A sludge resource utilization pretreatment system based on wet oxidation treatment technology

Abstract

The utility model discloses a sludge resource utilization pretreatment system based on wet type oxidation treatment technology, including sludge wet type oxidation treatment unit, mechanical dehydration unit, fine crushing unit, depth drying unit, crushing unit, grading unit and packing unit, sludge wet type oxidation treatment unit is used to generate sludge after wet type oxidation reaction, mechanical dehydration unit converts sludge after wet type oxidation reaction into mud block after rough crushing, fine crushing unit converts mud block after rough crushing into mud granule after fine crushing, depth drying unit dries mud granule after fine crushing into mud granule after depth drying, crushing unit converts mud granule after depth drying into mud granule after crushing, grading unit is used for screening mud fine granule after grading, and packing unit is used for packing mud fine granule after grading into finished product.

Description

Technical Field

[0001] This utility model relates to the field of sludge treatment and resource utilization technology, and in particular to a sludge resource utilization pretreatment system based on wet oxidation treatment technology. Background Technology

[0002] With the acceleration of urbanization and the continuous expansion of wastewater treatment scale, the amount of sludge generated is increasing daily. Sludge contains a large amount of pollutants such as organic matter, pathogens, and heavy metals. If not properly treated, it will cause serious environmental pollution. Traditional sludge treatment methods, such as landfill and incineration, not only pose a risk of secondary pollution but also have low resource utilization rates and high disposal costs. Therefore, developing efficient and environmentally friendly sludge resource utilization technologies is of great practical significance.

[0003] Wet oxidation treatment technology, as an effective sludge treatment method, can oxidize and decompose organic matter in sludge under high temperature and pressure, achieving sludge reduction, harmlessness, and stabilization. However, existing wet oxidation treatment processes for sludge have some shortcomings, such as unsatisfactory dewatering effect, high drying energy consumption, and low product added value. CN106832520A, CN107841906A, and CN107829334A propose using pretreated sludge as filler for containers for flowers and seedlings, molded pulp products, and paperboard. Related literature also indicates that harmless municipal sludge after wet oxidation can be used as a papermaking filler to prepare novel, low-cost, high-performance paperboard. This approach not only broadens the application range of sludge and improves the economic benefits of sludge treatment but also reduces papermaking costs, demonstrating promising resource utilization prospects.

[0004] However, while low- and medium-temperature partial wet oxidation processes for sludge offer lower investment and operating costs, their organic matter oxidation rate is limited. In particular, the dewatered sludge cake contains some low-boiling-point volatile organic compounds, making it difficult to meet the requirements for use as a raw material for packaging paper. Conversely, while medium- and high-temperature partial or complete wet oxidation processes can meet the requirements for packaging paper raw materials, the cost is higher. Therefore, these issues have become urgent problems to be solved in the resource utilization of dewatered sludge cake from wet oxidation processes as a raw material for packaging paper. Overcoming these shortcomings will greatly broaden the scope of sludge resource utilization, further improve the economic benefits of sludge treatment, and strongly promote low-carbon, low-cost, and high-quality operation in the sludge industry. Utility Model Content

[0005] The present invention aims to overcome the defects in the prior art and provide a sludge resource utilization pretreatment system based on wet oxidation treatment technology. This system enables low-cost deep drying of sludge to remove low-boiling-point volatile organic compounds and crushing and classifying the sludge, resulting in sludge-based packing material free of low-boiling-point volatile organic compounds and with uniform particle size distribution.

[0006] To achieve the above objectives, this utility model provides a sludge resource utilization pretreatment system based on wet oxidation treatment technology, comprising a sludge wet oxidation treatment unit, a mechanical dewatering unit, a fine crushing unit, a deep drying unit, a pulverizing unit, a grading unit, and a packaging unit connected in sequence. The sludge wet oxidation treatment unit is used to perform a wet oxidation reaction on the incoming sludge to generate wet-oxidized sludge. The mechanical dewatering unit includes a mechanical dewatering device and a screw conveyor. The mechanical dewatering device is used to dewater the sludge after wet oxidation reaction to generate a sludge cake with a moisture content of 30%-40%. The filtrate generated during the dewatering process of the mechanical dewatering device is the system wastewater. The screw conveyor is used to coarsely crush the sludge cake to obtain coarsely crushed sludge blocks with a particle size of 5-20mm. The fine crushing unit is used to finely crush the coarsely crushed mud blocks to generate finely crushed mud particles with a particle size ≤5mm. The deep drying unit is used to dry the finely crushed mud particles to obtain deeply dried mud particles with a moisture content of ≤10%. The crushing unit is used to crush the deeply dried mud particles to obtain crushed mud particles. The grading unit is used to screen the crushed mud particles to obtain graded fine mud particles and graded coarse mud particles, wherein the particle size of the graded fine mud particles is 1-100um. The packaging unit is used to package the graded fine mud particles to obtain the finished product.

[0007] Further configuration includes an air compressor unit, which supplies compressed air to the sludge wet oxidation treatment unit and supplies first hot air to the screw conveyor. The coarsely crushed sludge blocks in the screw conveyor exchange heat with the first hot air to achieve preliminary drying. The first hot air is converted into second humid hot air after heat exchange, and the second humid hot air is the system exhaust gas.

[0008] The unit is further configured such that the deep drying unit includes a deep drying device and a heat pump device. The heat pump device provides the deep drying device with the third hot air required for drying the finely crushed mud particles. The third hot air is converted into a fourth humid hot air after heat and mass exchange between the deep drying device and the finely crushed mud particles. The fourth humid hot air enters the heat pump device and is converted back into the third hot air after being processed by the heat pump device.

[0009] The heat pump device is further configured to include a heat exchanger, a first evaporator, a compressor, a condenser, a fan, and an expansion valve. The compressor, condenser, expansion valve and first evaporator are connected by pipelines to form a refrigerant path; The inlet of the hot-side pipe of the heat exchanger is connected to the air outlet of the deep drying device, the outlet of the hot-side pipe of the heat exchanger is connected to the inlet of the hot-side pipe of the first evaporator, the outlet of the hot-side pipe of the first evaporator is connected to the inlet of the cold-side pipe of the heat exchanger, the outlet of the cold-side pipe of the heat exchanger is connected to the inlet of the cold-side pipe of the condenser, the outlet of the cold-side pipe of the condenser is connected to the inlet of the fan, and the outlet of the fan is connected to the air inlet of the deep drying device. The condensate generated by the first evaporator during operation is the system wastewater.

[0010] A further configuration is provided: a second evaporator is also provided on the refrigerant pipeline between the first evaporator and the compressor, and the second evaporator is equipped with an auxiliary fan.

[0011] Further configuration includes: an exhaust gas purification unit for treating system exhaust gases.

[0012] Further configuration includes: a wastewater treatment unit for treating system wastewater.

[0013] The mechanical dewatering unit further includes a mud cake hopper, which is connected to the bottom of the mechanical dewatering device, and the bottom of the mud cake hopper is connected to a screw conveyor.

[0014] The method is further configured such that the graded coarse mud particles obtained by the grading unit are re-entered into the crushing unit for crushing.

[0015] The temperature of the third hot air is further set to 40-80℃.

[0016] Compared with existing technologies, it has at least the following beneficial effects: The wet oxidation technology for sludge achieves stabilization, volume reduction, and harmlessness of sludge. Through processes such as preliminary drying of sludge blocks using hot air from an air compressor and deep drying of sludge particles based on heat pump technology, the moisture content of the sludge-based filler is effectively reduced from 80% to below 10%, resulting in a volume reduction of over 80%. Furthermore, the process heat is recovered, resulting in significant energy savings and avoiding the high energy consumption problems of existing steam drying and electric heating drying processes. Compared to the latter two, energy savings are over 40%. Through processes such as coarse crushing, fine crushing, pulverizing, and grading units, the produced fine sludge particles meet the filler requirements for corrugated paper and other paperboard, replacing calcium carbonate filler and realizing the resource utilization of sludge. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the principle structure of a sludge resource utilization pretreatment system based on wet oxidation technology.

[0018] The following reference numerals are marked on the accompanying drawings: U1. Sludge wet oxidation treatment unit; U2. Mechanical dewatering unit; U21. Mechanical dewatering device; U22. Sludge cake silo; U23. Screw conveyor device; U3. Air compressor unit; U4. Fine crushing unit; U5. Deep drying unit; U51. Deep drying device; U52. Heat pump device; U6. Crushing unit; U7. Grading unit; U8. Packaging unit; U9. Wastewater treatment unit; U10. Wastewater external pump; U11. Wastewater treatment plant; U12. Exhaust gas purification unit; C1, Heat exchanger; C2, First evaporator; C3, Second evaporator; C4, Auxiliary fan; C5, Compressor; C6, Condenser; C7, Fan; C8, Expansion valve; OSW, sludge; OSP, finished product; S1, sludge after wet oxidation reaction; S2, sludge cake; S3, sludge lumps after coarse crushing; S4, sludge particles after fine crushing; S5, sludge particles after deep drying; S6, sludge particles after pulverization; S7, coarse sludge particles after grading; S8, fine sludge particles after grading. W1, filtrate; W2, condensate; G1, First hot air; G2, Second humid hot air; G3, Third hot air; G4, Fourth humid hot air; G5, Compressed air. Detailed Implementation

[0019] The following describes a specific embodiment of the present invention in detail with reference to the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0020] This utility model discloses a sludge resource utilization pretreatment system based on wet oxidation technology, such as... Figure 1 As shown, it includes a sludge wet oxidation treatment unit U1, a mechanical dewatering unit U2, an air compressor unit U3, a fine crushing unit U4, a deep drying unit U5, a pulverizing unit U6, a grading unit U7, a packaging unit U8, a wastewater treatment unit U9, a wastewater external pump U10, and a waste gas purification unit U12.

[0021] In this embodiment, the wet oxidation treatment unit U1 performs a wet oxidation reaction on municipal sludge OSW with a moisture content of 80%-85% at 150-230℃ and 1.0-2.5MPa, thereby achieving the degradation of organic matter and cell wall disruption, and then generating sludge S1 after wet oxidation reaction.

[0022] In this embodiment, the mechanical dewatering unit U2 includes a mechanical dewatering device U21, a sludge cake silo U22, and a screw conveyor U23. The bottom of the mechanical dewatering device U21 is connected to the sludge cake silo U22, and the bottom of the sludge cake silo U22 is connected to the screw conveyor U23. Thus, after the wet oxidation reaction, the sludge S1 enters the mechanical dewatering device U21 in the mechanical dewatering unit U2 for dewatering to generate a sludge cake S2 ​​with a moisture content of 30%-40%. The filtrate W1 produced by dewatering flows by gravity to the wastewater treatment unit U9 for treatment, satisfying the required standards. After meeting the relevant standards of the "Integrated Wastewater Discharge Standard", the wastewater is transported to the wastewater treatment plant U11 via the wastewater external pump U10 for treatment and then discharged after meeting the standards. The sludge cake S2 ​​produced by dewatering falls into the sludge cake silo U22 at the bottom under the action of gravity. Then, under the action of the bottom screw conveyor U23, the sludge cake S2 ​​is coarsely crushed to form coarsely crushed mud blocks S3 with an average particle size of 5-20mm. The screw conveyor U23 can be a shaftless screw conveyor, a shafted screw conveyor, or a two-stage screw conveyor. A shaftless screw conveyor is preferred to balance anti-clogging and crushing efficiency.

[0023] In this embodiment, the air compressor unit U3 is used to provide the required compressed air G5 to the sludge wet oxidation treatment unit U1. The air compressor unit U3 needs to be air-cooled during the production of compressed air G5, thereby generating a large amount of first hot air G1. The first hot air G1 generated by the air compressor unit U3 is introduced into the screw conveyor device U23 to exchange heat and mass with the sludge being coarsely crushed to achieve preliminary drying and further reduce the moisture content of the sludge. Since the water in the sludge is basically free water, it evaporates quickly under the action of the first hot air G1. The moisture content of the sludge is expected to decrease by about 20-30%. Preferably, the first hot air G1 exchanges heat and mass with the sludge being coarsely crushed in the screw conveyor device U23 in a countercurrent manner, which can significantly reduce the moisture content of the sludge. After being cooled and humidified in the screw conveyor device U23, the first hot air G1 is converted into second hot and humid air G2 (system exhaust gas). The second hot and humid air G2 is discharged into the exhaust gas purification unit U12 for treatment and then discharged in compliance with standards.

[0024] In this embodiment, the screw conveyor U23 is connected to the fine crushing unit U4. The coarsely crushed mud block S3 is conveyed to the fine crushing unit U4 for further fine crushing to form finely crushed mud particles S4. The average particle size of the finely crushed mud particles S4 is ≤5mm. The fine crushing unit U4 can be a double-stage screenless crusher, a double roller crusher, an impact crusher, a jaw crusher, or other similar devices.

[0025] In this embodiment, the fine crushing unit U4 is connected to the deep drying unit U5. The finely crushed mud particles S4 are transported to the deep drying unit U5 for further drying and dehydration until the moisture content is ≤10%. The deep drying unit U5 uses heat pump technology to dry the finely crushed mud particles S4. The COP of the heat pump device U52 is between 3 and 5, which has a significant energy-saving effect compared with the electric heating process.

[0026] Specifically, the deep drying unit U5 includes a deep drying device U51 and a heat pump device U52. The heat pump device U52 provides the deep drying device U51 with the third hot air G3 required for drying and crushing the mud particles S4. The temperature of the third hot air G3 is controlled at 40-80℃, preferably 50-65℃, to prevent the decomposition and destruction of organic matter in the mud particles. The heat pump device U52 includes a heat exchanger C1, an evaporator, a compressor C5, a condenser C6, a fan C7, and an expansion valve C8. The compressor C5, condenser C5, and fan C7 are among the components of the heat pump device U51. 6. Expansion valve C8 and the first evaporator C2 are connected via a refrigerant circulation path; the inlet of the hot-side pipe of heat exchanger C1 is connected to the air outlet of the deep drying device U51, the outlet of the hot-side pipe of heat exchanger C1 is connected to the inlet of the hot-side pipe of the first evaporator C2, the outlet of the hot-side pipe of the first evaporator C2 is connected to the inlet of the cold-side pipe of heat exchanger C1, the outlet of the cold-side pipe of heat exchanger C1 is connected to the inlet of the cold-side pipe of condenser C6, and the outlet of the cold-side pipe of condenser C6 is connected to the fan. The inlet of fan C7 is connected to the air outlet of the deep drying device U51, and the outlet of fan C7 is connected to the air inlet of the deep drying device U51. A second evaporator C3 is also installed on the refrigerant pipeline between the first evaporator C2 and the compressor C5. The second evaporator C3 is equipped with an auxiliary fan C4. Thus, the third hot air G3 generated by the heat pump device U52 enters the deep drying device U51 and exchanges heat and mass with the finely crushed mud particles S4. The moisture content of the finely crushed mud particles S4 is greatly reduced, and they become deeply dried mud particles S5. During the heat and mass exchange process, the third hot air G3 cools and humidifies the mud. The air becomes the fourth humid hot air G4 and returns to the heat pump unit U52. The fourth humid hot air G4 first passes through the heat exchanger C1 for heat exchange and cooling, and then is sent to the evaporator for further cooling and condensation to generate condensate W2 (system wastewater). The condensate W2 is discharged to the wastewater treatment unit U9. The cooled air then flows back to the heat exchanger C1 for heating, and then enters the condenser C6 for further heating. Finally, it is sent back to the deep drying unit U51 by the fan C7. This cycle can significantly reduce the heat required to dry the sludge particles.

[0027] In the above scheme, the heat pump device U52 uses refrigerant to complete the transfer and exchange of cold and heat. After the liquid refrigerant is throttled and depressurized by the expansion valve C8, it generates a low-temperature and low-pressure liquid-gas mixture. The low-temperature mixture absorbs heat from the fourth humid hot air G4 in the evaporator, thereby vaporizing into low-pressure gas. At the same time, it can further absorb heat from the environment through the action of the second evaporator C3 and the auxiliary fan C4 until it is completely vaporized into low-pressure gas. The low-temperature and low-pressure gaseous refrigerant is compressed into a high-temperature and high-pressure gas in the compressor C5. The high-temperature and high-pressure gas enters the condenser C6, releases heat to the cold side air and condenses into liquid, thereby heating the cold side air into the third hot air G3.

[0028] In this embodiment, the deep drying unit U5 is connected to the pulverizing unit U6. After deep drying, the sludge particles S5 enter the pulverizing unit U6 for pulverization to obtain pulverized sludge particles S6. The pulverizing unit U6 can be an air jet mill or a ball mill, etc. The pulverizing unit U6 is connected to the grading unit U7. The pulverized sludge particles S6 are conveyed to the grading unit U7 for sieving, thereby producing graded coarse sludge particles S7 and graded fine sludge particles S8. The average particle size of the graded fine sludge particles S8 is 1-100 μm, preferably 1-50 μm. Ultrafine particles (<1 μm) can easily reduce the retention rate of sludge-based fillers, and excessively large particle sizes increase the roughness of the cardboard, affecting its appearance and feel. The graded coarse sludge particles S7 can be returned to the pulverizing unit U6 for further pulverization, while the graded fine sludge particles S8 are conveyed to the packaging unit U8 for packaging into finished OSP for external sale.

[0029] In addition, if the wastewater treatment plant U11 has a strong treatment capacity and the filtrate W1 concentration is low, the filtrate W1 can be discharged directly to the wastewater treatment plant U11 for treatment without going through the wastewater treatment unit U9.

[0030] Compared with existing technologies, this utility model achieves stabilization, volume reduction, and harmlessness of sludge through wet oxidation technology. By using air compressor hot air for preliminary drying of sludge blocks and deep drying of sludge particles based on heat pump technology, it not only effectively reduces the moisture content of sludge-based fillers (from 80% to below 10%), resulting in a volume reduction of over 80%, but also recovers process heat, achieving significant energy savings and avoiding the high energy consumption problems of existing steam drying and electric heating drying processes. Compared to the latter two, it saves over 40% of energy. Through processes such as coarse crushing, fine crushing, pulverizing, and grading units, the produced fine sludge particles meet the filler requirements of corrugated paper and other paperboards, replacing calcium carbonate fillers and realizing the resource utilization of sludge.

[0031] The above-disclosed embodiments are merely examples of the present utility model. However, the present utility model is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present utility model.

Claims

1. A sludge resource utilization pretreatment system based on wet oxidation technology, characterized in that, It includes a sludge wet oxidation treatment unit, a mechanical dewatering unit, a fine crushing unit, a deep drying unit, a pulverizing unit, a grading unit, and a packaging unit connected in sequence; The sludge wet oxidation treatment unit is used to perform a wet oxidation reaction on the incoming sludge to generate wet-oxidized sludge. The mechanical dewatering unit includes a mechanical dewatering device and a screw conveyor. The mechanical dewatering device is used to dewater the sludge after wet oxidation reaction to generate a sludge cake with a moisture content of 30%-40%. The filtrate generated during the dewatering process of the mechanical dewatering device is the system wastewater. The screw conveyor is used to coarsely crush the sludge cake to obtain coarsely crushed sludge blocks with a particle size of 5-20mm. The fine crushing unit is used to finely crush the coarsely crushed mud blocks to generate finely crushed mud particles with a particle size ≤5mm. The deep drying unit is used to dry the finely crushed mud particles to obtain deeply dried mud particles with a moisture content of ≤10%. The crushing unit is used to crush the deeply dried mud particles to obtain crushed mud particles. The grading unit is used to screen the crushed mud particles to obtain graded fine mud particles and graded coarse mud particles, wherein the particle size of the graded fine mud particles is 1-100 μm. The packaging unit is used to package the graded fine mud particles to obtain the finished product.

2. The sludge resource utilization pretreatment system based on wet oxidation technology according to claim 1, characterized in that, It also includes an air compressor unit, which supplies compressed air to the sludge wet oxidation treatment unit and supplies first hot air to the screw conveyor. The coarsely crushed sludge blocks in the screw conveyor exchange heat with the first hot air to achieve preliminary drying. The first hot air is converted into second humid hot air after heat exchange, and the second humid hot air is the system exhaust gas.

3. The sludge resource utilization pretreatment system based on wet oxidation technology according to claim 1, characterized in that, The deep drying unit includes a deep drying device and a heat pump device. The heat pump device is used to provide the deep drying device with the third hot air required for drying the finely crushed mud particles. The third hot air is converted into a fourth humid hot air after heat and mass exchange between the deep drying device and the finely crushed mud particles. The fourth humid hot air enters the heat pump device and is processed by the heat pump device and converted back into the third hot air.

4. The sludge resource utilization pretreatment system based on wet oxidation technology according to claim 3, characterized in that, The heat pump device includes a heat exchanger, a first evaporator, a compressor, a condenser, a fan, and an expansion valve; The compressor, condenser, expansion valve and first evaporator are connected by pipelines to form a refrigerant path; The inlet of the heat transfer side pipe of the heat exchanger is connected to the air outlet of the deep drying device. The outlet of the heat side pipe of the heat exchanger is connected to the inlet of the heat side pipe of the first evaporator. The outlet of the heat side pipe of the first evaporator is connected to the inlet of the cold side pipe of the heat exchanger. The outlet of the cold side pipe of the heat exchanger is connected to the inlet of the cold side pipe of the condenser. The outlet of the cold side pipe of the condenser is connected to the inlet of the fan. The outlet of the fan is connected to the air inlet of the deep drying device. The condensate generated by the first evaporator during operation is the system wastewater.

5. The sludge resource utilization pretreatment system based on wet oxidation technology according to claim 4, characterized in that, A second evaporator is also installed on the refrigerant pipeline between the first evaporator and the compressor, and the second evaporator is equipped with an auxiliary fan.

6. The sludge resource utilization pretreatment system based on wet oxidation technology according to claim 2, characterized in that, It also includes an exhaust gas purification unit for treating system exhaust gases.

7. A sludge resource utilization pretreatment system based on wet oxidation technology according to claim 1 or 4, characterized in that, It also includes a wastewater treatment unit for treating system wastewater.

8. A sludge resource utilization pretreatment system based on wet oxidation technology according to claim 1, characterized in that, The graded coarse mud particles obtained by the grading unit are re-entered into the crushing unit for crushing.

9. A sludge resource utilization pretreatment system based on wet oxidation technology according to claim 1, characterized in that, The mechanical dewatering unit also includes a mud cake hopper, which is connected to the bottom of the mechanical dewatering device, and the bottom of the mud cake hopper is connected to a screw conveyor.

10. A sludge resource utilization pretreatment system based on wet oxidation technology according to claim 3, characterized in that, The temperature of the third hot air is 40-80℃.

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