Blending combustion system and method for blending combustion of pulverized coal and hydrogen

Abstract

The invention discloses a blending combustion system and method for blending combustion of pulverized coal and hydrogen, and belongs to the technical field of energy and power engineering.The blending combustion system comprises a raw coal conveying device, a pulverized coal bin, a coal mill, a boiler and a special blending combustion device; the blending combustion method comprises the following steps: S1, filtering and stabilizing pressure of externally supplied hydrogen, and then conveying the hydrogen into the hydrogen storage tank for storage; s2, hydrogen in the hydrogen storage tank enters combustors at the four corners of the boiler through hydrogen conveying pipelines, is mixed with pulverized coal in the combustors and is ignited for combustion; and S3, the combustion state is monitored in real time through a flame detector, and the hydrogen flow is adjusted according to the boiler load requirement. According to the invention, the combustion efficiency and the blending combustion ratio are improved, and the NOx emission is reduced; efficient blending combustion can be realized only by adding a special blending combustion device, so that the transformation cost is reduced; in the hydrogen blending combustion process, the hydrogen flow can be dynamically adjusted, the combustion state can be monitored in real time, the stability and safety of the combustion process can be ensured, environmental pollution is reduced, and the energy utilization efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy and power engineering, and in particular to a system and method for burning pulverized coal and hydrogen. Background Art

[0002] With the global emphasis on clean energy and environmental protection technologies, hydrogen blending technology, as an efficient and clean way of energy utilization, has been widely used in pulverized coal boilers, fluidized bed boilers, industrial boilers and other fields, and has shown broad development prospects. By mixing hydrogen with traditional fuels, not only can the combustion efficiency and energy utilization rate be significantly improved, but also carbon emissions can be effectively reduced, helping companies achieve energy conservation and emission reduction goals. However, despite the many advantages of hydrogen blending technology, traditional hydrogen blending still has some problems:

[0003] (1) Some traditional hydrogen blending methods are less safe. The combustion characteristics of hydrogen are significantly different from those of traditional fuels. Its high combustion speed and flammable and explosive properties easily pose safety hazards.

[0004] (2) The traditional hydrogen blending process may cause problems such as uneven temperature distribution in the furnace and unstable flue gas flow. Especially under low load or variable load conditions of the boiler, these problems will be further aggravated, affecting combustion efficiency and equipment life.

[0005] (3) During the operation of the burner, it is difficult to avoid the high-temperature flame eroding the boiler water-cooled wall and heating surface, resulting in frequent coking problems. The strong reducing atmosphere in the area close to the furnace wall is not fully considered, which easily causes high-temperature corrosion. Summary of the Invention

[0006] The purpose of the present invention is to provide a coal pulverized gas blending system and method to solve the problems of unstable combustion efficiency, insufficient equipment adaptability and limited blending ratio in the prior art when coal pulverized gas blending is blended with hydrogen.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a coal powder blending and hydrogen blending system, comprising a raw coal conveying device, a coal powder bin, a pulverized coal mill, and a boiler, which are arranged in sequence along the fuel conveying order, and also comprising a special blending device for introducing hydrogen into the boiler furnace, the special blending device comprising a hydrogen conveying pipeline, one end of the hydrogen conveying pipeline being connected to a hydrogen storage tank storing spare hydrogen, the other end of the hydrogen conveying pipeline being connected to the burners at the upper secondary air inlets at the four corners of the boiler through branch pipelines, the branch pipelines of each burner being independently equipped with a control valve group, the end of the burner close to the boiler being provided with a combustion air distribution system, and a flame detector being provided on the hydrogen conveying pipeline close to the burner; and also comprising a control system, the control valve group and the flame detector being electrically connected to the control system.

[0009] Furthermore, an anti-backfire flame arrester is provided at one end of the hydrogen delivery pipeline close to the boiler, and a pressure transmitter and a pressure indicator are also provided on the hydrogen delivery pipeline.

[0010] Furthermore, the control valve group includes a hydrogen flow regulating valve and a quick shut-off valve, and the hydrogen flow regulating valve and the quick shut-off valve are arranged on the branch pipeline.

[0011] A method for blending pulverized coal with hydrogen, using the blending system described above to perform blending operations, comprises the following steps:

[0012] S1, after filtering and stabilizing the pressure of the externally supplied hydrogen, transport it to the hydrogen storage tank for storage;

[0013] S2. The hydrogen in the hydrogen storage tank enters the burners at the four corners of the boiler through the hydrogen delivery pipeline, where it mixes with the pulverized coal and ignites and burns;

[0014] S3. Monitor the combustion state in real time through the flame detector and adjust the hydrogen flow rate according to the boiler load demand.

[0015] Furthermore, the flame diameter at the burner outlet is 0.8 to 1.2 meters, and the flame length is 3 to 5 meters.

[0016] Furthermore, the hydrogen blending ratio is 1.5-4% of the total fuel heat.

[0017] Furthermore, the working pressure in the hydrogen delivery pipeline is 0.01-0.06 MPa, and the temperature range is 20-50°C.

[0018] Furthermore, the control valve group adopts a gradual pressure increase method when starting, and the calculation formula is:

[0019] ;

[0020] in, is the pipeline pressure at time t, is the initial pressure, is the maximum allowable pressure, k is the pressure increase rate coefficient, The boost start time.

[0021] Furthermore, the combustion air distribution system has an air distribution volume of 125m³ / min.

[0022] Furthermore, before step S1, there is step S0: the externally supplied hydrogen is pressurized by a compressor and then transported to a hydrogen storage tank for storage.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] By optimizing the burner design and control strategy, this invention significantly improves combustion efficiency and the blending ratio, while also reducing NOx emissions. Furthermore, when upgrading a boiler with blending, modifications to existing pulverized coal boilers are minimal; only specialized blending equipment is required to achieve efficient blending, significantly reducing modification costs.

[0025] During the hydrogen blending combustion process, the present invention can not only dynamically adjust the hydrogen flow rate, but also monitor the combustion state in real time, thereby ensuring the stability and safety of the combustion process, reducing environmental pollution, and improving energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic structural diagram of a system for burning pulverized coal and hydrogen according to the present invention;

[0028] Figure 2 This is a schematic structural diagram of the special blending device of the present invention;

[0029] Figure 3 The present invention is a flow chart of the method for burning pulverized coal with hydrogen.

[0030] Explanation of the accompanying symbols: 1. Raw coal conveying device; 2. Pulverized coal silo; 3. Coal mill; 4. Boiler; 5. Special blending device; 51. Hydrogen conveying pipeline; 52. Burner; 53. Flame detector; 54. Combustion air distribution system; 55. Anti-backfire flame arrester; 56. Pressure transmitter; 57. Pressure indicator; 58. Hydrogen flow regulating valve; 59. Quick shut-off valve. DETAILED DESCRIPTION

[0031] like Figure 1-2As shown, a coal powder blending and hydrogen combustion system includes a raw coal conveying device 1, a coal powder bin 2, a pulverized coal mill 3, and a boiler 4 arranged in sequence along the fuel conveying order, and also includes a special blending device 5 for introducing hydrogen into the furnace of the boiler 4, the special blending device 5 includes a hydrogen delivery pipeline 51, one end of the hydrogen delivery pipeline 51 is connected to a hydrogen storage tank storing spare hydrogen, and the other end of the hydrogen delivery pipeline 51 is connected to the burner 52 at the upper secondary air outlet of the four corners of the boiler 4 through a branch pipeline, and each of the burners 52 is independently equipped with a control valve group on the branch pipeline, the control valve group includes a hydrogen flow regulating valve 58 and a quick shut-off valve 59, and the hydrogen flow regulating valve 58 and the quick shut-off valve 59 are arranged on the branch pipeline, the burner 52 is provided with a combustion air distribution system 54 at one end near the boiler 4, and a flame detector 53 is provided on the hydrogen delivery pipeline 51 near the burner 52; it also includes a control system, and the control valve group and the flame detector 53 are electrically connected to the control system.

[0032] In practice, externally supplied hydrogen is pressurized by a compressor and then transported to a hydrogen storage tank. This ensures a stable and continuous hydrogen supply, preventing system operational anomalies caused by supply interruptions. After filtration and pressure stabilization, the hydrogen in the tank enters the burners 52 at the upper secondary air inlets at each corner of the boiler through hydrogen delivery pipes 51. Each burner 52 is independently equipped with a hydrogen flow control valve 58 and a quick-shutoff valve 59 to precisely control the hydrogen flow and quickly shut it off in emergencies.

[0033] An anti-backfire flame arrester 55 is provided at one end of the hydrogen delivery pipeline 51 close to the boiler 4. The anti-backfire flame arrester 55 can effectively prevent the flame from propagating in the reverse direction along the hydrogen delivery pipeline, thereby ensuring the safe operation of the system; the hydrogen delivery pipeline 51 is also provided with a pressure transmitter 56 and a pressure indicator 57 for real-time monitoring and adjustment of the working pressure in the hydrogen delivery pipeline 51 to ensure that it is always within a safe range.

[0034] like Figure 3 As shown, a method for burning pulverized coal with hydrogen, using the above-mentioned burning system to carry out the burning operation, includes the following steps:

[0035] S1, after filtering and stabilizing the pressure of the externally supplied hydrogen, transport it to the hydrogen storage tank for storage;

[0036] S2. The hydrogen in the hydrogen storage tank enters the burners 52 at the four corners of the boiler 4 through the hydrogen delivery pipe 51, where it mixes with the pulverized coal and ignites and burns;

[0037] S3. The combustion state is monitored in real time by the flame detector 53, and the hydrogen flow rate is adjusted according to the load demand of the boiler 4.

[0038] Specifically, the flame diameter at the burner 52 outlet is 0.8 to 1.2 meters, and the flame length is 3 to 5 meters. This design ensures that the flame does not contact the heating surface of the boiler, while ensuring sufficient combustion and reducing the emission of unburned substances.

[0039] The hydrogen blending ratio is 1.5-4% of the total fuel calorific value. In actual operation, this ratio can be dynamically adjusted based on the load of boiler 4. For example, under low-load conditions, the hydrogen blending ratio can be appropriately reduced to approximately 1.5% (generally controlled at 1.5-4% under normal circumstances, and around 0.5% in extreme cases) to maintain stable operation of boiler 4. Under high-load conditions, the hydrogen blending ratio can be increased to 4% to fully utilize the high calorific value of hydrogen and improve overall combustion efficiency.

[0040] The working pressure in the hydrogen delivery pipeline 51 is 0.01-0.06 MPa and the temperature range is 20-50° C. to ensure the safety and stability of hydrogen delivery.

[0041] The control valve group adopts a gradual pressure increase method when starting, and its calculation formula is:

[0042] ;

[0043] in, is the pipeline pressure at time t, is the initial pressure, is the maximum allowable pressure, k is the pressure increase rate coefficient, The boost start time.

[0044] This control valve group uses nonlinear boosting to avoid system shocks caused by sudden pressure changes, thereby improving operational safety. In practical applications, the initial pressure is typically 0.02 MPa, the maximum allowable pressure is 0.06 MPa, the boost rate coefficient k is 0.5, and the boost start time is 5 seconds. With the appropriate setting of these parameters, the pressure in the hydrogen delivery pipeline 51 can be steadily increased to the target value in a short period of time, ensuring stable system operation.

[0045] A combustion air distribution system 54 is provided at one end of the burner 52 close to the boiler 4. The air distribution nozzle and the burner 52 are of an integrated design. Air starts blowing from the root of the burner 52, which has the function of externally blowing air to cool the burner and also blows air to the burner mouth to serve as combustion air distribution. The air volume is 125m³ / min. The function of the combustion air distribution system 54 is to provide combustion air distribution and additional cooling protection for the burner 52 to ensure stable hydrogen combustion and prevent the burner 52 from being damaged by overheating in a high-temperature environment. The cooling air nozzle adopts a fully wrapped design, and the air volume is controlled by the damper to meet the minimum air volume requirement. The design of the cooling air nozzle allows the cooling air to evenly cover the key parts of the burner, ensuring that it maintains stable performance during long-term operation. In addition, the introduction of combustion air distribution can also improve the oxygen distribution near the burner and further optimize the combustion effect.

[0046] Before step S1, there is step S0: the externally supplied hydrogen is pressurized by a compressor and then transported to a hydrogen storage tank for storage.

[0047] During actual operation, hydrogen from the hydrogen storage tank enters the burners 52 at the four corners of the boiler through the hydrogen delivery pipe 51. Pulverized coal is also introduced into the burners 52. The pulverized coal is transported to the pulverized coal bin 2 by the raw coal conveying device 1. It is then ground into fine powder by the pulverizer 3 and fed into the furnace of the boiler 4. The hydrogen and pulverized coal mix and ignite in the burner 52, forming a stable flame. To ensure combustion efficiency and safety, the flame detector 53 monitors the combustion status in real time and dynamically adjusts the hydrogen flow rate based on the boiler's load requirements. When the hydrogen supply to a burner 52 is shut down, the purge system uses nitrogen to purge the deactivated portion to displace the combustible gas, avoiding safety accidents such as hydrogen explosions. The signal from the flame detector 53 is transmitted to the control system, which calculates the optimal hydrogen flow rate based on the real-time monitoring data and adjusts it through the hydrogen flow control valve 58.

[0048] By optimizing the burner design and control strategy, this invention significantly improves combustion efficiency and the blending ratio, while maintaining NOx emissions. For example, in one practical application scenario, the implementation of this blending system increased the boiler's combustion efficiency from 90.5% to 92%, without increasing NOx emissions. Furthermore, this invention is suitable for upgrading existing pulverized coal boilers, requiring only the addition of a dedicated blending device to achieve efficient blending. This modification offers low cost and a short construction period.

[0049] The present invention utilizes an intelligent control algorithm during the hydrogen blending process ("intelligent control algorithm" refers to automatically adjusting the hydrogen supply based on changes in hydrogen pressure. It also automatically adjusts and balances the hydrogen supply at each corner of the furnace by monitoring the pressure of the four hydrogen guns, ensuring flue gas temperature balance across the furnace). This algorithm not only dynamically adjusts the hydrogen flow rate but also monitors the combustion status in real time, thereby ensuring the stability and safety of the combustion process. During performance testing, when the boiler load suddenly increased, the control system rapidly adjusted the hydrogen flow rate based on the signal from the flame detector 53, restoring the combustion state to stability within 5 seconds and preventing equipment damage caused by unstable combustion. Furthermore, by optimizing the blending ratio and burner design, the present invention significantly improves energy efficiency and reduces environmental pollution. During performance testing, in industrial boiler applications, the use of this blending method increased the thermal efficiency per unit fuel by approximately 1.5% and reduced CO2 emissions by approximately 4%.

[0050] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A coal pulverized gas-fired hydrogen-fired system comprising a raw coal conveying device (1), a coal pulverized gas bin (2), a coal mill (3), and a boiler (4) arranged in sequence along a fuel conveying sequence, characterized in that: The invention also includes a special blending device (5) for introducing hydrogen into the furnace of the boiler (4), wherein the special blending device (5) includes a hydrogen delivery pipeline (51), one end of the hydrogen delivery pipeline (51) is connected to a hydrogen storage tank storing spare hydrogen, and the other end of the hydrogen delivery pipeline (51) is connected to the burners (52) at the upper secondary air inlets at the four corners of the boiler (4) through branch pipelines, and each branch pipeline of the burner (52) is independently equipped with a control valve group, and a combustion air distribution system (54) is provided on one end of the burner (52) close to the boiler (4), and a flame detector (53) is provided on the hydrogen delivery pipeline (51) at a position close to the burner (52); and a control system is also included, wherein the control valve group and the flame detector (53) are both electrically connected to the control system.

2. The pulverized coal and hydrogen blending system according to claim 1, characterized in that: An anti-backfire flame arrester (55) is provided at one end of the hydrogen delivery pipeline (51) close to the boiler (4), and a pressure transmitter (56) and a pressure indicator (57) are also provided on the hydrogen delivery pipeline (51).

3. The coal pulverized and hydrogen blending system according to claim 1 is characterized in that: The control valve group comprises a hydrogen flow regulating valve (58) and a quick shut-off valve (59), and the hydrogen flow regulating valve (58) and the quick shut-off valve (59) are arranged on the branch pipeline.

4. A method for blending pulverized coal with hydrogen, wherein the blending system according to claim 2 or 3 is used for blending, characterized in that: The following steps are involved: S1, after filtering and stabilizing the pressure of the externally supplied hydrogen, transport it to the hydrogen storage tank for storage; S2, the hydrogen in the hydrogen storage tank enters the burners (52) at the four corners of the boiler (4) through the hydrogen delivery pipe (51), is mixed with the pulverized coal in the burner (52), and is ignited and burned; S3. Real-time monitoring of the combustion state through the flame detector (53) and adjusting the hydrogen flow rate according to the load demand of the boiler (4).

5. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: The flame diameter at the burner (52) outlet is 0.8 to 1.2 meters, and the flame length is 3 to 5 meters.

6. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: The hydrogen blending ratio is 1.5-4% of the total fuel heat.

7. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: The working pressure in the hydrogen delivery pipeline (51) is 0.01-0.06 MPa, and the temperature range is 20-50°C.

8. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: The control valve group adopts a gradual pressure increase method when starting, and its calculation formula is: ； in, is the pipeline pressure at time t, is the initial pressure, is the maximum allowable pressure, k is the pressure increase rate coefficient, The boost start time.

9. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: The combustion air distribution system (54) has an air distribution volume of 125 m³ / min.

10. The method for burning pulverized coal with hydrogen according to claim 4, characterized in that: Before step S1, there is step S0: the externally supplied hydrogen is pressurized by a compressor and then transported to a hydrogen storage tank for storage.

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