Patent Application
20230383192
The present invention relates to methods for separating contaminants from waste plastics pyrolysis streams, and more particularly relates to methods for separating solid contaminants from waste plastics pyrolysis streams by adding an effective amount of an additive and then separating the contaminants from the stream by a physical process.
It is well known that there is a very large amount of waste plastics in the world that is an enormous disposal problem with adverse effects on the environment. One approach for dealing with waste plastics is through conversion of waste plastic to lower molecular weight hydrocarbon materials, particularly valuable hydrocarbon materials such as hydrocarbon fuel materials. The decomposition of hydrocarbon polymers of waste plastics, which can have high molecular weights (i.e., long carbon-chain lengths) gives lower molecular-weight hydrocarbons (i.e., shorter carbon-chain lengths) that may be useful as fuels.
Producing fuel and other valuable low molecular weight hydrocarbon materials from the pyrolysis (thermal decomposition) of waste plastic may have environmental benefits both with respect to less reliance on traditional fuel production processes that may generate larger amounts of pollution and reduced levels of plastic waste sent to landfills or incinerated. Fuel production from decomposed waste plastic may also have advantages over other current alternative energy sources, such as for instance crop-plant biomass fuels (bio-fuels) and wind generators.
However, the residua of the waste plastic to fuel conversion process, also called waste plastics pyrolysis streams herein, typically contain considerable unwanted contaminants, in particular solids. These solids are not soluble in the residue matrix. The contaminants are unconvertible products of polymer processes and pyrolysis by-products that behave like insoluble coke. They also contain fouling material made of rather insoluble polynuclear aromatics and small unconverted polymers which makes them difficult for further processing at refinery units (e.g., crude units, thermal cracking units, hydrocracking units, etc.). These organic solids can contain a high level of metals; namely, metals coming from the catalysts left in the plastic matrix during polymerizations or from plastic additives. This residue is typically about 10% of the feed to the conversion units for pyrolysis/thermal decomposition waste plastic processes.
It is thus desirable to develop a method and compositions for removing these contaminants from waste plastics pyrolysis streams.
There is provided, in one form, a method for removing contaminants from a waste plastics pyrolysis stream containing the contaminants, where the method includes introducing to the waste plastics pyrolysis stream containing contaminants an effective amount to at least partially remove the contaminants therefrom of at least one additive selected from the group consisting of crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants/antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, and combinations thereof, and then separating the contaminants from the waste plastics pyrolysis stream by a physical process.
Additionally, there is provided a treated waste plastics pyrolysis stream that includes waste plastics from pyrolysis, contaminants, and an effective amount of an additive to at least partially remove the contaminants from the waste plastics pyrolysis stream, where the additive is selected from the group consisting of crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants/antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, and combinations thereof.
Waste plastic residua is the unconverted residue from waste plastic pyrolysis. Waste plastic pyrolysis converts polymers into hydrocarbons/fuel distillates by bond breaking while residuum is the portion not converted (not decomposed or retropolymerized/condensed into non distillable fraction), which is a byproduct that can be partially reused (recycled back to the pyrolysis reactor) and partially sent to other refinery conversion processes (mainly visbreaking and delayed coking), but only after the removal of solid contaminants. As defined herein, the solid contaminants include, but are not necessarily limited to, carbon material, carbon-type materials, organic polymers, inorganic solids including metal particles, including metals trapped within solids (e.g., metal particles trapped within organic polymers), and combinations of these. “Carbon-type materials” include, but are not necessarily limited to carbon nanomaterials (CNMs).
It has been discovered that certain additives introduced into waste plastics pyrolysis streams can improve the removal of unwanted fouling solids, coke and barely soluble material like polynuclear aromatics and asphaltenic material and associated contaminants therefrom. The additives improve the rate and amount of removal by settling and/or centrifugation or other separation techniques and processes. Moreover, the solids are dispersed, and asphaltenic-type material is stabilized versus problematic aggregation and phase separation. By “stabilized” is meant that it does not precipitate, or precipitation is inhibited or prevented. The methods and additives described herein are therefore relevant for improving the feasibility of a waste plastic to fuel process, and integration of such a process with petroleum refineries. Without such a method for removing contaminants, the untreated residue would limit the process application and economics of such a waste plastic to fuel process. In other words, it would be uneconomical to use such a process.
Conventional settling and centrifugation are effective physical ways to remove solids, but they are typically slow and/or only partially remove unwanted metal contaminants associated with the solids. It has been discovered that the efficiency and speed of the removal process can be much improved by introduction of the additives described herein, resulting in “cleaner” and easier to process plastics residue that is suitable for processing at refinery units, for example as a co-feed to visbreakers and delayed cokers. Apart from the removal of unwanted metallic contaminants, the removal of insoluble solids reduces the fouling and/or coking tendency to levels that allow processing of the residue at refinery plants. Moreover, the fouling problem of asphaltenic-like material from pyrolysis/thermal degradation can be reduced and mitigated.
The method and additives described herein improve the flexibility and feasibility of using waste plastics pyrolysis streams to fuel processes because they make the residue from plastics processing suitable for further conversion. This avoids the generation of about 10% unusable residual waste from the plastic to oil or fuel processes, thus making this waste usable as a feed to petroleum refinery processes.
The introduction of effective amounts of the additives improves the efficiency of solids and metals contaminants by physical processes including, but not necessarily limited to, settling and/or centrifugation. These additives improve the efficiency of the removal of solids and metal contaminants by centrifugation and/or settling, which makes the processes much faster and effective. Apart from the removal of contaminants, the fouling tendency of the remaining low solubility components, asphaltic-type materials from polymers pyrolysis and recombination, is mitigated by the additives.
In one non-limiting embodiment, the waste plastics pyrolysis stream may be from almost any type of polymer or plastic. In a non-restrictive version, the plastic may include, but is not necessarily limited to, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyethylene terephthalate (PETE), polystyrene (PS), polyurethane, polycarbonate (PC), polyamide, polymethyl Methacrylate (PMMA), and combinations thereof.
Suitable additives include, but are not necessarily limited to, crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants/antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, and combinations thereof. In more specific, but non-limiting embodiments, suitable crude oil demulsifiers include, but are not limited to, ethoxylated and/or propoxylated alkylphenol formaldehyde resins. Suitable crude oil wax control additives include, but are not necessarily limited to, poly(ethylene-co-vinylacetate). Suitable crude oil pour point reducers include, but are not necessarily limited to, ethylene vinyl acetates. Suitable dispersants/antifoulants include, but are not necessarily limited to, maleic anhydride/olefin polymers from olefins having C16-C18 carbon atoms and weight average molecular weights of from about 200 to about 300 as well as functionalized derivatives of maleic anhydride/olefin polymers having weight average molecular weights of from about 250 to about 350. More specifically, suitable functionalized derivatives of maleic anhydride/olefin polymers include, but are not necessarily limited to, amine/polyamine derivatives, copolymers of butadiene and C16-C18 anhydrides, alcohol/polyalcohol derivatives, carboxylic/fatty acid derivatives, and combinations thereof. Suitable additives may also include nanoscale metallic oxides that are magnesium oxide and/or calcium oxide. In a non-limiting example, a suitable overbased metal oxide carbonate is magnesium oxide overbase.
In another non-restrictive version, the effective amount of the additive introduced into the waste plastics pyrolysis stream ranges from about 10 independently to about 3000 ppm based on the waste plastics pyrolysis stream; alternatively, from about 100 independently to about 300 ppm. The term “independently” when used herein with respect to a range means that any endpoint may be combined with any other endpoint to give a suitable alternative range. For instance, a range of from about 10 ppm to about 300 ppm would be acceptable.
The temperature of the method is important because the waste plastics pyrolysis stream must be liquid and flowable to be processed. Thus, in one non-limiting embodiment, the temperature should be from about 100° C. independently to about 400° C.; alternatively, from about 150° C. independently to about 250° C.
Introducing the additive into the waste plastics pyrolysis stream may be accomplished by any suitable method. Mixing of the additive with the waste plastics pyrolysis stream should produce a good dispersion of the additive, which in one non-limiting embodiment includes introducing the additive while transferring the waste plastic resid product upstream of a pump that will impart shear stress and mixing. Injection may optionally be made with a good mixing device, such as a quill, which tends to generate small droplets of the additive liquid carrier in a solvent.
Suitable solvents for delivering the additive include, but are not necessarily limited to, gasoil, vacuum gasoil, fluid catalytic cracking light cycle oil, fluid catalytic cracking heavy cycle oil and fluid catalytic cracking slurry oil, ethylene cracker pyrolysis gasoline, ethylene cracker pyrolysis fuel oil, kerosene, naphtha and gasoline. The amount of the additive in the solvent may range from about 1:1 independently to about 50:1; alternatively, from about 5:1 independently to about 10:2 solvent to additive (solvent:additive) ratio by volume.
The method also includes separating the contaminants from the waste plastics pyrolysis stream by a physical process. Suitable physical separation processes include, but are not necessarily limited to, gravity settling, centrifugation, cyclones, and combinations thereof.
The invention will now be described with respect to particular embodiments which are not intended to limit the invention in any way, but which are simply to further highlight or illustrate the invention. All percentages (%) are weight percentages unless otherwise noted.
Demulsifiers were based on ethoxylated/propoxylated alkylphenol formaldehyde resins, and the antifoulant was based on maleic anhydride ester of hexadecane (C16) alpha olefins. The wax dispersant was composed of poly(ethylene-co-vinylacetate, while the “mag overbased” was based on a nanocolloid of emulsified magnesium oxide overbase.
In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been described as effective in providing methods and compositions for removing contaminants, particularly solid contaminants from waste plastics pyrolysis streams. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific waste plastics pyrolysis streams, crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants, antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, solvents, proportions, dosages, treatment conditions, physical separation processes, and other components and procedures falling within the claimed parameters, but not specifically identified or tried in a particular method or composition, are expected to be within the scope of this invention.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, there may be provided a method for removing contaminants from a waste plastics pyrolysis stream containing the contaminants, where the method comprises, consists essentially of, or consists of, introducing to the waste plastics pyrolysis stream containing contaminants an effective amount to at least partially remove the contaminants therefrom at least one additive selected from the group consisting of crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants/antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, and combinations thereof; and separating the contaminants from the waste plastics pyrolysis stream by a physical process.
Alternatively, there may be provided a treated waste plastics pyrolysis stream that comprises, consists essentially of, or consists of, waste plastics from pyrolysis, contaminants, an effective amount of an additive to at least partially remove the contaminants from the waste plastics pyrolysis stream, where the additive is selected from the group consisting of crude oil demulsifiers, crude oil wax control additives, crude oil pour point reducers, dispersants/antifoulants, nanoscale metallic oxides, overbased metal oxide carbonates, and combinations thereof.
In another non-restrictive version, the only dispersant or antifoulant in the additive is one or more waste plastic as defined herein.
The words “comprising” and “comprises” as used throughout, are to be interpreted to mean “including but not limited to” and “includes but not limited to”, respectively.
As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
