An absorbent liquid regeneration device

Abstract

This utility model discloses an absorbent regeneration device, including a heat exchanger and a regeneration tank. The pressure chamber and the collection chamber of the heat exchanger, as well as the collection chamber and the two-phase chamber, are connected by heat exchange pipes. The exhaust port at the top of the two-phase chamber connects to a gas collecting pipe, and the rich liquid pipe at the bottom connects to the regeneration tank. The heat exchanger is divided into upper and lower heat exchange boxes with similar structures by the collection chamber, and the upper and lower heat exchange boxes are connected by a connecting pipe. The lean liquid pipe at the top of the upper heat exchange box connects to the regeneration tank. Alternating baffles are arranged inside the heat exchange boxes to improve heat exchange efficiency. The top exhaust port of the regeneration tank connects to the gas collecting pipe, and the bottom has multiple irregularly distributed protrusions. Heating elements are installed in the outer grooves of these protrusions, and heat storage elements are adhered to the inner surface. This utility model achieves absorbent regeneration under high temperature, low pressure, or slightly negative pressure conditions inside the regeneration tank, and the series connection of regeneration tanks enhances the regeneration quality.

Description

Technical Field

[0001] This invention is applied in the chemical industry and relates to an absorbent liquid for removing acidic gases from ethylene cracking gas using an absorption method, specifically an absorbent liquid regeneration device. Background Technology

[0002] During ethylene production, the cracked gas from hydrocarbon cracking needs to be compressed, have acid wash gases removed, dried, and refrigerated in a compression system. The acidic gases in the cracked gas are mainly carbon dioxide, hydrogen sulfide, and other gaseous sulfides, which are typically removed by alkaline washing or by washing with monoethanolamine and diethanolamine absorbents. The waste alkaline solution after alkaline washing needs to be treated to meet discharge standards, and the treatment cost for large quantities of waste alkaline solution is high. Ethanolamine absorbents have drawbacks such as equipment corrosion, volatility, and high regeneration energy consumption. Ionic liquids have become a hot topic in the industry as a novel acidic gas absorbent. Ionic liquids have advantages such as high thermal stability, low vapor pressure, and low corrosivity. Their vapor pressure is almost zero, resulting in minimal loss during use. They also have good absorption capacity and regeneration ability. Ionic liquids are highly designable and have ideal absorption effects, gradually becoming the main research focus for acidic gas absorption. Examples of methods include CN119499859A (a CO2 capture and absorbent, capture and regeneration device, and capture process), CN104524927A (an ionic solution for absorbing carbon dioxide gas in flue gas and its manufacturing method), CN101993378B (an amine-containing ionic liquid for absorbing acidic gases and its preparation method and application), CN114853643B (a method for preparing mercapto esters or thioethers by catalyzing the reaction of H2S with carboxylate ionic liquids), CN113582891B (a method for preparing high-value-added mercapto alcohols by catalyzing the reaction of H2S with epoxides and enols using ionic liquids as catalysts), and CN107088401B (a method for rapidly preparing CO2 adsorbents using ionic liquid additives). Absorbent regeneration is an essential step in removing acidic gases from pyrolysis gas to achieve the recycling of the absorbent. CN111054098B discloses a method and apparatus for regenerating solvents containing acidic gases. By heating the solvent with microwaves, the temperature is increased, changing the gas-liquid balance conditions inside the solvent, thereby separating the acidic gases from the solvent and achieving solvent regeneration. Utility Model Content

[0003] The technical problem solved by this utility model is to provide an absorbent regeneration device that regenerates by heating and depressurization, and saves energy by using a heat exchanger.

[0004] The technical solution adopted in this utility model is as follows: The absorbent regeneration device of this utility model includes a heat exchanger and a regeneration tank. The bottom of the heat exchanger is a pressure chamber, the middle is a collection chamber, and the top is a two-phase chamber. The pressure chamber and the collection chamber, as well as the collection chamber and the two-phase chamber, are connected by heat exchange pipes. The two-phase chamber is connected to a gas collecting pipe through an exhaust port at the top, and the bottom of the two-phase chamber is connected to the regeneration tank through a rich liquid pipe. The heat exchanger is divided into upper and lower heat exchange boxes with similar structures by the collection chamber, and the upper and lower heat exchange boxes are connected by a connecting pipe; a lean liquid outlet is provided at the bottom of the lower heat exchange box, and the top of the upper heat exchange box is connected to the regeneration tank through a lean liquid pipe. Baffles are provided inside the heat exchange boxes, and the baffles are staggered to enhance heat exchange efficiency. The upper part of the regeneration tank is connected to a rich liquid pipe, the lower part is connected to a lean liquid pipe, and the top is provided with an exhaust port, which is connected to a gas collecting pipe. The bottom of the regeneration tank is provided with multiple protrusions, and heating elements are installed in the grooves on the outside of the protrusions. Heat storage elements are adhered to the inner surface of the grooves.

[0005] Furthermore, the regeneration tank is divided into a mechanically stirred regeneration tank and a pneumatically stirred regeneration tank; the liquid stirring in the mechanically stirred regeneration tank is achieved by using a motor, stirring rod, and blades; the pneumatically stirred regeneration tank is stirred by using gas supplied through a return gas pipe; a pressure pump is installed on the return gas pipe and connected to a gas collection pipe.

[0006] Furthermore, to reduce the thickness of the laminar flow on the inner wall of the regeneration tank, the protrusions are irregularly distributed; the stirring rod is not located at the center of the mechanically stirred regeneration tank.

[0007] Furthermore, to enhance the regeneration effect of the absorbent, two regeneration tanks are arranged in series. Both regeneration tanks in series can be mechanically agitated regeneration tanks. If the two regeneration tanks are a mechanically agitated regeneration tank and a pneumatically agitated regeneration tank, the pneumatically agitated regeneration tank is placed first, followed by the mechanically agitated regeneration tank.

[0008] Furthermore, a thermocouple is installed in the groove. The thermocouple not only measures the temperature to control the power supply of the heating element, but also determines whether the protrusion is leaking.

[0009] The beneficial effects of this invention are: It achieves absorbent regeneration under high temperature, low pressure, or slightly negative pressure conditions within the regeneration tank. Connecting two regeneration tanks in series enhances the regeneration effect. Utilizing a heat exchanger saves energy. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of Example 1;

[0011] Figure 2 This is a schematic diagram of the regeneration tank structure in Example 2;

[0012] Figure 3 This is a schematic diagram of the structure of Example 3;

[0013] Attached reference numerals: 1-Heat exchanger, 2-Regeneration tank, 3-Rich liquid inlet, 4-Lean liquid outlet, 5-Baffle plate, 6-Heat exchange tube, 7-Connecting pipe, 8-Lean liquid pipe, 9-Rich liquid pipe, 10-Gas collecting pipe, 11-Return gas pipe, 12-Heating element, 13-Heat storage element, 14-Collection chamber, 15-Pressure chamber, 16-Two-phase chamber;

[0014] 21-Mechanical stirring regeneration tank, 22-Motor, 23-Stirring rod, 24-Air stirring regeneration tank. Detailed Implementation

[0015] The attached diagram does not show the pump body and valves; arrows indicate the flow direction. Dashed arrows indicate the flow direction of gas, while solid arrows indicate the flow direction of liquid. Example

[0016] The structure of the absorbent regeneration device in this embodiment is shown in the attached figure. Figure 1 As shown, it includes a heat exchanger 1 and a regeneration tank 2.

[0017] The heat exchanger 1 has a pressure chamber 15 at the bottom, a collection chamber 14 in the middle, and a two-phase chamber 16 at the top. The pressure chamber 15 and the collection chamber 14, as well as the collection chamber 14 and the two-phase chamber 16, are connected by heat exchange tubes 6. An exhaust port is located at the top of the two-phase chamber 16, connecting to a gas collecting pipe 10. At the bottom of the two-phase chamber 16, a rich liquid pipe 9 connects to a regeneration tank 2. A rich liquid inlet 3 is located on the pressure chamber 15, connecting to an acid gas absorption device. The heat exchanger is divided into two structurally similar heat exchange boxes by the middle collection chamber 14, connected by a connecting pipe 7. A lean liquid outlet 4 is located at the bottom of the lower heat exchange box, and the top of the upper heat exchange box connects to the regeneration tank 2 via a lean liquid pipe 8. Baffles 5 are installed in each heat exchange box, staggered to ensure the liquid flows in a zigzag pattern, achieving prolonged and sufficient contact with the heat exchange tubes 6 to improve heat exchange efficiency.

[0018] The regeneration tank 2 stores the rich absorbent solution, connected to the rich absorbent solution pipe 9 at the top and the lean absorbent solution pipe 8 at the bottom. An outlet is located at the top and connects to the gas collecting pipe 10. At the bottom of the regeneration tank 2, multiple protrusions are formed, with grooves on the outside. Heating elements 12 are installed within these grooves, and heat storage elements 13 are adhered to the inner surface of the grooves. The heating elements 12 are electrically heated, and thermocouples are installed within the grooves to measure temperature and control the on / off state of the heating elements. At the bottom of the regeneration tank, a return gas pipe 11 connects to the gas collecting pipe 10, and a small-flow pressure pump is installed on the return gas pipe 11.

[0019] In this embodiment, the low-temperature rich liquid from the absorption tower enters the pressure chamber 15 through the rich liquid inlet 3, flows into the collecting chamber 14 through the heat exchange tubes in the lower heat exchange box, and then flows into the two-phase chamber 16 through the heat exchange tubes in the upper heat exchange box. As the rich liquid flows through the heat exchange tubes, it exchanges heat with the regenerated lean liquid in the heat exchange box, causing the lean liquid to cool down and the rich liquid to heat up. During the heating process of the rich liquid, a small amount of the absorbed acidic gas is released, and the released acidic gas enters the gas collecting pipe 10 from the exhaust port at the top of the two-phase chamber 16. The high-temperature rich liquid after heat exchange flows into the regeneration tank 2 from the rich liquid pipe 9. Normally, the gas collecting pipe 10 and the regeneration tank 2 are under negative pressure. The bottom of the regeneration tank is heated by a heating element, raising the temperature of the high-temperature rich liquid to 110-130°C. Under high temperature and negative pressure conditions, the rich liquid releases the absorbed acidic gas, achieving the regeneration of the absorbent. The acidic gas enters the gas collecting pipe 10 from the gas outlet at the top of the regeneration tank. During the regeneration process of acidic gas precipitated from the absorbent, a pressure pump draws a small amount of gas from the gas collecting pipe 10 and sends it into the regeneration tank through the return gas pipe 11. This agitates the liquid in the regeneration tank, promoting gas precipitation and absorbent regeneration. The irregularly distributed protrusions ensure turbulent flow of the agitated liquid, preventing the formation of a laminar flow layer and accelerating the precipitation and discharge of gas from the rich liquid. After regeneration, the absorbent becomes lean liquid and enters the upper heat exchanger through the lean liquid pipe at the bottom of the regeneration tank. The high temperature of the lean liquid is transferred to the rich liquid, and the cooled lean liquid is then sent to the absorption tower through the lean liquid outlet, forming a circulation of the absorbent.

[0020] To extend the service life of the absorbent regeneration unit, the pipes, tank panels, and other components in contact with the rich solution should be made of acid-resistant organic polymers, such as polytetrafluoroethylene (PTFE) or polypropylene (PP). The heat storage components should be made of refractory materials, and the bottom of the regeneration tank should be bonded with high-temperature adhesive. Within the temperature range where an object does not glow red, conduction is the most efficient heat transfer method. Although the thermal conductivity of the high-temperature adhesive is lower than that of metal, it is still higher than that of air, preventing thermal resistance from gaps. Furthermore, even if the tank bottom bulges and leaks, the liquid will lower the temperature of the heat storage components, which will be reflected in the thermocouple readings and will not affect the normal operation of the heating elements. Given the relatively low corrosiveness of the absorbent, to increase the heat exchange efficiency of the heat exchange tubes, metal tubes should be used. A thin layer of PTFE or PP coating should be applied to the inner surface of the metal tubes for corrosion protection.

[0021] The heat exchanger has an upper and lower box structure with a collection cavity in the middle. This structure serves several purposes: first, it reduces the length of the heat exchange tubes, facilitating the manufacture of metal heat exchange tubes lined with anti-corrosion coatings; second, it reduces the thermal expansion stress of the heat exchange tubes, preventing stress damage; and third, during the process of increasing the temperature of the rich liquid heat exchanger, it helps the precipitated acidic gas to concentrate into large bubbles. Example

[0022] In Example 1, the liquid in the regeneration tank is stirred using acidic gas supplied through the return gas pipe 11. The regeneration tank is a gas-stirred regeneration tank. The supplied acidic gas increases the gas pressure inside the regeneration tank, which has the drawback of affecting the regeneration effect of the absorbent. This example uses mechanical stirring, and the regeneration tank is a mechanically stirred regeneration tank 21, the structure of which is shown in the attached figure. Figure 2 As shown. The heating element 12 and heat storage element 13 at the bottom of the regeneration tank are the same as in Example 1. A stirring motor 22 is installed on the top plate. The stirring rod 23 connected to the motor 22 is sealed to the top plate. Blades are installed on the stirring rod 23. The rotating blades stir the liquid in the regeneration tank 21.

[0023] The stirring rod 23 should not be placed in the center of the regeneration tank to minimize the thickness of the laminar flow formed on the inner wall of the regeneration tank.

[0024] In this embodiment, the gas pressure inside the mechanically stirred regeneration tank 21 is basically the same as that inside the gas collecting pipe 10, which is lower than the gas pressure in the regeneration tank in embodiment 1. This is beneficial for the precipitation of acidic gas and the regeneration of the absorbent liquid. Example

[0025] In the above embodiment, there was only one regeneration tank, resulting in a small amount of incomplete regeneration of the rich solution, which flowed into the upper heat exchanger from the lean solution pipe, affecting the regeneration effect of the absorbent. This embodiment uses two regeneration tanks connected in series, as shown in the attached diagram. Figure 3 As shown. The two regeneration tanks can be a pneumatic regeneration tank 24 and a mechanical regeneration tank 21 connected in series, preferably with the pneumatic regeneration tank 24 first and the mechanical regeneration tank 21 second. Alternatively, two mechanical regeneration tanks 21 can be connected in series.

[0026] Compared to the two embodiments described above, this embodiment extends the time the rich solution spends in the regeneration tank, allowing for two stirring stages to separate the precipitate, thus improving the regeneration quality of the absorbent. The more thorough the absorbent regeneration, the less corrosive it is to the metal heat exchange tubes, and the more beneficial it is for absorbing acidic gases.

[0027] This invention utilizes a heat exchanger to save energy. The high temperature, low pressure, or slight negative pressure inside the regeneration tank cause acidic gases to rapidly precipitate from the rich liquid, achieving regeneration of the absorbent. Two regeneration tanks are connected in series to enhance the quality of absorbent regeneration.

Claims

1. An absorbent regeneration device, characterized in that: Including heat exchangers and regeneration tanks; The heat exchanger has a pressure chamber (15) at the bottom, a collection chamber (14) in the middle, and a two-phase chamber (16) at the top. The pressure chamber (15) and the collection chamber (14), as well as the collection chamber (14) and the two-phase chamber (16), are connected by heat exchange tubes (6). The two-phase chamber (16) is connected to a gas collection tube (10) through an exhaust port at the top. At the bottom of the two-phase chamber (16), it is connected to a regeneration tank through a rich liquid tube (9). The heat exchanger is divided into an upper heat exchange box and a lower heat exchange box with similar structures by the collection chamber (14). The upper heat exchange box and the lower heat exchange box are connected by a connecting pipe (7). The bottom of the lower heat exchange box is provided with a lean liquid outlet (4). The top of the upper heat exchange box is connected to the regeneration tank through a lean liquid tube (8). The heat exchange box is provided with partitions, which are staggered. The upper part of the regeneration tank is connected to the rich liquid pipe (9), the lower part is connected to the poor liquid pipe (8), and the top is provided with an air outlet, which is connected to the gas collection pipe (10); the bottom of the regeneration tank is provided with a protrusion, and a heating element (12) is provided in the groove outside the protrusion, and a heat storage element (13) is adhered to the inner surface of the groove.

2. The absorbent regeneration device according to claim 1, characterized in that: The regeneration tank is divided into a mechanically stirred regeneration tank and a pneumatically stirred regeneration tank. The liquid stirring in the mechanically stirred regeneration tank is achieved by using a motor, stirring rod, and blades. The pneumatically stirred regeneration tank is stirred by using gas fed into the gas return pipe (11). A pressurizing pump is installed on the gas return pipe (11) and connected to the gas collection pipe (10).

3. The absorbent regeneration device according to claim 2, characterized in that: The protrusions are irregularly distributed; the stirring rod is not located at the center of the mechanically stirred regeneration tank.

4. The absorbent regeneration device according to claim 2, characterized in that: The two regeneration tanks are connected in series.

5. The absorbent regeneration device according to claim 4, characterized in that: Both of the aforementioned regeneration tanks are mechanically stirred regeneration tanks.

6. The absorbent regeneration device according to claim 4, characterized in that: The two regeneration tanks are a mechanically stirred regeneration tank and a pneumatically stirred regeneration tank, with the pneumatically stirred regeneration tank in front and the mechanically stirred regeneration tank behind.

7. The absorbent regeneration device according to claim 1, characterized in that: A thermocouple is installed inside the groove.

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