Coal mill outlet air powder temperature adjusting system and method under low load

Abstract

The invention provides a coal mill outlet air powder temperature adjusting system and method under low load, the system comprises a temperature sensor group, a flow sensor, a coal powder concentration sensor, a temperature adjusting device and a control unit, the temperature sensor group is used for measuring the air powder temperature at different positions of a coal mill outlet pipeline; the flow sensor is used for measuring air powder flow at different positions of an outlet pipeline of the coal mill; the pulverized coal concentration sensor is used for detecting the concentration of pulverized coal in an outlet pipeline of the coal mill; the temperature adjusting device is used for adjusting the air powder temperature of the coal machine outlet pipeline; the control unit is used for receiving signals of the temperature sensor set, the flow sensor and the pulverized coal concentration sensor, calculating the temperature adjusting amount and outputting a signal to the temperature adjusting device to adjust the temperature of the pulverized coal at the outlet of the coal mill. The method ensures that the air powder temperature of the outlet of the coal mill is stabilized near a target value, improves the combustion efficiency, and ensures the stable operation of the whole thermodynamic system.

Description

Technical Field

[0001] The invention relates to the technical field of coal mills, and in particular to a system and method for regulating the temperature of coal mill outlet air and powder under low load. Background Art

[0002] In the thermal power generation industry, coal mills play a vital role. They are key equipment for breaking down lump raw coal into coal powder, which is then fed into boilers for efficient combustion to generate steam to drive turbine generators for power generation. However, during the operation of coal mills, especially under low load conditions, the temperature control of air and powder at the outlet of coal mills has become a technical problem.

[0003] When running at low load, the working state of the coal mill is very different from that at full load, and the outlet air and powder temperature often fluctuates greatly. Although 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 a certain extent, they have many limitations.

[0004] First, the adjustment accuracy of traditional adjustment methods is often not high enough. Under low-load conditions, the air-powder flow state, heat exchange efficiency, and coal powder combustion characteristics inside the pulverizer will undergo complex changes, and these changes are often difficult to accurately capture and predict by traditional control systems. Therefore, traditional temperature adjustment methods are often unable to adjust according to these changes in a timely and accurate manner, resulting in large fluctuations in the outlet air-powder temperature, affecting the combustion quality and efficiency of coal powder.

[0005] Secondly, the traditional method lacks sufficient consideration of the air-powder mixing state. Inside the coal mill, the mixing state of air and coal powder has an important influence on the outlet temperature distribution. If the mixing is uneven, it will lead to uneven temperature distribution, which will in turn affect the combustion effect of coal powder and the stable operation of the boiler. However, the traditional temperature control method often only focuses on the absolute value of the temperature, but ignores the influence of the air-powder mixing state on the temperature distribution, making it difficult to achieve precise control of the temperature distribution.

[0006] In addition, the traditional adjustment method is also poorly adaptable to different types of coal. In thermal power generation, the types of coal used are often diverse, and the physical and chemical properties of different types of coal vary greatly, which also have different effects on the operation of the coal mill and the combustion effect of coal powder. Under low-load conditions, this difference is particularly obvious. However, traditional temperature adjustment methods are often designed and adjusted only for one or several specific types of coal, and it is difficult to adapt to the complex changes of different types of coal under low load, thus affecting the stable operation of the coal mill and the combustion quality of coal powder.

[0007] In summary, the traditional method of regulating the temperature of air and pulverized coal at the outlet of the coal mill has many shortcomings when operating at low load. These problems not only affect the stable operation of the coal mill and the combustion quality of the pulverized coal, but may also lead to problems such as reduced combustion efficiency, increased equipment wear and environmental pollution. Therefore, it is necessary to develop more advanced and intelligent temperature regulation methods and technical means to solve these problems. Summary of the invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a system and method for regulating the air and powder temperature of a coal mill outlet under low load, which effectively solves the problem that the insufficient accuracy of traditional regulation methods affects the production process, ensures that the air and powder temperature of the coal mill outlet is stable near the target value, improves the combustion efficiency, and ensures the stable operation of the entire thermal system.

[0009] To achieve the above object, the present invention provides the following technical solution: a low-load coal mill outlet air and powder temperature control system, comprising a temperature sensor group, a flow sensor, a coal powder concentration sensor, a temperature control device and a control unit, wherein: The temperature sensor group includes multiple temperature sensors, which are respectively installed at different positions of the coal mill outlet pipeline, and the temperature sensors are used to measure the air and powder temperature; The flow sensors are installed on the air inlet duct and the powder outlet duct of the coal mill to measure the air-powder flow rate; The pulverized coal concentration sensor is arranged in the outlet pipe of the coal mill to detect the pulverized coal concentration; The temperature regulating device is arranged on the outlet pipe of the coal mill, and includes a heating element and a cooling element, and is used to regulate the temperature of the air and powder; The control unit is connected with the temperature sensor group, flow sensor, coal powder concentration sensor and temperature regulating device to receive signals from the temperature sensor group, flow sensor and coal powder concentration sensor, calculate the temperature regulation amount and output a signal to the temperature regulating device for the air-powder temperature at the outlet of the coal mill.

[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 coal powder concentration sensor is a laser scattering coal powder concentration sensor.

[0013] Furthermore, the control algorithm of the control unit includes an adjustment algorithm based on multi-parameter feedback and a local temperature compensation mechanism. The overall heat adjustment amount obtained by the adjustment algorithm based on multi-parameter feedback and the local adjustment amount calculated by the local temperature compensation mechanism are integrated 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. The temperature adjustment device adjusts the air powder temperature at the outlet of the coal mill.

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

[0015] in, Total heat of the wind powder mixture Heat brought in by hot air and the heat carried by the pulverized coal of and, It is the heat loss part of the pipeline; Q out The heat removed by the wind-powder mixture; When the current wind powder temperature T out <Target air powder temperature , the heat balance equation at the target temperature is = + , heat adjustment = - Q out = V total C total ( T target - T out ); When the current wind powder temperature T out >Target air powder temperature , heat adjustment = Q out - = V total C total ( T out -T target ); in, and are the total volume flow rate and average specific heat capacity of the air-powder mixture, V total = + , , Hot air flow, Pulverized coal flow rate; Specific heat capacity of hot air, Specific heat capacity of pulverized coal.

[0016] Furthermore, when the current wind powder temperature T out <Target air powder temperature , heating compensation is required, heat adjustment amount = - Q out = V total C total ( T target - T out ), the adjustment amount of the heating element of the temperature control device is the heating power express, = · t , t For time; When the current wind powder temperature T out >Target air powder temperature , cooling compensation is required, heat adjustment amount heat adjustment amount = Q out - = V total C total ( T out - T target ), the cooling element of the temperature regulating device determines the adjustment amount of the cooling element according to the heat dissipation capacity of the cooling element.

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

[0018] in, , For hot air flow, is the hot air temperature, is the specific heat capacity of hot air; , is the coal powder flow rate, is the coal powder temperature, is the specific heat capacity of coal powder; 2) Heat loss in pipes According to the thermal conductivity of the pipe h , Temperature difference between inside and outside of the pipeline And heat transfer area A Calculation, the calculation formula is:

[0019] in, h is the thermal conductivity; 3) Heat removed by the air-powder mixture Q out According to the total volume flow of the air-powder mixture V total , the 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 Among them, the outlet temperature of the air-powder mixture is the current temperature.

[0020] Furthermore, the local temperature compensation mechanism heats or cools the local temperature abnormal area according to the multi-point measurement results of the temperature sensor group and the coal powder concentration. The control unit 7 receives the multi-point temperature data from the temperature sensors 2 distributed at different positions of the coal mill outlet pipeline, uses the set temperature threshold to identify the local temperature is too high or too low area and calculates the heat adjustment amount. =, as follows: The target air powder temperature is , get the actual wind and powder temperature of the 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 the local temperature compensation mechanism is activated; like T local >0, indicating that the local actual temperature is lower than the target temperature, and heating compensation is required. = m × C × T local , the adjustment amount of the heating element of the temperature control device is the heating power express, = · t ; like T local <0, indicating that the local actual temperature is higher than the target temperature, and cooling compensation is required. == n × × T local , the cooling element of the temperature regulating device determines the adjustment amount of the cooling element according to the heat dissipation capacity of the cooling element; in, m , n is the proportionality coefficient, C is the coal powder concentration, t For time.

[0021] The present invention also provides a method for adjusting the air and powder temperature at the outlet of a coal mill under low load. The above-mentioned method for adjusting the air and powder temperature at the outlet of a coal mill under low load is performed by the following specific steps: The temperature sensor group, flow sensor and coal powder concentration sensor collect the air powder temperature, flow rate and coal powder concentration data and transmit them to the control unit; The control unit obtains the thermal physical characteristics of the coal type according to the type of coal, and calculates the overall heat regulation amount using the thermal physical characteristics of the coal type, the air powder temperature and flow rate; The control unit compares the actual air-powder temperature of the local area of ​​different temperature sensors with the target air-powder temperature. When the difference is greater than the set local allowable deviation value, the control unit calculates the local heat adjustment amount according to the coal powder concentration data and the difference between the actual air-powder temperature of the local area and the target air-powder temperature. The control unit obtains the overall heat adjustment amount and the local heat adjustment amount, and transmits them to the temperature adjustment device. The temperature adjustment device adjusts the air and powder temperature at the coal mill outlet according to the adjustment amount signal.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: The low-load coal mill outlet air and powder temperature control system provided by the present invention realizes high-precision control of the coal mill outlet air and powder temperature by integrating multiple temperature sensors, flow sensors, coal powder concentration sensors, temperature control devices and control units. Multiple sensors work together to obtain data on air and powder temperature, flow rate and coal powder concentration in real time and accurately, providing a reliable information basis for precise temperature control. At the same time, the control unit adopts a complex control algorithm, comprehensively considers multiple parameters, calculates the precise temperature control amount, and performs precise control through the temperature control device. This system effectively solves the problem of insufficient accuracy of traditional control methods, ensures that the coal mill outlet air and powder temperature is stable near the target value, thereby improving combustion efficiency and optimizing the operation of the thermal system.

[0023] The present invention also introduces a local temperature compensation mechanism, which heats or cools the local temperature abnormal area through multi-point temperature measurement and real-time monitoring of coal powder concentration. This mechanism makes the temperature distribution of air powder in the outlet pipe more uniform, avoiding the combustion instability caused by local excessively high or low temperatures. At the same time, the improvement in temperature uniformity also reduces the problem of local overheating or slagging of equipment caused by uneven temperature, further improving 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 the present invention, the stability and uniformity of the air and powder temperature at the outlet of the coal mill are significantly improved. This change directly reduces the changes in thermal stress of the equipment caused by temperature fluctuations and unevenness, thereby reducing the wear and corrosion rate of the equipment. Stable temperature regulation not only extends the service life of the coal mill and subsequent related equipment, but also reduces downtime and maintenance costs caused by equipment failure. In addition, the improvement in combustion efficiency also brings higher economic benefits, making the operation of the entire thermal system more economical and efficient.

[0025] In summary, the present invention has significant advantages in extending equipment life, reducing maintenance costs and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The overall layout diagram of the coal mill outlet air and powder temperature adjustment system under low load of the present invention; Figure 2A control algorithm flow chart of a coal mill outlet air and powder temperature regulating system under low load of the present invention; In the attached figure: 1. Coal mill; 2. Temperature sensor; 3. Flow sensor; 4. Coal powder concentration sensor; 5. Heating element; 6. Cooling element; 7. Control unit; 8. Human-computer interaction operation platform. DETAILED DESCRIPTION

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

[0028] like Figure 1 As shown, the present invention provides a low-load coal mill outlet air and powder temperature regulation system, 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 positions of the coal mill outlet pipeline, such as the inner wall of the pipeline, the air-powder mixing area, etc., to measure the air-powder temperature in the coal mill in real time and accurately. These temperature sensors can be thermocouple sensors or thermistor sensors, etc., with an accuracy range of ±0.5%, which can withstand the harsh environment (high temperature, high dust, etc.) of the coal mill outlet and provide high-precision temperature measurement data.

[0029] The flow sensor 3 is installed on the air inlet duct and the powder outlet duct of the coal mill to measure the flow of air and powder. It can be a differential pressure flow sensor, a vortex flow sensor, etc. By measuring the air inlet flow and the powder outlet flow, it provides data support for the subsequent temperature adjustment calculation to understand the conveying situation of air and powder and the change of the mixing ratio.

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

[0031] The heating element 5 is installed on the coal mill inlet pipe, and includes a heating element (such as an electric heating wire, a heat exchanger, etc.). According to the instruction of the control unit, the heating element can heat the air powder, thereby adjusting the air powder temperature.

[0032] The cooling element 6 is installed on the outlet pipe of the coal mill, 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 powder, thereby adjusting the air powder temperature.

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

[0034] A low-load coal mill outlet air and powder temperature regulating system of the present invention is used to regulate the coal mill outlet air and powder temperature during the low-load operation of the coal mill, 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 and coal powder concentration data of the coal mill outlet air powder 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 an adjustment algorithm based on multi-parameter feedback.

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

[0037] 4) Based on the overall and local adjustment quantities, the control unit sends a control signal to the heating element 5 or the cooling element 6 to adjust the working state of the heating element and the cooling element to achieve precise adjustment of the air powder temperature.

[0038] 5) Continuously monitor and adjust to ensure that the air-powder temperature at the outlet of the pulverizer is always stable within the target temperature range when operating at low load, to ensure that the air-powder is mixed evenly and at an appropriate temperature to meet the requirements of the subsequent combustion process.

[0039] The control algorithm built into the control unit 7 is specially designed for low load conditions, such as Figure 2 The following are the steps of the regulation algorithm based on multi-parameter feedback and local temperature compensation mechanism: Step 1: Data collection and preprocessing: The control unit 7 obtains the air-powder temperature data from the temperature sensors 2 installed at different positions of the coal mill outlet pipeline, the air-powder flow data from the flow sensors 3 on the air inlet pipeline and the powder outlet pipeline, and the coal powder concentration data from the coal powder concentration sensor 4 located in the coal mill outlet pipeline in real time.

[0040] A filtering method (sliding average filtering or median filtering) is used to remove noise and abnormal fluctuations from the temperature data to ensure the accuracy and stability of the data; the flow rate and coal powder concentration data are checked for rationality and obviously erroneous data points are removed; at the same time, these data are normalized and their value range is mapped to the interval 0~1 to facilitate comparison and calculation in subsequent calculations.

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

[0042] Step 3: Adjustment algorithm based on multi-parameter feedback; The control unit 7 comprehensively calculates the thermal balance state of the air-powder according to the measured value of the temperature sensor 2 and the air-powder flow measured by the flow sensor 3. Under low-load conditions, different combinations of coal types, air volumes, and powder volumes will result in different thermal balance characteristics. Through the thermal balance model, the heating or cooling power required to meet the target temperature is calculated by considering the relationship between these parameters and the characteristics of low-load operation. For example, when the temperature is lower than the target value, the heating power is increased; conversely, when the temperature is higher than the target value, the cooling power is appropriately increased or the heating power is reduced, as follows: 1) Thermal balance model calculation: According to the principle of heat transfer and the law of conservation of energy, the established thermal balance model is: = +

[0043] in, It is the sum of the heat brought in by the hot air and the heat carried by the coal powder. It is the heat loss part of the pipeline; Q out The heat taken away by the wind-powder mixture.

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

[0045] Heat carried by pulverized coal ( ), according to the pulverized coal flow rate ( )、Pulverized coal temperature( ) and the specific heat capacity of coal powder ( ) is used for calculation, and the calculation formula is:

[0046] Total calories of wind powder mixture is the sum of the two, namely: .

[0047] At the same time, the heat loss part of the pipeline , according to the thermal conductivity of the pipe h , Temperature difference between inside and outside of the pipeline And heat transfer area A Calculation, the calculation formula is: .

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

[0049] Heat removed by the wind-powder mixture Q out , based on the total volume flow of the air-powder mixture V total , the 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 Among them, the outlet temperature of the air-powder mixture is the current temperature.

[0050] 2) Parameter association and target temperature calculation Analyze the relationship between various parameters (air volume, coal powder volume, current temperature, etc.) and their impact on air-powder temperature. ), combined with the currently collected real-time flow and temperature data, the heat balance equation is used for reverse calculation to obtain the heat adjustment required to make the air powder temperature reach the target value .

[0051] Assume the target air powder temperature is , the current wind powder temperature is T out ,and T out < , we need to calculate the amount of heat we need to add Make the temperature reach the target value. According to the heat balance equation, the heat balance equation at the target temperature is = + , where the amount with a prime is the amount of heat corresponding to reaching the target temperature; For the convenience of calculation, it is assumed that the parameters of hot air (flow rate, specific heat capacity, temperature) and coal powder (flow rate, specific heat capacity, temperature) remain unchanged, and only the temperature of the air-powder mixture changes. Then the amount of heat adjustment required is It is mainly used to increase the temperature of the wind-powder mixture, i.e. = - Q out ; according to Q out = V total C total T out and = V total C total T target We can get: = V total C total ( T target - T out ).

[0052] when T out > Calculate the heat that needs to be removed , also 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 are the total volume flow rate and average specific heat capacity of the air-powder mixture, respectively, which can be calculated by the flow rate and specific heat capacity of hot air and coal powder. For example, if the hot air flow rate is , the pulverized coal flow rate is , the specific heat capacity of hot air is , the specific heat capacity of coal powder is ,but V total = + , C total According to the mixing rule to calculate.

[0054] In this way, the heat balance equation is used to invert the heat adjustment required to make the air powder temperature reach the target value. , and establishes the relationship between the previous parameter calculation formulas. In practical applications, the amount of heat can be adjusted according to 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 the heat loss of the coal mill, the work done by the coal powder and air in the coal mill due to heat expansion, the heat generated by the coal powder crushing friction, etc., the heat estimation generated by these factors is relatively complicated. Further, the temperature measurement point feedback can be used to adjust the ΔQ size.

[0056] Step 5: Local temperature compensation mechanism The control unit 7 receives multi-point temperature data from the temperature sensors 2 distributed at different positions of the coal mill outlet pipeline, and uses the set temperature threshold or cluster analysis algorithm to analyze these data to identify the areas where the local temperature is too high or too low. The difference between each local area and the overall average temperature and the area ratio parameter of the area are calculated to quantify the abnormal degree and impact range of the local temperature.

[0057] For low temperature areas, the additional heat required is calculated based on the temperature difference, area ratio and flow characteristics of the wind powder in the low temperature area. By adjusting the heating element close to the area (increasing the power of the corresponding electric heating wire), it can generate additional heat to compensate for the low temperature, so that the temperature of the local area approaches the overall average temperature.

[0058] For high-temperature areas, similarly, after analyzing the relevant parameters, the excess heat that needs to be removed is calculated, and then the temperature of the area is reduced to a suitable range by adjusting the cooling elements near the area (increasing the cooling water flow of the cooling water pipe in the area or increasing the ventilation volume of the air-cooled radiator) to achieve local temperature uniformity. During the adjustment process, the mutual influence between the local areas and the impact on the overall air powder temperature should be comprehensively considered to avoid new temperature anomalies in other areas due to excessive adjustment of a local area.

[0059] The target air powder temperature is , get the actual wind and powder temperature of the 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 the local temperature compensation mechanism is activated, if T local >0, it means the local actual temperature is lower than the target temperature and heating compensation is required; if T local <0, indicating that the local actual temperature is higher than the target temperature and cooling compensation is required.

[0060] The coal powder concentration is also related to the amount of heating or cooling required. Assuming that it represents the amount of heating or cooling, when heating is required, the coal powder concentration C is related to the heat adjustment amount. There is an approximate proportional relationship, which can be expressed as the heat adjustment amount = m × C , where m is the proportionality coefficient; when cooling is required, there is an inverse proportional relationship, such as = n × , n is another proportionality coefficient. This is because the higher the coal powder concentration, the greater the heating required to achieve the same temperature change; and when the concentration is higher, the cooling demand is relatively lower, because the high-concentration coal powder itself carries more heat; according to the target air-powder temperature and the actual wind and powder temperature in the local area T localAnd the coal powder concentration C can calculate the required heating or cooling amount. T local < When the coal powder concentration is C, the heating amount needs to be increased. According to the above positive proportional relationship, the heat adjustment amount = m × C × T local ;when T local > When cooling is required, the adjustment of cooling amount is calculated according to the inverse proportional relationship, such as = n × × T local .

[0061] The specific temperature compensation adjustment amount is determined by: When performing heating compensation, for the heating element (electric heating wire), according to the power characteristics of the electric heating wire (the heat generated per unit power is known), the heating power that needs to be increased or decreased is calculated from the heat adjustment amount ( ) to determine the amount of adjustment to be made to the heating element: = · t in, t For time, if is the heat per unit time, then = ; When performing cooling compensation, for cooling elements (such as cooling water pipes), according to the heat dissipation capacity of the cooling water pipes (the relationship between the heat removed per unit time and the water flow rate, water temperature difference, etc. is known), based on the heat adjustment amount ( ) Calculate the parameters such as the cooling water flow rate that need to be adjusted to determine the adjustment amount for the cooling element. Step 5: Comprehensively calculate the adjustment amount and output the control signal: The overall adjustment amount obtained by the adjustment algorithm based on multi-parameter feedback and the local adjustment amount calculated by the local temperature compensation mechanism are combined to obtain the final heating / cooling element adjustment amount. Then, the control unit outputs the corresponding control signal to the heating / cooling element (electric heating wire, cooling water pump and other equipment) to make it work according to the calculated adjustment amount to achieve the adjustment of the air powder temperature.

[0062] Step 6: Continuous monitoring and adjustment: The above steps are executed in a continuous cycle to collect data, determine the coal type, calculate the adjustment amount and output the control signal in real time, and continuously adjust according to the actual temperature of the air and powder at the outlet of the coal mill to ensure that the air and powder temperature is always stable within the target temperature range during low-load operation, and to ensure that the air and powder are mixed evenly and the temperature is appropriate 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 adjustment control process stops.

[0063] In the regulation algorithm based on multi-parameter feedback of the present invention, the control unit comprehensively calculates the thermal balance state of air and powder according to the measured value of the temperature sensor, the air-powder flow 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 types, air volumes, and powder volumes will lead to different thermal balance characteristics. Through the thermal balance model, the heating or cooling power required to meet the target temperature is calculated by considering the relationship between these parameters and the characteristics of low-load operation. For example, when the coal powder concentration increases, the air volume decreases (low-load characteristics) and the temperature is lower than the target value, the heating power is increased; conversely, when the temperature is higher than the target value, the cooling power is appropriately increased or the heating power is reduced.

[0064] Through the collaborative work of multiple sensors and complex adjustment algorithms, the present invention can achieve high-precision adjustment of the air-powder temperature at the outlet of the coal mill under low-load conditions, effectively solving the problem of insufficient accuracy of traditional adjustment methods, ensuring that the temperature is stable near the target value, and is conducive to improving combustion efficiency. The local temperature compensation mechanism makes the temperature distribution of the air-powder in the outlet pipe more uniform, avoids the combustion instability caused by local excessively high or low temperatures, reduces the problem of local overheating or slagging of equipment caused by uneven temperature, and improves the safety and reliability of the equipment. Stable temperature regulation reduces the changes in thermal stress of the equipment caused by temperature fluctuations and unevenness, reduces the wear and corrosion rate of the equipment, extends the service life of the coal mill and subsequent related equipment, and reduces maintenance costs.

Claims

1. A low-load coal mill outlet air and powder temperature control system, characterized in that: It includes a temperature sensor group, a flow sensor, a coal powder concentration sensor, a temperature regulating device and a control unit, wherein: The temperature sensor group includes multiple temperature sensors, which are respectively installed at different positions of the coal mill outlet pipeline, and the temperature sensors are used to measure the air and powder temperature; The flow sensors are installed on the air inlet duct and the powder outlet duct of the coal mill to measure the air-powder flow rate; The pulverized coal concentration sensor is arranged in the outlet pipe of the coal mill to detect the pulverized coal concentration; The temperature regulating device is arranged on the outlet pipe of the coal mill, and includes a heating element and a cooling element, and is used to regulate the temperature of the air and powder; The control unit is connected with the temperature sensor group, flow sensor, coal powder concentration sensor and temperature regulating device to receive signals from the temperature sensor group, flow sensor and coal powder concentration sensor, calculate the temperature regulation amount and output a signal to the temperature regulating device for the air-powder temperature at the outlet of the coal mill.

2. The low-load coal mill outlet air and powder temperature control system according to claim 1 is characterized in that: The temperature sensor is a thermocouple sensor or a thermistor sensor.

3. The low-load coal mill outlet air and powder temperature control system according to claim 1 is characterized in that: The flow sensor is a differential pressure flow sensor or a vortex flow sensor.

4. The low-load coal mill outlet air and powder temperature control system according to claim 1 is characterized in that: The coal powder concentration sensor is a laser scattering coal powder concentration sensor.

5. The low-load coal mill outlet air and powder temperature control system according to claim 1 is characterized in that: The control algorithm of the control unit includes an adjustment algorithm based on multi-parameter feedback and a local temperature compensation mechanism. The overall heat adjustment amount obtained by the adjustment algorithm based on multi-parameter feedback and the local adjustment amount calculated by the local temperature compensation mechanism are integrated 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. The temperature adjustment device adjusts the air powder temperature at the outlet of the coal mill.

6. The low-load coal mill outlet air and powder temperature control system according to claim 5, characterized in that: The multi-parameter feedback-based regulation algorithm calculates the air-powder thermal balance state according to the temperature and flow rate to determine the heat adjustment amount. , as follows: According to the principle of heat transfer and the law of conservation of energy, the established thermal balance model is: = + in, Total heat of the wind powder mixture Heat brought in by hot air and the heat carried by the pulverized coal of and, It is the heat loss part of the pipeline; Q out The heat removed by the wind-powder mixture; When the current wind powder temperature T out <Target air powder temperature , the heat balance equation at the target temperature is = + , heat adjustment = - Q out = V total C total ( T target - T out ); When the current wind powder temperature T out >Target air powder temperature , heat adjustment = Q out - = V total C total ( T out - T target ); in, and are the total volume flow rate and average specific heat capacity of the air-powder mixture, V total = + , , Hot air flow, Pulverized coal flow rate; Specific heat capacity of hot air, Specific heat capacity of pulverized coal.

7. The low-load coal mill outlet air and powder temperature control system according to claim 6, characterized in that: When the current wind powder temperature T out <Target air powder temperature , heating compensation is required, heat adjustment amount = - Q out = V total C total ( T target - T out ), the adjustment amount of the heating element of the temperature control device is the heating power express, = · t , t For time; When the current wind powder temperature T out >Target air powder temperature , cooling compensation is required, heat adjustment amount heat adjustment amount = Q out - = V total C total ( T out - T target ), the cooling element of the temperature regulating device determines the adjustment amount of the cooling element according to the heat dissipation capacity of the cooling element.

8. The low-load coal mill outlet air and powder temperature control system according to claim 5, characterized in that: 1) Total calories of the powder mixture Heat brought in by hot air and the heat carried by the pulverized coal The sum of, that is: in, , For hot air flow, is the hot air temperature, is the specific heat capacity of hot air; , is the coal powder flow rate, is the coal powder temperature, is the specific heat capacity of coal powder; 2) Heat loss in pipes According to the thermal conductivity of the pipe h , Temperature difference between inside and outside of the pipeline And heat transfer area A Calculation, the calculation formula is: in, h is the thermal conductivity; 3) Heat removed by the air-powder mixture Q out According to the total volume flow of the air-powder mixture V total , the 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 Among them, the outlet temperature of the air-powder mixture is the current temperature.

9. The low-load coal mill outlet air and powder temperature control system according to claim 5, characterized in that: The local temperature compensation mechanism heats or cools the local temperature abnormal area according to the multi-point measurement results of the temperature sensor group and the coal powder concentration. The control unit 7 receives the multi-point temperature data from the temperature sensors 2 distributed at different positions of the coal mill outlet pipeline, uses the set temperature threshold to identify the local temperature is too high or too low area and calculates the heat adjustment amount. =, as follows: The target air powder temperature is , get the actual wind and powder temperature of the 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 the local temperature compensation mechanism is activated; like T local >0, indicating that the local actual temperature is lower than the target temperature, and heating compensation is required. = m × C × T local , the adjustment amount of the heating element of the temperature control device is the heating power express, = · t ; like T local <0, indicating that the local actual temperature is higher than the target temperature, and cooling compensation is required. == n × × T local , the cooling element of the temperature regulating device determines the adjustment amount of the cooling element according to the heat dissipation capacity of the cooling element; in, m , n is the proportionality coefficient, C is the coal powder concentration, t For time.

10. A method for adjusting the air and powder temperature at the outlet of a coal mill under low load, characterized in that: The method is carried out by using a low-load coal mill outlet air and powder temperature regulating system according to any one of claims 1 to 9, and the specific steps are as follows: The temperature sensor group, flow sensor and coal powder concentration sensor collect the air powder temperature, flow rate and coal powder concentration data and transmit them to the control unit; The control unit obtains the thermal physical characteristics of the coal type according to the type of coal, and calculates the overall heat regulation amount using the thermal physical characteristics of the coal type, the air powder temperature and flow rate; The control unit compares the actual air-powder temperature of the local area of ​​different temperature sensors with the target air-powder temperature. When the difference is greater than the set local allowable deviation value, the control unit calculates the local heat adjustment amount according to the coal powder concentration data and the difference between the actual air-powder temperature of the local area and the target air-powder temperature. The control unit obtains the overall heat adjustment amount and the local heat adjustment amount, and transmits them to the temperature adjustment device. The temperature adjustment device adjusts the air and powder temperature at the coal mill outlet according to the adjustment amount signal.

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