Methods for separating ozone
View Patent ↗A method for separating ozone from a mixture of oxygen and ozone by feeding the mixture to at least one adsorbent bed containing an adsorbent material for adsorbing ozone. The adsorbent bed can be one of four adsorbent beds in a continuous adsorption cycle for producing ozone recycling the non-adsorbed oxygen together with make-up oxygen to the ozone generator or using it as a purge gas. An external purge gas is used to desorb the ozone to the customer process. With four beds present, for most of the time, two beds are in adsorption mode while the other two beds are in regeneration/production mode.
1. A method for the continuous production of ozone and recovery of oxygen in a purge cycle adsorption process having four adsorbent beds, in which the first, second, third and fourth beds each cycle sequentially through the following steps in an overlapping cycle:
a) Feeding an oxygen and ozone mixture from an ozone generator to a first bed, wherein ozone is adsorbed in the first bed and non-adsorbed oxygen passes through the first bed and is recycled back to the ozone generator;
b) Receiving rinse gas in a counter current direction to step a) from a third bed in step d) thereby desorbing ozone from the first bed to a customer process;
c) Feeding a nitrogen-rich purge gas in the counter current direction to step a) thereby desorbing the remaining ozone from the first bed to the customer process;
d) Feeding the oxygen and ozone mixture from the ozone generator to the first bed in the same direction as in step a) whereby ozone is adsorbed in the first bed and non-adsorbed oxygen rinse gas displaces the nitrogen-rich purge gas from the first bed and feeds the displaced nitrogen-rich purge gas to a third bed now in step b), preparing the first bed to repeat step a);
e) Feeding an oxygen and ozone mixture from an ozone generator to a second bed, wherein ozone is adsorbed in the second bed and non-adsorbed oxygen passes through the second bed and is recycled back to the ozone generator;
f) Receiving rinse gas in a counter current direction to step e) from a fourth bed in step h) thereby desorbing ozone from the second bed to a customer process;
g) Feeding a nitrogen-rich purge gas in the counter current direction to step e) thereby desorbing the remaining ozone from the second bed to the customer process;
h) Feeding the oxygen and ozone mixture from the ozone generator to the second bed in the same direction as in step e) whereby ozone is adsorbed in the second bed and non-adsorbed oxygen rinse gas displaces the nitrogen-rich purge gas from the second bed and feeds the displaced nitrogen-rich purge gas to a fourth bed now in step f), preparing the second bed to repeat step e);
wherein steps e) to h) are offset in time from steps a) to d) such that the beginning of steps a) and c) overlap with the end of steps e) and g) and the end of steps a) and c) overlap with the beginning of steps e) and g).
2. The method as claimed in claim 1 further comprising venting a portion of the rinse gas to the atmosphere at the start of step d) and step h).
3. The method as claimed in claim 1 in which make-up oxygen is mixed with recycled oxygen before it is fed to the ozone generator.
4. The method as claimed in claim 3 in which the mixture of recycled oxygen and make-up oxygen is fed through a blower to increase its pressure before being fed to the ozone generator.
5. The method as claimed in claim 3 in which the mixture of recycled oxygen and make-up oxygen is passed through an inline ozone destruct unit prior to being fed to the blower.
6. The method as claimed in claim 1 wherein the oxygen and ozone gas mixture that is fed to the adsorbent beds comprises about 1 to 30% by volume ozone.
7. The method as claimed in claim 6 wherein the oxygen and ozone gas mixture that is fed to the adsorbent beds comprises about 6 to 12% by volume ozone.
8. The method as claimed in claim 1 wherein a source of nitrogen is clean dry air.
9. The method as claimed in claim 1 wherein buffer tanks are connected to a source selected from the group consisting of the recovered ozone, the recycled oxygen and both.
10. The method as claimed in claim 1 wherein the first, second, third and fourth adsorbent beds contain an adsorbent material.
11. The method as claimed in claim 10 wherein the adsorbent material is selected from the group consisting of silica gel and high silica zeolites.
12. The method as claimed in claim 11 wherein the silica gel is of different particle sizes.
13. The method as claimed in claim 11 wherein the high silica zeolites are selected from the group consisting of DAY, MFI and dealuminated mordentite.
14. The method as claimed in claim 1 wherein the cycle is a concentration swing adsorption cycle.
15. The method as claimed in claim 1 wherein the duration of steps a) and c) and steps e) and g) are equal and in the range 5 to 500 seconds.
16. The method as claimed in claim 1 wherein the duration of steps a) and c) and steps e) and g) are equal and in the range of 50 to 300 seconds.
17. The method as claimed in claim 1 wherein the duration of steps a) and c) and steps e) and g) are equal and in the range of 60 to 180 seconds.
18. The method as claimed in claim 1 wherein the duration of steps b) and d) and steps f) and h) are equal and in the range of 5 to 90% of step a).
19. The method as claimed in claim 1 wherein the duration of steps b) and d) and steps f) and h) are equal and in the range of 30 to 80% of step a).