Sulfur trioxide removal unit, system and method using same

Abstract

The invention discloses a sulfur trioxide removal unit, which is used for a process for removing SO3 in flue gas by a dry method, and comprises solid alkali nozzles which are arranged at a flue gas outlet of a denitration channel and are uniformly distributed at intervals, the solid alkali nozzles receive an alkaline solid granular absorbent, and the spraying direction of the solid alkali nozzles is the same as the flow direction of the flue gas; the static mixing cylinders are arranged below the solid alkali nozzles, the number of the static mixing cylinders is matched with that of the nozzles, and the static mixing cylinders are used for receiving the heated and expanded alkaline solid particles and the flue gas and are in mixed contact in a vortex mode. The invention also discloses a sulfur trioxide removal system and a sulfur trioxide removal method. The removal unit is arranged at the outlet of the denitration flue, so that the process influence on the desulfurization tower can be effectively avoided; through the cooperation of the solid caustic soda nozzle and the static mixing cylinder, the sulfur trioxide removal efficiency is ensured, and the scaling phenomenon in the cylinder can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, and in particular to a sulfur trioxide dry removal unit, and a system and method using the unit. Background Art

[0002] The combustion of fossil fuels will generate a large amount of air pollutants, such as sulfur dioxide, nitrogen oxides, fine particulate matter, mercury and other heavy metals, which is one of the main causes of smog weather. In order to meet the strict emission standards, petrochemical enterprises have upgraded their environmental protection facilities, such as installing a selective catalytic reduction denitrification system (SCR) to reduce NO x The emission of sulfur trioxide in flue gas is effectively controlled. However, the use of SCR catalyst causes some SO2 to be oxidized into SO3, which increases the concentration of SO3 in flue gas. With the acceleration of industrialization, the emission of sulfur trioxide in flue gas is becoming more and more serious.

[0003] SO3 is a toxic air pollutant and one of the precursors of PM2.5. After passing through the wet flue gas desulfurization tower, SO3 forms submicron sulfuric acid aerosol, which makes the exhaust smoke of some chemical plants and power plants yellow or blue; after sulfuric acid settles, it will destroy buildings and vegetation, and cause damage to the mucous membrane of the human respiratory tract and lung structure. SO3 also has an adverse effect on the operation of the denitrification system. SO3 reacts with NH3 to form ammonium sulfate and ammonium bisulfate in the SCR system, which will cause catalyst deactivation and blockage. At the same time, ammonium bisulfate is sticky and acidic, and it is easy to deposit on the metal surface of the air preheater, causing the accumulation of particulate matter in the flue gas, causing the air preheater to block and the metal surface to corrode. Traditional wet flue gas desulfurization technology mainly targets sulfur dioxide gas contained in flue gas, but has little effect on the removal of sulfur trioxide gas. The existing sulfur trioxide removal technology has excessive absorbent due to uneven distribution of absorbent, which leads to scaling of subsequent process equipment.

[0004] Existing sulfur trioxide removal methods include light irradiation, liquid alkali absorption and dry removal. The light irradiation method is to use light of a specific wavelength to irradiate the flue gas to decompose the sulfur trioxide in the flue gas into SO2 and O2; the liquid alkali absorption method is to use liquid alkali as an absorbent; the dry method of removing SO3 from the flue gas generally involves desulfurizing the SO3 in the flue gas in a desulfurization tower by spraying powdered alkaline materials.

[0005] For example, Chinese patent application CN113368673A discloses a system and method for dry removal of sulfur trioxide from flue gas, including a hopper, a transmission device fixedly connected to the bottom end of the hopper, an end of the transmission device away from the hopper is located at the upper end of a raw material bin, an air cannon is fixedly connected to the outer wall of the raw material bin, a weighing feeder is fixedly connected to the bottom end of a discharge pipe of the raw material bin, a grinder is fixedly connected to the bottom end of a discharge port of the weighing feeder, one end of the grinder is fixedly connected to a primary air duct through a pipe one, the other end of the grinder is fixedly connected to a powder bin through a pipe two, a separator is fixedly connected to a separator, the lower end of the discharge pipe at the bottom of the powder bin is fixedly connected to a powder feeding bin, one end of the powder feeding bin is fixedly connected to a blower through a pipe three, the other end of the powder feeding bin is fixedly connected to a feeding pipe, a plurality of distribution pipes are fixedly connected to the end of the feeding pipe, and a plurality of nozzles are fixedly connected to the distribution pipe located in the desulfurization tower. Although the existing technology can ensure a certain desulfurization effect by desulfurizing the SO3 in the flue gas in the desulfurization tower by spraying powdered alkaline materials, the process is carried out in the desulfurization tower, which can easily cause the pH value of the liquid in the desulfurization tower to increase, resulting in the discharge of wastewater that does not meet the standards; at the same time, the irregular distribution of the powdered alkaline material spraying will lead to a decrease in the sulfur trioxide removal efficiency and the occurrence of equipment scaling and clogging.

[0006] Therefore, there is an urgent need for a dry sulfur trioxide removal unit, a system and a method using the unit, which will not adversely affect the process requirements of the desulfurization tower, and can ensure the sulfur trioxide removal efficiency while avoiding scaling and clogging of the equipment.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] The purpose of the present invention is to provide a sulfur trioxide dry removal unit, a system and a method using the unit. By arranging the removal unit at the outlet of the denitrification flue, the process impact on the desulfurization tower can be effectively avoided; through the coordinated cooperation of the solid alkali nozzle and the static mixing cylinder, the sulfur trioxide removal efficiency is guaranteed and the scaling phenomenon in the cylinder can be reduced.

[0009] To achieve the above-mentioned purpose, according to the first aspect of the present invention, there is provided a sulfur trioxide removal unit for use in a dry process for removing SO3 from flue gas, comprising: a solid alkali nozzle, which is arranged at the flue gas outlet of a denitrification channel and is evenly spaced, the solid alkali nozzle receiving an alkaline solid granular absorbent and the injection direction is the same as the flue gas flow direction; a static mixing cylinder, which is arranged below the solid alkali nozzle and the number of which is adapted to the nozzle, and is used to receive the alkaline solid particles and the flue gas that have expanded due to heat, and mix and contact them in a vortex manner.

[0010] Furthermore, in the above technical solution, the solid alkali nozzle can be designed as a truncated cone structure with a larger upper portion and a smaller lower portion, and strip-shaped through holes are evenly arranged along the circumferential direction at the lower portion of the cone surface for spraying alkaline solid particles.

[0011] Furthermore, in the above technical solution, the particle size of the alkaline solid particles can be selected to be 0.1 to 0.4 mm.

[0012] Furthermore, in the above technical solution, the alkaline solid particles expand after being heated by the flue gas, and microchannels extending from the inside to the outside are formed on the particles for three-dimensional contact with the flue gas.

[0013] Furthermore, in the above technical solution, the static mixing cylinder can be designed as a prism structure that is larger at the top and smaller at the bottom and has openings at both ends, including: a support beam, which is arranged on the side of the prism and extends from the top angle of the large opening to the bottom angle of the small opening; layer plates, which are arranged in layers and fixed at different heights of the support beam, and each layer of the layer plates is inclined to form interlayer gaps between the layer plates, and the layer plates are used to reflect the descending flue gas and alkaline solid particles, and the interlayer gaps are used to reduce the pressure drop in the static mixing cylinder.

[0014] Furthermore, in the above technical solution, the number of static mixing cylinders can be multiple and they can be arranged side by side according to the diameter of the flue gas outlet of the denitrification channel.

[0015] Furthermore, in the above technical solution, the flue gas may be the flue gas after SCR denitrification.

[0016] According to a second aspect of the present invention, the present invention provides a sulfur trioxide removal system, comprising any one of the aforementioned units.

[0017] Furthermore, in the above technical solution, the system may also include: a raw material bin, which is used to store the alkaline solid absorbent; and a grinder, which receives the alkaline solid absorbent from the raw material bin and processes it into particles.

[0018] Furthermore, in the above technical solution, the system may also include: a weighing device, which is connected between the raw material bin and the grinder, and is used to weigh the total amount of the alkaline solid absorbent being transported; a screw conveyor, which is used to transport the weighed alkaline solid absorbent to the grinder and control the conveying rate; a blower, which is arranged on the outlet pipeline of the grinder, and is used to provide injection power for the granular absorbent at the solid alkali nozzle.

[0019] According to the third aspect of the present invention, the present invention provides a method for removing sulfur trioxide, which is applied to the process of dry removal of SO3 in flue gas, and includes the following steps: A. Grinding the alkaline solid absorbent into particles and conveying it to the solid alkali nozzle located at the outlet of the denitrification channel at a certain speed; B. The absorbent particles ejected from the solid alkali nozzle are mixed with the flue gas running in the same direction in a static mixing cylinder, and a vortex is formed through the reflection of the layer plate; in the process of forming the vortex, the flue gas enters the microchannel formed by the absorbent particles that are expanded by heat, thereby expanding the contact area between the flue gas and the particles; C. After absorbing and removing SO3 in the flue gas, the flue gas and the absorbent particles flow out from the reduced diameter port at the bottom end of the static mixing cylinder.

[0020] Furthermore, in the above technical solution, the particle size of the particles after grinding in step A can be 0.1 to 0.4 mm; and the conveying rate can be controlled to be 80 to 150 kg / h.

[0021] Furthermore, in the above technical solution, during the mixing and contacting process of the flue gas and the absorbent in step B, the heating temperature of the absorbent particles can be 320-380° C.; and the residence time of the absorbent in the flue gas can be 0.1-10 seconds.

[0022] Furthermore, in the above technical solution, the chemical molar equivalent ratio of the amount of alkaline solid absorbent used to the amount of SO3 removed from the flue gas can be 1.0 to 4.0.

[0023] Furthermore, in the above technical solution, the alkaline solid absorbent may be one or more of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide and magnesium hydroxide.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention adopts solid alkali spraying to remove SO3 from flue gas (i.e., dry SO3 removal), and adjusts the spraying position to be in the denitrification flue, making full use of the solid alkali "popcorn effect". Under the heating of high-temperature flue gas (the flue gas is the flue gas after SCR denitrification), the solid alkali particles are heated and expanded, and the generated gas forms microchannels from the inside to the outside of the particles, which increases the flow area of ​​SO3, makes the solid alkali reaction faster and more sufficient, improves the removal effect of sulfur trioxide, and effectively avoids the increase of liquid pH in the desulfurization tower, the occurrence of substandard discharge of external wastewater, and scaling and clogging of equipment;

[0026] 2) The present invention chooses to process the particle size of the alkaline solid particles into 0.1-0.4 mm. When solid alkali particles within this particle size range are used, when the flue gas temperature in the denitration channel is 320-380°C, the alkaline solid particles are heated by the flue gas and expand, the formation of microchannels is easier and has a larger specific surface area, the particles are not easy to break, and the flue gas and particles can be better contacted in three dimensions. In addition, the reason why the particle size is limited to between 0.1 and 0.4 mm is that after the particle size is too large, the formed channels are easily blocked by particulate matter in the flue gas, slowing down the reaction rate, while the particle size that is too small will produce static electricity and adsorb on the flue wall, causing compaction and blockage;

[0027] 3) The strip-shaped through-hole design of the solid alkali nozzle of the present invention makes the sprayed solid particles roughly distributed in a circular shape, which is more conducive to accurately controlling the solid alkali injection flow rate, improving the uniformity of the solid alkali distribution on the cross section at the wide mouth of the static mixing cylinder, thereby improving the utilization rate of the solid alkali and reducing the solid alkali residue. At the same time, it avoids scaling or clogging of equipment such as the rear economizer or desulfurization tower caused by excessive alkali spraying;

[0028] 4) The structure of the static mixing cylinder adopted in the present invention can significantly improve the uniformity of the flue gas flow velocity distribution. When the flue gas flows through the static mixing cylinder of the present invention from top to bottom, the area of ​​the upper port is larger than the area of ​​the lower port, the flue gas flow area gradually decreases and the speed gradually increases, which is beneficial to accelerate the mixing of solid alkali and flue gas; due to the inclined setting of the layer plates, the flue gas and solid alkali particles collide and reflect during the circulation process, and the reflected flows from different directions converge so that horizontal swirl can be achieved at each layer of the layer plates. The swirl of each layer forms a vortex effect in the static mixing cylinder under the overall downward trend of the flue gas, which forces the solid alkali and flue gas to mix, enhances the mixing effect, and improves the mixing uniformity of the solid alkali particles and the flue gas; because the speed of the flue gas running downward gradually increases, a negative pressure is formed in the cylinder, and the vortex is not easy to escape from the gaps between the layers, so that most of the mixture can always rotate in the cylinder, which can effectively extend the residence time of the mixture, which can not only reduce the scaling phenomenon in the cylinder, but also effectively reduce the pressure drop between the layers;

[0029] 5) The present invention arranges multiple static mixing cylinders densely and in parallel, and each layer has interlayer gaps between the layer plates. A small amount of flue gas and solid alkali particles escaping between adjacent static mixing cylinders can form an interactive in and out movement under the action of horizontal swirl, further increasing the residence time of the mixture of flue gas and solid alkali particles in the static mixing cylinder, thereby further enhancing the mixing effect and sulfur trioxide removal efficiency.

[0030] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a connection schematic diagram of the sulfur trioxide removal system of the present invention.

[0032] Figure 2 It is a cross-sectional schematic diagram of the sulfur trioxide removal unit in the system of the present invention.

[0033] Figure 3 It is a schematic top view of a static mixing cylinder in a sulfur trioxide removal unit of the present invention.

[0034] Figure 4 It is a schematic diagram of the three-dimensional structure of a single static mixing cylinder of the present invention.

[0035] Figure 5 It is a schematic diagram of the three-dimensional structure of a single solid alkali nozzle of the present invention.

[0036] Figure 6 It is a top view schematic diagram of a single solid caustic soda nozzle of the present invention.

[0037] Figure 7 This is a schematic diagram of the absorbent and flue gas flow in the sulfur trioxide removal unit of the present invention (taking a single solid alkali nozzle and a static mixing cylinder as an example)

[0038] Figure 8 It is a schematic diagram of the solid alkali nozzle material supply control of the present invention.

[0039] Description of main reference numerals:

[0040] 100-denitrification channel, 101-denitrification channel inlet, 102-SCR catalyst bed, 103-denitrification channel outlet;

[0041] 1-solid alkali nozzle, 11-conical surface, 12-strip through hole, 13-one-way valve, 2-static mixing cylinder, 20A-lower port, 20B-upper port, 21-support beam, 22-layer plate, 23-interlayer gap, 3-raw material bin, 31-stirring paddle, 4-weighing weigher, 5-screw conveyor, 6-grinder, 7-blower. DETAILED DESCRIPTION

[0042] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0043] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0044] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different orientations of the object in use or operation in addition to the orientation depicted in the figure. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both below and above. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0045] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0046] The inventors have found that the dry method of removing SO3 from flue gas in the prior art is generally completed in a desulfurization tower. This method can easily cause the pH of the liquid in the desulfurization tower to increase, resulting in substandard discharge of wastewater, and the temperature at the outlet of the desulfurization tower has an adverse effect on the microchannel formation of the alkaline particles; at the same time, the irregular injection distribution of the powdered alkaline material will lead to a decrease in the sulfur trioxide removal efficiency, as well as equipment scaling and clogging.

[0047] In view of the above problems in the prior art, Figure 1 , 2As shown, the present invention provides a sulfur trioxide removal unit, which is used for the process of dry removal of SO3 from flue gas, and includes a solid alkali nozzle 1 and a static mixing barrel 2. The solid alkali nozzle 1 is arranged at the flue gas outlet 103 of the denitration channel 100 and is evenly spaced. The solid alkali nozzle 1 receives alkaline solid granular absorbent and the injection direction is the same as the flue gas flow direction (that is, both are from top to bottom). The static mixing barrel 2 is arranged below the solid alkali nozzle 1 and the number is adapted to the nozzle, and is used to receive the alkaline solid particles and flue gas after thermal expansion (that is, heated by the flue gas at the outlet of the denitration channel 100), and mix and contact in a vortex manner. The present invention adopts a solid alkali spraying method to remove SO3 from flue gas, and adjusts the spraying position to be in the denitrification flue 100, making full use of the solid alkali "popcorn effect". Under the heating of high-temperature flue gas (the flue gas is the flue gas after SCR denitrification), the solid alkali particles expand due to the heat, and the generated gas forms pores on the surface of the particles, which increases the flow area of ​​SO3, makes the solid alkali reaction faster and more sufficient, improves the removal effect of sulfur trioxide, and effectively avoids the increase of liquid pH in the desulfurization tower, the occurrence of substandard discharge of external wastewater and scaling and clogging of equipment.

[0048] Further Figure 5 , 6 As shown, the solid alkali nozzle 1 is a truncated cone structure with a larger top and a smaller bottom. The lower part of the cone surface 11 is evenly arranged with strip-shaped through holes 12 along the circumferential direction for spraying alkaline solid particles. Figure 7 The incoming material enters the wide mouth end of the solid alkali nozzle 1 from top to bottom, and then is ejected from the strip-shaped through hole 12. The shape of the through hole is designed so that the ejected solid particles are roughly distributed in a circular shape (refer to Figure 7 In the direction of the dashed arrow). This is more conducive to accurately controlling the solid alkali injection flow rate, improving the uniformity of the solid alkali distribution on the cross section at the wide mouth of the static mixing barrel 2, thereby improving the utilization rate of the solid alkali and reducing the solid alkali residue. At the same time, avoid excessive alkali spraying that causes scaling or clogging of equipment such as the rear-end economizer or desulfurization tower. Further, preferably but not restrictively, the particle size of the alkaline solid particles of the present invention can be 0.1-0.4 mm. The inventors have found through experiments that when solid alkali particles with this particle size range are used, when the flue gas temperature in the denitrification channel is 320-380°C, the alkaline solid particles are heated by the flue gas and expand, and microchannels extending from the inside to the outside can be formed on the particles. The formation of the microchannel is easier and the specific surface area is larger. The particles are not easy to break, and the flue gas and particles can be better contacted in three dimensions. The particle input of the solid alkali nozzle 1 is controlled by a one-way valve 13, reference Figure 8 .

[0049] Further Figure 3 , 4As shown, the static mixing cylinder 2 is a prism structure with a large top and a small bottom, and both ends are provided with openings (the openings are the upper port 20B and the lower port 20A). The static mixing cylinder 2 includes a support beam 21 and a layer plate 22. The support beam 21 is arranged on the side of the prism and extends from the top corner of the large opening (i.e., the upper port 20B) to the bottom corner of the small opening (i.e., the lower port 20A). Figure 4 A static mixing cylinder with a tetrahedral structure is illustrated in the figure, with a total of four supporting beams. The layers 22 are arranged in layers and fixed at different heights of the supporting beams 21. The layers 22 of each layer are tilted to form interlayer gaps 23 between the layers (similar to a shutter structure). The layers are used to reflect the descending flue gas and alkaline solid particles, and the interlayer gaps are used to reduce the pressure drop in the static mixing cylinder 2. The above-mentioned structure of the static mixing cylinder 2 can significantly improve the uniformity of the flue gas flow velocity distribution. When the flue gas flows from top to bottom through the static mixing cylinder of the present invention, the area of ​​its upper port is larger than the area of ​​its lower port, the flue gas flow area gradually decreases, and the speed gradually increases, which is conducive to accelerating the mixing of solid alkali and flue gas; due to the tilted arrangement of the layers, the flue gas and solid alkali particles collide and reflect during the circulation process, and the reflected flows from different directions converge so that horizontal swirl can be achieved at each layer of the layers (reference Figure 7 As the flue gas moves downward as a whole, the swirl flow of each layer forms a vortex effect in the static mixing cylinder, which forces the solid alkali and flue gas to mix, enhances the mixing effect, and improves the uniformity of the mixing of the solid alkali particles and the flue gas. As the speed of the flue gas moving downward gradually increases, a negative pressure is formed in the cylinder, and the vortex flow is not easy to escape from the gaps between the layers, so that most of the mixture can always rotate in the cylinder, which can effectively extend the residence time of the mixture, not only reducing scaling in the cylinder, but also effectively reducing the pressure drop between layers. Further, as shown in FIG. Figure 3 As shown, the number of static mixing cylinders 2 can be multiple and they are arranged side by side according to the diameter of the flue gas outlet of the denitrification channel. Through such dense parallel arrangement, and each layer of the layer plates 22 has an interlayer gap 23, a small amount of escaping flue gas and solid alkali particles between adjacent static mixing cylinders can form an interactive in and out movement under the action of horizontal swirl, further increasing the residence time of the mixture of flue gas and solid alkali particles in the static mixing cylinder, thereby further enhancing the mixing effect and sulfur trioxide removal efficiency.

[0050] The present invention also provides a sulfur trioxide removal system, which uses the aforementioned sulfur trioxide removal unit. In addition to the aforementioned removal unit, the system also includes a raw material bin 3 and a grinder 6. The raw material bin 3 is used to store alkaline solid absorbents. A stirring paddle 31 is provided in the raw material bin 3. Stirring can be performed when conveying the solid alkali absorbent to prevent the solid alkali from absorbing water and hardening, which affects the conveying process. The absorbent includes but is not limited to sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide, and magnesium hydroxide, etc., and one or more of the above materials can be used. The grinder 6 receives the alkaline solid absorbent from the raw material bin 3 and processes it into particles. Preferably, but not restrictively, the particle size of the ground particles is 0.1 to 0.4 mm, so as to better construct a microchannel of the particles from the inside to the outside at a suitable temperature of the flue gas. Taking sodium bicarbonate as an example, sodium bicarbonate decomposes under high temperature to generate carbon dioxide and water, both of which are gaseous. Since the original particles are solid particles, the gas is generated from the original substance, and the gas forms channels in the particles and is released to the external environment, causing the original particles to expand after being heated, forming irregular gas channels. After contacting with the flue gas, the flue gas reacts with the solid alkali particles through the channels, increasing the gas-solid contact area. This reaction occurs in an instant when the solid alkali particles enter the flue, with a short time and a fast speed, so it is called the popcorn effect. The above reaction can occur on any solid alkali particles that generate gaseous substances after being heated. In addition, the reason why the present invention adopts a particle size of 0.1 to 0.4 mm is that after being heated, the excessively large particle size will cause the formed channels to be easily blocked by particulate matter in the flue gas, slowing down the reaction rate, while the excessively small particle size will produce electrostatic effects, adsorb on the flue wall, causing compaction and blockage.

[0051] Further Figure 1 As shown, the system may also include a weighing device 4, a screw conveyor 5 and a blower 7. The weighing device 4 is connected between the raw material bin 3 and the grinder 6 to weigh the total amount of alkaline solid absorbent being conveyed. The screw conveyor 5 is used to convey the weighed alkaline solid absorbent to the grinder and control the conveying rate. The screw conveyor conveys the solid alkali at a rate of 0 to 200 kg / h, preferably 80 to 150 kg / h. The blower 7 is arranged on the outlet pipeline of the grinder 6 to provide the injection power of the granular absorbent at the solid alkali nozzle, and the solid alkali particles can be injected into the flue at a certain speed. The outlet pressure of the blower 7 can be set to 0 to 30 kPa, preferably 10 to 20 kPa.

[0052] The present invention also provides a sulfur trioxide removal method, which is applied to the dry method of removing SO3 from flue gas, and includes the following steps: A. grinding alkaline solid absorbent into particles and conveying them to the solid alkali nozzle located at the outlet of the denitration channel at a certain speed; B. the absorbent particles ejected from the solid alkali nozzle are mixed with the flue gas running in the same direction in a static mixing cylinder, and a vortex is formed through the reflection of the layer plate; in the process of forming the vortex, the flue gas enters the microchannel formed by the absorbent particles expanded by heat, and the contact area between the flue gas and the particles is expanded; C. after absorbing and removing SO3 from the flue gas, the flue gas and the absorbent particles flow out from the reduced diameter port at the bottom end of the static mixing cylinder. Thus, the removal of SO3 from the flue gas is completed.

[0053] Furthermore, in order to better form microchannels of the particles and avoid agglomeration and blockage, the particle size of the particles after grinding in the aforementioned step A is 0.1 to 0.4 mm; and the conveying rate is controlled to be 80 to 150 kg / h.

[0054] Since the sulfur trioxide removal position is set at the outlet of the denitration channel in the present invention, the heating temperature of the absorbent particles can reach 320-380°C during the mixed contact process of the flue gas and the absorbent, achieving the optimal thermal expansion temperature of the solid alkali particles. Due to the synergistic effect of the solid alkali nozzle and the static mixing barrel of the present invention, the residence time of the absorbent in the flue gas can reach 0.1-10 seconds. In addition, since the raw material bin of the solid alkali absorbent is connected to a weighing device, after experimental research, the chemical molar equivalent ratio of the amount of alkaline solid absorbent used to the amount of SO3 removed in the flue gas can be set to 1.0-4.0.

[0055] Example 1

[0056] In this embodiment, SO at the denitrification inlet x Concentration is 3000mg / Nm 3 , SO3 concentration is about 300mg / Nm 3 . The flue gas flow direction of the flue gas denitrification system is the denitrification channel inlet, SCR catalyst bed, solid alkali nozzle, static mixing cylinder and denitrification channel outlet. The solid alkali flow direction is the raw material warehouse, weighing and weighing device, screw conveyor, grinder, blower, sulfur trioxide removal unit. The raw material warehouse is filled with sodium bicarbonate alkaline absorbent material, and the screw conveyor conveys solid alkali at a rate of 100kg / h. The residence time of the solid alkali absorbent in the flue gas is 5 seconds, and the flue gas temperature is 350℃. The particle size range of solid alkali processed by the grinder is 0.2-0.3mm. The blower outlet pressure is 15kPa. The denitrification flue gas flow rate is 100,000m 3 / h. There is one layer of solid alkali nozzle and static mixing cylinder. The solid alkali nozzle is set just above the static mixing cylinder. The injection direction is the same as the flue gas flow direction. This injection method has little effect on the flue gas flow. The flue gas and solid alkali particles form a vortex in the static mixing cylinder, which makes the solid alkali and flue gas mix more evenly and react more thoroughly. The flue gas enters the microchannel in the particles, which makes the contact area between the flue gas and the solid alkali particles larger. After a long period of operation, the test results of sulfur trioxide concentration at the outlet of the flue gas denitrification channel showed that the sulfur trioxide removal rate can reach 85%, and the solid alkali utilization rate can reach 90%. At the same time, there is no scaling or blockage in equipment such as economizers or desulfurization towers. The blue smoke phenomenon of the flue gas at the outlet of the desulfurization tower was observed to decrease. The overall process unit can operate continuously for more than 1 year.

[0057] Comparative Example

[0058] The sulfur trioxide removal unit of the present invention is not used in the comparative example, and only solid alkali particles are sprayed at the outlet of the denitration channel, and other design indicators remain unchanged. After a long period of operation, the results of the sulfur trioxide concentration test at the outlet of the denitration channel show that the sulfur trioxide removal rate is 50% and the solid alkali utilization rate is 60%. At the same time, after the overall process device has been running for 6 months, the solid alkali injection device is stopped due to scaling or blockage of equipment such as the economizer or desulfurization tower. It is observed that the flue gas at the outlet of the desulfurization tower still has blue smoke.

[0059] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A sulfur trioxide removal unit, characterized in that: The process for dry removal of SO3 from flue gas includes: Solid alkali nozzles are arranged at the flue gas outlet of the denitration channel and are evenly spaced, and the solid alkali nozzles receive alkaline solid granular absorbents and the spraying direction is the same as the flue gas flow direction; The static mixing cylinder is arranged below the solid alkali nozzle and the number thereof is adapted to the nozzle, and is used for receiving the alkaline solid particles and the flue gas after being expanded by heat, and mixing and contacting them in a vortex manner.

2. The sulfur trioxide removal unit according to claim 1, characterized in that: The solid alkali nozzle is a truncated cone structure that is larger at the top and smaller at the bottom. Strip-shaped through holes are evenly arranged along the circumference at the lower part of the cone surface for spraying the alkaline solid particles.

3. The sulfur trioxide removal unit according to claim 1, characterized in that: The particle size of the alkaline solid particles is 0.1-0.4 mm.

4. The sulfur trioxide removal unit according to claim 3, characterized in that: The alkaline solid particles expand after being heated by the flue gas, and microchannels extending from the inside to the outside are formed on the particles for three-dimensional contact with the flue gas.

5. The sulfur trioxide removal unit according to claim 1, characterized in that: The static mixing cylinder is a prism structure with a larger top and a smaller bottom and both ends are open, and includes: A support beam is disposed on the side of the prism and extends from the top corner of the large opening to the bottom corner of the small opening; The layer plates are arranged in layers and fixed at different heights of the support beam. The layer plates of each layer are arranged obliquely to form interlayer gaps between the layer plates. The layer plates are used to reflect the descending flue gas and alkaline solid particles. The interlayer gaps are used to reduce the pressure drop in the static mixing cylinder.

6. The sulfur trioxide removal unit according to claim 5, characterized in that: The static mixing cylinders are multiple in number and are arranged side by side according to the diameter of the smoke outlet of the denitration channel.

7. The sulfur trioxide removal unit according to claim 1, characterized in that: The flue gas is the flue gas after SCR denitrification.

8. A sulfur trioxide removal system, characterized in that: A unit comprising any one of claims 1 to 7.

9. The sulfur trioxide removal system according to claim 8, characterized in that: The system further comprises: A raw material bin, which is used to store alkaline solid absorbent; A grinder receives the alkaline solid absorbent from the raw material bin and processes it into particles.

10. The sulfur trioxide removal system according to claim 9, characterized in that: The system further comprises: A weighing device connected between the raw material bin and the grinder for weighing the total amount of the alkaline solid absorbent delivered; A screw conveyor, which is used to convey the weighed alkaline solid absorbent to the grinder and control the conveying rate; A blower is arranged on the outlet pipeline of the grinding machine and is used to provide a jetting force for the granular absorbent at the solid alkali nozzle.

11. A method for removing sulfur trioxide, characterized in that: The process for dry removal of SO3 from flue gas includes the following steps: A. Grind the alkaline solid absorbent into particles and transport them to the solid alkali nozzle located at the outlet of the denitration channel at a certain speed; B. The absorbent particles sprayed from the solid alkali nozzle are mixed with the flue gas running in the same direction in the static mixing cylinder, and a vortex is formed through the reflection of the layer plate; in the process of forming the vortex, the flue gas enters the microchannel formed by the absorbent particles that are expanded by heat, thereby expanding the contact area between the flue gas and the particles; C. After absorbing and removing SO3 from the flue gas, the flue gas and absorbent particles flow out from the reduced diameter port at the bottom of the static mixing cylinder.

12. The method for removing sulfur trioxide according to claim 11, characterized in that: The particle size of the particles after grinding in step A is 0.1-0.4 mm; the conveying rate is controlled to be 80-150 kg / h.

13. The method for removing sulfur trioxide according to claim 11, characterized in that: In the process of mixing and contacting the flue gas and the absorbent in step B, the heating temperature of the absorbent particles is 320-380° C.; the residence time of the absorbent in the flue gas is 0.1-10 seconds.

14. The method for removing sulfur trioxide according to claim 11, characterized in that: The chemical molar equivalent ratio of the amount of the alkaline solid absorbent to the amount of SO3 removed from the flue gas is 1.0 to 4.

0.

15. The method for removing sulfur trioxide according to claim 11, characterized in that: The alkaline solid absorbent is one or more of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide and magnesium hydroxide.

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