Multistage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas

Abstract

The application discloses a multi-stage countercurrent absorption assembly for chlorine dioxide in tail gas of sodium chlorite process, and mainly relates to the technical field of tail gas treatment. The tail gas enters from a bottom gas inlet and is in contact with absorption liquid in a multi-stage countercurrent mode layer by layer upwards. A first type of atomizing nozzle continuously sprays downwards to form a stable main absorption liquid curtain covering the central region of the tower body, so that high-concentration chlorine dioxide in the tail gas is quickly captured. The absorption liquid flowing in the water ring jacket drives the synchronous rotation of the vortex fan blades. The liquid inlet of a second type of atomizing nozzle is periodically blocked by the blocking pieces distributed alternately with the blades, so that the second type of nozzle is intermittently sprayed upwards. The differential spraying mode and the self-driven metering mechanism of the water flow are combined to strengthen the gas-liquid mass transfer, and the partition pressure-temperature is cooperatively regulated to disperse the reaction heat, so that the technical problems of low-concentration chlorine dioxide in the traditional technology, such as low absorption efficiency, high alkali consumption and easy thermal decomposition, are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, specifically to a multi-stage countercurrent absorption assembly for chlorine dioxide in the exhaust gas of sodium chlorite processes. Background Technology

[0002] The essence of sodium chlorite tail gas treatment is to recover chlorine dioxide using the acid-base balance principle. The tail gas first enters a spray scrubbing tower, where it is sprayed countercurrently with clean water or dilute alkaline solution to remove entrained sulfuric acid mist and dust. Simultaneously, it pre-absorbs some of the soluble tail gas ClO2. Essentially, it first uses alkaline solution to preferentially absorb chlorine dioxide / chlorine gas, then uses hydrogen peroxide for complete reduction and absorption. However, the following issues need to be noted: Firstly, conventional countercurrent absorption can only handle medium to high concentrations of ClO2. The mass transfer efficiency of low-concentration tail gas is extremely low, making it impossible to achieve near-zero emissions. In particular, the countercurrent spraying process of clean water / dilute alkali solution also has a non-linear relationship with the absorption efficiency of chlorine dioxide. At the same time, the concentration of chlorine dioxide in the tail gas is difficult to measure accurately, the alkali consumption is high, and the concentration of sodium chlorite by-product is low, which has no recycling value and can only be treated as hazardous waste. Secondly, all the core absorption reactions in the treatment of sodium chlorite tail gas are strongly exothermic reactions. The stronger the reaction, the higher the heat released. However, ClO2 in the absorption process is prone to thermal decomposition / catalytic decomposition, producing secondary pollution (chlorine gas), and may even explode due to local concentration exceeding the standard.

[0003] In light of the above issues, a technical solution is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-stage countercurrent absorption assembly for chlorine dioxide in the tail gas of sodium chlorite process, in order to solve the above-mentioned technical problems.

[0005] The objective of this invention can be achieved through the following technical solution: a multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas, comprising a tower body and multiple water ring sleeves arranged sequentially along the height of the tower body; The tower body is divided into multiple atomizing spray zones by water rings, and a transition section is provided between each water ring. A water inlet is provided at the top of the tower body, and multiple water ring sleeves form a unidirectional water path through a conversion joint and are kept rotatably connected. The tower body is equipped with an atomizing nozzle and a pressure sensing component in the internal area of ​​the atomizing spray zone, wherein the pressure sensing component is positioned higher than the atomizing nozzle. Multiple type II atomizing nozzles are installed on the curved surface of the water ring sleeve, and the atomizing spray direction of each type II atomizing nozzle is inclined upward towards the inner wall of the tower.

[0006] The water ring sleeve is further configured such that both the upper and lower curved surfaces are in an upwardly curved arch shape, and the curvature of the lower curved surface of the water ring sleeve is greater than that of the upper curved surface.

[0007] The further configuration is as follows: the outer diameter of the water ring sleeve increases from bottom to top, and an air leakage gap is formed between the outer edge of the water ring sleeve and the inner wall of the tower body, and a temperature detection unit is set in each of the air leakage gaps.

[0008] The atomizing spray direction of the first type of atomizing nozzle is inclined downward towards the water ring sleeve, and the atomizing spray directions of the first type of atomizing nozzle and the second type of atomizing nozzle maintain an angular deviation.

[0009] The pressure sensing component is further configured to consist of a pressure sensor and multiple balloons, with the balloons located in the leakage gap.

[0010] The water ring sleeve is further configured to have turbine blades inside, and support frames for maintaining the rotation of the turbine blades are installed at the upper and lower positions of the water ring sleeve corresponding to the transition section.

[0011] The further configuration is as follows: the turbine blades maintain contact with the inner surface of the water ring sleeve, and a shielding plate is installed on the turbine blades at the position corresponding to the upper curved surface inside the water ring sleeve.

[0012] Further configuration: the turbine blades are composed of multiple blades, the number of blades installed and the tilt angle of the blades are linearly differentially distributed from bottom to top, the shielding plates and the type II atomizing nozzles are arranged in a ring array along the center point of the water ring, and the shielding plates are staggered relative to the blades.

[0013] The present invention has the following beneficial effects: 1. Firstly, a differentiated collaborative operation mode of continuous spraying with type 1 nozzles and intermittent spraying with type 2 nozzles is adopted. The kinetic energy of the absorbent liquid itself drives the turbine blades to rotate. The periodic blocking of the shielding plate automatically achieves stepless control of the spray volume of type 2 nozzles. No additional solenoid valves or other electronic control components are required to match the absorption load of each spray zone. The pulse droplets generated by intermittent spraying have stronger airflow penetration ability and can penetrate deep into the boundary layer of the tower wall to eliminate the problem of tail gas short-circuiting escape. Combined with multi-stage countercurrent contact to extend the gas-liquid interaction time, the mass transfer absorption efficiency of low-concentration chlorine dioxide is greatly enhanced. At the same time, combined with the closed-loop control system to dynamically match the total spray intensity and tail gas concentration fluctuations, the consumption of alkali solution is significantly reduced while ensuring that the tail gas meets emission standards.

[0014] 2. Secondly, relying on the pressure sensing component, the balloon achieves dual synchronous sensing of zoned pressure and temperature, which can accurately identify the fluctuation of exhaust gas flow concentration and local reaction exothermic situation in different spray zones. By differentially adjusting the spray intensity of the two-stage nozzles, precise temperature control of the zones can be achieved. Combined with the graded absorption design of the multi-stage atomized spray zone, the originally concentrated strong exothermic reaction is evenly dispersed into multiple independent zones. The atomization process of the absorbent liquid quickly removes the reaction heat, so that the temperature inside the tower is always controlled below the safe decomposition threshold of chlorine dioxide. This effectively inhibits the thermal decomposition and catalytic decomposition of chlorine dioxide, eliminates the risk of secondary chlorine pollution and explosion from the source, and greatly improves the operational safety and long-term continuous operation stability of the exhaust gas treatment system. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the multi-stage countercurrent absorption assembly for chlorine dioxide in the tail gas of the sodium chlorite process proposed in this invention. Figure 2 For the present invention Figure 1 Cross-sectional view of the central tower; Figure 3 For the present invention Figure 2 The front view; Figure 4 This is a schematic diagram of the water ring sleeve in this invention; Figure 5 For the present invention Figure 4 Cross-sectional view; Figure 6 For the present invention Figure 4 The front view; Figure 7 For the present invention Figure 4 A schematic diagram of the structure of a medium-sized turbofan blade.

[0017] In the diagram: 1. Tower body; 2. Water ring sleeve; 3. Transition section; 4. Type I atomizing nozzle; 5. Pressure sensing component; 6. Type II atomizing nozzle; 7. Turbine fan blades; 8. Shielding plate. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: Countercurrent spray tower technology is commonly used for tail gas treatment in sodium chlorite processes. The basic principle is to utilize acid-base balance and redox reactions to allow the tail gas to flow upwards from the bottom of the tower, where it comes into countercurrent contact with the clean water or dilute alkaline solution sprayed from the top. This pre-absorbs sulfuric acid mist and dust, while simultaneously reducing and absorbing chlorine dioxide through the synergistic effect of the alkaline solution and hydrogen peroxide. Figure 3 Explanation: Clean water or dilute alkaline solution is sprayed from Type I atomizing nozzle 4 and Type II atomizing nozzle 6, and the air intake of exhaust gas from bottom to top is further controlled; However, the "dissolving gas" process between the exhaust gas and the liquid medium needs to be considered. Firstly, the mass transfer efficiency of low-concentration chlorine dioxide is extremely low, making it impossible to achieve near-zero emissions. Furthermore, the alkali consumption is high, and the concentration of sodium chlorite produced as a byproduct is low, making it worthless for recycling. Secondly, the absorption reaction is a strongly exothermic process, and the accumulation of local heat can easily lead to the thermal decomposition of chlorine dioxide to produce chlorine gas, or even cause an explosion.

[0020] For reference Figures 1-7 This embodiment proposes a multi-stage countercurrent absorption component for chlorine dioxide in the tail gas of sodium chlorite process. The technical solution is as follows: multiple water rings 2 are separated within the tower body 1 to form a multi-stage atomizing spray zone. Combined with atomizing nozzles with complementary angles and a swirl enhancement structure, it can achieve efficient absorption of low-concentration chlorine dioxide and uniform dispersion of reaction heat. Through unidirectional water path design and staged spray control, it can dynamically match the changes in tail gas concentration. At the same time, the multi-stage heat absorption structure is used to inhibit the decomposition of chlorine dioxide, taking into account treatment efficiency, economy and safety. Essentially, it is still based on a liquid medium. The liquid medium is compressed by a high-pressure pump structure and enters two atomizing nozzles. Under high pressure, it forms a mist and comes into full contact with the exhaust gas. However, there are two atomization spraying methods. The key purpose is to meet the absorption process of exhaust gas at different concentrations and to control the temperature at multiple locations to avoid local overheating or temperature "correlation" in multiple areas that would affect the absorption process. Secondly, a differentiated spraying mode of one type of continuous spraying + two types of intermittent spraying is adopted. The water kinetic energy drives the turbine blades 7 to rotate, indirectly controlling the amount of atomized spraying in a single area. At the same time, the spherical pressure sensing component 5 realizes dual sensing of zone pressure and temperature, and dynamically adjusts the spraying intensity of the two-stage nozzles.

[0021] Example 2: The following supplement is made to the technical content of Example 1: Referring to conventional countercurrent absorption tower technology for exhaust gas, the exhaust gas enters from the bottom inlet of tower body 1 at a preset flow rate, and passes through each atomizing spray zone layer by layer from bottom to top along the inner cavity of tower body 1; the absorbent (a mixture of dilute alkali solution and hydrogen peroxide) is injected from the top inlet of tower body 1, and under its own gravity and high pressure, it flows through all the water rings 2 from top to bottom through the conversion section 3, forming a unidirectional series water path from top to bottom; the conversion section 3 adopts a rotary sealing structure, which not only ensures the water path connectivity between adjacent water rings 2, but also allows the water rings 2 to rotate circumferentially under the drive of water flow, avoiding the scaling and clogging problems caused by long-term operation; When the absorbent liquid is sprayed out through the type 1 atomizing nozzle 4 and the type 2 atomizing nozzle 6, it forms the following two modes: First path: The absorbent liquid is continuously sprayed downwards at an angle by a type of atomizing nozzle 4 installed on the inner wall of the tower body 1, corresponding to the atomizing spray area. The spray direction is precisely pointed to the center area of ​​the lower curved surface of the water ring sleeve 2 below, forming a high-density main absorbent liquid curtain covering a large cross-sectional area in the center of the tower body 1. This liquid curtain forms a strong countercurrent contact with the upward flowing tail gas, which can quickly capture 70%-80% of the medium and high concentration of chlorine dioxide in the tail gas, complete the main absorption reaction, and the continuous spray mode ensures the stable absorption capacity of the high-load area in the center and avoids the escape of chlorine dioxide due to the interruption of spraying. It should be added that: in the first type of spraying method, the sprayed mist absorbent liquid is mainly "concentrated" on the curved surface of the water ring sleeve 2, or it can be understood as: completely covering the air leakage gap, ensuring that the exhaust gas is in full contact with the absorbent liquid during the upward process, and it is in a continuous atomized spraying state.

[0022] Second path: The absorbent liquid is intermittently sprayed upward at an angle by multiple type II atomizing nozzles 6 installed in a curved annular array on the water ring sleeve 2. The spraying direction is biased towards the inner wall of the tower body 1 and forms an angle of 30°-45° with the vertical direction, forming an angle deviation of 90°-120° with the spraying direction of the type I atomizing nozzle 4. The pulsed droplets generated by intermittent spraying have stronger penetrating power and can penetrate deep into the boundary layer airflow near the wall, specifically filling the gas-liquid contact blind zone near the wall of tower body 1, preventing the exhaust gas from forming a "short-circuit airflow" and escaping directly, and improving the chlorine dioxide absorption rate in the edge area.

[0023] Regarding its intermittent spraying method, the following supplementary information is provided: Reference Figures 4-6 Inside the water ring sleeve 2, a turbofan blade 7 is installed through upper and lower support frames. When the absorbent flows through the water ring sleeve 2, the kinetic energy of the water flow drives the turbofan blade 7 to rotate. The water flow velocity directly determines the rotation speed of the turbofan blade 7, thereby indirectly controlling the atomization spray volume of the type II atomizing nozzle 6 in a single area. Specifically, the turbine blade 7 is equipped with a shielding plate 8 at the position of the upper curved surface inside the water ring sleeve 2. The shielding plate 8 and the blade are distributed in an alternating pattern, and the projected area of ​​the shielding plate 8 is completely matched with the liquid inlet area of ​​the type II atomizing nozzle 6. When the turbine blades 7 rotate, the baffle plate 8 periodically blocks the liquid inlet of the type II atomizing nozzle 6: when the baffle plate 8 passes the liquid inlet, the liquid inlet channel is blocked and the type II atomizing nozzle 6 stops spraying; when the baffle plate 8 leaves the liquid inlet, the liquid inlet channel is opened and the type II atomizing nozzle 6 starts spraying. This part is the basic principle of intermittent spraying. By adjusting the total inlet flow rate to change the water flow velocity inside the water ring sleeve 2, the rotation speed of the turbine blades 7 can be changed, thereby changing the blocking frequency of the baffle plate 8. This allows for stepless adjustment of the spray volume of the type II atomizing nozzle 6 within a single area. When the water flow velocity decreases, the blocking frequency decreases, the single spray time of the type II nozzle 6 is extended, the interval is shortened, and the spray volume increases. When the water flow velocity increases, the blocking frequency increases, the single spray time of the type II nozzle 6 is shortened, the interval is extended, and the spray volume decreases. This creates a spray volume adjustment characteristic that is negatively correlated with the water flow velocity, perfectly matching the need for higher spray intensity in low-concentration exhaust gas areas. However, it should be noted that the number of turbine blades 7 and their tilt angles are linearly distributed from bottom to top: the bottom water ring 2 has the most blades and the largest tilt angle, resulting in the fastest rotation speed at the same water flow rate, and the smallest spray volume from the type II nozzle 6, matching the highest tail gas concentration at the bottom of the tower; the top water ring 2 has the fewest blades and the smallest tilt angle, resulting in the slowest rotation speed at the same water flow rate, and the largest spray volume from the type II nozzle 6, matching the lowest tail gas concentration at the top of the tower. This staged design can accurately match the absorption load of each spray zone, avoiding the waste of alkali solution caused by excessive spraying. After all, when the tail gas is first pumped into the tower body 1, its ClO2 content is the highest, but as it is continuously absorbed in the countercurrent, its content gradually decreases.

[0024] Example 3: The following detection feedback mechanism is added to the technical content of Example 2; The pressure sensing components 5 installed in the tower body 1 for each atomizing spray zone are positioned higher than the type 1 atomizing nozzle 4 to avoid direct impact of spray droplets on their measurement accuracy. The pressure sensing components 5 consist of a pressure sensor and multiple elastic balloons located in the air leakage gap, which can simultaneously realize dual sensing of zone pressure and temperature, thereby indirectly controlling the spray volume of type 1 atomizing nozzle 4 and type 2 atomizing nozzle 6. The balloon is made of corrosion-resistant rubber material and can be directly exposed to the airflow in the leakage gap. Changes in exhaust gas pressure will cause the balloon to compress or expand, and the internal air pressure of the balloon will change accordingly and be transmitted to the air pressure sensor, which indirectly reflects the fluctuation of exhaust gas flow and concentration in this spray zone. Furthermore, the balloon is also made of temperature-sensitive rubber material. The local temperature rise caused by the exothermic reaction will cause the gas inside the balloon to expand due to heat, which will also cause changes in the air pressure inside the balloon. The air pressure sensor can separate the air pressure component caused by the temperature change through the algorithm to achieve indirect detection of zoned temperature. However, this type of temperature detection method is not accurate enough. Therefore, an independent temperature detection method needs to be set up, which can use conventional corrosion-resistant temperature sensors. Therefore, in actual operation, when the pressure of a certain spray zone increases (indicating an increase in exhaust gas concentration or flow rate), the total flow rate at the top of the tower is automatically increased. On the one hand, this directly increases the continuous spray volume of the first-type atomizing nozzle 4, strengthening the main absorption capacity of the central area. On the other hand, by increasing the water flow velocity inside the water ring sleeve 2, the rotation speed of the turbine blades 7 is accelerated, reducing the intermittent spray volume of the second-type atomizing nozzle 6, thus matching the absorption requirements of high-concentration exhaust gas. When a temperature rise is detected in a certain spray zone (indicating that the reaction in that zone is highly exothermic), the control system prioritizes increasing the spray volume of that level and above. By increasing the flow rate of the low-temperature absorbent liquid, the heat of reaction is quickly removed, and the temperature inside the tower is always kept below the decomposition temperature of chlorine dioxide, thus achieving precise temperature control by zone. However, it should be noted that the Type 1 atomizing nozzle 4 and the Type 2 atomizing nozzle 6 are two independent pumping systems. The pumping volume of the two needs to be changed according to the actual situation. It should be noted that changing the pumping volume of the Type 2 atomizing nozzle 6, which corresponds to the pumping volume of absorbent liquid per unit time, will also change the rotation state of the turbine blades 7 inside the water ring sleeve 2 and the intermittent spraying state of the absorbent liquid. The main purpose is to change the contact absorption state of the exhaust gas and absorbent liquid, and the key is to change the temperature in each area to avoid thermal decomposition. And reference Figure 6 Further details regarding the water ring sleeve 2 include: the water ring sleeve 2 adopts a double-arched curved surface design, with the curvature of the lower curved surface being greater than that of the upper curved surface. Its main functions are as follows: guiding the droplets sprayed by the type-1 atomizing nozzle 4 to spread evenly along the lower curved surface and undergo secondary atomization, expanding the liquid curtain coverage area, increasing the liquid volume and heat exchange area inside the water ring sleeve 2, enhancing the absorption and transfer capacity of reaction heat, forming an airflow guiding channel, causing the upward-flowing tail gas to converge towards the center of the tower body 1, strengthening the contact intensity with the main absorption liquid curtain, and ensuring that the tail gas and the absorption liquid remain in contact throughout the upward flow process.

[0025] In summary: the outer diameter of the water ring sleeve 2 increases from bottom to top, and the width of the air leakage gap formed between its outer edge and the inner wall of the tower body 1 also increases step by step. The purpose is to make the tail gas flow upward along the air leakage gap, extend the total residence time of the tail gas in each spray zone, especially for the tail gas whose concentration has been greatly reduced after the first few stages of absorption, and provide more sufficient gas-liquid contact opportunities to solve the core problem of low mass transfer efficiency of low concentration chlorine dioxide. The multi-stage atomized spray zone's graded absorption design disperses the strong exothermic reaction, which was originally concentrated in a single area, into multiple zones. The heat release of the reaction in each spray zone is only 1 / N of that in a traditional single-stage spray tower (where N is the number of spray zones). Combined with the zoned temperature control mechanism of the pressure sensing component 5, it can accurately identify and quickly handle local heat accumulation problems, effectively suppressing the thermal decomposition and catalytic decomposition of chlorine dioxide.

[0026] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-stage countercurrent absorption assembly for chlorine dioxide in the tail gas of sodium chlorite process, characterized in that, It includes a tower body (1) and multiple water ring sleeves (2) arranged sequentially along the height direction of the tower body (1); The tower body (1) is divided into multiple atomizing spray zones by water ring sleeves (2), and a transition section (3) is provided between each water ring sleeve (2). The tower body (1) is provided with a water inlet at the top, and multiple water ring sleeves (2) form a unidirectional water path through a conversion joint (3) and remain rotatably connected; The tower body (1) is equipped with a type atomizing nozzle (4) and a pressure sensing component (5) in the internal area of ​​the atomizing spray zone, wherein the pressure sensing component (5) is positioned higher than the type atomizing nozzle (4). Multiple type II atomizing nozzles (6) are installed on the curved surface of the water ring sleeve (2), and the atomizing spray direction of each type II atomizing nozzle (6) is inclined upward towards the inner wall of the tower body (1).

2. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 1, characterized in that, The upper and lower curved surfaces of the water ring sleeve (2) are both arched and curved upwards, and the curvature of the lower curved surface of the water ring sleeve (2) is greater than that of the upper curved surface.

3. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 2, characterized in that, The outer diameter of the water ring sleeve (2) increases from bottom to top, and an air leakage gap is formed between the outer edge of the water ring sleeve (2) and the inner wall of the tower body (1). A temperature detection unit is set in each of the air leakage gaps.

4. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 1, characterized in that, The atomizing spray direction of the first type atomizing nozzle (4) is inclined downward towards the water ring sleeve (2), and the atomizing spray directions of the first type atomizing nozzle (4) and the second type atomizing nozzle (6) maintain an angular deviation.

5. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 3, characterized in that, The pressure sensing component (5) consists of a pressure sensor and multiple balloons, which are located in the leakage gap.

6. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 1, characterized in that, The water ring sleeve (2) is provided with a turbofan blade (7) inside, and the water ring sleeve (2) is equipped with a support frame at the upper and lower positions corresponding to the conversion section (3) to maintain the rotation of the turbofan blade (7).

7. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 6, characterized in that, The turbine blade (7) is in contact with the inner surface of the water ring sleeve (2), and a shielding plate (8) is installed on the turbine blade (7) corresponding to the position of the upper curved surface inside the water ring sleeve (2).

8. The multi-stage countercurrent absorption assembly for chlorine dioxide in sodium chlorite process tail gas according to claim 7, characterized in that, The turbine blade (7) is composed of multiple blades. The number of blades installed and the tilt angle are linearly distributed from bottom to top. The shielding plate (8) and the type II atomizing nozzle (6) are arranged in a ring array along the center point of the water ring sleeve (2), and the shielding plate (8) is staggered relative to the blades.

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