Disclosure of Invention
The invention aims to provide porous calcium-based particles for directly driving thermochemical heat storage by solar energy, and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a porous composite calcium-based particle is prepared from calcium hydroxide, a porous template and a transition metal;
the porous template is selected from microcrystalline cellulose, green bristlegrass or charcoal, and the transition metal is transition metal salt or transition metal oxide;
the transition metal salt is a mixture of aluminum salt, ferric salt and manganese salt, and the transition metal oxide is a mixture of aluminum oxide, ferric oxide and manganese oxide.
Further, the aluminum salt is selected from aluminum nitrate, aluminum sulfate or aluminum hydrochloride, the iron salt is selected from ferric nitrate, ferric sulfate or ferric hydrochloride, and the manganese salt is selected from manganese nitrate, manganese sulfate or manganese hydrochloride.
The preparation method of the porous composite calcium-based particles comprises mixing Ca (OH)2Mixing the porous template and transition metal to prepare a precursor, adjusting the humidity of the precursor, then preparing the precursor mixture into spherical particles by an extrusion spheronization granulator, calcining the spherical particles in air atmosphere, and placing the spherical particles in CO2Carbonizing in the atmosphere to obtain the porous composite calcium-based particles.
Further, Ca in the precursor2+、Al3+、Fe3+、Mn2+In a molar ratio of 100:15:10:5, Ca (OH)2And the mass ratio of the porous template is 100: 40.
Further, the spherical particles are calcined in the air atmosphere for 2 hours at the temperature of 600-1000 ℃.
Further, in CO2The carbonation condition in the atmosphere is 600-800 ℃ for 1 h.
The porous composite calcium-based particles are applied to solar chemical heat storage.
According to the invention, the spectrum absorption enhancing substance transition metal ions are doped, the framework is enhanced in the circulating stability, and the granular porous composite calcium carbonate-calcium oxide granules are prepared by adopting an extrusion-spheronization-calcination method, so that on one hand, the calcium-based energy storage granules can directly absorb solar radiation, and therefore, the calcium-based energy storage granules can be applied to a bulk absorption type photo-thermal reactor, and thus, high-efficiency energy conversion and storage are realized; on the other hand, the composite calcium-based energy storage particles have abundant pore structures, so that the particles have excellent cycling stability, and have better reaction characteristics, namely lower reaction temperature and faster reaction rate compared with unmodified materials.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific examples, which should not be construed as limiting the invention. Modifications or substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit and scope of the invention. The experimental methods and reagents of the formulations not specified in the examples are in accordance with the conventional conditions in the art.
Example 1
As shown in fig. 1, the present invention employs an extrusion-spheronization-calcination process to prepare porous composite calcium-based particles. The method comprises the following specific steps:
step 1, adding Ca (OH)2And microcrystalline cellulose was milled in a planetary ball mill for 30 minutes (300 RPM) to mix well, Ca (OH)2The mass ratio of the precursor to the microcrystalline cellulose is 100:40, and precursor powder is obtained;
step 2, adding Al (NO)3)3⋅9H2O、Fe(NO3)3⋅9H2O、Mn(NO3)2Dissolving in water to prepare a precursor solution;
step 3, adding the precursor powder into the precursor solution, Ca2+、Al3+、Fe3+、Mn2+The molar ratio of the precursor to the solvent is 100:15:10:5, and the mixture is fully stirred until the mixture is completely uniform to obtain a precursor mixture;
step 4, airing the precursor mixture to a proper humidity (the water accounts for 10-60 wt% of the mixture), and preparing the precursor mixture into spherical particles through an extrusion spheronization granulator;
step 5, putting the spherical particles into a muffle furnace, and calcining for 2 hours at 900 ℃ in an air atmosphere to obtain composite CaO particles;
step 6, placing CaO particles into a tube furnace to carbonate for 1 hour in pure CO2 atmosphere, and setting the temperature to 700 ℃ to obtain composite CaCO3Particles;
step 7, finally, CaCO is screened through a standard sieve3The particles are divided into different particle size ranges, such as 600-710 μm.
Example 2
This example differs from example 1 in that NO microcrystalline cellulose, Al (NO) was added3)3⋅9H2O、Fe(NO3)3⋅9H2O and Mn (NO)3)2。
The preparation steps of the pure calcium titanate particles are as follows:
step 1, adding Ca (OH)2Mixing with 35 wt% -100 wt% of deionized water, and fully stirring until the mixture is completely uniform;
step 2, airing the precursor to a proper humidity (the water accounts for 10-60 wt% of the mixture), and preparing the precursor mixture into spherical particles through an extrusion spheronization granulator;
step 3, putting the spherical particles into a muffle furnace, and calcining for 2 hours at 900 ℃ in an air atmosphere to obtain pure CaO particles;
step 4, placing CaO particles into a tube furnace to be subjected to pure CO2Carbonation in an atmosphere at 700 ℃ for 1 hour to obtain pure CaCO3Particles;
step 5, finally passing throughStandard sieve mixing CaCO3The particles are divided into different particle size ranges, such as 600-710 μm.
Example 3
The specific steps of doping with oxide are as follows:
step 1, adding Ca (OH)2Microcrystalline cellulose and oxide were mixed and ground in a planetary ball mill for 30 minutes (300 RPM) to mix well, Ca (OH)2The mass ratio of the calcium carbonate to the microcrystalline cellulose is 100:40, and the content of the calcium carbonate is Ca2+、Al3+、Fe3+、Mn2+The molar ratio of 100:15:10:5 to obtain precursor powder;
step 2, mixing the precursor powder with 35 wt% -100 wt% of deionized water, and fully stirring until the mixture is completely uniform;
step 3, airing the precursor to a proper humidity (the water accounts for 10-60 wt% of the mixture), and preparing the precursor mixture into spherical particles through an extrusion spheronization granulator;
step 4, putting the spherical particles into a muffle furnace, and calcining for 2 hours at 900 ℃ in an air atmosphere to obtain composite CaO particles;
step 5, putting the composite CaO particles into a tube furnace to be subjected to pure CO2Carbonating for 1 hour in the atmosphere and setting the temperature at 700 ℃ to obtain the composite CaCO3Particles;
step 6, finally, the composite CaCO is screened through a standard sieve3The particles are divided into different particle size ranges, such as 600-710 μm.
The calcium-based granules obtained in example 1 and example 2 were subjected to the following performance test.
1. As shown in FIG. 2, the heat storage process is carried out in a bulk absorption reactor, sunlight directly irradiates the surface of the particles, the particles absorb the energy of solar radiation, the temperature is increased, and the particles are decomposed into CaO and CO2And the energy storage process is finished by respectively entering respective storage tanks for storage, when energy needs to be released, CaO and CO2 enter the acidification reactor for reaction, heat is released, and energy output at a target temperature can be obtained by controlling reactant flow, reaction atmosphere, temperature and working medium flow.
2. As shown in FIG. 3, the porous composite calcium-based energy storage particles have abundant poresThe structure of the gaps, which is generated by the decomposition of microcrystalline cellulose, nitrate and calcium hydroxide, can be CO2Diffusion provides a channel, thereby improving the performance of the material.
3. As shown in figure 4, the components in the porous composite calcium-based energy storage particles are divided by CaCO3CaO is mainly CaMnO outside3、Ca3Al2O6、Ca2Fe2O5、Ca2Al1.38Fe0.62O5、Ca2Fe1.5Mn1.5O8、Ca2AlMnO5And the like, which serve as a framework to prevent calcium carbonate/calcium oxide sintering deactivation and as a spectral absorption enhancing substance to improve the solar spectral absorption capacity of the particles.
4. Cyclic stability testing of porous calcium-based particles for solar direct drive thermochemical heat storage
Placing the composite calcium carbonate particles with the size of 600-710 mu m into a sample cell of an ultraviolet-visible spectrophotometer to be compacted, and testing the reflectivity of a sampleR(λ) The data interval is 5 nm, and the test range is 300-2000 nm. Absorption rate throughA(λ) = 1-R(λ) Thus obtaining the product. And then integrating the spectral absorption rate and the radiation energy distribution of the AM1.5 sun reaching the ground to obtain the total energy absorbed by the particles, and dividing the total energy of the sun radiation to obtain the average absorption rate.
Solar energy is used as an incident light source to directly provide energy for the composite energy storage particles, the average absorption rate of the porous composite particles is 80.3% in an AM1.5 spectral range of 300-2000 nm, and the pure calcium carbonate particles prepared by the same method are only 24.0%.
As shown in fig. 5, the porous composite calcium-based energy storage particles can absorb ultraviolet-visible light to store energy, and the solar weighted average spectral absorptivity is as high as 80.3% in AM1.5 spectrum.
5. Cyclic stability testing of porous calcium-based particles for solar direct drive thermochemical heat storage
Taking 3 mg of composite calcium carbonate particles with the size of 600-710 mu m, putting the composite calcium carbonate particles into a synchronous thermal analyzer, and setting a test program: the temperature is increased to 8 ℃ at the temperature rising rate of 10 ℃/min under the nitrogen atmosphereDecomposing at 00 deg.C for 10 min, and switching to 50% CO2The atmosphere was kept for 20 min for acidification and this process was repeated 25 times.
As shown in fig. 6, the energy storage density of the porous composite calcium carbonate particles was not substantially changed during 25 cycles, confirming excellent cycle stability of the particles.
As shown in fig. 4, the composition of the material did not change after 25 cycles, again confirming the excellent thermal stability of the particles.
In the process of carrying out cycle stability, data of one cycle is taken for analysis. As shown in figure 7, the porous calcium-based particles can be rapidly and completely decomposed within 2 min, 84% of the stored total energy can be released within 2 min, and the higher reactivity and reaction rate of the material are confirmed.
6. Wear resistance test of porous calcium-based particles for directly driving thermochemical heat storage by solar energy
10 g of porous composite calcium carbonate particles with the particle size of 600-710 mu m are taken and put into a ball mill for ball milling 24 so as to simulate the operation condition of the porous composite calcium carbonate particles in reactors such as a fluidized bed and the like. As shown in FIG. 8, the mass fraction of the particles having a particle diameter of 600 to 710 μm after the test was 96.2%, and only 0.3% was changed into powder, confirming the excellent wear resistance.
It should be noted that the above description of the embodiments is only for the purpose of assisting understanding of the method of the present application and the core idea thereof, and that those skilled in the art can make several improvements and modifications to the present application without departing from the principle of the present application, and these improvements and modifications are also within the protection scope of the claims of the present application.