Direct steam cracking methods for liquids produced from plastic waste
A method for steam cracking a plastic-derived liquid feedstock can comprise: steam cracking a plastic-derived liquid feedstock in a steam cracker to produce a cracked product, wherein the plastic-derived liquid feedstock has a final boiling point of about 550° C. or less and an olefin content of about 40 wt % or less; quenching the cracked product from a temperature of about 750° C. or greater to a temperature of about 350° C. or less with a quench oil; and wherein the method does not comprise hydrotreating and/or fractionating the plastic-derived liquid feedstock before steam cracking.
1 . A method comprising:
heating a plastic material to 300° C. to 320° C. to form molten plastics;
heating the molten plastics in a pyrolysis chamber to 390° C. to 410° C. in a nitrogen purged system while agitating the molten plastics to form a plastic derived liquid feedstock;
flash separating C 1 to C 4 hydrocarbons from the plastic-derived liquid feedstock;
directly supplying the plastic-derived liquid feedstock from the flash separating to a cracking furnace without any other intermediate processing including hydrotreating and fractionation;
heating the plastic-derived liquid feedstock by a flue gas in a first convection section of the cracking furnace to a temperature from 160° C. to 230° C., wherein the first convection section comprises an uppermost convection section of the cracking furnace;
diluting the plastic-derived liquid feedstock with steam between the first convection section and a second convection of the cracking furnace to give a diluted plastic-derived liquid feedstock;
passing the diluted plastic-derived feedstock sequentially through the second convection, a third convection section of the cracking furnace, and a fourth convection section of the cracking furnace, thereby heating by the flue gas the diluted plastic-derived liquid feedstock in the second convection section, the third convection section, and the fourth convection section;
steam cracking the diluted plastic-derived liquid feedstock in a steam cracker comprising the cracking furnace to produce a cracked product, wherein the plastic-derived liquid feedstock supplied to the first convection section has a final boiling point of about 500° C. to about 550° C. and an olefin content of about 40 wt % or less;
quenching the cracked product from a temperature of about 750° C. or greater to a temperature of about 350° C. or less by tangential injection or swirl-type injection of a quench oil comprising C 10 to C 15 hydrocarbon around and along an inside surface of a quenching unit, wherein a weight ratio of flow rate of quench oil to flow rate of cracked product is in a range of about 2 to about 15; and
wherein the method does not comprise hydrotreating the plastic-derived liquid feedstock before the steam cracking.
2 . The method of claim 1 , wherein the method does not comprise fractionating the plastic-derived liquid feedstock from the flash separating before the steam cracking.
3 . The method of claim 1 , further comprising:
fractionating the cracked product after quenching into a plurality of cuts.
4 . The method of claim 3 , wherein the plurality of cuts comprise one or more cuts selected from the group consisting of: an overheads cut, a diesel cut, a light vacuum gas oil cut, and an atmospheric bottoms cut.
5 . The method of claim 3 further comprising:
recycling one or more of the plurality of cuts back as at least a portion of the quench oil.
6 . The method of claim 1 , wherein the plastic-derived liquid feedstock supplied to the cracking furnace has an olefin content of about 0.1 wt % to about 40 wt %.
7 . The method of claim 1 , wherein the quench oil is at a temperature of about 325° C. or less.
8 . The method of claim 1 , wherein the quench oil is at a temperature of about 150° C. to about 325° C.
9 . The method of claim 1 , wherein in quenching the cracked product drops from the temperature of about 750° C. to about 925° C. to the temperature of about 225° C. to about 350° C.
10 . The method of claim 1 , wherein the steam cracking comprises steam cracking the diluted plastic-derived liquid feedstock in a pyrolysis section of the steam cracker.
11 . The method of claim 10 , wherein the flue gas flows from the pyrolysis section upward through the fourth convection section, the third convection section, the second convection section, and the first convection section.
12 . The method of claim 10 , wherein the diluted plastic-derived liquid feedstock is a vapor before the steam cracking.
13 . The method of claim 10 , wherein cracking is performed at a temperature of about 400° C. to about 900° C., a pressure of about 0.1 bar absolute (bara) to about 5 bara, and a residence time in the pyrolysis section of about 0.1 seconds to about 2.0 seconds.
14 . A method comprising:
producing a plastic-derived liquid feedstock from plastic material by heating the plastic material to 300° C. to 320° C. to form molten plastics without any feedstock pretreatment;
heating the molten plastics in a pyrolysis chamber to 390° C. to 410° C. in a nitrogen purged system while agitating the molten plastics to form the plastic derived liquid feedstock;
flash separating C 1 to C 4 hydrocarbons from the plastic-derived liquid feedstock;
directly supplying the plastic-derived liquid feedstock from the flash separating to a cracking furnace without any other intermediate processing including hydrotreating and fractionation;
heating the plastic-derived liquid feedstock by a flue gas in a first convection section of the cracking furnace to a temperature from 160° C. to 230° C., wherein the first convection section comprises an uppermost convection section of the cracking furnace;
diluting the plastic-derived liquid feedstock with steam between the first convection section and a second convection of the cracking furnace to give a diluted plastic-derived liquid feedstock;
passing the diluted plastic-derived feedstock sequentially through the second convection, a third convection section of the cracking furnace, and a fourth convection section of the cracking furnace, thereby heating by the flue gas the diluted plastic-derived liquid feedstock in the second convection section, the third convection section, and the fourth convection section;
steam cracking the diluted plastic-derived liquid feedstock in a steam cracker comprising the cracking furnace to produce a cracked product, wherein the plastic-derived liquid feedstock supplied to the first convection section has a final boiling point of about 500° C. to about 550° C. and an olefin content of about 40 wt % or less;
quenching the cracked product from a temperature of about 750° C. or greater to a temperature of about 350° C. or less with a quench oil; and
wherein the method does not comprise fractionating the plastic-derived liquid feedstock from the flash separating before the steam cracking.
15 . The method of claim 14 , further comprising:
fractionating the cracked product after quenching into a plurality of cuts.
16 . The method of claim 14 , wherein the plastic-derived liquid feedstock supplied to the first convection section has an olefin content of about 0.1 wt % to about 40 wt %.
17 . The method of claim 14 , wherein the quench oil is at a temperature of about 325° C. or less.
18 . The method of claim 14 , wherein the quench oil is at a temperature of about 150° C. to about 325° C.
19 . The method of claim 14 , wherein in quenching the cracked product drops from the temperature of about 750° C. to about 925° C. to the temperature of about 225° C. to about 350° C.
20 . A method comprising:
producing a plastic-derived liquid feedstock from plastic material by heating the plastic material to 300° C. to 320° C. to form molten plastics;
heating the molten plastics in a pyrolysis chamber to 390° C. to 410° C. in a nitrogen purged system while agitating the molten plastics to form a plastic derived liquid feedstock;
flash separating C 1 to C 4 hydrocarbons from the plastic-derived liquid feedstock;
directly supplying a plastic-derived liquid molten plastic feedstock from the flash separating to a cracking furnace without any other intermediate processing including hydrotreating and fractionation;
heating the plastic-derived liquid feedstock by a flue gas in a first convection section of the cracking furnace to a temperature from 160° C. to 230° C., wherein the first convection section comprises an uppermost convection section of the cracking furnace;
diluting the plastic-derived liquid feedstock with steam between the first convection section and a second convection of the cracking furnace to give a diluted plastic-derived liquid feedstock;
passing the diluted plastic-derived feedstock sequentially through the second convection, a third convection section of the cracking furnace, and a fourth convection section of the cracking furnace, thereby heating by the flue gas the diluted plastic-derived liquid feedstock in the second convection section, the third convection section, and the fourth convection section;
steam cracking the diluted plastic-derived liquid feedstock in a steam cracker comprising the cracking furnace to produce a cracked product, wherein the steam cracking has a weight ratio of steam to the diluted plastic-derived liquid feedstock is from 0.25:1 to about 0.75:1; wherein the plastic-derived liquid feedstock supplied to the first convection section has a final boiling point of about 500° C. to about 550° C. and an olefin content of about 40 wt % or less;
quenching the cracked product from a temperature of about 750° C. or greater to a temperature of about 350° C. or less by tangential injection or swirl-type injection of a quench oil comprising C 10 to C 15 hydrocarbon around and along an inside surface of a quenching unit, wherein a weight ratio of flow rate of quench oil to flow rate of cracked product is in a range of about 2 to about 15; and
wherein the method does not comprise hydrotreating the plastic-derived liquid feedstock before the steam cracking.