Integrated flue gas treatment process for lime kiln denitration

Abstract

This invention discloses an integrated denitrification flue gas treatment process for lime kilns in the field of industrial flue gas purification. The process includes the following steps: S1, flue gas enters a cyclone separator at a tangential velocity with a residence time of 2.5 s; S2, modified catalyst is processed into honeycomb-plate composite modules; arranged in layers according to the flue gas flow direction, with the first 20% of the volume being a honeycomb structure and the last 80% being a plate structure; S3, a porous ammonia injection grid is installed at the inlet of the cyclone reactor, based on online NO... x The monitor dynamically adjusts the ammonia injection rate based on real-time data to maintain the NH3 / NO ratio. x The molar ratio is 0.9; S4, and the flue gas enters the shell-and-tube waste heat boiler after denitrification. This invention solves five major technical problems: low efficiency of low-temperature denitrification of lime kiln flue gas, catalyst deactivation due to calcium poisoning, high ammonia escape rate, high system energy consumption, and large equipment footprint. It achieves integrated treatment of efficient and stable denitrification under low-temperature conditions of 180-220℃.

Description

Technical Field

[0001] This invention relates to the field of industrial flue gas purification technology, specifically to an integrated denitrification flue gas treatment process for lime kilns. Background Technology

[0002] In the field of industrial flue gas treatment, denitrification of lime kiln flue gas has always faced unique challenges. Lime kiln flue gas contains high concentrations of calcium-based dust, which easily poisons and deactivates traditional denitrification catalysts. While conventional SCR denitrification processes are widely used in stationary sources such as power plants, when directly applied to lime kiln conditions, the catalyst lifespan often falls below six months. Even more challenging is the fact that the temperature window of lime kiln flue gas is typically in the low-temperature range of 180-250℃, which happens to be the temperature range where the activity of traditional vanadium-tungsten-titanium catalysts significantly decreases. Existing technologies struggle to simultaneously achieve both low-temperature activity and resistance to calcium poisoning—two key performance indicators.

[0003] Currently, most lime kiln flue gas treatment employs a step-by-step dust removal and denitrification process, which has significant systemic flaws. While the process of removing dust before denitrification can reduce the direct impact of dust on the catalyst, it leads to increased equipment footprint and significantly higher operating energy consumption. More seriously, the step-by-step treatment process suffers from significant ammonia escape, which not only wastes reducing agent but also causes secondary pollution. Some improvement schemes attempt to add pretreatment equipment to the dust removal stage, but the resulting increase in pressure drop affects the overall system energy efficiency. These technical bottlenecks severely restrict the lime kiln industry's progress in achieving ultra-low emissions.

[0004] In recent years, researchers have conducted numerous explorations in catalyst modification, but none have completely solved the unique problems of lime kiln flue gas. Some studies have used molecular sieve supports to load transition metal oxides, which, while improving low-temperature activity to some extent, still lack sufficient resistance to calcium ions. Other approaches protect the catalyst through surface coatings, but often at the expense of active site density. Existing modification technologies generally suffer from complex processes and high costs, making industrial application difficult. Therefore, developing a novel treatment process that adapts to the characteristics of lime kiln operations and possesses both high-efficiency denitrification performance and long-term stability has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated denitrification flue gas treatment process for lime kilns, which solves the problems of low-temperature denitrification efficiency, catalyst calcium poisoning and deactivation, high ammonia escape rate, high system energy consumption, and large equipment footprint in existing lime kiln flue gas treatment systems.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] An integrated denitrification flue gas treatment process for lime kilns includes the following steps:

[0008] S1, the flue gas enters the cyclone separator at a tangential velocity, with a residence time of 2.5s;

[0009] S2, the modified catalyst is processed into a honeycomb-plate composite module; arranged in layers according to the flue gas flow direction, with the front 20% of the volume being a honeycomb structure and the rear 80% of the volume being a plate structure;

[0010] S3, a porous ammonia injection grid is installed at the inlet of the cyclone reactor, based on online NO... x The monitor dynamically adjusts the ammonia injection rate based on real-time data to maintain the NH3 / NO ratio. x The molar ratio is 0.9;

[0011] S4, after flue gas denitrification, enters the shell-and-tube waste heat boiler.

[0012] According to a preferred embodiment of the present invention, the cyclone separator was purchased from Zhangqiu Qunyi Machinery Manufacturing Co., Ltd.

[0013] According to a preferred embodiment of the present invention, in step S1, the tangential velocity is 15 m / s; the diameter of the cyclone separator is 1.2 meters and the height-to-diameter ratio is 3:1.

[0014] In this invention, when flue gas enters the cyclone separator at a specific tangential velocity, gas-solid separation is achieved through centrifugal force. The high tangential velocity generates a strong rotating flow field, causing denser lime dust particles to settle along the wall surface, while the purified flue gas forms an upward swirling stream and exits from the top. The optimized aspect ratio design extends the particle residence time, ensuring thorough separation.

[0015] According to a preferred embodiment of the present invention, in step S2, the cellular-panel composite module has a pore density of 300 cpsi and a wall thickness of 0.3 mm.

[0016] In this invention, the front honeycomb structure of the honeycomb-plate composite module generates turbulence through regular channels, enhancing the contact efficiency between flue gas and catalyst; the rear plate structure reduces airflow resistance. This combined design ensures both reaction kinetics requirements and optimized hydrodynamic performance. Specific pore density and wall thickness ensure sufficient specific surface area and mechanical strength.

[0017] The honeycomb structure described in this invention is an integral catalyst support structure with a regular parallel pore array. Its shape is a standard cylindrical or cuboid module, with a highly ordered hexagonal or square honeycomb grid arrangement in its cross-section. Each pore is a straight, parallel channel running along the airflow direction, separated by thin, uniform partitions. The pore density is precisely controlled at 300 pores per square inch (300 cpsi), with each pore exhibiting a regular pore diameter of 1.2-1.5 mm and a uniform wall thickness of 0.3 mm. This structure uses a cordierite ceramic matrix material, coated with a 20-30 micrometer-thick γ-alumina transition layer as the active component carrier. The pore walls have a hierarchical porous structure, containing macropores of 10-20 micrometers, mesopores of 5-10 nanometers, and micropores smaller than 2 nanometers. This multi-scale pore system ensures an open porosity of over 70% and provides ample specific surface area. The duct connection nodes feature a rounded transition design with localized thickening to 0.35 mm, and incorporate 0.1 mm high micro-guide fins. While ensuring a gas flow area ratio exceeding 75%, controllable turbulence is generated through a surface roughness of 5 micrometers. This meticulously designed geometry maintains a hydraulic diameter of approximately 1.8 mm, achieving both plug flow to reduce backmixing and significantly lowering system pressure drop. Simultaneously, an axial compressive strength of 8 MPa and a radial bending strength of 3 MPa ensure structural stability. (1.2 × 10⁻⁶) -6 Its coefficient of thermal expansion at ℃ gives it excellent thermomechanical properties, providing an ideal support platform for the active components of the catalyst.

[0018] The rear-section plate structure described in this invention is a layered catalyst support structure with parallel airflow channels. Its basic structure consists of a regular flow channel system composed of alternating flat corrugated plates and straight partitions. This structure uses the same cordierite ceramic matrix material as the honeycomb structure, and is manufactured into 0.3mm thick corrugated plates through a precision extrusion molding process. The corrugation shape is a continuous sine wave or trapezoidal wave, with a wave height controlled at 2-3mm and a wavelength maintained at equal intervals of 5-6mm. These corrugated plates and flat partitions are stacked at a 1:1 ratio, forming triangular or approximately rectangular airflow channels of uniform height. The equivalent diameter of the channels is approximately 3.5mm, and the surface is covered with a 20-30μm thick γ-alumina coating as a carrier for the active component. The plates are positioned and assembled using a special tongue-and-groove structure, and the contact surfaces are polished to ensure an assembly accuracy within 0.05mm. The overall porosity is maintained within the range of 65-70%. The corrugated plate surface features microgrooves 0.1-0.2 mm deep, complemented by hemispherical protrusions spaced 0.5-1 mm apart, enhancing airflow turbulence while maintaining a low pressure drop. The unique feature of this structure is its gradually decreasing corrugation amplitude along the airflow direction. The inlet section uses a 3 mm corrugation height to enhance turbulent mixing, while the outlet section reduces the height to 1.5 mm to lower drag, with the transition zone accounting for approximately one-third of the overall length. All plate edges are reinforced with 2 mm wide borders, forming an integral structure through high-temperature sintering. This ensures a flexural strength exceeding 1.5 MPa under high-temperature flue gas conditions, while the corrugated joints are locally thickened to 0.4 mm to resist airflow erosion. This meticulously designed geometry creates a specific secondary flow pattern within the channel, ensuring effective renewal of the catalyst surface boundary layer while controlling the pressure drop to 60-70% of that of a honeycomb structure, achieving an optimal balance between mass transfer efficiency and energy consumption.

[0019] According to a preferred embodiment of the present invention, in step S3, the porous ammonia injection grid has a pore size of 2 mm and an opening ratio of 40%; the porous ammonia injection grid is installed 1 meter in front of the reactor inlet; the reaction temperature of the reaction system is 180-220℃, and the space velocity is 3000 h⁻¹. -1 Under the operating conditions, the oxygen content in the flue gas shall not be less than 5%.

[0020] According to a preferred embodiment of the present invention, the porous ammonia-injected grid was purchased from Jiangsu Ruicheng Metal Technology Co., Ltd.

[0021] According to a preferred embodiment of the present invention, the ammonia gas is purchased from Tianjin Yongteng Gas Sales Co., Ltd.

[0022] According to a preferred embodiment of the present invention, the online NO x The monitoring instrument was purchased from Shenzhen Yifan Technology Co., Ltd.

[0023] In this invention, the injected ammonia gas is adsorbed and dissociated into NH4+ at the active sites on the catalyst surface. x Species. In the redox cycle provided by the Ce-Mn active component (Ce 4+ / Ce 3+ Mn 4+ / Mn 3+ Under the action of NH x with NO x A selective redox reaction occurs, producing N2 and H2O. Precise control of NH3 / NO... x This avoids both excessive and insufficient ammonia.

[0024] According to a preferred embodiment of the present invention, in step S4, the shell-and-tube waste heat boiler is made of stainless steel and has a volume of 316L.

[0025] According to a preferred embodiment of the present invention, the shell-and-tube waste heat boiler was purchased from Shandong Lujie Thermal Energy Equipment Co., Ltd.

[0026] In this invention, when the denitrified high-temperature flue gas passes through the shell-and-tube heat exchanger, the heat is conducted to the working fluid (water / steam) through the stainless steel wall. The corrosion resistance of the 316L material ensures long-term stable heat transfer in sulfur-containing flue gas environments.

[0027] According to a preferred embodiment of the present invention, the modification step of the modified catalyst includes:

[0028] S1. Place the ZSM-5 molecular sieve in a muffle furnace, heat to 550℃, and calcine for 4 hours. After cooling, immerse it in a 0.1 mol / L nitric acid solution and sonicate.

[0029] S2. Prepare a deionized water solution containing cerium nitrate hexahydrate and manganese acetate tetrahydrate. Mix the pretreated ZSM-5 molecular sieve with the solution at a mass ratio of 1:10 and stir in a water bath. Then transfer to a microwave reactor for radiation treatment; separate the solid product by vacuum filtration, wash three times with ethanol, and dry in an oven. Finally, calcine at 450℃ under a nitrogen atmosphere to obtain the Ce-Mn active component supported molecular sieve.

[0030] S3, Ce-Mn active component supported molecular sieve atomic layer deposition, the ALD reaction chamber temperature was set to 200℃, the vaporization chamber temperatures of trimethylaluminum and water were 25℃ and 30℃ respectively, and nitrogen was introduced as the carrier gas; each deposition cycle contained four steps: first, TMA gas was introduced for 0.1 seconds, followed by purging with nitrogen for 10 seconds; then water vapor was introduced for 0.1 seconds, followed by purging with nitrogen again for 10 seconds; this cycle was repeated 50 times to obtain a molecular sieve with a γ-type alumina shell coating;

[0031] S4, the molecular sieve coating the surface of the deposited alumina shell is placed into a tube furnace and evacuated to 10... -3 After Pa, the temperature is raised to 150℃. 3-Aminopropyltriethoxysilane vapor is introduced; under nitrogen protection, the temperature is raised to 300℃ and kept constant to allow the silane coupling agent to fully cure.

[0032] According to a preferred embodiment of the present invention, the ZSM-5 molecular sieve was purchased from China National Petroleum Corporation.

[0033] According to a preferred embodiment of the present invention, the muffle furnace is an AFD1200-40 model purchased from Nanjing Kejie Testing Technology Development Co., Ltd.

[0034] According to a preferred embodiment of the present invention, the nitric acid solution was purchased from Zibo Kunmao Economic and Trade Co., Ltd.

[0035] According to a preferred embodiment of the present invention, the cerium nitrate hexahydrate was purchased from Zhengzhou Aikem Chemical Co., Ltd.

[0036] According to a preferred embodiment of the present invention, the manganese acetate tetrahydrate was purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0037] According to a preferred embodiment of the present invention, the deionized water was purchased from Shanghai Binrun Environmental Protection Technology Co., Ltd.

[0038] According to a preferred embodiment of the present invention, the microwave reactor was purchased from Dongguan Huaqing Microwave Equipment Manufacturing Co., Ltd.

[0039] According to a preferred embodiment of the present invention, the ethanol was purchased from Nantong Runfeng Petrochemical Co., Ltd.

[0040] According to a preferred embodiment of the present invention, the oven was purchased from Shanghai Boxun Industrial Co., Ltd.

[0041] According to a preferred embodiment of the present invention, the ALD device was purchased from Jiangsu Microguide Nanotechnology Co., Ltd.

[0042] According to a preferred embodiment of the present invention, the TMA gas is trimethylaluminum.

[0043] According to a preferred embodiment of the present invention, the TMA gas was purchased from Jiangsu Yongjian Chemical Co., Ltd.

[0044] According to a preferred embodiment of the present invention, the tubular furnace was purchased from Zhengzhou Kejia Electric Furnace Co., Ltd.

[0045] According to a preferred embodiment of the present invention, the 3-aminopropyltriethoxysilane was purchased from Shanghai Hans Chemical Co., Ltd.

[0046] According to a preferred embodiment of the present invention, the silane coupling agent is purchased from Hubei Jianghan New Material Co., Ltd., specifically model KH550.

[0047] According to a preferred embodiment of the present invention, in step S1, the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 80, and the temperature is raised to 550°C at a heating rate of 5°C / min; the ultrasonic treatment power is 300W, and the treatment time is 30min.

[0048] In this invention, during the calcination process at 550℃, the molecular sieve framework undergoes dehydroxylation, generating Lewis acid sites. Nitric acid treatment further modulates the acid distribution through proton exchange: H... + Replacement skeleton Al 3+ Nearby Na + This forms Brønsted acid sites (≡Si-OH-Al≡). The cavitation effect generated by ultrasonic treatment produces microjets within the molecular sieve channels, effectively removing channel blockages and increasing the specific surface area by approximately 30%. A specific SiO2 / Al2O3 molar ratio (80) ensures appropriate acid density and thermal stability.

[0049] According to a preferred embodiment of the present invention, in step S2, the molar ratio of cerium to manganese is 1:2; the stirring time in the water bath is 6 hours; the radiation treatment power is 800W, the temperature is 80℃, and the time is 30 minutes; the drying in the oven is 12 hours, and the drying temperature is 110℃; the heating rate for calcination is 2℃ / min; and the calcination time is 3 hours.

[0050] In this invention, under water bath conditions, Ce 3+ and Mn 2+ It enters the molecular sieve supercage via ion exchange. Microwave radiation induces dielectric heating, promoting deep diffusion of the metal precursor: Ce. 3+ Mn preferentially occupies the β-cage sites of molecular sieves. 2+ Distributed within the α-cage. During calcination, a special phase is formed: CeO2 nanoparticles (5-8 nm) are anchored at the pore openings, while Mn2O3 clusters (2-3 nm) are dispersed within the pores. Strong interactions occur between Ce and Mn, and this special coordination environment becomes the active center for low-temperature SCR.

[0051] According to a preferred embodiment of the present invention, in step S3, the flow rate of nitrogen is 200 sccm; the reaction chamber pressure is 0.5 Torr when TMA gas is introduced; the reaction chamber pressure is 0.1 Torr when nitrogen is purged; the reaction chamber pressure is 0.5 Torr when water vapor is introduced; and the reaction chamber pressure is 0.1 Torr when nitrogen is purged again; the thickness of the γ-type alumina shell is 80 nm.

[0052] In this invention, the ALD process follows a self-limiting surface reaction mechanism: during TMA chemisorption, -CH3 reacts with -OH on the molecular sieve surface, releasing CH4 and forming Al-CH 3* Surface; H2O and Al-CH 3* The reaction produces Al-OH. * It releases CH4; 0.1 nm of Al2O3 is deposited per cycle, forming a gradient shell after 50 cycles: amorphous Al2O3 near the support (facilitating stress release), and γ-Al2O3 (thermally stable phase) on the outer side. The mesopores (3-5 nm) in the shell allow gas diffusion but block Ca2+. 2+ migrate.

[0053] According to a preferred embodiment of the present invention, in step S4, the rate of introducing 3-aminopropyltriethoxysilane vapor is 5 mL / min; the duration is 2 h; the temperature is increased to 300 °C at a rate of 3 °C / min under nitrogen protection, and the isothermal treatment time is 2 h.

[0054] In this invention, APTES is grafted via a three-step reaction: ethoxyl hydrolysis: Si(OC2H5)3 + 3H2O → Si(OH)3 + 3C2H5OH; condensation dehydration: Si(OH)3 + Al-OH → Si-O-Al + 2H2O; amino groups are oriented: -NH2 groups are tilted at approximately 60° towards the surface, forming a molecular-level "ammonia trapping network". Heat treatment promotes complete solidification of the Si-O-Al bonds, while some -NH2 is oxidized to -NH-, forming an electron delocalization system and enhancing the synergistic effect of NH3 adsorption-activation.

[0055] The beneficial effects of this invention are as follows:

[0056] This invention achieves a breakthrough in the field of lime kiln flue gas treatment through innovative process design and catalyst modification technology. In terms of denitrification performance, a specially structured modified catalyst module, combined with an intelligent ammonia injection control system, achieves highly efficient denitrification under low-temperature conditions, significantly outperforming traditional catalysts under the same temperature conditions. The unique core-shell structure catalyst effectively blocks the penetration of harmful components from lime dust through a protective layer, fundamentally solving the industry pain point of catalyst poisoning and deactivation. Optimized ammonia-nitrogen ratio control keeps ammonia slip at extremely low levels, significantly reducing the risk of secondary pollution.

[0057] In terms of system operational efficiency, this invention creatively integrates multiple processing units into a unified process flow. The highly efficient pretreatment device can separate large particulate dust in a short time, creating ideal conditions for subsequent denitrification. The innovative reactor structure design significantly reduces system resistance and substantially reduces energy consumption. The design concept of utilizing the waste heat of the flue gas itself to maintain the reaction temperature completely avoids the dependence on auxiliary heating devices in traditional processes, resulting in a qualitative improvement in system energy efficiency. The rational configuration of the waste heat recovery unit further optimizes the overall energy utilization efficiency.

[0058] Regarding the long-term stability of the catalyst, a protective layer constructed through advanced surface treatment technology, combined with a special surface modification process, enables the catalyst to exhibit excellent durability in high-calcium environments. The modified catalyst maintains stable performance even under high load conditions, resulting in a significant improvement in treatment capacity. The entire system adopts a compact design, greatly reducing the footprint and extending the maintenance cycle. These technological innovations not only overcome the technical challenges of lime kiln flue gas treatment but also provide a referable solution for the treatment of similar industrial flue gas. Detailed Implementation

[0059] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0060] Example 1:

[0061] Example 1:

[0062] Flue gas pretreatment: The flue gas from the lime kiln is introduced into a cyclone separator with a diameter of 1.2 meters and a height-to-diameter ratio of 3:1 at a tangential velocity of 15 m / s. The residence time of the flue gas in the separator is strictly controlled to 2.5 seconds.

[0063] Catalyst loading: The modified catalyst is processed into honeycomb-plate composite modules with a pore density of 300 cpsi and a wall thickness of 0.3 mm, with a total loading volume of 3.2 m³. The modules are arranged in layers according to the flue gas flow direction. The first 20% of the volume (0.64 m³) uses a honeycomb structure to enhance turbulent mixing, while the last 80% of the volume (2.56 m³) uses a plate structure to reduce system pressure drop. The honeycomb structure has hexagonal single channels with a pore diameter of 1.2 mm, while the plate structure consists of alternating corrugated plates and straight baffles with a corrugation height of 2 mm and a wavelength of 5 mm.

[0064] Denitrification reaction control: Install a porous ammonia injection grid with a pore size of 2mm and an opening rate of 40% 1 meter before the reactor inlet, based on online NO... x The monitor dynamically adjusts the ammonia injection rate based on real-time data to control the NH3 / NO ratio. xThe molar ratio is 0.9. The flue gas flow rate is 9600 Nm³ / h, corresponding to a space velocity of 3000 h⁻¹. -1 The reaction temperature was maintained at 195±5℃, and the oxygen content in the flue gas was 6.2 vol%. The ammonia injection rate was 12.7 kg / h, and the flow rate accuracy was ±0.5% through a PID control system.

[0065] Waste heat recovery: After denitrification, the flue gas enters a 316L stainless steel shell-and-tube waste heat boiler. The boiler is made of 316L stainless steel and has a heat exchange area of ​​85m². The flue gas passes through the tube side, and the shell-side water is heated to produce saturated steam at 0.8MPa. The steam output is 1.2t / h, and the heat recovery efficiency reaches 78%.

[0066] Catalyst preparation: 2.5 kg of ZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 80 was taken and calcined in a muffle furnace at a heating rate of 5℃ / min to 550℃ for 4 hours. After cooling, it was immersed in 500 mL of 0.1 mol / L nitric acid solution and ultrasonically treated at 300 W power for 30 minutes.

[0067] A mixed solution containing 148.2 g of cerium nitrate hexahydrate and 122.1 g of manganese acetate tetrahydrate (cerium-manganese molar ratio 1:2) was prepared, and 250 g of pretreated molecular sieve was added. The mixture was stirred in a water bath at 60 °C for 6 hours. The mixture was then transferred to a microwave reactor and irradiated at 800 W power and 80 °C for 30 minutes. After filtration, the mixture was washed three times with ethanol, dried at 110 °C for 12 hours, and finally calcined at 450 °C for 3 hours under a nitrogen atmosphere at a rate of 2 °C / min.

[0068] 500g of calcined material was placed in an ALD reaction chamber. The reaction chamber temperature was set to 200℃, the TMA vaporization chamber to 25℃, the water vaporization chamber to 30℃, and the nitrogen flow rate to 200 sccm. Each deposition cycle consisted of 0.1 seconds of TMA gas introduction (reaction chamber pressure 0.5 Torr), 10 seconds of nitrogen purging (0.1 Torr), 0.1 seconds of water vapor introduction (0.5 Torr), and 10 seconds of nitrogen purging (0.1 Torr), for a total of 50 cycles, forming an 80nm thick γ-type alumina shell.

[0069] The deposited material is placed in a tube furnace and evacuated to 100°C. -3 After Pa, the temperature was raised to 150℃, and 3-aminopropyltriethoxysilane vapor was introduced at a rate of 5 mL / min for 2 hours. Then, under nitrogen protection, the temperature was raised to 300℃ at a rate of 3℃ / min and kept at that temperature for 2 hours to allow the silane coupling agent to fully cure.

[0070] Example 2:

[0071] The specific implementation method is the same as in Example 1, except that the process conditions are adjusted: flue gas flow rate 7200 Nm³ / h (space velocity 2250 h⁻¹). -1 Catalyst loading: 3.2m³ 3 (0.8m³ honeycomb type + 2.4m³ panel type); ammonia injection rate 9.5kg / h (NH3 / NO) x =0.88); reaction temperature 205℃. Catalyst preparation: ZSM-5 dosage 3.0kg; cerium nitrate hexahydrate 177.8g + manganese acetate tetrahydrate 146.5g; ALD cycle 40 times (shell ≈ 64nm).

[0072] Example 3:

[0073] The specific implementation method is the same as in Example 1, except that the process conditions are adjusted: flue gas flow rate 12000 Nm³ / h (space velocity 3750 h⁻¹). -1 Catalyst loading: 3.2 m³ (0.48 m³ honeycomb type + 2.72 m³ plate type); Ammonia injection rate: 15.9 kg / h (NH3 / NO3). x =0.91); reaction temperature 185℃. Catalyst preparation: ZSM-5 dosage 2.0kg; cerium nitrate hexahydrate 118.5g + manganese acetate tetrahydrate 97.7g; ALD cycle 60 times (shell ≈96nm).

[0074] Comparative Example 1

[0075] The specific implementation method is the same as in Example 1, except that a separate SCR reactor (all honeycomb type) is used; V2O5-WO3 / TiO2 catalyst is used; and the space velocity is 2000 h⁻¹. -1 The reaction temperature is 220℃.

[0076] Comparative Example 2

[0077] The specific implementation method is the same as in Example 1, except that the ALD deposition step is omitted.

[0078] Comparative Example 3

[0079] The specific implementation method is the same as in Example 1, except that the single-structure reactor adopts a honeycomb structure throughout.

[0080] Performance testing

[0081] The preparation processes of Examples 1-3 and Comparative Examples 1-3 were tested and calculated according to the following methods:

[0082] 1. Denitrification efficiency: Measured according to standard GB / T 16157-2018; NO2 at the reactor inlet and outlet was continuously monitored using a flue gas analyzer (Testo 350). x Concentration, calculation: (Inlet NO)x -Export NO x ) / entranceNO x ×100%. Sampling location: Reactor inlet and outlet flanges.

[0083] 2. Ammonia slip: Performed according to standard HJ 533-2018; real-time monitoring using a laser ammonia analyzer (Siemens LDS 6), with a sampling probe equipped with a ceramic filter (200℃ constant temperature). Sampling location: centerline of the reactor outlet flue.

[0084] 3. Calcium poisoning analysis: Performed according to standard ISO 18560-2:2015; catalyst sampling after operation → XRF analysis of Ca content; BET specific surface area test (Micromeritics ASAP 2460). Sampling location: sampling point in the middle of the catalyst module.

[0085] 4. System pressure drop: measured according to standard GB / T 1236-2017; differential pressure transmitter (Rosemount 3051) measures the pressure difference between the reactor inlet and outlet. Sampling location: 1m straight pipe section before and after the reactor.

[0086] 5. Energy consumption indicators: Based on standard GB / T 15316-2020; electricity meters (0.5 grade) record fan / pump power consumption; steam flow meters measure waste heat recovery. Sampling location: distribution cabinets of each electrical device.

[0087] 6. Test Results:

[0088] Table 1: Test results of each embodiment and comparative example

[0089]

[0090] As shown in Table 1, this invention, through systematic testing data verification, comprehensively solves five major technical challenges in the field of lime kiln flue gas treatment. Regarding low-temperature denitrification efficiency, the use of a Ce-Mn / ZSM-5@Al2O3 catalyst combined with a composite reactor structure achieves a denitrification efficiency of over 90% at 180-220℃, a 32 percentage point improvement over traditional processes. This is mainly attributed to the oxygen vacancies formed by the gradient distribution of Ce-Mn oxides in the catalyst and the enhanced NH3 adsorption capacity through aminosilane modification. Addressing the catalyst calcium poisoning issue, the 80nm dense Al2O3 shell constructed using ALD technology controls the Ca deposition amount to below 1.1 mg / g after 15 months of operation, effectively protecting the internal active components. In terms of ammonia slip control, the turbulence effect generated by the front-end honeycomb structure and a precise online feedback system stabilize the ammonia slip concentration below 3.1 ppm, a 63% reduction compared to traditional processes. This is attributed to optimized airflow distribution and real-time control of NH3 / NO3. xThe molar ratio is (0.9±0.05). The significant reduction in system energy consumption is reflected in three aspects: the self-sustaining reaction temperature from flue gas waste heat eliminates the need for traditional electric heating devices; the composite structure design reduces pressure drop by 35%; and the waste heat boiler achieves 78% heat recovery, resulting in a 38% reduction in overall energy consumption. The equipment is compact through integrated process design and high space velocity (3000 h⁻¹). -1 The system achieves operational efficiency with a 45% reduction in floor space. The integrated layout of cyclone dust removal, catalytic denitrification, and waste heat recovery eliminates the need for connecting pipes and transition space required in traditional split-type processes. Particularly noteworthy is that, while maintaining high performance, the catalyst's resistance to calcium poisoning extends its service life to five times that of traditional catalysts. Furthermore, the adoption of a plate-type structure in the downstream section reduces pressure drop by 35% with only a 10% increase in volume. These innovations collectively constitute the core technological advantages of this invention, providing a reliable solution for the treatment of medium- and low-temperature industrial flue gas, such as that from lime kilns.

[0091] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An integrated denitrification flue gas treatment process for lime kilns, characterized in that, Includes the following steps: S1, the flue gas enters the cyclone separator at a tangential velocity, with a residence time of 2.5s; S2, the modified catalyst is processed into a honeycomb-plate composite module; arranged in layers according to the flue gas flow direction, with the front 20% of the volume being a honeycomb structure and the rear 80% of the volume being a plate structure; S3, a porous ammonia injection grid is installed at the inlet of the cyclone reactor, based on online NO... x The monitor dynamically adjusts the ammonia injection rate based on real-time data to maintain the NH3 / NO ratio. x The molar ratio is 0.9; S4, after denitrification, the flue gas enters the shell-and-tube waste heat boiler; The modification steps of the modified catalyst include: A1. Place the ZSM-5 molecular sieve in a muffle furnace, heat it to 550℃, calcine it for 4 hours, and after cooling, immerse it in a 0.1mol / L nitric acid solution and sonicate it. A2. Prepare a deionized water mixed solution containing cerium nitrate hexahydrate and manganese acetate tetrahydrate. Mix the pretreated ZSM-5 molecular sieve with the solution at a mass ratio of 1:10, stir in a water bath, and then transfer to a microwave reactor for radiation treatment. Separate the solid product by vacuum filtration, wash with ethanol three times, dry in an oven, and finally calcine at 450℃ under a nitrogen atmosphere to obtain Ce-Mn active component supported molecular sieve. A3, Ce-Mn active component-supported molecular sieve atomic layer deposition was performed. The ALD reaction chamber temperature was set at 200℃, and the vaporization chamber temperatures for trimethylaluminum and water were 25℃ and 30℃, respectively. Nitrogen gas was introduced as the carrier gas. Each deposition cycle consisted of four steps: first, TMA gas was introduced for 0.1 seconds, followed by purging with nitrogen for 10 seconds; then, water vapor was introduced for 0.1 seconds, followed by purging with nitrogen for 10 seconds again; this cycle was repeated 50 times to obtain a molecular sieve with a γ-alumina shell coating. A4, the molecular sieve coating the deposited alumina shell is placed in a tube furnace and evacuated to 10... -3 After Pa, the temperature is raised to 150°C, and 3-aminopropyltriethoxysilane vapor is introduced. The temperature was raised to 300°C under nitrogen protection and kept constant to allow the silane coupling agent to fully cure.

2. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step S1, the tangential velocity is 15 m / s; the diameter of the cyclone separator is 1.2 meters and the height-to-diameter ratio is 3:

1.

3. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step S2, the cellular-panel composite module has a pore density of 300 cpsi and a wall thickness of 0.3 mm.

4. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step S3, the porous ammonia injection grid has a pore size of 2 mm and an opening rate of 40%; the porous ammonia injection grid is installed 1 meter in front of the reactor inlet; the reaction temperature of the reaction system is 180-220℃, and the space velocity is 3000 h⁻¹. -1 Under the operating conditions, the oxygen content in the flue gas shall not be less than 5%.

5. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step S4, the shell-and-tube waste heat boiler is made of stainless steel and has a volume of 316L.

6. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step A1, the molar ratio of SiO2 to Al2O3 in the ZSM-5 molecular sieve is 80, and the temperature is raised to 550℃ at a heating rate of 5℃ / min; the ultrasonic treatment power is 300W, and the treatment time is 30min.

7. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step A2, the molar ratio of cerium to manganese is 1:2; the stirring time in the water bath is 6 hours; the radiation treatment power is 800W, the temperature is 80℃, and the time is 30 minutes; the drying in the oven is 12 hours at a drying temperature of 110℃; the heating rate for calcination is 2℃ / min; and the calcination time is 3 hours.

8. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step A3, the flow rate of nitrogen is 200 sccm; the reaction chamber pressure is 0.5 Torr when TMA gas is introduced; the reaction chamber pressure is 0.1 Torr when nitrogen is purged; the reaction chamber pressure is 0.5 Torr when water vapor is introduced; and the reaction chamber pressure is 0.1 Torr when nitrogen is purged again; the thickness of the γ-type alumina shell is 80 nm.

9. The integrated denitrification flue gas treatment process for lime kilns according to claim 1, characterized in that, In step A4, the rate of introducing 3-aminopropyltriethoxysilane vapor is 5 mL / min; the duration is 2 h; the temperature is increased to 300 °C at a rate of 3 °C / min under nitrogen protection, and the isothermal treatment time is 2 h.

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