Device and system for absorbing sulfur trioxide in flue gas and control method

Abstract

The invention discloses a device and a system for absorbing sulfur trioxide in flue gas and a control method, the device is used for treating denitrated flue gas, and at least comprises a detection unit arranged at a denitrated flue gas outlet and used for detecting the concentration of sulfur trioxide in the denitrated flue gas; the section where the detection position is located divides the flue gas channel into a plurality of areas to form distributed detection; the removal unit is arranged in the flue gas channel of the device and comprises a solid powder absorbent nozzle assembly capable of sliding up and down; and the control unit is arranged outside the device and is used for moving the nozzle assembly up and down and dynamically adjusting the spraying amount of the solid powder absorbent under the condition that the concentration of the sulfur trioxide fluctuates. According to the invention, through dynamic adjustment of the height of the absorbent nozzle and dynamic adjustment of the adding amount of the absorbent, effective coping can be carried out under the condition that the concentration of sulfur trioxide fluctuates, and the scaling problem caused by the absorbent is controlled to the greatest extent while the removal rate of sulfur trioxide is ensured.

Description

Technical Field

[0001] This invention relates to the field of petrochemical flue gas treatment technology, and in particular to a sulfur trioxide absorption device, system and control method for flue gas. Background Technology

[0002] SO3 is a toxic air pollutant and also a component of PM2.5. 2.5 One of the precursors. After passing through the wet desulfurization tower, SO3 forms submicron-sized sulfate aerosols, causing some of the equipment's exhaust to appear yellow or blue; after sulfuric acid settles, it can damage buildings and vegetation, and cause damage to the mucous membranes of the human respiratory tract and lung structure.

[0003] SO3 and the sulfuric acid mist formed by its dissolution in water are highly corrosive, requiring refining and chemical enterprises to incur significant additional costs for corrosion protection measures on equipment and walls near chimneys. SO3 also reacts with the reducing agent NH3 in SCR denitrification systems to produce ammonium bisulfate. This ammonium bisulfate tends to occupy the pores of the denitrification catalyst, thus reducing its denitrification capacity. Furthermore, this substance can enter the waste heat boiler with the flue gas and deposit on the surface of heat exchange elements, causing problems such as ash accumulation, scaling, blockage, and corrosion.

[0004] Chinese patent application CN114100347A discloses a device for removing SO3 using a urea direct injection pyrolysis jetting system. The urea direct injection pyrolysis jetting gun is inserted into the economizer outlet flue, the SCR inlet horizontal flue, or the SCR inlet vertical flue. The air compressor outlet is connected to the inlet of the metering and distribution module, the alkaline solution storage tank outlet is connected to the mixer inlet, the urea solution storage tank outlet is connected to the mixer outlet, the mixer outlet is connected to the metering and distribution module inlet, and the metering and distribution module outlet is connected to the urea direct injection pyrolysis jetting gun inlet. This device can remove SO3 from flue gas and features a simple system and high reliability. However, this type of solution uses a fixed urea injection rate. When SO3 concentration fluctuates, the device cannot respond immediately, easily leading to excessive SO3 emissions or excessive urea injection, causing flue corrosion and scaling.

[0005] Therefore, there is an urgent need for a sulfur trioxide absorption device, system, and control method in flue gas that can address fluctuations in sulfur trioxide concentration in a targeted manner, ensuring sulfur trioxide removal rate while minimizing scaling problems caused by the absorbent.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a sulfur trioxide absorption device, system and control method in flue gas. By dynamically adjusting the height of the absorbent nozzle and the amount of absorbent added, it can effectively deal with fluctuations in sulfur trioxide concentration, and while ensuring the sulfur trioxide removal rate, it can control the scaling problem caused by the absorbent to the greatest extent.

[0008] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a sulfur trioxide absorption device for flue gas treatment after denitrification, comprising at least: a detection unit disposed at the outlet of the denitrified flue gas for detecting the sulfur trioxide concentration in the denitrified flue gas; the cross section at the detection location divides the flue gas channel into multiple regions to form distributed detection; a removal unit disposed within the flue gas channel of the device, comprising a solid powder absorbent nozzle assembly that can slide up and down; and a control unit disposed outside the device for moving the nozzle assembly up and down and dynamically adjusting the injection volume of the solid powder absorbent when the sulfur trioxide concentration fluctuates.

[0009] Furthermore, in the above technical solution, the nozzle assembly may include: an annular pipe, which is integrally formed with the absorbent inlet and fixedly connected to a slide rail located on the inner wall of the flue gas channel; multiple nozzles evenly spaced along the inner edge of the annular pipe, the nozzles being in communication with the annular pipe and spraying in a radially inward direction, forming a mist-like surface in the flue gas channel during absorbent spraying and contacting the flue gas moving from top to bottom; and a screw, which is vertically set at the axial position of the annular pipe and threadedly connected to the annular pipe, driven by an external motor to rotate the screw, thereby driving the annular pipe to move up and down.

[0010] Furthermore, in the above technical solution, the detection unit is located upstream of the removal unit, and the cross-sectional shape of the detection position can be honeycomb-shaped.

[0011] Furthermore, in the above technical solution, the detection unit can use electrochemical, infrared, gas-sensitive or thermal conductivity methods to monitor the sulfur trioxide concentration in different areas of the honeycomb cross section in real time and generate sulfur trioxide concentration distribution data passing through the cross section, and then transmit the concentration distribution data to the control unit through an electrical signal.

[0012] Furthermore, in the above technical solution, the control unit may include: a data analysis module, which is used to receive sulfur trioxide concentration distribution data from the detection unit, process it by taking the median or mean value, and compare it with the concentration threshold; an injection volume control module, which is used to dynamically adjust the injection volume of the solid powder absorbent according to the comparison result of the data analysis module; and a movement control module, which is used to calculate and control the vertical movement distance of the annular pipe according to the comparison result of the data analysis module.

[0013] According to a second aspect of the present invention, the present invention provides a sulfur trioxide absorption system in flue gas, using any of the foregoing devices, and the system can be installed between a denitrification system and a desulfurization system.

[0014] Furthermore, in the above technical solution, the system may also include: an absorbent raw material silo, which is used to hold solid powder absorbent and is equipped with stirring blades inside; a weighing meter, which is used to weigh and measure the absorbent from the absorbent raw material silo and conveyed to the sulfur trioxide absorption device in the flue gas; and a screw conveyor, which, based on the sulfur trioxide concentration data obtained by the detection unit, conveys different quantities of absorbent to the absorbent inlet through a blower.

[0015] According to a third aspect of the present invention, the present invention provides a method for controlling the absorption of sulfur trioxide in flue gas, using the aforementioned system, comprising the following steps: A. Distributed detection of sulfur trioxide concentration in flue gas at the flue cross-section at the denitrification flue gas outlet, and obtaining the median or average concentration of each honeycomb region; B. Comparing the calculated median or average concentration with a concentration threshold to determine whether the real-time concentration is high, medium, or low; C. Controlling and adjusting the injection amount of solid powder absorbent according to the determination result to form a mist surface in the flue gas duct that contacts the flue gas moving from top to bottom, and / or, changing the mixing distance between the flue gas and the absorbent or adjusting the distribution range of the absorbent by calculating and controlling the vertical movement distance of the annular pipe.

[0016] Furthermore, in the above technical solution, the concentration threshold in step B may include a high concentration threshold and a low concentration threshold; the high concentration threshold may be set to 200 mg / Nm³. 3 The low concentration threshold can be set to 100 mg / Nm³. 3 High concentration specifically refers to a concentration greater than 200 mg / Nm³. 3 The concentration, specifically the medium concentration, is 100 mg / Nm³. 3 and 200mg / Nm 3 The concentration range is specified as low as less than 100 mg / Nm³. 3 The concentration.

[0017] Furthermore, in the above technical solution, step C can be specifically as follows: C1. When the sulfur trioxide concentration obtained in step A is high, the injection volume of the absorbent is increased by calculation, and the annular pipe is moved upward to the first height by calculation and control, thereby increasing the mixing distance between the flue gas and the absorbent; C2. When the sulfur trioxide concentration obtained in step A is medium, the injection volume of the absorbent is maintained by calculation, and the annular pipe is moved to the second height by calculation and control, and the annular pipe is reciprocated at the second height, thereby increasing the distribution range of the absorbent; C3. When the sulfur trioxide concentration obtained in step A is low, the injection volume of the absorbent is reduced by calculation, and the annular pipe is moved downward to the third height by calculation and control, thereby reducing the mixing distance between the flue gas and the absorbent and narrowing the distribution range of the absorbent.

[0018] Furthermore, in the above technical solution, the solid powder absorbent can be an alkaline absorbent, specifically one or more of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide, and magnesium hydroxide.

[0019] Furthermore, in the above technical solution, Na... + For SO3, the stoichiometric ratio of the absorbed dose to the real-time SO3 concentration in the flue gas can be 1.0–4.0; for Ca... 2+ SO3 or Mg 2+ For SO3, the stoichiometric ratio of the absorbed dose to the real-time concentration of SO3 in the flue gas can be 1.0 to 2.0.

[0020] Furthermore, in the above technical solution, the delivery rate of the absorbent can be adjusted according to the real-time SO3 concentration calculation, with an adjustment range of 30–100 kg / h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The sulfur trioxide absorption device in flue gas of the present invention can obtain the real-time concentration value of each part at the detection section through the distributed detection of the detection unit. By taking the median or average value of the concentration, the measured value of sulfur trioxide concentration is more accurate, which can create more favorable conditions for subsequent adjustment and control.

[0023] 2) By allowing the nozzle assembly of the removal unit to slide, the height of the nozzle can be adjusted according to the measured concentration, thereby adjusting the mixing distance between the flue gas and the absorbent. The control unit can control the up-and-down movement of the nozzle assembly and dynamically adjust the injection amount of the solid powder absorbent when the detected sulfur trioxide concentration fluctuates. Through such dynamic adjustment, the appropriate chemical molar ratio of absorbent to SO3 can be effectively maintained. While ensuring the SO3 removal rate, an appropriate amount of absorbent is always added, reducing costs and avoiding the occurrence of flue scale due to excessive absorbent.

[0024] 3) The sliding nozzle assembly of the present invention can be directly installed at the existing denitrification outlet flue, and the SO3 detection unit is installed at the front end of the sliding nozzle assembly. Only the existing device needs to be modified, which can effectively save modification costs.

[0025] 4) The sliding nozzle of this invention sprays radially inward, at a certain angle to the horizontal surface, ensuring that the spray direction of the absorbent is essentially the same as the flue gas flow direction. This avoids significant interference with the flue gas. Through this design, the absorbent forms a mist-like surface within the flue gas channel during spraying, contacting the flue gas flowing downwards. This mist-like surface ensures sufficient contact with the flue gas, preventing "escape" and eliminating leaks at the flue gas cross-section. This prevents unreacted SO3 from the absorbent and ensures that the SO3 emission concentration is less than 15 mg / Nm³. 3 ;

[0026] 5) This invention employs different control strategies for high, medium, and low concentrations. Under fluctuating sulfur trioxide concentrations, it can dynamically adjust the amount of absorbent used, the mixing distance between the flue gas and the absorbent, and the distribution range of the absorbent in real time, making it more targeted. Using this method, even with fluctuating sulfur trioxide concentrations in the flue gas, the SO3 removal rate can be guaranteed to be greater than 85%, the absorbent utilization rate greater than 90%, and absorbent costs saved by more than 25%. It also avoids flue corrosion caused by excessive sulfur trioxide emissions and solves problems such as flue scaling caused by excessive absorbent injection.

[0027] 6) The absorbent added in this invention is an alkaline absorbent, which can adjust the pH value of the flue gas. Since the flue gas subsequently enters the desulfurization system for desulfurization, an alkaline environment needs to be maintained. Therefore, the system of this invention has a certain synergistic effect with the desulfurization system, which can reduce the amount of alkaline solution added in subsequent operations, reduce scaling in the desulfurization system, and thus extend the operating time of the entire desulfurization and denitrification system.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the connection of the sulfur trioxide absorption system in flue gas according to the present invention.

[0030] Figure 2 This is a schematic cross-sectional view of the detection position of the detection unit of the absorption device of the present invention.

[0031] Figure 3 This is a schematic diagram of the removal unit structure of the absorption device of the present invention.

[0032] Figure 4 This is a schematic cross-sectional view of the annular pipe in the removal unit of the present invention.

[0033] Explanation of key figure labels:

[0034] 1-Detection unit, 11-Detection position section, 110-Honeycomb structure, 2-Removal unit, 20-Outer shell, 21-Annular pipe, 211-Nozzle, 22-Screw, 23-Motor, 24-Absorbent inlet, 25-Flue gas outlet, 26-Slide rail, 3-Control unit, 4-Absorbent raw material bin, 41-Agitator blade, 5-Weighing device, 6-Screw conveyor, 61-Blower;

[0035] 100 - Sulfur trioxide absorption system, 200 - Denitrification system, 300 - Desulfurization system. Detailed Implementation

[0036] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0037] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0038] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0039] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0040] like Figure 1 As shown, this invention provides a sulfur trioxide absorption device for flue gas after denitrification, comprising at least a detection unit 1, a removal unit 2, and a control unit 3. The detection unit 1 is located at the outlet of the denitrified flue gas (i.e.,...). Figure 1 The SO3 concentration in the flue gas after denitrification (located at the constriction point of the denitrification system 200) is used to detect the SO3 concentration. SO3 concentration in the flue gas can be monitored and analyzed using electrochemical, infrared, gas-sensitive, or thermal conductivity methods. After the flue gas flows through the detection section 11 of the detection unit 1, the detection unit transmits an electrical signal to the control unit 3, generating the SO3 distribution in the flue gas at the instant it passes through that section. This invention divides the flue gas channel into multiple regions at the detection position section, enabling distributed detection. Preferably, these multiple regions... Figure 2 The honeycomb structure 110 is divided into multiple channels with a certain height, allowing flue gas to enter each honeycomb unit separately. The detection cross-section can be located at the end of the channel, so that the flue gas flowing through the channel is rectified, which improves the detection accuracy. The removal unit 2 is set inside the flue gas channel of the device and includes a solid powder absorbent nozzle assembly that can slide up and down. The control unit 3 is set outside the device and is used to move the nozzle assembly up and down and dynamically adjust the injection volume of solid powder absorbent when the detected sulfur trioxide concentration fluctuates.

[0041] The sulfur trioxide absorption device in flue gas of this invention obtains real-time concentration values ​​at various locations along the detection cross-section through distributed detection by the detection unit. By subsequently taking the median or average of these concentrations, the measured sulfur trioxide concentration becomes more accurate, creating more favorable conditions for subsequent adjustment and control. The sliding nozzle assembly of the removal unit allows adjustment of the nozzle height based on different measured concentrations, thereby adjusting the mixing distance between the flue gas and the absorbent. The control unit can control the up-and-down movement of the nozzle assembly and dynamically adjust the injection volume of the solid powder absorbent when fluctuations in the detected sulfur trioxide concentration occur. This dynamic adjustment effectively maintains a suitable stoichiometric ratio of absorbent to SO3, ensuring a high SO3 removal rate while consistently adding an appropriate amount of absorbent, reducing costs and preventing flue gas scaling caused by excessive absorbent. The sliding nozzle assembly of this invention can be directly installed at the existing denitrification outlet flue gas duct, with the SO3 detection unit installed at the front end of the sliding nozzle assembly. Only modifications to the existing device are required, effectively saving costs.

[0042] Further as Figure 1 , 3 As shown in Figure 4, the aforementioned nozzle assembly may further include an annular pipe 21, a nozzle 211, and a screw 22. The annular pipe 21 may be integrally formed with the absorbent inlet 24 and located within the flue gas passage (i.e., Figure 3 , Figure 4 The slide rail 26 on the inner wall of the device housing 20 is fixedly connected (or can be integrally formed), that is, the slide rail 26, the annular pipe 21, and the absorbent inlet 24 can slide as a whole within the housing 20. A dynamic seal can be provided at the sliding interface to prevent flue gas leakage during the sliding process. Figure 4 As shown, multiple nozzles 211 are evenly spaced along the inner edge of the annular pipe 21. The nozzles 211 are connected to the annular pipe 21, and the spray direction is radially inward (with a certain angle to the horizontal surface, ensuring the absorbent spray direction is basically the same as the flue gas flow direction, avoiding significant interference with the flue gas). With this arrangement, the absorbent forms a mist-like surface within the flue gas channel during spraying and contacts the flue gas flowing downwards. The mist-like surface of the absorbent ensures sufficient contact with the flue gas, preventing the flue gas from "escaping." The screw 22 is vertically positioned at the axial center of the annular pipe 21 and threadedly connected to the annular pipe 21. Figure 4 (For illustration only, the connection between the screw and the annular pipe is not shown.) The screw 22 is rotated by the external motor 23, which in turn drives the annular pipe 21 to move up and down. The nozzles 211 are evenly distributed on the annular pipe. Depending on the actual flue gas characteristics, 4-24 nozzles can be installed, and the annular pipe can be arranged in 1-3 layers.

[0043] Further, preferably but not limitingly, the control unit may include a data analysis module, an injection quantity control module, and a movement control module. The data analysis module receives sulfur trioxide concentration distribution data from the detection unit, processes it by taking the median or mean value, and compares it with a concentration threshold. The injection quantity control module dynamically adjusts the injection quantity of the solid powder absorbent based on the comparison results from the data analysis module. The movement control module calculates and controls the vertical movement distance of the annular pipe based on the comparison results from the data analysis module. For specific data analysis, calculation, and control methods, please refer to the control method below.

[0044] like Figure 1 As shown, the present invention also provides a sulfur trioxide absorption system 100 in flue gas, which utilizes the aforementioned sulfur trioxide absorption device in flue gas. This system 100 is located between the denitrification system 200 and the desulfurization system 300. The system may further include an absorbent raw material silo 4, a weighing meter 5, and a screw conveyor 6. The absorbent raw material silo 4 is used to hold solid powder absorbent and is equipped with an internal stirring blade 41. The weighing meter 5 is used to weigh and measure the absorbent from the absorbent raw material silo 4 and conveyed to the sulfur trioxide absorption device in flue gas. The screw conveyor 6, based on the sulfur trioxide concentration data obtained by the detection unit 1, delivers different quantities of absorbent to the absorbent inlet 24 via a blower 61. Because the system of the present invention uses the aforementioned sulfur trioxide absorption device in flue gas, it can achieve the same technical effects as the aforementioned device.

[0045] Further reference Figures 1 to 4 The present invention also provides a method for controlling the absorption of sulfur trioxide in flue gas, which utilizes the aforementioned sulfur trioxide absorption system 100 in flue gas and includes the following steps:

[0046] Step S101: Distributed detection of sulfur trioxide concentration in flue gas is performed on the cross section of the flue gas outlet (i.e., detection location section 11), and the median or mean concentration of each honeycomb region is obtained.

[0047] Step S102: Compare the median or mean concentration calculated in step S101 with the concentration threshold to determine whether the real-time concentration is high, medium, or low. Specifically, the concentration threshold includes a high concentration threshold and a low concentration threshold, and the high concentration threshold is preferably set to 200 mg / Nm³. 3 The low concentration threshold is preferably set to 100 mg / Nm³. 3 The high concentration of this invention is greater than 200 mg / Nm³. 3 The concentration is 100 mg / Nm³. 3 and 200mg / Nm 3 The concentrations are between 100 mg / Nm³, with the lower concentration being less than 100 mg / Nm³. 3The concentration.

[0048] Step S103: Based on the judgment result, control and adjust the injection amount of solid powder absorbent to form a mist surface in the flue and contact the flue gas running from top to bottom, and / or, change the mixing distance between the flue gas and the absorbent or adjust the distribution range of the absorbent by calculating and controlling the vertical movement distance of the annular pipe.

[0049] In step S103, the solid powder absorbent may be a basic absorbent, such as one or more basic absorbents like sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide, and magnesium hydroxide. Preferably, but not limitingly, Na+ is used. + For SO3, the stoichiometric ratio of the absorbed dose to the real-time SO3 concentration in the flue gas is 1.0–4.0; for Ca... 2+ SO3 or Mg 2+ For SO3, the stoichiometric ratio of the absorbent dosage to the real-time SO3 concentration in the flue gas is 1.0–2.0. The delivery rate of the absorbent is adjusted based on the real-time SO3 concentration, preferably within the range of 30–100 kg / h.

[0050] When the sulfur trioxide concentration obtained in step S101 is high, the injection rate of the absorbent is increased by calculation, and the annular pipe is moved upward to a first height by calculation and control, thereby increasing the mixing distance between the flue gas and the absorbent. Specifically, the absorbent injection rate (i.e., the delivery rate) and the height of the annular pipe can be calculated using the following formulas:

[0051] Let the flue gas velocity be v, the flue gas volume be V, the flue cross-sectional area be s, the instantaneous SO3 concentration be c calculated by the detection unit, the absorbent addition amount be m, the motor speed be n, the distance l between the annular pipe 21 and the flue gas outlet 25 be l, the relative molecular mass of SO3 be M1, the relative molecular mass of the absorbent be M2, the initial height of the sliding nozzle assembly be h, and the reaction time t per unit volume of SO3 with the absorbent be t. The flue gas velocity v = V / s, and the reaction time t per unit volume of SO3 with the absorbent can be obtained through laboratory experiments.

[0052] When c>200mg / Nm 3When the sulfur trioxide concentration is high, the absorbent dosage is adjusted by the control unit 3 to m = c / M1*5*M2*V; the motor 23 is started by the control unit 3 to adjust the annular pipe 21 to the first height l = (c-200)V*t*v / M1 + 1 / 4h + (c-100)V*t*v / M1. Under high concentration conditions, the motor 23 performs an upward operation on the annular pipe for high-concentration SO3 (moving it to the first height), which not only increases the distribution range of the absorbent but also extends the mixing distance between the flue gas and the absorbent, making the contact reaction between the flue gas and the absorbent more complete; increasing the amount of absorbent delivered for high-concentration SO3 effectively maintains a suitable stoichiometric ratio of absorbent to SO3.

[0053] When the sulfur trioxide concentration obtained in step S101 is medium, the absorbent injection rate is maintained by calculation (i.e., adjusted to the initial injection rate set by the system). Simultaneously, the annular pipe is calculated and controlled to move to a second height, and its reciprocating motion is controlled at this second height, thereby increasing the distribution range of the absorbent. Specifically, the absorbent injection rate (i.e., the delivery rate) and the annular pipe height can be calculated using the following formulas:

[0054] In 100 <c<200mg / Nm 3 When the sulfur trioxide concentration is at a medium level, the absorbent dosage is adjusted to the initial injection rate by the control unit 3, and the added absorbent dosage is adjusted to m = c / M1*4.5*M2*V. The motor 23 is started by the control unit 3 to adjust the annular pipe 21 to the second height of l = 1 / 4h + (c-100)V*t*v / M1. Under the condition of medium concentration, the motor 23 moves the annular pipe to the initial position set by the system (i.e., the second height) for medium concentration SO3. On this basis, the annular pipe is made to move up and down in a reciprocating operation. In this way, the distribution range of the absorbent can be effectively adjusted, so that the contact reaction between the flue gas and the absorbent is more complete. At this time, the absorbent delivery rate is not changed (i.e., the initial injection rate set by the system is maintained), so as to maintain a suitable chemical molar equivalent ratio of absorbent to SO3.

[0055] When the sulfur trioxide concentration obtained in step S101 is low, the injection rate of the absorbent is reduced by calculation, and the annular pipe is moved downwards to a third height by calculation and control, thereby reducing the mixing distance between the flue gas and the absorbent and narrowing the distribution range of the absorbent. Specifically, the absorbent injection rate (i.e., the delivery rate) and the height of the annular pipe can be calculated using the following formulas:

[0056] When c < 100 mg / Nm 3When the sulfur trioxide concentration is low, the absorbent dosage is adjusted by the control unit 3 (i.e., reduced relative to the initial injection amount at medium concentration), and the added absorbent dosage is adjusted to m = c / M1*4*M2*V. The control unit 3 starts the motor 23 to adjust the annular pipe 21 to the third height l = 1 / 4h. Under low concentration conditions, the motor 23 performs an annular pipe descent operation (relative to the initial position) for low-concentration SO3, reducing the distribution range of the absorbent and preventing excessive adhesion of absorbent to the flue wall; correspondingly, the absorbent delivery amount is reduced for low-concentration SO3 to maintain an appropriate stoichiometric ratio of absorbent to SO3.

[0057] This invention employs different control strategies for high, medium, and low concentrations. Under fluctuating sulfur trioxide concentrations, it can dynamically adjust the amount of absorbent used, the mixing distance between the flue gas and the absorbent, and the distribution range of the absorbent in real time, making it more targeted. Using this method, even with fluctuating sulfur trioxide concentrations in the flue gas, the SO3 removal rate can be guaranteed to be greater than 85%, the absorbent utilization rate greater than 90%, and absorbent costs saved by more than 25%. It also avoids flue corrosion caused by excessive sulfur trioxide emissions and solves problems such as flue scaling caused by excessive absorbent injection.

[0058] Example 1

[0059] In this embodiment, the SO3 concentration at the denitrification flue gas outlet is approximately 200 mg / Nm³. 3 The flue gas flow direction of the denitrification system is as follows: denitrification flue gas inlet, SCR catalyst bed, denitrification flue gas outlet, SO3 detection unit, and sliding nozzle assembly. The absorbent flow direction is as follows: raw material silo, weighing scale, screw conveyor, blower, and sliding nozzle assembly. The raw material silo contains sodium bicarbonate basic absorbent material, and the screw conveyor transports the absorbent at a rate of 100 kg / h. The residence time of the absorbent in the flue gas is 5 seconds, the flue gas temperature is 350℃, and the blower outlet pressure is 15 kPa. The denitrification flue gas flow rate is 100,000 m³ / h. 3 The nozzles are evenly arranged within the annular pipe, with eight nozzles in total. The nozzles are positioned at a 60° angle to the horizontal plane, and the spray direction is essentially the same as the flue gas flow direction. This spray method minimizes the impact on flue gas flow. The absorbent supply unit, based on the SO3 distribution and concentration analysis within the flue gas at a given moment by the SO3 detection unit, adjusts the absorbent delivery rate in real time according to the aforementioned calculation results. Addressing the issue of varying SO3 concentrations at different points along the flue gas cross-section, the nozzle assembly is moved up and down to provide a suitable distance for uniform mixing of the flue gas and absorbent, further removing SO3.

[0060] After a long period of operation, the detection results of sulfur trioxide concentration at the flue gas outlet of the desulfurization system showed that the instantaneous concentration of sulfur trioxide emissions was less than 8 mg / Nm³. 3 The absorbent utilization rate can reach 96%, saving 30% in absorbent costs. Simultaneously, scaling or clogging of equipment such as economizers or desulfurization towers is reduced. No blue smoke is observed at the desulfurization tower outlet. The entire process unit can operate continuously for more than one year.

[0061] Comparative Example

[0062] In this comparative example, the denitrification device is equipped with absorbent nozzles for removing sulfur trioxide, but the annular duct containing these nozzles is fixed at a certain height within the flue. According to the SO3 detection unit at the denitrification flue gas outlet, the SO3 concentration is approximately 200 mg / Nm³. 3 The flue gas flow direction of the denitrification system is as follows: denitrification flue gas inlet, SCR catalyst bed, denitrification flue gas outlet, SO3 detection unit, and SO3 removal device. The absorbent flow direction is as follows: raw material silo, weighing device, screw conveyor, blower, and SO3 removal device. The raw material silo contains sodium bicarbonate basic absorbent material, and the absorbent is transported proportionally according to the maximum SO3 concentration at a rate of 100 kg / h. The residence time of the absorbent in the flue gas is 5 seconds, the flue gas temperature is 350℃, and the blower outlet pressure is 15 kPa. The denitrification flue gas flow rate is 100,000 m³ / h. 3 / h. The nozzles are evenly arranged inside the annular pipe, with a total of 8 nozzles, and the angle between the nozzles and the horizontal plane is 60°.

[0063] After a long period of operation, the detection results of sulfur trioxide concentration at the flue gas outlet of the desulfurization system showed that the instantaneous concentration of sulfur trioxide emissions was greater than 25 mg / Nm³. 3 The absorbent utilization rate was 75%. However, significant scaling or blockage occurred in equipment such as the economizer and desulfurization tower. Blue smoke was still observed at the desulfurization tower outlet. The entire process unit could operate continuously for approximately 6 months.

[0064] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A device for absorbing sulfur trioxide in flue gas, characterized in that, Used for flue gas treatment after denitrification, including: The detection unit is located at the denitrification flue gas outlet and is used to detect the sulfur trioxide concentration in the denitrification flue gas; the cross section where the detection location is located divides the flue gas channel into multiple areas, forming a distributed detection; The removal unit, which is located in the flue gas passage of the device, includes a solid powder absorbent nozzle assembly that can slide up and down; A control unit, located outside the device, is used to move the nozzle assembly up and down and dynamically adjust the injection volume of the solid powder absorbent when the sulfur trioxide concentration fluctuates.

2. The sulfur trioxide absorption device in flue gas according to claim 1, characterized in that, The nozzle assembly includes: The annular pipe is integrally formed with the absorbent inlet and fixedly connected to the slide rail located on the inner wall of the flue gas passage. The nozzles are arranged in multiple evenly spaced positions along the inner edge of the annular pipe. The nozzles are in communication with the annular pipe and the spray direction is radial inward. During the injection of the absorbent, a mist-like surface is formed in the flue gas channel and comes into contact with the flue gas moving from top to bottom. A screw is vertically positioned at the axial center of the annular pipe and threadedly connected to the annular pipe. The screw is driven to rotate by an external motor, thereby driving the annular pipe to move up and down.

3. The sulfur trioxide absorption device in flue gas according to claim 1, characterized in that, The detection unit is located upstream of the removal unit, and the cross-sectional shape of the detection location is honeycomb-shaped.

4. The sulfur trioxide absorption device in flue gas according to claim 3, characterized in that, The detection unit uses electrochemical, infrared, gas-sensitive, or thermal conductivity methods to monitor the sulfur trioxide concentration in different areas of the honeycomb cross section in real time and generates sulfur trioxide concentration distribution data passing through the cross section. Then, based on the concentration distribution data, it transmits the data to the control unit via an electrical signal.

5. The sulfur trioxide absorption device in flue gas according to claim 4, characterized in that, The control unit includes: The data analysis module is used to receive sulfur trioxide concentration distribution data from the detection unit, process the median or mean value, and compare it with the concentration threshold. The injection volume control module is used to dynamically adjust the injection volume of the solid powder absorbent based on the comparison results of the data analysis module. The movement control module is used to calculate and control the vertical movement distance of the annular pipe based on the comparison results of the data analysis module.

6. A sulfur trioxide absorption system for flue gas, characterized in that, The apparatus as described in any one of claims 1 to 5 is used, wherein the system is disposed between the denitrification system and the desulfurization system.

7. The sulfur trioxide absorption system in flue gas according to claim 6, characterized in that, The system also includes: The absorbent raw material silo is used to hold solid powder absorbent and is equipped with a stirring blade inside. A weighing meter is used to weigh and measure the absorbent from the absorbent feed silo and conveyed to the sulfur trioxide absorption device in the flue gas. The screw conveyor, based on the sulfur trioxide concentration data obtained by the detection unit, delivers different quantities of absorbent to the absorbent inlet via a blower.

8. A method for controlling the absorption of sulfur trioxide in flue gas, characterized in that, The application of the system as described in claim 6 or 7 includes the following steps: A. Distributed detection of sulfur trioxide concentration in flue gas was performed on the cross-section of the flue gas outlet at the denitrification flue gas outlet, and the median or mean concentration of each honeycomb region was obtained. B. Compare the calculated median or mean concentration with the concentration threshold to determine whether the real-time concentration is high, medium, or low. C. Based on the judgment results, control and adjust the injection amount of solid powder absorbent to form a mist surface in the flue and contact the flue gas running from top to bottom, and / or, change the mixing distance between the flue gas and the absorbent or adjust the distribution range of the absorbent by calculating and controlling the vertical movement distance of the annular pipe.

9. The method for controlling sulfur trioxide absorption in flue gas according to claim 8, characterized in that, The concentration threshold in step B includes a high concentration threshold and a low concentration threshold; the high concentration threshold is 200 mg / Nm³. 3 The low concentration threshold is 100 mg / Nm³. 3 The high concentration is greater than 200 mg / Nm³. 3 The concentration, wherein the medium concentration is 100 mg / Nm³ 3 and 200mg / Nm 3 The concentrations are between, where the low concentration is less than 100 mg / Nm³. 3 The concentration.

10. The method for controlling sulfur trioxide absorption in flue gas according to claim 9, characterized in that, Step C specifically involves: C1. When the sulfur trioxide concentration obtained in step A is high, the injection volume of the absorbent is increased by calculation, and the annular pipe is moved upward to the first height by calculation and control, thereby increasing the mixing distance between the flue gas and the absorbent. C2. When the sulfur trioxide concentration obtained in step A is medium, the injection volume of the absorbent is maintained by calculation, and the annular pipe is moved to the second height by calculation and control. At the second height, the annular pipe is reciprocated to increase the distribution range of the absorbent. C3. When the sulfur trioxide concentration obtained in step A is low, the injection amount of absorbent is reduced by calculation, and the annular pipe is moved downward to the third height by calculation and control, thereby reducing the mixing distance between flue gas and absorbent and narrowing the distribution range of absorbent.

11. The method for controlling sulfur trioxide absorption in flue gas according to claim 8, characterized in that, The solid powder absorbent is an alkaline absorbent, specifically one or more of sodium bicarbonate, sodium carbonate, sodium hydroxide, calcium carbonate, calcium hydroxide, and magnesium hydroxide.

12. The method for controlling sulfur trioxide absorption in flue gas according to claim 11, characterized in that, Take Na + For SO3, the stoichiometric ratio of the absorbed dose to the real-time SO3 concentration in the flue gas is 1.0–4.0; for Ca... 2+ SO3 or Mg 2+ For SO3, the stoichiometric ratio of the absorbed dose to the real-time concentration of SO3 in the flue gas is 1.0 to 2.

0.

13. The method for controlling sulfur trioxide absorption in flue gas according to claim 12, characterized in that, The delivery rate of the absorbent is adjusted based on the real-time SO3 concentration, with an adjustment range of 30–100 kg / h.

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