Natural gas boiler combustion efficiency optimization and dynamic regulation and control method

Abstract

The invention relates to a natural gas boiler combustion efficiency optimization and dynamic regulation and control method in the technical field of boilers, which comprises natural gas flow Qg, air flow Qa, smoke temperature Te, oxygen content O2 in smoke, hearth temperature Tf, smoke exhaust heat loss q2, chemical incomplete combustion heat loss q3 and mechanical incomplete combustion heat loss q4. A combustion efficiency calculation model and a dynamic regulation and control algorithm are constructed, an'efficiency-excess air 'dual-objective optimization function is adopted, PID feedback control is combined, and proportion regulation of natural gas and air supply is achieved. The combustion efficiency optimization formula and the dynamic regulation and control formula are introduced, the smoke exhaust loss and the incomplete combustion loss can be accurately calculated, and closed-loop regulation and control are achieved by solving the air excess coefficient lambda opt. According to the method, the combustion efficiency is remarkably improved and can reach 95% or above, emission of nitric oxide is reduced, the energy-saving rate is increased by 8%-15%, and the method can be used for intelligent energy-saving transformation of natural gas boilers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler, and is a natural gas boiler combustion efficiency optimization and dynamic regulation method. BACKGROUND

[0002] As a clean energy equipment, the combustion efficiency of natural gas boiler directly affects energy consumption and carbon emissions. Traditional boilers mostly use fixed air-fuel ratio or simple oxygen content feedback control, which has the following problems:

[0003] 1. Real-time calculation of combustion efficiency is not available, and regulation lacks quantitative basis;

[0004] 2. The excess air coefficient is too high, resulting in an increase in flue gas heat loss q2;

[0005] 3. Dynamic factors such as natural gas calorific value fluctuation and environmental temperature change are not considered;

[0006] 4. There is a lack of closed-loop feedback and multi-objective optimization mechanism, and the energy saving potential is not fully released

[0007] In the prior art, there is a feedback control based on oxygen content, but a complete efficiency model is not established. Usually, only fuzzy control is used, but it lacks mathematical optimization basis. Therefore, the present application provides a natural gas boiler combustion efficiency optimization and dynamic regulation method and paper to solve the above technical problems. SUMMARY

[0008] The present application is to overcome the above-mentioned deficiencies, and aims to provide a technical solution to solve the above-mentioned problems.

[0009] A natural gas boiler combustion efficiency optimization and dynamic regulation method, comprising the following steps: (1) real-time acquisition of natural gas boiler operating parameters, including: natural gas flow Q g , air flow Q a , flue gas temperature T e , oxygen content O2 in flue gas, furnace temperature T f , flue gas heat loss q2, chemical incomplete combustion heat loss q3 and mechanical incomplete combustion heat loss q4;

[0010] (2) based on the acquired parameters, the current combustion efficiency η is calculated by using the combustion efficiency optimization model, and it is judged whether it is lower than the preset threshold η set ;

[0011] (3) if η < η set , the dynamic regulation module is started, the air excess coefficient λ opt and the natural gas / air ratio adjustment amount ΔQ g , ΔQ a are calculated according to the optimization objective function and constraint condition;

[0012] (4) Send control instructions to the natural gas regulating valve and the blower frequency converter of the burner to adjust the supply of natural gas and air in real time, and realize dynamic optimization of the combustion process;

[0013] (5) Continuously monitor the combustion efficiency after regulation to form a closed-loop feedback control;

[0014] By collecting key parameters in real time and calculating the current combustion efficiency, the regulation is automatically started when the efficiency is lower than the set threshold, ensuring that the boiler always operates in the high-efficiency range and avoiding fuel waste caused by traditional fixed proportioning or extensive control. By optimizing the air excess coefficient (λ), reducing the exhaust gas heat loss (q2) and incomplete combustion loss (q3), the combustion efficiency can be improved to more than 95%. Through actual application verification, the energy saving rate can reach 8% to 15%, greatly reducing the consumption of natural gas and operating costs;

[0015] This method constructs a closed-loop feedback control system of "monitoring → calculation → judgment → regulation → re-monitoring", which realizes unattended intelligent operation without frequent manual intervention. The system can dynamically respond to changes in load, fluctuations in natural gas calorific value, changes in environmental temperature and other working conditions, always maintaining the combustion state, improving the stability and reliability of the boiler system, and accurately controlling the air-fuel ratio to avoid the increase of nitrogen oxides (NOx) caused by excessive air or the increase of carbon monoxide (CO) and hydrocarbons (HC) caused by insufficient air. The O2 content in the flue gas is effectively controlled in the ideal range of 3% to 5%, the NOx emission can be reduced by 10% to 20%, and the CO emission is reduced.

[0016] Further, the calculation formula of the combustion efficiency η is:

[0017] η = 100% - (q2 + q3 + q4)

[0018] Wherein:

[0019] q2 is the exhaust gas heat loss;

[0020] q3 is the chemical incomplete combustion heat loss;

[0021] q4 = 0 for mechanical incomplete combustion heat loss, q4 = 0 for natural gas boiler

[0022] c e is the average constant pressure specific heat capacity of flue gas (kJ / m 3 ·℃);

[0023] V fg is the actual flue gas volume (m 3 / m 3 );

[0024] Ta is the ambient temperature (℃);

[0025] Q net,ar is the received base calorific value of natural gas (kJ / m 3 )

[0026] [CO], [H2] are the volume concentrations of carbon monoxide and hydrogen in the flue gas (%);

[0027] Traditional boilers often rely on experience or a single parameter, such as oxygen content, to judge the combustion state, lacking accurate calculation of overall efficiency. The formula realizes measurable, calculable, and traceable quantitative evaluation by systematic modeling, decomposing combustion efficiency into the sum of various heat losses. The method is based on physical and thermodynamic principles for accurate calculation, providing objective and reliable data support for subsequent "whether to need regulation", making combustion optimization change from "experience-driven" to "data-driven". The formula clearly distinguishes flue gas heat loss (q2), chemical incomplete combustion loss (q3), and mechanical loss (q4), and sets q4 = 0 according to the characteristics of natural gas boilers.

[0028] q2 (flue gas loss) is the main heat loss item of natural gas boilers, accounting for 5% to 10%, and can be accurately evaluated by the formula to guide the reduction of flue gas temperature or optimization of air-fuel ratio; q3 (incomplete combustion loss) reflects the combustion sufficiency, and if the CO or H2 concentration is too high, it indicates that the air is insufficient or the mixing is poor, which needs to be adjusted in time. The explicit q4 = 0 reflects the accurate grasp of fuel characteristics, avoids model redundancy, and improves calculation efficiency and accuracy.

[0029] All parameters (T e , O2, [CO], Q_g) in the formula can be collected in real time by sensors, combined with preset constants (Q net,ar , c e ), to realize online continuous calculation of combustion efficiency. The formula is based on the standard heat balance method (GB / T 10180 "Industrial Boiler Thermal Performance Test Procedure"), and can be applied to natural gas boilers of different models and capacities without the need to re-establish complex models.

[0030] When the natural gas heat value Q net,ar changes, only the parameter needs to be updated, and the model is still applicable.

[0031] Further, the target function of the dynamic regulation is to maximize the combustion efficiency η and minimize the air excess coefficient λ to reduce the flue gas loss, and the optimization objective function is:

[0032] maxF(λ)=η(λ)-k·(λ-1) 2

[0033] wherein:

[0034] air excess ratio;

[0035] Q a0 , Q g0 , Q

[0036] k is a weight coefficient, the value range is 0.5-2.0, for balancing efficiency and energy consumption;

[0037] The constraint conditions include: λ∈[1.05,1.3], O2∈[3%,5%], T e ≤150℃;

[0038] The traditional combustion control often only focuses on a single target, such as only pursuing high efficiency or only controlling oxygen content. The present application proposes a double-target optimization function: maximizing the combustion efficiency η(λ) while minimizing the air excess ratio λ;

[0039] Avoid the "high efficiency but high energy consumption" trap: simply pursuing high efficiency may lead to λ being too large (too much air), although the combustion is sufficient, a large amount of heat is taken away by the excess air, and the exhaust gas loss q2 increases;

[0040] By k(λ-1) 2 , the adjustable weight coefficient k(0.5-2.0) is introduced, so that the system has configurable ability. When k takes a larger value (such as 1.8), the system tends to reduce λ, and when k takes a smaller value (such as 0.6), the system tends to maximize η;

[0041] λ∈[1.05,1.3] prevents serious air shortage, λ<1.05 leads to incomplete combustion or serious excess λ>1.3 leads to a sharp increase in exhaust gas loss;

[0042] O2∈[3%,5%] meets the safety operation specification of the boiler, avoiding the risk of deflagration;

[0043] T e ≤150℃ protects the tail heating surface and prevents low-temperature corrosion;

[0044] The objective function is an explicit mathematical expression, which can be differentiated, iterated and extremum solved, and the air excess ratio λ opt can be quickly calculated by numerical methods such as Newton method and gradient descent.

[0045] Further, the air excess ratio λ opt is obtained by solving the extremum of the objective function, and the calculation process is as follows:

[0046] (a) Establish a nonlinear relationship model of η and λ: η(λ) = a-b-λ-c / λ, where a, b, c are constants fitted based on historical data;

[0047] (b) Derive the target function F(λ):

[0048] (c) Let the derivative be zero, and solve the equation:

[0049] (d) Use numerical iteration method (such as Newton method) to solve λ opt .

[0050] Further, the dynamic control formula:

[0051]

[0052] Where:

[0053] e η = η set -η, the combustion efficiency deviation;

[0054] K p ,K i ,K d , PID control parameters;

[0055] ΔQ g , ΔQ a are the adjustment amounts of natural gas and air respectively.

[0056] Further, the method also includes the safety protection logic of the furnace temperature T f When , the natural gas flow Qg is reduced in priority to prevent the furnace from overheating.

[0057] Further, the method is realized by an embedded controller or an industrial PLC, supporting remote monitoring and parameter setting.

[0058] Compared with the prior art, the beneficial effects of the present application are:

[0059] 1. Precise quantification of each heat loss is achieved by establishing a scientific combustion efficiency calculation model; the dual-objective optimization strategy of "efficiency maximization + air excess coefficient minimization" is adopted to avoid the contradiction of "high efficiency and high energy consumption" in traditional control, compared with the traditional control method, the energy saving rate can reach 8% ~ 15%, greatly reducing the operating cost of natural gas;

[0060] 2. Effectively reduce pollutant emissions, promote green and low-carbon operation, and precisely control the air-fuel ratio to keep the oxygen content (O2) in the flue gas stable within the ideal range of 3% to 5%; reduce the generation of nitrogen oxides (NOx) caused by excessive air or the emission of carbon monoxide (CO) caused by insufficient air.

[0061] 3. Achieve intelligent closed-loop control, improve the system's automation level, and construct a fully closed-loop control process of "parameter acquisition → efficiency calculation → deviation judgment → optimization solution → dynamic control → re-monitoring"; reduce the frequency of on-site monitoring in the boiler combustion process without frequent intervention, and achieve integration with PLC, DCS or industrial Internet platforms through optimization, facilitating centralized monitoring and remote management. Detailed Implementation

[0062] The present invention will now be described in further detail with reference to specific embodiments.

[0063] In this embodiment, please refer to the specific implementation of a method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler, which includes the following steps: (1) Real-time acquisition of natural gas boiler operating parameters, including: natural gas flow rate Q g Airflow Q a Flue gas temperature T e Oxygen content (O2) in flue gas, furnace temperature (T) f The heat loss is q2 from exhaust gas, q3 from incomplete chemical combustion, and q4 from incomplete mechanical combustion.

[0064] (2) Based on the collected parameters, calculate the current combustion efficiency η using the combustion efficiency optimization model, and determine whether it is lower than the preset threshold η. set ;

[0065] (3) If η < η set Then the dynamic control module is activated, and the excess air coefficient λ is calculated based on the optimization objective function and constraints. opt and natural gas / air ratio adjustment amount ΔQ g ΔQ a ;

[0066] (4) Send control commands to the natural gas regulating valve and blower frequency converter of the burner to adjust the supply of natural gas and air in real time and realize dynamic optimization of the combustion process;

[0067] (5) Continuously monitor the combustion efficiency after regulation to form a closed-loop feedback control;

[0068] By real-time acquisition of key parameters and calculation of current combustion efficiency, automatic regulation is started when the efficiency is lower than the set threshold, ensuring that the boiler always runs in the high efficiency range, avoiding fuel waste caused by traditional fixed ratio or extensive control; By optimizing the air excess coefficient (λ), reducing the exhaust heat loss (q2) and incomplete combustion loss (q3), the combustion efficiency can be improved to more than 95%; Through actual application verification, the energy saving rate can reach 8%~15%, greatly reducing the consumption of natural gas and operating cost;

[0069] The method constructs a closed-loop feedback control system of "monitoring → calculation → judgment → regulation → re-monitoring", without frequent manual intervention, realizing unattended intelligent operation; The system can dynamically respond to load changes, natural gas heat value fluctuations, environmental temperature changes and other working conditions, always maintaining the combustion state, improving the stability and reliability of the boiler system, and by accurately controlling the air-fuel ratio, avoiding the increase of nitrogen oxides (NOx) caused by excessive air, or the increase of carbon monoxide (CO) and hydrocarbons (HC) caused by insufficient air, effectively controlling the O2 content in the flue gas in the ideal range of 3%~5%, reducing NOx emissions by 10%~20%, and reducing CO emissions.

[0070] Further, the calculation formula of the combustion efficiency η is:

[0071] η=100%-(q2+q3+q4)

[0072] Wherein:

[0073] q2 is the exhaust heat loss;

[0074] q3 is the chemical incomplete combustion heat loss;

[0075] q4 is the mechanical incomplete combustion heat loss, for natural gas boiler, q4=0

[0076] c e is the average constant pressure specific heat capacity of flue gas (kJ / m 3 ·℃);

[0077] V fg is the actual flue gas volume (m 3 / m 3 );

[0078] T a is the ambient temperature (℃);

[0079] Q net,ar is the received natural gas low heat value (kJ / m 3 )

[0080] [CO]、[H2] is the volume concentration of carbon monoxide and hydrogen in the flue gas (%)

[0081] Traditional boilers often rely on experience or a single parameter, such as oxygen content, to judge the combustion state, lacking accurate calculation of overall efficiency. The formula systematically models the combustion efficiency as the sum of various heat losses, achieving measurable, calculable, and traceable quantitative evaluation. The method is based on physical and thermodynamic principles for accurate calculation, providing objective and reliable data support for subsequent "whether to need regulation", changing combustion optimization from "experience-driven" to "data-driven". The formula clearly distinguishes between exhaust gas heat loss (q2), chemical incomplete combustion loss (q3), and mechanical loss (q4), and sets q4 = 0 based on the characteristics of natural gas boilers.

[0082] q2 (exhaust gas loss) is the main heat loss item of natural gas boilers, accounting for 5% to 10%, and can be accurately evaluated through the formula to guide the reduction of exhaust gas temperature or optimization of air-fuel ratio; q3 (incomplete combustion loss) reflects the combustion sufficiency, and if the CO or H2 concentration is too high, it indicates insufficient air or poor mixing, which needs to be adjusted in time. Setting q4 = 0 reflects accurate understanding of fuel characteristics, avoids model redundancy, and improves calculation efficiency and accuracy.

[0083] All parameters (T e , O2, [CO], Q_g) in the formula can be collected in real time by sensors, combined with pre-set constants (Q net,ar、ce ), to realize online continuous calculation of combustion efficiency. The formula is based on the standard heat balance method (GB / T 10180 "Industrial Boiler Thermal Performance Test Procedure"), and can be applied to natural gas boilers of different types and capacities without the need to re-establish complex models.

[0084] When the natural gas heat value Q net,ar changes, only the parameter needs to be updated, and the model is still applicable.

[0085] Further, the target function of the dynamic regulation is to maximize the combustion efficiency η and minimize the air excess coefficient λ to reduce the exhaust gas loss, and the optimization objective function is:

[0086] maxF(λ)=η(λ)-k·(λ-1) 2

[0087] Where:

[0088] is the air excess coefficient;

[0089] Q a0 , Q g0 are the theoretical air quantity and theoretical natural gas quantity;

[0090] k is a weight coefficient, the value range is 0.5-2.0, and is used for balancing efficiency and energy consumption;

[0091] The constraint conditions include: λ∈[1.05,1.3], O2∈[3%, 5%], T e ≤150℃;

[0092] Traditional combustion control often only focuses on a single target, such as only pursuing high efficiency or only controlling oxygen content. The present application proposes a double-target optimization function: maximizing the combustion efficiency η(λ) while minimizing the air excess coefficient λ;

[0093] Avoiding the "high efficiency but high energy consumption" trap: simply pursuing high efficiency can lead to a too large λ (too much air), although the combustion is sufficient, a large amount of heat is taken away by the excess air, and the exhaust gas loss q2 increases;

[0094] By k(λ-1) 2 The term suppresses a too large λ, introduces an adjustable weight coefficient k (0.5-2.0), so that the system has configurable ability, when k takes a larger value (such as 1.8), the system tends to reduce λ, and when k takes a smaller value (such as 0.6), the system tends to maximize η;

[0095] λ∈[1.05,1.3] prevents serious air deficiency, λ<1.05 leads to incomplete combustion or serious excess λ>1.3 leads to a dramatic increase in exhaust gas loss;

[0096] O2∈[3%, 5%] meets the safety operation specification of the boiler, and avoids the risk of deflagration;

[0097] T e ≤150℃ protects the tail heating surface and prevents low-temperature corrosion;

[0098] The objective function is an explicit mathematical expression, which can be differentiated, iterated and extremum solved, and the air excess coefficient λ opt .

[0099] Further, the air excess coefficient λ opt is obtained by solving the extremum of the objective function, and the calculation process is as follows:

[0100] (a) Establish a nonlinear relationship model of η and λ: η(λ)=a-b·λ-c / λ, wherein a, b and c are constants fitted based on historical data;

[0101] (b) Derive the objective function F(λ):

[0102] (c) Let the derivative be zero, and solve the equation:

[0103] (d) solving λ by numerical iteration method (such as Newton method) opt .

[0104] Further, the dynamic regulation formula is:

[0105]

[0106] Wherein:

[0107] e η = η set - η, the combustion efficiency deviation;

[0108] K p ,K i ,K d , PID control parameters;

[0109] ΔQ g , ΔQ a , respectively, the natural gas and air adjustment amount.

[0110] Further, the method also includes the safety protection logic of the furnace temperature T f When , the natural gas flow Qg is reduced in priority to prevent the furnace from overheating.

[0111] Further, the method is realized by an embedded controller or an industrial PLC, and supports remote monitoring and parameter setting.

[0112] Compared with the prior art, the beneficial effects of the present application are:

[0113] 1. By establishing a scientific combustion efficiency calculation model, each heat loss is accurately quantified; the dual-objective optimization strategy of "efficiency maximization + air excess coefficient minimization" is adopted to avoid the contradiction of "high efficiency and high energy consumption" in traditional control, and compared with the traditional control mode, the energy saving rate can reach 8% ~ 15%, greatly reducing the natural gas operation cost;

[0114] 2. Effectively reduce pollutant emissions, help green and low-carbon operation, accurately control the air-fuel ratio, and make the oxygen content (O2) of flue gas stable in the ideal interval of 3% ~ 5%; reduce the generation of nitrogen oxides (NOx) due to excessive air or carbon monoxide (CO) emissions due to insufficient air;

[0115] 3. Realize intelligent closed-loop regulation, improve the automation level of the system, and build a full-closed-loop control process of "parameter collection → efficiency calculation → deviation judgment → optimization solution → dynamic regulation → re-monitoring"; without frequent intervention, realize the reduction of the frequency of value keeping in the boiler combustion process, support integration with PLC, DCS or industrial internet platform through optimization, and facilitate centralized monitoring and remote management.

[0116] The above is further detailed description of the present application in combination with specific preferred embodiments, and cannot be deemed as limitation of the specific implementation of the present application to these descriptions. For ordinary skilled in the art to which the present application belongs, several simple deductions or replacements can be made without departing from the concept of the present application, and all should be regarded as the protection scope of the present application.

Claims

1. A method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler, characterized in that, Includes the following steps: (1) Real-time acquisition of natural gas boiler operating parameters, including: natural gas flow rate Q g Airflow Q a Flue gas temperature T e Oxygen content (O2) in flue gas, furnace temperature (T) f The heat loss is q2 from exhaust gas, q3 from incomplete chemical combustion, and q4 from incomplete mechanical combustion. (2) Based on the collected parameters, calculate the current combustion efficiency η using the combustion efficiency optimization model, and determine whether it is lower than the preset threshold η. set ; (3) If η < η set Then the dynamic control module is activated, and the excess air coefficient λ is calculated based on the optimization objective function and constraints. opt and natural gas / air ratio adjustment amount ΔQ g ΔQ a ; (4) Send control commands to the natural gas regulating valve and blower frequency converter of the burner to adjust the supply of natural gas and air in real time and realize dynamic optimization of the combustion process; (5) Continuously monitor the combustion efficiency after regulation to form a closed-loop feedback control.

2. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 1, characterized in that, The formula for calculating the combustion efficiency η is: η = 100% - (q² + q³ + q⁴) in: For heat loss from flue gas exhaust; This is due to heat loss from incomplete chemical combustion; q4 represents the heat loss due to incomplete combustion. For a natural gas boiler, q4 = 0. c e The average isobaric specific heat capacity of flue gas (kJ / m³) 3 ·℃); V fg Actual flue gas volume (m³) 3 / m 3 ); T a Ambient temperature (°C); Q net,ar The lower heating value of natural gas (kJ / m³) 3 ) [CO] and [H2] represent the volume concentrations (%) of carbon monoxide and hydrogen in the flue gas.

3. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 1, characterized in that, The objective function of the dynamic control is to maximize combustion efficiency η while minimizing the excess air coefficient λ to reduce exhaust losses. Its optimization objective function is: max F(λ)=η(λ)-k·(λ-1) 2 in: This refers to the excess air coefficient. Q a0 Q g0 , which represent the theoretical air volume and the theoretical natural gas volume; k is a weighting coefficient, ranging from 0.5 to 2.0, used to balance efficiency and energy consumption; The constraints include: λ∈[1.05,1.3], O2∈[3%,5%], T e ≤150℃.

4. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 3, characterized in that, The excess air coefficient λ opt The objective function is obtained by solving for its extreme value. The calculation process is as follows: (a) Establish a nonlinear relationship model between η and λ: η(λ)=ab·λ-c / λ, where a,b,c are constants fitted based on historical data; (b) Differentiate the objective function F(λ): (c) Set the derivative to zero and solve the equation: (d) Solve for λ using numerical iteration methods (such as Newton's method). opt .

5. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 1, characterized in that, The dynamic control formula is as follows: in: e η =η set -η represents the combustion efficiency deviation; K p ,K i ,K d , are PID control parameters; ΔQ g ΔQ a These are the regulation amounts for natural gas and air, respectively.

6. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 1, characterized in that, Also includes furnace temperature T f Security protection logic: When T f >T fmax At this time, the natural gas flow rate Qg should be reduced first to prevent the furnace from overheating.

7. The method for optimizing and dynamically controlling the combustion efficiency of a natural gas boiler according to claim 1, characterized in that, The method is implemented using an embedded controller or industrial PLC, and supports remote monitoring and parameter setting.

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