Process for treating a gas stream from plastic pyrolisis and/or biomass pyrolisis, and installation for integration into a steam cracker

1 . A process for treating at least one gas stream derived from pyrolysis of plastic and/or biomass, the process comprising:

quenching and washing with water the gas stream derived from pyrolysis of plastic and/or biomass in a quench/wash unit, and separating an aqueous phase from a washed gas stream;

compressing then cooling the washed gas stream to form a compressed gas stream;

washing the compressed gas stream under pressure to form a second washed gas stream;

passing the second washed gas stream through at least one acid removal unit to form an acid-depleted gas stream whereby carbon dioxide is removed from the second washed gas stream;

drying the acid-depleted gas stream to form a dry gas stream;

passing the dry gas stream through at least one impurity removal unit to form a purified gas stream; and

feeding the purified gas stream into a cryogenic absorption unit and supplying the cryogenic absorption unit with a hydrocarbon cryogenic solvent to obtain a light gas residue at a first outlet of the cryogenic absorption unit, and a fraction of C2+ hydrocarbons at a second outlet of the cryogenic absorption unit.

2 . The process according to claim 1 , wherein the gas stream derived from pyrolysis contains C2+ hydrocarbons and light carbons, including hydrogen and methane.

3 . The process according to claim 1 , wherein the gas stream derived from pyrolysis contains one or more of:

carbon containing components including carbon monoxide, carbon dioxide, nitrogen oxides and/or oxygen and oxygen derivatives including alcohols, aldehydes and/or ketones; and/or

nitrogen-containing compounds, including nitrogen and ammonia; and/or

acid compounds including hydrochloric acid and hydrocyanic acid; and/or,

chlorine-containing compounds; and/or

sulfur-containing compounds including mercaptans, carbon oxysulfides and hydrogen sulfide.

4 . The process according to claim 1 , wherein the hydrocarbon cryogenic solvent comprises C3 hydrocarbons and/or C4+ hydrocarbons.

5 . The process according to claim 1 , comprising separating the fraction of C2+ hydrocarbons into a fraction of C2 hydrocarbons and into at least one fraction of C3+ hydrocarbons, at least part of said fraction of C3+ hydrocarbons being recycled in the cryogenic absorption unit.

6 . The process according to claim 5 , wherein the separating comprises the production of a fraction of C3 hydrocarbons and a fraction of C4+ hydrocarbons, at least part of the fraction of C3 hydrocarbons being recycled in the cryogenic absorption unit.

7 . The process according to claim 1 , wherein the light gas residue contains fuel gas, including methane, hydrogen, and light compounds of the purified gas stream, the light compounds including carbon monoxide, nitrogen, nitrogen monoxide and/or oxygen.

8 . The process according to claim 1 , further comprising, conveying the light gas residue into a cracking unit including the combustible gas network of a steam cracker and/or is intended to form a fuel gas.

9 . The process according to claim 1 , wherein at least one acid removal unit comprises an amine unit or/and a caustic wash unit, the compressed gas stream passing through the amine unit or/and the caustic wash unit.

10 . The process according to claim 1 , wherein the impurity removal unit comprises at least one activated metal bed, including an activated alumina bed or a mixed adsorbent configured to retain one or more compounds from the dry gas stream on the at least one activated metal bed of the one or more compounds being selected from a list comprising:

sulfur-containing compounds including hydrogen oxysulfide and mercaptans, and/or

ammonia, and/or

nitrogen-containing compounds, and/or

chlorine-containing compounds, and/or

oxygen-containing compounds including alcohols, and/or

silicones contained in the dry gas stream.

11 . The process according to claim 1 , wherein at least one part of the fraction of C2+ hydrocarbons is fed into a cracker able to produce an ethylene fraction or into a self-contained unit able to produce an ethylene fraction.

12 . The process according to claim 1 , wherein at least one part of the aqueous phase produced at the quenching/washing is pressurized and placed in contact with the compressed gas stream at the high-pressure washing.

13 . The process according to claim 1 , further comprising, placing at least two streams from among the purified gas stream, the hydrocarbon cryogenic solvent, the light gas residue, and/or at least one reflux or condensate of the cryogenic absorption unit in heat exchange contact with one another in a cold box formed of a single item of plate-fin cryogenic equipment, comprising brazed aluminum.

14 . A process for treating at least one gas stream derived from pyrolysis of plastic and/or biomass, the process comprising:

quenching and washing with water the gas stream derived from pyrolysis of plastic and/or biomass in a first quench/wash unit, and separating an aqueous phase from a washed gas stream;

compressing then cooling the washed gas stream to form a compressed gas stream;

providing the compressed gas stream and a washing fluid to a second wash unit and washing the compressed gas stream under pressure in the second wash unit having a high-pressure washing chamber to form a second washed gas stream;

passing the second washed gas stream through at least one acid removal unit to form an acid-depleted gas stream

drying the acid-depleted gas stream to form a dry gas stream;

passing the dry gas stream through at least one impurity removal unit to form a purified gas stream; and

feeding the purified gas stream into a cryogenic absorption unit and supplying the cryogenic absorption unit with a hydrocarbon cryogenic solvent to obtain a light gas residue at a first outlet of the cryogenic absorption unit, and a fraction of C2+ hydrocarbons at a second outlet of the cryogenic absorption unit.

15 . The process according to claim 14 , further comprising, placing at least two streams from among the purified gas stream, the hydrocarbon cryogenic solvent, the light gas residue, and at least one reflux or condensate of the cryogenic absorption unit in heat exchange contact with one another in a cold box formed of a single item of plate-fin cryogenic equipment in brazed aluminium.

16 . A process for treating at least one gas stream derived from pyrolysis of plastic and/or biomass, the process comprising:

quenching and washing with water the gas stream derived from pyrolysis of plastic and/or biomass in a first quench/wash unit, and separating an aqueous phase from a washed gas stream;

compressing then cooling the washed gas stream to form a compressed gas stream;

providing the compressed gas stream and a washing fluid to a second wash unit and washing the compressed gas stream under pressure in the second wash unit having a high-pressure washing chamber to form a second washed gas stream;

passing the second washed gas stream through at least one acid removal unit to form an acid-depleted gas stream;

drying the acid-depleted gas stream to form a dry gas stream;

passing the dry gas stream through at least one impurity removal unit to form a purified gas stream;

feeding the purified gas stream into a cryogenic absorption unit and supplying the cryogenic absorption unit with a hydrocarbon cryogenic solvent to obtain a light gas residue at a first outlet of the cryogenic absorption unit, and a fraction of C2+ hydrocarbons at a second outlet of the cryogenic absorption unit;

feeding the fraction of C2+ hydrocarbons to a fractionating column and separating the fraction of C2+ hydrocarbons into a fraction of C2 hydrocarbons, a fraction of C3+ hydrocarbons, a fraction of C3 hydrocarbons, and a fraction of C4 hydrocarbons; and

recycling at least a portion of the fraction of C3+ hydrocarbons to an inlet side of the cryogenic absorption to mix with the cryogenic solvent; and

feeding a remaining fraction of the C2 hydrocarbons, a fraction of C3+ hydrocarbons, a fraction of C3 hydrocarbons, and a fraction of C4 hydrocarbons, and the light residue to a cracking installation.

17 . The process according to claim 16 , wherein the washing fluid is pressurized water.

18 . The process according to claim 16 , wherein the washing fluid is the aqueous phase separated from washed gas stream in the first quench/wash unit, and further comprising, providing the aqueous phase from the first quench/wash unit to an inlet of the high-pressure wash chamber of the second wash unit.

19 . The process according to claim 16 , wherein the washing fluid is pressurized water.