Coal and ammonia co-combustion method and system for conveying and pyrolyzing pulverized coal by using ammonia gas

Abstract

The invention discloses a coal and ammonia co-combustion method and system for conveying and pyrolyzing pulverized coal through ammonia gas, and relates to the technical field of fuel combustion. The method comprises the following steps that S1, coal powder is conveyed through high-temperature ammonia gas, and the coal powder is pyrolyzed into volatile components and coke solid particles in the conveying process; the high-temperature ammonia gas, the volatile components and the coke solid particles form mixed gas flow; s2, after the mixed gas flow enters a combustor, the mixed gas flow is separated into concentrated-phase coke gas flow and dilute-phase coke gas flow; and S3, the concentrated-phase coke airflow and the dilute-phase coke airflow are combusted at an outlet of the combustor. The coal powder conveying temperature can be increased under the inert atmosphere in the mode that ammonia gas is adopted for conveying coal powder, the coal powder is subjected to thermal desorption in advance in a coal mill or a pipeline to obtain volatile components and coke, the volatile components and the coke are fully mixed with the ammonia gas and then enter a hearth, mixed gas of the ammonia gas and the volatile components can be rapidly ignited and combusted, the low-load stable combustion capacity of the combustor is improved, and the combustion efficiency is improved. And the emission of nitrogen oxides is reduced by enhancing the reducing atmosphere.

Description

Technical Field

[0001] This invention relates to the field of fuel combustion technology, and in particular to a coal-ammonia co-combustion method and combustion system that utilizes ammonia gas to transport and pyrolyze pulverized coal. Background Technology

[0002] Ammonia-coal co-combustion technology, as an important carbon reduction solution, involves adding zero-carbon fuel—ammonia—to traditional coal-fired boilers to replace a portion of the coal for co-combustion. Ammonia does not produce carbon dioxide during combustion, thus directly reducing the carbon intensity per unit of energy output. This technology can utilize existing coal-fired power infrastructure, ensuring energy supply stability, while significantly reducing carbon dioxide emissions, making it particularly suitable for high coal-consuming power and industrial sectors. With the maturation and cost reduction of green ammonia preparation technology, ammonia-coal co-combustion is expected to become one of the effective paths for clean coal utilization and to facilitate the low-carbon transformation of the energy system.

[0003] While ammonia is a zero-carbon fuel, its large-scale combustion application still faces a series of technical challenges. First, ammonia's slow flame propagation speed, high ignition temperature, and narrow flammable range result in poor combustion stability, leading to difficulties in ignition and low combustion efficiency. When burned alone, it is prone to flameout or extinction. Second, the combustion process may produce nitrogen oxides (NOx) at high temperatures. x The large-scale generation of ammonia presents a far greater challenge to control and environmental risks than traditional fuels, necessitating complex and efficient denitrification technologies. Furthermore, ammonia is highly corrosive and readily dissolves in water to form an ammonia-water mixture, placing higher demands on the material safety of storage and transportation equipment and combustion systems.

[0004] Existing ammonia-coal co-combustion methods are divided into independent ammonia-coal combustion and mixed ammonia-coal combustion. The former uses a technique of co-firing pure ammonia burners and pure coal burners in the furnace, while the latter usually introduces ammonia directly into the pulverized coal primary air mixture or adds a separate ammonia pipeline to the pulverized coal burner. Both of these co-combustion methods face the problem of combustion instability. Specifically, in the independent ammonia-coal combustion method, the pure ammonia burner experiences unstable combustion at low loads; in the current mixed ammonia-coal combustion method, when ammonia is directly introduced into the pulverized coal primary air mixture, ammonia combustion easily generates high concentrations of nitrogen oxides. When using a separate ammonia pipeline, the mixing of ammonia fuel with pulverized coal after entering the furnace requires a process, which also leads to combustion instability. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a coal-ammonia co-combustion system and method that utilizes ammonia gas to transport and pyrolyze pulverized coal. This combustion method utilizes ammonia gas to transport and pyrolyze pulverized coal, ensuring complete pyrolysis of the coal before it enters the burner.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A coal-ammonia co-combustion method utilizing ammonia gas to transport and pyrolyze pulverized coal includes the following steps:

[0008] S1: High-temperature ammonia gas is used to transport pulverized coal. During the transport process, the pulverized coal is pyrolyzed into volatile matter and coke solid particles; high-temperature ammonia gas, volatile matter and coke solid particles form a mixed gas flow.

[0009] S2: After the mixed gas flow enters the burner, it is separated into a dense-phase coke gas flow and a dilute-phase coke gas flow. The mass concentration of coke solid particles in the dense-phase coke gas flow is 3-5 times that in the dilute-phase coke gas flow; the unit of mass concentration is kg / m³. 3 ;

[0010] S3: Dense-phase coke gas flow and dilute-phase coke gas flow are burned separately at the burner outlet; the dense-phase coke gas flow achieves complete combustion through coke-water-gas reaction, coke heterogeneous combustion reaction and NO reduction reaction; the dilute-phase coke gas flow relies on volatile matter to achieve rapid ignition and ignite premixed ammonia gas.

[0011] The temperature of the mixed airflow is 200℃~250℃.

[0012] In step S1, the coal powder is dry coal powder, which is obtained by drying with hot air.

[0013] Raw coal is ground to obtain wet coal powder, and hot air dries the wet coal powder to obtain dry coal powder. The free water and some bound water in the wet coal powder are evaporated and mixed with the hot air after the temperature drops to form humid exhaust gas.

[0014] The temperature of the hot air is 300℃~350℃, and the temperature of the exhaust air is 70℃~90℃.

[0015] In step S1, the coal powder is wet coal powder obtained by grinding raw coal. High-temperature ammonia gas dries and transports the wet coal powder. At this time, the mixed gas flow is a humid mixed gas including water vapor. The temperature of the high-temperature ammonia gas is 400℃~500℃.

[0016] When a direct-current coal-ammonia co-fired burner is used, the dense phase coke gas flow is ignited by the upstream flame, and at the same time, the dense phase coke gas flow is fully combusted with the aid of humid exhaust gas or humid mixed gas, and the dense phase coke is completely burned under the action of hot air; the dilute phase coke gas flow is ignited and burned with the aid of hot air, and the dilute phase coke is completely burned under the action of humid exhaust gas or hot air.

[0017] When a swirl coal-ammonia co-fired burner is used, the dilute phase coke gas stream is ignited by high-temperature flue gas heating under the combustion assistance of the central air; the dense phase coke gas stream is burned out under the combustion assistance of humid exhaust gas or hot air.

[0018] A coal-ammonia co-fired combustion system utilizing ammonia gas to transport and pyrolyze pulverized coal is provided for implementing the aforementioned coal-ammonia co-fired combustion method utilizing ammonia gas to transport and pyrolyze pulverized coal. The coal-ammonia co-fired combustion system includes a pulverizing section and a burner; the pulverizing section and the burner are connected via an ammonia gas conveying pipe; pulverized coal pyrolysis is completed in the pulverizing section and the ammonia gas conveying pipe.

[0019] The burner is equipped with an ammonia volatile coke channel, and a rich-lean separator is installed in the ammonia volatile coke channel. The rich-lean separator separates the mixed gas flow into a rich phase coke gas flow and a dilute phase coke gas flow, which then enter the furnace for combustion.

[0020] The burner is a DC coal-ammonia co-fired burner, and a DC ammonia volatilization coke channel is provided in the center of the DC ammonia volatilization coke channel. A DC concentration separator is provided in the DC ammonia volatilization coke channel.

[0021] The dense phase coke gas flow is close to the center of the furnace, and the dense phase coke gas flow enters the furnace for combustion through the direct-flow dense side coke channel;

[0022] The dilute phase coke gas flow approaches the furnace wall and enters the furnace for combustion through the direct-flow dilute side coke channel.

[0023] Specifically, a first DC channel for introducing humid exhaust gas or hot air is provided outside the DC rich-side coke channel, and a second DC channel for introducing hot air is provided outside the first DC channel; a third DC channel for introducing hot air is provided outside the DC light-side coke channel, and a fourth DC channel for introducing humid exhaust gas or hot air is provided outside the third DC channel.

[0024] The burner is a swirling coal-ammonia co-fired burner, and the cross-section of the swirling coal-ammonia co-fired burner is a concentric circle structure, consisting of a central air channel, a swirling ammonia volatile matter coke channel, a swirling first channel, and a swirling second channel from the inside out.

[0025] The swirling ammonia volatile matter coke channel is equipped with a swirling thick-thin separator, with the inner side being the swirling thin-side coke channel and the outer side being the swirling thick-side coke channel. The thick-phase coke gas flows through the swirling thick-side coke channel into the furnace for combustion, while the thin-phase coke gas flows through the swirling thin-side coke channel into the furnace for combustion.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The present invention uses ammonia to transport pulverized coal, which can increase the conveying temperature under an inert atmosphere. The pulverized coal completes thermal desorption in the coal mill or pipeline in advance to release volatiles and coke, and then enters the furnace after being fully mixed with ammonia. The mixture of ammonia and volatiles can be quickly ignited and burned, improving the low-load stable combustion capability of the burner.

[0028] (2) The present invention uses ammonia gas to transport and pyrolyze coal powder to achieve full mixing of ammonia gas and volatile coal powder before entering the furnace to enhance combustion, while avoiding premature contact between ammonia gas and combustion air, which is beneficial to suppressing the generation of high concentration of nitrogen oxides in the early stage of ammonia combustion.

[0029] (3) In this invention, after the mixed gas flow, namely ammonia, volatile matter and coke mixture, is separated into concentrated and diluted phases, the concentrated phase coke gas flow reacts with the moisture in the humid exhaust gas or humid mixed gas to generate a large amount of CO and H2. This not only promotes the coke combustion reaction, but also enhances the stable combustion capability of the burner by accelerating the heterogeneous reaction rate of coke, and can also reduce the NO generated by ammonia coal combustion.

[0030] (4) The present invention utilizes ammonia to transport pulverized coal and decouples the combustion air from the pulverized coal. This can resolve the contradiction between the minimum critical velocity of pneumatic conveying and the optimal primary air volume for pulverized coal combustion, and prevent pulverized coal blockage in the conveying pipe while achieving stable low-NOx combustion. Attached Figure Description

[0031] Figure 1 This is an overall schematic diagram of the medium-storage coal-ammonia co-combustion system of the present invention, which utilizes ammonia gas to transport and pyrolyze pulverized coal.

[0032] Figure 2 This is an overall schematic diagram of the direct-fired coal-ammonia co-combustion system of the present invention, which utilizes ammonia gas to transport and pyrolyze pulverized coal.

[0033] Figure 3 This is an overall schematic diagram of the DC coal-ammonia co-fired burner in the coal-ammonia co-fired combustion system of the present invention, which utilizes ammonia gas to transport and pyrolyze pulverized coal.

[0034] Figure 4 This is an overall schematic diagram of the swirling coal-ammonia co-fired burner in the coal-ammonia co-fired combustion system of the present invention, which utilizes ammonia gas to transport and pyrolyze pulverized coal.

[0035] The attached diagram is labeled as follows: 1-Raw coal bunker, 2-Coal drop pipe, 3-Coal mill, 4-Hot air pipe, 5-Pulverized coal conveying pipe, 6-Pulverized coal bunker, 7-Exhaust gas pipe, 8-Pulverized coal drop pipe from pulverized coal bunker, 9-Pulverized coal feeder, 10-Pulverized coal feeder drop pipe, 11-Ammonia pulverized coal conveying pipe, 12-Burner, 13-High temperature ammonia pipe;

[0036] 12-1-Square-round connector; 12-2-Rectangular shell; 12-3-DC ammonia volatile matter coke channel; 12-4-DC first channel; 12-5-DC second channel; 12-6-DC third channel; 12-7-DC fourth channel; 12-8-DC concentrated / dilute separator; 12-9-DC protective block; 12-10-DC partition plate; 12-11-DC wear-resistant coating; 12-12-DC blunt body; 12-13-DC concentrated side coke channel; 12-14-DC dilute side coke channel; 12-15-DC first channel outlet; 12-16-DC second channel outlet; 12-17-DC third channel outlet; 12-18-DC fourth channel outlet; 12-19-DC dense phase ignition and combustion zone; 12-20-DC dilute phase ignition and combustion zone; 12-21-DC dense phase burnout zone; 12-22-DC dilute phase burnout zone;

[0037] 12-23-Central air duct, 12-24-Swirl ammonia volatiles coke duct, 12-25-Swirl first duct, 12-26-Swirl second duct, 12-27-Swirl concentration separator, 12-28-Swirl partition plate, 12-29-Swirl protective block, 12-30-Swirl wear-resistant coating, 12-31-Swirl blunt body, 12-32-Central air duct outlet, 12-33-Swirl 12-34-Swirl coke channel on the rich side, 12-35-Swirl first channel outlet, 12-36-Swirl second channel outlet, 12-37-Central air cyclone, 12-38-Swirl first channel cyclone, 12-39-Swirl second channel cyclone; 12-40-Swirl dilute phase ignition and combustion zone, 12-41-Swirl dense phase ignition and combustion zone, 12-42-Swirl burnout zone. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] This invention provides a coal-ammonia co-combustion method that utilizes ammonia gas to transport and pyrolyze pulverized coal, comprising the following steps:

[0040] S1: High-temperature ammonia gas is used to transport pulverized coal. During the transport process, the pulverized coal is pyrolyzed into volatile matter and coke solid particles; high-temperature ammonia gas, volatile matter and coke solid particles form a mixed gas flow.

[0041] S2: After the mixed gas flows into the burner, it is separated into a dense phase coke gas flow and a dilute phase coke gas flow. The mass concentration of coke solid particles in the dense phase coke gas flow is 3-5 times that of the dilute phase coke gas flow.

[0042] S3: Dense-phase coke gas flow and dilute-phase coke gas flow are burned separately at the burner outlet; the dense-phase coke gas flow achieves complete combustion through coke-water-gas reaction, coke heterogeneous combustion reaction and NO reduction reaction; the dilute-phase coke gas flow relies on volatile matter to achieve rapid ignition and ignite premixed ammonia gas.

[0043] This invention utilizes high-temperature ammonia gas to pyrolyze pulverized coal before it enters the burner, releasing volatiles to generate a mixture of ammonia and volatiles, along with coke solid particles. The coke is then separated and burned using a concentration separator. On one hand, the rapid ignition capability of volatiles and the water-gas reaction and heterogeneous ignition of coke enhance the burner's stable combustion capability under low load. On the other hand, it slows down the mixing rate of ammonia and air and reduces nitrogen oxide emissions from ammonia-coal combustion in a reducing atmosphere of volatiles, coke, and water-gas.

[0044] Among them, pulverized coal pyrolysis is carried out in pipelines or directly in the coal mill.

[0045] Preferably, the temperature of the mixed gas flow is 200℃~250℃ to ensure that the volatile components of the pulverized coal are fully released.

[0046] In one embodiment, the coal powder in step S1 is dried coal powder, which is obtained by drying with hot air. In this embodiment, wet coal powder is first dried with hot air to obtain dry coal powder, which is then pyrolyzed by high-temperature ammonia gas in a pipeline.

[0047] The specific process is as follows: raw coal is ground to obtain wet coal powder, which is then dried with hot air to obtain dry coal powder. Free moisture and some bound water in the wet coal powder are evaporated and mixed with the cooled hot air to form a humid exhaust gas. The coal powder is then fed into an ammonia conveying pipe, where it undergoes efficient pyrolysis under the protective atmosphere of high-temperature ammonia, releasing volatiles and coke solid particles. The volatiles and high-temperature ammonia mix and are then pneumatically conveyed, carrying the coke solid particles into the burner for combustion. The volatiles, high-temperature ammonia, and the carried coke solid particles form a mixed gas flow.

[0048] The temperature of the hot air is 300℃~350℃; the temperature of the exhaust gas is 70℃~90℃ to prevent deflagration of the air-coal mixture.

[0049] In another embodiment, the pulverized coal in step S1 is wet pulverized coal obtained by grinding raw coal. High-temperature ammonia gas dries and transports the wet pulverized coal. At this time, pyrolysis is carried out in the coal mill. That is to say, high-temperature ammonia gas simultaneously dries and transports the wet pulverized coal and provides the heat required for pyrolysis. Therefore, the mixed gas flow in this embodiment is a humid mixed gas including water vapor.

[0050] The specific process is as follows: Raw coal is ground into pulverized coal. High-temperature ammonia gas enters the coal mill to dry and transport the pulverized coal. Free water and all bound water in the pulverized coal are evaporated. The pulverized coal undergoes partial pyrolysis inside the coal mill, separating volatile matter and coke solid particles. The volatile matter, high-temperature ammonia gas, and water vapor form a mixed gas. This mixed gas is pneumatically conveyed to send some of the dried and pyrolyzed coke solid particles into the burner. The unpyrolyzed pulverized coal continues to undergo pyrolysis and separation in the high-temperature environment of the ammonia gas conveying pipe. The volatile matter, high-temperature ammonia gas, water vapor, and the carried coke solid particles form a mixed gas flow.

[0051] The high-temperature ammonia gas is heated to 400℃~500℃ to ensure that the pulverized coal is fully dried and volatilized.

[0052] The combustion of the coal-ammonia co-fired combustion method of the present invention can be carried out in a direct-flow coal-ammonia co-fired burner or in a swirl coal-ammonia co-fired burner.

[0053] In a DC coal-ammonia co-fired burner, the dense phase coke gas stream is ignited by the upstream flame, and at the same time, the dense phase coke gas stream achieves complete combustion with the aid of humid exhaust gas or humid mixed gas, and the dense phase coke is completely burned under the action of hot air; the dilute phase coke gas stream is ignited and burned with the aid of hot air, and the dilute phase coke is completely burned under the action of humid exhaust gas or hot air.

[0054] In a swirling coal-ammonia co-fired burner, the dilute phase coke gas stream is ignited by high-temperature flue gas heating with the aid of central air; the dense phase coke gas stream is burned out with the aid of humid exhaust gas or hot air.

[0055] To achieve the above-mentioned coal-ammonia co-fired combustion method, the present invention also provides a coal-ammonia co-fired combustion system that utilizes ammonia gas to transport and pyrolyze pulverized coal, comprising a pulverizing section and a burner; the pulverizing section and the burner are connected by an ammonia gas pulverizing pipe 11; the burner is provided with an ammonia volatile coke channel, and a rich-lean separator is provided in the ammonia volatile coke channel, the rich-lean separator separating the mixed gas flow into a dense coke gas flow and a dilute coke gas flow, the dense coke gas flow and the dilute coke gas flow respectively entering the furnace for combustion.

[0056] Example 1

[0057] In this embodiment, the coal-ammonia co-fired combustion system that uses ammonia gas to transport and pyrolyze pulverized coal has a medium-storage type pulverizing device in its pulverizing section and a direct-flow coal-ammonia co-fired burner in its burner.

[0058] See Figure 1 The pulverizing section is a medium-storage pulverizing device, which includes a raw coal bunker 1, a coal chute 2, a coal mill 3, and a pulverizer 9. The raw coal bunker 1 is connected to the coal mill 3 through the coal chute 2. The coal mill 3 is equipped with a hot air inlet, a pulverized coal outlet, and a waste gas outlet. Hot air enters from the hot air inlet to dry the wet pulverized coal, which is then discharged from the pulverized coal outlet. Moist waste gas carrying a small amount of fine pulverized coal is discharged from the waste gas outlet. The dried pulverized coal enters the pulverizer 9 and then enters the ammonia gas conveying pipe, where the dried pulverized coal undergoes pyrolysis.

[0059] Specifically, the pulverizing process is as follows: Raw coal in raw coal bunker 1 falls into coal mill 3 through coal chutes 2. Some hot air enters coal mill 3 from the side and mixes with the raw coal. During the process of the raw coal being pulverized into coal powder by coal mill 3, the hot air dries and transports the coal powder. The free water and some bound water in the coal powder are evaporated and mixed with the hot air after the temperature drops to form humid exhaust gas.

[0060] Preferably, the medium-storage pulverizing device further includes a pulverized coal silo 6 for storing dried pulverized coal. In this embodiment, most of the dried pulverized coal is discharged from the pulverized coal outlet by moist exhaust gas and transported to the pulverized coal silo 6 via the pulverized coal conveying pipe 5. The moist exhaust gas carries a small amount of fine pulverized coal and is discharged from the exhaust gas outlet, then introduced into the burner 12 for combustion through the exhaust gas pipe 7. During use, the pulverized coal falls from the pulverized coal silo 6 into the pulverizer 9 via the pulverized coal drop pipe 8.

[0061] Of course, the pulverized coal silo 6 can be omitted. The dried pulverized coal can be directly fed into the ammonia gas conveying pipe 11 via the pulverizer 9.

[0062] The pyrolysis process is as follows: Dry coal powder is fed into ammonia conveying pipe 11 by feeder 9 through feeder drop pipe 10. The coal powder undergoes efficient pyrolysis under the protective atmosphere of high temperature ammonia, precipitating volatiles and coke solid particles. The volatiles and high temperature ammonia are mixed and then carried into burner 12 by pneumatic conveying to burn the coke solid particles.

[0063] See Figure 1 During combustion, another path of hot air enters the burner 12 directly through the hot air pipe 4 to assist combustion.

[0064] In this embodiment, the burner 12 is a DC coal-ammonia co-fired burner, which is used in a tangential combustion boiler.

[0065] See Figure 3In this embodiment, the cross-section of the DC coal-ammonia co-fired burner is rectangular, and the outer shell is a rectangular shell 12-2. The rectangular shell 12-2 is connected to the ammonia powder conveying pipe 11 by a square-round connector 12-1. The DC coal-ammonia co-fired burner has a DC ammonia volatile matter coke channel 12-3 in the center. A DC rich-lean separator 12-8 is installed in the DC ammonia volatile matter coke channel 12-3 to separate the mixed gas flow (ammonia + volatile matter + coke solid particles) into a rich phase coke gas flow and a dilute phase coke gas flow. The rich phase coke gas flow enters the furnace for combustion through the DC rich side coke channel 12-13, and the dilute phase coke gas flow enters the furnace for combustion through the DC dilute side coke channel 12-14.

[0066] Preferably, the DC coal-ammonia co-fired burner in this embodiment adopts an asymmetrical design on both sides, that is, the air distribution channels on both sides are in different order.

[0067] See Figure 3 Adjacent to the outside of the DC rich-side coke channel 12-13 is the DC first channel 12-4, which introduces exhaust gas. Adjacent to the outside of the DC first channel 12-4 is the DC second channel 12-5, which introduces hot air to aid combustion. Adjacent to the outside of the DC light-side coke channel 12-14 is the DC third channel 12-6, which introduces hot air to aid combustion. Adjacent to the outside of the DC third channel 12-6 is the DC fourth channel 12-7, which introduces exhaust gas to aid combustion.

[0068] In this embodiment, the proportion of exhaust gas or hot air introduced into the DC first channel 12-4, DC second channel 12-5, DC third channel 12-6 and DC fourth channel 12-7 can be adjusted according to the proportion of volatile matter in pulverized coal and coke, the proportion of coal-ammonia co-combustion, and the proportion of coke concentration separation.

[0069] Preferably, the DC concentration separator 12-8 adopts the form of elbow, baffle, mound, louver, etc.

[0070] Preferred, see Figure 3 A DC protection block 12-9 is welded to the front of the rectangular shell 12-2 on one side of the DC concentrated coke channel 12-13.

[0071] Preferably, a DC separator 12-10 is provided at the outlet end of the DC ammonia volatile matter coke channel 12-3 to isolate the dense phase coke gas flow and the dilute phase coke gas flow. More preferably, the DC separator 12-10 is centrally located.

[0072] Preferably, the leading edge of the DC protective block 12-9 and the side facing the DC rich-side coke channel 12-13 are coated with a DC wear-resistant coating 12-11, and the leading edge of the DC separator 12-10 and the side facing the DC rich-side coke channel 12-13 are also coated with a DC wear-resistant coating 12-11 to resist the erosion of rich-phase coke solid particles. In this embodiment, the leading edge refers to the end near the inlet of the mixed gas flow.

[0073] Preferably, the portion of the DC ammonia volatile coke channel 12-3 near the outlet end adopts a necking design to increase the airflow velocity and enhance the entrainment effect; a DC blunt body 12-12 is provided near the outlet of the DC ammonia volatile coke channel 12-3 to stabilize the flame.

[0074] The outlet of DC channel 12-4 is DC channel outlet 12-15, the outlet of DC channel 12-5 is DC channel outlet 12-16, the outlet of DC channel 12-6 is DC channel outlet 12-17, and the outlet of DC channel 12-7 is DC channel outlet 12-18. The outlets of DC channel 12-15, DC channel 2, DC channel 3, and DC channel 4 are designed with an inward-curving angle. Preferably, the inward angle of DC channel 12-15 and DC channel 3 is 10°~15°, and the inward angle of DC channel 12-16 and DC channel 4 is 15°~20°. This design enhances the disturbance and mixing of the outer airflow on the inner airflow during staged combustion.

[0075] In this embodiment, after pyrolysis and separation in the ammonia pulverizer pipe 11, the pulverized coal enters the DC ammonia volatile coke channel 12-3, where it is separated into a dense phase coke gas flow and a dilute phase coke gas flow. The dense phase coke gas flow is close to the center of the furnace and achieves heterogeneous ignition of coke in the DC dense phase ignition combustion zone 12-19 by relying on the ignition effect of the upstream flame of the tangential combustion boiler. At the same time, with the support of the moist exhaust gas, the dense phase coke gas flow generates a large amount of CO and H2 through the coke water-gas reaction and the coke heterogeneous combustion reaction, which can not only promote the coke combustion reaction, but also reduce the NO generated by the ammonia coal combustion. Finally, the hot air provided by the DC second channel 12-5 ensures that the remaining coke is burned out in the DC dense phase burnout zone 12-21.

[0076] The dilute-phase coke gas flow, located near the furnace wall, is primarily a mixture of ammonia and volatile matter. Pre-precipitation of volatile matter prevents the pulverized coal from pyrolysis and absorbing heat within the furnace, facilitating rapid ignition and combustion of the volatile matter in the DC dilute-phase ignition and combustion zone 12-20 with the aid of hot air in the DC third channel 12-6. After ignition, the volatile matter ignites the premixed ammonia, achieving rapid combustion of the mixture. Finally, the moist exhaust gas provided by the DC fourth channel 12-7 promotes the complete combustion of the dilute-phase coke in the DC dilute-phase burnout zone 12-22. The combined action of the dense-phase and dilute-phase flames ignites the downstream flames. The exhaust gas or hot air from the DC fourth channel 12-7 simultaneously ensures a lower-temperature oxidizing atmosphere near the furnace wall, preventing water-cooled wall corrosion and coking.

[0077] Example 2

[0078] In this embodiment, the pulverizing section of the coal-ammonia co-fired combustion system that utilizes ammonia gas to transport and pyrolyze pulverized coal is a direct-fired pulverizing device, and the burner 12 is a swirl coal-ammonia co-fired burner. In this embodiment, the swirl coal-ammonia co-fired burner is used in a counter-current combustion boiler.

[0079] See Figure 2 The pulverizing section is a direct-fired pulverizing device, which includes a raw coal bunker 1, a coal chute 2, and a coal mill 3. High-temperature ammonia gas enters the coal mill 3 through a high-temperature ammonia gas pipe 13 and mixes with the raw coal. During the process of the raw coal being pulverized into coal powder by the coal mill 3, the high-temperature ammonia gas dries and transports the coal powder, evaporating the free water and all bound water in the coal powder. The coal powder undergoes pyrolysis inside the coal mill 3, separating volatile matter and coke solid particles. The volatile matter, high-temperature ammonia gas, and water vapor form a mixed gas. The mixed gas is pneumatically conveyed to send part of the dried and pyrolyzed coal powder into the burner 12. At this time, the mixed gas and coke solid particles form a mixed airflow. The unpyrolyzed coal powder continues to undergo pyrolysis and separation in the high-temperature environment of the ammonia gas conveying pipe 11. Hot air enters the burner 12 directly through the hot air pipe 4 to assist combustion and does not participate in the coal powder drying and transportation process.

[0080] The temperature of the high-temperature ammonia gas should meet the requirements for the evaporation and volatilization of moisture in the pulverized coal. At the same time, depending on the moisture content of the coal, the temperature of the ammonia volatiles and coke mixture should be 20℃~30℃ higher than the saturation temperature of the water vapor contained in the mixture to prevent moisture from condensing and forming an ammonia-water mixture that corrodes the coal mill 3, the ammonia conveying pipe 11, and the burner 12.

[0081] Preferably, the heat source for hot air and high-temperature ammonia is provided by the waste heat of flue gas at the tail end of the boiler or other waste heat from the power plant, and the coal mill 3, ammonia powder conveying pipe 11, and burner 12 are made of ordinary heat-resistant carbon steel.

[0082] See Figure 4 In this embodiment, the cross-section of the swirl coal-ammonia co-fired burner is a concentric circle structure, consisting of a central air channel 12-23, a swirl ammonia volatile matter coke channel 12-24, a first swirl channel 12-25, and a second swirl channel 12-26 from the inside out. A swirl rich-lean separator 12-27 is arranged inside the swirl ammonia volatile matter coke channel 12-24 to separate the mixed gas flow (ammonia + volatile matter + coke solid particles) into a rich phase coke gas flow and a dilute phase coke gas flow. The rich phase coke gas flow enters the furnace for combustion through the swirl rich-side coke channel 12-33, while the dilute phase coke gas flow enters the furnace for combustion through the swirl dilute-side coke channel 12-34.

[0083] Preferably, the proportion of hot air in the central air duct 12-23 to the total air volume is 25% to 35%, the proportion of air volume in the first swirl channel 12-25 to the total air volume is 30% to 50%, and the proportion of air volume in the second swirl channel 12-26 to the total air volume is 25% to 35%.

[0084] Preferably, the cyclone thickener 12-27 adopts a conical annular pulverized coal thickener structure, with a smaller front end and a larger rear end. The front end refers to the end near the inlet of the cyclone ammonia volatile matter coke channel.

[0085] Preferably, a ring of cyclone separator 12-28 is provided in the cyclone thick-side coke channel 12-33, and preferably the cyclone separator 12-28 is located between the cyclone thick-lean separator 12-27 and the outlet end of the cyclone thick-side coke channel 12-33.

[0086] Preferably, a ring of cyclone protection blocks 12-29 is welded to the inner wall of the cyclone thick-side coke channel 12-33, and preferably the cyclone protection blocks 12-29 are placed between the cyclone thick-lean separator 12-27 and the outlet end of the cyclone thick-side coke channel 12-33.

[0087] Preferably, a swirling wear-resistant coating 12-30 is applied to the outer side of the swirling concentration separator 12-27, the outer side of the swirling partition plate 12-28, and the leading edge of the swirling protective block 12-29 to resist the scouring and erosion of coke solid particles on the concentrated side.

[0088] Preferably, the central air duct outlet 12-32 of the central air duct 12-23 adopts a flared design, and a swirling blunt body 12-31 is placed on the outside of the central air duct outlet 12-32 to enhance the recirculation of high-temperature flue gas in the central recirculation zone and promote the ignition and combustion of the volatile matter and ammonia mixture.

[0089] Preferably, the outlet of the first swirl channel 12-25 is the outlet of the first swirl channel 12-35, and the outlet of the second swirl channel 12-26 is the outlet of the second swirl channel 12-36. Both the outlet of the first swirl channel 12-35 and the outlet of the second swirl channel 12-36 adopt a flared design, and the flaring angle is preferably 15°~25°.

[0090] Preferably, a central air cyclone separator 12-37 is installed in the central air duct 12-23, a first cyclone separator 12-38 is installed in the first cyclone duct 12-25, and a second cyclone separator 12-39 is installed in each of the second cyclone ducts 12-26.

[0091] Even better, the central wind cyclone 12-37 and the first cyclone channel cyclone 12-38 adopt a tangential blade design to achieve strong swirling combustion, while the second cyclone channel cyclone 12-39 adopts an axial blade design to achieve weak swirling combustion.

[0092] See Figure 4 After the mixture in the swirling ammonia volatiles coke channel 12-24 undergoes concentration separation, the coke solid particles are distributed with a concentration distribution at the outermost layer and a concentration distribution at the innermost layer. The center is a dilute phase coke gas flow, and the outermost layer is a dense phase coke gas flow. The dilute phase coke gas flow, aided by hot air in the central air channel 12-23, is heated by high-temperature flue gas in the central recirculation zone, achieving rapid ignition of the volatiles and igniting the premixed ammonia gas. This results in rapid ignition and combustion of the mixture in the swirling dilute phase ignition combustion zone 12-40. The dense phase coke gas flow, after mixing with the hot air introduced in the first swirling channel 12-25, is heated by high-temperature flue gas in the outer recirculation zone. Simultaneously, coke, water, and gas react in the swirling dense phase ignition combustion zone 12-41. The combustion reactions are as follows: (C+H2O(g)→CO+H2 (high temperature conditions) and C+2H2O→CO2+2H2), coke combustion (C+O2→CO2 and C+O2→CO), and NO reduction (NO+CO→N2+CO2, NO+H2→N2+H2O, NO+C→N2+CO). Finally, the hot air in the second swirl channel 12-26 promotes the complete combustion of unburned coke in the swirl burnout zone 12-42.

[0093] Example 3

[0094] In this embodiment, the coal-ammonia co-fired combustion system that uses ammonia to transport and pyrolyze coal powder has a central storage type pulverizing device and a swirl coal-ammonia co-fired burner.

[0095] The specific structure of the medium-density pulverizing unit is the same as in Example 1, and the specific structure of the swirl coal-ammonia co-fired burner is the same as in Example 2. Moist exhaust gas is introduced into the first swirl channel 12-25 of the swirl coal-ammonia co-fired burner.

[0096] Example 4

[0097] In this embodiment, the coal-ammonia co-fired combustion system that uses ammonia gas to transport and pyrolyze coal powder has a direct-fired pulverizing device in its pulverizing section and a direct-flow coal-ammonia co-fired burner in its burner.

[0098] The specific structure of the direct-fired pulverizing device is the same as in Example 2, and the specific structure of the DC coal-ammonia co-fired burner is the same as in Example 1.

[0099] In this embodiment, the first DC channel 12-4, which introduces hot air, is located immediately outside the DC rich-side coke channel 12-13. The second DC channel 12-5, which introduces hot air to aid combustion, is located immediately outside the DC rich-side coke channel 12-13. The third DC channel 12-6, which introduces hot air to aid combustion, is located immediately outside the DC poor-side coke channel 12-14. The fourth DC channel 12-7, which introduces hot air to aid combustion, is located immediately outside the DC poor-side coke channel 12-14.

[0100] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0101] The parts not described in detail in this specification are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A method for coal-ammonia co-combustion using ammonia gas to transport and pyrolyze pulverized coal, characterized in that, Includes the following steps: S1: High-temperature ammonia gas is used to transport pulverized coal. During the transport process, the pulverized coal is pyrolyzed into volatile matter and coke solid particles; high-temperature ammonia gas, volatile matter and coke solid particles form a mixed gas flow. S2: After the mixed gas flows into the burner, it is separated into a dense phase coke gas flow and a dilute phase coke gas flow. The mass concentration of coke solid particles in the dense phase coke gas flow is 3-5 times that in the dilute phase coke gas flow. S3: Dense-phase coke gas flow and dilute-phase coke gas flow are burned separately at the burner outlet; the dense-phase coke gas flow achieves complete combustion through coke-water-gas reaction, coke heterogeneous combustion reaction and NO reduction reaction; the dilute-phase coke gas flow relies on volatile matter to achieve rapid ignition and ignite premixed ammonia gas.

2. The coal-ammonia co-combustion method according to claim 1, which utilizes ammonia gas to transport and pyrolyze pulverized coal, is characterized in that... The temperature of the mixed airflow is 200℃~250℃.

3. The coal-ammonia co-combustion method according to claim 1, which utilizes ammonia gas to transport and pyrolyze pulverized coal, is characterized in that... The coal powder mentioned in step S1 is dried coal powder, which is obtained by drying with hot air; Raw coal is ground to obtain wet coal powder, and hot air dries the wet coal powder to obtain dry coal powder. The free water and some bound water in the wet coal powder are evaporated and mixed with the hot air after the temperature drops to form humid exhaust gas. The temperature of the hot air is 300℃~350℃, and the temperature of the exhaust air is 70℃~90℃.

4. The coal-ammonia co-combustion method according to claim 1, which utilizes ammonia gas to transport and pyrolyze pulverized coal, is characterized in that... The coal powder mentioned in step S1 is wet coal powder obtained by grinding raw coal. High-temperature ammonia gas is used to dry and transport the wet coal powder. At this time, the mixed gas flow is a humid mixed gas including water vapor; wherein the temperature of the high-temperature ammonia gas is 400℃~500℃.

5. The coal-ammonia co-combustion method according to any one of claims 1 to 4, characterized in that, When a direct-flow coal-ammonia co-fired burner is used, the dense phase coke gas flow is ignited by the upstream flame, and at the same time, the dense phase coke gas flow achieves complete combustion with the aid of humid exhaust gas or humid mixed gas, and the dense phase coke is completely burned under the action of hot air; the dilute phase coke gas flow is ignited and burned with the aid of hot air, and the dilute phase coke is completely burned under the action of humid exhaust gas or hot air.

6. The coal-ammonia co-combustion method according to any one of claims 1 to 4, characterized in that, When a swirl coal-ammonia co-fired burner is used, the dilute phase coke gas stream is ignited by heating with high-temperature flue gas under the assistance of central air; the dense phase coke gas stream is burned out under the assistance of humid exhaust gas or hot air.

7. A coal-ammonia co-combustion system that utilizes ammonia gas to transport and pyrolyze pulverized coal, characterized in that, The coal-ammonia co-fired combustion system using ammonia gas to transport and pyrolyze pulverized coal is used to implement the coal-ammonia co-fired combustion method using ammonia gas to transport and pyrolyze pulverized coal as described in any one of claims 1 to 6; the coal-ammonia co-fired combustion system using ammonia gas to transport and pyrolyze pulverized coal includes a pulverizing section and a burner; the pulverizing section and the burner are connected through an ammonia gas conveying pipe; pulverized coal pyrolysis is completed in the pulverizing section and the ammonia gas conveying pipe; The burner is equipped with an ammonia volatile coke channel, and a rich-lean separator is installed in the ammonia volatile coke channel. The rich-lean separator separates the mixed gas flow into a rich phase coke gas flow and a dilute phase coke gas flow, which then enter the furnace for combustion.

8. The coal-ammonia co-combustion system for transporting and pyrolyzing pulverized coal using ammonia gas according to claim 7, characterized in that, The burner is a DC coal-ammonia co-fired burner, and a DC ammonia volatilization coke channel is provided in the center of the DC coal-ammonia co-fired burner. A DC concentration separator is provided in the DC ammonia volatilization coke channel. The dense phase coke gas flow is close to the center of the furnace, and the dense phase coke gas flow enters the furnace for combustion through the direct-flow dense side coke channel; The dilute phase coke gas flow approaches the furnace wall and enters the furnace for combustion through the direct-flow dilute side coke channel.

9. The coal-ammonia co-combustion system for transporting and pyrolyzing pulverized coal using ammonia gas according to claim 8, characterized in that, A first DC channel for introducing humid exhaust gas or hot air is provided outside the DC rich-side coke channel; a second DC channel for introducing hot air is provided outside the first DC channel; a third DC channel for introducing hot air is provided outside the DC light-side coke channel; and a fourth DC channel for introducing humid exhaust gas or hot air is provided outside the third DC channel.

10. The coal-ammonia co-combustion system for transporting and pyrolyzing pulverized coal using ammonia gas according to claim 7, characterized in that, The burner is a swirling coal-ammonia co-fired burner. The cross-section of the swirling coal-ammonia co-fired burner is a concentric circle structure, consisting of a central air channel, a swirling ammonia volatile matter coke channel, a swirling first channel, and a swirling second channel from the inside out. The swirling ammonia volatile matter coke channel is equipped with a swirling thick-thin separator, with the inner side being the swirling thin-side coke channel and the outer side being the swirling thick-side coke channel. The thick-phase coke gas flows through the swirling thick-side coke channel into the furnace for combustion, while the thin-phase coke gas flows through the swirling thin-side coke channel into the furnace for combustion.

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