Coal gas air heater energy-saving control method and device based on heat value fluctuation

Abstract

The application provides a coal gas air heater energy-saving control method and device based on heat value fluctuation, relates to the technical field of heater energy-saving control, and comprises the following steps: acquiring a heat value data sequence in a preset time window, extracting heat value disturbance characteristics through time domain analysis, and combining the deviation of the actual air outlet temperature and the target temperature to generate a basic air-fuel ratio set value compensated by the heat value; applying time compensation according to the transmission delay; dynamically defining the combustion stability margin according to the flame signal strength, limiting and correcting the air-fuel ratio control instruction to be within the safety boundary, and controlling the coal gas air heater. Through the application, the technical problem that the dynamic air-fuel ratio and the actual heat value demand are mismatched due to the rapid fluctuation of the coal gas heat value, the detection lag and the control time sequence mismatch in the prior art, which affects the combustion efficiency of the coal gas air heater, is solved, and the accurate dynamic matching of the air-fuel ratio, the improvement of the combustion efficiency and the guarantee of the operation safety are realized under the heat value fluctuation condition.

Description

Technical Field

[0001] This application relates to the field of heater energy-saving control technology, specifically to an energy-saving control method and device for coal gasification air heaters based on calorific value fluctuations. Background Technology

[0002] The coal gasification air heater is a key heat exchange and combustion device in the coal gasification production process. Its core function is to use the high-temperature flue gas generated by coal gasification combustion to heat the combustion air to the required high temperature through a heat exchanger, and then send the heated air into the gasifier or subsequent reaction equipment to maintain the temperature and efficiency of the gasification reaction. In existing coal gasification air heater combustion control schemes, a control strategy based on detecting the calorific value of the coal gas using a calorific value meter and combining feedback from the oxygen content of the flue gas or the outlet air temperature for air-fuel ratio correction is commonly adopted. However, because the calorific value of coal gas is significantly affected by factors such as the gasification feedstock, gasifying agent ratio, and operating conditions, it exhibits a wide range of fluctuations. Furthermore, the physical transmission distance caused by the calorific value meter's detection process and installation location means that the calorific value information cannot reflect the actual calorific value of the gas entering the furnace in real time when it is transmitted to the control system. Existing control methods based on feedback correction are unable to respond promptly to rapid and transient changes in calorific value. Meanwhile, in actual engineering, there are objective differences between gas regulating valves and air regulating valves in terms of pipeline length and fluid response characteristics. Existing systems usually send the air-fuel ratio setpoint after calorific value compensation to the actuators on both the gas and air sides at the same time, without taking into account the asynchronous response time of the two sides. This timing mismatch means that even if the air-fuel ratio setpoint is accurate in numerical terms, the gas and air cannot achieve synchronous mixing and combustion when entering the furnace, which further aggravates combustion instability and energy loss.

[0003] In summary, the existing technology has technical problems such as rapid fluctuations in the calorific value of coal gasification, lag in detection, and mismatch in control timing, which lead to a mismatch between the dynamic air-fuel ratio and the actual calorific value requirement, further affecting the combustion efficiency of the coal gasification air heater. Summary of the Invention

[0004] The purpose of this application is to provide an energy-saving control method and device for coal gasification air heaters based on calorific value fluctuations, in order to solve the technical problem in the prior art that the dynamic air-fuel ratio is mismatched with the actual calorific value demand due to rapid fluctuations in the calorific value of coal gasification, detection lag, and mismatch in control timing, which further affects the combustion efficiency of coal gasification air heaters.

[0005] To achieve the above objectives, this application provides an energy-saving control method and device for coal gasification air heaters based on calorific value fluctuations.

[0006] In a first aspect, this application provides an energy-saving control method for a coal-to-gas air heater based on calorific value fluctuations. This method is implemented using an energy-saving control device for a coal-to-gas air heater based on calorific value fluctuations. The method includes: acquiring a calorific value data sequence within a preset time window and extracting calorific value disturbance characteristics through time-domain analysis; applying a feedforward correction to a preset standard air-fuel ratio based on the calorific value disturbance characteristics to generate a calorific value-compensated basic air-fuel ratio setpoint; and introducing the actual outlet air temperature of the coal-to-gas air heater and comparing the actual outlet air temperature with a target outlet air temperature. The temperature deviation is obtained through difference calculation, and an air-fuel ratio feedback correction amount is generated based on the temperature deviation. The basic air-fuel ratio setpoint is superimposed with the air-fuel ratio feedback correction amount to form a fused air-fuel ratio setpoint. Time compensation is applied to the adjustment action corresponding to the fused air-fuel ratio setpoint based on the transmission delay between the calorific value detection point and the burner to generate an air-fuel ratio control command. The combustion stability margin is dynamically defined based on the flame signal intensity of the coal gas air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected based on the combustion stability margin. The air-fuel ratio control command after correction and limitation is constrained within the safety boundary and output to control the coal gas air heater.

[0007] Optionally, a calorific value data sequence within a preset time window is obtained, and calorific value disturbance features are extracted through time-domain analysis. The calorific value disturbance features include at least instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate: the absolute value of the difference between all adjacent sampled data points in the calorific value data sequence is calculated, and the maximum value of the absolute value is taken as the calorific value fluctuation amplitude; the difference between the last data point and the first data point in the calorific value data sequence is calculated and divided by the time length of the preset time window to obtain the calorific value change rate; the arithmetic mean of the calorific value data sequence is taken as the instantaneous calorific value.

[0008] Optionally, the ambient temperature, ambient pressure, and real-time oxygen content of the combustion air in the environment where the coal gas air heater is located, as well as the residual oxygen concentration of the flue gas from the combustion products, are obtained. The preset standard air-fuel ratio is then corrected based on the environmental benchmark to obtain an air-fuel ratio benchmark value adapted to the current air conditions. Based on the deviation between the instantaneous calorific value and the preset standard calorific value in the calorific value disturbance characteristics, the air-fuel ratio benchmark value is corrected for calorific value deviation to obtain a calorific value matching base value. The correction amplitude is determined according to the calorific value fluctuation amplitude, and the correction speed is determined according to the calorific value change rate to generate the feedforward correction amount. The feedforward correction amount is then safely calibrated using the real-time gas supply pressure and impurity deposition characterization of the coal gas. The result after safe calibration is superimposed on the calorific value matching base value to obtain the calorific value compensated base air-fuel ratio setting value.

[0009] Optionally, a preset allowable deviation dead zone threshold is defined. When the absolute value of the temperature deviation is less than or equal to the allowable deviation dead zone threshold, the air-fuel ratio feedback correction is zero. When the absolute value of the temperature deviation is greater than the allowable deviation dead zone threshold, an initial feedback correction is generated based on a proportional-integral control algorithm. The weighting coefficient of the initial feedback correction is dynamically set according to the calorific value fluctuation amplitude, wherein the weighting coefficient decreases non-linearly as the calorific value fluctuation amplitude increases. The maximum allowable adjustment step size is determined based on the calorific value fluctuation amplitude, and the initial feedback correction is amplitude-limited by combining the weighting coefficient to obtain the air-fuel ratio feedback correction.

[0010] Optionally, when the basic air-fuel ratio setting value is superimposed with the air-fuel ratio feedback correction value, if the calorific value fluctuation exceeds a preset severe fluctuation threshold, the air-fuel ratio feedback correction value is set to zero, so that the fused air-fuel ratio setting value is equal to the basic air-fuel ratio setting value.

[0011] Optionally, the physical transmission time of coal gas flowing from the calorific value detection point to the burner nozzle is obtained; the response time of combustion air from the action of the air flow regulating mechanism to entering the burner to participate in combustion is obtained; the difference between the physical transmission time and the response time is calculated as a time compensation offset; the fused air-fuel ratio setpoint is decomposed into corresponding gas regulating valve opening commands and combustion air regulating valve opening commands, and the effective timestamps of the two commands are marked according to the time compensation offset; based on the safety boundary and the adjustment limit, the timestamp-marked gas regulating valve opening commands and combustion air regulating valve opening commands are verified; after the verification is passed, the adjusted gas regulating valve opening commands and combustion air regulating valve opening commands, along with the corresponding effective timestamps, are encapsulated together to generate the air-fuel ratio control command.

[0012] Optionally, if the physical transmission time is greater than the response time, the effective timestamp of the combustion air regulating valve opening command is delayed by the time compensation offset; if the physical transmission time is less than the response time, the effective timestamp of the combustion air regulating valve opening command is advanced by the time compensation offset.

[0013] Optionally, the calibration extinction threshold of the coal gasification air heater is obtained, and a basic stability margin is obtained based on the difference between the flame signal intensity and the calibration extinction threshold. The basic stability margin is attenuated and corrected by combining the impurity deposition characterization quantity to obtain the combustion stability margin. The maximum single adjustment step size of the air-fuel ratio control command is used as the adjustment limit, and the adjustment limit is adjusted according to the combustion stability margin. Based on the theoretical air-fuel ratio, a safety boundary is preset, and the air-fuel ratio control command after adjustment limit correction is compared with the safety boundary. If it exceeds the boundary, it is truncated to the boundary edge. The truncated air-fuel ratio control command is timestamped and encapsulated, and finally the air-fuel ratio control command is output.

[0014] Optionally, if the actual outlet air temperature of the coal gasification air heater is stable within the allowable deviation range of the target outlet air temperature, and the stability margin is higher than a preset threshold, a slight disturbance is applied to the air-fuel ratio control command in a step-by-step manner; the response changes of the outlet air temperature and flame signal intensity are monitored simultaneously to determine the deviation direction of the real-time air-fuel ratio relative to the theoretical air-fuel ratio, and the air-fuel ratio control command is adjusted according to the deviation direction; when the theoretical air-fuel ratio is reached, the current air-fuel ratio control command is determined as the energy-saving operation benchmark parameter.

[0015] Secondly, this application also provides an energy-saving control device for a coal-to-gas air heater based on calorific value fluctuation, used to execute the energy-saving control method for a coal-to-gas air heater based on calorific value fluctuation as described in the first aspect. The energy-saving control device for the coal-to-gas air heater based on calorific value fluctuation includes: a calorific value data analysis module, used to acquire a calorific value data sequence within a preset time window and extract calorific value disturbance characteristics through time-domain analysis; a feedforward correction module, used to apply a feedforward correction amount to a preset standard air-fuel ratio based on the calorific value disturbance characteristics, generating a calorific value-compensated basic air-fuel ratio setpoint; and a temperature deviation calculation module, used to introduce the actual outlet air temperature of the coal-to-gas air heater and calculate the difference between the actual outlet air temperature and the target outlet air temperature to obtain the temperature. The system calculates the temperature deviation and generates an air-fuel ratio feedback correction value based on the deviation. An air-fuel ratio superposition module superimposes the basic air-fuel ratio setpoint with the air-fuel ratio feedback correction value to form a fused air-fuel ratio setpoint. A time compensation module applies time compensation to the adjustment action corresponding to the fused air-fuel ratio setpoint based on the transmission delay between the calorific value detection point and the burner, generating an air-fuel ratio control command. An adaptive correction control command module dynamically defines the combustion stability margin based on the flame signal intensity of the coal gas air heater, and adaptively corrects the adjustment limit of the air-fuel ratio control command based on the combustion stability margin, constraining the corrected air-fuel ratio control command within a safe boundary for output, thereby controlling the coal gas air heater.

[0016] One or more technical solutions provided in this application have at least the following technical effects or advantages: By acquiring a calorific value data sequence within a preset time window, calorific value disturbance characteristics are extracted through time-domain analysis; based on the calorific value disturbance characteristics, a feedforward correction is applied to a preset standard air-fuel ratio to generate a calorific value-compensated basic air-fuel ratio setpoint; the actual outlet air temperature of the coal gasification air heater is introduced, and a temperature deviation is obtained by calculating the difference between the actual outlet air temperature and the target outlet air temperature, and an air-fuel ratio feedback correction is generated based on the temperature deviation; the basic air-fuel ratio setpoint and the air-fuel ratio feedback correction are superimposed to form a fused air-fuel ratio setpoint; time compensation is applied to the adjustment action corresponding to the fused air-fuel ratio setpoint based on the transmission delay between the calorific value detection point and the burner to generate an air-fuel ratio control command; the combustion stability margin is dynamically defined based on the flame signal intensity of the coal gasification air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected based on the combustion stability margin, and the corrected air-fuel ratio control command is output within a safe boundary to control the coal gasification air heater. In other words, by extracting the time-domain calorific value disturbance characteristics for dynamic feedforward compensation, integrating temperature deviation feedback correction, implementing spatiotemporal alignment control based on transmission delay, and adaptively correcting and adjusting the amplitude limit according to the flame signal intensity, the air-fuel ratio can be accurately and dynamically matched under calorific value fluctuation conditions, thereby improving the combustion efficiency of the coal gasification air heater and ensuring operational safety.

[0017] The above description is merely an overview of the technical solution of this application. To better understand the technical means of this application and to facilitate its implementation according to the description, and to make the above and other objects, features, and advantages of this application more apparent, specific embodiments of this application are described below. It should be understood that the content described in this section is not intended to identify key or important features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent through the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of the energy-saving control method for coal gasification air heaters based on calorific value fluctuations in this application.

[0020] Figure 2 This is a schematic diagram of the energy-saving control device for a coal-to-gas air heater based on calorific value fluctuations, as described in this application.

[0021] Figure labeling: 11 Calorific value data analysis module, 12 Feedforward correction module, 13 Temperature deviation calculation module, 14 Air-fuel ratio superposition module, 15 Time compensation module, 16 Adaptive correction control command module. Detailed Implementation

[0022] This application provides an energy-saving control method and device for coal gasification air heaters based on calorific value fluctuations. It solves the technical problem in existing technologies where rapid fluctuations in the calorific value of coal gasification, detection lag, and mismatched control timing lead to a mismatch between the dynamic air-fuel ratio and actual calorific value requirements, further affecting the combustion efficiency of the coal gasification air heater. By extracting time-domain calorific value disturbance characteristics for dynamic feedforward compensation, integrating temperature deviation feedback correction, implementing spatiotemporal alignment control based on transmission delay, and adaptively adjusting the limiting amplitude based on flame signal intensity, precise dynamic matching of the air-fuel ratio is achieved under calorific value fluctuation conditions, improving the combustion efficiency of the coal gasification air heater and ensuring operational safety.

[0023] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. It should be understood that this application is not limited to the exemplary embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should also be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all of them.

[0024] Example 1, please refer to the appendix. Figure 1 This application provides an energy-saving control method for a coal-to-gas air heater based on calorific value fluctuations. The method is applied to an energy-saving control device for a coal-to-gas air heater based on calorific value fluctuations. The specific steps of the method are as follows: Obtain the calorific value data sequence within a preset time window, and extract the calorific value perturbation characteristics through time domain analysis.

[0025] Furthermore, this application also includes the following steps: acquiring a calorific value data sequence within a preset time window, extracting calorific value perturbation features through time-domain analysis, wherein the calorific value perturbation features include at least instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate; calculating the absolute value of the difference between all adjacent sampled data points in the calorific value data sequence, and taking the maximum value of the absolute value as the calorific value fluctuation amplitude; calculating the difference between the last data point and the first data point in the calorific value data sequence divided by the time length of the preset time window as the calorific value change rate; and taking the arithmetic mean of the calorific value data sequence as the instantaneous calorific value.

[0026] Specifically, a calorific value analyzer is installed on the coal gasification pipeline, with its probe in direct contact with the coal gas inside the pipeline. The analyzer continuously measures the calorific value of the coal gas flowing through that pipeline segment at a fixed sampling period, such as once per second. The results are then uploaded to the control system in real time as an electrical signal. Upon receiving the real-time calorific value signal, the control system stores it in a fixed-length circular buffer. The length of the buffer is the number of sampling points contained within a preset time window. For example, if the window length is 60 seconds and the sampling period is 1 second, the buffer capacity is 60 data points. Whenever new calorific value data arrives, the new data is added to the end of the buffer, while the oldest data at the beginning is removed, ensuring that the buffer always stores a complete sequence of calorific value data from the most recent time window.

[0027] Time-domain analysis was performed on the complete calorific value data sequence, extracting calorific value perturbation features in three parallel paths. Time-domain analysis directly performs mathematical operations on the calorific value data sequence on the time axis, rather than converting the data to the frequency domain. The purpose is to extract quantitative indicators describing the behavior of calorific value changes.

[0028] The process iterates through all adjacent sampling data points in the calorific value data sequence, calculating the absolute value of the difference between each pair of adjacent points. The maximum absolute value is taken as the calorific value fluctuation amplitude, reflecting the maximum jump in calorific value between any adjacent sampling times within the time window. The last data point in the calorific value data sequence (the current latest calorific value) and the calorific value at the first time point (the start of the window) are taken, and their difference is calculated. This difference is divided by the total duration of the preset time window, and the quotient is taken as the calorific value change rate, reflecting the overall trend and average speed of change of calorific value throughout the window period. An arithmetic mean is calculated for all sampling points in the calorific value data sequence, i.e., the sum of the calorific values ​​of all data points is divided by the total number of data points, and the average value is taken as the instantaneous calorific value at the current moment, used to characterize the current energy benchmark level of coal-to-gas. The instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate are output as the calorific value disturbance characteristics of the current coal-to-gas supply state.

[0029] By analyzing the time-domain data sequence of calorific value within a preset time window, three quantitative disturbance characteristics are extracted: instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate. Before the disturbance affects the outlet air temperature, a quantitative judgment is made on the direction, magnitude, and rate of change of calorific value, fundamentally solving the problem of lag in post-event adjustment.

[0030] Based on the calorific value perturbation characteristics, a feedforward correction is applied to the preset standard air-fuel ratio to generate a calorific value-compensated basic air-fuel ratio setting.

[0031] Furthermore, this application also includes the following steps: obtaining the ambient temperature, ambient pressure, and real-time oxygen content of the combustion air in the environment where the coal gas air heater is located, as well as the residual oxygen concentration of the flue gas from the combustion products; correcting the preset standard air-fuel ratio to an environmental benchmark to obtain an air-fuel ratio benchmark value adapted to the current air conditions; correcting the air-fuel ratio benchmark value to a calorific value deviation based on the deviation between the instantaneous calorific value and the preset standard calorific value in the calorific value disturbance characteristics to obtain a calorific value matching base value; determining the correction amplitude based on the calorific value fluctuation amplitude and the correction speed based on the calorific value change rate to generate the feedforward correction amount; performing a safety calibration on the feedforward correction amount using the real-time gas supply pressure and impurity deposition characterization of the coal gas; and superimposing the safety-calibrated result onto the calorific value matching base value to obtain the calorific value-compensated base air-fuel ratio setting value.

[0032] Specifically, temperature sensors, pressure sensors, oxygen content sensors on the combustion air duct, and residual oxygen analyzers on the flue gas exhaust duct are installed in the heater area to collect current ambient temperature, ambient pressure, real-time oxygen content of the combustion air, and residual oxygen concentration in the flue gas. Ambient temperature refers to the temperature of the atmosphere surrounding the coal gasification air heater installation location, affecting air density and oxygen mass flow rate; ambient pressure refers to the absolute atmospheric pressure at the heater installation location, affecting the conversion between air density and combustion air volume flow rate; real-time oxygen content of the combustion air is the actual volume percentage of oxygen in the combustion air entering the burner, typically approximately 20.6% to 20.9%, measured in real-time by the oxygen content sensor, affecting the actual amount of oxygen participating in combustion; residual oxygen concentration in the flue gas is the volume percentage of oxygen remaining in the exhaust gas after combustion, measured in real-time by the flue gas analyzer, used to determine whether combustion is complete.

[0033] Based on the variation of air density with temperature and pressure, the deviation of the actual oxygen content in the combustion air from the oxygen content under standard atmospheric conditions, and the excess air condition reflected by the residual oxygen concentration in the flue gas, a preset standard air-fuel ratio is comprehensively corrected to calculate a benchmark air-fuel ratio value that adapts to the current air physical state and combustion conditions. The preset standard air-fuel ratio is the theoretical air volume ratio required for the complete combustion of a unit volume of coal gas. For example, under standard conditions, with an ambient temperature of 20℃, an ambient pressure of 101.3 kPa, and an oxygen content of 20.9%, the preset standard air-fuel ratio is 4.2. Assuming the collected ambient temperature is 28℃, the ambient pressure is 96.5 kPa, the real-time oxygen content in the combustion air is 20.6%, and the residual oxygen concentration in the flue gas is 3.2%, the environmental benchmark correction coefficients are 0.9734 for temperature, 1.0497 for pressure, and 1.0146 for oxygen content. The current residual oxygen level of 3.2% is higher than the design value. Assuming the design value is 2.5%, this indicates that there is too much excess air. The correction factor is (20.9-3.2) / (20.9-2.5), which is approximately 0.962. Therefore, the comprehensive correction factor is approximately 0.997, and the calculated air-fuel ratio baseline value is approximately 4.1874.

[0034] The calorific value deviation is obtained by subtracting the instantaneous calorific value from the preset standard calorific value in the calorific value disturbance characteristics. The preset standard calorific value is the theoretical calorific value of coal gas under design conditions, used to compare with the measured instantaneous calorific value to determine the deviation from the energy benchmark. If the instantaneous calorific value is higher than the standard calorific value, it indicates that the current coal gas energy density is too high, and the air-fuel ratio should be appropriately reduced to decrease the air supply; conversely, the air-fuel ratio should be increased. The calorific value deviation is converted into an air-fuel ratio correction amount according to a preset proportional coefficient, and then superimposed on the air-fuel ratio benchmark value to obtain the calorific value matching base value, so that the ratio value matches the actual energy level of the current fuel.

[0035] Based on the fluctuation range of calorific value, a correction amplitude coefficient is determined through a preset mapping function. The larger the fluctuation range, the larger the correction amplitude coefficient, ensuring sufficient feedforward correction when the calorific value changes drastically. When the fluctuation range of calorific value is less than a lower threshold, such as 5 kcal / Nm³, the correction amplitude coefficient is adjusted accordingly. 3 The upper limit threshold is 30 kcal / Nm 3If the calorific value is considered relatively stable, no significant feedforward is required, and the correction amplitude is set to a minimum or zero. When the calorific value fluctuation range is between the lower and upper thresholds, the correction amplitude increases monotonically with increasing fluctuation range, i.e., correction amplitude = (calorific value fluctuation range - lower threshold) / (upper threshold - lower threshold) * 0.12. When the calorific value fluctuation range exceeds the upper threshold, it is considered that the calorific value has changed drastically, and the maximum intensity of feedforward correction is required, with the correction amplitude set to the saturation upper limit, such as 0.12. Through a preset mapping function relationship, the physical quantity value of the calorific value fluctuation range is converted into a dimensionless correction amplitude coefficient.

[0036] The correction rate coefficient is determined based on the rate of change of calorific value. The faster the rate of change, the larger the correction rate coefficient, ensuring that the feedforward correction provides sufficient advance response in the early stages of calorific value change to compensate for the impending change. When the absolute value of the rate of change is less than a lower threshold, such as 0.3 kcal / (Nm³), the correction rate is adjusted accordingly. 3 ·s), with an upper limit threshold of 2kcal / (Nm 3 If the rate of change is considered slow (e.g., ·s), no significant advance response is required, and the correction rate is set to a minimum or 0. When the absolute value of the rate of change is between the lower and upper thresholds, the correction rate monotonically increases with the increase of the absolute value of the rate, such as correction rate = (|calorific value change rate| - lower threshold) / (upper threshold - lower threshold) * 0.85. When the absolute value of the rate of change exceeds the upper threshold, the calorific value is considered to change extremely rapidly, and a maximum advance response is required, with the correction rate set to the saturation upper limit, such as 0.85. The direction of the feedforward correction is determined by the sign of the rate of change. If the rate is positive (calorific value increases), the feedforward correction should be negative, reducing air or increasing fuel gas; if the rate is negative (calorific value decreases), the feedforward correction should be positive, increasing air or decreasing fuel gas.

[0037] Multiplying the correction amplitude coefficient and the correction rate coefficient, and then multiplying by the baseline air-fuel ratio, generates a dynamic feedforward correction. The correction amplitude coefficient determines the absolute magnitude of this correction, while the correction rate coefficient determines its proportional strength relative to the current baseline value. Multiplying both by the baseline value then outputs an air-fuel ratio increment with practical physical meaning.

[0038] The real-time gas supply pressure of the coal-to-gas system is obtained from the pressure transmitter on the gas pipeline and compared with the internally set normal gas supply pressure range, such as 30 kPa to 45 kPa. If the real-time pressure is within the normal range, the gas supply pressure safety factor is set to 1, and no attenuation is applied to the feedforward correction. If the pressure is below the lower limit threshold but has not yet reached the emergency shutdown threshold, such as in the 20 kPa to 30 kPa range, it indicates a decrease in gas supply capacity. An attenuation coefficient less than 1 is calculated according to a preset linear or piecewise function relationship, and the feedforward correction is reduced proportionally to prevent abnormal negative pressure in the furnace caused by forcibly increasing fuel or air when the gas supply is insufficient. If the pressure is above the upper limit threshold, attenuation is applied in a similar manner to prevent over-adjustment and potential safety hazards caused by overpressure. If the pressure is below the emergency shutdown threshold, such as <20 kPa, the safety interlock is triggered directly, and no additional operation is performed.

[0039] The impurity deposition characterization value, stored internally, is estimated based on historical trends in pipeline pressure drop, cumulative burner operating time, and flame image characteristics. Initially set at 1, it gradually decreases over time, providing a second calibration for the feedforward correction. The impurity deposition characterization value is directly applied as a multiplicative coefficient to the feedforward correction: the more severe the deposition (closer to 0), the greater the attenuation of the feedforward correction. This is because deposition slows the actual gas flow rate entering the burner and reduces flow capacity; applying a large feedforward correction in this situation can easily cause the actual air-fuel ratio to deviate from the expected value, leading to combustion deterioration. If the characterization value falls below a certain severity threshold, such as below 0.6, not only is the feedforward correction attenuated, but an alarm signal is also output to remind maintenance personnel to check the pipeline.

[0040] Multiply the gas supply pressure safety factor by the impurity deposition safety factor to obtain the comprehensive safety calibration factor. Multiply the feedforward correction by the comprehensive safety calibration factor to obtain the safety-calibrated feedforward correction. Add the calibrated feedforward correction to the calorific value matching base value in algebraic sum form. The output result is the calorific value-compensated base air-fuel ratio setpoint.

[0041] Environmental baseline correction adapts the air-fuel ratio baseline value to the actual air conditions of current temperature, pressure, oxygen content, and residual oxygen concentration, eliminating the impact of environmental changes on the combustion ratio. Calorific value deviation correction matches the ratio value with the actual fuel energy baseline, ensuring the correct basic ratio. The correction amplitude and correction rate are determined by the calorific value fluctuation range and change rate, respectively, so that the feedforward correction amount can provide sufficient strength for correction when the calorific value jumps sharply, and can generate sufficient anticipatory response when the calorific value changes rapidly, rather than passively adjusting after temperature deviation occurs. Finally, safety calibration is performed by gas supply pressure and impurity deposition to prevent over-correction that could lead to combustion deterioration in the event of abnormal gas supply or pipeline blockage.

[0042] The actual outlet air temperature of the coal gasification air heater is introduced, and the difference between the actual outlet air temperature and the target outlet air temperature is calculated to obtain the temperature deviation. The air-fuel ratio feedback correction amount is generated based on the temperature deviation.

[0043] Furthermore, this application also includes the following steps: a preset allowable deviation dead zone threshold is established; when the absolute value of the temperature deviation is less than or equal to the allowable deviation dead zone threshold, the air-fuel ratio feedback correction is zero; when the absolute value of the temperature deviation is greater than the allowable deviation dead zone threshold, an initial feedback correction is generated based on a proportional-integral control algorithm; a weighting coefficient for the initial feedback correction is dynamically set according to the calorific value fluctuation amplitude, wherein the weighting coefficient decreases non-linearly as the calorific value fluctuation amplitude increases; the maximum allowable adjustment step size is determined based on the calorific value fluctuation amplitude, and the initial feedback correction is amplitude-limited by combining the weighting coefficient to obtain the air-fuel ratio feedback correction.

[0044] Specifically, the actual outlet air temperature is continuously collected by a temperature sensor installed on the outlet duct of the coal gasification air heater. The real-time temperature deviation is obtained by subtracting the actual outlet air temperature from the target outlet air temperature. The target outlet air temperature is the desired temperature of the heater outlet hot air set by the operator or the upper-level system according to the requirements of the downstream process.

[0045] A preset allowable deviation dead zone threshold is established, which is the permissible range for temperature deviation. When the absolute value of the deviation between the actual temperature and the target temperature falls within this range, the temperature is considered to meet the process requirements, and feedback correction is not initiated to prevent frequent actuator operation. If the absolute value of the temperature deviation is less than or equal to the allowable deviation dead zone threshold, it indicates that the current outlet air temperature is already within the process tolerance range, and no feedback correction is required. The air-fuel ratio feedback correction is directly set to 0, skipping all subsequent feedback calculation steps.

[0046] If the absolute value of the temperature deviation exceeds the allowable dead zone threshold, the feedback correction calculation process is initiated. The current temperature deviation value is input to the proportional-integral control algorithm module, which calculates the proportional term output (proportional coefficient × current deviation) and the integral term output (integral coefficient × cumulative deviation sum) according to the preset proportional and integral coefficients. The two are then added together to obtain the initial feedback correction amount.

[0047] For example, if the target outlet air temperature of the coal gasification air heater is 650℃, and the thermocouple installed in the outlet duct measures the current actual outlet air temperature as 638℃, the temperature deviation is -12℃. A negative value indicates under-temperature, requiring additional fuel or reduced air. The preset allowable deviation dead zone threshold is ±3℃. Therefore, if the absolute value of the temperature deviation exceeds the allowable deviation dead zone threshold, exceeding the dead zone, feedback correction calculation is initiated. The proportional coefficient Kp = 0.015, the integral coefficient Ki = 0.002, the sampling period is 1s, and the current integral cumulative term Σ(deviation × sampling period) = -150℃·s. This value is the historical cumulative value; a continuously negative value indicates a sustained period of under-temperature. The proportional term output = 0.015 × (-12.0) = -0.18; the integral term output = 0.002 × (-150.0) = -0.3. Therefore, the initial feedback correction amount is -0.48, a negative value indicating the need to reduce the air-fuel ratio, i.e., reduce air or increase fuel to raise the temperature.

[0048] The weighting coefficient is dynamically calculated based on the calorific value fluctuation amplitude using a nonlinear mapping function. The design principle of the nonlinear mapping function is as follows: when the calorific value fluctuation amplitude is small, the weighting coefficient is close to 1, and the feedback correction is fully preserved to eliminate steady-state temperature deviations; as the fluctuation amplitude increases, the weighting coefficient gradually decreases according to a nonlinear curve, such as exponential decay; when the fluctuation amplitude exceeds a preset threshold for severe fluctuations, the weighting coefficient is directly set to 0, completely disabling the feedback correction. The more severe the calorific value fluctuation amplitude, the more severe the hysteresis of the temperature feedback signal. In this case, excessive reliance on hysteretic feedback correction not only fails to improve the control effect but may also trigger reverse oscillations. Therefore, it is necessary to weaken or even cut off the feedback channel, making feedforward control the sole driver.

[0049] Based on the fluctuation range of calorific value, a maximum allowable adjustment step size is determined to limit the maximum output amplitude of a single feedback correction, preventing excessive feedback correction from causing severe combustion fluctuations. When the calorific value fluctuation range is small, the maximum allowable adjustment step size is set to a small value, such as 0.05, to avoid unnecessary disturbances under stable operating conditions. When the calorific value fluctuation range increases, the maximum allowable adjustment step size is moderately increased, such as increasing to a maximum of 0.3, allowing the feedback correction to have a sufficient range to cope with large temperature deviations. The maximum allowable adjustment step size is also constrained by the combustion stability margin. If the combustion stability margin is lower than a preset safety threshold, the maximum allowable adjustment step size will be further compressed. The preset safety threshold is used to reduce the maximum allowable adjustment step size, such as 1.5mA. If the flame detector signal noise is large, the preset safety threshold is appropriately increased, such as 2mA, to reduce the step size in advance to prevent disturbances; if the flame signal is stable and reliable, the preset safety threshold is appropriately decreased, such as 1mA, to allow a larger adjustment range.

[0050] The initial feedback correction is multiplied by a weighting coefficient to obtain a weighted correction. The absolute value of the weighted correction is compared with the maximum permissible adjustment step size, and amplitude limiting is applied. If the absolute value of the weighted correction is less than or equal to the maximum permissible adjustment step size, this value is retained as the final output. If the absolute value of the weighted correction is greater than the maximum permissible adjustment step size, it is truncated to the boundary value of the maximum permissible adjustment step size, i.e., the output value is the maximum permissible adjustment step size multiplied by the sign of the original value. The air-fuel ratio feedback correction is the final feedback correction output after both weighting coefficient scaling and amplitude limiting. It is a dimensionless value used for algebraic superposition with the feedforward basic air-fuel ratio setpoint.

[0051] By setting a dead zone, frequent reciprocating movements of the actuator are avoided when the temperature fluctuates slightly, extending the life of valves and other actuators. The combined action of proportional and integral terms in the PI control algorithm ensures the effective elimination of steady-state temperature deviations. By nonlinearly decaying the weighting coefficient with the amplitude of calorific value fluctuations, the ability to eliminate steady-state errors through feedback correction is preserved when the calorific value is stable. When the calorific value fluctuates drastically, the intervention of the lagging feedback signal on the control is weakened or even cut off, preventing reverse oscillations caused by feedback lag and ensuring that the fast response advantage dominated by feedforward is not disturbed. The stability margin judgment further limits the amplitude of the correction when the flame is unstable, ensuring combustion safety. The integral pause mechanism avoids the risk of subsequent overshoot caused by the continuous accumulation of integral terms when the command is limited.

[0052] The basic air-fuel ratio setting value is superimposed with the air-fuel ratio feedback correction value to form a fused air-fuel ratio setting value.

[0053] Furthermore, this application also includes the following steps: when the basic air-fuel ratio setting value is superimposed with the air-fuel ratio feedback correction amount, if the calorific value fluctuation exceeds a preset severe fluctuation threshold, the air-fuel ratio feedback correction amount is set to zero, so that the fused air-fuel ratio setting value is equal to the basic air-fuel ratio setting value.

[0054] Specifically, the fluctuation range of calorific value is compared with a preset threshold for severe fluctuations. The threshold for severe fluctuations is a pre-set upper limit for the fluctuation range of calorific value, such as 30 kcal / Nm³. 3 This is used to determine whether the current calorific value fluctuation is so severe that the temperature feedback signal becomes unreliable. If the equipment requires high combustion stability, the preset threshold for severe fluctuations can be appropriately lowered, such as to 25 kcal / Nm³. 3 Preemptively cut off feedback; if higher control precision is required, the preset threshold for severe fluctuations can be appropriately increased, such as 35 kcal / Nm³. 3 This allows for a wider range of feedback interventions.

[0055] If the fluctuation range of calorific value is less than or equal to the threshold of severe fluctuation, it indicates that the fluctuation of calorific value is within a controllable range, and the temperature feedback signal still has a certain reference value. The comprehensive set value is calculated according to the formula: Integrated air-fuel ratio set value = Basic air-fuel ratio set value + Air-fuel ratio feedback correction amount.

[0056] If the calorific value fluctuation exceeds the threshold for severe fluctuations, it indicates that the calorific value is in a state of violent transient change. At this time, the outlet air temperature signal measured by the temperature sensor is significantly lagging behind the actual combustion state. Continuing to introduce feedback correction based on the lagging temperature signal will not only fail to improve the control effect, but may also cause reverse oscillation of the control command. Based on this logic, the air-fuel ratio feedback correction is forcibly set to 0. At this time, the fused air-fuel ratio setpoint is equal to the basic air-fuel ratio setpoint, and the control is completely dominated by the feedforward channel.

[0057] By superimposing the feedforward and feedback, a synergistic effect is achieved. When the calorific value fluctuation does not exceed the threshold for severe fluctuations, the feedback correction precisely corrects the feedforward setpoint, eliminating steady-state temperature deviations that are difficult to overcome by simple feedforward control and improving control accuracy. When the calorific value fluctuation exceeds the threshold for severe fluctuations, it automatically determines that the temperature feedback signal is significantly lagging behind the actual combustion state, forcibly sets the feedback correction to 0, cuts off the interference of unreliable lagging signals on control commands, and prevents reverse oscillations or control instability caused by feedback signal lag. The steady-state accuracy advantage of feedback is fully utilized when disturbances are mild, while feedback intervention is promptly withdrawn when disturbances are severe, ensuring that the dominant role of the rapid response of the feedforward is not disturbed. This ensures that the integrated air-fuel ratio setpoint maintains both accuracy and stability across a wide range of operating conditions.

[0058] Based on the transmission delay between the calorific value detection point and the burner, time compensation is applied to the adjustment action corresponding to the fusion air-fuel ratio setpoint to generate an air-fuel ratio control command.

[0059] Furthermore, this application also includes the following steps: obtaining the physical transmission time of coal gas flowing from the calorific value detection point to the burner nozzle; obtaining the response time of combustion air from the action of the air flow regulating mechanism to entering the burner to participate in combustion; calculating the difference between the physical transmission time and the response time as a time compensation offset; decomposing the fused air-fuel ratio setpoint into corresponding gas regulating valve opening commands and combustion air regulating valve opening commands, and marking the effective timestamps of the two commands according to the time compensation offset; verifying the timestamp-marked gas regulating valve opening commands and combustion air regulating valve opening commands based on the safety boundary and the adjustment limit; after passing the verification, encapsulating the adjusted gas regulating valve opening commands and combustion air regulating valve opening commands, along with the corresponding effective timestamps, to generate the air-fuel ratio control command.

[0060] Furthermore, this application also includes the following steps: if the physical transmission time is greater than the response time, then the effective timestamp of the combustion air regulating valve opening command is delayed by the time compensation offset; if the physical transmission time is less than the response time, then the effective timestamp of the combustion air regulating valve opening command is advanced by the time compensation offset.

[0061] Specifically, the physical transmission time of coal gas is calculated based on pipeline design parameters and real-time operating data. The total length of the pipeline from the calorific value detection point to the burner nozzle is read, and the real-time supply pressure of the coal gas is obtained through a pressure transmitter. Simultaneously, the current impurity deposition level is read. The effective diameter of the gas pipeline is corrected based on the supply pressure and impurity deposition level. The actual average flow velocity of the gas in the pipeline under the current conditions is estimated, and then the physical transmission time is calculated, which is the ratio of the total pipeline length to the actual average flow velocity. The physical transmission time is the actual time required for the coal gas to flow from the calorific value detection point along the pipeline to the burner nozzle. The calorific value monitoring point is the installation location of the calorific value meter.

[0062] The response time of combustion air is calculated based on the mechanical action delay of the regulating valve, the pipeline transport time of air from the regulating valve to the burner nozzle, and the flow rate settling time. The pressure and temperature of the combustion air are obtained through pressure and temperature sensors installed on the air pipeline. Air density and flow rate are corrected for, and the final response time is synthesized. The response time is the total time required from the start of the air flow regulation mechanism's action to the actual entry of the resulting flow rate change into the burner for combustion. This includes the mechanical action delay of the regulating valve, the flow rate settling time after the valve opening changes, and the pipeline transport time of air from the valve position to the burner nozzle. The density and flow rate need to be corrected for based on the current air pressure and temperature.

[0063] The difference between physical transmission time and response time is calculated as a time compensation offset, which quantifies the degree of asymmetry in response time between the gas side and the air side. If the time compensation offset is positive, it means that the gas transmission is slower than the air transmission; if the time compensation offset is negative, it means that the air transmission is slower than the gas transmission.

[0064] The air-fuel ratio setpoint is substituted into the flow characteristic curve functions of the gas regulating valve and the combustion air regulating valve to calculate the corresponding valve opening percentage commands, namely the gas valve opening command and the air valve opening command. The flow characteristic curve functions of the gas valve and the air valve are then called separately, and the same air-fuel ratio setpoint is substituted into their respective functions to calculate the percentage by which the gas valve and the air valve should open to achieve that ratio under the current operating conditions. These two opening values ​​are usually different because of differences in the density of gas and air, valve diameter, and flow characteristics.

[0065] Using the current moment as the time reference point, the default effective timestamp of the gas valve command is fixed at 0 seconds, meaning the gas valve begins operation the instant the command is issued. For the combustion air valve command, its effective timestamp is adjusted according to the time compensation offset. If the time compensation offset is positive, the effective timestamp of the air valve command is set to 0 + the time compensation offset, i.e., delayed by the time compensation offset; if the time compensation offset is negative, the effective timestamp of the air valve command is set to 0 + the time compensation offset, i.e., advanced by the time compensation offset. Since the time compensation offset is negative, it is equivalent to subtracting the time compensation offset from the current moment. In other words, the total time from the start of gas valve operation to the arrival of its flow change at the burner (i.e., the command effective time plus the gas transmission time) should equal the total time from the start of air valve operation to the arrival of its flow change at the burner (i.e., the command effective time plus the air response time). By adjusting the effective time of the air valve, this equation is made true, thus achieving synchronous arrival of flow changes on both sides.

[0066] Two commands, each marked with a timestamp, are sent to the verification module for comparison with the safety boundary and adjustment limit. If the opening value of one command exceeds the safety boundary, it is truncated to the boundary value; if the change exceeds the adjustment limit, it is compressed to the limit value. After successful verification, the gas valve opening command and its effective timestamp, and the air valve opening command and its effective timestamp are encapsulated into a complete data frame, which is output to the fieldbus as the final air-fuel ratio control command. The actuators then execute the actions at the specified timestamps.

[0067] The combustion stability margin is dynamically defined based on the flame signal intensity of the coal gasification air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected based on the combustion stability margin. The air-fuel ratio control command after correction and limitation is constrained within the safety boundary and output to control the coal gasification air heater.

[0068] Furthermore, this application also includes the following steps: obtaining the calibration extinction threshold of the coal gas air heater; obtaining a basic stability margin based on the difference between the flame signal intensity and the calibration extinction threshold; attenuating the basic stability margin by combining the impurity deposition characterization quantity to obtain the combustion stability margin; using the maximum single adjustment step size of the air-fuel ratio control command as the adjustment limit, adjusting the adjustment limit according to the combustion stability margin; based on the theoretical air-fuel ratio, a preset safety boundary is established; the air-fuel ratio control command after adjustment limit correction is compared with the safety boundary; if it exceeds the boundary, it is truncated to the boundary edge; the truncated air-fuel ratio control command is timestamped and encapsulated; and finally, the air-fuel ratio control command is output.

[0069] Specifically, the calibrated flameout threshold, a value provided by the manufacturer of the coal gasification air heater, is read from the equipment parameter table. This threshold represents the minimum signal strength at which the flame detector can confirm the presence of a flame. When the flame signal strength falls below the calibrated flameout threshold, the flame is determined to be extinguished.

[0070] The measured value of the current flame signal intensity is continuously obtained by the flame detector. The flame signal intensity is subtracted from the calibrated flameout threshold, and the difference is recorded as the basic stability margin, which reflects the absolute safety margin of the current flame from the flameout boundary.

[0071] Because tar, dust, and other deposits on the inner walls of pipelines increase flow resistance, reduce flame propagation speed, and decrease combustion stability, the actual safety margin provided by the same base margin is lower when deposition is severe. Therefore, attenuation correction is necessary. The more severe the deposition, i.e., the smaller the impurity deposition characterization level, the lower the combustion stability margin after attenuation. Therefore, the impurity deposition characterization level is used as an attenuation coefficient and multiplied by the base stability margin to obtain the combustion stability margin.

[0072] The maximum allowable single adjustment step size of the air-fuel ratio control command is used as the reference value for the adjustment limit. This reference value is dynamically adjusted based on the calculated combustion stability margin. When the combustion stability margin is sufficient (above the preset safety threshold), the adjustment limit remains at a large reference value, allowing the control command to have a wide range of changes within a single cycle to improve response speed. When the combustion stability margin is low (below the preset safety threshold), the adjustment limit is correspondingly compressed to a smaller value, limiting the single-step change of the control command and preventing large adjustments from disturbing the already fragile flame stability. When the combustion stability margin is close to 0, the adjustment limit is compressed to the minimum safe value, allowing only extremely slow fine-tuning, while triggering an alarm to remind the operator.

[0073] The adjusted air-fuel ratio control command is compared with the safety boundary. If the air-fuel ratio control command is within the safety boundary range, the original value is retained; if the air-fuel ratio control command is below the lower boundary, it is truncated to the lower boundary value; if the air-fuel ratio control command is above the upper boundary, it is truncated to the upper boundary value. After truncation, the air-fuel ratio control command is decomposed into a gas regulating valve opening command and a combustion air regulating valve opening command. Each command is bound to its corresponding effective timestamp, and finally encapsulated into a complete data frame. This frame is output via the fieldbus to the actuators of the gas regulating valve and the combustion air regulating valve, driving the valves to begin operation at the specified timestamp. The safety boundary is the allowable range of air-fuel ratio set according to the theoretical air-fuel ratio. It represents the physically safe operating limit range of the coal gasification air heater; exceeding this range may cause backfire or flameout.

[0074] When the air-fuel ratio control command is truncated by the safety boundary or limited by the adjustment limit, the accumulation calculation of the integral term in the PI controller is paused simultaneously, and the integral term is kept unchanged at the value before the limit. The integral accumulation is only resumed when the next deviation exceeds the dead zone and the command is no longer restricted, so as to prevent subsequent temperature overshoot due to integral saturation.

[0075] Furthermore, this application also includes the following steps: if the actual outlet air temperature of the coal gasification air heater is stable within the allowable deviation range of the target outlet air temperature, and the stability margin is higher than a preset threshold, a slight disturbance is applied to the air-fuel ratio control command in a step-by-step manner; the response changes of the outlet air temperature and the flame signal intensity are monitored simultaneously to determine the deviation direction of the real-time air-fuel ratio relative to the theoretical air-fuel ratio, and the air-fuel ratio control command is adjusted according to the deviation direction; when the theoretical air-fuel ratio is reached, the current air-fuel ratio control command is determined as the energy-saving operation benchmark parameter.

[0076] Specifically, the operating status of the coal gasification air heater is continuously monitored. The self-optimizing perturbation function is triggered when both of the following conditions are met simultaneously: 1. The actual outlet air temperature has stabilized within the allowable deviation range of the target outlet air temperature, such as ±3℃, meaning the absolute value of the temperature deviation is less than or equal to the dead zone threshold, and has not exceeded this range for a continuous period of time, such as 60 seconds. 2. The current combustion stability margin is higher than the preset safety threshold, such as 1.5mA, ensuring that the flame is strong enough to maintain stable combustion after applying a slight perturbation, and will not trigger flameout due to the perturbation.

[0077] When both of the above conditions are met, the micro-disturbance optimization procedure is initiated. The step size and direction of the disturbance are designed. The step size is a small value, such as a change in air-fuel ratio of 0.02. The wind direction is either positive or negative. A positive wind increases the air-fuel ratio, i.e., increases the air volume; a negative wind decreases the air-fuel ratio, i.e. decreases the air volume. The order can be determined based on the deviation direction of the current air-fuel ratio relative to the historical baseline.

[0078] Based on the current air-fuel ratio control command, a first-step micro-disturbance, such as +0.02, is applied, and the perturbed command is output to the actuator. After the disturbance is applied, an observation and waiting phase begins, with the waiting time preset to be 2 to 3 times the system response time, such as 60 to 90 seconds, while simultaneously and continuously monitoring changes in the actual outlet air temperature and flame signal intensity.

[0079] After the observation period, analyze the trends in temperature and flame signal. If the temperature rises and the flame signal does not decrease significantly after applying a positive perturbation, it indicates that the current air-fuel ratio is lower than the stoichiometric air-fuel ratio, and the adjustment should continue to be made in the positive direction. If the temperature decreases or the flame signal weakens after applying a positive perturbation, it indicates that the current air-fuel ratio is higher than the stoichiometric air-fuel ratio, and the adjustment should be made in the reverse direction.

[0080] Based on the determined deviation direction, and under the constraint of maintaining a safe stability margin, the next perturbation is gradually applied in the correct direction, with each step having the same size. Between each step, the system is allowed to stabilize before proceeding to the next step. This process is repeated until the temperature begins to decrease after applying a positive perturbation, or begins to rise after applying a negative perturbation, indicating an inflection point in the temperature response. This signifies that the air-fuel ratio has exceeded its theoretical optimum. At this point, a step back is taken, and the current air-fuel ratio control command value is calibrated as an energy-saving operating reference parameter close to the theoretical air-fuel ratio, and stored in the controller's parameter table. The energy-saving operating reference parameter is the control command value closest to the theoretical air-fuel ratio, ultimately determined after optimization through small-amplitude perturbations.

[0081] In summary, the energy-saving control method for coal gasification air heaters based on calorific value fluctuations provided in this application has the following technical effects: It acquires a calorific value data sequence within a preset time window and extracts calorific value disturbance characteristics through time-domain analysis; based on the calorific value disturbance characteristics, it applies a feedforward correction to a preset standard air-fuel ratio to generate a calorific value-compensated basic air-fuel ratio setpoint; it introduces the actual outlet air temperature of the coal gasification air heater, calculates the temperature deviation by performing a difference calculation between the actual outlet air temperature and the target outlet air temperature, and generates an air-fuel ratio feedback correction based on the temperature deviation; and it applies the calorific value-compensated basic air-fuel ratio setpoint to the target air-fuel ratio setpoint. The basic air-fuel ratio setpoint and the air-fuel ratio feedback correction are superimposed to form a fused air-fuel ratio setpoint. Time compensation is applied to the adjustment action corresponding to the fused air-fuel ratio setpoint based on the transmission delay between the calorific value detection point and the burner, generating an air-fuel ratio control command. The combustion stability margin is dynamically defined based on the flame signal intensity of the coal gas air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected based on the combustion stability margin. The corrected and limited air-fuel ratio control command is then output within a safe boundary to control the coal gas air heater. In other words, by extracting time-domain calorific value disturbance characteristics for dynamic feedforward compensation, fusing temperature deviation feedback correction, implementing time-space alignment control based on transmission delay, and adaptively correcting the adjustment limit based on flame signal intensity, precise dynamic matching of the air-fuel ratio is achieved under calorific value fluctuation conditions, improving the combustion efficiency of the coal gas air heater and ensuring operational safety.

[0082] Example 2: Based on the same inventive concept as the energy-saving control method for coal gasification air heaters based on calorific value fluctuations in Example 1, this application also provides an energy-saving control device for coal gasification air heaters based on calorific value fluctuations. Please refer to the appendix. Figure 2The energy-saving control device for a coal-to-gas air heater based on calorific value fluctuation includes: a calorific value data analysis module 11, used to acquire calorific value data sequences within a preset time window and extract calorific value disturbance characteristics through time-domain analysis; a feedforward correction module 12, used to apply a feedforward correction amount to a preset standard air-fuel ratio based on the calorific value disturbance characteristics, generating a calorific value-compensated basic air-fuel ratio setpoint; a temperature deviation calculation module 13, used to introduce the actual outlet air temperature of the coal-to-gas air heater, calculate the temperature deviation by performing a difference calculation between the actual outlet air temperature and the target outlet air temperature, and generate an air-fuel ratio feedback correction amount based on the temperature deviation; and an air-fuel ratio superposition module 14, used for... The basic air-fuel ratio setpoint is superimposed with the air-fuel ratio feedback correction value to form a fused air-fuel ratio setpoint; the time compensation module 15 is used to apply time compensation to the adjustment action corresponding to the fused air-fuel ratio setpoint based on the transmission delay between the calorific value detection point and the burner, and generate an air-fuel ratio control command; the adaptive correction control command module 16 is used to dynamically define the combustion stability margin based on the flame signal intensity of the coal gas air heater, and adaptively correct the adjustment limit of the air-fuel ratio control command based on the combustion stability margin, and output the corrected air-fuel ratio control command within the safety boundary to control the coal gas air heater.

[0083] Furthermore, the calorific value data analysis module 11 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used for: acquiring a calorific value data sequence within a preset time window, extracting calorific value disturbance features through time-domain analysis, wherein the calorific value disturbance features include at least instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate; calculating the absolute value of the difference between all adjacent sampled data points in the calorific value data sequence, and taking the maximum value of the absolute value as the calorific value fluctuation amplitude; calculating the difference between the last data point and the first data point in the calorific value data sequence divided by the time length of the preset time window as the calorific value change rate; and taking the arithmetic mean of the calorific value data sequence as the instantaneous calorific value.

[0084] Furthermore, the feedforward correction module 12 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used for: acquiring the ambient temperature, ambient pressure, and real-time oxygen content of the combustion air in the environment where the coal gasification air heater is located, as well as the residual oxygen concentration of the flue gas from the combustion products; correcting the preset standard air-fuel ratio based on the environmental benchmark to obtain an air-fuel ratio benchmark value adapted to the current air conditions; correcting the air-fuel ratio benchmark value based on the deviation between the instantaneous calorific value and the preset standard calorific value in the calorific value disturbance characteristics to obtain a calorific value matching base value; determining the correction amplitude based on the calorific value fluctuation amplitude and the correction speed based on the calorific value change rate to generate the feedforward correction amount; performing a safety calibration on the feedforward correction amount using the real-time gas supply pressure and impurity deposition characterization of the coal gas; and superimposing the safety-calibrated result onto the calorific value matching base value to obtain the calorific value-compensated base air-fuel ratio setting value.

[0085] Furthermore, the temperature deviation calculation module 13 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used for: preset an allowable deviation dead zone threshold; when the absolute value of the temperature deviation is less than or equal to the allowable deviation dead zone threshold, the air-fuel ratio feedback correction is zero; when the absolute value of the temperature deviation is greater than the allowable deviation dead zone threshold, an initial feedback correction is generated based on a proportional-integral control algorithm; dynamically setting the weight coefficient of the initial feedback correction according to the calorific value fluctuation amplitude, wherein the weight coefficient decreases non-linearly as the calorific value fluctuation amplitude increases; determining the maximum allowable adjustment step size based on the calorific value fluctuation amplitude, and limiting the amplitude of the initial feedback correction in combination with the weight coefficient to obtain the air-fuel ratio feedback correction.

[0086] Furthermore, the air-fuel ratio superposition module 14 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used to: when the basic air-fuel ratio setting value is superimposed with the air-fuel ratio feedback correction amount, if the calorific value fluctuation amplitude exceeds the preset severe fluctuation threshold, then the air-fuel ratio feedback correction amount is set to zero, so that the fused air-fuel ratio setting value is equal to the basic air-fuel ratio setting value.

[0087] Furthermore, the time compensation module 15 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used for: acquiring the physical transmission time of coal gas flowing from the calorific value detection point to the burner nozzle; acquiring the response time of combustion air from the action of the air flow regulating mechanism to entering the burner to participate in combustion; calculating the difference between the physical transmission time and the response time as a time compensation offset; decomposing the fused air-fuel ratio setpoint into corresponding gas regulating valve opening commands and combustion air regulating valve opening commands, and marking the effective timestamps of the two commands according to the time compensation offset; verifying the gas regulating valve opening commands and combustion air regulating valve opening commands after the timestamps are marked based on the safety boundary and the adjustment limit; after the verification is passed, encapsulating the adjusted gas regulating valve opening commands and combustion air regulating valve opening commands, along with the corresponding effective timestamps, to generate the air-fuel ratio control command.

[0088] Furthermore, the time compensation module 15 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used to: if the physical transmission time is greater than the response time, then delay the effective timestamp of the combustion air regulating valve opening command by the time compensation offset; if the physical transmission time is less than the response time, then advance the effective timestamp of the combustion air regulating valve opening command by the time compensation offset.

[0089] Furthermore, the adaptive correction control command module 16 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used to: obtain the calibration extinction threshold of the coal gasification air heater; obtain a basic stability margin based on the difference between the flame signal intensity and the calibration extinction threshold; perform attenuation correction on the basic stability margin in combination with the impurity deposition characterization quantity to obtain the combustion stability margin; use the maximum single adjustment step size of the air-fuel ratio control command as the adjustment limit, and adjust the adjustment limit according to the combustion stability margin; based on the theoretical air-fuel ratio, preset a safety boundary, compare the air-fuel ratio control command after adjustment limit correction with the safety boundary, and if it exceeds the boundary, truncate it to the boundary edge; perform timestamp marking and encapsulation processing on the truncated air-fuel ratio control command, and finally output the air-fuel ratio control command.

[0090] Furthermore, the adaptive correction control command module 16 in the energy-saving control device for coal gasification air heater based on calorific value fluctuation is also used to: if the actual outlet air temperature of the coal gasification air heater is stable within the allowable deviation range of the target outlet air temperature, and the stability margin is higher than a preset threshold, apply a slight disturbance to the air-fuel ratio control command in a stepwise manner; simultaneously monitor the response changes of outlet air temperature and flame signal intensity, determine the deviation direction of the real-time air-fuel ratio relative to the theoretical air-fuel ratio, and adjust the air-fuel ratio control command according to the deviation direction; when the theoretical air-fuel ratio is reached, determine the current air-fuel ratio control command as the energy-saving operation benchmark parameter.

[0091] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The energy-saving control method and specific examples of the coal gasification air heater based on calorific value fluctuation in the foregoing embodiment 1 are also applicable to the energy-saving control device of the coal gasification air heater based on calorific value fluctuation in this embodiment. Through the foregoing detailed description of the energy-saving control method of the coal gasification air heater based on calorific value fluctuation, those skilled in the art can clearly understand the energy-saving control device of the coal gasification air heater based on calorific value fluctuation in this embodiment. Therefore, for the sake of brevity, it will not be described in detail here.

[0092] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0093] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of this application and its equivalents, this application also intends to include such modifications and variations.

Claims

1. An energy-saving control method for coal gasification air heaters based on calorific value fluctuations, characterized in that, include: Obtain the calorific value data sequence within a preset time window, and extract the calorific value perturbation characteristics through time-domain analysis; Based on the calorific value perturbation characteristics, a feedforward correction is applied to the preset standard air-fuel ratio to generate a calorific value compensated basic air-fuel ratio setting value. The actual outlet air temperature of the coal gasification air heater is introduced, and the temperature deviation is obtained by calculating the difference between the actual outlet air temperature and the target outlet air temperature. An air-fuel ratio feedback correction amount is generated based on the temperature deviation. The basic air-fuel ratio setpoint is superimposed with the air-fuel ratio feedback correction value to form a fused air-fuel ratio setpoint; Based on the transmission delay between the calorific value detection point and the burner, time compensation is applied to the adjustment action corresponding to the fusion air-fuel ratio set value to generate an air-fuel ratio control command. The combustion stability margin is dynamically defined based on the flame signal intensity of the coal gasification air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected based on the combustion stability margin. The air-fuel ratio control command after correction and limitation is constrained within the safety boundary and output to control the coal gasification air heater.

2. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 1, characterized in that, Obtain the calorific value data sequence within a preset time window, and extract calorific value perturbation features through time-domain analysis. These perturbation features include at least instantaneous calorific value, calorific value fluctuation amplitude, and calorific value change rate. Calculate the absolute value of the difference between all adjacent sampled data points in the calorific value data sequence, and take the maximum value of the absolute value as the calorific value fluctuation range; The difference between the last data point and the first data point in the calorific value data sequence is calculated and divided by the length of the preset time window to obtain the calorific value change rate. The arithmetic mean of the calorific value data sequence is used as the instantaneous calorific value.

3. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 2, characterized in that, Based on the aforementioned calorific value perturbation characteristics, a feedforward correction is applied to a preset standard air-fuel ratio to generate a calorific value-compensated baseline air-fuel ratio setpoint, including: The ambient temperature, ambient pressure, and real-time oxygen content of the combustion air in the environment where the coal gasification air heater is located, as well as the residual oxygen concentration of the flue gas from the combustion products, are obtained. The preset standard air-fuel ratio is then corrected based on the environmental benchmark to obtain an air-fuel ratio benchmark value that is adapted to the current air conditions. Based on the deviation between the instantaneous calorific value and the preset standard calorific value in the calorific value disturbance characteristics, the air-fuel ratio reference value is corrected for calorific value deviation to obtain the calorific value matching base value. The correction amplitude is determined based on the calorific value fluctuation range, and the correction speed is determined based on the calorific value change rate, thereby generating the feedforward correction amount; The feedforward correction is safely calibrated by using the real-time gas supply pressure and impurity deposition characterization of coal gasification. The calibrated result is then superimposed on the calorific value matching baseline value to obtain the calorific value compensated baseline air-fuel ratio setting value.

4. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 2, characterized in that, Introducing the actual outlet air temperature of the coal gasification air heater, comparing the actual outlet air temperature with the target outlet air temperature to obtain the temperature deviation, and generating an air-fuel ratio feedback correction amount based on the temperature deviation, including: A preset allowable deviation dead zone threshold is set. When the absolute value of the temperature deviation is less than or equal to the allowable deviation dead zone threshold, the air-fuel ratio feedback correction amount is zero. When the absolute value of the temperature deviation is greater than the allowable deviation dead zone threshold, an initial feedback correction amount is generated based on the proportional-integral control algorithm. Based on the calorific value fluctuation range, the weighting coefficient of the initial feedback correction amount is dynamically set, wherein the weighting coefficient decreases nonlinearly as the calorific value fluctuation range increases; The maximum allowable adjustment step size is determined based on the calorific value fluctuation range, and the initial feedback correction amount is limited by the weighting coefficient to obtain the air-fuel ratio feedback correction amount.

5. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 4, characterized in that, When the basic air-fuel ratio setting value is superimposed with the air-fuel ratio feedback correction value, if the calorific value fluctuation exceeds the preset severe fluctuation threshold, the air-fuel ratio feedback correction value is set to zero, so that the fused air-fuel ratio setting value is equal to the basic air-fuel ratio setting value.

6. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 1, characterized in that, Based on the transmission delay between the calorific value detection point and the burner, time compensation is applied to the adjustment action corresponding to the fusion air-fuel ratio setpoint to generate an air-fuel ratio control command, including: The physical transport time of coal gas from the calorific value detection point to the burner nozzle is obtained; The response time from the activation of the air flow regulation mechanism to the entry of combustion air into the burner for combustion; Calculate the difference between the physical transmission time and the response time, and use it as the time compensation offset; The fused air-fuel ratio setting value is decomposed into corresponding gas regulating valve opening commands and combustion air regulating valve opening commands, and the effective timestamps of the two commands are marked according to the time compensation offset. Based on the safety boundary and the adjustment limit, the gas regulating valve opening command and the combustion air regulating valve opening command after the timestamp are verified. After the verification is passed, the adjusted gas regulating valve opening command and the combustion air regulating valve opening command, along with the corresponding effective timestamp, are encapsulated together to generate the air-fuel ratio control command.

7. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 6, characterized in that, If the physical transmission time is greater than the response time, the effective timestamp of the combustion air regulating valve opening command will be delayed by the time compensation offset. If the physical transmission time is less than the response time, then the effective timestamp of the combustion air regulating valve opening command is advanced by the time compensation offset.

8. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 3, characterized in that, The combustion stability margin is dynamically defined based on the flame signal intensity of the coal gasification air heater, and the adjustment limit of the air-fuel ratio control command is adaptively corrected according to the stability margin. The corrected air-fuel ratio control command is then output within a safe boundary. The method further includes: The calibration extinction threshold of the coal gasification air heater is obtained, and the basic stability margin is obtained based on the difference between the flame signal intensity and the calibration extinction threshold. The combustion stability margin is obtained by attenuating the base stability margin based on the impurity deposition characterization. The maximum single adjustment step size of the air-fuel ratio control command is used as the adjustment limit, and the adjustment limit is adjusted according to the combustion stability margin. Based on the theoretical air-fuel ratio and a preset safety boundary, the air-fuel ratio control command after adjustment and limiting correction is compared with the safety boundary. If it exceeds the boundary, it is truncated to the edge of the boundary. The truncated air-fuel ratio control command is timestamped and encapsulated, and finally the air-fuel ratio control command is output.

9. The energy-saving control method for coal gasification air heaters based on calorific value fluctuations according to claim 8, characterized in that, If the actual outlet air temperature of the coal gasification air heater is stable within the allowable deviation range of the target outlet air temperature, and the stability margin is higher than the preset threshold, a slight disturbance is applied to the air-fuel ratio control command in a step-by-step manner. The system synchronously monitors the changes in the outlet air temperature and flame signal intensity to determine the direction of deviation of the real-time air-fuel ratio from the theoretical air-fuel ratio, and adjusts the air-fuel ratio control command according to the direction of deviation. When the theoretical air-fuel ratio is reached, the current air-fuel ratio control command is determined as the energy-saving operation benchmark parameter.

10. An energy-saving control device for a coal-to-gas air heater based on calorific value fluctuation, characterized in that, The step of implementing the energy-saving control method for a coal gasification air heater based on calorific value fluctuation according to any one of claims 1 to 9, wherein the energy-saving control device for the coal gasification air heater based on calorific value fluctuation comprises: The calorific value data analysis module is used to acquire the calorific value data sequence within a preset time window and extract calorific value perturbation features through time domain analysis; The feedforward correction module is used to apply a feedforward correction amount to the preset standard air-fuel ratio based on the calorific value disturbance characteristics, and generate a calorific value compensated basic air-fuel ratio set value. The temperature deviation calculation module is used to take the actual air outlet temperature of the coal gasification air heater, calculate the difference between the actual air outlet temperature and the target air outlet temperature to obtain the temperature deviation, and generate the air-fuel ratio feedback correction amount based on the temperature deviation. The air-fuel ratio superposition module is used to superimpose the basic air-fuel ratio setting value and the air-fuel ratio feedback correction amount to form a fused air-fuel ratio setting value; The time compensation module is used to apply time compensation to the adjustment action corresponding to the fusion air-fuel ratio set value based on the transmission delay between the calorific value detection point and the burner, and generate air-fuel ratio control command. The adaptive correction control command module is used to dynamically define the combustion stability margin based on the flame signal intensity of the coal gasification air heater, and adaptively correct the adjustment limit of the air-fuel ratio control command based on the combustion stability margin, so as to constrain the air-fuel ratio control command after correction and limit within the safety boundary and output it to control the coal gasification air heater.

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