IL41351A

IL41351A - Selective adsorption process for air separation

Info

Publication number: IL41351A
Application number: IL41351A
Authority: IL
Original assignee: Union Carbide Corp
Priority date: 1972-01-24
Filing date: 1973-01-21
Publication date: 1976-01-30
Also published as: IT1045927B; ATA55573A; FR2169162B2; ES410887A2; BR7300495D0; NL7300956A; FR2169162A2; NL167332C; SE399826B; ZA73482B; JPS4883078A; DE2303153C2; AT358545B; GB1424457A; AU475375B2; HK66276A; DE2303153A1; NL167332B; JPS549587B2; BE794425A

Claims

amui WHAT IS CLAIMED IS:

1. In an adiabatic pressure swing process for air separation by selectively adsorbing nitrogen alternately in at least three zeolitic molecular sieve adsorption beds at ambient temperature by introducing feed air to the inlet end of a first adsorption bed at highest superatmospheric pressure, discharging oxygen from the discharge end and introducing at least part of the oxygen to a purged bed for partial repressurization thereof, releasing additional oxygen from the first bed discharge end thereby cocurrently depressurizing said first bed and terminating such cocurrent depressuri zation when the first bed is at lower superatmospheric pressure, discharging one part of said oxygen from the first bed &s product and returning the balance of said oxygen for repressurization and purging of other adsorption beds, releasing waste gas from the first bed inlet end thereby countercurrently depressurizing same, introducing oxygen gas from another adsorption bed discharge end to the first bed discharge end as purge gas and flowing same therethrough at a lowest superatmospheric pressure for desorption of the nitrogen adsorbate and discharging the nitrogen adsorbate-containing purge gas from the first bed inlet end as waste gas, introducing oxygen gas from the discharge end of an other- than-first adsorption bed and at above said lowest superatmos heric ressure to the ur ed first bed for at least partial repressurization thereof, the improvement characterized by introducing said feed air to said first bed at highest superatmospheric pressure of 40-105 psia. , and terminating said cocurrent depressuri zation at lower superatmospheric pressure of 16-40 psia. with the feed air to cocurrent depressurization termination pressure ratio being at least 1.5, and maintaining an oxygen mass relationship of feed gas oxygen : oxygen gas from the first bed discharge end : oxygen return gas of 1:5 - 13.5 : 4 - 13.1.

2. An adiabatic pressure swing process according to claim 1 wherein said feed air is introduced to said first bed at highest superatmospheric pressure of 40-70 psia, said cocurrent depressurization is terminated at lower superatmospheric pressure of 16-32 psia and the oxygen mass relationship of feed gas oxygen : oxygen gas from the first bed discharge end : oxygen return gas is 1:5 - 9.5 : 4 - 9.1.

3. An adiabatic pressure swing process according to claim 1 with four adsorption beds wherein said feed air is introduced to said first bed at highest superatmospheric pressure and oxygen is simultaneously discharged at substantially the same pressure, the first bed is first higher pressure equalized with said second bed, cocurrently depressurized with oxygen the first part of such cocurrent depressurization to the discharge end of a countercurrently depressurized third bed as purge gas for the desorption of nitrogen adsorbate and such oxygen thereafter being returned to the purged third bed for partial repressurization thereof until the first and third beds are second lower pressure equalized, countercurrently depressurized, purged with oxygen gas from the discharge end of a cocurrently depressurizing fourth bed, partially repressurized with oxygen gas from said fourth bed as the second lower pressure equalization thereof, further repressurized with oxygen gas from said second bed as the first higher pressure equalization thereof, and thereafter still further repressurized with feed air to said highest superatmospheric pressure, and the aforedescribed steps are consecutively followed with the fourth, second and third beds in accordance with the flow cycle sequence of FIG. 4.

4. An adiabatic pressure swing process according to claim 1 with four beds wherein said feed air is introduced to said first bed at highest superatmospheric pressure and oxygen is simultaneously discharged at substantially the same pressure, the first bed is cocurrently depressurized with oxygen from the first bed discharge being returned during the first part of such cocurrent depressurization to the discharge end of a partially repressurized third bed for further repressurization thereof until the first and third beds oxygen being returned during the second part of such cocurrent depressurization to the discharge end of a purged fourth bed for partial repressurization thereof until the first and fourth beds are second lower pressure equalized, countercurrently depressurized, purged with oxygen gas from the discharge end of said third bed while same is receiving feed air, partially repressurized with oxygen gas from a cocurrently depressurizing s cond bed until the first and second beds are second lower pressure equalized, the partially repressurized first bed is isolated for a period and thereafter further repressurized with oxygen gas from the cocurrently de-pressurizing third bed until the first and third beds are first higher pressure equalized, the first bed is still further repressurized to said highest super-atmospheric pressure with oxygen gas from the discharge end of said fourth bed while same is receiving feed gas, and the aforedescribed steps are consecutively followed with the second, third and fourth beds in accordance with the flow cycle sequence of FIG. 5.

5. An adiabatic pressure swing process according to claim 1 with three adsorption beds wherein said first bed is initially at said lowest superatmospheric pre and purged of nitrogen adsorbate, feed air and oxygen gas are simultaneously introduced respectively to the first bed inlet end and discharge end initially at said end of a third bed initially at said highest super- atmospheric pressure and one part thereof discharged as product and the balance returned to the first bed discharge end for such simultaneous introduction with the gas flows continued until the first and third beds are first higher pressure equalized, the introduction of feed air to the first bed inlet end is continued after terminating the oxygen gas introduction to the discharge end until the first bed is repressurized to said highest superatmospheric pressure, oxygen is thereafter released from the repressurized first bed discharge end with one part thereof discharged as product and the balance returned to the discharge end of a partially repressurized second bed for simultaneous introduction during feed air introduction to the second bed inlet end until the first and second beds are first higher pressure equalized, the first bed is cocurrently depressurized to 16 - 32 psia. with one part of the oxygen discharged as product and the balance returned to the third bed discharge end during the first part of such cocurrent depressurization for purging of nitrogen adsorbate therefrom and thereafter returned to the third bed discharge end until the first and third beds are second lower pressure equalized, the first bed is thereafter countercurrently depressurized, oxygen from a cocurrently depressurizing second bed is returned to the first bed discharge end for purging thereof, and with the second and third beds in accordance with the flow cycle sequence of FIG. 8, the oxygen mass relationship of feed gas oxygen : oxygen gas from the first through third bed discharge ends : oxygen return gas being 1:5 - 9.5: 4 - 9.1. Attorney for Applicants