Denitration method and equipment for powder catalyst circulating entrained-flow bed

Abstract

The invention belongs to the technical field of flue gas purification, and particularly relates to a powder catalyst circulating entrained-flow bed denitration method and equipment which are suitable for low-temperature flue gas, adopt a powder catalyst and realize cyclic regeneration. The method comprises the following steps: spraying a new powdery catalyst and a reducing agent to a mixing section of the elbow flue to be fully mixed with flue gas; in the reaction section of the bent pipe flue, the new catalyst, the reducing agent and the flue gas are subjected to selective catalytic reduction reaction, and NOx in the flue gas is converted into N2 and H2O; and the reacted clean flue gas carries the catalyst to enter the dust removal and recovery mechanism, so that the clean flue gas is separated from the catalyst. The conveying bed process is innovatively adopted, the equipment structure is simple, the system pressure drop is low (smaller than or equal to 1000 Pa), the catalyst particle collision rate is low, efficient circulation and online regeneration of the catalyst are supported, low-temperature efficient denitration can be achieved, and the device has the advantages of being stable in operation, low in energy consumption and easy and convenient to maintain.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification technology, specifically relating to a method and equipment for denitrification of low-temperature flue gas using a powder catalyst circulating fluidized bed with cyclic regeneration. Background Technology

[0002] Nitrogen oxides (NO) x NOx, as one of the major air pollutants, is primarily emitted through industrial combustion processes (such as in the power, steel, cement, and glass industries) and mobile source fuel combustion. It causes environmental problems such as acid rain, photochemical smog, and fine particulate matter (PM2.5), seriously threatening the ecological environment and human health. To control NOx... x For emissions, selective catalytic reduction (SCR) technology has become the mainstream method due to its high efficiency (denitrification efficiency > 80%). Its core lies in the design and performance optimization of catalysts, as well as the way catalysts are used.

[0003] Currently, the most widely used industrial process in China is selective catalytic reduction (SCR) technology, which uses a catalyst to reduce NO... x It reacts with a reducing agent (usually ammonia (NH3)) to produce harmless nitrogen (N2) and water (H2O). Currently, denitrification catalysts mainly come in honeycomb, corrugated plate, or strip-shaped granules. During the denitrification process, the catalyst position, contact position with the flue gas, and contact area are all fixed, making online catalyst regeneration impossible. When the catalyst's denitrification efficiency gradually decreases and replacement or regeneration is required, it is usually done by shutting down the unit to unload the catalyst or regenerating it in situ. Furthermore, the vanadium-based catalysts (V2O5-WO3 / TiO2) commonly used in SCR denitrification exhibit high activity at 300-420℃ and require operation under high-temperature conditions. This makes them unsuitable for the low-temperature flue gas (<200℃) conditions in non-power industries, or requires heating, increasing energy consumption and denitrification costs. Therefore, designing a circulating denitrification process applicable to low-temperature flue gas is essential. Summary of the Invention

[0004] I. Technical problems to be solved The present invention aims to solve the technical problems of existing low-temperature denitrification technologies, especially fluidized bed denitrification processes, such as high system pressure drop, complex equipment, low catalyst utilization, and lack of intelligent control.

[0005] II. Technical Solution To achieve the above objectives, the first aspect of the present invention provides a method for denitrification of powder catalysts in a circulating fluidized bed, comprising: Step B involves injecting the new catalyst and reducing agent in powder form into the mixing section of the curved flue to fully mix with the flue gas. Step C: In the reaction section of the curved flue, the new catalyst and reducing agent undergo a selective catalytic reduction reaction with the flue gas, reducing NO in the flue gas. x It is converted into N2 and H2O; In step D, the clean flue gas after the reaction carries the catalyst into the dust removal and recovery mechanism to achieve the separation of the clean flue gas and the catalyst.

[0006] In some embodiments of the present invention, step A is included before step B, wherein the flue gas temperature is adjusted to the optimal reaction temperature range of the powder catalyst of <200°C.

[0007] In some embodiments of the present invention, in step B, the new catalyst is uniformly conveyed to the mixing section of the curved flue by the first pneumatic conveying device via the Venturi feeder.

[0008] In some embodiments of the present invention, in step C, the pressure drop during the selective catalytic reduction reaction is ≤1000Pa.

[0009] In some embodiments of the present invention, step D includes: the clean flue gas after reaction carries the catalyst into a pulse bag filter, and the clean flue gas and the catalyst are separated under the action of centrifugal force.

[0010] In some embodiments of the present invention, step D is followed by step E, in which the separated catalyst is circulated as a circulating catalyst and transported to the mixing section of the curved flue, wherein the catalyst is circulated ≥20 times.

[0011] In some embodiments of the present invention, step D is followed by step F, in which the separated clean flue gas is discharged in compliance with emission standards.

[0012] To achieve the above objectives, a second aspect of the present invention provides a powder catalyst circulating fluidized bed denitrification device. This powder catalyst circulating fluidized bed denitrification device includes: The conveying bed denitrification reactor includes: a curved flue; wherein, a flue gas inlet is provided at the upper part of the curved flue; and a reducing agent tube and a catalyst tube are connected to its upper side. The dust collection and recovery mechanism has its air inlet connected to the flue gas outlet of the conveying bed denitrification reactor.

[0013] In some embodiments of the present invention, the curved flue is an L-shaped flue; the L-shaped flue includes: a mixing section extending in a vertical direction; a reaction section extending in a horizontal direction; wherein, a reducing agent pipe and a catalyst pipe are connected to the mixing section; the downstream side of the mixing section is connected to the reaction section; the downstream side of the reaction section is connected to the dust collection and recovery mechanism; the mixing section and the reaction section are smoothly connected by an arc.

[0014] In some embodiments of the present invention, the mixing section includes: a primary mixing section and a secondary mixing section; wherein, the primary mixing section is connected to the flue gas inlet; the reducing agent pipe and / or catalyst pipe are tangentially connected to the primary mixing section at a preset angle α for preliminary mixing and generating swirl; the secondary mixing section is provided with a static mixer for accelerating and enhancing turbulent mixing, 10°≤α≤80°, where α is the angle between the reducing agent pipe and the catalyst pipe and the vertical direction.

[0015] In some embodiments of the present invention, the reducing agent tube and the catalyst tube are tangentially connected to the primary mixing section at a predetermined included angle α.

[0016] In some embodiments of the present invention, 30°≤α≤60°.

[0017] In some embodiments of the present invention, the static mixer is one of the following: a spiral plate static mixer or a mesh static mixer.

[0018] In some embodiments of the present invention, the reducing agent tube and the catalyst tube are connected to the first mixing section at a circumferential interval of 180° and in the same direction, which is either clockwise or counterclockwise.

[0019] In some embodiments of the present invention, the length L1 of the primary mixing section satisfies: L1=a1*D, 0.5≤a1≤1.5; the length L2 of the secondary mixing section satisfies: L2=a2*D, 2≤a2≤5; where D is the equivalent diameter of the curved flue.

[0020] In some embodiments of the present invention, the catalyst tube includes: a new catalyst tube and a circulating catalyst tube arranged vertically in parallel, wherein a new catalyst supply device is connected to the new catalyst tube; a circulating catalyst supply device is connected to the circulating catalyst tube; the powder catalyst circulating fluidized bed denitrification device further includes: NO x A concentration sensor is installed at the outlet of the dust collection and recovery mechanism; the control device has its first sensor signal input port connected to NO. x The concentration sensor, with its first control terminal and second control terminal connected to the new catalyst supply device and the circulating catalyst supply device respectively, is used to determine the concentration of NO. x NO at the flue gas outlet obtained by the concentration sensor x Content, controlling the amount and / or ratio of new catalyst and recycled catalyst input into the bend flue.

[0021] In some embodiments of the present invention, the new catalyst supply device includes: a new catalyst silo with its catalyst outlet facing downward; a first pneumatic conveying device with its controlled end connected to a first control end of a control device; and a first venturi tube section with its pneumatic inlet connected to the first pneumatic conveying device, its inlet connected to the catalyst outlet of the catalyst silo, and its outlet connected to the new catalyst tube.

[0022] In some embodiments of the present invention, the circulating catalyst supply device includes: a screw conveyor, the inlet of which is connected to the ash hopper outlet of the dust collection and recovery mechanism; a second pneumatic conveying device, the controlled end of which is connected to the first and second control ends of the control device; and a second Venturi tube section, the pneumatic port of which is connected to the second pneumatic conveying device, the inlet of which is connected to the outlet of the screw conveyor, and the outlet of which is connected to the circulating catalyst tube.

[0023] In some embodiments of the present invention, the control device executes the following control logic: when the NO at the flue gas outlet... x When the NO content exceeds the preset upper limit, the amount of new catalyst supplied is increased; when the NO at the flue gas outlet... x When the content is lower than the preset lower limit, reduce the amount of new catalyst supplied and increase the amount of recycled catalyst supplied.

[0024] In some embodiments of the present invention, the reaction section includes a retractable conduit of adjustable length.

[0025] In some embodiments of the present invention, the expandable pipeline is a expandable corrugated pipe.

[0026] In some embodiments of the present invention, the reaction section includes: N sections of expandable pipeline, where N > 1.

[0027] In some embodiments of the present invention, the length of the reaction section satisfies: L3 max ≤3*L3 min L3 min ≥10*D, L3 max ≤30*D, where L3 min and L3 min These are the maximum and minimum lengths of the reaction section, respectively, and D is the equivalent diameter of the bend in the flue.

[0028] In some embodiments of the present invention, the device further includes: a flue gas flow sensor disposed at the flue gas inlet; a pipeline length control device for controlling the length of the expandable pipeline in the reaction section; and a control device, wherein its second sensor input port is connected to the flue gas flow sensor and its second control terminal is connected to the controlled terminal of the pipeline length control device, for controlling the residence time τ of the flue gas in the curved flue by adjusting the length of the expandable pipeline, wherein 0.8s≤τ≤2s, and the residence time τ is defined as the ratio of the effective reaction volume to the standard volume flow rate.

[0029] In some embodiments of the present invention, the dust collection and recovery mechanism is a pulse-jet bag filter or a cyclone dust collector.

[0030] In some embodiments of the present invention, the reducing agent introduced into the reducing agent tube is one of the following: liquid ammonia, ammonia water, or urea.

[0031] In some embodiments of the present invention, the catalyst input through the catalyst tube is a powder catalyst with a particle size between 20-50 μm.

[0032] In some embodiments of the present invention, the invention further includes: an induced draft fan, the air inlet of which is connected to the air outlet of the dust collection and recovery mechanism, and the air outlet of which is connected to the chimney.

[0033] In some embodiments of the present invention, the device further includes: a flue gas temperature sensor disposed at the flue gas inlet of the curved flue; a flue gas temperature regulating device disposed on the upstream side of the curved flue, used to regulate the flue gas to be denitrified to a low temperature flue gas below 200°C; a control device, the third sensor input port of which is connected to the flue gas temperature sensor, and the third control terminal of which is connected to the flue gas temperature regulating device; wherein, the flue gas temperature regulating device is a steam-heated counter-flow shell-and-tube heat exchanger, and an electric steam regulating valve is disposed at the shell-side inlet of the counter-flow shell-and-tube heat exchanger; the control device has a pre-stored target flue gas temperature range, used to use the inlet flue gas temperature sensed by the flue gas temperature sensor as the main control quantity, and to adjust the electric steam regulating valve in conjunction to maintain the inlet flue gas temperature within the target flue gas temperature range.

[0034] III. Beneficial Effects As can be seen from the above technical solution, the present invention has at least one of the following beneficial effects compared to the prior art: (1) The present invention adopts a conveying bed process, in which the catalyst and reducing agent are directly injected into the flue gas pipeline and transported together with the flue gas, and the mixing and reaction are completed in the entire conveying pipeline; the conveying bed has no fixed bed layer, which avoids the blockage and channeling of the fluidized bed; at the same time, the catalyst particles in the conveying bed have a low collision probability, which is beneficial to extending the service life of the catalyst.

[0035] Furthermore, this invention employs a conveying bed process, which can directly utilize existing flues or simply designed pipes as reactors. The equipment is easy to manufacture and install, requires less initial investment, avoids the common problems of fluidized beds, and is easy to maintain.

[0036] Among them, the conveyor bed + single pulse bag filter reduces the flue gas resistance caused by the use of fluidized bed + multi-stage dust collection (cyclone dust collection + bag dust collection), reduces the pressure drop, reduces the load on the subsequent pulse bag filter, and at the same time, the power consumption of the induced draft fan is greatly reduced, and the operating cost is reduced.

[0037] (2) The present invention divides the curved flue into “primary mixing section - secondary mixing section - reaction section”, and the reducing agent pipe and / or catalyst pipe are tangentially connected to the primary mixing section at a preset included angle α, so that the force of the injected reducing agent and catalyst forms a swirling flow, thereby improving the mixing effect.

[0038] Furthermore, the primary mixing section achieves preliminary mixing of flue gas, powdered catalyst, and reducing agent, generating swirl. The secondary mixing section accelerates and enhances turbulent mixing through a static mixer, thereby achieving efficient mixing from macroscopic swirl premixing to microscopic turbulent enhancement. In addition, the reaction section pipeline length is adjusted to achieve precise control of the reaction residence time, significantly improving the low-temperature denitrification reaction rate and uniformity, and further ensuring the long-term stable operation and high efficiency of the system.

[0039] (3) In this invention, the new catalyst supply and the recycled catalyst supply are set separately, and the NO is supplied from the outlet side. x The closed-loop regulation of the concentration control between the two feed streams can maintain the outlet NO concentration even under fluctuating operating conditions. x The system stabilizes and reduces excessive addition of new catalyst powder, improving catalyst utilization. The dust collection and recovery mechanism is configured in a closed loop with the reaction section inlet and outlet, allowing the captured powdered catalyst to return to the reaction zone, reducing catalyst loss and environmental dust concentration, and shortening the circulation path of the powdered catalyst within the system. The sensor and control device feature a complete signal-execution chain with automated adjustment capabilities, reducing lag and fluctuations caused by manual intervention.

[0040] (4) In this invention, during the process of the catalyst being recycled and in contact with the flue gas, the flue gas temperature will promote the decomposition of ammonium bisulfate generated on the catalyst surface, so that the catalyst is partially regenerated online, while saving energy consumption.

[0041] (5) In this invention, only two sets of pneumatic conveying devices are required, the equipment investment is small, the process is simple, the complexity of the equipment and the failure points are reduced, the maintenance is convenient, and the operation is stable.

[0042] (6) In this invention, the lower end of the pulse bag filter is connected to a screw conveyor and a pneumatic conveyor. The separated catalyst can be immediately returned to the temperature-controlled flue gas pipeline for the next cycle reaction without time delay, so that the catalyst recycling rate is ≥95%, which improves the flue gas treatment efficiency of the catalyst.

[0043] (7) In this invention, the reaction section of the conveying bed equipment is used as a retractable pipeline, so that when it is necessary to increase the reaction intensity, the L-shaped flue can be lengthened; when it is necessary to increase the flue gas treatment speed, the L-shaped flue can be shortened, so that the conveying bed denitrification equipment in this embodiment is more flexible.

[0044] (8) In this invention, the catalyst is made of powder, which makes the catalyst active specific surface area large, improves the contact efficiency between the catalyst and the flue gas, and is beneficial to the catalytic reaction.

[0045] (9) In this invention, the flue gas temperature is adjusted to the optimal activity temperature range of the low-temperature powder catalyst by the flue gas temperature adjustment device, so that the catalyst activity reaches the highest level and thus achieves a denitrification efficiency of more than 85%.

[0046] Specifically, the flue gas temperature is adjusted to below 200°C upstream of the reactor to keep the gas flow entering the curved flue within the applicable range of the low-temperature denitrification catalyst, thereby improving the consistency of reaction activity in the low-temperature section. Low-temperature furnace entry also facilitates the compatibility of materials and filter media in the subsequent dust removal and recovery mechanism, reducing the thermal load on filter media and seals caused by high temperatures.

[0047] (10) In this invention, the control device controls NO x Real-time monitoring and closed-loop regulation of concentration, flue gas flow rate, and flue gas temperature ensure that catalyst dosage, circulation ratio, reaction section residence time, and inlet flue gas temperature are automatically optimized and matched according to changes in operating conditions, thereby ensuring that the denitrification reaction is always within the optimal catalytic activity range. Under complex operating conditions such as load fluctuations, changes in flue gas composition, or seasonal temperature variations, the control device can automatically increase or decrease the supply of new catalyst, adjust the amount of circulating catalyst, adjust the reaction section length, and maintain the inlet flue gas temperature within the target range, enabling the equipment to stably achieve efficient denitrification under all operating conditions. This control strategy not only significantly improves catalyst utilization, reduces new catalyst consumption, and lowers operating costs, but also effectively avoids errors from manual adjustments, enhances the reliability of continuous online operation, and enables the overall denitrification unit to achieve intelligent, adaptive, low-consumption, and high-efficiency operation. Attached Figure Description

[0048] Figure 1 This is a flowchart of the denitrification method for powder catalyst circulating airflow bed according to an embodiment of the present invention.

[0049] Figure 2 This is a schematic diagram of the structure of a powder catalyst circulating fluidized bed denitrification device applied to low-temperature flue gas according to an embodiment of the present invention.

[0050] Figure 3 for Figure 2 The diagram shows the mechanism of the conveying bed denitrification reactor in the circulating airflow denitrification equipment for powder catalysts.

[0051] [Explanation of key component symbols in the attached diagram] 1. Catalyst silo; 2. First pneumatic conveying device; 3. First Venturi tube section; 4. Recycled catalyst; 5. New catalyst; 6. Temperature-adjusted flue gas; 7. NH3-based reducing agent; 8. Conveyor bed denitrification reactor; 9. Pulse bag filter dust collector; 10. Screw conveyor; 11. Second pneumatic conveying device; 12. Second Venturi tube section; 13. Exhaust fan; 14. Chimney; 15. Flue gas purification; 16. Circulating catalyst pipe; 17. New catalyst tube; 18. Flue gas temperature control equipment; 19. Reducing agent tube; 20. Primary mixing section; 21. Secondary mixing section; 22. Reaction section; 23. Output pipe. Detailed Implementation

[0052] This invention provides a circulating fluidized bed denitrification device using a powder catalyst. The device employs a conveyor bed process, with air intake at the top of a curved flue and catalyst and reducing agent injected laterally through multiple pipes. This creates macroscopic swirling and microscopic turbulence in the mixing section, enhancing the contact and mixing of the reducing agent, powder catalyst, and flue gas. Simultaneously, the expandable reaction section provides controllable and sufficient reaction time, facilitating effective selective catalytic reduction reactions in the low-temperature region. The conveyor bed has no fixed bed layers, avoiding clogging and channeling in fluidized beds; furthermore, the low probability of catalyst particle collision in the conveyor bed helps extend the catalyst's lifespan.

[0053] Those skilled in the art should understand that although the following embodiments contain multiple innovations, other embodiments of the present invention may contain only one or two innovations, which can also solve the corresponding technical problems and obtain the corresponding beneficial effects, that is, can partially realize the present invention, and are also within the protection scope of the present invention.

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0055] The first aspect of this invention provides a method for denitrification using a circulating fluidized bed with a powder catalyst. In one exemplary embodiment of this invention, a method for denitrification using a circulating fluidized bed with a powder catalyst is provided. Figure 1 This is a flowchart of a circulating fluidized bed denitrification method for powder catalysts according to an embodiment of the present invention. Figure 1 As shown, the denitrification method for powder catalyst circulating fluidized bed in this embodiment includes: Step A, flue gas temperature adjustment In this step, the flue gas is the desulfurized flue gas, and the flue gas temperature is adjusted to the optimal reaction temperature range of the low-temperature powder catalyst (<200℃). Step B involves injecting the new catalyst and reducing agent in powder form into the mixing section of the curved flue to fully mix with the flue gas. In this step, the low-temperature powder catalyst in the new catalyst silo is uniformly conveyed to the temperature-controlled flue gas pipeline by the first pneumatic conveying device via a Venturi feeder. Catalyst particle size: 20-50μm.

[0056] In addition, the reducing agent is injected near the catalyst to form NH3 / NO. x Optimal ratio.

[0057] Step C: In the reaction section of the curved flue, the new catalyst and reducing agent undergo a selective catalytic reduction reaction with the flue gas, reducing NO in the flue gas. xIt is converted into N2 and H2O; In this step, the system pressure drop during the reaction process is ≤1000Pa.

[0058] Step D: The clean flue gas after the reaction carries the catalyst into the dust removal and recovery mechanism to achieve the separation of the clean flue gas and the catalyst; In this step, the clean flue gas after the reaction carries the catalyst into the pulse bag filter, where efficient gas-solid separation is achieved under centrifugal force.

[0059] Step E: The separated catalyst is used as a circulating catalyst and is circulated to the mixing section of the curved flue, wherein the catalyst is circulated ≥20 times. In this step, the separated catalyst is recycled back to the temperature-controlled flue gas duct through the screw conveyor and the second pneumatic conveyor at the bottom of the dust collector for the next catalytic reduction reaction. The catalyst recycling rate is ≥95%, and new catalyst is replenished as needed.

[0060] Step F: The separated clean flue gas is discharged in compliance with standards.

[0061] In this step, the separated purified flue gas is discharged to the chimney by an induced draft fan to meet emission standards, NO x The removal rate can reach over 85%.

[0062] This invention employs a conveyed bed process, where the catalyst and reducing agent are directly injected into the flue gas duct and transported along with the flue gas, completing mixing and reaction throughout the duct. The conveyed bed has no fixed bed layer, avoiding clogging and channeling issues common in fluidized beds. Simultaneously, the low probability of catalyst particle collision in the conveyed bed helps extend catalyst lifespan. Furthermore, this invention utilizes a conveyed bed process, allowing the direct use of existing flue gas ducts or simply designed pipelines as reactors. This reduces equipment manufacturing and installation difficulty, lowers initial investment, avoids common fluidized bed problems, and simplifies maintenance.

[0063] A second aspect of the present invention provides a powder catalyst circulating fluidized bed denitrification device. In an exemplary embodiment of the present invention, a powder catalyst circulating fluidized bed denitrification device is provided. Figure 2 This is a schematic diagram of the structure of a powder catalyst circulating fluidized bed denitrification device applied to low-temperature flue gas according to an embodiment of the present invention. Figure 3 for Figure 2 The diagram shows a schematic of the conveyor bed denitrification reactor in a powder catalyst circulating fluidized bed denitrification system. Figure 2 and Figure 3 As shown, the main equipment of the circulating airflow denitrification equipment for powder catalyst in this embodiment includes a catalyst silo 1, a conveying bed denitrification reactor 8, a dust removal and recovery mechanism, a chimney 14, a first pneumatic conveying device 2, and a second pneumatic conveying device 11.

[0064] Specifically, the circulating airflow denitrification equipment for powder catalysts in this embodiment includes: Flue gas temperature regulation device 18 is used to regulate the flue gas to be denitrified to a low temperature flue gas below 200°C; The conveying bed denitrification reactor 8 includes: a curved flue; wherein, a flue gas inlet is provided at the upper part of the curved flue and connected to a flue gas temperature regulating device; and a reducing agent pipe, a new catalyst pipe, and a circulating catalyst pipe are connected to its upper side. The new catalyst supply equipment is connected to the new catalyst tube; A circulating catalyst supply device is connected to the circulating catalyst pipeline; The dust collection and recovery mechanism has its flue gas inlet connected to the flue gas outlet of the conveying bed denitrification reactor; The exhaust fan 13 has its flue gas inlet connected to the flue gas outlet of the dust collection and recovery mechanism, and its flue gas outlet connected to the chimney 14. The control device, used to control the entire powder catalyst circulating fluidized bed denitrification equipment, includes: ①Based on NO at the flue gas outlet x Content, controlling the amount and / or ratio of new catalyst and recycled catalyst input into the bend flue; ② Control the length of the curved flue according to the flue gas flow rate at the flue gas inlet, so as to control the residence time τ of the flue gas in the L-shaped flue. ③ The flue gas temperature at the inlet is adjusted using a flue gas temperature regulation device to improve the denitrification efficiency.

[0065] The following is a detailed description of each component of the powder catalyst circulating airflow denitrification equipment in this embodiment.

[0066] In this embodiment, the catalyst is a powder with a particle size between 20-50 μm. The powder catalyst provides a large active surface area, improving the contact efficiency between the catalyst and the flue gas, which is beneficial for the catalytic reaction. The reducing agent introduced through the reducing agent pipe is one of the following: liquid ammonia, ammonia water, or urea.

[0067] like Figure 3 As shown, a flue gas temperature regulating device 18 is installed on the flue connected to the conveying bed denitrification reactor. On one side of the upper end of the primary mixing section 20 of the conveying bed denitrification reactor, there is a new catalyst pipe 17 and a circulating catalyst pipe 16, and on the other side of the upper end, there is a reducing agent pipe 19. The primary mixing section 20 of the conveying bed denitrification reactor is followed by the secondary mixing section 21. The reaction section 22 of the conveying bed denitrification reactor has an output pipe 23 at its tail end, and the output pipe 23 is connected to the dust removal and recovery mechanism.

[0068] In this invention, the flue gas temperature regulating device is one of the following: steam-heated or electric-heated. In this embodiment, the flue gas temperature regulating device is a steam-heated counter-flow shell-and-tube heat exchanger, where the flue gas flows through the tubes and the steam flows through the shell. An electric steam regulating valve, a filter, a pressure gauge, and a thermometer are installed at the shell-side inlet of the counter-flow shell-and-tube heat exchanger, and a steam trap, a check valve, and a condensate recovery pipeline are installed at the shell-side outlet. The control device has its third sensor input connected to a flue gas temperature sensor and its third control terminal connected to the flue gas temperature regulating device. It internally stores a target flue gas temperature range and uses the inlet flue gas temperature sensed by the flue gas temperature sensor as the main control variable to adjust the electric steam regulating valve in conjunction with the inlet flue gas temperature to maintain the inlet flue gas temperature within the target flue gas temperature range.

[0069] In this invention, the flue gas temperature is adjusted to below 200°C upstream of the reactor, ensuring that the airflow entering the curved flue remains within the applicable range for the low-temperature denitrification catalyst, thus improving the consistency of reaction activity in the low-temperature section. Low-temperature furnace entry also facilitates the compatibility of materials and filter media in the subsequent dust removal and recovery mechanisms, reducing the thermal load on the filter media and seals from high temperatures, and achieving a denitrification efficiency of over 85%.

[0070] In this embodiment, the curved flue is an L-shaped flue. This L-shaped flue includes a mixing section extending vertically and a reaction section extending horizontally. The mixing and reaction sections of the L-shaped flue are smoothly connected by an arc. The catalyst and reducing agent are directly injected into the flue gas duct, transported along with the flue gas, and mixed and reacted throughout the entire transport duct. It is a mode of simultaneous transport and reaction. The transport bed has no fixed bed layer, avoiding clogging and channeling in the fluidized bed; at the same time, the probability of catalyst particle collision in the transport bed is low, which helps to extend the catalyst's service life. Furthermore, this invention uses a transport bed process, which can directly utilize existing flues or simply designed pipes as reactors. The equipment is easy to manufacture and install, requires less initial investment, avoids the common problems of fluidized beds, and is easy to maintain.

[0071] Although this embodiment uses an L-shaped pipe as an example for illustration, those skilled in the art should understand that other types of pipes, such as S-shaped pipes and W-shaped pipes, although slightly less efficient than this embodiment, can also achieve the present invention and are also within the protection scope of the present invention.

[0072] In this embodiment, the L-shaped flue of the conveying bed denitrification reactor 8 adopts an innovative three-section design: a primary mixing section 20 and a secondary mixing section 21 extending vertically, and a reaction section 22 extending horizontally.

[0073] (a) Level 1 Mixed Section The primary mixing section 20 is directly connected to the flue gas inlet, and its length L1 is designed to be (0.5 ~ 1.5) * D, where D is the equivalent diameter of the curved flue. This design aims to quickly establish a stable flow field using a shorter distance. The reducing agent pipe 19, the circulating catalyst pipe 16, and the new catalyst pipe 17 are connected to the primary mixing section tangentially, forming an angle of 10° to 80° with the vertical axis. This allows the reducing agent and catalyst to immediately form a strong swirling flow with the mainstream flue gas after injection, completing the initial macroscopic mixing. Preferably, 30° ≤ α ≤ 60°, where α is the angle between the extension direction of the reducing agent pipe and the catalyst pipe and the vertical direction.

[0074] Preferably, in order to form a smooth and continuous swirl, the reducing agent tube and the catalyst tube are connected to the first mixing section at a circumferential interval of 180° and in the same direction, which is either clockwise or counterclockwise.

[0075] (ii) Secondary mixed section The secondary mixing section 21 follows the primary mixing section and is equipped with a spiral plate or mesh static mixer with a length L2 designed to be (2 ~ 5) * D. When the flue gas passes through the static mixer, it generates extremely high shear force and turbulence, which disperses the macroscopic swirling flow formed in the previous section, achieving rapid and uniform mixing of gas, reducing agent, and catalyst particles at the microscale, laying the foundation for efficient reaction.

[0076] (III) Reaction Section Reaction section 22 is the expandable piping section, forming the horizontal part of the L-shaped flue. Its minimum length is L3. min ≥10*D, maximum length L3 max The volume should be ≤30*D to ensure sufficient volume for the catalytic reduction reaction. Simultaneously, the reaction section is a retractable pipeline, allowing for adjustment of the flue gas residence time to ensure the catalytic reduction reaction proceeds fully.

[0077] In this embodiment, the L-shaped flue in the reaction section includes: N sections of expandable pipeline, where N≥1; the powder catalyst circulating fluidized bed denitrification equipment further includes: a pipeline length control device for controlling the length of the expandable pipeline; wherein, L3 satisfies: min ≤L3 max ≤3*L3 min L max and L min These are the longest and shortest lengths of the reaction section, respectively, and D is the equivalent diameter of the bend in the flue.

[0078] In this embodiment, the control device has its second sensor input port connected to the flue gas flow sensor and its second control terminal connected to the controlled terminal of the pipeline length control device. It is used to control the residence time τ of the flue gas in the L-shaped flue by adjusting the length of the telescopic pipeline, wherein 0.8s≤τ≤2s, and the residence time τ is defined as the ratio of the effective reaction volume to the standard volume flow rate.

[0079] In this embodiment, since the catalytic reaction takes place in the flue, a portion of the flue is used as a flexible pipeline. This allows the L-shaped flue to be lengthened when increased reaction intensity is needed, and shortened when increased flue gas treatment speed is required, making the conveyor bed denitrification equipment in this embodiment more flexible.

[0080] Please continue to refer to Figure 2 The powder catalyst circulating airflow denitrification equipment in this embodiment also includes: NO x A concentration sensor is connected to the flue gas outlet of the dust collection and recovery unit. The catalyst tubing includes: a new catalyst tubing 17, connected to a new catalyst supply device; and a circulating catalyst tubing 16, connected to a circulating catalyst supply device.

[0081] The new catalyst supply equipment includes: a catalyst silo 1 with its catalyst outlet facing downwards; a first venturi tube section 3, whose pneumatic inlet is connected to a first pneumatic conveying device 2, whose inlet is connected to the catalyst outlet of the catalyst silo, and whose outlet is connected to a new catalyst tube 17. The catalyst silo 1 stores low-temperature powder denitration catalyst. The outlet end of the catalyst silo 1 is connected to the first venturi tube section 3, and then the new catalyst discharged from the first venturi tube section 3 is injected into the conveying bed denitration reactor 8 through the first pneumatic conveying device 2.

[0082] The circulating catalyst supply equipment includes: a screw conveyor, the inlet of which is connected to the ash hopper outlet of the dust collection and recovery mechanism; and a second venturi tube section, the pneumatic inlet of which is connected to the second pneumatic conveying device, the inlet of which is connected to the outlet of the screw conveyor, and the outlet of which is connected to the circulating catalyst tube 16.

[0083] In this process, the new catalyst 5 is conveyed by the first pneumatic conveying device 2; the NH3-based reducing agent 7 is supplied by the ammonia production system, similar to existing technology; and the temperature-controlled flue gas 6 is adjusted to the optimal reaction temperature range of the low-temperature powder catalyst (<200℃) based on its original temperature. The temperature-controlled flue gas 6, carrying the new catalyst 5 and the NH3-based reducing agent 7, enters the conveying bed denitrification reactor 8 and is thoroughly mixed. The reducing agent and flue gas react under the action of the powder catalyst, reducing NO in the flue gas. x It reacts with NH3 to produce N2, thus eliminating NO in the flue gas. x The removal.

[0084] In this embodiment, the first pneumatic conveying device and the second pneumatic conveying device are one of the following: a fan, a vacuum pump, or an air compressor.

[0085] In this embodiment, the control device has its first sensor signal input port connected to NO. x The concentration sensor, with its first control terminal and first second control terminal respectively connected to the first pneumatic conveying device of the new catalyst supply equipment and the second pneumatic conveying device of the circulating catalyst supply equipment, is used to determine the concentration of NO. x NO at the flue gas outlet obtained by the concentration sensor x The content controls the amount and / or ratio of new catalyst and recycled catalyst entering the bend in the flue. Specifically, the control logic of the control device is as follows: when the NO content at the flue gas outlet... x When the NO content exceeds the preset upper limit, the amount of new catalyst supplied is increased; when the NO at the flue gas outlet... x When the content falls below a preset lower limit, the amount of new catalyst supplied is reduced, while the amount of recycled catalyst supplied is increased. This design significantly improves the catalyst recycling rate.

[0086] Those skilled in the art should understand that the upper intake of the curved flue and the lateral tangential injection of catalyst and reducing agent create macroscopic swirl and microscopic turbulence in the mixing section, enhancing the contact and mixing of the reducing agent and powdered catalyst with the flue gas. Simultaneously, the expandable reaction section provides controllable and sufficient reaction time, facilitating effective selective catalytic reduction reactions in the low-temperature region. The new catalyst supply and the recycled catalyst supply are separated, with the NO from the outlet side... x The closed-loop regulation of the concentration control between the two feed streams can maintain the outlet NO concentration even under fluctuating operating conditions. x This system stabilizes and reduces excessive addition of new catalyst powder, improving catalyst utilization. Simultaneously, the dust collection and recovery mechanism is configured in a closed loop with the reaction section inlet and outlet, allowing the captured powdered catalyst to return to the reaction zone, reducing catalyst loss and environmental dust concentration, and shortening the circulation path of the powdered catalyst within the system. Furthermore, the linkage between sensor and control device signals forms a complete execution chain, possessing automated adjustment capabilities and reducing lag and fluctuations caused by manual intervention.

[0087] In this embodiment, the dust collection and recovery mechanism is either a pulse-jet bag filter or a cyclone dust collector. Please continue to refer to... Figure 2 The conveying bed denitrification reactor 8 is connected to the air inlet of the pulse bag filter 9. Flue gas and catalyst enter the pulse bag filter 9 to separate the flue gas from the catalyst. The separated catalyst is conveyed to the second Venturi tube section 12 by the screw conveyor 10. The circulating catalyst is injected into the conveying bed denitrification reactor 8 through the second pneumatic conveying device 11. The air outlet of the pulse bag filter 9 is connected to the chimney 14 through the induced draft fan 13. The separated denitrification and dust removal flue gas enters the chimney 14 through the induced draft fan 13 to achieve the standard emission of purified flue gas 15.

[0088] In this embodiment, the conveying bed + single pulse bag filter reduces the flue gas resistance caused by using fluidized bed + multi-stage dust collection (cyclone dust collection + bag dust collection), reduces the pressure drop, reduces the load on the subsequent pulse bag filter, and at the same time significantly reduces the power consumption of the induced draft fan and lowers the operating cost.

[0089] In this embodiment, the lower end of the pulse bag filter is connected to a screw conveyor and a pneumatic conveyor. The separated catalyst can be immediately returned to the temperature-controlled flue gas duct for the next cycle reaction without time delay, so that the catalyst recycling rate is ≥95%, which improves the flue gas treatment efficiency of the catalyst.

[0090] Those skilled in the art will understand that, in other embodiments of the present invention, a cyclone dust collector can be used instead of a pulse bag dust collector for the dust collection and recovery mechanism.

[0091] As can be seen, this embodiment uses only two sets of pneumatic conveying devices (one new and one circulating), combined with a Venturi feeding mechanism, to achieve uniform catalyst injection and circulation, reducing system complexity and potential failure points. The use of a conveyor bed process combined with a single pulse bag filter keeps the overall system pressure drop below 1000Pa, significantly reducing the pressure drop in the circulating denitrification process.

[0092] The operation mode of the powder catalyst circulating airflow denitrification equipment in this embodiment is as follows: After the flue gas temperature is adjusted to below 200°C by the flue gas temperature regulating device, it is introduced into the conveying bed denitrification reactor. At the same time, the control device adjusts the NO temperature according to the NO... x The concentration sensor readings drive the new catalyst supply equipment and the circulating catalyst supply equipment, injecting a certain proportion of new catalyst and circulating catalyst into the reactor through a venturi tube section. The reducing agent is also injected simultaneously upstream of the reactor. The gas-solid-gas three phases are thoroughly mixed in the conveyed bed reactor and undergo a catalytic reduction reaction. After the reaction, the catalyst-containing flue gas enters a pulse-jet bag filter for gas-solid separation. The purified flue gas is sent to the chimney by an induced draft fan, while the collected catalyst is returned to the reactor for recycling via a screw conveyor and pneumatic conveying device.

[0093] This concludes the description of the various embodiments of the present invention. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0094] It should be noted that for certain implementation methods, if they are not the key content of this invention and are well known to those skilled in the art, they are not described in detail in the accompanying drawings or text due to space limitations. In such cases, they can be understood by referring to the relevant prior art.

[0095] Those skilled in the art will understand that in the claims and specification of this invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0096] Furthermore, the above embodiments are provided only to enable the invention to meet legal requirements, and the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein.

[0097] Similarly, it should be understood that, for the sake of brevity, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of invention should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, the various inventive aspects consist of fewer than all the features of the preceding single embodiment. Furthermore, embodiments may be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0098] The above specific embodiments have provided a detailed description of the purpose, technical means, and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to better understand the present invention, and it is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for denitrification using a powder catalyst in a circulating fluidized bed, characterized in that, include: Step B involves injecting the new catalyst and reducing agent in powder form into the mixing section of the curved flue to fully mix with the flue gas. Step C: In the reaction section of the curved flue, the new catalyst and reducing agent undergo a selective catalytic reduction reaction with the flue gas, reducing NO in the flue gas. x It is converted into N2 and H2O; In step D, the clean flue gas after the reaction carries the catalyst into the dust removal and recovery mechanism to achieve the separation of the clean flue gas and the catalyst.

2. The method for denitrification using a circulating fluidized bed with a powder catalyst according to claim 1, characterized in that, The procedure before step B includes: step A, adjusting the flue gas temperature to the optimal reaction temperature range of the powdered catalyst (<200℃); and / or, In step B, the new catalyst is uniformly conveyed to the mixing section of the curved flue via a venturi feeder by a first pneumatic conveying device; and / or, In step C, the pressure drop during the selective catalytic reduction reaction is ≤1000 Pa; and / or, Step D includes: the clean flue gas after the reaction, carrying the catalyst, enters a pulse bag filter, where centrifugal force separates the clean flue gas from the catalyst; and / or, Following step D, the process further includes step E, where the separated catalyst, as a circulating catalyst, is circulated to the mixing section of the curved flue, wherein the catalyst is circulated ≥20 times; and / or, The process after step D includes step F, in which the separated clean flue gas is discharged in compliance with emission standards.

3. A circulating fluidized bed denitrification device for powder catalysts, characterized in that, include: The conveying bed denitrification reactor includes: a curved flue; wherein, a flue gas inlet is provided at the upper part of the curved flue; and a reducing agent tube and a catalyst tube are connected to its upper side. The dust collection and recovery mechanism has its air inlet connected to the flue gas outlet of the conveying bed denitrification reactor.

4. The powder catalyst circulating airflow denitrification equipment according to claim 3, characterized in that, The curved flue is an L-shaped flue. The L-shaped flue includes: a mixing section extending vertically; and a reaction section extending horizontally. The reducing agent tube and the catalyst tube are connected to the mixing section; the downstream side of the mixing section is connected to the reaction section; the downstream side of the reaction section is connected to the dust removal and recovery mechanism; the mixing section and the reaction section are smoothly connected by an arc.

5. The powder catalyst circulating airflow denitrification equipment according to claim 4, characterized in that, The mixing section includes: a primary mixing section and a secondary mixing section; The primary mixing section is connected to the flue gas inlet; the reducing agent tube and / or catalyst tube are tangentially connected to the primary mixing section at a preset angle α for preliminary mixing and generating swirl; the secondary mixing section is equipped with a static mixer for accelerating and enhancing turbulent mixing, 10°≤α≤80°, where α is the angle between the reducing agent tube and the catalyst tube and the vertical direction.

6. The powder catalyst circulating airflow denitrification equipment according to claim 5, characterized in that, The reducing agent tube and the catalyst tube are tangentially connected to the primary mixing section at a predetermined included angle α, wherein: 30°≤α≤60°; and / or, The static mixer is one of the following: a spiral plate type or a mesh type static mixer; and / or, The reducing agent tube and the catalyst tube are connected to the first mixing section at circumferential intervals of 180°, and in the same direction, wherein the same direction is either clockwise or counterclockwise; and / or, The length L1 of the primary mixing section satisfies: L1=a1*D, 0.5≤a1≤1.5; the length L2 of the secondary mixing section satisfies: L2=a2*D, 2≤a2≤5; where D is the equivalent diameter of the curved flue.

7. The powder catalyst circulating airflow denitrification equipment according to claim 4, characterized in that, The catalyst tube includes: a new catalyst tube and a circulating catalyst tube arranged in parallel vertically, wherein the new catalyst supply device is connected to the new catalyst tube; and the circulating catalyst supply device is connected to the circulating catalyst tube. The circulating fluidized bed denitrification equipment for the powder catalyst also includes: NO x A concentration sensor is installed at the air outlet of the dust collection and recovery mechanism; The control device, whose first sensor signal input port is connected to NO x The concentration sensor, with its first control terminal and second control terminal connected to the new catalyst supply device and the circulating catalyst supply device respectively, is used to determine the concentration of NO. x NO at the flue gas outlet obtained by the concentration sensor x Content, controlling the amount and / or ratio of new catalyst and recycled catalyst input into the bend flue.

8. The powder catalyst circulating airflow denitrification equipment according to claim 7, characterized in that, The new catalyst supply equipment includes: a new catalyst silo with its catalyst outlet facing downwards; a first pneumatic conveying device, the controlled end of which is connected to a first control terminal of a control device; a first venturi tube section, its pneumatic inlet connected to the first pneumatic conveying device, its inlet connected to the catalyst outlet of the catalyst silo, and its outlet connected to the new catalyst tube; and / or, The circulating catalyst supply equipment includes: a screw conveyor with its inlet connected to the outlet of the dust collection hopper of the dust removal and recovery mechanism; a second pneumatic conveying device with its controlled end connected to the first and second control ends of the control device; a second Venturi tube section with its pneumatic inlet connected to the second pneumatic conveying device, its inlet connected to the outlet of the screw conveyor, and its outlet connected to the circulating catalyst tube; and / or, The control device executes the following control logic: when the NO at the flue gas outlet... x When the NO content exceeds the preset upper limit, the amount of new catalyst supplied is increased; when the NO at the flue gas outlet... x When the content is lower than the preset lower limit, reduce the amount of new catalyst supplied and increase the amount of recycled catalyst supplied.

9. The powder catalyst circulating airflow denitrification equipment according to claim 4, characterized in that, The reaction section includes: a telescopic pipeline with an adjustable length, wherein: The expandable conduit is: a expandable corrugated pipe; and / or, The reaction section includes: N sections of expandable piping, where N > 1; and / or, The length of the reaction section satisfies: L3 max ≤3*L3 min L3 min ≥10*D, L3 max ≤30*D, where L3 min and L3 min These are the maximum and minimum lengths of the reaction section, respectively, and D is the equivalent diameter of the bend in the flue; and / or, It also includes: a flue gas flow sensor, installed at the flue gas inlet; a pipeline length control device, used to control the length of the expandable pipeline in the reaction section; and a control device, whose second sensor input port is connected to the flue gas flow sensor and whose second control terminal is connected to the controlled terminal of the pipeline length control device, used to control the residence time τ of the flue gas in the curved flue by adjusting the length of the expandable pipeline, wherein 0.8s≤τ≤2s, and the residence time τ is defined as the ratio of the effective reaction volume to the standard volume flow rate.

10. The powder catalyst circulating fluidized bed denitrification equipment according to any one of claims 3 to 9, characterized in that, The dust collection and recovery mechanism is: a pulse-jet bag filter or a cyclone dust collector; and / or... The reducing agent introduced into the reducing agent tube is one of the following: liquid ammonia, ammonia water, or urea; and / or, The catalyst input to the catalyst tube is a powder catalyst with a particle size between 20-50 μm; and / or, It also includes: an induced draft fan, the inlet of which is connected to the outlet of the dust collection and recovery mechanism, and the outlet of which is connected to the chimney; and / or, It also includes: a flue gas temperature sensor installed at the flue gas inlet of the curved flue; a flue gas temperature regulating device installed on the upstream side of the curved flue, used to regulate the flue gas to be denitrified to a low temperature of less than 200°C; and a control device, whose third sensor input port is connected to the flue gas temperature sensor and whose third control terminal is connected to the flue gas temperature regulating device; wherein, the flue gas temperature regulating device is a steam-heated counter-flow tube heat exchanger, and an electric steam regulating valve is installed at the shell-side inlet of the counter-flow tube heat exchanger; the control device has a pre-stored target flue gas temperature range, used to use the inlet flue gas temperature sensed by the flue gas temperature sensor as the main control quantity, and to adjust the electric steam regulating valve in conjunction to maintain the inlet flue gas temperature within the target flue gas temperature range.

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