Modified manganese-iron composite metal oxide heat storage material and preparation method thereof

Abstract

The present invention provides a modified manganese-iron composite metal oxide heat storage material and a preparation method thereof, which can ensure that the main heat storage material (Mn 1‑x Fe x )2O3 has excellent heat storage reaction performance, avoids side reactions between the additive and the heat storage material itself, and improves the sintering resistance and cycle reaction life of the manganese-iron composite metal oxide heat storage material. The present invention provides a modified manganese-iron composite metal oxide heat storage material, which includes a manganese-iron composite metal oxide and an anti-sintering additive powder. The anti-sintering additive powder does not undergo a bulk chemical reaction with the manganese-iron composite metal oxide particles, and the anti-sintering additive powder is dispersed and adhered to the surface of the manganese-iron composite metal oxide.

Description

Technical Field

[0001] The present invention relates to the field of energy storage, and in particular to a modified manganese-iron composite metal oxide heat storage material and a preparation method thereof. Background Art

[0002] Energy storage is one of the key supporting technologies for achieving the "dual carbon" goals. The development and maturity of the energy storage industry is key to the sustained, stable development and large-scale utilization of renewable energy. Thermal storage is an important method for large-scale energy storage and an effective means of achieving the efficient use of renewable energy.

[0003] Heat storage mainly includes three forms: sensible heat, latent heat of phase change, and chemical reaction heat. Sensible heat storage (such as molten salt, thermal oil, water / steam, etc.) mainly uses the rise and fall of the medium temperature to achieve heat storage and release. The process is relatively simple and has the widest application. However, its heat storage temperature generally does not exceed 570°C, the heat storage energy density is low, and the temperature fluctuation range is large, which makes it difficult to meet the needs of the next generation of high-temperature application technology (>700°C); latent heat storage uses the latent heat of the medium phase change process to achieve heat storage and release, but the thermal conductivity is low, the heat exchange during the phase change process is difficult to control, and the phase change material usually needs to be encapsulated, the process is complex, and the cost is high. Chemical heat storage uses the thermal effect of reversible chemical reactions to store and release energy. Depending on the application scenario and storage / release requirements, the range of optional reactants is relatively wide. In addition, the energy storage density can be an order of magnitude higher than sensible heat, which is convenient for long-term storage or long-distance transportation. High-temperature thermochemical energy storage technology based on metal oxides (such as cobalt, manganese, copper, iron, etc.) stores and releases energy through reduction / oxidation reactions between metal oxides of different valence states. The heat storage temperature can reach above 800°C, and within a small temperature range, the energy storage density can reach 300-1000kJ / kg. Its typical reaction formula is as follows:

[0004] M x O y +z+△H==M x O y +z / 2*O2

[0005] Manganese-based metal oxide heat storage systems offer advantages such as low cost, suitable reaction temperature range, and non-toxicity. However, pure manganese oxide suffers from slow reoxidation kinetics after high-temperature reduction, and may even fail to reoxidize completely.

[0006] In this regard, the prior art proposes to dope manganese-based metal oxides with Fe elements to generate manganese-iron composite metal oxide heat storage materials (Mn 1-x Fe x)2O3, enhancing the oxygen adsorption capacity of manganese-based composite metal oxide thermal storage materials and increasing the oxygen ion diffusion rate. Furthermore, existing technologies often use materials such as zirconium dioxide, aluminum oxide, or silicon dioxide as additives to modify manganese-iron composite metal oxide thermal storage materials to improve their structural strength and thermal shock resistance.

[0007] However, on the one hand, the existing manganese-iron composite metal oxide heat storage material has poor cyclic heat storage performance, and sintering will occur after multiple cycles, making it impossible to achieve effective long-term circulation; on the other hand, the materials used as auxiliary agents in the existing technology will chemically react with the main heat storage material, or accelerate the sintering of the main heat storage material, resulting in the inactivation of the main heat storage material, which greatly affects the heat storage performance of the manganese-iron composite metal oxide heat storage material. Summary of the Invention

[0008] In view of the above problems, the present invention provides a modified manganese-iron composite metal oxide heat storage material and a preparation method thereof, which can ensure that the main heat storage material (Mn 1-x Fe x )2O3 has excellent heat storage reaction performance, while avoiding side reactions between the additive and the heat storage material itself, thereby improving the sintering resistance and cycle reaction life of the manganese-iron composite metal oxide heat storage material.

[0009] On the one hand, the present invention provides a modified manganese-iron composite metal oxide heat storage material, which includes manganese-iron composite metal oxide particles and anti-sintering aid powder. The anti-sintering aid powder does not undergo bulk chemical reaction with the manganese-iron composite metal oxide particles, and the anti-sintering aid powder is dispersed and attached to the surface of the manganese-iron composite metal oxide particles.

[0010] According to the technical solution, firstly, since the anti-sintering additive powder provided by the present invention does not react with the manganese-iron composite metal oxide particles in the bulk phase, the main heat storage material ((Mn 1-x Fe x )2O3) content is reduced, and the modified manganese-iron composite metal oxide heat storage material can still ensure that the amount of the main heat storage material remains basically unchanged after multiple storage / release cycles, thereby improving the cyclic heat storage performance of the manganese-iron composite metal oxide heat storage material.

[0011] Secondly, the applicant's experimental research found that there is a strong interaction between the anti-sintering aid powder and the manganese-iron composite metal oxide particles. The anti-sintering aid powder can adhere to the surface of the manganese-iron composite metal oxide particles and is not easy to fall off during multiple heat storage / release cycle reactions.

[0012] Finally, since the anti-sintering aid provided by the present invention can adhere to the surface of the main heat storage material, it can effectively block the contact of the main heat storage material and avoid the agglomeration and sintering of the main heat storage material under high temperature conditions. Moreover, in multiple cycles of heat storage / release reactions, the anti-sintering aid can stably exist on the surface of the main heat storage material. Therefore, the modified manganese-iron composite metal oxide heat storage material provided by the present invention has excellent cyclic heat storage / release performance and can maintain a high reduction conversion rate and reoxidation rate after multiple cycles.

[0013] In the preferred technical solution of the present invention, the general formula of the modified manganese-iron composite metal oxide heat storage material is (Mn 1- x Fe x )2O3·mC, wherein C represents the anti-sintering auxiliary powder, m is the mass ratio of the anti-sintering auxiliary powder, 0.1≤x≤0.4, 0 <m<0.4。

[0014] According to this technical solution, on the one hand, increasing the Fe doping amount can enhance the oxygen adsorption capacity of the manganese-based metal oxide heat storage material and increase the oxygen ion diffusion rate, but excessive Fe doping will lead to the generation of by-products, thereby reducing the content of the main reactant (manganese oxide system). Therefore, when 0.1≤x≤0.4, the Fe doping amount in the manganese-iron composite metal oxide heat storage material can increase the heat storage performance of the manganese-iron composite metal oxide heat storage material while reducing the impact on the content of the main reactant of the manganese-iron composite metal oxide heat storage material, thereby improving the overall heat storage performance of the manganese-iron composite metal oxide heat storage material.

[0015] On the other hand, since pure manganese-iron composite metal oxide will agglomerate and sinter after several cycles under high-temperature reaction conditions, the doping of anti-sintering aid powder can effectively block the manganese-iron composite metal oxide particles, and the higher the mass fraction of the anti-sintering aid and the more uniform the distribution, the better the barrier effect on the agglomeration between the manganese-iron composite metal oxide particles. However, at the same time, excessive doping of anti-sintering aid will also lead to a decrease in the content of the main reactant, affecting the heat storage density and reaction rate of the manganese-iron composite metal oxide. Therefore, the mass ratio of the anti-sintering aid to the manganese-iron composite metal oxide is between 0-0.4. While ensuring the anti-sintering effect of the modified manganese-iron composite metal oxide heat storage material after multiple cycles, it can also ensure the content of the main reactant of the modified manganese-iron composite metal oxide heat storage material.

[0016] In the preferred technical solution of the present invention, the manganese-iron composite metal oxide particles are (Mn 0.8 Fe 0.2 )2O3、(Mn 0.7 Fe 0.3 )2O3 and (Mn 0.75 Fe0.25 )2O3 or a mixture of one or more.

[0017] According to this technical solution, the three manganese-iron composite metal oxides have excellent heat storage properties, the raw materials are inexpensive and easy to prepare, which is more conducive to large-scale promotion and use in industry.

[0018] In the preferred technical solution of the present invention, 0.15≤x≤0.3, 0.01 <m<0.1。

[0019] According to this technical solution, the doping amount of Fe and the doping amount of the anti-sintering aid are further limited. The modified manganese-iron composite metal oxide heat storage material doped within this range has better heat storage density, reaction rate and cyclic heat storage performance.

[0020] In a preferred technical solution of the present invention, the anti-sintering additive powder is one or a combination of tungsten carbide, boron nitride, titanium nitride, niobium boride, titanium diboride, boron phosphate, titanium carbide, and brown manganese ore.

[0021] According to the technical solution, tungsten carbide has stable chemical properties, a melting point of over 2800°C, and good thermal conductivity; the crystal structure of hexagonal boron nitride has a similar graphite layered structure, good thermal conductivity, stable chemical properties, and can stably exist in multiple storage / release cycles without reacting with the main heat storage material to cause a decrease in energy storage density; titanium nitride has a melting point of 2950°C, a Mohs hardness of 8-9, good thermal shock resistance, and a higher melting point than most transition metal nitrides, while being dense. The melting point of niobium boride is 3050°C, and its properties are stable at high temperatures. Titanium diboride has a hexagonal crystal structure, is very hard, has a melting point of 2980°C, and has an oxidation resistance temperature of 1000°C. Boron phosphate has a melting point of 1400°C and is often used as a synthetic antioxidant and ceramic material. Titanium carbide is a gray metallic face-centered cubic lattice solid with a melting point of 3140±90°C and a boiling point of 4820°C. Brown manganese ore has a tetragonal crystal system with bipyramidal crystals and a stable structure. Technicians can select one or more suitable composite anti-sintering additives according to their needs to enhance the sintering resistance, cyclic stability, thermal conductivity, thermal shock resistance, structural strength, and other properties of the manganese-iron composite metal oxide.

[0022] In a preferred technical solution of the present invention, it is characterized in that the particle size of the anti-sintering additive powder is not greater than 1 / 3 of the particle size of the manganese-iron composite metal oxide particles.

[0023] According to this technical solution, the inventors have discovered through research that anti-sintering additive powder particles with smaller particle sizes can be evenly attached to the surface of manganese-iron composite metal oxide particles with larger particle sizes. As a result, without affecting the reaction area between the main heat storage material and the air, the additive particles evenly distributed on the surface of the main heat storage material can block the agglomeration of the coral structure of the main heat storage material, thereby maximizing the blocking effect of additives of the same mass proportion on the agglomeration phenomenon between the main heat storage materials.

[0024] In a preferred technical solution of the present invention, the oxidation / reduction reaction temperature of the manganese-iron composite metal oxide particles is in the range of 700-1000°C.

[0025] In a preferred technical solution of the present invention, after 50 heat storage and release cycles, the reduction reaction conversion rate and reoxidation rate of the modified manganese-iron composite metal oxide heat storage material are both higher than 60%.

[0026] The second aspect of the present invention further provides a method for preparing the modified manganese-iron composite metal oxide heat storage material in any of the above technical solutions, the preparation method comprising the following steps:

[0027] S1. Mixing a manganese source and an iron source to obtain a precursor;

[0028] S2. The precursor is calcined at high temperature and then ground to obtain manganese-iron composite metal oxide particles;

[0029] S3. Fully mix the manganese-iron composite metal oxide particles and the anti-sintering additive powder to synthesize a modified manganese-iron composite metal oxide heat storage material.

[0030] According to this technical solution, the manganese source and the iron source are first evenly mixed. The mixing method can be a ball mill, a blender or a rotary kiln, etc., which is not limited here. Then, the evenly mixed powder is compounded at high temperature. Under high temperature conditions, the evenly contacted solid interfaces undergo contact, reaction, nucleation, and crystal growth reactions to finally obtain the main heat storage material, manganese-iron composite metal oxide. This preparation method has low cost, high output, simple equipment and preparation process, and high production efficiency.

[0031] In addition, during the synthesis process of the uniformly mixed powdered main heat storage material and the auxiliary agent in step S3, the auxiliary agent can be evenly and firmly attached to the surface of the main heat storage material, thereby effectively improving the agglomeration and sintering phenomenon of the main heat storage material under high-temperature reaction conditions, and a modified manganese-iron composite metal oxide heat storage material with excellent cyclic heat storage / release performance can be obtained.

[0032] In a preferred technical solution of the present invention, step S3 further includes the following sub-steps:

[0033] S31. Mix the manganese-iron composite metal oxide particles with the anti-sintering additive powder, and calcine them at a high temperature of 700-900°C for 3-5 hours.

[0034] According to this technical solution, calcination is conducive to the composite between metal oxide particles and anti-sintering auxiliary agent powder. Under high temperature conditions, the anti-sintering powder can quickly coat the surface of the metal oxide particles and grow. In the modified manganese-iron composite metal oxide heat storage material, the metal oxide grains are blocked by the anti-sintering powder, which has better anti-sintering agglomeration performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of a method for preparing a modified manganese-iron composite metal oxide heat storage material in an embodiment of the present invention.

[0036] Figure 2 3 are SEM images of samples T1-T3 according to the embodiment of the present invention and the comparative sample DT1 after 50 cycles.

[0037] Figure 3 3 is a thermogravimetric analysis diagram of sample T1 after 50 cycles in an embodiment of the present invention.

[0038] Figure 4 3 is a thermogravimetric analysis diagram of sample T2 after 50 cycles in an embodiment of the present invention.

[0039] Figure 5 3 is a thermogravimetric analysis graph of sample T3 after 50 cycles in an embodiment of the present invention.

[0040] Figure 6 3 is a thermogravimetric analysis diagram of sample T4 after 50 cycles in an embodiment of the present invention.

[0041] Figure 7 3 is a thermogravimetric analysis graph of sample T5 after 50 cycles in an embodiment of the present invention.

[0042] Figure 8 3 is a thermogravimetric analysis graph of sample T6 after 70 cycles in an embodiment of the present invention.

[0043] Figure 9 3 is a thermogravimetric analysis graph of sample T7 after 100 cycles in an embodiment of the present invention.

[0044] Figure 10 This is a thermogravimetric analysis graph of sample T8 after 100 cycles in an embodiment of the present invention.

[0045] Figure 11 3 is a thermogravimetric analysis graph of the control sample DT1 after 50 cycles in an embodiment of the present invention.

[0046] Figure 123 is a thermogravimetric analysis graph of the control sample DT2 after 100 cycles in an embodiment of the present invention.

[0047] Figure 13 3 is a thermogravimetric analysis graph of the control sample DT3 after 50 cycles in an embodiment of the present invention.

[0048] Figure 14 3 is a thermogravimetric analysis graph of the control sample DT4 after 100 cycles in an embodiment of the present invention.

[0049] Figure 15 3 is a thermogravimetric analysis graph of the control sample DT5 after 50 cycles in an embodiment of the present invention.

[0050] Figure 16 3 is a thermogravimetric analysis graph of the control sample DT6 after 200 cycles in an embodiment of the present invention.

[0051] Figure 17 3 is a thermogravimetric analysis graph of the control sample DT7 after 50 cycles in an embodiment of the present invention.

[0052] Figure 18 3 is a thermogravimetric analysis graph of the control sample DT1′ after 100 cycles in an embodiment of the present invention.

[0053] Figure 19 3 is a thermogravimetric analysis graph of the control sample DT4′ after 100 cycles in an embodiment of the present invention.

[0054] Figure 20 3 is a thermogravimetric analysis graph of the control sample DT6′ after 200 cycles in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] 1. Material Preparation

[0057] The modified manganese-iron composite metal oxide heat storage material provided in this embodiment is prepared by a high-temperature solid-phase method. Figure 1 Flowchart of the method for preparing the modified manganese-iron composite metal oxide heat storage material provided in the embodiment of the present invention. Figure 1 As shown, the following steps are included:

[0058] Step S1. mixing a manganese source and an iron source to obtain a precursor;

[0059] Step S2. calcining the precursor at high temperature and then grinding it to obtain manganese-iron composite metal oxide particles;

[0060] Step S3: fully mixing the manganese-iron composite metal oxide particles and the anti-sintering additive powder to synthesize a modified manganese-iron composite metal oxide heat storage material.

[0061] Preferably, step S3 further includes the following sub-steps:

[0062] S31. Mix the manganese-iron composite metal oxide particles with the anti-sintering additive powder, and calcine them at a high temperature of 700-900°C for 3-5 hours.

[0063] In this embodiment, the manganese source and the iron source are first uniformly mixed. The mixing method can be a ball mill, a blender or a rotary kiln, etc., which is not limited here. Then, the uniformly mixed powder is compounded at a high temperature. Under high temperature conditions, the uniformly contacted solid interfaces undergo contact, reaction, nucleation, and crystal growth reactions to finally obtain the main heat storage material manganese-iron composite metal oxide. This preparation method has low cost, high output, simple equipment and preparation process, and high production efficiency.

[0064] In addition, during the synthesis process of the uniformly mixed powdered main heat storage material and the auxiliary agent in step S3, the auxiliary agent can be evenly and firmly attached to the surface of the main heat storage material, thereby effectively improving the agglomeration and sintering phenomenon of the main heat storage material under high-temperature reaction conditions, and a modified manganese-iron composite metal oxide heat storage material with excellent cyclic heat storage / release performance can be obtained.

[0065] Specifically, in this embodiment, 0.8 mol of reagent-grade MnO2 and 0.1 mol of reagent-grade Fe2O3 were weighed, placed in a ball mill, and ball-milled for 30 minutes to fully mix. The mixture was then placed in a muffle furnace and calcined at 1000°C for 8 hours. After cooling, the mixture was taken out and ground to obtain a black powdery heat storage main material Z1 (Mn 0.8 Fe 0.2 )2O3.

[0066] The heat storage main material Z1 and the anti-sintering additive C were weighed separately, placed in a ball mill, and ball milled for 30 minutes to fully mix. The mixture was then placed in a muffle furnace and calcined at 800 ° C for 4 hours to allow the additive to adhere to the surface of the heat storage main material, thereby obtaining the modified manganese-iron composite metal oxide heat storage material (Mn 0.8 Fe 0.2 )2O3·(C).

[0067] Among them, tungsten carbide is selected as the anti-sintering aid C1, and the doping mass ratio of the anti-sintering aid C1 is 0.05. The obtained modified manganese iron composite metal oxide heat storage material T1 is (Mn0.8 Fe 0.2 )2O3· 0.05 (WC).

[0068] The reagent α-NB (boron nitride) is selected as the anti-sintering aid C2, and the doping mass ratio of the anti-sintering aid C2 is 0.05. The obtained modified manganese iron composite metal oxide heat storage material T2 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (α-NB).

[0069] The reagent TiN is selected as the anti-sintering aid C3, and the doping mass ratio of the anti-sintering aid C3 is 0.05. The obtained modified manganese iron composite metal oxide heat storage material T3 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (TiN).

[0070] The reagent NbB is selected as the anti-sintering additive C4, and the doping mass ratio of the anti-sintering additive C4 is 0.05. The obtained modified manganese-iron composite metal oxide heat storage material T4 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (NbB).

[0071] The reagent B2Ti was selected as the anti-sintering additive C5, and the doping mass ratio of the anti-sintering additive C5 was 0.05. The modified manganese-iron composite metal oxide heat storage material T5 obtained was (Mn 0.8 Fe 0.2 )2O3· 0.05 (B2Ti).

[0072] The reagent BPO4 was selected as the anti-sintering additive C6, and the doping mass ratio of the anti-sintering additive C6 was 0.05. The modified manganese-iron composite metal oxide heat storage material T6 obtained was (Mn 0.8 Fe 0.2 )2O3· 0.05 (BPO4).

[0073] The reagent TiC is selected as the anti-sintering additive C7, and the doping mass ratio of the anti-sintering additive C7 is 0.05. The modified manganese-iron composite metal oxide heat storage material T7 obtained is (Mn 0.8 Fe 0.2 )2O3· 0.05 (TiC).

[0074] Select reagent Mn7SiO 12 As the anti-sintering aid C8, the anti-sintering aid C8 doping mass ratio is 0.05, and the obtained modified manganese iron composite metal oxide heat storage material T8 is (Mn0.8 Fe 0.2 )2O3· 0.05 (Mn7SiO 12 ).

[0075] The reagent Al2O3 was selected as the comparative additive DC1, and the anti-sintering additive DC1 doping mass ratio was 0.05. The comparative manganese iron composite metal oxide heat storage material DT1 was (Mn 0.8 Fe 0.2 )2O3· 0.05 (Al2O3).

[0076] The reagent Al2O3 was selected as the comparative additive DC1, and the anti-sintering additive DC1 doping mass ratio was 0.15. The comparative manganese-iron composite metal oxide heat storage material DT1' was (Mn 0.8 Fe 0.2 )2O3· 0.15 (Al2O3).

[0077] Select reagent SiC as the comparative additive DC2, the anti-sintering additive DC2 doping mass ratio is 0.05, and the comparative manganese iron composite metal oxide heat storage material DT2 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (SiC).

[0078] The reagent Si3N4 was selected as the comparative additive DC3, and the anti-sintering additive DC3 doping mass ratio was 0.05. The comparative manganese iron composite metal oxide heat storage material DT3 obtained was (Mn 0.8 Fe 0.2 )2O3· 0.05 (Si3N4).

[0079] Select reagent SiO2 as the comparative additive DC4, the anti-sintering additive DC4 doping mass ratio is 0.05, and the comparative manganese iron composite metal oxide thermal storage material DT4 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (SiO2).

[0080] Select reagent SiO2 as the comparative additive DC4, the anti-sintering additive DC4 doping mass ratio is 0.15, and the comparative manganese iron composite metal oxide heat storage material DT4' is (Mn 0.8 Fe 0.2 )2O3· 0.05 (SiO2).

[0081] The reagent ZrO2 was selected as the comparative additive DC5, and the anti-sintering additive DC5 doping mass ratio was 0.05. The comparative manganese-iron composite metal oxide heat storage material DT5 obtained was (Mn 0.8 Fe 0.2 )2O3· 0.05 (ZrO2).

[0082] Select reagent Ce 0.9 Gd 0.1 O2 is used as the comparative additive DC6, and the anti-sintering additive DC6 doping mass ratio is 0.05. The comparative manganese iron composite metal oxide heat storage material DT6 is (Mn 0.8 Fe 0.2 )2O3· 0.05 (Ce 0.9 Gd 0.1 O2).

[0083] Select reagent Ce 0.9 Gd 0.1 O2 is used as the comparative additive DC6, and the anti-sintering additive DC6 doping mass ratio is 0.15. The comparative manganese iron composite metal oxide heat storage material DT6' is (Mn 0.8 Fe 0.2 )2O3· 0.05 (Ce 0.9 Gd 0.1 O2).

[0084] The reagent ZnAl2O4 was selected as the comparative additive DC7, and the anti-sintering additive DC7 doping mass ratio was 0.05. The comparative manganese iron composite metal oxide heat storage material DT7 was (Mn 0.8 Fe 0.2 )2O3· 0.05 (ZnAl2O4).

[0085] 2. Material Characterization

[0086] 2.1 Micromorphology

[0087] Figure 2 is the SEM image of samples T1-T3 and comparative sample DT1 after 50 cycles. Figure 2As shown, it can be seen that the anti-sintering additive powder in samples T1-T3 prepared in this embodiment is dispersed and attached to the surface of the manganese-iron composite metal oxide particles, and the anti-sintering additive powder does not react with the manganese-iron composite metal oxide particles. In contrast, the comparative sample DT1 undergoes severe sintering and densification, and the additive powder and the manganese-iron composite metal oxide particles agglomerate into one. This shows that after multiple cycles of the modified manganese-iron composite metal oxide thermal storage material prepared in this embodiment, the anti-sintering additive can still stably exist on the surface of the manganese-iron composite metal oxide particles, forming a barrier between the manganese-iron composite metal oxide particles, thereby preventing the manganese-iron composite metal oxide particles from agglomerating, and improving the cyclic heat storage performance of the modified manganese-iron composite metal oxide thermal storage material.

[0088] 2.2 Heat storage performance

[0089] The following experiment was used to determine the heat storage performance of the modified manganese iron composite metal oxide heat storage material. The modified manganese iron composite metal oxide heat storage material (samples T1-T8, comparison samples DT1-DT7) was placed on a thermochemical experimental platform for a thermal cycling experiment. The temperature control program was: first heating from room temperature to 700°C, then heating from 700°C to 1000°C, and then cooling from 1000°C to 700°C; the heating and cooling rates were both 10°C / min, and the air flow rate was 1L / min (pO2=0.21). Heating from 700°C to 1000°C and then cooling to 700°C was one cycle. After 50 cycles of continuous operation, the heating was stopped. After the equipment was completely cooled, 8-11 mg of the modified manganese iron composite metal oxide heat storage material sample was taken for thermogravimetric analysis. The thermogravimetric analysis temperature program was as follows: first, heating from 150°C to 850°C and holding for 20 min; then, heating from 850°C to 1100°C; then, cooling from 1100°C to 850°C and holding for 20 min; and finally, cooling from 850°C to 150°C. The heating and cooling rates were both 10°C / min, and the air flow rate was 50 ml / min (pO2 = 0.21).

[0090] The experimental results are shown in Table 1 and Figure 3-20 Table 1 shows the experimental results of thermal cycling test and thermogravimetric analysis of samples T1-T8 and comparative samples DT1-DT7. Figure 3-20 Thermogravimetric analysis curves of samples T1-T8 and comparative samples DT1-DT7 respectively.

[0091] Table 1

[0092]

[0093]

[0094] The following table 1 and Figure 3-20, illustrating the heat storage performance of the modified manganese-iron composite metal oxide heat storage material samples T1-T8 prepared in this embodiment and the advantages of the modified manganese-iron composite metal oxide heat storage material samples T1-T8 prepared in this embodiment compared with the comparison samples DT1-DT7.

[0095] First, combining Table 1 and Figure 3 From the results of Table 1 and Table 2, the reduction conversion rate of sample T1 (5% WC) after 50 heat storage / release cycles was 92.64% and the reoxidation rate was 95.19%. Figure 4 From the results of Table 1 and Table 2, the reduction conversion rate of sample T2 (5% α-NB) after 50 cycles was 78.98% and the reoxidation rate was 77.56%. Figure 5 From the results of Table 1 and Table 2, the reduction conversion rate of sample T3 (5% TiN) after 50 cycles was 83.31% and the reoxidation rate was 84.05%. Figure 6 From the results of Table 1 and Table 2, the reduction conversion rate of sample T4 (5% NbB) after 50 cycles was 98.21% and the reoxidation rate was 92.44%. Figure 7 From the results of Table 1 and Table 2, the reduction conversion rate of sample T5 (5% B2Ti) after 50 cycles was 73.16% and the reoxidation rate was 73.04%. Figure 8 From the results of Table 1 and Table 2, the reduction conversion rate of sample T6 (5% BPO4) after 70 cycles was 64.66% and the reoxidation rate was 68.47%. Figure 9 From the results of Table 1 and Table 2, the reduction conversion rate of sample T7 (5% TiC) after 100 cycles was 77.78% and the reoxidation rate was 76.81%. Figure 10 For example, sample T8 (5% Mn7SiO 12 ) After 100 cycles, the reduction conversion rate of sample T8 measured in the thermogravimetric analysis experiment was 62.99%, and the reoxidation rate was 67.63%.

[0096] The thermal cycling and thermogravimetric test results of samples T1-T8 demonstrate that the manganese-iron composite metal oxide heat storage material doped with an anti-sintering aid prepared in this embodiment has excellent heat storage performance, especially in multiple cycles. The heat storage performance is improved, and after multiple cycles (50 times), the reduction reaction conversion rate and reoxidation rate can still be guaranteed to be higher than 60%.

[0097] Among them, preferably, sample T1 (5% WC) and sample T4 (5% NbB) have better cyclic heat storage properties than samples doped with other anti-sintering aids, and can maintain the reduction reaction conversion rate and reoxidation rate of the heat storage material higher than 92% after 50 cycles.

[0098] Secondly, combined with Table 1 and Figure 11 From the results of Table 1 and Table 2, the reduction reaction conversion rate of the comparative sample DT1 (5% Al2O3) was 72.29% and the reoxidation rate was 5.67% after 50 heat storage / release cycles. Figure 12 From the results of Table 1 and Table 2, the reduction conversion rate of the comparative sample DT2 (5% SiC) after 100 cycles was 58.40% and the reoxidation rate was 59.70%. Figure 13 From the results of Table 1 and Table 2, the reduction conversion rate of the comparative sample DT3 (5% Si3N4) after 50 cycles was 42.25% and the reoxidation rate was 42.19%. Figure 14 From the results of Table 1 and Table 2, the reduction conversion rate of the comparative sample DT4 (5% SiO2) after 100 cycles was 62.30% and the reoxidation rate was 65.73%. Figure 15 From the results of Table 1 and Table 2, the reduction conversion rate of the comparative sample DT5 (5% ZrO2) after 50 cycles was 67.66% and the reoxidation rate was 43.43%. Figure 16 For comparison, the DT6 (5% Ce 0.9 Gd 0.1 O2) After 200 cycles, the reduction conversion rate of the comparative sample DT6 measured in the thermogravimetric analysis experiment was 51.89%, and the reoxidation rate was 29.03%. Figure 17 It can be seen that after 50 cycles, the comparative sample DT7 (5% ZnAl2O4) was inactivated due to the compounding of the additive with the main heat storage material, and the redox reaction could not occur. The comparative sample DT7 measured in the thermogravimetric analysis experiment had almost no weight loss / weight gain.

[0099] The experimental results of comparative samples DT1-DT7 demonstrate that existing manganese-iron composite metal oxide thermal storage materials are prone to agglomeration reactions during the heat storage / release cycle, often resulting in low reoxidation rates after multiple cycles. The addition of existing additives does not effectively address this issue. Some additives, such as comparative sample DT7, even react with the manganese-iron composite metal oxide, creating a counterproductive effect. This makes it difficult for existing manganese-based composite metal oxide thermal storage materials to stably and continuously perform heat storage / release reactions, significantly impacting their cyclic heat storage performance. Furthermore, a comparison of the thermogravimetric analysis results of samples T1-T8 with those of comparative samples DT1-DT7 demonstrates that the modified manganese-iron composite metal oxide thermal storage material of this embodiment exhibits improved heat storage performance. Not only does it not affect the normal heat storage / release reactions of the main thermal storage material, it also mitigates the sintering and agglomeration issues of the manganese-iron composite metal oxide after multiple cycles, resulting in the modified manganese-iron composite metal oxide thermal storage material provided in this embodiment having higher reduction conversion rates and reoxidation rates after multiple cycles.

[0100] Finally, combined with Table 1, Figure 11 and Figure 18 From the results of Table 1, we can see that after 50 heat storage / release cycles, the reduction reaction conversion rate of the comparative sample DT1 (5% Al2O3) measured in the thermogravimetric analysis experiment was 72.29%, and the reoxidation rate was 5.67%; after 100 heat storage / release cycles, the reduction reaction conversion rate of the comparative sample DT1' (15% Al2O3) measured in the thermogravimetric analysis experiment was 24.85%, and the reoxidation rate was 5.04%. Figure 14 and Figure 19 From the results of Table 1, the reduction conversion rate of the comparative sample DT4 (5% SiO2) after 100 cycles was 62.30%, and the reoxidation rate was 65.73% as measured in the thermogravimetric analysis experiment; the reduction conversion rate of the comparative sample DT4' (15% SiO2) after 100 cycles was 31.64%, and the reoxidation rate was 29.86% as measured in the thermogravimetric analysis experiment. Figure 16 and Figure 20 For comparison, the DT6 (5% Ce 0.9 Gd 0.1 O2) after 200 cycles, the reduction conversion rate of the comparative sample DT6 measured in the thermogravimetric analysis experiment was 67.48%, and the reoxidation rate was 49.72%; the comparative sample DT6' (15% Ce 0.9 Gd 0.1 O2) After 200 cycles, the reduction conversion rate of the comparative sample DT6' measured in the thermogravimetric analysis experiment was 51.89%, and the reoxidation rate was 29.03%.

[0101] Since pure manganese-iron composite metal oxide particles will agglomerate and sinter under high-temperature reaction conditions, the doping of anti-sintering additive powder can effectively block the manganese-iron composite metal oxide particles, and the higher the mass fraction of the anti-sintering additive and the more uniform the distribution, the better the barrier effect on the agglomeration between the manganese-iron composite metal oxide particles. However, at the same time, excessive doping of anti-sintering additives will also lead to a decrease in the content of the main reactants, affecting the heat storage density and reaction rate of the manganese-iron composite metal oxide. The inventor's research shows that the mass ratio of the additive to the manganese-iron composite metal oxide is between 0-0.4. While ensuring the anti-sintering effect of the modified manganese-iron composite metal oxide heat storage material after multiple cycles, it can also ensure the content of the main reactants of the modified manganese-iron composite metal oxide heat storage material.

[0102] Further preferably, the modified manganese-iron composite metal oxide heat storage material prepared when the mass ratio of the additive to the manganese-iron composite metal oxide is between 0.01 and 0.1 has better heat storage performance.

[0103] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A modified manganese-iron composite metal oxide heat storage material, characterized in that: The invention comprises manganese-iron composite metal oxide particles and anti-sintering aid powder, wherein the anti-sintering aid powder does not undergo bulk chemical reaction with the manganese-iron composite metal oxide particles, and the anti-sintering aid powder is dispersed and attached to the surface of the manganese-iron composite metal oxide particles; The anti-sintering additive powder is one or a combination of tungsten carbide, boron nitride, titanium nitride, niobium boride, titanium diboride, boron phosphate, titanium carbide, and brown manganese ore; The general formula of the modified manganese-iron composite metal oxide heat storage material is (Mn 1-x Fe x )2O3·mC, wherein C represents the anti-sintering auxiliary powder, m is the mass ratio of the anti-sintering auxiliary powder, 0.1≤x≤0.4, 0 <m<0.4。 2. The modified manganese-iron composite metal oxide heat storage material according to claim 1, characterized in that: The manganese-iron composite metal oxide particles are (Mn 0.8 Fe 0.2 )2O3、(Mn 0.7 Fe 0.3 )2O3 and (Mn 0.75 Fe 0.25 )2O3 or a mixture of one or more.

3. The modified manganese-iron composite metal oxide heat storage material according to claim 1, characterized in that: 0.15≤x≤0.3,0.01 <m<0.1。 4. The modified manganese-iron composite metal oxide heat storage material according to any one of claims 1 to 3, characterized in that: The particle size of the anti-sintering additive powder is no more than 1 / 3 of the particle size of the manganese-iron composite metal oxide particles.

5. The modified manganese-iron composite metal oxide heat storage material according to any one of claims 1 to 3, characterized in that: The oxidation / reduction reaction temperature of the manganese-iron composite metal oxide particles is in the range of 700-1000°C.

6. The modified manganese-iron composite metal oxide heat storage material according to any one of claims 1 to 3, characterized in that: After 50 heat storage and release cycles, the reduction reaction conversion rate and reoxidation rate of the modified manganese-iron composite metal oxide heat storage material are both higher than 60%.

7. A method for preparing the modified manganese-iron composite metal oxide heat storage material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Mixing a manganese source and an iron source to obtain a precursor; S2. The precursor is calcined at high temperature and then ground to obtain manganese-iron composite metal oxide particles; S3. Fully mix the manganese-iron composite metal oxide particles and the anti-sintering additive powder to synthesize a modified manganese-iron composite metal oxide heat storage material.

8. The preparation method according to claim 7, wherein Step S3 further includes the following sub-steps: S31. Mix the manganese-iron composite metal oxide particles with the anti-sintering additive powder, and calcine them at a high temperature of 700-900°C for 3-5 hours.

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