System and method for separating co and h2 from coke oven gas

Abstract

The application discloses a system and method for separating CO and H2 from coke oven gas, which comprises a catalytic oxidation H2S unit, a pressure swing adsorption separation CO unit, a catalytic oxidation CO unit, an oxygen removal unit, a compression unit, a four-tower vacuum pressure swing adsorption unit and a double reflux pressure swing adsorption unit. Thus, by adopting physical adsorption and catalytic oxidation methods to sequentially separate effective components in the coke oven gas, the whole separation process is free of complicated chemical reactions and has a simple process route, and has the advantages of no complicated chemical reactions, a simple process flow, high separation efficiency, low energy consumption and the like, and the purity of high-purity hydrogen obtained by purification is higher than 99.992v%, and the CO content is lower than 0.2ppmv, which can meet the requirements of fuel cells.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and specifically to a system and method for separating CO and H2 from coke oven gas. Background Technology

[0002] The comprehensive utilization of coke oven gas (COG) is unique to China. China is a major global producer of coke, and coke oven gas, a byproduct of coking, is primarily composed of: H2: 25-28%, N2: 45-50%, CO: 10%, CO2: 5-10%, H2S: 100 ppmv, and O2: 3-8%. It is a high-calorific-value fuel. CO and H2 in coke oven gas are high-value-added basic chemical raw materials that can be used to synthesize many important chemical products; for example, CO can be hydrogenated to produce methanol. However, CO is a toxic gas, and even trace amounts can poison valuable catalysts, such as the platinum electrocatalyst in proton exchange membrane fuel cells when the CO content is below 0.2 ppmv. Furthermore, purifying fuel cell-grade hydrogen from coke oven gas can increase its value by 5-10 times.

[0003] The common methods for treating coke oven gas are combustion or direct emission, which not only wastes the high-value-added CO and H2 but also causes serious environmental pollution. To produce high-value-added CO and H2 from coke oven gas, it is essential to develop efficient separation technologies to simultaneously remove multiple impurities at a deep or even ultra-deep level. The main methods for separating CO and H2 include cryogenic separation, membrane separation, and adsorption separation. Adsorption separation is advantageous due to its simple operation, high degree of automation, and high separation purity. Based on the regeneration method, adsorption separation is divided into pressure swing adsorption (PSA) and total pressure swing adsorption (TSA). Commonly used commercial adsorbents such as activated carbon, molecular sieves, and silica gel rapidly increase their adsorption capacity for impurities in coke oven gas under low pressure; therefore, PSA is more competitive in terms of operational flexibility and economy.

[0004] PSA (Polymer Separation and Adsorption) technology is a highly efficient separation method, attracting significant attention due to its low energy consumption, lack of new impurities, and high product purity. The PSA process can produce hydrogen with a purity between 98% and 99.99%. A 12-tower PSA can achieve a recovery rate of 70%–90% at operating pressures greater than 2 MPa. Industrial PSA units typically consist of multiple parallel adsorption towers that sequentially undergo the same cycle at different times. The physical properties of the adsorbent are crucial for the separation of CO and H2. Extensive research has been conducted on the selectivity and kinetic parameters of materials such as 5A molecular sieves, 13X molecular sieves, silica gel, and activated carbon for CO and H2, which are typically layered into the adsorption towers in a specific ratio. Furthermore, coke oven gas has a high N2 content, and CO and N2, due to their similar adsorption characteristics, are difficult to separate effectively by commercial adsorbents such as activated carbon and 5A molecular sieves. Therefore, traditional PSA methods struggle to purify coke oven gas to fuel cell grade.

[0005] Chinese patent CN 113877605A discloses a catalyst for low-temperature CO oxidation and its preparation method. This catalyst exhibits high catalytic oxidation activity and stability for CO in various characteristic atmospheres (such as hydrogen-rich, carbon dioxide-rich, and sulfur-containing atmospheres). Chinese patent CN 108126708A discloses a room-temperature catalytic oxidation catalyst for CO, characterized by high catalytic activity and good stability, capable of completely oxidizing CO at room temperature. Chinese patent CN 111100714A discloses a method and apparatus for producing CO and H2 feedstock gas from coke oven gas combined with blast furnace gas or converter gas, optimizing the process flow.

[0006] In summary, while previous patents have reported some methods for purifying coke oven gas to produce hydrogen, these processes suffer from the following problems: a. The CO content in coke oven gas is high, making it difficult to completely separate CO and H2 using a single catalytic or pressure swing adsorption (PSA) technology; b. The process routes are relatively complex, hindering industrialization. Therefore, existing technologies require improvement. Summary of the Invention

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one object of this invention is to provide a system and method for separating CO and H2 from coke oven gas. This method sequentially separates the effective components from the coke oven gas using physical adsorption and catalytic oxidation. The entire separation process involves no complex chemical reactions and has a simple process route, offering advantages such as no complex chemical reactions, simple process flow, high separation efficiency, and low energy consumption. Furthermore, the purified high-purity hydrogen has a purity higher than 99.992 v%, with a CO content lower than 0.2 ppmv, which meets the requirements of fuel cells.

[0008] In one aspect of the invention, a system for separating CO and H2 from coke oven gas is provided. According to an embodiment of the invention, the system comprises:

[0009] A catalytic oxidation H2S unit, the catalytic oxidation H2S unit having a coke oven gas inlet, a first catalyst inlet, and a first processed gas outlet;

[0010] A pressure swing adsorption (PSA) CO separation unit, wherein the PSA CO separation unit has a first processing gas inlet, a first adsorbent inlet, a pure CO outlet, and a second processing gas outlet, wherein the first processing gas outlet is connected to the first processing gas inlet;

[0011] A catalytic oxidation CO unit, the catalytic oxidation CO unit having a second processed gas inlet, a second catalyst inlet, and a third processed gas outlet, the second processed gas outlet being connected to the second processed gas inlet;

[0012] A deoxygenation unit, the deoxygenation unit having a third processed gas inlet and a fourth processed gas outlet, the third processed gas outlet being connected to the third processed gas inlet;

[0013] A compression unit, the compression unit having a fourth processing gas inlet and a fifth processing gas outlet, the fourth processing gas outlet being connected to the fourth processing gas inlet;

[0014] The four-tower vacuum pressure swing adsorption unit has a fifth processing gas inlet, a second adsorbent inlet, a first desorption gas outlet, and a sixth processing gas outlet, wherein the fifth processing gas outlet is connected to the fifth processing gas inlet.

[0015] The dual-reflux pressure swing adsorption unit includes a sixth processing gas inlet, a third adsorbent inlet, a high-purity H2 outlet, and a second desorption gas outlet. The sixth processing gas outlet is connected to the sixth processing gas inlet.

[0016] The system for separating CO and H2 from coke oven gas according to an embodiment of the present invention sequentially passes the coke oven gas through a catalytic oxidation H2S unit, a pressure swing adsorption (PSA) CO separation unit, a catalytic oxidation CO unit, a deoxygenation unit, a compression unit, a four-tower vacuum PSA unit, and a dual reflux PSA unit. Specifically, the catalytic oxidation H2S unit and the deoxygenation unit remove H2S and some O2, thereby improving the efficiency of subsequent processing, reducing energy consumption, and increasing the purity of H2. The PSA CO separation unit and the catalytic oxidation CO unit enrich the high-concentration CO, improving the economic value of the coke oven gas. By combining the four-tower vacuum PSA unit and the dual reflux PSA unit, high-purity hydrogen is prepared while also increasing the yield. Therefore, by using physical adsorption and catalytic oxidation methods to sequentially separate the effective components in coke oven gas, the entire separation process does not involve complex chemical reactions and has a simple process route. It has the advantages of no complex chemical reactions, simple process flow, high separation efficiency, and low energy consumption. Moreover, the high-purity hydrogen obtained by purification has a purity higher than 99.992v, and the CO content is lower than 0.2ppmv, which can meet the requirements of fuel cells.

[0017] In addition, the system for separating CO and H2 from coke oven gas according to the above embodiments of the present invention may also have the following additional technical features:

[0018] In a second aspect, the present invention provides a method for separating CO and H2 from coke oven gas. According to an embodiment of the invention, the method includes:

[0019] (1) The coke oven gas is passed into the catalytic oxidation H2S unit to carry out the first reaction in order to obtain the first processed gas;

[0020] (2) The first processed gas is passed into the pressure swing adsorption separation CO unit to carry out the second reaction in order to obtain the second processed gas and pure CO;

[0021] (3) The second processed gas is passed into the catalytic oxidation CO unit to carry out the third reaction in order to obtain the third processed gas and CO2;

[0022] (4) The third processing gas is passed into the deoxygenation unit for deoxygenation in order to obtain the fourth processing gas;

[0023] (5) The fourth processing gas is passed into the compression unit for compression in order to obtain the fifth processing gas;

[0024] (6) The fifth processing gas is introduced into the four-tower vacuum pressure swing adsorption unit to carry out the fourth reaction in order to obtain the sixth processing gas and the first desorption gas;

[0025] (7) The sixth processing gas is passed into the double reflux pressure swing adsorption unit to carry out the fifth reaction in order to obtain the second desorption gas and high-purity H2.

[0026] The method for separating CO and H2 from coke oven gas according to embodiments of the present invention removes H2S and some O2 through catalytic oxidation of H2S and deoxygenation, thereby improving the efficiency of subsequent processing, reducing energy consumption, and increasing the purity of H2. By separating CO through pressure swing adsorption and catalytic oxidation of CO, a higher concentration of CO is enriched, improving the economic value of coke oven gas. By combining four-tower vacuum pressure swing adsorption and dual-reflux pressure swing adsorption, high-purity hydrogen is prepared while also increasing the yield. Therefore, by sequentially separating the effective components in coke oven gas using physical adsorption and catalytic oxidation methods, the entire separation process involves no complex chemical reactions and has a simple process route. It has advantages such as no complex chemical reactions, simple process flow, high separation efficiency, and low energy consumption. Moreover, the high-purity hydrogen obtained has a purity higher than 99.992 v%, with a CO content lower than 0.2 ppmv, which meets the requirements of fuel cells.

[0027] In addition, the method for separating CO and H2 from coke oven gas according to the above embodiments of the present invention may also have the following additional technical features:

[0028] In some embodiments of the present invention, in step (1), the H2S content in the first processed gas is less than 0.1 ppmv.

[0029] In some embodiments of the present invention, in step (2), the adsorbent for the second reaction includes at least one of copper-supported activated carbon adsorbent, copper-supported Y molecular sieve adsorbent, and copper-supported 5A adsorbent.

[0030] In some embodiments of the present invention, in step (3), the CO content in the third processing gas is less than 10,000 ppmv.

[0031] In some embodiments of the present invention, in step (4), the O2 content in the fourth processing gas is less than 0.1 ppmv.

[0032] In some embodiments of the present invention, in step (5), the pressure of the fifth processing gas is 0.5 to 1 MPa.

[0033] In some embodiments of the present invention, in step (6), the adsorbent of the fourth reaction comprises 70 wt% activated carbon and 30 wt% 13X molecular sieve.

[0034] In some embodiments of the present invention, in step (7), the adsorbent of the fifth reaction comprises 70 wt% activated carbon and 30 wt% 13X molecular sieve.

[0035] In some embodiments of the present invention, in step (7), the purity of the high-purity H2 is higher than 99.992v and the content of CO is lower than 0.2ppmv.

[0036] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 This is a schematic diagram of a system for separating CO and H2 from coke oven gas according to a specific embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of a four-tower vacuum pressure swing adsorption unit according to a specific embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of a dual-reflux pressure swing adsorption unit according to a specific embodiment of the present invention;

[0041] Figure 4 This is a process flow diagram of a method for separating CO and H2 from coke oven gas according to a specific embodiment of the present invention;

[0042] Among them, 1-adsorption tower; 2-buffer tank; 3-vacuum pump; 4-valve; 5-compressor; 6-first adsorption tower; 7-second adsorption tower. Detailed Implementation

[0043] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0044] Furthermore, the terms "first," "second," "third," "fourth," "fifth," and "sixth" 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 with "first," "second," "third," "fourth," "fifth," or "sixth" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] The gas composition of the coke oven gas of the present invention mainly includes H2, N2, CO, CO2, H2S, O2, etc. In some typical coke oven gases, the composition includes, by volume percentage: H2: 25-30%, N2: 45-50%, CO: 10%, CO2: 5-10%, H2S: 100ppmv, O2: 3-8%.

[0046] In one aspect of the invention, a system for separating CO and H2 from coke oven gas is provided. According to an embodiment of the invention, reference is made to… Figure 1 The system includes: a catalytic oxidation H2S unit 100, a pressure swing adsorption (PSA) CO separation unit 200, a catalytic oxidation CO unit 300, a deoxygenation unit 400, a compression unit 500, a four-tower vacuum PSA unit 600, and a dual reflux PSA unit 700.

[0047] According to a specific embodiment of the present invention, the catalytic oxidation H2S unit 100 has a coke oven gas inlet 101, a first catalyst inlet 102, and a first processed gas outlet 103. Specifically, the catalytic oxidation H2S unit 100 includes a fixed-bed reactor, in which coke oven gas enters the fixed-bed reactor packed with catalyst, H2S is catalytically oxidized to elemental sulfur, and the first processed gas, including CO, CO2, N2, and H2, flows out from the top of the fixed bed and enters the pressure swing adsorption separation CO unit 200.

[0048] Furthermore, the catalytic oxidation reaction is carried out at room temperature and standard atmospheric pressure, with a preferred metal oxide-based catalyst as the first catalyst, to remove H2S from the coke oven gas to below 0.1 ppmv.

[0049] According to a specific embodiment of the present invention, the pressure swing adsorption (PSA) CO separation unit 200 has a first processed gas inlet 201, a first adsorbent inlet 202, a pure CO outlet 203, and a second processed gas outlet 204. The first processed gas outlet 203 is connected to the first processed gas inlet 201. Specifically, the PSA CO separation unit 200 includes four adsorption towers connected in parallel. The first processed gas enters the adsorption tower filled with the first adsorbent. Each adsorption tower sequentially undergoes adsorption (AD), pressure drop (ED), displacement (RP), reverse release (BD), vacuuming (VU), pressure rise (ER), and final pressure rise (FR). Through pressure swing adsorption technology, CO in the first processed gas is adsorbed by the first adsorbent. The adsorbed CO is desorbed through reverse release and vacuuming. The desorbed gas at the bottom of the adsorption tower enters the storage tank as pure CO, thereby achieving the purpose of CO enrichment. The unadsorbed gas, i.e., the second processed gas, contains a small amount of CO and flows out from the top of the adsorption tower into the catalytic oxidation CO unit 300.

[0050] Furthermore, the pressure swing adsorption (PSA) is carried out at 303 K and an adsorption pressure of 0.8–1 MPa. The first adsorbent is preferably at least one of copper-supported activated carbon, copper-supported Y molecular sieve, and copper-supported 5A adsorbent. Since the adsorption between the adsorbent and CO is a π-complex adsorption, which differs from the general PSA method of removing impurities to obtain product gas, a vacuum step is required to desorb the CO adsorbed on the adsorbent to obtain the product gas, i.e., pure CO.

[0051] According to a specific embodiment of the present invention, the catalytic oxidation CO unit 300 has a second processed gas inlet 301, a second catalyst inlet 302, and a third processed gas outlet 303, with the second processed gas outlet 204 connected to the second processed gas inlet 301. Specifically, the catalytic oxidation CO unit 300 includes a fixed-bed reactor. The second processed gas enters the fixed-bed reactor packed with a second catalyst, where CO is catalytically oxidized to CO2. The third processed gas, comprising trace amounts of CO, CO2, N2, and H2, flows out from the top of the fixed bed and enters the deoxygenation unit 400.

[0052] Furthermore, the catalytic oxidation reaction is carried out at 100–200°C and atmospheric pressure. Moreover, the choice of the second catalyst is not particularly limited; those skilled in the art can select at least one of Pt metal-supported catalysts, PtRu bimetallic supported catalysts, and copper-supported ZnO catalysts as needed, thereby removing CO from the third treated gas to below 10,000 ppmv. The catalytic oxidation CO unit 300 does not require a large amount of catalyst and has low conversion requirements, achieving energy savings.

[0053] According to a specific embodiment of the present invention, the deoxygenation unit 400 has a third processed gas inlet 401, a fourth processed gas outlet 402, and a third processed gas outlet 303 connected to the third processed gas inlet 401. Optionally, the deoxygenation unit 400 can remove oxygen from the fourth processed gas to below 0.1 ppmv through at least one of vacuum deoxygenation, distillation deoxygenation, membrane separation deoxygenation, and catalytic deoxygenation.

[0054] According to a specific embodiment of the present invention, the compression unit 500 has a fourth processed gas inlet 501 and a fifth processed gas outlet 502, the fourth processed gas outlet 502 being connected to the fourth processed gas inlet 501. Specifically, the compression unit 500 is preferably a compressor, which compresses the fifth processed gas to 0.5 to 1 MPa.

[0055] According to a specific embodiment of the present invention, the four-tower vacuum pressure swing adsorption unit 600 has a fifth processing gas inlet 601, a second adsorbent inlet 602, a first desorption gas outlet 603, a sixth processing gas outlet 604, and the fifth processing gas outlet 502 is connected to the fifth processing gas inlet 601. Specifically, refer to... Figure 2 The four-tower vacuum pressure swing adsorption unit 600 includes four adsorption towers connected in parallel and a vacuum pump. The fifth processed gas enters the adsorption tower filled with the second adsorbent. Each adsorption tower is in a different stage of the time sequence, and each adsorption tower undergoes adsorption (AD), first pressure drop equalization (ED1), idle step (ID), second pressure drop equalization (ED2), vacuuming (VU), purging (PG), second pressure rise equalization (ER2), first pressure rise equalization (ER1), and final pressure rise (PR) at different times. The two equalization process saves energy and increases the recovery rate of H2 product gas. After the four-tower vacuum pressure swing adsorption, trace amounts of CO, CO2, and N2 are adsorbed and retained in the adsorption tower as strong adsorption components. The sixth processed gas contains H2, CO2, and N2, where the CO2 content is less than 0.1 ppmv, the N2 content is less than 3000 ppmv, and H2, as a weak adsorption component, flows out of the adsorption tower and enters the double reflux pressure swing adsorption unit 700 for further purification. A portion of the waste gas is discharged from the adsorption tower as the first desorption gas.

[0056] Furthermore, the second adsorbent is preferably 70 wt% activated carbon and 30 wt% 13X molecular sieve.

[0057] According to a specific embodiment of the present invention, the dual reflux pressure swing adsorption unit 700 includes a sixth processing gas inlet 701, a third adsorbent inlet 702, a high-purity H2 outlet 703, and a sixth processing gas outlet 604 connected to the sixth processing gas inlet 701.

[0058] For details, please refer to Figure 3The dual-reflux pressure swing adsorption unit 700 includes two parallel adsorption towers, a compressor, and a vacuum pump. First, the sixth processing gas is fed at high pressure from the middle of the first adsorption tower 6, producing high-purity hydrogen at the top. A portion of this hydrogen is collected as product gas, and the remainder is used as low-pressure purge gas for the second adsorption tower 7. Simultaneously, the heavy component gas produced at the bottom of the second adsorption tower 7 is refluxed back into the first adsorption tower 6, with the remainder discharged. Then, the first and second adsorption towers 6 are pressure-equalized to reduce energy consumption. Finally, the pressure of the first and second adsorption towers 6 is replaced. Strongly adsorbed components in the first adsorption tower 6 are extracted and pressurized before being fed into the second adsorption tower 7, raising the second adsorption tower 7 to the adsorption pressure for a symmetrical second half-cycle. During this process, trace amounts of CO, CO2, and N2 are adsorbed and retained in the adsorption towers as strongly adsorbed components, while H2, a weakly adsorbed component, flows out of the adsorption towers and can be recovered as high-purity hydrogen. A portion of the waste gas is also discharged from the adsorption towers as the second desorption gas. Among them, the purity of the high-purity H2 is higher than 99.992v, and the CO content is lower than 0.2ppmv.

[0059] Furthermore, the third adsorbent is preferably 70 wt% activated carbon and 30 wt% 13X molecular sieve.

[0060] It should be noted that the inventors have discovered that for the pressure swing adsorption (PSA) CO separation unit 200, the tail gas outlet flow rate and the displacement gas flow rate are important factors affecting the purity and yield of CO in the product gas; for the four-tower vacuum PSA unit 600, the feed-purge ratio, purge time, adsorption time, adsorption pressure, and product gas outlet flow rate are important factors affecting the purity and yield of H2 in the product gas; for the dual reflux PSA unit 700, the feed location, reflux ratio, adsorption time, and feed-purge ratio are important factors affecting the final high-purity H2. Therefore, in the system for separating CO and H2 from coke oven gas, the effects of these parameters must be comprehensively considered to ensure the purity and yield of CO and H2. As a preferred embodiment of the present invention, the operating pressure of the PSA CO separation unit 200 is 0.5–0.7 MPa, and the adsorption time is 70 s; the operating pressure of the four-tower vacuum PSA unit 600 is 0.5–1 MPa, the adsorption time is 110 s, and the feed-purge ratio is 0.3. The dual reflux pressure swing adsorption unit 700 operates at a pressure of 0.5–0.8 MPa, with an adsorption time of 50 s, a feed position of intermediate feed, and a feed-purge ratio of 0.2.

[0061] The system for separating CO and H2 from coke oven gas according to an embodiment of the present invention sequentially passes the coke oven gas through a catalytic oxidation H2S unit, a pressure swing adsorption (PSA) CO separation unit, a catalytic oxidation CO unit, a deoxygenation unit, a compression unit, a four-tower vacuum PSA unit, and a dual reflux PSA unit. Specifically, the catalytic oxidation H2S unit and the deoxygenation unit remove H2S and some O2, thereby improving the efficiency of subsequent processing, reducing energy consumption, and increasing the purity of H2. The PSA CO separation unit and the catalytic oxidation CO unit enrich the high-concentration CO, improving the economic value of the coke oven gas. By combining the four-tower vacuum PSA unit and the dual reflux PSA unit, high-purity hydrogen is prepared while also increasing the yield. Therefore, by using physical adsorption and catalytic oxidation methods to sequentially separate the effective components in coke oven gas, the entire separation process does not involve complex chemical reactions and has a simple process route. It has the advantages of no complex chemical reactions, simple process flow, high separation efficiency, and low energy consumption. Moreover, the high-purity hydrogen obtained by purification has a purity higher than 99.992v, and the CO content is lower than 0.2ppmv, which can meet the requirements of fuel cells.

[0062] In a second aspect, the present invention provides a method for separating CO and H2 from coke oven gas. According to an embodiment of the invention, reference is made to... Figure 4 The method includes:

[0063] S100: The coke oven gas is introduced into the catalytic oxidation H2S unit for the first reaction.

[0064] In this step, coke oven gas is passed into a catalytic oxidation H2S unit for a first reaction to obtain a first reaction gas. Specifically, the coke oven gas enters a fixed-bed reactor packed with catalyst, where H2S is catalytically oxidized to elemental sulfur. After the first reaction, the first processed gas (containing CO, CO2, N2, and H2) flows out from the top of the fixed bed and enters the pressure swing adsorption separation CO unit 200.

[0065] Furthermore, the first reaction, namely the catalytic oxidation reaction, is carried out at room temperature and standard atmospheric pressure, preferably using a metal oxide-based catalyst as the first catalyst, to remove H2S from the coke oven gas to below 0.1 ppmv.

[0066] S200: The first processed gas is passed into the pressure swing adsorption (PSA) CO separation unit to carry out the second reaction.

[0067] In this step, the first processed gas is passed into the pressure swing adsorption (PSA) CO separation unit 200 for a second reaction to obtain a second processed gas and pure CO. Specifically, the PSA CO separation unit 200 includes four adsorption towers connected in parallel. The first processed gas enters the adsorption tower filled with the first adsorbent. Each adsorption tower sequentially undergoes adsorption (AD), pressure drop (ED), displacement (RP), reverse release (BD), vacuuming (VU), pressure rise (ER), and final pressure rise (FR). Through PSA technology, CO in the first processed gas is adsorbed by the first adsorbent. The adsorbed CO is desorbed through reverse release and vacuuming. The desorbed gas at the bottom of the adsorption tower enters the storage tank as pure CO, thereby achieving the purpose of CO enrichment. The unadsorbed gas, i.e., the second processed gas, contains a small amount of CO and flows out from the top of the adsorption tower into the catalytic oxidation CO unit 300.

[0068] Furthermore, the pressure swing adsorption (PSA) is carried out at 303 K and an adsorption pressure of 0.8–1 MPa. The first adsorbent is preferably at least one of copper-supported activated carbon, copper-supported Y molecular sieve, and copper-supported 5A adsorbent. Since the adsorption between the adsorbent and CO is a π-complex adsorption, which differs from the general PSA method of removing impurities to obtain product gas, a vacuum step is required to desorb the CO adsorbed on the adsorbent to obtain the product gas, i.e., pure CO.

[0069] S300: The second processed gas is introduced into the catalytic oxidation CO unit to carry out the third reaction.

[0070] In this step, the second processed gas is introduced into the catalytic oxidation CO unit 300 to carry out a third reaction, so as to obtain a third processed gas and CO2. Specifically, the catalytic oxidation CO unit 300 includes a fixed-bed reactor. The second processed gas enters the fixed-bed reactor packed with a second catalyst, and CO is catalytically oxidized to CO2. The third processed gas, including trace amounts of CO, CO2, N2 and H2, flows out from the top of the fixed bed and enters the deoxygenation unit 400.

[0071] Furthermore, the catalytic oxidation reaction is carried out at 100–200°C and atmospheric pressure, preferably using at least one of a Pt metal-supported catalyst, a PtRu bimetallic supported catalyst, or a copper-supported ZnO catalyst, to remove CO from the third-processed gas to below 10,000 ppmv. The catalytic oxidation CO unit 300 does not require a large amount of catalyst and does not have high conversion requirements, thus achieving energy savings.

[0072] S400: The third-stage processing gas is introduced into the deoxygenation unit for deoxygenation.

[0073] In this step, the aforementioned third processed gas is passed into the deoxygenation unit 400 for deoxygenation to obtain the fourth processed gas. Optionally, the deoxygenation unit 400 can remove oxygen from the fourth processed gas to below 0.1 ppmv through at least one of vacuum deoxygenation, distillation deoxygenation, membrane separation deoxygenation, and catalytic deoxygenation.

[0074] S500: The fourth processing gas is introduced into the compression unit for compression.

[0075] In this step, the fourth processing gas is passed into the compression unit 500 for compression to obtain the fifth processing gas. Specifically, the compression unit 500 is preferably a compressor, which compresses the fifth processing gas to 0.5 to 1 MPa.

[0076] S600: The fifth processing gas is introduced into the four-tower vacuum pressure swing adsorption unit to carry out the fourth reaction.

[0077] In this step, the fifth processed gas is passed into the four-tower vacuum pressure swing adsorption unit 600 to undergo the fourth reaction, in order to obtain the sixth processed gas and the first desorbed gas. For details, refer to... Figure 2 The four-tower vacuum pressure swing adsorption unit 600 includes four adsorption towers connected in parallel and a vacuum pump. The fifth processed gas enters the adsorption tower filled with the second adsorbent. Each adsorption tower is in a different stage of the time sequence, and each adsorption tower undergoes adsorption (AD), first pressure drop equalization (ED1), idle step (ID), second pressure drop equalization (ED2), vacuuming (VU), purging (PG), second pressure rise equalization (ER2), first pressure rise equalization (ER1), and final pressure rise (PR) at different times. The two equalization process saves energy and increases the recovery rate of H2 product gas. After the four-tower vacuum pressure swing adsorption, trace amounts of CO, CO2, and N2 are adsorbed and retained in the adsorption tower as strong adsorption components. The sixth processed gas contains H2, CO2, and N2, where the CO2 content is less than 0.1 ppmv, the N2 content is less than 3000 ppmv, and H2, as a weak adsorption component, flows out of the adsorption tower and enters the double reflux pressure swing adsorption unit 700 for further purification. A portion of the waste gas is discharged from the adsorption tower as the first desorption gas.

[0078] S700: The sixth processed gas is introduced into the dual-reflux pressure swing adsorption unit to carry out the fifth reaction.

[0079] In this step, the sixth processed gas is passed into a dual-reflux pressure swing adsorption unit to undergo the fifth reaction, in order to obtain the second desorbed gas and high-purity H2. For details, refer to... Figure 3The dual-reflux pressure swing adsorption unit 700 includes two parallel adsorption towers, a compressor, and a vacuum pump. First, the sixth processing gas is fed at high pressure from the middle of the first adsorption tower 6, producing high-purity hydrogen at the top. A portion of this hydrogen is collected as product gas, and the remainder is used as low-pressure purge gas for the second adsorption tower 7. Simultaneously, the heavy component gas produced at the bottom of the second adsorption tower 7 is refluxed back into the first adsorption tower 6, with the remainder discharged. Then, the first and second adsorption towers 6 are pressure-equalized to reduce energy consumption. Finally, the pressure of the first and second adsorption towers 6 is replaced. Strongly adsorbed components in the first adsorption tower 6 are extracted and pressurized before being fed into the second adsorption tower 7, raising the second adsorption tower 7 to the adsorption pressure for a symmetrical second half-cycle. During this process, trace amounts of CO, CO2, and N2 are adsorbed and retained in the adsorption towers as strongly adsorbed components, while H2, a weakly adsorbed component, flows out of the adsorption towers and can be recovered as high-purity hydrogen. A portion of the waste gas is also discharged from the adsorption towers as the second desorption gas. Among them, the purity of the high-purity H2 is higher than 99.992v, and the CO content is lower than 0.2ppmv.

[0080] The method for separating CO and H2 from coke oven gas according to embodiments of the present invention removes H2S and some O2 through catalytic oxidation of H2S and deoxygenation, thereby improving the efficiency of subsequent processing, reducing energy consumption, and increasing the purity of H2. By separating CO through pressure swing adsorption and catalytic oxidation of CO, a higher concentration of CO is enriched, improving the economic value of coke oven gas. By combining four-tower vacuum pressure swing adsorption and dual-reflux pressure swing adsorption, high-purity hydrogen is prepared while also increasing the yield. Therefore, by sequentially separating the effective components in coke oven gas using physical adsorption and catalytic oxidation methods, the entire separation process involves no complex chemical reactions and has a simple process route. It has advantages such as no complex chemical reactions, simple process flow, high separation efficiency, and low energy consumption. Moreover, the high-purity hydrogen obtained has a purity higher than 99.992 v%, with a CO content lower than 0.2 ppmv, which meets the requirements of fuel cells.

[0081] It should be noted that the features and advantages described above for the system for separating CO and H2 from coke oven gas also apply to the method for separating CO and H2 from coke oven gas, and will not be repeated here.

[0082] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0083] Example 1

[0084] The method flow for separating CO and H2 from coke oven gas in this embodiment is as follows:

[0085] The composition and content of coke oven gas are shown in Table 1:

[0086] Table 1. Composition and content of coke oven gas

[0087] Content (V%) 30 8 10 48 0.01 3.99

[0088] (1) Coke oven gas enters a fixed-bed reactor filled with metal oxide-based catalyst. The catalytic oxidation reaction is carried out at room temperature and standard atmospheric pressure. The H2S content in the first treated gas is less than 0.1 ppmv.

[0089] (2) The first processed gas enters the adsorption tower filled with copper-supported activated carbon adsorbent. Pressure swing adsorption is carried out at 303k and the adsorption pressure is 0.8-1MPa. The desorbed gas at the bottom of the adsorption tower after treatment is pure CO (purity is 98.32v, yield is 93.1wt%) and enters the gas storage tank. The recovered pure CO can meet the industrial CO purity requirements. At the same time, the second processed gas is discharged from the top of the tower and enters the next unit.

[0090] (3) The second processed gas enters a fixed-bed reactor packed with a Pt metal-supported catalyst. The catalytic oxidation reaction is carried out at 100-200°C and atmospheric pressure. The third processed gas is discharged into the next unit. The composition and content of the third processed gas are shown in Table 2.

[0091] Table 2. Components and content of the third-stage treated gas

[0092] Content (V%) 35％ 19％ 1％ 45％

[0093] (4) The third processing gas enters the deoxygenation unit 400 for vacuum deoxygenation. After deoxygenation, the oxygen content in the fourth processing gas is less than 0.1 ppmv.

[0094] (5) The fourth processing gas enters the compressor, and after compression, the pressure of the fifth processing gas is 0.5 to 1 MPa;

[0095] (6) The fifth processed gas enters the four-tower vacuum pressure swing adsorption unit. The adsorbent is 70 wt% activated carbon and 30 wt% 13X molecular sieve. The four adsorption towers are connected in parallel. Each adsorption tower is in a different stage of the time sequence. The time sequence control table of the four-tower vacuum pressure swing adsorption unit is shown in Table 3. The composition and content of the sixth processed gas are shown in Table 4.

[0096] Table 3 Timing Control Table for Four-Tower Vacuum Pressure Swing Adsorption Unit

[0097]

[0098] Table 4. Components and content of the sixth-stage treated gas

[0099] content 99.68v％ Less than 0.1 ppmv Above 1 ppmv Above 2000 ppmv

[0100] (7) The sixth processed gas enters the double reflux pressure swing adsorption unit, using 70 wt% activated carbon and 30 wt% 13X molecular sieve as adsorbents. Four adsorption towers are connected in parallel. The composition and content of high-purity hydrogen are shown in Table 4.

[0101] Table 5. Components and Content of High-Purity Hydrogen

[0102] content 99.992％ Below 0.002 ppmv Below 0.05 ppmv Less than 100 ppmv

[0103] Comparative Example 1

[0104] Unlike Example 1, this process does not employ catalytic oxidation. The coke oven gas sequentially passes through a coke oven gas catalytic oxidation H2S removal unit, a pressure swing adsorption (PSA) CO separation unit, a coke compression unit, a four-tower vacuum PSA unit, and a dual reflux PSA unit. The final product gas obtained from the dual reflux PSA unit has a CO content higher than 3 ppmv.

[0105] The comparative examples lead to the conclusion that if the process does not incorporate catalytic oxidation of CO, the final product gas will have an excessively high CO content, failing to meet the hydrogen standards for fuel cells.

[0106] Comparative Example 2

[0107] Unlike Example 1, this process does not incorporate a pressure swing adsorption (PSA) CO unit. Instead, the coke oven gas sequentially passes through a coke oven gas catalytic oxidation H2S unit, a PSA CO separation unit, a deoxygenation unit, a compression unit, a four-tower vacuum PSA unit, and a dual reflux PSA unit. The final product gas obtained from the dual reflux PSA unit has a hydrogen content higher than 99.99 v and a CO content lower than 0.2 ppmv.

[0108] Based on Comparative Example 2, it can be concluded that if the process does not incorporate a pressure swing adsorption (PSA) CO separation unit, although the final CO content is less than 0.2 ppmv, directly oxidizing a large amount of CO into CO2 wastes a large amount of CO in the coke oven gas and increases the amount of catalyst loaded, resulting in higher energy consumption.

[0109] Comparative Example 3

[0110] Unlike Example 1, the CO separation unit in this process does not use one or more of copper-supported activated carbon adsorbent, copper-supported Y molecular sieve adsorbent, and copper-supported 5A adsorbent, but instead uses one or more of activated carbon, 5A molecular sieve, and 13X molecular sieve. The coke oven gas sequentially passes through a coke oven gas catalytic oxidation H2S unit, a pressure swing adsorption CO separation unit, a deoxygenation unit, a compression unit, a four-tower vacuum pressure swing adsorption unit, and a dual-reflux pressure swing adsorption unit. The final hydrogen purity meets fuel cell standards, but the resulting CO gas contains other gases such as CO2, N2, and H2, resulting in lower purity.

[0111] Based on Comparative Example 3, it can be concluded that if the CO separation unit in the process does not use one or more of copper-supported activated carbon adsorbent, copper-supported Y molecular sieve adsorbent, and copper-supported 5A adsorbent, but instead uses one or more of activated carbon, 5A molecular sieve, and 13X molecular sieve, CO and N2 cannot be effectively separated, resulting in a decrease in CO gas purity and affecting the overall economic value of coke oven gas.

[0112] Comparative Example 4

[0113] Unlike Example 1, this process does not employ a dual-reflux pressure swing adsorption (PSA) unit. Instead, the coke oven gas sequentially passes through a coke oven gas catalytic oxidation H2S unit, a PSA CO separation unit, a deoxygenation unit, a compression unit, and a four-tower vacuum PSA unit. The final product gas obtained from the four-tower PSA unit has an H2 purity of 99.68 v and a yield of 83.3%. The CO content is higher than 0.3 ppmv, and the N2 content is higher than 3000 ppmv.

[0114] Based on Comparative Example 4, it can be concluded that if a dual-reflux pressure swing adsorption unit is not used in the process, the CO and N2 content in the H2 product gas will be higher than the standard for hydrogen used in fuel cells.

[0115] Comparative Example 5

[0116] Unlike Example 1, the four-tower vacuum pressure swing adsorption (PSA) unit and the dual-reflux PSA unit do not use activated carbon and 13X molecular sieves; instead, they use 5A molecular sieves and 13X molecular sieves. The coke oven gas sequentially passes through a coke oven gas catalytic oxidation H2S removal unit, a coke oven gas PSA CO separation unit, a coke oven gas deoxygenation unit, a coke oven gas compression unit, a four-tower vacuum PSA unit, and a dual-reflux PSA unit. However, the final hydrogen gas has a CO2 content higher than 2 ppmv.

[0117] Based on Comparative Example 5, it can be concluded that if activated carbon and 13X molecular sieves are not used in the four-tower vacuum pressure swing adsorption unit and the dual-reflux vacuum pressure swing adsorption unit, but instead 5A molecular sieves and 13X molecular sieves are used, the CO2 content in the H2 product gas will be higher than the standard for hydrogen used in fuel cells.

[0118] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0119] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A system for separating CO and H2 from coke oven gas, characterized in that, The system includes: A catalytic oxidation H2S unit, wherein the catalytic oxidation H2S unit has a coke oven gas inlet, a first catalyst inlet, and a first processed gas outlet; A pressure swing adsorption (PSA) CO separation unit, wherein the PSA CO separation unit has a first processing gas inlet, a first adsorbent inlet, a pure CO outlet, and a second processing gas outlet, wherein the first processing gas outlet is connected to the first processing gas inlet; A catalytic oxidation CO unit, the catalytic oxidation CO unit having a second processed gas inlet, a second catalyst inlet, and a third processed gas outlet, the second processed gas outlet being connected to the second processed gas inlet; A deoxygenation unit, the deoxygenation unit having a third processed gas inlet and a fourth processed gas outlet, the third processed gas outlet being connected to the third processed gas inlet; A compression unit, the compression unit having a fourth processing gas inlet and a fifth processing gas outlet, the fourth processing gas outlet being connected to the fourth processing gas inlet; The four-tower vacuum pressure swing adsorption unit has a fifth processing gas inlet, a second adsorbent inlet, a first desorption gas outlet, and a sixth processing gas outlet. The fifth processing gas outlet is connected to the fifth processing gas inlet. The second adsorbent comprises 70 wt% activated carbon and 30 wt% 13X molecular sieve. A dual-reflux pressure swing adsorption unit, comprising a sixth processing gas inlet, a third adsorbent inlet, a high-purity H2 outlet, and a second desorption gas outlet, wherein the sixth processing gas outlet is connected to the sixth processing gas inlet; The first adsorbent includes at least one of copper-supported activated carbon adsorbent, copper-supported Y molecular sieve adsorbent, and copper-supported 5A adsorbent.

2. A method for separating CO and H2 from coke oven gas, using the system for separating CO and H2 from coke oven gas as described in claim 1, characterized in that, include: (1) The coke oven gas is passed into the catalytic oxidation H2S unit to carry out the first reaction in order to obtain the first processed gas; the H2S content in the first processed gas is less than 0.1 ppmv; (2) The first processed gas is passed into the pressure swing adsorption separation CO unit to carry out a second reaction in order to obtain a second processed gas and pure CO; the adsorbent for the second reaction includes at least one of copper-supported activated carbon adsorbent, copper-supported Y molecular sieve adsorbent and copper-supported 5A adsorbent. (3) The second processed gas is passed into the catalytic oxidation CO unit to carry out the third reaction in order to obtain the third processed gas; the CO content in the third processed gas is less than 10000 ppmv; (4) The third processing gas is passed into the deoxygenation unit for deoxygenation to obtain the fourth processing gas; the O2 content in the fourth processing gas is less than 0.1 ppmv; (5) The fourth processing gas is passed into a compression unit for compression to obtain a fifth processing gas; the pressure of the fifth processing gas is 0.5 to 1 MPa; (6) The fifth processing gas is passed into the four-tower vacuum pressure swing adsorption unit to carry out the fourth reaction in order to obtain the sixth processing gas and the first desorption gas; the adsorbent of the fourth reaction includes 70 wt% activated carbon and 30 wt% 13X molecular sieve. (7) The sixth processing gas is passed into the double reflux pressure swing adsorption unit to carry out the fifth reaction in order to obtain the second desorption gas and high-purity H2; the adsorbent of the fifth reaction includes 70 wt% activated carbon and 30 wt% 13X molecular sieve.

3. The method according to claim 2, characterized in that, The purity of the high-purity H2 is higher than 99.992v, and the CO content is lower than 0.2ppmv.

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