Coal underground efficient gasification method based on calcium-based catalyst injection and carbon dioxide geological storage method

Abstract

The invention discloses a coal underground efficient gasification method based on calcium-based catalyst injection and a carbon dioxide geological storage method. The calcium-based powder material adopts high-purity limestone, wherein the content of calcium oxide is greater than 50%. The method comprises the following steps: crushing a limestone raw material into micron-scale to nano-scale powder, putting the powder into a stirring device, mixing the powder with a coal underground gasification injection agent to obtain a suspension fluid, and injecting the suspension fluid into a coal underground gasification furnace which is in production; calcite minerals in limestone are decomposed into calcium oxide under the coal underground gasification high-temperature effect, and the calcium oxide adsorbs water and carbon dioxide to the surface of coal coke to generate a synergistic gasification reaction at the same time. Wherein the injectant and the calcium-based powder suspension fluid are prepared by adopting a foam suspension device provided with an ultrasonic generator, so that the suspension stability of the calcium-based powder in the suspension fluid is improved. According to the invention, the calcium-based material is injected into the coal underground gasification furnace as the catalyst, so that the moisture, carbon dioxide and carbon in the coal are subjected to co-gasification reaction, the coal underground gasification reaction rate and gasification efficiency can be obviously improved, the environmental pollution is reduced, and the maximum utilization of resources is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground coal gasification, and specifically relates to a method and device for improving underground coal gasification efficiency and reaction rate by injecting calcium-based powder materials, and further includes a carbon dioxide geological storage method. Background Art

[0002] With the continuous growth of global energy demand and the increasing awareness of environmental protection, the clean and efficient use of coal as an important part of traditional energy has become the focus of common concern of the international community. Although the traditional underground coal gasification technology can reduce the ecological damage and dust pollution caused by surface mining to a certain extent, due to the complex and changeable underground environment, the contact efficiency between coal and gasification agents (such as oxygen, water vapor, etc.) is limited, resulting in incomplete gasification reaction, unstable quality of generated gas, low energy conversion efficiency, and difficulty in controlling pollutant emissions. Summary of the invention

[0003] The present invention aims to provide an efficient underground coal gasification method and a carbon dioxide geological storage method based on calcium-based catalyst injection, so as to improve the underground coal gasification efficiency and reaction rate, reduce the environmental impact during the mining process, realize the geological storage of carbon dioxide, and ultimately maximize the utilization of resources.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for efficient underground coal gasification based on calcium-based catalyst injection, comprising:

[0006] A calcium-based material is used as a catalyst and is injected into an operating underground coal gasification furnace. The calcium-based material is calcium oxide, or a material whose main component is calcium oxide, or a material whose decomposition product contains calcium oxide under the operating environment of the underground coal gasification furnace.

[0007] As a preferred option:

[0008] The calcium-based material is limestone with a calcium oxide content greater than 50%;

[0009] The calcium-based material is crushed into micron- to nanometer-scale calcium-based powder after being subjected to coarse crushing, medium-fine crushing, fine crushing and ultra-fine crushing in sequence, and then subjected to ultrasonic foam suspension treatment, and then mixed with underground coal gasification injection agent to form a calcium-based suspension;

[0010] The calcium-based material in the form of a calcium-based suspension undergoes a co-gasification reaction with carbon dioxide in a gasifier and carbon in coal, and the co-gasification reaction includes:

[0011] CaCO3=CaO+CO2;

[0012] CaO+H2O=Ca(OH)2;

[0013] CO2+C=2CO;

[0014] CO + H2O = H2 + CO2;

[0015] C+H2O=H2+CO.

[0016] It should be pointed out that the suspension in the suspension refers to mixed suspension. The main component of limestone is calcium carbonate. The calcium oxide content is used to define it because it is more suitable to express its purity when converted into calcium oxide content. Calcium carbonate decomposes into calcium oxide and carbon dioxide after entering the gasifier, among which calcium oxide plays a major role. Therefore, it is more accurate to define it using calcium oxide content.

[0017] An underground coal gasification furnace, comprising:

[0018] A vertical well, wherein the vertical well is a gas outlet well;

[0019] A directional well, wherein the directional well is a gas inlet well, the vertical well is connected to the end of the directional well, and the connection position is located in the coal seam to be gasified and forms a gasification channel;

[0020] A coiled tube, wherein the coiled tube contains a plurality of pipelines, wherein at least two pipelines are respectively a calcium-based suspension injection pipeline and an oxygen-containing gas injection pipeline, and the coiled tube is connected to a safety valve and an overpressure protection device;

[0021] An injection head, the injection head is used to uniformly inject the calcium-based suspension into the gasifier, and the injection angle and direction of the injection head are adjustable;

[0022] A high-pressure pump, which is used to provide pressure to pressurize the calcium-based suspension and the oxygen-containing gas and inject them into the continuous tube;

[0023] An oxygen production station is used to prepare oxygen-containing gas.

[0024] Furthermore, the underground coal gasification furnace further comprises:

[0025] A crushing system, wherein the crushing system is used to obtain calcium-based powder in the micron to nanometer scale, and the crushing system comprises a coarse crushing device, a medium-fine crushing device, a fine crushing device and an ultra-fine crushing device;

[0026] A control system, wherein the control system is used to monitor and adjust in real time the delivery speed, injection pressure and flow rate of the calcium-based suspension and oxygen-containing gas, and the control system comprises a PLC controller, a touch screen operation interface, a pressure sensor, a flow sensor and a speed sensor;

[0027] The ultrasonic foam suspension device comprises an ultrasonic generator, which is used to form a suspension fluid from a calcium-based powder.

[0028] As a solution, the ultrasonic foam suspension device also includes:

[0029] A single-line discharge pipe, which is a calcium-based suspension output pipe;

[0030] A double-line feed pipe, wherein the double-line feed pipe is a mixed input pipe of a calcium-based powder input pipe and a water or underground coal gasification liquid injection agent input pipe;

[0031] A water tank, which provides water or other liquid injection agents for underground coal gasification;

[0032] A stirring chamber or a suspension chamber, wherein the stirring chamber or the suspension chamber is a chamber for mixing and stirring calcium-based powder and water, or calcium-based powder and underground coal gasification liquid injection agent, wherein the inlet end of the stirring chamber or the suspension chamber is connected to the double-pipeline feed pipe, and the outlet end of the stirring chamber or the suspension chamber is connected to the single-pipeline discharge pipe;

[0033] A reflecting surface, which is used to reflect ultrasonic waves to increase ultrasonic wave efficiency, and is placed above the stirring chamber or the suspension chamber;

[0034] A conical emitting end, which is an ultrasonic emitting end and is placed below the stirring chamber or the suspension chamber;

[0035] A horn, which is used to adjust the ultrasonic amplitude and is connected to the conical transmitting end;

[0036] A transducer, which is used to adjust ultrasonic energy and is connected to the horn;

[0037] The ultrasonic generator is an ultrasonic generating structure connected to the transducer.

[0038] Furthermore, the directional well includes a vertical section and a horizontal section, wherein the horizontal section is located in the coal seam to be gasified, and the gasification furnace to be ignited in the coal seam is operated to form a gasification channel, and the length of the horizontal section in the coal seam is 150 to 650 meters.

[0039] Furthermore, a supporting casing as a continuous pipe is placed in the directional well, wherein a screen pipe is used in the corresponding coal seam section, and a casing is used in the corresponding non-coal seam section.

[0040] An efficient gasification method of the aforementioned underground coal gasification furnace comprises the following steps:

[0041] Step 1: crush limestone with a calcium oxide content greater than 50% into coarse particles with a particle size less than 200 mm by a jaw crusher, crush it into medium-fine particles with a particle size less than 50 mm by an impact crusher, crush it into powder particles with a particle size less than 20 μm by a relatively low pressure crusher, and finally process it into micron- to nanometer-scale calcium-based powder by high-frequency vibration and high-speed airflow;

[0042] Step 2: construct a vertical well, drill to the end hole below the coal seam to be gasified, and complete the well with casing from the top of the coal seam to the wellhead;

[0043] Step 3: construct a directional well along the inclination of the target coal seam to be gasified, complete the well with a screen pipe in the coal seam section, complete the well with a casing from the coal seam top to the wellhead, and connect the directional well with the vertical well with a mechanical drilling rig; inject oxygen-containing gasifying agent through the directional well with a coiled tubing, ignite the coiled tubing, and start the gasifier operation when the coal seam is ignited;

[0044] Step 4, injecting the calcium-based powder and water into an ultrasonic foam suspension device to mix to form a calcium-based suspension as a catalyst;

[0045] Step 5: After the gasifier is running stably and the gasification channel is formed, the calcium-based suspension is evenly sprayed toward the combustion surface in multiple directions using a continuous tube and a spray head to improve the gasification efficiency.

[0046] As an option,

[0047] In the step 2, when constructing a vertical well, the final hole is drilled to 20 m below the coal seam to be gasified.

[0048] In the step 3, after the gasifier is constructed, a gasifying agent is continuously injected at the initial stage, and the gasifying agent is mainly oxygen-containing gas, so that the coal seam burns stably and forms a gasification channel;

[0049] In the step five, after the gasifier is stably operated and the gasification channel is formed, a calcium-based suspension is injected as a catalyst according to the reaction conditions in the gasifier. Specifically, in step three, a gasifier is constructed after the directional well is constructed, and an oxygen-containing gasifier is continuously injected in the initial stage. The gasifier is mainly air or low-to-medium oxygen-rich gasifier. As the gasification working face advances, the temperature in the coal seam continues to increase. When the temperature exceeds 600°C, a calcium-based catalyst can be appropriately injected to increase the gasification efficiency and solidify CO2; when the H2 content in the gas outlet well is significantly reduced and the CO content is greater than 20%, a calcium-based catalyst can be injected multiple times until the temperature drops to 600°C or the H2 content significantly rises to more than 35%. The available underground coal resources can be mined to the maximum extent through the gasifier.

[0050] A method for geological storage of carbon dioxide adopts the above-mentioned high-efficiency underground coal gasification method, injects micron-to-nanometer-scale calcium carbonate powder into an operating underground coal gasification furnace, and pyrolyzes the calcium carbonate into calcium oxide and carbon dioxide in an underground gasification environment of 600-1200°C, wherein a portion of the calcium oxide simultaneously adsorbs water and carbon dioxide to the surface of coal char, and carbon dioxide reduces carbon to generate carbon monoxide, and carbon monoxide and water are co-gasified to generate carbon dioxide and hydrogen, while another portion of the calcium oxide reacts exothermically with water to generate calcium hydroxide, and when the furnace temperature is lowered, the calcium hydroxide synthesizes calcium carbonate with carbon dioxide and releases water, and the calcium carbonate is deposited in the form of solid minerals, thereby storing carbon dioxide underground.

[0051] Compared with the prior art, the present invention provides an underground efficient coal gasification method and a carbon dioxide geological storage method based on calcium-based catalyst injection, and the present invention has the following characteristics:

[0052] (1) Environmentally friendly raw materials and reduced costs. The calcium-based catalyst uses natural high-purity limestone as raw material, which is prepared into micron to nanometer-scale powder only through physical crushing.

[0053] (2) The preparation procedure of the suspension fluid is simple and reliable. The calcium-based powder material and water are injected into a foam suspension device equipped with an ultrasonic generator to prepare a suspension fluid. Ultrasonic waves can effectively improve the suspension stability of the calcium-based powder in the suspension fluid and ensure the injection effect.

[0054] (3) The gasification reaction rate is greatly improved. The introduction of powdered calcium-based materials and the catalytic effect of calcium oxide effectively promote the co-gasification reaction of water and carbon dioxide with carbon in coal, thereby significantly improving the gasification reaction rate. (4) The gasification efficiency is improved. Due to the catalytic effect of powdered calcium-based materials, coal is more fully gasified in the underground gasifier, improving the gasification efficiency.

[0055] (5) Environmental protection and energy saving. The implementation of the present invention not only improves the efficiency of underground coal gasification, but also the calcium-based material can effectively fix carbon, which helps to reduce environmental pollution and achieve the goal of environmental protection and energy saving.

[0056] Through the verification of experiments and actual application data, the implementation of the present invention can significantly improve the reaction rate and gasification efficiency of underground coal gasification. Specifically, compared with the traditional underground coal gasification technology, the implementation of the present invention can increase the gasification reaction rate by more than about 30% and the gasification efficiency by more than about 20%. In addition, the present invention also has the advantages of simple operation and low cost, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is an injection pipeline and device diagram of the underground coal efficient gasification device based on calcium-based catalyst injection in the present invention;

[0058] Figure 2 A flow chart of a method for efficient underground coal gasification based on calcium-based catalyst injection;

[0059] In the figure: 1—vertical well; 2—injection head; 3—coiled tubing; 41—gasification channel; 42—directional well; 5—high-pressure pump; 6—single-line discharge pipe; 7—double-line feed pipe; 8—water tank; 9—reflection surface; 10—suspension chamber; 11—conical transmitting end; 12—horn; 13—transducer; 14—ultrasonic generator; 15—one-way gate valve; 16—cable; 17—crushing system; 18—control system; 19—oxygen production station. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0061] The present invention combines drilling engineering technology, underground coal gasification technology, and calcium-based catalytic technology. By injecting a stable calcium-based catalyst suspension into the gasifier, the underground coal reaction rate and gasification efficiency are significantly improved, environmental pollution is reduced, and maximum resource utilization is achieved.

[0062] like Figure 1 As shown, the underground coal efficient gasification device based on calcium-based catalyst injection in this embodiment includes a calcium-based suspension preparation system, an injection and injection system (including a gasifier structure). The calcium-based suspension preparation system includes a single-line discharge pipe 6, a double-line feed pipe 7, a water tank 8, a reflective surface 9, a suspension chamber 10, a conical transmitting end 11, a horn 12, a transducer 13, an ultrasonic generator 14, a one-way gate valve 15, a cable 16, a crushing system 17 and a control system 18. The preparation of a foam suspension device equipped with an ultrasonic generator helps to improve the suspension stability of the calcium-based powder in the suspension fluid. The injection and injection system includes a vertical well 1, an injection head 2, a continuous pipe 3, a gasification channel 41, a directional well 42, a high-pressure pump 5, a one-way gate valve 15, a cable 16 and an oxygen production station 19.

[0063] Figure 1In the figure, the vertical well 1 is a gas outlet well, the directional well 42 is a gas inlet well, the vertical well 1 is connected to the end of the directional well 42, and the connecting position is located in the coal seam to be gasified and forms a gasification channel 41; the continuous pipe 3 contains multiple pipelines, which can be a calcium-based catalyst and an oxygen-containing gas injection pipe, and is provided with a safety valve and an overpressure protection device 15; the injection head 2 is a calcium-based catalyst injection device, and the material of the injection head 2 is high-temperature resistant and corrosion-resistant stainless steel, which can evenly inject the catalyst to ensure that the catalyst can be evenly distributed in the gasifier, and the injection angle and direction can be adjusted to ensure that the catalyst can cover the target area in the gasifier; the high-pressure pump 5 can pressurize the catalyst and the oxygen-containing gas and inject them into the continuous pipe; the oxygen production station 19 is equipment for preparing oxygen-containing gas.

[0064] Figure 1 In the embodiment, the crushing system 17 includes multiple procedures such as coarse crushing, medium and fine crushing, fine crushing and ultrafine crushing, and finally forms micron-nanometer calcium-based powder. The control system 18 includes a PLC controller, a touch screen operation interface, sensors such as a pressure sensor, a flow sensor, etc., which can monitor and adjust the conveying and injection parameters such as conveying speed, injection pressure, flow rate, etc. in real time; the ultrasonic foam suspension device 20 is equipped with an ultrasonic generator, which can improve the suspension stability of the calcium-based powder in the suspension fluid.

[0065] Figure 1 In the figure, the single-line discharge pipe 6 is the output pipe of the calcium-based catalyst; the double-line feed pipe 7 is the input pipe of the calcium-based powder and water; the water tank 8 can provide water or liquid injection agent for underground coal gasification; the reflecting surface 9 is used to reflect ultrasonic waves to increase the ultrasonic efficiency; the stirring chamber or suspension chamber 10 is a chamber for mixing the calcium-based powder and water; the conical transmitting end 11 is the ultrasonic transmitting end; the amplitude rod 12 can adjust the ultrasonic amplitude; the transducer 13 can adjust the ultrasonic energy; the ultrasonic generator 14 is an ultrasonic generating device, which provides original ultrasonic waves.

[0066] During the construction process of the underground efficient coal gasification device based on calcium-based catalyst injection of this embodiment, calcium-based powder is first prepared for standby, then vertical well 1 is constructed, and then directional well 42 is sequentially constructed. Directional well 42 includes a vertical section and a horizontal section, wherein the horizontal section is located in the coal seam to be gasified, and the operation of the coal seam gasification furnace can form a gasification channel 41. The horizontal section of directional well 42 is located in the coal seam with a length of 150 to 650 m, and a supporting casing as a continuous pipe is placed in directional well 42. Among them, vertical well 1 is drilled to the end hole 20 m below the coal seam to be gasified, and casing is used to complete the well from the top of the coal seam to the wellhead. Directional well 42 is docked with vertical well 1, and a screen pipe is used in the coal seam section, and casing is used to complete the well from the top of the coal seam to the wellhead. The present invention improves the reaction rate and gasification efficiency of underground coal gasification by combining drilling engineering technology, underground coal gasification technology, and calcium-based catalytic technology, reduces the environmental impact during mining, and realizes the maximum utilization of resources. At the same time, the present invention can also significantly reduce carbon emissions and improve economic benefits. In addition, the present invention is flexible and scalable and can be applied to areas with different geological conditions and coal seam characteristics.

[0067] In brief, the method for efficient underground coal gasification based on calcium-based catalyst injection when applied in coal seams includes the following construction steps:

[0068] Step 1, first prepare high-purity limestone (CaO content>50%, limestone is generally light gray or dark gray, and the color changes when it contains more impurities. The chemical composition is calcium carbonate, theoretically with a calcium oxide content of 56.04% and a carbon dioxide content of 43.96%. Limestone is brittle and has a low hardness. It decomposes into calcium oxide and carbon dioxide when heated to 1000-1200°C. Calcium oxide content>50% indicates high purity) raw materials, firstly crushed by a jaw crusher into coarse particles with a particle size of <200mm, then finely crushed by an impact crusher into fine particles with a particle size of <50mm, and then finely crushed by a relatively low pressure crusher into powder particles with a particle size of <20μm, and finally processed by high-frequency vibration and high-speed airflow into micron to nanometer powder for standby use.

[0069] Step 2: First, construct a vertical well 1, drill to the end hole 20m below the coal seam to be gasified, and complete the well with casing from the top of the coal seam to the wellhead;

[0070] Step 3: construct a directional well 42 for gas intake or ignition along the inclination of the target coal seam to be gasified. The horizontal section of the directional well 42 is 150 to 650 meters long. The coal seam section is completed with a screen pipe, and the well is completed with a casing from the top of the coal seam to the wellhead. A mechanical drilling rig is used to connect it with the vertical well 1. The oxygen-containing gasifying agent is injected through the directional well 42 by using the coiled tubing 3, and the ignition system of the coiled tubing is used to ignite. When the coal seam is ignited, the operation process of the gasifier begins.

[0071] Step 4, injecting the calcium-based powder and water into an ultrasonic foam suspension device to mix to form a calcium-based catalyst suspension;

[0072] Step 5: After the gasifier is running stably, the gasification channel 41 is formed, and the continuous tube 3 and the injection head 2 are used to uniformly inject the calcium-based catalyst on the combustion surface in multiple directions to improve the gasification efficiency.

[0073] After constructing the gasifier through the directional well 42, oxygen-containing gasifier is continuously injected in the initial stage. The gasifier is mainly air or low-to-medium oxygen-rich gasifier. As the gasification working face advances, the temperature in the coal seam continues to increase. When the temperature exceeds 600°C, calcium-based catalyst can be appropriately injected to increase gasification efficiency and solidify CO2; when the H2 content in the gas outlet well is significantly reduced and the CO content is greater than 20%, calcium-based catalyst can be injected multiple times until the temperature drops to 600°C or the H2 content significantly rises to more than 35%. The available underground coal resources can be mined to the maximum extent through the gasifier. The above process can be summarized as the preparation of calcium-based powder, the construction of the gasifier, the preparation and injection of calcium-based suspension, and the efficient mining of the subsequent system, which together constitute the efficient underground coal gasification process and device based on calcium-based catalyst injection.

[0074] like Figure 1 and Figure 2 As shown, the underground coal efficient gasification device based on calcium-based catalyst injection includes a calcium-based suspension preparation system, an injection and injection system (including a gasifier structure), and a crushing system. The calcium-based suspension preparation system includes a single-line discharge pipe 6, a double-line feed pipe 7, a water tank 8, a reflective surface 9, a suspension chamber 10, a conical launch end 11, a horn 12, a transducer 13, an ultrasonic generator 14, a one-way gate valve 15, a cable 16, a crushing system 17, and a control system 18. The preparation of a foam suspension device equipped with an ultrasonic generator helps to improve the suspension stability of the calcium-based powder in the suspension fluid. The injection and injection system includes a vertical well 1, an injection head 2, a continuous pipe 3, a gasification channel 41, a directional well 42, a high-pressure pump 5, a one-way gate valve 15, a cable 16, and an oxygen production station 19. The crushing system is divided into multi-level and multi-granularity crushing.

[0075] The present invention can improve gasification efficiency and reaction rate by injecting calcium-based catalysts, increase the amount of coal converted per unit time, and improve resource utilization; on the other hand, by reducing pollutant emissions and enhancing the cleanliness of gasification products, the negative impact on the environment is reduced, which meets the strategic requirements of sustainable development.

[0076] The present invention also has wide adaptability and can be applied to coal resources of different geological conditions and types of coal, providing a valuable new energy utilization solution for regions with rich coal resources but great environmental pressure.

[0077] The innovative idea of ​​using calcium-based powder materials as catalysts proposed in the present invention is an important breakthrough in addressing the current bottleneck problem. Calcium-based catalysts, such as calcium oxide, calcium hydroxide and modified derivatives thereof decomposed or derived from calcium carbonate, have excellent catalytic activity and stability, can promote the gasification reaction of coal at a relatively low temperature, and accelerate the chemical conversion process between carbon and gasifying agents. Specifically, calcium-based catalysts can effectively reduce the activation energy of the gasification reaction, promote the reaction of carbon with water vapor to generate combustible gases such as hydrogen and carbon monoxide, and at the same time promote the cracking of heavy components such as tar and phenols, thereby improving the quality of gasification products. In addition, calcium-based catalysts can also effectively absorb harmful gases such as sulfur dioxide generated during the gasification process, achieve in-situ removal of pollutants, and reduce subsequent environmental protection treatment costs.

[0078] In order to achieve efficient use of calcium-based catalysts in the underground coal gasification process, the present invention has designed an integrated device, which specifically includes a catalyst preparation and injection system to ensure that the calcium-based powder material can be uniformly and continuously injected into the coal gasification area, and adjust the catalyst injection amount and gasification conditions according to key parameters such as temperature, pressure, and gas composition in the underground gasification process to achieve the best gasification effect.

[0079] The implementation of the present invention will significantly improve the technical economy and environmental friendliness of underground coal gasification, and promote the transformation of coal energy from traditional black to green. On the one hand, by improving the gasification efficiency and reaction rate, the amount of coal conversion per unit time is increased, and the resource utilization rate is improved; on the other hand, by reducing pollutant emissions and enhancing the cleanliness of gasification products, the negative impact on the environment is reduced, which meets the strategic requirements of sustainable development. In addition, the technology also has a wide range of adaptability and can be applied to coal resources of different geological conditions and types of coal, providing a valuable new energy utilization solution for areas with rich coal resources but high environmental pressure.

[0080] In summary, the underground efficient coal gasification process and equipment based on calcium-based catalyst injection is not only a technological innovation, but also an important milestone in the green transformation of the coal energy industry. It has broad application prospects and significant social value, and is worthy of in-depth research and extensive promotion.

[0081] Obviously, the above embodiments are only examples for clear explanation and limitation of the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to give examples of all the implementation methods here. However, the obvious or changes derived from this are still within the protection scope of the invention.

Claims

1. A method for efficient underground coal gasification based on calcium-based catalyst injection, characterized in that: include: A calcium-based material is used as a catalyst and is injected into an operating underground coal gasification furnace. The calcium-based material is calcium oxide, or a material whose main component is calcium oxide, or a material whose decomposition product contains calcium oxide under the operating environment of the underground coal gasification furnace.

2. The method for underground efficient coal gasification based on calcium-based catalyst injection according to claim 1, characterized in that: The calcium-based material is limestone with a calcium oxide content greater than 50%; The calcium-based material is crushed into micron- to nanometer-scale calcium-based powder after being subjected to coarse crushing, medium-fine crushing, fine crushing and ultra-fine crushing in sequence, and then subjected to ultrasonic foam suspension treatment, and then mixed with underground coal gasification injection agent to form a calcium-based suspension; The calcium-based material in the form of a calcium-based suspension undergoes a co-gasification reaction with carbon dioxide in a gasifier and carbon in coal, and the co-gasification reaction includes: CaCO3=CaO+CO2; CaO+H2O=Ca(OH)2; CO2+C=2CO; CO + H2O = H2 + CO2; C+H2O=H2+CO.

3. An underground coal gasification furnace, characterized in that: include: A vertical well (1), wherein the vertical well (1) is a gas outlet well; A directional well (42), wherein the directional well (42) is a gas intake well, the vertical well (1) is connected to the end of the directional well (42), and the connection position is located in the coal seam to be gasified and forms a gasification channel (41); A coiled tube (3), wherein the coiled tube (3) comprises a plurality of pipelines, wherein at least two pipelines are respectively a calcium-based suspension injection pipeline and an oxygen-containing gas injection pipeline, and the coiled tube (3) is connected to a safety valve and an overpressure protection device (15); An injection head (2), the injection head (2) is used to uniformly inject the calcium-based suspension into the gasifier, and the injection angle and direction of the injection head (2) are adjustable; A high-pressure pump (5), the high-pressure pump (5) is used to provide pressure so as to pressurize the calcium-based suspension and the oxygen-containing gas and inject them into the continuous tube (3); An oxygen production station (19) is used to prepare oxygen-containing gas.

4. The underground coal gasification furnace according to claim 3, characterized in that: The underground coal gasifier also includes: A crushing system (17), wherein the crushing system (17) is used to obtain calcium-based powder in the micrometer to nanometer scale, and the crushing system (17) comprises a coarse crushing device, a medium-fine crushing device, a fine crushing device and an ultra-fine crushing device; A control system (18), wherein the control system (18) is used to monitor and adjust in real time the delivery speed, injection pressure and flow rate of the calcium-based suspension and oxygen-containing gas, and the control system (18) comprises a PLC controller, a touch screen operation interface, a pressure sensor, a flow sensor and a speed sensor; An ultrasonic foam suspension device (20) comprises an ultrasonic generator and is used to form a suspension fluid from a calcium-based powder.

5. The underground coal gasification furnace according to claim 4, characterized in that: The ultrasonic foam suspension device (20) further comprises: A single-channel discharge pipe (6), wherein the single-channel discharge pipe (6) is a calcium-based suspension output pipe; A double-pipeline feed pipe (7), wherein the double-pipeline feed pipe (7) is a mixed input pipe of a calcium-based powder input pipe and a water or underground coal gasification liquid injection agent input pipe; A water tank (8), wherein the water tank (8) provides water or other liquid injection agents for underground coal gasification; A stirring chamber or a suspension chamber (10), wherein the stirring chamber or the suspension chamber (10) is a chamber for mixing and stirring calcium-based powder and water, or for mixing and stirring calcium-based powder and underground coal gasification liquid injection agent, wherein the inlet end of the stirring chamber or the suspension chamber (10) is connected to the double-pipeline feed pipe (7), and the outlet end of the stirring chamber or the suspension chamber (10) is connected to the single-pipeline discharge pipe (6); A reflecting surface (9), the reflecting surface (9) is used to reflect ultrasonic waves so as to increase the efficiency of ultrasonic waves, and the reflecting surface (9) is placed above the stirring chamber or the suspension chamber (10); A conical emitting end (11), which is an ultrasonic emitting end and is placed below the stirring chamber or the suspension chamber (10); A horn (12), the horn (12) is used to adjust the ultrasonic amplitude and is connected to the conical emitting end (11); A transducer (13), the transducer (13) is used to adjust ultrasonic energy and is connected to the horn (12); An ultrasonic generator (14), which is an ultrasonic generating structure and is connected to the transducer (13).

6. The underground coal gasification furnace according to claim 3, characterized in that: The directional well (42) comprises a vertical section and a horizontal section, wherein the horizontal section is located in the coal seam to be gasified. The coal seam is ignited and the gasification furnace is operated to form a gasification channel (41). The length of the horizontal section located in the coal seam is 150 to 650 meters.

7. The underground coal gasification furnace according to claim 3, characterized in that: A supporting casing as a continuous pipe (3) is placed in the directional well (42), wherein a screen pipe is used in the corresponding coal seam section and a casing is used in the corresponding non-coal seam section.

8. An efficient gasification method for an underground coal gasifier as claimed in claim 3, characterized in that: The following steps are involved: Step 1: crush limestone with a calcium oxide content greater than 50% into coarse particles with a particle size less than 200 mm by a jaw crusher, crush it into medium-fine particles with a particle size less than 50 mm by an impact crusher, crush it into powder particles with a particle size less than 20 μm by a relatively low pressure crusher, and finally process it into micron- to nanometer-scale calcium-based powder by high-frequency vibration and high-speed airflow; Step 2: construct a vertical well (1), drill to the end hole below the coal seam to be gasified, and complete the well with casing from the top of the coal seam to the wellhead; Step 3: construct a directional well (42) along the inclination of the target coal seam to be gasified, complete the well with a screen pipe from the coal seam section, complete the well with a casing pipe from the coal seam top to the wellhead, and connect the directional well (42) with the vertical well (1) by using a mechanical drilling rig; inject an oxygen-containing gasifying agent through the directional well (42) by using a coiled tubing (3), and start the gasification furnace operation when the coal seam is ignited by igniting the coiled tubing (3); Step 4, injecting the calcium-based powder and water into an ultrasonic foam suspension device (20) for mixing to form a calcium-based suspension as a catalyst; Step 5: After the gasifier is running stably and the gasification channel (41) is formed, the continuous tube (3) and the injection head (2) are used to uniformly inject the calcium-based suspension toward the combustion surface in multiple directions to improve the gasification efficiency.

9. The efficient gasification method according to claim 8, characterized in that: In the step 3, after the gasifier is constructed, a gasifying agent is continuously injected at the initial stage, wherein the gasifying agent is mainly oxygen-containing gas, so that the coal seam burns stably and forms a gasification channel (41); In the step 5, after the gasifier is stably operated and the gasification channel (41) is formed, a calcium-based suspension is injected as a catalyst according to the reaction conditions in the gasifier.

10. A method for geological storage of carbon dioxide, characterized in that: The method for underground efficient coal gasification as described in claim 1 is adopted, and micron to nanometer scale calcium carbonate powder is injected into an operating underground coal gasification furnace. In an underground gasification environment of 600 to 1200°C, the calcium carbonate is pyrolyzed into calcium oxide and carbon dioxide, wherein a portion of the calcium oxide simultaneously adsorbs water and carbon dioxide to the surface of coal char, and the carbon dioxide reduces carbon to generate carbon monoxide, and the carbon monoxide and water are co-gasified to generate carbon dioxide and hydrogen, while the other portion of the calcium oxide reacts exothermically with water to generate calcium hydroxide, and the calcium hydroxide synthesizes calcium carbonate with carbon dioxide and releases water when the furnace temperature is lowered, and the calcium carbonate is deposited in the form of solid minerals, thereby storing carbon dioxide underground.

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