Improvement method for combustion chamber of pot-type calcining furnace

Abstract

The invention discloses an improvement method for a combustion chamber of a pot-type calcining furnace, and belongs to the technical field of industrial calcining furnaces. The method aims to solve the problems of insufficient combustion, low heat utilization rate, high pollutant emission, non-uniform temperature distribution in a hearth, difficulty in maintenance and the like of the combustion chamber of the existing pot-type calcining furnace. The core of the method is that a high-efficiency, uniform, low-consumption and environment-friendly combustion environment is constructed through collaborative optimization of a combustion chamber structure, combustor configuration, an air supply system and a flue gas circulation path. The method specifically comprises the following steps that firstly, a combustion chamber is subjected to zoning construction and divided into a preheating drying zone, a main combustion zone and a burnout zone; through combined implementation of the method, the burn-off rate and the heat utilization efficiency of fuel are remarkably improved, the temperature field distribution in the hearth is more uniform, the emission concentration of harmful substances such as CO and NOx is greatly reduced, the service life of a furnace body refractory material is prolonged, and the operation and maintenance process is simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial heating furnace, in particular to a tank type calcining furnace for high-temperature treatment of powdery, granular or blocky materials. BACKGROUND

[0002] The tank type calcining furnace is widely used in chemical industry, metallurgy, building materials, environmental protection and other industries due to its relatively simple structure, wide range of material adaptation, convenient operation and other advantages, and is used for drying, roasting, activation, pyrolysis and other heat treatment processes of materials such as catalysts, molecular sieves, activated carbon, metal oxides, industrial waste residues and the like. The combustion chamber, as the heart of the tank type calcining furnace, directly determines the thermal performance, product quality, energy consumption and pollutant emission level of the entire equipment. However, in the long-term operation practice of the existing traditional tank type calcining furnace combustion chamber, the following several interrelated and difficult-to-root technical pain points are generally exposed: Low combustion efficiency and serious energy waste: the traditional combustion chamber design is usually relatively extensive, and multiple conventional burners are usually used to directly blow flames from the side wall or top of the furnace. This simple combustion organization method leads to an extremely unsatisfactory mixing process of fuel and air, especially in some "dead angle" areas of the furnace, the air coefficient deviates from the theoretical value, causing incomplete chemical and thermal combustion of the fuel. The operator often increases the total excess air coefficient to ensure the calcination effect of the material, but this directly leads to a sharp increase in exhaust gas heat loss. The flame cannot effectively cover the entire material bed, and a large amount of heat is taken away by the high-temperature flue gas without sufficient exchange, resulting in high unit product energy consumption of the furnace, which has become a key bottleneck restricting enterprise efficiency under the current background of high energy costs and huge pressure for energy saving and emission reduction.

[0003] Extremely uneven temperature field distribution in the furnace, making it difficult to ensure product quality: due to the primitive combustion organization method, the temperature in the center of the flame is too high, while the temperature away from the flame is too low, forming extremely uneven "high-temperature zones" and "low-temperature zones". This temperature gradient greatly affects the calcination process. On the one hand, the material in the high-temperature zone is prone to over-burning, melting and caking, resulting in deterioration of the physical and chemical properties of the product, such as a decrease in the specific surface area of the catalyst, sintering and deactivation of the active components, and a decrease in product yield. On the other hand, the material in the low-temperature zone is not calcined enough, and the reaction is incomplete, which requires longer calcination time to make up for it, but this further increases energy consumption. In order to obtain a relatively uniform product within a batch, the enterprise has to sacrifice efficiency and yield and adopt a conservative process of "low temperature and long time", which seriously affects the production rhythm. In addition, the local sustained high-temperature roasting also causes serious thermal stress impact on the refractory materials in the furnace, leading to premature cracking and spalling, shortening the furnace repair cycle and increasing maintenance costs.

[0004] Excessive pollutant emissions, huge environmental pressure: Incomplete combustion directly leads to excessive concentration of carbon monoxide (CO) and residual hydrocarbons (HC) in flue gas. In order to solve the problem of incomplete combustion, the measures of increasing furnace temperature and excess air coefficient actually create excellent conditions for the generation of nitrogen oxides (NOx). In the high-temperature oxygen-rich environment (especially when the temperature in the flame core area exceeds 1300℃), a large amount of nitrogen in the air is oxidized to generate thermal NOx, which becomes the main source of NOx. The traditional combustion chamber design has no control means for this. With the increasingly stringent national environmental regulations, many old tank calciners are facing the dilemma of either investing huge amounts of money in end flue gas treatment (such as SCR or SNCR denitrification) or being shut down and eliminated. The end treatment equipment not only has high initial investment, but also has high operating cost (such as ammonia water or urea consumption, catalyst replacement), which is a heavy burden for enterprises. SUMMARY

[0005] In order to solve the above problems, the present application proposes an improved method for the combustion chamber of a tank calciner, which more accurately solves the problems raised in the background art.

[0006] The present application is realized by the following technical solutions: The present application proposes an improved method for the combustion chamber of a tank calciner, which includes the following steps: Step one: partitioning and flow field reconstruction of the combustion chamber, in the combustion chamber along the flue gas flow direction, sequentially setting a preheating and drying zone, a main combustion zone and a burnout zone; and on the inner wall of the main combustion zone and the burnout zone, a guide rib structure made of refractory material with a preset radius of curvature is built or installed to guide the high-temperature flue gas in the furnace to form a macro vortex field rotating around the central axis of the hearth; Step two: configuring and regulating a multi-mode combined combustion system, in the main combustion zone, multiple groups of burners are arranged in layers along the height direction of the hearth and oppositely along the radial direction of the hearth; wherein the lower layer burners adopt high-speed flat flame burners, the injection axis of which forms a preset downward inclination angle with the radial plane of the hearth; the upper layer burners adopt low-nitrogen swirl burners, the injection axis of which forms a preset upward inclination angle with the radial plane of the hearth; and all the burners adopt opposite arrangement; Step three: establishing a coordinated air supply system, setting a main combustion air path and a secondary oxygen enrichment air path; the air in the main combustion air path is preheated by a tube-in-shell or plate heat exchanger arranged in the flue, and then supplied to each layer of burners; the secondary oxygen enrichment air path directly sprays oxygen-enriched air into a specific area between the flame root and the middle part of the main combustion zone through an independent pipeline; Step four: Constructing a double-circulation flue gas recirculation system, including internal high-temperature flue gas recirculation and external low-temperature flue gas recirculation; the internal high-temperature flue gas recirculation is achieved by setting an internal flue gas passage with high-temperature resistance between the burnout zone and the main combustion zone, so as to extract part of the high-temperature flue gas in the burnout zone and transport it to the vicinity of the burner nozzle of the main combustion zone; the external low-temperature flue gas recirculation is achieved by setting an air induction branch on the total flue gas duct of the calcining furnace, so as to mix the flue gas extracted from the furnace body after being cooled and dedusted with fresh combustion air, and then preheat the mixed flue gas in the heat exchanger.

[0007] Preferably, the flow guide rib structure in step one is a continuous boss spirally rising along the inner wall of the furnace or an intermittent flow guide vane, and the spiral rise angle is set to maintain the ratio of the tangential velocity component to the axial velocity component of the flue gas in the main combustion zone within a certain range.

[0008] Preferably, the downward inclination angle of the high-speed flat flame burner in step two is 5-15 degrees, which is used to wash and heat the materials at the bottom of the furnace by high-speed flame flow; the upward inclination angle of the low-nitrogen cyclone burner is 10-20 degrees, which is used to prolong the residence time of flue gas in the upper space and form a suction effect.

[0009] Preferably, the oppositely arranged burners in step two are not arranged with a 180-degree angle between the jet axes of the oppositely arranged burners in the horizontal projection plane, but with a 2-8-degree offset angle, so as to strengthen the shearing, mixing and rotating of the opposite flame.

[0010] Preferably, the temperature of the preheated main combustion air in step three reaches 60-85 percent of the difference between the flue gas temperature of the calcining furnace and the ambient temperature; the oxygen volume concentration of the oxygen-enriched air is 25-50 percent, and the supply flow rate is 3-10 percent of the total flow rate of the main combustion air.

[0011] Preferably, the annular arrangement of the jet of the secondary oxygen supplement air path is arranged outside the main burner, or the jet of the secondary oxygen supplement air path is integrated with the main burner as an integrated lance, and the jet direction is directed to the high-temperature zone of the flame core, so as to achieve accurate supplementary combustion of unburned hydrocarbons.

[0012] Preferably, the proportion of internal high-temperature flue gas recirculation in step four, i.e. the proportion of the amount of flue gas introduced back to the total amount of flue gas in the burnout zone, is 10-25 percent, and the high-temperature butterfly valve on the internal flue gas passage is used for online control.

[0013] Preferably, the proportion of external low-temperature flue gas recirculation in step four, i.e. the proportion of the amount of flue gas returned to the total amount of flue gas, is 5-15 percent; a Venturi mixer is arranged on the air induction branch, which is used to realize efficient and uniform mixing of low-temperature flue gas and fresh combustion air.

[0014] Preferably, the method further comprises an integrated control step: by means of multiple temperature, pressure, oxygen content and pollutant concentration sensors arranged at key positions of the furnace zones, flue, air path, etc., real-time data are input into a central control system, which, according to preset mathematical models and control logic, adjusts the fuel / air ratio of each burner, the secondary oxygen supplement flow, the opening degree of the internal and external flue gas recirculation valves, to realize closed-loop adaptive optimization control of the combustion process.

[0015] Preferably, a tank calciner combustion chamber improved by the improved method of the tank calciner combustion chamber, characterized in that the structure of the combustion chamber comprises: a preheating drying zone, a main combustion zone and a burnout zone divided in sequence in the height direction; a furnace wall with spiral flow guide ribs fixed on the inner wall; a combination of high-speed flat flame burners and low-nitrogen swirl burners arranged in layers and in opposite directions; a main combustion air path connected with a high-temperature air preheater and an independent oxygen-enriched air injection port; an internal flue gas circulation channel connecting the burnout zone and the main combustion zone, and an external flue gas circulation pipeline connecting the flue body flue gas main pipe and the combustion air fan inlet. Advantages

[0016] Compared with the prior art, the improved method provided by the present application has the following significant advantages: In the present application, through the cooperation of combustion chamber partitioning, forced vortex of flow guide ribs, and layered opposite-direction burners, the turbulent mixing of fuel, air and high-temperature flue gas is greatly strengthened, the uniformity and fullness of the combustion reaction in the furnace space are realized, and the effects of significantly improving the fuel burnout rate, reducing the excess air coefficient, and greatly reducing the comprehensive energy consumption per unit product are achieved.

[0017] In the present application, through the combined application of high-speed flat flame and low-nitrogen swirl burners, combined with the strong stirring action of the macro-vortex field, heat can be quickly and uniformly transferred to every corner of the furnace and the deep part of the material bed, eliminating local overheating and low-temperature dead zones, and realizing precise control of the furnace temperature field, thereby achieving the effects of improving the uniformity and pass rate of calcined products, protecting the refractory materials of the furnace body, and prolonging the service life of the equipment.

[0018] In the present application, through the coupled application of multiple technologies such as low-nitrogen burner technology, air staging, oxygen-enriched supplemental combustion, and internal and external double flue gas recirculation, systematic inhibition of the generation mechanism of NOx and CO is realized at the combustion source, the original emission concentration of main pollutants in flue gas meets the increasingly stringent environmental protection standards without relying on expensive end-of-pipe treatment equipment, and the purpose of greatly reducing environmental protection investment and operating costs of enterprises is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A process flow diagram of an improved method of a tank calciner combustion chamber is provided. DETAILED DESCRIPTION

[0020] In order to more clearly and completely illustrate the technical solutions of the present application, the present application is further described below with reference to the accompanying drawings. EMBODIMENT

[0021] This embodiment is directed to a vertical tank calciner for calcining petroleum catalyst with an inner diameter of 3.5 meters and an effective height of 6 meters. The original furnace adopts 4 conventional cyclone burners in single layer and uniform distribution, which has the problems of high energy consumption and partial sintering of catalyst. The specific steps of the improvement method are as follows: Step one: subarea of combustion chamber and flow field reconstruction Functional subarea: according to the temperature in the furnace and the reaction process of the material, the hearth is divided into three areas from bottom to top: the bottom 0.5-meter-high area is the preheating and drying zone, which mainly uses the waste heat of the rising flue gas to preheat and dehydrate the newly added wet material; the middle 0.5-meter-to-4.5-meter, a total of 4-meter-high area is the main combustion zone, which is the main place for fuel combustion and core reaction of the material; the top 4.5-meter-to-6-meter, a total of 1.5-meter-high area is the burnout zone to ensure complete combustion of combustible and make the temperature tend to be uniform.

[0022] Flow field reconstruction: in the inner wall of the hearth in the main combustion zone and the burnout zone, continuous spiral guide ribs are formed by on-site casting of high alumina refractory castable. The cross section of the rib is arc-shaped, the height is 150 mm, and the width is 250 mm. The spiral angle is designed to be 12 degrees, which is optimized by computational fluid dynamics (CFD) simulation, aiming to make the average tangential velocity of the flue gas in this area reach 0.8 times the axial velocity, so as to form a stable and strong macroscopic vortex, forcing the flue gas to move spirally upward in the hearth, greatly prolonging the flue gas travel and residence time in the hearth and strengthening the convective heat transfer.

[0023] Step two: configure multi-mode combined combustion system Burner selection and arrangement: remove the original burners and rearrange 8 burners.

[0024] Lower arrangement: 4 high-speed flat flame burners are arranged on the height plane 1.5 meters from the furnace bottom along the circumference. The outlet velocity of the burner is as high as 120 m / s, forming a thin and wall-adhering flame with strong scouring power and radiant heat transfer capacity. The downward inclination angle between the jet axis of the burner and the radial plane of the hearth is set to 10 degrees, which is to make the high-temperature flame directly scours and heats the material layer at the bottom of the hearth, quickly raises the temperature of the material, and at the same time uses its strong entraining capacity to stir the material to prevent caking.

[0025] Upper layer arrangement: At the height of 3.5 meters from the furnace bottom, 4 low-nitrogen cyclone burners are also evenly distributed. The burners form a strong rotation of fuel and air before being sprayed through the internal setting of the cyclone vane, realizing the air staged combustion. The upward inclination angle of the spray axis with the radial plane of the furnace is set to 15 degrees, which aims to throw the flame to the upper space of the furnace, cooperate with the spiral rising flue gas vortex, further prolong the residence time of the combustion products in the upper space, ensure complete combustion and achieve low-nitrogen combustion.

[0026] Offset and bias: All burners adopt a two-by-two offset arrangement. In order to avoid local high temperature caused by direct collision of flames, a 4-degree bias angle is set on the horizontal projection plane of the opposite burner spray axis. In this way, when the two flames intersect in the center area of the furnace, they will shear and rub each other, forming a stronger turbulent mixing area, rather than simply canceling out the energy.

[0027] Step three: Establish a collaborative air supply system Combustion air preheating: At the exhaust gas main pipe of the calciner (exhaust gas temperature about 650℃), a plate air preheater is installed. Fresh combustion air (ambient temperature 25℃) sent by the air blower is introduced into the preheater and counter-flow heat exchanged with high-temperature flue gas to preheat the air to above 550℃. The preheated high-temperature air is sent to the 8 burners above and below through the heat preservation pipeline, greatly recovering the waste heat of flue gas and improving the combustion efficiency.

[0028] Oxygen-enriched secondary combustion: A small-sized pressure swing adsorption (PSA) oxygen preparation device is used to prepare oxygen-enriched air with an oxygen volume concentration of 35%. Through an independent pipeline system, the oxygen-enriched air is delivered to the main combustion area. The nozzle is designed as a circle of small holes integrated in the outer circle of the lower high-speed flat flame burner nozzle, with the jet direction pointing to the middle and rear part of the flame. In the early stage of combustion, the burner itself is in a fuel over-concentration (α<1) state to inhibit the generation of NOx, while in the middle and rear part of the flame, the oxygen-enriched air is accurately injected to carry out efficient and rapid secondary combustion of the unburned CO and HC, ensuring that the final total air coefficient is moderate (α≈1.1), achieving the goal of low-nitrogen and complete combustion. The flow rate of oxygen-enriched air is dynamically adjusted by the central control system according to the CO concentration feedback of the online flue gas analyzer, and the average flow rate is about 5% of the total main combustion air flow rate.

[0029] Step four: Build a double-circulation flue gas recirculation system Internal high-temperature flue gas recirculation: Four flue gas extraction ports are opened on the furnace wall in the burnout zone (temperature about 850°C), and four built-in high-temperature resistant pipes made of silicon carbide are used to introduce this part of low-oxygen but high-temperature flue gas back to the vicinity of the injection port of the upper low-nitrogen swirl burner in the main combustion zone, where it mixes with the injected fuel and air. The amount of recirculated flue gas is about 15% of the total flue gas at this cross-section, and is controlled by adjusting the electric high-temperature butterfly valve on the pipe. This makes use of the heat capacity of high-temperature inert flue gas to suppress the peak temperature of the flame, which is an effective means of suppressing the generation of thermal NOx.

[0030] External low-temperature flue gas recirculation: After the air preheater, a flue gas extraction branch is set up on the flue gas duct (at this time the flue gas has been cooled to about 200°C), and a special corrosion-resistant induced draft fan is used to extract 10% of the total flue gas, which is further purified by a bag filter and then transported to the inlet of the main combustion air fan, where it is mixed with fresh air in a Venturi mixer. This part of low-temperature flue gas also plays a role in diluting the oxygen concentration and reducing the intensity of combustion, controlling the generation of NOx from the source.

[0031] Improvement effect: After the above systematic improvements and stable operation for three months, compared with the improvements before, the tank-type calcining furnace has achieved the following performance improvements: Energy consumption: The natural gas consumption per unit of product has decreased from 110 standard cubic meters / ton to 85 standard cubic meters / ton, with a energy-saving efficiency of more than 22%.

[0032] Product quality: Through sampling and testing of the finished catalyst, the batch stability of specific surface area and activity has significantly improved, and the rate of substandard products due to overburning has decreased from 5% to less than 1%. The temperature difference measured by multiple thermocouples in the furnace has decreased from ±80°C before the improvement to ±20°C.

[0033] Pollutant emissions: Without any end-of-pipe denitration and decarbonization devices, online monitoring data at the flue gas outlet shows that the NOx concentration has decreased from 450 mg / m³ to 120 mg / m³, and the CO concentration has decreased from 200 mg / m³ to less than 50 mg / m³, fully meeting the latest national emission standards.

[0034] Equipment maintenance: The overhaul cycle of the furnace refractory is expected to be extended from 2 years to more than 3.5 years. Example 1

[0035] This example is aimed at improving the combustion chamber of a horizontal rotary tank-type calcining furnace used for treating industrial organic waste residues, with the main goal of improving the burnout rate and heat value recovery rate of the waste residues. The main difference from Example 1 is: Burner arrangement: As the furnace is horizontally rotating, the burners are arranged on the end cover of the furnace. A combination of one central main burner (low-nitrogen cyclone type) and three auxiliary burners (high-speed flat flame type) in the outer ring is adopted. The main burner provides basic heat and controls NOx, and the auxiliary burners are inclined to the rolling material bed to enhance heat transfer and agitation.

[0036] Flow field reconstruction: In the fixed section of the combustion chamber, guide vanes with stronger guide effect are built on the inner wall to adapt to the complex air flow organization of the rotary kiln.

[0037] Coordinated air supply: Due to the large fluctuation of waste residue composition, this embodiment emphasizes the precise control of oxygen-enriched supplementary combustion. The oxygen-enriched air nozzles are arranged in multiple groups in the rear half of the combustion chamber, and according to the real-time monitoring of the oxygen content and CO concentration of the flue gas at the furnace tail, they are pulsed and injected in a zoned and timed manner, realizing "surgical operation" precise adjustment of the combustion process.

[0038] Flue gas recirculation: External low-temperature flue gas recirculation is emphasized, and the recirculation ratio is increased to 20% to adapt to the characteristics of high volatile matter in waste residue, intense combustion, and easy high-temperature deflagration, playing the role of "ballast" to stabilize the combustion condition.

[0039] Through this improvement, the burnout rate of waste residue is increased from 85% to more than 98%, realizing the harmless and resourceful treatment of waste residue, and the recovered heat meets part of the steam demand of the factory, achieving significant economic and environmental benefits. Example 2

[0040] This embodiment is an application of an integrated control system. On the basis of the physical structure improvement of Example 1, an intelligent combustion optimization system based on advanced process control (APC) is deployed.

[0041] Data acquisition: 20 K-type thermocouples are installed at different heights and radial positions in the furnace, mass flow meters are installed on the air and gas pipelines of the upper and lower burners, and multi-component (O2, CO, NOx, SO2) flue gas analyzers are installed on the flue.

[0042] Control model: The core of the control system is a mechanism model based on material balance, energy balance and chemical reaction kinetics, combined with a neural network algorithm, which can predict the combustion state and final product quality according to the input material characteristics (obtained by near-infrared online analyzer) and real-time operating parameters.

[0043] Closed-loop control: This system replaces the traditional manual adjustment. For example, when the system predicts that NOx will exceed the standard, it will automatically increase the opening of the internal flue gas recirculation valve and slightly reduce the excess air coefficient of the main combustion zone; at the same time, it will accurately instruct the oxygen-enriched supplementary combustion system to compensate according to the change of CO concentration, ensuring that the combustion efficiency is not affected while the NOx is reduced.

[0044] Optimization target: the operator only needs to set the final optimization target on the human-machine interface, such as "lowest energy consumption mode", "highest yield mode" or "lowest emission mode", and the system will automatically find and maintain the optimal operation parameter combination under the current working condition.

[0045] Through the application of the intelligent control system, the operation of the combustion chamber is improved to a new level, and the energy consumption is further reduced by 3-5% based on embodiment 1, and the stability of product quality is further guaranteed.

[0046] In summary, the present application provides a systematic, multi-dimensional and synergistic improvement method for the combustion chamber of a tank calciner. It is not a simple application of a single technology, but a complete technical solution formed by organically integrating fluid mechanics, combustion science, heat transfer and automatic control technology. The method has strong universality and is not only suitable for new furnace types, but also suitable for efficient and low-cost modernization of a large number of old tank calciners, and has high popularization value and broad application prospect.

[0047] Finally, it should be pointed out that: the above only describes the preferred embodiments of the present application and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for improving the combustion chamber of a pot-type calcining furnace, characterized in that, Includes the following steps: Step 1: Divide the combustion chamber into zones and reconstruct the flow field. In the combustion chamber, along the flue gas flow direction, set up a preheating and drying zone, a main combustion zone, and a burnout zone in sequence. On the inner walls of the main combustion zone and the burnout zone, build or install flow-guiding rib structures made of refractory material with a preset radius of curvature to guide the high-temperature flue gas in the furnace to form a macroscopic vortex field rotating around the central axis of the furnace. Step 2: Configure and control the multi-mode combined combustion system. In the main combustion zone, multiple sets of burners are arranged in layers along the height of the furnace and opposite each other along the radial direction of the furnace. The lower burner uses a high-speed flat flame burner, whose injection axis forms a preset downward angle with the radial plane of the furnace. The upper burner uses a low-NOx swirl burner, whose injection axis forms a preset upward angle with the radial plane of the furnace. All burners are arranged in an opposing manner. Step 3: Establish a coordinated air supply system, setting up a main combustion air path and a secondary oxygen supply air path; the air in the main combustion air path is preheated by a shell-and-tube or plate heat exchanger installed in the flue, and then supplied to each layer of burners; the secondary oxygen supply air path injects oxygen-enriched air directly into a specific area between the flame root and the middle of the main combustion zone through an independent pipe. Step 4: Construct a dual-circulation flue gas recirculation system, including internal high-temperature flue gas recirculation and external low-temperature flue gas recirculation. The internal high-temperature flue gas recirculation is achieved by setting up a built-in flue gas channel with high-temperature resistance between the burnout zone and the main combustion zone, extracting part of the high-temperature flue gas from the burnout zone and transporting it to the vicinity of the burner nozzle in the main combustion zone. The external low-temperature flue gas recirculation is achieved by setting up an induced draft branch on the main exhaust pipe of the calcining furnace, cooling and dust-removing part of the flue gas discharged from the furnace body, mixing it with fresh combustion air, and then entering the heat exchanger for preheating.

2. The improved method according to claim 1, characterized in that, The guide rib structure in step one is a continuous protrusion or intermittently arranged guide blade that spirals upward along the inner wall of the furnace. Its spiral angle is set to maintain the ratio of the tangential velocity component to the axial velocity component of the flue gas in the main combustion zone within a specific range.

3. The improved method according to claim 1, characterized in that, In step two, the downward tilt angle of the high-speed flat flame burner is 5-15 degrees, and its function is to use the high-speed flame to flush and heat the material at the bottom of the furnace; the upward tilt angle of the low-NOx swirl burner is 10-20 degrees, and its function is to prolong the residence time of the flue gas in the upper space and form a vortex effect.

4. The improved method according to claim 1 or 3, characterized in that, In step two, the angle between the opposing burner nozzles' injection axes on the horizontal projection plane is not 180 degrees, but rather an offset angle of 2-8 degrees, to enhance the shearing, mixing, and rotation of the opposing flames.

5. The improved method according to claim 1, characterized in that, In step three, the temperature of the preheated main combustion air reaches 60% to 85% of the difference between the flue gas temperature of the calcining furnace and the ambient temperature; the oxygen volume concentration of the oxygen-enriched air is 25% to 50%, and its supply flow rate is 3% to 10% of the total flow rate of the main combustion air.

6. The improved method according to claim 5, characterized in that, The nozzles of the secondary oxygen supply air path are arranged in a ring outside the main burner, or integrated with the main burner as an integrated spray gun, with the nozzle direction pointing towards the high-temperature zone of the flame core, so as to achieve precise reburning of unburned hydrocarbons.

7. The improved method according to claim 1, characterized in that, In step four, the proportion of internal high-temperature flue gas recirculation, i.e., the proportion of the flue gas drawn back to the total flue gas volume in the combustion zone, is between 10% and 25%, and is controlled online by adjusting the high-temperature butterfly valve on the built-in flue gas channel.

8. The improved method according to claim 1, characterized in that, In step four, the proportion of external low-temperature flue gas recirculation, i.e., the proportion of the returned flue gas to the total exhaust volume, is five to fifteen percent; a Venturi mixer is installed on the exhaust branch to achieve efficient and uniform mixing of low-temperature flue gas and fresh combustion air.

9. The improved method according to claim 1, characterized in that, The method also includes an integrated control step: by installing multiple temperature, pressure, oxygen content and pollutant concentration sensors at key locations such as furnace zones, flues, and air paths, real-time data is input into the central control system. Based on a preset mathematical model and control logic, the system adjusts the fuel / air ratio, secondary oxygen supply flow rate and internal and external flue gas recirculation valve opening of each burner in a coordinated manner to achieve closed-loop adaptive optimization control of the combustion process.

10. A combustion chamber of a pot-type calcining furnace improved by the method described in any one of claims 1 to 9, characterized in that, The structure of the combustion chamber includes: The preheating and drying zone, main combustion zone, and burnout zone are divided sequentially along the height direction; The furnace wall is fixed with spiral guide ribs on its inner wall; A combination of a high-speed flat flame burner and a low-NOx swirl burner arranged in a layered counter-current configuration; The main combustion air duct is connected to a high-temperature air preheater and an independent oxygen-enriched air injection port. An internal flue gas circulation channel connecting the burnout zone and the main combustion zone, and an external flue gas circulation pipeline connecting the furnace exhaust main pipe and the combustion fan inlet.

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