Process for controlling flue gas temperature at desulfurization and denitrification inlet of activated carbon

Abstract

The invention discloses a process for controlling flue gas temperature at an activated carbon desulfurization and denitrification inlet, which belongs to the technical field of flue gas treatment and comprises a plate heat exchanger and an axial flow fan. The plate heat exchanger comprises a smoke cavity and a heat exchange plate, and a plurality of flues are formed between the smoke cavity and the heat exchange plate. And the axial flow fan communicates with an inner cavity of the heat exchange plate and is provided with a feedback mechanism for adjusting the air volume according to the temperature of flue gas in the flue gas cavity. High-temperature flue gas and a cooling medium are subjected to interval heat transfer by the plate heat exchanger through the heat exchange plate, the flue gas is divided into a plurality of flues, the flue gas in the flues is in contact with the heat exchange plate to generate convective heat transfer and heat conduction, and the temperature of the flue gas is reduced along with the passing distance. The axial flow fan directly or indirectly supplies air to the smoke cavity, and controlled cooling airflow is formed. The feedback mechanism automatically adjusts the power of the axial flow fan according to the real-time temperature of an outlet or some key positions, so that the heat exchange side flow and the heat transfer intensity are adjusted, and the target of setting the tower entering temperature is achieved.

Description

Technical Field

[0001] This invention belongs to the field of flue gas treatment technology, specifically a process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification. Background Technology

[0002] The flue gas from sintering mills contains a variety of harmful pollutants, including sulfur dioxide, nitrogen oxides, particulate matter, dioxins, and heavy metals. Its composition is complex, and emissions are substantial. In recent years, activated carbon flue gas purification systems have been widely used in sintering mill flue gas treatment due to their significant advantages, such as integrated removal of multiple pollutants, resource recovery and utilization, and zero solid waste generation. This process utilizes the adsorption and catalytic effects of activated carbon to achieve the synergistic removal of multiple pollutants, including sulfur dioxide, nitrogen oxides, and dioxins, thereby meeting increasingly stringent ultra-low emission requirements.

[0003] However, the flue gas temperature discharged from the sintering main exhaust axial flow fan is typically between 140℃ and 200℃, significantly higher than the safe operating temperature range of the activated carbon adsorption tower. If the high-temperature flue gas enters the adsorption tower directly without effective cooling, it is highly likely to form "hot spots" within the bed, potentially even causing spontaneous combustion of the activated carbon and threatening the safe operation of the system. Therefore, the flue gas from the sintering machine head must be reliably cooled before entering the activated carbon adsorption tower.

[0004] Currently, the common cooling method used in industrial production is to incorporate cold air, controlling the temperature of the flue gas entering the tower by adjusting the air mixing ratio. While this method is simple, it still has the following drawbacks: air mixing is affected by factors such as airflow fluctuations and uneven mixing, making precise temperature control difficult and posing a risk of excessively high or low temperatures. Incorporating a large amount of air increases the total volumetric flow rate of the flue gas, thereby increasing the operating load and energy consumption of the axial flow fan. The dilution effect of air mixing increases the oxygen content in the exhaust stack by 1.5%–3.0%, making it difficult to meet subsequent ultra-low emission standards. The optimal reaction temperature for activated carbon desulfurization and denitrification processes is 125℃–140℃. Excessive cold air mixing can easily lead to excessive temperature drops, weakening the adsorption and reaction efficiency of activated carbon and affecting pollutant removal. Summary of the Invention

[0005] The purpose of this invention is to provide a process for controlling the inlet flue gas temperature in activated carbon desulfurization and denitrification, so as to solve the problems mentioned in the prior art.

[0006] A process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification is provided, comprising: A plate heat exchanger includes a flue gas chamber and heat exchange plates, wherein multiple flue channels are formed between the flue gas chamber and the heat exchange plates; An axial flow fan is connected to the inner cavity of the heat exchange plate, and the axial flow fan has a feedback mechanism for adjusting the air volume according to the flue gas temperature in the flue gas cavity.

[0007] As a further aspect of the present invention: the flue gas chamber has an flared section and a constricted section arranged sequentially from top to bottom, and the total cross-sectional area of ​​the flue gas in the constricted section is smaller than the total cross-sectional area of ​​the flue gas in the flared section.

[0008] Due to its larger cross-sectional area, the flue gas velocity entering the flared section is relatively lower, and the gas residence time in this section is longer, which facilitates full contact with the heat exchange plates and achieves enhanced heat transfer. Furthermore, the temperature differences between different parts of the flue gas gradually homogenize during residence, preventing localized hot spots. When the flue gas enters the constricted section after cooling in the flared section, the velocity increases rapidly due to the smaller cross-sectional area. This increased velocity brings a self-scouring effect, which reduces condensation and dust deposition problems that may occur due to flue gas cooling, lowers the risk of scaling, and keeps the flue unobstructed.

[0009] As a further aspect of the present invention: a mixing section is provided between the flared section and the constricted section to connect the various flues.

[0010] The mixing section facilitates the convergence and redistribution of airflows from different flue gas ducts. Within the flared section, the flue gas cools to varying degrees; direct entry into the constricted section could cause localized temperature differences. Through gas convergence and enhanced turbulence in the mixing section, the temperature field is further homogenized, resulting in a more uniform temperature distribution of the overall flue gas before entering the constricted section. This temperature homogenization avoids localized condensation and blockage problems caused by excessive flue gas temperature differences, while also improving overall heat exchange stability. Combined with the self-cleaning effect of the constricted section, this enhances the equipment's durability and temperature control accuracy.

[0011] As a further aspect of the present invention, a booster fan is provided at the output end of the plate heat exchanger.

[0012] When the flue gas flows through the flaring section where it slows down and exchanges heat, and then through the constriction section where it accelerates and scours, there is a certain pressure loss overall. The booster fan not only compensates for the flow resistance and enhances the flow velocity in the constriction section, but also ensures that the high-speed flue gas in the constriction section can smoothly enter the downstream adsorption tower. In particular, if the high-speed airflow scouring effect in the constriction section is accompanied by a certain pressure drop, the booster fan can maintain a stable system air volume and maintain the self-scouring effect of the constriction section.

[0013] As a further aspect of the present invention: the flue gas output temperature of the flared section is 140℃~145℃, and the flue gas output temperature of the constricted section is 125℃~135℃.

[0014] The condensation temperature of the flue gas at the sintering machine head is below 140℃. If the flue gas temperature drops directly below 140℃ in the initial heat exchange stage, condensation will form on the surface of the heat exchange plates, carrying dust and forming scale. By precisely controlling the outlet temperature of the flared section between 140℃ and 145℃, the overall heat of the flue gas can be effectively reduced while ensuring that the temperature is above the condensation point.

[0015] After initial cooling in the flaring section, the flue gas temperature further decreases to 125℃~135℃ upon entering the constriction section, falling within the optimal temperature range for activated carbon adsorption and catalytic reaction. Due to the reduced cross-sectional area in the constriction section, the flow velocity increases significantly. This high-speed airflow scours the heat exchange surfaces, ensuring that even when the flue gas temperature drops to near or slightly below the dew point, strong convection carries away initial condensate or attached particles, preventing droplets and dust from accumulating and forming caking on the surface.

[0016] As a further aspect of the present invention, the flue gas velocity at the input end of the flared section is 10m / s to 14m / s.

[0017] When the flue gas enters the flared section, the flow velocity is maintained between 10 m / s and 14 m / s. This provides sufficient kinetic energy to suspend and carry dust particles in the flue gas, preventing them from settling at the inlet of the flared section or accumulating at the inlet of the heat exchange plate. Within this velocity range, the flue gas flow is dominated by turbulence, resulting in a thin boundary layer between the airflow and the heat exchange plate surface, which increases the heat transfer coefficient and enhances the cooling effect of the flared section. If the flow velocity is too high, the high-speed impact of dust on the heat exchange plate can easily cause erosion, and the system resistance will increase sharply. The velocity range within which turbulent heat transfer is maintained without excessively aggravating wear and pressure drop represents a balance between efficiency and durability.

[0018] As a further aspect of the present invention: the flue gas velocity at the input end of the constricted section is 10m / s to 14m / s.

[0019] The key to the constriction section design lies in utilizing the increased flow velocity caused by the channel contraction to re-accelerate the flue gas, which loses kinetic energy while flowing through the flaring section, back to that velocity range. By controlling the flow velocity within the range of 10 m / s to 14 m / s, the high-speed flue gas exerts a significant scouring effect on the heat exchanger plate surface, carrying away any condensate droplets or dust that may adhere to it, preventing scale formation. If the flow velocity in the constriction section is too high, although the scouring is stronger, the wear of the metal surface by dust will increase dramatically, shortening the equipment's lifespan. Controlling the velocity within 10 m / s to 14 m / s not only provides sufficient scouring effect but also ensures the long-term reliability of the heat exchanger plate.

[0020] As a further aspect of the present invention: the inlet of the heat exchange plate located in the flared section is connected to a first air duct, and the inlet of the heat exchange plate located in the constricted section is connected to a second air duct.

[0021] Two independent air ducts supply cooling air to the flaring and constricting sections respectively, enabling zoned temperature control based on the flow rate and heat exchange requirements of each section. The flaring section receives a larger volume of cold air for initial cooling and temperature homogenization, while the constricting section receives a smaller, more concentrated volume of cold air for fine cooling. Through staged cooling and precise zoned control, the flaring and constricting sections can each meet their respective heat exchange and scouring needs while working synergistically to ensure a stable and controllable flue gas temperature entering the tower.

[0022] As a further aspect of the present invention: a wave-shaped structure with continuous alternating transitions between flaring and contraction is formed between the heat exchange plates located in the flared section.

[0023] The wavy transition causes the flue gas to form periodic expansion and contraction flows within the flared section, generating multiple velocity fluctuations and local turbulence. The expansion section enhances residence and heat transfer, while the contraction section brings scouring and redistribution. The alternating superposition of these two elements further enhances temperature homogenization and anti-fouling effects.

[0024] As a further aspect of the present invention: the heat exchange plates located in the constricted section have a continuous straight-through structure.

[0025] The constriction section employs a continuous straight-through flow channel, avoiding the additional resistance caused by the wave-like structure. This ensures that the high-speed flue gas maintains a stable scouring effect in this area, and the self-cleaning efficiency is not reduced due to structural complexity. This guarantees the continued high flow velocity and scouring effect of the constriction section, reduces condensate accumulation and dust adhesion, and improves the long-term operational stability of the equipment.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: Plate heat exchangers transfer heat between high-temperature flue gas and the cooling medium through intermittent heat exchange plates. The flue gas is divided into multiple flue channels, where convective and conductive heat transfer occurs as the flue gas contacts the heat exchange plates, and the flue gas temperature decreases with the distance traveled. Axial flow fans directly or indirectly supply air to the flue gas chamber, forming a controlled cooling airflow. A feedback mechanism automatically adjusts the axial flow fan power based on real-time outlet or temperature at certain key locations, thereby regulating the flow rate and heat transfer intensity on the heat exchange side to achieve the set inlet temperature target. This process achieves precise and dynamic control of the inlet temperature, significantly reducing the risk of hot spots and spontaneous combustion of activated carbon. Compared with direct mixing of cold air, it reduces the amount of oxygen introduced and the overall volumetric flow rate, improves system energy efficiency, and facilitates subsequent ultra-low emission control. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the overall structure of the process for controlling the inlet flue gas temperature in activated carbon desulfurization and denitrification. Figure 2 This is an internal structural diagram of a plate heat exchanger provided in an embodiment of the present invention.

[0029] In the diagram: 1. Flue gas chamber; 11. Expanded section; 12. Shrinking section; 13. Mixing section; 2. Heat exchange plate; 3. Flue; 4. Axial flow fan; 5. Booster fan; 61. First air duct; 62. Second air duct. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0031] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0032] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0033] Please see Figures 1-2 As shown in the embodiment of the present invention, a process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification includes a plate heat exchanger and an axial flow fan 4. The plate heat exchanger includes a flue gas chamber 1 and heat exchange plates 2, with multiple flue ducts 3 forming between the flue gas chamber 1 and the heat exchange plates 2. The axial flow fan 4 is connected to the inner cavity of the heat exchange plates 2, and the axial flow fan 4 has a feedback mechanism for adjusting the airflow according to the flue gas temperature in the flue gas chamber 1.

[0034] Flue 3 is a vertical channel, and the flue gas flows from top to bottom from the top of the plate heat exchanger. On the one hand, gravity will cause the dust to settle naturally to the bottom of the plate heat exchanger. On the other hand, the appropriate flue gas flow rate can also realize the self-purification function of the flue gas, thereby greatly avoiding the dust from the flue gas adhering to the heat exchange elements and ensuring that the heat exchange efficiency of the plate heat exchanger does not decrease.

[0035] In a plate heat exchanger, flue gas flows from top to bottom. Heat exchange air, driven by an axial fan 4, enters the heat exchange plate 2 from the side of the plate heat exchanger and exits from the other side. During this process, the heat from the flue gas is dissipated through the indirect heat exchange of the heat exchange plate 2, thus cooling the flue gas. The heat exchange plate 2 is made of stainless steel and transfers heat from the high-temperature flue gas to ambient-temperature air. Low-temperature air is horizontally fed into the plate heat exchanger by the axial fan 4, which can reduce the flue gas temperature from 140℃~200℃ to 125℃~140℃ at the output.

[0036] The axial flow fan 4 has a feedback mechanism that adjusts the airflow based on the flue gas temperature in the flue gas chamber 1. The cooling temperature of the flue gas is adjusted by regulating the amount of air supplied to the plate heat exchanger, and the airflow is controlled by adjusting the frequency of the axial flow fan motor. The cooling device can be monitored and controlled in real-time via the control panel on the equipment's electrical control cabinet or a remote control interface.

[0037] In one specific embodiment, the axial flow fan 4 is a variable frequency axial flow fan. The variable frequency axial flow fan forms a feedback loop with the variable frequency controller through a temperature sensor installed at the outlet of the flue gas chamber 1. When the temperature at the outlet of the flue gas chamber 1 is detected to be higher than the set value, the variable frequency controller automatically increases the fan speed and increases the cooling air volume; when the detected temperature is lower than the set value, the controller reduces the fan speed and reduces the cold air input, thereby realizing dynamic closed-loop control of the flue gas temperature.

[0038] In traditional air-cooling systems, cooling is achieved by directly mixing ambient air with high-temperature flue gas, thereby lowering the temperature of the mixture. This method suffers from significant energy waste: the introduced cold air does not participate in any energy recovery and instead dilutes the energy density of the flue gas; further heating or utilization of waste heat requires additional energy to reheat the gas. In contrast, the heat exchange plate cooling scheme used in this application transfers heat from the flue gas to the air or cooling medium on the other side, achieving heat transfer rather than energy dilution. The heat absorbed by the air on the other side can be used as preheated air or a heat source for recycling. The heat exchange process is conducted in a closed loop, without altering the flue gas composition, achieving both cooling and waste heat utilization.

[0039] The flue gas chamber 1 has a flared section 11 and a constricted section 12 arranged sequentially from top to bottom. The total cross-sectional area of ​​the flue duct 3 in the constricted section 12 is smaller than that in the flared section 11. The larger cross-sectional area of ​​the flared section 11 necessitates a reduction in local flow velocity and a longer residence time. This longer residence time allows for sufficient contact between the flue gas and the heat exchange surface, enabling the boundary layer to develop and be disrupted by the heat exchange plate 2, thereby increasing the overall heat transfer per unit volume of flue gas. The smaller cross-sectional area of ​​the constricted section 12 results in increased flow velocity for the same volumetric flow rate, creating enhanced shear stress and producing a self-scouring effect.

[0040] A booster fan 5 is installed at the output end of the plate heat exchanger. During the segmented heat exchange process in flue 3, the flue gas undergoes changes in cross-sectional area, corrugated plate disturbance, and turbulence generation, all of which contribute to local resistance and overall pressure drop. The constriction section 12 relies on a relatively high local flow velocity to generate wall shear stress, carrying away condensate or loose dust. However, the flow velocity of the flue gas has already been significantly reduced after exiting the flaring section 11, and the increase in flow velocity due to the constriction is limited and unstable. Without pressure compensation, the actual flow velocity in the constriction section 12 may be lower than the design value, thus weakening the self-cleaning effect. The booster fan 5 at the output end actively increases the static pressure on the outlet side to compensate for the pressure loss inside and outside the plate heat exchanger, keeping the constriction section within the target flow velocity range and ensuring effective self-cleaning.

[0041] With the booster fan 5 providing output pressure assurance, stronger disturbance or denser plates can be used in the flared section 11 to reduce the flue gas velocity and improve the turbulence effect, thereby increasing heat exchange efficiency.

[0042] Furthermore, the air mixing scheme introduces a large amount of ambient temperature air, causing drastic changes in flue gas flow rate and density. On the one hand, this will cause the fan operating point to drift, and fluctuations in air pressure and flow rate; on the other hand, the increased gas density after the cold air is mixed in will make the system drag coefficient unstable. If cold air is used for cooling, it will cause the oxygen content of the activated carbon exhaust chimney to increase. In addition, the baseline oxygen content at the sintering flue gas exhaust outlet is 16%. If the outlet oxygen content reaches 17%, it means that the sulfur dioxide and nitrogen oxides at the outlet, before oxygen conversion, need to be lower to achieve the 16% oxygen conversion standard.

[0043] The heat exchange plate cooling is a closed heat exchange, and the flue gas mass flow rate remains constant: without changing the flue gas composition and flow distribution, the booster fan 5 can operate at the optimal efficiency point for a long time; after the temperature decreases, the flue gas density increases moderately, which improves the intake efficiency of the booster fan 5 and reduces energy consumption and mechanical load.

[0044] Furthermore, activated carbon adsorption towers typically have minimum requirements for inlet flow rate, inlet pressure differential, and uniformity of distribution. The booster fan 5 provides stable pressure and flow at the output end, ensuring that the plate heat exchanger outlet can still provide stable and controllable airflow conditions to the adsorption tower even when operating conditions fluctuate.

[0045] In actual operation, the multiple parallel flues 3 within the flared section 11 often exhibit inconsistent cooling levels and local resistance. This is due to factors such as inlet deviation, differences in plate manufacturing or deposition, resulting in variations in temperature and velocity among the flues before reaching the constriction section 12. Therefore, a mixing section 13 is provided between the flared section 11 and the constriction section 12 to connect the various flues 3. The mixing section 13, through connecting channels, allows the fluids in these parallel flues 3 to converge and exchange positions, thereby breaking down temperature and momentum stratification and making the flow field more uniform.

[0046] In one specific embodiment, the mixing section 13 is a tapered shape with a gradually decreasing cross-sectional area from the flared section 11 to the constricted section 12, which increases the flow velocity of the fluid in the constricted section 12 by gradually compressing the fluid.

[0047] The condensation temperature of the flue gas at the sintering machine head is below 140℃. If the flue gas temperature drops directly below 140℃ during the initial heat exchange, the self-flushing effect will significantly decrease due to the reduced flue gas velocity at the tail end of the flared section 11, leading to condensation on the surface of the heat exchange plate 2 at the tail end of the flared section 11. The condensate will carry dust and adhere to the heat exchange plate, rapidly forming scale. Strictly controlling the outlet temperature of the flared section between 140℃ and 145℃ effectively reduces the total heat of the flue gas, creating conditions for further cooling; it also maintains the temperature above the dew point, preventing condensate formation and avoiding the risk of caking and blockage on the heat exchange plate 2 at the tail end of the flared section 11 due to the reduced flue gas velocity.

[0048] After initial cooling in the flaring section 11, the flue gas is further cooled to 125℃~135℃ upon entering the constriction section 12. This temperature range covers the optimal reaction temperature for activated carbon adsorption of pollutants such as SO2, NOx, and dioxins. The reduced cross-sectional area of ​​the constriction section 12 increases the flow velocity. During this process, although the flue gas temperature may be close to or even slightly below the dew point, the condensate and dust are promptly carried away by the strong convective airflow due to the self-scouring effect of the high-speed airflow, making it difficult for them to remain and adhere to the surface of the heat exchange plate 2 for a long time.

[0049] The inlet of the heat exchange plate 2 located in the flared section 11 is connected to a first air duct 61, and the inlet of the heat exchange plate 2 located in the constricted section 12 is connected to a second air duct 62. These two independent air ducts allow for independent adjustment of the cooling air source for the flared section 11 and the constricted section 12. The flared section 11 can use a larger airflow to achieve coarse adjustment and temperature homogenization; the constricted section 12 can use a smaller airflow to achieve fine adjustment.

[0050] In one embodiment, the first air duct 61 and the second air duct 62 are each equipped with an axial flow fan 4 for independent control. When the flue gas cools too little after passing through the flared section 11, the axial flow fan in the second air duct 62 switches to low power output to reduce the flue gas temperature drop in the constricted section 12. When the flue gas cools insufficiently after passing through the flared section 11, the axial flow fan in the second air duct 62 switches to high power output to increase the flue gas temperature drop in the constricted section 12.

[0051] In one embodiment, the first air duct 61 and the second air duct 62 are supplied with airflow by a general axial flow fan 4, and each of the first air duct 61 and the second air duct 62 is equipped with a damper for airflow control. When the flue gas is cooled too little after passing through the flared section 11, the flow rate of the dampers in the first air duct 61 and / or the second air duct 62 is reduced. When the flue gas is not cooled enough after passing through the flared section 11, the flow rate of the dampers in the first air duct 61 and / or the second air duct 62 is increased.

[0052] It should be noted that the number of air ducts is not limited to two; more than two can be arranged depending on the height and width of the plate heat exchanger.

[0053] A wave-shaped structure with continuous alternating expansion and contraction is formed between the heat exchange plates 2 located in the flared section 11. When the flue gas flows between the wave-shaped heat exchange plates 2, it experiences continuous local expansion and contraction sections. In the expansion section, the cross-sectional area increases, the flue gas velocity decreases, and the residence time increases; in the contraction section, the cross-sectional area decreases, the flue gas velocity increases, and local scouring occurs. This velocity fluctuation creates multiple velocity fluctuations and local turbulence, which is beneficial for sufficient contact between the flue gas and the heat exchange plates 2, improving heat exchange efficiency.

[0054] Without experiencing local expansion and contraction, the additional pressure drop and flow disturbance are smaller. The constriction section 12 is a supplementary section for further cooling of the flue gas, with a smaller cross-sectional area and significantly increased flow velocity. The straight-through structure ensures that the high-speed flue gas can flow stably through the entire constriction section 12, making the scouring effect continuous and effective. The high-speed flow can carry away condensate and attached dust, avoiding caking or blockage problems even when the flue gas temperature is close to the dew point.

[0055] The flue gas velocity at the input end of the flared section 11 is 10 m / s to 14 m / s, and the flue gas velocity at the input end of the constricted section 11 is 10 m / s to 14 m / s.

[0056] Example 1 Performance tests of the plate heat exchanger were conducted under different flue gas flow rates. The SO2 concentration in the flue gas was approximately 1500 mg / Nm³, the designed moisture content of the flue gas was 10%, and the acid dew point temperature of the flue gas was 137℃.

[0057] Table 1 shows the test results for flue gas velocity in plate heat exchangers.

[0058]

[0059] When the flow velocity in the flared section 11 is between 10 m / s and 14 m / s, the flue gas turbulence is stable, the boundary layer is thin, and the heat transfer coefficient increases with increasing velocity. Dust suspension also improves with velocity; at low velocities, local dust settles easily, but scouring is weak; at high velocities, dust suspension is sufficient, but plate wear increases slightly. Below 10 m / s, the flue gas velocity is too low, dust settling is significant, initial temperature homogenization is poor, heat transfer efficiency decreases, and scouring capacity is insufficient. Above 14 m / s, the heat transfer coefficient increases slightly, but high-speed dust impact on the heat exchange plates causes significant wear, increases system resistance, and is detrimental to long-term operation.

[0060] The constriction section 12 utilizes channel contraction to increase local flow velocity, raising the flue gas velocity back to 10 m / s–14 m / s. At low flow velocities, the scouring effect is moderate, and condensate or dust may accumulate locally. At intermediate flow velocities, the scouring and temperature control effects are optimal, keeping the plate surface clean. At high flow velocities, scouring is strongest, and temperature is precise, but plate wear increases significantly. When the flow velocity is below 10 m / s, high-speed scouring is insufficient, condensate droplets may adhere to the plate surface, dust deposition is significant, and temperature control accuracy decreases. When the flow velocity is above 14 m / s, scouring is significantly enhanced, but dust impact increases, heat exchange plate wear is severe, system pressure drop increases, and long-term use is unfavorable.

[0061] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A process for controlling the inlet flue gas temperature in activated carbon desulfurization and denitrification, characterized in that, include: A plate heat exchanger includes a flue gas chamber (1) and a heat exchange plate (2), wherein a plurality of flue ducts (3) are formed between the flue gas chamber (1) and the heat exchange plate (2); An axial flow fan (4) is connected to the inner cavity of the heat exchange plate (2), and the axial flow fan (4) has a feedback mechanism for adjusting the air volume according to the flue gas temperature in the flue gas chamber (1).

2. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 1, characterized in that, The flue gas chamber (1) has an flared section (11) and a constricted section (12) arranged sequentially from top to bottom. The total cross-sectional area of ​​the flue (3) of the constricted section (12) is smaller than the total cross-sectional area of ​​the flue (3) of the flared section (11).

3. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, A mixing section (13) is provided between the flared section (11) and the narrowed section (12) to connect the various flues (3) to each other.

4. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, A booster fan (5) is installed at the output end of the plate heat exchanger.

5. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, The flue gas output temperature of the flared section (11) is 140℃~145℃, and the flue gas output temperature of the constricted section (12) is 125℃~135℃.

6. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, The flue gas velocity at the input end of the flared section (11) is 10 m / s to 14 m / s.

7. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, The flue gas velocity at the input end of the constricted section (11) is 10 m / s to 14 m / s.

8. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, The inlet of the heat exchange plate (2) located in the flared section (11) is connected to the first air duct (61), and the inlet of the heat exchange plate (2) located in the constricted section (12) is connected to the second air duct (62).

9. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 2, characterized in that, A wave-shaped structure with continuous alternating transitions between flaring and contraction is formed between the heat exchange plates (2) located in the flaring section (11).

10. The process for controlling the inlet flue gas temperature for activated carbon desulfurization and denitrification according to claim 9, characterized in that, The heat exchange plates (2) located in the constricted section (12) have a continuous straight-through structure.

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