Cascade recycling device for papermaking wastewater

Abstract

The invention belongs to the field of waste water recycling, and particularly relates to a papermaking waste water stepped recycling device which comprises an evaporation box and a spiral extrusion dehydrator, a plurality of evaporation tables are arranged in the evaporation box and are vertically arranged at equal intervals, an exhaust valve is fixedly connected to the top of the evaporation box, and the exhaust valve is fixedly connected to the bottom of the evaporation box. A mixing tank is arranged on one side of the evaporation box, a steam valve used for inputting and outputting steam is fixedly connected to the outer side of the evaporation box, a concentrated liquid valve is installed at the bottom of the evaporation box, through the arrangement, papermaking wastewater can be rapidly and efficiently recycled in a stepped mode, and in the recycling work of a large paper mill, large-size wastewater can be rapidly treated; in the method, all solid filter residues and concentrated liquid are finally converted into fuel to be burnt, so that the biggest pain point of sludge treatment is fundamentally bypassed; and waste materials which are difficult to utilize originally are effectively utilized, so that the effect of making the best use of materials is achieved.

Description

A cascade recycling device for papermaking wastewater Technical Field

[0001] This invention belongs to the field of wastewater recycling, specifically a cascade recycling device for papermaking wastewater. Background Technology

[0002] Papermaking wastewater refers to the wastewater generated during the paper production process, mainly from the pulping and papermaking stages. Its quality and quantity vary depending on the raw materials and processes, typically characterized by high organic matter concentration, high suspended solids content, and deep color. Papermaking wastewater cascade recycling is a resource recovery model based on water quality differences, recovering and utilizing wastewater at each stage. Its core concept is to divide the wastewater into "three gradients": White water (mainly containing fibers and fillers) is preferentially recovered through filtration and other technologies, directly reused in the pulping or papermaking system to maximize resource utilization; secondly, intermediate stage wastewater undergoes advanced treatment and is reused in washing and floor cleaning processes with lower water quality requirements. This generally adopts a "physicochemical pretreatment + biological treatment" process route, removing suspended solids through sedimentation and flotation, and then using anaerobic and aerobic biological methods to degrade organic pollutants to achieve compliant discharge or water resource recycling; finally, the remaining wastewater meets discharge standards or is further reused after advanced oxidation.

[0003] Traditional papermaking wastewater cascade recycling systems often employ primary physicochemical isolation treatment, secondary biochemical degradation treatment, and tertiary deep separation treatment to treat wastewater. This requires multiple processes and the coordinated operation of numerous large pieces of equipment to complete the recycling process. This not only occupies a large space due to the large number of devices, but also results in generally low treatment efficiency. When large volumes of wastewater are encountered, they cannot be treated promptly, leading to gradual wastewater accumulation. Furthermore, the biochemical system inevitably produces residual sludge, which has a high water content, contains harmful substances, and incurs high disposal costs, placing a significant burden on environmental protection.

[0004] Therefore, the present invention provides a cascade recycling device for papermaking wastewater. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: A cascade recycling device for papermaking wastewater, comprising an evaporator and a screw extrusion dewatering machine, wherein the evaporator has multiple evaporation platforms arranged vertically at equal intervals, an exhaust valve is fixed to the top of the evaporator, a mixing tank is located on one side of the evaporator, a steam valve for inputting and outputting steam is fixed to the outside of the evaporator, and a concentrate valve is installed at the bottom of the evaporator. This configuration allows for rapid and efficient cascade recycling of papermaking wastewater, enabling the rapid processing of large volumes of wastewater in large paper mills. Furthermore, traditional methods generate large amounts of difficult-to-dispose-of residual sludge, while this method converts all solid filter residue and concentrate into fuel for combustion, fundamentally bypassing the major challenge of sludge disposal. It also effectively utilizes previously unusable waste materials, achieving maximum resource utilization. Moreover, traditional multi-stage filtration processes involve numerous and large pieces of equipment with low integration and a large footprint, which is unfavorable for production needs. This device has high integration, a small footprint, and is suitable for various types of production workshops.

[0007] Preferably, the evaporation platform has a hole in the middle, and the diameter of the holes in multiple evaporation platforms increases from top to bottom. The middle part of the evaporation platform can move up and down. During operation, multiple evaporation platforms can work simultaneously or in batches. When working simultaneously, an appropriate amount of primary wastewater is injected into the surface of each evaporation platform. At high temperature, the water in the primary wastewater evaporates and moves upward, and is discharged outward through the exhaust valve. After a period of time, the middle parts of all evaporation platforms are moved downward, so that the top surface of the evaporation platform forms a tilted downward and inward shape, allowing the still fluid concentrate to move towards the central hole and finally flow to the bottom of the evaporation tank to complete the collection of the concentrate. When working in batches, the wastewater on the surface of multiple evaporation platforms is in different states, namely, adding, just added, evaporating, evaporating finished, and discharging. In this way, multiple evaporation platforms can be tilted in sequence, so that the wastewater treatment process can be uninterrupted and the water storage pressure is reduced. The different hole design of the evaporation platforms can ensure that when the upper evaporation platform is tilted, the concentrate will not be poured into the lower evaporation platform.

[0008] Preferably, the evaporation platform is composed of multiple isolation pads, with adjacent isolation pads bonded and fixed together. The isolation pads are made of a high-temperature resistant flexible material. The cross-section of the evaporation chamber is polygonal. The outer edge of the isolation pads is fixed to the inner wall of the evaporation chamber. During operation, the center of the evaporation platform faces upwards during evaporation, allowing the waste liquid to be positioned above the evaporation platform. The center of the evaporation platform can be periodically raised and lowered to agitate the waste liquid above, ensuring uniform heating. The isolation pads can be made of PTFE fiberglass cloth, which can withstand temperatures exceeding 250 degrees Celsius and has a hydrophobic surface, making it less prone to sticking.

[0009] Preferably, multiple connecting rings are fixed between adjacent isolation pads, and steel cables are installed through the multiple connecting rings. One end of the steel cable is fixed to the inner wall of the evaporator, and the other end of the steel cable is fixed to a lifting ring that can move up and down. During operation, the lifting and lowering of the steel cable drives the connecting rings and isolation pads to move up and down. The steel cable is not fixed to the connecting rings. During the lifting and lowering process, the isolation pads can be relaxed and tightened. When the lifting ring moves to the highest and lowest positions, the isolation pads are fully tightened to ensure the discharge of the concentrate.

[0010] Preferably, a power platform is fixedly connected to the top of the evaporator, and a central column is fixedly connected to the bottom of the power platform. The central column is located inside the evaporator, and its diameter is smaller than the diameter of the holes in the evaporator. The lifting rings are slidably engaged with the outside of the central column. The power platform has multiple moving ends, all located inside the central column, and is connected to multiple lifting rings via transmission grooves. During operation, the power platform controls the lifting of different lifting rings to complete the shape transformation of the evaporator, ensuring the smooth operation of evaporation and discharge. Each output end of the power platform can be independently controlled to complete the independent operation of different lifting rings.

[0011] Preferably, the bottom of the evaporator is a bottom cover, the concentrate valve is fixed to the bottom of the bottom cover, a support platform is fixed to the outer side of the bottom of the bottom cover, multiple support frames are fixed between the bottom cover and the bottom of the central column, and steam pipes are fixed to both sides of the bottom cover. During operation, the support frames ensure the stability of the central column. It can not only fill the steam jacket of the evaporator with steam, but also directly introduce steam into the evaporator through the steam pipes to ensure rapid internal heating, accelerate the concentration process, and carry steam out quickly. Since the steam pipes are located on the bottom side, they will not affect the normal discharge of the concentrate.

[0012] Preferably, a vertical feeding pipe is provided on the outside of the evaporator, and a power pump is fixedly connected to the bottom of the feeding pipe. Multiple conveying pipes connected to the evaporator are fixedly connected to the outside of the feeding pipe. During operation, the power pump increases the power of the primary waste liquid being conveyed, and the waste liquid is conveyed to different evaporation platforms through the conveying pipes. This allows for both synchronous feeding and batch-by-batch uninterrupted feeding.

[0013] Preferably, the top of the screw extrusion dewatering machine is fixedly connected to a feeding frame, the inside of the mixing tank is equipped with a vibrating cylinder, the bottom of the vibrating cylinder is installed with a discharge valve, and a vibrating element is fixedly connected inside the mixing tank. The drive end of the vibrating element is connected to the vibrating cylinder. During operation, the wastewater to be treated is injected into the screw extrusion dewatering machine through the feeding frame. Multiple screw extrusion dewatering machines can be set up to achieve rapid solid-liquid separation. The bottom outlet of the screw extrusion dewatering machine is connected to a power pump to complete the primary wastewater transfer. The solid waste from the screw extrusion dewatering machine can be directly fed into a coal-fired furnace for combustion. The concentrated liquid discharged from the concentrated liquid valve is poured into the vibrating cylinder of the mixing tank in batches, and an appropriate amount of carbon powder is added. Alternatively, the solid waste from the screw extrusion dewatering machine can be crushed and mixed with the concentrated liquid. The mixture is coarsely mixed by the high-frequency vibration of the vibrating cylinder. Then, the mixed fuel is discharged from the bottom discharge valve and injected into the coal-fired furnace for combustion, thereby achieving the effect of comprehensive wastewater recycling.

[0014] Preferably, the mixing tank has a steam chamber inside, which is connected to one of the exhaust valves. A drain valve is installed at the bottom of the steam chamber. During operation, some of the steam discharged from the exhaust valve of the evaporator can be condensed and used, while some can be directly introduced into the steam chamber to maintain the high temperature of the mixing tank. This not only cools the steam to facilitate subsequent condensation but also evaporates the moisture in the mixture, increasing the calorific value. The water generated during heating is discharged through the drain valve and can be directly recycled.

[0015] Preferably, a spray gun is fixed to the inner ring of the mixing tank near the top, and the output end of the spray gun faces the inside of the vibrating cylinder. During operation, the spray gun is used to spray carbon powder into the vibrating cylinder to ensure the mixing of the two, and can also spray the crushed slag into the vibrating cylinder.

[0016] The beneficial effects of this invention are as follows: 1. The papermaking wastewater cascade recycling device of this invention, through the setting of evaporator and mixing tank, can quickly and efficiently recycle papermaking wastewater in stages. In the recycling work of large paper mills, it can quickly process large volumes of wastewater; and traditional methods will produce a large amount of difficult-to-dispose-of residual sludge, while in this method all solid filter residue and concentrate are eventually converted into fuel and burned, fundamentally bypassing the biggest pain point of sludge disposal; it also effectively utilizes the waste that was originally difficult to use, achieving the effect of making the most of resources; and in the traditional multi-stage filtration process, there are many large pieces of equipment, low integration, and a large footprint, which is not conducive to production needs. This equipment has a high degree of integration, a small footprint, and can be applied to various types of production workshops.

[0017] 2. The papermaking wastewater cascade recycling device of the present invention, through the setting of evaporation platforms, allows multiple evaporation platforms to work simultaneously or in batches. During simultaneous operation, an appropriate amount of primary wastewater is injected onto the surface of each evaporation platform. At high temperatures, the water in the primary wastewater evaporates and moves upwards, being discharged through an exhaust valve. After a period of time, the middle of all evaporation platforms is moved downwards, allowing the still-flowing concentrate to move towards the central hole and eventually flow to the bottom of the evaporation tank, completing the collection of the concentrate and enabling large-scale wastewater treatment at once. During batch operation, the wastewater on the surfaces of multiple evaporation platforms is in different states: adding, just added, evaporating, evaporating finished, and discharging. This allows multiple evaporation platforms to be tilted sequentially, ensuring uninterrupted wastewater treatment and reducing storage pressure. Attached Figure Description

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] Figure 1 is a perspective view of the present invention; Figure 2 is a perspective view of the evaporator of the present invention; Figure 3 is a cross-sectional view of the evaporator of the present invention; Figure 4 is a perspective view of the evaporation platform and bottom cover of the present invention; Figure 5 is a perspective view of the evaporation platform of the present invention; Figure 6 is a partial structural diagram of the evaporation platform of the present invention; Figure 7 is a cross-sectional view of the mixing tank of the present invention; In the figures: 1, evaporator; 2, screw extrusion dehydrator; 3, mixing tank; 4, feeding frame; 5, support platform; 6, bottom cover; 7, steam valve; 8, exhaust valve; 9, power platform; 10, feeding pipe; 11, conveying pipe; 12, concentrate valve; 13, power pump; 14, central column; 15, evaporation platform; 16, isolation pad; 17, steel cable; 18, lifting ring; 19, transmission groove; 20, connecting ring; 21, steam chamber; 22, vibrating cylinder; 23, unloading valve; 24, drain valve; 26, spray gun; 27, support frame; 28, steam pipe. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] As shown in Figures 1 to 7, the papermaking wastewater cascade recycling device of this embodiment includes an evaporator 1 and a screw press dewatering machine 2. The evaporator 1 has multiple evaporation platforms 15 arranged vertically at equal intervals. An exhaust valve 8 is fixed to the top of the evaporator 1, a mixing tank 3 is located on one side of the evaporator 1, and a steam valve 7 for inputting and outputting steam is fixed to the outside of the evaporator 1. A concentrate valve 12 is installed at the bottom of the evaporator 1. The papermaking wastewater to be treated is fed into the screw press dewatering machine 2. The screw press dewatering machine 2 uses rotation, extrusion, and centrifugation to compress large-volume waste materials in the wastewater into slag, which is discharged from one end. The primary wastewater after extrusion is discharged from the bottom. The discharged primary wastewater is fed into evaporator 1, and steam is introduced into steam valve 7 of evaporator 1 to raise the internal temperature to over 100 degrees Celsius. After being discharged into evaporator 1, the primary wastewater is spread evenly on evaporation platform 15 to increase the evaporation area. As the liquid in the primary wastewater gradually evaporates, the resulting steam rises and is discharged through exhaust valve 8. This steam can be condensed and used as industrial water and boiler feedwater. After a period of evaporation and concentration, the primary wastewater forms a concentrated liquid. The concentrated liquid is discharged downwards and transported through concentrated liquid valve 12. The slag produced by screw extrusion dewatering machine 2 is mainly composed of short fibers and pulp slag, with a high calorific value. The concentrated liquid mainly contains dissolved organic matter, such as lignin and hemicellulose. The wastewater contains vitamins, low-molecular-weight sugars, and some inorganic salts; it has a low calorific value and requires mixing with other substances with higher calorific value for combustion. The concentrated liquid needs to be mixed with substances with higher calorific value in mixing tank 3, such as charcoal powder. Then, the slag and the mixed concentrated liquid are fed into a coal-fired furnace for combustion, providing fuel. The resulting ash is mixed with the ash from normal coal combustion and can be recycled without pollution. The fly ash and flue gas produced can be discharged after purification, provided the coal-fired furnace has a basic purification system. This setup allows for rapid and efficient cascade recycling of papermaking wastewater. In large paper mills, it can quickly process large volumes of wastewater. Furthermore, traditional methods produce large amounts of difficult-to-dispose-of residual sludge, while this method... Solid filter residue and concentrate are ultimately converted into fuel and burned, fundamentally bypassing the biggest pain point of sludge disposal; it also effectively utilizes waste that was originally difficult to use, achieving the effect of making the most of resources; in addition, traditional multi-stage filtration processes involve many large pieces of equipment with low integration and a large footprint, which is not conducive to production needs. This equipment has a high degree of integration, a small footprint, and can be applied to various types of production workshops; it should be noted that the coal-fired furnace is an essential piece of equipment in paper mills, mainly used to produce steam for the entire process of pulping and cooking, drying cylinders, and power generation. It can be connected to this equipment without transportation pressure, while the steam required for evaporator 1 can be directly provided by the steam generated by the coal-fired furnace, or the steam from the alkali furnace flue gas recovery system, which is essential for paper mills;The waste heat recovery steam temperature from the alkali furnace flue gas can reach over 150 to 200 degrees Celsius, which is perfectly suitable for the equipment.

[0022] The evaporation platform 15 has a hole in its center, and the diameter of the holes in the multiple evaporation platforms 15 increases sequentially from top to bottom. The center of the evaporation platform 15 can move up and down. During operation, the multiple evaporation platforms 15 can work simultaneously or in batches. When working simultaneously, an appropriate amount of primary wastewater is injected into the surface of each evaporation platform 15. Under high temperature, the water in the primary wastewater evaporates and moves upward, and is discharged outward through the exhaust valve 8. After a period of time, the center of all evaporation platforms 15 is moved downward, so that the top surface of the evaporation platform 15 forms a tilted downward and inward shape. The still-flowing concentrate moves towards the central hole and eventually flows to the bottom of the evaporator 1, completing the collection of the concentrate. During batch operation, the wastewater on the surfaces of multiple evaporator platforms 15 is in different states: adding, just added, evaporating, evaporating finished, and discharging. This allows multiple evaporator platforms 15 to be poured in sequence, ensuring uninterrupted wastewater treatment and reducing water storage pressure. The different hole designs of the evaporator platforms 15 ensure that when the concentrate is poured from the upper evaporator platform 15, it will not fall into the lower evaporator platform 15.

[0023] The evaporation platform 15 is composed of multiple isolation pads 16, which are attached and fixed to each other. The isolation pads 16 are made of high-temperature resistant flexible material. The cross-section of the evaporation chamber 1 is polygonal. The outer edge of the isolation pads 16 is fixed to the inner wall of the evaporation chamber 1. During operation, the center of the evaporation platform 15 faces upward during evaporation, so that the waste liquid is above the evaporation platform 15. The center of the evaporation platform 15 can be periodically raised and lowered to agitate the waste liquid above, ensuring uniform heating. The material of the isolation pads 16 can be PTFE fiberglass cloth, which can withstand temperatures exceeding 250 degrees Celsius and has a hydrophobic surface, making it less prone to sticking.

[0024] Multiple connecting rings 20 are fixed between adjacent isolation pads 16. A steel cable 17 is installed through the multiple connecting rings 20. One end of the steel cable 17 is fixed to the inner wall of the evaporator 1, and the other end of the steel cable 17 is fixed to a lifting ring 18 that can move up and down. During operation, the lifting of the steel cable 17 drives the connecting rings 20 and the isolation pads 16 to move up and down. The steel cable 17 is not fixed to the connecting rings 20. During the lifting process, the isolation pads 16 can be relaxed and tightened. When the lifting ring 18 moves to the highest and lowest positions, the isolation pads 16 are fully tightened to ensure the discharge of the concentrate.

[0025] A power platform 9 is fixedly connected to the top of the evaporator 1, and a central column 14 is fixedly connected to the bottom of the power platform 9. The central column 14 is located inside the evaporator 1, and its diameter is smaller than the diameter of the hole in the evaporator 15. The lifting ring 18 is slidably engaged with the outside of the central column 14. The power platform 9 has multiple moving ends, all located inside the central column 14, and is connected to multiple lifting rings 18 via a transmission groove 19. During operation, the power platform 9 controls the lifting of different lifting rings 18 to complete the shape transformation of the evaporator 15, ensuring the smooth operation of evaporation and discharge. Each output end of the power platform 9 can be independently controlled to complete the independent operation of different lifting rings 18.

[0026] The bottom of the evaporator 1 is a bottom cover 6, and the concentrate valve 12 is fixed to the bottom of the bottom cover 6. A support platform 5 is fixed to the outer side of the bottom of the bottom cover 6. Multiple support frames 27 are fixed between the bottom cover 6 and the bottom of the central column 14. Steam pipes 28 are fixed to both sides of the bottom cover 6. During operation, the support frames 27 ensure the stability of the central column 14. Steam can be filled into the steam jacket of the evaporator 1, and steam can also be directly introduced into the evaporator 1 through the steam pipes 28 to ensure rapid heating inside, accelerate the concentration process, and carry steam out quickly. Since the steam pipes 28 are located on the bottom side, they will not affect the normal discharge of the concentrate.

[0027] A vertical feeding pipe 10 is provided on the outside of the evaporator 1. A power pump 13 is fixedly connected to the bottom of the feeding pipe 10. Multiple conveying pipes 11 connected to the evaporator 1 are fixedly connected to the outside of the feeding pipe 10. During operation, the power pump 13 increases the power of the primary waste liquid being conveyed, and the waste liquid is conveyed to different evaporation platforms 15 through the conveying pipes 11. The feeding can be carried out synchronously or in batches without interruption.

[0028] The top of the screw extrusion dewatering machine 2 is fixedly connected to a feeding frame 4. A vibrating cylinder 22 is installed inside the mixing tank 3, and a discharge valve 23 is installed at the bottom of the vibrating cylinder 22. A vibrating element is fixedly connected inside the mixing tank 3, and the drive end of the vibrating element is connected to the vibrating cylinder 22. During operation, wastewater to be treated is injected into the screw extrusion dewatering machine 2 through the feeding frame 4. Multiple screw extrusion dewatering machines 2 can be set up to achieve rapid solid-liquid separation. The bottom outlet of the screw extrusion dewatering machine 2 is connected to a power pump 13. The waste from the solid end of the screw extrusion dewatering machine 2 is directly fed into the coal-fired furnace for combustion after the primary wastewater transfer is completed. The concentrated liquid discharged from the concentrated liquid valve 12 is poured into the vibrating cylinder 22 of the mixing tank 3 in batches, and an appropriate amount of carbon powder is added. Alternatively, the waste from the solid end of the screw extrusion dewatering machine 2 can be crushed and mixed with the concentrated liquid. The mixture is coarsely mixed by the high-frequency vibration of the vibrating cylinder 22. Then, the mixed fuel is discharged from the bottom discharge valve 23 and injected into the coal-fired furnace for combustion, thereby achieving the effect of comprehensive wastewater recycling.

[0029] The mixing tank 3 has a steam chamber 21 inside, which is connected to one of the exhaust valves 8. A drain valve 24 is installed at the bottom of the steam chamber 21. During operation, some of the steam discharged from the exhaust valve 8 of the evaporator 1 can be condensed and used, while some can be directly introduced into the steam chamber 21 to maintain the high temperature of the mixing tank 3. This not only cools the steam to facilitate subsequent condensation but also evaporates the moisture in the mixture, increasing the calorific value. The water generated during heating is discharged through the drain valve 24 and can be directly recycled.

[0030] A spray gun 26 is fixed to the top of the inner ring of the mixing tank 3. The output end of the spray gun 26 faces the inside of the vibrating cylinder 22. During operation, the spray gun 26 is used to spray carbon powder into the vibrating cylinder 22 to ensure the mixing of the two, and can also spray the crushed slag into the vibrating cylinder 22.

[0031] During operation, the papermaking wastewater to be treated is fed into the screw press dewatering machine 2. The screw press dewatering machine 2 uses rotation, extrusion, and centrifugation to compress the large-volume waste material in the wastewater into slag, which is then discharged from one end. The primary wastewater after extrusion is discharged from the bottom. The discharged primary wastewater is fed into the evaporator 1, and steam is introduced into the steam valve 7 of the evaporator 1 to raise the internal temperature to over 100 degrees Celsius. After being discharged into the evaporator 1, the primary wastewater is spread evenly on the evaporation platform 15 to increase the evaporation area. As the liquid in the primary wastewater gradually evaporates, the resulting steam rises and is discharged through the exhaust valve 8. This steam can be condensed and then... As industrial water and boiler feedwater, the primary wastewater, after evaporation and concentration for a period of time, forms a concentrated liquid. This concentrated liquid is discharged downwards and transported via the concentrated liquid valve 12. The slag produced by the screw extrusion dewatering machine 2 is mainly composed of short fibers and pulp slag, with a high calorific value. The concentrated liquid, however, mainly contains dissolved organic matter, such as lignin, hemicellulose, low-molecular-weight sugars, and some inorganic salts, with a lower calorific value. Combustion requires mixing with other substances of higher calorific value. The concentrated liquid needs to be mixed with higher-calorific-value substances in the mixing tank 3, such as charcoal powder. Afterwards, the slag and the mixed concentrated liquid are fed into a coal-fired furnace for combustion, providing fuel for the coal-fired furnace. The resulting ash is mixed with the ash from normal coal combustion and can be recycled without pollution. The fly ash and flue gas produced can be purified before being discharged, provided the coal-fired boiler has a basic purification system. This setup allows for rapid and efficient cascade recycling of papermaking wastewater, enabling the quick processing of large volumes of wastewater in large paper mills. Furthermore, traditional methods generate large amounts of difficult-to-dispose-of residual sludge, while this method converts all solid filter residue and concentrate into fuel for combustion, fundamentally bypassing the major challenge of sludge disposal. It also effectively utilizes previously unusable waste materials, achieving maximum resource utilization. In multi-stage filtration processes, the equipment is numerous and large, with low integration and a large footprint, which is not conducive to production needs. This equipment has a high degree of integration, a small footprint, and can be applied to various types of production workshops. It should be noted that the coal-fired furnace is an essential piece of equipment in paper mills, mainly used to produce steam for the entire process of pulping and cooking, drying cylinders, and power generation. It can be connected to this equipment without transportation pressure. The steam required for evaporator 1 can be directly provided by the steam generated by the coal-fired furnace, or it can use the steam from the alkali furnace flue gas recovery system, which is essential for paper mills. The temperature of the waste heat recovery steam from the alkali furnace flue gas can reach 150 to 200 degrees Celsius or higher, which is perfectly suitable for the equipment.

[0032] Multiple evaporation platforms 15 can operate simultaneously or in batches. When operating simultaneously, a suitable amount of primary wastewater is injected into the surface of each evaporation platform 15. At high temperatures, the water in the primary wastewater evaporates and moves upwards, being discharged through the exhaust valve 8. After a period of time, the middle of all evaporation platforms 15 is moved downwards, causing the top surface of each evaporation platform 15 to tilt downwards and towards the center, allowing the still-flowing concentrate to move towards the central hole and eventually flow to the bottom of the evaporation tank 1, completing the collection of the concentrate. When operating in batches, the wastewater on the surfaces of multiple evaporation platforms 15 is in different states: adding, just added, evaporating, evaporating finished, or being discharged. This allows multiple evaporation platforms 15 to be poured out sequentially, ensuring uninterrupted wastewater treatment and reducing storage pressure. The different hole designs of the evaporation platforms 15 ensure that when pouring concentrate from an upper evaporation platform 15, it does not fall into a lower evaporation platform 15.

[0033] With the flexible isolation pad 16, the center of the evaporation platform 15 faces upward during evaporation, allowing the waste liquid to be above the evaporation platform 15. The center of the evaporation platform 15 can be periodically raised and lowered to agitate the waste liquid above, ensuring uniform heating. The isolation pad 16 can be made of PTFE fiberglass cloth, which can withstand temperatures exceeding 250 degrees Celsius and has a hydrophobic surface, making it less prone to sticking.

[0034] The lifting and lowering of the steel cable 17 drives the connecting ring 20 and the isolation pad 16 to rise and fall. The steel cable 17 is not fixed to the connecting ring 20. During the lifting and lowering process, the isolation pad 16 can be relaxed and tightened. When the lifting ring 18 moves to the highest and lowest positions, the isolation pad 16 is fully tightened to ensure the discharge of the concentrate.

[0035] The different lifting rings 18 are raised and lowered by the power station 9 to complete the shape transformation of the evaporation platform 15, ensuring the smooth operation of evaporation and discharge. Each output end of the power station 9 can be controlled independently to complete the independent operation of different lifting rings 18.

[0036] The support frame 27 ensures the stability of the central column 14; it can not only fill the steam jacket of the evaporator 1 with steam, but also directly introduce steam into the evaporator 1 through the steam pipe 28 to ensure rapid internal heating, accelerate the concentration process, and carry steam out quickly; since the steam pipe 28 is located on the bottom side, it will not affect the normal discharge of the concentrate.

[0037] The power pump 13 increases the power of the primary waste liquid being transported, and the waste liquid is transported to different evaporation platforms 15 through the conveying pipe 11. This allows for both synchronous and batch-by-batch uninterrupted feeding.

[0038] Wastewater requiring treatment is injected into the screw extrusion dewatering machine 2 through the feeding frame 4. Multiple screw extrusion dewatering machines 2 can be set up to achieve rapid solid-liquid separation. The bottom outlet of the screw extrusion dewatering machine 2 is connected to the power pump 13 to complete the primary wastewater transfer. The waste material from the solid end of the screw extrusion dewatering machine 2 can be directly fed into the coal-fired furnace for combustion. The concentrated liquid discharged from the concentrated liquid valve 12 is poured into the vibrating cylinder 22 of the mixing tank 3 in batches. An appropriate amount of carbon powder is added, or the waste material from the solid end of the screw extrusion dewatering machine 2 is directly crushed and mixed with the concentrated liquid. The mixture is coarsely mixed by the high-frequency vibration of the vibrating cylinder 22. Then, the mixed fuel is discharged from the bottom discharge valve 23 and injected into the coal-fired furnace for combustion, thereby achieving the effect of comprehensive wastewater recycling.

[0039] The steam discharged from the exhaust valve 8 of the evaporator 1 can be partially condensed and used, and partially directly introduced into the steam chamber 21 to maintain the high temperature of the mixing tank 3. This not only cools the steam to facilitate subsequent condensation, but also evaporates the moisture in the mixture and increases the calorific value of combustion. The water generated by heating is discharged through the drain valve 24 and can be directly recycled.

[0040] The spray gun 26 is used to spray charcoal powder into the vibrating cylinder 22 to ensure the mixing of the two, and can also spray the crushed slag into the vibrating cylinder 22.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cascade recycling device for papermaking wastewater, characterized in that: The device includes an evaporator and a screw extrusion dehydrator. The evaporator has multiple evaporation platforms arranged vertically at equal intervals. An exhaust valve is fixed to the top of the evaporator. A mixing tank is located on one side of the evaporator. A steam valve for inputting and outputting steam is fixed to the outside of the evaporator. A concentrate valve is installed at the bottom of the evaporator.

2. The papermaking wastewater cascade recycling device according to claim 1, characterized in that: The evaporation platform has a hole in the middle, and the diameter of the holes in the multiple evaporation platforms increases from top to bottom. The middle part of the evaporation platform can move up and down.

3. The papermaking wastewater cascade recycling device according to claim 2, characterized in that: The evaporation platform is composed of multiple isolation pads, which are attached and fixed to each other. The isolation pads are made of high-temperature resistant flexible material. The cross-section of the evaporation box is polygonal, and the outer edge of the isolation pads is fixed to the inner wall of the evaporation box.

4. The papermaking wastewater cascade recycling device according to claim 3, characterized in that: Multiple connecting rings are fixed between adjacent isolation pads, and steel cables are installed through the multiple connecting rings. One end of the steel cable is fixed to the inner wall of the evaporator, and the other end of the steel cable is fixed to a lifting ring that can move up and down.

5. The papermaking wastewater cascade recycling device according to claim 4, characterized in that: A power platform is fixedly connected to the top of the evaporator, and a central column is fixedly connected to the bottom of the power platform. The central column is located inside the evaporator, and its diameter is smaller than the diameter of the hole in the evaporator. The lifting ring is slidably engaged with the outside of the central column. The power platform has multiple moving ends, all located inside the central column, and is connected to multiple lifting rings via transmission grooves.

6. The papermaking wastewater cascade recycling device according to claim 5, characterized in that: The bottom of the evaporator is a bottom cover, the concentrate valve is fixed to the bottom of the bottom cover, a support platform is fixed to the outer side of the bottom of the bottom cover, multiple support frames are fixed between the bottom cover and the bottom of the central column, and steam pipes are fixed to both sides of the bottom cover.

7. The papermaking wastewater cascade recycling device according to claim 6, characterized in that: A vertical feeding pipe is provided on the outside of the evaporator. A power pump is fixed to the bottom of the feeding pipe, and multiple conveying pipes connected to the evaporator are fixed to the outside of the feeding pipe.

8. The papermaking wastewater cascade recycling device according to claim 7, characterized in that: The top of the screw extrusion dewatering machine is fixedly connected to a feeding frame. The inside of the mixing tank is equipped with a vibrating cylinder. The bottom of the vibrating cylinder is equipped with a discharge valve. The inside of the mixing tank is fixedly connected to a vibrating element, and the driving end of the vibrating element is connected to the vibrating cylinder.

9. A cascade recycling device for papermaking wastewater according to claim 8, characterized in that: The mixing tank has a steam chamber inside, which is connected to one of the exhaust valves, and a drain valve is installed at the bottom of the steam chamber.

10. A cascade recycling device for papermaking wastewater according to claim 9, characterized in that: A spray gun is fixed to the top of the inner ring of the mixing tank, and the output end of the spray gun faces the inside of the vibrating cylinder.

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