Method for refining calcium-based synthesis gas by regulating and controlling calcium carbonate crystal phase coupled with green hydrogen

Abstract

The invention discloses a method for refining calcium-based synthesis gas by regulating calcium carbonate crystal phase coupling green hydrogen. The method comprises the following steps: preparing green hydrogen by using renewable energy as power drive; determining a calcium carbonate crystal phase, and determining a high-temperature pyrolysis in-situ reduction temperature according to the calcium carbonate crystal phase; and introducing green hydrogen serving as reducing gas into the calcium carbonate with the determined crystal phase, and performing high-temperature pyrolysis reduction treatment to obtain the calcium-based synthesis gas. According to the invention, green hydrogen prepared from renewable energy is coupled with calcium carbonate with different crystal phases for co-thermal coupling in-situ reduction, so that the calcium-based synthesis gas is prepared in an energy-saving, emission-reducing and synergistic manner; according to the method, the optimal high-temperature pyrolysis in-situ reduction temperature is determined by determining the calcium carbonate crystal phase in the early stage, meanwhile, the high-added-value synthesis gas is generated through in-situ reduction of heat released by high-temperature decomposition, emission of carbon dioxide is inhibited, the greenhouse effect is greatly relieved, the energy-saving, emission-reducing and consumption-reducing effects are remarkable, and the method is suitable for industrial production. And the preparation of the calcium-based synthesis gas and the green low-carbon cycle development of the carbonate pyrolysis industry are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing calcium-based syngas with low carbon emissions, and specifically relates to a method for regulating calcium carbonate crystal phase and coupling green hydrogen to refine calcium-based syngas. Background Art

[0002] Process industries such as cement, steel, refractories, and calcium carbide are the basic pillars of the national economic development and play an important role. As the main raw material for these industries, carbonate undergoes high-temperature thermal decomposition (>900 °C) to produce metal oxides, while releasing a large amount of carbon dioxide. The carbon emissions from this process account for more than 50% of the total industrial emissions in China, posing a major challenge to the environment and energy consumption. Carbon capture and utilization (CCU) technology: converting the captured carbon dioxide into high-value chemicals, as a promising solution for reducing carbon emissions, has received extensive attention. However, carbon dioxide itself has thermodynamic stability and chemical inertness, and a large amount of energy needs to be input from external sources to activate and promote its conversion. This challenge emphasizes the need to adopt innovative methods to improve the efficiency and feasibility of the carbon dioxide utilization process. Therefore, there is an urgent need to develop innovative and sustainable carbonate pyrolysis strategies to achieve energy conservation, consumption reduction, and emission reduction, and improve the technical and economic feasibility.

[0003] At the same time, the traditional high-temperature calcination of calcium carbonate to prepare calcium oxide has a high preparation temperature, high energy consumption, and a large amount of carbon dioxide emissions, which exacerbates the greenhouse effect. Summary of the Invention

[0004] The present invention is proposed to overcome the disadvantages existing in the prior art, and its purpose is to provide a method for regulating calcium carbonate crystal phase and coupling green hydrogen to refine calcium-based syngas.

[0005] The present invention is achieved by the following technical solutions:

[0006] A method for regulating calcium carbonate crystal phase and coupling green hydrogen to refine calcium-based syngas, comprising the following steps:

[0007] (Ⅰ) Using renewable energy as the driving force to prepare green hydrogen;

[0008] (Ⅱ) Determining the calcium carbonate crystal phase and determining the high-temperature pyrolysis reduction temperature based on the calcium carbonate crystal phase;

[0009] (Ⅲ) Introducing the green hydrogen prepared in step (Ⅰ) as a reducing gas into the calcium carbonate with a determined crystal phase for high-temperature pyrolysis reduction treatment, thereby obtaining calcium-based syngas.

[0010] In the above technical solution, the renewable energy includes any one or several of wind energy, solar energy, or tidal energy.

[0011] In the above technical solution, the technology for preparing green hydrogen includes any one or more of hydrogen production by electrolysis of water, hydrogen production by photolysis of water, or hydrogen production by photoelectrolysis of water.

[0012] In the above technical solution, the calcium carbonate crystal phase is any one of calcite phase, vaterite phase, or aragonite phase.

[0013] In the above technical solution, the volume concentration of hydrogen in the reducing gas is 10% - 100%, preferably 100%.

[0014] In the above technical solution, the gas flow rate of the reducing gas is 20 mL / min - 20 L / min.

[0015] In the above technical solution, when the calcium carbonate crystal phase is calcite phase, the optimal high-temperature pyrolysis reduction temperature is 700 °C, the reaction time is 100 min, and the heating rate is 5 °C / min - 50 °C / min; when the calcium carbonate crystal phase is vaterite phase, the optimal high-temperature pyrolysis reduction temperature is 700 °C, the reaction time is 100 min, and the heating rate is 5 °C / min - 50 °C / min; when the calcium carbonate crystal phase is aragonite phase, the optimal high-temperature pyrolysis reduction temperature is 550 °C, the reaction time is 100 min, and the heating rate is 5 °C / min - 50 °C / min.

[0016] The beneficial effects of the present invention are:

[0017] The present invention provides a method for regulating the calcium carbonate crystal phase and coupling green hydrogen to refine calcium-based syngas. By coupling "green hydrogen" prepared from renewable energy with different crystal phases of calcium carbonate (calcite, vaterite, and aragonite) for co-thermal coupling reduction, calcium-based syngas (high-purity calcium oxide and syngas) is prepared with energy conservation, emission reduction, and increased efficiency. Compared with the traditional process of preparing calcium oxide by high-temperature calcination of calcium carbonate (calcite) and releasing a large amount of carbon dioxide, by regulating the calcium carbonate crystal phase, the optimal high-temperature pyrolysis reduction temperature is determined in advance, avoiding energy waste. Coupling with "green hydrogen" significantly reduces the preparation temperature of high-purity calcium oxide. At the same time, the heat released by high-temperature decomposition is used to in-situ reduce to produce high-value-added syngas, inhibiting carbon dioxide emissions and greatly alleviating the greenhouse effect. The energy-saving and consumption-reducing effect is remarkable, realizing the preparation of calcium-based syngas and the green and low-carbon circular development of the carbonate pyrolysis industry, and having broad application prospects. Description of the Drawings

[0018] Figure 1 are the scanning electron microscope images of calcium carbonate with different crystal phases in Examples 1, 2, and 3 of the present invention (from left to right are calcite phase, vaterite phase, and aragonite phase);

[0019] Figure 2SEM images of different crystal phases of calcium carbonate after hydrogenation at 700 °C in Examples 1, 2, and 3 of the present invention (from left to right: calcite phase, vaterite phase, aragonite phase);

[0020] Figure 3 XRD patterns of different crystal phases of calcium carbonate and after hydrogenation at 700 °C in Examples 1, 2, and 3 of the present invention;

[0021] Figure 4 Hydrogenation performance graph of calcite phase calcium carbonate at different temperatures in Example 1 of the present invention;

[0022] Figure 5 Hydrogenation performance graph of vaterite phase calcium carbonate at different temperatures in Example 2 of the present invention;

[0023] Figure 6 Hydrogenation performance graph of aragonite phase calcium carbonate at different temperatures in Example 3 of the present invention.

[0024] For those of ordinary skill in the art, without creative efforts, other relevant drawings can be obtained based on the above drawings. Detailed implementation manners

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the drawings in the specification and through specific implementation manners.

[0026] "Green hydrogen" in the present invention refers to hydrogen prepared by using renewable energy as the driving force, that is, green hydrogen, and the preparation method adopts electrolytic water hydrogen production, photocatalytic water splitting hydrogen production or photoelectrolytic water splitting hydrogen production technology; "calcium-based syngas" refers to the conversion of carbon dioxide into syngas (CO and H2) by co-heating and in-situ reduction of calcium carbonate while realizing the recycling of calcium oxide, and calcium-based syngas includes but is not limited to CaO + syngas.

[0027] Example 1

[0028] The calcium carbonate used in this example is calcite phase calcium carbonate. The specific steps for coupling calcite phase calcium carbonate with green hydrogen to save energy, reduce emissions and increase efficiency in refining "calcium-based syngas" are as follows:

[0029] (Ⅰ) Using renewable energy as the driving force to prepare "green hydrogen"

[0030] Using nickel-iron hydrotalcite as the anode, commercial Pt / C catalyst as the cathode, and 30 wt% potassium hydroxide solution as the electrolyte, under the condition of a current density of 200 mA / cm -2 Hydrogen is prepared by electrolytic water technology, and the prepared gas is directly connected to a tubular furnace after passing through a recovery system and a filtration system. The gas flow rate of hydrogen is set to 100 mL / min;

[0031] (II) Feed the "green hydrogen" prepared in step (I) into calcite-phase calcium carbonate and conduct high-temperature pyrolysis treatment to obtain "calcium-based syngas".

[0032] Take 10 g of calcite-phase calcium carbonate and spread it flat in a tubular furnace. Set the pyrolysis temperature at 700 °C, the heating rate at 10 °C / min, and the reaction time at 100 min. After calcination, calcium oxide is obtained, and the ratio of H2 to CO in the syngas is 3:1.

[0033] As can be seen from Figure 1 , different crystal-phase calcium carbonates exhibit different morphological characteristics. Calcite has an obvious rhombic block structure with uniform size of 4 - 8 μm. Secondly, vaterite shows a consistent spherical morphology with a particle size between 4 and 6 μm. Aragonite has a uniform rod-like structure with a size of 5 - 8 μm. Figure 2 Figure

[0034] Example 2

[0035] The calcium carbonate used in this example is vaterite-phase calcium carbonate. The specific steps for coupling vaterite-phase calcium carbonate with green hydrogen for energy conservation, emission reduction, and efficiency improvement in refining calcium-based syngas are as follows:

[0036] (I) Use renewable energy as the driving force to prepare "green hydrogen".

[0037] Use nickel-iron hydrotalcite as the anode, commercial Pt / C catalyst as the cathode, and 30 wt% potassium hydroxide solution as the electrolyte. Under the condition of a current density of 200 mA / cm -2 , prepare hydrogen through electrolysis water technology. The prepared gas is directly connected to a tubular furnace after passing through a recovery system and a filtration system. The gas flow rate of hydrogen is set at 100 mL / min.

[0038] (II) Feed the "green hydrogen" prepared in step (I) into vaterite-phase calcium carbonate and conduct high-temperature pyrolysis treatment to obtain "calcium-based syngas".

[0039] Take 10 g of vaterite-phase calcium carbonate and spread it flat in a tubular furnace. Set the pyrolysis temperature at 700 °C, the heating rate at 10 °C / min, and the reaction time at 100 min. After calcination, calcium oxide is obtained, and the ratio of H2 to CO in the syngas is 3:1.

[0040] Figure 3X-ray diffraction patterns of calcite, vaterite and aragonite calcium carbonate and their co-heating coupled in-situ reduction at 700 °C. It can be seen from the figure that calcium carbonate with different crystal phases was successfully prepared and high-purity calcium oxide was produced after hydrothermal decomposition at 700 °C.

[0041] Example 3

[0042] The calcium carbonate used in this example is aragonite calcium carbonate. The specific steps for coupling aragonite calcium carbonate with green hydrogen to save energy, reduce emissions and increase efficiency in the refining of calcium-based syngas are as follows:

[0043] (Ⅰ) Using renewable energy as the driving force to prepare "green hydrogen"

[0044] Using nickel-iron hydrotalcite as the anode, commercial Pt / C catalyst as the cathode, and 30 wt% potassium hydroxide solution as the electrolyte, hydrogen gas was prepared by electrolyzing water technology under the condition of a current density of 200 mA / cm -2 The prepared gas was directly connected to a tube furnace after passing through a recovery system and a filtration system. The gas flow rate of hydrogen was set at 100 mL / min;

[0045] (Ⅱ) Introducing the "green hydrogen" prepared in step (Ⅰ) into aragonite calcium carbonate and performing high-temperature pyrolysis treatment to obtain "calcium-based syngas";

[0046] Take 10 g of aragonite calcium carbonate and spread it flat in a tube furnace. Set the pyrolysis temperature at 700 °C, the heating rate at 10 °C / min, and the reaction time at 100 min. Calcium oxide was obtained after roasting, and the ratio of H2 to CO in the syngas was 3:1.

[0047] Figure 4 、 5 And 6 are the performances of calcite, vaterite and aragonite calcium carbonate in co-heating coupled in-situ hydrogenation reduction at different temperatures. It can be seen from the figure that compared with calcite, vaterite has higher CO selectivity and formation rate at different temperatures, reaching 96% and 0.80 mmol min respectively at 700 °C -1 , showing good hydrogenation performance. However, aragonite shows excellent hydrogenation performance at relatively low temperatures (550 °C).

[0048] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for regulating calcium carbonate crystal phase coupling with green hydrogen to produce calcium-based synthesis gas, characterized in that: The following steps are involved: (I) Using renewable energy as a driving force to produce green hydrogen; (II) determining the calcium carbonate crystal phase and determining the high temperature pyrolysis reduction temperature based on the calcium carbonate crystal phase; (III) The green hydrogen prepared in step (I) is introduced as a reducing gas into calcium carbonate of a certain crystalline phase, and subjected to high-temperature pyrolysis in-situ reduction treatment to obtain calcium-based synthesis gas.

2. The method for producing calcium-based synthesis gas by regulating calcium carbonate crystal phase coupling with green hydrogen according to claim 1, characterized in that: The renewable energy includes any one or more of wind energy, solar energy or tidal energy.

3. The method for regulating calcium carbonate crystal phase coupling with green hydrogen to produce calcium-based synthesis gas according to claim 1, characterized in that: The technology for preparing green hydrogen includes any one or more of water electrolysis to produce hydrogen, water photolysis to produce hydrogen, or water photolysis to produce hydrogen.

4. The method for regulating calcium carbonate crystal phase coupling with green hydrogen to produce calcium-based synthesis gas according to claim 1, characterized in that: The calcium carbonate crystal phase is any one of a calcite phase, a vaterite phase or an aragonite phase.

5. The method for regulating calcium carbonate crystal phase coupling with green hydrogen to produce calcium-based synthesis gas according to claim 1, characterized in that: The volume concentration of hydrogen in the reducing gas is 10% to 100%.

6. The method of controlling the calcium carbonate crystal phase coupled with green hydrogen to produce calcium-based synthesis gas according to claim 1, characterized in that: The air flow rate of the reducing gas is 20 mL / min to 20 L / min.

7. The method for producing calcium-based synthesis gas by regulating calcium carbonate crystal phase coupling with green hydrogen according to claim 1, characterized in that: When the calcium carbonate crystal phase is a calcite phase, the high-temperature pyrolysis reduction temperature is 700°C, the reaction time is 100 min, and the heating rate is 5°C / min to 50°C / min; when the calcium carbonate crystal phase is a vaterite phase, the high-temperature pyrolysis reduction temperature is 700°C, the reaction time is 100 min, and the heating rate is 5°C / min to 50°C / min; when the calcium carbonate crystal phase is an aragonite phase, the high-temperature pyrolysis reduction temperature is 550°C, the reaction time is 100 min, and the heating rate is 5°C / min to 50°C / min.

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