A method and control system and apparatus for recycling old clothing and textiles

Abstract

A method, control system, and apparatus for recycling old clothes and textiles, the method comprising the following steps: (1) raw material pretreatment; (2) detecting and diverting the composition of the mixed fiber waste through an identification system: batches of mixed fiber waste with a natural fiber content ≥ the diversion boundary value by mass fraction enter the natural fiber biological treatment line and then enter the high-pressure reaction equipment; otherwise, they directly enter the high-pressure reaction equipment; (3) the high-pressure reaction equipment is heated in stages according to the melting range of different synthetic fibers, and the melt is discharged in each stage. The method for recycling old clothes and textiles of the present invention, after obtaining mixed fiber waste through pretreatment and detecting the content of natural fibers in each batch, automatically diverts it into different treatment paths according to the diversion boundary value, and finally, in the high-pressure reaction equipment, the different synthetic fibers are heated in stages and the melt is discharged in stages to complete the efficient regeneration and conversion treatment.

Description

Technical Field

[0001] This invention relates to the field of waste textile resource utilization technology, specifically to a wet-heat segmented melting separation and recycling method for multi-component blended textile waste (including waste clothing and industrial textile waste), and its intelligent control system and device. Background Technology

[0002] With the rapid development of the global textile industry and the upgrading of consumption, the replacement cycle of textiles is constantly shortening, leading to a surge in the amount of waste textiles generated year by year. This includes not only scraps and substandard fabrics generated during textile production, but also discarded clothing from the consumer end (such as outdated clothes, damaged clothes, old shoes and bags, and other textile products). In China alone, as the world's largest producer and consumer of textiles, the scale of waste textiles generated annually exceeds 20 million tons, and this figure continues to grow at an average annual rate of 5%-8%.

[0003] However, the current recycling system for waste textiles still has significant shortcomings, with the core bottleneck being the extremely low rate of high-value utilization. Data shows that more than 70% of waste textiles globally have not yet achieved high-value recycling at the fiber level, and are only disposed of through extensive methods such as incineration and landfill, or are limited to low-value-added recycling applications (such as making recycled wadding, industrial rags, and sound insulation filling materials), unable to be reused in high-value-added fields such as textile fabrics, high-end nonwoven fabrics, and functional fiber products, resulting in huge resource waste.

[0004] Further analysis reveals that the complexity of the composition of waste textiles (especially discarded clothing) is a key factor restricting their high-value recycling. These waste textiles are mostly multi-component mixed fiber structures, typically containing blends or interweavings of natural fibers (such as cotton, wool, silk, and linen) and synthetic polymer fibers (such as polyester PET, nylon PA, acrylic PAN, and spandex PU). For example, common casual wear is often a cotton / polyester blend (the blend ratio is usually 60 / 40, 50 / 50, etc.), wool coats often contain wool / nylon blends, and sportswear often contains a cotton / spandex / polyester composite structure. Because there are significant differences in the chemical structure and physical properties (such as melting point, solvent resistance, mechanical strength, and thermal stability) between natural fibers and synthetic polymer fibers, and even between synthetic polymer fibers themselves, existing traditional recycling technologies struggle to achieve efficient and low-cost separation of the two.

[0005] Specifically, existing recycling technologies have the following main drawbacks:

[0006] Limitations of physical recycling technology: Traditional physical recycling methods such as mechanical crushing, opening, and carding can only break down waste textiles into short fiber mixtures, and cannot achieve precise separation of different fiber components. These mixed recycled fibers have low purity, short length, and severely deteriorated mechanical properties (such as breaking strength and elongation), and can only be used in low-strength, low-value-added applications, failing to meet the production requirements of high-value-added textile products.

[0007] Chemical recycling technologies suffer from poor selectivity: While existing chemical recycling technologies (such as acid hydrolysis, alkaline hydrolysis, organic solvent dissolution, and thermal pyrolysis) can degrade or dissolve single fiber components (e.g., using strong acids to degrade natural cotton fibers or using specific solvents to dissolve polyester fibers), they suffer from poor selectivity when dealing with multi-component mixed systems, ultimately failing to achieve effective separation of the two components. Furthermore, chemical recycling processes also suffer from high reagent consumption, high recycling costs, and the potential for secondary pollution (such as waste liquid and waste gas), hindering industrial-scale promotion.

[0008] The aforementioned technical deficiencies directly lead to a serious waste of waste textile resources and exacerbate the environmental burden. Synthetic polymer fibers (such as polyester and nylon) have degradation cycles of decades to centuries in the natural environment. Landfill disposal would occupy land resources for a long time and potentially pollute soil and groundwater through leaching; incineration would release toxic and harmful gases such as dioxins and volatile organic compounds (VOCs), exacerbating air pollution. Furthermore, the mixed nature of natural and synthetic fibers further increases the difficulty of subsequent disposal of waste textiles, creating a vicious cycle of "resource waste - environmental pollution," severely hindering the green and sustainable development of the textile industry.

[0009] Therefore, developing a technical solution that can efficiently separate different fiber components from multi-component mixed waste clothing and textiles, while taking into account both recycling added value and environmental friendliness, has become an urgent technical problem to be solved in the field of waste textile recycling. Summary of the Invention

[0010] To address the problem of low added value and serious pollution caused by the inefficient separation and recycling of old clothes and textiles in existing technologies, this invention provides a method and intelligent control system for recycling old clothes and textiles that is adapted to blended structures, can automatically identify components, can avoid carbonization of natural fibers, and can achieve segmented melting and separation in humid, hot, and low-oxygen environments.

[0011] The technical solution of the present invention is as follows:

[0012] A method for recycling old clothes and textiles, characterized by comprising the following steps:

[0013] (1) Raw material pretreatment: including crushing and removing impurities from the recycled materials to obtain mixed fiber waste;

[0014] (2) The components of the mixed fiber waste are detected and diverted by an identification system: the batches of mixed fiber waste with a natural fiber content ≥ the diversion threshold value by mass fraction enter the natural fiber biological treatment line and are treated by enzymatic hydrolysis. The resulting residual mixture then enters the high-pressure reaction equipment; the batches of mixed fiber waste with a natural fiber content < the diversion threshold value directly enter the high-pressure reaction equipment; the diversion threshold value is the proportion of natural fiber content that ensures the natural fiber will not burn or carbonize when the mixed fiber waste directly enters the high-pressure reaction equipment.

[0015] (3) The high-pressure reaction equipment is heated in stages according to the melting range of different synthetic fibers, and the melt is discharged in each stage.

[0016] Preferably, the diversion boundary value is the critical proportion under conditions of humid and hot saturated steam environment and O2 < 3% where natural fibers do not undergo carbonization. More preferably, the diversion boundary value is 60%.

[0017] In a further preferred embodiment, in step (2),

[0018] The heating process is carried out in the following three stages:

[0019] First stage: 120–150℃, 0.20–0.50MPa, heat preservation for 20–40min, mainly to discharge PP and / or PE melt;

[0020] Second stage: 180–220℃, 1.0–2.3MPa, hold for 20–40min, mainly to discharge nylon 6 and / or nylon 12 melt;

[0021] The third stage: 230–260℃, 2.9–4.7MPa, heat treatment for 20–45 minutes, mainly to discharge PET and / or Nylon 66 melt.

[0022] In a further preferred embodiment, the heating rate of each section is ≤3℃ / min, and the melt is continuously discharged through the bottom guide valve. The natural fiber residue remains in a solid phase under humid heat and is subsequently discharged for further processing.

[0023] Preferably, the identification system is a near-infrared (NIR) or mid-infrared spectroscopy system, and is automatically shunted by an AI system; the high-pressure reaction equipment is equipped with an AI-adaptive temperature control module, which automatically adjusts the heating curve and stop time according to the spectral identification data.

[0024] Preferably, the high-temperature reaction equipment is selected from at least one of the following: a wet-heat rotary reaction drum, a steam reflux tower reactor, a high-pressure circulating reactor with hot water circulation and / or steam reflux mode, and a saturated steam fluidized separator.

[0025] Preferably, the steam is condensed, recovered, and recycled.

[0026] Preferably, in step (1), after removing impurities, the mixed fiber waste is further crushed to 2–5 cm.

[0027] Preferably, in step (2), the enzymatic hydrolysis uses a composite enzyme system for different components:

[0028] (1) For mixed fiber waste with cellulose as the main component, use 15–30 FPU / g of acidic cellulase and 10–20 IU / g of β-glucosidase, and react for 12–24 hours at 45–55°C and pH 4.8–5.2.

[0029] (2) For mixed fiber waste with hemicellulose and hemp fiber as the main components, use a hemicellulase and pectinase system to react for 8–16 hours at 50–60°C and pH 5.0–5.5.

[0030] (3) For mixed fiber waste including residual lignin or coating, it is removed by a mixed system of pectinase, laccase and / or protease.

[0031] In a further preferred embodiment, the mixed fiber waste is pretreated with 2–5 wt% NaOH for 0.5–1 h before enzymatic hydrolysis.

[0032] Preferably, step (1) further includes an ultrasonic module and / or a microwave module and / or a solvent-assisted module.

[0033] More preferably, the ultrasonic module, microwave module, and solvent-assisted module are arranged in a modular structure, and the intelligent system automatically selects whether to activate or bypass them based on the raw material detection results.

[0034] More preferably, the ultrasonic module employs a 20–28kHz high-frequency transducer array with a cavitation energy density of 10–30W / L.

[0035] More preferably, when the mixed fiber waste includes a coating or adhesive structure, it is treated with NMP / DMF swelling agent for 10–20 min under ultrasonic cavitation conditions at 40–60°C and 20–28 kHz.

[0036] More preferably, the microwave module is arranged outside the mixed fiber waste flow channel, with a frequency of 2.45 GHz and a power density of 0.5–1 kW / L.

[0037] More preferably, when the mixed fiber waste is composite fiber, it is heated by 2.45 GHz microwave at a heating rate of 5–10°C / min and held for 10–15 min.

[0038] More preferably, the solvent-assisted module includes a corrosion-resistant stirred tank equipped with a solvent recovery and condensation tower.

[0039] More preferably, the solvent-assisted module includes three sub-stages: low-temperature polar co-solvent immersion, swelling and stripping, and recycling and regeneration.

[0040] More preferably, when the mixed fiber waste includes a refractory coating, a catalytic swelling system of 0.3–0.8 wt% ethylene glycol + zinc acetate is used, and the reaction is carried out at 190–210°C for 15 min.

[0041] Preferably, the remaining natural fiber residue in the high-pressure reaction equipment in step (3) is converted into regenerated cellulose or bio-based materials through enzymatic hydrolysis.

[0042] Preferably, the high-temperature reaction equipment is equipped with an outer layer microwave module.

[0043] The control system for the aforementioned method of recycling old clothes and textiles is characterized by being a closed-loop system of identification-control-optimization, the system comprising three stages:

[0044] (1) T0 stage: Pre-separation identification before material loading - component detection and process strategy generation,

[0045] Near-infrared (NIR) and mid-infrared (MIR) spectral sensor arrays and a high-speed camera recognition system are set in the feeding section to perform rapid spectral scanning on the mixed fiber waste.

[0046] The AI ​​system identifies the proportion of major components based on spectral characteristic peaks and automatically generates corresponding heating curve templates, including the temperature zones for segmented heating, heating rate, and holding time.

[0047] (2) T1 stage: segmented heating with real-time monitoring – online feedback control,

[0048] A spectral probe and a temperature and pressure sensor are installed in the high-pressure reaction equipment to monitor the state changes of the material during the staged heating process;

[0049] The system analyzes the changes in the spectral absorption peaks on the material surface in real time, determines the melting start point and completion time, and automatically fine-tunes the heating rate, holding time and the timing of the flow guide valve opening.

[0050] The AI ​​system writes real-time feedback results into the controller to achieve segmented condition adaptive optimization and prevent local overheating or incomplete melting.

[0051] (3) T2 stage: Post-separation feedback - data write-back optimization,

[0052] An online spectrometer and image recognition module are installed at the outlet of the separated products to detect the purity of each polymer melt segment;

[0053] If the purity is insufficient, the system will automatically write back the data and adjust the heating curve and stop time for the next batch.

[0054] Preferably, in stage (1), the system is equipped with a dual-layer security lock of spectral recognition + AI judgment: if any natural fiber spectral signal is detected, including C-O and O-H characteristic peaks, the dry heating command is prohibited;

[0055] Preferably, if the steam pressure or humidity is lower than the safety threshold in stage (2), the AI ​​system will automatically stop heating and issue an alarm to prevent localized dry heat.

[0056] A wet-heat segmented melting reaction apparatus for a method of recycling old clothes and textiles, as described above, includes a pretreatment modular device, an online detection unit and control module, a wet-heat sealed high-pressure reaction equipment, a segmented heating system, a steam input and condensation recovery system, and a bottom guide discharge assembly.

[0057] Preferably, the pretreatment modular device includes a crushing and impurity removal module, a particle size control module, an ultrasonic module, a microwave module and / or a solvent-assisted module, as well as a conveying and linkage interface module and a modular control unit.

[0058] Preferably, the humid heat sealed high-pressure reaction equipment includes an outer layer microwave module and a stirring structure.

[0059] Preferably, the device includes a three-stage closed-loop control system, comprising a component identification unit, a parameter generation unit, a segmented temperature rise monitoring unit, a control execution unit, a result write-back unit, and a double-layer safety lock structure.

[0060] The technical effects of this invention are as follows:

[0061] This invention discloses a method for recycling used clothing and textiles. After pretreatment to obtain mixed fiber waste and detecting the natural fiber content of each batch, the waste is automatically diverted into different processing paths based on a diversion boundary value. Finally, in a high-pressure reaction device, the different melting temperatures of various synthetic fibers are utilized to heat the material in stages and remove the melt separately, completing a highly efficient regeneration and conversion process. The specific basis for setting the diversion boundary point is as follows:

[0062] Experiments and material analysis revealed that when the natural fiber content exceeds a certain proportion, the mixed fiber waste system becomes dominated by natural fibers. The cellulose exhibits high crystallinity and strong hygroscopicity. Directly introducing it into a high-pressure thermal reaction would lead to agglomeration, coking, uneven heat transfer, and excessive energy consumption. Carbonization or combustion would occur within the 200–300℃ range (i.e., the segmented heating range). Therefore, it is necessary to first undergo wet-heat enzymatic hydrolysis to loosen and partially degrade the fibers before introducing them into the high-pressure reaction equipment. When the natural fiber content is below a certain proportion, the mixed fiber waste contains a higher proportion of synthetic fibers. These components can be directly melted and separated in segments during the high-pressure reaction, and the natural fiber residue can be discharged, ensuring that carbonization or combustion does not occur, eliminating the need for a pre-existing enzymatic hydrolysis step.

[0063] Testing showed that a 60% flow separation threshold can prevent carbonization or combustion. This means that batches with a natural fiber content ≥60% enter the "natural fiber biochemical treatment line," undergoing wet-heat enzymatic hydrolysis / thermal treatment before entering a high-pressure reaction device for staged heating. Batches with a natural fiber content below 60% directly enter the high-pressure reaction device for staged heating.

[0064] The two routes thus formed are operational boundaries determined based on the differences in the physicochemical properties of the raw materials, with the aim of reducing energy consumption and improving reaction uniformity and product quality.

[0065] In the high-pressure reaction equipment, this invention utilizes the difference in melting temperature of different synthetic fibers to perform staged heating within the high-pressure reaction equipment:

[0066] -PP / PE, melt at 120–150℃;

[0067] -Nylon 6 / 12, melts at 180–220℃;

[0068] -PET / Nylon 66, melt at 230–260℃;

[0069] The above segmentation design can basically cover most synthetic fibers used in clothing and textiles. Maintaining efficient heat transfer under the closed conditions of the high-temperature reaction equipment and segmented flow discharge achieves efficient separation.

[0070] For low-natural-fiber mixed fiber waste that directly enters the high-pressure circulating reactor, a humid and low-oxygen environment can be used to avoid dry-heat combustion of the material. Natural fiber can also basically maintain a solid phase under humid and hot conditions and will not be carbonized. It is then transferred to the (alkali pretreatment +) enzymatic hydrolysis module to be converted into regenerated cellulose.

[0071] The core principle is that when natural fibers (cotton, linen, silk, wool, etc.) are detected in the mixture, regardless of the proportion, the system should be operated in a humid, saturated steam environment. The level of natural fiber content does not affect the safety strategy; all raw materials containing natural fibers are operated under humid, low-oxygen conditions (O2 ≤ 3%). However, batches with a natural fiber content ≥ 60% must undergo enzymatic hydrolysis and loosening treatment under humid conditions before entering the high-pressure segmented melting equipment.

[0072] The high-temperature reaction equipment can be a high-pressure circulating reactor, a wet-heat rotary reaction drum, a steam reflux tower, or a saturated steam fluidized separator, etc., equipped with hot water circulation and / or steam reflux mode (preferably steam reflux), which are devices with wet-heat conditions. The heat transfer medium is saturated steam or high-temperature water, and the oxygen concentration in the reactor is controlled to ≤3% to prevent the natural fibers from being carbonized or burned by dry heat.

[0073] The aforementioned damp heat protection and diversion mechanism can avoid the risk of combustion, ensure the safe and stable operation of the synthetic fiber melting section, and realize the "damp heat low oxygen segmented heating and melting separation of multi-component blended fiber waste".

[0074] To address situations where complex components affect separation efficiency or where certain specific fibers have high content, such as spandex, PU coating, and composite adhesive layers, an intelligent control step of "spectral / infrared recognition - AI-controlled optimal heating curve" is added to the separation process. In addition to the high-pressure circulating reactor, a "modular combination scheme" (ultrasonic unit, solvent-assisted unit, enzymatic hydrolysis unit) is added, which can be flexibly combined according to the raw material composition to improve fiber separation efficiency and adaptability.

[0075] In this invention, the technical objective of pretreatment is to achieve uniform size of the recycled materials and improve subsequent impurity removal and reaction efficiency. When the raw material is a large piece of fabric or tangled cloth, it needs to be crushed or pulverized; however, if the raw material itself is already in small pieces, fibrous, or strip-like structures, only impurity removal and sorting are required, without further pulverization. Therefore, the pulverization step in pretreatment is optional and depends on the shape and size of the recycled materials.

[0076] Pretreatment may further include an ultrasonic module, a microwave module, and a solvent-assisted module.

[0077] The purpose of pulverization is to increase the specific surface area and reaction contact interface, so as to facilitate the uniformity of subsequent ultrasonic cavitation and microwave heating. Therefore, when using multiple pretreatment methods, the pulverization step is preferably set before the ultrasonic and solvent-assisted modules to improve the dispersibility of raw materials and the uniformity of subsequent reactions. For example, the sequence is: crushing - pulverization - ultrasonic / microwave treatment - solvent-assisted reaction.

[0078] For recycled fabrics with coatings, adhesive layers, or composite adhesive layers, an ultrasonic module can be added during pretreatment. Ultrasonic cavitation promotes surface peeling. Adding polar solvents such as NMP (N-methylpyrrolidone) or DMF (N,N-dimethylformamide) at this stage can swell the adhesive layer and accelerate peeling. When the system is aqueous, NMP / DMF can act as synergistic solvents to improve interfacial desorption efficiency. Combined with subsequent solvent-assisted modules, this can further enhance the removal efficiency of coatings and adhesive layers.

[0079] The ultrasonic module is not limited to a traditional water tank-type device for cleaning, but refers to a processing unit capable of generating ultrasonic energy in a liquid medium (including aqueous solutions or non-aqueous solvent systems). The liquid medium can be water, a polar organic solvent or a mixture thereof, or a low-liquid phase or mist medium, used to achieve ultrasonic cavitation, stripping, or diffusion treatment on the surface of the recovered material.

[0080] The microwave module serves as a pretreatment heating unit before the high-temperature reaction, used to preheat, soften, or promote swelling and diffusion of the mixed fiber waste before it enters the high-pressure circulating reactor, thereby improving the efficiency of the subsequent reaction.

[0081] The solvent-assisted module includes a corrosion-resistant stirred tank. The solvent-assisted module comprises three sub-stages: "low-temperature immersion, swelling and peeling, and recycling and regeneration." Adding a low-temperature solvent layer or introducing a polar co-solvent is the initial pretreatment step of this module, used to reduce the material's interfacial energy, promote swelling, and improve the interfacial diffusion rate and desorption efficiency.

[0082] For polymer adhesives such as polyurethane, epoxy, and PVAc, the chemical dissolution or softening temperature is generally in the range of 190–210°C. Below 190°C, swelling is insufficient; above 210°C, the substrate is prone to degradation. Therefore, the system automatically adjusts the temperature within the 190–210°C range after determining the coating type through an intelligent detection module.

[0083] The outer jacket of the high-temperature reaction equipment can also be further equipped with an outer jacket microwave module. Its function is to serve as a rapid heating and temperature equalization device for the high-temperature reaction equipment. Its main role is to provide heat energy for the reaction stage, accelerate the heating rate, and maintain a uniform temperature field in the reactor. Due to the molecular polarization and rapid volume heating characteristics of microwave heating, it can also simultaneously promote the softening, melting, or loosening of the material in the initial stage of the reaction.

[0084] The present invention further provides a control system that adopts a three-stage AI closed-loop control system of "T0 pre-separation identification → T1 real-time process control → T2 result feedback optimization".

[0085] Pre-separation identification (T0) determines the process path and initial parameters, enabling advance decisions on the process route (whether to proceed with segmented heating, whether to activate ultrasonic / enzymatic hydrolysis), effectively reducing energy consumption and carbonization risks. Real-time monitoring during separation (T1) provides real-time identification and feedback for fine-tuning, ensuring precise and controllable melting in each segment. Post-separation feedback (T2) is used for model self-learning, continuously providing learning data for the AI ​​model to achieve "self-optimization" operation. These three stages are interconnected, forming a dynamic temperature curve control based on spectral data, enabling automatic matching of the optimal heating strategy to different batches of mixed fiber waste. Through this three-stage intelligent control of "pre-separation identification + segmented process monitoring + result feedback correction," the system achieves truly adaptive heating and safe, efficient separation. Attached Figure Description

[0086] Figure 1 This is a flowchart illustrating a method according to an embodiment of the present invention. Detailed Implementation

[0087] To better understand the present invention, the invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0088] Example 1

[0089] In this embodiment, the used clothing to be recycled is blended fabric clothing, such as... Figure 1 As shown, it includes the following steps:

[0090] Step (1): Raw material pretreatment. This includes:

[0091] ① After being crushed manually or mechanically to remove impurities such as buttons and zippers, the mixed fiber waste is pulverized to 2-5cm.

[0092] ② Ultrasonic module cleaning, frequency 25kHz, temperature 50°C, time 15min, the solvent for ultrasonic cleaning is 2wt% Na2CO3 aqueous solution;

[0093] ③ Microwave softening: 2.45 GHz, heating at 8°C / min, holding for 12 min, to loosen the interface of the blended layer;

[0094] Step (2): The mixed fiber composition is detected by a near-infrared spectroscopy (NIR) identification system. It contains approximately 45% polyester, 20% nylon, 25% cotton and linen, and a small amount of other synthetic fiber mixed components. It is then directly introduced into a high-pressure circulating reactor.

[0095] Step (3):

[0096] The high-pressure circulating reactor is heated in stages:

[0097] First stage: 120–150°C, 0.30–0.40MPa, most PP / PE melts and is discharged;

[0098] Second stage: 180–220°C, 1.3–1.8MPa, most of PA6 / 12 melts and is discharged;

[0099] Third stage: 230–260°C, 3.5–4.2MPa, most of the PET melts and is discharged;

[0100] Low oxygen levels (O2 < 3%) between each stage, heating rate ≤ 3°C / min, holding at that temperature for approximately 30 minutes, maintaining saturated steam conditions under humid heat. Specific parameters are as follows:

[0101]

[0102] Step (4): Residue enzymatic hydrolysis: After alkalizing the remaining natural fiber with 3wt% NaOH solution at 50°C for 1h, enzymatic hydrolysis (using 25FPU / g Cellulase and 15IU / g β-glucosidase, reacting at 50°C and pH 5.0 for 18h) converts it into glucose;

[0103] Step (5): Condensation and waste heat recovery: Steam condensation recovery rate is 92%, and energy consumption is reduced by about 28%.

[0104] Result detection:

[0105] (1) Separation rate detection method:

[0106] ① Sample preparation: Dry the mixed textile waste to constant weight and record the initial mass m0;

[0107] ② Separation process: AI separation → ionization separation → steam separation

[0108] ③ Collect plastic, fiber, and residue, and dry and weigh them separately (mp, mf, mr).

[0109] ④ Calculate the separation rate = (mp + mf) / m0 × 100%.

[0110] (2) PET recycling degree testing method:

[0111] ①Prepare raw PET and recycled PET samples

[0112] ② Conduct melt flow rate (MFR) test (190°C, 2.16kg)

[0113] ③ Perform FTIR infrared spectroscopy (structural peak comparison)

[0114] ④ Calculate the difference in regeneration degree to determine the degree of regeneration.

[0115] (3) Method for detecting the saccharification rate of cotton and linen natural fiber residue, used to evaluate the saccharification capacity of cellulose structure after steam or thermal pretreatment:

[0116] ①Dry the fiber residue to constant weight and record the mass m0.

[0117] ② Carry out enzymatic hydrolysis reaction (50℃×48h, 15FPU / g solid).

[0118] ③ The amount of reducing sugar in the saccharified solution was determined by the DNS method (ms (540nm)).

[0119] ④ Saccharification rate = ms / (m0×1.11)×100%

[0120] After testing, the separation rate was >96%, the purity of recycled PET was >98%, and the saccharification rate of natural fiber residues such as cotton and linen was 85%.

[0121] Example 2

[0122] This embodiment uses blended shirts as the recycling target.

[0123] Step (1): Raw material pretreatment. This includes:

[0124] After being crushed manually or mechanically to remove impurities such as buttons and zippers, the recycled materials are pulverized into mixed fiber waste with a particle size of about 2 to 5 cm.

[0125] Step (2): The mixed fiber waste is detected and analyzed by the NIR near-infrared identification module. Its reflectance spectrum characteristics indicate that the sample is mainly composed of natural cellulose fibers (cotton and linen), with a total cotton and linen content of over 70%, and is identified as "high natural fiber waste". Based on the identification results, the control system automatically diverts this type of high natural fiber waste from the mixing line and introduces it into a dedicated natural fiber recycling line.

[0126] After entering the natural fiber recycling line, it undergoes enzymatic hydrolysis:

[0127] Pre-soaking with 3wt% NaOH at 50℃, followed by adding cellulase (25FPU / g) and β-glucosidase (15IU / g) for 18h to degrade natural fiber into soluble oligosaccharides or glucose solution.

[0128] The remaining residue is then transported to a high-pressure circulating reactor.

[0129] Step (3):

[0130] The high-pressure circulating reactor is heated in stages, with the same parameter settings as in Example 1. Step (4): Condensation and waste heat recovery: Steam condensation recovery rate is 92%, and energy consumption is reduced by about 28%.

[0131] After testing, the separation rate was >94%, the purity of recycled PET was >97%, and the saccharification rate of natural fiber residue was 83%.

[0132] The sugar solution obtained by enzymatic hydrolysis can be concentrated and used for fermentation to produce ethanol, lactic acid or bio-based plastic monomers; the thermal decellulose products can be neutralized and separated and reused as raw materials for regenerated cellulose.

[0133] In this embodiment, when a high natural fiber content is detected, the system can intelligently select the "natural fiber recycling path" and automatically match the corresponding enzymatic hydrolysis process to achieve precise diversion and efficient resource utilization. This embodiment can intuitively demonstrate how the control system triggers different recycling modules (enzymatic hydrolysis first) after identifying high natural fiber textile waste, highlighting the "adaptive control logic based on material recognition" of this invention.

[0134] In other embodiments, the parameter ranges in step (3) (such as reaction temperature, pressure, heating rate, oxygen content, steam environment and energy recovery rate, etc.) can be adjusted according to the specific implementation.

[0135] The process parameters of this invention (including temperature range, pressure range, heating rate, oxygen content control, and energy recovery ratio, etc.) are all reasonable working ranges determined through experiments. However, in embodiments of different production scenarios, appropriate adjustments can be made according to specific conditions such as raw material composition, equipment capacity, material loading, reaction scale, and energy supply method.

[0136] The 60% threshold value described in this invention is the critical proportion of natural fibers that do not carbonize under humid heat steam (O2≤3%) conditions, as determined experimentally. Its adjustability is based on the following scientific basis and technical logic:

[0137] 1. Differences in the thermophysical properties of different raw material systems.

[0138] Different polymer materials (such as PP / PE, PA6 / 12, PET) in waste have different thermal stability, softening temperature and decomposition activation energy, and their optimal reaction temperature range is adjusted with the change of ratio.

[0139] For example, when the polyamide content in the mixed waste is high, the upper limit of the middle temperature zone (180-220°C) can be slightly increased to 230°C to ensure full melting; while if the polyolefin content is high, the lower limit of the first temperature zone (120-150°C) is sufficient to complete the fluidization process.

[0140] 2. Differences in equipment size and heat exchange conditions.

[0141] Different specifications of reactors or continuous reactors have differences in heat transfer coefficients and internal flow field distribution. Therefore, the heating rate, holding time and pressure control need to be fine-tuned according to the characteristics of the equipment.

[0142] In large-scale equipment, to prevent local overheating, it is recommended to control the heating rate at 2-3℃ / min; while in experimental equipment, where heat transfer is fast, the rate can be relaxed to 5℃ / min without affecting the main reaction effect.

[0143] 3. Oxygen content and atmosphere control can be flexibly adjusted according to safety and reaction requirements.

[0144] This invention recommends that the process be carried out under low oxygen (O2 < 3%) conditions to prevent oxidation side reactions; however, in certain special processes (such as those that require promoting surface oxidation to improve polymer surface activity), a short-term rise in O2 to 5% may be permitted.

[0145] The type of atmosphere can also be selected according to the equipment design, such as inert gas (nitrogen, carbon dioxide) or high-pressure steam system, without changing the essence of the process.

[0146] 4. Energy recovery and thermal efficiency parameters vary depending on the moisture content of the raw materials, calorific value, and the efficiency of the equipment recovery system.

[0147] The typical range for waste heat recovery rate is 20-30%. If a two-stage heat exchanger or a multi-stage condensing system is used, the energy recovery rate can be increased to 35%-40%. For small-scale equipment or batch operations, the actual recovery rate is about 15%-20%, which is a reasonable fluctuation.

[0148] 5. Pressure and pressure drop parameters can be adjusted according to the system reaction characteristics.

[0149] In the process of moist heat softening and volatilization / desorption migration, appropriate pressurization can improve heat transfer efficiency and control the product escape rate.

[0150] For example, the pressure limit in the aforementioned embodiment can ensure stable gas phase flow and energy transfer. However, for small experimental reactors, the pressure can be finely adjusted within ±10% or 0.05 MPa (whichever is greater) of the set value boundary in each section to ensure gas phase stability and safety boundaries without affecting the repeatability of the results.

[0151] 6. Overall Adjustment Principle

[0152] This invention emphasizes "parameter range + adjustable logic," rather than a fixed, unique condition. Specific numerical adjustments in different embodiments should follow the following constraint logic:

[0153] Each temperature adjustment range is ≤ ±10%; each pressure adjustment range is ≤ ±0.5MPa; the heating rate adjustment range is ≤ ±2℃ / min.

[0154] The purpose of the adjustment is to maintain the system operating under conditions of stable melting, controlled volatilization, and energy balance.

[0155] Based on the above principles, the parameters mentioned above (including reaction temperature, pressure, heating rate, oxygen content, and energy recovery rate, etc.) are preferred values ​​in the embodiments of this invention. In practical applications, they can be automatically or manually adjusted within the range specified in this invention based on the proportion of waste components, equipment heat exchange performance, and feedback signals from the control system, to ensure the stability of the reaction system, optimal energy consumption, and best separation effect. Adjustments to these parameters do not affect the essential content of the process principle and control logic of this invention.

[0156] Based on the above principles, the following preferred embodiments are further provided:

[0157] In a preferred embodiment, the high-pressure reaction equipment is equipped with an AI-adaptive temperature control module that automatically adjusts the heating curve and stop time based on spectral recognition data; and automatically diverts the flow through the AI ​​system.

[0158] In some preferred embodiments, the high-temperature reaction equipment may also use a wet-heat rotary reaction drum, a steam reflux tower reactor, a high-pressure circulating reactor, or a saturated steam fluidized bed separator.

[0159] In a preferred embodiment, in step (2), the enzymatic hydrolysis employs a complex enzyme system for different components identified by the AI ​​system:

[0160] (1) For the cellulose main component, use 15–30 FPU / g acidic cellulase + 10–20 IU / g β-glucosidase, and react for 12–24 hours at 45–55°C and pH 4.8–5.2.

[0161] (2) For hemicellulose and hemp fiber components, a hemicellulase + pectinase system was used to react for 8–16 hours at 50–60°C and pH 5.0–5.5;

[0162] (3) Residual lignin or coating parts are removed by a mixed system of pectinase, laccase and / or protease.

[0163] In some preferred embodiments, step (1) further includes an ultrasonic module, a microwave module, and a solvent-assisted module. The ultrasonic unit, microwave unit, and solvent-assisted unit can be arranged in a modular structure, and the intelligent system can automatically select whether to activate or bypass them based on the raw material detection results.

[0164] The ultrasonic module employs a 20–28 kHz high-frequency transducer array with a cavitation energy density of 10–30 W / L. When the mixed fiber waste includes coatings or adhesive structures, it is treated with NMP / DMF swelling agent for 10–20 min under ultrasonic cavitation conditions at 40–60°C and 20–28 kHz.

[0165] The microwave module is positioned outside the mixed fiber waste flow channel, with a frequency of 2.45 GHz and a power density of 0.5–1 kW / L. When the mixed fiber waste includes a composite fiber layer, it is heated using 2.45 GHz microwaves at a heating rate of 5–10°C / min and held for 10–15 min.

[0166] The solvent-assisted module includes a corrosion-resistant stirred tank, equipped with a solvent recovery and condensation tower, and three sub-stages: low-temperature polar co-solvent immersion, swelling and peeling, and recovery and regeneration.

[0167] In a further preferred embodiment including a solvent-assisted module, when the coating is difficult to dissolve, 0.3–0.8 wt% of ethylene glycol + zinc acetate is used as a catalytic swelling system, and the reaction is carried out at 190–210°C for 15 min.

[0168] In a preferred embodiment, the high-temperature reaction apparatus is provided with an outer layer microwave module.

[0169] The above embodiments have been verified to achieve at least the separation and recovery effect of Embodiment 1 or 2, and have further improved in terms of separation sufficiency, reaction uniformity and stability.

[0170] Example 3

[0171] This embodiment is an example of a control system employing the above method, which is a closed-loop system of identification-control-optimization, comprising three stages:

[0172] (1) T0 stage: Pre-separation identification before material loading - component detection and process strategy generation,

[0173] Near-infrared (NIR) and mid-infrared (MIR) spectral sensor arrays and a high-speed camera recognition system are installed in the feeding section to perform rapid spectral scanning on the mixed old clothes.

[0174] The AI ​​system identifies the proportion of major components based on spectral characteristic peaks and automatically generates corresponding heating curve templates, including the temperature zones for segmented heating, heating rate, and holding time.

[0175] Feedback control: The identification and path selection results are automatically uploaded to the PLC system, and the current processing batch status is displayed in real time and recorded in the control database.

[0176] (2) T1 stage: segmented heating with real-time monitoring – online feedback control,

[0177] A spectral probe and a temperature and pressure sensor are installed in the high-pressure reaction equipment to monitor the state changes of the material during the staged heating process;

[0178] The system analyzes the changes in the spectral absorption peaks on the material surface in real time, determines the melting start point and completion time, and automatically fine-tunes the heating rate, holding time and the timing of the flow guide valve opening.

[0179] The AI ​​system writes real-time feedback results into the controller to achieve segmented condition adaptive optimization and prevent local overheating or incomplete melting.

[0180] (3) T2 stage: Post-separation feedback - data write-back optimization,

[0181] An online spectrometer and image recognition module are installed at the outlet of the separated products to detect the purity of each polymer melt segment;

[0182] If the purity is insufficient, the system will automatically write back the data and adjust the heating curve and stop time for the next batch.

[0183] In a preferred embodiment, the system is equipped with a dual-layer security lock of spectral recognition + AI judgment: if any natural fiber spectral signal is detected, including C–O and O–H characteristic peaks, the dry heating command is prohibited;

[0184] In a preferred embodiment, if the steam pressure or humidity is lower than the safety threshold in step (2), the AI ​​system automatically stops heating and alarms to prevent localized dry heat.

[0185] Example 4

[0186] This embodiment is a wet-heat segmented melting reaction device applied to the aforementioned embodiment, including a pretreatment modular device applied in step (1), an online detection unit and control module applied in step (2), and a wet-heat closed high-pressure reaction device, a segmented heating system, a steam input and condensation recovery system, and a bottom guide discharge assembly applied in step (3).

[0187] The pretreatment modular device includes a crushing and impurity removal module, a particle size control module, an ultrasonic module, a microwave module and / or a solvent-assisted module, as well as a conveying and linkage interface module and a modular control unit.

[0188] The humid heat sealed high-pressure reaction equipment includes an outer layer microwave module and a stirring structure.

[0189] It also includes a three-stage closed-loop control system device, which includes a component identification unit, a parameter generation unit, a segmented temperature rise monitoring unit, a control execution unit, a result write-back unit, and a double-layer safety lock structure.

[0190] Economic benefit calculation and prospects of the above embodiments:

[0191] Steam consumption per ton of clothing: approximately 0.4–0.6 tons (reduced to 0.25 tons after closed-loop circulation).

[0192] Power consumption: 20–35 kWh / ton.

[0193] Energy consumption cost: approximately 300–400 yuan / ton.

[0194] Product performance and application areas:

[0195] 1) Recycled PET particles

[0196] -Performance indicators: Melting point 250–260℃, crystallinity slightly lower than that of the original, strength maintained at 85–90%.

[0197] -Application areas: Respun polyester staple fiber and filament, food-grade packaging bottles, engineering plastic modification.

[0198] - Improvement measures: Adding chain extenders can restore molecular weight and meet food-grade requirements.

[0199] 2) Recycled Nylon (PA6, PA66)

[0200] -Performance indicators: Tensile strength decreased by 10–20%, and moisture absorption increased.

[0201] - Application areas: automotive parts, electronic and electrical housings, and spinning tows.

[0202] - Improvement measures: Blended with glass fiber for reinforcement, its performance is close to or even better than that of native nylon.

[0203] 3) Recycled PP / PE materials

[0204] -Performance indicators: Melt index increases, toughness decreases.

[0205] - Application areas: building materials, low-end injection molding, packaging.

[0206] - Improvement measures: Blend with virgin materials or add antioxidants.

[0207] 4) Natural fiber byproducts

[0208] -Performance indicators: After enzymatic hydrolysis, it can be converted into glucose, which can be further used to produce bio-based chemical products.

[0209] - Application areas: regenerated cellulose fiber, non-woven fabric, biodegradable plastic raw materials.

[0210] Market prospects and economic forecasts:

[0211]

[0212] Mass production requires an investment of approximately 600-800 million yuan, with an annual output value of 700-800 million yuan and a payback period of only 3-5 years.

Claims

1. A method for recycling textiles, characterized in that, Includes the following steps: (1) Raw material pretreatment: including crushing and removing impurities from the recycled materials to obtain mixed fiber waste; (2) The composition of the mixed fiber waste is detected and diverted by an identification system: the batches of mixed fiber waste with a natural fiber content ≥ the diversion threshold value by mass fraction enter the natural fiber biological treatment line and are treated by enzymatic hydrolysis. The resulting residual mixture then enters the high-pressure reaction equipment; the batches of mixed fiber waste with a natural fiber content < the diversion threshold value directly enter the high-pressure reaction equipment; the diversion threshold value is: the proportion of natural fiber content that will not burn or carbonize when the mixed fiber waste directly enters the high-pressure reaction equipment under humid and hot saturated steam environment and O2 < 3% conditions, and the diversion threshold value is 60%; (3) The high-pressure reaction equipment is heated in stages according to the melting range of different synthetic fibers, and the melt is discharged in each stage.

2. The method according to claim 1, characterized in that, In step (2), The heating process is carried out in the following three stages: First stage: 120–150℃, 0.20–0.50MPa, heat preservation for 20–40min, mainly to discharge PP and / or PE melt; Second stage: 180–220℃, 1.0–2.3MPa, hold for 20–40min, mainly to discharge nylon 6 and / or nylon 12 melt; The third stage: 230–260℃, 2.9–4.7MPa, heat treatment for 20–45 minutes, mainly to discharge PET and / or Nylon 66 melt.

3. The method according to claim 2, characterized in that, The heating rate of each section is ≤3℃ / min, and the melt is continuously discharged through the bottom guide valve. The natural fiber residue remains in a solid phase under humid heat and is subsequently discharged for further processing.

4. The method according to claim 1, characterized in that, The identification system uses near-infrared (NIR) or mid-infrared spectroscopy and automatically shunts the flow through an AI system; the high-pressure reaction equipment is equipped with an AI-adaptive temperature control module that automatically adjusts the heating curve and stop time based on the spectral identification data.

5. The method according to claim 1, characterized in that, The high-pressure reaction equipment is selected from at least one of the following: wet heat rotary reaction drum, steam reflux tower reactor, high-pressure circulating reactor with hot water circulation and / or steam reflux mode, and saturated steam fluidized separator.

6. The method according to claim 5, characterized in that, Steam is condensed, recovered, and recycled.

7. The method according to claim 1, characterized in that, In step (1), after removing impurities, the mixed fiber waste is further crushed to 2–5 cm.

8. The method according to claim 1, characterized in that, In step (2), the enzymatic hydrolysis uses a complex enzyme system for different components: (1) For mixed fiber waste with cellulose as the main component, use 15–30 FPU / g of acidic cellulase and 10–20 IU / g of β-glucosidase, and react for 12–24 hours at 45–55°C and pH 4.8–5.

2. (2) For mixed fiber waste with hemicellulose and hemp fiber as the main components, use a hemicellulase and pectinase system to react for 8–16 hours at 50–60°C and pH 5.0–5.

5. (3) For mixed fiber waste including residual lignin or coating, it is removed by a mixed system of pectinase, laccase and / or protease.

9. The method according to claim 8, characterized in that, The mixed fiber waste is first pretreated with 2–5 wt% NaOH for 0.5–1 h.

10. The method according to claim 1, characterized in that... Step (1) also includes an ultrasonic module and / or a microwave module and / or a solvent-assisted module.

11. The method according to claim 10, characterized in that... The ultrasonic module, microwave module, and solvent-assisted module are arranged in a modular structure, and the intelligent system automatically selects whether to activate or bypass them based on the raw material detection results.

12. The method according to claim 10, characterized in that... The ultrasonic module employs a 20–28kHz high-frequency transducer array with a cavitation energy density of 10–30W / L.

13. The method according to claim 12, characterized in that... When the mixed fiber waste includes a coating or adhesive structure, it is treated with NMP / DMF swelling agent for 10–20 min under ultrasonic cavitation conditions at 40–60°C and 20–28 kHz.

14. The method according to claim 10, characterized in that... The microwave module is positioned outside the mixed fiber waste flow channel, with a frequency of 2.45 GHz and a power density of 0.5–1 kW / L.

15. The method according to claim 14, characterized in that... When the mixed fiber waste is composite fiber, it is heated using 2.45 GHz microwave at a heating rate of 5–10°C / min and held for 10–15 min.

16. The method according to claim 10, characterized in that... The solvent-assisted module includes a corrosion-resistant stirred tank and is equipped with a solvent recovery and condensation tower.

17. The method according to claim 16, characterized in that... The solvent-assisted module comprises three sub-stages: low-temperature polar co-solvent immersion, swelling and stripping, and recycling and regeneration.

18. The method according to claim 16, characterized in that... When the mixed fiber waste includes a refractory coating, a catalytic swelling system of 0.3–0.8 wt% ethylene glycol + zinc acetate is used, and the reaction is carried out at 190–210°C for 15 min.

19. The method according to claim 1, characterized in that... The remaining natural fiber residue in the high-pressure reaction equipment in step (3) is converted into regenerated cellulose or bio-based materials through enzymatic hydrolysis.

20. The method according to claim 1, characterized in that... The high-pressure reaction equipment is equipped with an outer layer microwave module.

21. A control system for a textile recycling method according to any one of claims 1-20, characterized in that... To form a closed-loop system of identification-control-optimization, the system comprises three stages: (1) T0 stage: Pre-separation identification before material loading - component detection and process strategy generation, Near-infrared (NIR) and mid-infrared (MIR) spectral sensor arrays and a high-speed camera recognition system are set in the feeding section to perform rapid spectral scanning on the mixed fiber waste. The AI ​​system identifies the proportion of major components based on spectral characteristic peaks and automatically generates corresponding heating curve templates, including the temperature zones for segmented heating, heating rate, and holding time. (2) T1 stage: segmented heating with real-time monitoring – online feedback control, A spectral probe and a temperature and pressure sensor are installed in the high-pressure reaction equipment to monitor the state changes of the material during the staged heating process; The system analyzes the changes in the spectral absorption peaks on the material surface in real time, determines the melting start point and completion time, and automatically fine-tunes the heating rate, holding time and the timing of the flow guide valve opening. The AI ​​system writes real-time feedback results into the controller to achieve segmented condition adaptive optimization and prevent local overheating or incomplete melting. (3) T2 stage: Post-separation feedback - data write-back optimization, An online spectrometer and image recognition module are installed at the outlet of the separated products to detect the purity of each polymer melt segment; If the purity is insufficient, the system will automatically write back the data and adjust the heating curve and stop time for the next batch.

22. The control system according to claim 21, characterized in that... In stage (1), the system is equipped with a dual-layer security lock of spectral recognition + AI judgment: if any natural fiber spectral signal is detected, including C-O and O-H characteristic peaks, the dry heating command is prohibited.

23. The control system according to claim 21, characterized in that... If the steam pressure or humidity is lower than the safety threshold in stage (2), the AI ​​system will automatically stop heating and issue an alarm to prevent localized dry heat.

24. A textile recycling device, characterized in that... A textile recycling method according to any one of claims 1–20 includes a wet-heat segmented melting reaction device, wherein the reaction device includes an online detection unit and control module, a wet-heat sealed high-pressure reaction equipment, a segmented heating system, a steam input and condensation recovery system, and a bottom guide discharge assembly.

25. The apparatus according to claim 24, characterized in that... It also includes a pretreatment modular device, which includes a crushing and impurity removal module, a particle size control module, an ultrasonic module, a microwave module and / or a solvent-assisted module, as well as a conveying and linkage interface module and a modular control unit.

26. The apparatus according to claim 24, characterized in that... The humid heat sealed high-pressure reaction equipment includes an outer layer microwave module and a stirring structure.

27. The apparatus according to any one of claims 24-26, characterized in that... It includes a three-stage closed-loop control system device, which includes a component identification unit, a parameter generation unit, a segmented temperature rise monitoring unit, a control execution unit, a result write-back unit, and a double-layer safety lock structure.

Images