A method for optimizing the energy efficiency of a gas-steam boiler heating supply

Abstract

The application discloses a kind of gas steam boiler heating energy efficiency optimization control method, it is related to boiler control technical field.The application generates the response speed deviation of gas regulating valve and air supply regulating valve, associated flow gain and response speed to obtain nonlinear deviation, compensates the transient air-fuel ratio deviation caused by valve response inconsistency and stroke nonlinearity;Utilize carbon monoxide concentration, gas calorific value, exhaust gas temperature and boiler air inlet temperature to estimate energy efficiency loss value and dynamically generate air-fuel ratio target with the goal of reducing loss, then combine the change amount of furnace combustion intensity to correct the lag oxygen content signal to obtain virtual oxygen content, eliminate the influence of measurement lag;Finally, based on multivariable coordination, determine the optimization parameter and close-loop correction, so that under the load step disturbance, gas and air can quickly and synchronously match the theoretical best air-fuel ratio, inhibit the incomplete combustion loss and exhaust gas heat loss at the same time increase, solve the problem that traditional feedback cannot correct dynamic deviation in real time.

Description

Technical Field

[0001] This invention relates to the field of boiler control technology, specifically to a method for optimizing the heating efficiency control of a gas-fired steam boiler. Background Technology

[0002] In practical scenarios of heating efficiency control for gas-fired steam boilers, when the heating load command changes abruptly, the combustion state in the furnace exhibits transient and nonlinear dynamic imbalance characteristics. Existing technologies reveal the following shortcomings:

[0003] Firstly, existing technologies fail to couple and quantify the difference in response speed between the gas regulating valve and the air supply regulating valve with the inherent nonlinear characteristics of the valve stroke. This makes it impossible to match the actual deviation of the air-fuel ratio during transient processes, resulting in a lack of objective quantitative basis for the time synchronization and flow matching of gas and air entering the furnace, leading to a severe deficiency in the accuracy of air-fuel ratio control. Secondly, existing solutions lack a real-time air-fuel ratio correction mechanism adapted to the dynamic response characteristics and nonlinear deviations of the valves, making it impossible to achieve coordinated compensation control of the gas regulating valve and the air supply regulating valve based on transient speed deviations and nonlinear distortions. Simultaneously, traditional flue gas oxygen content feedback, due to the distance of the measurement point from the furnace and the lag in flue gas transmission, cannot reflect the instantaneous changes in combustion intensity within the furnace in real time. This means that correction cannot be made immediately when dynamic deviations occur, leading to a simultaneous increase in incomplete combustion losses and flue gas heat losses. Furthermore, over-adjustment or under-adjustment caused by the lag signal results in oscillations and slow convergence during the energy efficiency optimization process.

[0004] Therefore, there is an urgent need for a boiler heating energy efficiency optimization control method that can quantify valve response speed deviation and stroke nonlinearity deviation, dynamically generate air-fuel ratio optimization targets, and use virtual oxygen content to eliminate the effect of measurement lag, in order to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for optimizing the heating efficiency control of a gas-fired steam boiler. This method solves the problem that when the heating load command changes abruptly, the response speed and stroke nonlinear characteristics of the gas regulating valve and the air supply regulating valve are inconsistent, causing the air-fuel ratio to deviate from the theoretical optimal value during the transient process. This results in a simultaneous increase in incomplete combustion losses and flue gas heat losses. Furthermore, traditional flue gas oxygen content feedback cannot correct this dynamic deviation in real time due to measurement lag.

[0006] To achieve the above objectives, the present invention provides a method for optimizing the heating efficiency control of a gas-fired steam boiler, comprising the following steps:

[0007] The response speed of the gas regulating valve and the air supply regulating valve is determined based on the position feedback signals of the gas regulating valve and the air supply regulating valve, and the response speed deviation is generated.

[0008] Based on the opening degree of the gas regulating valve and the air supply regulating valve, the gas flow gain and air flow gain are obtained by combining the gas flow and air flow, and then nonlinear deviation is generated by relating them to the response speed of the gas regulating valve and the air supply regulating valve.

[0009] Based on the carbon monoxide concentration and total calorific value of the fuel gas in the flue, combined with the flue gas temperature and boiler inlet air temperature, the energy efficiency loss value is estimated, and the air-fuel ratio target is generated with the goal of reducing the energy efficiency loss value.

[0010] The change in combustion intensity within the boiler furnace is determined, and the measured oxygen content in the flue gas is corrected to obtain the virtual oxygen content.

[0011] Based on multivariate coordination of response speed deviation, nonlinear deviation, air-fuel ratio target, and virtual oxygen content, the optimal parameters of the gas regulating valve and the air supply regulating valve are determined.

[0012] After taking action based on the optimized parameters, the incomplete combustion loss value and the instantaneous value of flue gas sensible heat loss are re-estimated and it is determined whether the decreasing trend is met. If not, the optimized parameters are corrected.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention compensates for transient air-fuel ratio deviations caused by inconsistent valve responses and stroke nonlinearity by generating a nonlinear deviation between the response speed of the gas regulating valve and the air supply regulating valve, and correlated with the flow gain and response speed. Simultaneously, it uses real-time estimation of energy efficiency loss values ​​based on carbon monoxide concentration, gas calorific value, flue gas temperature, and boiler inlet air temperature to dynamically generate an air-fuel ratio target with the goal of reducing losses. Then, it combines the change in furnace combustion intensity to correct the lag in oxygen content signal, obtaining a virtual oxygen content and eliminating the influence of measurement lag. Finally, based on multivariate coordination, it determines optimized parameters and performs closed-loop correction, enabling gas and air to quickly and synchronously match the theoretically optimal air-fuel ratio under load step disturbances. This suppresses both incomplete combustion losses and flue gas heat losses, solving the problem that traditional feedback cannot correct dynamic deviations in real time. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the module connections for the gas-fired steam boiler heating energy efficiency optimization control method of the present invention.

[0016] Figure 2 This is a flowchart illustrating the generation of response speed deviation in the gas-fired steam boiler heating energy efficiency optimization control method of the present invention.

[0017] Figure 3 This is a flowchart illustrating the generation of nonlinear deviations in the gas-fired steam boiler heating efficiency optimization control method of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Please refer to the accompanying drawings. Figure 1 This invention provides a technical solution: a method for optimizing the heating efficiency control of a gas-fired steam boiler, comprising the following steps:

[0019] S1. Determine the response speed of the gas regulating valve and the air supply regulating valve based on the position feedback signals of the gas regulating valve and the air supply regulating valve, and generate the response speed deviation.

[0020] Considering that when the heating load command undergoes a step change, the gas regulating valve and the air supply regulating valve often have inconsistent starting times and rates of position change during operation due to mechanical inertia and differences in actuators. If both valves are driven simultaneously according to the same command, the actual gas and air entering the furnace will be out of sync, causing the instantaneous air-fuel ratio to deviate from the theoretical optimal value. Therefore, it is necessary to quantify the degree of speed inconsistency between the two valves during the dynamic response process to provide a quantitative basis for compensation. Specifically, such as... Figure 2 As shown, the process of generating response speed deviation is as follows:

[0021] S101. When a step change in the heating load command is detected, continuous recording of the position feedback signals of the gas regulating valve and the air supply regulating valve is started simultaneously. The time when the position feedback signals of the gas regulating valve and the air supply regulating valve begin to change is taken as the response start time of the gas regulating valve and the air supply regulating valve, respectively.

[0022] S102. Starting from the initial moment of the response, perform differential calculations on the changes in the position feedback signals of the gas regulating valve and the air supply regulating valve over time to obtain the position change rates of the gas regulating valve and the air supply regulating valve, which are used as the response speeds of the gas regulating valve and the air supply regulating valve.

[0023] S103. The response speed deviation is obtained by subtracting the response speed of the gas regulating valve from the response speed of the air supply regulating valve hourly. Hourly subtraction means subtracting the response speed of the air supply regulating valve from the response speed of the gas regulating valve at the same time index (i.e., the same sampling time).

[0024] The position feedback signal of the gas regulating valve is the real-time feedback value of the current opening degree of the gas regulating valve, with a value range of 0 to 1 (0 represents fully closed, 1 represents fully open). It is continuously collected by the position sensor built into the valve and has a dimensionless value of 1. The position feedback signal of the air supply regulating valve is the real-time feedback value of the current opening degree of the air supply regulating valve, and is obtained in the same way as the gas regulating valve.

[0025] Differential calculation involves taking the derivative of the position feedback signal with time to obtain the rate of position change, which is achieved by dividing the difference between adjacent sampled values ​​by the sampling period.

[0026] A positive response speed deviation indicates that the gas regulating valve operates faster than the air supply regulating valve, while a negative value indicates that the air supply regulating valve operates faster than the gas regulating valve. The larger the absolute value, the more severe the speed inconsistency.

[0027] This embodiment synchronously records the position feedback of the two valves when the heating load command changes stepwise, determines the start time of their respective responses, calculates the rate of position change by differentiation, and then subtracts them hour by hour. This directly and in real time quantifies the degree of speed inconsistency between the gas regulating valve and the air supply regulating valve in the dynamic process. It can capture the trend and magnitude of the air-fuel ratio deviation as soon as the valve action deviation occurs, avoiding the continuous expansion of dynamic deviation caused by the inability to know the valve speed difference in real time.

[0028] S2. Based on the opening degree of the gas regulating valve and the air supply regulating valve, the gas flow rate gain and the air flow rate gain are obtained by combining the gas flow rate and the air flow rate, and nonlinear deviation is generated by relating them to the response speed of the gas regulating valve and the air supply regulating valve.

[0029] It should be noted that the relationship between flow rate and opening degree of gas regulating valves and air regulating valves is not ideally linear, and this nonlinearity varies with different factors at different opening positions. Dynamic measurement during valve movement is affected by speed changes and inertia, making it difficult to obtain accurate static characteristics. Therefore, it is necessary to determine the flow gain within each action step cycle, during the brief moment when the valve completes its action and stabilizes. This flow gain reflects the actual flow change caused by a unit opening degree change within a local opening range. Specifically, the process for obtaining the gas flow gain and air flow gain is as follows:

[0030] S201. In each action step cycle of the gas regulating valve and the air supply regulating valve, after the valve completes its action and stabilizes, the opening degree of the gas regulating valve and the air supply regulating valve at the current stopping position is collected, and the gas flow rate through the gas regulating valve and the air flow rate through the air supply regulating valve corresponding to the opening degree are collected.

[0031] S202. Subtract the opening degree of the gas regulating valve and the air supply regulating valve, the gas flow rate and the air flow rate at the previous data collection time, respectively, to obtain the changes in the opening degree of the gas regulating valve, the opening degree of the air supply regulating valve, the gas flow rate and the air flow rate.

[0032] S203. If the change in the gas regulating valve opening is not zero, the gas flow rate change is divided by the change in the gas regulating valve opening to obtain the gas flow rate gain; if the change in opening is zero (the valve is not activated), the gas flow rate gain remains the previously calculated value or is set to the default value of 1. Similarly, the air flow rate change is divided by the change in the air supply regulating valve opening to obtain the air flow rate gain.

[0033] The action step cycle is the complete cycle of the valve adjusting from one stable position to the next stable position and then pausing again, including the movement time and the rest time, and is determined by the execution rhythm of the control system. For gas regulating valves, a positive value indicates a larger opening, and a negative value indicates a smaller closing. The same applies to air supply regulating valves.

[0034] In this embodiment, within each action step cycle, the valve opening and flow data at the stable dwell time are used to directly output the gas flow gain and air flow gain through differential calculation. This reflects the actual flow response sensitivity of the valve at different opening positions (i.e., the flow change caused by a unit change in opening). Since the gain is measured based on the actual dwell time of the valve, interference from the dynamic motion process is eliminated, allowing the system to accurately know the local flow characteristics of the gas and air sides near the current opening. Thus, when the valve stroke nonlinearity causes the flow change to be disproportionate to the opening change, the gain will be correspondingly larger or smaller, providing a direct quantitative input for generating nonlinear deviations.

[0035] Because the gas flow gain and air flow gain are measured on different time axes, and the response speeds of the gas regulating valve and the air supply regulating valve differ, the two gain data cannot be directly compared in time. Therefore, it is necessary to realign the gas flow gain according to the time axis of the air supply regulating valve's response speed, so that the relationship between the actual flow sensitivity on the gas side and the operating speed of the air supply regulating valve can be compared under the same time index. In summary, as described above... Figure 3 As shown, the process of generating nonlinear deviation is as follows:

[0036] S204. Align the gas flow gain point by point according to the time axis of the air supply regulating valve response speed, and calculate the deviation of the gas flow gain relative to the air supply regulating valve response speed at the same time index.

[0037] S205. Align the air flow gain point by point according to the time axis of the gas regulating valve response speed, and calculate the deviation of the air flow gain relative to the gas regulating valve response speed at the same time index.

[0038] S206. The deviation amplitude of the gas side and the deviation amplitude of the air side are taken as two components of the nonlinear deviation.

[0039] The calculation process for the deviation of the gas supply air regulating valve is as follows: For the gas flow gain values ​​at three consecutive sampling times, first calculate the change in the current gain relative to the previous gain, then divide it by the absolute value of the previous gain to obtain the relative rate of change of the gas flow gain. Similarly, for the response speed of the air supply regulating valve, calculate the change in the current speed relative to the previous speed, divide it by the absolute value of the previous speed to obtain the relative rate of change of the air supply regulating valve response speed. Then, the absolute value of the difference between the two relative rates of change is taken as the deviation of the gas supply air regulating valve.

[0040] Similarly, when calculating the deviation of the air-gas regulating valve, the intensity of the change in airflow gain is changed to the relative rate of change of airflow gain, and the intensity of the change in gas regulating valve response speed is changed to the relative rate of change of gas regulating valve response speed, and the same rules are applied.

[0041] It should be noted that if the air supply regulating valve operates quickly at a certain moment, but the direction of change in the gas gain is opposite or the intensity is mismatched, it indicates an abnormal flow response caused by stroke nonlinearity on the gas side. Similarly, aligning the air flow gain with the time axis of the gas regulating valve's response speed reflects the nonlinear anomaly on the air side. Finally, by vector combining the two deviation magnitudes, a comprehensive nonlinear deviation that can simultaneously characterize the nonlinear coupling effects on both sides can be obtained.

[0042] This embodiment directly and in real-time separates the abnormal flow response caused by valve stroke nonlinearity on the gas and air sides, while eliminating time axis interference caused by the different response speeds of the two valves. Thus, during transient processes of load step changes, a comprehensive nonlinear deviation value can be obtained instantly, allowing the system to identify problems within the same control cycle where the nonlinear deviation occurs. This prevents the continuous increase in incomplete combustion losses and flue gas heat losses due to feedback lag.

[0043] S3. Based on the carbon monoxide concentration and total calorific value of the fuel gas in the flue, combined with the flue gas temperature and boiler inlet air temperature, estimate the energy efficiency loss value, and generate the air-fuel ratio target with the goal of reducing the energy efficiency loss value.

[0044] Considering that boiler energy efficiency loss mainly consists of two parts: firstly, the chemical energy loss caused by incomplete combustion of fuel gas (manifested as unreleased heat carried by carbon monoxide in the flue gas), and secondly, the sensible heat loss caused by the direct discharge of high-temperature flue gas. Direct measurement of energy efficiency loss requires an expensive direct calorimeter, which has a slow response time. Therefore, it is necessary to estimate it in real time using continuously measurable auxiliary parameters. Specifically, the process of estimating the energy efficiency loss value is as follows:

[0045] S301. Continuously collect the carbon monoxide concentration (volume fraction, dimensionless, based on actual flue gas volume) and flue gas volumetric flow rate (volumetric flow rate converted to standard conditions at 0℃ and 101.325kPa, unit Nm³ / s) in the flue gas duct. Simultaneously acquire the standard conditions carbon monoxide calorific value (unit kJ / Nm³, approximately 12600kJ / Nm³ under standard conditions). Multiply the carbon monoxide concentration by the standard conditions flue gas volumetric flow rate to obtain the standard conditions carbon monoxide volumetric flow rate (Nm³ / s), then multiply by the standard conditions carbon monoxide calorific value to obtain the instantaneous value of incomplete combustion loss (kW).

[0046] S302. Continuously collect the flue gas temperature (°C) and boiler inlet air temperature (°C) in the flue gas duct, convert them to Kelvin temperature, and calculate the Kelvin temperature difference between the flue gas temperature and the boiler inlet air temperature. Continuously collect the flue gas volumetric flow rate (Nm³ / s) and the average specific heat capacity of the flue gas (kJ / (Nm³·K)). Multiply the flue gas volumetric flow rate by the average specific heat capacity of the flue gas, and then multiply by the Kelvin temperature difference to obtain the instantaneous value of the flue gas sensible heat loss (kW).

[0047] S303. Add the instantaneous value of incomplete combustion loss to the instantaneous value of sensible heat loss from flue gas to obtain the energy efficiency loss value.

[0048] A higher carbon monoxide concentration indicates less complete combustion and greater chemical loss. Flue gas volumetric flow rate is the volume of flue gas flowing through the exhaust duct per unit time; a higher value indicates a larger exhaust volume. Total calorific value of fuel gas is the heat released by the complete combustion of a unit volume of fuel gas; a higher value indicates higher fuel quality, and this value is read from a fuel gas composition analyzer or online calorific value meter.

[0049] The larger the instantaneous value of incomplete combustion loss, the more severe the incomplete combustion loss.

[0050] The average specific heat capacity of flue gas is the amount of heat absorbed (or released) by 1 standard cubic meter of flue gas under standard conditions for every 1 Kelvin (1 K) increase in temperature. It can be obtained from a flue gas physical property table, and the value is generally between 1.30 and 1.35. The instantaneous value of sensible heat loss in flue gas is the amount of sensible heat lost per unit time, expressed in kW. A higher value indicates a more severe heat loss.

[0051] The energy efficiency loss value reflects the current total heat loss level of the boiler; the smaller the value, the higher the energy efficiency.

[0052] It should be noted that the air-fuel ratio is defined as the ratio of the volumetric flow rate of air under standard conditions (0℃, 101.325kPa) to the volumetric flow rate of fuel gas under standard conditions, and is dimensionless. The actual measured air and fuel flow rates are converted to standard conditions through temperature and pressure compensation before being used in the calculation. The conversion process is existing technology and will not be elaborated here.

[0053] This embodiment calculates energy efficiency using real-time data collection of carbon monoxide concentration, fuel gas calorific value, flue gas temperature, and boiler inlet air temperature, employing fixed physical conversion factors and ratio constants, without relying on offline testing or complex combustion analyzers. This allows for immediate acquisition of current energy efficiency losses within each control cycle, enabling the determination of air-fuel ratio adjustment directions and solving the problems of lagging and inability to update online traditional energy efficiency assessments.

[0054] It should be noted that while the energy efficiency loss value can reflect the overall heat loss level under the current air-fuel ratio in real time, it cannot directly indicate in which direction the air-fuel ratio should be adjusted to reduce the loss. Blindly adjusting randomly can lead to energy efficiency fluctuations or even deterioration. Therefore, a local trial-and-error method is used to determine which direction can reduce energy efficiency loss, and then use that direction as the direction for air-fuel ratio correction.

[0055] Specifically, the process of generating the air-fuel ratio target with the aim of reducing energy efficiency loss is as follows:

[0056] S304. For the current opening combination of the gas regulating valve and the air supply regulating valve, record the current actual operating value of the air-fuel ratio. Adjust the current actual operating value of the air-fuel ratio by a fixed small step in the direction of increasing the air flow. After the gas regulating valve and the air supply regulating valve stabilize, re-estimate the energy efficiency loss value to obtain the energy efficiency loss value after increasing the air flow.

[0057] S305. Adjust the current actual air-fuel ratio value by the same fixed small step size in the direction of reducing air flow. After the gas regulating valve and air supply regulating valve stabilize, re-estimate the energy efficiency loss value to obtain the energy efficiency loss value after reducing the air flow.

[0058] S306. Compare the energy efficiency loss value after increasing the air side with the energy efficiency loss value after decreasing the air side, and select the adjustment direction that makes the energy efficiency loss value smaller as the air-fuel ratio correction direction.

[0059] S307. The air-fuel ratio correction direction is superimposed with the current actual air-fuel ratio value to generate the air-fuel ratio target.

[0060] The fixed microstep is a preset, very small change in the air-fuel ratio (e.g., 0.05 or 0.1), which is dimensionless.

[0061] In this embodiment, the energy efficiency loss is determined by comparing the measured energy efficiency loss values ​​under two disturbance directions: if the energy efficiency loss is smaller after increasing the air side, the correction is made in the direction of increasing air; if the energy efficiency loss is smaller after decreasing the air side, the correction is made in the direction of decreasing air. This process does not require knowledge of the boiler combustion model or the analytical relationship between the air-fuel ratio and the loss. It only relies on the actual measured energy efficiency loss value for directional optimization, thereby automatically adjusting the air-fuel ratio target to move in the direction of reducing energy efficiency loss when the load changes or the operating condition drifts. This solves the problem that traditional methods cannot adaptively determine the optimal air-fuel ratio online.

[0062] S4. Determine the change in combustion intensity in the boiler furnace and correct the measured value of oxygen content in the flue gas to obtain the virtual oxygen content.

[0063] Traditional flue gas oxygen content measurement points are typically located in the exhaust duct, some distance from the boiler furnace, and flue gas transmission takes time. When the combustion intensity in the furnace changes (e.g., due to air-fuel ratio fluctuations caused by a load command step), the oxygen content measured in the exhaust duct lags behind the actual oxygen content change in the furnace. This measurement lag prevents the control system from promptly sensing the current true combustion state, easily leading to over-adjustment or under-adjustment. Therefore, it is necessary to utilize rapidly responsive measurement signals (flame brightness, furnace negative pressure) to estimate the real-time change in combustion intensity, and combine this with the flue gas transmission time constant and oxygen content change rate to perform feedforward correction on the measured values, obtaining a virtual oxygen content that reflects the current true state of the furnace, thereby eliminating the adverse effects of measurement lag on control.

[0064] The specific process is as follows:

[0065] S401. Continuously acquire the flame brightness signal and furnace negative pressure fluctuation signal inside the boiler furnace. Calculate the relative rate of change of the flame brightness signal: divide the difference between the current moment and the previous moment by the absolute value of the previous moment to obtain the flame brightness change rate. Calculate the relative rate of change of the furnace negative pressure fluctuation signal: divide the difference between the current moment and the previous moment by the absolute value of the previous moment (if the absolute value of the previous moment is close to zero, then take a preset small constant) to obtain the furnace negative pressure change rate. Multiply the flame brightness change rate and the furnace negative pressure change rate by preset weighting coefficients (the sum of the two is 1), and sum them to obtain the change in combustion intensity.

[0066] S402. Simultaneously measure the length of the flue from the boiler furnace to the flue gas oxygen content measurement point and the flue gas velocity in the flue. Divide the flue length by the flue gas velocity to obtain the flue gas transmission time constant.

[0067] S403. Continuously collect the measured value of oxygen content in flue gas in the flue gas duct, and calculate the rate of change of oxygen content in flue gas by differentiating the measured value of oxygen content in flue gas with respect to time.

[0068] S404. Multiply the change in combustion intensity by the flue gas transmission time constant, and then multiply by an empirical coefficient determined by on-site measurement to obtain the oxygen content correction deviation.

[0069] S405. Add the oxygen content correction deviation to the current measured value of flue gas oxygen content to obtain the virtual oxygen content.

[0070] The flame brightness signal represents the electrical signal indicating the brightness of the flame inside the furnace, typically measured in light intensity. It is continuously collected by a photoelectric sensor or flame detector installed at the furnace peephole; a higher value indicates more vigorous combustion. The furnace negative pressure fluctuation signal is the difference between the pressure inside the furnace and atmospheric pressure (usually negative pressure), measured in Pa (Pascals). It is continuously collected by a furnace pressure transmitter, and the fluctuation amplitude reflects combustion stability and airflow matching.

[0071] The rate of change in flame brightness is calculated by dividing the difference between adjacent sampled values ​​by the sampling period; a positive value indicates an increase in brightness (enhanced combustion), while a negative value indicates a decrease. The rate of change in negative pressure fluctuations is calculated using the same numerical derivative. A positive value indicates an increase in pressure (possibly due to a sudden increase in fuel), while a negative value indicates a decrease in pressure.

[0072] The change in combustion intensity comprehensively reflects the real-time direction and magnitude of the change in combustion intensity; a positive value indicates that combustion is intensifying, while a negative value indicates that it is weakening.

[0073] The flue gas velocity within the flue is the average flow velocity of the flue gas, measured in m / s. It is calculated using the flue cross-sectional area and volumetric flow rate, or measured using a flow meter. A higher value indicates a shorter transmission delay. The flue gas transmission time constant is the flue length divided by the flue gas velocity, measured in seconds (s). It represents the average time required for the flue gas to travel from the furnace to the measurement point; a higher value indicates a greater lag. The measured oxygen content in the flue gas is the actual volume percentage of oxygen measured in the exhaust pipe, measured as a percentage (%). The value is typically 1%–10% (for gas-fired boilers).

[0074] The rate of change of oxygen content in flue gas is the derivative of the measured oxygen content with respect to time, expressed as % / s. A positive value indicates an increase in oxygen content (due to excess air or reduced fuel gas), while a negative value indicates a decrease. The oxygen content correction deviation, expressed as a percentage, is used to compensate for deviations caused by measurement lag.

[0075] The virtual oxygen content is the result of adding the oxygen content correction deviation to the current flue gas oxygen content measurement value, expressed as a percentage. The value represents the estimated current oxygen content in the furnace after correcting for transmission delay.

[0076] The empirical coefficient is a preset constant with dimensions of % / s. Its physical meaning is the rate of change in flue gas oxygen content caused by a unit change in combustion intensity per unit time. The tuning method for this empirical coefficient is as follows: Under steady-state boiler operation, a step disturbance of a known opening degree is applied to the air supply regulating valve. The steady-state change in flue gas oxygen content (in %) before and after the disturbance is recorded. Simultaneously, the integral value of the change in combustion intensity over time (in dimensionless seconds), calculated from the rate of change in flame brightness and the rate of change in furnace negative pressure during the disturbance, is recorded. The steady-state change in flue gas oxygen content is divided by the product of the flue gas transmission time constant and the time integral value of the change in combustion intensity. The result is used as the empirical coefficient.

[0077] In this embodiment, the virtual oxygen content is calculated by dividing the change in combustion intensity by the rate of change in oxygen content to obtain a dynamic response coefficient. This coefficient is then multiplied by the flue gas transport time constant and the rate of change in oxygen content to calculate the oxygen content correction deviation, which is then added to the measured oxygen content. This process utilizes the rapid response characteristics of flame brightness and furnace negative pressure to predict the trend of oxygen content change during the flue gas transport delay. This allows the output virtual oxygen content to track the actual combustion state in the furnace in real time, solving the control deviation problem caused by the lag in traditional oxygen content measurement, without the need for more expensive fast-response sensors.

[0078] S5. Based on response speed deviation, nonlinear deviation, air-fuel ratio target and virtual oxygen content, multivariate coordination is performed to determine the optimal parameters of the gas regulating valve and the air supply regulating valve.

[0079] It should be noted that optimizing the parameters of the gas regulating valve and the air supply regulating valve requires simultaneously handling multiple dynamic disturbances: inconsistent response speeds leading to instantaneous air-fuel ratio deviations, valve stroke nonlinearity causing abnormal flow response, air-fuel ratio deviations from the target value, and oxygen content measurement lag. A single adjustment method cannot address these coupled problems. Therefore, it is necessary to convert the response speed deviation into a position compensation amount and directly superimpose it onto the slow valve drive signal to reduce the speed difference; multiply the two deviation amplitudes in the nonlinear deviation by the drive signals of the two valves respectively to correct the nonlinear distortion on their respective sides; then perform closed-loop feedforward adjustment based on the air-fuel ratio deviation and virtual oxygen content; finally, algebraically sum all adjustment amounts within the same control cycle to obtain comprehensive optimized parameters. In this way, the final drive signal of each valve simultaneously includes speed compensation, nonlinear correction, air-fuel ratio deviation correction, and oxygen content feedforward, achieving multi-variable collaborative control.

[0080] Therefore, the process of determining the optimal parameters for the gas regulating valve and the air supply regulating valve is as follows:

[0081] S501. Multiply the response speed deviation by the duration of the control cycle to obtain the position compensation amount of the air supply regulating valve drive signal, and add the position compensation amount to the current drive signal of the air supply regulating valve to reduce the difference between the response speed of the air supply regulating valve and the response speed of the gas regulating valve.

[0082] S502. Multiply the deviation amplitudes of the gas supply air regulating valve and the air-gas regulating valve in the nonlinear deviation by the current drive signals of the gas regulating valve and the air supply air regulating valve, respectively, to obtain the first correction amount of the gas regulating valve drive signal and the second correction amount of the air supply air regulating valve drive signal.

[0083] S503. Calculate the current ratio of gas flow rate to air flow rate in real time, and use the difference between the current ratio and the air-fuel ratio target as the air-fuel ratio deviation signal. A value greater than 0 indicates a relative excess of gas or insufficient air, while a value less than 0 indicates a relative excess of air.

[0084] S504. Based on the air-fuel ratio deviation signal and the virtual oxygen content, the drive signals of the gas regulating valve and the air supply regulating valve are adjusted again.

[0085] S505. All adjustment values ​​for the air supply regulating valve drive signal and the gas regulating valve drive signal are algebraically summed within the same control cycle to obtain the optimized parameters of the air supply regulating valve drive signal and the gas regulating valve drive signal.

[0086] The position compensation amount represents the valve position difference caused by the speed difference within a control cycle, which is superimposed on the air supply regulating valve drive signal to catch up with the gas regulating valve.

[0087] It should be noted that when the response speed deviation is positive, it means that the gas regulating valve acts faster than the air supply regulating valve. In this case, the position compensation is positive and should be added to the drive signal of the air supply regulating valve to increase the opening rate of the air supply regulating valve so that it catches up with the gas regulating valve. Conversely, if it is negative, the drive signal of the air supply regulating valve should be reduced.

[0088] This embodiment eliminates the speed difference between the two valves by converting the response speed deviation into a position compensation amount and superimposing it on the slow valve drive signal. The deviation amplitude in the nonlinear deviation is multiplied into the corresponding valve drive signal to correct the abnormal flow response caused by stroke nonlinearity. Then, the two valves are adjusted in a closed loop according to the air-fuel ratio deviation and the virtual oxygen content. Finally, all adjustment amounts are algebraically summed in the same cycle to obtain the optimized parameters. Thus, under load step disturbance, the dynamic deviation caused by valve response inconsistency, flow nonlinear distortion, air-fuel ratio static error, and oxygen content measurement lag is solved simultaneously. This enables the gas regulating valve and the air supply regulating valve to quickly, synchronously, and linearly match the theoretically optimal air-fuel ratio, directly reducing incomplete combustion loss and flue gas heat loss.

[0089] The process of readjusting the gas regulating valve drive signal and the air supply regulating valve drive signal based on the air-fuel ratio deviation signal and the virtual oxygen content is as follows:

[0090] When the air-fuel ratio deviation signal indicates excessive air on the air side, decrease the air supply regulating valve drive signal and increase the gas regulating valve drive signal. When the air-fuel ratio deviation signal indicates excessive gas on the gas side, increase the air supply regulating valve drive signal and decrease the gas regulating valve drive signal.

[0091] The virtual oxygen content is compared with the virtual oxygen content of the previous control cycle to obtain the direction of oxygen content change. When the virtual oxygen content increases, the drive signal of the air supply regulating valve is reduced, and when the virtual oxygen content decreases, the drive signal of the air supply regulating valve is increased.

[0092] It should be noted that the adjustment range is calculated as follows: the adjustment range for the air supply regulating valve drive signal is equal to the absolute value of the air-fuel ratio deviation signal multiplied by the current drive signal value of the air supply regulating valve; the adjustment range for the gas regulating valve drive signal is equal to the absolute value of the air-fuel ratio deviation signal multiplied by the current drive signal value of the gas regulating valve. For adjustments caused by virtual oxygen content, only the air supply regulating valve is affected, and the adjustment range is equal to the absolute value of the virtual oxygen content change multiplied by the current drive signal value of the air supply regulating valve.

[0093] The change in virtual oxygen content is equal to the current virtual oxygen content minus the virtual oxygen content of the previous control cycle.

[0094] This embodiment determines whether there is an excess of air or gas on the air-fuel ratio side by indicating the sign of the air-fuel ratio deviation signal. The absolute value of the deviation is multiplied by the current drive signal to determine the adjustment range, ensuring that the excess side is corrected in real time. Simultaneously, the air supply volume is increased or decreased in advance based on the direction (increasing or decreasing) of the virtual oxygen content change and its absolute rate of change, thus suppressing impending oxygen content fluctuations. In this way, under load step disturbances, the air-fuel ratio deviation is quickly eliminated, and the feedforward effect of the virtual oxygen content avoids over-adjustment or oscillation caused by measurement lag, thereby directly reducing incomplete combustion losses and exhaust heat losses.

[0095] S6. After taking action based on the optimized parameters, re-estimate the incomplete combustion loss value and the instantaneous value of flue gas sensible heat loss and determine whether the decreasing trend is met. If not, correct the optimized parameters.

[0096] Although the optimized parameters obtained after multivariate coordinated optimization should theoretically reduce energy efficiency loss, it is necessary to re-estimate the instantaneous values ​​of incomplete combustion loss and sensible heat loss in flue gas after the optimization parameters are applied, and compare them with the previous estimates. By calculating the changes in loss and summing them, the total change in energy efficiency loss is obtained. If the total is positive (i.e., loss increases), it indicates that the optimization direction is incorrect or the step size is too large, and it should be determined that the reduction trend is not met, and the optimization parameters need to be corrected (e.g., adjusted in the opposite direction or the step size is reduced). If it is negative or zero, it indicates that the optimization is effective, and the current parameters should be maintained.

[0097] Specifically, the process of determining whether a downward trend is met is as follows:

[0098] S601. Subtract the previously estimated values ​​of incomplete combustion loss and instantaneous sensible heat loss from the current incomplete combustion loss value and the current instantaneous value of flue gas heat loss, respectively, to obtain the change in incomplete combustion loss and the change in flue gas heat loss, and add them together to obtain the total change in total energy efficiency loss.

[0099] S602. When the total change in total energy efficiency loss is greater than zero, it is determined that the decreasing trend is not met; otherwise, it is determined that the trend is met.

[0100] This embodiment obtains two changes by subtracting the current value of incomplete combustion loss and the instantaneous value of sensible heat loss from the previous value, and then summing them to obtain the total change in energy efficiency loss. Based on this, it directly determines whether the energy efficiency meets the decreasing trend (a total value greater than 0 indicates non-compliance, otherwise it indicates compliance). This determination provides the only quantitative basis for whether to subsequently adjust the optimization parameters: when the total value is greater than 0, the system actively adjusts the optimization parameters (e.g., reverse adjustment or reduction of step size) to prevent the energy efficiency loss from continuing to increase; when the total value is not greater than 0, the current parameters are maintained. In this way, without relying on external models or manual intervention, the system can automatically identify and correct ineffective optimization actions, and after multiple iterations, converge to the optimal parameters that truly reduce the total energy efficiency loss, solving the energy efficiency deterioration problem that may be caused by open-loop optimization.

[0101] The process of revising the optimization parameters is as follows: First, cancel the current optimization parameters to restore the valve to the previous drive signal; second, change the air-fuel ratio target by half the step size in the opposite adjustment direction; finally, reduce the two weighting coefficients in the nonlinear deviation by 10% each to reduce the magnitude of subsequent adjustments. After several iterations, if the total change in total energy efficiency loss remains positive, continue to reduce the step size and weights until the loss begins to decrease.

[0102] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0103] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0104] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0105] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0106] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the heating energy efficiency control of a gas-fired steam boiler, characterized in that, Includes the following steps: The response speed of the gas regulating valve and the air supply regulating valve is determined based on the position feedback signals of the gas regulating valve and the air supply regulating valve, and the response speed deviation is generated. Based on the opening degree of the gas regulating valve and the air supply regulating valve, the gas flow gain and the air flow gain are obtained by combining the gas flow and the air flow, and nonlinear deviation is generated by relating them to the response speed of the gas regulating valve and the air supply regulating valve. Based on the carbon monoxide concentration and total calorific value of the fuel gas in the flue, combined with the flue gas temperature and boiler inlet air temperature, the energy efficiency loss value is estimated, and the air-fuel ratio target is generated with the goal of reducing the energy efficiency loss value. The change in combustion intensity within the boiler furnace is determined, and the measured oxygen content in the flue gas is corrected to obtain the virtual oxygen content. Based on multivariate coordination of response speed deviation, nonlinear deviation, air-fuel ratio target and virtual oxygen content, the optimal parameters of gas regulating valve and air supply regulating valve are determined. After taking action based on the optimized parameters, the incomplete combustion loss value and the instantaneous value of flue gas sensible heat loss are re-estimated and it is determined whether the decreasing trend is met. If not, the optimized parameters are corrected.

2. The method for optimizing the heating efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of generating response speed deviation is as follows: The time when the position feedback signals of the gas regulating valve and the air supply regulating valve begin to change is taken as the response start time, respectively. Starting from the initial moment of response, the position feedback signals of the gas regulating valve and the air supply regulating valve are differentiated and calculated over time to obtain the position change rates of the gas regulating valve and the air supply regulating valve, which are used as the response speeds of the gas regulating valve and the air supply regulating valve, respectively. The response speed deviation is calculated by subtracting the response speed of the gas regulating valve from that of the air supply regulating valve hourly.

3. The method for optimizing the heating efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of obtaining the gas flow gain and air flow gain is as follows: The gas regulating valve and the air supply regulating valve are collected at their current positions, and the gas flow rate through the gas regulating valve and the air flow rate through the air supply regulating valve are collected in accordance with the corresponding openings. Subtract the opening degree of the gas regulating valve and the air supply regulating valve, the gas flow rate and the air flow rate at the previous data collection time, respectively, to obtain the changes in the opening degree of the gas regulating valve, the changes in the opening degree of the air supply regulating valve, the changes in the gas flow rate and the changes in the air flow rate. The ratio of the change in gas flow rate to the change in the opening of the gas regulating valve is taken as the gas flow rate gain, and the ratio of the change in air flow rate to the change in the opening of the air supply regulating valve is taken as the air flow rate gain.

4. The method for optimizing the heating energy efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of generating nonlinear bias is as follows: Align the gas flow gain point by point according to the time axis of the air supply regulating valve response speed, and calculate the deviation of the gas flow gain relative to the air supply regulating valve response speed at the same time index. Align the airflow gain point by point along the time axis of the gas regulating valve response speed, and calculate the deviation of the airflow gain relative to the gas regulating valve response speed at the same time index. The deviation amplitude on the gas side and the deviation amplitude on the air side are considered as two components of the nonlinear deviation.

5. The method for optimizing the heating energy efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of estimating energy efficiency loss is as follows: The carbon monoxide concentration and flue gas volume flow rate in the flue gas duct are continuously collected. At the same time, the calorific value of carbon monoxide under standard conditions is obtained. The carbon monoxide concentration is multiplied by the flue gas volume flow rate under standard conditions to obtain the carbon monoxide volume flow rate under standard conditions. Then, it is multiplied by the calorific value of carbon monoxide under standard conditions to obtain the instantaneous value of incomplete combustion loss. The flue gas temperature and boiler inlet air temperature are continuously collected in the flue gas duct and converted into Kelvin temperature. The Kelvin temperature difference between the flue gas temperature and the boiler inlet air temperature is calculated. The flue gas volume flow rate and the average specific heat capacity of the flue gas are continuously collected. The flue gas volume flow rate is multiplied by the average specific heat capacity of the flue gas and then multiplied by the Kelvin temperature difference to obtain the instantaneous value of the flue gas sensible heat loss. The instantaneous value of incomplete combustion loss is added to the instantaneous value of sensible heat loss from flue gas to obtain the energy efficiency loss value.

6. The method for optimizing the heating energy efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of generating an air-fuel ratio target with the aim of reducing energy efficiency loss is as follows: Adjust the current actual air-fuel ratio value by a fixed small step in the direction of increasing air flow. After the gas regulating valve and air supply regulating valve stabilize their operation, re-estimate the energy efficiency loss value to obtain the energy efficiency loss value after increasing the air flow. Adjust the current actual air-fuel ratio value by the same fixed small step size in the direction of reducing air flow. After the gas regulating valve and air supply regulating valve stabilize their operation, re-estimate the energy efficiency loss value to obtain the energy efficiency loss value after reducing the air flow. By comparing the energy efficiency loss values ​​after increasing the air-side pressure with those after decreasing the air-side pressure, the adjustment direction that minimizes the energy efficiency loss value is selected as the air-fuel ratio correction direction. The air-fuel ratio correction direction is superimposed with the current actual air-fuel ratio value to generate the air-fuel ratio target.

7. The method for optimizing the heating efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of determining the change in combustion intensity within the boiler furnace and correcting the measured oxygen content in the flue gas to obtain the virtual oxygen content is as follows: The flame brightness signal and furnace negative pressure fluctuation signal inside the boiler furnace are continuously collected. The flame brightness change rate and furnace negative pressure change rate are calculated and weighted summation is used to obtain the change in combustion intensity. Simultaneously, the length of the flue from the boiler furnace to the flue gas oxygen content measurement point and the flue gas velocity in the flue are measured. The flue gas transmission time constant is obtained by dividing the flue length by the flue gas velocity. The rate of change of oxygen content in flue gas is obtained by differentiating the measured value of oxygen content in flue gas with time. Multiply the change in combustion intensity by the flue gas transmission time constant, and then multiply by an empirical coefficient to obtain the oxygen content correction deviation; The virtual oxygen content is obtained by adding the oxygen content correction deviation to the current measured value of flue gas oxygen content.

8. The method for optimizing the heating energy efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process of determining the optimal parameters for the gas regulating valve and the air supply regulating valve is as follows: The position compensation amount is obtained by multiplying the response speed deviation by the duration of the control cycle and then superimposed on the current drive signal of the air supply regulating valve. Multiply the deviation of the gas supply valve in the nonlinear deviation by the current drive signal of the gas regulating valve to obtain the first correction amount of the gas regulating valve drive signal; multiply the deviation of the air supply valve by the current drive signal of the air supply regulating valve to obtain the second correction amount of the air supply regulating valve drive signal. The current ratio of gas flow rate to air flow rate is calculated in real time, and the difference between the current ratio and the air-fuel ratio target is used as the air-fuel ratio deviation signal. The gas regulating valve drive signal and the air supply regulating valve drive signal are readjusted based on the air-fuel ratio deviation signal and the virtual oxygen content. The optimized parameters of the air supply regulating valve drive signal and the gas regulating valve drive signal are obtained by algebraically summing all the adjustment amounts for the air supply regulating valve drive signal and the gas regulating valve drive signal within the same control cycle.

9. The method for optimizing the heating efficiency control of a gas-fired steam boiler according to claim 8, characterized in that, The process of readjusting the gas regulating valve drive signal and the air supply regulating valve drive signal based on the air-fuel ratio deviation signal and the virtual oxygen content is as follows: When the air-fuel ratio deviation signal indicates excessive air on the air side, decrease the air supply regulating valve drive signal and increase the gas regulating valve drive signal; when the air-fuel ratio deviation signal indicates excessive gas on the gas side, increase the air supply regulating valve drive signal and decrease the gas regulating valve drive signal. The virtual oxygen content is compared with the virtual oxygen content of the previous control cycle to obtain the direction of oxygen content change. When the virtual oxygen content increases, the drive signal of the air supply regulating valve is reduced, and when the virtual oxygen content decreases, the drive signal of the air supply regulating valve is increased.

10. The method for optimizing the heating energy efficiency control of a gas-fired steam boiler according to claim 1, characterized in that, The process for determining whether a downward trend is met is as follows: Subtract the previously estimated values ​​of incomplete combustion loss and instantaneous sensible heat loss from the current incomplete combustion loss value and the current instantaneous value of sensible heat loss in flue gas, respectively, to obtain the change in incomplete combustion loss and the change in flue gas heat loss. Add them together to obtain the total change in total energy efficiency loss. When the total change in total energy efficiency loss is greater than zero, it is determined that the downward trend is not met; otherwise, it is determined that the trend is met.

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