Process and device for finely removing impurities from carbon monoxide after cryogenic separation of synthesis gas

Abstract

The invention belongs to the technical field of coal ethylene glycol, and particularly relates to a process and a device for finely removing impurities from carbon monoxide after cryogenic separation of synthesis gas, the device comprises an impurity removal device, the impurity removal device comprises a desulfurization tank, a dechlorination tank and a decarbonylation tank which are sequentially connected in series, or an adsorption tower which is sequentially filled with desulfurization, dechlorination and decarbonylation adsorbents; the impurity removal device is arranged to remove trace hydrogen sulfide, hydrogen chloride, carbonyl iron and carbonyl nickel in CO after cryogenic separation, so that ppb-level removal of impurities in CO is realized, poisoning of a downstream dimethyl oxalate (DMO) synthesis catalyst is avoided, the service life of the catalyst is prolonged, the production cost of an enterprise is reduced, and the operation stability of the device is improved.

Description

[0001] This invention belongs to the field of coal-to-ethylene glycol technology, specifically relating to a process and apparatus for carbon monoxide purification after cryogenic separation of syngas. Background Technology

[0002] In the coal-to-ethylene glycol process, after the syngas is cryogenically separated and purified to CO, it needs to be transported to the DMO synthesis section to react with methyl nitrite to produce DMO. The core catalyst in this section is a palladium-based noble metal catalyst, which is extremely sensitive to impurities such as S, Cl, Fe, and Ni. When the H2S content exceeds 0.1 ppm, HCl exceeds 0.01 ppm, and carbonyl compounds (Fe+Ni) exceed 0.01 ppm, irreversible poisoning will occur, leading to rapid decline in catalyst activity and selectivity, thereby shortening the catalyst's lifespan and increasing the frequency of unit shutdowns for maintenance and production costs.

[0003] Current technologies generally employ a "centralized purification before cryogenic separation" strategy. This involves controlling impurities to the ppm level through low-temperature methanol washing, fine desulfurization, dechlorination, and carbonyl decomposition / adsorption units before the CO enters the cryogenic separation system. However, in actual production, upstream purification units experience issues such as adsorbent breakthrough, operating condition fluctuations, and start-up / shutdown shocks. These problems lead to a rebound of trace impurities in CO after cryogenic separation, directly threatening the safety of DMO catalysts. Furthermore, there is a technological bias within the industry that "no impurity removal is necessary after cryogenic separation," assuming that impurities are already extremely low after cryogenic separation. The low-temperature, high-pressure environment after cryogenic separation is also believed to lead to poor adsorbent activity, difficult regeneration, and excessively high costs. Therefore, current technologies do not design dedicated fine impurity removal schemes for CO after cryogenic separation, failing to provide a "double insurance" for impurity removal, and the risk of catalyst poisoning remains. Summary of the Invention

[0004] This invention aims to solve the problem in existing technologies where trace impurities in CO after cryogenic separation easily lead to poisoning of DMO catalysts and short service life. It provides a process and apparatus for removing impurities from carbon monoxide after cryogenic separation of syngas, used to remove trace amounts of hydrogen sulfide (H2S), hydrogen chloride (HCl), iron carbonyl (Fe(CO)5), and nickel carbonyl (Ni(CO)4) from CO after cryogenic separation. This achieves ppb-level removal of impurities from CO, avoids poisoning of downstream dimethyl oxalate (DMO) synthesis catalysts, extends catalyst service life, reduces enterprise production costs, and improves the operational stability of the equipment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A process for removing impurities from syngas after cryogenic separation and carbon monoxide purification includes the following steps: Syngas is purified by a cryogenic separation unit to obtain CO product gas with a pressure of 2.0~5.0 MPa, a temperature of 20~40℃, and a purity ≥99.9%, containing trace amounts of H2S (≤0.1 ppm), HCl (≤0.01 ppm), Fe(CO)5 (≤0.01 ppm), and Ni(CO)4 (≤0.005 ppm). The CO product gas is then passed into a purification device, where an adsorbent is used to adsorb and remove impurities from the CO product gas. The entire process operates at 20℃~40℃ and a pressure of 2.0~5.0 MPa. The impurity content is monitored in real time using an online monitoring instrument. The qualified CO product gas with impurities removed is then transported to the DMO synthesis section.

[0006] Furthermore, the CO inlet of the impurity removal device is connected to the CO outlet of the cryogenic separation device via a pipeline, and the CO outlet of the impurity removal device is connected to the CO inlet of the DMO synthesis device via a pipeline; the impurity removal device includes a desulfurization tank, a dechlorination tank, and a decarbonylation tank connected in series.

[0007] Furthermore, the CO inlet of the impurity removal device is connected to the CO outlet of the cryogenic separation device via a pipeline, and the CO outlet of the impurity removal device is connected to the CO inlet of the DMO synthesis device via a pipeline; the impurity removal device is an adsorption tower, and the adsorption tower is sequentially filled with desulfurization adsorbent, dechlorination adsorbent, and decarbonylation adsorbent.

[0008] Furthermore, the impurity removal device is also equipped with a backup impurity removal device, which automatically switches to the backup impurity removal device when the impurity content in the qualified CO product gas approaches the threshold.

[0009] Furthermore, the desulfurization tank is filled with nano-ZnO-CeO2 composite adsorbent, the dechlorination tank is filled with CuO-γ-Al2O3 modified adsorbent, and the decarbonylation tank is filled with Fe2O3-modified coconut shell activated carbon adsorbent.

[0010] Furthermore, the impurities in the CO product gas include H2S, HCl, Fe(CO)5, and Ni(CO)4. After impurity removal treatment, H2S ≤ 0.01 ppm, HCl ≤ 0.001 ppm, and carbonyl compounds (Fe+Ni) ≤ 0.001 ppm.

[0011] A device for removing impurities from carbon monoxide after cryogenic separation of syngas includes an impurity removal unit, which comprises a desulfurization tank, a dechlorination tank, and a decarbonylation tank connected in series, as well as an online monitoring and automatic control unit. The desulfurization tank, dechlorination tank, and decarbonylation tank are all pressure-resistant tanks, and the bed inside the tanks is filled in sections with a gradient pore size. The online monitoring and automatic control unit includes an online total sulfur monitor, an online total chlorine monitor, an online carbonyl compound monitor, a switching valve, and a controller. The monitors and the switching valve are electrically connected to the controller.

[0012] A device for removing impurities from carbon monoxide after cryogenic separation of syngas includes an impurity removal device, which is an adsorption tower. The adsorption tower is sequentially equipped with a desulfurization section, a dechlorination section, and a decarbonylation section. The online monitoring and automatic control unit includes an online total sulfur monitor, an online total chlorine monitor, an online carbonyl compound monitor, a switching valve, and a controller. The monitors and the switching valve are electrically connected to the controller.

[0013] Furthermore, the desulfurization adsorbent is a nano-ZnO-CeO2 composite adsorbent with an adsorption capacity ≥15wt%; it selectively adsorbs H2S and COS at room temperature; the dechlorination adsorbent is a CuO-γ-Al2O3 modified adsorbent, which adsorbs HCl and trace amounts of organic chlorine with a removal rate ≥99.9%; and the decarbonylation adsorbent is a Fe2O3-modified coconut shell activated carbon adsorbent, which simultaneously decomposes and adsorbs Fe(CO)5 and Ni(CO)4 with a removal rate ≥99.5%.

[0014] Furthermore, the gradient pore size segmented filling is as follows: the upper layer is filled with fine pore adsorbent with a pore size of 1~3nm, and the lower layer is filled with coarse pore adsorbent with a pore size of 5~10nm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. Breakthrough overcoming technical bias: For the first time, a dual-insurance strategy of "pre-cryogenic primary removal + post-cryogenic fine removal as a backup" was proposed, which solved the industry pain points of upstream purification fluctuations leading to impurity rebound and catalyst poisoning in existing technologies, and filled the technical gap in the fine removal of trace CO impurities after cryogenic removal.

[0016] 2. Significant impurity removal effect: H2S, HCl, and carbonyl compounds are reduced to the ppb level, meeting the stringent requirements of DMO palladium catalysts, thereby extending catalyst life and significantly reducing catalyst replacement costs and the number of shutdowns for maintenance.

[0017] 3. High operational stability: Online monitoring and automatic control enable intelligent operation, while backup impurity removal devices ensure continuous production, preventing full-line shutdowns caused by excessive impurities and improving the reliability and safety of the equipment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structural composition of the present invention; Figure 2 This is a schematic diagram of the structural composition of the present invention (b); In the diagram: 1-CO pipeline; 2-Desulfurization tank; 3-Dechlorination tank; 4-Decarbonylation tank; 5-Standby desulfurization tank; 6-Standby dechlorination tank; 7-Standby decarbonylation tank; 8-CO delivery pipe; 9-Adsorption tower; 10-Desulfurization section; 11-Dechlorination section; 12-Decarbonylation section; 13-Standby adsorption tower. Detailed Implementation Example 1

[0019] Reference Figure 1 To extend the service life of DMO catalysts, reduce production costs, and improve the operational stability of the equipment, this invention provides a process for carbon monoxide purification after cryogenic separation of syngas. The process includes: cryogenic separation of syngas to obtain CO product gas with a pressure of 3.5 MPa, a temperature of 30°C, and a purity of 99.92%, containing 0.08 ppm H2S, 0.008 ppm HCl, 0.007 ppm Fe(CO)5, and 0.003 ppm Ni(CO)4.

[0020] The CO product gas is introduced into the impurity removal device of this invention through CO pipeline 1. The impurity removal device consists of a desulfurization tank 2, a dechlorination tank 3, and a decarbonylation tank 4 connected in series. The desulfurization tank 2 is filled with nano-ZnO-CeO2 adsorbent with a bed height of 2.5m; the dechlorination tank 3 is filled with CuO-γ-Al2O3 adsorbent with a bed height of 2.0m; and the decarbonylation tank 4 is filled with Fe2O3-modified coconut shell activated carbon adsorbent with a bed height of 3.0m. The entire process operates at 30℃ and 3.5MPa. The desulfurization tank 2, dechlorination tank 3, and decarbonylation tank 4 are respectively equipped with a backup desulfurization tank 5, a backup dechlorination tank 6, and a backup decarbonylation tank 7.

[0021] The desulfurization tank 2, dechlorination tank 3, and decarbonylation tank 4 are equipped with online total sulfur monitors, online total chlorine monitors, and online carbonyl compound monitors, respectively, to monitor the impurity content in the CO product gas in real time. This ensures that the purified CO product gas contains H2S ≤ 0.01 ppm, HCl ≤ 0.001 ppm, and carbonyl compound (Fe+Ni) ≤ 0.001 ppm, achieving a CO purity of 99.99%. This qualified gas is then transported to the DMO synthesis section via CO delivery pipe 8. The palladium-based catalyst is less prone to deactivation, maintaining high activity for extended periods and extending its service life, thereby reducing the company's catalyst replacement costs. Example 2

[0022] Reference Figure 2 To extend the service life of DMO catalysts, reduce production costs, and improve the operational stability of the equipment, this invention provides a process for carbon monoxide purification after cryogenic separation of syngas. The process includes: cryogenic separation of syngas to obtain CO product gas with a pressure of 3.5 MPa, a temperature of 30°C, and a purity of 99.95%, wherein the content of H2S is 0.06 ppm, HCl is 0.006 ppm, Fe(CO)5 is 0.005 ppm, and Ni(CO)4 is 0.002 ppm.

[0023] The CO product gas is introduced into the impurity removal device of the present invention through CO pipeline 1. The impurity removal device is an adsorption tower 9 that is sequentially filled with desulfurization, dechlorination and decarbonylation adsorbents. The desulfurization adsorbent is nano ZnO-CeO2 adsorbent with a bed height of 3.0m, the dechlorination adsorbent is CuO-γ-Al2O3 adsorbent with a bed height of 3.0m, and the decarbonylation adsorbent is Fe2O3-modified coconut shell activated carbon adsorbent with a bed height of 4.0m. The entire process is carried out at 35℃ and 4.0MPa. The adsorption tower 9 is equipped with a backup adsorption tower 13.

[0024] The adsorption tower is equipped with online total sulfur monitors, online total chlorine monitors, and online carbonyl compound monitors at the end of the desulfurization section 10, the end of the dechlorination section 11, and the end of the decarbonylation section 12, respectively. These monitors are used to monitor the impurity content in the CO product gas in real time, ensuring that the purified CO product gas contains H2S ≤ 0.01 ppm, HCl ≤ 0.001 ppm, and carbonyl compound (Fe+Ni) ≤ 0.001 ppm, thus increasing the CO purity to 99.99%. This qualified gas is transported to the DMO synthesis section through CO delivery pipe 8. The palladium-based catalyst is not easily deactivated and maintains high activity for a long time, extending its service life and reducing the company's catalyst replacement costs.

[0025] Another embodiment differs from Embodiment 1 in that the CO product gas pressure is 2.0 MPa, the temperature is 20°C, the purity is 99.97%, and the content of H2S is 0.04 ppm, HCl is 0.004 ppm, Fe(CO)5 is 0.005 ppm, and Ni(CO)4 is 0.002 ppm.

[0026] Another embodiment differs from Embodiment 1 in that the CO product gas pressure is 3.0 MPa, the temperature is 25°C, the purity is 99.99%, and the content of H2S is 0.02 ppm, the content of HCl is 0.002 ppm, the content of Fe(CO)5 is 0.003 ppm, and the content of Ni(CO)4 is 0.001 ppm.

[0027] Another embodiment differs from Embodiment 1 in that the CO product gas pressure is 5.0 MPa and the temperature is 40°C.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for carbon monoxide purification and impurity removal after cryogenic separation of syngas, characterized in that, Includes the following: After purification by a cryogenic separation unit, the syngas yields CO product gas with a pressure of 2.0~5.0 MPa, a temperature of 20~40℃, and a purity of ≥99.9%. The CO product gas is then passed into a purification unit, where an adsorbent is used to adsorb and remove impurities from the CO product gas. The entire process operates at a temperature of 20℃~40℃ and a pressure of 2.0~5.0 MPa. The impurity content is monitored in real time by an online monitoring instrument. The qualified CO product gas with impurities removed is then transported to the DMO synthesis section.

2. The process for removing impurities from syngas after cryogenic separation using carbon monoxide, as described in claim 1, is characterized in that: The impurity removal device includes a desulfurization tank, a dechlorination tank, and a decarbonylation tank connected in series. The desulfurization tank, dechlorination tank, and decarbonylation tank are respectively filled with desulfurization adsorbent, dechlorination adsorbent, and decarbonylation adsorbent.

3. The process for removing impurities from carbon monoxide after cryogenic separation of syngas according to claim 1, characterized in that: The impurity removal device is an adsorption tower, which is equipped with a desulfurization section, a dechlorination section, and a decarbonylation section in sequence. The desulfurization section, dechlorination section, and decarbonylation section are respectively filled with desulfurization adsorbent, dechlorination adsorbent, and decarbonylation adsorbent.

4. The process for removing impurities from carbon monoxide after cryogenic separation of syngas according to claim 2 or 3, characterized in that: The desulfurization adsorbent is a nano-ZnO-CeO2 composite adsorbent, the dechlorination adsorbent is a CuO-γ-Al2O3 modified adsorbent, and the decarbonylation adsorbent is a Fe2O3-modified coconut shell activated carbon adsorbent.

5. A process for removing impurities from carbon monoxide after cryogenic separation of syngas according to any one of claims 1-4, characterized in that: The impurity removal device is also equipped with a backup impurity removal device, which automatically switches to the backup impurity removal device when the impurity content in the qualified CO product gas approaches the threshold.

6. The process for removing impurities from carbon monoxide after cryogenic separation of syngas according to claim 1, characterized in that: Impurities in CO product gas include H2S, HCl, Fe(CO)5, and Ni(CO)4. After treatment, H2S ≤ 0.01 ppm, HCl ≤ 0.001 ppm, and carbonyl compounds (Fe+Ni) ≤ 0.001 ppm.

7. A device for carbon monoxide purification and impurity removal after cryogenic separation of syngas, characterized in that: The device includes an impurity removal unit, whose CO inlet is connected to the CO outlet of a cryogenic separation unit via a pipeline, and whose CO outlet is connected to the CO inlet of a DMO synthesis unit via a pipeline. The impurity removal unit comprises a desulfurization tank, a dechlorination tank, and a decarbonylation tank connected in series, as well as an online monitoring and automatic control unit. All three tanks are pressure-resistant, and each is filled with a desulfurization adsorbent, dechlorination adsorbent, and decarbonylation adsorbent, respectively. The online monitoring and automatic control unit includes an online total sulfur monitor, an online total chlorine monitor, an online carbonyl compound monitor, a switching valve, and a controller. The monitors and switching valves are electrically connected to the controller.

8. A device for carbon monoxide purification and impurity removal after cryogenic separation of syngas, characterized in that: The system includes a purification device, whose CO inlet is connected to the CO outlet of a cryogenic separation unit via a pipeline, and whose CO outlet is connected to the CO inlet of a DMO synthesis unit via a pipeline. The purification device is an adsorption tower, which is sequentially equipped with a desulfurization section, a dechlorination section, and a decarbonylation section. The desulfurization section, dechlorination section, and decarbonylation section are respectively filled with desulfurization adsorbent, dechlorination adsorbent, and decarbonylation adsorbent. The online monitoring and automatic control unit includes an online total sulfur monitor, an online total chlorine monitor, an online carbonyl compound monitor, a switching valve, and a controller. The monitors and the switching valve are electrically connected to the controller.

9. The apparatus for carbon monoxide purification after cryogenic separation of syngas according to claim 7, characterized in that: The adsorbent beds inside the desulfurization tank, dechlorination tank, and decarbonylation tank are filled in sections with gradient pore sizes.

10. A carbon monoxide purification and impurity removal device after cryogenic separation of syngas according to claim 9, characterized in that: The gradient pore size segmented filling is as follows: the upper layer is filled with fine pore adsorbent with a pore size of 1~3nm, and the lower layer is filled with coarse pore adsorbent with a pore size of 5~10nm.

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