%. Hot air enters the main combustion zone through the secondary air duct and the secondary air nozzle in sequence, with the secondary air rate accounting for 70%. The excess air coefficient of the main combustion zone is controlled at 0.8, and the residence time of the main combustion zone is controlled at about 1.0 s.

S2, 15% high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe and enters the reburning burner. The composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 10: 10. At the same time, 5% tempered gas _CH4 enters the reburning burner through the tempered gas pipe, tempered gas nozzle and recirculating flue gas nozzle in turn. The high volatile coal fuel and tempered gas are mixed in the reburning burner and enter the reburning zone. The excess air coefficient of the reburning zone is 0.85, and the residence time in the reburning zone is controlled at 0.8 s.

S3, hot air enters the burnout burner through the separation burnout air duct and the separation burnout air nozzle in turn, and burns 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, and the residual charcoal is burned out.

Example 9

A combustion method of a device for reducing NO _x by reburning coal powder with active gas conditioning, comprising the following steps: S1, 80% 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, and 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, and the secondary air rate accounts for 70%. The excess air coefficient of the main combustion zone is controlled at 0.75, and the residence time of the main combustion zone is controlled at about 1.0 s.

S2, 20% of high volatile coal fuel is carried by the recirculating flue gas through the reburning coal pulverized pipe into the reburning burner, and the composition of the recirculating flue gas is _N2 : _CO2 : _O2 = 80: 16: 4. At the same time, 3% of the tempered gas carbon monoxide CO enters the reburning burner through the tempered gas pipe, the tempered gas nozzle and the recirculating flue gas nozzle in turn. The high volatile coal fuel and the tempered gas are mixed in the reburning burner and then enter the reburning zone. The excess air coefficient of the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

S3, hot air enters the burnout burner through the separate burnout air duct and the separate burnout air nozzle in turn, and burns 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 charcoal.

Comparative Example 1

S1. 80% of high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through primary air duct and primary air nozzle in turn, with the primary air rate accounting for 30%. Hot air enters the main combustion zone through secondary air duct and secondary air nozzle in turn, with the secondary air rate accounting for 70%. The excess air coefficient of 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.

S2, 20% of high volatile coal fuel is carried by the circulating flue gas through the reburning coal powder pipeline into the reburning burner and then into the reburning zone. The circulating flue gas composition is N ₂ : CO ₂ : O ₂ = 80:14:6. The excess air coefficient of the reburning zone is 0.7, and the residence time of the reburning zone is controlled at 1.0 s.

S3, hot air enters the burnout burner through the separate burnout air duct and the separate burnout air nozzle in turn, and burns 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 charcoal.

Comparative Example 2

S1. 80% of high-volatile coal fuel is carried by primary air and sprayed into the main combustion zone through primary air duct and primary air nozzle in turn, with the primary air rate accounting for 30%. Hot air enters the main combustion zone through secondary air duct and secondary air nozzle in turn, with the secondary air rate accounting for 70%. The excess air coefficient of 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.

S2. 20% of high volatile coal fuel is carried by hot air through the reburning coal powder pipeline into the reburning burner and then into the reburning zone. The excess air coefficient of the reburning zone is 0.7, and the residence time in the reburning zone is controlled at 1.0 s.

S3, hot air enters the burnout burner through the separate burnout air duct and the separate burnout air nozzle in turn, and burns 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 charcoal.

Test Example 1

a. Test NO reduction capacity using microfluidized bed reaction analyzer (MFBRA)

The MFBRA system rapidly heats the sample and monitors the gas phase products after combustion with a mass spectrometer to obtain the actual conversion process of coal char. The test temperature is 1073 K, and the test atmosphere is a simulated coal reburning zone atmosphere (4% O ₂ , 20% CO ₂ , 500 ppm NO, and the rest is Ar). Each experiment uses 3±0.01 mg of sample.

During the data processing, in order to facilitate the comparison of the NO reduction capabilities of Example 3 (methane), Example 6 (coal gasification), Example 7 (hydrogen), Example 9 (carbon monoxide) and Comparative Example 1 (circulating flue gas), all NO reduction capability data were normalized to 1 mg, and preliminary experiments were performed to prove that all samples had 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 sample being tested in the reactor. The instantaneous NO concentration is integrated over the reaction time, and the absolute value of the area below the line with a NO concentration of 500 ppm is A _1. The absolute value of the area below the line with a NO concentration of 500 ppm is A _2. The difference between _{A 1} and A ₂ represents the ability of the coke to reduce NO.

As shown in FIG2 , (a) in FIG2 is the trend of NO concentration change when reducing NO in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1; (b) in FIG2 is a comparison chart of NO reduction capabilities of Example 3, Example 6, Example 7, Example 9 and Comparative Example 1. As shown in FIG2 , compared with the case of conveying pulverized coal by circulating flue gas alone in Comparative Example 1, the ability of coke to reduce NO after CH ₄ activation in Example 3 is enhanced by nearly 75%, the ability of coke to reduce NO after CO activation in Example 9 is enhanced by nearly 5%, and the ability of coke to reduce NO after H ₂ activation in Example 7 is enhanced by nearly 19%.

b. Specific surface area test

As shown in FIG3 , (a) in FIG3 is a comparison diagram of the specific surface areas of activated coal coke in Example 3, Example 6, Example 7, Example 9 and Comparative Example 1, and (b) in FIG3 is a comparison diagram of the 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 gasification), Example 7 (hydrogen), Example 9 (carbon monoxide) and Comparative Example 1 (circulating flue gas), compared with the pulverized coal transported by circulating flue gas alone in Comparative Example 1, the specific surface area of the coke in Example 3 after CH ₄ activation increased by nearly 54.2%, the specific surface area of the coke in Example 9 after CO activation increased by nearly 3%, and the specific surface area of the coke in Example 7 after H ₂ activation increased by nearly 12.3%. It can be seen that the combustion method of the present invention utilizes the heat released instantly by the combustion of the quenching gas and oxygen to promote the release of volatiles, thereby enriching the pore structure of the coal coke.

c. _NOx removal efficiency

As shown in FIG4 , compared with Comparative Example 2, the _NOx removal efficiency of Example 8 is increased by 36.9%, and compared with Comparative Example 1, the _NOx removal efficiency of Example 8 is increased by 22.2% (at a level where the converted oxygen content in the flue gas is 6%).

Therefore, the present invention adopts the above-mentioned structure to use active gas to temper coal powder and reburn to reduce _NOx . The tempering gas is used to temper the solid fuel, which not only ensures the effect of reducing _NOx emissions, but also alleviates problems such as poor burnout caused by using a high proportion of reburned coal powder.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims (10)

A method for reducing _NOx by reburning pulverized coal tempered by active gas, characterized in that it comprises the following steps: S1, 75-90% medium-high volatile coal fuel is carried by primary air and sprayed into a main burner on one side of a pulverized coal combustion chamber through a primary air duct and a primary air nozzle in sequence, and hot air enters a main combustion zone through a secondary air duct, a secondary air nozzle and a main burner in sequence; S2, 10-25% of medium-high volatile coal fuel is carried by the recycled flue gas through the reburning coal powder pipeline and the reburning coal powder nozzle into the reburning burner above the main burner. At the same time, 0-6% of the tempering gas enters the reburning burner through the tempering gas pipeline, the tempering gas nozzle and the reburning coal powder nozzle in sequence. The medium-high volatile coal fuel and the tempering gas are mixed in the reburning burner and then enter the reburning zone. Once the medium-high volatile coal fuel is sprayed into the reburning zone, it is quickly activated by the tempering gas into gaseous CH _i , CO, OH and H and highly reactive coke; S3. The hot air passes through the separation burnout air duct, the separation burnout air nozzle and the burnout burner above the reburning burner in sequence and enters the burnout zone to burn out the combustion products. The method for reducing _NOx by reburning pulverized coal tempered by active gas according to claim 1 is 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 about 0.2~1.4 s. The method for reducing _NOx by reburning pulverized coal tempered by active gas according to claim 1 is characterized in that the excess air coefficient in the reburning zone is 0.6~0.95, and the flue gas residence time is controlled at 0.2~1.3 s. The method for reducing _NOx by reburning pulverized coal tempered by active gas according to claim 1 is characterized in that the excess air coefficient in the burnout zone is 1.05-1.4, and the flue gas residence time is controlled at 0.2-1.8 s. The method for reducing NO _x by reburning pulverized coal tempered by active gas according to claim 1 is characterized in that the recycled flue gas includes CO ₂ =10-18%, O ₂ =4-10%, N ₂ =66-80%, and H ₂ O =0-16%. According to the method of reducing _NOx by reburning pulverized coal using active gas conditioning as claimed in claim 1, it is characterized in that the conditioning gas includes one or more of natural gas, carbon monoxide, hydrogen, methane, coal gas and unsaturated hydrocarbon gas. A method and device for reducing _NOx by reburning pulverized coal tempered by active gas according to any one of claims 1 to 6, characterized in that it includes a pulverized coal combustion chamber in which a main combustion zone, a reburning zone and a burnout zone are 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, the reburning pulverized coal nozzle is connected to a tempering gas nozzle, and the burnout burner connected to the burnout zone is provided with a separation burnout air nozzle. According to the method and device for reducing _NOx by reburning pulverized coal tempered by active gas as described in claim 7, it is characterized in that the end of the primary air nozzle away from the main burner is connected to the primary air duct, and the end of the secondary air nozzle away from the main burner is connected to the secondary air duct. According to the method and device for reducing _NOx by reburning pulverized coal tempered by active gas as described in claim 7, it is characterized in that the end of the reburning pulverized coal nozzle away from the reburning burner is respectively connected to the reburning pulverized coal pipeline and the tempering gas nozzle, and the end of the tempering gas nozzle away from the reburning burner is connected to the tempering gas pipeline. According to the method and device for reducing _NOx by reburning pulverized coal tempered by active gas as described in claim 7, it is characterized in that the end of the separation overburnt air nozzle away from the overburnt burner is connected to the separation overburnt air duct.