초록 ▼

Process of reducing water, CO2 and N2O in feed air, which: a first adsorbent such as alumina (25-40% volume) and a second adsorbent such as X zeolite (60-75% volume) are used; the online time of the adsorbent is determined by determining the concentration measured by an analyzer for CO2 concentratio

Process of reducing water, CO2 and N2O in feed air, which: a first adsorbent such as alumina (25-40% volume) and a second adsorbent such as X zeolite (60-75% volume) are used; the online time of the adsorbent is determined by determining the concentration measured by an analyzer for CO2 concentration at a position within the length of the second adsorbent when a maximum level of N2O is simultaneously obtained at the downstream end of the second adsorbent in the feed direction, wherein the online time is the time taken from commencing passing the feed air to the first and second adsorbents to the measurement by the analyzer of the determined concentration of CO2; at least the second adsorbent is regenerated by heated regeneration gas at a temperature of 140° C.-220° C.; and the molar ratio of the regenerating gas to feed air supplied during one iteration of the cycle is 0.08-0.5.

대표청구항 ▼

1. A method for determining conditions for the reduction, prior to cryogenic distillation, of the level of water, carbon dioxide and nitrous oxide in a feed air stream in a process comprising: (a) passing said feed air stream at a feed pressure in a feed direction through a first adsorbent which has

1. A method for determining conditions for the reduction, prior to cryogenic distillation, of the level of water, carbon dioxide and nitrous oxide in a feed air stream in a process comprising: (a) passing said feed air stream at a feed pressure in a feed direction through a first adsorbent which has a Henry's Law selectivity for carbon dioxide over nitrous oxide measured at 30° C. of at least 12.5, and subsequently through a second adsorbent whose Henry's Law constant for the adsorption of N2O measured at 30° C. is less than 500 mmol/g/atm and whose Henry's Law selectivity for CO2 over N2O is at most 5;(b) ceasing to pass said feed air stream to said first and second adsorbents after a first time period;(c) depressurising the gas in contact with the first and second adsorbents to a second pressure less than the feed pressure;(d) passing regenerating gas at the second pressure and at a first temperature which is in the range 140 to 220° C. to at least the second adsorbent in a direction opposite to the feed direction for a second time period, and subsequently passing the regenerating gas at the second pressure and a second temperature less than the first temperature to the second and first adsorbents in a direction opposite to the feed direction for a third time period;(e) ceasing passing regenerating gas to the first and second adsorbents;(f) repressurising the gas in contact with the first and second adsorbents to the feed pressure;(g) repeating steps (a) to (f);wherein the first adsorbent occupies from 25% to 40% by volume of the total volume occupied by the first and second adsorbents; and wherein the molar ratio of the regenerating gas to the feed air supplied during each iteration of the steps (a) to (f) is from 0.08 to 0.5;which method comprises:(i) placing an analyser for CO2 concentration measurement at a chosen position within the length of the second adsorbent;(ii) determining the threshold concentration measured by the CO2 analyser when a desired maximum level of N2O is simultaneously obtained at the downstream end of the second adsorbent in the feed direction;(iii) using the result of step (ii) to determine the maximum duration of the first time period, such that the maximum duration of the first time period is the time taken from commencing passing the feed air stream to the first and second adsorbents to the measurement by the analyser of the determined threshold concentration of CO2. 2. The method of claim 1, wherein the analyser for measurement of the concentration of CO2 is placed at a point is up to 45% of the way along the length of the second adsorbent in the feed direction. 3. The method of claim 1, wherein the nitrous oxide level downstream of the second adsorbent is at most 20% of its original level in the feed air stream. 4. A process for the reduction of the level of water, carbon dioxide and nitrous oxide in a feed air stream prior to cryogenic distillation, comprising: (a) passing said feed air stream at a feed pressure in a feed direction through a first adsorbent which has a Henry's Law selectivity for carbon dioxide over nitrous oxide measured at 30° C. of at least 12.5, and subsequently through a second adsorbent whose Henry's Law constant for the adsorption of N2O measured at 30° C. is less than 500 mmol/g/atm and whose Henry's Law selectivity for CO2 over N2O is at most 5;(b) ceasing to pass said feed air stream to said first and second adsorbents after a first time period;(c) depressurising the gas in contact with the first and second adsorbents to a second pressure less than the feed pressure;(d) passing regenerating gas at the second pressure and at a first temperature which is in the range 140 to 220° C. to at least the second adsorbent in a direction opposite to the feed direction for a second time period, and subsequently passing the regenerating gas at the second pressure and a second temperature less than the first temperature to the second and first adsorbents in a direction opposite to the feed direction for a third time period;(e) ceasing passing regenerating gas to the first and second adsorbents;(f) repressurising the gas in contact with the first and second adsorbents to the feed pressure;(g) repeating steps (a) to (f);wherein the first adsorbent occupies from 25% to 40% by volume of the total volume occupied by the first and second adsorbents;wherein the method further comprises:(i) placing an analyser for CO2 concentration measurement at a chosen position within the length of the second adsorbent; and(ii) determining the threshold concentration measured by the CO2 analyser when a desired maximum level of N2O is simultaneously obtained at the downstream end of the second adsorbent in the feed direction;wherein the maximum duration of the first time period is the time taken from commencing passing the feed air stream to the first and second adsorbents to the measurement by the analyser of the determined threshold concentration of CO2; andwherein the molar ratio of the regenerating gas to the feed air supplied during one iteration of the steps (a) to (f) is from 0.08 to 0.5. 5. The process of claim 4, wherein the second adsorbent is selected from the group consisting of NaX having a Si/Al ratio of from 1.25 to 1.0, 4A zeolite, 5A zeolite, mordenite, chabazite and clinoptilolite. 6. The process of claim 4, wherein the analyser for measurement of the concentration of CO2 is placed at a point is up to 45% of the way along the length of the second adsorbent in the feed direction. 7. The process of claim 4, wherein the ratio of the second time period to the first time period is less than 35%. 8. The process of claim 4, wherein the first time period is from 100 to 300 min. 9. The process of claim 4, wherein the second time period is from 20 min to 100 min. 10. The process of claim 4, wherein the temperature of the heated regenerating gas is from 140 to 180° C. 11. The process of claim 4, wherein the third time period is from 50 to 220 min. 12. The process of claim 4, wherein the first adsorbent occupies from 28% to 37% by volume of the total volume occupied by the first and second adsorbents. 13. The process of claim 5, wherein the second adsorbent is selected from NaX zeolite having a Si/Al ratio of from 1.25 to 1.0 and 5A zeolite. 14. The process of claim 4, wherein the first adsorbent is selected from alumina or impregnated alumina. 15. The process of claim 4, wherein the nitrous oxide level downstream of the second adsorbent is at most 20% of its original level in the feed air stream. 16. An apparatus for the reduction of the level of water, carbon dioxide and nitrous oxide from a feed air stream prior to cryogenic distillation, comprising: in an adsorbent bed, a layer of a first adsorbent which has a Henry's Law selectivity for carbon dioxide over nitrous oxide measured at 30° C. of at least 12.5 and a second adsorbent whose Henry's Law constant for the adsorption of N2O measured at 30° C. is less than 500 mmol/g/atm and whose Henry's Law selectivity for CO2 over N2O is at most 5, wherein the first adsorbent occupies from 25% to 40% by volume of the total volume occupied by the first and second adsorbents; andan analyser for carbon dioxide placed within the length of the second adsorbent. 17. The apparatus of claim 16, wherein the analyser for measurement of the concentration of CO2 is placed at a point is up to 45% of the way along the length of the second adsorbent in the feed direction. 18. The apparatus of claim 16, wherein the second adsorbent is selected from the group consisting of NaX having a Si/Al ratio of from 1.25 to 1.0, 4A zeolite, 5A zeolite, mordenite, chabazite and clinoptilolite. 19. The apparatus of claim 18, wherein the second adsorbent is selected from NaX zeolite having a Si/Al ratio of from 1.25 to 1.0 and 5A zeolite. 20. The apparatus of claim 16, wherein the first adsorbent is selected from alumina or impregnated alumina. 21. The apparatus of claim 16, wherein the first adsorbent occupies from 28% to 37% by volume of the total volume occupied by the first and second adsorbents. 22. A method of upgrading an apparatus designed to reduce the levels of carbon dioxide, nitrous oxide and water from a feed air stream by a temperature swing adsorption process in order that it can provide a reduction in the level of nitrous oxide in the feed air stream without use of an adsorbent having a Henry's Law selectivity measured at 30° C. for nitrous oxide compared to carbon dioxide of 0.5 or more, in which the adsorbents contained in the apparatus are removed and replaced with an identical total volume of adsorbent consisting of a layer of a first adsorbent which has a Henry's Law selectivity for carbon dioxide over nitrous oxide measured at 30° C. of at least 12.5 and a second adsorbent whose Henry's Law constant for the adsorption of N2O measured at 30° C. is less than 500 mmol/g/atm and whose Henry's Law selectivity for CO2 over N2O is at most 5, wherein the first adsorbent occupies from 25% to 40% by volume of the total volume occupied by the first and second adsorbents, and in which an analyser for carbon dioxide is placed within the length of the second adsorbent. 23. The method of claim 22, wherein the analyser for measurement of the concentration of CO2 is placed at a point is up to 45% of the way along the length of the second adsorbent in the feed direction. 24. The method of claim 22, wherein the second adsorbent is selected from the group consisting of NaX having a Si/Al ratio of from 1.25 to 1.0, 4A zeolite, 5A zeolite, mordenite, chabazite and clinoptilolite. 25. The method of claim 24, wherein the second adsorbent is selected from NaX zeolite having a Si/Al ratio of from 1.25 to 1.0 and 5A zeolite. 26. The method of claim 22, wherein the first adsorbent is selected from alumina or impregnated alumina. 27. The method of claim 22, wherein the first adsorbent occupies from 28% to 37% by volume of the total volume occupied by the first and second adsorbents.