Continuous efficient decolorizing and bleaching system and process for preparing recycled pulp from waste textiles

Abstract

The invention discloses a continuous efficient decolorizing and bleaching system and process for preparing recycled pulp from waste textiles, and belongs to the technical field of waste textile recycling. The decolorizing and bleaching machine with a sectional type screw rod structure, process unit integration and the like is adopted for carrying out pretreatment, decolorizing treatment, first cleaning treatment, bleaching treatment and second cleaning treatment, so that continuous and efficient decolorizing, bleaching and cleaning on the waste textiles (especially the waste textiles containing indigo dyes) under the condition of medium and high concentration (10-30%) are realized; consumption of chemical agents and water resources is reduced, the technological process is shortened, and the technological requirements are met.

Description

Technical Field

[0001] This invention relates to a continuous and efficient decolorization and bleaching system and process for preparing recycled pulp from waste textiles, specifically a screw conveyor-based continuous and efficient decolorization and bleaching system and process for preparing recycled pulp from waste textiles, particularly suitable for the decolorization and bleaching process of recycled pulp from waste textiles containing indigo dyes, belonging to the field of waste textile recycling technology. Background Technology

[0002] Currently, the recycling, reuse, and recycling of waste textiles has become an inevitable trend for the green development of the fiber industry. However, the recycling of waste textiles (especially denim fabrics containing indigo dyes) still faces the following technical challenges: I. Problems include low decolorization and bleaching efficiency, cumbersome processing steps, environmental unfriendliness, and high energy consumption. For example, multi-step oxidation / reduction decolorization and bleaching under low concentration (<5%) conditions of waste textile materials leads to large consumption of chemical agents, serious waste of water resources, and long processing cycles. Examples include CN116856192A, CN116397450A, and CN117210958A, which are mostly applicable to the treatment of low concentration waste textile materials. Second, some waste textiles contain indigo dyes, which have a stable structure and require multiple decolorization and bleaching processes to achieve the pulp whiteness requirements for fiber (such as Lyocell fiber) production. This process also uses large amounts of chemical agents and water, causing significant environmental problems and wasting a large amount of energy and water resources. Third, existing equipment (such as ordinary reaction vessels) is difficult to achieve continuous production, which limits the efficiency of industrial application; The high production cost, poor quality of recycled pulp, and limited equipment in the preparation of recycled pulp from waste textiles seriously affect the smooth progress of the waste textile recycling process.

[0003] Therefore, there is an urgent need for an integrated system that can achieve continuous and efficient decolorization and bleaching under medium-to-high concentration conditions in waste textile materials, reducing process steps, lowering resource consumption, and ensuring the quality of recycled pulp products. Summary of the Invention

[0004] To address the problems of high production costs, poor quality of recycled pulp, and limited equipment in existing technologies for preparing recycled pulp from waste textiles, which seriously affect the smooth progress of waste textile recycling processes, a continuous and efficient decolorization and bleaching system and process for preparing recycled pulp from waste textiles is proposed.

[0005] In this technical solution, by adopting a segmented screw structure and process unit integration, continuous and efficient decolorization, bleaching and cleaning of waste textiles (especially waste textiles containing indigo dyes) is achieved under medium-to-high concentration (10-30%) conditions of waste textile slurry, reducing the consumption of chemical agents and water resources, shortening the process flow, and meeting process requirements.

[0006] To achieve the above technical objectives, the following technical solution is proposed: The primary objective of this technical solution is to provide: a decolorizing and bleaching machine for preparing recycled pulp from waste textiles, comprising a housing and a decolorizing unit, a cleaning unit I, a bleaching unit, and a cleaning unit II disposed within the housing, wherein the decolorizing unit, the cleaning unit I, the bleaching unit, and the cleaning unit II are arranged sequentially in the direction of conveying waste textile materials. Decolorization unit: It contains a screw I, with multiple orifice injection heads I evenly distributed along the axial direction of screw I. The multiple orifice injection heads I are located at the top of the decolorization unit and are connected to a decolorizing agent pipeline. The orifice diameter of the multiple orifice injection head I is 0.2–1.0 mm, the injection pressure is 0.5–3.0 MPa, and the multiple orifice injection head I is connected to a decolorizing agent storage tank (which is either a ClO2 generator or a Na2S2O4 storage tank) via the decolorizing agent pipeline. Among them, the following controls are applied: decolorization time ≤ 20 min, temperature 40~80℃, and pulp whiteness ≥ 65% (according to ISO 2470 standard). Among them, the pore diameter of the porous injection head I is 0.2 to 1.0 mm, which is conducive to precise control of the amount of decolorizing agent injected, thereby ensuring the degree and effect of decolorization; Cleaning Unit I: It is equipped with a screw II and a spray mechanism I is installed on the top. The spray mechanism I is distributed along the axial direction of the screw II. A flow meter I is installed on the spray mechanism I and a speed sensor I is installed on the screw II. The flow meter I and the speed sensor I are interlocked by an electrical signal to ensure that the spray water flow rate of the spray mechanism I and the speed of the screw II are dynamically matched. Among them, the liquid-to-solid ratio of the spray is controlled to be 1:5 to 10, and the resulting cleaning waste liquid is used to recover the decolorizing agent through a membrane separation device, with a reuse rate of ≥80%. Bleaching unit: It is equipped with a screw III, and multi-hole injection heads II are distributed equidistantly along the axial direction of the screw III. The multi-hole injection heads II (1031) are located at the top of the bleaching unit and are connected to the bleaching agent pipeline. The orifice diameter of the multi-hole injection head is 0.2 to 1.0 mm, the injection pressure is 0.5 to 3.0 MPa, and the multi-hole injection head II is connected to the bleaching agent storage tank (the bleaching agent storage tank is a hydrogen peroxide storage tank) through the bleaching agent pipeline. Among them, the following controls are applied: bleaching time ≤ 10 min, temperature 60~80℃, and pulp whiteness ≥ 85% (according to ISO 2470 standard). Among them, the pore size of the porous injection head II is 0.2-1.0 mm, which is conducive to precise control of the amount of bleaching agent entering, thereby ensuring the degree and effect of debleaching; Cleaning Unit II: It is equipped with a screw IV and a spray mechanism II installed on the top. The spray mechanism II is distributed along the axial direction of the screw IV. A flow meter II is installed on the spray mechanism II and a speed sensor II is installed on the screw IV. The flow meter II and the speed sensor II are interlocked by an electrical signal to ensure that the spray water flow rate of the spray mechanism II is dynamically matched with the speed of the screw IV. Among them, the liquid-to-solid ratio of the spray is controlled to be 1:5 to 10, and the bleaching agent in the resulting cleaning waste liquid is recovered through a membrane separation device, with a reuse rate of ≥80%. Screw I is connected to screw II, and the decolorization unit is connected to cleaning unit I, forming a decolorization subsystem; Screw III is connected to screw IV, and the bleaching unit is connected to the cleaning unit II, forming a bleaching subsystem; The decolorization subsystem and the bleaching subsystem are connected by a pipe. The decolorization unit, cleaning unit I, pipelines, bleaching unit, and cleaning unit II form a continuous pathway for the transfer, mixing, decolorization, bleaching, and cleaning of waste textile pulp.

[0007] Preferably, the outer side of the housing is provided with a heat insulation jacket, and the heat insulation jacket is provided with a temperature sensor; one side of the heat insulation jacket is connected to a temperature regulating inlet pipe, and the other side is connected to a temperature regulating outlet pipe. The temperature regulating inlet pipe is provided with a temperature control valve, and the temperature control valve and the temperature sensor are interlocked by an electrical signal to ensure that the temperature inside the housing is dynamically matched with the process temperature in the corresponding unit.

[0008] Preferably, the housing is further provided with an exhaust port I connected to the decolorization unit and an exhaust port II connected to the bleaching unit, with an exhaust control valve I sleeved in the exhaust port I and an exhaust control valve II sleeved in the exhaust port II; The decolorization unit is equipped with pressure sensor I, which is interlocked with exhaust control valve I via an electrical signal. The bleaching unit is equipped with pressure sensor II, which is interlocked with exhaust control valve II via an electrical signal. The system includes exhaust port I, exhaust port II, exhaust control valve I, exhaust control valve II, pressure sensor I, and pressure sensor II, which are used to regulate the pressure within the decolorization unit and the bleaching unit (decolorization pressure 0.3–1.5 MPa, bleaching pressure 0.8–1.2 MPa).

[0009] Preferably, the housing is also equipped with pH sensors. More preferably, there are four pH sensors, which are distributed in the decolorization unit, cleaning unit I, bleaching unit and cleaning unit II, respectively, for detecting the pH value in each process unit.

[0010] Preferably, the housing is also equipped with slurry concentration detectors. More preferably, there are four slurry concentration detectors, which are respectively distributed in the decolorization unit, cleaning unit I, bleaching unit and cleaning unit II, for detecting the slurry concentration in each process unit.

[0011] Preferably, screw I and screw II are connected by a coupling, and screw III and screw IV are connected by a coupling. This arrangement facilitates the assembly and maintenance of the decolorizing and bleaching machine.

[0012] Preferably, screw I and screw II are integrally formed, and screw III and screw IV are integrally formed. This configuration improves the integrity of the screws in the decolorization unit and cleaning unit I, and the screws in the bleaching unit and cleaning unit II, thereby improving the continuity of material mixing, decolorization, bleaching, and cleaning during conveying.

[0013] Preferably, all screws in screws I, II, III, and IV employ staggered threaded elements, with the thread pitch being 0.5 to 1.2 times the screw diameter. If the thread pitch is too large, a large amount of slurry will enter, leading to uneven processing during decolorization or bleaching; if the thread pitch is too small, the amount of slurry processed per unit time will be small, thus affecting the decolorization and bleaching efficiency. Therefore, selecting a thread pitch of 0.5 to 1.2 times the screw diameter ensures both effective decolorization and bleaching while improving processing efficiency.

[0014] The second objective of this technical solution is to provide: a continuous and efficient decolorizing and bleaching system for preparing recycled pulp from waste textiles, comprising the aforementioned decolorizing and bleaching machine, decolorizing agent storage tank, bleaching agent storage tank, and water storage tank, wherein... The decolorizing agent storage tank is connected to the decolorizing unit in the decolorizing and bleaching machine via a decolorizing agent pipeline, and a decolorizing agent control valve I is installed on the decolorizing agent pipeline; The bleaching agent storage tank is connected to the bleaching unit in the decolorizing bleaching machine via a bleaching agent pipeline, and a bleaching agent control valve is installed on the bleaching agent pipeline; The water storage tank is connected to the cleaning unit I in the decolorizing and bleaching machine through the cleaning water inlet pipe I, and the cleaning water inlet pipe I is equipped with a cleaning control valve I; the water storage tank is also connected to the cleaning unit II in the decolorizing and bleaching machine through the cleaning water inlet pipe II, and the cleaning water inlet pipe II is equipped with a cleaning control valve II.

[0015] Preferably, the decolorization and bleaching system is connected to a waste liquid recovery system. Both cleaning unit I and cleaning unit II in the decolorization and bleaching machine are connected to the waste liquid recovery system, which includes a membrane separation device.

[0016] The third objective of this technical solution is to provide: a continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles, comprising the following steps: S1 Pretreatment: Shred waste textiles to a length of 0.2-1cm, add water, and adjust the slurry concentration to 10-30%; S2 Decolorization Treatment: The slurry treated in step S1 is continuously fed into the decolorization unit via the mixing unit. A decolorizing agent is added to the decolorization unit. The injection pressure of the porous injection head I is controlled at 0.5–3.0 MPa. The slurry and decolorizing agent are forcibly mixed at a mass ratio of 1:0.05–0.2, with a mixing time ≤2 min. The shear rate of screw I within the decolorization unit is controlled at 100–500 s. -1 The decolorization reaction temperature is 40–80℃, the pressure is 0.3–1.5 MPa, and the residence time (i.e., reaction time) is 10–20 min. The dosage of decolorizing agent entering the decolorization unit is controlled by adjusting the injection pressure; therefore, the injection pressure is limited to 0.5–3.0 MPa. The mass ratio of slurry to decolorizing agent is 1:0.05–0.2. If the mass ratio is too low, too much decolorizing agent is added, wasting it and increasing processing costs; if the mass ratio is too high, too little decolorizing agent is added, resulting in incomplete decolorization and affecting subsequent processes and the slurry's decolorization and bleaching effect. The shear rate determines the slurry processing volume per unit time. If the shear rate is low, the processing volume per unit time is small, affecting efficiency; if the shear rate is too high, the decolorization reaction will be insufficient, thus affecting the decolorization effect. Regarding the decolorization temperature, when the decolorizing agent is an oxidizing agent (such as ClO2 aqueous solution), the preferred decolorization temperature is 40–60℃; when the decolorizing agent is a reducing agent (such as sodium hydrosulfite), the preferred decolorization temperature is 60–80℃. If the decolorization reaction temperature is too low, the decolorization time will be prolonged, and the decolorization efficiency will decrease; if the decolorization temperature is too high, the decolorization reaction will be violent, damaging the fibers in the slurry. A residence time of 10–20 minutes ensures a sufficient and thorough decolorization reaction, while also improving processing efficiency. S3 First Cleaning Process: The decolorized slurry is conveyed to the cleaning unit I by the screw conveyor in the decolorization unit of step S2. Cleaning water is sprayed into the cleaning unit I. The liquid-solid ratio is controlled to be 1:5 to 10, the cleaning temperature in the cleaning unit I is 60 to 70°C, and the residence time is 3 to 5 minutes. The control of a liquid-to-solid ratio of 1:5 to 10, a cleaning temperature of 60 to 70°C in cleaning unit I, and a residence time of 3 to 5 minutes is beneficial to subsequent bleaching efficiency. For example, if the residence time is too short, the cleaning will be incomplete, thus affecting the quality and efficiency of subsequent bleaching; if the residence time is too long, it will affect the unit throughput and reduce efficiency. Limiting the solid-to-liquid ratio controls the amount of cleaning water used, thereby ensuring that the decolorizing agents and other contaminants in the slurry are completely removed. S4 Bleaching Treatment: The slurry after cleaning in step S3 is conveyed to the bleaching unit through a pipeline. Bleaching agent is added to the bleaching unit. The following controls are applied: the injection pressure of the porous injection head II is 0.5-3.0 MPa, the pressure in the bleaching unit is 0.8-1.2 MPa, the temperature is 60-80℃, and the residence time is 2-10 min. The dosage of bleaching agents entering the bleaching unit is controlled by adjusting the injection pressure; therefore, the injection pressure is limited to 0.5–3.0 MPa. Regarding bleaching temperature, if the bleaching reaction temperature is too low, the bleaching time is prolonged, and the bleaching efficiency decreases; if the bleaching temperature is too high, the bleaching reaction is too vigorous, which can damage the fibers in the pulp. A residence time of 2–10 minutes ensures a sufficient and thorough bleaching reaction, while also improving processing efficiency. S5 Second cleaning process: The bleached slurry is conveyed to the cleaning unit II by the screw IV in the bleaching unit of step S4. Cleaning water is sprayed into the cleaning unit II. The liquid-solid ratio is controlled to be 1:5 to 10, the cleaning temperature in the cleaning unit II is 60 to 70°C, and the residence time is 3 to 5 minutes to obtain bleached waste textile slurry. The indicators of the bleached waste textile pulp include: whiteness ≥ 85% (ISO 2470 standard); The quality of the final waste textile slurry is ensured by controlling the liquid-to-solid ratio to be 1:5–10, the cleaning temperature in cleaning unit II to be 60–70℃, and the residence time to be 3–5 minutes. For example, too short a residence time will result in incomplete cleaning, thus affecting the quality of the waste textile slurry; too long a residence time will reduce the unit throughput and decrease efficiency. Limiting the solid-to-liquid ratio controls the amount of cleaning water used, thereby ensuring that bleach and other contaminants in the slurry are completely removed.

[0017] Preferably, the decolorizing agent is an oxidizing agent or a reducing agent. The type of decolorizing agent can be selected based on the type of waste textiles. The oxidizing agent is an aqueous solution of ClO2 with a concentration of 0.05–0.5 g / L; the reducing agent is sodium hydrosulfite, used at a concentration of 2.0–4.0% of the dry weight of the sizing agent. The decolorizing agents involved are environmentally friendly and produce few harmful substances.

[0018] Preferably, the bleaching agent is H2O2, and the amount of H2O2 used is 0.05-1.0% of the dry weight of the pulp, and 0.01-0.05% sodium silicate is used as the bleaching activator. With the addition of the bleaching activator, the whiteness of the pulp is increased by approximately 2%.

[0019] The mechanisms involved in this technical solution include: In the decolorization process, oxidizing decolorizing agents (such as H2O2, NaClO, ClO2, etc.) can oxidize the amino groups (-NH2) in the macromolecular structure of dyes, causing the azo groups (-N = N-) to break and the carboxyl groups (-COOH) to become methylated, thereby achieving the purpose of stripping the dye from the fabric. For example, ClO2, as a selective oxidizing agent, has an oxidation potential higher than that of pigments and impurities attached to the fibers, but lower than that of the fibers themselves. Its oxidation performance is between that of chlorates and hypochlorites, and it acts slowly on carbohydrates. When using ClO2 to strip dye from fabric fibers, it can remove pigments and impurities from the fibers without damaging the fibers themselves. In addition, indigo dye belongs to the anthraquinone class of vat dyes, and its molecular formula is C 16 H 10 N2O2 has a planar conjugated structure. ClO2 destroys the color of indigo by breaking the conjugated bonds of the indigo molecule.

[0020] Reducing stripping agents (such as bleaching powder, sodium hyposulfite, urea, and sulfur dioxide) decompose into reducing substances under alkaline and heating conditions. These substances can cleave the azo groups in azo dyes, thus achieving the purpose of stripping. For example, sodium hydrosulfite (Na2S2O4) generates strongly reducing S2O4 in an alkaline medium. 2- The ions reduce the carbonyl group (C=O) in the indigo molecule to a hydroxyl group (-OH) through two-electron transfer, thereby destroying its conjugated color-producing system and ultimately achieving the purpose of decolorization.

[0021] The positional relationships such as "inner", "between", "upper", "top", "middle", "one side", "outer side", "other side", "below", and "middle" involved in this technical solution are defined according to the actual usage conditions and are conventional terms in this technical field, as well as conventional terms used by those skilled in the art in actual use.

[0022] In the description of this technical solution, it should be noted that, unless otherwise explicitly specified and limited, the terms "setting" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] The beneficial technical effects of adopting this technical solution are as follows: I. The decolorizing and bleaching machine of this invention, through the integrated design of the screw and process unit, breaks through the limitations of the traditional single reactor. While continuously processing the slurry (conveying, mixing, decolorizing, bleaching, and washing), it achieves continuous material conveying and efficient mixing, ensuring the smooth progress of the waste textile recycling process. Furthermore, the strong shear force of the segmented screw, while continuously processing the slurry (conveying, mixing, decolorizing, bleaching, and washing), can handle medium to high concentration (10-30%) slurries, overcoming the limitation of existing technologies that can only handle low-concentration slurries, and effectively reducing water consumption (by 40-70%). It also achieves efficient degradation of indigo dye: utilizing the localized high temperature (up to 120°C) and high pressure (2.0 MPa) environment generated by the screw extrusion, i.e., localized high temperature and high pressure enhanced reaction, accelerates the degradation of indigo molecules in indigo dyes, increasing decolorization efficiency by more than 50%. Second, in this invention, a multi-step reaction process unit integration is adopted (which separately completes the transfer, mixing, decolorization, bleaching and cleaning), reducing the energy consumption of traditional multi-step processes, etc. Third, in this invention, the design of the decolorizing and bleaching machine achieves low maintenance costs: the equipment is easy to start, and the damage level of the threaded components and the inner bushing of the barrel can be detected at any time, so as to carry out effective maintenance and replacement, and reduce unnecessary consumption caused by problems during the production process. IV. In this invention, process parameters are matched, such as screw speed (e.g., shear rate 100-500 s). - ¹) Temperature gradient (decolorization reaction temperature 40-80℃, first cleaning temperature 60-70℃, bleaching temperature 60-80℃, second cleaning temperature 60-70℃), pressure control (decolorization pressure 0.3-1.5MPa, bleaching pressure 0.8-1.2MPa), etc., shorten the decolorization and bleaching time by more than 50%, effectively improving the decolorization and bleaching efficiency; V. In this invention, by controlling parameters such as screw speed, residence time, temperature, and pressure, the decolorization time is ensured to be ≤20 min and the whiteness ≥85% (ISO 2470 standard). Through real-time monitoring of slurry concentration, pH value, temperature, pressure, and flow rate using sensors, residence time and screw speed can be dynamically adjusted, and the whiteness fluctuation of the finished slurry is controlled within ±2% (ISO2470 standard), increasing the product qualification rate to over 98%. VI. This invention can achieve continuous decolorization of waste textile slurries containing medium to high concentrations of indigo dyes. Compared with traditional indigo decolorization, which requires multiple steps at low concentrations (<5%), this invention, based on the screw's strong shear force, mixing, and conveying design, can achieve continuous decolorization of slurry concentrations of 10-30%, breaking through the bottleneck of resource consumption and realizing industrial production. This invention is the first to integrate the four-step process of mixing, decolorizing, bleaching and cleaning into a single screw compressor, replacing the traditional fragmented process of "reactor + multi-stage cleaning", ultimately shortening the processing cycle and reducing energy consumption. Furthermore, the decolorization and bleaching process can be fully automated by dynamically adjusting parameters (such as shear rate, temperature, and pressure). It also offers options for oxidative decolorization and reductive decolorization processes based on production conditions and requirements. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the decolorizing and bleaching machine in this invention; Figure 2 This is a schematic diagram illustrating the working principle of the decolorization and bleaching system in this invention; Figure 3 This is a flowchart illustrating the decolorization and bleaching process involved in this invention; Figure 4 The whiteness results of the decolorized waste textile sizing agents obtained by adding different concentrations of ClO2 aqueous solution in Examples 9-13; Figure 5 As shown in Example 1, the whiteness results of the decolorized waste textile sizing were obtained by using different decolorization temperatures; Figure 6 As shown in Example 3, the whiteness results of the decolorized waste textile sizing were obtained by using different decolorization temperatures; In the diagram, 1 is the decolorizing and bleaching machine, 100 is the casing, 1000 is the exhaust port I, 1001 is the exhaust port II, 1002 is the exhaust control valve I, and 1003 is the exhaust control valve II. 101. Decolorization unit; 1010. Screw I; 1011. Multi-hole injection head I; 102. Cleaning Unit I; 1020. Screw II; 1021. Spraying Mechanism I; 103. Bleaching unit; 1030. Screw III; 1031. Multi-hole injection head II; 104. Cleaning Unit II; 1040. Screw IV; 1041. Spraying Mechanism II; 106. Motor I; 108. Motor II; 110. Feeding hopper; 111. Mixing unit; 1110. Screw V; 112. Motor III; 113. Feeding port; 119. Rotating shaft; 2. Decolorizing agent storage tank; 3. Bleaching agent storage tank; 4. Water storage tank; 5. Decolorizing agent pipeline; 6. Decolorizing agent control valve I; 7. Bleaching agent pipeline; 8. Bleaching agent control valve; 9. Cleaning water inlet pipe I; 10. Cleaning control valve I; 11. Cleaning water inlet pipe II; 12. Cleaning control valve II; 13. Waste liquid recovery system. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following embodiments, a YQ-Z-48A whiteness colorimeter was used to measure the whiteness of the processed samples during whiteness testing. The R value of each sample was measured, and each sample was tested three times, and the average value was calculated.

[0027] Example 1 This embodiment provides: a decolorizing and bleaching machine for preparing recycled pulp from waste textiles, such as... Figure 1 As shown, the device includes a housing 100 and a decolorizing unit 101, a cleaning unit I 102, a bleaching unit 103, and a cleaning unit II 104 disposed within the housing 100. The decolorizing unit 101, the cleaning unit I 102, the bleaching unit 103, and the cleaning unit II 104 are arranged sequentially in the direction of conveying waste textile materials. The decolorizing unit 101 is equipped with a screw I 1010, and the cleaning unit I 102 is equipped with a screw II 1020. The screw I 1010 and the screw II 1020 are connected. The decolorizing unit 101 and the cleaning unit I 102 are connected to each other, and the two form a decolorizing subsystem. The bleaching unit 103 is equipped with a screw III 1030, and the cleaning unit II 104 is equipped with a screw IV 1040. The screw III 1030 and the screw IV 1040 are connected. The bleaching unit 103 and the cleaning unit II 104 are connected to each other, and the two form a bleaching subsystem. The decolorization subsystem and the bleaching subsystem are connected by a pipe. A continuous pathway for the transfer, mixing, decolorization, bleaching, and cleaning of waste textile pulp is formed between the decolorization unit 101, the cleaning unit I 102, the pipeline, the bleaching unit 103, and the cleaning unit II 104.

[0028] By adopting segmented screw structures and process unit integration, continuous and efficient decolorization, bleaching and cleaning of waste textiles (especially waste textiles containing indigo dyes) can be achieved under medium-to-high concentration (10-30%) conditions of waste textile slurry, reducing the consumption of chemical agents and water resources, shortening the process flow, and meeting process requirements.

[0029] Example 2 Based on Example 1, this example further defines the decolorization subsystem to further illustrate the technical solution.

[0030] like Figure 2As shown, in the decolorizing unit 101, there are porous injection heads I1011 equidistantly distributed along the axial direction of the screw I1010. The porous injection heads I1011 are located at the top of the decolorizing unit 101. The diameter of the pores in the porous injection heads I1011 is 0.2 to 1.0 mm. The porous injection heads I1011 are connected to the decolorizing agent storage tank 2 through the decolorizing agent pipeline 5. The top of the cleaning unit I102 is equipped with a spray mechanism I1021, which is distributed along the axial direction of the screw II1020. A flow meter I is installed on the spray mechanism I1021, and a speed sensor I is installed on the screw II1020. The flow meter I and the speed sensor I are interlocked by an electrical signal to ensure that the spray water flow rate of the spray mechanism I1021 is dynamically matched with the speed of the screw II1020. Both screw I 1010 and screw II 1020 employ staggered threaded elements, with the thread pitch being 0.5 to 1.2 times the screw diameter. This configuration ensures the continuity of material mixing, decolorization, and cleaning during conveying. Screw I 1010 and screw II 1020 are connected by a coupling. The segmented arrangement of screws I 1010 and II 1020 facilitates the assembly and maintenance of the decolorizing and bleaching machine 1. Alternatively, screws I 1010 and II 1020 can be integrally formed, improving the integrity of the screws within the decolorizing unit 101 and the cleaning unit I 102, thereby enhancing the continuity of material mixing, decolorization, and cleaning during conveying.

[0031] Example 3 Based on Examples 1-2, this example further defines the bleaching subsystem to further illustrate the technical solution.

[0032] In the bleaching unit 103, there are porous injection heads II 1031 equidistantly distributed along the axial direction of the screw III 1030. The porous injection heads II 1031 are located at the top of the bleaching unit 103. The diameter of the holes in the porous injection heads II 1031 is 0.2 to 1.0 mm. The porous injection heads II 1031 are connected to the bleaching agent storage tank 3 through the bleaching agent pipeline 7. The top of the cleaning unit II104 is equipped with a spray mechanism II1041, which is distributed along the axial direction of the screw IV1040. The spray mechanism II1041 is equipped with a flow meter II, and the screw IV1040 is equipped with a speed sensor II. The flow meter II and the speed sensor II are interlocked by an electrical signal to ensure that the spray water flow rate of the spray mechanism II1041 is dynamically matched with the speed of the screw IV1040. Both screws III 1030 and IV 1040 employ staggered threaded elements, with the thread pitch ranging from 0.5 to 1.2 times the screw diameter. This configuration ensures the continuity of material mixing, bleaching, and cleaning during conveying. Screws III 1030 and IV 1040 are connected by a coupling. The segmented arrangement of screws III 1030 and IV 1040 facilitates the assembly and maintenance of the decolorizing and bleaching machine 1. Alternatively, screws III 1030 and IV 1040 can be integrally formed, improving the overall integrity of the screws within the bleaching unit 103 and the cleaning unit II 104, thereby enhancing the continuity of material mixing, bleaching, and cleaning during conveying.

[0033] Example 4 Based on Examples 1-3, this example further specifies the following to ensure the orderly and effective feeding of waste textile pulp: Screw I 1010 is connected to motor I 106, and screw III 1030 is connected to motor II 108. Motors I 106 and II 108 provide power, and the rotational speeds of screws I 1010, II 1020, III 1030, and IV 1040 can be adjusted by controlling the power of motors I 106 and II 108, thereby regulating the residence time (reaction time) of waste textiles in the bleaching subsystem.

[0034] A temperature and pressure regulating box is provided on one side of the housing 100. The temperature and pressure regulating box contains a control system for the decolorization subsystem and the bleaching subsystem. The control system realizes the control of temperature and pressure.

[0035] The housing 100 is provided with a feeding hopper 110 that communicates with the decolorizing unit 101. The feeding hopper 110 is provided with a mixing unit 111, and the feeding hopper 110 is provided with a feeding port 113 that communicates with the mixing unit 111. In one specific embodiment, the mixing unit 111 is provided with a screw V 1110, and the screw V 1110 is connected to the motor III 112 through a rotating shaft 119.

[0036] Example 5 Based on Examples 1-4, this example further specifies the following to achieve a highly efficient, continuous, and controllable decolorization and bleaching process for the decolorization and bleaching machine 1: The outer side of the housing 100 is provided with a heat insulation jacket, and a temperature sensor is provided on the heat insulation jacket; a temperature regulating inlet pipe is connected to one side of the heat insulation jacket, and a temperature regulating outlet pipe is connected to the other side; a temperature control valve is provided on the temperature regulating inlet pipe, and the temperature control valve and the temperature sensor are interlocked by an electrical signal. The housing 100 is also provided with an exhaust port I 1000 connected to the decolorizing unit 101 and an exhaust port II 1001 connected to the bleaching unit 103. An exhaust control valve I 1002 is fitted in the exhaust port I 1000 and an exhaust control valve II 1003 is fitted in the exhaust port II 1001. The decolorization unit 101 is equipped with a pressure sensor I, and the pressure sensor I is interlocked with the exhaust control valve I 1002 by an electrical signal; The bleaching unit 103 is equipped with a pressure sensor II, which is interlocked with the exhaust control valve II 1003 via an electrical signal. pH sensors are distributed on the housing 100; The housing 100 is also equipped with slurry concentration detectors, such as online near-infrared moisture detectors, specifically the XKCON-NIR-MA series.

[0037] Among them, the slurry concentration, temperature, pressure and flow rate are monitored in real time by various sensors and detectors, and the residence time and screw speed can be dynamically adjusted.

[0038] Example 6 Based on Examples 1-5, this example provides: a continuous and efficient decolorizing and bleaching system for preparing recycled pulp from waste textiles, including the above-mentioned decolorizing and bleaching machine 1, decolorizing agent storage tank 2, bleaching agent storage tank 3 and water storage tank 4, wherein the decolorizing agent storage tank 2 is connected to the decolorizing unit 101 in the decolorizing and bleaching machine 1 through a decolorizing agent pipeline 5, and a decolorizing agent control valve I6 is provided on the decolorizing agent pipeline 5; The bleaching agent storage tank 3 is connected to the bleaching unit 103 in the decolorizing bleaching machine 1 through the bleaching agent pipeline 7, and the bleaching agent pipeline 7 is equipped with a bleaching agent control valve 8; Water storage tank 4 is connected to cleaning unit I102 in decolorizing and bleaching machine 1 through cleaning water inlet pipe I9, and cleaning control valve I10 is provided on cleaning water inlet pipe I9; water storage tank 4 is also connected to cleaning unit II104 in decolorizing and bleaching machine 1 through cleaning water inlet pipe II11, and cleaning control valve II12 is provided on cleaning water inlet pipe II11.

[0039] In addition, the decolorization and bleaching system is connected to the waste liquid recovery system 13. The cleaning unit I 102 and the cleaning unit II 104 in the decolorization and bleaching machine 1 are both connected to the waste liquid recovery system 13. The waste liquid recovery system 13 includes a membrane separation device, which can achieve: a decolorizing agent recycling rate of ≥80%, a bleaching agent recycling rate of ≥80%, a waste liquid discharge reduction of more than 60%, and at the same time, a reduction of reagent (decolorizing agent, bleaching agent) cost of about 35%, thus constructing an environmentally friendly treatment system. The proposed continuous and efficient decolorization and bleaching system can be well integrated with the continuous and efficient decolorization and bleaching process in the preparation of recycled pulp from waste textiles, thereby achieving continuous and efficient decolorization and bleaching of waste textile pulp and finally obtaining pulp with a whiteness of ≥85% (ISO 2470 standard). This provides an effective prerequisite for the preparation and reuse of recycled pulp.

[0040] Example 7 Based on Examples 1-6, this example provides: a continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles, such as... Figure 3 As shown, the above-described decolorizing and bleaching machine 1, or the above-described decolorizing and bleaching system, includes the following steps: S1 Pretreatment: Crush waste textiles, add water, and adjust the slurry concentration to 10-30%; S2 Decolorization Treatment: The slurry pretreated in step S1 is continuously fed into the decolorization unit 101 via the mixing unit 111. A decolorizing agent is added to the decolorization unit 101, and forced mixing is performed. The mass ratio of the slurry pretreated in step S1 to the decolorizing agent is controlled as follows: 1:0.05-0.2; the injection pressure of the porous injection head I1011 is 0.5-3.0 MPa; and the shear rate of the screw I1010 is 100-500 s. -1 The decolorization reaction temperature is 40-80℃, and the residence time is 10-20 min, to obtain a decolorized waste textile sizing agent with a whiteness ≥65%. The decolorizing agent is either an oxidizing agent or a reducing agent; the oxidizing agent is an aqueous solution of ClO2 with a concentration of 0.05–0.5 g / L; the reducing agent is sodium hydrosulfite, and the dosage is 2.0–4.0% of the dry weight of the waste textile sizing agent. S3 First Cleaning Process: The decolorized slurry is conveyed to the cleaning unit I 102 by the screw I 1010 in the decolorization unit 101 of step S2. Cleaning water is sprayed into the cleaning unit I 102. The solid-liquid ratio of the slurry after decolorization in step S2 to the cleaning water is controlled to be 1:5 to 10, the cleaning temperature is 60 to 70°C, and the residence time is 3 to 5 minutes. S4 Bleaching Treatment: The slurry after cleaning in step S3 is conveyed to the bleaching unit 103 through the pipeline. Bleaching agent is added to the bleaching unit 103 for bleaching. The injection pressure of the multi-hole injection head II 1031 is 0.5-3.0 MPa, the bleaching temperature is 60-80℃, and the residence time is 2-10 min, to obtain bleached waste textile slurry with a whiteness ≥85%. The bleaching agent is H2O2, and the amount of H2O2 used is 0.05-1.0% of the dry weight of the waste textile sizing agent, and 0.01-0.05% of sodium silicate is used as the bleaching activator. S5 Second Cleaning Process: The bleached slurry is conveyed to the cleaning unit II 104 by the screw IV 1040 in the bleaching unit 103 of step S4. Cleaning water is sprayed into the cleaning unit II 104. The solid-liquid ratio of the bleached slurry and the cleaning water in step S4 is controlled to be 1:5 to 10, the cleaning temperature is 60 to 70°C, and the residence time is 3 to 5 minutes.

[0041] This is achieved through matching process parameters, such as screw speed (e.g., shear rate 100–500 s). - ¹) Temperature gradient (decolorization reaction temperature 80-120℃, first cleaning temperature 60-70℃, bleaching temperature 60-80℃, second cleaning temperature 60-70℃), pressure control (decolorization pressure 0.3-1.5MPa, bleaching pressure 0.8-1.2MPa), etc., shorten the decolorization and bleaching time by more than 50%, effectively improving the decolorization and bleaching efficiency; Furthermore, by controlling parameters such as screw speed, residence time, temperature, and pressure, the decolorization time is ensured to be ≤20min and the whiteness is ≥85% (ISO 2470 standard).

[0042] Example 8 This embodiment provides a specific implementation method, using 100kg of waste textiles containing indigo dyes as raw material to prepare recycled pulp, wherein the decolorization and bleaching process involved specifically includes: S1 Pretreatment: Shred waste textiles to a length of 0.2cm, add water, and prepare a slurry with a concentration of 30%; S2 Decolorization Treatment: The slurry is continuously fed into the decolorization unit 101 via the mixing unit 111. A 0.05 g / L ClO2 aqueous solution is added to the decolorization unit 101 for forced mixing. The mass ratio of slurry to ClO2 is controlled as follows: 1:0.05; the injection pressure of the porous injection head I1011 is 0.5 MPa; and the shear rate of the screw I1010 is 100 s⁻¹. -1 The decolorization reaction temperature was 50℃, the residence time was 10min, and the decolorized waste textile pulp with a whiteness of 67% was obtained. S3 First Cleaning Process: The decolorized slurry is conveyed to the cleaning unit I102 by the screw I1010. Cleaning water is sprayed into the cleaning unit I102. The solid-liquid ratio of the slurry after decolorization in step S2 to the cleaning water is 1:5, the cleaning temperature is 60℃, and the residence time is 3min. S4 Bleaching Treatment: The cleaned slurry is conveyed to the bleaching unit 103 through a pipeline. H2O2 is added to the bleaching unit 103 for bleaching. The H2O2 dosage is 0.05% of the dry weight of the waste textile slurry, and 0.01% sodium silicate is used as the bleaching activator. The injection pressure of the porous injection head II 1031 is 0.5 MPa, the bleaching temperature is 60℃, and the residence time is 2 min, resulting in bleached waste textile slurry with a whiteness of 72%. S5 Second Cleaning Process: The bleached slurry is conveyed to the cleaning unit II 104 by the screw IV 1040. Cleaning water is sprayed into the cleaning unit II 104. The solid-liquid ratio of the slurry after step S4 bleaching to the cleaning water is controlled at 1:5, the cleaning temperature is 60℃, and the residence time is 3min, resulting in 96kg of slurry with a whiteness of 75%.

[0043] Example 9 Based on Example 8, this example differs in that: a 0.10 g / L ClO2 aqueous solution is added to the decolorization unit 101, otherwise the same as in Example 8. The whiteness of the resulting decolorized waste textile slurry is as follows: Figure 4 As shown.

[0044] Example 10 Based on Example 8, this example differs in that: a 0.14 g / L ClO2 aqueous solution is added to the decolorization unit 101, otherwise the same as in Example 8. The whiteness of the resulting decolorized waste textile slurry is as follows: Figure 4 As shown.

[0045] Example 11 Based on Example 8, this example differs in that: a 0.18 g / L ClO2 aqueous solution is added to the decolorization unit 101, otherwise the same as in Example 8. The whiteness of the resulting decolorized waste textile slurry is as follows: Figure 4 As shown.

[0046] Example 12 Based on Example 8, this example differs in that: a 0.22 g / L ClO2 aqueous solution is added to the decolorization unit 101, otherwise the same as in Example 8. The whiteness of the resulting decolorized waste textile slurry is as follows: Figure 4 As shown.

[0047] Example 13 Based on Example 8, this example differs in that: a 0.26 g / L ClO2 aqueous solution is added to the decolorization unit 101; otherwise, it is the same as in Example 8. The whiteness of the resulting decolorized waste textile slurry is as follows: Figure 4 As shown.

[0048] Example 14 This embodiment provides a specific implementation method, using 100kg of waste textiles containing indigo dyes as raw material to prepare recycled pulp, wherein the decolorization and bleaching process involved specifically includes: S1 Pretreatment: Shred waste textiles to a length of 1cm, add water, and prepare a slurry with a concentration of 10%; S2 Decolorization Treatment: The slurry is continuously fed into the decolorization unit 101 via the mixing unit 111. A 0.5 g / L ClO2 aqueous solution is added to the decolorization unit 101 for forced mixing. The mass ratio of slurry to ClO2 is controlled at 1:0.2. The injection pressure of the porous injection head I1011 is 3.0 MPa, and the shear rate of the screw I1010 is 500 s⁻¹. -1 The decolorization reaction temperature was 60℃, the residence time was 20min, and the decolorized waste textile pulp with a whiteness of 50% was obtained. S3 First Cleaning Process: The decolorized slurry is conveyed to the cleaning unit I102 by the screw I1010. Cleaning water is sprayed into the cleaning unit I102. The solid-liquid ratio of the slurry after decolorization in step S2 to the cleaning water is 1:10, the cleaning temperature is 70℃, and the residence time is 5min. S4 Bleaching Treatment: The cleaned slurry is conveyed to the bleaching unit 103 through a pipeline. H2O2 is added to the bleaching unit 103 for bleaching. The H2O2 dosage is 1.0% of the dry weight of the waste textile slurry, and 0.05% sodium silicate is used as the bleaching activator. The injection pressure of the porous injection head II 1031 is 3.0 MPa, the bleaching temperature is 80℃, and the residence time is 10 min, resulting in bleached waste textile slurry with a whiteness of 71%. S5 Second Cleaning Process: The bleached slurry is conveyed to the cleaning unit II 104 by the screw IV 1040. Cleaning water is sprayed into the cleaning unit II 104. The solid-liquid ratio of the slurry after step S4 bleaching to the cleaning water is controlled to be 1:10, the cleaning temperature is 70℃, and the residence time is 5min, resulting in 97kg of slurry with a whiteness of 73%.

[0049] Example 15 This embodiment provides a specific implementation method, using 100kg of waste textiles containing indigo dyes as raw material to prepare recycled pulp, wherein the decolorization and bleaching process involved specifically includes: S1 Pretreatment: Shred waste textiles to a length of 0.6cm, add water, and prepare a slurry with a concentration of 20%; S2 Decolorization Treatment: The slurry is continuously fed into the decolorization unit 101 via the mixing unit 111. 3 kg of sodium hydrosulfite is added to the decolorization unit 101 for forced mixing. The mass ratio of slurry to sodium hydrosulfite is controlled at 1:0.1. The injection pressure of the porous injection head I1011 is 2.0 MPa, and the shear rate of the screw I1010 is 320 s⁻¹. -1 The decolorization reaction temperature was 70℃, the residence time was 15min, and the decolorized waste textile pulp with a whiteness of 47% was obtained. S3 First Cleaning Process: The decolorized slurry is conveyed to the cleaning unit I102 by the screw I1010. Cleaning water is sprayed into the cleaning unit I102. The solid-liquid ratio of the slurry after decolorization in step S2 to the cleaning water is 1:8, the cleaning temperature is 65℃, and the residence time is 4min. S4 Bleaching Treatment: The cleaned slurry is conveyed to the bleaching unit 103 through a pipeline. H2O2 is added to the bleaching unit 103 for bleaching. The H2O2 dosage is 0.6% of the dry weight of the waste textile slurry, and 0.03% sodium silicate is used as the bleaching activator. The injection pressure of the porous injection head II 1031 is 2.0 MPa, the bleaching temperature is 70℃, and the residence time is 6 min, resulting in bleached waste textile slurry with a whiteness of 77%. S5 Second Cleaning Process: The bleached slurry is conveyed to the cleaning unit II 104 by the screw IV 1040. Cleaning water is sprayed into the cleaning unit II 104. The solid-liquid ratio of the slurry after step S4 bleaching to the cleaning water is controlled at 1:8, the cleaning temperature is 65℃, and the residence time is 4min, resulting in 98kg of slurry with a whiteness of 78%.

[0050] Compare with Example 1 Based on Example 8, the difference in this comparative example is that in the S2 decolorization process, decolorization temperatures of 30°C, 40°C, 60°C and 70°C are used respectively, while the rest is the same as in Example 8.

[0051] The results are as follows Figure 5 As shown in the figure. Therefore, it can be concluded that 40–60℃ is the suitable temperature for decolorization, ensuring the decolorization effect while saving energy. Below 40℃, the reaction is incomplete; above 60℃, the excessive temperature accelerates the decomposition of chlorine dioxide, resulting in a worse decolorization effect and wasted energy.

[0052] Compare with Example 2 Based on Example 15, the difference in this comparative example is that in the S2 decolorization treatment, the ratio of slurry and decolorizing agent is changed, and 1 kg, 2 kg, 4 kg and 5 kg of sodium hydrosulfite are used respectively, while the rest is the same as in Example 15.

[0053] Then, the whiteness of the slurry after the first cleaning treatment and the slurry after the second cleaning treatment were tested, and the results are shown in Table 1.

[0054] Table 1

[0055] Therefore, it can be seen that when the dosage of the bleaching agent (sodium hydrosulfite) is 2.0% to 4.0% of the dry weight of the waste textile sizing agent, the whiteness of the treated product can be guaranteed and the cost controlled. If the dosage of the bleaching agent is insufficient, the bleaching will be incomplete and the bleaching effect will be poor; while if the dosage of the bleaching agent is excessive, the cost will increase.

[0056] Compare with Example 3 Based on Example 15, the difference in this comparative example is that in the S2 decolorization process, decolorization temperatures of 50°C, 60°C, 80°C and 90°C are used respectively, while the rest is the same as in Example 15.

[0057] The results are as follows Figure 6 As shown. Therefore, it can be seen that 60-80℃ is the suitable temperature for decolorization. Below 60℃, the reaction is insufficient and the decolorization effect is poor; above 80℃, the temperature is too high, which accelerates the decomposition of hydrogen peroxide, thus making the bleaching effect worse and increasing energy consumption.

[0058] Compare with Example 4 Based on Example 15, the difference in this comparative example is that: in the first cleaning process of S3, cleaning temperatures of 35°C, 45°C, 55°C, 75°C, and 85°C are also used, while the rest is the same as in Example 15.

[0059] Then, the whiteness of the slurry after the first cleaning treatment and the slurry after the second cleaning treatment were tested, and the results are shown in Table 2.

[0060] Table 2

[0061] As shown in Table 2, it can be seen that 60-70℃ is the suitable temperature for decolorization. When the temperature of the washing water is below 60℃, the indigo dye will recolor, and the decolorization effect will be poor; when it is above 70℃, it will cause waste of resources and increase costs.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A decolorizing and bleaching machine for preparing recycled pulp from waste textiles, characterized in that, The device includes a housing (100) and a decolorizing unit (101), a cleaning unit I (102), a bleaching unit (103) and a cleaning unit II (104) disposed within the housing (100). The decolorizing unit (101), the cleaning unit I (102), the bleaching unit (103) and the cleaning unit II (104) are arranged sequentially in the direction of conveying waste textile materials. The decolorizing unit (101) is equipped with screw I (1010), and the cleaning unit I (102) is equipped with screw II (1020). Screw I (1010) and screw II (1020) are connected. The decolorizing unit (101) and the cleaning unit I (102) are connected to each other, and the two form a decolorizing subsystem. The bleaching unit (103) is equipped with screw III (1030), and the cleaning unit II (104) is equipped with screw IV (1040). Screw III (1030) and screw IV (1040) are connected. The bleaching unit (103) and the cleaning unit II (104) are connected to form a bleaching subsystem. The decolorization subsystem and the bleaching subsystem are connected by a pipe. A continuous pathway for the transfer, mixing, decolorization, bleaching and cleaning of waste textile pulp is formed between the decolorization unit (101), the cleaning unit I (102), the pipeline, the bleaching unit (103) and the cleaning unit II (104).

2. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 1, characterized in that, In the decolorizing unit (101), there are porous injection heads I (1011) evenly distributed along the axial direction of screw I (1010). The porous injection heads I (1011) are located at the top of the decolorizing unit (101). The diameter of the porous injection head I (1011) is 0.2 to 1.0 mm. The porous injection head I (1011) is connected to the decolorizing agent storage tank (2) through the decolorizing agent pipeline (5). The top of the cleaning unit I (102) is equipped with a spray mechanism I (1021), which is distributed along the axial direction of the screw II (1020). A flow meter I is provided on the spray mechanism I (1021), and a speed sensor I is provided on the screw II (1020). The flow meter I and the speed sensor I are interlocked by an electrical signal.

3. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 1, characterized in that, In the bleaching unit (103), there are porous injection heads II (1031) evenly distributed along the axial direction of screw III (1030). The porous injection heads II (1031) are located at the top of the bleaching unit (103). The diameter of the porous injection heads II (1031) is 0.2 to 1.0 mm. The porous injection heads II (1031) are connected to the bleaching agent storage tank (3) through the bleaching agent pipeline (7). The top of the cleaning unit II (104) is equipped with a spray mechanism II (1041). The spray mechanism II (1041) is distributed along the axial direction of the screw IV (1040). A flow meter II is provided on the spray mechanism II (1041), and a speed sensor II is provided on the screw IV (1040). The flow meter II and the speed sensor II are interlocked by an electrical signal.

4. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 2 or 3, characterized in that, Screw I (1010) and screw II (1020) are connected by a coupling, and screw III (1030) and screw IV (1040) are connected by a coupling. Screw I (1010), screw II (1020), screw III (1030) and screw IV (1040) all use staggered thread elements, and the pitch of the thread elements is 0.5 to 1.2 times the screw diameter.

5. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 2 or 3, characterized in that, Screw I (1010) and screw II (1020) are integrally formed, and screw III (1030) and screw IV (1040) are integrally formed; screw I (1010), screw II (1020), screw III (1030) and screw IV (1040) all adopt staggered thread elements, and the pitch of the thread elements is 0.5 to 1.2 times the screw diameter.

6. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 1, characterized in that, The housing (100) is provided with a feeding hopper (110) that communicates with the decolorization unit (101), the feeding hopper (110) is provided with a mixing unit (111), and the feeding hopper (110) is provided with a feeding port (113) that communicates with the mixing unit (111).

7. The decolorizing and bleaching machine for preparing recycled pulp from waste textiles according to claim 1, characterized in that, The outer side of the housing (100) is provided with a heat insulation jacket, and a temperature sensor is provided on the heat insulation jacket; a temperature regulating inlet pipe is connected to one side of the heat insulation jacket, and a temperature regulating outlet pipe is connected to the other side; a temperature control valve is provided on the temperature regulating inlet pipe, and the temperature control valve and the temperature sensor are interlocked by an electrical signal. The housing (100) is also provided with an exhaust port I (1000) connected to the decolorization unit (101) and an exhaust port II (1001) connected to the bleaching unit (103). An exhaust control valve I (1002) is fitted in the exhaust port I (1000) and an exhaust control valve II (1003) is fitted in the exhaust port II (1001). The decolorization unit (101) is equipped with a pressure sensor I, and the pressure sensor I is interlocked with the exhaust control valve I (1002) by an electrical signal; The bleaching unit (103) is equipped with a pressure sensor II, and the pressure sensor II is interlocked with the exhaust control valve II (1003) by an electrical signal; pH sensors are distributed on the housing (100); The housing (100) is also equipped with a slurry concentration detector.

8. A continuous and efficient decolorization and bleaching system for preparing recycled pulp from waste textiles, characterized in that, The bleaching machine (1), decolorizing agent storage tank (2), bleaching agent storage tank (3), and water storage tank (4) are described in any one of claims 1-7, wherein the decolorizing agent storage tank (2) is connected to the decolorizing unit (101) in the bleaching machine (1) through a decolorizing agent pipeline (5), and a decolorizing agent control valve I (6) is provided on the decolorizing agent pipeline (5); The bleaching agent storage tank (3) is connected to the bleaching unit (103) in the decolorizing bleaching machine (1) through the bleaching agent pipeline (7), and the bleaching agent pipeline (7) is equipped with a bleaching agent control valve (8). The water storage tank (4) is connected to the cleaning unit I (102) in the decolorizing and bleaching machine (1) through the cleaning water inlet pipe I (9), and the cleaning control valve I (10) is provided on the cleaning water inlet pipe I (9); the water storage tank (4) is also connected to the cleaning unit II (104) in the decolorizing and bleaching machine (1) through the cleaning water inlet pipe II (11), and the cleaning control valve II (12) is provided on the cleaning water inlet pipe II (11).

9. The continuous and efficient decolorization and bleaching system for preparing recycled pulp from waste textiles according to claim 8, characterized in that, The decolorization and bleaching system is connected to a waste liquid recovery system (13). The cleaning unit I (102) and cleaning unit II (104) in the decolorization and bleaching machine (1) are both connected to the waste liquid recovery system (13). The waste liquid recovery system (13) includes a membrane separation device.

10. A continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles, characterized in that, The decolorizing and bleaching machine (1) according to any one of claims 1-7, or the decolorizing and bleaching system according to claim 8 or 9, comprises the following steps: S1 Pretreatment: Crush waste textiles, add water, and adjust the slurry concentration to 10-30%; S2 Decolorization Treatment: The slurry after the pretreatment in step S1 is continuously fed into the decolorization unit (101) through the mixing unit (111). A decolorizing agent is added into the decolorization unit (101) and forced mixing is performed. The injection pressure of the porous injection head I (1011) is 0.5-3.0 MPa, and the shear rate of the screw I (1010) is 100-500 s. -1 The decolorization reaction temperature is 40-80℃, and the residence time is 10-20 min, to obtain a decolorized waste textile sizing agent with a whiteness ≥65%. S3 First cleaning process: The slurry after decolorization is conveyed to the cleaning unit I (102) by the screw I (1010) in the decolorization unit (101) of step S2. Cleaning water is sprayed into the cleaning unit I (102). The cleaning temperature is controlled to be 60-70℃ and the residence time is 3-5min. S4 Bleaching Treatment: The slurry after cleaning in step S3 is conveyed to the bleaching unit (103) through the pipeline. Bleaching agent is added to the bleaching unit (103) for bleaching. The injection pressure of the multi-hole injection head II (1031) is 0.5-3.0 MPa, the bleaching temperature is 60-80℃, and the residence time is 2-10 min to obtain bleached waste textile slurry with a whiteness ≥85%. S5 Second cleaning process: The bleached slurry is conveyed to the cleaning unit II (104) by the screw IV (1040) in the bleaching unit (103) of step S4. Cleaning water is sprayed into the cleaning unit II (104). The cleaning temperature is controlled at 60-70℃ and the residence time is 3-5 minutes.

11. The continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles according to claim 10, characterized in that, In step S2, the mass ratio of the slurry after the pretreatment in step S1 to the decolorizing agent is 1:0.05 to 0.

2.

12. The continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles according to claim 10, characterized in that, In step S3, the solid-liquid ratio of the slurry after decolorization in step S2 to the washing water is 1:5 to 10. In step S5, the solid-liquid ratio of the slurry after bleaching in step S4 to the washing water is 1:5 to 10.

13. The continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles according to claim 10, characterized in that, The decolorizing agent is an oxidizing agent or a reducing agent; The oxidizing agent is an aqueous solution of ClO2 with a concentration of 0.05–0.5 g / L; The reducing agent is sodium hydrosulfite, and the dosage is 2.0 to 4.0% of the dry weight of the waste textile sizing agent.

14. The continuous and efficient decolorization and bleaching process for preparing recycled pulp from waste textiles according to claim 10, characterized in that, The bleaching agent is H2O2, and the amount of H2O2 used is 0.05-1.0% of the dry weight of the waste textile sizing agent, and 0.01-0.05% sodium silicate is used as the bleaching activator.

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