Ammonia water evaporation device for medium-temperature SCR (Selective Catalytic Reduction) denitration process

Abstract

According to the ammonia water evaporation device for the medium-temperature SCR denitration process, high-temperature purified flue gas obtained after denitration is used as a unique heat source to evaporate ammonia water into gaseous ammonia, so that an external heat source does not need to be arranged, energy is saved, energy consumption and operation cost of a system are reduced, operation is simple, and cost is low. Comprising a dilution fan, an ammonia water spray gun, an ammonia water evaporator and an ammonia spraying grid, an ammonia water spray gun is mounted at an inlet of the ammonia water evaporator and is communicated with external compressed air and ammonia water; an inlet of the dilution fan is communicated with denitrated high-temperature clean flue gas through a pipeline, and an outlet of the dilution fan is communicated with an inlet of the ammonia water evaporator through a pipeline, so that the denitrated high-temperature clean flue gas is introduced into the ammonia water evaporator through the dilution fan, and the denitrated high-temperature clean flue gas is used as a unique heat source to heat and evaporate ammonia water; an outlet of the ammonia water evaporator is communicated with the ammonia spraying grid through a pipeline, and the ammonia spraying grid is communicated with downstream denitration equipment through a pipeline.

Description

Technical Field

[0001] This utility model belongs to the field of flue gas denitrification technology, and relates to the preparation technology of reducing agent for flue gas denitrification, specifically an ammonia water evaporation device for medium-temperature SCR denitrification process. Background Technology

[0002] Flue gas denitrification (FGD) technology is a core means of controlling nitrogen oxide (NOx) emissions and is widely used in waste gas treatment in coal-fired power plants, industrial boilers, and other fields. Medium-temperature selective catalytic reduction (SCR) denitrification technology has become one of the most widely used denitrification technologies due to its high catalyst activity and good operational stability. In the medium-temperature SCR process, ammonia is introduced into the flue gas as a reducing agent, and under the action of the catalyst, NOx is converted into harmless nitrogen (N2) and water (H2O). The preparation and supply of the reducing agent are key aspects of the medium-temperature SCR system, directly affecting denitrification efficiency and operating costs.

[0003] Traditional methods for preparing ammonia reducing agents mainly include liquid ammonia evaporation, urea pyrolysis, urea hydrolysis, and ammonia water evaporation. Among these, liquid ammonia evaporation presents high safety risks related to the storage and use of liquid ammonia, while urea decomposition for ammonia production consumes a large amount of energy. Compared to liquid ammonia evaporation, urea pyrolysis, and urea hydrolysis, ammonia water evaporation offers advantages such as high safety and ease of operation. However, current methods for preparing ammonia reducing agents using ammonia water evaporation rely on external heat sources, such as external hot air furnaces or direct-fired furnaces, to heat and evaporate the ammonia water, resulting in complex system structures and high energy consumption. Utility Model Content

[0004] To overcome the problems of complex structure and high energy consumption in the existing medium-temperature SCR denitrification process using ammonia water evaporation to prepare ammonia reducing agent, this utility model provides an ammonia water evaporation device for medium-temperature SCR denitrification process. It uses the high-temperature purified flue gas after denitrification as the only heat source to evaporate ammonia water into gaseous ammonia, thus eliminating the need for an external heat source, saving energy, reducing system energy consumption and operating costs, and simplifying operation.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] An ammonia evaporation device for a medium-temperature SCR denitrification process includes a dilution fan, an ammonia spray gun, an ammonia evaporator, and an ammonia spray grid.

[0007] An ammonia spray gun is installed at the inlet of the ammonia evaporator, which is connected to external compressed air and ammonia. The inlet of the dilution fan is connected to the high-temperature clean flue gas after denitrification through a pipeline, and the outlet of the dilution fan is connected to the inlet of the ammonia evaporator through a pipeline, so as to introduce the high-temperature clean flue gas after denitrification into the ammonia evaporator through the dilution fan, and use the high-temperature clean flue gas after denitrification as the sole heat source to heat and evaporate the ammonia. The outlet of the ammonia evaporator is connected to the ammonia injection grid through a pipeline, and the ammonia injection grid is connected to the downstream denitrification equipment through a pipeline.

[0008] Furthermore, the ammonia evaporator has a cavity structure, including a shell, an inlet variable diameter section located at the bottom inlet of the shell, and an outlet variable diameter section located at the top outlet of the shell; the inlet variable diameter section has a trumpet-shaped structure, and its diameter gradually increases from the bottom inlet port towards the shell; the outlet variable diameter section has a trumpet-shaped structure, and its diameter gradually increases from the top outlet port towards the shell.

[0009] Furthermore, the ammonia spray gun is a dual-fluid type, which is installed at the inlet diameter-changing section of the ammonia evaporator.

[0010] Furthermore, the temperature of the denitrified high-temperature clean flue gas is 210–280°C, and it originates directly from the denitrified clean flue gas pipeline.

[0011] The beneficial effects of this utility model include:

[0012] This invention utilizes the aforementioned technical solution to design an ammonia evaporation device for medium-temperature SCR denitrification processes. The purified flue gas after medium-temperature denitrification typically reaches 210–280°C. A dilution fan introduces a portion of this high-temperature purified flue gas into the ammonia evaporator, evaporating the atomized ammonia water sprayed from the ammonia water nozzle into an ammonia-air mixture, which then enters the ammonia injection grid and downstream equipment for denitrification. This invention directly utilizes the high-temperature purified flue gas after medium-temperature SCR denitrification as the sole heat source to evaporate the ammonia water into gaseous ammonia, eliminating the need for external heat source equipment such as hot air furnaces or direct-fired furnaces. This saves energy, significantly reduces system energy consumption and operating costs, and facilitates operation and management. By omitting external heat source equipment, the system architecture is simplified, maintenance costs are reduced, and the footprint is minimized, making it suitable for the renovation of existing denitrification systems and new construction projects.

[0013] A dual-fluid ammonia spray gun, aided by compressed air atomization, ensures thorough ammonia atomization and uniform mixing with high-temperature flue gas, improving evaporation efficiency. The funnel-shaped design of the inlet and outlet diameter-changing sections of the ammonia evaporator optimizes airflow distribution, reduces local eddies and resistance, and further enhances ammonia evaporation. An ammonia-air mixture is uniformly injected into the downstream denitrification equipment inlet via an ammonia spray grid. Combined with the optimized design of the ammonia evaporator, this ensures thorough mixing of ammonia and flue gas, preventing excessively high or low local ammonia concentrations and improving denitrification efficiency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0015] Figure 2 This is a schematic diagram of the ammonia evaporator structure of this utility model.

[0016] In the diagram: 1. Dilution fan; 2. Ammonia spray gun; 3. Ammonia evaporator; 4. Ammonia spray grid; 5. Inlet reducer section; 6. Shell; 7. Outlet reducer section. Detailed Implementation

[0017] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0018] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0019] Example 1: This application is applicable to medium-temperature SCR denitrification process projects. It uses the high-temperature clean flue gas after denitrification as a heat source to quickly and completely evaporate ammonia water into ammonia gas, and mixes the ammonia gas with the flue gas to be purified, thereby improving the efficiency and stability of the denitrification reaction, ensuring compliance with emission standards, reducing dependence on external energy, and reducing the system's energy consumption and operating costs.

[0020] refer to Figure 1 An ammonia evaporation device for a medium-temperature SCR denitrification process includes a dilution fan 1, an ammonia spray gun 2, an ammonia evaporator 3, and an ammonia spray grid 4. The ammonia evaporator 3 has a cavity structure, including a shell 6, an inlet reducing section 5 located at the bottom inlet of the shell 6, and an outlet reducing section 7 located at the top outlet of the shell 6. The ammonia spray gun 2 is a dual-fluid type and is installed at the inlet reducing section 5 of the ammonia evaporator 3. The number of ammonia spray guns 2 can be set to one or more. The ammonia spray gun 2 is connected to external compressed air and ammonia, using compressed air as an atomizing medium to atomize the ammonia into tiny droplets of 10-50 micrometers, ensuring sufficient contact between the ammonia and the high-temperature flue gas.

[0021] The inlet of the dilution fan 1 is connected to the high-temperature clean flue gas after denitrification via a pipeline. The temperature of the high-temperature clean flue gas after denitrification is 210-280℃ and it comes directly from the clean flue gas pipeline after denitrification. The outlet of the dilution fan 1 is connected to the inlet reducer section 5 of the ammonia evaporator 3 via a pipeline. The outlet reducer section 7 of the ammonia evaporator 3 is connected to the ammonia injection grid 4 via a pipeline. The ammonia injection grid 4 is connected to the downstream denitrification equipment via a pipeline.

[0022] Preferred, Reference Figure 2 The inlet variable diameter section 5 is a trumpet-shaped structure, with its diameter gradually increasing from the bottom inlet port towards the shell 6, which is used to optimize airflow distribution and improve ammonia evaporation efficiency; the outlet variable diameter section 7 is a trumpet-shaped structure, with its diameter gradually increasing from the top outlet port towards the shell 6, which is used to reduce airflow resistance and ensure uniform output of ammonia-air mixed gas.

[0023] The working principle of this invention is as follows: High-temperature purified flue gas (210-280℃) from the medium-temperature denitrification process is introduced into the ammonia evaporator 3 via a dilution fan 1. Ammonia water with a concentration of 20%-30% is atomized and sprayed into the evaporator 3 through an ammonia spray gun 2. The high-temperature purified flue gas, acting as the sole heat source, evaporates the atomized ammonia water into an ammonia-air mixture with an ammonia concentration of less than 5%. During evaporation, the funnel-shaped inlet variable diameter section 5 and the funnel-shaped outlet variable diameter section 7 of the ammonia evaporator 3 optimize the airflow distribution, reducing local eddies and resistance, ensuring uniform ammonia evaporation. The ammonia-air mixture flows out from the outlet variable diameter section 7 of the ammonia evaporator 3 and enters the ammonia injection grid 4 through a pipeline. The ammonia injection grid 4 evenly injects the ammonia-air mixture into the SCR reactor, ensuring thorough mixing of ammonia with NOx in the flue gas. In the SCR reactor, ammonia and NOx undergo a selective catalytic reduction reaction under the action of a catalyst, generating harmless nitrogen (N2) and water (H2O), achieving efficient denitrification.

[0024] Example 2: Preferably, based on Example 1, an ammonia concentration sensor is installed near the inlet of the ammonia-air mixture gas pipeline between the outlet variable diameter section 7 of the ammonia evaporator 3 and the ammonia injection grid 4 to monitor the ammonia concentration of the ammonia-air mixture gas in real time. Temperature sensors are installed on both the inlet and outlet pipelines of the ammonia evaporator 3 to monitor the temperature of the high-temperature clean flue gas and the ammonia-air mixture gas in real time. A high-temperature clean flue gas flow sensor is installed on the outlet pipeline of the dilution fan 1 to monitor the flow rate of the high-temperature clean flue gas introduced by the dilution fan 1. An ammonia flow regulating valve is installed on the connecting pipeline between the ammonia spray gun 2 and the ammonia storage device to dynamically adjust the ammonia injection volume and control the total amount of ammonia generated. A controller is installed and electrically connected to the ammonia concentration sensor, temperature sensor, high-temperature clean flue gas flow sensor, ammonia flow regulating valve, and dilution fan 1, respectively, to adjust the ammonia flow regulating valve and dilution fan 1 according to the monitoring values ​​of each sensor, thereby adjusting the ammonia injection volume and the high-temperature clean flue gas flow rate to control the concentration of the evaporated ammonia-air mixture gas.

[0025] Example 3: Further preferred embodiment: Due to the high catalyst activity in the high-temperature region of the SCR reactor, the reaction rate of NOx and NH3 is fast, requiring less ammonia. In the low-temperature region, the catalyst activity decreases, the reaction rate slows down, and more ammonia is required. Based on Example 1 or Example 2, this embodiment includes an ammonia injection grid 4 structure comprising a main ammonia injection pipe and multiple branch ammonia injection pipes. Each branch ammonia injection pipe is equipped with an ammonia injection port and an ammonia injection regulating valve, used to reduce the ammonia injection rate in the high-temperature region and increase the ammonia injection rate in the low-temperature region according to the temperature distribution of the flue gas at the SCR reactor inlet.

[0026] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An ammonia water evaporation device for a medium-temperature SCR denitration process, characterized by, The device comprises a dilution fan (1), an ammonia water spray gun (2), an ammonia water evaporator (3) and an ammonia injection grid (4); The ammonia water spray gun (2) is installed at the inlet of the ammonia water evaporator (3) and is connected with external compressed air and ammonia water; the inlet of the dilution fan (1) is connected with the high-temperature flue gas after denitrification through a pipeline, and the outlet of the dilution fan (1) is connected with the inlet of the ammonia water evaporator (3) through a pipeline, so that the high-temperature flue gas after denitrification is introduced into the ammonia water evaporator (3) through the dilution fan (1) and the high-temperature flue gas after denitrification is used as the only heat source to evaporate the ammonia water; the outlet of the ammonia water evaporator (3) is connected with the ammonia injection grid (4) through a pipeline, and the ammonia injection grid (4) is connected with the downstream denitrification equipment through a pipeline. 2.The ammonia water evaporation device for a medium-temperature SCR denitration process according to claim 1, characterized in that, The ammonia water evaporator (3) is a hollow structure comprising a shell (6), an inlet variable-diameter section (5) arranged at the bottom inlet of the shell (6) and an outlet variable-diameter section (7) arranged at the top outlet of the shell (6); the inlet variable-diameter section (5) is a horn-shaped structure with a gradually increasing diameter from the bottom inlet port to the shell (6); the outlet variable-diameter section (7) is a horn-shaped structure with a gradually increasing diameter from the top outlet port to the shell (6). 3.The ammonia water evaporation device for a medium-temperature SCR denitration process according to claim 2, characterized in that, The ammonia water spray gun (2) is a double-fluid type and is installed at the inlet variable-diameter section (5) of the ammonia water evaporator (3).

4. The ammonia water evaporation device for medium-temperature SCR denitration process according to any one of claims 1-3, characterized in that, The temperature of the high-temperature flue gas after denitrification is 210-280℃ and is directly obtained from the flue gas pipeline after denitrification.

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