MELTING AND DISSOLVING WASTE PLASTIC INTO VGO

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 63/645,305 filed May 10, 2024, the complete disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to a system and process for effectively melting and dissolving waste plastics into petroleum feeds.

BACKGROUND

The reduction, reuse, and recycling of waste plastic, key aspects of a circular economy, represent critical components of environmental protection. M any approaches have been developed towards the aim of advancing the circular economy. One such approach relates to the conversion of waste plastic into sustainable fuel and circular plastic. Use of waste plastic for fuel and circular chemicals creation reduces the accumulation of waste plastics by reusing and recycling the plastics to create sustainable fuel and circular plastic.

However, the conversion of waste plastics into fuel and circular chemicals presents challenges at nearly every step throughout the conversion process. Waste plastic feedstocks originating from recycling centers typically contain a plurality of plastic types, each with their own unique thermal dynamic characteristics which must be considered. The variety of plastic types continues to present issues in the mixing stage, where some plastics float in certain conditions while other plastics settle. Moreover, waste plastic feedstocks often contain organic and inorganic impurities, further compounding the difficulty of converting the feedstock into fuel and circular chemicals.

Melted plastic is known for its shear-thinning properties that tends to agglomerate at low shear rate locations and stick to any surfaces, which could significantly compromise the normal operation. The impurities in the waste plastics that are insoluble in vacuum gas oil (VGO) could also accumulate inside the mixing tank causing operational issues.

Considering the myriad of challenges, novel and more efficient processes for processing waste plastic to produce fuels and chemicals would be of great interest to the industry.

SUMMARY

Against this backdrop the present invention was developed. In one embodiment a process is provided for effectively melting and dissolving waste plastics into petroleum feedstocks, such as vacuum gas oil (VGO). The process uses a continuous processing unit with a minimum maintenance requirement.

In one embodiment the process comprises providing a feedstock of VGO or other petroleum feed to a processing unit which can hold liquids. Waste plastic is added to hot VGO in the processing unit in a continuous manner. The residence time for the VGO and plastic in the processing unit is sufficiently long to melt the plastic, and have the VGO and melted plastic well mixed until a homogeneously mixed liquid product is achieved. The mixed liquid product can then be collected from the processing unit and tested for viscosity. In one embodiment, the entire process is controlled based on the viscosity of the product. In one embodiment the continuous processing unit can be used in series with another unit.

In one embodiment a continuous processing unit to facilitate the present process of melting and dissolving waste plastics into VGO is provided. According to one embodiment the unit comprises one or more separation baffles, and one or more radial impellers. According to another embodiment the unit further comprises a jacket, a shaped bottom, and a slurry pump. According to still another embodiment, the processing unit is rectangular or tubular with multi-mixing zones, and each zone comprises an overhead mixer with impellers.

Among other factors, the present process and associated equipment permits the effective melting and dissolving of waste plastics into a petroleum feed such as VGO or light cycle oil (LCO), heavy cycle oil (HCO), hydrotreated oil, hydrocracked oil, reformate oil, atmospheric gas oil (AGO). Dissolving oil can be a pure hydrocarbon such as benzene, toluene, xylene, or C9-C16 aromatics. The process can continuously generate a stream of blended plastic and VGO liquids that can be further treated or purified to meet fluid catalytic cracking (FCC) feedstock specifications. The entire stream can then be sent to an FCC unit to convert waste plastics into high quality fuel products or chemicals for polymerization. The use of the present process and associated equipment offers significant economic and environmental benefits if adopted in industrial refineries.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a flow diagram of one embodiment of the present process of melting and dissolving waste plastics into a petroleum oil, such as VGO, using a continuous melting unit. The process comprises generating a stream of the mixture of oil and plastic, filtering the mixture, and conveying the mixture to a conversion reactor.

FIG. 2 depicts a flow diagram of one embodiment of the present process of melting and dissolving waste plastics into VGO using a continuous melting unit for generating a stream of the mixture of VGO and plastic, filtering the mixture, and conveying them mixture to an FCC reactor in a refinery.

FIG. 3 depicts one embodiment of a mixing and melting unit for plastic and VGO blending including a rounded and/or conical bottom, internal baffles and a slurry pump.

FIG. 4 depicts one embodiment of a mixing and melting unit for plastic and VGO blending including vertical and horizontal internal baffles.

FIG. 5 depicts one embodiment of a rectangular or tubular multi-zone mixing and melting unit for plastic and VGO blending.

FIG. 6 depicts one embodiment of a continuous filtration unit for use in connection with the present process.

DETAILED DESCRIPTION

Before the processes for melting and dissolving waste plastic into a petroleum feed such as VGO, and the mixing units used in the processes, are disclosed and described, it is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a step” may include multiple steps, reference to “producing” or “products” of a reaction or treatment should not be taken to be all of the products of a reaction/treatment, and reference to “treating” may include reference to one or more of such treatment steps. As such, the step of treating can include multiple or repeated treatment of similar materials/streams to produce identified treatment products.

Numerical values with “about” include typical experimental variances. As used herein, the term “about” means within a statistically meaningful range of a value, such as a stated particle size, concentration range, time frame, molecular weight, temperature, or pH. Such a range can be within an order of magnitude, typically within 10%, and more typically within 5% of the indicated value or range. Sometimes, such a range can be within the experimental error typical of standard methods used for the measurement and/or determination of a given value or range. The allowable variation encompassed by the term “about” will depend upon the particular system under study, and can be readily appreciated by one of ordinary skill in the art. Whenever a range is recited within this application, every whole number integer within the range is also contemplated as an embodiment of the invention.

The present application in one embodiment relates to a process for mixing and melting waste plastic into a petroleum feed such as VGO. In one embodiment of the process, VGO and waste plastic are added to a continuous processing unit and mixed until the waste plastic has melted and essentially dissolved in and combined with the VGO to form a mixed product. The amount of plastic added to the oil can range from 1-20 wt. % of the mixed product. In one embodiment, the amount of plastic ranges from 5-10 wt. %. In another embodiment, the amount of plastic is about 5 wt. %.

In one embodiment, waste plastic is melted and dissolved into a petroleum feed such as vacuum gas oil (VGO) or light cycle oil (LCO), heavy cycle oil (HCO), hydrotreated oil, hydrocracked oil, reformate oil, atmospheric gas oil (AGO) and Coker Gas Oil (CGO). The dissolving oil can also be a pure hydrocarbon such as benzene, toluene, xylene, or C7-C10 aromatic solvent.

In one embodiment, the mixed product can then be collected and tested with a viscometer. The entire process may be controlled based on the viscosity measurement given by the viscometer. In one embodiment controlling the process comprises sounding an alarm when the viscosity of the mixed product reaches a high level or low level. Controlling the process can comprise adjusting the amount of waste plastic added to the continuous processing unit or the amount of petroleum feed such as VGO added to the mixing unit. The temperature of the mixing unit core can also be adjusted, as well a purge of gas through the mixing unit can be used. In one embodiment the mixed product can be filtered after collection in order to remove solid impurities or large particles of mixed product.

Central to the process is the continuous processing unit. The continuous processing unit permits the mixing and melting of waste plastic into a petroleum feed such as VGO. In one embodiment this processing unit comprises internal baffles and an overhead mixer with impellers. The internal baffles can be used for fluid flow regulation within the continuous processing unit. The overhead mixer with impellers can be used to mix the waste plastic into the VGO within the continuous processing unit to produce a mixed product. In one embodiment the continuous processing unit comprises atmospheric operation with constant N₂ purge. The constant N₂ purge can be done to vent gases created during the reaction. In one embodiment the continuous processing unit further comprises atmospheric operation to elevated pressure operation with back pressure regulation to vent gases created during the reaction.

In another embodiment the continuous processing unit comprises an inlet for VGO wherein VGO can be added to the unit using the inlet. In still another embodiment the continuous processing unit comprises an inlet for waste plastic wherein waste plastic can be added to the unit using the inlet. In one embodiment the inlet for waste plastic further comprises a rotary valve. This rotary valve helps control the quantity of waste plastic added to the continuous processing unit and the rate at which it is added. The rotary valve may be opened or closed depending on properties of the mixed product. The speed of the rotary valve may also be controlled depending on the properties of the mixed product, such as the viscosity. In one embodiment the rotary valve can be closed or slowed down if the viscosity of the mixed product becomes too high. In one embodiment the mixed processing unit comprises a product drain.

The product drain runs from the bottom of the continuous processing unit to the next mixing tank and/or filter in the system and can be used to remove undesirable components from the mixed product from the unit. In one embodiment the operation of the continuous processing unit can be controlled in combination with an on-line viscometer. In one embodiment, the process control comprises adjusting the rotary valve speed depending on the change of the measure viscosity of the mixed product. The process control can comprise sounding an alarm when the viscosity of the mixed product reaches a High level. The process control can further comprise shutting off the rotary inlet valve when the viscosity of the mixed product reaches a High-High level.

In one embodiment the continuous processing unit can be used in series with one or multiple continuous processing units to reduce the back mixing of unmelted/undissolved waste plastic particles for highest efficiency. This arrangement may comprise any other embodiment disclosed herein, and any equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. In another embodiment the continuous processing unit functions as a single vessel.

In one embodiment a jacket can be used for temperature control. The jacket can include a manway in each zone for ease of maintenance.

In another embodiment the shape of the bottom of the continuous processing unit can be modified. For example, the bottom of the unit can comprise a round shape, or in another embodiment comprise a conical shape. Both shapes help to reduce dead zones in the continuous processing unit where waste plastics are deposited at the bottom of the unit and cannot be moved by the impellers.

In one embodiment, the melting and dissolving of waste plastic into VGO can be greatly enhanced by intimate mixing provided by an overhead mixer. In one embodiment two or more impellers can provide the mixing action of the continuous processing unit. In one embodiment these impellers comprise a top impeller and a bottom impeller. In this embodiment the top impeller functions to drag floating solids into the mix liquid. The top impeller preferably has a high down-pumping capacity. The bottom impeller functions to breakdown large viscous droplets and/or agglomerates. In one embodiment the bottom impeller comprises one or more turbines or other types of radial impellers. Preferably the bottom impeller is a high shear impeller.

In one embodiment, a light cycle oil or any other suitable solvent can be injected into the mixing tank through the shaft of the overhead mixer to clean up or dissolve any agglomerate of waste plastics that stick on the shaft where the shear rate is known to be the lowest in the entire mixing tank.

In one embodiment the product drain further comprises a pump around loop to improve solid suspension and enhance shearing of agglomerates. In another embodiment a slurry pump can be used to handle solids.

In one embodiment the continuous processing unit can create multiple zones using separation horizontal baffles in a single vessel. In another embodiment the separation baffles can be used to create plug flow through the continuous processing unit by being placed closely. In one embodiment the separation horizontal baffles are set within the continuous processing unit at a slight angle. Angling the horizontal separation baffles in this way can be useful in avoiding the creation of dead zones within the unit and/or accumulation of solid particles on the baffles. In one embodiment the continuous processing unit further comprises at least one overhead radial mixer with impellers placed in each zone created by the separation baffles. The placement of a radial impeller in each zone has been found to be beneficial for the mixing action of the unit. In one embodiment the overhead radial mixer comprises one or more turbine impellers. Preferably the bottom impeller is a high shear impeller.

In one embodiment the continuous processing unit comprises a rectangular or cylindrical tank. The rectangular or cylindrical tank continuous processing unit can be separated into multiple mixing zones using vertical walls. The unit can comprise a pump around loop. In another embodiment the continuous processing unit does not have a pump around loop.

Referring now to the figures of the drawing, FIG. 1 depicts a schematic of one embodiment of the present process. Waste plastic 10 can be sorted 20, or not. If sorted, in one embodiment, polypropylene plastic and polyethylene plastics are primarily selected 30. The waste plastic 10 can comprise industrial waste plastic, consumer waste plastic or municipal waste plastic.

An oil storage tank 40 provides a petroleum feed that is heated 50 and then mixed with the plastic waste 60 in a mixing and melting zone or unit 75. The resulting mixed product can be collected and tested in one embodiment, and the entire process can be altered or adjusted based on the testing results. The mixed product can also be filtered 70, with the filtration in one embodiment being a hot filtration, with the filtration run at a temperature in a range of from about 300-450° F., for example. In one embodiment, the preparation of the blend and the filtration ranges from about 300-400° F. The resulting hot mixed blend 80 is then passed to a conversion reactor 90.

The conversion reactor 90 can be a standalone conversion reactor such as a hydrocracker or fluid catalytic cracker (FCC) or coker or pyrolysis unit. The reactor does not have to be part of a refinery. The reactor can be outside a refinery and used to prepare products which can be further refined, whether in a refinery or not. A heavy by product 100 can be recovered from the reactor and used for further refinement as well.

A naphtha and/or liquid petroleum gas (LPG) stream 110 can also be recovered from the reactor 90. The stream can be passed to a cracker such as a steam cracker 120 to prepare ethylene 130, which can be polymerized 140 to create circular polyethylene 150. Products 160 can then be made from the circular polyethylene.

FIG. 2 shows a schematic design of one embodiment of the present process comprising effectively melting and dissolving waste plastics into VGO to form a mixture, and further comprising treating the mixture, and converting the mixture into FCC products and fuel in a refinery.

In this embodiment waste plastic can be added to hot VGO in a continuous processing unit. The waste plastic 200 can comprise industrial waste plastic, consumer waste plastic, or municipal waste plastic. The plastic can be pre-sorted 210 or not. If presorted, selecting polyethylene or polypropylene is preferred 220. The plastic can then be mixed into hot VGO 230 obtained from a VGO storage tank 240 in a mixing and melting zone 250. The hot VGO can first be heated by a FCC preheater unit, for example. The mixed product can be collected and tested, and the entire process can be altered based on the testing results. The mixed product can also be filtered 260 prior to feeding to an FCC unit 270 in a refinery.

A light fraction (propane/propylene mix, C₄ and naphtha stream) 280 can be recovered from the FCC unit 270 and passed to a cracker 290 to prepare ethylene 300. The ethylene can then be polymerized at 310 to prepare circular polyethylene 320 from which polyethylene products 330 can be prepared. FCC fuel products 340 can also be recovered from the FCC reactor 270. The fuel products 340 can be further refined in the refinery. Alternatively, the propane/propylene mix can be polymerized to prepare circular polypropylene.

FIG. 3 shows an embodiment of a mixing and melting unit, which in one embodiment can be used for blending waste plastic and VGO. The embodiment of FIG. 3 comprises a continuous processing unit 2000, internal baffles 2001, and an overhead mixer 2002, N₂ purge line 2009, VGO inlet 2004, waste plastic inlet 2010, product drain 2006, overhead vent 2012, and on-line viscometer 2007. The embodiment of FIG. 3 further comprises a jacket 2003, shaped bottom 2011, two or more impellers 2005, and slurry pump 2008. The embodiment of FIG. 3 may optionally include a pump-around loop 2013 to further improve the mixing, and a control loop 2014 that may adjust the plastic addition rate depending on the viscosity measured by the on-line viscometer 2007. Cleaning solvent, such as light cycle oil may be injected to overhead mixer shaft to keep the shaft clean and with minimum deposit (not shown).

FIG. 4 shows an embodiment of a mixing and melting unit, which in one embodiment can be used for blending waste plastic and VGO. The embodiment of FIG. 4 comprises a continuous processing unit 3000, internal baffles 3001, and an overhead mixer 3002, N₂ purge line 3003, VGO inlet 3004, waste plastic inlet 3011, product drain 3007, overhead vent 3013 and on-line viscometer 3008. The embodiment of FIG. 4 further comprises horizontal separation baffles 3012, two different kinds of radial impellers 3005 and 3009, jacket 3006 for temperature control, and a slurry pump 3010. The embodiment of FIG. 4 may optionally include a level gauge 3014 and level control loop 3015 to adjust the flow rate of the product output, and a control loop 3016 that may adjust the plastic addition rate depending on the viscosity measured by the on-line viscometer 3008. Cleaning solvent, such as light cycle oil may be injected to overhead mixer shaft to keep the shaft clean and with minimum deposit (not shown).

FIG. 5 shows an embodiment of a mixing and melting unit, which in one embodiment can be used for blending waste plastic and VGO. The embodiment of FIG. 5 comprises a rectangular or cylindrical continuous processing unit 4000, internal walls 4001, and an overhead mixer 4002 in each zone, N₂ purge 4003, VGO inlet 4006, waste plastic inlet 4007, plural product drains 4004, overhead vent 4011, and on-line viscometer 4005. The embodiment of FIG. 5. further comprises one or more baffles 4010, pumping down impellers 4009, one or more vertical high shear impellers 4008 and a slurry pump 4012. The embodiment further comprises one or more cleaning solvent line 4013 where solvent such as light cycle oil may be injected to overhead mixer shaft to keep the shaft clean with minimum deposit. The embodiment of FIG. 5 may optionally include a control loop 4014 that may adjust the plastic addition rate depending on the viscosity measured by the on-line viscometer 4005.

The present process and associated equipment as described and illustrated allow for effectively melting and dissolving waste plastics into petroleum feeds such as VGO. The process can continuously generate a stream of blended plastic and VGO liquids that can be further treated or purified to meet fluid catalytic cracking (FCC) feedstock specifications. The entire stream can then be sent to a conversion reactor, such as a FCC unit in a refinery, to convert waste plastics into high quality fuel products or chemicals for polymerization. The associated equipment comprises a continuous processing unit with minimum maintenance requirement.

When filtration of the blend is conducted prior to the blend being sent to a reactor, the filtration unit can be run at a temperature in the range of from 300 to 450° F. This allows for polyethylene and polypropylene to dissolve while other less desirable plastics, and solid waste are filtered out and removed. Thus, the less desirable plastics and solid waste are not sent to the conversion reactor, such as an FCC unit in a refinery.

FIG. 6 depicts a continuous filtration unit suitable for use in one embodiment of the present continuous process for plastic and petroleum feed blend preparation. The filter unit 5000 has an filter housing 5001, an inlet 5002 for the plastic/VGO blend. The unit can have an inner cylinder of wire filer screen 5003, which is the filtration medium. The size of the filter pores can be chosen as needed. An outlet 5004 for the filtered blend allows the blend then to be passed to a conversion reactor. There is also an outlet 5005 for solid removal, such as in solid/VGO slurry. In one embodiment, a clearing disk 5006 can move up and down the inside of the wire cylinder to remove solids from the filter screen 5003 and move the solids to the solids outlet 5005. In one embodiment a pressure differential (dP) between inlet and outlet 5007 is measured. The delta P can be used to control the valve opening of the solid/VGO slurry outlet 5005.

Alternatively, undesirable solids in the plastic/VGO can be removed as a solid/VGO slurry using a back-wash filter or a centrifuge at an elevated temperature in the range of 300-450° F. Another embodiment is using a cartridge-based filter unit to remove the solids with disposable filter cartridges. Another embodiment is using a filter press at an elevated temperature where the solids can be removed as a filter cake.

As used in this disclosure the word “comprises” or “comprising” is intended as an open-ended transition meaning the inclusion of the named elements, but not necessarily excluding other unnamed elements. The phrase “consists essentially of” or “consisting essentially of” is intended to mean the exclusion of other elements of any essential significance to the composition. The phrase “consisting of” or “consists of” is intended as a transition meaning the exclusion of all but the recited elements except for only minor traces of impurities.

As those skilled in the art will appreciate, numerous modifications and variations of the present invention are possible considering these teachings, and all such are contemplated hereby. For example, in addition to the embodiments described herein, the present invention contemplates and claims those inventions resulting from the combination of features of the invention cited herein and those of the cited prior art references which complement the features of the present invention. Similarly, it will be appreciated that any described material, feature, or article may be used in combination with any other material, feature, or article, and such combinations are considered within the scope of this invention.

All of the publications cited in this disclosure are incorporated by reference herein in their entireties for all purposes.