A high-temperature plasma cooperating with a converter for high-temperature flue gas heat chemical waste heat recovery method and system

Abstract

The application discloses a high-temperature plasma cooperates with a converter to recover high-temperature flue gas heat-chemical waste heat, and belongs to the technical field of metallurgical process waste heat recovery and coal gas resource utilization. The method sprays carbonaceous powder into the primary flue gas of the converter at 1400-1600 DEG C, and converts the physical sensible heat of the flue gas into chemical energy of the coal gas by using the Boudou gasification reaction; the power-adjustable plasma heating device is arranged along the reaction zone, the high-grade electric heat is actively compensated for the reaction endothermic temperature drop, the temperature of the reaction zone is maintained above 1200 DEG C, the conversion rate is improved to 85-95% through the closed-loop regulation and control of the temperature and the CO2 conversion rate. The system comprises a carbon powder spraying device, a plasma heat-supplying reaction section, a detection unit and an intelligent regulation and control unit. The application uses the electric consumption of about 10-16 kWh / t of steel to pry the chemical energy recovery of 84-129 MJ / t of steel, the energy amplification ratio reaches 2-3.5 times, and the application has the advantages of accurate temperature control, second-level response, cleanness, high efficiency, low valley electric energy storage upgrading and the like.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery and coal gas resource utilization in metallurgical processes, specifically to a method and system for high-temperature plasma-assisted converter high-temperature flue gas thermochemical waste heat recovery. Background Technology

[0002] The steel industry is a pillar industry of my country's national economy and also an energy-intensive industry, consuming approximately 15-18% of the country's total industrial energy consumption. In the long-process steel production process, the converter steelmaking process is the core step in refining blast furnace iron through oxidation, decarburization, dephosphorization, and desulfurization to obtain qualified molten steel. During the blowing process, industrial pure oxygen (purity ≥99.5%) is injected at high speed into the molten pool through an oxygen lance. The carbon elements in the molten iron are violently oxidized to generate a large amount of CO gas, which carries liquid slag and iron particles splashed from the molten pool, dust, and some of the inhaled air, escaping from the furnace mouth as high-temperature flue gas, which is the primary flue gas of the converter.

[0003] The primary flue gas from the converter has the following significant characteristics: (1) High temperature and high enthalpy. During the peak blowing period, the flue gas temperature at the furnace mouth reaches 1400~1600℃, and the sensible enthalpy of the flue gas is about 2.0~2.5MJ / Nm. 3 It is an extremely high-grade industrial waste heat resource. Taking a 120t converter as an example, the total physical sensible heat carried by the flue gas in a single furnace (about a smelting cycle of 35~40 minutes) is about 180~250GJ, which is equivalent to 6~8.5tce of standard coal, and the energy density is very considerable.

[0004] (2) High CO concentration. The volume fraction of CO in the flue gas is usually in the range of 55% to 70%, CO2 accounts for about 12% to 18%, and the remainder is N2, trace amounts of O2 and H2O. The lower heating value on a dry basis is about 6.7 to 8.4 MJ / Nm³. 3 It is itself a medium-calorific-value combustible gas (converter gas). In other words, converter primary flue gas has the dual energy attributes of high physical sensible heat and high chemical latent heat, and is the second largest secondary energy carrier in integrated iron and steel enterprises, second only to blast furnace gas.

[0005] (3) Intermittent and drastic fluctuations. Converter smelting is a typical periodic intermittent operation. In a complete smelting cycle (iron charging → blowing → sampling and temperature measurement → tapping → slag splashing for furnace protection), flue gas is only released during the blowing period (about 13~18 min), and during this period, the flue gas flow rate, temperature and composition also fluctuate drastically with the change of the decarburization rate of the molten pool: in the early stage of blowing (silicon-manganese oxidation period), the flue gas volume is small and the CO concentration is low; in the middle stage of blowing (decarburization peak period), the peak flue gas volume can reach 2~3 times the average value, and the CO concentration rises to the highest level; in the late stage of blowing, the flue gas volume decreases sharply and the CO concentration drops. This non-steady-state characteristic places stringent requirements on the operating condition adaptability of the recovery system.

[0006] Currently, in domestic and international industrial practices, the existing technical routes for waste heat recovery from converter flue gas and their shortcomings are as follows: the waste heat recovery from primary converter flue gas mainly follows two major technical routes: physical methods and chemical methods. However, both have deep-seated technical defects and have failed to fully tap the potential of the dual energy attributes of the flue gas.

[0007] (a) Physical recovery method: vaporization cooling combined with downstream waste heat boiler This route is currently the standard configuration for converter flue gas systems both domestically and internationally. The process flow is as follows: high-temperature flue gas from the furnace mouth enters a fixed, fully vaporized cooling flue through a movable fume hood. Within the flue's heating surface, the sensible heat of the flue gas is transferred to the circulating cooling water via film boiling, generating saturated or slightly superheated steam. After vaporization cooling, the flue gas temperature drops to approximately 800-1000℃, and is further cooled to below approximately 200℃ via an evaporative cooling tower or waste heat boiler before being sent to an electrostatic precipitator or baghouse filter. The cleaned gas is then pressurized by a fan and sent to the gas holder.

[0008] The inherent flaws of this route are mainly reflected in the following aspects: First, the high-grade heat energy is irreversibly degraded, resulting in significant energy loss. According to the second law of thermodynamics, the grade of heat energy is determined by its temperature. The flue gas inlet temperature is as high as approximately 1450℃ (about 1723K), and its heat energy is ultimately converted into saturated steam (such as 2.5MPa saturated steam, corresponding to a saturation temperature of approximately 224℃). During this process, the flue gas temperature drops by approximately 1200℃. The irreversible entropy increase in the heat transfer process under such a huge temperature difference leads to a large amount of energy being dissipated. Based on Carnot efficiency estimates, the reversible heat-work conversion efficiency of a 1450℃ heat source is approximately 82.7%, while the corresponding efficiency of a 224℃ heat source is only about 43.1%, a difference of nearly double. In other words, the existing vaporization cooling system essentially degrades high-temperature usable work into medium- and low-temperature heat, which is an inefficient and extensive energy recovery method.

[0009] Secondly, drastic fluctuations in operating conditions lead to unstable steam quality and limited availability. Converters operate intermittently, producing steam only during the blowing phase of a smelting cycle; and the dramatic fluctuations in flue gas flow and temperature during the blowing phase cause significant oscillations in steam output and parameters. Although steam accumulators can be installed for short-term buffering, their limited volume means the overall continuity and quality of steam supply are still inferior to conventional power plant boilers. Consequently, the resulting saturated steam is typically only connected to the low-pressure steam header (0.5~1.3MPa) in the steel plant's steam network for use in applications with low steam parameter requirements, such as heating, heat tracing, and vacuum refining steam jet pumps. This results in high-grade waste heat being underutilized and its value significantly reduced.

[0010] Third, the massive vaporization cooling system incurs high investment and maintenance costs. The fully vaporized cooling flue is composed of densely packed water-cooled wall tubes, resulting in a complex structure and a massive amount of steel consumption. The membrane water-cooled walls operate under the constant pressure of high-temperature, dusty flue gas, facing multiple failure mechanisms such as wear, corrosion, scaling, and thermal fatigue, requiring frequent repairs and incurring high maintenance costs. Furthermore, a leak in the flue could pose a significant safety hazard, as the water coming into contact with the high-temperature molten steel could cause an explosion.

[0011] (ii) Chemical recovery route: Injecting carbonaceous powder for gasification reaction Given that physical recovery methods only utilize sensible heat and discard the chemical conversion potential of CO2 in flue gas, academia and industry have long recognized the technological approach of using the Bourdon reaction of carbon to transfer the sensible heat of flue gas to the chemical energy of coal gas. C(s) + CO2(g) → 2CO(g), ΔH° 298 =+172.5kJ / mol; This reaction is strongly endothermic, with a thermal effect of approximately 14,375 kJ / kg (carbon). The technical logic is as follows: carbonaceous powders (coke powder, coal powder, semi-coke powder, etc.) are injected into the high-temperature converter flue gas. The sensible heat of the flue gas drives the aforementioned gasification reaction, reducing CO2 in the flue gas to CO. During this process, the physical sensible heat of the flue gas is absorbed and converted into the chemical energy (i.e., heat of combustion) of the product CO gas. The net effect is: the calorific value of the gas is increased (CO content increases), while the flue gas temperature decreases due to the endothermic reaction. The residual sensible heat of the cooled flue gas can still be conventionally recovered by a downstream waste heat boiler, achieving a cascaded synergistic conversion of physical heat and chemical energy.

[0012] Within the actual temperature range of converter flue gas (1000~1450℃), the CO2→CO conversion is thermodynamically highly favorable, with the reaction equilibrium heavily biased towards CO formation. Thermodynamics itself does not constitute a limiting factor for the conversion rate. However, this technical route faces a fundamental physical bottleneck in practical engineering, determined by the thermodynamic characteristics of the reaction itself: the Bourdon reaction is a strongly endothermic reaction, absorbing a large amount of sensible heat from the flue gas as soon as it occurs, causing the temperature in the reaction zone to drop rapidly. When the temperature falls below approximately 1000℃, although CO formation remains thermodynamically favorable, the reaction kinetic rate decreases sharply, and the rate constant of the gas-solid heterogeneous reaction decreases exponentially with temperature (following Arrhenius's law). The actual reaction almost stagnates (its thermodynamic critical temperature is 707℃, i.e., the equilibrium point where ΔG=0; below this temperature, the reaction reverses). This negative feedback loop of endothermic reaction → cooling → self-quenching constitutes the core bottleneck of chemical recovery: the available sensible heat of the flue gas (the heat released as the temperature drops from the initial temperature to the practical quenching temperature) directly determines the upper limit of the amount of carbon that can participate in the reaction; the amount of reactable carbon, in turn, determines the upper limit of the actual CO2 conversion rate; under typical operating conditions, the actual CO2 conversion rate is capped at about 55-60% by the available sensible heat of the flue gas when simply injecting carbon, meaning that about 40-45% of CO2 is discharged with the flue gas without reacting. In other words, the real bottleneck of chemical recovery is neither a limitation of thermodynamic equilibrium (the equilibrium is already extremely biased towards CO at high temperatures) nor a limitation of carbon particle reaction kinetics, but rather the spontaneous collapse of the temperature in the reaction zone caused by the endothermic reaction.

[0013] (III) Existing technological attempts to address the above-mentioned bottlenecks and their shortcomings Several improvement ideas have been proposed to address the limited conversion rate of carbon injection, but none of them have fundamentally overcome the self-quenching bottleneck: (1) Excessive carbon injection strategy. This strategy attempts to compensate for the low single-pass conversion rate by increasing the amount of carbon injected. However, due to the existence of the temperature self-quenching mechanism, excess carbon powder exceeding the available sensible heat carrying capacity will not participate in the reaction. Instead, it will escape with the flue gas as unreacted particles, increasing the load on the downstream dust removal system and potentially increasing the risk of slagging and blockage due to the deposition of fly ash and coke powder in the flue. At the same time, the emission of unreacted carbon powder results in the waste of carbon resources and an increase in dust pollution.

[0014] (2) Partial flue gas recirculation. Part of the cooled flue gas is recirculated back to the inlet of the reaction zone, and the residual heat carried by the recirculated gas is used to delay the temperature drop of the reaction zone. However, the recirculation increases the air volume load of the system, and the heating effect of the recirculated gas is limited by its own temperature level, which has a limited contribution to maintaining the high temperature window of the reaction zone. In addition, it increases the investment and operating energy consumption of pipelines and fans.

[0015] (3) Catalytic gasification route. Alkali metal or transition metal catalysts are used to lower the activation energy of the reaction in order to maintain the reaction rate at a lower temperature. However, under the actual operating conditions of converter flue gas (high dust content, drastic atmosphere fluctuations, difficult and costly catalyst recovery), there is no precedent for industrialization of the catalytic gasification route in terms of both economic efficiency and engineering feasibility.

[0016] In summary, existing converter flue gas waste heat recovery technologies suffer from the inherent flaw of irreversible degradation of high-grade heat energy in physical methods, while chemical methods are limited by the negative feedback bottleneck of the Bourdon reaction's endothermic reaction → cooling → self-quenching, capping the CO2 single-pass conversion rate at approximately 55-60%. Neither approach achieves the full synergistic utilization of the flue gas's physical sensible heat and chemical potential. Currently, no technical solution has been found that proposes actively compensating for the endothermic temperature drop of the reaction with an external high-grade heat source to overcome these bottlenecks. This invention addresses this technological gap. Summary of the Invention

[0017] To address the shortcomings of existing technologies, this invention aims to solve the technical challenges in chemical waste heat recovery from converter flue gas. These challenges stem from the strong endothermic effect of the Bourdon reaction, which causes a spontaneous temperature collapse in the reaction zone and caps the CO2 conversion rate due to the available sensible heat of the flue gas (single-pass conversion rate of only about 55-60%), hindering the full release of chemical recovery potential. This invention provides a waste heat recovery method and system that can actively, controllably, and efficiently maintain the reaction zone temperature within a high conversion rate window, significantly increasing the CO2 conversion rate from approximately 58% to 85-95%, while simultaneously achieving precise temperature control, clean and efficient operation, and upgraded energy storage. Furthermore, this invention aims to provide a novel industrial-grade Power-to-Gas technology path that can convert surplus renewable electricity from off-peak grid hours or curtailed wind and solar power into high-grade coal gas chemical energy. Combined with the injection of renewable carbon sources such as biomass powder or biomass carbon powder, carbon emission reduction can be achieved, satisfying the dual benefits of waste heat and carbon assets.

[0018] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for thermochemical waste heat recovery of high-temperature flue gas from a high-temperature plasma-coordinated converter, comprising the following steps: Carbonaceous powder is injected into the primary flue gas duct of the converter in stages, so that the carbonaceous powder reacts with CO2 in the flue gas to undergo a Bourdon gasification reaction, converting the physical sensible heat of the flue gas into the chemical energy of the coal gas. Multiple adjustable plasma heating devices are pre-set in the reaction zone along the flue gas flow direction. Heat is added to the flue gas according to the real-time temperature of the reaction zone to compensate for the endothermic temperature drop of the Büdör gasification reaction and keep the temperature of the reaction zone above the lower limit temperature of the high conversion rate range of the Büdör gasification reaction. With the reaction zone temperature and flue gas CO2 conversion rate as control targets, the input power of the plasma heating device and the blowing rate of carbonaceous powder are adjusted in a closed loop to stabilize the CO2 conversion rate within the target range. The flue gas after the gasification reaction and its residual physical sensible heat are recovered.

[0019] As a preferred embodiment of the present invention, the lower limit temperature of the high conversion rate range of the Bourdon gasification reaction is 1200°C.

[0020] As a preferred embodiment of the present invention, the high conversion rate range temperature of the Büdor gasification reaction is 1200~1300℃.

[0021] As a preferred embodiment of the present invention, the target range of the CO2 conversion rate is 85-95%.

[0022] As a preferred embodiment of the present invention, the plasma heating device is arranged in three sections along the flue gas flow direction: The preheating section is located in the front part of the reaction zone near the converter outlet, and is used to raise the temperature of the flue gas entering the reaction zone to above 1550~1650℃. The main reaction section is located in the middle of the reaction zone and is used to continuously compensate for the temperature drop caused by the endothermic reaction and maintain the temperature of the reaction zone in the high conversion rate range. The supplementary heating section, located in the rear region of the reaction zone, is used to provide supplementary heat for the final conversion of residual CO2.

[0023] As a preferred embodiment of the present invention, the plasma heating device is a DC arc plasma torch or an induction-coupled plasma torch, with a single torch power range of 10kW~2MW, supporting stepless power adjustment; the working gas of the plasma heating device is one or more of nitrogen, argon, CO2, and purified and recovered converter gas.

[0024] As a preferred embodiment of the present invention, the closed-loop regulation adopts a cascade control logic that prioritizes temperature and follows CO2 conversion rate: First-level temperature control: When the temperature in the middle and rear part of the reaction zone is lower than the set lower limit, the output power of the plasma heating device in the middle and rear part is increased to raise the temperature back to the set range. Second-stage CO2 conversion rate control: When the temperature in the middle and rear of the reaction zone meets the requirements but the CO2 conversion rate is lower than the lower limit of the target range, the amount of carbonaceous powder injected into the middle and rear and the plasma heating power are increased simultaneously. The third-level overconversion correction: When the CO2 conversion rate is higher than the upper limit of the target range or the temperature of the reaction zone reaches or exceeds the upper limit of the process safety, the blowing rate of the carbonaceous powder in the middle and rear and the output power of the plasma heating device are gradually reduced.

[0025] As a preferred technical solution of the present invention, a phased operation control strategy is adopted for the periodic intermittent operation of converter smelting: In the initial stage of blowing, the plasma heating device is started at low power to preheat the lining of the reaction zone. After the flue gas flow and temperature rise to the preset range, the plasma power and carbon powder blowing volume are gradually increased to raise the temperature to the set range. During the middle stage of blowing, the temperature of the flue gas entering the reaction zone is raised to 1550~1650℃ using the preheating section plasma heating device, and the closed-loop regulation adopts a cascade control logic that prioritizes temperature and follows conversion rate. Towards the end of the blowing process, the carbon powder injection rate and plasma power are reduced proportionally as the flue gas parameters decrease. When the flue gas parameters fall below the preset threshold, carbon injection is stopped and the plasma heating device is turned off.

[0026] As a preferred embodiment of the present invention, the carbonaceous powder is selected from one or more of the following: coke powder, anthracite powder, semi-coke powder, biomass powder, and biomass carbon powder.

[0027] As a preferred technical solution of the present invention, the plasma heating device is preferentially operated during periods of low grid load or surplus renewable energy, and the surplus electrical energy is stored in the form of coal gas chemical energy.

[0028] Secondly, the present invention provides a system for realizing the aforementioned high-temperature plasma-coordinated converter high-temperature flue gas thermochemical waste heat recovery method, comprising a converter hood and rising flue, a water-cooled flue, and a waste heat recovery unit that are sequentially fluidly connected along the flue gas flow direction, and further comprising: Carbon powder injection device is used to inject carbonaceous powder into the flue gas stream; A plasma heating device is installed inside the converter hood and / or rising flue to supplement the flue gas with heat in order to maintain the temperature of the reaction zone. The detection unit is located inside the converter hood and / or rising flue, and is used to collect temperature signals and flue gas composition signals in the reaction zone; The intelligent control unit is connected to the toner spraying device, the plasma heating device, and the detection unit. The intelligent control unit is used to receive the data collected by the detection unit and output control signals to adjust the spraying rate of the toner spraying device and the heating power of the plasma heating device in a closed loop, so as to maintain the temperature of the reaction zone and control the CO2 conversion rate.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention addresses the core defects of traditional carbon injection gasification processes, where the strong endothermic reaction of the Bourdon reaction leads to a spontaneous temperature collapse in the reaction zone, and the CO2 conversion rate is capped at 55-60% by the sensible heat of the flue gas. This invention actively compensates for the endothermic temperature drop by using external plasma heating, stabilizing the reaction zone temperature within a high conversion kinetic range above 1200℃. This increases the single-pass CO2 conversion rate to 85-95%, an improvement of over 25 percentage points compared to existing technologies. After deep reduction of CO2 to CO, the lower heating value of the converter gas increases by 15-20%, significantly improving the gas quality and industrial utilization value, thus providing a promising application prospect for using converter gas as feedstock.

[0030] 2. This invention employs a three-stage plasma flow path arrangement scheme consisting of a preheating section, a main reaction section, and a supplementary heating section. This achieves gradient supplementary heating for inlet flue gas temperature increase, reaction flow path heat preservation, and residual CO2 end-stage conversion, precisely matching the differentiated heat requirements throughout the flue gas reaction process. Simultaneously, a three-level cascade closed-loop control logic prioritizing temperature and following conversion rate is constructed, coupled with a phased control strategy of slow start-up in the initial blowing stage, stable operation in the middle stage, and gradual withdrawal in the final stage. Leveraging the plasma's second-level power response characteristics, it can quickly adapt to the periodic and drastic fluctuations in converter flue gas flow, temperature, and composition, ensuring stable reaction conditions and controllable conversion rate at all times.

[0031] 3. This invention, with an electrical energy input of 10-16 kWh / t of steel, can additionally recover 84-129 MJ / t of chemical energy from the steel, achieving an energy amplification ratio of 2-3.5 times. It can convert off-peak electricity and surplus renewable electricity into long-term storable coal gas chemical energy, forming a power-to-gas energy storage path in industrial scenarios, possessing both deep waste heat recovery and power system peak shaving functions. Simultaneously, by adopting an energy utilization mode that prioritizes chemical energy conversion and performs cascade recovery of physical sensible heat, it significantly improves the utilization efficiency of high-grade waste heat compared to the high loss problem of traditional physical waste heat recovery methods, avoiding irreversible degradation of high-temperature thermal energy.

[0032] 4. Precise temperature-carbon powder matching and control ensures more complete gasification of carbonaceous powder, effectively reducing unreacted carbon powder escaping with flue gas, and alleviating the operating load of downstream dust removal systems and the risk of flue duct slagging and blockage. Plasma heating uses pure electricity as its energy input, without introducing impurities such as ash and sulfur, and generates no additional pollutants compared to combustion heating routes. Furthermore, the reduction of CO2 to CO achieves indirect carbon emission reduction, and when combined with renewable carbon sources such as biomass powder and biomass carbon powder, the carbon reduction effect can be further enhanced, achieving synergistic effects in pollution reduction and carbon reduction.

[0033] 5. The core plasma reheating reaction unit adopts a modular flue structure, which can be directly connected to the existing converter flue gas system through standard connection flanges without the need for large-scale modification of the converter body and the original flue. It is suitable for the construction of supporting facilities for new converter production lines, as well as for the energy-saving upgrade and renovation of existing production lines. The project is easy to implement, has a short renovation cycle, and controllable investment costs, and has a good foundation for large-scale promotion in the industry. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the waste heat recovery system of the present invention.

[0035] Figure 2 The present invention provides a closed-loop intelligent control logic block diagram for temperature and composition.

[0036] Figure 3 The curve showing the relationship between the reaction zone temperature and CO2 conversion rate in this invention (comparing two operating conditions: simple carbon injection and plasma-assisted heating).

[0037] Figure reference numerals: 1. Converter; 2. Reaction zone; 3. Plasma heating device; 301. Preheating section; 302. Main reaction section; 303. Reheating section; 4. Carbon powder nozzle; 5. Converter hood; 6. Rising flue; 7. Water-cooled flue; 8. Waste heat recovery unit. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present patent. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present patent.

[0039] This invention discloses a thermochemical energy storage waste heat recovery method for converting the physical sensible heat of flue gas into the chemical energy of coal gas in the primary flue gas system of an oxygen top-blown converter (BOF) or a top-bottom combined blowing converter, by injecting carbonaceous powder and coupling it with a high-temperature plasma reheating device, as well as the system apparatus for implementing this method. This invention is particularly applicable to the deep recovery and low-carbon upgrading of secondary energy in the converter steelmaking process of steel enterprises. The core concept of this invention is: a synergistic technical route that integrates temperature-composition closed-loop control through the gasification of carbonaceous reducing agents combined with precise external plasma reheating. Specifically: while injecting carbonaceous powder into the primary flue gas of the converter to drive the Büdow gasification reaction, an adjustable power plasma high-temperature heat source is set along the flue gas reaction path. Based on the real-time monitoring of the reaction zone temperature feedback, high-grade external electric heating is used to accurately compensate for the flue gas temperature drop caused by the reaction endothermic heat, actively maintaining the reaction zone temperature in a high conversion rate range of not less than 1200℃. Through a closed-loop control strategy of adjusting the plasma torch input power and carbon powder injection amount in real time, the CO2 conversion rate is stably maintained in the target window of 85~95%.

[0040] Example 1: Heat balance calculation and benefit assessment under baseline operating conditions This embodiment uses 1000 Nm 3 Using the primary flue gas of the converter (dry basis) as the calculation basis, a detailed thermal calculation and effect description of the method of the present invention are performed.

[0041] Baseline operating parameters: Converter primary flue gas flow rate (dry basis): 1000 Nm 3 ; Initial flue gas temperature T1: 1450℃ (1723K); Initial flue gas composition (volume fraction): CO≈60%, CO2≈16% (i.e., 160 Nm³) 3 CO2), N2≈17%, and the rest (H2O, O2, etc.)≈7%; Injected carbonaceous powder: coke powder, fixed carbon content 85wt%, particle size D 90 ≤200μm, apparent density ≈1000kg / m 3 ; Under simple carbon spraying conditions (comparative example): The available sensible heat that can be provided by the flue gas as it cools from its initial temperature T1 = 1450℃ to its practical quenching temperature Tq ≈ 1000℃ is: Q available = V·cp·ΔT = 1000 × 1.6 × (1450 - 1000) = 720 MJ.

[0042] The maximum amount of carbon gasification that this heat can drive is: mC,max = 720,000 / 14,375 ≈ 50.1 kg of carbon.

[0043] The amount of CO2 consumed is: (50.1 / 12)×22.4≈93.6 Nm³ 3 .

[0044] The corresponding CO2 conversion rate is: ηCO2,max = 93.6 / 160 = 58.5%.

[0045] This is the ceiling of the conversion rate of existing simple carbon injection technology, which is capped by the sensible heat of the flue gas, at approximately 58%.

[0046] The plasma heating conditions of this invention are as follows: To increase the CO2 conversion rate to the target value η, the additional heat required is: Qcomplement = Qtotal heat absorbed (η) - Qavailable.

[0047] Where the total heat absorption Q (η) is η × 160 Nm 3 The total heat required for the complete reaction of CO2: Total heat absorbed (Q) = η × (160 × 1000 / 22.4) × 172.5 × 10 -3 MJ.

[0048] Taking η=90% as an example: Total heat absorbed Q = 0.9 × (7142.9) × 172.5 × 10 -3 ≈1,109MJ, Q_complement = 1,109 - 720 = 389MJ, power consumption (ηel ≈ 85%) = 389 / 3.6 / 0.85 ≈ 127kWh.

[0049] Based on a converter gas recovery rate of 80~110 Nm 3 Based on a conversion rate of 1 ton of steel, the plasma heat recovery is 31~50 MJ / ton of steel, the power consumption is 10~16 kWh / ton of steel, and the corresponding carbon injection is 6.5~9 kg of coke powder / ton of steel. The additional chemical energy recovered by this power input is 84~129 MJ / ton of steel, with an energy amplification ratio of 2~3.5 times.

[0050] Energy Saving Benefits: A single 120t converter produces approximately 1.2 million tons of steel annually, with an annual increase in recovered chemical energy of approximately 28,000 to 43,000 tons of standard coal equivalent (tce). Energy Storage Benefits: Equivalent to building a Power-to-Gas energy storage system of 10-16 kWh / t × 1.2 million tons / year ≈ 12-19 GWh / year, converting fluctuating off-peak electricity into long-term storable converter gas chemical energy. Carbon Emission Reduction Benefits: Indirect emission reduction effects from CO2 conversion, and the comprehensive carbon emission reduction contribution from replacing high-carbon fuels after the calorific value of the gas is increased.

[0051] Example 2: Complete Implementation Process of the Thermochemical Waste Heat Recovery Method of the Present Invention This embodiment describes in detail the complete implementation process of the high-temperature plasma-coordinated converter high-temperature flue gas thermochemical waste heat recovery method of the present invention.

[0052] Step S1: Carbon powder blowing At a suitable location within the primary flue gas duct of converter 1 (preferably located inside converter hood 5 and / or rising flue duct 6), carbonaceous powder is quantitatively injected into the high-temperature flue gas at a set injection rate via a pneumatic conveying system.

[0053] The carbonaceous powder is selected from one or more of the following: coke powder, anthracite powder, semi-coke powder, biomass powder, and biomass carbon powder. The carbon content (dry basis) is not less than 60 wt%, and the particle size D... 90 No larger than 200μm, preferably D 50 The particle size is 20~100μm. The powder is pressurized and transported by compressed nitrogen, CO2 or recovered coal gas, and uniformly injected into the flue gas cross section in the form of a multi-nozzle array to ensure rapid dispersion and full contact of the carbon powder in the high-temperature flue gas.

[0054] The carbon powder is injected in stages: Instead of being injected at a single point, the powder is introduced through multiple inlets along the flue gas flow path, at the front, middle, and rear of the reaction zone. Front: This allows the carbon powder to mix with the high-temperature flue gas as early as possible, initiating the reaction. Middle (Main Reaction Section): Carbon is continuously supplied to the most vigorous reaction area. Rear (Heating Section): A carbon source is replenished for the remaining CO2 at the end of the reaction. This spatial staggered approach is designed to match the carbon powder requirements of the Büdör gasification reaction at different stages, avoiding waste or incomplete reaction due to excessive initial input.

[0055] Stoichiometric matching calculations were performed based on flue gas flow rate, initial CO2 concentration, and the expected actual reaction temperature achievable under reheating conditions, considering an unreacted carbon powder margin of approximately 5-10%. The injection rate was matched stoichiometrically to reduce 85-95% of the CO2 in the flue gas, equivalent to 6.5-9 kg coke powder (dry basis) / t steel. For a typical 1000 Nm³ / t steel... 3 Converter primary flue gas (CO2 160 Nm) 3 To achieve a 90% CO2 conversion rate, approximately 77 kg of carbonaceous powder (based on pure carbon) needs to be sprayed in.

[0056] After the injected carbonaceous powder is rapidly dispersed in the high-temperature flue gas, it undergoes a Bourdon gasification reaction with CO2 in the flue gas: C(s) + CO2(g) → 2CO(g), converting the physical sensible heat of the flue gas into the chemical energy of the coal gas.

[0057] Step S2: Precise Plasma Heating Along the Path Multiple independently adjustable plasma heating devices 3 (plasma torch arrays) are pre-installed in reaction zone 2 along the flue gas flow direction. The plasma heating devices 3 can be DC arc plasma torches (DCArcPlasmaTorch) or inductively coupled plasma torches (ICP), with DC non-transfer arc plasma torches being preferred. The power range of a single torch is 10kW~2MW, supporting stepless power adjustment. The working gas of the plasma heating devices 3 is one or more of nitrogen, argon, CO2, and purified / recovered converter gas.

[0058] The plasma heating device 3 is arranged in three sections along the flue gas flow direction: Preheating section 301 (P1): Located in the front area of ​​reaction zone 2 near the converter outlet, it is used to raise the temperature of the flue gas entering the reaction zone to 1550~1650℃, providing a high starting temperature for the gasification reaction.

[0059] Main reaction section 302 (P2): Located in the middle of reaction zone 2, it is the main reaction zone. Multiple plasma torches are arranged along the process to continuously compensate for the temperature drop caused by the endothermic reaction of the Bourdon reaction and maintain the temperature of the reaction zone in the high conversion rate range, i.e., not lower than 1200℃, preferably in the kinetic high efficiency range of 1200~1300℃.

[0060] Reheating section 303 (P3): Located in the rear region of reaction zone 2, it provides supplementary heating at the end of the reaction zone to the residual CO2 for final refining and conversion based on the conversion rate achieved.

[0061] The power output of the plasma heating device 3 is controlled in a closed loop by an intelligent control unit. The heat replenishment capacity is ample: the plasma arc core temperature reaches 3000~8000℃ (depending on the working gas and power), far exceeding the temperature range required for the reaction, providing sufficient power output margin. The required heat replenishment is determined by the following formula: Qreplenishment = Qtotal endothermic reaction - Qavailable sensible heat of flue gas. This invention determines the optimal engineering conversion rate range as ηCO2 = 85~95%, corresponding to a plasma heat replenishment of 390~450 MJ / 1000 Nmm. 3 Flue gas, equivalent to 127~147 kWh / 1000 Nm³ of electricity consumption. 3 Flue gas (the plasma electrothermal conversion efficiency is calculated as 85%).

[0062] Step S3: Closed-loop intelligent control of temperature and composition Multiple temperature sensors (high-temperature thermocouples or infrared radiation thermometers with a response time ≤1s) and an online flue gas composition analyzer (non-dispersive infrared or laser gas analyzer, capable of real-time output of CO and CO2 volume fractions) are installed along the flue gas flow direction in reaction zone 2. A closed-loop control logic is constructed using the reaction zone temperature (preferably the measured flue gas temperature T2 in the middle and rear of the reaction zone) and the flue gas CO2 conversion rate ηCO2 as the controlled variables, and the total input power of the plasma torch array, the power distribution ratio of each section, and the carbon powder blowing rate as the control variables.

[0063] The closed-loop control adopts a cascade control strategy that prioritizes temperature and follows CO2 conversion rate. First-level temperature control (priority strategy): When the temperature in the middle and rear part of reaction zone 2 is lower than the set lower limit (1200℃), regardless of the conversion rate, the output power of the plasma heating device is increased first to maintain the temperature and allow it to rise back to the set range (1200~1300℃). The conversion rate is then judged after the temperature recovers.

[0064] Second-stage CO2 conversion rate control (follow-up strategy): When the temperature in the middle and rear part of reaction zone 2 meets the requirements (T2≥1200℃) but the CO2 conversion rate is lower than the lower limit of the target range (ηCO2<85%), the amount of carbonaceous powder injected in the middle and rear part is increased simultaneously (increasing the supply of reaction substrate) and the plasma heating power (matching the newly added reaction endothermic heat according to the stoichiometric heating increment) while keeping the temperature from falling below the lower limit.

[0065] The third-level overconversion correction (energy-saving strategy): When the CO2 conversion rate is higher than the upper limit of the target range (ηCO2>95%) or the temperature of reaction zone 2 reaches or exceeds the upper limit of process safety (e.g., 1500℃), the blowing rate of carbonaceous powder in the middle and rear and the output power of the plasma heating device are gradually reduced to save energy.

[0066] The plasma heating device 3 is electrically adjustable and has a second-level response (power increases from 10% to 100% in about 0.5~3s). It can effectively adapt to the drastic fluctuations in flue gas flow and temperature during the converter blowing period, and quickly rebalance when the operating conditions change, so that the conversion rate is always kept within the target range (85~95%).

[0067] Step S4: Product gas extraction and residual sensible heat utilization After the gasification reaction, the high-CO gas (outlet flue gas temperature approximately 800~1200℃) enters the subsequent process: it enters the waste heat recovery unit 8 (waste heat boiler) via water-cooled flue 7, where steam is conventionally generated, achieving the cascaded comprehensive utilization of physical waste heat. The flue gas energy is first chemically converted and stored in CO chemical bonds, and the residual sensible heat is then recovered by steam generation via the traditional route, achieving the optimal configuration of all energy grades with priority conversion of chemical energy and cascaded utilization of physical heat. The water-cooled flue 7, waste heat recovery unit 8, and plasma heating device 3 can organically form a steam-water system, achieving comprehensive heat utilization. In some examples, the carbon powder injection device can also be integrated with the plasma heating device using a jacketed design.

[0068] Example 3: Staged Operation Control Strategy for Converter Intermittent Fluctuation Conditions Converter steelmaking is a typical periodic batch process. In a complete smelting cycle (taking a 120t converter as an example, approximately 35-40 minutes), flue gas is generated only during the blowing period (approximately 13-18 minutes). During the blowing period, flue gas parameters dynamically evolve with changes in the carbon content of the molten pool. For example... Figure 2 As shown, the intelligent control unit of the present invention designs the following phased operation control strategy to address the above-mentioned operating condition fluctuation characteristics: (1) In the initial stage of blowing (0~3min), start with slow heating. The initial stage of the blowing process mainly involves silicon and manganese oxidation and slag melting. The decarburization rate is low, the flue gas volume is small (approximately 40-60% of normal), the flue gas temperature is relatively low (approximately 1200-1350℃), and the CO concentration is low. Before the flue gas parameters reach a steady state, the control system starts the plasma heating device at low power (10% of the normal operating power of the plasma torch) to preheat the refractory lining of the reaction zone. After the flue gas flow rate and temperature stabilize and rise to the preset range (1000-1200℃), the plasma power and carbon powder injection volume are gradually increased to raise the temperature to the set range (1200-1300℃).

[0069] (2) Mid-stage of blowing (3~12 min), stable operation and regulation This is the main operating period of the system. During the peak decarbonization period, the carbon content in the molten pool drops rapidly from about 3% to about 0.5-0.8%, the CO generation rate reaches its peak, the flue gas volume is the largest (up to 120-200% of the normal volume), the flue gas temperature is the highest (about 1450-1600℃), and the CO concentration is the highest (60-70%).

[0070] The intelligent control unit uses the measured temperature T2 of the rear part of reaction zone 2 (main reaction section and supplementary heating section) and the outlet CO2 conversion rate ηCO2 as input signals. It utilizes the plasma heating device 3 in the preheating section to raise the temperature of the flue gas entering reaction zone 2 to 1550~1650℃, and executes the closed-loop regulation described in step S3 of Example 2: employing a cascade control logic that prioritizes temperature and follows conversion rate. First priority (safety and heat preservation): If T2 < 1200℃, regardless of the conversion rate, immediately increase the power of plasma heating device 3 (preset power ramp-up rate ≥ 500kW / s) until the temperature recovers to above 1200℃; Second priority (conversion meets the standard): After the temperature meets the condition, if ηCO2<85%, while keeping T2≥1200℃, simultaneously increase the carbon powder injection rate (rate ≤10% of the set value / s) and plasma power (matched according to the stoichiometric heat supplementation increment). Third priority (energy saving adjustment): If ηCO2>95% or T2 is too high and reaches or exceeds the process safety limit (1500℃), the intelligent control unit adjusts the carbon powder injection volume and plasma power based on the built-in algorithm.

[0071] (3) At the end of the blowing process (12 min to the end of the blowing process), gradually withdraw. The carbon content in the molten pool has dropped below 0.3%, the decarburization rate has decreased sharply, the flue gas volume has dropped rapidly, the CO concentration has decreased, and the O2 content in the flue gas has gradually increased. As the flue gas parameters decrease, the system proportionally reduces the carbon powder injection rate and plasma power; when the flue gas flow rate is lower than a certain preset threshold (such as 30% of the normal amount) or the CO concentration drops abnormally, the plasma heating device is gradually shut down and carbon injection stops, and the system enters standby mode.

[0072] (4) Rapid switching between furnace cycles Utilizing the second-level start-stop and power regulation capabilities of the plasma heating device 3, the system can complete a full reset before the next heat cycle begins after the previous heat cycle ends, adapting to the continuous operation rhythm of multiple heat cycles in the converter.

[0073] Example 4: Off-peak electricity storage operation mode The plasma heating device 3 of the present invention is preferentially operated during periods of low grid power load or during periods of surplus renewable power such as wind power and photovoltaic power, and the surplus electrical energy is stored in the form of coal gas chemical energy (Power-to-Gas).

[0074] The specific implementation method is as follows: During periods of low grid load (such as at night) or periods of high wind and solar power generation, the intelligent control unit, based on the power dispatch signal, appropriately increases the input power of the plasma heating device and simultaneously increases the carbon powder injection volume, while ensuring that the temperature of reaction zone 2 is not lower than 1200℃, so as to convert more CO2 into CO and stabilize the CO2 conversion rate within the target window of 85~95%, storing the off-peak electricity or abandoned wind and solar power in the converter gas in the form of coal gas chemical energy.

[0075] This operating mode combines the dual functions of deep waste heat recovery and flexible power system regulation. Taking a 120t converter as an example, it can recover approximately 28,000 to 43,000 tons of standard coal equivalent (tce) of chemical energy annually, which is equivalent to building a 12 to 19 GWh / year Power-to-Gas energy storage system. This system converts fluctuating off-peak electricity into converter gas chemical energy that can be stored for a long time without the need for additional gas storage facilities.

[0076] Example 5: Specific structure of the thermochemical waste heat recovery system of the present invention like Figure 1 As shown, the system of the present invention includes the following components: The converter hood 5 and the rising flue 6 are located above the furnace mouth of converter 1 and are used to collect the high-temperature primary flue gas escaping from the furnace mouth of converter 1. The converter hood 5 is a movable hood that can be raised and lowered as converter 1 tilts. The rising flue 6 is sealed to the hood and guides the flue gas into the subsequent processing unit.

[0077] The carbon powder injection device includes a carbon powder storage bin, a pneumatic conveying system, and a multi-layer carbon powder nozzle array arranged on the flue gas cross-section. Carbon powder nozzles 4 are installed inside the converter hood and / or rising flue, and can quantitatively and uniformly inject carbonaceous powder into the flue gas flow. Each layer of the carbon powder nozzle array consists of multiple carbon powder nozzles 4 arranged circumferentially inside the converter hood and / or rising flue, with staggered or sequential arrangement between upper and lower layers, preferably staggered. The carbon powder is pressurized and conveyed by compressed nitrogen, CO2, or recovered coal gas, and uniformly injected into the flue gas cross-section in the form of a multi-nozzle array, ensuring rapid dispersion and sufficient contact of the carbon powder in the high-temperature flue gas. Simultaneously, the carbon powder nozzles can receive a small amount of carbon powder particles captured by the subsequent flue gas dust collector of the converter for re-injection into the furnace reaction.

[0078] The plasma reheating reaction zone is a flue reactor lined with refractory and heat-insulating material, located inside the rising flue 6. The inner wall of reaction zone 2 is constructed with high-temperature resistant (≥1700℃) and thermal shock resistant high-alumina or chromium corundum refractory castable. Its interior is divided into three sections, each with independently adjustable plasma heating device arrays arranged along the flue gas flow direction. Preheating section 301 (P1): Located in front of reaction zone 2, containing one or more plasma torches; Main reaction section 302 (P2): Located in the middle of reaction zone 2, with one or more plasma torches arranged along the process; Reheating section 303 (P3): Located at the rear of reaction zone 2, containing one or more plasma torches.

[0079] Each plasma torch is arranged circumferentially inside the rising flue, with 3 to 6 torches per layer. The upper and lower layers are arranged in a staggered or sequential manner, with staggered arrangement being preferred.

[0080] Each plasma heating device 3 is equipped with an independent power supply and control module. The plasma heating device 3 is installed on the side wall or top of the reaction zone 2 via a water-cooled flange or air-cooled seal, with the torch nozzle pointing towards the mainstream of the flue gas or at a slight angle to promote mixing of the jet and the flue gas. The plasma heating device 3 is a DC arc plasma torch or an induction-coupled plasma torch, with a single torch power range of 10kW~2MW, supporting stepless power adjustment; the working gas is one or more of nitrogen, argon, CO2, and purified / recovered converter gas.

[0081] The temperature and composition detection unit includes high-temperature thermocouples (or infrared radiation temperature probes with a response time ≤1s) arranged at multiple points along the axial direction of the reaction zone, as well as an online CO / CO2 gas analyzer (non-dispersive infrared or laser gas analysis) to acquire temperature and composition signals in real time. The detection unit is located inside the converter hood and / or the rising flue.

[0082] The intelligent control unit is connected to the carbon powder injection device, plasma heating device, and detection unit. It receives data from the detection unit, incorporates a PID control algorithm and AI logic judgment module, and outputs control commands to adjust the input power of each segment of the plasma heating device array and the injection rate of the carbon powder injection device in a closed loop. This maintains the reaction zone temperature at no less than 1200℃ (preferably 1200~1300℃) and keeps the CO2 conversion rate stable within the target range of 85~95%. The intelligent control unit can be used in conjunction with a converter intelligent steelmaking system.

[0083] The waste heat recovery unit is a waste heat boiler used to recover the residual physical sensible heat of the flue gas at the outlet of the reaction zone and generate steam for production or power generation.

[0084] Example 6 With 1000Nm 3 The primary flue gas from the converter (dry basis, initial CO2 volume fraction 16%) was used as the treatment object. The CO2 conversion rate under the following operating conditions was investigated, and the results are shown in Table 1.

[0085] Table 1 Combination Figure 3 Based on Table 1, the experimental results are analyzed as follows: Under simple carbon injection conditions, the reaction zone temperature spontaneously collapses to approximately 1000°C due to the strong endothermic effect of the Büdow reaction, capping the CO2 conversion rate at approximately 58% using sensible heat, consistent with the thermodynamic calculation results of Example 1. When plasma heating is used to maintain the reaction zone temperature at 1100°C and 1150°C, the CO2 conversion rate improves (to 65% and 75%, respectively), but does not reach the lower limit of the target window of 85%, indicating that although there is significant improvement in the 1100-1150°C range, the kinetic rate is still insufficient. When the reaction zone temperature is maintained in the 1200-1300°C range, the CO2 conversion rate stabilizes within the target window of 88-95%, fully verifying the technical effect of maintaining the reaction zone temperature at no less than 1200°C (preferably 1200-1300°C). 1200°C is the effective lower limit temperature of the high conversion rate range of the Büdow gasification reaction; below this temperature, the conversion rate is difficult to stably reach 85%. When the temperature continues to rise above 1300℃, the rate of increase in conversion rate slows down, but the power consumption increases significantly, indicating that 1200~1300℃ is the high conversion rate range with the best overall energy efficiency.

[0086] The above experimental results fully verify the rationality and technical effect of the preferred parameter ranges in the claims of this invention: by maintaining the reaction zone temperature at not less than 1200℃ (preferably 1200~1300℃), the CO2 conversion rate can be significantly increased from about 58% with simple carbon injection to 85%~95%; the corresponding supplementary heat is 390~450MJ / 1000Nm 3 Flue gas, power consumption 127~147kWh / 1000Nm 3 The flue gas yields an equivalent of 10-16 kWh / t of steel and 6.5-9 kg of coke powder / t of steel, with an energy amplification ratio of 2-3.5 times. Simultaneously, maintaining a high temperature in the reaction zone ensures a more complete carbon gasification reaction, significantly reducing unreacted carbon powder emissions. Plasma heating uses electricity as the sole energy input, introducing no additional ash, sulfur, or other pollutants, making it cleaner.

[0087] The above are merely specific embodiments of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for recovering thermochemical waste heat from high-temperature flue gas in a high-temperature plasma-coordinated converter, characterized in that, Includes the following steps: Carbonaceous powder is injected into the primary flue gas duct of the converter in stages, so that the carbonaceous powder reacts with CO2 in the flue gas to undergo a Bourdon gasification reaction, converting the physical sensible heat of the flue gas into the chemical energy of the coal gas. Multiple adjustable plasma heating devices are pre-set in the reaction zone along the flue gas flow direction. Heat is added to the flue gas according to the real-time temperature of the reaction zone to increase the flue gas temperature, compensate for the endothermic temperature drop of the Büdör gasification reaction, and keep the temperature of the reaction zone above the lower limit temperature of the high conversion rate range of the Büdör gasification reaction. With the reaction zone temperature and flue gas CO2 conversion rate as control targets, the input power of the plasma heating device and the blowing rate of carbonaceous powder are adjusted in a closed loop to stabilize the CO2 conversion rate within the target range. The flue gas after the gasification reaction and its residual physical sensible heat are recovered.

2. The method for high-temperature flue gas thermochemical waste heat recovery in a high-temperature plasma-coordinated converter according to claim 1, characterized in that, The lower limit temperature of the high conversion rate range of the Bourdon gasification reaction is 1200℃.

3. The method for high-temperature flue gas thermochemical waste heat recovery in a high-temperature plasma-coordinated converter according to claim 1, characterized in that, The target range for CO2 conversion rate is 85-95%.

4. The method for high-temperature flue gas thermochemical waste heat recovery in a high-temperature plasma-coordinated converter according to claim 1, characterized in that, The plasma heating device is arranged in three sections along the flue gas flow direction: The preheating section is located in the front part of the reaction zone near the converter outlet, and is used to raise the temperature of the flue gas entering the reaction zone to above 1550~1650℃. The main reaction section is located in the middle of the reaction zone and is used to continuously compensate for the temperature drop caused by the endothermic reaction and maintain the temperature of the reaction zone in the high conversion rate range. The supplementary heating section, located in the rear region of the reaction zone, is used to provide supplementary heat for the final conversion of residual CO2.

5. The method for high-temperature flue gas thermochemical waste heat recovery from a high-temperature plasma-coordinated converter according to claim 1 or 4, characterized in that, The plasma heating device is a DC arc plasma torch or an induction-coupled plasma torch, with a single torch power range of 10kW~2MW, supporting stepless power adjustment; the working gas of the plasma heating device is one or more of nitrogen, argon, CO2, and purified and recovered converter gas.

6. The method for high-temperature flue gas thermochemical waste heat recovery from a high-temperature plasma-coordinated converter according to claim 1 or 4, characterized in that, The closed-loop regulation employs a cascade control logic that prioritizes temperature and follows CO2 conversion rate. First-level temperature control: When the temperature in the middle and rear part of the reaction zone is lower than the set lower limit, the output power of the plasma heating device in the middle and rear part is increased to raise the temperature back to the set range. Second-stage CO2 conversion rate control: When the temperature in the middle and rear of the reaction zone meets the requirements but the CO2 conversion rate is lower than the lower limit of the target range, the amount of carbonaceous powder injected into the middle and rear and the plasma heating power are increased simultaneously. The third-level overconversion correction: When the CO2 conversion rate is higher than the upper limit of the target range or the temperature of the reaction zone reaches or exceeds the upper limit of the process safety, the blowing rate of the carbonaceous powder in the middle and rear and the output power of the plasma heating device are gradually reduced.

7. The method for high-temperature flue gas thermochemical waste heat recovery in a high-temperature plasma-coordinated converter according to claim 6, characterized in that, For the periodic intermittent operation of converter smelting, a phased operation and control strategy is adopted: In the initial stage of blowing, the plasma heating device is started at low power to preheat the lining of the reaction zone. After the flue gas flow and temperature rise to the preset range, the plasma power and carbon powder blowing volume are gradually increased to raise the temperature to the set range. During the middle stage of blowing, the temperature of the flue gas entering the reaction zone is raised to 1550~1650℃ using the preheating section plasma heating device, and the closed-loop regulation adopts a cascade control logic that prioritizes temperature and follows conversion rate. Towards the end of the blowing process, the carbon powder injection rate and plasma power are reduced proportionally as the flue gas parameters decrease. When the flue gas parameters fall below the preset threshold, carbon injection is stopped and the plasma heating device is turned off.

8. The method for high-temperature flue gas thermochemical waste heat recovery from a high-temperature plasma-coordinated converter according to claim 1, characterized in that, The carbonaceous powder is selected from one or more of the following: coke powder, anthracite powder, semi-coke powder, biomass powder, and biomass carbon powder.

9. The method for high-temperature flue gas thermochemical waste heat recovery in a high-temperature plasma-coordinated converter according to claim 1, characterized in that, The plasma heating device operates preferentially during periods of low grid load or surplus renewable energy, storing the surplus electrical energy in the form of coal gas chemical energy.

10. A system for implementing the high-temperature plasma-coordinated converter high-temperature flue gas thermochemical waste heat recovery method according to any one of claims 1-9, characterized in that, Including a converter hood and rising flue, a water-cooled flue, and a waste heat recovery unit that are sequentially fluidly connected along the flue gas flow direction, and also including: Carbon powder injection device is used to inject carbonaceous powder into the flue gas stream; A plasma heating device is installed inside the converter hood and / or rising flue to supplement the flue gas with heat in order to maintain the temperature of the reaction zone. The detection unit is located inside the converter hood and / or rising flue, and is used to collect temperature signals and flue gas composition signals in the reaction zone; The intelligent control unit is connected to the toner spraying device, the plasma heating device, and the detection unit. The intelligent control unit is used to receive the data collected by the detection unit and output control signals to adjust the spraying rate of the toner spraying device and the heating power of the plasma heating device in a closed loop, so as to maintain the temperature of the reaction zone and control the CO2 conversion rate.

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