Method of Separating a First Contaminant from a Feed Stream and Reactor System for Carrying Out the Method

Abstract

The invention relates to a method of separating a first contaminant from a feed stream further comprising a condensation polymer. The invention further relates to a reactor system for carrying out the method, comprising at least one depolymerization vessel, configured for depolymerizing a condensation polymer into monomer, dimer, trimer and/or oligomer, which depolymerizing occurs in an alcoholic solvent, wherein said condensation polymer is provided as a feed stream further comprising a first contaminant, the reactor system comprising a separation stage, said separation stage comprising a separation vessel, downstream of the depolymerization vessel, configured for collecting a first contaminant, wherein said first contaminant is separated from the alcoholic solvent on the basis of a density separation so that the first contaminant is arranged on top of the alcoholic solvent.

Claims

1-40. (canceled)

41. Method of separating a first contaminant from a feed stream further comprising a condensation polymer, which method comprises the steps of: supplying the feed stream, an alcoholic solvent and optionally a depolymerization catalyst into a depolymerization vessel and mixing thereof to form a reaction mixture; depolymerizing at least a portion of said condensation polymer in said reaction mixture into monomer, dimer, trimer and/or oligomer under said reaction conditions; transferring the reaction mixture after the depolymerization of at least a portion of said condensation polymer in said reaction mixture to a separation stage comprising a separation vessel, and collecting the first contaminant, wherein said first contaminant is separated from the alcoholic solvent on the basis of a density separation in the separation stage, in particular so that first contaminant is arranged on top of the alcoholic solvent in the separation vessel; further comprising the step of cooling the reaction mixture with cooling means before the collecting step to ensure that the reaction mixture in the separation vessel is at a lower temperature than the depolymerization vessel such that the first contaminant that is liquid and/or dissolved in the depolymerization vessel at least partially precipitates and the cooled reaction mixture separates into a main phase that comprises the reaction products from the depolymerization and the alcoholic solvent, and a first contaminant phase in the form of solid particles and/or a solid layer.

42. Method of claim 41, wherein the separation vessel is provided with a top outlet, of which the position is adjustable and wherein the method comprises the steps of: detecting the location of the first contaminant; adjusting the position of the top outlet for collecting the first contaminant.

43. Method of claim 41, further comprising the step of introducing water into the separation vessel, wherein optional the water provides the cooling means for the step of cooling the reaction mixture.

44. Method of claim 41, wherein the collecting step further comprises transferring the reaction mixture from the separation vessel to a sieve bend unit arranged downstream of the separation vessel for separating the first contaminant from a filtrate stream comprising the alcoholic solvent via an inclined screen.

45. Method of claim 44, wherein the filtrate stream is at least partly recirculated to the separation vessel.

46. Method of claim 41, wherein the reaction mixture is separated by at least one cyclone device arranged downstream of the depolymerization vessel into a low-density stream comprising the first contaminant and a high-density stream comprising the alcoholic solvent on the basis of a density separation.

47. Method of claim 41, wherein the reaction mixture is separated by at least one cyclone device arranged downstream of the separation vessel into a low-density stream comprising the first contaminant and a high-density stream comprising the alcoholic solvent on the basis of a density separation.

48. Method of claim 46, wherein a filter device is arranged for receiving at least one low density stream from said at least one cyclone device to filter the first contaminant from the alcoholic solvent.

49. Method of claim 41, further comprising the step of collecting a second contaminant or a mixture comprising a second contaminant with a bottom outlet, wherein the second contaminant is supplied as part of the feed stream.

50. Method of claim 41, further comprising the step of holding back the top and/or second contaminant with a respective underflow and/or overflow baffle, arranged in the separation vessel.

51. Method of claim 41, wherein the first contaminant comprises or is a polyolefin, optionally further comprising a pigment, preferably a blue pigment.

52. Method of claim 41, wherein the condensation polymer is a polyester, more preferably polyethylene terephthalate.

53. Method of claim 41, wherein the step of bringing the reaction mixture under said reaction conditions comprises the step of heating the reaction mixture to a temperature of between 170° C. and 200° C.

54. Method of claim 53, wherein the separation vessel is cooled to a temperature that is between 10° C. and 110° C. lower than the temperature to which the reaction mixture is heated.

55. Method of claim 41, wherein the step of depolymerizing is by glycolysis, and the alcoholic solvent is an alkanediol, such as ethylene glycol.

56. A reactor system for carrying out the method in accordance with claim 41, the reactor system comprising: at least one depolymerization vessel, configured for depolymerizing a condensation polymer into monomer, dimer, trimer and/or oligomer, which depolymerizing occurs in an alcoholic solvent, wherein said condensation polymer is provided as a feed stream further comprising a first contaminant, a separation stage, downstream of the depolymerization vessel, configured for collecting the first contaminant, said separation stage comprising a separation vessel and optionally a sieve bend unit arranged downstream of the separation vessel for separating the first contaminant from a filtrate stream comprising the alcoholic solvent via an inclined screen, and/or one or more cyclone devices, which separation vessel has an inlet for introducing the reaction mixture originating from the depolymerization vessel into the separation vessel, in which separation vessel said first contaminant is separated from the alcoholic solvent on the basis of a density separation so that first contaminant is arranged on top of the alcoholic solvent, wherein the reactor system further comprises a cooling means for ensuring that the separation vessel is at a lower temperature than the depolymerization vessel such that the first contaminant that is liquid and/or dissolved in the depolymerization vessel at least partially precipitates and the cooled reaction mixture separates into a main phase that comprises the reaction products from the depolymerization and the alcoholic solvent, and a first contaminant phase in the form of solid particles and/or a solid layer.

Description

BRIEF INTRODUCTION OF THE FIGURES

[0128] These and other aspects of the method and the reactor system of the invention will be further elucidated with reference to the figures, which are purely diagrammatical in nature and not drawn to scale, wherein:

[0129] FIG. 1 shows a schematic diagram of embodiment of the reactor system according to the invention;

[0130] FIG. 2 shows a first embodiment of a separation vessel in for the reactor system according to FIG. 1;

[0131] FIG. 3 shows a second embodiment of a separation vessel in for the reactor system according to FIG. 1;

[0132] FIG. 4 shows a third embodiment of a separation vessel in for the reactor system according to FIG. 1;

[0133] FIG. 5 shows a fourth embodiment of a separation vessel in for the reactor system according to FIG. 1;

[0134] FIG. 6 shows a fifth embodiment of a separation vessel in for the reactor system according to FIG. 1;

[0135] FIG. 7 shows an embodiment of a further separation means for the reactor system according to FIG. 1;

[0136] FIG. 8 shows an embodiment of a method according to the invention;

[0137] FIG. 9 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a sieve bend unit;

[0138] FIG. 10 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a number of cyclones;

[0139] FIG. 11 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a sieve bend unit.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0140] In the following, equal or corresponding parts in different figures will be referred to with equal reference numerals. The illustrated embodiments are intended for explanation and illustration and are not intended to limit the scope of the claims.

[0141] In FIG. 1, a schematic diagram of an embodiment of a reactor system 100 according to the invention is disclosed. The reactor system 100 comprises a depolymerization vessel 101 for depolymerizing a condensation polymer in a stream further comprising a contaminant such as a waste stream, and a separation vessel 102, downstream of the depolymerization vessel 101. Optionally, the reactor system further comprises a further separation means 103, upstream of the depolymerization vessel.

[0142] The depolymerization vessel 101 may be any vessel considered suitable for the intended purpose as described in the preceding sections. The separation vessel 102 may be embodied in a number of ways, of which a few examples 200, 300, 400, 500 are disclosed in FIGS. 2 to 6.

[0143] In each of the embodiments, the embodiment 200, 300, 400, 500, 600 comprises a separation vessel 201, 301, 401, 501, 601 with a bottom 202, 302, 402, 502, 602 and side walls 203, 303, 403, 503, 603, and which is in use filled with a mixture 204, 304, 404, 504, 604 up to a level L. In each of the embodiments 200, 300, 400, 500, 600, the separation vessel 201, 301, 401, 501, 600 extends from an inlet 205, 305, 405, 505, 605 downstream of the depolymerization vessel 101 towards a number of outlets, which in these cases comprise a skimmer 206, 406, 506, 606 or an adjustable scum pipe 306, each for collecting a first contaminant 220, 320, 420, 520, 620 in the mixture 204, 304, 404, 504, 604, i.e. a contaminant which has a density lower than the depolymerized condensation polymer in the mixture 204, 304, 404, 504, 604, and which will float on the solvent and a bottom outlet 207, 307, 407, 507, 607, for collecting a second contaminant, i.e. a contaminant which has a density higher than the depolymerized condensation polymer in the mixture 204, 304, 404, 504, 604. In each of the embodiments 200, 300, 400, 500, 600, the separation vessel 201, 301, 401, 501, 601 is further provided with a further inlet 208, 308, 408, 508, 608, which is connected to a water supply, and which is used to introduce water into the separation vessel 201, 301, 401, 501, 601 and thereby cools the mixture 204, 304, 404, 504, 604 to a temperature lower than in the depolymerization vessel 101 such that at least contaminant that is liquid and/or dissolved in the depolymerization vessel 101 forms a separate phase and/or at least partially precipitates in the separation vessel 201, 301, 401, 501, 601. In each of the embodiments 200, 300, 400, 500, 600, the separation vessel 201, 301, 401, 501, 601 is further provided with mixing means for mixing the reaction mixture originating from the depolymerization vessel 101 with the water (or other aqueous solution) originating from the water supply, introduced through further inlet 208, 308, 408, 508, 608. In some embodiments, the mixing means comprise a mixer 209, 309, 409, 609 arranged in the separation vessel 201, 301, 401, 601, downstream of the inlet 205, 305, 405, 605. In another embodiment, the mixing means are arranged in the supply lines 505, 508 to the separation vessel 501, and may be embodied as an inline mixer. In each of the embodiments 200, 300, 400, 500, 600, the separation vessel 201, 301, 401, 501, 601 is further provided with a discharge outlet 210, 310, 410, 510, 610 for discharging the depolymerized condensation polymer, e.g. to a post-processing unit.

[0144] In the separation vessel 201, 301, 401, 501, 601, the contaminant in the mixture 204, 304, 404, 504, 604 that is liquid and/or dissolved in the depolymerization vessel, which is introduced through the inlet 205, 305, 405, 505, 605, originating from the depolymerization vessel 101, and which further comprises an at least partially depolymerized condensation polymer and a solvent, will form a separate phase and/or at least partially precipitates in the separation vessel 201, 301, 401, 501, 601.

[0145] It is important to emphasize that the features which are common to each of the previous embodiments are not necessary in order to obtain the effects of the invention.

[0146] In the embodiments 200, 300, 400, 500 and 600, the separation vessel is provided with a pervious plate 211, 311, 411, 511, 611, arranged in the separation vessel 201, 301, 401, 501, 601, for settling the mixture 204, 304, 404, 504, 604, downstream of and adjacent to the mixing means 209, 309, 409, 505; 508, 609.

[0147] In the embodiments 200, 300 and 400, the discharge outlet 210, 310, 410 is provided with an upright baffle 212, 312, 412 arranged on the bottom 202, 302, 402 of the separation vessel 201, 301, 401 upstream of the discharge outlet 210, 310, 410, in order to prevent any contaminants, precipitating contaminants in particular, from entering the discharge outlet 210, 310, 410.

[0148] In the embodiments 200, 300, 400 and 600, the or part of the mixing means 209, 309, 409, 609 are arranged downstream of and adjacent to the inlet 205, 305, 405, 609 and the further inlet 208, 308, 408, 608, whereas in the embodiment 500, the mixing means 509 are arranged within the supply line 505; 508.

[0149] In the second embodiment 300, the position of the opening 306a of the scum pipe 306 may be changed by rotation of the scum pipe 306 around its axis 306b, in order to accommodate for changes in the fluid level L.

[0150] In the third embodiment 400, a set of packed plates 413 is arranged between the pervious plate 411 and the top outlet 406 (which is moved independent of the position of outlets 407, 410 to a location further downstream of the inlet 405 in order to create space for the set of packed plates 413). These packed plates 413 lift the mixture 404 in the separation vessel 401 and thereby make the contaminants collide onto the plates, thereby increase the ease and speed of separation of the contaminants from the mixture 404.

[0151] In the fourth and fifth embodiments 500, 600, the separation vessels 501, 601 are furthermore provided with an underflow baffle 514, 614 for holding back a contaminant which has a density lower than the depolymerized condensation polymer and an overflow baffle 515, 615, downstream of the underflow baffle 514, 614, for holding back a second contaminant. The baffles 514; 515, 614; 615 are arranged in the first half of the separation vessel 501, 601 in the main direction of flow, i.e. from inlets 505, 605 towards discharge outlets 510; 610, and are arranged adjacent to each other in order to direct the flow of the mixture 504, 604 in a direction substantially perpendicular to the bottom 502, 602 of the separation vessels 501, 601, overlapping in regions 516, 616 defining a channel 517, 617 in between the walls 514; 515, 614; 615, defining a volume within the separation vessel 501, 601 for building a main phase buffer downstream of the baffles 514; 515, 614; 615.

[0152] The fifth embodiment 600 further comprises an optional further mixing means 618 for mixing the mixture 604 downstream of the baffles 614; 615, to reduce the chance that any contaminants which have passed baffles 614; 615 are able to settle.

[0153] A possible embodiment 1100 of a further separation means 103 is disclosed in FIG. 7. This separation means 1100 comprises a separation vessel 1101 with an open top and an outlet 1102, connected to the inlet of depolymerization vessel 101. A stream may be introduced from the top of the separation vessel 1101 and dissolved in an alcoholic solvent, such as ethylene glycol. Floating material 1103 may be removed from the open top, and the bottom fraction 1104, which typically comprises most of the condensation polymer flakes, is transferred to the depolymerization vessel 101 for depolymerization.

[0154] An embodiment 1000 of a method according to the invention, disclosed in FIG. 8, comprises:

[0155] the step 1001 of bringing the stream which constitutes a reaction mixture that further comprises a solvent, selected to be a solvent for the condensation polymer and/or for reaction products obtained from said condensation polymer by depolymerization, and optionally a catalyst under said reaction conditions in a depolymerization vessel 101;

[0156] the step 1002 of depolymerizing at least a portion of said condensation polymer in said reaction mixture into monomer, dimer, trimer and/or oligomer under said reaction conditions;

[0157] the step 1003 of transferring the reaction mixture after the depolymerization of at least a portion of said condensation polymer in said reaction mixture to a separation vessel 201, 301, 401, 501, 601 through the inlet 205, 305, 405, 505, 605 thereof;

[0158] the step 1004 of cooling the reaction mixture by the introduction of water via a further inlet 208, 308, 408, 508, 608 to ensure that the separation vessel 201, 301, 401, 501, 601 is at a lower temperature than the depolymerization vessel 101, and such that the contaminant that is liquid and/or dissolved in the depolymerization vessel 101 forms a separate phase and/or at least partially precipitates;

[0159] the step 1005 of mixing the reaction mixture with the water introduced into the separation vessel with mixing means 209, 309, 409, 609 arranged in the separation vessel 201, 301, 401, 601, downstream of to the inlet 205, 305, 405, 505, 605 and the further inlet 208, 308, 408, 508, 608;

[0160] the step 1006 of collecting a first contaminant with the top outlet based on density separation in the separation vessel, and

[0161] the step 1007 of discharging the depolymerized condensation polymer from the separation vessel 201, 301, 401, 501, 601.

[0162] FIG. 9 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a sieve bend unit. The reactor system comprises the depolymerization vessel 101 for depolymerizing a condensation polymer in a stream further comprising a contaminant such as a waste stream. The reactor system further comprises a separation stage 700, which comprises a separation vessel 701 and a sieve bend unit 720. The separation stage 700 is arranged downstream of the depolymerization vessel 101. A stream of reaction mixture is fed to the separation vessel 701 via inlet 705.

[0163] Optionally, a heat exchanger is arranged between the depolymerization vessel 101 and the separation vessel 701 to cool the reaction mixture such that the first contaminant forms a separate phase having solid first contaminant. In particular, the reaction mixture may separate into a first contaminant phase comprising the first contaminant and a main phase, which predominantly comprises other components, such as the alcoholic solvent. The solid first contaminant has a density lower than the depolymerized condensation polymer and the alcoholic solvent in the reaction mixture.

[0164] Alternatively or additionally, water is introduced into the separation vessel 701 in order to cool the reaction mixture 704 in the separation vessel 701 such that the first contaminant may form a separate phase having solid first contaminant.

[0165] In particular, the reaction mixture separates into a first contaminant phase comprising the first contaminant having a solid state and a main phase, which predominantly comprises other components, such as the alcoholic solvent. The first contaminant in the solid state has a density lower than the depolymerized condensation polymer and the alcoholic solvent in the reaction mixture.

[0166] In particular, the reaction mixture 704 is cooled such that first contaminant at least partially precipitates to form a solid phase in the form of solid particles and/or a solid layer.

[0167] The separation vessel 701 further comprises mixing means 709 to mix the reaction mixture 704 to enhance the cooling of the reaction mixture 704 after adding water via the water inlet 708. The reaction mixture 704 may be present in the separation vessel 701 up to a liquid surface level L.

[0168] The separation vessel 701 further comprises a top outlet 706 and a bottom outlet 710. The top outlet 706 is arranged at a level to carry off the first contaminant phase. The first contaminant phase is transferred to the sieve bend unit 720. The sieve bend unit 720 comprises a screen 722 for separating the first contaminant 724 from a filtrate stream 726 comprising the alcoholic solvent. The filtrate stream 726 may in particularly comprise other constituents than the first contaminant, such as the alcoholic solvent and the depolymerized condensation polymer. In this embodiment, the sieve bend unit is coupled to the top outlet of the separation vessel for receiving the first contaminant phase. The screen is an inclined screen 722. The screen is arranged inclined to allow the residue 724 comprising the solid first contaminant part to slide downwards along the inclined sieve bend 722 towards a storage vessel 730. The storage vessel 730 is arranged for storing the solid first contaminant part, which falls due to gravity into the storage vessel 730 via a chute.

[0169] The filtrate stream 726 may be selectively guided by the valve 728 in a product stream 728A to the post-processing vessel 740 and/or may be at least partly recirculated to the separation vessel 701 in a recirculation stream 728B. Additionally, the bottom outlet 710 is arranged at a level to carry off the main phase 712 towards to the post-processing vessel 740.

[0170] FIG. 10 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a number of cyclones. The reactor system comprises the depolymerization vessel 101. The reactor system further comprises a separation stage 800, which comprises a separation vessel 801 and a number of cyclones 850, 852. The separation stage 800 is arranged downstream of the depolymerization vessel 101. The separation vessel 801 comprises an inlet 805, a top outlet 806, a water inlet 808, a bottom outlet 810, mixing means 809 and holds the reaction mixture 804 in a same way is shown in the embodiment of FIG. 9. Optional a heat exchanger 816 as cooling means is arranged between the depolymerization vessel 101 and the separation vessel 801 to cool the reaction mixture 804 such that the first contaminant may form a separate phase having solid first contaminant.

[0171] The top outlet 806 is arranged at a level to carry off the first contaminant phase to the first cyclone 850. The first contaminant phase is transferred to the first cyclone 850, where it is separated into a low density stream A comprising the first contaminant and a high density stream B comprising the alcoholic solvent on the basis of a density separation. The low density stream A is transferred to a second cyclone 852, where the low density stream A is further separated into a low density stream A comprising the first contaminant and a high density stream B comprising the alcoholic solvent on the basis of a density separation. The high density stream B of the first cyclone 850 and the high density stream B of the second cyclone 852 are transferred to a post-processing vessel 840. The low density stream A of the second cyclone 852 is transferred to a filter device 820, such as a sieve bend unit or any other filter unit, for separating the, solid, first contaminant 824 from the liquid phase of the low density stream A. The liquid phase 826, which comprises the alcoholic solvent and/or the depolymerized condensation polymer components, is transferred to the post-processing vessel 840. The solid first contaminant 824, being the residue of the filter device 820 is collected in a storage vessel 830, e.g. by allowing the solid first contaminant 824 to fall due to gravity into the storage vessel 830 via a chute.

[0172] FIG. 11 shows a further embodiment of the reactor system according to the invention comprising a separation stage including a sieve bend unit. The embodiment is a modified embodiment compared to the embodiment shown in FIG. 9. The separation vessel 901 comprises an inlet 905, a water inlet 908, a bottom outlet 910, mixing means 909 and holds the reaction mixture 904 in a same way is shown in the embodiment of FIG. 9. In the embodiment of FIG. 11, the bottom outlet 910 is arranged to carry off the reaction mixture 904, preferably the whole contents, of the separation vessel 901, including a first contaminant phase and a main phase, to the sieve bend unit 920. The reaction mixture is processed by the sieve bend unit 920 in a same way as sieve bend unit 720, thereby the first contaminant 924 from a filtrate stream 926 comprising the alcoholic solvent. The sieve bend unit 920 is similar to a sieve bend unit 720, i.e. having an inclined screen 922. The screen is arranged inclined to allow the residue 924 comprising the solid first contaminant part to slide downwards along the inclined sieve bend 922 towards a storage vessel 930.

[0173] The filtrate stream 926 may be selectively guided by the valve 928 in a product stream 928A to the post-processing vessel 940 and/or may be at least partly recirculated to the separation vessel 901 in a recirculation stream 928B.

[0174] The embodiment has the advantage that the whole content 904 of the separation vessel 901 is processed by the sieve bend unit 920. The main phase, which may be predominantly disposed below the first contaminant phase due to density separation in the separation vessel 901, will predominantly be processed first by the sieve bend unit 920 prior to the first contaminant phase. This has the advantage of an efficient and fast separation of the filtrate stream 926 from the first contaminant 924.

[0175] In all of the embodiments, the inclined screen 722, 922 preferably has a plurality of slits, each having a slit spanning dimension in the range of 250-500 μm. The longitudinal direction of the slits is arranged substantially perpendicular to a feed direction of the material over the inclined screen.

[0176] In an even further embodiment, the embodiment of FIG. 10 having a separation stage 800, comprising a separation vessel 801 and a number of cyclones 850, 852, is modified by connecting the bottom outlet 810 to the number of cyclones 850, 852 to process the whole contents 804 of the separation vessel 801 by the cyclones 850, 852 and by the filter device 820 in a similar way is described for the embodiment shown in FIG. 10 for the first contaminant phase.