Boiler stable combustion method and device based on peak regulation period

Abstract

The invention relates to the technical field of stable combustion of coal-fired boilers, in particular to a boiler stable combustion method and device based on a peak regulation period, and the device comprises a boiler, an air pre-heater, a hot secondary air heater and a steam turbine. The boiler is provided with an air inlet, a smoke outlet and a steam outlet, the steam outlet is connected with the steam turbine through a main steam pipeline, the smoke outlet is connected with a smoke side inlet of the air pre-heater through a smoke exhaust pipeline, the air inlet is connected with an air side outlet of the hot secondary air heater through an air pipeline, and an air side inlet of the hot secondary air heater is connected with the air pre-heater through an air side pipeline. Primary heating gas of the air pre-heater can be sent to a boiler hearth after being heated for the second time. In addition, a control assembly is arranged at the steam main pipe, the steam flow can be controlled according to the pulverized coal combustion degree and the industrial steam demand quantity, and therefore air heating and steam supply in the whole system can be effectively regulated and controlled.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power unit adjustment, and in particular to a boiler stable combustion method and device based on a peak regulation period. Background Art

[0002] In recent years, coal-fired thermal power units will transform from the main power source of power guarantee value to the regulating power source. my country has further proposed to promote the "three reforms and linkages" of coal-fired power, assist in the construction of a new power system, and promote the clean and low-carbon transformation of energy.

[0003] The "three reforms in linkage" refer to three technical transformations carried out on coal-fired power units: energy-saving and carbon-reduction transformation is aimed at reducing coal consumption per kilowatt-hour and carbon dioxide emissions of coal-fired power units; heating transformation is to enable coal-fired power units to bear more heating loads and replace inefficient, high-emission decentralized small boilers; flexibility transformation is to enable coal-fired power units to further improve their load regulation capabilities, release more electricity space for the consumption of new energy, and help the power grid operate safely and stably.

[0004] Currently, coal-fired boilers Figure 1 As shown in the figure, when the boiler is burning coal, the superheated steam is input to the high-pressure cylinder through the pipeline, the secondary heated steam is input to the medium-pressure cylinder through the pipeline, and the other part is supplied to the industry after passing through the desuperheater. Even if the current coal-fired boiler has a good stable combustion ability, it cannot improve the overall economy of the thermal power unit. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a boiler stable combustion method and device based on the peak load period in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the current boiler cannot take into account both stable combustion capability and economic optimization.

[0006] The objective of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a boiler combustion stabilization device based on peak load regulation, comprising: a boiler, an air preheater, a hot secondary air heater and a steam turbine; The boiler is provided with an air inlet, a smoke outlet and a steam outlet; the steam outlet is connected to the steam turbine through a steam main pipe; the smoke outlet is connected to the smoke side inlet of the air preheater through a smoke exhaust pipe; the air inlet is connected to the air side outlet of the hot secondary air heater through an air duct; the air side inlet of the hot secondary air heater is connected to the air preheater through an air side duct, so as to perform secondary heating on the gas heated once in the air preheater; the secondary heated gas is transmitted to the boiler furnace through the air duct; The steam main pipe is also provided with a control component, which is used to control the steam flow of industrial steam supply according to the degree of coal powder combustion and the industrial steam demand.

[0007] As a further improvement of the present invention, a control component is arranged on a branch pipe, which is used to connect the steam main pipe with the steam inlet of the hot secondary air heater. The control component is used to control the steam flow entering the hot secondary air heater, and the control component includes a manual control valve and an automatic control valve.

[0008] As a further improvement of the present invention, a steam detection device is also provided on the branch pipe between the steam main pipe and the hot secondary air heater, and the steam detection device is used to monitor the temperature drop on the steam side; the steam detection device includes a flow meter, a steam pressure sensor and a temperature sensor.

[0009] As a further improvement of the present invention, temperature sensing devices are provided at the wind side inlet and outlet of the hot secondary air heater, and the temperature sensing devices are used to monitor the inlet air temperature and the outlet air temperature of the hot secondary air heater, and the wind side temperature rise of the hot secondary air heater is obtained based on the inlet air temperature and the outlet air temperature.

[0010] As a further improvement of the present invention, the steam side outlet of the hot secondary air heater is used to supply steam to industry through a steam outlet pipeline.

[0011] As a further improvement of the present invention, the hot secondary air heater adopts a fin-tube heat exchanger.

[0012] In a second aspect, the present invention provides a method for stabilizing boiler combustion during peak load regulation, comprising: A hot secondary air heater is added at the outlet of the air preheater in the boiler system, and the air side inlet of the hot secondary air heater is connected to the air preheater through an air side pipeline; During the coal combustion process of the boiler system, the flue gas discharged from the tail of the boiler is discharged into the air preheater, and the flue gas is used to heat the input cold air. The heated gas is then heated for the second time by the hot secondary air heater, and the gas after the second heating is sent to the boiler furnace; The reheated steam generated when the boiler is burning coal flows to the steam turbine through the steam main pipeline. The reheated steam is also input into the hot secondary air heater. According to the degree of coal powder combustion and the industrial steam demand, the steam flow of the hot secondary air heater is controlled, thereby controlling the outflow of industrial steam supply steam.

[0013] As a further improvement of the present invention, a branch pipe is provided on the steam main pipe, and the branch pipe is connected to the steam side inlet of the hot secondary air heater. The branch pipe is used to transmit the secondary heated steam to the hot secondary air heater to supply steam for industry after heating.

[0014] As a further improvement of the present invention, the steam flow outflow of the steam main pipe is controlled according to the degree of coal powder combustion and the industrial steam demand, and the steam detection equipment is used to monitor the temperature drop on the steam side of the steam main pipe in real time; the steam detection equipment is arranged in a branch pipe between the steam main pipe and the hot secondary air heater, and the steam detection equipment includes a flow meter, a steam pressure sensor and a temperature sensing device.

[0015] As a further improvement of the present invention, the steam flow rate outflow of the steam main pipe is controlled according to the degree of coal powder combustion and the industrial steam demand, specifically including: During the deep peak load regulation period, the frequency conversion speed regulating device is used to control the air supply speed on the wind side of the hot secondary air heater according to the load and combustion conditions; According to the monitored pressure, temperature and steam flow results, the control components installed in the branch pipe are adjusted to change the steam flow entering the hot secondary air heater so that the steam pressure control deviation is within ±0.2MPa and the temperature control deviation is within ±5℃.

[0016] The beneficial effects of the present invention are: the cold air is heated once by the air preheater, and then the hot secondary air heater is used for secondary heating, and the secondary heated gas is sent to the boiler furnace. This two-stage heating method can effectively increase the temperature of the gas entering the furnace, so that the pulverized coal can be better ignited and stably burned during low-load peak-shaving. During the peak-shaving process, the temperature in the furnace is prone to fluctuations when the load is reduced. Stable secondary air with appropriate temperature helps to maintain a stable combustion environment and reduce the interruption or instability of pulverized coal combustion due to insufficient temperature. The control component at the steam main pipe controls the steam flow according to the degree of pulverized coal combustion and the demand for industrial steam. During the peak-shaving period, the combustion state of pulverized coal varies greatly, and reasonable steam flow control can ensure the heat balance in the furnace. When the degree of pulverized coal combustion is weak, appropriate adjustment of the steam flow can maintain a suitable pressure and temperature in the furnace, create conditions for continuous and stable combustion of pulverized coal, and avoid the deterioration of the combustion conditions in the furnace due to unreasonable steam flow.

[0017] The control components at the steam main pipe control the steam flow rate according to the degree of pulverized coal combustion and the demand for industrial steam. During the peak-shaving period, the pulverized coal combustion state varies greatly, and reasonable steam flow control can ensure the heat balance in the furnace. When the pulverized coal combustion degree is weak, appropriate adjustment of the steam flow rate can maintain appropriate pressure and temperature in the furnace, create conditions for continuous and stable combustion of pulverized coal, and avoid the deterioration of the combustion conditions in the furnace due to unreasonable steam flow. The control components at the steam main pipe control the steam flow rate according to the degree of pulverized coal combustion and the demand for industrial steam. During the peak-shaving period, the pulverized coal combustion state varies greatly, and reasonable steam flow control can ensure the heat balance in the furnace. When the pulverized coal combustion degree is weak, appropriate adjustment of the steam flow rate can maintain appropriate pressure and temperature in the furnace, create conditions for continuous and stable combustion of pulverized coal, and avoid the deterioration of the combustion conditions in the furnace due to unreasonable steam flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the structure of a boiler stable combustion system in the prior art; Figure 2 It is a schematic diagram of the structure of the boiler combustion stabilization device based on the peak load period of the present invention; Figure 3 It is a schematic flow chart of a method for stabilizing combustion of a boiler during a peak load period according to the present invention; In the figure, 1-boiler, 2-air preheater, 3-hot secondary air heater, 4-steam main pipe, 5-steam turbine, 6-control component, 61-manual control valve, 62-automatic control valve, 7-steam detection equipment, 71-flow meter, 72-steam pressure sensor, 73-temperature sensor, 8-temperature sensing device, 9-thermometer, 10-pressure sensor. DETAILED DESCRIPTION

[0020] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, wherein the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0022] Example 1 like Figure 2-Figure 3 As shown, this embodiment provides a boiler combustion stabilization device based on the peak load period. The device includes a boiler 1, an air preheater 2, a hot secondary air heater 3 and a steam turbine 5.

[0023] The boiler 1 is provided with an air inlet, a smoke outlet and a steam outlet; the steam outlet of the boiler is connected to the steam turbine 5 through a steam main pipe 4; the smoke outlet is connected to the flue gas side inlet of the air preheater 2 through a smoke exhaust pipe; the air inlet is connected to the wind side outlet of the hot secondary air heater 3 through an air duct. The wind side inlet of the hot secondary air heater 3 is connected to the air preheater 2 through an air side pipe, which is used to reheat the gas heated once in the air preheater; the gas heated after the second heating is transmitted to the furnace of the boiler 1 through the air duct; the steam main pipe 4 includes a superheated steam pipe and a reheated steam pipe. The superheated steam pipe connects the steam outlet of the boiler and the high-pressure cylinder in the steam turbine 5. The reheated steam pipe connects the steam outlet of the boiler and the low-pressure cylinder in the steam turbine 5, and the reheated steam pipe is also connected to the hot secondary air heater 3.

[0024] A control component 6 is also provided at the steam main pipe, and the control component 6 is used to control the steam flow rate according to the degree of coal powder combustion and the industrial steam demand. The control component 6 is arranged on the branch pipe, and the branch pipe is used to connect the steam main pipe with the steam inlet of the hot secondary air heater. The control component 6 includes a manual control valve 61 and an automatic control valve 62. The automatic control valve in the control component introduces a fuzzy logic control algorithm, takes the degree of coal powder combustion and the industrial steam demand as input variables, and the steam flow control signal as the output variable. When the degree of coal powder combustion is weak and the industrial steam demand is low, the steam flow rate is appropriately reduced, but a certain furnace temperature must be maintained. The fuzzy logic control algorithm can better handle complex nonlinear systems and improve the adaptability of the control component to various working conditions. The automatic control valve 62 also adopts a predictive control algorithm, combined with historical operation data and real-time sensor data, to predict the degree of coal powder combustion and industrial steam demand in the future. According to the prediction results, the steam flow rate is adjusted in advance to achieve a smoother control process. For example, when the load changes, the predictive control algorithm can adjust the opening of the automatic control valve in advance to avoid excessive fluctuations in steam flow due to changes in demand, thereby improving the stability of the system and energy saving effects.

[0025] In addition, the valves in the control assembly are multi-valve combinations, including fine-tuning valves and emergency shut-off valves. The fine-tuning valve can finely adjust the steam flow during normal operation to further improve the accuracy of flow control. The emergency shut-off valve can quickly cut off the steam supply in abnormal situations (such as steam pipeline leakage, equipment failure, etc.) to prevent the accident from expanding.

[0026] A steam detection device 7 is also provided on the branch pipe between the steam main pipe and the hot secondary air heater. The steam detection device is used to monitor the temperature drop on the steam side. The steam detection device includes a flow meter 71, a steam pressure sensor 72 and a temperature sensor 73.

[0027] The air side inlet and outlet of the hot secondary air heater are both provided with temperature sensing devices 8, which are used to monitor the inlet air temperature and outlet air temperature of the hot secondary air heater, and obtain the air side temperature rise of the hot secondary air heater according to the inlet air temperature and outlet air temperature. The steam side outlet of the hot secondary air heater is used to supply steam to the industry through the steam outlet pipe, and the steam outlet pipe is also provided with a thermometer 9 and a pressure sensor 10. The hot secondary air heater in this embodiment adopts a finned tube heat exchanger. The inside of the tube is a hot reheat steam flow channel, and the outside of the tube is an air flow channel. The heat exchange is used to increase the temperature of the hot secondary air, so that the heat absorption of the secondary air in the furnace is reduced, creating a good environmental condition for the ignition and stable combustion of coal powder, which can improve the stable combustion performance of the boiler, and also improve the burnout performance of coal powder; the reheated steam after heat exchange and cooling is led to the industrial heating users, creating conditions for reducing the water for industrial heating spraying and cooling. The hot secondary air heater is equivalent to replacing the original desuperheater function, reducing the irreversible loss of water spraying and cooling, and achieving better machine-boiler coupling.

[0028] The boiler stable combustion process is: The coal enters the boiler furnace and is mixed with air and burned by the burner. A large amount of heat energy is released during the combustion process, which increases the temperature in the furnace.

[0029] The heat is transferred to the water in the boiler, causing it to evaporate and form steam. The steam continues to accumulate in the boiler, and the pressure and temperature gradually increase.

[0030] At this time, the flue gas discharged from the tail of the boiler passes through the air preheater. At the same time, the cold air enters the air preheater and is heated by the waste heat of the flue gas. The heated air is divided into primary air and secondary air. The primary air is used to transport pulverized coal, and the secondary air is used to support combustion.

[0031] The flue gas discharged from the tail of the boiler carries a large amount of waste heat and enters the air preheater through the flue gas exhaust duct. At the same time, cold air enters the air preheater from the air inlet. In the air preheater, the waste heat of the flue gas is used to heat the cold air once, and the heated air is divided into primary air and secondary air according to its purpose. The primary air is mainly responsible for conveying pulverized coal. It needs to have a certain pressure and speed to ensure that the pulverized coal can be stably transported from the pulverized coal bin to the burner and fully mixed with the secondary air in the burner. The secondary air is mainly used to support combustion. After mixing with the pulverized coal and the primary air in the furnace, it provides sufficient oxygen for combustion, making the combustion more complete and stable. Therefore, the heated secondary air gas is heated for the second time by the hot secondary air heater, and the gas after secondary heating is sent to the boiler furnace.

[0032] The steam generated when the boiler burns coal flows to the steam turbine through the steam main pipe. According to the degree of coal powder combustion and the demand for industrial steam, the steam flow rate of the steam main pipe is controlled to flow out to the steam turbine. The steam turbine includes a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder.

[0033] During the combustion process of the boiler, the high-temperature, high-pressure steam generated enters the high-pressure cylinder through the superheated steam channel. The high-pressure steam expands and works in the high-pressure cylinder, driving the impeller and blades to rotate. In this process, the pressure and temperature of the steam gradually decrease, and after the high-pressure cylinder expands and works at various levels, the thermal energy of the steam is converted into mechanical energy.

[0034] At this time, the steam input into the high-pressure cylinder returns to the boiler for reheating to obtain reheated steam, and the reheated steam enters the medium-pressure cylinder through the reheat steam pipe.

[0035] The intermediate pressure cylinder receives the reheated steam output from the boiler. The reheated steam continues to expand and do work in the intermediate pressure cylinder, driving the impeller and blades to rotate, further converting the thermal energy of the steam into mechanical energy. In this process, the pressure and temperature of the steam are reduced again. The steam output from the intermediate pressure cylinder enters the low pressure cylinder to continue to do work.

[0036] The low-pressure cylinder receives the steam output from the medium-pressure cylinder. The steam continues to expand and do work in the low-pressure cylinder, driving the impeller and blades to rotate, converting the thermal energy of the steam into mechanical energy. In this process, the pressure and temperature of the steam continue to decrease. For example, after the low-pressure cylinder expands and does work at each stage, the steam pressure may drop to about 4.9kPa and the temperature may drop to about 36 degrees Celsius.

[0037] The mechanical energy output by the low-pressure cylinder is transmitted to the generator through the shaft system, driving the generator to generate electricity. At the same time, the working efficiency and performance of the low-pressure cylinder also affect the efficiency and power generation capacity of the entire steam turbine.

[0038] Example 2 This embodiment provides a method for stabilizing combustion of a boiler during a peak load period, which is implemented based on the device for stabilizing combustion of a boiler during a peak load period in Embodiment 1. The method mainly includes: A hot secondary air heater is added at the outlet of the air preheater in the boiler system, and the inlet of the hot secondary air heater is connected to the air preheater through a steam flow pipeline; During the coal combustion process of the boiler system, the flue gas discharged from the tail of the boiler is discharged into the air preheater, and the input cold air is heated by the flue gas. The heated gas is heated for the second time by the hot secondary air heater, and the gas after the second heating is sent to the boiler furnace; The steam generated when the boiler burns coal flows to the steam turbine through the superheated steam pipe in the steam mother pipe. After the steam turbine returns the steam to the boiler, the boiler heats the steam again to obtain reheated steam. The reheated steam is input into the steam turbine through the reheated steam pipe in the steam mother pipe. The reheated steam also passes through the hot secondary air heater to supply steam for industry. The steam flow rate of industrial steam supply is controlled according to the degree of coal powder combustion and the demand for industrial steam.

[0039] A branch pipe is arranged on the steam main pipe, and the branch pipe is connected to the steam side inlet of the hot secondary air heater. The branch pipe is used to transmit the secondary heated steam to the hot secondary air heater, and then the steam is supplied to the industry after heating.

[0040] In addition, according to the degree of coal powder combustion and the demand for industrial steam, the steam flow outflow of the steam main pipe is controlled, and the temperature drop on the steam side of the steam main pipe is monitored in real time through steam detection equipment; the steam detection equipment is arranged in a branch pipe between the steam main pipe and the hot secondary air heater, and the steam detection equipment includes a flow meter, a steam pressure sensor and a temperature sensor.

[0041] In addition, during the deep peak load period, the variable frequency speed control device is used to control the air supply speed on the wind side of the hot secondary air heater according to the load and combustion conditions; According to the monitored pressure, temperature and steam flow results, the control components installed in the branch pipe are adjusted to control the steam flow entering the hot secondary air heater, so that the steam pressure control deviation can be controlled within ±0.2MPa, and the temperature control deviation can be controlled within ±5℃.

[0042] The control component of this embodiment uses a predictive control algorithm and a fuzzy logic control algorithm to control the opening of the valve, thereby avoiding excessive fluctuations in steam flow due to changes in demand and improving the stability of the system and the energy-saving effect.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A boiler combustion stabilization device based on peak load period, characterized in that: include: Boilers, air preheaters, hot secondary air heaters and steam turbines; The boiler is provided with an air inlet, a smoke outlet and a steam outlet; the steam outlet is connected to the steam turbine through a steam main pipe; the smoke outlet is connected to the smoke side inlet of the air preheater through a smoke exhaust pipe; the air inlet is connected to the air side outlet of the hot secondary air heater through an air duct; the air side inlet of the hot secondary air heater is connected to the air preheater through an air side duct, so as to perform secondary heating on the gas heated once in the air preheater; the secondary heated gas is transmitted to the boiler furnace through the air duct; The steam main pipe is also provided with a control component, which is used to control the steam flow of industrial steam supply according to the degree of coal powder combustion and the industrial steam demand.

2. The boiler combustion stabilization device based on the peak load period according to claim 1 is characterized in that: The control component is arranged on a branch pipe, the branch pipe is used to connect the steam main pipe with the steam inlet of the hot secondary air heater, the control component is used to control the steam flow entering the hot secondary air heater, and the control component includes a manual control valve and an automatic control valve.

3. The boiler combustion stabilization device based on the peak load period according to claim 2 is characterized in that: A steam detection device is also provided on the branch pipe between the steam main pipe and the hot secondary air heater, and the steam detection device is used to monitor the temperature drop on the steam side; the steam detection device includes a flow meter, a steam pressure sensor and a temperature sensor.

4. The boiler combustion stabilization device based on the peak load period according to claim 1 is characterized in that: Temperature sensing devices are provided at the wind side inlet and outlet of the hot secondary air heater. The temperature sensing devices are used to monitor the inlet air temperature and outlet air temperature of the hot secondary air heater, and obtain the wind side temperature rise of the hot secondary air heater based on the inlet air temperature and outlet air temperature.

5. The boiler combustion stabilization device based on the peak load period according to claim 1 is characterized in that: The steam side outlet of the hot secondary air heater is used to supply steam to industry through a steam outlet pipeline.

6. The boiler combustion stabilization device based on the peak load period according to claim 1 is characterized in that: The hot secondary air heater adopts a fin tube heat exchanger.

7. A method for stabilizing boiler combustion during peak load period, characterized in that: include: A hot secondary air heater is added at the outlet of the air preheater in the boiler system, and the air side inlet of the hot secondary air heater is connected to the air preheater through an air side pipeline; During the coal combustion process of the boiler system, the flue gas discharged from the tail of the boiler is discharged into the air preheater, and the input cold air is heated by the flue gas. The heated gas is heated for the second time by the hot secondary air heater, and the gas after the second heating is sent to the boiler furnace; The reheated steam generated when the boiler is burning coal flows to the steam turbine through the steam main pipeline. The reheated steam is also input into the hot secondary air heater. According to the degree of coal powder combustion and the industrial steam demand, the steam flow of the hot secondary air heater is controlled, thereby controlling the outflow of industrial steam supply steam.

8. The method for boiler stable combustion during peak load period according to claim 7, characterized in that: The steam main pipe is provided with a branch pipe, which is connected to the steam side inlet of the hot secondary air heater. The branch pipe is used to transmit the secondary heated steam to the hot secondary air heater to supply steam for industry after heating.

9. The method for boiler stable combustion during peak load period according to claim 7, characterized in that: According to the degree of coal powder combustion and the demand for industrial steam, the steam flow outflow of the steam main pipe is controlled, and the steam detection equipment is used to monitor the temperature drop on the steam side of the steam main pipe in real time; the steam detection equipment is arranged in a branch pipe between the steam main pipe and the hot secondary air heater, and the steam detection equipment includes a flow meter, a steam pressure sensor and a temperature sensor.

10. The method for boiler stable combustion during peak load period according to claim 9, characterized in that: According to the degree of pulverized coal combustion and the demand for industrial steam, the steam flow outflow of the steam main pipe is controlled, including: During the deep peak load regulation period, the frequency conversion speed regulating device is used to control the air supply speed on the wind side of the hot secondary air heater according to the load and combustion conditions; According to the monitored pressure, temperature and steam flow results, the control components installed in the branch pipe are adjusted to change the steam flow entering the hot secondary air heater so that the steam pressure control deviation is within ±0.2MPa and the temperature control deviation is within ±5℃.

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