초록 ▼

The present invention relates to a process for purifying a syngas of the CO/H2 or N2/H2 type, which consists in removing CO2 and possibly other gaseous impurities (water, etc.) before the gas undergoes a cryogenic process. These impurities are adsorbed by the gas stream to be purified passing over

The present invention relates to a process for purifying a syngas of the CO/H2 or N2/H2 type, which consists in removing CO2 and possibly other gaseous impurities (water, etc.) before the gas undergoes a cryogenic process. These impurities are adsorbed by the gas stream to be purified passing over an NaLSX-type zeolite and then desorbed during a regeneration step which may be performed by raising the temperature (TSA) and/or reducing the pressure (PSA or VSA).

대표청구항 ▼

The invention claimed is: 1. A process for purifying syngas comprising hydrogen and at least one gas selected from the group consisting of carbon monoxide and nitrogen, contaminated with impurities comprising H2O and carbon dioxide, said process comprising the following successive steps: a) passing

The invention claimed is: 1. A process for purifying syngas comprising hydrogen and at least one gas selected from the group consisting of carbon monoxide and nitrogen, contaminated with impurities comprising H2O and carbon dioxide, said process comprising the following successive steps: a) passing the syngas to be purified through an adsorption zone comprising: adsorbent capable of selectively adsorbing carbon dioxide, which comprises at least one X zeolite of the faujasite type with an Si/Al ratio of 0.9 to 1.1 (NaLSX-type zeolite), at least 70% of the exchangeable sites of which are occupied by sodium ions, the rest of the cationic sites being occupied by a monovalent or polyvalent cation, at least one adsorbent, capable of selectively adsorbing each of other impurities except for CO2 and H2O, at least one adsorbent capable of selectively adsorbing H2O, the adsorbents being either intimately mixed or in the form of separate beds in successive layers; and b) desorbing the carbon dioxide and the other impurity or impurities adsorbed on the adsorbent or adsorbents described in a) by increasing the temperature and/or reducing the pressure, and optionally recycling some of a first purified gas. 2. A process according to claim 1 for purifying a syngas containing heavy hydrocarbons as a further impurity in addition to CO2, and H2O said adsorption zone comprising adsorbent capable of adsorbing heavy hydrocarbons, either intimately mixed with the adsorbent capable of selectively adsorbing CO2 or in the form of separate beds, the bed or beds of adsorbent(s) capable of selectively adsorbing the heavy hydrocarbons being placed upstream of the bed of adsorbent capable of selectively adsorbing CO2. 3. A process according to claim 1 for purifying a syngas containing one or more light hydrocarbons and/or NOx as impurities in addition to CO2 and water, wherein an adsorbent or adsorbents capable of adsorbing the light hydrocarbons and/or the NOx, is or are independently an alumina, a silica gel or an A-type or an X-type zeolite, are either intimately mixed with an adsorbent capable of selectively adsorbing the CO2 and optionally an adsorbent or adsorbents capable of adsorbing the heavy hydrocarbons, or in the form of separate beds, the bed or beds of adsorbent(s) capable of selectively adsorbing the light hydrocarbons and/or the NOx being placed downstream of the bed of adsorbent capable of selectively adsorbing the CO2. 4. A process according to claim 1 for purifying a syngas containing mercury as impurity in addition to CO2 and water and optionally heavy hydrocarbons and/or light hydrocarbons and/or NOx, wherein the adsorption zone comprises a bed based on a silver-exchanged zeolite. 5. A process according to claim 1 for purifying a syngas containing mercury as impurity in addition to CO2 and water and optionally heavy hydrocarbons and/or light hydrocarbons and/or NOx, further comprising an additional step comprising passing a gas stream from which mercury has to be stripped, upstream or downstream of the adsorption zone over active carbons impregnated with iodine or with sulphur. 6. A syngas purification process according to claim 1, wherein the NaLSX-type zeolite is present in agglomerated form with an agglomerating binder, the binder optionally being converted into a zeolite, representing from 5 to 30 parts by weight of the total weight of the agglomerate, the agglomerates optionally having a mean diameter ranging from about 0.2 to about 5 mm. 7. A syngas purification process according to claim 1, wherein the CO2 concentration of the gas mixture to be purified is less than or equal to 1,000 ppm, for adsorption pressures of around 3 MPa, and in that the CO2 partial pressure is less than or equal to 3 Pa. 8. A syngas purification process according to claim 1, comprising at least one adsorption system selected from the group consisting of the PSA, VSA and TSA. 9. A process according to claim 1, wherein said rest of the cationic sites are occupied by a cation selected from the group consisting of K, Ca, and mixtures thereof. 10. A process according to claim 1, wherein the Si/Al ratio is 1 to 1.05. 11. A process according to claim 1, wherein the Si/Al ratio is 1 to 1. 12. A process according to claim 1, wherein at least 90% of the exchangeable sites are occupied by sodium ions. 13. A process according to claim 10, wherein at least 90% of the exchangeable sites are occupied by sodium ions. 14. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is greater than or equal to 0.5 MPa. 15. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is greater than or equal to 2 MPa. 16. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is less than or equal to 7 MPa. 17. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is less than or equal to 5 MPa. 18. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is less than or equal to 3 MPa. 19. A syngas purification process according to claim 1, wherein the pressure of the syngas to be purified during adsorption is 2-3 MPa. 20. A syngas purification process according to claim 1, wherein the temperature of the syngas entering the adsorption zone is 0-80째 C. 21. A syngas purification process according to claim 1, wherein the temperature of the syngas entering the adsorption zone is 20-50째 C. 22. A syngas purification process according to claim 1, wherein the desorption temperature is 100-300째 C. 23. A syngas purification process according to claim 1, wherein the temperature of the syngas entering the adsorption zone is 150-250째 C. 24. A syngas purification process according to claim 1, wherein the CO2 concentration of the syngas to be purified is less than or equal to 100 ppm for adsorption pressures of around 3 MPa. 25. A syngas purification process according to claim 1, wherein the CO2 partial pressure in the syngas to be purified is less than or equal to 0.3 Pa. 26. A process according to claim 1, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and H2O, is intimately mixed with the adsorbent capable of selectively adsorbing CO2. 27. A process according to claim 1, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and H2O, is downstream of the adsorbent capable of selectively adsorbing carbon dioxide. 28. A process according to claim 1, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and H2O, adsorbs hydrocarbons and nitrogen oxides. 29. A process according to claim 28, wherein the hydrocarbons are light hydrocarbons or heavy hydrocarbons and the nitrogen oxides are N2O, NO and NO2. 30. A process according to claim 1, further comprising increasing the pressure in the adsorption zone by introducing a flow of a purified gas via the outlet of the adsorption zone and/or cooling the adsorption zone by flushing with at least some of a cold second purified gas. 31. A process according to claim 1, wherein the adsorption zone comprises an upstream bed of said adsorbent capable of selectively adsorbing H2O and a downstream bed of said adsorbent capable of selectively adsorbing carbon dioxide. 32. A process according to claim 1, wherein the syngas comprises hydrogen and carbon monoxide. 33. A process according to claim 1, wherein the syngas comprises hydrogen and nitrogen. 34. A process for purifying syngas comprising hydrogen and at least one gas selected from the group consisting of carbon monoxide and nitrogen, contaminated with impurities comprising carbon dioxide, comprising the following successive steps: a) passing the syngas to be purified through an adsorption zone comprising: adsorbent capable of selectively adsorbing carbon dioxide, which comprises at least one X zeolite of the faujasite type with an Si/Al ratio of 0.9 to 1.1 (NaLSX-type zeolite), at least 70% of the exchangeable sites of which are occupied by sodium ions, the rest of the cationic sites being occupied by a monovalent or polyvalent cation, at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and water, the at least one adsorbent being either intimately mixed or in the form of separate beds in successive layers; b) desorbing the carbon dioxide and the other impurity or impurities adsorbed on the adsorbent or adsorbents described in a) by increasing the temperature and/or reducing the pressure, and optionally recycling some of a first purified gas; and c) increasing the pressure in the adsorption zone by introducing a flow of a purified gas via the outlet of the adsorption zone and/or cooling the adsorption zone by flushing with at least some of a cold second purified gas. 35. A process according to claim 34 for purifying a syngas containing at least one of water and heavy hydrocarbons as impurities in addition to CO2, said adsorption zone comprising adsorbent capable of adsorbing heavy hydrocarbons, either intimately mixed with the adsorbent capable of selectively adsorbing CO2 or in the form of separate beds, the bed or beds of adsorbent(s) capable of selectively adsorbing the heavy hydrocarbons being placed upstream of the bed of adsorbent capable of selectively adsorbing CO2. 36. A process according to claim 34 for purifying a syngas containing one or more light hydrocarbons and/or NOx as impurities in addition to CO2 and optionally water and/or heavy hydrocarbons, wherein an adsorbent or adsorbents capable of adsorbing the light hydrocarbons and/or the NOx, is or are independently an alumina, a silica gel or an A-type or an X-type zeolite, are either intimately mixed with the adsorbent capable of selectively adsorbing the CO2 and optionally an adsorbent or adsorbents capable of adsorbing the heavy hydrocarbons, or in the form of separate beds, the bed or beds of adsorbent(s) capable of selectively adsorbing the light hydrocarbons and/or the NOx being placed downstream of the bed of adsorbent capable of selectively adsorbing the CO2. 37. A process according to claim 34 for purifying a syngas containing mercury as impurity in addition to CO2 and optionally in addition to water and/or heavy hydrocarbons, light hydrocarbons and/or NOx, wherein the adsorption zone comprises a bed based on a silver-exchanged zeolite. 38. A process according to claim 34 for purifying a syngas containing mercury as impurity in addition to CO2 and optionally water and/or heavy hydrocarbons, light hydrocarbons and/or NOx, further comprising an additional step comprising passing a gas stream from which mercury has to be stripped, upstream or downstream of the adsorption zone over active carbons impregnated with iodine or with sulphur. 39. A syngas purification process according to claim 34, wherein the NaLSX-type zeolite is present in agglomerated form with an agglomerating binder, the binder optionally being converted into a zeolite, representing from 5 to 30 parts by weight of the total weight of the agglomerate, the agglomerates optionally having a mean diameter ranging from about 0.2 to about 5 mm. 40. A syngas purification process according to claim 34, wherein the CO2 concentration of the gas mixture to be purified is less than or equal to 1,000 ppm, for adsorption pressures of around 3 MPa, and in that the CO2 partial pressure is less than or equal to 3 Pa. 41. A syngas purification process according to claim 34, comprising at least one adsorption system selected from the group consisting of the PSA, VSA and TSA. 42. A process according to claim 34, wherein said rest of the cationic sites are occupied by a cation selected from the group consisting of K, Ca, and mixtures thereof. 43. A process according to claim 34, wherein the Si/Al ratio is 1 to 1.05. 44. A process according to claim 34, wherein the Si/Al ratio is 1 to 1. 45. A process according to claim 34, wherein at least 90% of the exchangeable sites are occupied by sodium ions. 46. A process according to claim 43, wherein at least 90% of the exchangeable sites are occupied by sodium ions. 47. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is greater than or equal to 0.5 MPa. 48. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is greater than or equal to 2 MPa. 49. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is less than or equal to 7 MPa. 50. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is 0.5-7 MPa. 51. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is less than or equal to 5 MPa. 52. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is less than or equal to 3 MPa. 53. A syngas purification process according to claim 34, wherein the pressure of the gas mixture to be purified during adsorption is 2-3 MPa. 54. A syngas purification process according to claim 34, wherein the temperature of the gas stream entering the adsorption zone is 0-80째 C. 55. A syngas purification process according to claim 34, wherein the temperature of the gas stream entering the adsorption zone is 20-50째 C. 56. A syngas purification process according to claim 34, wherein the desorption temperature is 100-300째 C. 57. A syngas purification process according to claim 34, wherein the desorption temperature is 150-250째 C. 58. A syngas purification process according to claim 34, wherein the CO2 concentration of the gas mixture to be purified is less than or equal to 100 ppm for adsorption pressures of around 3 MPa. 59. A syngas purification process according to claim 34, wherein the CO2 partial pressure is less than or equal to 0.3 Pa. 60. A process according to claim 34, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and water, is intimately mixed with the adsorbent capable of selectively adsorbing CO2. 61. A process according to claim 34, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and water, is downstream of the adsorbent capable of selectively adsorbing carbon dioxide. 62. A process according to claim 34, wherein the at least one adsorbent, capable of selectively adsorbing each of other impurities aside from CO2 and water, adsorbs hydrocarbons and nitrogen oxides. 63. A process according to claim 62, wherein the hydrocarbons are light hydrocarbons or heavy hydrocarbons and the nitrogen oxides are N2O, NO and NO2.