Solar multistage latent heat recovery type sludge drying system and method
The solar multi-stage latent heat recovery sludge drying system utilizes solar concentrators and heat storage devices combined with hydrophobic heat-conducting layers, hydrophilic heat-conducting layers, and supporting purification layers to achieve efficient sludge drying. This solves the problems of high energy consumption, complex equipment, and secondary pollution in existing technologies, and improves the efficiency of solar energy utilization and the continuous operation capability of the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG UNIV
- Filing Date
- 2025-03-06
- Publication Date
- 2026-06-26
AI Technical Summary
Existing sludge drying technologies suffer from high energy consumption, large equipment investment, complex operation, high maintenance costs, and secondary pollution problems. Solar low-temperature drying technology is inefficient and requires a large area.
A solar-powered multi-stage latent heat recovery sludge drying system is adopted, which provides heat through solar concentrators and heat storage devices. It utilizes hydrophobic and hydrophilic thermal conductive layers to achieve multi-stage recovery of latent heat of vapor during the sludge drying process. Combined with a supportive purification layer to purify the vapor, it achieves continuous sludge drying.
It reduces energy consumption, improves solar energy utilization efficiency, reduces environmental impact, reduces equipment footprint, and solves the problem of secondary pollution through multi-stage latent heat recovery and purification layer design.
Smart Images
Figure CN120081580B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sludge drying equipment technology, specifically to a solar multi-stage latent heat recovery type sludge drying system and method. Background Technology
[0002] The high moisture content of sludge is a key issue restricting its subsequent disposal. Existing sludge drying technologies include electric sludge drying, hot water drying, steam drying, and waste heat sludge drying using furnace flue gas. Among these, electric sludge drying has high energy consumption and is not suitable for wastewater treatment plants with tight power supply and large sludge production. Hot water drying requires high-quality heat exchangers, and the process may be limited by the stability of the heat source and the supply of hot water. Although steam drying has high efficiency, steam drying equipment is usually complex and has high maintenance costs. Waste heat sludge drying using furnace flue gas may cause secondary pollution to the sludge due to harmful substances in the flue gas. In addition, the drying efficiency will be affected when the flue gas temperature is low or the supply is insufficient.
[0003] Therefore, existing sludge drying technologies generally suffer from high energy consumption, large initial equipment investment, difficult operation and management, and high maintenance costs. Solar energy, as a clean energy source, can significantly reduce energy consumption in sludge drying, and its operation and management are relatively simple. However, solar low-temperature drying technology is not yet mature and has drawbacks such as low drying efficiency, easy secondary pollution, and large footprint. Summary of the Invention
[0004] To address the problems existing in the prior art, this invention provides a solar multi-stage latent heat recovery sludge drying system and method, which can improve the solar energy utilization efficiency of the system, reduce energy consumption and environmental impact, and solve the problems of high energy consumption and complex operation in the sludge drying process, as well as the technical problems of low efficiency, easy secondary pollution and large footprint of solar drying technology.
[0005] The technical solution of the present invention is as follows:
[0006] In a first aspect of the invention, a solar-powered multi-stage latent heat recovery sludge drying system is provided, comprising a solar concentrator, a solar thermal storage device, and a sludge drying device. The sludge drying device includes multiple sludge drying spaces and multiple steam flow spaces, which are arranged alternately from top to bottom. The steam flow spaces are separated from the sludge drying spaces above them by a supporting purification layer, and from the sludge drying spaces below them by a hydrophilic thermal conductive layer and a hydrophobic thermal conductive layer. A solar absorption layer and a transparent insulation layer are arranged sequentially above the uppermost sludge drying space. The uppermost sludge drying space uses solar energy as a heat source to dry the sludge, while the remaining sludge drying spaces use the latent heat released from steam liquefaction as a heat source to dry the sludge. The solar concentrator provides heat to the sludge drying device during the day, and the solar thermal storage device provides heat to the sludge drying device at night.
[0007] In some embodiments of the present invention, the supporting purification layer of the sludge drying device is drawer-shaped and made of fiberboard, with an adsorbent material coated on the top of the fiberboard, the coating thickness of the adsorbent material being 0.1-1 mm.
[0008] In some embodiments of the present invention, the hydrophilic heat-conducting layer includes a grooved heat-conducting plate, which is made of hydrophilic foamed copper. The grooves on the grooved heat-conducting plate serve as a steam flow space, and water outlets are provided on the grooved heat-conducting plate.
[0009] In some embodiments of the present invention, the hydrophobic thermal conductive layer includes a thermal conductive plate, the surface of which is chemically etched with a hydrophobic material to obtain a hydrophobic coating, the thickness of which is 0.5-2 mm.
[0010] In some embodiments of the present invention, the solar concentrator includes multiple Fresnel lenses and a reflector. The Fresnel lenses are placed at different positions and simultaneously focus sunlight onto the reflector. The reflector reflects the focused sunlight onto a solar absorption layer above the sludge drying device.
[0011] In some embodiments of the present invention, the solar energy storage device includes a molten salt tank and a heat-conducting pipe. The photothermal material coating on the surface of the molten salt tank can absorb and focus sunlight and convert it into heat energy stored in the molten salt. The heat-conducting pipe transfers the heat stored in the molten salt to a hydrophobic heat-conducting layer above the sludge at night to further dry the sludge.
[0012] In some embodiments of the present invention, the hydrophilic thermal conductive layer is located below the steam flow space, and the hydrophobic thermal conductive layer is located above the sludge drying space.
[0013] In some embodiments of the present invention, a gap is formed between the supporting purification layer and the hydrophobic and thermally conductive layer at a set distance, and the gap serves as a sludge drying space.
[0014] In a second aspect of the invention, a method for operating a solar multi-stage latent heat recovery type sludge drying system is provided, comprising:
[0015] Sunlight passes through the transparent insulation layer and is absorbed by the sunlight absorption layer, where it is converted into heat.
[0016] Heat is transferred to the sludge in the sludge drying space through the hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the steam flow space through the supporting purification layer.
[0017] Steam liquefies and releases latent heat in the steam flow space. The heat is transferred to the sludge in the next stage sludge drying space through the next stage hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the next stage steam flow space through the next stage support purification layer. This process is repeated to recover and utilize the latent heat of steam in multiple stages.
[0018] One or more technical solutions of the present invention have the following beneficial effects:
[0019] (1) The drying system provided by the present invention provides heat to the sludge drying device during the day through the solar concentrator and provides heat to the sludge drying device at night through the solar thermal storage device, which enables the continuous operation of the sludge drying device; at the same time, by utilizing solar energy, an abundant clean energy source, the light energy is converted into heat energy through the solar absorption layer for sludge drying, which greatly reduces energy consumption and effectively solves the problem of high energy consumption in current methods such as thermal sludge drying; by setting a transparent heat insulation layer on the solar absorption layer, full sunlight transmission can be ensured and heat loss can be reduced.
[0020] (2) This invention enables the directional transfer of latent heat from sludge through the provision of a hydrophobic thermally conductive layer and a trough-type hydrophilic thermally conductive layer, thereby achieving multi-stage latent heat recovery from sludge and further improving solar energy utilization efficiency. This solves the problems of low drying efficiency and large footprint associated with traditional solar-powered sludge drying methods. The hydrophobic thermally conductive layer transfers heat to the sludge while ensuring that the steam generated by the sludge does not liquefy on its surface. The sludge dries by heat, generating hot steam; the hydrophilic thermally conductive layer ensures that the hot steam liquefies on its surface, absorbing the latent heat released by the steam liquefaction and using it as a heat source to heat the next stage of sludge.
[0021] (3) The present invention can purify the steam generated by drying sludge by setting a support purification layer, which solves the problem of toxic gases generated in traditional sludge drying methods and the problem of secondary pollution. The support purification layer is made by coating fiberboard with adsorption materials such as activated carbon, and the adsorption purification efficiency can reach more than 90%. No additional purification equipment is required, which reduces costs. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of the solar multi-stage latent heat recovery sludge drying system of the present invention;
[0023] Figure 2 This is a cross-sectional view of the sludge drying device of the present invention;
[0024] Figure 3 This is a schematic diagram of the sludge drying device of the present invention.
[0025] In the diagram: 1. Transparent insulation layer; 2. Solar absorption layer; 3. Hydrophobic heat conduction layer; 4. Sludge; 5. Supporting purification layer; 6. Purified hot steam; 7. Hydrophilic heat conduction layer; 8. Water outlet; 9. Fresnel lens; 10. Reflector; 11. Molten salt tank; 12. Heat conduction pipe. Detailed Implementation
[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0027] Example 1
[0028] In a typical embodiment of the present invention, a solar multi-stage latent heat recovery type sludge drying system is proposed, such as... Figure 1-3 As shown, the device includes a solar concentrator, a solar thermal storage device, and a sludge drying device. The sludge drying device comprises multiple sludge drying spaces and multiple steam flow spaces, which are arranged alternately from top to bottom. The steam flow space is separated from the sludge drying space above it by a supporting purification layer 5, and from the sludge drying space below it by a hydrophilic thermal conductive layer 7 and a hydrophobic thermal conductive layer 3. Above the uppermost sludge drying space, a solar absorption layer 2 and a transparent insulation layer 1 are arranged in sequence. The uppermost sludge drying space uses solar energy as a heat source to dry the sludge, while the remaining sludge drying spaces use the latent heat released by steam liquefaction as a heat source. The solar concentrator provides heat to the sludge drying device during the day, and the solar thermal storage device provides heat to the sludge drying device at night.
[0029] In this embodiment, the solar concentrator includes multiple Fresnel lenses 9 and a reflector 10. The Fresnel lenses 9 are placed in different positions and simultaneously focus sunlight onto the reflector 10. The reflector 10 reflects the focused sunlight onto the solar absorption layer above the sludge drying device. The solar energy storage device includes a molten salt tank 11 and a heat pipe 12. The photothermal material coating on the surface of the molten salt tank 11 can absorb the focused sunlight and convert it into heat energy stored in the molten salt. At night, the heat pipe 12 transfers the heat stored in the molten salt to the hydrophobic heat-conducting layer above the sludge to further dry the sludge.
[0030] In this embodiment, the supporting purification layer 5 includes a fiberboard, with an adsorbent material coated on top of the fiberboard. The coating thickness of the adsorbent material is 0.1-1 mm. An adsorbent material coating (such as activated carbon) with a thickness in the range of 0.1-1 mm can effectively adsorb odorous gases and volatile organic compounds (VOCs) generated during sludge drying. An excessively thick coating may reduce adsorption efficiency and increase costs, while an excessively thin coating will not meet purification requirements.
[0031] The supporting purification membrane can be manually pulled out to fill sludge, and it also has a purification function, capable of purifying odorous gases and volatile organic compounds generated during sludge drying. The supporting purification layer 5 is drawer-shaped, and a gap of 0.5-2 cm is formed between it and the hydrophobic and thermally conductive layer 3 at a set distance. This gap serves as a sludge drying space for holding the sludge.
[0032] Specifically, the supporting purification layer is made by coating a fiberboard with adsorbent materials such as activated carbon. The thickness of the supporting purification membrane is 0.5-2 mm, and the area is 100-10000 cm². 2 The coating thickness of the activated carbon and other adsorption and purification materials is 0.1-1 mm, and the adsorption and purification efficiency can reach over 90%. In one specific embodiment of this example, activated carbon is coated onto a fiberboard to obtain a supported purification membrane. The supported purification membrane has a thickness of 1 mm and an area of 100 cm². 2 The activated carbon coating is 0.2 mm thick. The supporting purification layer is then pulled out and filled with sludge, which is 0.5 cm thick and has an area of 100 cm². 2 .
[0033] In this embodiment, the hydrophilic heat-conducting layer 7 includes a grooved heat-conducting plate, which is made of hydrophilic foamed copper. The grooves on the grooved heat-conducting plate serve as a steam flow space, and water outlets 8 are provided on the grooved heat-conducting plate.
[0034] Specifically, the top opening of the trough-shaped hydrophilic thermal conductive layer is covered by a supporting purification layer. This layer ensures that hot steam liquefies on its surface and absorbs the latent heat released during liquefaction, thus serving as a heat source to heat the next stage of sludge. The trough-shaped hydrophilic thermal conductive layer is fabricated from composite materials such as hydrophilic copper foam and graphene using methods such as template making. Its thickness ranges from 0.5 to 2 mm, and its area is 100 to 10000 cm². 2 After steam liquefies on the surface of the hydrophilic thermal conductive layer, it flows towards the outlet 8 due to gravity, where purified condensate is discharged. The outlet is located at the bottom of the lower side of the trough-type hydrophilic thermal conductive layer to collect the condensate after steam liquefaction. In one specific embodiment, the trough-type heat-conducting plate is made from commercially available hydrophilic foamed copper using a template method, with a thickness of 1 mm and an area of 100 cm². 2 Its thermal conductivity is 500 W / (m·K).
[0035] In this embodiment, the hydrophobic thermally conductive layer 3 includes a heat-conducting plate. The surface of the heat-conducting plate is chemically etched with a hydrophobic material to obtain a hydrophobic coating. The thickness of the hydrophobic coating is 0.5-2 mm. The thickness of the hydrophobic coating directly affects the heat transfer efficiency. A thickness range of 0.5-2 mm ensures efficient heat transfer to the sludge drying space while preventing steam from liquefying on its surface, thereby avoiding heat loss. Simultaneously, the coating thickness enhances the durability of the hydrophobic thermally conductive layer, reducing material damage caused by coatings that are too thin or too thick.
[0036] Specifically, the hydrophobic thermally conductive layer 3 is placed below the solar absorption layer 2, which can transfer the heat generated by the solar absorption layer 2 to the sludge for heating and drying. At the same time, its hydrophobic properties can ensure the directional transfer of latent heat of vapor. The hydrophobic thermally conductive layer is made by preparing a hydrophobic coating on the surface of materials with good thermal conductivity such as copper plates, aluminum plates, and carbon plates. Its thickness is 0.5-2mm and its thermal conductivity is 200-3500W / (m·K).
[0037] In one specific embodiment of this invention, a commercially obtained copper plate is chemically etched using a mixed solution of ferric chloride and hydrochloric acid to obtain a hydrophobic and thermally conductive layer with a thickness of 1 mm and an area of 100 cm². 2 Its thermal conductivity is 400 W / (m·K).
[0038] In this embodiment, the solar absorption layer 2 is in close contact with the transparent heat insulation layer 1. The solar absorption layer can efficiently absorb a wide range of sunlight and convert it into heat. The solar absorption layer 1 is made by coating with a photothermal material, and its thickness is 0.5-2 mm, with an area of 100-10000 cm². 2The photothermal conversion efficiency is approximately 60-90%. The thickness of the solar absorption layer affects the photothermal conversion efficiency; a thickness range of 0.5-2 mm ensures that the absorption layer efficiently absorbs sunlight and converts it into heat energy while minimizing heat loss to the outside. The solar absorption layer is prepared using low-cost photothermal materials such as graphene, copper oxide, and biochar through coating methods and chemical vapor deposition. In one specific embodiment of this example, commercially available graphene is used to prepare the solar absorption layer via a coating method, with a thickness of 1 mm and an area of 100 cm². 2 The photothermal conversion efficiency is approximately 85%.
[0039] In this embodiment, the transparent insulation layer 1 is made of a high-temperature transparent material, such as quartz glass or fused alumina. This ensures that sunlight can pass through while reducing heat exchange between the bottom light-absorbing layer and the external environment, thereby further concentrating heat within the system and reducing heat loss. The thickness of the transparent insulation layer is 0.5-2 mm, and the area is 100-10000 cm². 2 The solar transmittance is approximately 80-95%. The thickness of the transparent insulation layer is 0.5-2mm. This thickness range effectively reduces heat loss while ensuring high solar transmittance (80-95%).
[0040] In one specific embodiment of this example, the thickness is 1 mm and the area is 100 cm². 2 Quartz glass is used as a transparent insulation layer, with a transmittance of 85% in the solar spectrum range (approximately 300 nm to 2500 nm).
[0041] In this embodiment, the hydrophilic thermal conductive layer 7 is located below the steam flow space, and the hydrophobic thermal conductive layer 3 is located above the sludge drying space.
[0042] The solar-powered multi-stage latent heat recovery sludge drying system provided in this embodiment is divided into multiple stages. Each stage includes a hydrophobic thermally conductive layer 3, a sludge drying layer 4, a supporting purification layer 5, and a hydrophilic thermally conductive layer 7. The first stage also includes a transparent insulation layer 1 and a solar absorption layer 2. The heat source for the first stage is solar energy. From the second stage onwards, the heat source changes from solar energy to the latent heat generated by steam in the previous stage. The amount of latent heat recovered depends on the selection of the aforementioned photothermal materials and thermally conductive materials, enabling successful drying of 2-3 stages of sludge. The entire system is tilted to obtain more solar flux; the tilt angle is determined by the latitude of the application area. In specific applications, different light-absorbing materials can be used to improve solar absorption rate; the system structure can be adjusted, such as changing the material design of the transparent insulation layer and the hydrophilic thermally conductive layer, to adapt to different application environments and improve efficiency; different thermal calculation methods can be used to determine the optimal system size parameters to achieve higher solar energy utilization efficiency.
[0043] The working principle of the solar-powered multi-stage latent heat recovery sludge drying system provided in this embodiment is as follows: Solar energy is obtained through the top light-absorbing layer to heat and dry the sludge. A transparent insulating layer 1 ensures full sunlight transmission, reducing heat loss. A solar absorption layer 2 efficiently absorbs sunlight and converts it into heat. A hydrophobic thermally conductive layer 3 transfers heat to the sludge 4 while ensuring that the steam generated by the heated sludge does not liquefy on its surface. The sludge dries by heat, generating hot steam. A supporting purification layer holds the sludge 4 and has a purification function, purifying the steam that passes through it. A hydrophilic thermally conductive layer 7 ensures that the hot steam liquefies on its surface, absorbing the latent heat released by the steam liquefaction as a heat source to heat the next stage of sludge.
[0044] Example 2
[0045] In a typical embodiment of the present invention, a method for operating a solar multi-stage latent heat recovery type sludge drying system is provided, comprising:
[0046] Sunlight passes through the transparent insulation layer and is absorbed by the sunlight absorption layer, where it is converted into heat.
[0047] Heat is transferred to the sludge in the sludge drying space through the hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the steam flow space through the supporting purification layer.
[0048] Steam liquefies and releases latent heat in the steam flow space. The heat is transferred to the sludge in the next stage sludge drying space through the next stage hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the next stage steam flow space through the next stage support purification layer. This process is repeated to recover and utilize the latent heat of steam in multiple stages.
[0049] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.
Claims
1. A solar-powered multi-stage latent heat recovery type sludge drying system, characterized in that, The system includes a solar concentrator, a solar thermal storage device, and a sludge drying device. The sludge drying device comprises multiple sludge drying spaces and multiple steam flow spaces, which are arranged alternately from top to bottom. Each steam flow space is separated from the sludge drying space above it by a supporting purification layer, and from the sludge drying space below it by a hydrophilic thermal conductive layer and a hydrophobic thermal conductive layer. Above the uppermost sludge drying space, a solar absorption layer and a transparent insulation layer are arranged sequentially. The uppermost sludge drying space uses solar energy as a heat source to dry the sludge, while the remaining sludge drying spaces use the latent heat released from steam liquefaction as a heat source. The solar concentrator provides heat to the sludge drying device during the day, and the solar thermal storage device provides heat to the sludge drying device at night. The solar concentrator includes multiple Fresnel lenses and a reflector; The hydrophilic heat-conducting layer includes a grooved heat-conducting plate, which is made of hydrophilic foamed copper. The grooves on the grooved heat-conducting plate serve as a steam flow space, and water outlets are provided on the grooved heat-conducting plate. The hydrophobic thermal conductive layer includes a thermal conductive plate, the surface of which is chemically etched with a hydrophobic material to obtain a hydrophobic coating.
2. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, The supporting purification layer of the sludge drying device is drawer-shaped and made of fiberboard. The top of the fiberboard is coated with an adsorbent material, and the coating thickness of the adsorbent material is 0.1-1mm.
3. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, The thickness of the hydrophobic coating is 0.5-2 mm.
4. The solar multi-stage latent heat recovery sludge drying system according to claim 1, characterized in that, The solar absorption layer is closely attached to the transparent insulation layer. The solar absorption layer is made of photothermal material and has a thickness of 0.5-2 mm.
5. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, The Fresnel lenses are placed in different positions and simultaneously focus sunlight onto the reflectors, which then reflect the focused sunlight onto the sunlight absorption layer above the sludge drying device.
6. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, The solar thermal storage device includes a molten salt tank and a heat-conducting pipe. The photothermal material coating on the surface of the molten salt tank can absorb and focus sunlight and convert it into heat energy that is stored in the molten salt. At night, the heat-conducting pipe transfers the heat stored in the molten salt to the hydrophobic heat-conducting layer above the sludge to further dry the sludge.
7. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, The hydrophilic thermal conductive layer is located below the steam flow space, and the hydrophobic thermal conductive layer is located above the sludge drying space.
8. The solar multi-stage latent heat recovery sludge drying system as described in claim 1, characterized in that, A gap is formed between the supporting purification layer and the hydrophobic and thermally conductive layer at a set distance, and the gap serves as a sludge drying space.
9. A method for operating a solar-powered multi-stage latent heat recovery sludge drying system as described in any one of claims 1-8, characterized in that, include: Sunlight passes through the transparent insulation layer and is absorbed by the sunlight absorption layer, where it is converted into heat. Heat is transferred to the sludge in the sludge drying space through the hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the steam flow space through the supporting purification layer. Steam liquefies and releases latent heat in the steam flow space. The heat is transferred to the sludge in the next stage sludge drying space through the next stage hydrophobic heat-conducting layer for drying. During the sludge drying process, the steam generated by the evaporation of water enters the next stage steam flow space through the next stage support purification layer. This process is repeated to recover and utilize the latent heat of steam in multiple stages. Furthermore, during the day, sunlight from the solar concentrator is reflected onto the solar absorption layer above the sludge drying device; at night, the solar thermal storage device transfers the heat stored in the molten salt to the hydrophobic thermal conductive layer above the sludge.