Thermal chemical heat storage particles with stable particle size and batch preparation method thereof
Thermochemical heat storage particles with stable particle size were prepared through wet granulation and coating processes, which solved the problem of unstable particle size of Ca(OH)2/CaO materials during heat storage and exothermic process, and achieved efficient thermochemical heat storage and mass production.
Patent Information
- Application Number
- CN202510392360.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-08-22
AI Technical Summary
The existing Ca(OH)2/CaO thermochemical heat storage materials have large volume changes and poor mechanical properties during the heat storage and exothermic process, resulting in unstable particle size and easy agglomeration, affecting the uniformity of heat transfer and mass transfer in the reactor. The existing preparation technology is complex and is not suitable for mass production.
The heat storage materials, pore-forming agents, and binders are used as raw materials, and the shell is formed through wet granulation and coating processes, combined with ceramic materials to form a shell to prepare thermal chemical heat storage particles with stable particle size, and mass production is achieved using wet granulators and coating machines.
The batch preparation of thermochemical heat storage particles with stable particle size is realized, the mechanical properties and porosity are improved, and the efficient thermochemical heat storage process is ensured. It is suitable for reactors such as fluidized beds.
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Figure CN120519135A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of thermochemical heat storage, and in particular relates to thermochemical heat storage particles with stable particle size and a batch preparation method thereof. Background Art
[0002] To address increasingly severe energy and environmental challenges, we need to increase the development and utilization of renewable energy. However, most renewable energy sources, such as solar, wind, and geothermal energy, suffer from a mismatch between supply and demand in both space and time. Thermal energy storage technology can balance the supply and demand of renewable energy and improve energy efficiency.
[0003] Compared with sensible heat and phase change heat storage technologies, thermochemical heat storage technology has a high energy storage density, a wide operating temperature range, can achieve cross-seasonal heat storage, and has great development prospects. Among them, Ca(OH)2 / CaO thermochemical heat storage materials have the advantages of low price, low environmental pollution, high energy storage density, and a working temperature range in the medium and high temperature range, making it have high application value in the fields of solar thermal power generation and industrial waste heat recovery. However, during the heat storage and release process, the volume of Ca(OH)2 / CaO material changes greatly and its mechanical properties are poor. The small particle size material produced after crushing is easy to agglomerate, resulting in uneven distribution of material pores, which seriously affects the uniformity of heat and mass transfer in the reactor, making it difficult for the reactor to achieve an efficient heat storage and release process. Therefore, it is particularly important to stabilize the particle size of Ca(OH)2 / CaO during the heat storage and release process.
[0004] Granulation using a binder is a simple method. However, most binders easily fail at high temperatures, resulting in granules that break easily after several cycles of heat storage and release, making it difficult to maintain a stable particle size. Furthermore, these granules have poor wear resistance, making them difficult to use in reactors with high heat and mass transfer efficiencies, such as fluidized beds, stirred beds, and rotary kilns. This severely limits the realization of efficient thermochemical heat storage processes. Wrapping the heat storage material in a rigid shell can limit its volume changes during cycles and achieve a stable particle size. However, while maintaining a stable particle size, the shell material must not chemically react with the internal heat storage material or hinder the transport of the reactant gases. Therefore, the shell material must possess high strength, high porosity, and high inertness, which poses certain challenges in its selection. Furthermore, these high requirements for the shell material limit its scalability. Existing preparation techniques, such as the sol-gel method, are complex and require expensive precursors. Achieving ideal performance requires strict control of multiple parameters, such as reaction temperature, pH, and reaction time. Mass production requires long reaction times, which cannot meet the needs of large-scale production. Summary of the Invention
[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.
[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.
[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for batch preparation of thermochemical heat storage particles with stable particle size.
[0008] In order to solve the above technical problems, the present invention provides the following technical solution, including: using heat storage material, pore-forming agent, and adhesive as raw materials, mixing them in a mixer, adding them to a wet granulator, spraying them with deionized water, granulating them, drying them, and sieving them to obtain core particles;
[0009] Ceramic material, pore-forming agent and adhesive are used as raw materials and mixed in a mixer to obtain shell powder;
[0010] Add the core particles into the coating machine, spray deionized water while the pot rotates, and after the core surface is moistened, add the shell powder, rotate the pot to coat, and repeat the coating operation 1 to 8 times to obtain coated particles;
[0011] The thermochemical heat storage particles with stable particle size are obtained by calcining at high temperature in a muffle furnace and sieving after cooling.
[0012] Calculated by mass percentage of raw materials, the core particles include 60-80% heat storage material, 5-20% pore former, and 5-20% binder; the shell powder includes 80-90% ceramic material, 5-10% pore former, and 5-15% binder.
[0013] As a preferred solution of the batch preparation method of the thermochemical heat storage particles with stable particle size described in the present invention, the heat storage material includes calcium hydroxide.
[0014] As a preferred solution of the batch preparation method of the thermochemical heat storage particles with stable particle size described in the present invention, wherein: during the granulation process of the wet granulator, the mass ratio of the granulation raw material to deionized water is 1:(0.5-1.5).
[0015] As a preferred solution of the batch preparation method of the thermochemical heat storage particles with stable particle size according to the present invention, the drying temperature of the core particles is 50-60°C.
[0016] As a preferred solution of the batch preparation method of the thermochemical heat storage particles with stable particle size according to the present invention, the particle size of the core particles after sieving is 0.1-5 mm.
[0017] As a preferred embodiment of the batch preparation method of the thermochemical heat storage particles with stable particle size described in the present invention, the heat storage material includes calcium hydroxide; the pore-forming agent includes one or more of carbon powder, starch, and rice husk; the binder includes one or more of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, and polyvinyl alcohol; and the ceramic material includes one or more of aluminum oxide, silicon carbide, zirconium oxide, and silicon nitride.
[0018] As a preferred embodiment of the batch preparation method of the thermochemical heat storage particles with stable particle size described in the present invention, during the coating process, the mass ratio of the core particles to deionized water is 1:(0.1-1), and the mass ratio of the core particles to the shell powder is 1:(0.1-10).
[0019] As a preferred solution of the batch preparation method of the thermochemical heat storage particles with stable particle size described in the present invention, wherein: the calcination, wherein the calcination temperature is 1200-1600° C., and the calcination time is 2-4 hours.
[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a thermochemical heat storage particle with a stable particle size, wherein the particle size of the thermochemical heat storage particle with a stable particle size is 0.5-10 mm.
[0021] Beneficial effects of the present invention:
[0022] The present invention provides thermochemical heat storage particles with stable particle size and a method for their mass production. Ceramic coating of the heat storage material improves mechanical properties and stabilizes the particle size. Furthermore, the addition of organic pore-forming agents, such as carbon powder, starch, and rice hulls, to the shell and heat storage materials increases the porosity of the particles, providing pathways for the transport of reactant gases and enabling a highly stable, high-reaction-rate thermochemical heat storage process. Utilizing a wet granulator and coating machine, this method provides a controllable, repeatable, and mass-produced granulation process with promising industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive efforts. Among them:
[0024] Figure 1The figure is a flow chart of thermochemical heat storage particles with stable particle size and their batch preparation method.
[0025] Figure 2 These are coated particles.
[0026] Figure 3 It is a granular structure formed by high temperature calcination. DETAILED DESCRIPTION
[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.
[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0029] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.
[0030] Unless otherwise specified, the raw materials used in the present invention are all commercially available.
[0031] Example 1
[0032] This embodiment provides a method for batch preparation of thermochemical heat storage particles with stable particle size. Figure 1 , specifically:
[0033] 1) Weigh 12kg of calcium hydroxide, 6kg of carbon powder, and 2kg of sodium carboxymethylcellulose, and mix them in a rotary mixer at a rotation speed of 80r / min for 24h. Then add them to a wet granulator with a mixing frequency of 2.5Hz and a cutting frequency of 20Hz, and spray 10kg of deionized water for wet granulation. After the deionized water spraying is completed, continue to run at the same mixing and cutting frequency for 1h to obtain core particles. Then, dry in a blast drying oven for 24h at a drying temperature of 60°C. After screening with a vibrating screen, core particles with a particle size of 1-2mm are obtained, and the forming rate is above 85%.
[0034] 2) Weigh 13.6 kg of aluminum oxide, 3.4 kg of zirconium oxide, 1 kg of carbon powder, and 2 kg of polyvinyl alcohol, and mix them in a rotary mixer at a rotation speed of 80 r / min for 24 hours to obtain a shell material.
[0035] 3) Take 15kg of core particles and add them to the coating machine. The pan rotates at 30r / min. After spraying 1.5kg of deionized water once, add 3kg of shell powder for coating. Repeat this coating step 5 times. Figure 2 As shown, coated granules were obtained.
[0036] 4) Place the coated particles in a muffle furnace and calcine at a temperature of 1300°C for 3 hours. After screening with a vibrating screen, core particles with a particle size of 2-4.5 mm are obtained, with a forming rate of more than 90%. Figure 3 As shown, after the particles are artificially broken, it can be seen that the prepared heat storage particles are composed of two parts: an outer shell and an internal heat storage core.
[0037] The prepared particles were subjected to 20 heat storage and release cycles, in which the hydration reaction was carried out in a drying oven filled with water vapor for 30 minutes, and the dehydration reaction was carried out in a muffle furnace at 600°C for 50 minutes. The particles did not break after 20 cycles and maintained a stable structure. After separating the shell from the core, the porosity of the shell was tested by mercury intrusion before and after 20 cycles. The results showed that the porosity of the shell did not change much and could be maintained at around 80%. The compressive strength of the heat storage particles was tested by a mechanical properties tester before and after 20 cycles. The results showed that the compressive strength of the particles could be stabilized at around 13N. Therefore, the prepared heat storage particles can maintain a stable structure under the action of the ceramic shell. At the same time, the higher porosity on the shell can also provide a channel for the transport of reaction gases.
[0038] Example 2
[0039] The difference between this embodiment and embodiment 1 is that the drying temperature of the core after wet granulation is adjusted to 40° C., and the rest of the preparation process is the same as that of embodiment 1 to prepare heat storage particles.
[0040] Example 3
[0041] The difference between this embodiment and embodiment 1 is that the drying temperature of the core after wet granulation is adjusted to 70° C., and the rest of the preparation process is the same as that of embodiment 1 to obtain heat storage particles.
[0042] The performance of the materials prepared in the above embodiment was tested, and the comparison results with those in Example 1 are shown in Table 1.
[0043] Table 1
[0044] Example 1 Example 2 Example 3 Core forming rate 85％ 85％ 60％
[0045] As can be seen from the table above, adjusting the core drying temperature after wet granulation significantly affects the core forming rate of thermochemical heat storage particles. This is because the granules evaporate more vigorously at high temperatures after wet granulation, and the generated water vapor causes the core particles to become sticky, reducing the core forming rate. When the drying temperature is below 50°C, the core forming rate does not significantly increase, but the drying speed is slowed. Based on the results in the table above, the best technical effect is achieved when the core is dried at 60°C in the present invention.
[0046] Example 4
[0047] The difference between this embodiment and embodiment 1 is that the number of coating times is adjusted to 1 time, and the rest of the preparation process is the same as that of embodiment 1 to prepare heat storage particles.
[0048] Example 5
[0049] The difference between this embodiment and embodiment 1 is that the number of coating times is adjusted to 3 times, and the rest of the preparation process is the same as that of embodiment 1 to prepare heat storage particles.
[0050] The performance of the materials prepared in the above embodiment was tested, and the comparison results with those in Example 1 are shown in Table 1.
[0051] Table 2
[0052] Example 1 Example 4 Example 5 Compressive strength 13N 0N 9N Heat storage particle forming rate 90％ 0％ 90％
[0053] As can be seen from the table above, adjusting the number of coatings significantly affects the performance of thermochemical heat storage particles. The greater the number of coatings, the higher the compressive strength of the particles. This is because the compressive strength of heat storage particles is primarily determined by the outer shell. More coatings and more outer shell material provide higher strength. However, excessive outer shell material can reduce heat storage density. Therefore, the number of coatings should be determined based on the strength requirements of the actual application.
[0054] Comparative Example 1
[0055] The difference between this embodiment and Example 1 is that 10.67 kg of calcium hydroxide, 5.33 kg of carbon powder, and 4 kg of sodium carboxymethyl cellulose are weighed, and after the heat storage core is prepared, the ceramic shell coating is not performed, and the heat storage core is directly used for storage and release cycle testing.
[0056] Comparative Example 2
[0057] The difference between this embodiment and Example 1 is that 6.67 kg of calcium hydroxide, 3.33 kg of carbon powder, and 10 kg of sodium carboxymethyl cellulose are weighed, and after the heat storage core is prepared, the ceramic shell coating is not performed, and the heat storage core is directly used for storage and release cycle testing.
[0058] Compared with Example 1, it was found that the particles of Comparative Examples 1 and 2 broke after the first cycle. The adhesive easily failed during the cycle. Increasing the proportion of adhesive in the heat storage core did not stabilize the particle size. To achieve the stability of the particle size of the heat storage material, a stable shell needs to be constructed.
[0059] The present invention provides thermochemical heat storage particles with stable particle size and a method for their mass production. Ceramic coating of the heat storage material improves mechanical properties and stabilizes the particle size. Furthermore, the addition of organic pore-forming agents, such as carbon powder, starch, and rice hulls, to the shell and heat storage materials increases the porosity of the particles, providing pathways for the transport of reactant gases and enabling a highly stable, high-reaction-rate thermochemical heat storage process. Utilizing a wet granulator and coating machine, this method provides a controllable, repeatable, and mass-produced granulation process with promising industrial applications.
[0060] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A method for batch preparation of thermochemical heat storage particles with stable particle size, characterized by: include, Heat storage material, pore-forming agent and adhesive are used as raw materials, mixed in a mixer and then added into a wet granulator, sprayed with deionized water for granulation, dried and sieved to obtain core particles; Ceramic material, pore-forming agent and adhesive are used as raw materials and mixed in a mixer to obtain shell powder; Add the core particles into the coating machine, spray deionized water while the pot rotates, and after the core surface is moistened, add the shell powder, rotate the pot to coat, and repeat the coating operation 1 to 8 times to obtain coated particles; The thermochemical heat storage particles with stable particle size are obtained by calcining at high temperature in a muffle furnace and sieving after cooling. Calculated by mass percentage of raw materials, the core particles include 60-80% heat storage material, 5-20% pore former, and 5-20% binder; the shell powder includes 80-90% ceramic material, 5-10% pore former, and 5-15% binder.
2. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: The heat storage material includes calcium hydroxide.
3. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: During the granulation process of the wet granulator, the mass ratio of the granulation raw material to the deionized water is 1:(0.5-1.5).
4. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: The drying temperature of the core particles is 40-70°C.
5. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1 or 4, characterized in that: The particle size of the core particles after sieving is 0.1-5 mm.
6. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: The pore-forming agent includes one or more of carbon powder, starch, and rice husk; the adhesive includes one or more of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, and polyvinyl alcohol.
7. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: The ceramic material includes one or more of aluminum oxide, silicon carbide, zirconium oxide, and silicon nitride.
8. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: During the coating process, the mass ratio of the core particles to deionized water is 1:(0.1-1), and the mass ratio of the core particles to the shell powder is 1:(0.1-10).
9. The method for batch preparation of thermochemical heat storage particles with stable particle size according to claim 1, characterized in that: The calcination process comprises a calcination temperature of 1200-1600° C. and a calcination time of 2-4 hours.
10. A thermochemical heat storage particle with stable particle size prepared by the batch preparation method according to any one of claims 1 to 4 and 6 to 9, characterized in that: The particle size of the thermochemical heat storage particles with stable particle size is 0.5-10 mm.