Composite geopolymer energy storage material, method of preparation and use thereof

Abstract

The present application relates to the technical field of medium-high temperature thermochemical energy storage and solid waste resource utilization, and provides a composite geopolymer energy storage material, a preparation method and application thereof. The material is prepared by taking steel slag and calcium-based / magnesium-based industrial solid waste as main materials, being activated by low-sodium alkali, introducing an inert refractory skeleton, being carbonized and cured by industrial tail gas CO2, and being activated by high-temperature calcination, can reversibly store and release heat at 600-1000 DEG C, and can build a CO2 closed loop in the process. It has high energy storage density, long cycle life and excellent sintering resistance, and is suitable for industrial park energy systems.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of medium-high temperature thermochemical energy storage and solid waste resource utilization, and particularly relates to a composite geopolymer energy storage material, a preparation method and application thereof. BACKGROUND

[0002] With the increasing proportion of renewable energy grid connection and the widespread existence of process industrial waste heat, it is crucial for energy system flexible scheduling to achieve efficient and large-scale heat storage in the medium-high temperature range of 600-1000℃. Thermochemical energy storage (TCES) realizes the conversion of "thermal-chemical energy" based on reversible reactions (such as CaCO3 / CaO and MgCO3 / MgO), has the advantages of high energy density, long-term lossless storage, and great development potential.

[0003] However, the existing TCES technology route still has many bottlenecks:

[0004] Firstly, at the material level, the mainstream scheme mostly uses natural limestone or high-purity calcium carbonate as the precursor, which faces the pressure of raw material cost and mining footprint; and the calcium / magnesium-rich industrial solid waste (such as steel slag, carbide slag, and papermaking white mud) with huge reserves and low cost has the problems of poor cycle stability and uncertain environmental compliance when directly used for TCES due to large composition fluctuation, high content of impurities (such as Cl － , heavy metals), and complex phase composition.

[0005] Secondly, at the structure level, CaO / CaCO3 and MgO / MgCO3 are prone to grain sintering and pore throat contraction during high-temperature multiple cycles, resulting in decreased activity, limited mass transfer, and insufficient power density. In addition, conventional sodium / potassium-rich geopolymer materials are prone to glass transition and skeleton softening when the temperature exceeds 800℃, and cannot withstand high-temperature cycles.

[0006] Thirdly, at the process and system level, the existing technology usually separates the "carbonation curing" (used to improve strength) and "TCES cycle" (used for energy storage) processes of the material. The carbonation stage often relies on high-purity CO2, while the CO2 released during the calcination stage is not effectively recycled, and the "tail gas CO2→ material curing→ calcination release→ recycling" closed loop at the park level is not formed, resulting in low system energy efficiency and difficulty in achieving the synergistic effect of solid waste resource utilization, CO2 recycling, and energy storage.

[0007] Therefore, there is an urgent need in the art for an integrated technical solution that can balance raw material economy, high-temperature cycle stability, high energy density, and CO2 process internal closed-loop utilization. SUMMARY

[0008] In view of the problems of high raw material cost, poor cycle stability, CO2 not closed-loop utilization and low system energy efficiency in the prior art, the present application aims to provide a composite geopolymer energy storage material with high energy storage density and long service life, a preparation method and applications thereof. The core purpose of the present application is to realize the synergistic effect of medium-high temperature thermochemical energy storage and industrial solid waste and tail gas CO2 resource utilization through the integrated design of "material-structure-process-system".

[0009] To solve the above technical problems, the present application is implemented as follows:

[0010] The present application provides a preparation method of a composite geopolymer energy storage material, comprising the following steps:

[0011] Step S1, raw material preparation: taking steel slag as the main material, cooperated with calcium-based and / or magnesium-based industrial solid waste, and adding inert refractory skeleton powder and low-sodium alkali activator;

[0012] Step S2, pretreatment: crushing, magnetic separation, grading, and desalination / dedichlorination and wet pile aging or low-pressure pre-carbonization are performed on the raw materials;

[0013] Step S3, slurry preparation and molding: dry materials and low-sodium alkali activator are prepared into slurry according to the formula and molded into particles or honeycomb bodies;

[0014] Step S4, initial solidification and drying: curing for 12-24h under the conditions of 20-40℃ and relative humidity ≥90%, and drying at 40-60℃ under low temperature;

[0015] Step S5, industrial tail gas CO2 carbonization curing: under the conditions of 0.2-0.5MPa and 20-40℃, 2-5vol% water vapor is added for carbonization for 2-6h, so that fine dispersed carbonates are generated in situ in the pores;

[0016] Step S6, high-temperature calcination activation: under the conditions of inert or micro-oxygen atmosphere, heat preservation at 850-950℃ for 1-2h, so that the carbonates are decomposed into fine dispersed CaO and / or MgO;

[0017] Step S7, heat storage cycle: under the conditions of 900-950℃ and pCO2≤0.1bar, the decomposition endothermic reaction occurs, under the conditions of 650-700℃ and pCO2=1bar, the carbonation exothermic reaction occurs, and process intensification is carried out by using pressure swing and steam assisted carbonation;

[0018] Step S8, CO2 closed loop: the CO2 released in the calcination section is recovered, and after heat exchange, drying, compression and buffering, it is sent back to the carbonization section, realizing the closed loop utilization within the process.

[0019] Optionally, in step S3, the proportion of the dry material is 35-45wt% of steel slag, 20-30wt% of carbide slag and / or paper mill white mud, 15-25wt% of inert skeleton powder, 5-10wt% of active MgO, 2-5wt% of pore-forming agent, and the rest is formula adjustment and loss; wherein the inert skeleton powder is selected from one or more of Al2O3, MgAl2O4, and ZrO2.

[0020] Optionally, in step S1, the low-sodium alkali activator is composed of low-modulus water glass with a modulus of 1.0-1.4 and lime milk, so that the Na2O equivalent of the system is ≤5wt%.

[0021] Optionally, in step S3, the formed body is a φ1-3mm particle, wherein D50=1.5-2.0mm, and the sphericity factor is ≥0.85; or a honeycomb body with a channel of 1-2mm, a wall thickness of 0.3-1.0mm, and an opening rate of ≥60%.

[0022] Optionally, in step S5, the carbonization maintenance adopts a pulse flow or reverse flow organization form, and the mass weight gain of 5-10% and the CO2 breakthrough curve platform at the outlet are used as the carbonization end point judgment.

[0023] Optionally, in step S6, the heating rate during the calcination activation process is 3-5℃·min －1 The calcination tail gas CO2 is stored in a buffer tank after waste heat recovery, condensation drying and multi-stage compression, and is used when the gas is insufficient or the tail gas fluctuates in the carbonization section.

[0024] Optionally, in step S7, the high-low pressure switching period of the heat storage cycle is 2-10min; and the carbonation section is carried out under the condition that pCO2=1bar and H2O is 2-10vol%.

[0025] Optionally, in step S3, 1-5wt% of a heat-conducting phase is added to the particle formula, and the heat-conducting phase is selected from SiC, AIN or graphite-based materials; or a pipe / fin heat exchange structure is adopted, so that the equivalent heat conduction coefficient of the bed layer is increased by ≥30%, and the bed temperature difference ΔT is ≤30K.

[0026] Optionally, through 3-10wt% of micro-doping of active MgO and 15-25wt% of inert skeleton coordination, the capacity retention of the material is ≥60% after 100-500 cycles, and the capacity recovery is realized through 680-750℃ steam reactivation and medium-temperature finishing calcination.

[0027] The application also provides a composite geopolymer energy storage material prepared by the method, and the microstructure of the composite geopolymer energy storage material is that finely dispersed CaO or CaO / MgO dual-phase is uniformly distributed in a multi-level pore skeleton, the BET specific surface area is ≥5m 2 ·g－1 The pore diameter is mainly mesopore of 10-500 nm, and the pores are through and intersected; and the particle crushing strength is greater than or equal to 25 N.

[0028] Optionally, carbonation exothermicity is carried out at 650-700 DEG C and pCO2=1 bar, and decomposition endothermicity is carried out at 900-950 DEG C and pCO2≤0.1 bar, and the effective energy storage density of the first circle is greater than or equal to 1.0 MJ·kg －1 The volume energy density is greater than or equal to 0.8 GJ·m －3 , and the leaching toxicity meets the standard.

[0029] The present application also provides a thermal chemical energy storage and CO2 closed loop device, comprising:

[0030] A raw material processing and forming unit;

[0031] A carbonization reactor with CO2 gas inlet, condensation drying and impurity purification interface, supporting pulse / reverse switching and steam blending;

[0032] A calcination / decomposition reactor supporting inert or micro-oxygen atmosphere;

[0033] A CO2 recovery-compression-buffering-return loop;

[0034] A heat exchange network;

[0035] A process control system for online monitoring of temperature, pressure, flow, CO2 concentration and pressure drop;

[0036] Safety interlocking, including CO2 / low oxygen alarm, overtemperature / overpressure, dust explosion prevention and static grounding.

[0037] Optionally, the heat exchange surface density of the heat exchange network is 150-400 m 2 ·m －3 , and the bed height is 0.3-1.0 m; the CO2 loop comprises a tail gas purification module and a bypass switching module to realize flexible switching of tail gas and closed loop CO2 and stable pressure supply.

[0038] Optionally, the impurity control of the industrial tail gas CO2 meets the requirements of residual SO2<10 ppm, NO x <50 ppm, dew point ≤-10 DEG C, and the carbonization section CO2 utilization rate is greater than or equal to 70%, and the process CO2 recovery rate is greater than or equal to 85%.

[0039] Optionally, the heat level coupling is carried out with kiln tail gas, molten salt heat storage or steam conduit to realize carbonation exothermicity docking process steam / hot air and regional heating, decomposition endothermicity and high temperature flue / molten salt side coupling, so that stable output with a return efficiency of greater than or equal to 70% and CO2 park level closed loop utilization are obtained in large-scale operation.

[0040] The present application has the following beneficial effects compared with the prior art:

[0041] (1) The unification of high energy density and high power density is realized: through inert skeleton confinement and structured carrier design, the material has an effective energy storage density ≥1.0 MJ·kg －1 , a volume energy density ≥0.8 GJ·m －3 , a small bed temperature difference (ΔT≤30K), and a high power density (up to 0.2~1.0 MW·m －3 ).

[0042] (2) Excellent long cycle life and renewability: low-sodium formula and inert skeleton effectively inhibit high-temperature sintering and glassification, combined with steam reactivation technology, the capacity retention rate of the material can still reach 60~80% after 100~500 cycles, and the activity can be restored after attenuation through regeneration.

[0043] (3) Process internal closed-loop utilization of industrial tail gas CO2 is realized: the CO2 released in the calcination section is recycled and used in the carbonation section, forming an internal cycle of "waste treatment with waste", the CO2 utilization rate in the carbonation section is ≥70%, the CO2 recovery rate in the whole process is ≥85%, and the carbon benefit is significantly improved.

[0044] (4) High-value resource utilization and cost reduction of solid waste are realized: low-priced / negative-priced industrial solid waste such as steel slag and calcium carbide slag is used as the main raw material, which greatly reduces the raw material cost, and realizes the synergy of solid waste disposal and energy storage material production, with outstanding economic and environmental benefits.

[0045] (5) Excellent high-temperature shape stability and sintering resistance: a low-sodium calcium-rich system combined with a refractory skeleton such as MgAl2O4 / ZrO2 ensures the structural stability of the material in a wide temperature range of 600~1000℃, and the pore network remains open during the cycle.

[0046] (6) Process intensification improves system efficiency and response speed: pressure swing (PSA) operation and steam-assisted carbonation are used to realize near-isothermal heat storage and release cycles, with high round-trip efficiency (≥70%), fast response, and good grid peak shaving capability.

[0047] (7) Environmentally friendly and safety compliant: the Cl － and alkali metal contents are strictly controlled through raw material pretreatment, the product leaching toxicity meets the standards, and the device is equipped with a perfect safety interlocking system to ensure the environmental and operational safety of the whole process.

[0048] (8) Strong engineering adaptability and robustness to raw material fluctuations: the formula and process parameters have a wide window, which can be flexibly adjusted according to the composition of different solid waste in the park, the carrier form and reactor type have strong selectivity, and it is easy to scale up and promote the application. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0050] Figure 1 A comparison chart of key performance indicators between the embodiments and comparative examples provided by the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] The terms "first," "second," etc., used in this specification are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the specification, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0053] This invention provides a method for preparing a composite geopolymer energy storage material, comprising the following steps:

[0054] Step S1 Raw material preparation: mainly steel slag, combined with calcium-based and / or magnesium-based industrial solid waste, and added inert refractory skeleton powder and low sodium alkali activator;

[0055] Step S2, Pretreatment: The raw materials are crushed, magnetically separated, classified, and desalted / dechlorinated and wet-stacked or pre-carbonized.

[0056] Step S3, Pulping and Molding: Pulp the dry materials and activator according to the formula and mold them into granules or honeycomb structures;

[0057] Step S4, initial curing and drying: cure at 20~40℃ and relative humidity ≥90% for 12~24h, and then dry at a low temperature of 40~60℃;

[0058] Step S5, carbonation curing of industrial tail gas CO2: under the conditions of 0.2-0.5 MPa and 20-40℃, 2-5vol% water vapor is incorporated for carbonation for 2-6h, so that finely dispersed carbonates are generated in situ in the pores;

[0059] Step S6, high-temperature calcination activation: under an inert or micro-oxygen atmosphere, heat preservation is carried out at 850-950℃ for 1-2h, so that the carbonates are decomposed into finely dispersed CaO and / or MgO;

[0060] Step S7, heat storage and release cycle: under the conditions of 900-950℃ and pCO2≤0.1bar, the decomposition endothermic reaction is carried out, under the conditions of 650-700℃ and pCO2=1bar, the carbonation exothermic reaction is carried out, and process intensification is carried out by using pressure swing and steam assisted carbonation;

[0061] Step S8, CO2 closed loop: the CO2 released in the calcination section is recovered, heat exchanged, dried, compressed, buffered and then sent back to the carbonation section, so that the process is closed and utilized.

[0062] In step S1, the low-sodium alkali activator is composed of low-modulus water glass with a modulus of 1.0-1.4 and lime milk, so that the Na2O equivalent of the system is ≤5wt%, and preferably, the Na2O equivalent is ≤4wt%.

[0063] In step S3, the dry material is mixed in a mass fraction of 35-45wt% of steel slag, 20-30wt% of carbide slag and / or paper mill white mud, 15-25wt% of inert skeleton powder, 5-10wt% of active MgO, 2-5wt% of pore-forming agent, and the rest is formula adjustment and loss; wherein the inert skeleton powder is selected from one or more of Al2O3, MgAl2O4 and ZrO2.

[0064] The formed body is a φ1-3mm particle, wherein D50=1.5-2.0mm and the sphericity factor is ≥0.85; or a honeycomb body with a channel of 1-2mm, a wall thickness of 0.3-1.0mm and an opening rate of ≥60%.

[0065] Further, 1-5wt% of a heat-conducting phase selected from SiC, AIN or graphite-based materials is added to the particle formula; or a pipe / fin heat exchange structure is used to increase the equivalent heat conduction coefficient of the bed by ≥30% and the temperature difference ΔT in the bed is ≤30K.

[0066] In step S5, the carbonation curing adopts a pulse flow or reverse flow organization form, and the mass weight gain of 5-10% and the CO2 breakthrough curve platform at the outlet are used as the carbonation end point judgment.

[0067] In step S6, the heating rate during the calcination activation process is 3-5℃·min －1The CO2 in the calcination tail gas is stored in a buffer tank after waste heat recovery, condensation drying and multi-stage compression, and is switched for use when there is insufficient gas or tail gas fluctuation in the carbonation section.

[0068] In step S7, the high-low pressure switching period of the pressure swing operation in the heat storage cycle is 2-10 min; the carbonation section is carried out under the conditions of pCO2≈1 bar and H2O of 2-10 vol%.

[0069] By 3-10 wt% micro-doping of active MgO and 15-25 wt% synergy confinement of inert framework, the capacity retention is ≥60% after 100-500 cycles, preferably ≥80%, and the capacity recovery is realized by steam reactivation at 680-750℃ and medium temperature finishing calcination.

[0070] The application also provides a composite geopolymer energy storage material prepared by the method, which has a microstructure in which finely dispersed CaO or CaO / MgO dual-phase is uniformly distributed in a multi-level pore framework, a BET specific surface area ≥5m 2 ·g －1 , preferably a BET specific surface area ≥8m 2 ·g －1 , a pore size mainly in the form of 10-500 nm mesopores with through interporous pores; and a particle crushing strength ≥25N, preferably a particle crushing strength ≥40N.

[0071] The material is carbonated exothermically at 650-700℃ and pCO2≈1 bar, and is decomposed endothermically at 900-950℃ and pCO2≤0.1 bar, with an effective energy storage density of ≥1.0 MJ·kg －1 , a volumetric energy density of ≥0.8 GJ·m －3 , preferably an effective energy storage density of ≥1.5 MJ·kg －1 , a volumetric energy density of ≥1.5 GJ·m －3 , and leaching toxicity meeting the standards.

[0072] The application also provides a thermochemical energy storage and CO2 closed loop device, comprising:

[0073] A raw material processing and forming unit;

[0074] A carbonation reactor with CO2 gas inlet, condensation drying and impurity purification interface, supporting pulse / reverse switching and steam mixing;

[0075] A calcination / decomposition reactor supporting inert or micro-oxygen atmosphere;

[0076] A CO2 recovery-compression-buffering-return loop;

[0077] A heat exchange network;

[0078] Process control system for temperature, pressure, flow, CO2 concentration and pressure drop online monitoring;

[0079] Safety interlock including CO2 / low oxygen alarm, over-temperature / over-pressure, dust explosion prevention and static grounding.

[0080] The heat exchange surface density of the heat exchange network is 150-400 m 2 ·m －3 , and the bed height is 0.3-1.0 m; the CO2 circuit comprises a tail gas purification module and a bypass switching module, realizing flexible switching of tail gas and closed-loop CO2 and stable pressure supply.

[0081] The impurity control of the industrial tail gas CO2 meets the requirements of residual SO2 < 10 ppm, NO x < 50 ppm, dew point ≤-10°C, and the utilization rate of CO2 in the carbonization section is ≥ 70%, and the process CO2 recovery rate is ≥ 85%.

[0082] The heat level coupling is carried out with kiln tail gas, molten salt heat storage or steam conduit, realizing the heat exchange of carbonation and heat exchange of decomposition, and the coupling of high-temperature flue gas / molten salt side, so that the stable output of ≥ 70% return efficiency and CO2 park-level closed-loop utilization are obtained in large-scale operation.

[0083] The preparation method of the composite geopolymer energy storage material provided by the present application will be described in detail below with specific examples and comparative examples.

[0084] Example 1: Ca-dominated particles (target: high energy density)

[0085] Raw materials and formulations: LF slag (f-CaO 8.5wt%) 40wt%, paper mill white mud 25wt%, α-Al2O3 20wt%, active MgO 5wt%, and starch pore former 3wt%. The activator is water glass with a modulus of 1.2 and Ca(OH)2, and the Na2O equivalent is ≤ 4.0wt%, and the water-solid ratio is 0.22.

[0086] Preparation and process: disc granulation to obtain D50≈2.0mm particles; curing at 25°C, RH≥95% for 20h, and drying at 50°C for 6h; using cement kiln tail gas (CO2 78-82vol%) for pulse flow carbonization at 0.30MPa, 30°C for 4h (doped with 3vol% H2O), mass gain 6.4%; calcination under N2 atmosphere at a heating rate of 3.5°C / min to 900°C and holding for 90min.

[0087] Performance test: cyclic test in an embedded tube fixed bed (decomposition: 920°C, pCO2 0.05 bar; carbonation: 680°C, pCO2 1.0 bar, H2O 5 vol%; pressure swing period 5 min). Results: first cycle effective energy density 1.28 MJ / kg, volumetric energy density 1.06 GJ / m3, round trip efficiency 73%; capacity retention 68% after 300 cycles; carbonation section CO2 utilization 75.5%, overall CO2 recovery 88-90%; TCLP compliant.

[0088] Example 2: Ca-Mg dual phase honeycomb (goal: high volumetric power density with low pressure drop)

[0089] Raw materials and formulation: BOF steel slag 35wt%, desalted carbide slag 20wt%, magnesia kiln dust calcine 10wt%, MgAl2O4 20wt%, ZrO2 3wt%, NaHCO3 pore former 4wt%. Modulus of activator 1.1, Na2O equivalent <4.5wt%.

[0090] Preparation and process: extrusion into honeycomb with channel 1.5mm, wall thickness 0.6mm; carbonation with converter gas, counter flow, mass gain 7.1%; calcination conditions same as example 1.

[0091] Performance test: first cycle volumetric power density peak 0.84 MW / m 3 , effective energy density 1.12 MJ / kg; capacity retention 62% after 500 cycles; CO2 utilization 72.5%.

[0092] Example 3: high salt CKD adaptation (goal: salt corrosion resistance and compliance)

[0093] Raw materials and formulation: incoming CKD (Cl － 0.9wt%) pre-processed by water washing to reduce Cl － to 0.12wt%. Formulation: LF steel slag 38wt%, desalted CKD 28wt%, a-Al2O3 18wt%, active MgO 7wt%, wood powder pore former 3wt%, Na2O equivalent 3.5wt%.

[0094] Performance test: first cycle effective energy density 1.05 MJ / kg; capacity retention 69% after 300 cycles; leaching toxicity compliant, proving effective treatment of high salt solid waste and ensuring environmental compliance.

[0095] Example 4: high power fast response (goal: fast peak shaving)

[0096] Raw materials and formulation: 3wt% SiC micro powder added as thermal conducting phase in the formulation. Fine particles with D50≈1.2mm prepared by spray granulation.

[0097] Preparation and process: The cycle time of the pressure swing was shortened to 3 minutes using a circulating fluidized bed (CFB) reactor.

[0098] Performance test: The peak volumetric power density was up to 1.05 MW / m 3 , and maintained at 0.9-0.95 MW / m 3 under steady state, showing excellent fast response peak shaving capability.

[0099] Example 5: High proportion of CO2 closed loop (target: maximize carbon utilization and system energy efficiency)

[0100] Preparation and process: The carbonization gas source was provided by mixing 70% of the recovered CO2 from the calcination section and 30% of the lime kiln tail gas. The compressed waste heat was reused for front-end tail gas drying.

[0101] Performance test: The CO2 utilization rate of the carbonization section was increased to 79-81%, and the overall CO2 recovery rate was up to 91-93%. The system primary energy efficiency was improved by about 12% compared with the no-integration baseline, achieving double optimization of carbon and energy efficiency.

[0102] Comparative example

[0103] Scheme: No inert skeleton powder was added, and the modulus of the activator was increased to Ms≈1.6, so that the Na2O equivalent was increased to 7.0 wt%. The remaining steps were consistent with Example 1.

[0104] Results: After calcination, the material showed serious glass softening, and the BET specific surface area dropped to 2.1 m 2 / g. The effective energy storage density of the first cycle was only 0.78 MJ / kg, the capacity retention rate after 100 cycles was as low as 48%, the particles were seriously pulverized, and the CO2 utilization rate was reduced to 63.5%. The comparison proved that the use of low-sodium alkali activation system and the introduction of inert refractory skeleton are indispensable key technical features to ensure the high-temperature structural stability and long cycle life of the material.

[0105] The key performance comparison of the above examples and comparative examples is shown in Table 1 and Figure 1 .

[0106] Table 1 Comparison of sample performance

[0107]

[0108] It should be noted that, as used in this place, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0109] Furthermore, it is to be understood that the scope of the present application is not limited to the specific embodiments discussed in this place, but rather only by the claims. The specific embodiments discussed in this place are illustrative only and other embodiments can be made without departing from the spirit and scope of the present application. In addition, features described in relation to one example can be combined in other examples.

[0110] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are merely illustrative, not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the scope of the present application.

Claims

1. A method of preparing a composite geopolymer energy storage material, characterised by, The method comprises the following steps: Step S1, raw material preparation: taking steel slag as the main raw material, cooperated with calcium-based and / or magnesium-based industrial solid waste, and adding inert refractory skeleton powder and low-sodium alkali activator; Step S2, pretreatment: performing crushing, magnetic separation, grading, and desalination / dedchlorination and wet pile aging or low-pressure pre-carbonization on the raw materials; Step S3, slurry preparation and molding: preparing slurry from dry materials and low-sodium alkali activator according to the formula and molding into particles or honeycomb bodies; Step S4, initial solidification and drying: curing for 12-24 hours under the condition of 20-40°C and relative humidity ≥ 90%, and drying at a low temperature of 40-60°C; Step S5, carbonization curing with industrial tail gas CO2: under the condition of 0.2-0.5 MPa and 20-40°C, carbonization is carried out by mixing 2-5 vol% water vapor for 2-6 hours, so that finely dispersed carbonates are generated in situ in the pores; Step S6, high-temperature calcination activation: under the condition of inert or micro-oxygen atmosphere, calcination is carried out at 850-950°C for 1-2 hours, so that the carbonates are decomposed into finely dispersed CaO and / or MgO; Step S7, heat storage and release cycle: under the condition of 900-950°C and pCO2≤0.1 bar, the decomposition endothermic reaction is carried out, under the condition of 650-700°C and pCO2=1 bar, the carbonation exothermic reaction is carried out, and process intensification is carried out by using pressure swing and steam assisted carbonation; Step S8, CO2 closed loop: the CO2 released in the calcination section is recovered, and after heat exchange, drying, compression and buffering, it is sent back to the carbonization section, realizing the closed loop utilization in the process.

2. The method of claim 1, wherein: In step S3, the proportion of the dry materials is 35-45 wt% of steel slag, 20-30 wt% of carbide slag and / or paper mill white mud, 15-25 wt% of inert skeleton powder, 5-10 wt% of active MgO, 2-5 wt% of pore forming agent, and the rest is formula adjustment and loss; wherein the inert skeleton powder is selected from one or more of Al2O3, MgAl2O4 and ZrO2.

3. The method of claim 1, wherein: In step S1, the low-sodium alkali activator is composed of low-modulus water glass with a modulus of 1.0-1.4 and lime milk, so that the Na2O equivalent of the system is ≤5 wt%.

4. The method of claim 1, wherein: In step S3, the molded body is φ1-3mm particles, wherein D50=1.5-2.0mm and the spherical factor is ≥0.85; or a honeycomb body with a channel of 1-2mm, a wall thickness of 0.3-1.0mm and an opening rate of ≥60%.

5. The method of claim 1, wherein: In step S5, the carbonization curing adopts pulse flow or reverse flow organization form, and the mass weight gain of 5-10% and the CO2 breakthrough curve platform at the outlet are used as the carbonization end point judgment.

6. The method of claim 1, wherein: In step S6, the temperature rising rate in the calcination activation process is 3-5℃·min －1 The calcination tail gas CO2 is stored in the buffer tank after waste heat recovery, condensation drying and multi-stage compression, and is used when the gas is insufficient or the tail gas fluctuates in the carbonization section.

7. The method of claim 1, wherein: In step S7, the high-low pressure switching period of the pressure swing operation in the heat storage and release cycle is 2-10min; the carbonation section is carried out under the condition of pCO2=1 bar and H2O of 2-10 vol%.

8. The method of claim 1, wherein: In step S3, 1-5 wt% of a heat-conducting phase is added to the particle formula, and the heat-conducting phase is selected from SiC, AIN or graphite-based materials; or a pipe / fin heat exchange structure is used to improve the equivalent heat conduction coefficient of the bed by ≥30%, and the bed temperature difference ΔT is ≤30K.

9. A composite geopolymer energy storage material, characterized by: It is prepared by the method of any one of claims 1-8, and its microstructure is that fine dispersed CaO or CaO / MgO dual-phase is uniformly distributed in the multi-level pore framework, the BET specific surface area is ≥5m 2 ·g －1 , the pore size is mainly mesoporous with a pore size of 10-500 nm and has through interporous; the particle crushing strength is ≥25 N.

10. Use of the composite geopolymer energy storage material of claim 9 in district energy and industrial parks. The heat level coupling with the kiln tail gas, molten salt heat storage or steam conduit is carried out to realize the carbonation exothermic interfacing process steam / hot air and regional heating, decomposition endothermic and high temperature flue / molten salt side coupling, so that the stable output with the round trip efficiency ≥70% and the park level closed loop utilization of CO2 are obtained in the large-scale operation.

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