Electric heating boiler hot air system and thermal power generating unit

Abstract

This invention discloses an electric heating boiler hot air system and a thermal power unit, including a fan, an air preheater, an electric heater, and a power supply system. The fan outlet is connected to the air preheater inlet, and the air preheater outlet is connected to the boiler furnace and / or pulverizing system via a hot air duct. The electric heater is installed on the hot air duct between the air preheater outlet and the boiler furnace and / or pulverizing system for secondary heating of the hot air after it has been heated by the air preheater. The electric heater is connected to the power supply system via a control system. The control system is configured to start the electric heater when the generator unit's operating load is lower than a preset low load threshold, and adjust its output power according to a preset target air temperature to control the temperature of the hot air entering the boiler. This invention also provides a corresponding control method and a thermal power unit including this system. This invention solves the problem of poor combustion stability caused by the decrease in boiler hot air temperature under low load conditions, broadens the peak-shaving range of thermal power units, and improves the capacity for renewable energy absorption and the economic efficiency of unit operation.

Description

Technical Field

[0001] This invention belongs to the field of boiler equipment technology, specifically relating to an electric heating boiler hot air system and a thermal power unit. Background Technology

[0002] Under the new power system with renewable energy as the mainstay, thermal power units are required to have a wide range of peak-shaving capabilities. This means reducing their own load and the amount of electricity fed into the grid when renewable energy generation output is high, in order to improve the utilization rate of renewable energy generation and reduce the curtailment of wind and solar power. However, due to the inherent characteristics of boiler equipment, the minimum load of thermal power units can only reach 20%-30%, and continuous regulation from 0% to 100% is not possible. A large amount of electricity is still fed into the grid at low loads, making it difficult to effectively solve the problem of renewable energy curtailment. Moreover, when the unit is running at low load, the reduced fuel consumption leads to a decrease in combustion intensity and temperature in the furnace, and the boiler hot air temperature drops simultaneously, further aggravating combustion instability and creating a vicious cycle.

[0003] Furthermore, at low boiler loads, the flue gas temperature at the furnace outlet decreases, and the inlet flue gas temperature of the denitrification unit cannot meet process requirements. This necessitates additional measures such as economizer bypass and flue gas bypass to raise the temperature, increasing equipment operating costs and operational complexity. Simultaneously, the boiler steam temperature decreases, deviating from the turbine's rated inlet steam temperature, leading to a significant drop in unit thermal efficiency. To ensure combustion stability at low loads, thermal power units require dedicated burners, and even fuel oil systems or plasma ignition heating devices, which are economically and operationally unsafe, and cannot meet the peak-shaving requirements of new power systems for thermal power units. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an electric heating boiler hot air system that enables precise control of hot air temperature under low-load boiler conditions, improves combustion stability and unit operation safety, expands the peak-shaving range of thermal power units, and simultaneously realizes the recycling and utilization of abandoned renewable energy, improves the economic efficiency of thermal power units under low-load operation, and fully adapts to the development needs of new power systems.

[0005] This invention is achieved through the following technical solution: An electric heating boiler hot air system, comprising: Fans, air preheaters, electric heaters, and power supply systems; The outlet of the blower is connected to the inlet of the air preheater, and the outlet of the air preheater is connected to the boiler furnace and / or pulverizing system through a hot air duct. The electric heater is installed on the hot air duct between the air preheater outlet and the boiler furnace and / or pulverizing system, and is used to reheat the hot air after it has been heated by the air preheater. The electric heater is connected to the power supply system via a control system; The control system is configured to: when the operating load of the generator set is lower than the preset low load threshold, or when the electricity price is lower than the set electricity price threshold, start the electric heater and adjust the output power of the electric heater according to the preset target air temperature to control the temperature of the hot air entering the boiler furnace and / or pulverizing system.

[0006] Preferably, a temperature measuring point is provided on the hot air duct and located at the outlet side of the electric heater. The temperature measuring point is connected to the control system signal for real-time feedback of the hot air temperature at the outlet of the electric heater. The control system dynamically adjusts the output power of the electric heater based on the deviation between the real-time temperature fed back from the temperature measuring point and the preset target air temperature.

[0007] Preferably, the temperature measuring points include multiple temperature sensors spaced apart along the axial direction of the hot air duct, and / or multiple temperature sensors arranged at different radial depths on the same cross section of the hot air duct.

[0008] Preferably, the hot air duct includes a separately installed primary hot air duct and a secondary hot air duct; The electric heater is installed on the primary hot air duct and / or on the secondary hot air duct.

[0009] Preferably, when electric heaters are installed on both the primary hot air duct and the secondary hot air duct, the two sets of electric heaters are equipped with independent power regulators and temperature measuring points. The control system sets the target temperatures for primary and secondary air based on the unit load and operating conditions, and independently controls the output power of the two electric heaters.

[0010] Preferably, the control system includes a controller, a power regulator, and a temperature acquisition module; The temperature acquisition module is connected to the temperature measuring point signal and is used to collect hot air temperature data and transmit it to the controller; The controller is connected to the power regulator by signal. Based on the deviation between the real-time temperature and the target wind temperature, it calculates the power adjustment command according to the PID control algorithm and sends it to the power regulator. The power regulator continuously adjusts the output power of the electric heater according to the power adjustment command.

[0011] Preferably, the plant high-voltage power supply system is connected to the power plant's high-voltage plant power busbar, including: The high-voltage access unit connects to the plant's high-voltage busbar and is used to enable power connection, disconnection, and protection. The voltage conversion unit, when the electric heater is a low-voltage device, is equipped with a step-down transformer to convert the plant's high voltage into the working voltage of the electric heater; The power distribution control unit receives start / stop commands from the control system and controls the on / off state of the electric heater.

[0012] Preferably, the new energy power supply system is connected to an off-site new energy power generation station, including: An external power supply access unit is connected to the transmission line of the new energy power station to receive new energy power. The voltage conversion unit converts the new energy power supply voltage into the operating voltage of the electric heater; The power switching control unit is connected to the control system signals of the new energy dispatching system and the electric heater, respectively, to obtain information on the abandonment of new energy and the operating status of the electric heater in real time. The power switching control unit is configured to switch the power supply of the electric heater to the new energy power supply system when the electric heater is in operation and the new energy source is detected to be abandoned.

[0013] A control method for an electric heating boiler hot air system includes the following steps: Real-time monitoring of the operating load of thermal power units and the transaction price of electricity; When the operating load is lower than the preset low load threshold, or when the electricity price is lower than the set electricity price threshold, the electric heater installed on the hot air duct at the air preheater outlet is activated. The hot air temperature at the outlet of the electric heater is collected in real time by setting a temperature measuring point on the hot air duct on the outlet side of the electric heater. Based on the deviation between the collected hot air temperature and the preset target air temperature, the output power of the electric heater is dynamically adjusted so that the measured temperature approaches and stabilizes near the target air temperature. Repeat the temperature acquisition and power adjustment steps until the electric heater stops operating.

[0014] A thermal power unit includes a boiler and the electric heating boiler hot air system.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The electric heating boiler hot air system provided in this application involves installing an electric heater on the hot air duct between the air preheater outlet and the boiler furnace or pulverizing system, and configuring a control system that works in conjunction with the power supply system. The control system monitors the generator set's operating load and the electricity trading price (purchase price, selling price) in real time. When the generator set load is lower than a preset low load threshold, or when the electricity price is lower than a set price threshold, the electric heater is activated to reheat the hot air after it has been heated by the air preheater. The output power of the electric heater is adjusted according to the preset target air temperature to achieve precise control of the temperature of the hot air entering the boiler. This technical solution addresses the challenge of decreased combustion stability caused by the drop in boiler hot air temperature during low-load operation of thermal power units. It maintains the hot air temperature within the ideal range through active heat supplementation, thereby ensuring combustion stability under low-load conditions and creating conditions for deep peak shaving. It significantly improves boiler combustion stability at low loads, ensuring safe unit operation; broadens the peak shaving range of thermal power units, freeing up grid connection space for renewable energy generation; increases the inlet flue gas temperature of the denitrification unit, meeting environmental protection requirements; increases boiler steam production temperature, improving turbine efficiency; and comprehensively enhances the economy and adaptability of thermal power units during low-load operation. Furthermore, it recovers surplus renewable energy, converting it into heat for boiler use, reducing boiler coal consumption and contributing to energy conservation and emission reduction in thermal power units. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the electric heating boiler hot air system of the present invention (powered by the plant power system); Figure 2 This is a schematic diagram of the structure of the electric heating boiler hot air system of the present invention (powered by an external power supply system); In the diagram: 1-Air preheater, 2-Fan, 3-Electric heater, 4-Power regulator, 5-Temperature measuring point, 6-Electric control cabinet, 7-Transformer, 8-DCS system, 11-Hot air duct, 12-Boiler furnace / pulverizing system. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] An electric heating boiler hot air system includes a fan 2, an air preheater 1, an electric heater 3, and a power supply system; The outlet of the fan 2 is connected to the air preheater 1, which is connected to the boiler via a hot air duct. The electric heater 3 is installed on the hot air duct and is used to reheat the preheated hot air. The electric heater 3 is connected to the power supply system through a control system, which is used to control the working status of the electric heater. When the operating load of the generator set is lower than the set load, the electric heater 3 is started to control the temperature of the preheated hot air.

[0025] In some embodiments, a temperature measuring point is provided on the hot air duct and located on the outlet side of the electric heater 3, for measuring the temperature of the hot air after it has been regulated by the electric heater 3.

[0026] Furthermore, the temperature measuring point is a temperature sensor installed on the hot air duct.

[0027] The temperature measuring points are connected to the control system. The control system has a preset target air temperature curve corresponding to the unit's operating load. When the generator unit's operating load is lower than the preset low load threshold, the control system starts the electric heater 3 and dynamically adjusts the output power of the electric heater 3 through the power regulator based on the deviation between the real-time temperature fed back from the temperature measuring points and the target air temperature, forming a closed-loop control.

[0028] Specifically, when the real-time temperature is lower than the target air temperature, the control system increases the output duty cycle of the power regulator to increase the heating power of the electric heater 3; when the real-time temperature is higher than the target air temperature, the control system decreases the output duty cycle of the power regulator to reduce the heating power; when the real-time temperature is close to the target air temperature, the current power output is maintained, so that the temperature of the hot air entering the boiler is stably maintained within the preset target range.

[0029] In addition, the temperature measuring point also has an over-temperature protection function. The control system is equipped with a safety protection threshold. When the real-time temperature fed back by the temperature measuring point exceeds the threshold, the control system immediately issues an alarm signal and cuts off the power supply to the electric heater 3 to ensure the safe operation of the system.

[0030] Furthermore, to improve the reliability and accuracy of temperature monitoring, multiple temperature measuring points are spaced apart along the airflow direction on the hot air duct at the outlet side of the electric heater 3.

[0031] The multiple temperature measuring points can be insertion-type temperature sensing elements at different radial depths to monitor the temperature distribution on the cross-section of the air duct; or they can be redundant temperature sensing elements arranged along the duct axis for mutual verification and data backup. The control system receives signals from multiple temperature measuring points and can use the average value, median value, or preferred value as feedback control parameters. When an anomaly occurs at a certain measuring point, the system automatically switches to other valid measuring points to ensure the continuity and safety of control.

[0032] Multiple temperature measuring points can be arranged at intervals along the airflow direction to improve the accuracy and reliability of temperature monitoring. The average value or preferred value of the measuring point signal can be used as the control parameter to ensure the continuity and stability of the control.

[0033] In some embodiments, the hot air duct includes a primary air duct and a secondary air duct, and the electric heater 3 is disposed on the primary air duct or the secondary air duct.

[0034] The primary air duct is used to supply hot air to the pulverizing system for drying and conveying pulverized coal; the secondary air duct is used to directly supply hot air to the furnace to provide the air required for combustion. The electric heater 3 can be selected to be installed on the primary air duct, the secondary air duct, or both, depending on the actual needs of the boiler system.

[0035] When the electric heater 3 is only installed on the primary air duct, it is mainly used to increase the temperature of the coal powder drying medium under low load conditions, ensure the drying quality and conveying stability of the coal powder, improve the ignition performance of the coal powder airflow, and prevent the coal powder from becoming damp, blocked, or delayed in combustion due to excessively low air temperature.

[0036] When the electric heater 3 is only installed on the secondary air duct, it is mainly used to increase the temperature of the combustion air under low load conditions, enhance the combustion reaction in the furnace, increase the flame temperature and combustion efficiency, enhance the boiler combustion stability, and reduce the loss of incomplete combustion.

[0037] When electric heater 3 is installed on both the primary and secondary air ducts, coordinated heating of the primary and secondary air can be achieved. The control system sets the target temperatures for the primary and secondary air respectively based on the unit load, coal quality characteristics, and burner operating status, and adjusts the output power of the electric heaters on the primary and secondary air ducts separately through independent power regulators. This coordinated heating mode can simultaneously optimize two key aspects: pulverized coal drying and furnace combustion, maximizing the boiler's operating performance and safety under deep peak-shaving conditions.

[0038] Regardless of which of the above settings is adopted, the electric heaters 3 installed on the primary air duct and / or secondary air duct are connected to the control system, and a temperature measuring point is set on the outlet side of the electric heaters 3 to provide real-time feedback on the air temperature after heating, forming a closed-loop control to ensure that the temperature of the hot air entering the pulverizing system or furnace is stable within the preset target range.

[0039] Furthermore, the primary air duct and the secondary air duct are respectively connected to the primary air fan and the secondary air fan.

[0040] In some implementations, the control system includes a controller, a power regulator, and a temperature acquisition module.

[0041] The temperature acquisition module is connected to the temperature measuring point signal set on the outlet side of the electric heater 3. It is used to collect the hot air temperature data after heating in real time and convert the temperature signal into a standard electrical signal (such as a 4-20mA current signal or a thermocouple millivolt signal) and transmit it to the controller.

[0042] The controller, as the core of the control system, is connected to the temperature acquisition module, power regulator, and distributed control system (DCS) of the generator set. It receives the measured temperature signal from the temperature acquisition module, compares it with the preset target wind temperature, and calculates the required power adjustment command based on the deviation value according to the built-in control algorithm (such as PID algorithm).

[0043] The power regulator is connected to the controller and receives power adjustment commands from the controller. By triggering and controlling power electronic devices (such as thyristors, IGBTs, etc.), it can accurately adjust the output power of the electric heater 3, thereby controlling the hot air temperature to remain stable within the target range.

[0044] When the unit's operating load exceeds the low load threshold, or the electricity price exceeds the set price threshold, electric heater 3 is shut down, and hot air enters the boiler directly after passing through the air preheater. When the unit's operating load drops below the low load threshold, or the electricity price falls below the set price threshold, the controller automatically starts electric heater 3 and dynamically adjusts the output power of the power regulator according to the preset target air temperature and control mode through PID control and feedforward compensation algorithms, ensuring that the outlet air temperature of electric heater 3 remains stable within the target range. Simultaneously, all operating data is uploaded to the DCS system in real time for remote monitoring and operation. Through the above control system settings, intelligent, automated, and high-precision control of electric heater 3 can be achieved, ensuring that the boiler can still obtain a stable hot air temperature under deep peak-shaving conditions, effectively improving combustion stability and operational economy.

[0045] In some embodiments, the power supply system includes a plant high-voltage power supply system or a new energy power supply system, used to provide operating power for the electric heater 3. Depending on the actual situation and operational needs of the power plant, one of the systems can be configured alone, or two systems can be configured simultaneously to form a dual-source power supply mode.

[0046] I. Plant High-Voltage Power Supply System See Figure 1 The plant's high-voltage power supply system is connected to the power plant's high-voltage busbar, forming the basic power supply for electric heater 3. This system includes: High-voltage access unit: Connected to the plant's high-voltage busbar (such as 6kV or 10kV busbar), including disconnecting switches, vacuum circuit breakers, current transformers, voltage transformers, and intelligent protection devices, used to realize the connection, disconnection, measurement, and protection of power supply.

[0047] Voltage conversion unit: When the electric heater 3 is a low-voltage device, a step-down transformer is installed to convert the plant's high voltage to the operating voltage of the electric heater 3 (such as 380V, 660V, or 1140V). The transformer is an energy-saving dry-type transformer, and an appropriate protection level is selected according to the installation environment.

[0048] Power distribution control unit: Includes distribution cabinet, circuit breaker, contactor, etc., used for power distribution and on / off control. The power distribution control unit receives start / stop commands from the control system and controls the start and stop of electric heater 3 through contactors.

[0049] Monitoring and protection unit: Monitors the electrical parameters of the power supply system in real time, provides protection functions such as overcurrent, overload, short circuit, undervoltage, and grounding, and uploads the monitoring data to the control system.

[0050] The plant high-voltage power supply system features reliable power supply, mature technology, and convenient maintenance, and is suitable for the power supply needs of electric heaters under various working conditions.

[0051] II. New Energy Power Supply System See Figure 2 The new energy power supply system is connected to off-site new energy power generation stations to absorb abandoned new energy power and achieve green and low-carbon operation. This system includes: External power supply access unit (power plant step-up substation): connected to the transmission lines of the new energy power plant, including grid connection switch, power meter, anti-islanding protection device and synchronization detection device, to ensure safe and reliable access to new energy power.

[0052] Voltage conversion unit (transformer 7): Based on the matching of the new energy power supply voltage and the working voltage of the electric heater 3, a step-up or step-down transformer is set up to perform voltage conversion.

[0053] Power quality management unit: includes active power filters, static var generators and other equipment, used to suppress harmonics and compensate reactive power to ensure that the power quality of the input electric heater 3 meets the requirements.

[0054] Energy storage buffer unit (optional): Configured with battery energy storage or supercapacitors to smooth out the fluctuations of new energy power and improve power supply stability.

[0055] Power switching control unit: It is connected to the control system signals of the new energy dispatching system, the power plant DCS system and the electric heater 3 respectively, and is used to obtain information on the abandonment of new energy and the operating status of the electric heater 3 in real time. The power switching control unit is configured as follows: When the electric heater 3 is already in operation (i.e., the unit load is below the low load threshold) and the curtailment of renewable energy is detected, the power supply of the electric heater 3 is automatically switched to the renewable energy power supply system, and the output power of the electric heater 3 is dynamically adjusted according to the amount of curtailed electricity. When the curtailment of renewable energy ends, if electric heater 3 still needs to continue operating (the unit is still under low load), it will automatically switch back to the plant's high-voltage power supply system; if electric heater 3 no longer needs to operate, a shutdown command will be issued.

[0056] New energy power supply systems can convert previously abandoned new energy electricity into heat energy and store it in the boiler working fluid, realizing "electricity-heat" conversion and energy time shift. This not only reduces wind and solar curtailment but also replaces some coal combustion, resulting in significant energy-saving and carbon-reducing benefits.

[0057] III. Dual-source power supply system When both a plant-use high-voltage power supply system and a new energy power supply system are configured simultaneously, a dual-source power supply mode is formed, which can further improve power supply reliability and energy utilization efficiency. A dual-source power supply system includes: The plant's high-voltage power supply branch is connected to the plant's high-voltage busbar.

[0058] The new energy power supply branch is connected to the new energy power station.

[0059] The power switching and energy management unit is connected to two power supply branches, electric heater 3, power plant DCS system and new energy dispatch system to realize intelligent power switching and energy optimization management.

[0060] The dual-source power supply system operates as follows: Under normal circumstances, the system monitors the status of both power sources and information on renewable energy curtailment in real time. When the electric heater 3 needs to be started, the energy management unit selects the optimal power source or allocates the load according to a preset strategy and controls the switching equipment of the corresponding branch to connect the power. During operation, the energy management unit continuously monitors the power status and automatically switches the power source when necessary. All operational data is uploaded to the DCS system in real time for remote monitoring and recording.

[0061] The above power supply system configuration can provide reliable, flexible and economical power supply for electric heater 3, meet the operation requirements of different application scenarios, and provide technical support for new energy consumption and energy conservation and carbon reduction.

[0062] In some embodiments, the air preheater is installed in the boiler tail flue to heat the air entering the boiler using the waste heat from the boiler exhaust, thereby reducing the exhaust temperature and improving the boiler thermal efficiency.

[0063] The flue gas inlet of the air preheater is connected to the boiler tail flue, the air inlet is connected to the fan outlet, and the air outlet is connected to the boiler via a hot air duct. The air preheater contains heat exchange elements; the flue gas and air flow across these elements and exchange heat, raising the air temperature before it enters the boiler.

[0064] After being heated by the air preheater, part of the hot air is used as primary air to enter the pulverizing system for drying and conveying pulverized coal, while the other part is used as secondary air to directly enter the furnace for combustion. When the unit load decreases, the outlet air temperature of the air preheater drops accordingly. At this time, the electric heater 3 is activated to reheat the hot air after it has been heated by the air preheater, so that the temperature of the hot air entering the boiler meets the combustion requirements under low load conditions.

[0065] Correspondingly, this application also provides a control method for an electric heating boiler hot air system, which is applied to thermal power units and implemented based on the aforementioned electric heating boiler hot air system. This method achieves stable regulation of the hot air temperature under low boiler load conditions by real-time monitoring of the unit load and precise control of the electric heater output power, ensuring combustion stability and improving the unit's peak-shaving capacity.

[0066] The control system is connected to the distributed control system (DCS) of the thermal power unit to obtain the unit's current operating load data in real time.

[0067] The control system has preset low load threshold and electricity price threshold. The low load threshold is determined based on the boiler combustion characteristics and the unit's peak shaving needs, and is preferably 30% of the rated load. The electricity price threshold is determined with the goal of saving fuel costs more than electricity costs.

[0068] Fuel cost savings are mainly affected by electricity prices. For example, when introducing electricity from renewable energy sources, the purchase price of electricity is the main factor; a lower purchase price can save more fuel costs. On the other hand, when introducing electricity from one's own plant power system, the selling price of electricity is the main factor.

[0069] When the real-time monitored operating load is lower than the low load threshold or the electricity price threshold, the control system automatically issues a start command, which closes the main circuit of the electric heater through the contactor in the electrical control cabinet, so that the electric heater is powered on and put into operation.

[0070] After the heating device is started, the temperature measuring point set on the hot air duct at the outlet side of the electric heater begins to work. The temperature measuring point uses an industrial-grade high-precision temperature sensor to collect the temperature data of the hot air after being heated by the electric heater in real time, and converts the temperature signal into a standard electrical signal (such as a 4-20mA current signal or a thermocouple millivolt signal) and transmits it to the control system.

[0071] The control system has a preset target air temperature curve or data table corresponding to the unit load. The target air temperature is determined based on the boiler combustion optimization requirements and unit characteristics. The control system compares the real-time temperature collected step by step with the target air temperature corresponding to the current load and calculates the deviation value. Based on the deviation value, the control system calculates the power adjustment command according to the built-in control algorithm and dynamically adjusts the output power of the electric heater so that the measured temperature approaches and stabilizes near the target air temperature. Repeat the temperature acquisition and power adjustment steps until the electric heater stops operating.

[0072] Example 1 This embodiment provides an electric heating boiler hot air system whose power source is taken from the plant power system, which is applied to the pulverized coal boiler of a thermal power generator set.

[0073] like Figure 1 As shown, the system includes an air preheater 1, a fan 2, an electric heater 3, a power regulator 4, a temperature measuring point 5, an electrical control cabinet 6, an embedded control system, and a unit DCS system 8.

[0074] The flue gas inlet of the air preheater 1 is connected to the tail flue of the boiler, and the flue gas outlet is connected to the flue gas treatment and emission system. The air inlet of the air preheater 1 is connected to the outlet of the blower 2, and the air outlet is connected to the boiler furnace and the pulverizing system 12 respectively through the hot air duct 11. The hot air duct 11 includes an independently set primary hot air duct and a secondary hot air duct. The primary hot air duct is connected to the pulverizing system for drying and conveying pulverized coal, and the secondary hot air duct is connected to the boiler furnace for providing combustion air.

[0075] Electric heaters 3 are fixedly installed on both the primary and secondary hot air ducts at the outlet of air preheater 1. The two sets of electric heaters 3 are used to reheat the primary and secondary air respectively, and can be independently put into operation and adjusted according to operational needs.

[0076] Each electric heater 3 is independently equipped with a power regulator 4 and an electrical control cabinet 6. The power input terminal of the electrical control cabinet 6 is electrically connected to the high-voltage power system of the thermal power plant (such as a 6kV or 10kV busbar) to provide operating power for the electric heater 3; the power output terminal of the electrical control cabinet 6 is connected to the electric heater 3 via the power regulator 4. The power regulator 4 adopts thyristor power regulation cabinet technology, which can continuously and steplessly adjust the output power of the electric heater 3 within the range of 0-100%, and has the characteristics of fast response speed, high adjustment accuracy, and low harmonic content.

[0077] Temperature measuring points 5 are fixedly installed on the hot air duct 11 at the outlet side of each electric heater 3. The temperature measuring points 5 adopt industrial-grade high-precision temperature sensors with a sampling frequency of not less than 1 time / second, and are used to collect the temperature of the hot air after being heated by the electric heater 3 in real time.

[0078] The signal output terminal of temperature measuring point 5 is electrically connected to the field embedded control system. The embedded control system has pre-stored hot air temperature setpoint curves or data tables for the boiler under different low-load conditions. The setpoints are determined according to the boiler combustion optimization requirements and unit characteristics.

[0079] The working logic of the control system 7 is as follows: it receives the measured temperature signal fed back from the temperature measuring point 5 in real time, compares it with the set value corresponding to the current load, and calculates the deviation value; it generates a power adjustment command according to the built-in PID control algorithm based on the deviation value, and sends the command to the power regulator 4; the power regulator 4 dynamically adjusts the output power of the electric heater 3 according to the command, so that the measured temperature quickly approaches and stabilizes near the set value, and the temperature control error can be controlled within ±2℃, effectively avoiding overheating.

[0080] All operating data of the electric heater 3, power regulator 4, and temperature measuring point 5, including the measured value of hot air temperature, output power of electric heater, equipment commissioning status, and fault alarm signals, are transmitted to the DCS system 8 of the thermal power unit through an industrial-grade communication module (such as Modbus, Profibus, or OPC UA protocol).

[0081] Operators can monitor the system's operating status in real time on the DCS operator station, view historical trend curves, and remotely issue start-up and shutdown commands for the electric heater 3, or switch between automatic and manual control modes. In manual mode, operators can directly set the output power of the electric heater 3; in automatic mode, the system's closed-loop regulation is independently completed by the embedded control system 7, with the DCS only handling monitoring and parameter setting functions.

[0082] This embodiment divides the operating conditions into two categories based on the unit load: 1. High load conditions (unit load > 30%) When the unit load exceeds 30%, the hot air temperature generated by the boiler itself is high enough to meet the requirements of normal combustion and pulverized coal drying, resulting in good combustion stability. At this time, the electric heater 3 is in a shutdown state, the power regulator 4 output is zero, and the hot air from the outlet of the air preheater 1 directly enters the boiler furnace and pulverizing system 12 through the hot air duct 11. The boiler operates normally according to the original process flow without consuming additional electrical energy.

[0083] 2. Low load condition (unit load ≤ 30%) When the unit load drops to 30% or below, the boiler is in a deep peak-shaving state. The hot air temperature at the outlet of air preheater 1 drops significantly as the load decreases, leading to problems such as poor combustion stability in the furnace, reduced pulverized coal drying effect, insufficient flue gas temperature at the inlet of the denitrification device, and a drop in the main steam temperature.

[0084] At this point, the control system automatically detects that the unit load is lower than the set threshold and triggers the following workflow: The control system 7 issues a start command, the contactor in the electrical control cabinet 6 closes, and the electric heater 3 is powered on and put into operation; the temperature measuring point 5 collects the hot air temperature at the outlet of the electric heater 3 in real time and feeds the signal back to the control system; the control system compares the measured temperature with the preset value and issues a power adjustment command to the power regulator 4 according to the deviation; the power regulator 4 dynamically adjusts the output power of the electric heater 3 so that the primary air and secondary air temperatures are raised to the set target values ​​respectively; The heated high-temperature primary air enters the pulverizing system to improve the drying effect and conveying stability of pulverized coal; the high-temperature secondary air enters the furnace to enhance the combustion reaction and increase the flame temperature and combustion efficiency. As the hot air temperature increases, the flue gas temperature at the furnace outlet also increases, and the flue gas temperature at the inlet of the denitrification unit returns to the normal operating temperature range of the catalyst, eliminating the need to activate other temperature-raising measures such as economizer bypass or flue gas bypass. The boiler steam temperature has been effectively increased, getting closer to the turbine's rated inlet steam temperature, thus improving the unit's thermal efficiency under low load.

[0085] The implementation of this embodiment achieves the following technical effects: 1. Increasing the boiler hot air temperature when the boiler is under low load improves the boiler combustion stability, ensuring safer and more reliable operation of the unit. At the same time, it reduces the minimum load of the thermal power unit, increases the peak-shaving range of the thermal power unit, and makes the coal-fired power unit more in line with the needs of the new power system. 2. When thermal power units are at low load, it is generally the period when renewable energy power generation load is high. Turning on electric heaters can reduce the amount of electricity fed into the grid from thermal power units, increase the amount of electricity fed into the grid from renewable energy power generation, and reduce the amount of renewable energy wasted. 3. When the boiler is operated at low load, the hot air temperature of the boiler is increased, and the amount of coal fed into the boiler is reduced by using low-priced or zero-priced electricity, thereby improving the operating economy of the unit at low load. At the same time, the increase in the boiler inlet air temperature can also ensure that the inlet flue gas temperature of the denitrification device meets the requirements, and the steam temperature at the boiler outlet is closer to the rated value than when the electric heater is not in operation, thereby improving the efficiency of the steam turbine and further promoting the operating economy of the unit at low load.

[0086] 4. The power adjustment cabinet technology can achieve a power adjustment range of 0-100%, with high control accuracy, short response time, and low harmonic content. It can meet the needs of electric heaters for stepless power adjustment with high power, high voltage, high precision, wide range, fast response, high speed, and low harmonics.

[0087] Example 2 A thermal power unit includes a boiler and the electric heating boiler hot air system described in Example 1.

[0088] The boiler hot air system of this invention, when activated under low boiler load, uses electrical energy to heat the boiler hot air, increasing the boiler inlet air temperature and thus improving the stability and safety of boiler combustion. The increased boiler inlet air temperature also raises the flue gas temperature in the furnace and tail flue, ensuring that the inlet flue gas temperature of the denitrification device meets requirements without additional technical measures. Simultaneously, the increased steam temperature supplied to the turbine is closer to the rated operating temperature, improving the unit's thermal efficiency. This system reduces the amount of electricity fed into the grid, providing more space for renewable energy power; it also reduces the amount of electricity fed into the grid during periods of low electricity prices at thermal power plants, enabling electricity recovery and reuse, reducing coal consumption during these periods, and improving the unit's economic efficiency under certain conditions, making thermal power generating units more suitable for the needs of new power systems.

[0089] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A hot air system for an electric heating boiler, characterized in that, include: Fans, air preheaters, electric heaters, and power supply systems; The outlet of the blower is connected to the inlet of the air preheater, and the outlet of the air preheater is connected to the boiler furnace and / or pulverizing system through a hot air duct. The electric heater is installed on the hot air duct between the air preheater outlet and the boiler furnace and / or pulverizing system, and is used to reheat the hot air after it has been heated by the air preheater. The electric heater is connected to the power supply system via a control system; The control system is configured to: when the operating load of the generator set is lower than the preset low load threshold, or when the electricity price is lower than the set electricity price threshold, start the electric heater and adjust the output power of the electric heater according to the preset target air temperature to control the temperature of the hot air entering the boiler furnace and / or pulverizing system.

2. The electric heating boiler hot air system according to claim 1, characterized in that, A temperature measuring point is provided on the hot air duct and located at the outlet side of the electric heater. The temperature measuring point is connected to the control system signal and is used to provide real-time feedback on the hot air temperature at the outlet of the electric heater. The control system dynamically adjusts the output power of the electric heater based on the deviation between the real-time temperature fed back from the temperature measuring point and the preset target air temperature.

3. The electric heating boiler hot air system according to claim 1, characterized in that, The temperature measuring points include multiple temperature sensors spaced apart along the axial direction of the hot air duct, and / or multiple temperature sensors arranged at different radial depths on the same cross section of the hot air duct.

4. The electric heating boiler hot air system according to claim 1, characterized in that, The hot air duct includes independently installed primary hot air duct and secondary hot air duct; The electric heater is installed on the primary hot air duct and / or on the secondary hot air duct.

5. The electric heating boiler hot air system according to claim 4, characterized in that, When electric heaters are installed on both the primary hot air duct and the secondary hot air duct, the two sets of electric heaters are each equipped with independent power regulators and temperature measuring points. The control system sets the target temperatures for primary and secondary air based on the unit load and operating conditions, and independently controls the output power of the two electric heaters.

6. The electric heating boiler hot air system according to claim 1, characterized in that, The control system includes a controller, a power regulator, and a temperature acquisition module; The temperature acquisition module is connected to the temperature measuring point signal and is used to collect hot air temperature data and transmit it to the controller; The controller is connected to the power regulator by signal. Based on the deviation between the real-time temperature and the target wind temperature, it calculates the power adjustment command according to the PID control algorithm and sends it to the power regulator. The power regulator continuously adjusts the output power of the electric heater according to the power adjustment command.

7. The electric heating boiler hot air system according to claim 1, characterized in that, The plant high-voltage power supply system is connected to the power plant's high-voltage plant busbar, including: The high-voltage access unit connects to the plant's high-voltage busbar and is used to enable power connection, disconnection, and protection. The voltage conversion unit, when the electric heater is a low-voltage device, is equipped with a step-down transformer to convert the plant's high voltage into the working voltage of the electric heater; The power distribution control unit receives start / stop commands from the control system and controls the on / off state of the electric heater.

8. The electric heating boiler hot air system according to claim 1, characterized in that, The new energy power supply system is connected to an off-site new energy power generation station, including: An external power supply access unit is connected to the transmission line of the new energy power station to receive new energy power. The voltage conversion unit converts the new energy power supply voltage into the operating voltage of the electric heater; The power switching control unit is connected to the control system signals of the new energy dispatching system and the electric heater, respectively, to obtain information on the abandonment of new energy and the operating status of the electric heater in real time. The power switching control unit is configured to switch the power supply of the electric heater to the new energy power supply system when the electric heater is in operation and the new energy source is detected to be abandoned.

9. A control method for an electric heating boiler hot air system according to any one of claims 1-8, characterized in that, Includes the following steps: Real-time monitoring of the operating load of thermal power units; When the operating load is lower than the preset low load threshold, or when the electricity price is lower than the set electricity price threshold, the electric heater installed on the hot air duct at the air preheater outlet is activated. The hot air temperature at the outlet of the electric heater is collected in real time by setting a temperature measuring point on the hot air duct on the outlet side of the electric heater. Based on the deviation between the collected hot air temperature and the preset target air temperature, the output power of the electric heater is dynamically adjusted so that the measured temperature approaches and stabilizes near the target air temperature. Repeat the temperature acquisition and power adjustment steps until the electric heater stops operating.

10. A thermal power unit, characterized in that, Includes boilers and electric heating boiler hot air systems as described in any one of claims 1 to 8.

Images