Alkali metal sulfate and metal oxide modified calcium-based energy storage medium and preparation method thereof

Abstract

The invention discloses an alkali metal sulfate and metal oxide modified calcium-based energy storage medium and a preparation method thereof, and belongs to the technical field of thermochemical energy storage. The alkali metal sulfate and metal oxide modified calcium-based energy storage medium is prepared from the following components in percentage by mass through wet mixing: 5-40% of alkali metal sulfate, 5-30% of metal oxide and the balance of calcium oxide. According to the invention, the conversion rate and the cycling stability of calcium oxide are effectively improved, so that the CO2 adsorption performance of calcium oxide is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermochemical energy storage, and more specifically to an alkali metal sulfate and metal oxide modified calcium-based energy storage medium and a preparation method thereof. Background Art

[0002] The increasing content of CO2 in the atmosphere has caused a series of environmental problems. In order to control carbon emissions, the capture of CO2 in fossil fuel combustion products has become particularly important. The three widely used carbon capture processes are pre-combustion capture, post-combustion capture and oxygen-enriched combustion. Among them, pre-combustion capture is methane steam reforming, which converts carbon-containing fuel methane into clean energy H2 through reforming reaction. CO2 is one of the reaction products. Capturing CO2 as early as possible can shift the equilibrium to the right and increase the H2 yield. On the other hand, the generated CO2 can be fixed, separated and purified to reduce CO2 emissions. For this process, the development of high-efficiency adsorption materials that can be used under high temperature conditions is a key factor.

[0003] Calcium oxide is a CO2 adsorption material with high theoretical adsorption capacity and an adsorption temperature of about 650-800°C. It is suitable for methane steam reforming reaction. Moreover, its abundant content and low cost make it have great potential value in CO2 capture, utilization and storage (CCUS).

[0004] However, the biggest problem faced by this type of material is that it is prone to sintering after multiple cycles. The calcium oxide particles grow so that CO2 is difficult to diffuse inward, and the diffusion reaction stage is difficult to proceed. Therefore, the low adsorption performance of ordinary large-particle calcium oxide is also a key factor affecting the direct use of natural calcium oxide. Summary of the invention

[0005] In view of the above problems, the present invention provides an alkali metal sulfate and metal oxide modified calcium-based energy storage medium and a preparation method. The present invention is based on calcium oxide, and metal sulfate is added to enhance the adsorption effect of calcium oxide. In view of the problem that calcium oxide is easily deactivated during high-temperature cycling, metal oxide is added to prevent sintering. A calcium-based energy storage medium that is efficient, simple, economical, and has good cycle stability is constructed. The calcium-based energy storage medium can effectively improve the adsorption performance of calcium oxide for CO2.

[0006] The first object of the present invention is to provide an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, which is obtained by wet mixing the following components in mass percentage: 5% to 40% alkali metal sulfate, 5% to 30% metal oxide, and the rest is calcium oxide.

[0007] In a preferred embodiment, the alkali metal sulfate is selected from lithium sulfate, sodium sulfate and potassium sulfate.

[0008] In a preferred embodiment, the metal oxide is selected from zinc oxide, copper oxide, iron oxide, aluminum oxide, magnesium oxide, manganese oxide, zirconium oxide, cerium oxide, and titanium oxide.

[0009] The second object of the present invention is to provide a method for preparing the above-mentioned alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0010] Weigh the components according to the following mass percentages: 5% to 40% alkali metal sulfate, 5% to 30% metal oxide, and the rest calcium oxide;

[0011] Raw material pretreatment: calcium oxide is dried, and alkali metal sulfate is ground and sieved;

[0012] Wet mixing: metal oxide, pretreated calcium oxide and alkali metal sulfate are mixed with water and then ultrasonically stirred, and then evaporated, dried and ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0013] In a preferred embodiment, in the raw material pretreatment step: the drying condition is vacuum drying at 80-120° C. for 3-6 hours.

[0014] In a preferred embodiment, in the raw material pretreatment step, the sieve mesh number is 400 mesh.

[0015] In a preferred embodiment, in the wet mixing step, the ultrasonic time is 0.5-3 h and the ultrasonic frequency is 40 kHz.

[0016] In a preferred embodiment, in the wet mixing step, the evaporation condition is vacuum drying at 120-150° C. for 8-12 hours.

[0017] In a preferred embodiment, in the wet mixing step, the drying condition is vacuum drying at 400-500° C. for 1-3 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The alkali metal sulfate and metal oxide provided by the present invention are used to modify the calcium-based energy storage medium, so that the material has a fast reaction rate and good cycle stability.

[0020] (2) The calcium oxide used in the present invention is common commercial calcium oxide, and all alkali metal sulfates are common salts. The preparation method adopted is a simple wet mixing method, and the preparation process is simple. The addition of alkali metal sulfates greatly improves the material conversion rate, and the addition of metal oxides plays an important role in improving the sintering problem of materials, extending the service life of materials, and improving the cycle stability of materials. Alkali metal sulfates and metal oxides have a synergistic effect, and their joint addition improves the conversion rate and cycle stability of calcium oxide.

[0021] (3) The present invention provides a new approach for developing efficient, simple and economical calcium-based energy storage media, while achieving fast reaction rate and good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The XRD pattern of the modified calcium-based energy storage medium prepared in Comparative Example 1 at 780°C during the cycle treatment process;

[0023] Figure 2 The SEM images of the modified calcium-based energy storage medium prepared in the present invention after five cycles, wherein 1 is Comparative Example 1, and 2-6 are Examples 1-5;

[0024] Figure 3 The cyclic stability diagram of the modified calcium-based energy storage medium prepared in Comparative Example 1 and Examples 1-5;

[0025] Figure 4 Graph showing the cyclic stability of the modified calcium-based energy storage media prepared in Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0027] As a CO2 adsorption material, calcium oxide is prone to sintering after multiple cycles. The calcium oxide particles grow, making it difficult for CO2 to diffuse inward, and the diffusion reaction stage is difficult to proceed. Therefore, the low adsorption performance of ordinary large-particle calcium oxide is also a key factor affecting the direct use of natural calcium oxide.

[0028] Based on the above problems, the present invention is based on calcium oxide, and first adds alkali metal sulfate, so that the conversion rate of the material is greatly improved, and when the proportion of alkali metal sulfate is further increased, this improvement effect is more obvious. When the molar ratio of alkali metal sulfate to calcium oxide is 0.25:5, the initial conversion rate of the material is 0.675; when this ratio increases to 1:5, the initial conversion rate of the material is 0.779. The addition of alkali metal sulfate can form a coordination compound with calcium oxide. Taking sodium sulfate as an example, according to the preparation method of Comparative Example 2 below, calcium oxide is modified with sodium sulfate to obtain an alkali metal sulfate-modified calcium-based energy storage medium, such as Figure 1 As shown, in-situ XRD was used to test during the cyclic treatment process. The results showed that during the cyclic treatment process, sodium sulfate and calcium oxide produced CaNa2(SO4)2. The production of coordination compounds can cause volume expansion, produce a popcorn effect, and promote the reaction.

[0029] However, an increase in the proportion of alkali metal sulfate will also make the material easier to sinter. Therefore, metal oxides are introduced to inhibit this sintering phenomenon and construct a calcium-based energy storage medium that is efficient, simple, economical, and has good cycle stability.

[0030] The invention provides an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, which is prepared by mixing metal oxide as an inert carrier and alkali metal sulfate as a promoter with calcium oxide through a wet method.

[0031] Metal oxides are inert carriers with high melting points. They can serve as atomic skeletons to stabilize the microstructure of calcium-based adsorbents, delaying the growth of grains and the closure of pores, and increasing the cyclic stability of calcium-based adsorbents. Sodium sulfate, as a promoter, can effectively improve the reaction kinetics. In addition, the lattice constant of the coordination compound should be large, and its formation will produce a popcorn effect, resulting in volume expansion, which is beneficial to the transportation and transfer of CO2. The combined effect of the two allows the material to have good cyclic stability while maintaining a high conversion rate.

[0032] The specific technical solution is:

[0033] An alkali metal sulfate and metal oxide modified calcium-based energy storage medium is obtained by wet mixing the following components in mass percentage: 5% to 40% alkali metal sulfate, 5% to 30% metal oxide, and the rest is calcium oxide;

[0034] In a preferred embodiment, the alkali metal sulfate is selected from lithium sulfate, sodium sulfate and potassium sulfate.

[0035] In a preferred embodiment, the metal oxide is selected from one or more of zinc oxide, copper oxide, iron oxide, aluminum oxide, magnesium oxide, manganese oxide, zirconium oxide, cerium oxide, and titanium oxide.

[0036] The present invention also provides a method for preparing the above-mentioned alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0037] S1. Weigh the components according to the following mass percentages: 5% to 40% alkali metal sulfate, 5% to 30% metal oxide, and the rest calcium oxide;

[0038] S2. Raw material pretreatment

[0039] The calcium oxide and the metal oxide are dried, and the alkali metal sulfate is ground and sieved, and the sieve mesh number is 400 mesh;

[0040] Calcium oxide, metal oxides, and alkali metal sulfates are commercially available and are not particularly limited in the present invention. The calcium oxide used in the present invention is analytically pure and does not require further purification after purchase. It is directly dried and then used.

[0041] Preferably, the drying condition is vacuum drying at 80-120° C. for 3-6 hours.

[0042] Some alkali metal sulfates are easily deliquescent and form large crystals, so the present invention grinds them into fine powder using a mortar to make the alkali metal sulfate easier to dissolve and weigh;

[0043] S3, wet mixing

[0044] The metal oxide, the pretreated calcium oxide and the alkali metal sulfate are added to an appropriate amount of deionized water and ultrasonically stirred at a frequency of 40KHz for 0.5-3h, and then evaporated, dried and ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium. In this step, the purpose of adding deionized water is to mix the calcium oxide, the metal oxide and the alkali metal sulfate evenly, so the present invention is not particularly limited here.

[0045] The evaporation conditions are vacuum drying at 120-150°C for 8-12 hours.

[0046] The drying conditions are vacuum drying at 400-500°C for 1-3h.

[0047] The evaporation step removes the water in the uniform mixing process. At this time, calcium oxide and water will react to form calcium hydroxide. At this time, the water that has reacted with calcium oxide cannot be removed at the evaporation temperature. When the temperature is raised to above 400°C, calcium hydroxide will decompose into water and calcium oxide. At this time, the excess water can be removed, so that calcium hydroxide is converted into calcium oxide.

[0048] It should be noted that zinc oxide is ZnO, copper oxide is CuO, iron oxide is Fe2O3, aluminum oxide is Al2O3, magnesium oxide is MgO, manganese oxide is MnO, zirconium oxide is ZrO2, cerium oxide is CeO2, and titanium oxide is TiO2.

[0049] The implementation scheme of different raw material doping ratios is shown in Table 1 below:

[0050] Table 1 Implementation plan of different raw material doping ratios

[0051]

[0052] The following is specifically described by examples:

[0053] Example 1

[0054] The preparation method of the present embodiment using sodium sulfate as a doped alkali metal sulfate and metal oxide modified calcium-based energy storage medium comprises the following steps:

[0055] S1. Raw material pretreatment:

[0056] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0057] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0058] S2, wet mixing:

[0059] 1.4 g of pretreated calcium oxide, 0.2035 g of zinc oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0060] Example 2

[0061] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0062] S1. Raw material pretreatment:

[0063] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0064] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0065] S2, wet mixing:

[0066] 1.4 g of pretreated calcium oxide, 0.308 g of zirconium oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0067] Example 3

[0068] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0069] S1. Raw material pretreatment:

[0070] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0071] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0072] S2, wet mixing:

[0073] 1.4 g of pretreated calcium oxide, 0.1988 g of copper oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0074] Example 4

[0075] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0076] S1. Raw material pretreatment:

[0077] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0078] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0079] S2, wet mixing:

[0080] 1.4 g of pretreated calcium oxide, 0.2173 g of manganese oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0081] Example 5

[0082] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0083] S1. Raw material pretreatment:

[0084] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0085] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0086] S2, wet mixing:

[0087] 1.4 g of pretreated calcium oxide, 0.2549 g of aluminum oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 3 h at 400 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0088] Example 6

[0089] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0090] S1. Raw material pretreatment:

[0091] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 80°C for 6 hours.

[0092] Grinding lithium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, lithium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0093] S2, wet mixing:

[0094] 1.4 g of pretreated calcium oxide, 0.6462 g of magnesium oxide, and 0.11 g of lithium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 3 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 10 h at 120 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 3 h at 400 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0095] Example 7

[0096] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0097] S1. Raw material pretreatment:

[0098] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 120°C for 3 hours.

[0099] Grinding potassium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0100] S2, wet mixing:

[0101] 1.4 g of pretreated calcium oxide, 0.255 g of metal oxide, aluminum oxide, and 0.87 g of potassium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 0.5 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 12 h at 140 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0102] The initial conversion rate of the alkali metal sulfate and metal oxide modified calcium-based energy storage medium prepared in this embodiment is 0.856. Compared with Comparative Example 1, the conversion efficiency is increased by 52.3%.

[0103] Example 8

[0104] This embodiment provides a method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0105] S1. Raw material pretreatment:

[0106] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 80°C for 6 hours.

[0107] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, lithium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0108] S2, wet mixing:

[0109] 1.4 g of pretreated calcium oxide, 0.1273 g of cerium oxide, and 1.02 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 3 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 8 h at 150 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 1 h at 450 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0110] Example 9

[0111] The preparation method of the present embodiment using sodium sulfate as a doped alkali metal sulfate and metal oxide modified calcium-based energy storage medium comprises the following steps:

[0112] S1. Raw material pretreatment:

[0113] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0114] Grinding sodium sulfate: Since some alkali metal sulfates are easily deliquescent and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. Sodium sulfate absorbs water to form sodium sulfate decahydrate. The purpose of this treatment is to dehydrate the alkali metal sulfate so that the weighing is more accurate.

[0115] S2, wet mixing:

[0116] 1.4 g of pretreated calcium oxide, 0.2035 g of iron oxide, and 0.71 g of sodium sulfate were mixed and dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and then moved into an oven and vacuum dried for 10 h at 150 ° C. The concentrated mixture was then moved into a tube furnace and vacuum dried for 2 h at 500 ° C. The obtained sample was ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing a calcium-based energy storage medium, comprising the following steps:

[0119] Raw material pretreatment:

[0120] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0121] Comparative Example 2

[0122] This comparative example provides a method for preparing an alkali metal sulfate-modified calcium-based energy storage medium, comprising the following steps:

[0123] S1. Raw material pretreatment:

[0124] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0125] Grinding sodium sulfate: Since some alkali metal sulfates are easy to deliquesce and form large crystals, the sodium sulfate is ground into fine powder in a mortar and passed through a 400-mesh sieve. The purpose of this treatment is to make the alkali metal sulfate easier to dissolve and weigh;

[0126] S2, wet mixing:

[0127] 1.4 g of pretreated calcium oxide and 0.71 g of sodium sulfate were mixed, dissolved in 20 mL of deionized water, ultrasonically stirred for 2 h at an ultrasonic frequency of 40 kHz in a flask, and moved into an oven for vacuum drying at 140° C. for 12 h. The concentrated mixture was then moved into a tube furnace for vacuum drying at 500° C. for 2 h, and the obtained sample was ground to obtain the alkali metal sulfate-modified calcium-based energy storage medium.

[0128] Comparative Example 3

[0129] This comparative example provides a method for preparing a metal oxide modified calcium-based energy storage medium, comprising the following steps:

[0130] S1. Raw material pretreatment:

[0131] Dry calcium oxide: The purchased calcium oxide was of analytical purity and was not further purified before use. It was only dried under vacuum at 100°C for 4 hours.

[0132] Metal oxides: Metal oxides were purchased of analytical purity and used without further treatment.

[0133] S2, wet mixing:

[0134] 1.4 g of pretreated calcium oxide and 0.2035 g of zinc oxide were mixed, dissolved in 20 mL of deionized water, ultrasonically stirred in a flask for 2 h, and moved into an oven for vacuum drying at 140 ° C for 12 h. The concentrated mixture was then moved into a tube furnace for vacuum drying at 500 ° C for 2 h, and the obtained sample was ground to obtain the metal oxide modified calcium-based energy storage medium.

[0135] Examples 1-5 and Comparative Examples 1-3 were subjected to a cycle treatment. The cycle conditions were as follows: the temperature was raised from 700°C to 850°C at a rate of 5°C / min, and the atmosphere during this process was CO2. When the temperature was raised to 850°C, the atmosphere was switched to N2 and kept warm for ten minutes. This heating and keeping warm process was counted as one cycle.

[0136] It should be noted that Figure 2 and Figure 3 The serial number 1 is comparative example 1, and the serial numbers 2-6 correspond to examples 1-5. Figure 4 The serial numbers 1, 3, and 4 in the table correspond to comparative examples 1 to 3, respectively. Figure 4The sequence number 2 in the figure corresponds to Example 1.

[0137] Figure 2 The SEM images of Examples 1-5 and the comparative example after 5 cycles of testing are shown in Figure 1. The SEM test results show that after doping with alkali metal sulfate and metal oxide, the material can still maintain a rich porous structure after multiple cycles, which facilitates the diffusion of CO2 into the interior of the material, thereby significantly improving the cycle conversion rate.

[0138] Figure 3 The conversion efficiency diagram of Examples 1-5 and Comparative Example 1 shows that, compared with Comparative Example 1, the initial conversion efficiency of Examples 1-5 is increased by 71.4%, 67.8%, 63.7%, 49.3%, and 70%, respectively. This shows that the preparation method of the present invention can effectively improve the conversion efficiency and cycle stability of calcium oxide. Figure 2 The results are consistent.

[0139] Figure 4 The conversion efficiency of Example 1 and Comparative Examples 1-3 is shown in Figure 1. The initial conversion efficiency of Example 1 is the highest, reaching 0.963. Compared with Comparative Examples 1-3, the initial conversion rates are increased by 71.4%, 23%, and 65%, respectively. This shows that the combined effect of alkali metal sulfate and metal oxide can effectively improve the conversion efficiency and cycle stability of calcium oxide.

[0140] Ordinary calcium oxide adsorbs carbon dioxide on its surface, forming calcium carbonate on the surface, which prevents CO2 from entering the internal reaction. In addition, calcium-based energy storage materials will have the problem of high-temperature sintering, which will cause the material to deactivate. Therefore, the smaller the particles and the higher the specific surface area of ​​calcium oxide, the better the adsorption performance. The present invention uses alkali metal sulfate as a promoter and metal oxide as a stabilizer. The prepared calcium-based energy storage material improves the adsorption performance while ensuring good cycle stability, and the material will not deactivate quickly. It is specifically reflected in the cycle conversion rate. The cycle conversion rate is the CO2 that can be absorbed per unit of calcium oxide. The higher the cycle conversion rate, the higher the adsorption performance of the calcium oxide in the material for CO2.

[0141] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0142] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0143] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An alkali metal sulfate and metal oxide modified calcium-based energy storage medium, characterized in that: The invention is obtained by wet mixing the following components in mass percentage: 5% to 40% of alkali metal sulfate, 5% to 30% of metal oxide, and the rest of calcium oxide.

2. The alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 1, characterized in that: The alkali metal sulfate is selected from one of lithium sulfate, sodium sulfate and potassium sulfate.

3. The alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 1, characterized in that: The metal oxide is selected from one of zinc oxide, copper oxide, iron oxide, aluminum oxide, magnesium oxide, manganese oxide, zirconium oxide, cerium oxide and titanium oxide.

4. A method for preparing the alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 1, characterized in that: The following steps are involved: Weigh the components according to the following mass percentages: 5% to 40% alkali metal sulfate, 5% to 30% metal oxide, and the rest calcium oxide; Raw material pretreatment: calcium oxide is dried, and alkali metal sulfate is ground and sieved; Wet mixing: metal oxide, pretreated calcium oxide and alkali metal sulfate are mixed with water and then ultrasonically stirred, and then evaporated, dried and ground to obtain the alkali metal sulfate and metal oxide modified calcium-based energy storage medium.

5. The method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 4, characterized in that: In the raw material pretreatment step: the drying condition is vacuum drying at 80-120°C for 3-6 hours.

6. The method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 4, characterized in that: In the raw material pretreatment step, the sieving mesh number is 400 mesh.

7. The method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 4, characterized in that: In the wet mixing step, the ultrasonic time is 0.5-3h and the ultrasonic frequency is 40kHz.

8. The method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 4, characterized in that: In the wet mixing step, the evaporation condition is vacuum drying at 120-150° C. for 8-12 hours.

9. The method for preparing an alkali metal sulfate and metal oxide modified calcium-based energy storage medium according to claim 4, characterized in that: In the wet mixing step, the drying condition is vacuum drying at 400-500° C. for 1-3 hours.

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