Centrifugal density separation of waste plastic
AssigneeEastman Chemical Company
InventorsBruce Roger DeBruin, Kenny Randolph Parker, Charles Stuart Everett, Kyle Lyn Collings, James Stewart Nelson
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Abstract
Methods and systems for separating mixed plastic waste are provided herein. The methods generally comprise separating the mixed plastic waste into a PET-enriched stream and one or more PET-depleted streams. The separating may be accomplished using the combinations of two or more density separation stages. Exemplary density separation stages include sink-float separators and centrifugal force separators. The PET-enriched and PET-depleted streams may be recovered and/or directed to downstream chemical recycling processes.
Claims17
A waste plastic separation method comprising:
- (a) introducing mixed plastic waste (MPW) particulates into a first-sink-float density separation stage, said sink-float density separation stage being the first density separation stage in said separation method and having a target separation density of at least 1.31 g/cc;
- and
- (b) feeding an output stream from said first density separation stage into a second centrifugal density separation stage having a target separation density lower than the first sink float density separation stage, wherein said first output stream comprises a first PET-enriched stream comprising at least 55 weight percent PET on a dry plastics basis.
A waste plastic separation method comprising:
- (a) introducing mixed plastic waste (MPW) particulates into a high-density sink-float density separation stage;
- and
- (b) feeding an output stream from said high-density sink-float density separation stage, comprising a first PET-enriched stream comprising at least 55 weight percent PET on a dry plastics basis, into a low-density centrifugal density separation stage,
- wherein said high-density separation stage has a target separation density that is greater than 1.35 g/cc and/or less than 1.45 g/cc,
- wherein said low-density separation stage has a target separation density that is at least 0.01 g/cc less than the target separation density of said high-density separation stage.
A waste plastic separation method comprising:
- (a) introducing MPW particulates into a high-density sink-float density separation stage to form a particulate plastic solids output stream, comprising a first PET-enriched stream comprising at least 55 weight percent PET on a dry plastics basis, and a high-density particulate plastic solids stream having a higher average particulate plastic solids density than said output stream, and
- (b) feeding at least a portion of said particulate plastic solids output stream into a centrifugal density separation stage to form a medium density particulate plastic solids stream and a low-density particulate plastic solids stream,
- wherein the medium density particulate plastic solids stream comprises at least 90 weight percent PET on a dry plastic basis based on the weight of the medium density stream, and the average particulate plastic solids density of said high density particulate plastic solids stream is greater than the average particulate plastic solids density of said medium density particulate plastic solids stream, and wherein said medium density particulate plastic solids stream has an average particulate plastic solids density that is greater than the average particulate plastic solids density of said low density particulate plastic solids stream.
Dependencies are inferred from the claim text.