Dual-purpose ammonia desulfurization and ammonia adding tank for ammonia water and ammonia gas

Abstract

The application discloses an ammonia-water / ammonia dual-purpose ammonia desulfurization and ammonia adding tank, which comprises an ammonia adding tank body, an ammonia adding port and a reflux liquid inlet respectively arranged at the bottom and the top of the ammonia adding tank body, and an ammonia distributor, a wire mesh demister, a reflux liquid distributor and a pipeline mixer sequentially arranged in the ammonia adding tank body from bottom to top. The ammonia adding port is communicated with the ammonia distributor through a pipeline, and the reflux liquid inlet is communicated with the pipeline mixer and the reflux liquid distributor. The ammonia-water can be introduced to carry out a desulfurization reaction, and the ammonia gas can be directly introduced. The ammonia gas is mixed with the desulfurization liquid returned from a desulfurization tower through a special spray gun and a mixing structure in the tank body to generate a high-concentration ammonia water solution, which is then pumped into the desulfurization tower by a circulating pump to participate in the desulfurization reaction, so that the ammonia gas can quickly and stably participate in the desulfurization system reaction.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization, specifically to an ammonia desulfurization tank that can be used for both ammonia water and ammonia gas. Background Technology

[0002] Ammonia desulfurization is a commonly used flue gas desulfurization method in thermal power plants. Sulfur dioxide in the flue gas reacts with ammonia water to form ammonium sulfate, thereby removing the harmful sulfur dioxide gas from the flue gas. How to add ammonia to the desulfurization system is a core issue in the ammonia desulfurization process.

[0003] Traditional ammonia-based desulfurization processes generally do not have an ammonia charging tank. The ammonia charging process involves injecting a pre-mixed ammonia solution (approximately 12% concentration) into the oxidation section of the desulfurization tower via pipeline. After the ammonia solution mixes and reacts with the desulfurization reaction liquid in the oxidation section, it is then injected into the absorption section of the desulfurization tower via a dedicated pump set for spraying, reacting with sulfur dioxide in the flue gas to remove it. The disadvantages of this desulfurization process are its slow reaction time and long settling time. Due to the large internal volume of the oxidation section, typically exceeding 600 m³, it takes a considerable amount of time for the ammonia solution to mix evenly with the desulfurization liquid after injection. In emergency situations where sulfur dioxide levels in the exhaust gas exceed the standard, using this method to reduce sulfur dioxide levels takes a very long time, and even after the sulfur dioxide levels decrease, escaped ammonia levels often exceed the standard, making control difficult.

[0004] In Chinese patent CN210645809U, an ammonia addition tank was created within the oxidation section of the desulfurization tower using a baffle plate. This significantly improved the desulfurization adjustment effect and speed. However, after a period of operation, some issues were identified that require improvement. The ammonia addition tank, located inside the desulfurization tower, suffers from poor equipment visibility and inconvenient maintenance. Furthermore, the ammonia-desulfurization reaction liquid mixer has a high failure rate, and the ammonia distribution is uneven, affecting the desulfurization reaction rate and consequently the desulfurization effect, thus impacting the sulfur dioxide levels in the exhaust gas.

[0005] Traditional ammonia-based desulfurization processes require the purchase of liquid ammonia for ammonia water preparation. This liquid ammonia is stored in tanks, and when needed, it is diluted with water to create a 12% ammonia solution. A liquid ammonia storage tank exceeding 10 tons constitutes a major hazard, requiring stringent setup, operation, and maintenance, which severely impacts the safety of surrounding production facilities. If the storage capacity is too small, or if 12% ammonia water is purchased directly, significant time and expense are incurred in the frequent procurement and transportation of liquid ammonia and ammonia water. Furthermore, the ammonia desulfurization system requires a continuous supply of ammonia water during operation; insufficient ammonia water storage threatens its normal operation. If ammonia gas could be directly used in the desulfurization system, these problems would not exist. However, currently, there are almost no processes that allow direct use of ammonia gas for desulfurization. Therefore, the key to solving these problems lies in how to quickly, continuously, and stably convert ammonia gas into an ammonia solution, thereby enabling a continuous supply of this solution to the desulfurization system for the desulfurization reaction. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide an ammonia addition tank for ammonia-based desulfurization that can be used for both ammonia water and ammonia gas. This tank can either introduce ammonia water for the desulfurization reaction or directly introduce ammonia gas. The ammonia gas is mixed with the desulfurization liquid returning from the desulfurization tower through a unique spray gun and mixing structure inside the tank, generating a high-concentration ammonia solution. This solution is then pumped into the desulfurization tower via a circulating pump to participate in the desulfurization reaction, thereby achieving the goal of rapid and stable participation of ammonia gas in the desulfurization system reaction. This completely eliminates the hazard of liquid ammonia storage tanks, ensuring the safety of the equipment and operators, saving time and transportation costs associated with frequent ammonia water purchases, simplifying the ammonia addition process, and enabling ammonia gas to be directly used in ammonia-based desulfurization enterprises, ensuring the long-term stable operation of the desulfurization system.

[0007] To solve the aforementioned technical problem, the technical solution adopted by the present invention is: an ammonia desulfurization ammonia addition tank for both ammonia water and ammonia gas, comprising an ammonia addition tank body, an ammonia addition port and a reflux liquid inlet located at the bottom and top of the ammonia addition tank body respectively, and an ammonia distributor, a wire mesh demister, a reflux liquid distributor and a pipeline mixer arranged sequentially from bottom to top inside the ammonia addition tank body. The ammonia addition port is connected to the ammonia distributor through a pipeline, and the reflux liquid inlet is connected to the pipeline mixer and the reflux liquid distributor.

[0008] Furthermore, the ammonia distributor is a circular distribution plate composed of 6 spray gun main pipes I arranged at a 60° angle. The end of the spray gun main pipe I away from the center is closed, and the end of the spray gun main pipe I near the center is connected to the ammonia inlet. Each spray gun main pipe I has two rows of upward-facing ammonia outlet holes.

[0009] Furthermore, the angle between the ammonia outlet and the horizontal direction is 60°.

[0010] Furthermore, the reflux distributor is a circular distribution plate composed of four spray gun main pipes II arranged at a 90° angle. The end of the spray gun main pipe II away from the center is closed, and the end of the spray gun main pipe II near the center is connected to the reflux inlet. Each spray gun main pipe II has three rows of downward reflux outlets.

[0011] Furthermore, one row of return fluid outlets is located directly below the spray gun main pipe II, and the other two rows of return fluid outlets are at an angle of 45° to the horizontal direction.

[0012] Furthermore, the pipe mixer is a spiral finned pipe mixer, which is a combined type, divided into three parts from top to bottom. The first part is an acute-angled fin with a spiral angle of 30°. There are a total of 6 acute-angled fins on the cross-section of the mixer. The acute-angled fins have a first circular hole. The second part is a spiral fan blade with a total of 5 blades, which are evenly distributed around the central fully sealed bearing. The third part is an inclined fin with a spiral angle of 45°. There are a total of 4 inclined fins on the cross-section of the mixer. The inclined fins have a second circular hole.

[0013] Furthermore, the diameter of the first circular hole is 6mm, and the diameter of the second circular hole is 4mm.

[0014] Furthermore, a buffer chamber is provided between the ammonia inlet and the ammonia distributor, and the ammonia inlet and the ammonia distributor are connected through the buffer chamber.

[0015] Furthermore, the reflux inlet is an inner tube, the reflux distributor is located at the end of the reflux inlet, and the pipeline mixer is located 1 / 3 of the distance from the end of the reflux inlet.

[0016] The beneficial effects of this invention are: The ammonia charging tank is independently set up, making equipment management better and maintenance more convenient. An ammonia distributor is installed at the bottom of the ammonia charging tank. Ammonia water is evenly distributed through the ammonia distributor and participates in the desulfurization oxidation-reduction reaction. Alternatively, ammonia gas can be directly introduced into the ammonia charging tank. The ammonia gas passes through the ammonia distributor and mixes with the reflux liquid in the ammonia charging tank to prepare ammonia water, which then participates in the desulfurization oxidation-reduction reaction. After passing through the ammonia distributor, the ammonia water and ammonia gas are more evenly distributed, reducing the ammonia escape rate to less than 1%, thus improving utilization. A reflux liquid distributor is installed at the top of the ammonia charging tank, and a spiral finned pipe mixer is installed inside the reflux pipe to fully turbulently and evenly mix the desulfurization reflux liquid for further reaction with ammonia gas. The reflux liquid is evenly sprayed onto the cross-sectional area of ​​the ammonia charging tank through the reflux liquid distributor, effectively capturing escaped ammonia. A wire mesh demister is installed between the ammonia distributor and the reflux liquid distributor to increase the contact surface area between the reflux liquid and ammonia gas, ultimately reducing the overall ammonia escape rate to less than 0.1%. Meanwhile, the reflux liquid mixes more evenly with the ammonia water, increasing the rate of the redox reaction. The heat released when ammonia dissolves in water does not require an additional radiator; it is cooled through its own circulation, achieving heat release in a circular manner.

[0017] After being put into operation, this invention can be used for both ammonia water and ammonia gas, with flexible switching and convenient operation. The ammonia distributor minimizes ammonia escape and maximizes utilization. It completely eliminates the danger posed by liquid ammonia storage tanks, ensuring the safety of the equipment and operators, saving time and transportation costs associated with frequent ammonia water purchases, simplifying the ammonia addition process, and enabling ammonia gas to be directly used in ammonia-based desulfurization enterprises, ensuring long-term stable operation of the desulfurization system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the ammonia charging tank described in this invention;

[0019] Figure 2 This is a schematic diagram of an ammonia distributor.

[0020] Figure 3 This is a schematic diagram of the ammonia orifice on the ammonia distributor;

[0021] Figure 4 This is a schematic diagram of the reflux liquid distributor;

[0022] Figure 5 This is a schematic diagram of the reflux outlet on the reflux distributor;

[0023] Figure 6 Schematic diagram of a spiral finned pipe mixer;

[0024] In the diagram: 1. Ammonia tank body, 2. Ammonia inlet, 3. Buffer chamber, 4. Ammonia distributor, 5. Wire mesh demister, 6. Return liquid inlet, 7. Return liquid distributor, 8. Pipe mixer, 9. Spray gun main pipe I, 10. Ammonia outlet, 11. Spray gun main pipe II, 12. Return liquid outlet, 13. Acute-angle spiral fins, 14. Spiral fan blades, 15. Fully sealed bearing, 16. Inclined spiral fins. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] This invention discloses an ammonia addition tank for ammonia desulfurization that can be used for both ammonia water and ammonia gas. The ammonia addition tank is independently set up, making the equipment easier to manage and more convenient to maintain. Figure 1 As shown, the ammonia charging tank includes an ammonia charging tank body 1, an ammonia charging port 2 located at the bottom and top of the ammonia charging tank body 1 respectively, and a reflux liquid inlet 6. Inside the ammonia charging tank body 1, an ammonia distributor 4, a wire mesh demister 5, a reflux liquid distributor 7, and a pipeline mixer 8 are arranged sequentially from bottom to top. The ammonia charging port 2 is connected to the ammonia distributor 4 via a pipeline, and the reflux liquid inlet 6 is connected to the pipeline mixer 8 and the reflux liquid distributor 7.

[0027] Ammonia inlet 2 is used to introduce ammonia water or ammonia gas. The pipe diameter of ammonia inlet 2 is determined according to the flow rate of ammonia water or ammonia gas. The flow velocity of ammonia water does not exceed 1 m / s, and the flow velocity of ammonia gas does not exceed 12 m / s. The process for adding ammonia gas is the same as that for adding ammonia water. A buffer chamber 3 is provided between ammonia inlet 2 and ammonia distributor 4. Ammonia inlet 2 is connected to buffer chamber 3 through a straight pipe section. After a brief buffer in buffer chamber 3, ammonia water enters ammonia distributor 4 for uniform distribution. After being uniformly distributed by ammonia distributor 4, ammonia gas mixes with the reflux liquid in the ammonia tank to prepare ammonia water, which then participates in the desulfurization oxidation-reduction reaction. After passing through ammonia distributor 4, the distribution of ammonia water and ammonia gas is more uniform, the ammonia slip rate is reduced to less than 1%, and the ammonia utilization rate is improved.

[0028] like Figure 2 , 3 As shown, the ammonia distributor 4 is a circular distribution plate composed of six spray gun manifolds I9 arranged at a 60° angle. The ends of the spray gun manifolds I9 furthest from the center are closed, while the ends of the spray gun manifolds I9 closest to the center are connected to the ammonia inlet 2. Each spray gun manifold I9 has two rows of upward-facing ammonia outlet holes 10. The angle between the ammonia outlet holes 10 and the horizontal direction is 60°. This ammonia outlet hole diameter and angle are the optimal schemes obtained after calculation by FLUENT computer flow field simulation software. After the ammonia water is distributed through the ammonia distributor 4, it can fully mix with the process liquid in the ammonia tank to carry out the desulfurization oxidation-reduction reaction.

[0029] The reflux inlet 6 is used to introduce reflux liquid. The diameter of the reflux inlet 6 is determined according to the flow rate of the reflux liquid, and the flow velocity of the reflux liquid is 1.5-2 m / s. The reflux inlet 6 is an inner extension pipe. A spiral finned pipe mixer 8 is installed at 1 / 3 of the distance from the end of the inner extension pipe. The purpose of the pipe mixer 8 is to fully agitate and mix the desulfurization reaction liquid returning from the desulfurization tower, and at the same time, to ensure that the chemical reaction that was not completely reacted in the desulfurization tower: (NH4)2SO3 + SO2 + H2O = 2NH4HSO3 is completely reacted, so as to further react with ammonia.

[0030] like Figure 6As shown, the spiral finned pipe mixer 8 is a combined type, divided into three parts from top to bottom. The first part consists of acute-angled fins 13 with a spiral angle of 30°. There are six fins in the cross-section of the mixer, with circular holes of 6mm diameter on each fin. This structure allows the reflux liquid returning from the desulfurization tower to rotate and mix fully. The holes on the fins reduce fin resistance, ensuring smooth gravity flow of the mixed liquid. The second part consists of five spiral fan blades 14, evenly distributed around a central fully sealed bearing 15. The reflux liquid from the acute-angled fins 13 rapidly impacts the spiral fan blades 14, causing them to rotate rapidly and throw the reflux liquid onto the inner wall of the pipe, creating a strong convection state and resulting in more uniform liquid mixing. The fully sealed bearing 15 ensures continuous high-speed rotation of the fan blades, reducing gravity flow resistance and preventing liquid accumulation and blockage of the mixer. The third part consists of four inclined fins 16 with a helical angle of 45°. The mixer cross-section has four fins, each with a 4mm diameter circular hole. This structure allows the high-speed rotating reflux liquid to break the strong convection state, gradually dividing the reflux liquid into four streams for distribution before the reflux liquid distributor 7. The holes in the fins reduce fin resistance, allowing liquid to flow between the four channels and stabilizing the fully mixed reflux liquid.

[0031] The reflux inlet 6 is connected to the reflux distributor 7 at its end, such as... Figure 4 , 5 As shown, the reflux distributor 7 is a circular distribution plate composed of four spray gun manifolds II11 arranged at a 90° angle. The ends of the spray gun manifolds II11 furthest from the center are closed, while the ends of the spray gun manifolds II11 closest to the center are connected to the reflux inlet 6. Each spray gun manifold II11 has three rows of downward-facing reflux outlets 12. One row of reflux outlets 12 is located directly below the spray gun manifold II11, while the other two rows of reflux outlets 12 form an angle of 45° with the horizontal direction. The orifice diameter and angle of the reflux outlets 12 are optimized schemes obtained after calculation using FLUENT computer flow field simulation software. After being distributed by the reflux distributor 7, the reflux liquid is evenly sprayed onto the transverse cross-section of the ammonia charging tank.

[0032] The wire mesh demister 5 is positioned at half the distance between the ammonia distributor 4 and the reflux liquid distributor 7. This demister 5 allows the uniformly sprayed reflux liquid to flow evenly on the outer wall of the wire mesh, reacting with the evenly distributed upward-flowing ammonia gas. It effectively captures any small amount of escaping ammonia after passing through the ammonia distributor, increasing the contact surface area between the reflux liquid and ammonia gas, ultimately reducing the overall ammonia escape rate to below 0.1%. Simultaneously, the reflux liquid (mainly composed of NH4HSO3) mixes more evenly with the ammonia water, promoting the rapid chemical reaction: NH4HSO3 + NH3 = (NH4)2SO3. This facilitates the large-scale entry of NH4HSO3 solution into the desulfurization tower absorption section via the circulating pump for desulfurization, with the reaction equation: (NH4)2SO3 + SO2 + H2O = 2NH4HSO3. This significantly increases the redox reaction rate, thereby improving the overall desulfurization efficiency of the desulfurization system.

[0033] Furthermore, since the dissolution of ammonia in water is an exothermic reaction, this invention eliminates the need for a heat sink. Instead, the fully reacted hot mixture is directly pumped into the desulfurization tower via a circulating pump. Inside the tower, the mixture undergoes a chemical reaction and heat transfer with the flue gas. The high-temperature mixture is cooled, and the cooled mixture is then returned to the ammonia charging tank to dissolve the ammonia, thus creating a heat cycle. The hot flue gas, after heat exchange, is discharged from the desulfurization system through a chimney.

[0034] Comparative Example 1: Ammonia-based desulfurization plant A purchases liquid ammonia from a synthetic ammonia production plant and then uses a 12% ammonia solution for desulfurization. Due to the large volume of boiler flue gas, a large amount of ammonia solution is used daily, and the liquid ammonia storage tank has a capacity exceeding 10 tons. This adds one major hazard source, which is regularly monitored by the local special equipment regulatory authority. The safety distance requirements between the major hazard source and surrounding production facilities are high, requiring it to be far away from production facilities and surrounding residential areas. This increases the plant's land area usage and poses serious safety hazards to the surrounding area.

[0035] Comparative Example 2: Company B, using the ammonia-based desulfurization method, directly purchases 12% ammonia water from the synthetic ammonia production plant for desulfurization. Due to the large volume of ammonia water used, frequent purchases are necessary, resulting in significant time and effort spent on logistics. Furthermore, ammonia water is primarily water, and its price is relatively high, leading to high operating costs and poor economic viability for the company.

[0036] Comparative Example 3: Ammonia desulfurization enterprise C is located in a comprehensive chemical industrial park. The park contains ammonia synthesis units, which produce ammonia gas. As in Example 1, purchasing liquid ammonia would require constructing large liquid ammonia spherical tanks (with a storage capacity of over 500 tons) around the ammonia synthesis production unit, constituting a major hazard source. This effectively transfers the major hazard source to the ammonia synthesis production enterprise, without eliminating the hazard itself. Similarly, as in Example 2, purchasing 12% ammonia water would require setting up a liquid ammonia storage tank area before proportioning and selling it.

[0037] Example 1: Ammonia desulfurization plant D is located in a comprehensive chemical industrial park. An ammonia gas pipeline is directly connected from the synthetic ammonia production plant to the ammonia charging tank. Two branches are installed on the external pipeline connecting to the ammonia charging port at the bottom of the tank. One branch connects to an ammonia solution (as a backup pipeline in case of an abnormal ammonia gas outage), and the other connects to the ammonia gas pipeline. A check valve is added before the two branches merge into the external main pipe of the ammonia charging tank to prevent cross-contamination between the ammonia solution and the ammonia gas pipeline. The diameter of the ammonia charging port at the bottom of the tank is DN150, the flow velocity of the ammonia solution is 0.92 m / s, and the flow velocity of the ammonia gas is 11.4 m / s. The ammonia charging port is connected to a buffer chamber via a straight pipe section. The buffer chamber is a DN350 pipe section. After a brief buffering in the buffer chamber, the ammonia solution / gas enters the ammonia distributor for uniform distribution. The ammonia distributor consists of six spray gun main pipes I arranged at a 60° angle, each with a diameter of DN150. Each spray gun main pipe I has two rows of holes diagonally upwards, 30 holes per row, with a hole diameter of 8mm. The angle between these two rows of holes and the 90° angle directly above is 30°. Figure 5 After being distributed by the ammonia distributor, ammonia water / ammonia gas can be fully mixed with the process liquid in the ammonia charging tank to carry out desulfurization oxidation-reduction reactions. After passing through the ammonia distributor, the distribution of ammonia water and ammonia gas is more uniform and the ammonia utilization rate is higher. A reflux liquid inlet is set at the top of the ammonia charging tank. The reflux liquid inlet pipe diameter is DN500, and the reflux liquid flow velocity is 1.83m / s. After being disturbed by the spiral finned pipe mixer, the reflux liquid enters the end reflux liquid distributor. The reflux liquid distributor consists of four spray gun main pipes II arranged at a 90° angle. The diameter of spray gun main pipes II is DN200. Each spray gun main pipe II has three rows of holes facing upwards, with 20 holes in each row. The hole diameter is 36mm. These three rows of holes are at a 90° angle directly above and at a 45° angle to the 90° angle directly above. Figure 3 (Opening) The reflux liquid is distributed through a reflux liquid distributor and then evenly sprayed onto the transverse cross-section of the ammonia charging tank. A wire mesh demister is installed between the ammonia distributor and the reflux liquid distributor to increase the contact surface area between the reflux liquid and ammonia gas, ultimately reducing the overall ammonia escape rate to below 0.1%. Simultaneously, the reflux liquid and ammonia water mix more evenly, improving the oxidation-reduction reaction rate. This essentially achieves the goal of directly introducing ammonia gas into ammonia-based desulfurization plant.

Claims

1. An ammonia desulfurization tank that can be used for both ammonia water and ammonia gas, characterized in that: It includes an ammonia charging tank body, an ammonia charging port and a reflux inlet located at the bottom and top of the ammonia charging tank body respectively, and an ammonia distributor, a wire mesh demister, a reflux distributor and a pipeline mixer arranged in sequence from bottom to top inside the ammonia charging tank body. The ammonia charging port is connected to the ammonia distributor through a pipeline, and the reflux inlet is connected to the pipeline mixer and the reflux distributor.

2. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 1, characterized in that: The ammonia distributor is a circular distribution plate composed of 6 spray gun main pipes I arranged at a 60° angle. The end of the spray gun main pipe I away from the center is closed, and the end of the spray gun main pipe I near the center is connected to the ammonia inlet. Each spray gun main pipe I has two rows of upward-facing ammonia outlet holes.

3. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 2, characterized in that: The angle between the ammonia outlet and the horizontal direction is 60°.

4. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 1, characterized in that: The reflux distributor is a circular distribution plate composed of four spray gun main pipes II arranged at a 90° angle. The end of the spray gun main pipe II away from the center is closed, and the end of the spray gun main pipe II near the center is connected to the reflux inlet. Each spray gun main pipe II has three rows of downward reflux outlets.

5. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 4, characterized in that: One row of return fluid outlets is located directly below the spray gun main pipe II, and the other two rows of return fluid outlets are at an angle of 45° to the horizontal direction.

6. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 1, characterized in that: The pipe mixer is a spiral finned pipe mixer, which is a combined type, divided into three parts from top to bottom. The first part consists of acute-angled fins with a spiral angle of 30°, with a total of 6 acute-angled fins on the cross-section of the mixer. The acute-angled fins have a first circular hole. The second part consists of spiral fan blades, with a total of 5 spiral fan blades evenly distributed around a central fully sealed bearing. The third part consists of inclined fins with a spiral angle of 45°, with a total of 4 inclined fins on the cross-section of the mixer. The inclined fins have a second circular hole.

7. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 6, characterized in that: The diameter of the first circular hole is 6mm, and the diameter of the second circular hole is 4mm.

8. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 1, characterized in that: A buffer chamber is provided between the ammonia inlet and the ammonia distributor, and the ammonia inlet and the ammonia distributor are connected through the buffer chamber.

9. The ammonia desulfurization tank for both ammonia water and ammonia gas as described in claim 1, characterized in that: The reflux inlet is an inner tube, the reflux distributor is located at the end of the reflux inlet, and the pipeline mixer is located 1 / 3 of the distance from the end of the reflux inlet.

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