Coal mill outlet air temperature regulating system and method under low load

Abstract

The present application provides a kind of low load under coal mill outlet wind powder temperature regulating system and method, including temperature sensor group, flow sensor, coal dust concentration sensor, temperature regulating device and control unit, wherein: temperature sensor group is used to measure the wind powder temperature of different positions of coal mill outlet pipeline;Flow sensor is used to measure the wind powder flow of different positions of coal mill outlet pipeline;Coal dust concentration sensor is used to detect the coal dust concentration in the coal mill outlet pipeline;Temperature regulating device is used to adjust the wind powder temperature of coal mill outlet pipeline;Control unit is used to receive the signal of temperature sensor group, flow sensor, coal dust concentration sensor, calculate temperature regulating amount and output signal to temperature regulating device to the wind powder temperature of coal mill outlet.The present application ensures that the wind powder temperature of coal mill outlet is stable near the target value, improves the combustion efficiency, and ensures the stable operation of the entire thermal system.

Description

Technical Field

[0001] This invention relates to the field of coal mill technology, and in particular to a coal mill outlet air-coal temperature regulation system and method under low load. Background Technology

[0002] In the thermal power generation industry, coal mills play a crucial role. They are key equipment for refining lumpy raw coal into pulverized coal, which is then fed into a boiler for efficient combustion to generate steam to drive a turbine generator. However, during the operation of coal mills, especially under low-load conditions, controlling the temperature of the air and pulverized coal at the mill outlet has become a technical challenge.

[0003] When operating at low load, the working condition of a coal mill differs significantly from that at full load, and its outlet air-coal temperature often fluctuates considerably. Traditional temperature control methods, such as adjusting the coal feed rate, ventilation volume, or heating elements of the coal mill, can achieve temperature control to some extent, but they have many limitations.

[0004] First, traditional control methods often lack sufficient precision. Under low-load conditions, the air-coal flow pattern, heat exchange efficiency, and pulverized coal combustion characteristics within the coal mill undergo complex changes, which are often difficult for traditional control systems to accurately capture and predict. Therefore, traditional temperature control methods often fail to adjust in a timely and accurate manner based on these changes, resulting in significant fluctuations in the outlet air-coal temperature, which negatively impacts the combustion quality and efficiency of the pulverized coal.

[0005] Secondly, traditional methods lack sufficient consideration of the air-coal mixing state. Inside the coal mill, the mixing state of air and pulverized coal has a significant impact on the outlet temperature distribution. Uneven mixing leads to uneven temperature distribution, which in turn affects the combustion efficiency of the pulverized coal and the stable operation of the boiler. However, traditional temperature control methods often only focus on the absolute value of the temperature, neglecting the influence of the air-coal mixing state on the temperature distribution, thus making it difficult to achieve precise temperature control.

[0006] Furthermore, traditional temperature control methods are poorly adaptable to different coal types. In thermal power generation, a wide variety of coal types are used, with significant differences in their physical and chemical properties, which in turn affect the operation of the coal mill and the combustion efficiency of pulverized coal. These differences are particularly pronounced under low-load conditions. However, traditional temperature control methods are often designed and adjusted only for one or a few specific coal types, making it difficult to adapt to the complex changes in different coal types under low loads, thus affecting the stable operation of the coal mill and the combustion quality of pulverized coal.

[0007] In summary, traditional methods for regulating the outlet air and pulverized coal temperature in coal mills have numerous shortcomings during low-load operation. These problems not only affect the stable operation of the coal mill and the combustion quality of pulverized coal, but may also lead to reduced combustion efficiency, accelerated equipment wear, and environmental pollution. Therefore, it is necessary to develop more advanced and intelligent temperature regulation methods and technologies to address these issues. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a coal mill outlet air-coal temperature regulation system and method under low load, which effectively solves the problem of insufficient precision of traditional regulation methods affecting the production process, ensures that the coal mill outlet air-coal temperature is stable near the target value, improves combustion efficiency, and guarantees the stable operation of the entire thermal system.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a coal mill outlet air-coal temperature regulation system under low load, comprising a temperature sensor group, a flow sensor, a coal powder concentration sensor, a temperature regulation device, and a control unit, wherein: The temperature sensor group includes multiple temperature sensors, which are installed at different locations on the coal mill outlet pipe. The temperature sensors are used to measure the temperature of the air and coal. Flow sensors are installed on the air inlet and coal outlet pipes of the coal mill to measure the air-coal flow rate. The pulverized coal concentration sensor is installed inside the coal mill outlet pipe to detect the pulverized coal concentration; The temperature control device is installed on the coal mill outlet pipe and includes heating and cooling elements to regulate the temperature of the air and coal. The control unit is connected to the temperature sensor group, flow sensor, pulverized coal concentration sensor and temperature regulation device to receive signals from the temperature sensor group, flow sensor and pulverized coal concentration sensor, calculate the temperature regulation amount and output a signal to the temperature regulation device to regulate the air and pulverized coal temperature at the coal mill outlet.

[0010] Furthermore, the temperature sensor is a thermocouple sensor or a thermistor sensor.

[0011] Furthermore, the flow sensor is a differential pressure flow sensor or a vortex flow sensor.

[0012] Furthermore, the pulverized coal concentration sensor is a laser scattering type pulverized coal concentration sensor.

[0013] Furthermore, the control algorithm of the control unit includes a multi-parameter feedback-based adjustment algorithm and a local temperature compensation mechanism. The overall heat adjustment amount obtained by the multi-parameter feedback-based adjustment algorithm and the local adjustment amount calculated by the local temperature compensation mechanism are combined to obtain the final adjustment amount of the temperature regulating device. The control unit obtains the adjustment amount signal of the temperature regulating device and outputs it to the temperature regulating device, so that the temperature regulating device can regulate the temperature of the coal mill outlet air and pulverized coal.

[0014] Furthermore, the multi-parameter feedback-based adjustment algorithm calculates the air-powder thermal balance state based on temperature and flow rate to determine the amount of heat adjustment. The details are as follows: Based on the principles of heat transfer and the law of conservation of energy, the established heat balance model is as follows: = +

[0015] in, The total heat of the air-powder mixture Heat brought in by hot air and the heat carried by pulverized coal The sum of, This is the portion of heat lost through the pipes; Q out The heat carried away by the air-powder mixture; When the current air powder temperature T out <Target air powder temperature The heat balance equation at the target temperature is: = + calorie adjustment = - Q out = V total C total ( T target - T out ); When the current air powder temperature T out >Target air-powder temperature calorie adjustment = Q out - = V total C total ( T out -T target ); in, and These are the total volumetric flow rate and average specific heat capacity of the air-powder mixture, respectively. V total = + , , Hot air flow rate Pulverized coal flow rate; Hot air specific heat capacity Specific heat capacity of pulverized coal.

[0016] Furthermore, when the current air-powder temperature T out <Target air powder temperature Heating compensation and heat adjustment are required. = - Q out = V total C total ( T target - T out The adjustment amount of the heating element in the temperature regulating device is expressed as heating power. express, = · t , t For time; When the current air powder temperature T out >Target air-powder temperature Cooling compensation is required; heat adjustment amount. = Q out - = V total C total ( T out - T target The adjustment amount of the cooling element in the temperature regulating device is determined based on the heat dissipation capacity of the cooling element.

[0017] Furthermore, 1) the total heat of the air-powder mixture Heat brought in by hot air and the heat carried by pulverized coal The sum, that is:

[0018] in, , For hot air flow, For hot air temperature, The specific heat capacity of hot air; , For pulverized coal flow rate, For pulverized coal temperature, The specific heat capacity of pulverized coal; 2) Heat loss from pipes Based on the thermal conductivity of the pipe h Temperature difference between inside and outside the pipe and heat transfer area A The calculation formula is as follows:

[0019] in, h Thermal conductivity; 3) The heat carried away by the air-powder mixture Q out Based on the total volumetric flow rate of the air-powder mixture V total Specific heat capacity of the air-powder mixture C total and the outlet temperature of the air-powder mixture T out Calculation, the calculation formula is: Q out= V total C total T out The outlet temperature of the air-powder mixture is the current temperature.

[0020] Furthermore, the local temperature compensation mechanism adjusts the heating or cooling of local temperature anomaly areas based on multi-point measurement results from the temperature sensor group and the coal powder concentration. The control unit 7 receives multi-point temperature data from temperature sensors 2 distributed at different locations in the coal mill outlet pipe, identifies areas with excessively high or low local temperatures using a set temperature threshold, and calculates the amount of heat adjustment. =, as detailed below: The target air-powder temperature is Obtain the current actual air-powder temperature in a local area. T local Calculate the temperature deviation: T local = -T local When | T local | Greater than the set local allowable deviation value T allowlocal At that time, the local temperature compensation mechanism is activated; like T local A value greater than 0 indicates that the actual local temperature is lower than the target temperature, requiring heating compensation and adjustment of the heat amount. = m × C × T local The adjustment amount of the heating element in the temperature regulating device is expressed as heating power. express, = · t ; like T local A value less than 0 indicates that the actual local temperature is higher than the target temperature, requiring cooling compensation and heat adjustment. == n × × T local The adjustment amount of the cooling element in the temperature regulating device is determined based on the heat dissipation capacity of the cooling element. in, m , n Where C is the proportionality coefficient and C is the coal powder concentration. t For time.

[0021] This invention also provides a method for adjusting the outlet air-coal temperature of a coal mill under low load, which is implemented using the aforementioned low-load coal mill outlet air-coal temperature adjustment system. The specific steps are as follows: Temperature sensor group, flow sensor and pulverized coal concentration sensor collect air-powder temperature, flow rate and pulverized coal concentration data and transmit them to control unit; The control unit obtains the thermophysical properties of the coal type based on the coal type, and calculates the overall heat regulation amount using the thermophysical properties of the coal type, the air-coal temperature and flow rate; The control unit compares the current actual air-coal temperature in a local area with the target air-coal temperature from different temperature sensors. When the difference exceeds the set local allowable deviation value, the control unit calculates the local heat adjustment amount based on the coal powder concentration data and the difference between the current actual air-coal temperature in the local area and the target air-coal temperature. The control unit acquires the overall heat adjustment amount and the local heat adjustment amount and transmits them to the temperature control device. The temperature control device adjusts the coal mill outlet air-coal temperature according to the adjustment amount signal.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: The coal mill outlet air-coal temperature regulation system provided by this invention achieves high-precision regulation of the coal mill outlet air-coal temperature by integrating multiple temperature sensors, flow sensors, coal powder concentration sensors, temperature regulation devices, and control units. The collaborative operation of multiple sensors enables real-time and accurate acquisition of air-coal temperature, flow rate, and coal powder concentration data, providing a reliable information foundation for precise temperature regulation. Simultaneously, the control unit employs a complex regulation algorithm, comprehensively considering multiple parameters to calculate the precise temperature regulation amount, which is then accurately adjusted through the temperature regulation device. This system effectively solves the problem of insufficient precision in traditional regulation methods, ensuring that the coal mill outlet air-coal temperature remains stable near the target value, thereby improving combustion efficiency and optimizing the operation of the thermal system.

[0023] This invention also introduces a local temperature compensation mechanism, which adjusts the temperature by heating or cooling areas with abnormal local temperatures through multi-point temperature measurement and real-time monitoring of pulverized coal concentration. This mechanism makes the temperature distribution of air and pulverized coal in the outlet pipe more uniform, avoiding combustion instability caused by excessively high or low local temperatures. Simultaneously, the improved temperature uniformity reduces local overheating or slagging problems caused by uneven temperature, further enhancing the safety and reliability of the equipment. This innovation not only improves the operating efficiency of the coal mill but also extends the service life of the equipment and reduces maintenance costs.

[0024] Through the high-precision temperature control system and local temperature compensation mechanism of this invention, the stability and uniformity of the coal mill outlet air-coal temperature are significantly improved. This change directly reduces the changes in thermal stress on the equipment caused by temperature fluctuations and inhomogeneities, thereby reducing the wear and corrosion rate of the equipment. Stable temperature control not only extends the service life of the coal mill and related downstream equipment, but also reduces downtime and maintenance costs caused by equipment failures. In addition, the improved combustion efficiency also brings higher economic benefits, making the operation of the entire thermal system more economical and efficient.

[0025] In summary, this invention demonstrates significant advantages in extending equipment lifespan, reducing maintenance costs, and improving economic efficiency. Attached Figure Description

[0026] Figure 1 This invention provides an overall layout diagram of a coal mill outlet air-coal temperature regulation system under low load. Figure 2Flowchart of the control algorithm for a coal mill outlet air-coal temperature regulation system under low load according to the present invention; In the attached diagram: 1. Coal mill; 2. Temperature sensor; 3. Flow sensor; 4. Pulverized coal concentration sensor; 5. Heating element; 6. Cooling element; 7. Control unit; 8. Human-machine interface platform. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, this invention provides a coal mill outlet air-coal temperature regulation system under low load, including a temperature sensor group, a flow sensor group, a coal powder concentration sensor 4, a control unit, a heating element, and a cooling element. Specifically: The temperature sensor group includes multiple temperature sensors 2, which are installed at different locations in the coal mill outlet pipe, such as the inner wall of the pipe and the air-coal mixing area, to measure the air-coal temperature in the coal mill in real time and accurately. These temperature sensors can be thermocouple sensors or thermistor sensors, with an accuracy range of ±0.5%, and can withstand the harsh environment (high temperature, high dust, etc.) at the coal mill outlet, providing high-precision temperature measurement data.

[0029] Flow sensor 3 is installed on the air inlet and coal outlet pipes of the coal mill to measure the flow rate of air and coal. It can be a differential pressure flow sensor, a vortex flow sensor, etc. By measuring the air inlet flow and coal outlet flow, it provides data support for subsequent temperature regulation calculations to understand the air-coal conveying status and mixing ratio changes.

[0030] The pulverized coal concentration sensor 4 is located inside the coal mill outlet pipe and is used to detect the pulverized coal concentration. A laser scattering type pulverized coal concentration sensor is used to accurately obtain the concentration information of pulverized coal in the air-coal mixture, because the pulverized coal concentration affects the heat capacity and temperature change characteristics of the air-coal mixture.

[0031] Heating element 5 is installed on the inlet pipe of the coal mill and includes heating elements (such as electric heating wires, heat exchangers, etc.). According to the instructions of the control unit, the heating element can heat the air and coal, thereby realizing the regulation of the air and coal temperature.

[0032] Cooling element 6 is installed on the coal mill outlet pipe and includes cooling elements (such as cooling water pipes, air-cooled radiators, etc.). According to the instructions of the control unit, the cooling element can cool the air and coal, thereby realizing the regulation of air and coal temperature.

[0033] The control unit 7, based on a programmable logic controller (PLC) or microprocessor, receives signals from the temperature sensor group, flow sensor group, and pulverized coal concentration sensor. The control unit incorporates a control algorithm specifically designed for low-load conditions. This algorithm can calculate the required temperature adjustment based on real-time data and output a control signal. The human-machine interaction platform 8 is connected to the control unit 7 and is used to input the type of coal powder. Common coal types can be divided into lignite, bituminous coal and anthracite.

[0034] The present invention provides a low-load coal mill outlet air-coal temperature regulation system for regulating the coal mill outlet air-coal temperature during low-load operation, comprising the following steps: 1) During the low-load operation of the coal mill, the temperature sensor group, flow sensor 3 and coal powder concentration sensor 4 collect the temperature, flow rate and coal powder concentration data of the coal mill outlet air and coal in real time, and transmit these data to the control unit.

[0035] 2) Based on the received data, the control unit 7 first calculates the overall required temperature adjustment direction and adjustment amount according to the thermophysical characteristic parameters of the corresponding coal type under low load using a multi-parameter feedback-based adjustment algorithm.

[0036] 3) At the same time, the control unit 7 analyzes the multi-point temperature data of the temperature sensor group, identifies local temperature abnormal areas, and determines the amount of heating or cooling adjustment for these areas through a local temperature compensation mechanism.

[0037] 4) By combining the overall and local adjustment amounts, the control unit sends a control signal to the heating element 5 or the cooling element 6 to adjust the working status of the heating element and the cooling element, thereby achieving precise adjustment of the air powder temperature.

[0038] 5) Continuously monitor and adjust to ensure that the coal mill outlet air-coal temperature remains stable within the target temperature range during low-load operation, ensuring uniform air-coal mixing and suitable temperature to meet the requirements of the subsequent combustion process.

[0039] The control unit 7 has a built-in control algorithm specifically designed for low-load operating conditions, such as... Figure 2 The diagram shows: a multi-parameter feedback-based adjustment algorithm and a local temperature compensation mechanism. The specific algorithm steps are as follows: Step 1, Data Acquisition and Preprocessing: The control unit 7 obtains air-coal temperature data in real time from temperature sensors 2 installed at different locations in the coal mill outlet pipe, air-coal flow data from flow sensors 3 on the air inlet pipe and coal outlet pipe, and coal powder concentration data from coal powder concentration sensor 4 located in the coal mill outlet pipe.

[0040] Temperature data is filtered (moving average filtering or median filtering) to remove noise and abnormal fluctuations, ensuring data accuracy and stability; flow rate and pulverized coal concentration data are validated for rationality, and obviously erroneous data points are removed; at the same time, these data are normalized to map their value range to the interval 0~1, which facilitates comparison and calculation in subsequent calculations.

[0041] Step 2: Obtain the corresponding thermophysical property parameters of the coal type: To obtain coal type information, control unit 7 retrieves the thermophysical property parameters of the coal type from a pre-stored database. These parameters include specific heat capacity (…). ), heat generation ( ), volatile matter content, ash content, etc., are used to consider the characteristics of different coal types in subsequent adjustment algorithms.

[0042] Step 3: Adjustment algorithm based on multi-parameter feedback; The control unit 7 calculates the thermal balance state of the air and coal based on the measured values ​​from temperature sensor 2 and the air-coal flow rate measured by flow sensor 3. Under low-load conditions, different combinations of coal type, air volume, and coal quantity will lead to different thermal balance characteristics. Using a thermal balance model, considering the interrelationships between these parameters and the characteristics of low-load operation, the heating or cooling power required to meet the target temperature is calculated. For example, when the temperature is below the target value, the heating power is increased; conversely, when the temperature is above the target value, the cooling power is appropriately increased or the heating power is reduced, as detailed below: 1) Thermal equilibrium model calculation: Based on the principles of heat transfer and the law of conservation of energy, the established heat balance model is as follows: = +

[0043] in, This is the sum of the heat brought in by the hot air and the heat carried by the pulverized coal. This is the portion of heat lost through the pipes; Q out The heat carried away by the air-powder mixture.

[0044] Among them, the heat brought in by the hot air ( ), through hot air flow ( ), hot air temperature ( ) and the specific heat capacity of hot air ( To calculate, that is: .

[0045] The heat carried by pulverized coal ( Based on pulverized coal flow rate ( ), coal powder temperature ( ) and the specific heat capacity of pulverized coal ( The calculation is done using the following formula:

[0046] Total heat of the air-powder mixture The sum of the two is: .

[0047] Meanwhile, heat loss from the pipes Based on the thermal conductivity of the pipe h Temperature difference between inside and outside the pipe and heat transfer area A The calculation formula is as follows: .

[0048] Among them, thermal conductivity h The value is related to factors such as the shape and size of the pipe, the properties of the fluid, and the surrounding environment, and is calculated according to the correlation formula: The reference parameters (C = 0.54, n = 0.25) are provided based on the actual experimental data and can be modified on-site according to the actual situation.

[0049] Heat carried away by the powder mixture Q out Based on the total volumetric flow rate of the air-powder mixture V total Specific heat capacity of the air-powder mixture C total and the outlet temperature of the air-powder mixture T out Calculation, the calculation formula is: Q out= V total C total T out The outlet temperature of the air-powder mixture is the current temperature.

[0050] 2) Parameter correlation and target temperature calculation Analyze the interrelationships between various parameters (air volume, pulverized coal quantity, current temperature, etc.) and their impact on the air-coal temperature. Based on the set target air-coal temperature ( By combining the currently collected real-time flow and temperature data, the amount of heat adjustment required to bring the air-powder temperature to the target value is calculated using the heat balance equation. .

[0051] Assuming the target air-powder temperature is The current air-powder temperature is T out ,and T out < We need to calculate the additional calories required. To bring the temperature to the target value. According to the heat balance equation, the heat balance equation at the target temperature is: = + The amount marked with an apostrophe represents the amount of heat required to reach the target temperature; For ease of calculation, we assume that the parameters of the hot air (flow rate, specific heat capacity, temperature) and the parameters of the pulverized coal (flow rate, specific heat capacity, temperature) remain constant, and only the temperature of the air-coal mixture changes. Therefore, the required heat adjustment amount is... It is mainly used to increase the temperature of the air-powder mixture, that is = - Q out ; according to Q out = V total C total T out and = V total C total T target We can obtain: = V total C total ( T target - T out ).

[0052] when T out > At that time, calculate the amount of heat that needs to be removed. Similarly, according to the heat balance equation, at this time: = Q out - = V total C total ( T out - T target).

[0053] In the above formula and These are the total volumetric flow rate and average specific heat capacity of the air-coal mixture, respectively, which can be calculated using the flow rates and specific heat capacities of the hot air and pulverized coal. For example, if the hot air flow rate is... The coal powder flow rate is The specific heat capacity of hot air is The specific heat capacity of pulverized coal is ,but V total = + , C total According to the mixing rules To calculate.

[0054] This allows us to deduce the amount of heat adjustment required to bring the air-powder temperature to the target value using the heat balance equation. Furthermore, it establishes a connection between this formula and the calculation formulas for the previously mentioned parameters. In practical applications, the amount can be adjusted based on the heat output. To determine the adjustment amount of the heating or cooling element, such as adjusting the power of the heating wire or the water flow rate of the cooling water pipe.

[0055] Considering factors such as heat loss in the coal mill, the work done by the thermal expansion of pulverized coal and air inside the mill, and the heat generated by friction during pulverized coal crushing, estimating the heat generated by these factors is relatively complex. Further adjustments can be made by using temperature measurement point feedback. ΔQ Size.

[0056] Step 5, Local Temperature Compensation Mechanism The control unit 7 receives multi-point temperature data from temperature sensors 2 located at different positions in the coal mill outlet pipe. It analyzes this data using algorithms such as set temperature thresholds or cluster analysis to identify areas with excessively high or low temperatures. The difference between each local area and the overall average temperature, as well as the area percentage of that area, are calculated to quantify the degree of local temperature anomaly and its impact range.

[0057] For low-temperature areas, the required additional heat is calculated based on the temperature difference, area ratio, and flow characteristics of the air and powder. By adjusting the heating elements near these areas (increasing the power of the corresponding heating wires), they generate additional heat to compensate for the low temperature, bringing the temperature of this localized area closer to the overall average temperature.

[0058] For high-temperature areas, after analyzing relevant parameters, the excess heat that needs to be removed is calculated. Then, by adjusting the cooling elements near this area (increasing the cooling water flow rate in the cooling water pipes or enhancing the ventilation of the air-cooled radiator), the temperature in this area is reduced to a suitable range, achieving localized temperature uniformity. During the adjustment process, the mutual influence between different local areas and the impact on the overall fan and powder temperature must be comprehensively considered to avoid causing new temperature anomalies in other areas due to over-adjustment of a certain local area.

[0059] The target air-powder temperature is Obtain the current actual air-powder temperature in a local area. T local Calculate the temperature deviation: T local = - T local When | T local | Greater than the set local allowable deviation value T allowlocal When this happens, a local temperature compensation mechanism is activated. T local A value >0 indicates that the actual local temperature is lower than the target temperature, requiring heating compensation; if T local A value less than 0 indicates that the actual local temperature is higher than the target temperature, and cooling compensation is required.

[0060] The concentration of pulverized coal is also related to the amount of heating or cooling required. Assuming represents the amount of heating or cooling, when heating is required, the pulverized coal concentration C is related to the amount of heat adjustment. There is an approximate direct proportional relationship, which can be expressed as the amount of heat adjustment. = m × C Where m is a proportionality constant; when cooling is required, an inverse proportional relationship exists, such as... = n × , n This is another proportionality coefficient. This is because the higher the pulverized coal concentration, the greater the heating required to achieve the same temperature change; conversely, the higher the concentration, the lower the cooling requirement, because high-concentration pulverized coal itself carries more heat; based on the target air-powder temperature... and the current actual air-powder temperature in the local area T localThe required heating or cooling amount can be calculated based on the pulverized coal concentration C. T local < Furthermore, when the pulverized coal concentration is C, the heating amount needs to be increased. Based on the above direct proportional relationship, the heat adjustment amount... = m × C × T local ;when T local > When cooling is required, the adjustment of the cooling amount should be calculated according to the inverse proportional relationship, such as... = n × × T local .

[0061] The specific temperature compensation adjustment amount is determined as follows: When performing heating compensation, for the heating element (electric heating wire), based on the power characteristics of the electric heating wire (the heat generated per unit power is known), the required increase or decrease in heating power is calculated from the heat adjustment amount. To determine the adjustment amount for the heating element: = · t in, t For time, if If the heat is per unit time, then = ; When performing cooling compensation, for cooling components (such as cooling water pipes), the heat dissipation capacity of the cooling water pipes is considered (the relationship between the heat removed per unit time and the water flow velocity, water temperature difference, etc.), based on the heat adjustment amount (…). Calculate the parameters such as the cooling water flow rate that need to be adjusted, and then determine the amount of adjustment to the cooling element. Step 5: Calculate the adjustment amount and output the control signal: The overall adjustment amount obtained from the multi-parameter feedback adjustment algorithm and the local adjustment amount calculated by the local temperature compensation mechanism are combined to obtain the final adjustment amount for the heating / cooling element. Then, the control unit outputs the corresponding control signal to the heating / cooling element (electric heating wire, cooling water pump, etc.) so that it operates according to the calculated adjustment amount, thereby regulating the temperature of the air and coal.

[0062] Step Six: Continuous Monitoring and Adjustment The above steps are continuously executed in a loop, collecting data in real time, determining the coal type, calculating the adjustment amount, and outputting control signals. The system continuously adjusts the air and pulverized coal temperature based on the actual temperature of the coal mill outlet air and pulverized coal to ensure that the air and pulverized coal temperature remains stable within the target temperature range during low-load operation, ensuring uniform air and pulverized coal mixing and suitable temperature to meet the requirements of the subsequent combustion process. When the coal mill stops running or receives an external command to stop control, the program ends and the temperature regulation and control process stops.

[0063] In this invention, the control unit, based on a multi-parameter feedback regulation algorithm, comprehensively calculates the thermal balance state of the air and coal based on the measurements from the temperature sensor, the air-coal flow rate measured by the flow sensor, and the coal powder concentration measured by the coal powder concentration sensor. Under low-load conditions, different combinations of coal type, air volume, and coal powder quantity will lead to different thermal balance characteristics. By using a thermal balance model, considering the interrelationships between these parameters and the characteristics of low-load operation, the heating or cooling power required to meet the target temperature is calculated. For example, when the coal powder concentration increases, the air volume decreases (low-load characteristics), and the temperature is below the target value, the heating power is increased; conversely, when the temperature is above the target value, the cooling power is appropriately increased or the heating power is decreased.

[0064] This invention, through multi-sensor collaborative operation and a complex adjustment algorithm, enables high-precision regulation of the coal mill outlet air-coal temperature under low-load conditions. This effectively solves the problem of insufficient precision in traditional adjustment methods, ensuring temperature stability near the target value and improving combustion efficiency. The local temperature compensation mechanism makes the temperature distribution of air and coal within the outlet pipe more uniform, avoiding combustion instability caused by excessively high or low local temperatures. It also reduces localized overheating or slagging problems caused by uneven temperature, improving equipment safety and reliability. Stable temperature regulation reduces thermal stress changes caused by temperature fluctuations and unevenness, lowering wear and corrosion rates, extending the service life of the coal mill and related downstream equipment, and reducing maintenance costs.

Claims

1. A coal mill outlet air-coal temperature regulation system under low load, characterized in that, It includes a temperature sensor group, a flow sensor, a pulverized coal concentration sensor, a temperature control device, and a control unit, wherein: The temperature sensor group includes multiple temperature sensors, which are installed at different locations on the coal mill outlet pipe. The temperature sensors are used to measure the temperature of the air and coal. Flow sensors are installed on the air inlet and coal outlet pipes of the coal mill to measure the air-coal flow rate. The pulverized coal concentration sensor is installed inside the coal mill outlet pipe to detect the pulverized coal concentration; The temperature control device includes a heating element and a cooling element. The heating element is installed on the inlet pipe of the coal mill, and the cooling element is installed on the outlet pipe of the coal mill. It is used to regulate the temperature of the air and pulverized coal. The control unit is connected to the temperature sensor group, flow sensor, pulverized coal concentration sensor and temperature regulation device to receive signals from the temperature sensor group, flow sensor and pulverized coal concentration sensor, calculate the temperature regulation amount and output a signal to the temperature regulation device to regulate the air and pulverized coal temperature at the coal mill outlet. The control algorithm of the control unit includes a multi-parameter feedback-based adjustment algorithm and a local temperature compensation mechanism. The overall heat adjustment amount obtained by the multi-parameter feedback-based adjustment algorithm and the local adjustment amount calculated by the local temperature compensation mechanism are combined to obtain the final adjustment amount of the temperature adjustment device. The control unit obtains the adjustment amount signal of the temperature adjustment device and outputs it to the temperature adjustment device, so that the temperature adjustment device can adjust the air and coal temperature at the outlet of the coal mill. The multi-parameter feedback-based adjustment algorithm calculates the air-powder thermal balance state based on temperature and flow rate to determine the amount of heat adjustment. The details are as follows: Based on the principles of heat transfer and the law of conservation of energy, the established heat balance model is as follows: = + in, The total heat of the air-powder mixture; Heat brought in by hot air and the heat carried by pulverized coal The sum of, This is the portion of heat lost through the pipes; Q out The heat carried away by the air-powder mixture; When the current air powder temperature T out <Target air powder temperature The heat balance equation at the target temperature is: = + Calorie adjustment: = - Q out = V total C total ( T target - T out )； Heating compensation is required; the adjustment of the heating element is measured by the heating power. express, = · t , t For time; When the current air powder temperature T out >Target air-powder temperature Calorie adjustment amount: = Q out - = V total C total ( T out - T target )； Cooling compensation is required, and the adjustment amount of the cooling element should be determined based on its heat dissipation capacity. in, and These are the total volumetric flow rate and average specific heat capacity of the air-powder mixture, respectively. V total = + in, Hot air flow rate Pulverized coal flow rate; Hot air specific heat capacity Specific heat capacity of pulverized coal; When the current air powder temperature T out <Target air powder temperature Heating compensation and heat adjustment are required. = - Q out = V total C total ( T target - T out The adjustment of the heating element is expressed as heating power. express, = · t , t For time; When the current air powder temperature T out >Target air-powder temperature Cooling compensation and heat adjustment are required. = Q out - = V total C total ( T out - T target The adjustment amount of the cooling element is determined based on its heat dissipation capacity. The local temperature compensation mechanism adjusts the heating or cooling of areas with abnormal local temperatures based on multi-point measurement results from the temperature sensor group and the coal powder concentration. The control unit receives multi-point temperature data from temperature sensors distributed at different locations in the coal mill outlet pipe, identifies areas with excessively high or low local temperatures using a set temperature threshold, and calculates the amount of heat adjustment. The details are as follows: The target air-powder temperature is Obtain the current actual air-powder temperature in a local area. T local Calculate the temperature deviation: T local = - T local When | T local | Greater than the set local allowable deviation value T allowlocal At that time, the local temperature compensation mechanism is activated; like T local A value greater than 0 indicates that the actual local temperature is lower than the target temperature, requiring heating compensation and adjustment of the heat amount. = m × C × T local The adjustment of the heating element is expressed as heating power. express, = · t ; like T local A value less than 0 indicates that the actual local temperature is higher than the target temperature, requiring cooling compensation and heat adjustment. == n × × T local The adjustment amount of the cooling element is determined based on its heat dissipation capacity; in, m , n Where C is the proportionality coefficient and C is the coal powder concentration. t For time.

2. The coal mill outlet air-coal temperature regulation system under low load according to claim 1, characterized in that, The temperature sensor is a thermocouple sensor or a thermistor sensor.

3. The coal mill outlet air-coal temperature regulation system under low load according to claim 1, characterized in that, The flow sensor is a differential pressure flow sensor or a vortex flow sensor.

4. The coal mill outlet air-coal temperature regulation system under low load according to claim 1, characterized in that, The coal powder concentration sensor is a laser scattering type coal powder concentration sensor.

5. The coal mill outlet air-coal temperature regulation system under low load according to claim 1, characterized in that, 1) Total heat of the air-powder mixture Heat brought in by hot air and the heat carried by pulverized coal The sum, that is: in, , For hot air flow, For hot air temperature, The specific heat capacity of hot air; , For pulverized coal flow rate, For pulverized coal temperature, The specific heat capacity of pulverized coal; 2) Heat loss from pipes Based on the thermal conductivity of the pipe h Temperature difference between inside and outside the pipe and heat transfer area A The calculation formula is as follows: in, h Thermal conductivity; 3) The heat carried away by the air-powder mixture Q out Based on the total volumetric flow rate of the air-powder mixture V total Specific heat capacity of the air-powder mixture C total and the outlet temperature of the air-powder mixture T out Calculation, the calculation formula is: Q out= V total C total T out The outlet temperature of the air-powder mixture is the current temperature.

6. A method for adjusting the outlet air-coal temperature of a coal mill under low load, characterized in that, The coal mill outlet air-coal temperature regulation system under low load, as described in any one of claims 1 to 5, is used, and the specific steps are as follows: Temperature sensor group, flow sensor and pulverized coal concentration sensor collect air-powder temperature, flow rate and pulverized coal concentration data and transmit them to control unit; The control unit obtains the thermophysical properties of the coal type based on the coal type, and calculates the overall heat regulation amount using the thermophysical properties of the coal type, the air-coal temperature and flow rate; The control unit compares the current actual air-coal temperature in a local area with the target air-coal temperature from different temperature sensors. When the difference exceeds the set local allowable deviation value, the control unit calculates the local heat adjustment amount based on the coal powder concentration data and the difference between the current actual air-coal temperature in the local area and the target air-coal temperature. The control unit acquires the overall heat adjustment amount and the local heat adjustment amount and transmits them to the temperature control device. The temperature control device adjusts the coal mill outlet air-coal temperature according to the adjustment amount signal.

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