A process for removing carbon dioxide from a fischer-tropsch tail gas

Abstract

The present disclosure relates to a method for removing carbon dioxide in Fischer-Tropsch synthesis tail gas, which makes the micro-bubble generator immerse in the carbon-rich liquid, and the Fischer-Tropsch synthesis tail gas generates a large number of micro-bubbles in the carbon-rich liquid through the micro-bubble generator, which can make the gas-liquid fully contact, and further improve the decarburization effect. At the same time, the reaction between the activator in the fresh decarburization liquid and the oxygen-containing organic matter in the Fischer-Tropsch synthesis tail gas can reduce the viscosity of each solution in the carbon dioxide absorption tower, and under the action of the micro-bubble generator, more micro-bubbles can be stably generated, which can accelerate the absorption rate of carbon dioxide and further improve the decarburization effect.

Description

Technical Field

[0001] This disclosure relates to the field of exhaust gas decarbonization, and more specifically, to a method for removing carbon dioxide from Fischer-Tropsch synthesis exhaust gas. Background Technology

[0002] Fischer-Tropsch synthesis is a chemical process that produces higher-carbon hydrocarbons from coal, natural gas, or other carbon-containing materials via syngas production, and it is an important coal-to-oil technology route. Fischer-Tropsch synthesis can be divided into two categories: iron-based Fischer-Tropsch synthesis and cobalt-based Fischer-Tropsch synthesis. Iron-based Fischer-Tropsch synthesis is a process that uses iron-based catalysts, and most industrial Fischer-Tropsch synthesis plants employ iron-based catalysts.

[0003] Iron-based Fischer-Tropsch synthesis has advantages such as readily available catalyst raw materials, low cost, and less stringent requirements on the sulfur content of the syngas. However, it exhibits high carbon dioxide selectivity. Therefore, iron-based Fischer-Tropsch synthesis is typically accompanied by a tail gas decarbonization system. Carbon dioxide removal processes mainly include low-temperature methanol washing, hot potassium hydroxide, and pressure swing adsorption (PSA). Low-temperature methanol washing operates at low temperatures, requiring high-quality equipment and piping materials, numerous heat exchangers, a complex process, and significant investment. PSA can operate at ambient temperature and pressure and has a high degree of automation; however, hydrocarbon molecules in the Fischer-Tropsch synthesis tail gas can damage the molecular sieve adsorbent in the PSA process, and it has very strict requirements on the water content of the tail gas, making it unsuitable for decarbonization of Fischer-Tropsch synthesis tail gas.

[0004] Existing industrial plants generally use the hot potassium alkali decarbonization process. Although the hot potassium alkali decarbonization process has advantages such as low solution price, strong absorption capacity, high purity of regenerated gas, high degree of decarbonization, and low loss of hydrocarbon molecules, it still has problems such as insufficient gas-liquid contact and uneven liquid distribution, which limit the processing capacity and decarbonization effect of the decarbonization device and reduce operational flexibility. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for removing carbon dioxide from the tail gas of Fischer-Tropsch synthesis, in order to solve the problems of poor decarbonization effect and poor operational flexibility caused by insufficient gas-liquid contact and uneven liquid distribution in the prior art.

[0006] To achieve the above objectives, this disclosure provides a method for removing carbon dioxide from Fischer-Tropsch synthesis tail gas, the method comprising: The carbon-lean liquid and semi-carbon-lean liquid are respectively introduced into the carbon dioxide absorption tower from the upper and middle parts, and contacted countercurrently with the Fischer-Tropsch synthesis tail gas to obtain decarbonized tail gas and carbon-rich liquid; the carbon-rich liquid is introduced into a first desorption tower for first separation to obtain the semi-carbon-lean liquid and first regeneration gas; a portion of the semi-carbon-lean liquid is introduced into a second desorption tower for second separation to obtain decarbonized liquid and second regeneration gas; the decarbonized liquid is mixed with fresh decarbonized liquid to form the carbon-lean liquid; During the countercurrent contact process, the Fischer-Tropsch synthesis tail gas is passed through the microbubble generator at the bottom of the carbon dioxide absorption tower to form microbubbles. The fresh decarbonation solution comprises potassium carbonate, an activator, and water; the activator comprises one or more of ethanolamine, piperazine, diisopropanolamine, and 1-aminopropyl-3-methylimidazolium bromide. The viscosity of the lean carbon liquid at 20°C is 0.00005-0.0007 Pa·s, and the average particle size of the microbubbles is 200-1500 μm.

[0007] Optionally, the carbon number index of the lean liquor is 1.2-1.3, and the carbon number index of the semi-lean liquor is 1.4-1.5.

[0008] Optionally, based on the total weight of the fresh decarbonated liquid, the content of potassium carbonate is 20-45% by weight, the content of the activator is 5-15% by weight, and the content of water is 40-75% by weight.

[0009] Optionally, the carbon dioxide absorption tower includes a shell, a gas chamber partition plate, the microbubble generator, structured packing, and a liquid distributor; the gas chamber partition plate, the microbubble generator, the structured packing, and the liquid distributor are disposed inside the shell; The gas chamber partition plate is disposed at the lower part of the shell to divide the internal cavity of the shell into a gas chamber and a decarbonization chamber from bottom to top; the gas chamber partition plate is provided with a Fischer-Tropsch synthesis tail gas through hole; the inlet of the microbubble generator is connected to the Fischer-Tropsch synthesis tail gas through hole so that the Fischer-Tropsch synthesis tail gas in the gas chamber enters the decarbonization chamber through the microbubble generator; The decarbonization chamber is provided with a first structured packing layer, a first liquid distributor, a second structured packing layer, and a second liquid distributor in sequence from bottom to top; The bottom of the gas chamber is provided with a Fischer-Tropsch synthesis tail gas inlet for communication with the Fischer-Tropsch synthesis tail gas source; the lower part of the decarbonization chamber is provided with a carbon-rich liquid outlet, which is connected to the inlet of the first desorption tower; the inlet of the first liquid distributor extends to the outside of the shell to form a semi-carbon-lean liquid inlet; the inlet of the second liquid distributor extends to the outside of the shell to form a carbon-lean liquid inlet.

[0010] Optionally, the microbubble generator is made of porous ceramic material.

[0011] Optionally, the pore size of the porous ceramic material is 100-900 μm.

[0012] Optionally, the packings in the first structured packing layer and the second structured packing layer each independently include mesh corrugated packing and / or plate corrugated packing.

[0013] Optionally, the flow rate ratio of the semi-lean carbon liquid returned to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is (0.5-2):1.

[0014] Optionally, the operating conditions of the carbon dioxide absorption tower include: a temperature of 60-105℃, a pressure of 1.5-3.0MPa, and an empty tower gas velocity of 0.1-0.9m / s.

[0015] Optionally, the operating conditions of the first desorption tower include: a temperature of 100-130℃ and a pressure of 130-260kPa; the operating conditions of the second desorption tower include: a pressure of 1-20kPa and a temperature of 90-120℃.

[0016] The above technical solution involves immersing the microbubble generator in a carbon-rich liquid. The Fischer-Tropsch synthesis tail gas generates a large number of microbubbles in the carbon-rich liquid, ensuring sufficient gas-liquid contact and thus improving the decarbonization effect. Simultaneously, the activator in the fresh decarbonization liquid reacts with the oxygen-containing organic matter in the Fischer-Tropsch synthesis tail gas, reducing the viscosity of various solutions in the carbon dioxide absorption tower. Under the action of the microbubble generator, more microbubbles are stably generated, accelerating the carbon dioxide absorption rate and further enhancing the decarbonization effect.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a system for removing carbon dioxide from the tail gas of Fischer-Tropsch synthesis.

[0019] Figure 2 This is a schematic diagram of a carbon dioxide absorption tower disclosed herein.

[0020] Figure 3 This is a schematic diagram of a microbubble generator disclosed herein.

[0021] Explanation of reference numerals in the attached figures 1. Carbon dioxide absorption tower; 2. Heat exchanger; 3. First desorption tower; 4. Second desorption tower; 5. Concentrate pump; 6. Semi-lean carbon liquid pump; 7. Feed pump; 8. Lean carbon liquid pump; 9. Lean carbon liquid tank; 10. Regeneration ejector; 11. Shell; 12. Gas chamber partition plate; 13. Microbubble generator; 14. First structured packing layer; 15. First liquid distributor; 16. Second structured packing layer; 17. Second liquid distributor; a. Fischer-Tropsch synthesis tail gas; b. decarbonization tail gas; c. lean carbon liquid; d. semi-lean carbon liquid; e. rich carbon liquid; f. semi-lean carbon liquid; g. first regeneration gas; h. decarbonization liquid; i. second regeneration gas; j. regeneration gas; k. fresh decarbonization liquid. Detailed Implementation

[0022] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0023] In this disclosure, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its normal operating state, for example, as shown in the reference. Figure 2 In the drawing orientation, "inner" and "outer" refer to those relative to the outline of the device. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] like Figure 1 As shown, this disclosure provides a method for removing carbon dioxide from Fischer-Tropsch synthesis tail gas, the method comprising: The carbon-lean liquid and semi-carbon-lean liquid are respectively introduced into the carbon dioxide absorption tower from the upper and middle parts, and contacted countercurrently with the Fischer-Tropsch synthesis tail gas to obtain decarbonized tail gas and carbon-rich liquid; the carbon-rich liquid is introduced into a first desorption tower for first separation to obtain the semi-carbon-lean liquid and first regeneration gas; a portion of the semi-carbon-lean liquid is introduced into a second desorption tower for second separation to obtain decarbonized liquid and second regeneration gas; the decarbonized liquid is mixed with fresh decarbonized liquid to form the carbon-lean liquid; During the countercurrent contact process, the Fischer-Tropsch synthesis tail gas is passed through the microbubble generator at the bottom of the carbon dioxide absorption tower to form microbubbles. The fresh decarbonation solution comprises potassium carbonate, an activator, and water; the activator comprises one or more of ethanolamine, piperazine, diisopropanolamine, and 1-aminopropyl-3-methylimidazolium bromide. The viscosity of the lean carbon liquid at 20°C is 0.00005-0.0007 Pa·s, and the average particle size of the microbubbles is 200-1500 μm.

[0025] The above technical solution immerses the microbubble generator in a carbon-rich liquid. The Fischer-Tropsch synthesis tail gas, through the microbubble generator, produces a large number of microbubbles in the carbon-rich liquid, ensuring sufficient gas-liquid contact and thus improving the decarbonization effect. Simultaneously, the viscosity of each solution in the fresh decarbonization liquid decreases, allowing for the stable generation of more microbubbles under the action of the microbubble generator. This accelerates the carbon dioxide absorption rate, further enhancing the decarbonization effect.

[0026] In one embodiment, the average particle size of the microbubbles described in this disclosure is measured using conventional methods in the art. This application does not make any special requirements. For example, one or more of the following methods can be used: conductivity method, probe method, optical fiber method, light transmission method, and microscopic imaging method. Preferably, the average particle size of the microbubbles described in this disclosure can be measured using the conductivity method or the optical fiber method.

[0027] like Figure 2 As shown, the carbon dioxide absorption tower of this disclosure includes a shell, a gas chamber partition plate, the microbubble generator, structured packing, and a liquid distributor; the gas chamber partition plate, the microbubble generator, the structured packing, and the liquid distributor are disposed inside the shell; The gas chamber partition plate is disposed at the lower part of the shell to divide the internal cavity of the shell into a gas chamber and a decarbonization chamber from bottom to top; the gas chamber partition plate is provided with a Fischer-Tropsch synthesis tail gas through hole; the inlet of the microbubble generator is connected to the Fischer-Tropsch synthesis tail gas through hole so that the Fischer-Tropsch synthesis tail gas in the gas chamber enters the decarbonization chamber through the microbubble generator; The decarbonization chamber is provided with a first structured packing layer, a first liquid distributor, a second structured packing layer, and a second liquid distributor in sequence from bottom to top; The bottom of the gas chamber is provided with a Fischer-Tropsch synthesis tail gas inlet for communication with the Fischer-Tropsch synthesis tail gas source; the lower part of the decarbonization chamber is provided with a carbon-rich liquid outlet, which is connected to the inlet of the first desorption tower; the inlet of the first liquid distributor extends to the outside of the shell to form a semi-carbon-lean liquid inlet; the inlet of the second liquid distributor extends to the outside of the shell to form a carbon-lean liquid inlet.

[0028] In this embodiment, the Fischer-Tropsch synthesis tail gas enters the gas chamber through the Fischer-Tropsch synthesis tail gas inlet, and then enters the microbubble generator through the Fischer-Tropsch synthesis tail gas through-hole of the gas chamber partition plate. It then enters the amine-rich liquid above the gas chamber partition plate through the microbubble generator. Since the microbubble generator contains a large number of tiny pores, it can form a large number of tiny bubbles in the amine-rich liquid. As the bubbles gradually move upward, they can sequentially come into countercurrent contact with the semi-lean and lean liquids to achieve the purpose of decarbonization.

[0029] In one implementation, such as Figure 3As shown, the air inlet of the microbubble generator described in this disclosure is connected to the Fischer-Tropsch synthesis tail gas through-hole on the gas chamber partition plate. The gas phase entering the microbubble generator enters the carbon-rich liquid through multiple holes of the microbubble generator and forms a large number of microbubbles.

[0030] In one embodiment, the microbubble generator described in this disclosure is made of one or more of the following materials: carbon nanotubes, stainless steel porous membranes, glass fibers, and porous ceramic materials, preferably porous ceramic materials.

[0031] In a preferred embodiment, the pore size of the porous ceramic material is 100-900 μm.

[0032] In a further preferred embodiment, the pore size of the porous ceramic material can be any one or any combination of 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm, 750μm, 800μm, and 850μm.

[0033] In the above embodiments, the microbubble generator made of a material with appropriate pore size can obtain microbubbles of suitable size and quantity. Furthermore, when the Fischer-Tropsch synthesis tail gas is ejected, a large pressure is generated, which can increase the diffusion radius of the microbubbles, improve the uniformity of the microbubble distribution, and thus improve the decarbonization effect.

[0034] In one embodiment, the microbubble generator described in this disclosure is shaped like a bullet, with air outlets evenly distributed on the sidewalls of the generator. In this embodiment, using a microbubble generator of a suitable shape allows the Fischer-Tropsch synthesis exhaust gas to be expelled in all directions, improving the uniformity of bubble distribution and further enhancing the decarbonization effect.

[0035] In one embodiment, a plurality of Fischer-Tropsch synthesis tail gas through holes are uniformly provided on the gas chamber partition plate, and each Fischer-Tropsch synthesis tail gas through hole corresponds to a microbubble generator.

[0036] In one embodiment, in order to further improve the number and uniformity of microbubbles, 500 to 2000 microbubble generators are provided inside the carbon dioxide absorption tower.

[0037] In one embodiment, the first liquid distributor of the present disclosure is disposed in the middle of the carbon dioxide absorption tower, and the second liquid distributor is disposed in the upper part of the carbon dioxide absorption tower.

[0038] In one embodiment, the first liquid distributor and the second liquid distributor described in this disclosure are both conventional choices in the art, and this application does not make any special requirements.

[0039] In one embodiment, the materials of the first liquid distributor and the second liquid distributor are each independently selected, including 304 stainless steel or 316 stainless steel.

[0040] In one embodiment, the packing materials of the first and second structured packing layers described in this disclosure each independently include corrugated mesh packing and / or corrugated plate packing. In this embodiment, both corrugated mesh packing and corrugated plate packing are conventional choices in the art, and this application does not impose special requirements. During the upward movement of microbubbles, they may aggregate into larger bubbles. Sequentially placing the first and second structured packing layers above the decarbonization chamber allows the large bubbles to break upon contact with the packing material, further increasing the gas-liquid contact area, enhancing the mass transfer process, and improving the carbon dioxide absorption effect.

[0041] In one embodiment, a decarbonized gas outlet is provided at the top of the shell of the carbon dioxide absorption tower for discharging the decarbonized gas.

[0042] In one embodiment, the size and parameters of the carbon dioxide absorption tower and its components can be flexibly selected according to the actual production and processing needs, which will not be elaborated further in this application.

[0043] In one embodiment, the operating conditions of the carbon dioxide absorption tower include: a temperature of 60-105℃, a pressure of 1.5-3.0MPa, and an empty tower gas velocity of 0.1-0.9m / s.

[0044] In a preferred embodiment, the operating conditions of the carbon dioxide absorption tower include: a temperature of 80-95℃, a pressure of 2-2.5MPa, and an empty tower gas velocity of 0.3-0.5m / s.

[0045] In this embodiment, when decarbonization is performed using appropriate operating conditions of the carbon dioxide absorption tower, the microbubble generator can produce a suitable number of microbubbles with appropriate size and uniform dispersion, in combination with the properties and structural characteristics of the solution inside the carbon dioxide absorption tower. This further increases the gas-liquid contact area, strengthens the mass transfer process, and improves the carbon dioxide absorption effect.

[0046] In one embodiment, the carbon number index of the lean liquor is 1.2-1.3, and the carbon number index of the semi-lean liquor is 1.4-1.5.

[0047] In a preferred embodiment, the carbon number index of the lean liquor is 1.21-1.25, and the carbon number index of the semi-lean liquor is 1.40-1.44.

[0048] In this embodiment, the carbon number index as described in this disclosure refers to the ratio of the number of moles of CO2 dissolved in the solution to the number of moles of K2O in the solution. As the decarbonization treatment time increases, fresh decarbonization solution can be continuously added to the lean solution tank 9 to ensure that the carbon number index of the lean and semi-lean solutions is always within a suitable parameter range. Alternatively, fresh decarbonization solution can be added to the lean solution tank 9 at regular intervals.

[0049] In a preferred embodiment, the present disclosure adopts a method of periodically adding fresh decarbonization liquid, that is, adding fresh decarbonization liquid to the lean liquid tank 9 every 3-15 days.

[0050] In one embodiment, the ratio of the amount of decarbonized liquid to the amount of fresh decarbonized liquid added is (1-5):1.

[0051] In a preferred embodiment, the ratio of the amount of decarbonized liquid to the amount of fresh decarbonized liquid added is (2-4):1.

[0052] In a further preferred embodiment, the ratio of the amount of decarbonized liquid to the amount of fresh decarbonized liquid added is (2-3):1.

[0053] In this embodiment, by using an appropriate amount of fresh decarbonization liquid, on the one hand, the carbon number index of the lean and semi-lean liquids can always be within a suitable parameter range during operation, which can further improve the decarbonization effect; on the other hand, it can not affect the viscosity of the solution in the carbon dioxide absorption tower, thereby further improving the decarbonization effect.

[0054] In one embodiment, based on the total weight of the fresh decarbonated liquid, the content of potassium carbonate is 20-45% by weight, the content of the activator is 5-15% by weight, and the content of water is 40-75% by weight.

[0055] In a preferred embodiment, based on the total weight of the fresh decarbonated liquid, the content of potassium carbonate is 26-35% by weight, the content of the activator is 8-12% by weight, and the content of water is 53-66% by weight.

[0056] In a preferred embodiment, the activator is a composition of diisopropanolamine and piperazine, wherein the content of diisopropanolamine is 60-90% by weight and the content of piperazine is 10-40% by weight, based on the total weight of the composition.

[0057] In one embodiment, the operating conditions of the first desorption tower include: a temperature of 100-130°C, preferably 110-120°C; and a pressure of 130-260 kPa, preferably 160-200 kPa.

[0058] In one embodiment, the operating conditions of the second desorption tower include: a pressure of 1-20 kPa, preferably 4-8 kPa; and a temperature of 90-120°C, preferably 100-110°C.

[0059] In this embodiment, after the first separation, most of the carbon dioxide, syngas, hydrocarbons, and other gaseous phases of the carbon-rich liquid are discharged from the top of the tower. The desorbed carbon-rich liquid still contains a large amount of carbon dioxide, becoming a semi-lean liquid, which is discharged from the bottom of the tower. Part of it is sent to the carbon dioxide absorption tower, and part of it enters the second desorption tower for further processing. The semi-lean liquid enters the second desorption tower via the feed pump 7, where the carbon dioxide in the semi-lean liquid is further desorbed into carbon dioxide gas, which is discharged from the top of the tower. The carbon dioxide concentration in the semi-lean liquid is further reduced, becoming a lean liquid, which enters the lean liquid tank from the bottom of the tower. The gas phase from the first desorption tower is drawn into the second desorption tower by the regeneration ejector 10 to control the pressure of the second desorption tower.

[0060] In one embodiment, the flow rate ratio of the semi-lean carbon liquid returned to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is (0.5-2):1, preferably (1-1.5):1.

[0061] In this embodiment, when the flow ratio of the semi-lean carbon liquid returned to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is within a suitable range, on the one hand, the semi-lean carbon liquid can be further contacted countercurrently with the Fischer-Tropsch synthesis tail gas, further improving the carbon dioxide absorption efficiency and absorption effect; on the other hand, a suitable amount of decarbonized liquid can be obtained. When a suitable amount of decarbonized liquid is mixed with fresh decarbonized liquid, a lean carbon liquid of suitable viscosity can be obtained, further improving the carbon dioxide absorption efficiency and absorption effect.

[0062] In a preferred embodiment, the viscosity of the carbon-lean liquid at 20°C is 0.00006-0.0004 Pa·s.

[0063] In one embodiment, the method further includes, before the Fischer-Tropsch synthesis tail gas and the lean carbon liquid enter the shell side and tube side of a heat exchanger respectively for heat exchange.

[0064] In one implementation, such as Figure 1 As shown, the methods for removing carbon dioxide from the tail gas of Fischer-Tropsch synthesis include: The Fischer-Tropsch synthesis tail gas a first exchanges heat with the lean carbon liquid c through the heat exchanger 2, and then enters the gas chamber of the carbon dioxide absorption tower 1 through the Fischer-Tropsch synthesis tail gas inlet. Then, it enters the microbubble generator 13 through the Fischer-Tropsch synthesis tail gas through hole of the gas chamber partition plate 12, and enters the amine-rich liquid e above the gas chamber partition plate through the microbubble generator 13 to form a large number of microbubbles with an average particle size of 200-1500μm. Microbubbles are sequentially passed through a first structured packing layer 14, a first liquid distributor 15, a second structured packing layer 16, and a second liquid distributor 17, and sequentially come into countercurrent contact with semi-lean carbon liquid d and lean carbon liquid c to obtain decarbonized tail gas b and carbon-rich liquid e; the operating conditions of the carbon dioxide absorption tower 1 include: temperature of 60-105℃, pressure of 1.5-3.0MPa, and empty tower gas velocity of 0.1-0.9m / s; the carbon number index of the lean carbon liquid c is 1.2-1.3, and the carbon number index of the semi-lean carbon liquid d is 1.4-1.5; The carbon-rich liquid is fed into the first desorption tower 3 via the concentrate pump 5 for first separation to obtain the semi-carbon-lean liquid f and the first regeneration gas g; the operating conditions of the first desorption tower 3 include: temperature of 100-130℃ and pressure of 130-260kPa. A portion of the semi-lean carbon liquid f is fed into the second desorption tower 4 via the feed pump 7 for second separation, yielding decarbonized liquid h and second regenerated gas i; another portion of the semi-lean carbon liquid f is returned to the carbon dioxide absorption tower 1 via the semi-lean carbon liquid pump 6 and enters the first liquid distributor 15; the flow ratio of the semi-lean carbon liquid f returning to the carbon dioxide absorption tower 1 to the semi-lean carbon liquid f entering the second desorption tower 4 is (0.5-2):1; the operating conditions of the second desorption tower 4 include: pressure of 1-20 kPa and temperature of 90-120℃; The first regenerated gas g and the second regenerated gas i are passed through the regenerated injector 10 to form regenerated gas j exiting the system. The decarbonized liquid h enters the lean carbon liquid tank 9 and mixes with the fresh decarbonized liquid k to form the lean carbon liquid c. The lean carbon liquid c in the lean carbon liquid tank 9 is then pumped by the lean carbon liquid pump 8 into the second liquid distributor 17 of the carbon dioxide absorption tower 1. The ratio of the amount of decarbonized liquid h to the amount of fresh decarbonized liquid k added is (1-5):1. Based on the total weight of the fresh decarbonized liquid k, the content of potassium carbonate is 20-45% by weight, the content of activator is 5-15% by weight, and the content of water is 40-75% by weight. The activator is composed of 60-90% by weight of diisopropanolamine and 10-40% by weight of piperazine.

[0065] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0066] Example 1 use Figure 1 The system shown and Figure 2 The carbon dioxide absorption tower is used for decarbonization treatment; the carbon dioxide absorption tower has an inner diameter of 8.0 meters and a height of 50.0 meters. Methods for removing carbon dioxide from Fischer-Tropsch synthesis tail gas include: The intake volume is 650 kNm 3The Fischer-Tropsch synthesis tail gas, at a temperature of 42℃ and a pressure of 2.4MPa, first exchanges heat with the lean carbon liquid in heat exchanger 2 to reach 90℃, and then enters the gas chamber of the carbon dioxide absorption tower 1 through the Fischer-Tropsch synthesis tail gas inlet. It then enters the microbubble generator 13 through the Fischer-Tropsch synthesis tail gas through-hole of the gas chamber partition plate 12, and enters the amine-rich liquid above the gas chamber partition plate through the microbubble generator 13, forming a large number of microbubbles with an average particle size of 300μm. These microbubbles then sequentially pass through the first structured packing layer 14, the first liquid distributor 15, the second structured packing layer 16, and the second liquid distributor 17, and sequentially contact the semi-lean carbon liquid and the lean carbon liquid in countercurrent flow, resulting in a flow rate of 520kNm³. 3 / h of decarbonized tail gas and carbon-rich liquid; the operating conditions of the carbon dioxide absorption tower include: temperature of 80℃, pressure of 2.4MPa; the flow rate of the carbon-lean liquid is 2200t / h, and the carbon number index is 1.22; the flow rate of the semi-carbon-lean liquid is 2600t / h, and the carbon number index is 1.41. The carbon-rich liquid is pumped by a concentrate pump 5 into a first desorption tower 3 for first separation, yielding the semi-lean carbon liquid and the first regeneration gas. The operating conditions of the first desorption tower include a temperature of 120°C and a pressure of 220 kPa. The semi-lean carbon liquid with a flow rate of 2400 t / h is pumped by a feed pump 7 into a second desorption tower 4 for second separation, yielding decarbonized liquid and the second regeneration gas. The semi-lean carbon liquid with a flow rate of 2400 t / h is pumped by a semi-lean carbon liquid pump 6 back to the carbon dioxide absorption tower 1 and into the first liquid distributor 15. The operating conditions of the second desorption tower include a pressure of 5 kPa and a temperature of 110°C. The first and second regenerated gases are processed by the regeneration injector 10 to form regenerated gas with a concentration of 110 kNm. 3 / h of traffic leaving the system; The decarbonized liquid is introduced into the lean carbon liquid tank 9, and fresh decarbonized liquid is added to it every 7 days to form the lean carbon liquid, wherein the viscosity of the lean carbon liquid at 20°C is 0.00024 Pa·s; the lean carbon liquid in the lean carbon liquid tank 9 is introduced into the second liquid distributor 17 of the carbon dioxide absorption tower 1 via the lean carbon liquid pump 8; the ratio of the amount of decarbonized liquid added to the amount of fresh decarbonized liquid is 2:1; based on the total weight of the fresh decarbonized liquid, the content of potassium carbonate is 40% by weight, the content of activator is 12% by weight, and the content of water is 48% by weight, wherein the activator is composed of 8% by weight of diisopropanolamine and 4% by weight of piperazine.

[0067] The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 1. Table 1 Composition of decarbonization tail gas and regeneration gas

[0068] Example 2 The system and method used in this embodiment are the same as those in Embodiment 1, except that Raschig ring packing is used in the carbon dioxide absorption tower.

[0069] The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 2. Table 2 Composition of decarbonization tail gas and regeneration gas

[0070] Example 3 The system and carbon dioxide absorption tower used in this embodiment are the same as in Embodiment 1, except that the carbon number index of the lean liquid is 1.36, and the carbon number index of the semi-lean liquid is 1.55. The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 3. Table 3 Composition of decarbonization tail gas and regeneration gas

[0071] Example 4 The system and carbon dioxide absorption tower used in this embodiment are the same as in Embodiment 1, except that the flow ratio of the semi-lean carbon liquid returning to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is 1.5:1. The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 4. Table 4 Composition of decarbonization tail gas and regeneration gas

[0072] Example 5 The system and carbon dioxide absorption tower used in this embodiment are the same as in Embodiment 1, except that the viscosity of the lean carbon liquid at 20°C is 0.0003 Pa·s. The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 5.

[0073] Table 5 Composition of decarbonization tail gas and regeneration gas

[0074] Comparative Example 1 The system and method used in this embodiment are the same as those in Embodiment 1, except that a common tubular gas distributor is used instead of a microbubble generator in the carbon dioxide absorption tower.

[0075] The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 6. Table 6 Composition of decarbonization tail gas and regeneration gas

[0076] Comparative Example 2 The system and carbon dioxide absorption tower used in this embodiment are the same as in Embodiment 1, except that the viscosity of the lean carbon liquid at 20°C is 0.0009 Pa·s. The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 7.

[0077] Table 7 Composition of decarbonization tail gas and regeneration gas

[0078] Comparative Example 3 The system and carbon dioxide absorption tower used in this embodiment are the same as in Embodiment 1, except that an equal weight of boric acid activator is used instead of the activator in Embodiment 1. The composition of the decarbonization tail gas and regeneration gas in this embodiment is shown in Table 8.

[0079] Table 8 Composition of Decarbonization Tail Gas and Regenerated Gas

[0080] As shown in Tables 1-8, a comparison of the data from Examples 1-5 and Comparative Examples 1-3 reveals that immersing the microbubble generator in the carbon-rich liquid, and generating a large number of microbubbles from the Fischer-Tropsch synthesis tail gas in the carbon-rich liquid via the microbubble generator, allows for sufficient gas-liquid contact, thereby improving the decarbonization effect. Simultaneously, the activator in the fresh decarbonization liquid reacts with the oxygen-containing organic matter in the Fischer-Tropsch synthesis tail gas, reducing the viscosity of each solution in the carbon dioxide absorption tower. Under the action of the microbubble generator, more microbubbles can be stably generated, further enhancing the decarbonization effect. A comparison of the data from Examples 1 and 2 shows that when the packing materials of the first and second structured packing layers in the carbon dioxide absorption tower independently include corrugated mesh packing and / or corrugated plate packing, the decarbonization effect can be improved. A comparison of the data from Examples 1 and 3 shows that when the carbon number index of the lean liquid is 1.2-1.3 and the carbon number index of the semi-lean liquid is 1.4-1.5, the decarbonization effect can be improved. A comparison of the data from Examples 1 and 4 shows that when the flow ratio of the semi-lean carbon liquid returning to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is (0.5-2):1, the decarbonization effect can be improved. A comparison of the data from Examples 1, 5, and Comparative Example 2 shows that when the viscosity of the lean carbon liquid at 20°C is 0.00005-0.0007 Pa·s, the decarbonization effect can be improved.

[0081] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0082] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0083] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for removing carbon dioxide from Fischer-Tropsch synthesis tail gas, characterized in that, The method includes: The carbon-lean liquid and semi-carbon-lean liquid are respectively introduced into the carbon dioxide absorption tower from the upper and middle parts, and contacted countercurrently with the Fischer-Tropsch synthesis tail gas to obtain decarbonized tail gas and carbon-rich liquid; the carbon-rich liquid is introduced into a first desorption tower for first separation to obtain the semi-carbon-lean liquid and first regeneration gas; a portion of the semi-carbon-lean liquid is introduced into a second desorption tower for second separation to obtain decarbonized liquid and second regeneration gas; the decarbonized liquid is mixed with fresh decarbonized liquid to form the carbon-lean liquid; During the countercurrent contact process, the Fischer-Tropsch synthesis tail gas is passed through the microbubble generator at the bottom of the carbon dioxide absorption tower to form microbubbles. The fresh decarbonation solution comprises potassium carbonate, an activator, and water; the activator comprises one or more of ethanolamine, piperazine, diisopropanolamine, and 1-aminopropyl-3-methylimidazolium bromide. The viscosity of the lean carbon liquid at 20°C is 0.00005-0.0007 Pa·s, and the average particle size of the microbubbles is 200-1500 μm.

2. The method according to claim 1, characterized in that, The carbon number index of the lean carbon solution is 1.2-1.3, and the carbon number index of the semi-lean carbon solution is 1.4-1.

5.

3. The method according to claim 1, characterized in that, Based on the total weight of the fresh decarbonation liquid, the content of potassium carbonate is 20-45% by weight, the content of activator is 5-15% by weight, and the content of water is 40-75% by weight.

4. The method according to claim 1, characterized in that, The carbon dioxide absorption tower includes a shell, a gas chamber partition plate, a microbubble generator, structured packing, and a liquid distributor; the gas chamber partition plate, the microbubble generator, the structured packing, and the liquid distributor are disposed inside the shell; The gas chamber partition plate is disposed at the lower part of the shell to divide the internal cavity of the shell into a gas chamber and a decarbonization chamber from bottom to top; the gas chamber partition plate is provided with a Fischer-Tropsch synthesis tail gas through hole; the inlet of the microbubble generator is connected to the Fischer-Tropsch synthesis tail gas through hole so that the Fischer-Tropsch synthesis tail gas in the gas chamber enters the decarbonization chamber through the microbubble generator; The decarbonization chamber is provided with a first structured packing layer, a first liquid distributor, a second structured packing layer, and a second liquid distributor in sequence from bottom to top; The bottom of the gas chamber is provided with a Fischer-Tropsch synthesis tail gas inlet for communication with the Fischer-Tropsch synthesis tail gas source; the lower part of the decarbonization chamber is provided with a carbon-rich liquid outlet, which is connected to the inlet of the first desorption tower; the inlet of the first liquid distributor extends to the outside of the shell to form a semi-carbon-lean liquid inlet; the inlet of the second liquid distributor extends to the outside of the shell to form a carbon-lean liquid inlet.

5. The method according to claim 1, characterized in that, The microbubble generator is made of porous ceramic material.

6. The method according to claim 5, characterized in that, The porous ceramic material has a pore size of 100-900 μm.

7. The method according to claim 5, characterized in that, The packings in the first and second structured packing layers each independently include mesh corrugated packing and / or plate corrugated packing.

8. The method according to claim 1, characterized in that, The flow rate ratio of the semi-lean carbon liquid returning to the carbon dioxide absorption tower to the semi-lean carbon liquid entering the second desorption tower is (0.5-2):

1.

9. The method according to claim 1, characterized in that, The operating conditions of the carbon dioxide absorption tower include: temperature of 60-105℃, pressure of 1.5-3.0MPa, and empty tower gas velocity of 0.1-0.9m / s.

10. The method according to claim 1, characterized in that, The operating conditions of the first desorption tower include: temperature of 100-130℃ and pressure of 130-260kPa; The operating conditions of the second desorption tower include: pressure of 1-20 kPa and temperature of 90-120℃.

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