A process for treating a plastics pyrolysis oil: a) selective hydrogenation of feedstock in the presence of hydrogen and at least one selective hydrogenation catalyst, at 100 to 150° C., a partial pressure of hydrogen of 1.0 to 10.0 MPa abs. and an hourly space velocity of 1.0 to 10.0 h.sup.−1, to obtain a hydrogenated effluent; b) hydrotreatment of hydrogenated effluent in the presence of hydrogen and at least one hydrotreatment catalyst, at 250 to 370° C., a partial pressure of hydrogen of 1.0 to 10.0 MPa abs. and an hourly space velocity of 1.0 to 10.0 h.sup.−1, to obtain a hydrotreatment effluent; c) separation of hydrotreatment effluent obtained from b) in the presence of an aqueous stream, at a temperature of 50 to 370° C., to obtain at least one gaseous effluent, an aqueous liquid effluent and a hydrocarbon liquid effluent.

A process for treating a plastics pyrolysis oil: a) selective hydrogenation of feedstock in the presence of hydrogen and at least one selective hydrogenation catalyst, at 100 to 150° C., a partial pressure of hydrogen of 1.0 to 10.0 MPa abs. and an hourly space velocity of 1.0 to 10.0 h.sup.−1, to obtain a hydrogenated effluent; b) hydrotreatment of hydrogenated effluent in the presence of hydrogen and at least one hydrotreatment catalyst, at 250 to 370° C., a partial pressure of hydrogen of 1.0 to 10.0 MPa abs. and an hourly space velocity of 1.0 to 10.0 h.sup.−1, to obtain a hydrotreatment effluent; c) separation of hydrotreatment effluent obtained from b) in the presence of an aqueous stream, at a temperature of 50 to 370° C., to obtain at least one gaseous effluent, an aqueous liquid effluent and a hydrocarbon liquid effluent.

A method for steam cracking of a hydrocarbon feed is disclosed. The method can include heating a hydrocarbon feed stream with a first quench water stream to form a heated hydrocarbon feed stream and a second quench water stream having a temperature lower than the first quench water stream, steam cracking the heated hydrocarbon feed stream to form a cracked stream comprising cracked gases, contacting the cracked stream with a quench water to form a gaseous stream comprising quenched cracked gases and a crude water stream comprising heated quench water and pyrolysis gasoline, and separating the crude water stream to form the first quench water stream.

Provided in one embodiment is a continuous process for converting waste plastic into recycle for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene, and passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a pyrolysis oil and optionally pyrolysis wax comprising a naphtha/diesel fraction and heavy fraction, and char. The pyrolysis oil and wax is passed to a refinery FCC feed pretreater unit. A heavy fraction is recovered and sent to a refinery FCC unit, from which a C.sub.3 olefin/paraffin mixture fraction is recovered, which is passed to a steam cracker for ethylene production. In another embodiment, a propane fraction (C.sub.3) is recovered from a propane/propylene splitter and passed to the steam cracker.

Provided in one embodiment is a continuous process for converting waste plastic into recycle for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene, and passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a pyrolysis oil and optionally pyrolysis wax comprising a naphtha/diesel fraction and heavy fraction, and char. The pyrolysis oil and wax is passed to a refinery FCC feed pretreater unit. A heavy fraction is recovered and sent to a refinery FCC unit, from which a C.sub.3 olefin/paraffin mixture fraction is recovered, which is passed to a steam cracker for ethylene production. In another embodiment, a propane fraction (C.sub.3) is recovered from a propane/propylene splitter and passed to the steam cracker.

Method for driving machines, in an ethylene plant steam generation circuit, the method including recovering heat as high pressure steam from a cracking furnace; providing said high pressure steam to at least one steam turbine, wherein the steam turbine is configured to drive a machine, such as a process compressor; condensing at least part of the high pressure steam in a condenser; pumping condensed steam as boiler feed water back to the cracking furnace.

Method for driving machines, in an ethylene plant steam generation circuit, the method including recovering heat as high pressure steam from a cracking furnace; providing said high pressure steam to at least one steam turbine, wherein the steam turbine is configured to drive a machine, such as a process compressor; condensing at least part of the high pressure steam in a condenser; pumping condensed steam as boiler feed water back to the cracking furnace.

Saturation of a pyrolysis stream is achieved while managing exotherms. The pyrolysis stream is split into at least two feed streams for at least two saturation reactors. The process may split the hydrogen stream into at least two streams for the at least two saturation reactors. A recycle stream may also be provided to manage the exotherm. The feed may comprise at least 5 wt % aromatics.

Saturation of a pyrolysis stream is achieved while managing exotherms. The pyrolysis stream is split into at least two feed streams for at least two saturation reactors. The process may split the hydrogen stream into at least two streams for the at least two saturation reactors. A recycle stream may also be provided to manage the exotherm. The feed may comprise at least 5 wt % aromatics.

Methods for producing olefins through hydrocarbon steam cracking include passing a hydrocarbon feed that includes one or more hydrocarbons to a hydrocarbon cracking unit and passing one or more sulfur-containing compounds to the hydrocarbon cracking unit. The sulfur- containing compounds include at least hydrogen sulfide gas, and a flow rate of the sulfur- containing compounds to the hydrocarbon cracking unit is sufficient to produce a molar concentration of elemental sulfur in the hydrocarbon cracking unit of from 10 ppm to 200 ppm. The methods include cracking the hydrocarbon feed in the hydrocarbon cracking unit to produce a cracker effluent and contacting the cracker effluent with a quench fluid in a quench unit to produce at least a cracked gas and a first pygas. The first pygas has a concentration of carbon disulfide less than 50 ppmw based on the total mass flow rate of the first pygas.