Decoloring and bleaching machine and system suitable for preparing recycled pulp from waste textiles

Abstract

The utility model discloses be applicable to with the preparation recovery pulp technology's decoloring bleaching machine and system of waste and old textile belongs to waste and old textile recycling technical field. Among them, decoloring bleaching machine includes casing, decoloring unit, cleaning unit I, bleaching unit and cleaning unit II, and decoloring unit, cleaning unit I, bleaching unit and cleaning unit II are sequentially arranged in the conveying direction of waste and old textile material, wherein, by adopting the decoloring bleaching machine of sectional type screw rod structure, process unit integration, realize the continuous efficient decoloring bleaching of waste and old textile under the condition of medium high concentration (10~30%) of waste and old textile material, reduce chemical reagent and water resource consumption, reduce energy consumption, shorten technological process to satisfy the process requirement.

Description

Technical Field

[0001] This utility model relates to a decolorizing and bleaching machine and system, specifically to a decolorizing and bleaching machine and system applicable to the process of preparing recycled pulp from waste textiles, belonging to the field of waste textile recycling technology. Background Technology

[0002] With people's growing awareness of environmental protection and the promotion of recycling and reuse of recyclable materials, some textile factories are recycling, processing and reusing waste textiles (waste yarn, waste fiber, scraps, etc.) in order to achieve a green economy and a circular economy.

[0003] Currently, the processing of waste textiles generally includes impurity removal, sorting, crushing, separation, dispersion, decolorization and bleaching, washing, impregnation, pressing, and cooking, ultimately forming a recycled pulp that meets the requirements for fiber production. However, in the decolorization and bleaching of waste textiles, conventional decolorization and bleaching machines (such as reaction kettles) are generally used, as shown in CN116949798A, CN116856192A, and CN220284471U. This involves directly adding decolorizing and bleaching agents into the decolorization and bleaching machine to carry out the decolorization and bleaching reaction. Such decolorization often needs to be carried out at a low material concentration (<5%), which leads to high energy consumption, large chemical consumption, and insufficient purity of the final recycled pulp. In addition, existing decolorization and bleaching machines are difficult to achieve continuous production, limiting the industrial efficiency of the process for preparing recycled pulp from waste textiles. Summary of the Invention

[0004] To overcome the limitations of existing technologies in the decolorization and bleaching process of preparing recycled pulp from waste textiles, which typically only handles low-concentration (<5%) waste textile materials (specifically, waste textile pulp formed after crushing, separation, dispersion, and water addition), resulting in high energy consumption, large chemical consumption, and poor quality of the obtained recycled pulp product; and to address the inability to achieve continuous production, which seriously affects the efficiency of industrial-scale recycled pulp preparation, a decolorization and bleaching machine and system suitable for the process of preparing recycled pulp from waste textiles is proposed.

[0005] This technical solution proposes a decolorizing and bleaching machine with a segmented screw structure and integrated process units. This machine enables continuous and efficient decolorizing and bleaching of waste textiles under medium-to-high concentration (10-30%) conditions, reducing the consumption of chemical agents and water resources, lowering energy consumption, and shortening the process flow to meet 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 suitable for the process of 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 implemented: decolorization time ≤ 20 min, temperature 40~80℃, and slurry whiteness ≥ 65% (according to ISO 2470 standard); the pore diameter of the multi-hole injection head I is 0.2~1.0 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 recycled by a membrane separation device to recover the decolorizing agent, with a reuse rate of ≥80%. Bleaching unit: It is equipped with a screw III, and multi-hole injection heads II are evenly distributed along the axial direction of the screw III. The multi-hole injection heads II 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 0.2-1.0 mm, the injection pressure is 0.5-3.0 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 implemented: bleaching time ≤ 10 min, temperature 60~80℃, and pulp whiteness ≥ 85% (according to ISO 2470 standard); the orifice diameter 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. Alternatively, screw I and screw II can be integrally formed, and screw III and screw IV can be 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.

[0012] 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.

[0013] The second objective of this technical solution is to provide: a decolorizing and bleaching system suitable for the process of preparing recycled pulp from waste textiles, including 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.

[0014] 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.

[0015] 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.

[0016] 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 utility model based on the specific circumstances.

[0017] The beneficial technical effects of adopting this technical solution are as follows: I. In this utility model, the decolorizing and bleaching machine, through the integrated design of screw and process unit, breaks through the limitations of traditional single reactor. While continuously processing the slurry (transfer, mixing, decolorizing, bleaching and washing), it realizes continuous material transfer and efficient mixing, ensuring the smooth progress of the waste textile recycling process. Furthermore, the strong shearing force of the segmented screw can process medium to high concentration (10-30%) slurries while continuously processing them (transferring, mixing, decolorizing, bleaching and cleaning), breaking through the limitation of existing technologies that can only process low concentration slurries, and effectively reducing water consumption (by 40-70%). In addition, it can achieve efficient degradation of indigo dye: it also utilizes the local high temperature (up to 120°C) and high pressure (2.0 MPa) environment generated by screw extrusion, that is, local high temperature and high pressure to enhance the reaction, accelerate the degradation of indigo molecules in indigo dyes, and improve the decolorization efficiency by more than 50%. Second, this utility model adopts a multi-step reaction process unit integration (completing conveying, mixing, decolorization, bleaching, and cleaning separately), reducing the energy consumption of traditional multi-step processes. Furthermore, the design of the decolorization and bleaching machine achieves low maintenance costs: the equipment is easy to start, and the damage level of threaded components and the inner bushing of the barrel can be detected at any time, allowing for effective inspection and replacement, reducing unnecessary consumption caused by problems during production; Third, in this utility model, based on the specific arrangement of the decolorizing and bleaching machine, the decolorizing agent storage tank, the bleaching agent storage tank and the water storage tank, the decolorizing and bleaching process is ensured to proceed smoothly and stably, and ultimately, continuous production is achieved, ensuring the efficiency of industrial-scale preparation of recycled pulp, etc. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the decolorizing and bleaching machine in this utility model; Figure 2 This is a schematic diagram illustrating the working principle of the decolorization and bleaching system in this utility model; 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

[0019] The technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0020] 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.

[0021] Example 1 This embodiment provides: a decolorizing and bleaching machine 1 suitable for the process of 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 a multi-hole injection head I 1011 at its top. The multi-hole injection heads I 1011 are equidistantly distributed along the axial direction of the screw I 1010 and are connected to a decolorizing agent pipeline 5. The cleaning unit I 102 is equipped with a screw II 1020 and a spray mechanism I 1021 at its top. The spray mechanism I 1021 is distributed along the axial direction of the screw II 1020 and is connected to a cleaning water inlet pipe I 9. The decolorizing unit 101 and the cleaning unit I 102 are connected to each other, forming a decolorizing subsystem. The bleaching unit 103 is equipped with a screw III 1030, and a multi-hole injection head II 1031 is provided at the top of the bleaching unit 103. The multi-hole injection head II 1031 is equidistantly distributed along the axial direction of the screw III 1030, and the multi-hole injection head II 1031 is connected to the bleaching agent pipeline 7. The cleaning unit II 104 is equipped with a screw IV 1040, and a spray mechanism II 1041 is provided at the top of the cleaning unit II 104. The spray mechanism II 1041 is distributed along the axial direction of the screw IV 1040, and the spray mechanism II 1041 is connected to the cleaning water inlet pipe II 11. 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 conveying, mixing, decolorizing, bleaching, and cleaning of waste textile materials is formed between the decolorizing unit 101, the cleaning unit I 102, the pipe-through unit, the bleaching unit 103, and the cleaning unit II 104.

[0022] 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.

[0023] Example 2 Based on Example 1, this example further defines the decolorization subsystem to further illustrate the technical solution.

[0024] like Figure 2 As shown, in the decolorization unit 101, the pore size of the porous injection head I 1011 is 0.2 to 1.0 mm, which is conducive to precise control of the amount of decolorizing agent entering, thereby ensuring the degree and effect of decolorization; In the cleaning unit Ⅰ102, 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 and the speed of the screw Ⅲ1030 are dynamically matched. 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.

[0025] Example 3 Based on Examples 1-2, this example further defines the bleaching subsystem to further illustrate the technical solution.

[0026] In the bleaching unit 103, the pore size of the porous injection head II 1031 is 0.2 to 1.0 mm, which is conducive to precise control of the amount of bleaching agent entering, thereby ensuring the degree and effect of debleaching; A spray mechanism II1041 is installed at the top of the cleaning unit II104. A flow meter II is installed on the spray mechanism II1041, and a speed sensor II is installed on the screw IV1040. 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 and the speed of the screw IV1040 are dynamically matched. Both screws III 1030 and IV 1040 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, 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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. Preferably, there are four pH sensors, which are respectively distributed in the decolorization unit 101, cleaning unit I 102, bleaching unit 103 and cleaning unit II 104, for detecting the pH value in each process unit; The housing 100 is also equipped with slurry concentration detectors, such as online near-infrared moisture detectors, specifically the XKCON-NIR-MA series. Preferably, there are four slurry concentration detectors, respectively distributed in the decolorization unit 101, cleaning unit I 102, bleaching unit 103 and cleaning unit II 104, for detecting the slurry concentration in each process unit; 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.

[0031] Example 6 Based on Examples 1-5, this example provides a decolorizing and bleaching system suitable for the process of preparing recycled pulp from waste textiles, including the aforementioned decolorizing and bleaching machine 1, decolorizing agent storage tank 2, bleaching agent storage tank 3, and water storage tank 4. The decolorizing agent storage tank 2 is connected to the decolorizing unit 101 in the decolorizing and bleaching machine 1 via a decolorizing agent pipeline 5, and a decolorizing agent control valve I6 is installed on the decolorizing agent pipeline 5. The bleaching agent storage tank 3 is connected to the bleaching unit 103 in the decolorizing and bleaching machine 1 via a bleaching agent pipeline 7, and a bleaching agent control valve 8 is installed on the bleaching agent pipeline 7. The water storage tank 4 is connected to the cleaning unit I102 in the decolorizing and bleaching machine 1 via a cleaning water inlet pipe I9, and a cleaning control valve I10 is installed on the cleaning water inlet pipe I9. The water storage tank 4 is also connected to the cleaning unit II104 in the decolorizing and bleaching machine 1 via a cleaning water inlet pipe II11, and a cleaning control valve II12 is installed on the cleaning water inlet pipe II11.

[0032] In addition, the decolorization 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.

[0033] Example 7 Based on Examples 1-6, this example provides a decolorization and bleaching process suitable for preparing recycled pulp from waste textiles, using the above-mentioned decolorization and bleaching machine or the above-mentioned decolorization and bleaching system, including 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 via the mixing unit. A decolorizing agent is added to the decolorization unit, 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 I is 0.5-3.0 MPa; and the shear rate of screw I 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 by the screw I in the decolorization unit of step S2. Cleaning water is sprayed into the cleaning unit I. 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 the cleaning treatment in step S3 is conveyed to the bleaching unit through the pipeline. Bleaching agent is added to the bleaching unit for bleaching. The injection pressure of the multi-hole injection head II 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 by the screw IV in the bleaching unit of step S4. Cleaning water is sprayed into the cleaning unit II. The solid-liquid ratio of the bleached slurry to 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.

[0034] 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). In this solution, by 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℃), and pressure control (decolorization pressure 0.3–1.5 MPa, bleaching pressure 0.8–1.2 MPa), the decolorization and bleaching time is shortened by more than 50%, effectively improving the decolorization and bleaching efficiency. The decolorizing agent can be either an oxidizing agent or a reducing agent. The choice of decolorizing agent can be 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 dosage 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.

[0035] The bleaching agent is H2O2, and the amount of H2O2 used is 0.05-1.0% of the dry weight of the pulp. Sodium silicate is used as the bleaching activator at a concentration of 0.01-0.05%. With the addition of the bleaching activator, the brightness of the pulp increases by approximately 2%. The mechanisms involved 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.

[0036] 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 ⁻ ion reduces 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.

[0037] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model 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 utility model should be included within the protection scope of the present utility model.

Claims

1. A decolorizing and bleaching machine suitable for the process of 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 a screw I (1010) and a multi-hole injection head I (1011) at the top of the decolorizing unit (101). The multi-hole injection heads I (1011) are equidistantly distributed along the axial direction of the screw I (1010) and are connected to a decolorizing agent pipeline (5). The cleaning unit I (102) is equipped with a screw II (1020) and a spray mechanism I (1021) at the top of the cleaning unit I (102). The spray mechanism I (1021) is distributed along the axial direction of the screw II (1020) and is connected to a cleaning water inlet pipe I (9). The decolorizing unit (101) and the cleaning unit I (102) are connected to each other and form a decolorizing subsystem. The bleaching unit (103) is equipped with a screw III (1030) and a multi-hole injection head II (1031) at the top of the bleaching unit (103). The multi-hole injection head II (1031) is equidistantly distributed along the axial direction of the screw III (1030) and is connected to a bleaching agent pipeline (7). The cleaning unit II (104) is equipped with a screw IV (1040) and a spray mechanism II (1041) at the top of the cleaning unit II (104). The spray mechanism II (1041) is distributed along the axial direction of the screw IV (1040) and is connected to a cleaning water inlet pipe II (11). The bleaching unit (103) and the cleaning unit II (104) are connected to each other and form a bleaching subsystem. The decolorization subsystem and the bleaching subsystem are connected by a pipe. A continuous pathway for the conveying, mixing, decolorizing, bleaching and cleaning of waste textile materials is formed between the decolorizing unit (101), the cleaning unit I (102), the pipe-connecting and bleaching unit (103) and the cleaning unit II (104).

2. The decolorizing and bleaching machine according to claim 1, applicable to the process of preparing recycled pulp from waste textiles, is characterized in that, The pore size of the porous injection head I (1011) is 0.2 to 1.0 mm.

3. The decolorizing and bleaching machine according to claim 1, applicable to the process of preparing recycled pulp from waste textiles, is characterized in that, The spray mechanism I (1021) is equipped with a flow meter I, and the screw II (1020) is equipped with a speed sensor I. The flow meter I and the speed sensor I are interlocked by an electrical signal.

4. The decolorizing and bleaching machine according to claim 1, applicable to the process of preparing recycled pulp from waste textiles, is characterized in that, The pore size of the porous injection head II (1031) is 0.2 to 1.0 mm.

5. The decolorizing and bleaching machine according to claim 1, applicable to the process of preparing recycled pulp from waste textiles, is characterized in that, The spray mechanism II (1041) is equipped with a flow meter II, and the screw IV (1040) is equipped with a speed sensor II. The flow meter II and the speed sensor II are interlocked by an electrical signal.

6. The decolorizing and bleaching machine according to claim 1, applicable to the process of preparing recycled pulp from waste textiles, is 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; a pH value sensor and a slurry concentration detector are distributed on the housing (100).

7. The decolorizing and bleaching machine according to claim 1 or 6, applicable to the process of preparing recycled pulp from waste textiles, characterized in that, 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 sleeved in the exhaust port I (1000) and an exhaust control valve II (1003) is sleeved 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) by an electrical signal.

8. The decolorizing and bleaching machine according to claim 7, applicable to the process of preparing recycled pulp from waste textiles, is characterized in that, 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; 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; Alternatively, screw I (1010) and screw II (1020) may be integrally formed, and screw III (1030) and screw IV (1040) may be integrally formed.

9. A decolorization and bleaching system suitable for the process of preparing recycled pulp from waste textiles, characterized in that, It includes a decolorizing bleaching machine (1), a decolorizing agent storage tank (2), a bleaching agent storage tank (3), and a water storage tank (4) as described in any one of claims 1-8. The decolorizing agent storage tank (2) is connected to the decolorizing unit (101) in the decolorizing bleaching machine (1) through the decolorizing agent pipeline (5), and the decolorizing agent pipeline (5) is equipped with a decolorizing agent control valve I (6). 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).

10. The decolorization and bleaching system according to claim 9, applicable to the process of preparing recycled pulp from waste textiles, 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.

Images