Process for removing oxygenated contaminates from an ethylene stream

Abstract

The present invention is a process for removing oxygenated contaminants from an ethylene stream comprising: a) providing a dried ethylene stream (A) comprising essentially ethylene, up to 1 w % oxygenates, ethane, CO, CO2, H2, CH4 and C3+ hydrocarbons, b) sending said stream (A) to a C2 splitter/deethanizer to produce a bottom stream comprising essentially ethane, oxygenates and C3+ hydrocarbons, an overhead comprising the remaining components, c) sending said overhead to a fixed bed CO2 adsorption zone to recover a stream essentially free of CO2, d) sending said stream essentially free of CO2 to a demethanizer/CO stripper to recover an overhead comprising H2, CH4 and CO, liquid ethylene at the bottoms. In another embodiment the CO2 removal step can be made on the recovered ethylene.

Claims

1. A process for removing oxygenated contaminants from an ethylene stream comprising: a) providing a dried ethylene stream (A) comprising essentially ethylene, up to 1 w % oxygenates, ethane, CO, CO.sub.2, H.sub.2, CH.sub.4 and C.sub.3+ hydrocarbons; b) sending the dried ethylene stream (A) to a C.sub.2 splitter/deethanizer to produce a bottom stream comprising essentially ethane, oxygenates and C.sub.3+ hydrocarbons; and an overhead comprising the remaining components; c) sending the overhead from the C.sub.2 splitter/deethanizer to a fixed bed CO.sub.2 adsorption zone to recover a stream essentially free of CO.sub.2; d) sending the stream from the fixed bed CO.sub.2 adsorption zone, wherein the stream is essentially free of CO.sub.2, directly to a demethanizer/CO stripper without passing the stream through a wash column or a caustic wash to recover an overhead comprising H.sub.2, CH.sub.4 and CO; and liquid ethylene at the bottoms.

2. The process of claim 1, wherein the C.sub.2 splitter/deethanizer and the demethanizer operate at the same pressure, except a pressure drop between the C.sub.2 splitter/deethanizer and the demethanizer for transfer of fluids, wherein the pressure ranges from 15 to 45 barg.

3. The process of claim 1, wherein a pressure of the C.sub.2 splitter/deethanizer is lower than a pressure of the demethanizer/CO stripper, wherein the pressure of the C.sub.2 splitter/deethanizer ranges from 15 to 25 barg, and a pressure difference between the demethanizer/CO stripper and the C.sub.2 splitter/deethanizer ranges from 10 to 25 barg.

4. The process according to claim 3, wherein the overhead of the C.sub.2 splitter/deethaniser is condensed, sent to a decanter to obtain a liquid phase that is sent as a reflux to said C.sub.2 splitter/deethaniser and to obtain a gaseous phase that is sent to a compressor to obtain a compressed stream that is sent to the CO.sub.2 adsorption zone.

5. The process of claim 3, wherein the overhead of the C.sub.2 splitter/deethaniser is sent to a compressor, optionally cooled and sent to the CO.sub.2 adsorption zone to recover a stream essentially free of CO.sub.2; wherein the stream essentially free of CO.sub.2 is cooled and sent to a decanter to produce a liquid phase that is sent as a reflux to the C.sub.2 splitter deethanizer and to produce a gaseous phase that is sent to the demethanizer/CO stripper.

6. The process of claim 1, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 10/90.

7. The process of claim 1, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 10/90 and above 0.1/99.9.

8. The process of claim 1, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 5/95.

9. The process of claim 1, wherein a proportion of oxygenates in the dried ethylene stream (A) is from 50 wppm to 7000 wppm.

10. The process of claim 1, wherein a proportion of oxygenates in the dried ethylene stream (A) is up to 3000 wppm.

11. The process of claim 1, wherein a proportion of oxygenates in the dried ethylene stream (A) is up to 2000 wppm.

12. The process of claim 1, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is from 5 to 1000 wppm.

13. The process of claim 1, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is up to 800 wppm.

14. The process of claim 1, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is up to 500 wppm.

15. The process of claim 1, wherein the dried ethylene stream (A) originates from the dehydration of ethanol.

16. A process for removing oxygenated contaminants from an ethylene stream comprising: a1) providing a dried ethylene stream (A) comprising essentially ethylene, up to 1 w % oxygenates, ethane, CO, CO.sub.2, H.sub.2, CH.sub.4 and C.sub.3+ hydrocarbons; b1) sending the dried ethylene stream (A) to a C.sub.2 splitter/deethanizer to produce a bottom stream comprising essentially ethane, oxygenates and C.sub.3+ hydrocarbons; and an overhead comprising the remaining components; c1) sending the overhead stream to a demethanizer/CO stripper to recover an overhead comprising H.sub.2, CH.sub.4 and CO; and a liquid ethylene stream at the bottoms, wherein the liquid ethylene stream comprises CO.sub.2; d1) sending the liquid ethylene stream from the demethanizer/CO stripper directly to a fixed bed CO.sub.2 adsorption zone without passing the liquid ethylene stream through a wash column or a caustic wash to recover an ethylene stream essentially free of CO.sub.2.

17. The process of claim 16, wherein the C.sub.2 splitter/deethanizer and the demethanizer operate at the same pressure, except a pressure drop between the C.sub.2 splitter/deethanizer and the demethanizer for transfer of fluids, and wherein the pressure ranges from 15 to 45 barg.

18. The process of claim 16, wherein a pressure of the C.sub.2 splitter/deethanizer is lower than a pressure of the demethanizer/CO stripper; wherein the pressure of the C.sub.2 splitter/deethanizer ranges from 15 to 25 barg; and wherein a pressure difference between the demethanizer/CO stripper and the C.sub.2 splitter/deethanizer ranges from 10 to 25 barg.

19. The process of claim 16, wherein the overhead of the C.sub.2 splitter/deethaniser is condensed and sent to a decanter to obtain a liquid phase that is sent as a reflux to said C.sub.2 splitter/deethaniser and to obtain a gaseous phase that is sent to a compressor to obtain a compressed stream that is sent to the demethanizer/CO stripper.

20. The process of claim 16, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 10/90.

21. The process of claim 16, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 10/90 and above 0.1/99.9.

22. The process of claim 16, wherein a weight ratio of ethane+CO+CO.sub.2+H.sub.2+CH.sub.4+C.sub.3+ hydrocarbons to ethylene in the dried ethylene stream (A) is less than 5/95.

23. The process of claim 16, wherein a proportion of oxygenates in the dried ethylene stream (A) is from 50 wppm to 7000 wppm.

24. The process of claim 16, wherein a proportion of oxygenates in the dried ethylene stream (A) is up to 3000 wppm.

25. The process of claim 16, wherein a proportion of oxygenates in the dried ethylene stream (A) is up to 2000 wppm.

26. The process of claim 16, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is from 5 to 1000 wppm.

27. The process of claim 16, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is up to 800 wppm.

28. The process of claim 16, wherein a proportion of H.sub.2 in the dried ethylene stream (A) is up to 500 wppm.

29. The process of claim 16, wherein the dried ethylene stream (A) originates from the dehydration of ethanol.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 depicts an embodiment with the C.sub.2 splitter deethanizer, the CO.sub.2 adsorbers, and the demethanizer/CO stripper.

(2) FIG. 2 depicts an embodiment in which the pressure of the C.sub.2 splitter/deethanizer is lower than the pressure of the demethanizer/CO stripper.

(3) FIG. 3 depicts another embodiment with the C.sub.2 splitter deethanizer, the CO.sub.2 adsorbers, and the demethanizer/CO stripper.

(4) FIG. 4 depicts an embodiment with a compressor.

(5) FIG. 5 depicts an embodiment derived from the embodiment shown in FIG. 2, in which the position of the condenser and decanter are changed to be located between the outlet of the C.sub.2 splitter/deethaniser and the compressor.

DETAILED DESCRIPTION OF THE INVENTION

(6) As regards the oxygenated contaminants, also referred to as oxygenates, one can cite ethanol, C3 alcohols; ethers such as diethylether and methyl ethyl ether; carboxylic acids such as acetic acid; aldehydes such as acetaldehyde; ketones such as acetone; and esters such as methyl esters. Particularly problematic oxygenate contaminants in an alcohol dehydration are aldehydes.

(7) As regards the ethylene stream (A) of step a), it can be originating from the dehydration of ethanol. Said dehydration can be made in one or more ethanol dehydration reactors. As regards alcohol dehydration, such process is described in WO-2009-098262, WO-2009-098267, WO-2009-098268 and WO-2009-098269 the content of which is incorporated in the present application. The present invention is very efficient for the purification of ethylene produced by dehydration of ethanol.

(8) The outlet of said dehydration reactor comprises essentially ethylene and steam as well as minor amounts of oxygenates, ethane, CO, CO2, H2, CH4 and C3+ hydrocarbons. “Minor amounts” means the weight ratio of ethane+CO+CO2+H2+CH4+C3+ hydrocarbons to ethylene is less than 20/80 and most of time less than 10/90.

(9) Said outlet of dehydration reactor is initially cooled, typically in a quench tower employing water as the quench medium. In the quench tower, most of the water contained in the outlet of dehydration reactor is condensed and is removed from the bottom of the tower as a liquid water bottom stream. A part of said water bottom stream is cooled in a heat exchanger and recycled as quenching medium to the top of the quench column. The part of the water bottom stream which is not recycled as quenching medium may contain a part of the oxygenates and mostly unconverted ethanol if any. Said stream can be treated in a stripping column to recover a pure water stream. Ethylene, oxygenates, ethane, CO, CO2, H2, CH4 and C3+ hydrocarbons are removed from the top of the quench tower at a pressure typically such as 1 to 16 bars absolute and are referred to as the contaminated ethylene stream. Advantageously said contaminated ethylene stream is successively compressed and cooled in one or more steps to remove the major part of water, further fed to a fixed bed drying zone and finally to the C2 splitter/deethanizer of step b).

(10) In the previous compression steps the recovered water contains a part of the oxygenated contaminants and hydrocarbons dissolved. The contaminated hydrocarbon stream can also be cooled before the first compression step and water recovered. In an embodiment the water recovered upon each cooling further to a compression step and upon cooling, if any, before the first compression step is sent to a stripping column to produce an overhead stream comprising essentially oxygenated contaminants and hydrocarbons and an essentially pure water bottoms stream. Optionally the overhead stream is burned to destroy the oxygenated contaminants and recover heat.

(11) After the compression steps the contaminated ethylene stream is further fed to a fixed bed drying zone and finally to the C2 splitter/deethanizer of step b). The fixed bed drying zone is known in itself.

(12) As regards the C2 splitter/deethanizer of step b), it is advantageously a distillation column. The overhead is a mixture of ethylene, CO, CO2, H2 and CH4.

(13) As regards the fixed bed CO2 adsorption zone of step c), it can be any component capable to selectively remove CO2. By way of example it is an available commercial fixed bed adsorption (PSA for pressure swing adsorption or TSA for temperature swing adsorption) using molecular sieves or basic oxides, supported basic oxides, high surface area carbons, organo-metallic framework components (MOF's) or mixture thereof. The molecular sieves are preferably low silica zeolites, having 8 (among which zeolite A) or 12 membered (among which zeolite X) rings and exchanged with alkali, alkaline earth or lanthanide cations. Other molecular sieves are crystalline titanosilicates (ETS family materials). Supported basic oxides are preferably, alkali, alkaline earth or lanthanide oxides supported on high surface area carbons, alumina, silica, zirconia or titania. The removal of CO2 can be carried out with a liquid stream or with a gaseous ethylene stream depending on the pressure and temperature. A stream essentially free of CO2 is recovered. As only trace amounts of CO2 have to be removed from the ethylene, the preferred process cycle is of the thermal swing adsorption (TSA) type. Said fixed bed adsorbent, once saturated with CO2, can be regenerated, during regeneration the desorption produces a stream which can be treated anywhere. In a TSA process cycle, the regeneration is done while sweeping the saturated adsorbent with an inert gas by increasing the temperature until desorption of the CO2 occurs. Eventually the saturated adsorbent can be replaced by new adsorbent and the saturated adsorbent either be disposed of or regenerated ex-situ for further use. “Essentially” has to be interpretated in the light of the further use of ethylene. Should ethylene to be polymerized CO2 has to be 1 ppm vol or less and preferably 0.5 ppm vol or less.

(14) As regards the demethanizer, purpose is to recover an overhead comprising H2, CH4 and CO and liquid ethylene at the bottoms. It is advantageously a distillation column.

(15) As regards the operating conditions, The demethanizer of step d) has to be at a pressure high enough to operate at temperatures which are not too low. A demethanizer to recover an overhead comprising H2, CH4 and CO and liquid ethylene at the bottoms operating at 40 barg has an overhead temperature of around 0 to −10° C. and a bottom temperature of around 0° C. The same demethanizer operating at 21 barg has an overhead temperature of −30° C. and a bottom temperature of around −24° C.

(16) These temperatures and pressures are a function of the proportion of H2, CH4 and CO in the ethylene stream (A) and mainly of the proportion of H2. The proportion of H2, CH4 and CO in the ethylene stream (A) and mainly the proportion of H2 governs also the pressure and temperature of the C2 splitter/deethanizer located upstream said demethanizer.

(17) In an embodiment the pressure of step b) is selected to have a temperature of the C2 splitter/deethanizer bottoms such as there is no oligomerization or polymerization of the oxygenates. By way of example said temperature should not exceed 150° C. and advantageously not exceed 100° C. This temperature is function of the pressure and of the proportion of oxygenates in the mixture of oxygenates+ethane+C3+ hydrocarbons. The higher the proportion of oxygenates the higher the temperature. The higher the pressure the higher the temperature.

(18) In an embodiment the C2 splitter/deethanizer and the demethanizer are operating at the same pressure except the pressure drop between the C2 splitter/deethanizer and the demethanizer for transfer of fluids. Advantageously the pressure is ranging from 15 to 45 barg. In this embodiment the contaminated ethylene stream coming from the quench column is advantageously compressed in two to four compression stages in series (depending on dehydration reactor pressure), sent to the driers and finally to the C2 splitter deethanizer.

(19) Said embodiment is described on FIG. 1 wherein (1) is the C2 splitter deethanizer, (2) and (3) the CO2 adsorbers and (4) the demethanizer/CO stripper. The contaminated ethylene stream from the quench column has been dried and sent to the C2 splitter deethanizer (1) to produce a bottom stream comprising essentially ethane, oxygenates and C3+ hydrocarbons and an overhead comprising ethylene, CO, CO2, H2 and CH4 (condenser, decanter and reflux of C2 splitter deethanizer are not shown, reboiler of C2 splitter deethanizer is not shown). Said overhead is sent to the CO2 adsorbers (2) and (3) to recover a stream essentially free of CO2 and then to the demethanizer/CO stripper (4) to recover an overhead comprising H2, CH4 and CO and liquid ethylene at the bottoms. Condenser, decanter and reflux of the demethanizer/CO stripper are not shown, reboiler of the demethanizer/CO stripper is not shown.

(20) In a specific example according to FIG. 1 the pressure of the C2 splitter/deethanizer is around 15 to 25 barg, the top of said splitter/deethanizer is at a temperature around −20° C. to −30° C., condensed at a temperature in the range −20° C. to −30° C., the temperature on bottoms of said splitter/deethanizer is around 70 to 90° C., the pressure of the demethanizer/CO stripper around 15 to 25 barg, the top of the demethanizer/CO stripper is around −15° C. to −35° C., is condensed at a temperature around −15 to −35° C. and the temperature on bottoms of the demethanizer/CO stripper is around −15° C. to −35° C.

(21) Advantageously the pressure of the C2 splitter/deethanizer is around 18 to 25 barg, the top of said splitter/deethanizer is at a temperature around −18° C. to −28° C., condensed at a temperature in the range −18° C. to −28° C., the temperature on bottoms of said splitter/deethanizer is around 75 to 85° C., the pressure of the demethanizer/CO stripper around 18 to 25 barg, the top of the demethanizer/CO stripper is around −20° C. to −30° C., is condensed at a temperature around −20 to −30° C. and the temperature on bottoms of the demethanizer/CO stripper is around −20° C. to −30° C.

(22) In an embodiment the pressure of the C2 splitter/deethanizer is lower than the pressure of the demethanizer/CO stripper. Advantageously the pressure of the C2 splitter/deethanizer is ranging from 15 to 25 barg and simultaneously the pressure difference between the demethanizer/CO stripper and the C2 splitter/deethanizer is ranging from 10 to 25 barg In this embodiment the contaminated ethylene stream coming from the quench column is advantageously compressed in two to three compression stages in series, sent to the driers and finally to the C2 splitter deethanizer. Then the overhead of the C2 splitter deethanizer is compressed and sent through the CO2 adsorbers to the demethanizer/CO stripper. Optionally the essentially CO2 free stream leaving the fixed bed CO2 adsorption zone is cooled, sent to a decanter to produce a liquid phase sent as a reflux to the C2 splitter/deethanizer and a gaseous phase sent to the demethanizer/CO stripper.

(23) Said embodiment is described on FIG. 2. The contaminated ethylene stream from the quench column has been dried and sent at a pressure around 15 to 25 barg to the C2 splitter deethanizer (1) to produce a bottom stream (the reboiler is not shown) comprising essentially ethane, oxygenates and C3+ hydrocarbons and an overhead comprising ethylene, CO, CO2, H2 and CH4. Said overhead (top of the the C2 splitter deethanizer) is sent to the compressor (6) to increase the pressure with 10 to 25 barg over the C2 splitter/deethanizer pressure, optionally cooled (the cooler is not shown) and sent to the CO2 adsorbers (2) and (3) to recover a stream essentially free of CO2. Then said CO2 free stream is cooled (the cooler is not shown) and sent to the decanter (5) to produce a liquid phase sent as a reflux to the C2 splitter deethanizer (1) and a gaseous phase sent to the demethanizer/CO stripper (4). Said demethanizer/CO stripper (4) produces an overhead (the condenser, decanter and reflux are not shown) comprising H2, CH4 and CO and liquid ethylene at the bottoms (the reboiler is not shown).

(24) Alternatively, the condenser and decanter (5) can be installed between the top outlet of the C2 splitter/deethaniser (1) and the compressor (6). The produced liquid phase is sent as a reflux to the C2 splitter/deethaniser (1) while the gaseous phase is sent to the compressor (6). In other words the contaminated ethylene stream from the quench column has been dried and sent to the C2 splitter deethanizer (1) to produce a bottom stream comprising essentially ethane, oxygenates and C3+ hydrocarbons and an overhead comprising ethylene, CO, CO2, H2 and CH4 Said overhead, the top outlet of the C2 splitter/deethaniser (1), is condensed, sent to a decanter to get a liquid phase sent as a reflux to the C2 splitter/deethaniser (1) and a gaseous phase sent to the compressor (6). Then the compressed stream is sent to the CO2 adsorbers (2) and (3) to recover a stream essentially free of CO2 and then to the demethanizer/CO stripper (4) to recover an overhead comprising H2, CH4 and CO and liquid ethylene at the bottoms.

(25) In a specific example according to FIG. 2 the pressure of the splitter/deethanizer is around 15 to 25 barg, the temperature on top of said splitter/deethanizer around −25° C. to −35° C., the temperature on bottoms of said splitter/deethanizer around 70 to 90° C., the pressure of the demethanizer/CO stripper around 35 to 45 barg, the top of the demethanizer/CO stripper is around −10° C. to 10° C., is condensed at a temperature around −35 to −45° C. and the temperature on bottoms of the demethanizer/CO stripper is around −10 to 10° C.

(26) Advantageously the pressure of the splitter/deethanizer is around 18 to 20 barg, the temperature on top of said splitter/deethanizer around −28° C. to −32° C., the temperature on bottoms of said splitter/deethanizer around 78 to 82° C., the pressure of the demethanizer/CO stripper around 38 to 42 barg, the top of the demethanizer/CO stripper is around −5° C. to 5° C., is condensed at a temperature around −38 to −42° C. and the temperature on bottoms of the demethanizer/CO stripper is around −2 to 2° C.

(27) As regards the other embodiment wherein the CO2 removal step is made on the recovered ethylene, it works in a similar way as explained above in which the CO2 removal step is before the demethanizer/CO stripper.

(28) In an embodiment the C2 splitter/deethanizer and the demethanizer are operating at the same pressure except the pressure drop between the C2 splitter/deethanizer and the demethanizer for transfer of fluids. Advantageously the pressure is ranging from 15 to 45 barg. In this embodiment the contaminated ethylene stream coming from the quench column is advantageously compressed in two to four compression stages in series (depending on dehydration reactor pressure), sent to the driers and finally to the C2 splitter deethanizer.

(29) Said embodiment is described on FIG. 3 wherein (1) is the C2 splitter deethanizer, (2) and (3) the CO2 adsorbers and (4) the demethanizer/CO stripper. The contaminated ethylene stream from the quench column has been dried and sent to the C2 splitter deethanizer (1) to produce a bottom stream (the reboiler is not shown) comprising essentially ethane, oxygenates and C3+ hydrocarbons and an overhead (the condenser, the decanter and the reflux are not shown) comprising ethylene, CO, CO2, H2 and CH4. Said overhead is sent the demethanizer/CO stripper (4) to recover an overhead (the condenser, the decanter and the reflux are not shown) comprising H2, CH4 and CO and liquid ethylene comprising CO2 at the bottoms (the reboiler is not shown). Said ethylene comprising CO2 is sent to a fixed bed CO2 adsorption zone, the CO2 adsorbers (2) and (3) to recover an ethylene stream essentially free of CO2.

(30) In a specific example according to FIG. 3 the pressure of the C2 splitter/deethanizer is around 15 to 25 barg, the top of said splitter/deethanizer is at a temperature around −20° C. to −30° C., condensed at a temperature in the range −20° C. to −30° C., the temperature on bottoms of said splitter/deethanizer is around 70 to 90° C., the pressure of the demethanizer/CO stripper around 15 to 25 barg, the top of the demethanizer/CO stripper is around −15° C. to −35° C., is condensed at a temperature around −15 to −35° C. and the temperature on bottoms of the demethanizer/CO stripper is around −15° C. to −35° C.

(31) Advantageously the pressure of the C2 splitter/deethanizer is around 18 to 25 barg, the top of said splitter/deethanizer is at a temperature around −18° C. to −28° C., condensed at a temperature in the range −18° C. to −28° C., the temperature on bottoms of said splitter/deethanizer is around 75 to 85° C., the pressure of the demethanizer/CO stripper around 18 to 25 barg, the top of the demethanizer/CO stripper is around −20° C. to −30° C., is condensed at a temperature around −20 to −30° C. and the temperature on bottoms of the demethanizer/CO stripper is around −20° C. to −30° C.

(32) In an embodiment the pressure of the C2 splitter/deethanizer is lower than the pressure of the demethanizer/CO stripper. Advantageously the pressure of the C2 splitter/deethanizer is ranging from 15 to 25 barg and simultaneously the pressure difference between the demethanizer/CO stripper and the C2 splitter/deethanizer is ranging from 10 to 25 barg. In this embodiment the contaminated ethylene stream coming from the quench column is advantageously compressed in two to three compression stages in series, sent to the driers and finally to the C2 splitter deethanizer. Then the overhead of the C2 splitter deethanizer is compressed and sent to the demethanizer/CO stripper.

(33) Said embodiment is described on FIG. 4. In addition to FIG. 3 there are additional equipment: a compressor (6). The contaminated ethylene stream from the quench column has been dried and sent at a pressure around 15 to 25 barg to the C2 splitter deethanizer (1) to produce a bottom stream (the reboiler is not shown) comprising essentially ethane, oxygenates and C3+ hydrocarbons and an overhead comprising ethylene, CO, CO2, H2 and CH4. Said overhead is condensed, sent to a decanter to get a liquid phase sent as a reflux to (1) and a gaseous phase sent to the compressor (6). Said condenser, decanter and reflux are not shown). The compressor (6) increases the pressure with 10 to 25 barg over the C2 splitter/deethanizer pressure, and the compressed stream is sent to the demethanizer/CO stripper (4). Said demethanizer/CO stripper (4) produces an overhead (the condenser, the decanter and the reflux are not shown) comprising H2, CH4 and CO and at the bottom liquid ethylene comprising CO2 (the reboiler is not shown). Said ethylene comprising CO2 is sent to a fixed bed CO2 adsorption zone, the CO2 adsorbers (2) and (3) to recover an ethylene stream essentially free of CO2.

(34) In a specific example according to FIG. 4 the pressure of the splitter/deethanizer is around 15 to 25 barg, the top of said splitter/deethanizer is at a temperature around −25° C. to −35° C., condensed at a temperature in the range −25° C. to −35° C., the temperature on bottoms of said splitter/deethanizer is around 70 to 90° C., the pressure of the demethanizer/CO stripper around 35 to 45 barg, the top of the demethanizer/CO stripper is around −10° C. to 10° C., is condensed at a temperature around −35 to −45° C. and the temperature on bottoms of the demethanizer/CO stripper is around −10 to 10° C.

(35) Advantageously the pressure of the splitter/deethanizer is around 18 to 20 barg, the top of said splitter/deethanizer is at a temperature around −28° C. to −32° C., the temperature on bottoms of said splitter/deethanizer around 78 to 82° C., the pressure of the demethanizer/CO stripper around 38 to 42 barg, the top of the demethanizer/CO stripper is around −5° C. to 5° C., is condensed at a temperature around −38 to −42° C. and the temperature on bottoms of the demethanizer/CO stripper is around −2 to 2° C.

EXAMPLE

(36) The process according to FIG. 5 is operated. FIG. 5 is derived from FIG. 2 by changing the position of the condenser and decanter (5), they are located between the outlet of the C2 splitter/deethaniser and the compressor. The results are on the following table.

(37) TABLE-US-00001 stream No on FIG. 5 1 2 3 4 6 5 C2 splitter C2 splitter C2 splitter Demethanizer Demethanizer Ethylene feed bottoms vapor distillat feed purge product Temperature ° C. 15 80 −30 −2 −40 20 Pressure bar g 20 19 19 40 40 20 H2 kg/h 8 8 8 8 CO kg/h 1 1 1 1 CO2 kg/h 1 1 ethane kg/h 23 11 12 12 12 ethylene kg/h 25108 30 25078 25078 90 24988 acetaldehydes kg/h 150 150 C3+ kg/h 715 715 Total kg/h 26006 906 25100 25099 99 25000