PROCESS FOR PRODUCTION OF USEFUL HYDROCARBON MATERIALS FROM PLASTIC WASTE AND REACTION SYSTEM THEREFOR

Abstract

A process for production of useful hydrocarbon materials from plastic waste and reaction system therefor is provided. The process includes frequentatively thermolyzing of high molecular weight hydrocarbons such as plastic waste to produce useful medium molecular weight hydrocarbons and low molecular weight hydrocarbons. The process utilizes low molecular weight hydrocarbons as solution reactants which helps in reducing the viscosity of the material for more effective heat transfer. The process also includes addition of one or more low molecular weight olefins and solution reactants to high molecular weight hydrocarbons to augment the free radical environment. The process also includes hydrogenating and oxidizing the high molecular weight hydrocarbons. The process enables production of the useful, predominantly hydrocarbon materials such as waxes, lube oil base-stocks, refinery feedstocks, intermediates or fuel additives. The present invention also provides a reaction system comprising thermolysis reactor including a primary zone and an optional secondary zone for production of useful hydrocarbon materials from plastic waste.

Claims

1. A process for production of hydrocarbon materials from at least one of plastic waste and high boiling hydrocarbons or combination thereof comprising: a. mixing high molecular weight hydrocarbons, and lower molecular weight hydrocarbons to obtain a uniform mixture representative of low viscosity dissolved polymer phase, wherein the high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic, un-shredded waste plastic, high boiling hydrocarbons, other similar materials such as ethers and substituted hydrocarbons, and combinations thereof, wherein the uniform mixture comprises 70% wt-30% wt of the high molecular weight hydrocarbons, and 30% wt-70% wt of the lower molecular weight hydrocarbons; b. heating the uniform mixture to obtain a molten state; c. separating heavy contaminants and light contaminants from molten uniform mixture prior to thermolysis reaction; d. frequentatively thermolyzing the molten uniform mixture at a predefined temperature, pressure and duration to initiate free radical chemical reactions and causing breakdown of the uniform mixture, wherein the predefined temperature ranges from 350° C. to 425° C., the predefined pressure ranges from 3-20 bar, and predefined duration ranges from 1 to 4 hours; and separating thermolyzed uniform mixture into at least three streams, wherein the at least three streams comprises dissolved hydrocarbon gases including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material.

2. The process as claimed in claim 1, wherein the lower molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range material, n-paraffin, decalin, coker gas oils and diesel.

3. The process as claimed in claim 1, wherein the uniform mixture comprises 40% wt of the high molecular weight hydrocarbons, and 60% wt of the low molecular weight hydrocarbons.

4. The process as claimed in claim 1, wherein the uniform mixture being heated at temperature ranging from 180° C. to 250° C.

5. The process as claimed in claim 1, wherein the frequentatively thermolyzing of the molten uniform mixture is carried out at 15 bar pressure.

6. The process as claimed in claim 1, wherein the crude thermolyzed product material from the at least three streams comprises heavy waxes with molecular weight ranging from 1,500 to 6,000 Dalton.

7. The process as claimed in claim 1, wherein the steps (a) to (e) are operated intermittently in a batch mode.

8. The process as claimed in claim 7, wherein the batch mode is configured to convert medium molecular weight hydrocarbons to low molecular weight hydrocarbons.

9. The process as claimed in claim 1, wherein the steps (a) to (e) are operated in a continuous mode.

10. The process as claimed in claim 1, further comprises recycling the three streams by supplying back to at least one step of the mixing of high molecular weight hydrocarbons and lower molecular weight, the heating of the uniform mixture, and the frequentatively thermolyzing molten uniform mixture.

11. The process as claimed in claim 10, wherein the recycling of the three streams by supplying back comprises supplying the light naphtha range material as fuel for one of the heating the uniform mixture and the thermolyzing the molten uniform mixture.

12. The process as claimed in claim 10, wherein the recycling of the three streams by supplying back comprises supplying back the stream of naphtha through light wax as solution reactant to the mixing step.

13. The process as claimed in claim 1, further comprises adding one or more low molecular weight olefins selected from a group comprising 1 octene and 1-hexene to the step (a) to undergo supplementary reactions in the free radical environment.

14. The process as claimed in claim 1, further comprises adding a solution reactants after the thermolysis and before hydrotreating process to reduce viscosity of the product to accelerate a hydrogenation process, wherein the adding of the solution reactants after the thermolysis enables separation of waxy molecules from non-waxy molecules by differential solidification, wherein the solution reactants comprise the lower molecular weight hydrocarbons.

15. The process as claimed in claim 1, further comprises carrying out short path distillation (SPD) to separate the crude thermolyzed product into fractions.

16. The process as claimed in claim 15, wherein the SPD is carried out at temperature 360° C.

17. The process as claimed in claim 1, further comprises hydrogenating the high molecular weight hydrocarbons.

18. The process as claimed in claim 1, further comprises oxidizing the high molecular weight hydrocarbons.

19. A reaction system, comprising: at least one surge hopper adapted to receive high molecular weight hydrocarbons, wherein the high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic and un-shredded waste plastic; a melter fluidically connected to the at least one surge hopper via first set of one or more valves, wherein the melter is adapted to mix the high molecular weight hydrocarbons and the lower molecular weight hydrocarbons, via mixing means, to obtain a uniform mixture representative of low viscosity dissolved polymer phase, and heat the uniform mixture to yield a molten state, and wherein the melter comprises one or more openings to receive at least one of low molecular weight hydrocarbons as solution reactant and heavy wax, and one or more openings to release dissolved hydrocarbon gases including light naphtha range material, and a molten uniform mixture of the high molecular weight hydrocarbons and the low molecular weight hydrocarbons; a thermolysis reactor fluidically connected to the melter via second set of one or more valves and adapted to produce hydrocarbon materials comprising medium molecular weight hydrocarbons to low molecular weight hydrocarbons, wherein the thermolysis reactor comprises a primary zone, an optional secondary zone, one or more openings to receive hydrocarbon liquids, and one or more openings to release at least one of a vapour phase of the thermolysis reactor and a thermolyzed material, wherein the primary zone being adapted to convert the molten mixture into a condensed phase at a moderate temperature with a relatively long residence time, and the optional secondary zone being adapted to convert the molten mixture into a vapor phase at high temperature with a short residence time, and wherein the optional secondary zone is adapted to receive vapors circulated from the primary zone.

20. The reaction system as claimed in claim 19, wherein the melter is adapted to melt the uniform mixture at a temperature ranging from 180° C. to 250° C.

21. The reaction system as claimed in claim 19, wherein the low molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range, n-paraffin, decalin, diphenyl ether, coker gas oils and diesel.

22. The reaction system as claimed in claim 19, wherein the mixing means comprises at least one of an agitator and an impeller.

23. The reaction system as claimed in claim 19, wherein the mixing means comprises an external pump circuit which circulates liquid for effective mixing.

24. The reaction system as claimed in claim 19, wherein the optional secondary zone is adapted to have a surface temperature between 500° C. and 1000° C., preferably between 600° C. and 750° C.

25. The reaction system as claimed in claim 19, wherein the optional secondary zone is adapted to produce low molecular weight olefins from low molecular weight hydrocarbons, where the low molecular weight olefins comprise ethylene and propylene.

26. The reaction system as claimed in claim 19, wherein the thermolyzed material comprises dissolved hydrocarbon gases including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material.

27. The reaction system as claimed in claim 19, wherein the thermolysis reactor being operated at isothermal condition by soft heating by circulating hot oil.

28. The reaction system as claimed in claim 19, further comprises a riser and a downcommer fluidically connected to the melter via third set of one or more valves, wherein the riser and downcommer combination operates as a trap, and adapted to receive the molten uniform mixture and automatically separate heavy contaminant and light contaminants from the molten mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:

[0030] FIG. 1 is a flow diagram 100 representing steps involved in a process for production of useful hydrocarbon materials from plastic waste, in accordance with an embodiment of the present invention;

[0031] FIG. 2 is a schematic representation of a reaction system 200 used for batch mode thermolysis reaction, in accordance with an embodiment of the present invention;

[0032] FIG. 3 is a schematic representation of a riser 401 for automated separation of heavy contaminants and light contaminants from the uniform mixture flowing from the melter 201, in accordance with an embodiment of the present invention; and

[0033] FIG. 4 is a schematic representation of a device 400 for automated collection of batch distillation, in accordance with an embodiment of the present invention.

[0034] Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the method steps, chemical compounds, and parameters used herein may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.

DETAILED DESCRIPTION

[0035] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

[0036] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more components, compounds, and ingredients preceded by “comprises . . . a” does not, without more constraints, preclude the existence of other components or compounds or ingredients or additional components. Appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.

[0038] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

[0039] Embodiments of the present invention relates to a process for production of useful hydrocarbon materials from plastic waste. The process mainly focuses on frequentative thermolysis process.

[0040] The present invention deals with the production of useful, predominantly hydrocarbon materials such as waxes, lube oil base-stocks, refinery feedstocks, intermediates or fuel additives from high molecular weight hydrocarbon materials such as plastic waste with possible supplementary use of low molecular weight hydrocarbon materials. The present invention uses low molecular weight hydrocarbon materials as “solution reactants”, functioning as solvents or swelling agents for the high molecular weight materials. The solution reactant helps in reducing the viscosity of the material for more effective heat transfer. The solution reactant also function as selective solvents for the secondary purpose of dissolving the more desirable materials for the process (such as aliphatic resins) while leaving fewer desirable materials (such as highly polar resins and inert fillers) as undissolved solids or immiscible liquids. Further, in certain cases the solution reactant acts as a reactant, combining with fragments from the plastic to form new substances.

[0041] FIG. 1 is a flow diagram 100 representing steps involved in the process for production of useful hydrocarbon materials from plastic waste, in accordance with an embodiment of the present invention.

[0042] The process for production of useful hydrocarbon materials from plastic waste begins with mixing high molecular weight hydrocarbons and lower molecular weight hydrocarbons to obtain a uniform mixture representative of low viscosity dissolved polymer phase at step 102. The high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic and un-shredded waste plastic. The low molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range, n-paraffin, decalin, diphenyl ether, coker gas oils and diesel. The uniform mixture comprises 70% wt.-30% wt. of the high molecular weight hydrocarbons, and 30% wt.-70% wt. of the low molecular weight hydrocarbons. The uniform mixture preferably comprises 40% wt of the high molecular weight hydrocarbons, and 60% wt of the low molecular weight hydrocarbons.

[0043] The use of shredded plastic is convenient in the process. However, it is possible to deal with the un-shredded plastic. The un-shredded plastic is used by mechanically circulating a hot liquid on the un-shredded plastic. The hot liquid includes solution reactant, wax, or plastic mixture.

[0044] The process may also be applied to high boiling hydrocarbons or other heavy materials which may substitute for waste plastic in any proportion up to 100%. In an embodiment, the other heavy material include high molecular mass or high boilinghydrocarbon materials such as, but not limited to, residual material from crude oil, residual material recovered from the oil produced by pyrolysis of tires, herein referred to as “residuum”.

[0045] In an embodiment, the process includes heating the uniform mixture to obtain a molten state at step 104. In such an embodiment, the uniform mixture may be heated at temperature ranging from 180° C. to 250° C.

[0046] In alternative embodiment, the process may start with heating the low molecular weight hydrocarbon material and then adding the high molecular weight material over time while continuing heating to finish with a uniform mixture at a temperature between 180° C. and 250° C.

[0047] In an embodiment, the process includes separating heavy contaminants and light contaminants from molten uniform mixture prior to thermolysis reaction at step 106. The separating the heavy contaminants and light contaminants from the molten uniform mixture enables removal of impurities from the high molecular weight hydrocarbons.

[0048] In an embodiment, the process includes frequentatively thermolyzing the molten uniform mixture at a predefined temperature, pressure and duration to initiate free radical chemical reactions and causing breakdown of the uniform mixture at step 108. In such an embodiment, the predefined temperature may range from 350° C. to 425° C., the predefined pressure may range from 3-20 bar, and predefined duration may range from 1 to 4 hours. The frequentatively thermolyzing of the molten uniform mixture is preferably carried out at 15 bar pressure. The pressure, temperature and residence time are selected so that the short to medium length hydrocarbons are able to participate in the free radical reactions (in addition to the long chain hydrocarbons). This is accomplished by using moderately high pressure to ensure such materials are significantly present in the liquid phase at process temperature. The process temperature may range from 350° C. to 425° C. and it is selected so that reaction rate remains moderate and consequently the process is controllable and coke formation is suppressed. The residence time is typically relatively long, from 1 to 4 hours consistent with the deliberate, relatively slow rate of reaction.

[0049] The small to medium sized molecules present in a liquid phase are liable to lose a hydrogen atom to become a free radical (due to chain reaction with pre-existing free radicals, i.e. by chain-transfer reaction). Such low molecular weight free radicals readily disproportion into a smaller radical and an olefinic fragment. The olefin fragment being of low carbon number is highly active (compared to other materials present) and readily attaches as a side chain to a free radical in the substrate molecule. Alternatively, the free radicals initially formed (or the free radical fragment remaining after an olefin has formed) participate in the free radical chain reactions, including possibly chain termination by attaching to a free radical in the substrate. As a consequence, the process is able to convert at least a portion of less desirable naphtha and/or distillate range molecules into lightly branched higher molecular weight molecules.

[0050] The high molecular weight hydrocarbons crack to mainly wax range materials with a less amount of liquid range materials and lesser gas range materials. The low molecular weight hydrocarbons initially crack to smaller olefins and paraffins. The olefins attach to the wax range material making it more highly branched while the paraffins are less reactive but eventually are able themselves to react to form smaller olefin and paraffin fragments. Consequently, if reaction is continued for a very long time, the final material has a broad molecular weight distribution with less amount of very high molecular weight hydrocarbons, a large amount of medium molecular weight hydrocarbons (somewhat branched chain) and low molecular weight predominantly paraffinic material.

[0051] In an embodiment, the process includes separating thermolyzed uniform mixture into at least three streams at step 110. The at least three streams comprises dissolved hydrocarbon gases (including light naphtha range material), naphtha through light wax material, and a crude thermolyzed product material. The crude thermolyzed product material from the at least three streams comprises heavy waxes with molecular weight ranging from 1,500 to 6,000 Dalton.

[0052] In another embodiment, the steps 102 to 110 of the process for production of useful hydrocarbon materials from plastic waste being operated intermittently in a batch mode without adding high molecular weight hydrocarbons. The batch mode is configured to convert medium molecular weight hydrocarbons to low molecular weight hydrocarbons.

[0053] In yet another embodiment, the process in the batch mode is carried out using batch distillation as a product recovery step. The batch distillation is carried out in at least one of thermolysis reactor and separate equipment which is specifically designed for the purpose. In either situation, the large mass of material is maintained at a high temperature, but somewhat lower than the thermolysis temperature to slow down the rate of reaction. The steps 102 to 110 are performed in this embodiment under reduced to atmospheric pressure. Thereafter, the temperature is maintained while the pressure is further reduced using vacuum equipment. Reducing the pressure at this stage is typically advantageous. This is feasible using several boosters (such as roots blowers) with a primary vacuum pump (such as a liquid ring pump). Initially the boosters operate at low speed and the vacuum is essentially provided by the primary pump. The distillate material gradually becomes heavier as the distillation continues and can be collected in fractions. It is possible to automate the collection by fractions with fractions defined by melting point using a device such as that depicted in FIG. 4 (described later).

[0054] In an embodiment, the steps 102 to 110 of the process for production of useful hydrocarbon materials from plastic waste being operated in a continuous mode.

[0055] The process in the continuous mode includes feeding shredded plastic waste with recycled liquid and recycled heavy wax into a heated, well stirred tank known as a melter or dissolver. The shredded plastic waste comprises clean recycle polyethylene (PE) or mixed waste plastic, which can have contaminants within reason. The melter is maintained at a temperature ranging from 180° C. to 250° C. using a steam, hot oil or electric coil. The melter is maintained at atmospheric pressure, which is convenient for addition of the shredded plastic waste. The electric coil used with wall temperature limited to 400° C. or less. The melter therefore contains a solution of molten plastic and wax in hydrocarbon liquid together with minor amounts of contaminants (heavy contaminants and light contaminants) which came with the plastic and recycled wax. For example, small amounts of polar resins (such as PET), paper from labels, inorganic materials from pigments and fillers, or possibly coke from downstream. The heavy contaminants and the light contaminants from the solution of molten plastic and wax in diesel is separated prior to thermolysis reaction. The vapours from the melter are continuously withdrawn and condensed. Condensate thus collected is added to the thermolysis reactor. The frequentative thermolysis reaction is carried causing breakdown of the solution of molten plastic and wax in diesel. The solution of molten plastic and wax in diesel is separated into at least three streams, wherein the at least three streams comprise dissolved hydrocarbon gases, including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material. This is a very unique aspect of the present invention.

[0056] In the continuous mode of the process for production of useful hydrocarbon materials from plastic waste, the thermolysis reactor consist of a continuous stirred tank reactor (CSTR) followed by a plug flow reactor (PFR). Residence time of the CSTR is maintained significantly higher than that of the PFR. The PFR is adapted to avoid any possibility of unreacted plastic bypassing. A system employing the CSTR followed by the PFR confers the ability to engineer both the residence time distribution and the temperature history of the material.

[0057] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises recycling the at least three streams by supplying back to at least one step of the mixing of high molecular weight hydrocarbons and lower molecular weight, the heating of the uniform mixture, and the frequentatively thermolyzing molten uniform mixture. The recycling of the at least three streams by supplying back comprises supplying the light naphtha range material as fuel to provide a hot utility required for the process (for example to supply the fuel for a hot oil system or for direct heating). The recycling of the at least three streams by supplying back comprises supplying back the stream of naphtha through light wax as solution reactant to the mixing step. All the aliphatic molecules that are not in the desired size range for the products are recycled back to a thermolysis reaction zone (frequentative thermolysis) being part of the solution reactant material.

[0058] The recycled solution reactant material has beneficial actions such as a high affinity for aliphatic resins (such as polyethylene and polypropylene), a much lower affinity for polar resins (such as polyethylene terephthalate and PVC) and inert solids (such as coke and fillers) and consequently enables a degree of separation of the materials (such as PE and PP) that are precursors to desirable waxy molecules from materials (such as PET and PVC). The solution reactant greatly reduces the viscosity of the melt which facilitates efficient heat transfer and also makes it possible to separate undesirable materials (solids and incompatible melts or liquids) from the desirable materials, either by settling or filtration.

[0059] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises adding one or more low molecular weight olefins to the step 102. The low molecular weight olefins are selected from a group comprising maleic anhydride, 1-octene and 1-hexene, such materials being available to react with the substrate material in the free radical environment. The addition of low molecular weight olefins, such as 1-octene and 1-hexene increases the amount of branched chain material in the product as these materials typically graft to the substrate to form a short side chain of 8 or 6 carbon atoms respectively. The addition of maleic anhydride introduces alkenyl succinic anhydride functionality to the product of the thermolysis reaction. Since maleic anhydride is an extremely polar material, thus has limited solubility in aliphatic solvent and consequently only a limited amount of maleic anhydride is introduced. The amount of maleic anhydride can be increased by selecting a solvent which has higher capacity for maleic anhydride while retaining adequate solvency for the polyolefins. For example, decalin or the commercially available eutectic mixture of biphenyl and diphenyl ether (known as Dowtherm A). The maleic anhydride can be gradually added during the course of the reaction using a volatile solvent with high capacity for maleic anhydride, such as tetrahydrofuran. In such case, the solvent or maleic anhydride mixture can be added drop-wise over the course of the reaction.

[0060] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises adding the solution reactants after the thermolysis and before hydrotreating process to reduce viscosity of the product to accelerate a hydrogenation process. The adding of the solution reactants after the thermolysis enables separation of waxy molecules from non-waxy molecules by differential solidification.

[0061] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises carrying out short path distillation (SPD) to separate the crude thermolyzed product into convenient fractions. The SPD being carried at temperature 360° C. which enables the process to operate with a less extreme vacuum system. Using higher than typical SPD temperatures reduces cost by requiring less extreme vacuum and the associated equipment.

[0062] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises hydrogenating the high molecular weight hydrocarbons.

[0063] A further embodiment of the process is a method to produce essentially straight chain materials (n-paraffins) from feed rich in polyethylene. This embodiment exploits the fact that the most common polyethylene materials available are actually comonomers of ethylene and 1-butene and as such have ethyl side branches. Since ethyl side branches are very stable, compared to longer branches, thermolysis is more likely to result in scission of the carbon-carbon bond in what would normally be described as the main chain. This leads directly to one of two distinct types of molecules:

##STR00001##

The molecule (1) is more common and accounts for approximately 70% of the total of the above two types of molecules.
After hydrogenation, the molecule (1) and molecule (2) convert into the following:

##STR00002##

Note that after hydrogenation, ˜30% of the material is straight chain and 70% is lightly branched having a methyl group on the 3.sup.rd carbon from chain end. In many cases such material is sufficiently straight chained. The presence of the methyl group in a predictable place (3.sup.rd carbon from chain end) makes it possible for such materials to crystalize more easily than equivalent materials with the side branch randomly assigned. However, in cases where minimizing the amount of branched chain materials is important, it is possible to obtain fully normal paraffin material by subjecting such hydrogenated materials to a second thermolysis treatment. The methyl branch on the third carbon is a quite stable group and additional thermolysis will involve scission on the main chain, either removing 2-butene or removing 2-methyl 1-butene, in either case the mildly branched material is replaced by an unbranched molecule containing 4 or 5 fewer carbon atoms. The resulting molecules are typically hydrogenated and separated a second time; however, the additional processing helps in production of a high yield of n-paraffinic material.

[0064] In a further embodiment of the process for production of useful hydrocarbon materials from plastic waste, the process comprises oxidizing the high molecular weight hydrocarbons.

[0065] The present invention also provides for a reaction system 200 designed specifically for production of hydrocarbon materials from plastic waste.

[0066] FIG. 2 is a schematic representation of the reaction system 200 used for batch mode thermolysis reaction, in accordance with an embodiment of the present invention.

[0067] In an embodiment, the reaction system 200 comprises at least one surge hopper 102 adapted to receive high molecular weight hydrocarbons via a flowline 101. The surge hopper 102 also enables delivery of the high molecular weight hydrocarbons at a predetermined rate to the melter 201 via a flowline 103. The high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic and un-shredded waste plastic.

[0068] In an embodiment, the reaction system 200 comprises the melter 201 fluidically connected to the at least one surge hopper 102 via first set of one or more valves 104. The melter 201 comprises one or more openings to receive at least one of the low molecular weight hydrocarbons as solution reactant, the heavy wax, and one or more openings to release dissolved hydrocarbon gases including light naphtha range material from the melter 201, and a molten uniform mixture of the high molecular weight hydrocarbons and the low molecular weight hydrocarbons. The melter 201 receives the solution reactant through a flowline 202. The melter 201 receives the heavy wax through a flowline 203 from holding tanks using pumps or other conventional methods to induce flow such as gravity or head-space pressure. The melter 201 first receives heavy wax, secondly the solution reactant and finally the high molecular weight hydrocarbons. The particular sequence of receiving the components helps in maintaining the low viscosity in the melter 201.

[0069] The melter 201 is adapted to mix the high molecular weight hydrocarbons and the lower molecular weight hydrocarbons, via mixing means 209, to obtain a uniform mixture representative of low viscosity dissolved polymer phase. The mixing means may comprise of an agitator or impeller, alternatively mixing may be obtained by circulating liquid externally using a pump. The melter 201 is also adapted to heat the uniform mixture to yield a molten state, alternatively to heat the liquid prior to addition of the solids over time so that the material remains “pumpable” (low viscosity) throughout the process. The heating of the uniform mixture may be performed at temperature ranging from 180° C. to 250° C. The low molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range, n-paraffin, decalin, diphenyl ether, coker gas oils and diesel. The melter 201 also comprises heating coil 208 to provide at least part of the heat needed to melt the plastic. The part of the heat needed to melt the plastic is received by hot recycled wax. The hydrocarbon vapours may be formed in the melter 201 as a result of heating. A vapour flowline 204 connects the vapor phase of the melter 201 to a condenser 205 which recovers liquid from the vapours. The recovered liquid is directed towards storage via flowline 206 and releases uncondensed vapours via flowline 207. The recovered liquid is separately directed towards the thermolysis reactor 301. The fraction of recycled liquid which is able to evaporate ranges between 0% to 20% of total recycled liquid.

[0070] Once the molten state of uniform mixture is obtained, the heavy contaminants and the light contaminants are manually separated from the molten uniform mixture. The manual separation of the heavy contaminants and the light contaminants is carried using a sight glass and manual valves. The separation can be automated based on an online physical measurement such as infra-red spectroscopy or can be passively automated using density differences to open and close appropriate paths for the discharged material. A flow-line 210 is directed towards a valve 211 which is closed during the dissolution cycle and opened to allow the molten uniform mixture to flow towards valves 212, 213 and 214. The valve 212 is adapted to purge the heavy contaminants. The valve 213 is adapted to direct the molten uniform mixture to the thermolysis reactor 301. The valve 214 is adapted to purge the light contaminants. The sequence of operation is such that, the valve 212 is opened first, until the appearance of the draining liquid, or continuously measured density or other convenient property indicates that the heavy contaminants have been purged. The valve 212 is then closed and the valve 213 is opened until light contaminants are detected. The valve 213 is then closed and the valve 214 is opened to purge the light contaminants. The molten uniform mixture may contain small amounts of solids and entrained liquids. These may be removed between the melter 201 and thermolysis reactor 301 using suitable filters such as a cartridge filter not shown in the FIG. 2. Transferring the molten uniform mixture to the thermolysis reactor 301 may be done using a pump, head space pressure differential or gravity as convenient.

[0071] In an embodiment, the reaction system 200 comprises the thermolysis reactor 301 fluidically connected to the melter 201 via second set of one or more valves 213. The thermolysis reactor 301 being operated at isothermal condition by soft heating by circulating hot oil. The thermolysis reactor 301 comprises a primary zone, an optional secondary zone, one or more openings to receive hydrocarbon liquids, and one or more openings to release at least one of a vapour phase of the thermolysis reactor 301 and a thermolyzed material. The thermolyzed material comprises at least three streams comprising dissolved hydrocarbon gases, including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material.

[0072] The thermolysis reactor 301 also comprises a heating coil 302 and a gas induction agitator 303. The heating coil 302 provides a heat required for thermolysis reaction. The gas induction agitator 303 ensures proper mixing of components of the thermolysis reactor 301. The thermolysis reactor 301 is operated at a temperature ranging from 350° C. to 425° C. and at pressure about 20 bar for a duration ranging from 30 minutes to 4 hours. The thermolysis reactor 301 headspace can be filled with either nitrogen or hydrogen prior to commencing the thermolysis reaction. Trace amounts of oxygen play a role as initiators of the free radical reactions. The oxygen required for initiating free radical reaction is entrained either with the molten uniform mixture initially fed to the thermolysis reactor 301 or in the nitrogen stream.

[0073] A flowline 305 is directed towards a condenser 306 adapted to condense vapours coming out of the vapour phase of the thermolysis reactor 301. The condensed liquid from the condenser 306 being removed via flowline 307 and directed towards the storage or back to the thermolysis reactor 301 via flowline 308. The condensed liquid may be sent to the storage and an equal amount of liquid pumped from the storage via flowline 304. The uncondensed vapours are directed to the fuel system via flowline 309. The pressure in the thermolysis reactor 301 is controlled by modulating the amount of vapour flow from the condenser using a conventional pressure control loop. The purpose of the condenser 306 during the thermolysis reaction is to recover material as liquid for recycle to the thermolysis reaction, so initially the condenser 306 operates with effectively 100% reflux and retention of all molecules within the thermolysis reactor 301.

[0074] The primary zone is adapted to react the molten mixture in the condensed phase at a moderate temperature with a relatively long residence time. The moderate temperature applied in the primary zone for reacting the molten mixture ranges from 325° C. to 450° C. A vapor zone is always present above the primary zone and in all cases vapor from the vapor zone is recirculated through the liquid in the primary zone. The vapor space may optionally function as a secondary zone, which employs high temperature and short residence time to crack vapor phase components. This requires suitable optional secondary zone heating such as an electrical coil (not shown). The optional secondary zone is adapted to produce low molecular weight olefins (predominantly ethylene and propylene) from low molecular weight hydrocarbons. For example, by inclusion of a heating coil within the optional secondary zone which has a surface temperature between 500° C. and 1000° C., preferably between 600° C. and 750° C.

[0075] The optional secondary zone is incorporated within the vapor phase of the thermolysis reactor 301 that operates using a gas induction agitator 303 to circulate gases through the reacting liquid bulk.

[0076] The low molecular weight hydrocarbons crack to small olefins during the short residence time of the optional secondary zone at temperature above 650° C. The resulting vapor from the optional secondary zone contain a significant amount of low molecular weight olefins in particular ethylene and propylene. The hot gases or vapours leaving the optional secondary zone are immediately quenched in the primary zone. The ethylene, propylene and other low molecular weight olefins attach to the liquid phase material in the primary zone to form side branches. The use of such a secondary thermolysis zone effectively eliminates naphtha range liquids and significantly increases the degree of branching of the primary zone product which is useful when a branched chain material is the target product such as the case of lube base stock.

[0077] After the reaction has been substantially completed, the thermolysis reactor 301 is gradually depressurized. The depressurization is accomplished by directing the liquid phase from the condenser 306 to storage rather than reflux. (the pressure control valve which directs vapour phase to fuel gas will tend to close as the low molecular weight hydrocarbons are sent to storage rather than refluxed). A significant amount of vapor flushes off during this process and is condensed in the condenser 306 of the thermolysis reactor 301. The rate of cooling of the thermolysis reactor 301 is dependent on the sizing of the condenser 306. As the thermolysis reaction time progresses the condensed material gradually increase in carbon number, starting out as a naphtha range material and finishing up as distillate making possible (but not essential) to send the liquid to different tanks as the molecular weight changes, which is done automatically, for example based on density. As a result, sufficient light liquid is retained as a supplementary fuel while the heavier liquid is all recycled to extinction.

[0078] After the depressurization of the thermolysis reactor 301 above atmospheric pressure, the crude thermolyzed material is transferred via flowline 310 to the crude thermolyzed material storage tank.

[0079] In a further embodiment of the reaction system 200, the reaction system 200 comprises a riser 401 and downcommer 402 combination fluidically connected to the melter 201 via third set of one or more valves. The riser 401 and downcommer 402 combination operates as a trap which separates light and heavy contaminants from the molten uniform mixture and automatically directs the heavy contaminant and light contaminants to separate zones for removal and disposal.

[0080] FIG. 3 is a schematic representation of the riser 401 for automated separation of heavy contaminants and light contaminants from the uniform mixture flowing from the melter 201, in accordance with an embodiment of the present invention.

[0081] The riser 401 receives the molten uniform mixture via the flowline 210. The riser 401 is sized so that the up flow velocity remains low, thereby enabling settling of the heavy contaminants against the rising flow. The heavy contaminants are purged periodically via the valve 212. The light contaminants are purged from the riser 401 via the flowline 214. The molten uniform mixture is then released from the riser 401 through the valve 213.

[0082] The FIG. 4 is a schematic representation of a device for automated collection of liquid product from batch distillation, in accordance with an embodiment of the present invention. The device uses the fact that the congeal temperature of the overhead product steadily increases as lighter materials are withdrawn as product. Indeed, a key specification for wax products is the congeal point. The concept of the device is to automatically redirect the distillate once the congeal temperature passes certain threshold values. For illustrative purposes in FIG. 4, the device is shown to comprises three heat exchangers. It will be clear to one skilled in the art that more or fewer exchangers could be employed in the same concept. The liquid from the condenser passes through a horizontal, heat traced or jacketed pipe with a number of full bore tees with the branches oriented vertically downwards. From each tee, piping runs vertically downwards into a jacketed section. The jacketed section functions as a double pipe heat exchanger and cools any liquid passing through to a temperature defined by the temperature of the coolant and the diameter of the inner pipe. The coolant circulating in the three exchangers shown is controlled at three different temperatures, with the first exchanger coolest and the third exchanger hottest of the three. Initially, the liquid flows through the first exchanger to a collection tank below as this is the “path of least resistance” for the overhead liquid. However, as the distillation progresses, the material becomes higher in congeal point until a time is reached when the material freezes in the first heat exchanger. After that flow is no longer possible through the first exchanger which blocks with frozen hydrocarbon, consequently the new “path of least resistance” is through the second heat exchanger. This exchanger uses a higher temperature coolant and consequently will initially be open and will remain open until the congeal temperature is exceeded and the second exchanger plugs in its turn with liquid directed to the next new “path of least resistance”. In principle any number of such devices could be used to collect fractions by melting point. In the embodiment shown in FIG. 4, 3 such devices are used. Typically the circulating coolant temperatures will be 20° C., 55° C. and 75° C. which enables the overhead condensate to be collected in distinct cuts: liquids (congeal point <20° C.), light wax (congeal point 20-55° C.), medium wax (congeal point 55-75° C.) and heavy wax (congeal point >75° C.). Once distillation of a batch is finished, the outlets are cleared by increasing the coolant temperatures in each device and then resetting the temperatures ready for the next batch.

[0083] The present invention discloses an efficient process for production of useful hydrocarbon materials from plastic waste. The process enables reducing energy requirement as bulk liquid is also considered as product along with vapour phase. The process provided by the present invention is energy efficient and ensures purity of the product. The process provides higher yield due to recycling of all aliphatic molecules that are not in the desired size range for the products. The process enables recycling heavy molecules to extinction and alternative to consider them as heavy waxes creates significant flexibility and potential for high value products. The process provides the possibility to incorporate externally sourced medium carbon number molecules including specialty materials such as decalin which creates significant flexibility and potential for high value products. The possibility to operate the process in batch mode allows to operate the process intermittently without heavy feed (i.e. without waste plastics) thus can be configured to convert any outside low cost medium molecular weight materials (heavy naphtha, distillate, light wax) to lightly branched molecules. Addition of low molecular weight olefins from external sources enables valuable lube base stocks to be produced from ethylene and lube range materials. Arrangement of the second zone into the thermolysis reactor 301 to produce low molecular weight olefins enables lube base stocks to be produced from medium and low molecular weight materials. Maintaining the thermolysis reactor 301 at isothermal conditions avoids the complications of coke formation. Addition of solution reactant after thermolysis and before hydrotreating facilitates finishing process. The separation of the thermolyzed material into different streams facilitates maximizing the product slate value while recycling less valuable material and providing fuel for the process. The present invention also provides a reaction system 200 for production of useful hydrocarbon materials from plastic waste. The reaction system 200 comprises the thermolysis reactor 301 comprising primary zone and optional secondary zone. The optional secondary zone enables optional further cracking of low molecular hydrocarbons to smaller olefins which contribute to obtaining the product in various ranges of hydrocarbons.

[0084] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

[0085] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependant on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.