Solid waste blending combustion flue gas purification system and control method thereof

Abstract

The invention discloses a solid waste blending combustion flue gas purification system and a control method thereof, and belongs to the technical field of solid waste recycling and flue gas purification. The system comprises a boiler, a denitration device, a flue injection device, a pre-dust remover, a flue gas circulating fluidized bed semi-dry desulfurization reactor and a bag-type dust remover which are connected in sequence. And an online monitoring device, a control unit and a modification mixing device are also arranged. And the online monitoring device synchronously monitors the concentrations of HCl and chlorobenzene. The control unit adjusts the injection amount of the pre-dechlorination absorbent in real time according to the concentration of HCl, and adjusts the bed pressure drop, the water injection amount and the flue gas recirculation amount of the desulfurization reactor through cooperative control logic with dynamic safety as constraint according to the concentration of chlorobenzene, flue gas parameters and solid waste feeding amount signals. And the modification mixing device mixes and modifies part of desulfurized fly ash and primary solid waste and then returns the modified desulfurized fly ash to the boiler. According to the method, whole-process collaborative optimization is achieved, passive treatment is converted into active control, and the problems of working condition fluctuation, equipment hardening and pollution control are solved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and flue gas purification technology, specifically relating to a solid waste co-firing flue gas purification system and its control method. Background Technology

[0002] Co-incinerating solid wastes such as municipal and industrial sludge in coal-fired boilers is an effective way to reduce, render harmless, and utilize them as resources, and it also helps reduce carbon emissions from pure coal combustion, aligning with the policy direction of circular economy and low-carbon development. However, solid waste fuels are characterized by complex composition and fluctuating sources, and their co-incineration significantly alters flue gas characteristics, posing a severe challenge to end-of-pipe treatment: on the one hand, solid waste combustion produces high concentrations of unconventional pollutants such as hydrogen chloride, dioxins, and heavy metals; on the other hand, some solid wastes, such as municipal sludge, have high humidity and high viscosity, leading to unstable feed into the boiler. In addition, the co-incineration rate often fluctuates significantly with upstream supply, causing drastic fluctuations in key parameters such as flue gas flow rate and pollutant concentration at the boiler outlet.

[0003] Currently, when the proportion of solid waste co-firing is low, most projects follow the traditional "boiler + denitrification + high-efficiency dust collector + wet desulfurization" process. However, the wet desulfurization process has limited efficiency in the synergistic removal of pollutants such as dioxins and gaseous mercury. With increasingly stringent environmental requirements and higher co-firing ratios, the risk of failing to meet emission standards under this route is becoming increasingly prominent.

[0004] The circulating fluidized bed semi-dry desulfurization process is a treatment technology with high desulfurization rate and efficient synergistic removal of multiple pollutants, particularly suitable for the complex flue gas treatment of boilers that co-fire solid waste. However, in practical application to boilers that co-fire solid waste, this technology faces two prominent bottlenecks: First, the reaction of high-concentration HCl flue gas with calcium-based absorbents generates a large amount of highly hygroscopic calcium chloride, which easily absorbs moisture and caking in the reactor, ash hopper, and return system, disrupting the stable operation of the system; Second, facing the large and rapid changes in flue gas volume and pollutant concentration caused by fluctuations in solid waste feed, traditional control methods are slow to respond, making it difficult to maintain the stability of the fluidized bed (prone to bed collapse or ash shedding), and unable to optimize and adjust in real time to adapt to instantaneous peak loads such as dioxins, resulting in unstable emissions or even exceeding standards. Summary of the Invention

[0005] The purpose of this invention is to provide a solid waste co-firing flue gas purification system and its control method, employing a process of denitrification + flue gas duct injection of highly active calcium-based absorbent for dechlorination + pre-dust collector + flue gas circulating fluidized bed semi-dry desulfurization (fluidized bed reactor + bag filter). This invention monitors the HCl concentration in the raw flue gas to achieve feedforward adjustment of the flue gas duct injection, enabling dynamic and efficient pre-dechlorination with the highly active absorbent, preventing high-chlorine flue gas from entering the semi-dry desulfurization unit and thus avoiding caking problems. It also utilizes the concentration of chlorobenzene, a dioxin characterizer, in the raw flue gas to achieve feedforward dynamic adjustment of the bed pressure drop in the semi-dry desulfurization unit, achieving real-time compliance with emission standards for unconventional pollutants. Furthermore, it uses desulfurization ash to modify the solid waste, improving the stability of the solid waste feed and reducing fluctuations in flue gas volume, humidity, and pollutant concentration. Simultaneously, it couples the solid waste feed rate with the flue gas volume to control the opening of the flue gas recirculation duct damper in the semi-dry desulfurization unit, ensuring the stability of the semi-dry desulfurization fluidized bed when the solid waste co-firing amount fluctuates.

[0006] In a first aspect, embodiments of the present invention provide a solid waste co-firing flue gas purification system, comprising a boiler, a denitrification device, a flue gas injection device, a pre-dust collector, a flue gas circulating fluidized bed semi-dry desulfurization reactor, and a bag filter connected in sequence; the system further includes: An online monitoring device is installed in the flue downstream of the denitrification device to simultaneously monitor the concentration of HCl and the concentration of chlorobenzene, a dioxin characterizer, in the flue gas. The control unit is communicatively connected to the online monitoring device, the flue gas injection device, the flue gas circulating fluidized bed semi-dry desulfurization reactor, and the solid waste feeding system, respectively. The control unit is configured to: adjust the injection volume of the highly active calcium-based absorbent in the flue gas injection device in real time according to the HCl concentration monitored by the online monitoring device to achieve pre-removal of HCl; and dynamically adjust the bed pressure drop and process water injection volume of the flue gas circulating fluidized bed semi-dry desulfurization reactor through a collaborative control logic constrained by dynamic safe operation, based on the monitored chlorobenzene concentration, flue gas temperature, flue gas humidity and solid waste feed rate signal from the solid waste feeding system, and simultaneously adjust the flue gas recirculation volume of the flue gas circulating fluidized bed semi-dry desulfurization reactor in a feedforward control mode, at least based on the solid waste feed rate signal and the flue gas flow rate, to stabilize the fluidization velocity. The modified mixing device is connected to the desulfurization ash discharge port of the bag filter via a conveying pipeline to transport a portion of the desulfurization ash to the modified mixing device. The modified mixing device is also connected to the inlet pipeline of high-moisture viscous solid waste to mix and modify the transported desulfurization ash with the high-moisture viscous solid waste to form modified solid waste. The outlet of the modified mixing device is connected to the solid waste inlet of the boiler to send the modified solid waste back to the boiler for co-firing.

[0007] Secondly, embodiments of the present invention provide a method for purifying flue gas from co-firing solid waste, the method comprising: Coal and highly moist, sticky solid waste are fed into a boiler for incineration, producing flue gas containing pollutants. The flue gas is sequentially subjected to denitrification treatment, flue gas injection pre-dechlorination treatment based on real-time monitoring of HCl concentration, pre-dust removal treatment, flue gas circulating fluidized bed semi-dry desulfurization treatment, and bag filter dust removal treatment before being discharged. In the denitrification flue, the concentration of HCl in the flue gas and the concentration of chlorobenzene, which is a dioxin characterizer, are monitored simultaneously in real time. Based on the monitored HCl concentration, the injection volume of the highly active calcium-based absorbent in the pre-dechlorination treatment is adjusted in real time. Based on the monitored chlorobenzene concentration, flue gas temperature, flue gas humidity, and solid waste feed rate signal, the bed pressure drop and process water spray rate in the semi-dry desulfurization process are dynamically adjusted through a collaborative control logic constrained by dynamic safe operation. Meanwhile, using a feedforward control method, the amount of flue gas recirculation in the semi-dry desulfurization process is adjusted based at least on the solid waste feed rate signal and the flue gas flow rate to stabilize the fluidization velocity. A portion of the desulfurization ash collected during the bag filter dust removal process is mixed and modified with the high-moisture, viscous solid waste to be co-combusted, forming a modified solid waste with stable physical properties. The modified solid waste is returned to the boiler and burned together with coal.

[0008] The solid waste co-firing flue gas purification system provided by this invention achieves precise dynamic pre-dechlorination of the flue gas injection unit by real-time monitoring of the concentrations of HCl and chlorobenzene (a dioxin characterizer) in the raw flue gas and using these as key control parameters. This prevents high-chlorine flue gas from entering the subsequent semi-dry desulfurization unit from the source, completely eliminating the equipment caking problem caused by the generation of hygroscopic CaCl2. Simultaneously, based on the feedforward signal of chlorobenzene concentration, the bed pressure drop of the semi-dry desulfurization unit is dynamically and intelligently adjusted, ensuring efficient and stable removal of unconventional pollutants such as dioxins and real-time compliance with emission standards. Furthermore, by recycling dry desulfurization ash at the front end to modify high-moisture viscous solid waste, the uniformity of fuel properties and feeding stability are significantly improved, reducing fluctuations in flow rate, humidity, and pollutant concentration of the flue gas entering the furnace from the source. In addition, by coupling the solid waste feed rate and flue gas flow rate to perform feedforward control of the flue gas recirculation rate of the semi-dry desulfurization unit, the fluidized bed's hydrodynamic stability is ensured when the co-firing rate fluctuates. This system, through a closed-loop design encompassing "monitoring-pre-removal-coordinated control-source modification," transforms traditional passive end-of-pipe treatment into proactive process control. It systematically addresses challenges such as large fluctuations in solid waste co-firing conditions, equipment caking, and difficulty in pollutant control, comprehensively improving the reliability, adaptability, and overall operational efficiency of the flue gas purification system. Attached Figure Description

[0009] Figure 1 A flow chart of a solid waste co-firing flue gas purification system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a solid waste co-firing flue gas purification system provided in an embodiment of the present invention; Figure 3 for Figure 2 The flowchart in this embodiment shows the precise control of the control unit performing flue gas injection dechlorination. Figure 4 for Figure 2 The flowchart in this embodiment shows the coordinated control of the flue gas circulating fluidized bed semi-dry desulfurization reactor by the control unit. Figure 5 The images show a comparison of the morphology of sludge and dry desulfurization ash before and after modification. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0011] The co-firing of municipal solid waste in coal-fired boilers is currently in a stage of vigorous policy promotion and rapid development of large-scale application, but it faces increasing technical challenges and environmental supervision. Municipal solid waste mainly includes municipal sludge, industrial solid waste, and biomass. The co-firing process brings three problems: (1) The amount of solid waste co-firing cannot be controlled by itself and is directly related to the supply from the source. Therefore, the amount of co-firing fed into the furnace flues greatly. (2) Municipal solid waste, represented by municipal sludge, also has the problems of high viscosity, high humidity, and unstable feeding, which further aggravates the fluctuation range of the amount of co-firing fed into the furnace. (3) Usually, after solid waste is co-fired into the furnace, the humidity, dioxin concentration, HCl concentration, and heavy metal concentration of the flue gas will increase significantly compared with the pure coal-fired condition. Therefore, solid waste co-firing boilers have the characteristics of large fluctuations in flue gas conditions and complex pollutant composition, which brings great challenges to flue gas treatment.

[0012] Currently, among all treatment processes, the circulating fluidized bed semi-dry desulfurization method possesses the characteristic of synergistic treatment of multiple pollutants such as dioxins and heavy metals, making it highly suitable for flue gas treatment in boilers with co-firing solid waste. The circulating fluidized bed semi-dry desulfurization method mainly relies on material recirculation and the establishment of a high-concentration, high-density absorbent bed through a fluidized bed reactor to achieve the adsorption and removal of heavy metals and dioxins from the flue gas. However, when applied to boilers with co-firing solid waste, the aforementioned characteristics of these boilers can lead to problems in the operation of the desulfurization system, specifically as follows: First, the flue gas from boilers that co-fire solid waste has high humidity and high HCl concentration. In the semi-dry flue gas desulfurization process using circulating fluidized bed reactors, the reaction of Ca(OH)2 with high-concentration HCl generates a significant amount of CaCl2, leading to an increased proportion of CaCl2 in the downstream baghouse dust collector ash hopper and the recirculated material. CaCl2 is hygroscopic, therefore, it easily clumps in the ash hopper and circulating chute, making it difficult for the desulfurization system to operate stably.

[0013] Secondly, the large fluctuations in the amount of solid waste co-combusted and the instability of solid waste entering the furnace lead to significant fluctuations in flue gas volume, as well as in the concentrations of SO2, humidity, HCl, dioxins, and heavy metals. In particular, large fluctuations in flue gas volume, if not controlled promptly, can cause fluctuations in the reactor bed, even leading to ash shedding and bed collapse. These fluctuations in flue gas volume causing bed fluctuations, in turn, result in large fluctuations in pollutant emissions, especially for pollutants such as dioxins and heavy metals that rely on adsorption for removal. The fluctuations in the concentration of pollutants in the flue gas themselves can also easily lead to emissions exceeding standards.

[0014] This invention first establishes the following flue gas purification scheme: boiler flue gas first passes through a denitrification device, then successively through a flue gas injection device, a pre-dust collector, and enters a flue gas circulating fluidized bed semi-dry desulfurization reactor and a bag filter, finally being discharged into the chimney under the action of an induced draft fan. Online sampling devices for HCl and chlorobenzene are installed in the flue gas duct after denitrification. HCl concentration can be monitored online using methods such as Fourier transform infrared spectroscopy (FTIR) or tunable semiconductor laser absorption spectroscopy (TDLAS). While online monitoring of dioxins is not possible, chlorobenzene, as a characterizer of dioxins, exhibits a very high correlation with them. By monitoring chlorobenzene, changes in dioxin concentration can be indirectly measured. Chlorobenzene detection can be achieved using methods such as Fourier transform infrared spectroscopy (FTIR) and catalytic combustion + CO2 monitoring.

[0015] Real-time monitoring data of HCl in the raw flue gas is sent to the feeder regulation and control system of the flue gas injection device to control the injection volume of highly active calcium-based absorbent, thereby achieving pre-removal of HCl. The dechlorinated flue gas first passes through a pre-dust collector to remove dust containing dechlorination product CaCl2. The low-HCl-concentration flue gas after pre-dechlorination and pre-dust removal then enters the downstream flue gas circulating fluidized bed semi-dry desulfurization unit, which uses common calcium-based absorbents such as slaked lime or carbide slag. During operation, based on real-time monitoring of multiple parameters such as chlorobenzene concentration and humidity in the flue gas, the system dynamically and precisely adjusts the bed pressure drop and process water injection volume of the flue gas circulating fluidized bed semi-dry desulfurization reactor through a built-in intelligent control model. Simultaneously, to stabilize the fluidization state within the reactor, the system controls the circulation volume by adjusting the opening of the damper on the flue gas recirculation duct. Its control logic is as follows: the amount of solid waste fed into the furnace is used as a feedforward signal for coarse adjustment, and the real-time flue gas volume at the inlet of the device is used as a feedback signal for fine control, so as to ensure that the fluidized bed can operate stably under various working conditions.

[0016] After desulfurization, the flue gas enters the downstream bag filter for final particulate matter removal. The collected desulfurization ash is collected in the ash hopper of the dust collector and then disposed of in three ways: most of it is returned to the flue gas circulating fluidized bed reactor via a return chute to maintain and regulate the bed pressure drop; the remainder is diverted via a pneumatic conveying system, with one portion sent to the boiler inlet and the other to an ash silo. The desulfurization ash sent to the boiler inlet is mixed and modified with high-humidity, high-viscosity primary solid waste (such as municipal sludge, oil sludge, papermaking sludge, starch residue, pharmaceutical bacterial residue, etc.). In this process, the desulfurization ash acts as a conditioning agent, effectively adsorbing moisture and reducing viscosity, transforming the originally difficult-to-transport solid waste into physically stable and easily uniformly fed "modified solid waste." Through this closed-loop design, the system not only achieves resource utilization of desulfurization ash and reduces its end-of-pipe disposal pressure, but more importantly, it improves the feeding stability of solid waste entering the boiler from the source, thereby enhancing the stability of boiler combustion and the operational reliability of subsequent flue gas treatment facilities.

[0017] Through the aforementioned technical solutions, utilizing the prediction of fuel input or real-time monitoring data of key pollutants (such as HCl and chlorobenzene), and the graded treatment of pollutants, the system can proactively or synchronously adjust downstream purification units (injection volume, CFB bed pressure) and even upstream modification processes (desulfurization ash addition ratio), achieving dynamic synergistic optimization from front to back. This enables the system to proactively adapt to fluctuations in sludge composition, transforming the passive and delayed "end-of-pipe treatment" of traditional technologies into proactive and preventative "process control," improving the operating environment of the CFB semi-dry desulfurization unit, and enhancing the stability of the flue gas treatment system.

[0018] Through the aforementioned technical solution, the system comprehensively utilizes predictive information on the fuel entering the furnace and real-time monitoring data on key pollutants such as HCl and chlorobenzene. Combined with a graded pollutant treatment strategy, it can adjust downstream purification units (such as absorbent injection volume and circulating fluidized bed pressure drop) and even upstream fuel modification processes (such as the proportion of desulfurization ash addition) in advance or synchronously, achieving dynamic and coordinated optimization of the entire process from fuel pretreatment to flue gas purification. This design enables the system to proactively adapt to fluctuations in the composition of solid waste such as sludge, transforming the traditional passive and relatively lagging "end-of-pipe treatment" mode into a proactive and preventative "process control" mode. This not only significantly improves the operating environment of the circulating fluidized bed semi-dry desulfurization unit but also enhances the overall adaptability and operational stability of the flue gas treatment system.

[0019] To ensure the plan is clearly described, we will first combine... Figure 1 The system flowchart shown illustrates in detail the technical solution of the embodiment of the present invention.

[0020] like Figure 1 As shown, the solid waste co-firing flue gas purification system provided in this embodiment includes a boiler and a denitrification device connected sequentially through a flue. Figure 1 (abbreviated as denitrification in Chinese), air preheater ( Figure 1 (referred to as air preheater in Chinese) and flue gas injection device ( Figure 1 (referred to as flue gas dechlorination) and pre-dust collector ( Figure 1 (referred to as pre-dust removal in Chinese), flue gas circulating fluidized bed semi-dry desulfurization reactor ( Figure 1 The system is referred to as a fluidized bed reactor and a bag filter. It also includes an online monitoring device, a control unit, and a modified mixing device. Figure 1 (Not shown in the image).

[0021] I. The flue gas purification and energy recovery process is as follows: Coal and solid waste are co-fired in the boiler. This solid waste can include municipal sludge, industrial sludge, oil refinery sludge, papermaking black liquor, starch residue, pharmaceutical microbial residue, furfural residue, construction waste, and agricultural and forestry biomass. The flue gas from this co-firing contains high concentrations of pollutants such as HCl, dioxins, and heavy metals. After leaving the boiler, the flue gas first passes through a denitrification unit (using SNCR, SCR, or a combination thereof) to remove nitrogen oxides. The high-temperature flue gas after denitrification flows through an air preheater, where it exchanges heat with the cold air entering the boiler, recovering waste heat to improve boiler efficiency and simultaneously cooling the flue gas temperature to a range suitable for downstream treatment (e.g., 130-180℃).

[0022] The cooled flue gas enters the flue gas injection device. The control unit precisely adjusts and injects a highly active calcium-based absorbent (such as highly active lime) based on real-time monitoring of the HCl concentration. The gas-solid mixing device within the unit achieves rapid and thorough mixing with the flue gas, thus efficiently pre-removing HCl (removal rate can reach over 95%). Subsequently, the flue gas enters a pre-dust collector (such as a single-field to three-field electrostatic precipitator, bag filter, or electrostatic-bag composite dust collector), where the dust generated during the pre-dechlorination reaction, containing a large amount of hygroscopic CaCl2, is pre-captured and removed, ensuring that the flue gas entering the downstream main purification system is low in HCl concentration.

[0023] The pretreated flue gas then enters the core flue gas circulating fluidized bed semi-dry desulfurization reactor. In this reactor, the flue gas reacts with injected common calcium-based absorbents (such as slaked lime or carbide slag) in the fluidized bed, efficiently removing SO2 and SO3. Simultaneously, the high-concentration, high-density solid material bed is used to adsorb and remove pollutants such as dioxins and heavy metals. Finally, the flue gas enters a baghouse dust collector for gas-solid separation, and the clean flue gas is discharged through a chimney by an induced draft fan.

[0024] II. The intelligent collaborative control process is as follows: In the flue gas duct after the denitrification unit and before the air preheater, an online monitoring device (which can use Fourier transform infrared spectroscopy, FTIR) is used to simultaneously monitor the concentration of HCl and the concentration of chlorobenzene, which is a dioxin characterizer, in real time.

[0025] The control unit receives this monitoring data and solid waste feed rate signals from the fuel system, and executes two sets of core control logic: The first core control logic is precise control of HCl pre-dechlorination: based on the real-time HCl concentration and flue gas flow rate, the injection amount of highly active calcium-based absorbent in the flue gas injection device is dynamically calculated and adjusted through a feedforward-feedback composite algorithm to ensure efficient dechlorination and fundamentally eliminate the risk of downstream equipment caking caused by excessive CaCl2 generation.

[0026] The second core control logic is the collaborative optimization control of the flue gas circulating fluidized bed semi-dry desulfurization reactor. First, using the solid waste feed rate as a feedforward signal, combined with the reactor inlet flue gas flow rate, the flue gas recirculation rate is adjusted to proactively address the airflow impact caused by fuel fluctuations, ensuring the hydrodynamic stability of the fluidized bed foundation. Second, using multi-source signals such as chlorobenzene concentration, flue gas temperature, and humidity as inputs, a collaborative control logic constrained by dynamic safe operation intelligently decides and adjusts the reactor bed pressure drop and process water spray rate. This logic ensures that all adjustments are performed within safe boundaries to prevent condensation and caking, and prioritizes responses to changes in chlorobenzene concentration to ensure the stable and efficient removal of unconventional pollutants such as dioxins.

[0027] III. The material closed-loop and fuel modification process is as follows: Most of the desulfurization ash collected in the ash hopper of the bag filter is recycled back into the flue gas circulating fluidized bed semi-dry desulfurization reactor through the return chute to maintain the bed material density; a small portion is diverted through the pneumatic conveying system, one of which is sent to the ash silo, and the other is sent to the modified mixing device in front of the boiler.

[0028] In the modified mixing unit, the incoming desulfurization ash and highly viscous primary solid waste (such as municipal sludge, oil sludge, etc.) are mixed and modified according to the optimal ratio determined in advance through experiments (for municipal sludge, the dry basis mass ratio of desulfurization ash to sludge is usually not less than 1). This process includes: crushing and premixing in a primary mixer (such as a biaxial shear mixer) to achieve rapid water absorption and initial de-viscosity; high-intensity shearing and micro-homogenization in a secondary high-speed mixing unit (such as a high-speed vortex activation mixer) to achieve deep modification and microbial inhibition; and finally, molding and aging to obtain granular modified solid waste with stable physical properties, good flowability, and easy precise measurement. This modified solid waste is then returned to the boiler's feeding system, completing a closed-loop material process of "treating waste with waste."

[0029] The technical solution provided by this invention, by real-time monitoring of the concentrations of HCl and dioxin characterizer chlorobenzene in the raw flue gas and using them as key control parameters, firstly achieves precise dynamic pre-dechlorination of the flue gas injection unit, preventing high-chlorine flue gas from entering the subsequent semi-dry desulfurization unit from the source, thereby fundamentally solving the equipment caking problem caused by CaCl2 formation; simultaneously, based on the feedforward signal of chlorobenzene concentration, the bed pressure drop of the semi-dry desulfurization unit is dynamically adjusted, ensuring efficient and stable removal of pollutants such as dioxins and real-time compliance with emission standards, and improving the overall energy efficiency of the system, achieving energy saving and carbon reduction; furthermore, by recycling dry desulfurization ash for front-end solid waste modification, the physical stability of the solid waste feed is effectively improved, reducing the fluctuation range of flue gas flow, humidity, and pollutant concentration; in addition, by coupling the solid waste feed rate and flue gas flow rate signals, the opening of the flue gas recirculation damper of the semi-dry desulfurization unit is controlled by feedforward, ensuring the hydrodynamic stability of the fluidized bed under fluctuating co-firing conditions, thereby comprehensively enhancing the system's adaptability and operational reliability in the face of fluctuations in solid waste fuel.

[0030] After a detailed description of the system flow of the embodiments of the present invention, the following will be combined with Figure 2 A detailed description of a solid waste co-firing flue gas purification system according to an embodiment of the present invention is provided.

[0031] like Figure 2As shown in the figure, the solid waste co-firing flue gas purification system 20 provided in this embodiment of the invention includes a boiler 210, a denitrification device 220, a flue gas injection device 230, a pre-dust collector 240, a flue gas circulating fluidized bed semi-dry desulfurization reactor 250, and a bag filter 260 connected in sequence; the system also includes an online monitoring device 270, a control unit 280, and a modified mixing device 290.

[0032] The functions and connections of the main components are as follows: 1. Boiler 210: Used for co-firing coal and solid waste, and is the source of flue gas and pollutants.

[0033] 2. Denitrification device 220: connected to the boiler outlet, used to remove nitrogen oxides from the flue gas.

[0034] 3. Air preheater (in) Figure 2 (In the embodiment, the actual output is as follows): Located after the denitrification device 220, it is used to recover the waste heat of flue gas to heat the boiler intake air, while cooling the flue gas to a temperature suitable for downstream treatment.

[0035] 4. Online monitoring device 270: installed in the flue downstream of the denitrification device 220 (before or after the air preheater) to synchronously and in real time monitor the HCl concentration and the chlorobenzene concentration, which is a dioxin characterizer, in the flue gas.

[0036] 5. Flue gas injection device 230: Located downstream of the air preheater, it is used to inject a highly active calcium-based absorbent (such as highly active lime) into the flue gas duct to perform efficient pre-removal of HCl under the command of the control unit 280.

[0037] 6. Pre-dust collector 240: Immediately following the flue gas injection device, it is used to capture dust containing a large amount of CaCl2 generated by the pre-dechlorination reaction and remove it from the system to protect downstream core equipment.

[0038] 7. Flue gas circulating fluidized bed semi-dry desulfurization reactor 250: Receives pretreated flue gas with low HCl concentration, injects ordinary calcium-based absorbent (such as slaked lime), and efficiently removes SO2 and SO3 through the established fluidized bed, while also adsorbing and removing pollutants such as dioxins and heavy metals.

[0039] 8. Baghouse Dust Collector 260: Used for the final removal of particulate matter from flue gas, achieving ultra-clean emissions. Its ash hopper collects desulfurization ash.

[0040] 9. Control Unit 280: As the brain of the system, it is connected to the online monitoring device 270, the flue gas injection device 230, the flue gas circulating fluidized bed semi-dry desulfurization reactor 250, and the solid waste feeding system of the boiler.

[0041] 10. Modified mixing device 290: Connected to the desulfurization ash discharge port of bag filter 260 via a conveying pipeline to receive a portion of the desulfurization ash; simultaneously connected to the feed pipeline for high-moisture viscous solid waste (such as municipal sludge). Its discharge port is connected to the solid waste feed port of boiler 210.

[0042] The system's operation and control process is as follows: The control unit 280 dynamically calculates and adjusts the injection volume of the highly active calcium-based absorbent in the flue gas injection device 230 based on the real-time HCl concentration monitored by the online monitoring device 270, thereby achieving precise and efficient HCl pre-removal and fundamentally preventing caking of downstream equipment.

[0043] Meanwhile, the control unit 280, based on the monitored chlorobenzene concentration (characterizing dioxins), flue gas temperature, flue gas humidity, and solid waste feed rate signal from the feeding system, intelligently adjusts the bed pressure drop and process water spray rate of the flue gas circulating fluidized bed semi-dry desulfurization reactor 250 through a set of collaborative control logic constrained by dynamic safe operation, in order to optimize pollutant removal efficiency and ensure operational safety.

[0044] In addition, the control unit 280 uses a feedforward control method to adjust the flue gas recirculation rate of the flue gas circulating fluidized bed semi-dry desulfurization reactor 250 based at least on the solid waste feed rate signal and the flue gas flow rate at the reactor inlet, so as to actively compensate for fuel fluctuations, stabilize the fluidized bed wind speed, and prevent bed collapse.

[0045] The closed-loop and modification process of the material is as follows: The desulfurization ash collected by the bag filter 260 is divided into three paths: most of it is returned to the flue gas circulating fluidized bed semi-dry desulfurization reactor 250 through the return chute to maintain the bed density; a portion is discharged to the ash silo; and the remaining portion is sent to the modified mixing device 290 through the conveying pipeline.

[0046] In the modified mixing unit 290, desulfurization ash and high-moisture, viscous raw solid waste are mixed and modified in multiple stages according to a preset ratio (for example, for municipal sludge, the mass ratio of desulfurization ash to sludge is not less than 1). This process includes crushing and premixing, high-speed shearing homogenization, molding, and aging, resulting in modified solid waste with stable physical properties that is easy to transport. Finally, the modified solid waste is sent back to the solid waste inlet of boiler 210, completing the closed loop of "desulfurization ash - modifier - stable fuel," thereby improving the stability of combustion and flue gas conditions from the source.

[0047] The solid waste co-firing flue gas purification system provided by this invention achieves precise dynamic pre-dechlorination of the flue gas injection unit by real-time monitoring of the concentrations of HCl and chlorobenzene (a dioxin characterizer) in the raw flue gas and using these as key control parameters. This prevents high-chlorine flue gas from entering the subsequent semi-dry desulfurization unit from the source, completely eliminating the equipment caking problem caused by the generation of hygroscopic CaCl2. Simultaneously, based on the feedforward signal of chlorobenzene concentration, the bed pressure drop of the semi-dry desulfurization unit is dynamically and intelligently adjusted, ensuring efficient and stable removal of unconventional pollutants such as dioxins and real-time compliance with emission standards. Furthermore, by recycling dry desulfurization ash at the front end to modify high-moisture viscous solid waste, the uniformity of fuel properties and feeding stability are significantly improved, reducing fluctuations in flow rate, humidity, and pollutant concentration of the flue gas entering the furnace from the source. In addition, by coupling the solid waste feed rate and flue gas flow rate to perform feedforward control of the flue gas recirculation rate of the semi-dry desulfurization unit, the fluidized bed's hydrodynamic stability is ensured when the co-firing rate fluctuates. This system, through a closed-loop design encompassing "monitoring-pre-removal-coordinated control-source modification," transforms traditional passive end-of-pipe treatment into proactive process control. It systematically addresses challenges such as large fluctuations in solid waste co-firing conditions, equipment caking, and difficulty in pollutant control, comprehensively improving the reliability, adaptability, and overall operational efficiency of the flue gas purification system.

[0048] exist Figure 2 Based on the illustrated embodiment, as one implementation of the present invention, the control unit is configured to perform precise control of flue gas injection dechlorination, such as... Figure 3 As shown, it specifically includes: S310 acquires in real time the raw HCl concentration signal from the online monitoring device, the flue gas volumetric flow rate signal from the flue gas flow meter, and the feedback signal of absorbent injection amount or feeder opening from the flue gas injection device feeding system; performs validity verification and smoothing filtering on the raw HCl concentration signal and the flue gas volumetric flow rate signal to obtain a smoothed HCl concentration value for control.

[0049] Specifically, the raw HCl concentration signal C_HCl_raw(t) from the FTIR analyzer, the flue gas volume flow rate signal Q_flue(t) from the flue gas flow meter, and the feedback signal M_hrcd(t) from the current high-activity calcium-based absorbent injection rate or feeder opening from the feeding system are read in real time.

[0050] First, signal quality and validity are assessed for C_HCl_raw(t) and Q_flue(t), including checking whether the signal is within the valid range and whether the rate of change has abnormally jumped. If the data is invalid, the flue gas injection device is controlled to maintain the output of the previous control cycle, and an alarm for abnormal monitoring data is triggered. If the data is valid, the valid raw HCl concentration signal is subjected to moving average or low-pass filtering to eliminate measurement noise and obtain a smoothed HCl concentration value C_HCl(t) for control.

[0051] S320 calculates the total amount of HCl to be removed based on the target dechlorination efficiency, smoothed HCl concentration value, and flue gas volume flow rate signal. Based on the preset theoretical calcium-chlorine molar ratio, effective calcium content of absorbent, and total amount of HCl to be removed, it calculates the theoretically required absorbent feedforward amount.

[0052] Specifically, based on the set target dechlorination efficiency η_target (e.g., 95%) and the smoothed concentration value C_HCl(t) and flue gas volumetric flow rate Q_flue(t) obtained in step S310, the total amount of HCl to be removed is calculated as M_HCl_remove(t) = C_HCl(t) * Q_flue(t) * η_target. Based on the preset theoretical calcium-chlorine molar ratio Ca / Cl_stoich determined through on-site commissioning and the effective calcium content X_Ca of the highly active calcium-based absorbent used, the theoretically required absorbent feedforward is calculated as M_hrcd_ff(t) = M_HCl_remove(t) * Ca / Cl_stoich / X_Ca.

[0053] S330 compares the smoothed HCl concentration value with the preset safety threshold concentration to obtain the concentration deviation, and uses a proportional-integral controller to calculate the feedback correction amount based on the concentration deviation.

[0054] Specifically, the smoothed HCl concentration value C_HCl(t) is compared with the system's preset "safe threshold concentration" C_HCl_safe (this threshold is far below the critical concentration that may cause downstream caking), resulting in the concentration deviation e(t) = C_HCl(t) - C_HCl_safe. This deviation e(t) is then input into a proportional-integral controller to calculate the feedback correction M_hrcd_fb(t) = Kp * e(t) + Ki * ∫ e(t) dt, where Kp and Ki are pre-tuned controller parameters.

[0055] S340 synthesizes the theoretical feedforward injection quantity and feedback correction quantity, generates the final absorbent injection control command, and outputs it to the feeding system of the flue gas injection device for execution.

[0056] Specifically, the feedforward and feedback correction quantities are synthesized to generate the final absorbent injection control command M_hrcd_cmd(t) = M_hrcd_ff(t) + M_hrcd_fb(t). The actuator module, based on the feeder's mechanical characteristics, limits the command's speed (to prevent sudden changes in actuator opening) and position (to ensure the command remains within the feeder's maximum and minimum capabilities). Finally, the processed command is converted into a motor speed or valve opening signal and sent to the precision feeder of the flue gas injection system for execution.

[0057] Through the above closed-loop control process, the system can dynamically optimize the injection volume of highly active calcium-based absorbent based on the real-time fluctuation of the inlet HCl load. While ensuring efficient pre-dechlorination (removal rate can reach over 95%) and completely eliminating the risk of caking in downstream equipment, it also achieves precise and economical addition of absorbent.

[0058] exist Figure 3 Based on the flue gas injection dechlorination control process embodiment shown, as a specific implementation of this invention, step S310 involves validating and smoothing the original HCl concentration signal and flue gas volume flow rate signal to obtain a smoothed HCl concentration value for control. This specifically includes the following steps: Step a1: Perform signal quality judgment on the original HCl concentration signal and the flue gas volume flow rate signal respectively. The signal quality judgment includes judging whether the signal value is within the preset range and judging whether the rate of change of the signal exceeds the preset abnormal jump threshold.

[0059] Specifically, real-time signal quality assessments are performed on the raw HCl concentration signal C_HCl_raw(t) acquired from an online monitoring device (such as an FTIR analyzer) and the flue gas volumetric flow rate signal Q_flue(t) acquired from a flue gas flow meter. This assessment includes two aspects: first, determining whether the signal value is within the preset effective range of the sensor or instrument to identify faults such as sensor failure or signal loss; second, determining whether the instantaneous rate of change of the signal exceeds a preset abnormal jump threshold based on process possibilities, in order to filter out drastic fluctuations in signals caused by electromagnetic interference, sampling anomalies, or other non-realistic physical processes.

[0060] Step a2: If any signal is determined to be invalid, the control flue gas injection device maintains the absorbent injection volume of the previous control cycle and triggers an alarm for abnormal monitoring data.

[0061] If either the C_HCl_raw(t) or Q_flue(t) signal is determined to be invalid in step a1, the current monitoring data is deemed unreliable. In this case, the control unit will immediately implement a safety maintenance strategy: sending a command to the feeder of the flue gas injection device to maintain the absorbent injection rate of the previous control cycle, thus avoiding process fluctuations caused by erroneous adjustments based on incorrect data. Simultaneously, the system triggers a "monitoring data anomaly" alarm, notifying operators to inspect and intervene.

[0062] Step a3: If the signal is valid, perform a moving average or low-pass filtering on the original HCl concentration signal to eliminate measurement noise and obtain a smooth HCl concentration value.

[0063] If both C_HCl_raw(t) and Q_flue(t) are deemed valid, further digital signal processing is performed on C_HCl_raw(t) to suppress noise. Specifically, a moving average filter or low-pass filter algorithm is used to filter out high-frequency random measurement noise and minor interference. After this processing, a smooth, stable signal that accurately reflects the trend of HCl concentration changes is output, which is the smoothed HCl concentration value C_HCl(t) used for control, providing a reliable data foundation for subsequent feedforward and feedback precision control calculations.

[0064] Through the rigorous data preprocessing steps described above, the system ensures the high quality and reliability of the input data upon which the core control algorithm relies. This is a crucial prerequisite for achieving precise and stable pre-dechlorination of flue gas injection and ultimately eradicating the caking problem in downstream equipment.

[0065] exist Figure 3 Based on the illustrated flue gas injection dechlorination control process embodiment, as a specific implementation of this invention, step S340, which synthesizes the theoretical feedforward injection quantity and feedback correction quantity to generate the final absorbent injection control command, and outputs it to the feeding system of the flue gas injection device for execution, specifically includes the following steps: Step b1: The theoretically required absorbent feedforward amount and the feedback correction amount are superimposed to generate the initial control command.

[0066] Specifically, the theoretically required absorbent feedforward quantity M_hrcd_ff(t) calculated based on the flue gas HCl load is algebraically superimposed with the feedback correction quantity M_hrcd_fb(t) calculated based on the concentration deviation using a proportional-integral controller, to generate the initial absorbent injection quantity control command M_hrcd_cmd_raw(t) = M_hrcd_ff(t) + M_hrcd_fb(t). This step combines the rapid response of the feedforward with the precise adjustment of the feedback.

[0067] Step b2: Compare the smoothed HCl concentration value with the preset warning threshold concentration. If the smoothed HCl concentration value is continuously higher than the warning threshold concentration in multiple consecutive sampling periods, and the current feeding capacity of the flue gas injection device's feeding system has reached its upper limit, then generate and output an alarm signal to prompt a reduction in the amount of solid waste co-combustion.

[0068] Specifically, the filtered and smoothed HCl concentration value C_HCl(t) is compared with a preset "warning threshold concentration" C_HCl_warn, which is higher than the safety threshold. If the system detects that C_HCl(t) is consistently higher than C_HCl_warn for multiple consecutive sampling periods (e.g., N), it determines that it has entered a high-risk operating condition. At this time, if the actual current feed rate of the flue gas injection device feeding system has reached its maximum capacity (i.e., full load operation), it means that the system can no longer cope with such a high HCl load through its own adjustment. Therefore, the control unit will generate and output a high-level alarm signal to the boiler main control system or operator interface, clearly indicating that it is necessary to "reduce the amount of solid waste co-combustion" from the source to prevent the risk of caking in downstream equipment due to incomplete HCl removal.

[0069] Step b3 involves performing rate and position limiting processing on the initial control commands to ensure they conform to the mechanical execution characteristics of the solid waste feeding system, and then converting the processed commands into control signals to drive the feeder.

[0070] Specifically, considering the physical limitations and operational stability requirements of actuators such as the feeder, the initial control command M_hrcd_cmd_raw(t) generated in step b1 undergoes two processes: First, rate limiting is applied to restrict the speed of command change, preventing sudden changes in feeder opening that could cause mechanical shock and process disturbances; second, position limiting is applied to ensure that the final command value is within the feeder's rated minimum and maximum feeding capacity range. After these limiting processes, the final, safely executable absorbent injection quantity command M_hrcd_cmd(t) is obtained. Finally, the control unit converts this digital command into a physical control signal (such as a 4-20mA current signal or pulse signal) that can directly drive the feeder motor (to adjust the speed) or valve (to adjust the opening) and outputs it, thus completing the closed loop from control calculation to physical execution.

[0071] Through the complete process of instruction synthesis, safety judgment and execution adaptation, the system not only achieves precise control of dechlorination dosage, but also incorporates operating condition risk assessment and equipment protection mechanisms, ensuring that the pre-dechlorination unit can operate safely, stably and efficiently under various operating conditions.

[0072] The removal of dioxins in a fluidized bed reactor mainly relies on the adsorption effect of the high-density fluidized bed. Therefore, a high-density fluidized bed is key to achieving efficient dioxin removal. When the initial dioxin concentration increases, the bed pressure drop should be appropriately increased to enhance adsorption capacity; conversely, when the initial dioxin concentration decreases, the bed pressure drop should be appropriately decreased to achieve energy conservation and carbon reduction.

[0073] Currently, dioxin detection requires high-resolution gas chromatography-mass spectrometry (HRGC-HRMS), with a detection cycle of 7-15 days and a single detection cost of tens of thousands of yuan. This is not only expensive but also fails to meet the basic requirements for dynamic control of flue gas treatment facilities in terms of timeliness. Chlorobenzene is one of the core precursors of dioxins. Chlorinated organic compounds (such as PVC and chlorinated pesticides) decompose into monocyclic aromatic hydrocarbons such as chlorobenzene and chlorophenol during combustion. These substances, catalyzed by metal oxides (Cu, Fe, etc.) on the surface of fly ash, undergo condensation and cyclization reactions to generate polycyclic dioxins. In scenarios such as municipal solid waste incineration and industrial solid waste co-incineration, when combustion conditions are stable, the correlation coefficient between the emission concentrations of monochlorobenzene, dichlorobenzene, and dioxins can reach 0.75-0.9.

[0074] Therefore, this invention employs an online monitoring method for dioxin-based characterization of chlorobenzene pollutants in raw flue gas. The detection of chlorobenzene can utilize methods such as Fourier transform infrared spectroscopy (FTIR) or catalytic combustion + CO2 monitoring, achieving monitoring response times ranging from seconds to minutes. The monitoring data is sent as input variables to the control system of the fluidized bed reactor to control the opening of the material circulation valve, thereby achieving dynamic adjustment of the pressure drop in the fluidized bed reactor bed.

[0075] exist Figure 2 Based on the system embodiment shown, as a specific implementation of this invention, the control unit is configured to perform coordinated control of the flue gas circulating fluidized bed semi-dry desulfurization reactor. This control logic aims to address the strong coupling fluctuations of multiple flue gas parameters caused by solid waste co-firing, and its process is as follows: Figure 4 As shown, the specific configuration and steps include the following: S410 simultaneously collects chlorobenzene concentration, flue gas temperature, flue gas humidity, flue gas flow rate, measured bed pressure drop, solid waste feed rate, and current water spray rate.

[0076] During each control cycle, all key real-time data reflecting the system status are synchronously collected and acquired. These data include: chlorobenzene concentration C_CB(t) from the online monitoring device (as a correlated signal of dioxin formation potential); flue gas inlet temperature T_in(t) and outlet temperature T_out(t) from the temperature sensor; flue gas humidity H_flue(t) from the hygrometer; flue gas flow rate Q_flue(t) from the flow meter; measured bed pressure drop ΔP_bed(t) from the differential pressure transmitter; solid waste feed rate M_waste(t) and rate of change R_waste(t) from the feed control system; and current process water spray rate F_water(t).

[0077] S420 determines the upper limit of bed pressure drop, the upper limit of water spray volume, and the lower limit of outlet temperature under the current operating conditions based on flue gas temperature and humidity.

[0078] Specifically, a dynamic safety assessment is performed based on the collected flue gas temperature and humidity. First, the flue gas dew point temperature T_dp(t) under the current operating conditions is calculated in real time based on the flue gas humidity H_flue(t). Then, a preset safety temperature margin (e.g., 10-20℃) is added to T_dp(t) to determine the lower limit of the safe outlet temperature T_out_min(t) to ensure that condensation does not occur. Simultaneously, using the real-time flue gas temperature T_out(t) and humidity H_flue(t) as inputs, a preset dynamic safety operating envelope model is queried or calculated to obtain the upper limit of the allowable bed pressure drop ΔP_max(t) and the upper limit of the spray water volume F_water_max(t) under the current operating conditions. This step delineates an inviolable safe operating zone for the entire coordinated control system.

[0079] S430 determines the desired bed pressure drop based at least on the chlorobenzene concentration and the desired spray volume based on the temperature control target. It then conducts conflict arbitration within the boundaries of the upper limit of the allowable bed pressure drop, the upper limit of the allowable spray volume, and the lower limit of the safe outlet temperature to generate preliminary bed pressure drop and spray volume settings.

[0080] Specifically, based at least on the chlorobenzene concentration C_CB(t), the desired bed pressure drop ΔP_desired(t) required to achieve the target dioxin removal efficiency is determined by consulting a pre-defined mapping table or function model of "chlorobenzene concentration-bed pressure drop-removal efficiency". This relationship is obtained through preliminary combustion tests and calibration to ensure that a higher chlorobenzene concentration corresponds to a higher bed pressure setting to enhance adsorption.

[0081] Based on the deviation between the temperature control target (usually set as T_target(t) = T_dp(t) + 20℃) and the current outlet temperature T_out(t), the desired process water spray volume F_water_desired(t) is calculated to adjust the temperature and humidity environment inside the reactor.

[0082] It is determined whether the "desired operating point" composed of ΔP_desired(t) and F_water_desired(t) exceeds the dynamic safety boundary (ΔP_max(t), F_water_max(t), T_out_min(t)) determined in step S420. If a conflict exists, for example, if satisfying both conditions simultaneously would cause the outlet temperature to approach or fall below T_out_min(t), an arbitration mechanism is initiated. This mechanism follows the "safety first" principle. Within the safety envelope, by adjusting the weights or using a constraint relaxation algorithm, a set of suboptimal solutions that satisfy both safety requirements and efficiency and temperature control objectives is recalculated, i.e., generating the initial bed pressure drop setpoint ΔP_set(t) and spray volume setpoint F_water_set(t).

[0083] S440 predicts the impact of changes in the water spray rate setpoint on flue gas humidity and material viscosity; based on the predicted impact, it calculates the bed pressure drop compensation required to maintain a stable fluidization state. The bed pressure drop compensation is then superimposed on the initial bed pressure drop setpoint to obtain the final bed pressure drop control command.

[0084] Based on the changes in F_water_set(t) generated in step S430, its potential impact on flue gas humidity, particle surface humidity and material viscosity in the reactor is predicted, and the potential disturbance of this impact on the fluidization quality of the bed is assessed.

[0085] Based on the predicted level of disturbance, the required bed pressure drop compensation ΔP_comp_water(t) to offset the disturbance and maintain ideal fluidization is calculated. The compensation is then superimposed on the initial setpoint to generate the final bed pressure drop control command ΔP_cmd(t) = ΔP_set(t) + ΔP_comp_water(t), thereby achieving dynamic decoupling at the control level.

[0086] S450 sends the final bed pressure drop control command and the spray water volume setpoint to the reactor's bed pressure drop control model and process spray water volume control model, respectively.

[0087] The bed pressure drop control model is configured to receive bed pressure drop control commands and, in conjunction with the solid waste feed rate feedforward signal, output adjustment signals for the material circulation valve and flue gas recirculation damper through control calculations. The process water spray rate control model is configured to receive the water spray rate setpoint and, in conjunction with the solid waste feed rate feedforward signal and the outlet temperature feedback signal, output adjustment signals for the process water regulating valve through control calculations.

[0088] Specifically, ΔP_cmd(t) is sent to the bed pressure drop control model. After receiving the instruction, the model combines the solid waste feedforward signal M_waste(t) and its rate of change, and outputs adjustment signals for the material circulation valve and flue gas recirculation damper through control calculations (such as PID algorithm). By changing the circulating ash amount and recirculation air volume, the model can accurately track the target bed pressure.

[0089] The F_water_set(t) is sent to the process water spray control model. After receiving the command, the model combines the feedforward signal of solid waste feed rate and the feedback signal of outlet temperature T_out(t), and outputs the adjustment signal of process water regulating valve through control calculation to achieve precise control of water spray rate and stabilize reactor outlet temperature.

[0090] Through the coordinated control of the above multi-step process, the system can intelligently respond to multiple fluctuations in chlorobenzene (dioxin) concentration, flue gas parameters, and fuel quantity. Under the premise of ensuring absolute safety by preventing condensation and caking, it dynamically optimizes the bed state and water spraying conditions, thereby simultaneously achieving the comprehensive goals of efficient pollutant removal, stable fluidized bed operation, and energy saving and consumption reduction. This realizes a fundamental shift from passive response to proactive and preventive process control.

[0091] exist Figure 4 Based on the illustrated embodiment, as one implementation of the present invention, the upper limit of allowable bed pressure drop, the upper limit of allowable water injection volume, and the lower limit of safe outlet temperature under the current operating conditions are determined based on flue gas temperature and humidity, including: Calculate the dew point temperature of the flue gas based on the flue gas humidity; determine the lower limit of the outlet temperature by summing the dew point temperature with the preset safety temperature margin; and obtain the upper limit of the bed pressure drop and the upper limit of the water spray volume based on the flue gas temperature and humidity by querying the preset dynamic safety operation envelope model. Furthermore, the control unit is also configured to perform safety status diagnostics, including: Based on the measured bed pressure drop, the current water flow rate, and the outlet temperature, determine whether the current operating point is within the safety envelope defined by the upper limit of the allowable bed pressure drop, the upper limit of the allowable water flow rate, and the lower limit of the safe outlet temperature. If the measured bed pressure drop exceeds the upper limit of the allowable bed pressure drop, or enters the preset boundary ratio area below the upper limit of the allowable bed pressure drop, or the current water spray volume exceeds the upper limit of the allowable water spray volume, or enters the preset boundary ratio area below the upper limit of the allowable water spray volume, or the outlet temperature is lower than the lower limit of the safe outlet temperature, or enters the preset boundary ratio area above the lower limit of the safe outlet temperature, a safety warning signal will be generated and output.

[0092] Specifically, firstly, based on the real-time collected flue gas humidity H_flue(t), the dew point temperature T_dp(t) of the flue gas under the current operating conditions is calculated in real time using thermodynamic formulas (or empirical models). Then, this dew point temperature is added to a preset safety temperature margin (e.g., a 10~20℃ margin set to reliably prevent condensation), and the sum is determined as the strictly enforceable lower limit of the outlet temperature safety margin T_out_min(t), i.e., T_out_min(t) = T_dp(t) + ΔT_safe (where ΔT_safe is the safety margin value).

[0093] Using the real-time collected flue gas temperature T_out(t) and flue gas humidity H_flue(t) as joint inputs, a pre-built dynamic safe operating envelope model stored in the control unit is queried. This model defines the extreme operating conditions that the system can withstand to avoid condensation, caking, and fluidization deterioration under different temperature and humidity combinations. Through querying, the system obtains in real-time the upper limit of bed pressure drop ΔP_max(t) and the upper limit of water spray volume F_water_max(t) that strictly correspond to the current operating conditions.

[0094] Furthermore, the control unit is configured to continuously perform safety status diagnostics both simultaneously with and after determining the aforementioned dynamic safety boundaries, the logic of which includes: First, the system assesses the safety of the operating point: Based on the real-time measured bed pressure drop ΔP_bed(t), the current water flow rate F_water(t), and the outlet temperature T_out(t), the system constructs and tracks the currently operating "operating point" (ΔP_bed(t), F_water(t), T_out(t)). The core diagnostic task is to determine whether the operating point is located within the safe area enclosed by the real-time updated three-dimensional safety envelope determined in step S420. This safe area is jointly defined by ΔP_max(t), F_water_max(t), and T_out_min(t).

[0095] Second, the warning signal generation logic: The system performs multiple condition checks in real time. If any of the following conditions are met, the system will immediately generate and output a safety warning signal of the corresponding level: Condition 1: If ΔP_bed(t) exceeds ΔP_max(t), or enters the preset boundary ratio region below ΔP_max(t) (for example, entering the 90%-100% range of the upper limit value, i.e., the "warning zone"); Condition 2: If F_water(t) exceeds F_water_max(t), or enters the preset boundary ratio region below F_water_max(t); Condition 3: If T_out(t) is lower than T_out_min(t), or enters a preset boundary ratio region above T_out_min(t) (for example, the temperature margin is lower than a certain ratio of the set safety value).

[0096] The safety warning signal can include different levels (such as reminder, warning, alarm) and can be directly linked to the human-machine interface, log system or higher-level interlocking protection logic to ensure that operators can be aware of risks in a timely manner, and the system can also automatically take conservative control strategies or contingency measures accordingly.

[0097] Through the implementation of this embodiment, the system can not only accurately quantify the safe operation boundary based on real-time operating conditions, but also has the ability to continuously monitor its own operating status and provide early warnings. This upgrades the operation safety of the semi-dry desulfurization reactor from traditional fixed-value protection to dynamic, intelligent, and preventive safety protection that adapts to fluctuations in operating conditions, greatly improving the system's inherent reliability and risk resistance when dealing with complex solid waste co-firing flue gas.

[0098] exist Figure 4 Based on the illustrated embodiment, as one implementation of this invention, the desired bed pressure drop is determined at least based on the chlorobenzene concentration, and the desired spray volume is determined based on the temperature control target. Conflict arbitration is performed within the boundaries to generate preliminary bed pressure drop and spray volume setpoints. This may include the following steps: Step c1: Based on the chlorobenzene concentration, determine the expected bed pressure drop corresponding to the given chlorobenzene concentration by querying a preset chlorobenzene concentration-bed pressure drop mapping relationship or by calculating according to a preset function. The mapping relationship or function characterizes the correspondence between the chlorobenzene concentration and the bed pressure drop required to achieve the target removal efficiency.

[0099] Specifically, based on the real-time collected chlorobenzene concentration C_CB(t), the system directly determines the expected bed pressure drop ΔP_desired(t) corresponding to the concentration by querying a preset chlorobenzene concentration-bed pressure drop mapping relationship (such as a data lookup table) or by using a preset calculation function. This mapping relationship or function was established through extensive combustion commissioning experiments, performance tests, and data analysis. Its core lies in characterizing the quantitative correspondence between chlorobenzene concentration (a key indicator of dioxin formation potential) and the bed pressure drop required to achieve the system's target removal efficiency. The basic principle is that a higher chlorobenzene concentration indicates a higher risk of dioxin formation, therefore the mapped or calculated ΔP_desired(t) value is correspondingly higher, allowing for enhanced adsorption and removal capacity by increasing bed density and adsorbent retention; conversely, a lower ΔP_desired(t) value corresponds to a lower ΔP_desired(t) value, which is beneficial for energy-saving operation.

[0100] Step c2: Calculate the dew point temperature of the flue gas based on the flue gas humidity, determine the target temperature based on the dew point temperature and the preset safety temperature margin, and determine the expected water spray volume based on the target temperature and the current outlet temperature.

[0101] Specifically, the system first calculates the current dew point temperature T_dp(t) of the flue gas based on the real-time flue gas humidity H_flue(t) using established thermodynamic formulas. Then, according to process safety and reaction requirements, T_dp(t) is added to a preset safety temperature margin (e.g., 20℃) to determine the target temperature under the current operating conditions: T_target(t) = T_dp(t) + 20℃. Finally, based on the deviation between this T_target(t) and the reactor's measured current outlet temperature T_out(t), the desired water spray volume F_water_desired(t) required to achieve the target temperature is calculated using a temperature control algorithm (such as proportional-integral control). This step ensures that water spray regulation always prioritizes maintaining the reactor within a safe and efficient temperature and humidity window.

[0102] Step c3: When the combination of the desired bed pressure drop and the desired spray volume will cause the operating point to exceed the safety boundary defined by the upper limit of the allowable bed pressure drop, the upper limit of the allowable spray volume, and the lower limit of the safe outlet temperature, the arbitration mechanism is activated. The desired bed pressure drop and / or the desired spray volume are adjusted with the safety boundary as a constraint to generate a preliminary bed pressure drop setting value and a spray volume setting value that meet all safety boundary conditions.

[0103] Specifically, the system constructs a "desired operation point" from ΔP_desired(t) and F_water_desired(t) calculated in steps c1 and c2, and determines whether the point is located within the three-dimensional safe operation envelope enclosed by the dynamic safety boundary (i.e., ΔP_max(t), F_water_max(t), T_out_min(t)) determined in step S420.

[0104] If the point is within the safety envelope, it is directly adopted as the initial set value: ΔP_set(t) = ΔP_desired(t), F_water_set(t) = F_water_desired(t).

[0105] If it is determined that the desired operating point will exceed the safety boundary (for example, if both ΔP_desired(t) and F_water_desired(t) are satisfied, the predicted outlet temperature will be lower than T_out_min(t), or ΔP_desired(t) itself exceeds ΔP_max(t)), then the arbitration mechanism is immediately initiated.

[0106] This arbitration mechanism uses a safety boundary as an insurmountable rigid constraint. Its core logic is to find a feasible solution within the safety envelope that best approximates the original desired point and balances removal efficiency with temperature control objectives. This may involve making trade-off adjustments to ΔP_desired(t) and / or F_water_desired(t) according to preset rules or optimization algorithms (e.g., when temperature safety margins are tight, prioritizing T_out_min(t) while moderately reducing ΔP_desired(t) or adjusting F_water_desired(t)).

[0107] The arbitration output is the initial bed pressure drop setpoint ΔP_set(t) and water flow setpoint F_water_set(t) that satisfy all safety boundary conditions.

[0108] Through the implementation of this embodiment, the system deeply integrates and intelligently coordinates efficiency optimization control based on pollutant concentration with safety constraint control based on physical conditions, ensuring that the generation of control commands is based on the fundamental premise of safe and stable system operation under any operating condition, thereby achieving dual protection of efficient removal and safe operation.

[0109] exist Figure 4 Based on the illustrated embodiment, as one implementation of this invention, the control unit is further configured to perform performance evaluation and model adaptive optimization, specifically including the following steps: Step d1: In subsequent control cycles, evaluate the effectiveness of the coordinated control. The key indicators used for evaluation include at least: the trend of chlorobenzene concentration change, the stability of the safety margin between the outlet temperature and the dew point temperature, and the tracking error of the measured bed pressure drop value to the final bed pressure drop control command.

[0110] In one or more subsequent control cycles after the issuance and execution of coordinated control commands, the system quantitatively evaluates the control effectiveness of the previous stage. The key performance indicators used for this evaluation include at least: 1. Pollutant removal trend indicators: Monitor and analyze the changing trend of chlorobenzene concentration C_CB(t) in the purified flue gas, such as its average value, peak reduction rate or concentration fluctuation standard deviation, to indirectly evaluate the removal stability of dioxins.

[0111] 2. Operational safety status indicators: Calculate and evaluate the stability of the safety margin ΔT_margin(t) between the outlet temperature T_out(t) and the real-time dew point temperature T_dp(t), and monitor its minimum, average and fluctuation to ensure that the operation is always away from the risk of condensation.

[0112] 3. Control command tracking performance indicators: Calculate the tracking error (such as cumulative error, maximum deviation, etc.) of the measured bed pressure drop value ΔP_bed(t) to the issued final bed pressure drop control command ΔP_cmd(t), which is used to evaluate the response speed and accuracy of the bottom control loop.

[0113] Step d2 involves analyzing the control effect and parameter combinations under different operating conditions based on historical operating data collected according to a predetermined cycle.

[0114] The system automatically archives historical operational data according to a predetermined statistical period (e.g., daily or weekly). This data includes not only the evaluation indicators from step d1, but also synchronously records corresponding operating parameters, such as solid waste co-combustion amount, flue gas inlet parameters, and setpoints generated by the collaborative control model. Based on this massive amount of data, the system (or through offline analysis tools) analyzes the correlation between the actual control effect and the control parameter combination used under different typical operating condition combinations (e.g., high chlorobenzene-high humidity, low load-low humidity, etc.), identifying operating condition areas where the control effect is excellent or poor under the existing model parameters.

[0115] Step d3: Based on the analysis results, optimize and adjust the coefficients and dynamic safe operation envelope of the feedforward prediction model used in the collaborative control. The feedforward prediction model must include at least a mapping relationship or function model for determining the desired bed pressure drop based on the chlorobenzene concentration.

[0116] Based on the statistical analysis results of step d2, the system fine-tunes and optimizes the core model parameters relied upon in the collaborative control logic to achieve continuous improvement in overall performance, specifically including: 1. Optimize the coefficients of the feedforward prediction model: calibrate the key coefficients in the mapping relationship or function model described in step c1, which is used to determine the desired bed pressure drop based on chlorobenzene concentration. For example, if a systematic deviation is found between the actual required removal efficiency and the model prediction within a specific operating range, the slope of the mapping relationship or the function parameters are adaptively adjusted to make the model prediction more closely match the actual process requirements.

[0117] 2. Calibrate the dynamic safety operating envelope: Based on data accumulated over long-term operation regarding the actual safety limits of the system under different temperature and humidity conditions (such as boundary points that are close to but do not condense), fine-tune the dynamic safety operating envelope model used in step S420. This makes the safety boundary more accurate and closer to the actual characteristics of the device over time, thereby potentially releasing greater optimization space while ensuring safety.

[0118] Through the implementation of this embodiment, the system evolves from a "static" optimization control system based on a fixed model and parameters into a "dynamic" intelligent system with continuous learning and self-calibration capabilities. It can absorb actual operating experience and continuously optimize its internal core model, thereby becoming increasingly adaptable to the specific solid waste fuel characteristics and operating habits of the plant over time, achieving steady long-term performance improvement and further reduction of operational risks.

[0119] To mitigate the negative impact of solid waste co-firing fluctuations on the stability of the fluidized bed in a semi-dry incineration process, this invention also involves transporting dry desulfurization ash to the pre-incineration treatment stage of solid waste. This ash is mixed and modified with high-humidity, high-viscosity solid waste, adsorbing molecular water between solid waste particles, reducing moisture content, altering the physical properties of the solid waste, enhancing fluidity, and improving incineration efficiency. Extensive experimental research has shown that, taking sludge with high humidity and high viscosity as an example, modification with dry desulfurization ash significantly improves its dispersibility and fluidity. (See below.) Figure 5 As shown in Table 1. Figure 5 The images show a comparison of the morphology of sludge and dry desulfurization ash before and after modification; Table 1 shows the changes in moisture content and sliding angle of sludge and dry desulfurization ash before and after modification.

[0120] Table 1

[0121] The calcium hydroxide, calcium carbonate and other components in dry desulfurization ash can solidify heavy metals, act as bactericides and bacteriostatic agents to prevent the reproduction of microorganisms in sludge, and serve as excellent acid gas absorbents to inhibit the generation of pollutants such as HCl and VOCs, thereby controlling the concentration of pollutants emitted at the outlet.

[0122] After modification, the stability and continuity of solid waste feeding and weighing in the furnace are greatly improved, and the fluctuation of flue gas parameters is significantly reduced, thereby improving the stability of fluidized bed semi-dry desulfurization after the furnace.

[0123] As one implementation of this invention, a modified mixing device mixes and modifies desulfurization ash and highly moist, viscous solid waste to form modified solid waste, which may specifically include the following steps: Step e1 involves transporting desulfurization ash from the conveying pipeline and highly moist and viscous solid waste from the incoming material pipeline to the first-stage mixing equipment according to a preset ratio for crushing and preliminary mixing. This allows the desulfurization ash to absorb free water from the surface of the solid waste, achieving preliminary breaking down and loosening. The preset ratio is a mixing proportion of desulfurization ash and highly moist and viscous solid waste determined in advance through experiments based on the type of highly moist and viscous solid waste.

[0124] Dry desulfurization ash from the desulfurization ash discharge pipeline of the bag filter dust collector, and raw solid waste from the inlet pipeline of highly moist and viscous solid waste (such as municipal sludge, oil sludge, papermaking sludge, starch residue, or pharmaceutical bacterial residue), are transported to the first-stage mixing equipment (e.g., a biaxial shear mixer) according to a preset ratio. The preset ratio is the optimal mixing proportion of desulfurization ash and solid waste determined through prior systematic experimental research based on the specific type of highly moist and viscous solid waste (e.g., for municipal sludge, the mass ratio is usually not less than 1). At this stage, the desulfurization ash, with its large specific surface area and strong water absorption, quickly adsorbs free water from the surface of the solid waste and breaks down the viscous network of the solid waste through mechanical shearing, achieving initial "breaking of adhesion" and loosening of the material, forming loose flocs.

[0125] Step e2 involves conveying the pre-mixed material to a second-stage mixing unit for high-intensity shearing and micro-homogenization, which allows the desulfurization ash particles to be deeply embedded inside the solid waste particles, further adsorbing internal moisture and undergoing some chemical reactions to reduce viscosity and inhibit microbial activity.

[0126] Specifically, the pre-mixed material is conveyed to a second-stage mixing device (e.g., a high-speed vortex activated mixer). In the high-intensity shear field and vortex generated by this device, the fine particles of desulfurization ash are forced to deeply embed and encapsulate with the solid waste particles at a microscopic level. The desulfurization ash (especially the porous structure derived from semi-dry spray drying processes) acts as a highly efficient micro-container, further adsorbing capillary water and some bound water (i.e., "molecular water") inside the solid waste particles. This is key to significantly reducing the overall moisture content of the material and greatly improving particle flowability. Simultaneously, under the localized heating (approximately 40-50°C) generated by mixing friction and the alkaline environment (pH>10) provided by the desulfurization ash, components such as Ca(OH)2 in the desulfurization ash undergo partial saponification reactions with humic acid and oils in the solid waste, further breaking down viscosity. The high pH environment also instantly inhibits and kills pathogenic microorganisms, eliminating instability factors in subsequent storage and transportation caused by fermentation gas production.

[0127] Step e3: The homogenized material is shaped into homogeneous particles within a predetermined particle size range.

[0128] The deeply homogenized and chemically modified material is fed into a forming device (such as a low-strength granulator, disc granulator, or roller granulator). Under controlled mechanical force, the material is rolled or extruded into dense, homogeneous particles within a predetermined particle size range (e.g., 5-15 mm). This step imparts a regular physical morphology to the modified product, greatly improving its flowability and the ease of metering.

[0129] Step e4 involves aging the shaped homogeneous particles to achieve final stabilization and obtain modified solid waste.

[0130] The shaped homogeneous granules are transported to a closed aging chamber for aging. During the 12-24 hour settling period, the unreacted CaO components in the desulfurization ash undergo a slow, complete hydration reaction with the residual moisture inside the granules, releasing heat and further solidifying the granule structure, thus improving its mechanical strength. Simultaneously, heavy metal ions that may be present in the solid waste undergo a long-term stabilization reaction with the aluminosilicates and alkaline substances in the desulfurization ash, becoming chemically bonded or encapsulated, significantly reducing their volatility during subsequent incineration. After the complete aging process, the material is finally stabilized, resulting in a modified solid waste product with uniform physical properties, good flowability, and ease of storage and transportation.

[0131] Through the four-step modification process described in detail in this embodiment, the system achieves a closed loop in converting difficult-to-dispose-of desulfurization ash and highly moist, sticky solid waste that is difficult to use directly into high-quality derivative fuel. This process not only fundamentally solves the core problem of unstable raw solid waste feeding through physical conditioning (water absorption, de-sticking, homogenization, and shaping), providing a stable fuel input for the boiler and its subsequent flue gas purification system; it also achieves preliminary source control of pollutants through chemical action (passivation of heavy metals and inhibition of microorganisms), and opens up an internal channel for the high-value resource utilization of desulfurization ash.

[0132] This invention also provides a method for purifying flue gas from co-firing solid waste, the method comprising the following steps: Coal and highly moist, sticky solid waste are fed into a boiler for incineration, producing flue gas containing pollutants. The flue gas is sequentially subjected to denitrification treatment, flue gas injection pre-dechlorination treatment based on real-time monitoring of HCl concentration, pre-dust removal treatment, flue gas circulating fluidized bed semi-dry desulfurization treatment, and bag filter dust removal treatment before being discharged. In the denitrification flue, the concentration of HCl in the flue gas and the concentration of chlorobenzene, which is a dioxin characterizer, are monitored simultaneously in real time. Based on the monitored HCl concentration, the injection volume of the highly active calcium-based absorbent in the pre-dechlorination treatment is adjusted in real time. Based on the monitored chlorobenzene concentration, flue gas temperature, flue gas humidity, and solid waste feed rate signal, the bed pressure drop and process water spray rate in the semi-dry desulfurization process are dynamically adjusted through a collaborative control logic constrained by dynamic safe operation. Meanwhile, using a feedforward control method, the amount of flue gas recirculation in the semi-dry desulfurization process is adjusted based at least on the solid waste feed rate signal and the flue gas flow rate to stabilize the fluidization velocity. A portion of the desulfurization ash collected during the bag filter dust removal process is mixed and modified with the high-moisture, viscous solid waste to be co-combusted, forming a modified solid waste with stable physical properties. The modified solid waste is returned to the boiler and burned together with coal.

[0133] It should be noted that since the method implementation and the system implementation correspond to each other and their implementation principles are the same, they will not be described again here.

Claims

1. A solid waste co-combustion flue gas purification system, characterized by, The system includes, in sequence, a boiler, a denitrification unit, a flue gas injection unit, a pre-dust collector, a flue gas circulating fluidized bed semi-dry desulfurization reactor, and a bag filter; the system also includes: An online monitoring device is installed in the flue downstream of the denitrification device to simultaneously monitor the concentration of HCl and the concentration of chlorobenzene, a dioxin characterizer, in the flue gas. The control unit is communicatively connected to the online monitoring device, the flue gas injection device, the flue gas circulating fluidized bed semi-dry desulfurization reactor, and the solid waste feeding system, respectively. The control unit is configured to: adjust the injection volume of the highly active calcium-based absorbent in the flue gas injection device in real time according to the HCl concentration monitored by the online monitoring device to achieve pre-removal of HCl; and dynamically adjust the bed pressure drop and process water injection volume of the flue gas circulating fluidized bed semi-dry desulfurization reactor through a collaborative control logic constrained by dynamic safe operation, based on the monitored chlorobenzene concentration, flue gas temperature, flue gas humidity and solid waste feed rate signal from the solid waste feeding system, and simultaneously adjust the flue gas recirculation volume of the flue gas circulating fluidized bed semi-dry desulfurization reactor in a feedforward control mode, at least based on the solid waste feed rate signal and the flue gas flow rate, to stabilize the fluidization velocity. The modified mixing device is connected to the desulfurization ash discharge port of the bag filter via a conveying pipeline to transport a portion of the desulfurization ash to the modified mixing device. The modified mixing device is also connected to the inlet pipeline of high-moisture viscous solid waste to mix and modify the transported desulfurization ash with the high-moisture viscous solid waste to form modified solid waste. The outlet of the modified mixing device is connected to the solid waste inlet of the boiler to send the modified solid waste back to the boiler for co-firing.

2. The system of claim 1, wherein, The control unit is configured to perform precise control of flue gas injection dechlorination, specifically including: The system acquires in real time the raw HCl concentration signal from the online monitoring device, the flue gas volume flow signal from the flue gas flow meter, and the feedback signal from the absorbent injection amount or feeder opening of the feeding system of the flue gas injection device; it performs validity verification and smoothing filtering on the raw HCl concentration signal and the flue gas volume flow signal to obtain a smoothed HCl concentration value for control. Based on the target dechlorination efficiency, the smoothed HCl concentration value, and the flue gas volume flow rate signal, the total amount of HCl to be removed is calculated. Based on the preset theoretical calcium-chlorine molar ratio, the effective calcium content of the absorbent, and the total amount of HCl to be removed, the theoretically required absorbent feedforward amount is calculated. The smoothed HCl concentration value is compared with a preset safety threshold concentration to obtain the concentration deviation, and a proportional-integral controller is used to calculate the feedback correction amount based on the concentration deviation. The theoretical feedforward injection quantity and the feedback correction quantity are combined to generate the final absorbent injection control command, which is then output to the feeding system of the flue gas injection device for execution.

3. The system of claim 2, wherein, The original HCl concentration signal and flue gas volume flow rate signal are subjected to validity verification and smoothing filtering to obtain a smoothed HCl concentration value for control, including: The original HCl concentration signal and the flue gas volume flow rate signal are respectively subjected to signal quality judgment. The signal quality judgment includes judging whether the signal value is within a preset range and judging whether the rate of change of the signal exceeds a preset abnormal jump threshold. If any signal is determined to be invalid, the flue gas injection device is controlled to maintain the absorbent injection volume of the previous control cycle, and an alarm for abnormal monitoring data is triggered. If the signal is valid, the original HCl concentration signal is subjected to moving average or low-pass filtering to eliminate measurement noise and obtain a smooth HCl concentration value.

4. The system of claim 2, wherein, The process of synthesizing the theoretical feedforward injection quantity and the feedback correction quantity to generate the final absorbent injection control command, and outputting it to the feeding system of the flue gas injection device for execution, includes: The theoretically required absorbent feedforward amount is superimposed with the feedback correction amount to generate the initial control command; The smoothed HCl concentration value is compared with the preset warning threshold concentration. If the smoothed HCl concentration value is continuously higher than the warning threshold concentration for multiple consecutive sampling periods, and the current feeding capacity of the feeding system of the flue gas injection device has reached the upper limit, an alarm signal is generated and output to prompt the reduction of solid waste co-combustion. The initial control command is subjected to rate and position limiting processing to conform to the mechanical execution characteristics of the solid waste feeding system, and the processed command is converted into a control signal output to drive the feeder.

5. The system of claim 1, wherein, The control unit is configured to perform coordinated control of the flue gas circulating fluidized bed semi-dry desulfurization reactor, specifically configured as follows: Simultaneously collect data on chlorobenzene concentration, flue gas temperature, flue gas humidity, flue gas flow rate, measured bed pressure drop, solid waste feed rate, and current water spray rate; Based on the flue gas temperature and humidity, determine the upper limit of bed pressure drop, the upper limit of water spray volume, and the lower limit of outlet temperature under the current operating conditions; The desired bed pressure drop is determined at least based on the chlorobenzene concentration, and the desired water spray volume is determined based on the temperature control target. Conflict arbitration is carried out within the boundaries of the upper limit of the allowable bed pressure drop, the upper limit of the allowable water spray volume, and the lower limit of the safe outlet temperature to generate preliminary bed pressure drop and water spray volume settings. The effects of changes in the water spray volume setpoint on flue gas humidity and material viscosity are predicted; based on the predicted effects, the bed pressure drop compensation required to maintain a stable fluidization state is calculated; the bed pressure drop compensation is superimposed on the initial bed pressure drop setpoint to obtain the final bed pressure drop control command. The final bed pressure drop control command and the spray water volume setpoint are respectively sent to the bed pressure drop control model and the process spray water volume control model of the reactor. The bed pressure drop control model is configured to receive the bed pressure drop control command and, in conjunction with the solid waste feed rate feedforward signal, output adjustment signals for the material circulation valve and the flue gas recirculation damper through control calculation. The process spray water volume control model is configured to receive the spray water volume setpoint and, in conjunction with the solid waste feed rate feedforward signal and the outlet temperature feedback signal, output adjustment signals for the process water regulating valve through control calculation.

6. The system of claim 5, wherein, The determination of the upper limit of allowable bed pressure drop, the upper limit of allowable water injection volume, and the lower limit of safe outlet temperature under the current operating conditions based on flue gas temperature and humidity includes: Calculate the dew point temperature of the flue gas based on the flue gas humidity; determine the lower limit of the outlet temperature by summing the dew point temperature with the preset safety temperature margin; and obtain the upper limit of the bed pressure drop and the upper limit of the water spray volume by querying the preset dynamic safety operation envelope model based on the flue gas temperature and flue gas humidity. Furthermore, the control unit is also configured to perform safety status diagnostics, including: Based on the measured bed pressure drop, the current water spray volume, and the outlet temperature, determine whether the current operating point is within the safety envelope defined by the upper limit of the allowable bed pressure drop, the upper limit of the allowable water spray volume, and the lower limit of the safe outlet temperature; If the measured bed pressure drop exceeds the upper limit of the allowable bed pressure drop, or enters a preset boundary ratio region below the upper limit of the allowable bed pressure drop, or the current water spray volume exceeds the upper limit of the allowable water spray volume, or enters a preset boundary ratio region below the upper limit of the allowable water spray volume, or the outlet temperature is lower than the lower limit of the safe outlet temperature, or enters a preset boundary ratio region above the lower limit of the safe outlet temperature, then a safety warning signal is generated and output.

7. The system of claim 5, wherein, The process of determining the desired bed pressure drop based at least on the chlorobenzene concentration and the desired water spray volume based on the temperature control target, and performing conflict arbitration within the stated boundaries to generate preliminary bed pressure drop and water spray volume setpoints, includes: Based on the chlorobenzene concentration, the desired bed pressure drop corresponding to the chlorobenzene concentration is determined by querying a preset chlorobenzene concentration-bed pressure drop mapping relationship or by calculating according to a preset function; wherein, the mapping relationship or function characterizes the correspondence between the chlorobenzene concentration and the bed pressure drop required to achieve the target removal efficiency; The dew point temperature of the flue gas is calculated based on the flue gas humidity. The target temperature is determined based on the dew point temperature and the preset safety temperature margin. The expected water spray volume is determined based on the target temperature and the current outlet temperature. When the combination of the desired bed pressure drop and the desired water flow rate causes the operating point to exceed the safety boundary defined by the upper limit of the allowable bed pressure drop, the upper limit of the allowable water flow rate, and the lower limit of the safe outlet temperature, an arbitration mechanism is initiated. The desired bed pressure drop and / or the desired water flow rate are adjusted with the safety boundary as a constraint to generate the preliminary bed pressure drop setting value and water flow rate setting value that satisfy all safety boundary conditions.

8. The system of claim 6, wherein, The control unit is also configured to perform performance evaluation and model adaptive optimization, specifically including: In subsequent control cycles, the effectiveness of the coordinated control is evaluated. The key indicators used for the evaluation include at least: the trend of chlorobenzene concentration, the stability of the safety margin between the outlet temperature and the dew point temperature, and the tracking error of the measured bed pressure drop value to the final bed pressure drop control command. Based on historical operating data collected according to a predetermined cycle, the control effect and parameter combination under different operating conditions are analyzed. Based on the analysis results, the coefficients and dynamic safe operation envelope of the feedforward prediction model used in the collaborative control are optimized and adjusted; wherein, the feedforward prediction model includes at least a mapping relationship or function model for determining the desired bed pressure drop based on the chlorobenzene concentration.

9. The system of claim 1, wherein, The modified mixing device mixes and modifies desulfurization ash and highly moist, viscous solid waste to form modified solid waste, specifically including: The desulfurization ash from the conveying pipeline and the highly moist and viscous solid waste from the incoming material pipeline are conveyed to the first-stage mixing equipment according to a preset ratio for crushing and preliminary mixing. This allows the desulfurization ash to absorb free water from the surface of the solid waste, achieving preliminary breaking down and loosening. The preset ratio is a mixing proportion of desulfurization ash and highly moist and viscous solid waste determined in advance through experiments based on the type of highly moist and viscous solid waste. The pre-mixed material is conveyed to the second-stage mixing unit for high-intensity shearing and micro-homogenization, which allows the desulfurization ash particles to be deeply embedded in the solid waste particles, further adsorbing internal moisture and undergoing some chemical reactions to reduce viscosity and inhibit microbial activity. The homogenized material is shaped into homogeneous particles within a predetermined particle size range; The shaped homogeneous particles are aged to achieve final stabilization, resulting in the modified solid waste.

10. A method for purifying flue gas from solid waste co-firing, characterized in that, The method includes: Coal and highly moist, sticky solid waste are fed into a boiler for incineration, producing flue gas containing pollutants. The flue gas is sequentially subjected to denitrification treatment, flue gas injection pre-dechlorination treatment based on real-time monitoring of HCl concentration, pre-dust removal treatment, flue gas circulating fluidized bed semi-dry desulfurization treatment, and bag filter dust removal treatment before being discharged. In the denitrification flue, the concentration of HCl in the flue gas and the concentration of chlorobenzene, which is a dioxin characterizer, are monitored simultaneously in real time. Based on the monitored HCl concentration, the injection volume of the highly active calcium-based absorbent in the pre-dechlorination treatment is adjusted in real time. Based on the monitored chlorobenzene concentration, flue gas temperature, flue gas humidity, and solid waste feed rate signal, the bed pressure drop and process water spray rate in the semi-dry desulfurization process are dynamically adjusted through a collaborative control logic constrained by dynamic safe operation. Meanwhile, using a feedforward control method, the amount of flue gas recirculation in the semi-dry desulfurization process is adjusted based at least on the solid waste feed rate signal and the flue gas flow rate to stabilize the fluidization velocity. A portion of the desulfurization ash collected during the bag filter dust removal process is mixed and modified with the high-moisture, viscous solid waste to be co-combusted, forming a modified solid waste with stable physical properties. The modified solid waste is returned to the boiler and burned together with coal.

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