Sandwich type desiccant composite vacuum membrane dehumidification assembly and desiccant preparation method

Abstract

This invention relates to the field of air humidity control technology, providing a sandwich-type desiccant composite vacuum membrane dehumidification component and a method for preparing the desiccant. The component includes a water vapor selectively permeable membrane, a porous support layer, a membrane support substrate, a desiccant, an internal heat source, and an external negative pressure source. The membrane support substrate has multiple cavities internally, which are interconnected by channels, and the desiccant is filled within these cavities. Water vapor in the humid air permeates through the water vapor selectively permeable membrane into the permeate-side space and is adsorbed by the desiccant, thereby reducing the partial pressure of water vapor on the permeate side and enhancing the mass transfer driving force across the membrane. Under the action of the external negative pressure source and the internal heat source, the water adsorbed by the desiccant can be desorbed and discharged through the channels, achieving regeneration. This invention improves dehumidification efficiency and reduces regeneration energy consumption by constructing a membrane separation and adsorption coupling structure. In particular, by constructing a desiccant-filled structure, a continuous reduction in water vapor partial pressure is achieved, thereby significantly improving the membrane dehumidification mass transfer efficiency.

Description

Technical Field

[0001] This invention belongs to the field of air humidity control technology, and particularly relates to a sandwich-type desiccant composite planar vacuum membrane dehumidification component and desiccant preparation method suitable for large-area places such as industrial plants, data centers and large laboratories. It achieves deep and efficient dehumidification through membrane separation, vacuum negative pressure, internal heat source and desiccant synergistic effect, which can meet the air humidity control needs of large air volume. Background Technology

[0002] Precise control of air humidity is crucial in fields such as precision electronic device storage, optical instrument storage, and industrial environmental control. Existing dehumidification technologies mainly include condensation dehumidification, adsorption dehumidification, and membrane separation dehumidification. Condensation dehumidification relies on temperature differences to achieve water vapor condensation, making it highly susceptible to ambient temperature and prone to icing at low temperatures, leading to system instability. While adsorption dehumidification offers high dehumidification depth, it typically requires heating for adsorbent regeneration, resulting in high energy consumption, complex equipment, and the risk of thermal damage. Membrane separation dehumidification utilizes the selective permeation of water vapor through a membrane for gas separation, offering advantages such as simple structure and low energy consumption. However, its dehumidification capacity is limited by the water vapor partial pressure difference across the membrane; as the water vapor concentration on the permeate side increases, the mass transfer driving force decreases, limiting dehumidification efficiency. To improve membrane dehumidification efficiency, existing technologies primarily optimize airflow organization or membrane area expansion, but research on controlling the water vapor partial pressure on the permeate side is relatively insufficient, especially regarding achieving high-efficiency dehumidification without increasing energy consumption, where a technological gap remains. Therefore, it is necessary to provide a composite structure that can create a low water vapor partial pressure environment on the membrane permeation side and has both adsorption and regeneration capabilities, so as to improve the mass transfer efficiency of the membrane dehumidification process and the stability of system operation. Summary of the Invention

[0003] The purpose of this invention is to provide a sandwich-type desiccant composite vacuum membrane dehumidification component and a desiccant preparation method. By filling the permeate side of the water vapor selectively permeable membrane with desiccant material, an adsorption-permeation coupling structure is constructed to reduce the water vapor partial pressure and relative humidity of the air on the permeate side, thereby enhancing the mass transfer driving force on both sides of the membrane and realizing in-situ regeneration of the desiccant under negative pressure conditions, improving dehumidification efficiency and reducing energy consumption.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a sandwich-type desiccant composite vacuum membrane dehumidification component and a desiccant preparation method, comprising a water vapor selectively permeable membrane, a porous support layer, a membrane support substrate, a desiccant, an internal heat source, and an external negative pressure source; To make full use of the available space, water vapor selectively permeable membranes are provided on both the front and back sides of the membrane support substrate. The membrane support substrate is a plate-like structure with an internal cavity, and the porous support layer and the water vapor selectively permeable membrane are provided on both its upper and lower surfaces.

[0005] To ensure that the water vapor selectively permeable membrane is subjected to uniform stress under the action of the external negative pressure source, a porous support layer is provided between the water vapor selectively permeable membrane and the membrane support substrate; the porous support layer has good air permeability, with an air permeability pressure drop ≤50Pa at a face wind speed of 0.5m / s, a compressive strength ≥0.2MPa, and does not collapse or break under a pressure of 0.1MPa; To expel water vapor or other gases from the membrane support substrate, a gas outlet is provided on the side of the membrane support substrate. This gas outlet is connected to an external negative pressure source. Under negative pressure, water vapor within the membrane support substrate collects at the gas outlet through the internal channels of the membrane support substrate and is then expelled. The vacuum level generated by the external negative pressure source relative to ambient pressure ranges from 40 kPa to 80 kPa. The internal channels of the membrane support substrate are grooves or microchannels between adjacent internal cavities of the membrane support substrate, forming a mesh-like or staggered structure to create a multi-path gas transport network.

[0006] To enhance the desorption effect of the desiccant after absorbing water vapor, the internal cavity of the membrane support substrate is filled with the desiccant and the internal heat source. The internal heat source promotes the desorption of water vapor adsorbed by the desiccant by increasing the temperature of the desiccant. The temperature of the internal heat source is between 35°C and 80°C. The internal heat source is achieved by heating with an insulating layer, a micro heat pipe, or microwave heating.

[0007] To facilitate the filling of the desiccant, the desiccant is a granular desiccant with a particle diameter of 0.5 mm to 5 mm, and the material composition is one or more combinations of silica gel, molecular sieve, montmorillonite, hygroscopic salt, adsorbent metal-organic framework material, or polyacrylamide-activated carbon-sand desiccant.

[0008] To facilitate the installation of the sandwich-type desiccant composite vacuum membrane dehumidification assembly, positioning holes are provided through the corners of the membrane support substrate. These positioning holes are used to install and fix a single component or to stack and assemble multiple components.

[0009] To ensure the sealing performance of the sandwich-type desiccant composite vacuum membrane dehumidification component and to better create an internal negative pressure environment, sealant, foam gaskets, or O-rings are used to seal the gaps.

[0010] In order to adjust the adsorption and desorption properties of the desiccant according to actual engineering needs, the preparation method of the polyacrylamide-activated carbon-sand desiccant includes the following steps: Step 1: Mix sand, activated carbon, and polyacrylamide evenly according to the following mass ratio: sand to activated carbon in a 1:1 ratio, and the mass of polyacrylamide should be 5-50% of the total mass of sand and activated carbon. Step 2: Add deionized water to the mixture prepared in Step 1, making the total amount of water 3 to 10 times the mass of the mixture, and stir until the polyacrylamide is completely dissolved, forming a homogeneous wet mixture; Step 3: Process the wet mixture prepared in Step 2 into particles with a diameter of 0.5~5 mm; Step 4: Prepare a calcium chloride solution by dissolving calcium chloride in deionized water to obtain a calcium chloride concentration of 5-40 wt%. Step 5: Soak the wet granules prepared in Step 3 in the calcium chloride solution prepared in Step 4 for 0.5 to 12 hours, stirring the calcium chloride solution gently every 0.5 hours to allow the calcium chloride solution to gradually penetrate and react with the polyacrylamide to form a stable cross-linked structure. Step 6: Take out the soaked granules from Step 5 and place them in an oven. Set the temperature to 40~80℃ and dry for 12~24 hours. The dried granules are the desiccant.

[0011] In the polyacrylamide-activated carbon-sand desiccant, activated carbon is used to increase particle porosity and specific surface area, thereby improving the desiccant's water vapor adsorption capacity and mass transfer rate; sand, as an inorganic skeleton filler, is used to improve the particle's compressive strength, anti-breakage performance, and bulk density, preventing particles from breaking, migrating, or agglomerating during filling, use, and regeneration; polyacrylamide, as a binder and crosslinking matrix, is used to uniformly bond the sand and activated carbon into shape, and undergoes a crosslinking reaction with calcium chloride to form a stable three-dimensional network, ensuring the integrity of the particle structure.

[0012] Compared with the prior art, the present invention has the following beneficial effects: By filling the permeate side of the membrane with desiccant, water vapor permeating through the membrane is adsorbed in real time, which significantly reduces the water vapor partial pressure and relative humidity on the permeate side, thereby continuously enhancing the mass transfer driving force on both sides of the membrane and improving dehumidification efficiency. This invention organically combines the membrane separation process with the adsorption process, so that water vapor is quickly captured after passing through the membrane, avoiding mass transfer attenuation caused by water vapor accumulation on the permeate side. Under negative pressure and internal heat source, the moisture adsorbed by the desiccant can be directly desorbed and discharged, reducing system energy consumption and simplifying the structure; The desiccant is filled in an independent cavity, effectively avoiding the problems of easy migration and agglomeration of traditional bulk desiccants; This component can be integrated as an independent functional unit into different types of vacuum membrane dehumidification systems, exhibiting excellent adaptability and scalability.

[0013] The features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the membrane support substrate structure of the sandwich-type desiccant composite vacuum membrane dehumidification component of the present invention.

[0015] Figure 2 This is a schematic diagram of the assembly method of the sandwich-type desiccant composite vacuum membrane dehumidification component of the present invention.

[0016] Figure 3 This is a schematic diagram of the sandwich-type desiccant composite vacuum membrane dehumidification component of the present invention after multiple layers are stacked.

[0017] Figure reference numerals: 1-1 Gas outlet, 1-2 Internal cavity of membrane support substrate, 1-3 Internal channel of membrane support substrate, 1-4 Positioning hole; 2-1 Water vapor selective permeable membrane, 2-2 Porous support layer, 2-3 Membrane support substrate.

[0018] like Figures 1-3 As shown, in the sandwich-type desiccant composite vacuum membrane dehumidification assembly of the present invention: The membrane support substrate (2-3) is a plate-shaped component with an internal cavity structure, and multiple internal cavities (1-2) are provided inside the membrane support substrate. The internal cavities (1-2) are used to contain desiccant materials. The internal cavities (1-2) of the membrane support substrate are interconnected through internal channels (1-3). The internal channels (1-3) of the membrane support substrate can be grooves or microchannel structures set between adjacent cavities to realize the flow and collection of gas in the permeate side space. The upper and lower surfaces of the membrane support substrate (2-3) are respectively provided with the porous support layer (2-2) and the water vapor selective permeable membrane (2-1), which together form a permeation side space; The gas outlet (1-1) is located on the side of the membrane support substrate (2-3) and communicates with the internal channel (1-3) of the membrane support substrate, and is used to discharge gas under external negative pressure. The positioning holes (1-4) are located at the corners of the membrane support substrate (2-3) to enable the installation and positioning of components or multi-layer stacking.

[0019] In this embodiment, as Figure 1 – Figure 3 As shown: The membrane support substrate (2-3) has a flat plate structure, and multiple internal cavities (1-2) arranged in an array are provided inside the membrane support substrate. Each internal cavity (1-2) of the membrane support substrate is used to fill particulate desiccant material. The internal cavities (1-2) of the membrane support substrate are interconnected through internal channels (1-3). The internal channels (1-3) of the membrane support substrate are distributed in a mesh or staggered manner, so that each cavity forms an interconnected gas flow network. A porous support layer (2-2) and a water vapor selectively permeable membrane (2-1) are respectively disposed on the upper and lower surfaces of the membrane support substrate (2-3), thereby forming a relatively closed permeable side space between the membrane and the substrate; Water vapor in the humid air passes through the water vapor selective permeation membrane (2-1) into the internal cavity (1-2) of the membrane support substrate and is adsorbed by the desiccant filled therein, thereby reducing the water vapor partial pressure on the permeate side; The gas outlet (1-1) provided on the side of the membrane support substrate (2-3) is connected to the internal channel (1-3) of the membrane support substrate. Under the action of an external negative pressure source, the unadsorbed water vapor and the water vapor generated by desorption can be collected through the internal channel (1-3) of the membrane support substrate and discharged through the gas outlet (1-1). Under continuous negative pressure, the moisture adsorbed by the desiccant can be desorbed, and the desorbed water vapor is discharged through the internal channels (1-3) and gas outlet (1-1) of the membrane support substrate, thereby realizing the regeneration of the desiccant; The internal heat source and the desiccant are placed inside the internal cavity (1-2) of the membrane support substrate. The internal heat source enhances the desorption of moisture from the desiccant, and the desiccant reduces the relative humidity of the air inside the internal cavity (1-2) of the membrane support substrate, thereby enhancing the transmembrane transfer of water vapor.

Claims

1. A sandwich desiccant composite vacuum membrane dehumidifying assembly, characterized in that: It includes a water vapor selectively permeable membrane, a porous support layer, a membrane support substrate, a desiccant, an internal heat source, and an external negative pressure source; The membrane support substrate is a plate-shaped structure with an internal cavity, and the porous support layer and the water vapor selectively permeable membrane are provided on both its upper and lower surfaces. The porous support layer is located between the water vapor selectively permeable membrane and the membrane support substrate, and is used to support the water vapor selectively permeable membrane and ensure air permeability. The membrane support substrate has multiple independent cavities inside, which are interconnected by internal channels. The cavities are filled with the desiccant and the internal heat source. The membrane support substrate is provided with a gas outlet on its side, which is connected to the external negative pressure source. Under the action of negative pressure, water vapor in the membrane support substrate is collected in the gas outlet through the internal channels of the membrane support substrate and is discharged. The gaps in the sandwich-type desiccant composite vacuum membrane dehumidification component are sealed using a sealing structure.

2. The sandwich desiccant composite vacuum membrane dehumidifying assembly according to claim 1, characterized in that: The porous support layer has an air permeability pressure drop of ≤50Pa at a surface wind speed of 0.5m / s, a compressive strength of ≥0.2MPa, and does not collapse or break under a pressure of 0.1MPa.

3. The sandwich desiccant composite vacuum membrane dehumidifying assembly according to claim 1, characterized in that: The internal channels of the membrane support substrate are grooves or microchannels between adjacent internal cavities of the membrane support substrate, and are distributed in a mesh or staggered structure to form a multi-path gas transport network.

4. The sandwich desiccant composite vacuum membrane dehumidifying assembly according to claim 1, characterized in that: The desiccant is a granular desiccant with a particle diameter of 0.5 mm to 5 mm, and the material composition is one or more combinations of silica gel, molecular sieve, montmorillonite, hygroscopic salt, adsorbent metal-organic framework material, or polyacrylamide-activated carbon-sand desiccant.

5. The sandwich-type desiccant composite vacuum membrane dehumidification assembly according to claim 1, characterized in that: The membrane support substrate has positioning holes at its corners, which are used to install and fix a single component or to stack and assemble multiple components.

6. The sandwich-type desiccant composite vacuum membrane dehumidification assembly according to claim 1, characterized in that: The internal heat source is an insulating heating wire, a miniature heat pipe, or a microwave heating device, with a heating temperature set to 35℃~80℃.

7. The sandwich-type desiccant composite vacuum membrane dehumidification assembly according to claim 1, characterized in that: The vacuum level generated by the external negative pressure source relative to the ambient pressure is in the range of 40 kPa to 80 kPa.

8. A method for preparing a polyacrylamide-activated carbon-sand desiccant for use in the sandwich-type desiccant composite vacuum membrane dehumidification assembly according to any one of claims 1-7, characterized in that: The method for producing this desiccant includes the following steps: Step 1: Mix sand, activated carbon, and polyacrylamide evenly according to the following mass ratio: sand to activated carbon in a 1:1 ratio, and the mass of polyacrylamide should be 5-50% of the total mass of sand and activated carbon. Step 2: Add deionized water to the mixture prepared in Step 1, making the total amount of water 3-10 times the mass of the mixture, and stir until the polyacrylamide is completely dissolved, forming a homogeneous wet mixture; Step 3: Process the wet mixture prepared in Step 2 into particles with a diameter of 0.5~5 mm; Step 4: Prepare a calcium chloride solution by dissolving calcium chloride in deionized water to obtain a calcium chloride concentration of 5-40 wt%. Step 5: Soak the wet granules prepared in Step 3 in the calcium chloride solution prepared in Step 4 for 0.5 to 12 hours, stirring the calcium chloride solution gently every 0.5 hours to allow the calcium chloride solution to gradually penetrate and react with the polyacrylamide to form a stable cross-linked structure. Step 6: Take out the soaked granules from Step 5 and place them in an oven. Set the temperature to 40~80°C for drying. The drying time is 12~24 hours. The dried granules are the desiccant.

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