CN106345244A - Device and method for removing sulfur trioxide from coal-fired flue gas - Google Patents

Abstract

The invention relates to a device and method for removing sulfur trioxide from coal-fired flue gas. The lower part of the type feeder is connected to the main pipeline; the air from the blower is sent into the main pipeline after being dried by the air dryer, and the alkaline absorbent from the weightless feeder is conveyed by pneumatic force; the terminal of the main pipeline is connected to the separator; the separator will The main pipeline is evenly divided into multiple branches, each branch is connected to a spray gun; the spray guns are evenly arranged on the flue section, and a static mixer is installed in the downstream flue of the spray gun to ensure that the alkaline absorbent sprayed by the spray gun and the smoke Mix the air evenly. According to different flue gas conditions and flue positions, the present invention selects different types of alkaline absorbents, sprays alkaline absorbents into the flue through a spray gun to absorb SO ₃ in the flue gas, reduces the harm of SO ₃ to the operation of the power plant, and realizes Ultra-low emissions of SO ₃ .

Description

Device and method for removing sulfur trioxide from coal-fired flue gas

technical field

The invention belongs to the technical field of air pollutant control, and in particular relates to a device and method for removing sulfur trioxide from coal-fired flue gas.

Background technique

SO ₂ and NO _X are one of the main air pollutants in the flue gas of coal-fired power plants. In order to reduce NO _X emissions, most coal-fired power plants have installed SCR denitrification devices. The SCR catalyst may catalyze and oxidize part of SO ₂ to SO ₃ , and the SO ₃ generated in the furnace will make SO ₃ reach a certain concentration, which will cause harm to the power plant, such as catalyst poisoning, air preheater blockage, flue corrosion, etc. Electrostatic precipitators and wet desulfurization towers have limited ability to remove SO ₃ , and the discharge of SO ₃ into the atmosphere will aggravate smog and cause environmental pollution. _The problem caused by SO3 is even more serious when burning high-sulfur coal. Realizing the deep removal of SO ₃ is of great significance to the safe and economical operation of the power plant and the improvement of the atmospheric environment.

In order to reduce the harm of SO ₃ to the operation of power plants and control the emission of SO ₃ , the method of spraying alkaline absorbent into the flue is mostly used at present. Chinese patent CN103055684A discloses a device and process for removing sulfur trioxide from flue gas by using trona. The flue gas from the outlet of the SCR reactor is sprayed with trona slurry to absorb SO ₃ , and then enters the air preheater; Chinese patent CN104857841A discloses A device for removing sulfur trioxide in flue gas is proposed, including a silo, a screw feeder, a spray gun, a denitration reactor and a spoiler, etc., and absorbs SO ₃ in front of the denitration reactor by spraying strong alkaline substances; Chinese patent CN104474897A discloses a method for removing sulfur trioxide in coal-fired flue gas, spraying it into the flue gas in the flue before the inlet end of the denitrification device, and in the flue gas between the outlet end of the denitrification device and the air preheater A certain amount of alkaline particles can remove sulfur trioxide in flue gas. Although the above method can control the emission of SO ₃ to a certain extent, it cannot effectively deal with the removal of SO ₃ under different flue gas conditions, and cannot well meet the requirements of ultra-low emission of SO ₃ .

Contents of the invention

Aiming at the problem of SO3 generation in coal _- fired flue gas, the present invention proposes a coal-fired flue gas sulfur trioxide removal device and method suitable for different flue gas conditions. In view of the differences in the flue gas conditions of different coal-fired power plants, according to the flue gas temperature, SO ₃ concentration, atmosphere and other conditions, spray alkaline absorbents at different flue positions to efficiently remove SO ₃ in the flue gas and reduce SO ₃ Harm to power plant equipment, meet the requirements of SO ₃ ultra-low emission.

A device for removing sulfur trioxide from coal-fired flue gas, including a flue, and the device also includes a sequentially connected coarse material bin, a screw feeder, an air classifying mill, a fine material bin, and a weightless feeder , a main pipe, a separator and a spray gun, the spray gun is arranged in the flue, and a static mixer is arranged in the downstream flue of the spray gun; the main pipe is also communicated with the blower through an air dryer.

The lower part of the weightless feeder of the present invention is connected with the main pipeline, the air of the blower is sent into the main pipeline after being dried by the air dryer, and the alkaline absorbent from the weightless feeder is transported by pneumatic force; the terminal of the main pipeline is connected with the separator, The separator divides the main pipe evenly into multiple branches, and each branch is connected to a spray gun; the spray guns are evenly arranged on the flue section, and a static mixer is installed in the downstream flue of the spray gun to ensure the alkaline absorption of the spray gun spray The agent is evenly mixed with the flue gas. According to different flue gas conditions and flue positions, select different types of alkaline absorbents, spray alkaline absorbents into the flue through the spray gun to absorb SO ₃ in the flue gas, reduce the harm of SO ₃ to the operation of the power plant, and achieve SO ₃ ultra-low emissions.

Preferably, the main pipeline communicates with several pipeline branches through a separator, and each pipeline branch communicates with a corresponding spray gun respectively.

Preferably, the fine material bin is a sealing device, and a drying device is installed inside to prevent the alkaline absorbent from agglomerating, scaling, and blocking pipelines caused by water absorption; the number of pipeline branches is four.

As a preference, the position where the alkaline absorbent is injected is the following single or multiple positions: between the economizer and the SCR reactor, between the SCR reactor and the air preheater, between the air preheater and the dust collector, between the dust removal Between the device and the desulfurization tower.

A method for removing sulfur trioxide from coal-fired flue gas, comprising the steps of:

(1) Select different flue positions, as well as the type and particle size of the alkaline absorbent;

(2) When the system is running, the selected solid particle alkaline absorbent is stored in the coarse material bin, the bottom of the coarse material bin is connected with the screw feeder, and the absorbent is sent into the air classification mill by the screw feeder, Grind the absorbent to the required fineness, and then send it to the fine material bin for standby;

(3) The fine material bin is connected with the weightless feeder, and the feeding rate is controlled by the weightless feeder;

(4) The lower part of the loss-in-weight feeder is connected to the main pipeline for transporting alkaline absorbent, and the fine alkaline absorbent particles from the loss-in-weight feeder are transported in the air pipeline by means of pneumatic conveying, and the wind generated by the blower first passes through Dry in an air dryer to prevent absorbent particles from agglomerating and clogging pipes;

(5) The fine absorbent particles in the main pipeline are first sent to the separator, which is divided into multiple branches by the separator, each branch is connected with the corresponding spray gun, and the spray gun is evenly arranged on the flue section, and the alkaline absorbent Particles are ejected from the spray gun;

(6) Arrange a static mixer in the downstream flue of the spray gun to ensure that the alkaline absorbent particles are evenly mixed with the flue gas;

(7) SO ₃ is absorbed by the alkaline absorbent particles to form sulfate and removed, and the reaction products and unreacted particles are removed through the downstream particle removal device.

The present invention selects different flue positions based on the characteristics of the flue gas, and uses the device to spray a certain amount and fineness _of alkaline absorbent particles into the flue, so that SO3 reacts with the alkaline absorbent particles and is removed, and the flue gas Particles in are removed by downstream particle removal equipment.

Preferably, in step (2), the solid alkaline absorbent particles in the coarse silo are calcium-based alkaline absorbent particles (CaO, Ca(OH) ₂ , CaCO ₃ , etc.), magnesium-based alkaline absorbent particles particles (MgO, Mg(OH) ₂ , MgCO ₃ magnesium, etc.), or sodium-based alkaline absorbent particles (Na ₂ CO ₃ , NaHCO ₃ , trona, etc.); the solid alkaline absorbent particles and smoke The molar ratio of SO ₃ in the medium is between 0.5:1 and 30:1, and the particle size of the solid alkaline absorbent particles in the coarse hopper is below 1cm; the air classification mill grinds the solid alkaline absorbent particles to between 10 μm and 100 μm In the meantime, further, the absorbent is ground to 40-60 μm.

Preferably, in step (4), during pneumatic conveying, the solid-gas ratio is controlled to be 0.1-25:1, the flow velocity is 18-30 m/s, and the gas pressure is 0.5-1 Mpa.

As a preference, in step (5), the spraying of the alkaline absorbent adopts one or more stages of spraying, and the distance before each two-stage spraying device is 5-15 m.

Preferably, the position where the alkaline absorbent is injected includes the following single or multiple positions: the flue between the economizer and the SCR reactor, the flue between the SCR reactor and the air preheater, the air preheater and the air preheater The flue between the dust collector, the flue between the dust collector and the desulfurization tower; at different absorbent injection positions, the temperature of the flue gas is between 100°C and 450°C, and the concentration of SO ₃ is between 10ppm and 100ppm , The residence time of the alkaline absorbent in the flue is 0.01s to 4s.

In the flue between the economizer and the SCR reactor, choose to inject sodium-based absorbents (Na ₂ CO ₃ , NaHCO ₃ , trona, etc.); in the flue between the SCR reactor and the air preheater, choose Spray magnesium-based absorbents (MgO, Mg(OH) ₂ , MgCO ₃ magnesium, etc.); in the flue between the air preheater and the dust collector, and between the dust collector and the desulfurization tower, choose to spray calcium-based Absorbents (CaO, Ca(OH) ₂ , CaCO ₃ etc.). When burning high-sulfur coal, inject alkaline absorbent into the flue between the economizer and the SCR reactor to remove SO ₃ and reduce the damage of SO ₃ to the catalyst; when the conversion rate of SO ₂ /SO ₃ of the SCR catalyst When it is higher, spray alkaline absorbent into the flue between the SCR reactor and the air preheater to remove SO ₃ , and reduce the harm of the formation of ammonium bisulfate to the air preheater; when the main purpose is to reduce the SO ₃ When discharging and corroding power plant equipment, spray alkaline absorbent into the flue before and after the dust collector to remove SO ₃ .

Preferably, the method for removing sulfur trioxide from coal-fired flue gas comprises the following steps:

(1) The flue is located between the economizer and the SCR reactor, the flue gas temperature is 400°C, and the SO ₃ concentration is 25ppm; trona is used as an absorbent, and the average particle size of trona is 2mm;

(2) When the system is running, trona is stored in the coarse material bin, and the bottom of the coarse material bin is connected with the screw feeder, and the trona with coarse particles is sent into the air classification mill by the screw feeder, and the trona is milled The average particle size is 40 μm, and then sent to the fine material bin for standby, the fine material bin is a sealed device and is equipped with a drying device;

(3) The fine material bin is connected with the weightless feeder, and the feeding rate is controlled by the weightless feeder, so that the molar ratio of trona to SO is ₂ :1;

(4) The lower part of the weightless feeder is connected to the main pipeline for transporting alkaline absorbent, and the fine trona particles from the weightless feeder are transported in the air pipeline by means of pneumatic conveying, and the wind generated by the blower is first air-dried machine drying;

(5) The fine trona particles in the main pipeline are first sent to the separator, which is divided into four branches by the separator, each branch is connected with the corresponding spray gun, and the spray gun is evenly arranged on the flue section, and the alkaline absorbent The particles are ejected from the spray gun and flow in the same direction as the flue gas;

(6) Arrange a static mixer in the downstream flue of the spray gun;

(7) SO ₃ is absorbed by the alkaline absorbent particles to form sulfate and removed, and the reaction products and unreacted particles are removed through the downstream particle removal device.

The beneficial effects of the present invention are:

(1) The separator divides the main pipe evenly into multiple branches, and each branch is connected to a spray gun; the spray guns are evenly arranged on the flue section, and a static mixer is installed in the downstream flue of the spray gun to ensure the spraying of the spray gun The alkaline absorbent is evenly mixed with the flue gas;

(2) According to different flue gas conditions and flue positions, select the appropriate alkaline absorbent, by removing SO ₃ at specific flue positions, effectively prevent the blockage of the denitrification catalyst and air preheater, and reduce the impact of SO ₃ on the power plant operating hazards, and achieve ultra-low emissions of SO ₃ .

Instructions attached

Fig. 1 is the structural representation of the device for removing sulfur trioxide from coal-fired flue gas of the present invention;

1-coarse silo, 2-screw feeder, 3-air classification mill, 4-fine silo, 5-loss-in-weight feeder, 6-blower, 7-air dryer, 8-main pipe, 9 - separator, 10 - pipe branch, 11 - spray gun, 12 - static mixer, 13 - flue.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

Example 1

With reference to Fig. 1, a kind of coal-fired flue gas sulfur trioxide removal device comprises flue 13, and described device also comprises the coarse stock bin 1 that is connected in sequence, screw type feeder 2, air classification mill 3, fine Stock bin 4, loss-in-weight feeder 5, main pipeline 8, separator 9 and spray gun 11, described spray gun 11 is arranged in the flue 13, and static mixer 12 is arranged in the downstream flue of spray gun 11; Said main pipeline 8 is also communicated with blower 6 through air dryer 7 .

The main pipeline 8 communicates with several pipeline branches 10 through a separator 9, and each pipeline branch communicates with a corresponding spray gun 11; the number of the pipeline branches is four. The fine material bin is a sealing device, and is equipped with a drying device to prevent the alkaline absorbent from agglomerating, scaling, and blocking the pipeline due to water absorption.

The location where the alkaline absorbent is injected is the following single or multiple locations: between the economizer and the SCR reactor, between the SCR reactor and the air preheater, between the air preheater and the dust collector, between the dust collector and the desulfurization between the towers. When burning high-sulfur coal, inject alkaline absorbent into the flue between the economizer and the SCR reactor to remove SO ₃ and reduce the damage of SO ₃ to the catalyst; when the conversion rate of SO ₂ /SO ₃ of the SCR catalyst When it is higher, spray alkaline absorbent into the flue between the SCR reactor and the air preheater to remove SO ₃ , and reduce the harm of the formation of ammonium bisulfate to the air preheater; when the main purpose is to reduce the SO ₃ When discharging and corroding power plant equipment, spray alkaline absorbent into the flue before and after the dust collector to remove SO ₃ .

Example 2

To remove SO ₃ in the flue before SCR, the flue is located between the economizer and the SCR reactor. The flue gas temperature is 400°C, and the SO ₃ concentration is 25ppm. According to the flue gas conditions there, choose trona (Na ₂ CO ₃ ·NaHCO ₃ ·2H ₂ O) as the absorbent, and the molar ratio of trona to SO ₃ is 2:1. The average particle size of the trona coarse material is 2mm, the average particle size of the fine material is determined to be 40μm, and the residence time of the alkaline absorbent in the flue is 2s.

As shown in Figure 1, when the system is running, a large amount of trona coarse material is stored in the coarse material bin 1, with an average particle size of 2 mm. The bottom of the coarse material bin 1 is connected with the screw feeder 2; the trona with coarse particles is sent to the air classification mill 3 by the screw feeder 2, and the trona is ground to an average particle size of 40 μm, and then sent into the fine material bin 4 The fine material bin is a sealed device and is equipped with a drying device to prevent the alkaline absorbent from agglomerating, scaling, and blocking pipes due to water absorption; the fine material bin 4 is connected to the weightless feeder 5, and the weightless The feeder 5 controls the feed rate to achieve a molar ratio of trona to SO ₃ of 2:1; the lower part of the weightless feeder 5 is connected to the main pipeline 8 for conveying the absorbent; the main pipeline 8 is transported by pneumatic conveying From the fine trona granule of loss-in-weight type feeder 5, flow velocity control is 22m/s, and gas pressure is 0.8Mpa; The wind that air blower 6 produces is first dried through air drier 7, to prevent the trona granule from absorbing water and agglomerating, clogging pipeline; The fine trona particles in the main pipeline 8 are first sent to the separator 9, and are divided into four pipeline branches 10 by the separator 9, and each pipeline branch is connected with a corresponding spray gun 11; the alkaline absorbent particles are sprayed from the spray gun 11 , flowing in the same direction as the flue gas _; a static mixer 12 is arranged in the downstream flue of the spray gun to ensure that the alkaline absorbent and the flue gas are evenly mixed, and the alkaline absorbent particles react with SO in the flue gas to form sulfate and be remove.

Under the design working conditions, the removal efficiency of SO ₃ can be guaranteed to be 90%. At the same time, since the injected trona accounts for less than 0.5% of the total mass ratio of flue gas fly ash, it will not have a great impact on the downstream SCR catalyst. .

Example 3

The difference between this example and Example 2 is that SO ₃ in the flue before the air preheater is removed, and the flue is located between the SCR reactor and the air preheater. The flue gas temperature is 250°C, and the SO ₃ concentration is 40ppm. According to the flue gas conditions here, Mg(OH) ₂ is selected as the absorbent, and the molar ratio of Mg(OH) ₂ to SO ₃ is 4:1. The particle size of Mg(OH) ₂ coarse material is 3mm, the average particle size of fine material is determined to be 60μm, and the residence time of alkaline absorbent in the flue is 1s.

Under the design working conditions, the removal efficiency of SO ₃ can be guaranteed to be 84%. Effectively prevent the clogging and corrosion of the air preheater.

Example 4

The difference between this embodiment and embodiment 2 is that the SO ₃ in the flue before the dust collector is removed, and the flue is located between the SCR air preheater and the dust collector. The flue gas temperature is 150°C, and the SO ₃ concentration is 30ppm. According to the flue gas conditions here, Ca(OH) ₂ is selected as the absorbent, and the molar ratio of Ca(OH) ₂ to SO3 is ₆ :1. The average particle size of the Ca(OH) ₂ coarse material is 4 mm, the average particle size of the fine material is determined to be 50 μm, and the residence time of the alkaline absorbent in the flue is 4 s.

Under the design working conditions, the removal efficiency of SO ₃ can be guaranteed to be 85%. Effectively prevent the corrosion of the dust collector and downstream equipment.

Example 5

The difference between this embodiment and embodiment 2 is that the SO ₃ in the flue before the desulfurization tower is removed, and the flue is located between the SCR dust collector and the desulfurization tower. The flue gas temperature is 90°C, and the SO ₃ concentration is 15ppm. According to the flue gas conditions here, Ca(OH) ₂ is selected as the absorbent, and the molar ratio of Ca(OH) ₂ to SO3 is ₃ :1. The average particle size of the Ca(OH) ₂ coarse material is 4 mm, and the average particle size of the fine material is determined to be 40 μm.

Under the design working conditions, the removal efficiency of SO ₃ can be guaranteed to be 80%. Effectively prevent the corrosion of the desulfurization tower and the generation of visible plume.

Claims (10)

1. A coal-fired flue gas sulfur trioxide removal device, comprising a flue, characterized in that: the device also includes a sequentially connected coarse feed bin, a screw feeder, an air classification mill, and a fine feed bin , a weightless feeder, a main pipeline, a separator and a spray gun, the spray gun is arranged in the flue, and a static mixer is arranged in the downstream flue of the spray gun; the main pipeline is also communicated with the blower through an air dryer. 2. The coal-fired flue gas sulfur trioxide removal device according to claim 1, characterized in that: the main pipeline communicates with several pipeline branches through a separator, and each pipeline branch is respectively connected to a corresponding spray gun connected. 3. The coal-fired flue gas sulfur trioxide removal device according to claim 2, characterized in that: the fine material bin is a sealing device, and a drying device is installed inside, and the number of the pipeline branches is four. 4. The coal-fired flue gas sulfur trioxide removal device according to claim 1, characterized in that: the position where the alkaline absorbent is injected is the following single or multiple positions: between the economizer and the SCR reactor The flue, the flue between the SCR reactor and the air preheater, the flue between the air preheater and the dust collector, the flue between the dust collector and the desulfurization tower. 5. A method for removing sulfur trioxide from coal-fired flue gas, characterized in that: the device according to claim 1 is adopted, Include the following steps: (1) Select different flue positions, as well as the type and particle size of the alkaline absorbent; (2) When the system is running, the selected solid particle alkaline absorbent is stored in the coarse material bin, the bottom of the coarse material bin is connected with the screw feeder, and the absorbent is sent into the air classification mill by the screw feeder, Grind the absorbent to the required fineness, and then send it to the fine material bin for standby; (3) The fine material bin is connected with the weightless feeder, and the feeding rate is controlled by the weightless feeder; (4) The lower part of the loss-in-weight feeder is connected to the main pipeline for transporting alkaline absorbent, and the fine alkaline absorbent particles from the loss-in-weight feeder are transported in the air pipeline by means of pneumatic conveying, and the wind generated by the blower first passes through air dryer drying; (5) The fine absorbent particles in the main pipeline are first sent to the separator, which is divided into multiple branches by the separator, each branch is connected with the corresponding spray gun, and the spray gun is evenly arranged on the flue section, and the alkaline absorbent Particles are ejected from the spray gun; (6) Arrange a static mixer in the downstream flue of the spray gun; (7) SO ₃ is absorbed by the alkaline absorbent particles to form sulfate and removed, and the reaction products and unreacted particles are removed through the downstream particle removal device. 6. The method for removing sulfur trioxide from coal-fired flue gas according to claim 5, characterized in that: in step (2), the solid alkaline absorbent particles in the coarse feed bin are calcium-based alkaline absorbent particles , magnesium-based alkaline absorbent particles, or sodium-based alkaline absorbent particles; the molar ratio _of the solid alkaline absorbent particles to SO in the flue gas is between 0.5:1 and 30:1, and the coarse The particle size of the solid alkaline absorbent particles in the bin is below 1cm; the air classification mill grinds the solid alkaline absorbent particles to between 10 μm and 100 μm. 7. The method for removing sulfur trioxide from coal-fired flue gas according to claim 5, characterized in that: in step (4), during pneumatic conveying, the solid-gas ratio is controlled to be 0.1-25:1, and the flow rate is 18-30m /s, the gas pressure is 0.5~1Mpa. 8. The method for removing sulfur trioxide from coal-fired flue gas according to claim 5, characterized in that: in step (5), the injection of the alkaline absorbent adopts one-stage or multi-stage injection, and before every two-stage injection device The distance is 5 ~ 15m. 9. The method for removing sulfur trioxide from coal-fired flue gas according to claim 5, characterized in that: the position where the alkaline absorbent is injected includes the following single or multiple positions: between the economizer and the SCR reactor The flue between the SCR reactor and the air preheater, the flue between the air preheater and the dust collector, the flue between the dust collector and the desulfurization tower; at different absorbent injection positions, the flue gas The temperature is between 100°C and 450°C, the concentration of SO ₃ is between 10ppm and 100ppm, and the residence time of the alkaline absorbent in the flue is 0.01s to 4s. 10. The method for removing sulfur trioxide from coal-fired flue gas according to claim 5, characterized in that it comprises the following steps: (1) The flue is located between the economizer and the SCR reactor, the flue gas temperature is 400°C, and the SO ₃ concentration is 25ppm; trona is used as an absorbent, and the average particle size of trona is 2mm; (2) When the system is running, trona is stored in the coarse material bin, and the bottom of the coarse material bin is connected with the screw feeder, and the trona with coarse particles is sent into the air classification mill by the screw feeder, and the trona is milled The average particle size is 40 μm, and then sent to the fine material bin for standby, the fine material bin is a sealed device and is equipped with a drying device; (3) The fine material bin is connected with the weightless feeder, and the feeding rate is controlled by the weightless feeder, so that the molar ratio of trona to SO is ₂ :1; (4) The lower part of the weightless feeder is connected to the main pipeline for transporting alkaline absorbent, and the fine trona particles from the weightless feeder are transported in the air pipeline by means of pneumatic conveying, and the wind generated by the blower is first air-dried machine drying; (5) The fine trona particles in the main pipeline are first sent to the separator, which is divided into four branches by the separator, each branch is connected with the corresponding spray gun, and the spray gun is evenly arranged on the flue section, and the alkaline absorbent The particles are ejected from the spray gun and flow in the same direction as the flue gas; (6) Arrange a static mixer in the downstream flue of the spray gun; (7) SO ₃ is absorbed by the alkaline absorbent particles to form sulfate and removed, and the reaction products and unreacted particles are removed through the downstream particle removal device.