An ultra-low nitrogen flameless combustion system for low calorific value associated gas

Abstract

The present invention discloses a low calorific value associated gas ultra-low nitrogen flameless combustion system, which relates to the field of combustion control technology. The system comprises a gas acquisition module, which acquires low calorific value gas through an inlet pipeline valve group to obtain dry low calorific value gas, and a premixing control module, which adopts multivariable coordinated control to adjust the mixing ratio of low calorific value gas and air with stable pressure to obtain premixed gas with stable flow rate. The low calorific value associated gas ultra-low nitrogen flameless combustion system adopts a recirculation channel and dynamic power distribution to adjust the combustion process, collects combustion state data through a flame probe and a temperature sensor, adjusts the airflow distribution of a porous ceramic burner according to the data, and finally achieves stable combustion output. The method can effectively improve the combustion efficiency and stability of low calorific value gas, reduce emissions, and is suitable for the efficient and clean utilization of low calorific value gases such as industrial waste gas.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion control, and in particular to an ultra-low nitrogen flameless combustion system for low calorific value associated gas. Background Art

[0002] In current low-calorific-value gas combustion systems, achieving efficient utilization of gases with varying methane contents while maintaining combustion stability is a key technical challenge. Traditional systems generally rely on fixed premixing control strategies, which are unable to cope with fluctuations in combustion calorific value caused by dynamic changes in methane concentration.

[0003] Especially when the premix ratio and flow rate need to be adjusted in real time based on the pressure and composition of the inlet gas, it is very easy to cause an unstable combustion process, resulting in problems such as backfire and flameout. In addition, flameless combustion technology is currently widely used to reduce nitrogen oxide (NOx) emissions. Although this technology has advantages in terms of environmental protection, it requires higher control of the temperature field and mixing uniformity within the combustion chamber, thereby increasing the difficulty of designing and operating the combustion control system. To further optimize emission control, existing systems also introduce flue gas recirculation channels to adjust the thermal field distribution within the combustion chamber, reduce local temperature peaks, and suppress NOx generation. However, while this method reduces the temperature, it may affect combustion efficiency and increase the complexity of the control system's coordinated regulation of the flow field and thermal field. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-low nitrogen flameless combustion system for calorific value associated gas to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a low calorific value associated gas ultra-low nitrogen flameless combustion system, comprising:

[0006] The gas acquisition module obtains low calorific value gas through the inlet pipeline valve group to obtain dry low calorific value gas;

[0007] The premixing control module uses multivariable coordinated control to adjust the mixing ratio of low calorific value gas and air with stable pressure to obtain premixed gas with stable flow rate;

[0008] The anti-backfire module uses a flame arrester to perform anti-backfire treatment on the premixed gas with stable flow. A flow sensor is used to obtain the flow data of the processed premixed gas. Combined with load adaptive regulation, the gas transmission efficiency is optimized to obtain the premixed gas with anti-backfire treatment.

[0009] The flameless combustion module uses a porous ceramic burner to flamelessly burn the premixed gas that has been treated for backfire prevention. The recirculation channel uses feedback from the combustion chamber temperature and flue gas exhaust temperature, combined with dynamic power distribution to adjust the recirculation airflow ratio to obtain a combustion gas with a balanced thermal field.

[0010] The flame detection module uses a flame probe to collect the flame state spectral characteristics of the combustion gas with thermal field equilibrium, uses a temperature sensor to obtain the combustion chamber gas temperature and flue gas exhaust temperature, and uses a flow sensor to obtain the premixed gas flow data for anti-backfire treatment. The control signal smoothing process is used to generate a combustion state data set;

[0011] A stable output module generates a first control signal, uses the first control signal to adjust the airflow distribution in the ceramic pores of the porous ceramic burner, and optimizes operating parameters in combination with motor temperature rise monitoring and fault diagnosis signals. If the flow data and combustion chamber temperature meet a preset deviation threshold, a second control signal is generated, which is used to lock the burner parameters to obtain a stable combustion output;

[0012] The premixing control module further comprises the step of continuously collecting inlet pressure data of the dry low calorific value gas through a high-precision pressure sensor, processing the pressure signal using a low-pass filtering algorithm, and obtaining a filtered inlet pressure signal.

[0013] The method of obtaining the premixed gas with a stable flow rate in the premixing control module further includes detecting the methane concentration in the low calorific value gas with a stable pressure in real time by using an infrared gas analyzer, querying a pre-established dynamic ratio database, obtaining a flow ratio coefficient corresponding to the methane content, and determining the methane content ratio parameter;

[0014] The premixing control module further comprises obtaining a premixed gas with a stable flow rate by using a premixing device to adjust the mixing ratio of the low calorific value gas with stable pressure and air using multivariable coordinated control according to the filtered inlet pressure signal and the methane content ratio parameter to obtain the premixed gas;

[0015] Obtaining a stable flow of premixed gas in the premixing control module also includes driving a gas delivery pump through a variable frequency motor, using variable frequency speed control to precisely adjust the pump speed, combining real-time speed feedback to monitor the operating status, and using differential predictive control to adjust the premixed gas flow rate based on a filtered inlet pressure signal and methane content ratio parameters. If the methane concentration is lower than a preset methane concentration threshold, low methane protection logic is triggered to reduce the pump output power to obtain a stable flow of premixed gas.

[0016] Preferably, the gas acquisition module uses a gas-liquid separation device to separate liquid impurities in the gas to obtain dry low calorific value gas.

[0017] Preferably, obtaining the premixed gas with a stable flow rate in the premixing control module also includes performing pressure stabilization processing on the dry low calorific value gas through a pressure stabilizing device, and using proportional gain adjustment to generate a control output amplitude for the pressure deviation in the filtered inlet pressure signal, and combining the integral time constant to eliminate the steady-state error to obtain the low calorific value gas with a stable pressure.

[0018] Preferably, the premixing control module includes a methane content detection device and a ratio regulating valve, and the ratio regulating valve dynamically adjusts the mixing ratio of air and low calorific value gas according to the output signal of the methane content detection device.

[0019] Preferably, the flame arrester in the anti-backfire module is a metal corrugated structure or a ceramic honeycomb structure, so as to improve the backfire suppression effect.

[0020] Preferably, it also includes an inlet pipeline valve group, a vapor-liquid separation device, a flow device, a pressure stabilizing device and a gas main pipeline valve group connected in sequence, the gas main pipeline valve group is respectively connected to a gas cut-off device and a gas ignition pipeline valve group, the gas ignition pipeline valve group is connected to a flame arrester, the flame arrester is connected to a flameless combustion device, the flameless combustion device is connected to a boiler, the gas cut-off device is connected in series with an electric valve, the electric valve is connected to the combustion-supporting pipeline valve group, the combustion-supporting pipeline valve group is also connected to the flameless combustion device, the inlet pipeline valve group is also connected to the inlet combustion-supporting valve group, the inlet combustion-supporting valve group is connected to a fan, and the fan is also connected to the combustion-supporting pipeline valve group.

[0021] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0022] This low-calorific-value associated gas ultra-low-nitrogen flameless combustion system obtains low-calorific-value gas through an inlet pipeline valve group. After vapor-liquid separation and pressure stabilization, the methane concentration is detected in real time and dynamically proportioned. Multivariable coordinated control is used to adjust the mixing ratio with air. The gas delivery pump is driven by a variable-frequency motor to accurately control the premixed gas flow rate. Flameless combustion is performed after flame arrester anti-backfire treatment. The present invention also uses a recirculation channel and dynamic power distribution to regulate the combustion process. The combustion state data is collected through a flame probe and temperature sensor. The airflow distribution of the porous ceramic burner is adjusted according to the data, ultimately achieving stable combustion output. This method can effectively improve the combustion efficiency and stability of low-calorific-value gas, reduce emissions, and is suitable for the efficient and clean utilization of low-calorific-value gases such as industrial waste gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a connection diagram of the system modules of the present invention;

[0024] Figure 2 It is a process flow chart of the present invention.

[0025] In the figure: 1. Inlet pipeline valve group; 2. Gas-liquid separation device; 3. Flow device; 4. Pressure stabilizing device; 5. Gas main pipeline valve group; 6. Inlet combustion-supporting valve group; 7. Fan; 8. Gas shut-off device; 9. Gas ignition pipeline valve group; 10. Electric valve; 11. Combustion-supporting pipeline valve group; 12. Flame arrester; 13. Flameless combustion device; 14. Boiler. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, the present invention provides a technical solution: an ultra-low nitrogen flameless combustion system for low calorific value associated gas, comprising:

[0028] The gas acquisition module obtains low calorific value gas through the inlet pipeline valve group to obtain dry low calorific value gas;

[0029] The premixing control module uses multivariable coordinated control to adjust the mixing ratio of low calorific value gas and air with stable pressure to obtain premixed gas with stable flow rate;

[0030] The anti-backfire module uses a flame arrester to perform anti-backfire treatment on the premixed gas with stable flow. A flow sensor is used to obtain the flow data of the processed premixed gas. Combined with load adaptive regulation, the gas transmission efficiency is optimized to obtain the premixed gas with anti-backfire treatment.

[0031] The flameless combustion module uses a porous ceramic burner to flamelessly burn the premixed gas that has been treated for backfire prevention. The recirculation channel uses feedback from the combustion chamber temperature and flue gas exhaust temperature, combined with dynamic power distribution to adjust the recirculation airflow ratio to obtain a combustion gas with a balanced thermal field.

[0032] The flame detection module uses a flame probe to collect the flame state spectral characteristics of the combustion gas with thermal field equilibrium, uses a temperature sensor to obtain the combustion chamber gas temperature and flue gas exhaust temperature, and uses a flow sensor to obtain the premixed gas flow data for anti-backfire treatment. The control signal smoothing process is used to generate a combustion state data set;

[0033] The stable output module generates a first control signal, uses the first control signal to adjust the ceramic pore airflow distribution of the porous ceramic burner, and optimizes the operating parameters in combination with the motor temperature rise monitoring and fault diagnosis signal. If the flow data and the combustion chamber temperature meet the preset deviation threshold setting, a second control signal is generated. The burner parameters are locked through the second control signal to obtain a stable combustion output.

[0034] First, in the gas acquisition stage, an external low calorific value gas source, such as oilfield associated gas, is connected through the inlet pipeline valve group. The main components of this type of gas are usually methane, ethane, a small amount of nitrogen and sulfide. It is preliminarily estimated that its calorific value is not less than 3MJ / m 3In order to ensure the stability of subsequent combustion, the system filters and dries the original gas to remove water vapor, oil mist and particulate impurities. Entering the premixing control stage, the core is to control the mixing ratio of low calorific value gas and air, so that the generated premixed gas has a stable flow and pressure while maintaining an appropriate air-fuel ratio. The volume ratio of air to gas is often measured by the "λ value" (that is, the ratio of the actual air supply to the amount of air required for theoretical combustion). This value is usually controlled between 1.1-1.2 to ensure lean burn and flameless combustion. For example, if the low calorific value gas flow rate per unit time is Qf (unit: m 3 / h), its calorific value is LHV (unit: MJ / m 3 ), the theoretical air demand can be expressed as: Qa=Qf×LHV / (η×Hu), where Qa is the theoretical air flow, η is the combustion efficiency (set to 0.95), and Hu is the heat that can be provided by each cubic meter of air (approximately 3.7 MJ / m 3The system uses gas flow and pressure sensors to monitor Qf in real time. The central control module then calculates and adjusts the air proportional valve opening to ensure the mixed gas remains within the aforementioned λ value range. The anti-backfire module utilizes the physical structure of a flame arrester to intercept flames that could potentially propagate in the opposite direction. It also incorporates a flow feedback mechanism to monitor the gas flow velocity v in real time. If the detected value falls below the safety threshold v_min (e.g., 0.5 m / s), the system adaptively increases the fan speed or reduces the gas channel cross-section to ensure the flow velocity returns to above the critical range and prevent flame rollback. The key to the flameless combustion module lies in the use of a porous ceramic burner. The gases mix and diffuse evenly within the porous medium, then burn in a planar manner, avoiding the formation of localized high-temperature flames. The ceramic's thermal conductivity and heat capacity help maintain a uniform temperature in the combustion zone while reducing NOx generation. To stabilize the thermal field, the system incorporates a recirculating gas channel, returning the high-temperature post-combustion gas to the front end in proportion β to remix it with the premixed gas. This ratio is dynamically adjusted using the following empirical model: β = k × (Tt - Ts); where Tt is the combustion chamber temperature, Ts is the flue gas exhaust temperature, and k is a proportional coefficient, set based on furnace model experience. This adjustment achieves a balanced thermal field distribution and improves combustion efficiency. The flame detection module uses a spectral flame probe to identify radiation signals in specific wavelength bands within the flame (such as the emission characteristics of CH* and OH* free radicals). Combining temperature sensor readings with previous flow data, a signal smoothing algorithm removes high-frequency disturbances, generating a ternary data set consisting of flow rate, temperature, and spectral intensity, which is used to determine combustion stability. Finally, in the stable output module, the system uses a first control signal to adjust the airflow pore distribution in different areas of the porous ceramic burner. For example, increasing the pore diameter in areas with low heat load can enhance local gas supply. Simultaneously, the system monitors motor temperature rise parameters and abnormality diagnostic information to adjust operating parameters in real time. If both the combustion flow rate and chamber temperature are determined to be within set thresholds (e.g., ±5%), the system issues a second control signal to lock the current combustion parameters and maintain stable output. Through the coordination and control of the above-mentioned entire process, not only is the efficient and clean utilization of low-calorific value fuel gas achieved, but the continuity, safety and environmental protection performance of the entire combustion process are also ensured, and it has good industrial applicability.

[0035] Through its modular design, the system effectively integrates multiple functions, including gas purification, mixing control, backfire prevention, safe combustion, and intelligent detection, enhancing combustion safety and system stability. Multivariable coordinated control and recirculation airflow adjustment mechanisms ensure high combustion efficiency and balanced thermal field distribution, effectively suppressing NOx generation. Furthermore, signal fusion and adaptive regulation enhance system robustness, providing excellent self-correction and fault protection capabilities. Furthermore, the flameless combustion design significantly reduces visible flames and thermal shock, achieving the environmental goal of ultra-low emissions. The system operates with low noise and has strong adaptability to load changes, making it suitable for complex industrial scenarios.

[0036] The gas acquisition module uses a vapor-liquid separator to separate liquid impurities from the gas, producing dry low-calorific-value gas. In this embodiment, the structure of the gas acquisition module has been further optimized. By introducing a vapor-liquid separator, the purity of the low-calorific-value gas before it enters the combustion system is effectively improved. Due to its complex sources, low-calorific-value gas often contains water vapor, oil mist, or other liquid impurities. If these liquid components enter the combustion system directly, they can lead to incomplete combustion, reduced energy efficiency, and even safety risks such as deflagration. Therefore, this system incorporates a vapor-liquid separator at the inlet as a core component of gas purification. Specifically, this separator utilizes a combination of inertial separation and condensation separation. First, the low-calorific-value gas enters the separation chamber. The gas flow rate suddenly decreases and changes direction in the pipeline. Due to the significant density difference between the gas and liquid, the liquid droplets, due to their greater inertia, cannot flexibly turn with the airflow and are thrown toward the inner wall of the separator. There, they form a liquid film on the wall and collect in the bottom sump for discharge. The efficiency of this process depends on the airflow velocity, droplet diameter, and channel geometry. The system design ensures that the average flow rate at the gas inlet is controlled at approximately 10 meters per second, ensuring that droplets with a diameter of 50 microns or more have sufficient momentum to achieve inertial separation. The gas then enters the condensation and separation zone, where a metal cooling tube system is installed to reduce the gas temperature to below the dew point. Under these temperature conditions, the water vapor and light hydrocarbon components, which were originally in a gaseous state, begin to liquefy, adhere to the cooling surface, and then slide down the wall to be collected. To ensure the condensation effect, the system calculates that the target cooling temperature must be approximately 5 degrees Celsius lower than the dew point of the original gas. For example, when the gas pressure is at atmospheric pressure and the dew point is 30 degrees Celsius, the temperature of the cooling zone must be stably controlled within 25 degrees Celsius. The required cooling power can be estimated by looking up a table and an empirical formula: the heat required for condensation is equal to the water vapor content per unit volume of gas multiplied by its latent heat of condensation, multiplied by the hourly flow rate, which gives the total cooling energy required per hour. This calculation process is implemented in the system design as follows: "First, the moisture content per unit gas (grams per cubic meter) is evaluated, multiplied by the latent heat of vaporization of water (approximately 2257 joules per gram), and then combined with the hourly gas throughput (cubic meters per hour), the required cooling power (in kilowatts) of the cooling stage is calculated. After vapor-liquid separation, the resulting gas is dried and enters the subsequent premixing control module. Its moisture content has been significantly reduced, with a typical value of less than 0.5%. This treatment significantly improves the stability, thermal efficiency, and safety of the subsequent combustion process.

[0037] This embodiment significantly improves the dryness of the gas before it enters the combustion system by introducing a vapor-liquid separation device, thus avoiding the risks of liquid impurities corroding the burner, flameout, and explosion at the source, while also reducing the potential for incomplete combustion byproducts such as carbon monoxide and unburned hydrocarbons produced during combustion. Particularly when processing biogas or oilfield associated gas with large fluctuations in moisture content, the module can automatically adjust the condensation temperature based on the incoming gas dew point to achieve dynamic and efficient separation. Furthermore, the precisely controlled flow rate and cooling temperature zone design ensure high dehumidification efficiency without introducing additional energy consumption, effectively guaranteeing operational stability and emission control during the combustion phase of the entire system.

[0038] The premixing control module also maintains a stable premixed gas flow rate by continuously collecting inlet pressure data for the dry, low-calorific-value gas using a high-precision pressure sensor. The pressure signal is then processed using a low-pass filtering algorithm to obtain a filtered inlet pressure signal. In this embodiment, to further improve the stability and control accuracy of the premixed gas flow rate, a high-precision pressure sensor and a signal filtering algorithm are integrated into the premixing control module to obtain and optimize the pressure state of the dry gas before it enters the mixing chamber in real time. Due to the unstable source of low-calorific-value gas, its delivery process is often affected by factors such as pressure fluctuations at the source, pipeline vibration, and equipment switching. If not addressed, this can directly lead to a disrupted premixing ratio and even combustion instability. First, a high-precision pressure sensor is positioned before the gas enters the premixer, continuously collecting raw inlet gas pressure data per unit time. Such sensors typically have millibar-level resolution and sampling frequencies exceeding tens of hertz, effectively capturing pressure trends and transient shocks. However, directly using raw pressure data is susceptible to transient noise. Therefore, after data acquisition, the system smoothes the data using a low-pass filtering algorithm embedded in the control system. Low-pass filtering is an algorithm that retains only low-frequency trends in data while suppressing high-frequency disturbances. Essentially, it introduces a weighted average between current and historical data. For example, the system weights each current pressure value proportionally to the filter output at the previous moment. The choice of weight depends on the sampling interval and the expected response speed. If a fast response is desired, the current value is given a higher weight; if strong interference immunity is required, the historical value is given a higher weight. In practice, the control system processes the raw pressure value collected each second and takes a weighted average of it with the previous processed result to generate the current "filtered pressure value." This processing effectively eliminates sudden pressure fluctuations caused by airflow turbulence, electromagnetic interference, or mechanical vibration, ensuring more stable and reliable data for subsequent air ratio valve adjustments. The filtered pressure signal is then fed into the premix ratio control logic, where it is matched and corrected with the current set gas-to-air ratio. This ensures that even when the source gas pressure fluctuates, the system can maintain the target air-fuel ratio by dynamically adjusting the air flow rate, thereby maintaining premix flow stability.

[0039] By introducing high-precision pressure sensors and a low-pass filtering algorithm, this system achieves real-time suppression of gas source fluctuations during the premixing phase, significantly improving the composition consistency and flow rate stability of the premixed gas. This strategy effectively avoids combustion fluctuations caused by transient disturbances, particularly under conditions of rapid load changes or unstable source gas pressure. Furthermore, this strategy reduces the pressure on the air conditioning system's response speed, helping to extend the service life of control valves and actuators, and improving the overall robustness and regulation accuracy of the system.

[0040] Obtaining a premixed gas with a stable flow rate in the premixing control module also includes stabilizing the pressure of the dry low-calorific value gas through a pressure stabilizing device. Based on the pressure deviation in the filtered inlet pressure signal, a proportional gain adjustment is used to generate a control output amplitude, and the steady-state error is eliminated in combination with an integral time constant to obtain a low-calorific value gas with a stable pressure.

[0041] In this embodiment, to further enhance the premixing control module's ability to ensure gas flow stability, a pressure stabilization device and a proportional-integral control strategy are introduced based on the filtered signal to achieve precise control of inlet pressure. After vapor-liquid separation and drying, the gas source enters the pressure stabilization unit. The front end of this unit receives the inlet pressure signal, which has been processed by a low-pass filtering algorithm. This signal represents the current actual gas pressure and is compared in real time with the preset target inlet pressure. The difference between the two is the "pressure deviation," which reflects the difference between the current system operating state and the ideal state. The system initiates a control strategy based on this pressure deviation: First, the proportional gain control module linearly amplifies the deviation. Specifically, when the pressure deviation is large, the control system outputs a larger control command; as the pressure deviation approaches zero, the control amplitude decreases accordingly, ensuring a sensitive system response. The proportional gain determines the sensitivity of the control. Setting it too high may cause oscillation, while setting it too low may result in sluggish control. To address the "steady-state error" that can occur with proportional control—that is, the system's inability to maintain the actual pressure at the set target for an extended period without external disturbances—the present invention further introduces an integral control mechanism. The system accumulates pressure deviations over a continuous period of time and applies them to the control signal weighted by the integral time constant. Simply put, if the pressure deviates from the set value for a long period of time, even if the deviation is small, the integrator will gradually accumulate this error, generating an additional correction factor, which drives the control valve for further fine-tuning, ultimately eliminating the error. The setting of the integral time constant determines the duration and slowness of the correction effect and is generally adjusted based on the system's response speed. The combined action of proportional gain adjustment and integral correction forms a common proportional-integral control strategy, the output of which is used to drive the gas control valve (such as an electric control valve or a servo control valve) in the pressure stabilization device. The control valve finely controls the opening of the gas channel to maintain the passing gas pressure near the set target, achieving continuous stabilization of the inlet gas pressure. The low calorific value gas after pressure stabilization will be sent to the subsequent mixing chamber, premixed with air in a certain proportion, and then enter the combustion module to complete the front-end gas source regulation part of the entire combustion control process.

[0042] By introducing a proportional-integral control mechanism based on filtering, this implementation significantly improves the system's response speed and regulation accuracy to gas source pressure fluctuations. In particular, when there are long-term slight deviations in the inlet pressure, it can achieve active fine-tuning and ultimately eliminate residual errors, ensuring the long-term stability of the system. This control method not only optimizes the stability of the premixed gas, but also delays mechanical fatigue of the valves and actuators, helping to extend equipment maintenance cycles and improve operational reliability. In addition, this pressure stabilization solution has good flexibility in adapting to different gas source fluctuation conditions and can be widely used in various low calorific value gas scenarios such as coke oven gas, biogas, and associated gas.

[0043] Obtaining a premixed gas with a stable flow rate in the premixing control module also includes real-time detection of the methane concentration in the low calorific value gas with stable pressure by an infrared gas analyzer, querying a pre-established dynamic proportioning database, obtaining a flow proportioning coefficient corresponding to the methane content, and determining the methane content proportioning parameters.

[0044] In this embodiment, the system incorporates an infrared gas analyzer to address the high volatility of low calorific value gas composition. This system monitors the pressure-stabilized gas before it enters the premixing module in real time, focusing specifically on changes in methane content. This analyzer dynamically adjusts the air-to-gas ratio by querying a pre-set database, achieving intelligent air-fuel ratio adjustment and precise matching of the premix flow rate. The infrared gas analyzer illuminates the gas under test with an infrared light source of a specific wavelength. Because methane molecules selectively absorb infrared light of this wavelength, the system measures the attenuation of the light intensity to infer the methane volume fraction. These measurements are output to the central control system as a real-time data stream, typically updated every few seconds, providing real-time visibility into fluctuations in the gas source composition. The system pre-establishes a dynamic ratio database, which, through experimental calibration and engineering experience, records the optimal air-to-gas flow ratio for different methane volume fractions. For example, if the methane concentration is 30%, the air-to-gas volume ratio is 6.5:1; if the methane concentration drops to 20%, it must be increased to 7.8:1 to maintain the same calorific value output. The database covers the full range of methane concentrations from 10% to 60%, and supports interpolation to obtain intermediate values. When the infrared analyzer detects the current methane content in the gas, the control system automatically reads the corresponding database entry to obtain the air-gas flow ratio coefficient required at the current concentration. This coefficient is called the "methane content ratio parameter" and is then transmitted to the air control valve control module. Based on the current gas flow feedback, the volume of air to be delivered is dynamically calculated to adjust the premixed gas composition to ensure that the mixing ratio in the premixing chamber is always within the control range for efficient combustion. This adjustment process is automatically repeated after each methane concentration refresh, allowing the system to respond quickly and correct the mixing ratio in a timely manner even when the gas source input has rapidly fluctuating methane content, ensuring the stability and efficiency of the combustion process.

[0045] This implementation significantly improves the system's adaptability to fluctuating low-calorific-value gas composition, particularly when processing multi-component, frequently changing gases such as coke oven gas, biogas, or oilfield associated gas. By integrating an infrared analyzer with a dynamic database, real-time tracking of methane content allows for precise adjustment of air supply, preventing the risk of incomplete combustion or detonation caused by air-fuel ratio imbalance. This strategy further enhances system combustion efficiency, reduces emissions, and extends the life of the ceramic burner, demonstrating its industrial applicability and potential for widespread adoption.

[0046] Obtaining a premixed gas with a stable flow rate in the premixing control module also includes obtaining the premixed gas by using a premixing device to adjust the mixing ratio of the low calorific value gas with stable pressure and air based on the filtered inlet pressure signal and the methane content ratio parameter using multivariable collaborative control.

[0047] Building on the aforementioned filtering and composition detection, this embodiment further incorporates a multivariable coordinated control mechanism within the premixing device to precisely adjust the gas-air mixture ratio. This control mechanism comprehensively considers two core variables: the real-time inlet gas pressure and the methane content ratio parameter. These two variables work together to ensure that the premixed gas generated maintains a stable flow rate and balanced composition under varying operating conditions, meeting the requirements for flameless combustion. First, the inlet pressure signal is filtered and outputs the actual pressure value of the current gas source, representing the dynamic trend of the available gas flow rate. An increase in pressure indicates an increase in gas supply, requiring an appropriate increase in air supply to maintain a constant air-fuel ratio. Conversely, a decrease in pressure requires a simultaneous reduction in air flow to prevent incomplete combustion due to excessive air in the mixed gas. Second, the methane content ratio parameter is derived from real-time methane concentration measurements by an infrared gas analyzer and combined with a dynamic ratio database. This parameter determines the theoretical air volume ratio required for the current mixture and is the core basis for the control system to maintain calorific value balance. In multivariable coordinated control, the premixing device control unit receives these two types of input information and makes real-time decisions through an embedded logic module. The control unit first assesses the gas supply capacity corresponding to the current gas pressure, then queries the target air flow ratio corresponding to the methane ratio parameter. It then calculates the appropriate air valve opening and gas throttling ratio. This calculation considers not only the individual trends of the two parameters but also their interaction. For example, when the gas pressure rises slightly while the methane concentration decreases, the system requires comprehensive processing to avoid misjudgments that could lead to excess or insufficient air. The control logic employs a layered structure: the base layer performs ratio calculations and responses, prioritizing maintaining the set ratio target. The optimization layer smoothly adjusts to sudden changes through historical data tracking, disturbance estimation, and response lag compensation. The overall control process can be viewed as a real-time trajectory optimization within a two-dimensional parameter space, ensuring that the mixed gas remains within the optimal range for calorific value output efficiency. After adjusting the mixture ratio, the premixing unit introduces the gas and air into the mixing chamber at the set ratio. Using built-in spoilers or static mixing elements, the gas mixture is homogeneously mixed, ultimately forming a stable premixed gas suitable for flameless combustion, which is then fed into the subsequent flashback prevention and combustion modules.

[0048] Through a multivariable coordinated control strategy, this invention achieves a coordinated response to input pressure fluctuations and changes in methane concentration. This allows for a stable output of highly consistent premixed gas under complex load and dynamic composition changes, thereby improving the thermal efficiency and safety of the entire combustion system. Compared to single-variable or sequential control approaches, this control strategy significantly reduces response lag, ratio errors, and system oscillation. It is particularly suitable for use in scenarios with uneven fuel quality, such as oil fields, coking plants, and biogas, offering greater adaptability and robustness.

[0049] Obtaining a stable flow of premixed gas in the premixing control module also includes driving the gas delivery pump through a variable frequency motor, using variable frequency speed control to precisely adjust the pump speed, combining real-time speed feedback to monitor the operating status, and using differential predictive control to adjust the premixed gas flow based on the filtered inlet pressure signal and methane content ratio parameters. If the methane concentration is lower than the preset methane concentration threshold, the low methane protection logic is triggered to reduce the pump output power to obtain a stable flow of premixed gas.

[0050] In this embodiment, to achieve precise control of the low-calorific-value gas supply flow rate, a gas delivery pump driven by a variable-frequency motor is incorporated into the premix control module. This, combined with a differential predictive control algorithm and a real-time feedback mechanism, improves the system's response speed and accuracy in regulating gas flow, ensuring the generated premixed gas remains stable and controllable. First, the variable-frequency motor, serving as the core driver, dynamically adjusts its output frequency based on an external control signal, thereby varying the speed of the gas delivery pump. Pump speed changes directly affect the gas delivery flow rate per unit time and are a key factor in regulating the premixed gas supply. The system determines the stability of the gas source based on the filtered inlet pressure signal and, combined with the flow ratio parameters corresponding to the current methane concentration, determines the target gas supply volume. To achieve even more precise control response, a "differential predictive control" mechanism is incorporated into the control logic. This mechanism analyzes the short-term trends of methane content and pressure signals to predict their future impact on gas demand. For example, if the system detects a slow decrease in methane concentration and a stable pressure, it can predict that it may need to reduce the air mixture and slightly reduce the pump speed to maintain a balanced air-fuel ratio. Conversely, if it detects an upward trend in concentration or a rebound in pressure, it can proactively increase the pump speed to improve gas supply capacity. This prediction isn't based on a single moment in time, but rather on trend analysis based on the differential relationship between continuous data over a short period of time, allowing the control target to be adjusted in real time. Furthermore, the system monitors the actual motor speed through real-time feedback, comparing the measured speed every second with the control target to determine whether the actuator is responding properly. If the error exceeds a preset tolerance, the system will automatically correct the control signal or issue an alarm to prevent gas flow accuracy from being affected by response lag or execution deviation. To address the potential for a critical lower limit of methane concentration in low-calorific-value gases, the system incorporates "low methane protection logic." When the infrared analyzer detects that the methane concentration is lower than the preset minimum safety concentration threshold, such as 15% volume fraction, the system immediately triggers the protection mode, reduces the output power of the variable frequency motor to the lowest working gear, significantly reduces the gas supply rate, and prevents dangerous conditions such as unstable combustion, flameout or flashback of the mixed gas below the flammability boundary. At the same time, the system will start the alarm prompt to prompt the operator to check the gas source composition to ensure safe operation. The above control mechanism combines the actuator adjustment capability with the real-time feedback of multivariable signals to achieve dynamic adaptive adjustment under the complex working conditions of low calorific value gas, and continuously outputs premixed gas with stable flow and controllable composition to support the stable progress of the subsequent flameless combustion process.

[0051] By incorporating a variable-frequency motor, differential predictive control, and a methane concentration protection mechanism, this system achieves high-precision, real-time control of low-calorific-value gas flow. This system provides proactive regulation in response to methane content fluctuations or pressure disturbances, significantly outperforming traditional fixed-frequency drive or single-variable feedback systems. Furthermore, the system incorporates fault protection and abnormal condition alarms, further enhancing operational safety and intelligence. It is suitable for deployment in industrial sites where associated gas fluctuates frequently or compositionally varies dramatically.

[0052] The premixing control module includes a methane content detection device and a ratio regulating valve. The ratio regulating valve dynamically adjusts the mixing ratio of air and low calorific value gas according to the output signal of the methane content detection device.

[0053] In this embodiment, to further improve the response accuracy and control flexibility of the low-calorific value associated gas and air mixing ratio, the premixing control module is equipped with a methane content detection device and a ratio control valve. These two devices work together to dynamically match the air supply with the gas composition, ensuring a stable calorific value output for the premixed gas. The methane content detection device typically employs a non-dispersive infrared sensor to perform real-time analysis of the infrared absorption characteristics of methane molecules in the low-calorific value gas flow. As the mixed gas flows through the detection chamber, methane molecules absorb infrared light in a specific wavelength range, with the degree of absorption proportional to their concentration. The device converts the acquired absorption signal into methane concentration data and outputs it as an analog voltage or digital signal to the premixing control module's main controller. Upon receiving the methane content detection value, the controller first compares it with the set target combustion conditions. Since methane is the primary combustible component in low-calorific value gas, its concentration directly affects the combustion calorific value per unit volume of gas. Therefore, the system sets the corresponding air demand based on the different concentrations. If the methane content is high, a relatively small amount of air is required to prevent an overly lean mixture and incomplete combustion. Conversely, if the methane content is low, an appropriate increase in air supply is required to improve combustion efficiency and fully oxidize residual hydrocarbons. The proportional control valve, as the core of the air supply control, is driven by an electric actuator, and its opening is continuously adjusted according to a control signal. When the methane concentration fluctuates, the control system calculates the required air volume change in real time and issues a control command to adjust the valve opening, thereby achieving instant adjustment of the air flow. The control logic generally uses a proportional algorithm, linearly adjusting the valve opening based on the amplitude of the methane detection signal. Hysteresis compensation and disturbance suppression mechanisms are also introduced to avoid frequent fluctuations. The entire control process maintains a closed-loop operation mode, namely a continuous cycle of detection, judgment, control, and feedback. This ensures that even under conditions where the low calorific value gas composition frequently changes, the composition of the premixed gas remains within an acceptable range for combustion conditions, effectively supporting thermal field stability during the flameless combustion phase.

[0054] This implementation achieves intelligent dynamic adjustment of the gas mixing process through real-time methane concentration detection and linked control of the ratio control valve, avoiding mixing deviations and combustion instability caused by fixed ratio settings. This structure requires no complex modeling or database support, offers rapid response, and features a simple structure, making it particularly suitable for small or site-constrained industrial systems. Furthermore, this configuration is compatible with other gas concentration detection devices, offering excellent scalability and field adaptability.

[0055] The flame arrester in the anti-backfire module utilizes a metal corrugated structure or a ceramic honeycomb structure to enhance flashback suppression. In this embodiment, to further enhance system safety during gas transmission, particularly preventing flame backflow caused by factors such as unstable combustion and transient reverse pressure, a structurally optimized flame arrester is selected. This structure, which can be a metal corrugated or ceramic honeycomb structure, leverages the structural influence on the flame propagation path and heat conduction behavior to effectively enhance flashback suppression. The metal corrugated flame arrester operates by creating a multi-stage deflection path through its complex internal folded metal sheet channels. This forces the gas to continuously change direction during passage, generating intense turbulence and shear effects between multiple layers. When a flame enters this structure, the kinetic energy of the flame front and the gas is rapidly dissipated. At the same time, the excellent thermal conductivity of the metal corrugated sheets rapidly absorbs the heat transferred from the flame, thereby reducing the flame temperature and preventing further flame propagation. This structure offers excellent blocking performance for high-speed, short-range flames and is suitable for operating environments with high flashback frequencies or dynamic loads. On the other hand, the ceramic honeycomb structure flame arrester relies on the high heat capacity and high temperature resistance of the ceramic material. The interior is arranged with porous uniform channels. The gas maintains a high flow rate during the flow, but the flame is not easy to penetrate. Its working mechanism is mainly through heat dissipation. That is, when the flame front enters the honeycomb channel, the ceramic pore wall absorbs heat rapidly, the core temperature of the flame drops significantly, and the combustion reaction rate drops sharply, causing the flame to go out. In addition, the honeycomb structure naturally has a large specific surface area, which further enhances the heat exchange efficiency and improves the backfire blocking ability. In specific applications, the system selects the appropriate flame arrester structure according to the type of gas, pressure range and operating conditions: metal corrugation is suitable for scenarios with high gas flow rate and the need for rapid heat dissipation, while ceramic honeycomb is more suitable for complex gas environments with high temperature, high humidity or the presence of corrosive impurities. Both structures can be integrated into standard modules and are easy to replace and maintain, ensuring the long-term safe and reliable operation of the system.

[0056] This implementation effectively enhances the system's safety performance against flashback by utilizing a structurally optimized flame arrester. The metal corrugated structure offers fast response and strong suppression, adapting to complex airflow dynamics; while the ceramic honeycomb structure offers high-temperature resistance and long-lasting flame resistance, making it suitable for use in harsh environments. Both significantly reduce the risk of equipment damage or system flameout due to flashback, providing reliable assurance for stable and continuous system operation while also enhancing the overall safety level and engineering suitability of the gas system.

[0057] like Figure 2 As shown, the low calorific value associated gas ultra-low nitrogen flameless combustion system also includes an inlet pipeline valve group 1, a vapor-liquid separation device 2, a flow device 3, a pressure stabilizing device 4 and a gas main pipeline valve group 5 connected in sequence, the gas main pipeline valve group 5 is respectively connected to a gas cut-off device 8 and a gas ignition pipeline valve group 9, the gas ignition pipeline valve group 9 is connected to a flame arrester 12, the flame arrester 12 is connected to a flameless combustion device 13, the flameless combustion device 13 is connected to a boiler 14, the gas cut-off device 8 is connected in series with an electric valve 10, the electric valve 10 is connected to a combustion-supporting pipeline valve group 11, the combustion-supporting pipeline valve group 11 is also connected to the flameless combustion device 13, the inlet pipeline valve group 1 is also connected to an inlet combustion-supporting valve group 6, the inlet combustion-supporting valve group 6 is connected to a fan 7, and the fan 7 is also connected to the combustion-supporting pipeline valve group 11.

[0058] This embodiment utilizes modular partitioning and process-based integrated design for the system structure, ensuring clear functionalities and efficient coordination among various components, while also enabling safe combustion, stable heat supply, and rapid response control for abnormal conditions. During system startup, low-calorific-value gas first enters the system through inlet pipeline valve group 1. This valve group, equipped with on / off control, pressure detection, and leak prevention functions, serves as the primary control point for gas entering the system. The gas then enters vapor-liquid separation device 2, which performs preliminary purification of the raw gas, removing liquid impurities such as moisture and oil mist, ensuring a pure and dry gas source and facilitating subsequent combustion efficiency and safety improvements. The separated gas flows into flow device 3, equipped with a high-precision gas mass flow meter that monitors gas flow in real time and feeds data back to the main control system for gas-air ratio calculation and combustion control parameter adjustment. The gas then enters pressure stabilization device 4, which regulates and buffers fluctuations in the gas supply pressure, ensuring that the downstream combustion device receives gas at a stable pressure, ensuring the continuity and consistency of the combustion reaction. The gas after pressure stabilization enters the main gas pipeline valve group 5, which is a system diversion node. One of its paths leads to the gas shut-off device 8, and the other path leads to the gas ignition pipeline valve group 9. During the system startup phase, the ignition valve group is opened first, and the low calorific value gas enters the flame arrester 12 through this path and is sent to the flameless combustion device 13 for pre-combustion. The heat generated by the combustion is conducted to the boiler 14 for heating water or steam output. When the combustion is stable, the system automatically opens the main gas path, and the gas shut-off device and the subsequent electric valve 10 are connected in series to form a safety logic loop that controls the main on and off. The electric valve automatically adjusts whether the main gas path is open according to the control system instructions, playing a role of rapid response protection. The electric valve is connected to the combustion-supporting pipeline valve group 11, which merges the main gas flow and the auxiliary air source. In order to ensure the stability of the combustion-supporting air supply, the inlet pipeline valve group 1 is also connected to the inlet combustion-supporting valve group 6, and further connected to the fan 7. The fan, serving as a source of combustion air, also delivers its output through pipelines to the combustion-supporting valve block 11, where it mixes with the natural gas and enters the flameless combustion device 13, improving combustion efficiency and ensuring flameless stability. The entire system feeds back multiple detection signals (including gas flow, pressure, temperature, and combustion status) to the central control module, enabling multi-channel coordinated regulation, dynamic flow distribution, and emergency control for abnormal conditions. This ensures efficient, stable, and low-emission combustion of low-calorific-value gases under all operating conditions.

[0059] This implementation clearly categorizes key modules, ensuring smooth cascading and seamless functional integration, creating a complete, closed-loop, flameless combustion treatment path for low-calorific-value gases. This system architecture boasts robust operational stability, responsive control, and comprehensive safety and security features, making it particularly suitable for industrial sites with high water content, fluctuating composition, and unstable gas supply sources. Its flexible configuration and ease of maintenance facilitate rapid deployment and system integration for industrial users.

[0060] Under complex working conditions, the gas ignition pipeline can be set up as an independent subsystem and connected to an auxiliary ignition source (such as electric heating or fuel ignition); a flow limiter or a check valve can be installed between the gas main line valve group 5 and the electric valve 10 to further improve safety; the fan system can use a variable frequency speed regulation fan to achieve intelligent combustion-supporting air supply control linked to the combustion load; the entire valve group and pipeline system can also adopt a modular combination design to facilitate maintenance, replacement and site adaptation.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A low calorific value associated gas ultra-low nitrogen flameless combustion system, characterized in that: include: The gas acquisition module obtains low calorific value gas through the inlet pipeline valve group to obtain dry low calorific value gas; The premixing control module uses multivariable coordinated control to adjust the mixing ratio of low calorific value gas and air with stable pressure to obtain premixed gas with stable flow rate; The anti-backfire module uses a flame arrester to perform anti-backfire treatment on the premixed gas with stable flow. A flow sensor is used to obtain the flow data of the processed premixed gas. Combined with load adaptive regulation, the gas transmission efficiency is optimized to obtain the premixed gas with anti-backfire treatment. The flameless combustion module uses a porous ceramic burner to flamelessly burn the premixed gas that has been treated for backfire prevention. The recirculation channel uses feedback from the combustion chamber temperature and flue gas exhaust temperature, combined with dynamic power distribution to adjust the recirculation airflow ratio to obtain a combustion gas with a balanced thermal field. The flame detection module uses a flame probe to collect the flame state spectral characteristics of the combustion gas with thermal field equilibrium, uses a temperature sensor to obtain the combustion chamber gas temperature and flue gas exhaust temperature, and uses a flow sensor to obtain the premixed gas flow data for anti-backfire treatment. The control signal smoothing process is used to generate a combustion state data set; A stable output module generates a first control signal, uses the first control signal to adjust the airflow distribution in the ceramic pores of the porous ceramic burner, and optimizes operating parameters in combination with motor temperature rise monitoring and fault diagnosis signals. If the flow data and combustion chamber temperature meet a preset deviation threshold, a second control signal is generated, which is used to lock the burner parameters to obtain a stable combustion output; The premixing control module further comprises the step of continuously collecting inlet pressure data of the dry low calorific value gas through a high-precision pressure sensor, processing the pressure signal using a low-pass filtering algorithm, and obtaining a filtered inlet pressure signal. The method of obtaining the premixed gas with a stable flow rate in the premixing control module further includes detecting the methane concentration in the low calorific value gas with a stable pressure in real time by using an infrared gas analyzer, querying a pre-established dynamic ratio database, obtaining a flow ratio coefficient corresponding to the methane content, and determining the methane content ratio parameter; The premixing control module further comprises obtaining a premixed gas with a stable flow rate by using a premixing device to adjust the mixing ratio of the low calorific value gas with stable pressure and air using multivariable coordinated control according to the filtered inlet pressure signal and the methane content ratio parameter to obtain the premixed gas; Obtaining a stable flow of premixed gas in the premixing control module also includes driving a gas delivery pump through a variable frequency motor, using variable frequency speed control to precisely adjust the pump speed, combining real-time speed feedback to monitor the operating status, and using differential predictive control to adjust the premixed gas flow rate based on a filtered inlet pressure signal and methane content ratio parameters. If the methane concentration is lower than a preset methane concentration threshold, low methane protection logic is triggered to reduce the pump output power to obtain a stable flow of premixed gas.

2. The ultra-low nitrogen flameless combustion system for low calorific value associated gas according to claim 1, characterized in that: The gas acquisition module uses a gas-liquid separation device to separate liquid impurities in the gas to obtain dry low calorific value gas.

3. The ultra-low nitrogen flameless combustion system for low calorific value associated gas according to claim 1, characterized in that: Obtaining a premixed gas with a stable flow rate in the premixing control module also includes performing pressure stabilization processing on the dry low-calorific value gas through a pressure stabilization device, using a proportional gain adjustment to generate a control output amplitude based on the pressure deviation in the filtered inlet pressure signal, and combining an integral time constant to eliminate steady-state errors to obtain a low-calorific value gas with a stable pressure.

4. The ultra-low nitrogen flameless combustion system for low calorific value associated gas according to claim 1, characterized in that: The premixing control module includes a methane content detection device and a ratio regulating valve. The ratio regulating valve dynamically adjusts the mixing ratio of air and low calorific value gas according to the output signal of the methane content detection device.

5. The ultra-low nitrogen flameless combustion system for low calorific value associated gas according to claim 1, characterized in that: The flame arrester in the anti-backfire module is a metal corrugated structure or a ceramic honeycomb structure, which is used to improve the backfire suppression effect.

6. The ultra-low nitrogen flameless combustion system for low calorific value associated gas according to claim 1, characterized in that: The invention also includes an inlet pipeline valve group (1), a vapor-liquid separation device (2), a flow device (3), a pressure stabilizing device (4) and a gas main pipeline valve group (5) connected in sequence, wherein the gas main pipeline valve group (5) is respectively connected to a gas cut-off device (8) and a gas ignition pipeline valve group (9), the gas ignition pipeline valve group (9) is connected to a flame arrester (12), the flame arrester (12) is connected to a flameless combustion device (13), the flameless combustion device (13) is connected to a boiler (14), the gas cut-off device (8) is connected in series with an electric valve (10), the electric valve (10) is connected to a combustion-supporting pipeline valve group (11), the combustion-supporting pipeline valve group (11) is also connected to the flameless combustion device (13), the inlet pipeline valve group (1) is also connected to an inlet combustion-supporting valve group (6), the inlet combustion-supporting valve group (6) is connected to a fan (7), and the fan (7) is also connected to the combustion-supporting pipeline valve group (11).

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