Method of purifying a gas stream contaminated by CO
View Patent ↗The present invention relates to a novel method of purifying a gas stream contaminated by CO 2 , hydrocarbons and/or nitrogen oxides, in particular a gas stream based on air or a syngas, by adsorption on a bed of aggregated zeolitic adsorbent based on an LSX zeolite or LSX and X zeolites, of which at least 90% of the exchangeable cationic sites of the LSX zeolite or of the LSX/X zeolite blend are occupied by sodium ions, and the inert binder of which represents at most 5% of the weight of the adsorbent.
1. A method of purifying a gas stream from both carbon dioxide and at least one other impurity chosen from among hydrocarbons and nitrogen oxides, said method comprising:
A—bringing the gas stream to be purified into contact with at least one adsorbent in aggregated form
either comprising at least 85% by weight of zeolite LSX having at least 90% of the exchangeable sites occupied by sodium ions, and the rest of the cations optionally being-potassium and up to 5% by weight of a binder that is inert to the adsorption, or 5-25 parts by weight of a zeolitized clay binder per 100 parts of final aggregate (type A aggregate);
or comprising at least 70%, by weight of a blend of at least 20% of zeolite X and of at most 80%, by weight of zeolite LSX, said blend having at least 90%, of the exchangeable sites of the said zeolites X and LSX of which are occupied by sodium ions, the rest of the cations optionally being, potassium cations, and up to 5% by weight of a binder that is inert to the adsorption or 5-25 parts by weight of a zeolitized clay binder per 100 parts of final aggregate and optionally up to 25% of one or more other zeolites (type B aggregate); and wherein the number average size of zeolite LSX crystals in aggregate A and aggregate B is less than 4 microns;
B—adsorbing at least some of the carbon dioxide, and at least some of the hydrocarbons and/or N x O y on the said adsorbent;
C—desorbing the impurities adsorbed on the said adsorbent; and
D—regenerating the adsorbent.
2. A method according to claim 1 , characterized in that the gas stream to be purified comprises air.
3. A method according to claim 1 , characterized in that the gas stream to be purified comprises syngas.
4. A method according to claim 1 , the adsorbent comprises at least one bed comprising a blend of several adsorbents including adsorbent type B.
5. A method according to claim 1 , wherein the adsorbent comprises a binder which is a zeolitized clay in a concentration of 5-25 parts by weight.
6. A method according to claim 5 , wherein the adsorbent comprises a type A aggregate.
7. A method according to claim 5 , wherein the adsorbent comprises a type B aggregate.
8. A method according to claim 6 , wherein at least 98% of the exchangeable sites in the zeolite LSX are occupied by sodium ions.
9. A method according to claim 7 , wherein at least 98% of the exchangeable sites in zeolites X and LSX are occupied by sodium ions.
10. A method according to claim 9 , wherein the blend comprises at least 30% and at most 80% zeolite X.
11. A method according to claim 1 , wherein the binder is inert to adsorption.
12. A method according to claim 1 , wherein said adsorbing step B removes carbon dioxide, to the extent that the concentration leaving the adsorbent constitutes about 1-5% of the initial concentration in the gas stream being adsorbed.
13. A method according to claim 12 , characterized in that the gas stream to be purified comprises air.
14. A method according to claim 12 , characterized in that the gas stream to be purified comprises syngas.
15. A method according to claim 6 characterized in that a PSA, TSA, TPSA or TEPSA-type process is carried out.