Process for separating hydrogen from an olefin hydrocarbon effluent vapor stream

1. A process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, which process comprises:

a. introducing the olefin hydrocarbon rich compressed effluent vapor stream into a heat exchanger;

b. cooling the olefin hydrocarbon rich compressed effluent vapor stream in the heat exchanger;

c. separating hydrogen from olefin and heavy paraffinic components in the cooled olefin hydrocarbon rich compressed effluent vapor stream in a first separator to provide a first vapor stream and a first liquid stream;

d. cooling a first vapor stream in the heat exchanger;

e. separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream in a second separator to provide a second vapor stream and a second liquid stream;

f. dividing the second vapor stream into a first split stream and a second split stream;

g. warming the first split stream in the heat exchanger to produce a gas product;

h. withdrawing the gas product from the heat exchanger;

i. lowering the pressure of the second split stream in a first control valve, wherein the temperature of the second spilt stream is reduced;

j. cooling a liquid paraffinic stream in the heat exchanger;

k. combining the cooled liquid paraffinic stream with the cooled second split stream to provide a combined feed;

l. vaporizing the combined feed in the heat exchanger;

m. withdrawing the vaporized combined feed;

n. lowering the pressure of the first liquid stream in a control valve;

o. partially vaporizing the first liquid stream in the heat exchanger;

p. flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas, which travels to a rectifier connected to the liquid product drum;

q. combining the hydrogen-rich gas and the second liquid stream in the rectifier, further purifying the hydrogen-rich gas;

r. warming the hydrogen-rich gas from the rectifier in the heat exchanger to provide a flashed vapor stream;

s. pumping a third liquid stream from the liquid product drum to the heat exchanger, wherein it is warmed; and

t. providing a liquid product,

wherein cooling of the olefin hydrocarbon rich compressed effluent vapor stream, the first vapor stream, and the liquid paraffinic stream in the heat exchanger is provided by a cascade refrigeration system comprising a plurality of refrigeration cycles, wherein each refrigeration cycle comprises:

a refrigerant;

one or more compressors;

one or more discharge condensers or discharge coolers;

one or more refrigeration control valves; and

one or more thermosiphon vessels.

2. The process of claim 1 , wherein each refrigeration cycle is a closed-loop system.

3. The process of claim 1 , wherein each refrigerant of the plurality of refrigeration cycles comprises propane, propylene, or any combinations thereof.

4. The process of claim 1 , wherein each refrigerant of the plurality of refrigeration cycles comprises methane, ethane, ethylene, or any combinations thereof.

5. The process of claim 1 , wherein the refrigerant of each refrigeration cycle is circulated through the one or more compressors, the one or more discharge coolers or discharge condensers, the one or more refrigeration control valves, the one or more thermosiphon vessels, and the heat exchanger.

6. The process of claim 1 , wherein the one or more compressors pressurize the refrigerant of each refrigeration cycle.

7. The process of claim 1 , wherein the one or more discharge coolers or discharger condensers cool and condense the refrigerant of each refrigeration cycle, respectively.

8. The process of claim 1 , wherein the heat exchanger cools, condenses, and liquefies the refrigerant of each refrigeration cycle subsequent to pressurization and cooling of the refrigerant via the one or more compressors and the one or more discharge condensers or discharge coolers.

9. The process of claim 8 , wherein, for each refrigeration cycle, the cooled, condensed, and liquefied refrigerant of each refrigeration cycle flows to a first thermosiphon vessel to provide a cold or warm liquid refrigerant stream and a flashed vapor stream.

10. The process of claim 9 , wherein, for each refrigeration cycle, a first refrigeration control valve of the one or more refrigeration control valves lowers the pressure of the cooled, condensed, and liquefied refrigerant before the refrigerant flows to the first thermosiphon vessel.

11. The process of claim 9 , wherein, for each refrigeration cycle, the flashed vapor stream flows to the one or more compressors.

12. The process of claim 9 , wherein, for each refrigeration cycle, the cold or warm liquid refrigerant stream is circulated from a bottom outlet of the first thermosiphon vessel, through the heat exchanger, and then back to an upper inlet of the first thermosiphon vessel to maintain a steady internal liquid level within the first thermosiphon vessel.

13. The process of claim 12 , wherein, for each refrigeration cycle, the cold or warm liquid refrigerant stream flowing through the heat exchanger provides refrigeration to the olefin hydrocarbon rich compressed effluent vapor stream, the first vapor stream, and the liquid paraffinic stream.

14. The process of claim 13 , wherein, for each refrigeration cycle, the warm liquid refrigerant stream additionally flows from the bottom outlet of the first thermosiphon vessel to a subsequent thermosiphon vessel to provide a second cold liquid refrigerant and a second flashed vapor stream.

15. The process of claim 14 , wherein, for each refrigeration cycle, a second refrigeration control valve of the one or more refrigeration control valves, lowers the pressure of the warm liquid refrigerant stream before the refrigerant flows to the subsequent thermosiphon vessel.

16. The process of claim 14 , wherein, for each refrigeration cycle, the second flashed vapor stream flows to the one or more compressors.

17. The process of claim 14 , wherein, for each refrigeration cycle, the second cold liquid refrigerant stream is circulated from a bottom outlet of the subsequent thermosiphon vessel, through the heat exchanger, and then back to an upper inlet of the subsequent thermosiphon vessel to maintain a steady internal liquid level within the subsequent thermosiphon vessel.

18. The process of claim 17 , wherein, for each refrigerant cycle, the second cold liquid refrigerant stream flowing through the heat exchanger provides refrigeration to the olefin hydrocarbon rich compressed effluent vapor stream, the first vapor stream, and the liquid paraffinic stream.