Composite adsorption medium and adsorption bed based on the same

Abstract

The application provides a composite adsorption medium and an adsorption bed based on the composite adsorption medium, and a preparation method of the composite adsorption medium is as follows: S1, silica gel, metal organic framework material and a binder are uniformly mixed according to a mass ratio of 1:1:0.15 to obtain a mixed powder; S2, deionized water is heated to 60 DEG C, the mixed powder is added, and stirring is uniformly carried out, and then standing and cooling to room temperature are carried out to obtain a mixed solution; S3, a macroporous scale porous medium is prepared and pretreated to remove surface oxides; S4, the pretreated macroporous scale porous medium is immersed in the mixed solution, liquid accumulation in the pores is blown off, and the immersion is repeated for multiple times; and S5, drying treatment is carried out after the immersion. The application also provides the adsorption bed based on the composite adsorption medium, the adsorption bed has higher adsorption capacity, heat and mass transfer effects are better, and structural stability is good, and the adsorption bed can be applied to an adsorption refrigeration or dehumidification system, and system performance can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adsorption refrigeration or adsorption dehumidification technology, and in particular to a composite adsorption medium and an adsorption bed based on the composite adsorption medium. BACKGROUND

[0002] To improve energy utilization efficiency and reduce energy consumption, waste heat utilization as a technology for energy cascade utilization and overall energy efficiency improvement has become a necessary way for energy saving and carbon reduction. Adsorption refrigeration technology and adsorption dehumidification technology as typical waste heat utilization technologies can be driven by low-grade heat sources and have significant advantages in the utilization of low-grade energy such as industrial waste heat, industrial waste heat, fuel cell waste heat, tail gas waste heat and solar energy. They have the advantages of energy saving and environmental protection, no noise during operation, no corrosion and crystallization problem of the system, simple control, etc., and have been widely studied and concerned.

[0003] In the adsorption refrigeration and adsorption dehumidification system, the adsorption and desorption characteristics of the adsorbent material largely determine the performance of the system. In traditional physical adsorbent materials, silica gel is one of the most widely used inorganic materials in adsorption refrigeration machines and desiccant dehumidifiers, with the characteristics of low price, abundant natural reserves and high porosity. Its disadvantage is that the adsorption performance is not high, which leads to low system efficiency. The heat transfer performance of the adsorption bed also greatly affects the performance of the system. The adsorption bed is mainly a packed adsorption bed, and there is a large contact thermal resistance between the heat exchange metal surface and the adsorbent. The contact thermal resistance between the particles in the adsorbent is also large, which leads to low overall heat transfer capacity of the adsorption bed.

[0004] Therefore, it is urgent to design an adsorption medium and an adsorption bed to enhance the heat and mass transfer effect of the adsorption refrigeration system or the adsorption dehumidification system, and thus improve the overall performance of the system. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provides a composite adsorption medium and an adsorption bed based on the composite adsorption medium, which has a higher adsorption capacity, better heat and mass transfer effect, good structural stability, can be applied to an adsorption refrigeration or dehumidification system, and the performance of the system can be greatly improved.

[0006] The present application provides the following technical solutions:

[0007] The present application provides a preparation method of a composite adsorption medium, comprising the following steps:

[0008] S1, silica gel, metal organic framework material and binder are mixed uniformly according to a mass ratio of 1:1:0.15 to obtain a mixed powder;

[0009] S2, the deionized water is heated to 60℃, the mixed powder is added, stirred uniformly, and cooled to room temperature to obtain a mixed solution;

[0010] S3, preparing a macroporous medium and pre-treating to remove surface oxides;

[0011] S4, immersing the pre-treated macroporous medium into a mixed solution, blowing off the accumulated liquid in the pores, and repeating the immersion multiple times;

[0012] S5, drying treatment after immersion.

[0013] The metal organic framework material has high surface area and high adsorption capacity, the composite adsorbent with good comprehensive performance and low cost is prepared by compounding low-cost silica gel and metal organic framework material with high adsorption performance, the composite adsorbent is immersed and coated in the macroporous medium with high specific surface area, the coating area can be effectively increased, the contact thermal resistance is reduced, the adsorption capacity is improved, and the adsorption performance of the adsorption medium is improved.

[0014] Further, the macroporous medium has a non-uniform porosity, and the porosity gradually decreases along the airflow adsorption direction.

[0015] By adopting the non-uniform porosity and the specific setting of different porosity sections, the porosity of the macroporous medium gradually decreases along the airflow adsorption direction, so that the heat transfer performance of the composite adsorption medium is improved, the adsorption temperature is reduced, and the adsorption capacity is improved.

[0016] Further, the specific preparation process of the macroporous medium is as follows: foam plastic or high polymer material with different porosities is used as a module mold, the module mold is used to prepare an integral mold according to the required porosity distribution, high-temperature metal liquid is injected into the integral mold, and the macroporous medium is obtained.

[0017] Further, the macroporous medium is a rectangular macroporous medium with a pore size of 20 ppi.

[0018] Further, the pre-treatment is to place the macroporous medium in 5% dilute hydrochloric acid for cleaning and soaking, then clean with deionized water, and dry.

[0019] Further, the drying treatment is as follows: the initial temperature is kept at 60℃, the temperature is increased by 15℃ every 20 minutes, the temperature is kept at 120℃ after being increased to 120℃, and the weight is taken every 20 minutes until the weight is constant.

[0020] Further, the metal organic framework material includes MIL-100, DUT-67 or UiO-66, and the binder includes PVP, PVA, PVB, HEC or HPMC.

[0021] Further, the method further comprises repeating the step S4 and the step S5 to ensure that the composite adsorbent is coated on the macroporous scale porous medium framework and the macroporous scale porous medium retains sufficient air flow channels.

[0022] The application further provides the composite adsorption medium prepared by the preparation method.

[0023] The application further provides an adsorption bed comprising a structural member and the composite adsorption medium, the composite adsorption medium being fixedly arranged between two adjacent structural members, the structural member being provided with a fluid channel, the fluid channel being arranged perpendicularly to the air flow adsorption direction, and the porosity of the composite adsorption medium gradually decreasing along the air flow adsorption direction.

[0024] The adsorption bed effectively improves the adsorbent mass and heat transfer capacity per unit volume of the adsorption bed, and improves the overall adsorption performance of the adsorption bed, and based on the characteristics of the composite adsorption medium, the adsorption bed has strong impact resistance, excellent shock absorption capacity and strong structural stability.

[0025] The application has the following beneficial effects:

[0026] 1. The adsorption material of the application is a composite material with lower cost and higher adsorption performance, which is coated on the macroporous scale porous medium with high specific surface area and high thermal conductivity, so as to effectively improve the adsorbent mass and heat transfer capacity per unit volume of the adsorption bed, and further improve the overall adsorption performance of the adsorption bed. Meanwhile, the macroporous scale porous medium modules with different porosities are arranged and distributed along the air flow direction in a manner that the porosity gradually decreases, so as to effectively improve the heat transfer performance of the adsorption bed and reduce the adsorption temperature (which is helpful to improve the adsorption capacity).

[0027] 2. The adsorption bed of the application adopts the micro-channel heat exchanger structure, which can effectively improve the heat exchange effect and make the adsorption bed more compact. The macroporous scale porous medium structure form used between the micro-channels can reinforce the structural stability of the adsorption bed and improve its durability. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0029] Figure 1 It is a schematic diagram of the porosity distribution of the adsorption bed in the embodiment of the application.

[0030] Figure 2 It is a schematic diagram of the structure of the adsorption bed in the embodiment 1 of the application.

[0031] Figure 3 This is a schematic diagram of the structure of the composite adsorption medium in Example 1 of the present invention;

[0032] Figure 4 This is a top view of the adsorption bed in Embodiment 1 of the present invention;

[0033] Figure 5 This is a schematic diagram of the porosity distribution of the adsorption bed in Embodiment 1 of the present invention;

[0034] Figure 6 This is a schematic diagram of the porosity distribution of the adsorption bed in Embodiment 2 of the present invention;

[0035] Figure 7 This is a schematic diagram of the porosity distribution of the adsorption bed in Embodiment 3 of the present invention;

[0036] Figure 8 This is a schematic diagram of the porosity distribution of the adsorption bed in Comparative Example 1 of the present invention;

[0037] Figure 9 This is a bar chart showing the refrigeration performance of the adsorption bed in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a composite adsorption medium, the preparation method of which includes the following steps:

[0040] S1, silicone, metal-organic framework material, and binder are mixed evenly in a mass ratio of 1:1:0.15 to obtain a mixed powder;

[0041] S2. Heat deionized water to 60°C, slowly add the mixed powder in multiple batches, stirring evenly to prevent clumping and splashing, and let it stand to cool to room temperature to obtain a mixed solution.

[0042] S3. Prepare macroporous media, and soak the macroporous media in 5% dilute hydrochloric acid for 40 minutes, then clean it with deionized water, and then dry it in a 90℃ drying oven to remove surface oxides.

[0043] S4. Immerse the pretreated macroporous medium into the mixed solution, and use an air compressor to blow away the liquid accumulated in the pores of the macroporous medium. Repeat the immersion process multiple times.

[0044] S5, set the oven at 60℃, and put the macroporous medium after impregnation into the oven for drying, and increase the temperature by 15℃ every 20 minutes (heat according to the temperature gradient to prevent the coating effect from being affected by too rapid temperature increase); when the temperature increases to 120℃, continue to keep the temperature for a period of time, and then take out and weigh every 20 minutes until the mass is unchanged, which indicates that the drying is complete, and the mass after complete drying is recorded.

[0045] To ensure that the composite adsorption medium has sufficient amount of adsorbent, the method further comprises repeating steps S4 and S5 to ensure that the macroporous medium framework is coated with the composite adsorbent, and the macroporous medium retains sufficient air flow channels.

[0046] Specifically, the macroporous medium has a non-uniform porosity, and the porosity gradually decreases along the air flow adsorption direction, and the preparation process is as follows: a foam plastic with different porosities is used as a module mold, the module mold is used to prepare a whole mold according to the required porosity distribution, a high-temperature metal liquid is injected, and a macroporous medium is obtained, and the prepared macroporous medium is a 20 ppi rectangular macroporous medium.

[0047] Since copper has good heat conduction performance compared with other metal materials, and the strain characteristics are also better than other metal materials, the volume proportion is small, the heat transfer can be enhanced, and the structure stability can be reinforced, therefore, the macroporous medium in the application adopts copper material.

[0048] In specific embodiments, the metal organic framework material used is MIL-100, DUT-67 or UiO-66, and the binder used is PVP, PVA, PVB, HEC or HPMC.

[0049] The embodiment of the application also provides an adsorption bed based on the above adsorption medium, which comprises a structural member and a composite adsorption medium, the composite adsorption medium is fixedly arranged between two adjacent structural members, a fluid channel is formed in the structural member, the fluid channel is arranged vertically to the air flow adsorption direction, the porosity of the composite adsorption medium gradually decreases along the air flow adsorption direction, and the porosity distribution of the adsorption bed is as shown in Figure 1 i The value of the number N of the porosity zones of the macroporous medium and the distribution of the porosity can be set in different ways according to actual application conditions.

[0050] Specifically, the structural member is a parallel flow microchannel heat exchanger, which has strong heat exchange capacity and compact structure, and the composite adsorption medium is welded with the structural member to ensure close combination.

[0051] The design and performance of the adsorption bed are described below through specific embodiments.

[0052] Embodiment 1​

[0053] Referring to Figure 2 , the embodiment provides an adsorption bed when the number N of porosity regions of a macropore scale porous medium is 2, comprising a composite adsorption medium 1, a heat exchange fluid 2, a fluid channel 3, a structure 4, an adsorbate 5, a composite adsorbent 6, the composite adsorption medium is arranged between two adjacent structures 4, the heat exchange fluid 2 flows in the fluid channel 3 arranged on the structure 4, the adsorbate 5 flows along the composite adsorption medium 1 in a direction perpendicular to the direction of the heat exchange fluid 2;

[0054] Referring to Figure 3 , Figure 4 , the porosity of the composite adsorption medium is not uniform, and the porosity gradually decreases along the flow direction of the adsorbate 5 (region I > region II). It should be noted that the figure is only an example of the porosity distribution of the composite adsorption medium, and different distribution conditions and different numbers N of regions can be used according to actual application conditions.

[0055] Referring to Figure 5 , wherein 7 is a heat exchange fin, 8 is a fin spacing, 9 is a fin height, II corresponds to the porosity of 0.2 of the adsorption bed, and I corresponds to the porosity of 0.4 of the adsorption bed. In order to control the average porosity of the whole adsorption bed to be 0.3, the volume ratio of the II and I adsorption bed is 1:1.

[0056] When the adsorption bed starts the adsorption process, the heat exchange fluid 2 flows through the fluid flow channel 3 in the structure 4 to perform cooling and heat exchange, the adsorbate 5 flows along the composite adsorption medium 1 between the two structures 4 in a direction perpendicular to the direction of the heat exchange fluid 2, the composite adsorbent 6 coated on the composite adsorption medium 1 is adsorbed, and the adsorbate 5 first passes through a macropore scale porous medium structure with a large porosity and then passes through a macropore scale porous medium structure with a small porosity. Compared with a traditional structure, the porosity gradually decreases along the flow direction, the overall mass transfer performance is improved, the adsorption temperature is reduced (which helps to improve the adsorption capacity), and the system performance is improved. The use of a macropore scale porous medium structure form can strengthen the structural stability of the adsorption bed, improve its durability, improve the overall heat transfer effect of the adsorption bed, and at the same time, due to the large specific surface area of the macropore scale porous medium, the mass per unit volume of the coated composite adsorbent is higher than that of the ordinary adsorbent coated per unit volume under the fin, which is beneficial to improve the system performance. The composite adsorbent 6 has better comprehensive performance than pure silica gel, that is, better adsorption performance at a lower cost.

[0057] Example 2

[0058] The difference from example 1 is that, as shown in Figure 6 , III corresponds to the porosity of 0.35 of the adsorption bed, the average porosity of the whole adsorption bed is 0.3, and the volume ratio of the II and III adsorption bed is 1:2.

[0059] Example 3

[0060] The difference from Example 1 is that, as shown in Figure 7 , the porosity of IV corresponding to the adsorption bed is 0.5, the average porosity of the whole adsorption bed is 0.3, and the volume ratio of II to IV adsorption bed is 2:1.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that, as shown in Figure 8 , wherein the porosity of V corresponding to the adsorption bed is 0.3.

[0063] The performance of the adsorption bed with the porosity distribution in the above-mentioned Example 1, Example 2, Example 3 and Comparative Example 1 is applied in the adsorption refrigeration system, and the comparison of the results under different structural sizes is shown in Figure 9 , wherein it is seen that for the adsorption bed with larger fin spacing, the refrigeration performance of the example with step porosity is obviously higher than that of the comparative example with uniform porosity, wherein when the fin spacing is 43mm, the COP of Example 1, Example 2 and Example 3 is respectively 12.91%, 12.62% and 11.63% higher than that of the comparative example, and the SCP is respectively 95.49%, 94.33% and 92.02% higher than that of the comparative example. The COP of Example 1, Example 2 and Example 3 is higher than that of the comparative example under different fin heights, and in summary, the porosity gradient distribution mode of the porous medium module proposed in the present application can effectively ensure that the adsorption bed has better overall performance.

[0064] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of preparing a composite adsorbent medium, characterized by, The method comprises the following steps: S1, uniformly mixing silica gel, metal organic framework material and binder in a mass ratio of 1:1:0.15 to obtain a mixed powder; S2, heating deionized water to 60 DEG C, adding the mixed powder, stirring uniformly, and standing to cool to room temperature to obtain a mixed solution; S3, preparing a macroporous medium and pre-treating the same to remove surface oxides; the macroporous medium has a non-uniform porosity which gradually decreases along the airflow adsorption direction; the macroporous medium is prepared by using foamed plastic or high polymer material with different porosities as a module mold, preparing a whole mold according to the required porosity distribution, and injecting high-temperature metal liquid into the whole mold to obtain the macroporous medium; S4, immersing the pre-treated macroporous medium in the mixed solution, blowing off the liquid in the pores, and repeatedly immersing multiple times; S5, drying treatment after immersion.

2. The method of claim 1, wherein: The macroporous medium is a rectangular macroporous medium with a pore size of 20 ppi.

3. The method of claim 1, wherein: The pre-treatment is cleaning and soaking the macroporous medium in 5% dilute hydrochloric acid, then cleaning with deionized water, and drying.

4. The method of claim 1, wherein: The drying treatment is specifically: maintaining an initial temperature of 60 DEG C, increasing by 15 DEG C every 20 minutes, increasing to 120 DEG C and continuously maintaining the temperature, and taking out and weighing every 20 minutes until the mass is unchanged.

5. The method of claim 1, wherein: The metal organic framework material includes MIL-100, DUT-67 or UiO-66, and the binder includes PVP, PVA, PVB, HEC or HPMC.

6. The method of claim 1, wherein: The method further comprises repeating steps S4 and S5 to ensure that the macroporous medium framework is coated with a composite adsorbent, and the macroporous medium retains sufficient air flow channels.

7. A composite adsorbent medium, characterized by, Prepared by the preparation method of any one of claims 1-6.

8. An adsorption bed, characterized in that The composite adsorption medium of claim 7 is fixedly arranged between two adjacent structural members, the structural members are provided with fluid channels, the fluid channels are arranged perpendicular to the airflow adsorption direction, and the porosity of the composite adsorption medium gradually decreases along the airflow adsorption direction.

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