Method and system for recycling polyester-cotton blend textiles using a rotary hydrolysis reactor

Abstract

A method for treating polyester-cotton blend textile waste includes the step of adding the polyester-cotton blend textile waste to a rotating drum of a rotary hydrolysis reactor. Water and a base are added to the rotary hydrolysis reactor and heated. The polyester-cotton blend textile waste is agitated by a plurality of ribs by rotating the inner drum relative to the housing of the rotary hydrolysis reactor to hydrolyze PET into a TPA and ethylene glycol solution so as to obtain regenerated cotton free of PET. The TPA and ethylene glycol solution are separated from the regenerated cotton solids and led to a hydrolysis product recovery container. In the hydrolysis product recovery container, TPA precipitates and is separated from the remaining liquid, and then ethylene glycol is recovered.

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications]

[0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 355,140, filed on June 24, 2022, and is incorporated by reference.

[0002] [Background of the Invention]

[0002] Millions of tons of textile waste are produced every year. Most of this textile waste ultimately ends up in landfills. Most of the textile waste sent to landfills consists of blended fabrics that contain both cotton and synthetic polyester materials. The polyester portion of these blended fabrics can take up to 200 years to decompose in a landfill. Thus, polyester - cotton blend textile waste has a substantially harmful impact on the environment, including greenhouse gas emissions and the leaching of toxins and dyes into the surrounding soil and water.

[0003]

[0003] To reduce this environmental impact, several processes and systems are used to recycle at least a portion of this textile waste. Most of these processes require mechanically shredding or reducing the textile waste so that these fabrics can be reused as rags, stuffing, and insulation. Mechanical reduction produces the most valuable products when the waste stream is pure, such as 100% polyester fabric or 100% cotton fabric. Blended fabrics can also be mechanically reduced, but the products that can use these blended fabrics are of considerably lower value. Essentially, all mechanical reduction of textiles degrades the textiles and results in low - quality yarns when spinning yarns from the shredded textile materials. As a result, the final products that can be economically produced using mechanically shredded textiles are limited.

[0004]

[0004] Other methods for recycling polyester-cotton blend textile waste have been proposed, which involve chemically separating cotton from polyester (polyethylene terephthalate or PET). Some of these methods use a depolymerization reaction to dissolve the PET fibers, thereby separating the PET from the cotton fibers. Known depolymerization processes are not economically viable when scaled up. For example, many of these processes focus on recycling low-value PET, and the separated cotton has degraded to the cellulose level and requires reconstitution. Such processes require additional steps that are too costly for the cotton to be reusable, or else the cotton is destroyed. In some cases, the cotton degrades to a cellulose material that must be reconstituted to produce viscose fibers. Furthermore, recycled PET has limited use in new products and is mainly used in low-value plastic water bottles. Some of these methods produce some of the PET used in the lower-grade fibers used in some textiles. As a result, in these processes, the separated cotton and PET are not used very efficiently.

[0005]

[0005] Known depolymerization processes for separating polyester and cotton also have other drawbacks and are not suitable for using them in large-scale textile recycling. For example, this process, and the equipment used in such processes, require significant amounts of energy, water, and chemicals to ensure an effective depolymerization reaction. Just the requirements for energy, water, and chemicals increase the operating costs of such processes. Furthermore, the equipment used in such processes cannot be easily scaled up for large-scale recycling operations.

[0006]

[0006] In particular, conventional batch reactors that can be used to perform a depolymerization process have a limited input volume with respect to solid textile products. Furthermore, even after manually removing the solid material, such reactors require internal cleaning, and loading and unloading are difficult and time-consuming. As a result, a significant amount of human resources is required to operate a batch reactor for this type of application. Since such reactors need to raise the temperature to effectively separate PET and cotton, a relatively long operating time is also required. Due mainly to the type of agitation and mixing mechanisms used in these machines, which are mainly rotary agitators or paddles, a larger amount of water is also required in this type of reactor as the corresponding chemical substances increase. If the volume of water is not sufficient, the paddles are obstructed by the textile caught on the paddles. For this reason, the costs of water and chemicals, as well as the labor required, increase significantly. Furthermore, batch reactors are difficult to clean and require a significant amount of time and resources to maintain. Due to the significant production downtime, high operating costs, and low production rates associated with such devices, using them in large-scale textile recycling operations becomes uneconomical.

[0007] [Object of the Invention]

[0007] In view of the above, a general object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that can be operated at low cost and scaled up for mass production.

[0008]

[0008] Another object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that require a minimum amount of human resources for operation.

[0009]

[0009] A further object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that produce high-quality end products suitable for general reuse.

[0010]

[0010] A related object of the present invention is to enable the constituent materials used in blended textiles to be used in 100% cotton products, and on the other hand, to make available pure terephthalic acid and ethylene glycol, which can be used to produce cooling liquids, working fluids and paints, especially with respect to polyester or other plastics, or ethylene glycol, and to provide a method and system for recycling polyester-cotton blend textiles.

[0011]

[0011] Another related object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that enables the regeneration of buttons, zippers and other metal parts from clothing and melamine buttons.

[0012]

[0012] A further object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that is energy efficient.

[0013]

[0013] Another object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that uses a minimal amount of water and chemicals.

[0014]

[0014] A related object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that enables the regeneration of the chemicals and clean water used.

[0015]

[0015] A further object of the present invention is to provide a method and system for recycling polyester-cotton blend textiles that can be quickly and easily loaded and unloaded mechanically.

[0016]

[0016] Other objects and advantages of the present invention will become apparent upon reading the following detailed description and referring to the drawings. The specific objects are not intended to limit the present invention.

[0017] [Brief Description of the Multiple Figures of the Drawings]

[0017] Figure 1 is a flow diagram showing exemplary steps of a method for recycling a polyester-cotton blend textile material according to the present disclosure.

[0018]

[0018] Figure 2 is a flow diagram showing additional exemplary steps of a method for recycling a polyester-cotton blend textile material according to the present disclosure.

[0019]

[0019] Figure 3 is a schematic diagram of an exemplary hydrolysis and cotton recovery system of a method for recycling a polyester-cotton blend textile material according to the present disclosure.

[0020]

[0020] Figure 4 is a schematic diagram of an exemplary chemical recovery system of a method for recycling a polyester-cotton blend textile material according to the present disclosure.

[0021]

[0021] Figure 5 is a front view of an exemplary rotary hydrolysis reactor for use in a polyester-cotton blend textile recycling method according to the present disclosure.

[0022]

[0022] Figure 6 is a side view of the rotary hydrolysis reactor of Figure 5.

[0023]

[0023] Figure 7 is a side view of the rotary hydrolysis reactor of Figure 5 showing the reactor in the loading position.

[0024]

[0024] Figure 8 is a side view of the rotary hydrolysis reactor of Figure 5 showing the reactor in the unloading position.

[0025]

[0025] Figure 9 is a schematic diagram of an exemplary slurry heating system for the rotary hydrolysis reactor of Figure 5.

[0026]

[0026] Figure 10 is a cross-sectional view in perspective drawing of the side of the rotary hydrolysis reactor of FIG. 5, showing that the reactor is in the extraction position and the front door is in the open position.

[0027]

[0027] Figure 11 is a cross-sectional view of the side of the rotary hydrolysis reactor of FIG. 5, showing that the reactor is in the extraction position and the front door is in the open position.

[0028]

[0028] Figure 12 is a side view of the inner drum of the rotary hydrolysis reactor of FIG. 5.

[0029]

[0029] Figure 13 is an end view of the inner drum of FIG. 12.

[0030]

[0030] Figure 14 is a cross-sectional view of the inner drum of FIG. 12 along line 14-14, showing one of the ribs on the inner wall of the inner drum.

[0031]

[0031] Figure 15 is a side view of the rotary hydrolysis reactor of FIG. 5, equipped with a hopper assembly instead of the front door and showing the hopper in the low position.

[0032]

[0032] Figure 16 is a side view of the rotary hydrolysis reactor of FIG. 9, showing the front hopper in the high position.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

[0034] [Detailed Description of the Invention]

[0033] Referring to FIGS. 1 - 4 of the drawings, a schematic diagram of an exemplary method and system for a particular use in recycling polyethylene terephthalate (PET)-cotton blend textile materials is provided. Such materials are commonly referred to as polyester-cotton blend textiles and are sometimes referred to herein as blended textiles. These blended textiles may take any form and may have any amount of polyester fibers and cotton fibers. In particular, polyester-cotton blends form the basis of many textile or fabric items, such as bedding, sheets, towels, and clothing. The ratio of polyester to cotton in such materials is not limited, but in many cases is 50:50, 40:60, or 35:65. The polyester component of the blended textile may be a discontinuous element, such as a label or a decorative part as small as an element, or the polyester fibers may be integrated with the cotton fibers throughout the textile. In some aspects, the methods and systems of the present disclosure use the entire blended textile. In other aspects, the textile is initially a fragment. Fragments of the blended textile can be prepared using any suitable cutting method (e.g., cutting, shredding, tearing, mechanical shearing, etc.). Thus, it should be understood that the present invention is not limited to any particular type or form of polyester-cotton blend textile.

[0035]

[0034] Although the present invention is described with respect to blended textiles, it should be understood that the present invention is not limited to using blended textiles in recycling. For example, textiles or other items made entirely of polyester, such as plastic bags, can also be recycled using the methods of the present invention. Thus, the present invention is not limited to the recycling of a particular material.

[0036]

[0035] Figure 1 is a flow diagram showing exemplary steps of a recycling method according to the present disclosure. The steps of Figure 1 can be considered the first stage of a method that is completed using a rotary hydrolysis reactor. The illustrated method uses a hydrolysis reaction to depolymerize PET and separate the PET from the cotton in the blended textile material. It will be appreciated from the following description that not all of the steps included in Figure 1 are necessary to carry out a method for recycling blended textiles, and further that the illustrated method steps may be carried out in a different order. In the first step 10, polyester-cotton blend textile waste is provided to a rotary hydrolysis reactor. Exemplary rotary hydrolysis reactors that provide several important advantages are shown in Figures 5-14 and described in further detail below. The method is described as being carried out on multiple polyester-cotton blend textiles at once, but it should be understood that the method can be carried out on a single polyester-cotton blend textile, although such usage is not very efficient.

[0037]

[0036] When a polyester-cotton blend textile is introduced into a rotary hydrolysis reactor, in steps 12, 14, and 16, water, a strong base, and optionally a catalyst can be added to the polyester-cotton blend textile, respectively, to provide a mixture. The strong base can hydrolyze PET to form monomer components that are terephthalic acid (TPA) and ethylene glycol. The strong base is any suitable base having a pH of 9 or higher (e.g., 9.2 or higher, 9.5 or higher, 9.8 or higher, 10 or higher, 10.2 or higher, 10.5 or higher, 10.8 or higher, 11 or higher, 11.2 or higher, 11.5 or higher, 11.8 or higher, 12 or higher, 12.2 or higher, 12.5 or higher, 12.8 or higher, 13 or higher, 13.2 or higher, 13.5 or higher, or 13.8 or higher). The upper limit of the pH is 14. The pH of the strong base can be adjusted as long as the pH is at least 9 or higher. In some aspects of the method, the strong base is an alkali metal (Group I of the periodic table) hydroxide, an alkaline earth metal (Group II of the periodic table) hydroxide, or ammonium hydroxide. Usually, the strong base is in the form of an aqueous solution, such as a solution of 10% or more (e.g., 10% solution, 15% solution, 25% solution, 40% solution, 50% solution). In one example, the strong base is a 50% aqueous solution of sodium hydroxide or potassium hydroxide.

[0038]

[0037] The amount of the strong base is any effective amount that enables the hydrolysis reaction. Generally, the strong base is used at least 1 part by weight (pbw) (e.g., at least 2 pbw, at least 5 pbw, at least 8 pbw, at least 10 pbw, at least 12 pbw, at least 15 pbw, at least 18 pbw, or at least 20 pbw) of the total liquid composition. Usually, the upper limit of the amount of the strong base is 25 pbw or less (e.g., 20 pbw or less, 18 pbw or less, 15 pbw or less, 10 pbw or less, 8 pbw or less, 5 pbw or less, or 2 pbw or less). Any two of the aforementioned endpoints can be used to define a closed range, or a single endpoint can be used to define an open range. In one example, the amount of the strong base is 5 - 15 pbw, or 8 - 12 pbw, or about 10 pbw.

[0039]

[0038] When a catalyst is used, the catalyst can include a catalyst capable of depolymerizing PET into TPA and ethylene glycol. In some embodiments, the catalyst is a phase transfer catalyst. Suitable examples of phase transfer catalysts include polymeric phase transfer catalysts such as benzyltrimethylammonium chloride (BTMAC), benzyltriethylammonium chloride (BETEC), benzyltributylammonium chloride (BTBAC), tetrabutylammonium hydrogen sulfate, methyltributylammonium chloride (MTBAC), tetraethylammonium bromide (TEAB), tetrabutylammonium bromide (TBAB), or combinations thereof. In a preferred embodiment, the catalyst includes benzyltributylammonium chloride (BTBAC).

[0040]

[0039] This method is designed to operate on a large scale, including industrial scales on the order of liters (e.g., 300 L (80 gallons) scale) and kilograms (e.g., 90 kg (200 pounds) scale). Considering such end - uses, the ratio of liquid in the container to the textile after all liquids are added is about 1 - 5 L:0.25 - 2 kg (e.g., 1.9 L:0.5 kg or 0.5 gallons:1.0 pound).

[0041]

[0040] When water, a strong base, and an optional catalyst are added to a polyester - cotton blend textile in a rotary hydrolysis reactor, in steps 18 and 20, the resulting mixture can be heated and stirred in the rotary hydrolysis reactor. The mixture should be heated and stirred sufficiently to provide a solution / slurry containing water, terephthalic acid (TPA), ethylene glycol, and other chemicals that can be separated from the raw cotton, which is solid and contains no PET or other chemical components as - is.

[0042]

[0041] The heating step may be carried out at any temperature suitable for depolymerizing polyester terephthalate into TPA and ethylene glycol. The temperature can be varied based on the reaction conditions, such as the specific strong base and its concentration used, and / or the catalyst if used. For example, the temperature is usually about 50 °C or higher (e.g., 55 °C or higher, 60 °C or higher, 65 °C or higher, 70 °C or higher, 75 °C or higher, 80 °C or higher, 85 °C or higher, 90 °C or higher, 95 °C or higher, 100 °C or higher). In some embodiments, the temperature can be about 90 °C to about 95 °C. The upper limit of the heating temperature is not particularly limited, but generally, it is about 200 °C or lower (e.g., 190 °C or lower, 180 °C or lower, 170 °C or lower, 160 °C or lower, 150 °C or lower, 140 °C or lower, 130 °C or lower, 120 °C or lower, 110 °C or lower, 100 °C or lower, 95 °C or lower, or 90 °C or lower). Any two of the aforementioned endpoints can be used to define a closed range, or a single endpoint can be used to define an open range. In one example, the heating step is carried out at 60 °C or higher, 70 °C or higher, 80 °C or higher, 60 - 110 °C, 70 - 100 °C, 80 - 95 °C, or about 93 °C.

[0043]

[0042] The duration of heating and stirring of the mixture of blended textile, water, strong base, and catalyst is not particularly limited. Generally, the hydrolysis reaction is at least 20 minutes (e.g., at least 30 minutes, at least 40 minutes, at least 60 minutes, at least 90 minutes, at least 120 minutes, at least 150 minutes, at least 180 minutes, or at least 210 minutes). Usually, the hydrolysis reaction is completed within 240 minutes (e.g., within 210 minutes, within 180 minutes, within 150 minutes, within 120 minutes, within 90 minutes, within 60 minutes, within 40 minutes, or within 30 minutes). Any two of the aforementioned endpoints can be used to define a closed range, or a single endpoint can be used to define an open range. In one example, the reaction time is about 30 - 60 minutes, about 40 - 50 minutes, or about 40 minutes.

[0044]

[0043] When the hydrolysis reaction is complete, the solution containing TPA and ethylene glycol and the solid regenerated cotton can be separated in step 22. Advantageously, the cotton / solution separation step can be carried out using centrifugation performed using a rotating hydrolysis reactor. Alternatively, the solution can be separated from the solid regenerated cotton by any suitable solid-liquid separation method. For example, the separating step can be filtration sieving, separating funnel, pumping, centrifugation, or a combination of these steps.

[0045]

[0044] The solid regenerated cotton can be washed (e.g., with water) as in step 24 and / or dried as in step 26. In some embodiments, the solid regenerated cotton is washed with water to remove residual base. The resulting regenerated cotton can be reused in textile applications, such as to form a polyester-cotton blend fabric. Optionally, the regenerated cotton can be spun back into yarn. Alternatively, the regenerated cotton can be used to form regenerated cellulose-based fibers such as viscose or lyocell.

[0046] Optionally, the isolated TPA and polyethylene glycol solution can be recovered and further processed to produce additional recycled products as shown in the flowchart of Figure 2. The steps of Figure 2 can be considered the second stage of the textile recycling method and can be carried out using conventional reactors currently used to process liquids / chemicals, as well as conventional condensers and dryers already used in the chemical industry. This second stage may include step 28 of adding an acid to the isolated solution to precipitate the TPA. The acid can be any suitable acid capable of precipitating the TPA from the solution. Generally, the acid has a pH of about 5 or less (e.g., 4.8 or less, 4.5 or less, 4.2 or less, 4 or less, 3.8 or less, 3.5 or less, 3.2 or less, 3 or less, 2.8 or less, 2.5 or less, or 2.2 or less). The lower limit of the pH is 1. The pH of the acid can be adjusted as long as the pH is 5 or less. In one example, the acid has a pH in the range of 2 - 5 or 2 - 3. The acid can be, for example, an inorganic acid or an organic acid. In some embodiments, the acid is a mineral acid such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrobromic acid, perchloric acid, hydroiodic acid, or a combination thereof. In a preferred embodiment, the mineral acid is hydrochloric acid, sulfuric acid, nitric acid, or a combination thereof. In a particularly preferred embodiment, the mineral acid is sulfuric acid.

[0047]

[0046] After the TPA has precipitated, the precipitated TPA can be separated in step 30. The precipitated TPA can be washed (e.g., with water) as in step 32 and / or dried as in step 34. In some embodiments, the precipitated TPA is washed with water to remove residual acid. Optionally, the isolated TPA can be further purified. For example, the particle size of the isolated TPA can vary based on the conditions used to isolate and / or purify the TPA. The isolated TPA can be reused, optionally, for polymerization with one or more diols to produce a new polyester.

[0048]

[0047] Optionally, ethylene glycol can be isolated from the remaining liquid in step 36. Ethylene glycol can be isolated using any suitable method. Typically, ethylene glycol can be isolated by first distilling water from the mixture and subsequently distilling the ethylene glycol. The ethylene glycol can be further purified and then reused in additional processes such as polyester formation. In some embodiments, the water isolated by distillation is recycled for reuse in the depolymerization process. When water and ethylene glycol are distilled, some of the water-soluble components of the original hydrolysis reaction may remain. Such water-soluble components can include, for example, dyes and crosslinking agents.

[0049]

[0048] Referring to FIG. 3, a hydrolysis and cotton recovery system 40 capable of performing the method of FIG. 1 is shown. As discussed above, the system of FIG. 3 includes a rotary hydrolysis reactor 42. To provide water for the hydrolysis reaction, the rotary hydrolysis reactor 42 is connected to a water supply 44 via a suitable supply line 46. The water supply 44 can be a water source that stores water at the pressure desired for the hydrolysis process. Alternatively, as shown in FIG. 3, a water pump 48 may be provided between the water supply 44 and the rotary hydrolysis reactor 42. A water flow meter 50 may be provided in the water supply line 46 downstream of the water supply 44 to monitor the presence of water and / or to monitor the amount of water added to the rotary hydrolysis reactor 42.

[0050]

[0049] To introduce the chemicals necessary for the hydrolysis reaction, the rotary hydrolysis reactor 42 may be in fluid communication with a strong base supply 52 and a liquid catalyst supply 54. In this case, the strong base supply 52 is connected to the rotary hydrolysis reactor 42 by a base supply line 56, and the catalyst supply 54 is connected to the rotary hydrolysis reactor 42 by a catalyst supply line 58. Alternatively, one or both of the chemicals may be added manually to the rotary hydrolysis reactor 42. In particular, depending on the scale of the recycling operation and the amount of catalyst used, manual addition of the catalyst may be preferred. In the illustrated embodiment, a base dosing pump 60 and a base flow meter 62 are arranged in the base supply line 56 to enable monitoring and measurement of the amount of base added to the rotary hydrolysis reactor 42. A catalyst dosing pump 64 and a catalyst flow meter 66 are similarly provided in the catalyst supply line 58 to monitor and measure the addition of the catalyst to the reactor 42.

[0051]

[0050] The supply of the polyester-cotton blend textile waste 68 is also further schematically shown in FIG. 3. This supply can take any desired form, such as a transport container or other storage container. The line 70 connecting the textile waste supply 68 to the rotary hydrolysis reactor 42 represents any suitable method for transporting or delivering the textile waste to the reactor. In one embodiment, an overhead sling, which may be part of a sling conveyor system, is used to transport the textile waste to the rotary hydrolysis reactor 42. Other types of conveyors or wheeled cart systems can also be used. However, the overhead sling system can be particularly advantageous when recycling large quantities of polyester-cotton blend textile waste.

[0052]

[0051] After the hydrolysis reaction is complete, the solid recycled cotton can be conveyed from the rotary hydrolysis reactor 42 to the dryer 71. On the other hand, the isolated TPA and ethylene glycol solution are sent to the hydrolysis product recovery system via line 128 (see Figure 4). In one embodiment, the dryer 71 can be a conventional gas-fueled dryer such as those used in commercial laundries. The line 73 from the rotary hydrolysis reactor 42 to the dryer 71 in Figure 3 is intended to represent any suitable method for conveying the recycled cotton to the dryer 71. According to one embodiment, a conveyor system is used to convey the recycled cotton to the dryer 71. Other types of conveying systems such as wheeled carts or hoppers can also be used.

[0053]

[0052] Exemplary embodiments of the rotary hydrolysis reactor 42 for use in a method of recycling blended textiles are shown in FIGS. 5-14. In the illustrated embodiment, the hydrolysis reactor 42 includes a reactor housing 72 disposed in this case on a support frame 74 (see, for example, FIG. 6). The illustrated support frame 74 includes a base 76 configured to engage the ground and a pair of laterally spaced front legs 78 extending upwardly from the base 76 to an upper arm assembly 80. A pair of cross braces 82 are provided to further provide structural support to the support frame 74, each extending between one lower end of each of the front legs 80 and the upper arm assembly 80. It should be understood that the illustrated support frame 74 provides certain advantages with respect to the loading and unloading of the hydrolysis reactor as compared to conventional reactors, as will be described in more detail below, but support frames having other structures can also be used.

[0054]

[0053] To agitate the textile material, water and reaction chemicals during the hydrolysis reaction stage, and to extract liquid from the cotton recovered during the cotton recovery stage, the reactor housing 72 defines an internal chamber 84, as shown in FIGS. 10 and 11. Inside the internal chamber 84, the inner drum 86 is supported for rotation relative to the reactor housing 72. The internal chamber 84 of the reactor housing 72 provides a space for receiving and containing water and chemicals associated with the depolymerization reaction, while the inner drum 86 receives and contains textile waste materials. A plurality of holes 90 are drilled in the side wall 88 of the inner drum 86 so that the water and chemicals in the internal chamber 84 can pass in and out of the inner drum 86. As best shown in FIGS. 12-14, the interior of the rotating inner drum 86 can also include a plurality of circumferentially spaced ribs 92 disposed inside the side wall 88 to facilitate agitation of the textile waste materials, water and chemicals. In the illustrated embodiment, the inner drum 86 is equipped with four ribs 92 equally spaced around the inner drum 86 (see FIG. 13). As shown in FIG. 14, each rib 92 can be composed of opposing side surfaces 93 angled to converge with each other as they extend inward from the side wall 88 of the inner drum 86. In the illustrated embodiment, each side surface 93 terminates in a flat end face 95. Other ribs 92 having other structures can also be used. The inner drum 86 may have any desired volume. For example, in one embodiment, the inner drum 86 and the reactor housing 72 are configured to have a volume of up to approximately 1000 pounds of textile waste. The reactor housing 72 and the inner drum 86 may be made of any suitable corrosion-resistant material, such as stainless steel for example.

[0055]

[0054] The use of the rotating inner drum 86 with ribs 92 provides several advantages compared to conventional hydrolysis reactors. For example, the mechanical agitation created by the rotating inner drum 86 and ribs 92 enables an effective polymerization reaction using less water and reaction chemicals. This allows the process to be operated in a much more efficient, energy-efficient and cost-effective manner with much smaller quantities. In some embodiments, the disclosed rotary hydrolysis reactor enables the use of up to 12 times less water than conventional reactors. The disclosed rotary hydrolysis reactor can also make individual pieces of textile waste relatively larger in size than conventional reactors, which often require shredding of textile waste before adding it to the reactor to achieve sufficient agitation. The inner drum 86 with the arrangement of ribs 92 also contributes to the recovery of high-quality cotton fibers that can be used in a variety of valuable products. Further, the mechanical agitation provided by the rotating inner drum 86 and ribs 92 not only promotes the depolymerization reaction, but also facilitates the mechanical removal of non-polyester components of textile waste such as zippers, buttons, labels, and / or decorative elements. The arrangement of the inner drum 86 and ribs 92 is also much easier to clean than agitators used in conventional hydrolysis reactors, substantially reducing manufacturing downtime and maintenance costs.

[0056]

[0055] To drive the rotation of the inner drum 86 relative to the reactor housing 72, the illustrated reactor 42 includes a rotary drive assembly 94 that includes an electric motor 96 effectively connected to the drive shaft 98 of the inner drum 86 in this case (see, for example, FIGS. 6, 10, and 11). The arrangement of the drive shaft 98 and the inner drum 86 can also be seen in FIG. 12. The rotary drive assembly 94 can be configured to rotate the inner drum 86 relative to the reactor housing 72 at various speeds depending on the stage of the hydrolysis process. For example, during the depolymerization reaction, the inner drum 86 can rotate relative to the reactor housing 72 in a manner that optimizes the agitation of the textile waste material, water, and reaction chemicals. Then, during the separation step, the inner drum 86 can rotate at a higher speed to generate sufficient centrifugal force to discharge the liquid TPA and ethylene glycol solution from the solid recycled cotton. This centrifugally separated liquid exits the inner drum 86 through the perforations in the sidewall 88 of the inner drum 86. The separated liquid is then collected in the reactor housing 72 and removed from the rotary hydrolysis reactor 42 via an internal drain pump provided in the reactor. According to one embodiment, the inner drum 86 and the drive assembly 94 are configured such that the inner drum 86 can rotate at a speed of up to about 500 rpm.

[0057]

[0056] To maintain water and chemicals at a desired temperature for the hydrolysis reaction, the rotary hydrolysis reactor 42 may be equipped with a slurry heating system 170. An exemplary embodiment of a suitable slurry heating system 170 is shown in FIG. 9. The slurry heating system 170 of FIG. 9 uses a pump 172 to draw water and chemical slurry from the bottom portion 174 of the rotary hydrolysis reactor 42 through an outlet line 176. The outlet line 176 directs the slurry to an inlet end 178 of a heat exchanger 180 that is operated to heat the slurry to the desired temperature for the hydrolysis reaction. In this case, the heat exchanger 180 is heated via a steam generator 182. Steam from the steam generator 182 is directed through a steam supply line 184 to the heat exchanger 180 and can be controlled by a steam control valve 186. When heated, the heated slurry exits the heat exchanger 180 at its outlet end 188 and is returned to the upper portion 190 of the rotary hydrolysis reactor 42 via a slurry inlet line 192. The cooled condensate exits the heat exchanger 180 via a condensate outlet 194. During operation, the slurry heating system 170 withdraws the cooled slurry from the bottom portion 174 of the reactor 42, heats the slurry to the desired temperature, and then reintroduces the hot slurry to the upper portion 190 of the reactor 42. The slurry heating system 170 may be controlled to maintain the slurry in the reactor at the desired temperature. Although the arrangement of a steam heat exchanger is shown, it should be understood that heating can be accomplished using devices other than a steam heat exchanger.

[0058]

[0057] To enable the polyester-cotton blend textile waste to be introduced into the inner drum 86, the rotary hydrolysis reactor 42 shown in FIGS. 5 to 8, 10, and 11 includes a movable outer door 108. More specifically, the outer door 108 is rotatably connected to the reactor housing 72 so as to move between an open position and a closed position with respect to the door opening 110 in the wall of the reactor housing 72. In the open position, the door opening 110 in the reactor housing 72 is accessible for the introduction of the textile waste material into the inner drum 86 and the removal of the textile waste material from the inner drum 86 (see, for example, FIG. 10). In the closed position (see, for example, FIG. 5), the outer door 108 closes the door opening 110 of the reactor housing 72, and as a result, the depolymerization hydrolysis reaction can be carried out safely and effectively. In this case, as shown in FIG. 5, the outer door 108 is hinged on the side, and as a result, the outer door 108 pivots horizontally between the open position and the closed position, but other door pivoting arrangements may be used. A seal assembly may be provided around one or both of the outer door 108 and the door opening 110 to ensure a tight seal with the door opening 110 of the reactor housing 72. The seal assembly may be designed in particular to be used with the chemicals used in the depolymerization process.

[0059]

[0058] To make it easier to load the textile waste into the inner drum 86, the reactor support frame 74 may be configured such that the front end of the reactor housing 72 can be tilted upward from the normal horizontal operating position (e.g., as shown in FIG. 6) to the loading position shown in FIG. 7. This upwardly tilted loading position is particularly useful when loading into the reactor 42 via an overhead sling. At the end of the hydrolysis process, to make it easier to remove the regenerated solid cotton from the inner drum 86, the reactor support frame 74 may be configured such that the front end of the reactor housing 72 can be tilted downward from the normal horizontal operating position to the removal position shown in FIG. 8. This downwardly tilted removal position is particularly useful when the regenerated cotton is removed, for example, onto a belt conveyor for conveyance to a dryer 71. In the illustrated embodiment shown in FIGS. 6 - 8, the connection 112 of the front leg 78 of the support frame 74 to the base 76 of the support frame allows movement between the loading position, the operating position, and the removal position. To allow the front leg 78 to pivot relative to the base 76, at least one tilting actuator 114 may be provided between the reactor housing 72 and the base 76 of the support frame 74. The tilting actuator 114 in this case is configured such that the extension and contraction of the actuator pivots the leg 78 relative to the base 76, thereby moving the reactor housing 72 between various positions.

[0060] As an alternative to the hinged outer door, in order to facilitate the introduction of textile waste from the overhead sling into the inner drum 86 in particular, the rotary hydrolysis reactor 42 may be equipped with a hopper assembly 116 as shown in FIGS. 15 and 16. More specifically, the hopper assembly 116 may be attached to the front side of the reactor housing 72 in an overlapping relationship with the front opening 110 of the reactor housing 72. In this case, the hopper assembly 116 includes a chute 118 that opens upward, and a hopper door 120 that is movable between an open position and a closed position is provided at the upper end of the chute 118. In the lowered closed position shown in FIG. 16, the hopper door 120 closes the upper end of the chute 118. This closed position of the chute door 120 is used both at the removal position of the reactor 42 (shown in FIG. 16) and at the operating position of the reactor 42, and at the operating position, the hopper door 120 seals the rotary hydrolysis reactor 42 so that the depolymerization process can be carried out. In the raised open position of the hopper door as shown in FIG. 15, the upper open end of the chute 118 allows the introduction of textile material into the chute 118 without hindrance, and guides the textile material through the door opening of the reactor housing 72 into the inner drum 86. A door actuating device may be provided to pivot the hopper door between the open position and the closed position.

[0061]

[0060] To enable the recovered cotton to be removed from the inner drum, the hopper assembly 116 can be supported on the reactor housing 72 for movement between a lowered position and a raised position. In the lowered position, the chute 118 is disposed adjacent to the front face of the reactor housing 72. In this position, when the reactor housing 72 is in the loading position (see FIG. 15), the chute 118 can be used for loading the rotary hydrolysis reactor. The lowered position of the chute is the position used during operation of the reactor. In the raised position, as shown in FIG. 16, the hopper chute 118 is pivoted upwardly with respect to the reactor housing 42 and away from the opening of the reactor housing. This raised position enables the removal of the rotary hydrolysis reactor 42 without interference from the hopper assembly 116 after the hydrolysis cycle. The movement of the hopper assembly 116 between the raised and lowered positions may be driven by one or more hopper tilt actuators 122 (see FIG. 16).

[0062]

[0061] Since the reactor can be moved between the loading position and the removal position, the rotary hydrolysis reactor can be interlocked with the bulk handling system both during loading and removal, whereby the reactor can efficiently process a very large amount of textile waste, particularly as compared to conventional hydrolysis reactors. Further, this arrangement enables a large amount of material to be loaded and removed quickly and easily with minimal effort. In certain applications, the hopper assembly can further facilitate loading into the reactor. Thus, the rotary reactor housing provides a hydrolysis process that can be easily and inexpensively scaled up for recycling a large amount of textile waste.

[0063] Referring to FIG. 4, a system for recovering TPA and ethylene glycol from a liquid solution separated from the solid regenerated cotton after the hydrolysis reaction by the method of FIG. 2 is shown. In the illustrated embodiment, the recovery system 124 includes a recovery vessel 126 configured to receive the liquid hydrolyzate from the rotary hydrolysis reactor 42. The liquid hydrolyzate may be directed from the rotary hydrolysis reactor 42 via line 128 shown in FIG. 4. To maintain a well-mixed solution during processing, the recovery vessel 126 may be equipped with a suitable agitator 130. The recovery vessel 126 may also be provided with a heating system 132, which can be used when it is desired to heat the contents of the recovery vessel. A temperature sensor 134 may also be provided to monitor the temperature of the contents of the recovery vessel 126.

[0064]

[0063] An acid supply 136 also communicates with the recovery vessel 126 via line 138. An acid dosing pump 140 may be provided in line 138 to control the delivery of acid to the recovery vessel 126. Further, a pH meter 142 is provided in the recovery vessel 126 to monitor the pH of the solution in the recovery vessel 126 when acid is added, and thereby detect when the pH of the solution in the recovery vessel 126 has dropped to the point at which TPA precipitates from the hydrolyzate solution.

[0065]

[0064] Once the pH of the recovery vessel 126 reaches the desired level, the hydrolyzate in the recovery vessel 126 can be directed through lines 144 and the recovery vessel pump 146, etc., to pass through the TPA recovery filter 148. The TPA recovery filter 148 can be configured to capture TPA precipitates when the hydrolyzate passes through the filter. After passing through the filter, the remaining liquid can be returned to the recovery vessel 126 via the recirculation line 150 for recirculation. The hydrolyzate can circulate through the recovery vessel 126 and the TPA recovery filter 148 until substantially all of the TPA precipitates are removed. In the illustrated embodiment, the TPA recovery filter 148 may communicate with the water supply 152 via the water supply line 153 to wash the filter cake in the TPA recovery filter 148 once the separation of the precipitated TPA is complete. To facilitate this washing step, the TPA recovery filter 148 may have an inlet valve and an outlet valve, and the valves are arranged to isolate the TPA recovery filter 148 from the rest of the system when the valves are closed while water is being directed to the filter. The washed TPA precipitates can then be conveyed to the dryer 154. This conveyance is schematically referenced by line 156 in FIG. 4 and is meant to refer to any method of conveyance to the dryer 154, including manual conveyance of the TPA precipitates.

[0066]

[0065] Once the TPA precipitate is separated, the recovery vessel 126 may begin heating the remaining contents in preparation for distilling water from the ethylene glycol and then, subsequently, distilling ethylene glycol from the residual salts and residual compounds. The agitator 130 within the recovery vessel may continue to operate during the distillation process. Once the water in the hydrolyzate within the recovery vessel 126 has boiled off and evaporated, the temperature within the recovery vessel may be raised to the boiling point of ethylene glycol to separate the ethylene glycol from the salts and other impurities. The ethylene glycol vapor is then directed to the glycol recovery condenser 158. The glycol recovery condenser 158 can be cooled via any suitable means, such as recirculation of a coolant. Once condensed, the ethylene glycol can be directed from the condenser 158 to a suitable storage container 160.

[0067]

[0066] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference in their entirety to the same extent as if each reference had been individually and specifically indicated to be incorporated by reference and were set forth in full herein.

[0068] In the context of describing the present invention (particularly in the context of the following claims), when the terms "a", "an", "the", and "at least one", as well as similar indicative terms, are used, unless otherwise specifically stated herein or clearly contradicted by the context, they are to be construed as covering both the singular and the plural. When a list of one or more items follows the use of the term "at least one" (e.g., "at least one of A and B"), unless otherwise specifically stated herein or clearly contradicted by the context, it is to be construed to mean one item selected from the listed items (A or B), or any combination of two or more of the listed items (A and B). The terms "comprising", "having", "including", and "containing" are to be construed as open-ended terms (i.e., meaning "including but not limited to") unless otherwise specifically stated. The recitation of a range of values herein is, unless otherwise specifically stated herein, merely intended to serve as a shorthand way of referring individually to each separate value that falls within the range, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise specifically stated herein or clearly contradicted by the context. The use of any example, or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the invention and does not limit the scope of the invention unless otherwise specifically stated. No representation in this specification should be construed as implying that any non-claimed element is essential for the practice of the invention.

[0069]

[0068] Preferred embodiments of the invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of the preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors expect that such variations will be adopted by those skilled in the art as appropriate, and the inventors intend the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the appended claims as permitted by applicable law. Moreover, any combination of the above-described items in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein or clearly contradicted by context.

Claims

1. A method for treating polyester-cotton blend textile waste, comprising: adding the polyester-cotton blend textile waste to a rotating drum of a rotary hydrolysis reactor, the rotating drum having a plurality of ribs disposed on an inner surface thereof; adding water and a base to the rotary hydrolysis reactor; heating the water and the base added to the rotary hydrolysis reactor; rotating an inner drum with respect to a housing of the rotary hydrolysis reactor to stir the polyester-cotton blend textile waste by the plurality of ribs, hydrolyzing PET into TPA and ethylene glycol solution so as to obtain regenerated cotton solids free of PET; separating the TPA and ethylene glycol solution from the regenerated cotton solids and guiding the separated TPA and ethylene glycol solution to a hydrolysis product recovery container; adding an acid to the separated TPA and ethylene glycol solution in the hydrolysis product recovery container to precipitate TPA; separating the precipitated TPA from the remaining liquid in the hydrolysis product recovery container; isolating ethylene glycol from the remaining liquid in the hydrolysis product recovery container. A method comprising the above steps.

2. The method according to claim 1, wherein the base has a pH of 9 or higher.

3. The method according to claim 2, wherein the base comprises an aqueous solution of 10% or more.

4. The method according to claim 1, further comprising adding a catalyst to the rotary hydrolysis reactor.

5. The method according to claim 4, wherein the catalyst is a phase transfer catalyst.

6. The method according to claim 1, wherein after the water and the base are added, a ratio of liquid to textile waste in the base is 1-5 L of liquid: 0.25-2 kg of textile waste.

7. The method according to claim 1, wherein the water and the base in the rotary hydrolysis reactor are heated to about 50 °C or higher.

8. The method according to claim 1, wherein the water and the base in the rotary hydrolysis reactor are heated to about 90 °C to about 95 °C.

9. The method according to claim 1, wherein the hydrolysis reaction is completed within 60 minutes.

10. The method according to claim 1, further comprising washing the regenerated cotton solids.

11. The method according to claim 1, wherein the acid has a pH of about 5 or less.

12. The method according to claim 1, further comprising the step of washing the precipitated TPA.

13. The method according to claim 1, wherein during the step of separating TPA and ethylene glycol from the solid recycled cotton, the rotary drum rotates at a relatively faster speed than during the stirring step.

14. A rotary hydrolysis reactor for treating polyester-cotton blend textile waste, a reactor housing defining an internal chamber for receiving water and a chemical slurry related to the hydrolysis reaction, an inner drum supported within the internal chamber so as to rotate with respect to the reactor housing, the inner drum including a side wall perforated with a plurality of holes, for receiving polyester-cotton blend textile waste, a plurality of spaced ribs supported on an inner surface of the side wall of the inner drum for agitating the polyester-cotton blend textile waste when the inner drum rotates with respect to the reactor housing, a slurry heating system including a slurry outlet line communicating with the internal chamber of the reactor housing for drawing the water and the chemical slurry from a bottom portion of the reactor housing, the slurry outlet line leading the water and the chemical slurry to a heat exchanger, the heat exchanger being operable to heat the water and the chemical slurry to a desired temperature, the slurry heating system further including a slurry inlet line communicating with the reactor housing and configured to return and direct the heated water and the chemical slurry from the heat exchanger back into the internal chamber of the reactor housing, A rotary hydrolysis reactor comprising.

15. The rotary hydrolysis reactor according to claim 14, further comprising a rotary drive assembly for rotating the inner drum at a variable speed with respect to the reactor housing.

16. The rotary hydrolysis reactor according to claim 14, wherein the reactor housing is supported on a support frame configured to tilt the reactor housing between a loading position, an operating position, and an unloading position.

17. Further comprising a hopper assembly disposed on the front side of the reactor housing so as to overlap the front opening of the reactor housing, the hopper assembly including a chute having a hopper door at the upper end, the rotary hydrolysis reactor according to claim 14.

18. A system for treating polyester-cotton blend textile waste, comprising: a rotary hydrolysis reactor, a reactor housing defining an internal chamber for receiving water and a chemical slurry related to the hydrolysis reaction, an inner drum supported within the internal chamber so as to rotate relative to the reactor housing, the inner drum including a side wall perforated with a plurality of holes, for receiving polyester-cotton blend textile waste, a plurality of spaced ribs supported on the inner surface of the side wall of the inner drum for agitating the polyester-cotton blend textile waste when the inner drum rotates relative to the reactor housing a rotary hydrolysis reactor, and a hydrolysis product recovery system configured to receive a liquid hydrolysis product from the rotary hydrolysis reactor, a recovery container configured to receive the liquid hydrolysis product from the rotary hydrolysis reactor, the recovery system including a stirrer and a heating system, an acid supply system for introducing an acid into the recovery container, a TPA recovery filter configured to capture TPA precipitate when the liquid hydrolysis product from the recovery container is led through the TPA recovery filter, a glycol recovery condenser communicating with the recovery container for receiving ethylene glycol vapor from the recovery container and condensing it into a liquid a hydrolysis product recovery system a system comprising.

19. The slurry heating system includes a slurry outlet line that communicates with the internal chamber of the reactor housing to draw water and chemical slurry from the bottom portion of the reactor housing, the slurry outlet line being operable to direct the water and chemical slurry to a heat exchanger, the heat exchanger being operable to heat the water and chemical slurry to a desired temperature, and the slurry heating system further including a slurry inlet line that communicates with the reactor housing and is configured to return the heated water and chemical slurry from the heat exchanger back to the internal chamber of the reactor housing. The system of claim 18.

20. The system of claim 19, further comprising a recirculation line that directs the remaining liquid portion back to the collection vessel after passing through the TPA recovery filter.

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