A method for controlling oxygen-enriched combustion gas supply of a chain grate rotary kiln

Abstract

The present application relates to the technical field of pellet induration control, and relates to a kind of chain grate rotary kiln oxygen-enriched combustion gas supply control methods.The present application is based on the temperature distribution data of grate bed surface in each temperature zone of chain grate, obtains temperature deviation value by combining corresponding target temperature interval, generates initial opening degree adjustment instruction of throttle valve, determines change state according to the current running speed of grate bed, determines partition gas supply control amount with temperature zone initial gas supply set value, combines combustion air fan real-time air volume and oxygen-enriched gas supply pipeline real-time flow, adjusts and regulates throttle valve opening degree and combustion air fan air volume according to target oxygen-enriched mixing ratio, detects chain grate discharge end incoming ferrous oxide content and converts into oxidation oxygen demand coefficient at the same time, obtains target gas supply amount by combining oxygen concentration feedback adjustment amount fusion, sets gas supply response compensation time according to material transmission time delay, generates target gas supply amount control instruction, improves oxygen-enriched combustion efficiency and pellet induration quality stability.

Description

Technical Field

[0001] This invention relates to the field of pellet roasting control technology, and specifically to a method for controlling the oxygen-enriched combustion gas supply in a rotary kiln with a chain grate. Background Technology

[0002] The chain grate rotary kiln system is a key piece of equipment in pellet production. It uses a chain grate to dry and preheat green pellets before conveying them to a rotary kiln for high-temperature roasting. During roasting, oxygen-enriched combustion technology is used to improve combustion efficiency and enhance the pellet oxidation reaction. However, the chain grate rotary kiln system involves complex operating conditions such as multi-temperature zone coordination and material transport delays. The precision of gas supply control directly affects the preheating quality, oxidation level, and thermal stability of the rotary kiln. How to dynamically and precisely control the oxygen-enriched gas supply based on the actual thermal state of each temperature zone of the chain grate, the grate bed operating conditions, and the oxidation characteristics of the material is a technical challenge for improving the operating efficiency and product quality of the chain grate rotary kiln system.

[0003] In the prior art, Chinese Patent Publication No. CN113566563A discloses an intelligent combustion control method for a rotary kiln. This method collects the first temperature of the firing zone inside the rotary kiln and determines the pulverized coal flow rate per unit time based on the first temperature. Based on the length of the firing zone and the pulverized coal flow rate per unit time, it determines the total air flow rate per unit time at the air outlet of the rotary kiln. Based on the pulverized coal flow rate per unit time, it determines the air flow rate per unit time required for complete combustion of the pulverized coal. Combined with the total air flow rate per unit time, it determines the required waste gas flow rate per unit time. Based on the pulverized coal flow rate per unit time, the air flow rate per unit time, and the waste gas flow rate per unit time, it adjusts the pulverized coal outlet valve and the corresponding valve of the blower to ensure that the oxygen is just right for complete combustion of the pulverized coal, thereby reducing energy waste and environmental pollution.

[0004] The existing technology has the following technical defects: 1. The existing technology only determines the amount of pulverized coal and the total amount of air based on the temperature data of the rotary kiln firing zone. It does not monitor and control the temperature distribution of the grate surface in each temperature zone of the chain grate machine, and cannot allocate and correct the air supply according to the actual thermal demand differences in each temperature zone of the preheating section of the chain grate machine. This results in insufficient temperature control accuracy in each temperature zone of the chain grate machine, making the enhanced effect of oxygen-enriched combustion unstable, affecting the uniformity of green pellet preheating and the subsequent calcination quality of the rotary kiln.

[0005] 2. Existing technology determines the amount of air and exhaust gas introduced based on the amount of pulverized coal passed per unit time. This is a feedforward ratio control based on the amount of fuel. It does not take into account the ferrous oxide content of the material coming from the discharge end of the chain grate for feedback adjustment. It cannot dynamically adjust the oxygen supply according to the actual oxidation state of the material, resulting in a mismatch between the oxygen supply and the actual oxidation demand of the material, causing energy waste or insufficient oxidation, which affects the oxidation roasting effect of the pellets.

[0006] 3. Existing technologies do not consider the material transmission time delay between the chain grate and the rotary kiln head, as well as the transmission delay of oxygen-enriched gas in the supply pipeline, when adjusting the valve opening. This results in a lack of compensation response in gas supply regulation, causing gas supply regulation to lag behind the actual changes in the material state, affecting the stability of combustion at the rotary kiln head and the oxidative roasting efficiency of the pellets. Summary of the Invention

[0007] The present invention aims to overcome the defects in the prior art and provide a method for controlling the oxygen-enriched combustion gas supply of a rotary kiln with a chain grate machine. This method achieves control of initial adjustment of zoned temperature control, grate speed linkage gas supply regulation, oxygen-enriched blending and synergistic correction, and fusion of oxidation demand and flue gas feedback, thereby improving the oxygen-enriched combustion efficiency and the stability of pellet roasting quality.

[0008] The technical solution adopted by the present invention to solve its technical problem is as follows: The present invention provides a method for controlling the oxygen-enriched combustion gas supply of a rotary kiln for a chain grate machine, including: S1, based on the temperature distribution data of the surface of the grate bed in each temperature zone of the chain grate machine, combined with the temperature deviation value obtained by comparing with the target temperature range of the corresponding temperature zone, generating an initial opening adjustment command for the throttle valve.

[0009] S2. Determine the corresponding change state of the grate's operating speed based on the current operating speed of the grate, and determine the zoned gas supply control amount for each temperature zone based on the change state and the initial gas supply setting value of each temperature zone.

[0010] S3. Based on the real-time air volume of the combustion fan and the real-time flow rate of the oxygen-enriched gas supply pipeline, the opening of the throttle valve and the air volume of the combustion fan are corrected and adjusted according to the target oxygen enrichment mixing ratio and the zoned gas supply control amount.

[0011] S4. Real-time detection of the ferrous oxide content of the incoming material at the discharge end of the chain grate, conversion of the ferrous oxide content into the oxidation oxygen demand coefficient, obtaining the oxygen concentration feedback adjustment amount based on the oxygen concentration of the flue gas at the rotary kiln head, and integrating it with the oxidation oxygen demand coefficient to obtain the target air supply.

[0012] S5. Set the gas supply response compensation time based on the material transmission time delay from the chain grate machine to the rotary kiln head, and generate the target gas supply volume control command for oxygen-enriched gas in combination with the target gas supply volume.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention obtains the temperature distribution data of the grate surface of each temperature zone of the chain grate machine, compares it with the target temperature range of the corresponding temperature zone to obtain the temperature deviation value, and generates the initial opening adjustment command of the throttle valve to realize the fine-grained zonal control of the gas supply of each temperature zone of the chain grate machine, so that the temperature of each temperature zone can accurately approach the target temperature range, improve the temperature uniformity and thermal stability of the preheating section of the chain grate machine, provide a guarantee for the subsequent calcination quality of the rotary kiln, and reduce the quality fluctuation of the subsequent rotary kiln calcination.

[0014] (2) The present invention determines the change state based on the current operating speed of the grate, determines the zoned gas supply control amount based on the change state and the initial gas supply setting value of each temperature zone, and combines the real-time air volume of the combustion blower and the real-time flow of the oxygen-enriched gas supply pipeline. Based on the target oxygen-enriched mixing ratio, the opening of the throttle valve and the air volume of the combustion blower are corrected and adjusted to achieve dynamic matching between the gas supply and the operating state of the grate and precise control of the oxygen-enriched mixing ratio. This ensures that the actual oxygen concentration in the furnace is stably close to the target value, fully exerts the strengthening effect of oxygen-enriched combustion, and improves the stability and combustion efficiency of oxygen-enriched combustion.

[0015] (3) This invention detects the ferrous oxide content of the material at the discharge end of the chain grate in real time and converts it into an oxidation oxygen demand coefficient. Combined with the oxygen concentration of the flue gas at the kiln head of the rotary kiln, the oxygen concentration feedback adjustment amount is obtained. The target gas supply amount is obtained by superimposing and integrating the oxygen supply amount. This achieves a precise match between the oxygen supply amount and the actual oxidation demand of the material, so that the oxygen-enriched gas supply can be dynamically adjusted according to the oxidation state of the material and the flue gas feedback, thereby improving the oxidation roasting efficiency and energy utilization rate of the pellets.

[0016] (4) The present invention sets the gas supply response compensation time based on the material transmission time delay from the chain grate machine to the rotary kiln head, and combines the target gas supply volume control command to generate oxygen-enriched gas with the target gas supply volume, thereby realizing the forward-looking time compensation of gas supply control, effectively eliminating the control lag caused by material transmission and gas pipeline transmission, ensuring the synchronization between the combustion of the rotary kiln head and the actual state of the material, and improving the stability of the pellet roasting process and the consistency of product quality. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the method steps of the present invention;

[0019] Figure 2 This is a schematic diagram illustrating the steps for correcting and adjusting the throttle valve opening and the combustion fan air volume in this invention.

[0020] Figure 3 This is a schematic diagram illustrating the steps of the target gas supply control command for generating oxygen-enriched gas in this invention. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0022] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0023] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0024] Please see Figure 1 As shown, the present invention provides a method for controlling the oxygen-enriched combustion gas supply of a rotary kiln for a chain grate machine, comprising: S1, based on the temperature distribution data of the surface of the grate bed in each temperature zone of the chain grate machine, and by comparing the temperature deviation value with the target temperature range of the corresponding temperature zone, generating an initial opening adjustment command for the throttle valve.

[0025] S2. Determine the corresponding change state of the grate's operating speed based on the current operating speed of the grate, and determine the zoned gas supply control amount for each temperature zone based on the change state and the initial gas supply setting value of each temperature zone.

[0026] S3. Based on the real-time air volume of the combustion fan and the real-time flow rate of the oxygen-enriched gas supply pipeline, the opening of the throttle valve and the air volume of the combustion fan are corrected and adjusted according to the target oxygen enrichment mixing ratio and the zoned gas supply control amount.

[0027] S4. Real-time detection of the ferrous oxide content of the incoming material at the discharge end of the chain grate, conversion of the ferrous oxide content into the oxidation oxygen demand coefficient, obtaining the oxygen concentration feedback adjustment amount based on the oxygen concentration of the flue gas at the rotary kiln head, and integrating it with the oxidation oxygen demand coefficient to obtain the target air supply.

[0028] S5. Set the gas supply response compensation time based on the material transmission time delay from the chain grate machine to the rotary kiln head, and generate the target gas supply volume control command for oxygen-enriched gas in combination with the target gas supply volume.

[0029] Considering that the preheating section of a chain grate machine is typically divided into multiple temperature zones, such as a drying zone, a first preheating zone, and a second preheating zone, and that the thermal requirements of each zone differ, failure to monitor and control the temperature distribution on the grate surface in real time will cause the temperature in each zone to deviate from the target range, affecting the uniformity of green pellet preheating and the dehydration effect. Therefore, it is necessary to collect temperature distribution data for each zone and generate initial opening adjustment commands for the throttle valves to achieve independent control of the air supply to each zone.

[0030] Based on this, the specific implementation of the initial opening adjustment command for generating the throttle valve in this invention includes: S11, setting up several temperature detection points on the surface of the grate in each temperature zone, collecting the temperature of each temperature detection point, and combining the spatial distance between all temperature detection points in each temperature zone and the center of the material layer, and performing weighted calculations to obtain the actual temperature of each temperature zone.

[0031] It should be noted that the temperature detection points are arranged at equal intervals along the length of the grate bed, covering the entire length of the corresponding temperature zone, and at equal intervals along the width of the grate bed, covering the effective working width of the grate bed; and thermocouple temperature sensors are installed at each temperature detection point to collect the temperature of the corresponding temperature detection point.

[0032] Preferably, in a specific embodiment of the present invention, the present invention constructs temperature weighting coefficients for each temperature detection point based on spatial distance, and performs weighted calculations on the temperatures of each temperature detection point to obtain the actual temperature of each temperature zone. The temperature weighting coefficients are negatively correlated with spatial distance, and a weighting allocation method based on a Gaussian kernel function is adopted. The calculation formula is as follows: ;in, For the first Temperature weighting coefficient for each temperature detection point For the first The spatial distance between each temperature detection point and the center of the material layer The space attenuation coefficient is determined based on a preset proportion of the grate width, for example, one-quarter of the effective working width of the grate.

[0033] S12. Retrieve the target temperature range corresponding to each temperature zone, compare the actual temperature of each temperature zone with the target temperature range of the corresponding temperature zone, and obtain the temperature deviation value and positive / negative sign of each temperature zone.

[0034] It should be noted that the target temperature range is a temperature control range pre-set according to the requirements of the pellet preheating process.

[0035] The temperature deviation value is calculated by subtracting the actual temperature from the limit of the target temperature range. For example, if the actual temperature is higher than the upper limit of the target temperature range, the temperature deviation value is calculated by subtracting the upper limit of the target temperature range from the actual temperature. If the actual temperature is lower than the lower limit of the target temperature range, the temperature deviation value is calculated by subtracting the lower limit of the target temperature range from the actual temperature. When the actual temperature is within the target temperature range, the temperature deviation value is zero.

[0036] The positive and negative signs indicate the direction of deviation of the actual temperature from the target temperature range. A positive value indicates that the actual temperature is higher than the target temperature range, and a negative value indicates that the actual temperature is lower than the target temperature range.

[0037] S13. Based on the temperature deviation value and positive / negative sign of each temperature zone, the opening adjustment direction and opening adjustment amount of the corresponding throttle valve for each temperature zone are mapped and generated, forming the initial opening adjustment command of the throttle valve.

[0038] Preferably, in a specific embodiment of the present invention, the method of mapping to generate the opening adjustment direction and opening adjustment amount of the throttle valve corresponding to each temperature zone is as follows: S131, extract the positive and negative signs of the temperature deviation value. If the temperature deviation value is positive, it is determined that the surface temperature of the grate bed in the corresponding temperature zone is higher than the target temperature range, and the opening adjustment direction of the throttle valve closing direction is generated.

[0039] S132. If the temperature deviation value is negative, it is determined that the surface temperature of the corresponding temperature zone grate is lower than the target temperature range, and the opening adjustment direction of the throttle valve is generated.

[0040] S133. Retrieve the pre-built mapping relationship between temperature deviation and opening adjustment step size, match the corresponding opening adjustment step size according to the temperature deviation value, and use it as the opening adjustment amount.

[0041] It should be noted that the pre-constructed mapping relationship between temperature deviation and opening adjustment step size is determined through historical data statistics. The larger the temperature deviation value, the larger the corresponding opening adjustment step size. The specific construction process is as follows: First, retrieve the temperature deviation values ​​of each temperature zone under different operating conditions and the corresponding throttle valve opening adjustment records from the historical operation records of the rotary kiln of the chain grate machine.

[0042] Then, different temperature deviation values ​​are extracted from the historical operation records, the historical operation records of each temperature deviation value are filtered, the distribution characteristics of all historical opening adjustment values ​​corresponding to each temperature deviation value are statistically analyzed, and the average opening adjustment step size is used as the opening adjustment step size of the corresponding temperature deviation value.

[0043] Finally, the temperature deviation value is correlated with the corresponding opening adjustment step size to establish a mapping relationship between temperature deviation and opening adjustment step size.

[0044] It should be noted that the mapping relationship is periodically updated and corrected during the operation of the rotary kiln of the chain grate machine based on the actual adjustment effect, in order to adapt to the drift of adjustment characteristics caused by changes in the operating conditions of the chain grate machine.

[0045] This invention acquires temperature distribution data of the grate surface in each temperature zone of the chain grate machine, compares it with the target temperature range of the corresponding temperature zone to obtain the temperature deviation value, and generates an initial opening adjustment command for the throttle valve. This enables precise zoned control of the air supply in each temperature zone of the chain grate machine, allowing the temperature of each zone to accurately approach the target temperature range. This improves the temperature uniformity and thermal stability of the preheating section of the chain grate machine, ensuring the quality of subsequent rotary kiln firing and reducing quality fluctuations in subsequent rotary kiln firing.

[0046] Considering that the operating speed of the grate directly affects the amount of material passing through each temperature zone and the heat exchange intensity per unit time, if the air supply to each temperature zone is not dynamically adjusted according to changes in the grate operating speed, a mismatch between material throughput and oxygen supply capacity will occur. During high-speed operation, insufficient oxygen supply per unit mass of material will affect preheating quality and oxidation degree, while during low-speed operation, excessive oxygen supply will lead to energy waste and an imbalance in the oxygen concentration within the furnace. Therefore, it is necessary to determine the changes in the grate operating speed and adjust the air supply to different zones to achieve dynamic matching between air supply and material throughput.

[0047] Based on this, the specific implementation of determining the zoned gas supply regulation amount in this invention includes: S21, comparing the current operating speed of the grate bed with the preset target operating speed range to determine the corresponding change state of the grate bed operating speed.

[0048] It should be noted that the method for determining the changing state of the grate's operating speed is as follows: when the current operating speed of the grate is within the target operating speed range, the operating speed of the grate is determined to be in a stable state.

[0049] When the current operating speed of the grate exceeds the upper limit of the target operating speed range, the operating speed of the grate is determined to be in an overspeed change state.

[0050] When the current operating speed of the grate is lower than the lower limit of the target operating speed range, the operating speed of the grate is determined to be in a low-speed change state.

[0051] S22. When the grate bed operating speed is stable, the initial air supply setting value of each temperature zone in the target operating speed range is used as the zone air supply control amount for the corresponding temperature zone.

[0052] When the grate operating speed is in an overspeed change state, the overspeed ratio between the current operating speed of the grate and the upper limit of the target operating speed range is obtained. The overspeed ratio is then amplified by the initial air supply setpoint to obtain the zoned air supply control amount.

[0053] When the grate's operating speed is in a low-speed variation state, the low-speed ratio between the current operating speed of the grate and the lower limit of the target operating speed range is obtained. The low-speed ratio is then used to reduce the initial air supply setpoint to obtain the zoned air supply control amount.

[0054] It should be noted that the calibration method for the initial gas supply setting value is as follows: under the steady-state conditions that the rotary kiln of the chain grate is in rated capacity operation, the grate bed running speed is in the target running speed range, and the temperature of each temperature zone is in the corresponding target temperature range, the gas supply of each temperature zone is adjusted to stabilize the temperature of each temperature zone within the target temperature range, and the gas supply of each temperature zone at this time is recorded as the initial gas supply setting value.

[0055] The amplification and reduction operations are performed by multiplying the initial air supply setting value with the overspeed ratio or the low speed ratio, respectively. The target operating speed range is set according to the design capacity and process requirements of the chain grate machine, for example, it is set to ±5% of the rated operating speed.

[0056] This invention determines the corresponding change state of the grate's operating speed based on the current operating speed of the grate, and determines the zoned air supply control amount of each temperature zone based on the change state and the initial air supply setting value of each temperature zone. This achieves dynamic adaptation between the air supply and the operating state of the grate, avoids the drift of thermal parameters in each temperature zone caused by grate speed fluctuations, and ensures the stability and continuity of the preheating process of the chain grate machine.

[0057] Considering that the mixing ratio of oxygen-enriched gas and combustion air directly affects combustion efficiency and flame characteristics during oxygen-enriched combustion, failure to dynamically adjust based on real-time combustion airflow and oxygen-enriched gas pipeline flow will cause the actual oxygen concentration to deviate from the target value, affecting combustion performance. Therefore, it is necessary to adjust the throttle valve opening and combustion airflow to ensure the stability of the actual oxygen concentration inside the furnace.

[0058] Based on this, such as Figure 2 As shown, the specific implementation of the correction and adjustment of the throttle valve opening and the combustion fan air volume in this invention includes: S31, retrieving the target oxygen enrichment mixing ratio corresponding to the rotary kiln head, and using the product of the target oxygen enrichment mixing ratio and the real-time air volume of the combustion fan as the target flow rate of oxygen enrichment gas.

[0059] The real-time air volume of the combustion air blower is measured in real time by an ultrasonic gas flow meter installed on the outlet pipe of the combustion air blower, which measures the volumetric flow rate of the combustion air entering the rotary kiln system of the chain grate machine.

[0060] It should be noted that the target oxygen-enriched mixing ratio is the ratio of the volumetric flow rate of oxygen-enriched gas to the volumetric flow rate of combustion air, which is pre-calibrated based on the rated combustion characteristics of the rotary kiln head burner.

[0061] S32. Obtain the real-time flow rate of the oxygen-enriched gas supply pipeline through a flow meter installed in the oxygen-enriched gas supply pipeline. Based on the real-time flow rate of the oxygen-enriched gas supply pipeline, compare the difference between the target flow rate of the oxygen-enriched gas and the real-time flow rate of the oxygen-enriched gas supply pipeline to obtain the oxygen-enriched gas flow rate deviation value.

[0062] S33. Based on the deviation value of the oxygen-enriched gas flow rate, and combined with the flow rate and opening characteristics of the throttle valve on the oxygen-enriched gas supply pipeline, determine the corrected opening of the throttle valve.

[0063] It should be noted that the flow rate and opening characteristics are characteristic curves obtained in advance through calibration experiments, representing the flow capacity at different valve openings. These flow rate and opening characteristics are established through point-by-point calibration before the system is put into operation.

[0064] The method for determining the corrected opening of the throttle valve is as follows: based on the absolute value of the deviation value of the oxygen-enriched gas flow rate, the corrected opening value is obtained by referring to the characteristic curve corresponding to the throttle valve opening and the flow rate; the direction of opening adjustment is determined by combining the positive and negative values ​​of the deviation value of the oxygen-enriched gas flow rate, with the valve being adjusted to open wider when the deviation value is positive and to close narrower when the deviation value is negative; at the same time, the corresponding adjustment range is matched according to the magnitude of the absolute value of the deviation, with a larger absolute value of the deviation resulting in a higher adjustment range to avoid overshoot.

[0065] S34. Convert the zoned gas supply control amount of each temperature zone into the air supply volume change amount, accumulate the air supply volume change amounts of each temperature zone to obtain the total air supply volume correction value of the combustion fan, compare the difference between the total air supply volume correction value of the combustion fan and the real-time air volume of the combustion fan to obtain the corrected air volume of the combustion fan.

[0066] The conversion method for the change in air supply volume is as follows: the ratio analysis of the zoned air supply control volume of each temperature zone with the target oxygen enrichment mixing ratio is used to obtain the change in air supply volume.

[0067] S35. Based on the corrected opening of the throttle valve and the corrected air volume of the combustion fan, the opening of the throttle valve and the air volume of the combustion fan are corrected and adjusted.

[0068] This invention determines the changing state based on the current operating speed of the grate, determines the zoned gas supply regulation amount based on the changing state and the initial gas supply setpoint of each temperature zone, and combines the real-time air volume of the combustion blower and the real-time flow rate of the oxygen-enriched gas supply pipeline. According to the target oxygen-enriched blending ratio, the opening of the throttle valve and the air volume of the combustion blower are corrected and adjusted to achieve dynamic matching between the gas supply and the operating state of the grate and precise control of the oxygen-enriched blending ratio. This ensures that the actual oxygen concentration in the furnace is stably close to the target value, fully exerts the enhancing effect of oxygen-enriched combustion, and improves the stability and combustion efficiency of oxygen-enriched combustion.

[0069] Considering that the ferrous oxide content in the feed material at the chain grate discharge end reflects the degree of oxidation and remaining oxidation demand in the preheating section of the chain grate, failure to dynamically adjust the oxygen supply to the rotary kiln head based on the ferrous oxide content will lead to insufficient oxidation or excessive oxygen supply, resulting in energy waste. Simultaneously, the oxygen concentration in the flue gas at the rotary kiln head is a feedback indicator of whether the combustion process is at the optimal excess air coefficient. Without feedback adjustment based on the flue gas oxygen concentration, the impact of combustion condition fluctuations on the oxidation process cannot be eliminated. Therefore, it is necessary to detect the ferrous oxide content in real time and convert it into an oxidation oxygen demand coefficient, combining this with the feedback adjustment of the flue gas oxygen concentration to obtain the target air supply, achieving a precise match between the oxygen supply and the material's oxidation demand and combustion state.

[0070] Based on this, the specific implementation of converting ferrous oxide content into an oxidation oxygen demand coefficient in this invention includes: S41, real-time collection of the ferrous oxide mass percentage content of the incoming material sample using a ferrous oxide content detection device installed at the discharge end of the chain grate. The ferrous oxide content detection device is an online X-ray fluorescence spectrometer, installed at the sampling point at the discharge end of the chain grate, collecting incoming material samples according to a preset sampling cycle and analyzing the ferrous oxide mass percentage content therein.

[0071] S42. Based on the chemical reaction relationship of ferrous oxide oxidation to ferric oxide in pellets, the theoretical oxidation consumption per unit mass of ferrous oxide is calculated.

[0072] It should be noted that the chemical reaction relationship is as follows: The theoretical oxidation consumption per unit mass of ferrous oxide can be calculated based on chemical reaction relationships as follows: ;in, This represents the theoretical oxidation consumption per unit mass of ferrous oxide undergoing an oxidation reaction. Here is the molar mass of oxygen. is the molar mass of ferrous oxide.

[0073] S43. Obtain the real-time incoming material processing flow rate at the discharge end of the chain grate machine, and calculate the additional oxygen requirement required for the oxidation reaction of ferrous oxide in the incoming material per unit time based on the ferrous oxide mass percentage content.

[0074] S44. Calculate the ratio of the additional oxygen demand to the standard oxidation oxygen demand under the preset baseline operating conditions to obtain the oxidation oxygen demand coefficient. The oxidation oxygen demand coefficient characterizes the degree of oxidation oxygen demand of the current operating conditions relative to the baseline operating conditions. When the oxidation oxygen demand coefficient is greater than 1, it indicates that the current material oxidation demand is higher than the baseline operating conditions; when the oxidation oxygen demand coefficient is less than 1, it indicates that the current material oxidation demand is lower than the baseline operating conditions.

[0075] It should be noted that the preset benchmark operating conditions refer to the operating conditions of the chain grate machine under rated capacity, set material layer thickness, and set ferrous oxide content. The standard oxidation oxygen demand is the theoretical oxygen requirement for the material oxidation reaction per unit time under this operating condition, serving as a benchmark reference for enhancing oxidation demand.

[0076] Preferably, in a specific embodiment of the present invention, the method for calculating the additional oxygen requirement required for the oxidation reaction of ferrous oxide in the incoming material per unit time is as follows: S431, collect the real-time operating speed and real-time thickness of the material layer of the chain grate, and calculate the total mass of incoming material output by the discharge end of the chain grate per unit time in combination with the rated operating width of the grate and the material bulk density, which is used as the real-time material processing flow rate.

[0077] The calculation process for the total mass of incoming material is as follows: the real-time operating speed, the real-time thickness of the material layer, and the rated operating width of the grate are multiplied to obtain the material layer accumulation volume. The material layer accumulation volume is then multiplied with the material bulk density to obtain the total mass of incoming material.

[0078] S432. Multiply the real-time incoming material processing flow rate with the ferrous oxide mass percentage to obtain the total mass of ferrous oxide contained in the incoming material per unit time.

[0079] S433. Multiply the total mass of ferrous oxide by the theoretical oxidation consumption to calculate the additional oxygen required for the material oxidation reaction per unit time.

[0080] Based on this, the specific implementation of the target gas supply in this invention includes: S45, based on the flue gas oxygen concentration at the flue gas outlet of the rotary kiln head, performing a difference calculation between the flue gas oxygen concentration and the preset target oxygen concentration to obtain the oxygen concentration deviation, and determining the oxygen concentration feedback adjustment direction according to the positive or negative sign of the oxygen concentration deviation.

[0081] The oxygen concentration in the flue gas is obtained in real time by a zirconia oxygen analyzer installed at the flue gas outlet of the rotary kiln head.

[0082] The preset target oxygen concentration is a target value of flue gas oxygen concentration set according to the requirements of the rotary kiln oxygen-enriched combustion process, which represents the excess oxygen level that is expected to be maintained during combustion, for example, set to a volume concentration of 3% to 5%.

[0083] The oxygen concentration feedback adjustment direction is as follows: when the oxygen concentration deviation is positive, it indicates that the actual flue gas oxygen concentration is higher than the preset target oxygen concentration, and a feedback adjustment direction of reducing the gas supply is generated; when the oxygen concentration deviation is negative, it indicates that the actual flue gas oxygen concentration is lower than the preset target oxygen concentration, and a feedback adjustment direction of increasing the gas supply is generated.

[0084] S46. Compare the oxygen concentration deviation with the preset different oxygen concentration deviation ranges to determine the oxygen concentration deviation range to which the oxygen concentration deviation belongs, and use it as the target oxygen concentration deviation range.

[0085] S47. Retrieve the pre-constructed mapping relationship between oxygen concentration deviation range and feedback adjustment amplitude, match the corresponding feedback adjustment amplitude according to the target oxygen concentration deviation range, and generate oxygen concentration feedback adjustment amount in combination with oxygen concentration feedback adjustment direction.

[0086] S48. The gas supply control amounts of each temperature zone are accumulated to obtain the gas supply baseline value. The oxidation oxygen demand coefficient is multiplied by the gas supply baseline value to obtain the basic oxygen-enriched gas supply amount.

[0087] S49. The oxygen concentration feedback adjustment amount is superimposed with the basic oxygen-enriched gas supply amount to obtain the target gas supply amount.

[0088] Preferably, in a specific embodiment of the present invention, the mapping relationship between the pre-constructed oxygen concentration deviation range and the feedback adjustment amplitude is constructed as follows: First, under the preset benchmark operating conditions of the chain grate rotary kiln, the oxygen-enriched gas supply is adjusted stepwise within the range of -5% to +5% with an adjustment step size of 1% of the total combustion air supply, so that the flue gas oxygen concentration deviates from the preset target oxygen concentration, and the oxygen concentration deviation corresponding to different adjustment step sizes is obtained. At the same time, the feedback adjustment amplitude required to be applied for the oxygen concentration deviation is recorded.

[0089] Then, the oxygen concentration deviation is divided into intervals according to its absolute value, for example, into four intervals: 0-0.5%, 0.5%-1.0%, 1.0%-2.0%, and greater than 2.0%. Statistical analysis is performed on the amplitude of all feedback regulation in each oxygen concentration deviation interval, and the median of the amplitude of feedback regulation in each oxygen concentration deviation interval is taken as the amplitude of feedback regulation in the corresponding interval.

[0090] Finally, the oxygen concentration deviation range is correlated with the corresponding feedback adjustment amplitude to establish a mapping relationship between the oxygen concentration deviation range and the feedback adjustment amplitude.

[0091] This invention detects the ferrous oxide content of the material at the discharge end of the chain grate in real time and converts it into an oxidation oxygen demand coefficient. Combined with the oxygen concentration of the flue gas at the rotary kiln head, it obtains the oxygen concentration feedback adjustment amount. The target gas supply is obtained by superimposing and integrating these parameters, achieving a precise match between the oxygen supply and the actual oxidation demand of the material. This allows the oxygen-enriched gas supply to be dynamically adjusted according to the oxidation state of the material and the flue gas feedback, thereby improving the oxidation roasting efficiency and energy utilization rate of pellets.

[0092] Considering the material transport distance between the discharge end of the chain grate and the kiln head of the rotary kiln, and the pipeline transport delay in delivering oxygen-enriched gas from the flow throttle valve of the supply pipeline to the kiln head, if this time delay is not compensated, the gas supply control command will lag behind the actual changes in the material's state, causing fluctuations in the kiln head combustion conditions and asynchronous oxidation reactions. Therefore, it is necessary to calculate the material transport time and pipeline transport delay time, and set a gas supply response compensation time to achieve proactive time compensation for gas supply control.

[0093] Based on this, such as Figure 3 As shown, the specific implementation of the target gas supply control command for generating oxygen-enriched gas in this invention includes: S51, obtaining the material transmission path distance between the discharge end of the chain grate machine and the kiln head of the rotary kiln, and calculating the material transmission time required for the material to be transmitted from the discharge end of the chain grate machine to the kiln head of the rotary kiln in combination with the real-time operating speed of the chain grate machine.

[0094] It should be noted that the material conveying path distance is the fixed conveying distance between the discharge end of the chain grate machine and the kiln head of the rotary kiln, and the material conveying time is the ratio of the material conveying path distance to the real-time operating speed of the chain grate machine.

[0095] S52. Obtain the pipeline length and gas velocity from the throttle valve to the rotary kiln burner in the oxygen-enriched gas supply pipeline, and calculate the pipeline transmission delay time of the oxygen-enriched gas in the pipeline.

[0096] It should be noted that the gas flow rate is calculated based on the real-time flow rate and cross-sectional area of ​​the oxygen-enriched gas supply pipeline, and the pipeline transmission delay time is the ratio of the pipeline length to the gas flow rate.

[0097] S53. The material transmission time and pipeline transmission delay time are superimposed to obtain the gas supply response compensation time.

[0098] S54. Compare the difference between the target gas supply and the current actual gas supply of the oxygen-enriched gas supply pipeline to obtain the gas supply deviation. Based on the gas supply deviation and the gas supply response compensation time, generate the target gas supply control command for oxygen-enriched gas.

[0099] The target gas supply control command for generating oxygen-enriched gas is to output the control command in advance based on the gas supply deviation and the gas supply response compensation time, so that the time when the oxygen-enriched gas arrives at the rotary kiln head burner is synchronized with the time when the corresponding material arrives at the kiln head.

[0100] This invention sets a gas supply response compensation time based on the material transmission time delay from the chain grate to the rotary kiln head, and combines it with the target gas supply volume control command to generate oxygen-enriched gas based on the target gas supply volume. This achieves forward-looking time compensation for gas supply control, effectively eliminating the control lag caused by material transmission and gas pipeline transmission, ensuring the synchronization between the combustion at the rotary kiln head and the actual state of the material, and improving the stability of the pellet roasting process and the consistency of product quality.

[0101] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0102] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0103] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0104] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0105] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine, characterized in that, include: Based on the temperature distribution data of the grate surface in each temperature zone of the chain grate machine, and by comparing the temperature deviation value with the target temperature range of the corresponding temperature zone, the initial opening adjustment command of the throttle valve is generated. The current operating speed of the grate is used to determine the corresponding change state of the grate operating speed, and the zoned gas supply control amount of each temperature zone is determined based on the change state and the initial gas supply setting value of each temperature zone. Based on the real-time air volume of the combustion blower and the real-time flow rate of the oxygen-enriched gas supply pipeline, the opening of the throttle valve and the air volume of the combustion blower are corrected and adjusted according to the target oxygen-enriched mixing ratio and the zoned gas supply control amount. The ferrous oxide content of the material at the discharge end of the chain grate is detected in real time. The ferrous oxide content is converted into an oxidation oxygen demand coefficient. The oxygen concentration feedback adjustment amount is obtained based on the oxygen concentration of the flue gas at the rotary kiln head. This amount is then fused with the oxidation oxygen demand coefficient to obtain the target air supply. The gas supply response compensation time is set according to the material transmission time delay from the chain grate to the rotary kiln head, and the target gas supply volume control command for oxygen-enriched gas is generated in combination with the target gas supply volume.

2. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 1, characterized in that, The method for generating the initial opening adjustment command of the throttle valve is as follows: Several temperature detection points are set up on the surface of the grate bed in each temperature zone. The temperature of each temperature detection point is collected. The actual temperature of each temperature zone is obtained by weighted calculation based on the spatial distance between all temperature detection points in each temperature zone and the center of the material layer. Retrieve the target temperature range corresponding to each temperature zone, compare the difference between the actual temperature of each temperature zone and the target temperature range of the corresponding temperature zone, and obtain the temperature deviation value and positive or negative sign of each temperature zone. Based on the temperature deviation value and positive / negative sign of each temperature zone, the opening adjustment direction and opening adjustment amount of the corresponding throttle valve for each temperature zone are mapped and generated, forming the initial opening adjustment command of the throttle valve.

3. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 2, characterized in that, The method for mapping and generating the opening adjustment direction and adjustment amount of the throttle valve corresponding to each temperature zone is as follows: Extract the sign of the temperature deviation value. If the temperature deviation value is positive, it is determined that the surface temperature of the corresponding temperature zone grate is higher than the target temperature range, and the opening adjustment direction of the throttle valve is generated. If the temperature deviation value is negative, it is determined that the surface temperature of the corresponding temperature zone grate is lower than the target temperature range, and the opening adjustment direction of the throttle valve is generated. Retrieve the pre-built mapping relationship between temperature deviation and opening adjustment step size, match the corresponding opening adjustment step size according to the temperature deviation value, and use it as the opening adjustment amount.

4. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 1, characterized in that, The method for determining the zoned gas supply regulation volume for each temperature zone is as follows: The current operating speed of the grate is compared with the preset target operating speed range to determine the corresponding change state of the grate operating speed; When the grate operating speed is stable, the initial air supply setting value of each temperature zone in the target operating speed range is used as the zone air supply control amount for the corresponding temperature zone. When the grate operating speed is in an overspeed change state, obtain the overspeed ratio between the current operating speed of the grate and the upper limit of the target operating speed range, and amplify the overspeed ratio with the initial air supply setpoint to obtain the zone air supply control amount. When the grate's operating speed is in a low-speed variation state, the low-speed ratio between the current operating speed of the grate and the lower limit of the target operating speed range is obtained. The low-speed ratio is then used to reduce the initial air supply setpoint to obtain the zoned air supply control amount.

5. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 4, characterized in that, The method for determining the changing state of the grate operating speed is as follows: When the current operating speed of the grate is within the target operating speed range, the operating speed of the grate is determined to be in a stable state. When the current operating speed of the grate exceeds the upper limit of the target operating speed range, the operating speed of the grate is determined to be in an overspeed change state. When the current operating speed of the grate is lower than the lower limit of the target operating speed range, the operating speed of the grate is determined to be in a low-speed change state.

6. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 1, characterized in that, The method for correcting and adjusting the throttle valve opening and the combustion blower air volume is as follows: Retrieve the target oxygen enrichment ratio corresponding to the rotary kiln head, and use the product of the target oxygen enrichment ratio and the real-time air volume of the combustion blower as the target flow rate of the oxygen enrichment gas. Based on the real-time flow rate of the oxygen-enriched gas supply pipeline, the difference between the target flow rate of the oxygen-enriched gas and the real-time flow rate of the oxygen-enriched gas supply pipeline is compared to obtain the oxygen-enriched gas flow rate deviation value. Based on the deviation value of the oxygen-enriched gas flow rate, and combined with the flow rate and opening characteristics of the throttle valve on the oxygen-enriched gas supply pipeline, the corrected opening of the throttle valve is determined. The zoned gas supply control volume of each temperature zone is converted into the air supply volume change volume. The air supply volume changes of each temperature zone are accumulated to obtain the total air supply volume correction value of the combustion fan. The difference between the total air supply volume correction value of the combustion fan and the real-time air volume of the combustion fan is compared to obtain the corrected air volume of the combustion fan. Based on the corrected opening of the throttle valve and the corrected air volume of the combustion blower, the opening of the throttle valve and the air volume of the combustion blower are adjusted.

7. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 1, characterized in that, The method for converting ferrous oxide content into oxidation oxygen demand coefficient is as follows: The ferrous oxide content detection device installed at the discharge end of the chain grate machine collects the ferrous oxide mass percentage of the incoming material samples in real time. Based on the chemical reaction relationship of ferrous oxide oxidation to ferric oxide in pellets, the theoretical oxidation consumption corresponding to the oxidation reaction of a unit mass of ferrous oxide is calculated. Get the real-time incoming material processing flow rate at the discharge end of the chain grate machine, and calculate the additional oxygen required for the oxidation reaction of ferrous oxide in the incoming material per unit time based on the ferrous oxide mass percentage content. The oxidation oxygen demand coefficient is obtained by calculating the ratio of the additional oxygen demand to the standard oxidation oxygen demand under preset benchmark conditions.

8. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 7, characterized in that, The method for calculating the additional oxygen requirement for the oxidation reaction of ferrous oxide in the incoming material per unit time is as follows: The real-time operating speed and material layer thickness of the chain grate are collected, and combined with the rated operating width of the grate and the material bulk density, the total mass of incoming material output at the discharge end of the chain grate per unit time is calculated as the real-time material processing flow rate. The total mass of ferrous oxide contained in the incoming material per unit time is obtained by multiplying the real-time incoming material flow rate with the ferrous oxide mass percentage content. Multiply the total mass of ferrous oxide by the theoretical oxidation consumption to calculate the additional oxygen required for the material oxidation reaction per unit time.

9. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 7, characterized in that, The method for obtaining the target gas supply volume through fusion is as follows: Based on the oxygen concentration of the flue gas at the flue gas outlet of the rotary kiln head, the difference between the flue gas oxygen concentration and the preset target oxygen concentration is calculated to obtain the oxygen concentration deviation. The direction of oxygen concentration feedback adjustment is determined according to the positive or negative sign of the oxygen concentration deviation. The oxygen concentration deviation is compared with the preset oxygen concentration deviation ranges to determine the oxygen concentration deviation range to which the deviation belongs, which is then used as the target oxygen concentration deviation range. Retrieve the pre-constructed mapping relationship between oxygen concentration deviation range and feedback adjustment amplitude, match the corresponding feedback adjustment amplitude according to the target oxygen concentration deviation range, and generate oxygen concentration feedback adjustment amount by combining the oxygen concentration feedback adjustment direction. The gas supply control amounts of each temperature zone are summed to obtain the gas supply baseline value. The oxidation oxygen demand coefficient is multiplied by the gas supply baseline value to obtain the basic oxygen-enriched gas supply amount. The target gas supply is obtained by superimposing the oxygen concentration feedback adjustment amount with the basic oxygen-enriched gas supply amount.

10. The method for controlling oxygen-enriched combustion gas supply in a rotary kiln using a chain grate machine according to claim 1, characterized in that, The method for controlling the target gas supply volume for generating oxygen-enriched gas is as follows: Obtain the material transport path distance between the discharge end of the chain grate and the kiln head of the rotary kiln, and calculate the material transport time required to transport the material from the discharge end of the chain grate to the kiln head of the rotary kiln by combining the real-time operating speed of the chain grate. Obtain the pipeline length and gas velocity from the throttle valve to the rotary kiln burner in the oxygen-enriched gas supply pipeline, and calculate the pipeline transmission delay time of the oxygen-enriched gas in the pipeline. The gas supply response compensation time is obtained by superimposing the material transmission time and the pipeline transmission delay time. The target gas supply volume is compared with the current actual gas supply volume of the oxygen-enriched gas supply pipeline to obtain the gas supply volume deviation. Based on the gas supply volume deviation and the gas supply response compensation time, a gas-enriched gas target gas supply volume control command is generated.

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