A method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam.

Abstract

This invention provides a method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam, comprising: Step 1: Water source softening and purification: Tap water is softened, precisely filtered, and desulfurized and dechlorinated to obtain purified water; Step 2: Superheated steam preparation and preliminary deoxygenation: The purified water is heated at high temperature, separated from steam, and superheated to obtain superheated steam; Step 3: Palladium-based catalytic adsorption for deep deoxygenation: The superheated steam is catalytically deoxygenated to obtain deoxygenated superheated steam; Step 4: Deoxygenated superheated steam injection and displacement: The deoxygenated superheated steam is injected into the coal seam to achieve gas extraction. This invention achieves the dual goals of "safety without risk and high-efficiency production increase" by precisely controlling the "purity, temperature, pressure, and oxygen content" of the steam.

Description

Technical Field

[0001] This invention relates to the field of safe coal mining technology, and particularly to a method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam. Background Technology

[0002] Coal seam gas (mainly composed of methane) is both a clean energy source found in coal seams and a major threat to coal mine safety—it can easily trigger gas explosions during mining. Traditional coal seam gas mining mainly employs the "pressure reduction and desorption" method, which involves lowering reservoir pressure by draining water to promote the desorption and production of gas adsorbed on the coal matrix surface. However, this method has limited effectiveness in low-permeability, highly adsorbed, or easily spontaneously combustible coal seams, often requiring enhanced displacement through fluid injection.

[0003] Currently used displacement technologies all have significant limitations: air displacement is inexpensive, but its high oxygen content (up to 21%) can easily cause coal oxidation or even spontaneous combustion after injection. Furthermore, the gas-air mixture explodes when exposed to an ignition source when the methane volume fraction is 5%-15%, resulting in poor safety. Nitrogen displacement effectively suppresses oxidation and explosion risks by utilizing inert gases, but nitrogen itself does not have a thermal effect, making it difficult to promote gas desorption, resulting in low displacement efficiency and high nitrogen production costs. Conventional steam displacement enhances gas desorption by using high-temperature thermal energy, but the trace oxygen carried in the steam can still cause slow oxidation of the coal during long-term injection. At the same time, the liquid water formed by steam condensation can easily block coal pores (i.e., the "water lock effect"), which inhibits gas seepage.

[0004] Therefore, developing a new displacement method that combines "ultimate safety" (eliminating the risk of oxidation and explosion) with "highly efficient displacement capability" (thermal modification to promote desorption and reduce water lock damage) has become the key to achieving efficient and safe mining of gas in easily spontaneously combustible coal seams. Summary of the Invention

[0005] In response to the problems mentioned in the background technology, this invention proposes a method for safely and efficiently displacing coal seam gas with deoxygenated superheated steam, in order to overcome the defects of poor safety and low efficiency of existing coal seam gas displacement technologies. By precisely controlling the "purity, temperature, pressure and oxygen content" of the steam, the dual goals of "safe and risk-free, and high-efficiency production increase" are achieved.

[0006] In a first aspect, the present invention provides a method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam, comprising:

[0007] Step 1: Water softening and purification: Tap water is softened, finely filtered, and desulfurized and dechlorinated to become purified water;

[0008] Step 2: Superheated steam preparation and preliminary deoxygenation: Superheated steam is obtained by heating purified water at high temperature, separating steam and water, and superheating.

[0009] Step 3: Palladium-based catalytic adsorption for deep deoxygenation: Superheated steam is deoxygenated by catalytic deoxygenation to obtain deoxygenated superheated steam;

[0010] Step 4: Injection and displacement of deoxygenated superheated steam: Inject deoxygenated superheated steam into the coal seam to achieve gas extraction.

[0011] In some embodiments, the softening treatment employs cation exchange resin to adsorb Ca from the water source. 2+ Mg 2+ The hardness of the effluent is 0.02 mmol / L.

[0012] In some embodiments, the precision filtration involves allowing water to settle for 48 hours and then filtering it through a precision filter to remove impurities, resulting in an effluent suspended solids concentration of 0.08 mg / L. In some embodiments, the filter element in the precision filter is made of polypropylene pleated material, with a filtration accuracy of 0.1-1 μm.

[0013] In some embodiments, the desulfurization and dechlorination treatment uses ZnO desulfurizing agent adsorption and columnar activated carbon adsorption in a desulfurization and dechlorination device to obtain purified water with a sulfur content of 0.0007 mg / L and a chlorine content of 0.003 mg / L. In some embodiments, the upper layer of the desulfurization and dechlorination device is ZnO desulfurizing agent, and the lower layer is columnar activated carbon.

[0014] In some embodiments, the high-temperature heating is achieved using an industrial boiler with a rated pressure of 0.5-10 MPa and a rated temperature of 151-311°C. The high-temperature heating generates saturated wet steam containing liquid water, with a steam output reaching 12 m³ / s. 3 / h. In some embodiments, the industrial boiler is a horizontal water-tube and fire-tube structure.

[0015] In some embodiments, the steam-water separation refers to feeding saturated wet steam into a cyclone steam-water separator, where liquid water is separated by the centrifugal force of a spiral guide plate to obtain dry saturated steam with a dryness of ≥99.5%. In some embodiments, the cyclone steam-water separator has a built-in spiral guide plate.

[0016] In some embodiments, the superheating treatment refers to stabilizing dry saturated steam with a pressure-regulating valve and then heating it to 200-250°C in a tubular superheater to form superheated steam, reducing the steam oxygen content to 0.005 mg / L. In some embodiments, the heating medium of the tubular superheater is high-temperature flue gas or an electric heating wire, and the superheating temperature is set according to the coal seam depth; the deeper the coal seam, the higher the temperature of the injected superheated steam.

[0017] In some embodiments, the catalytic deoxygenation refers to precisely controlling the molar ratio of H2 to O2 in steam to 2.1:1-2.5:1 using a proportional valve, and obtaining deoxygenated superheated steam by catalysis with a Pd / Al2O3 supported catalyst under a superheated environment of 200-250°C, with the oxygen content reduced to 0.00008 mg / L. In some embodiments, the Pd / Al2O3 supported catalyst is disposed in a palladium-based catalyst fixed bed; the bottom of the palladium-based catalyst fixed bed is provided with a quartz sand support layer, the middle is filled with Pd / Al2O3 supported catalyst, and a hydrogen regeneration interface is provided on the side.

[0018] In some embodiments, the injection pressure of the injected coal seam is higher than the original pressure of the coal seam, and the injection flow rate is 10-12 m³ / s. 3 / h, deoxygenated superheated steam emitted by a steam emitter continuously heats the coal seam. Under high temperature and displacement, the coal seam desorbs a large amount of gas, which flows through fractures to the gas drainage borehole and is then drained through the gas drainage pipe. In some embodiments, the casing of the injection well used for injecting into the coal seam is made of stainless steel, and the wellhead is equipped with a pressure regulating valve and a check valve to prevent backflow of coal seam fluid.

[0019] This invention provides a method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam, aiming to overcome the key defects of traditional fluid displacement technologies (such as air drive and conventional steam drive), such as high risk of coal seam spontaneous combustion and methane explosion, and low displacement efficiency. This method is based on an integrated process of "water source pretreatment - steam generation - deep deoxygenation - coal seam injection." Water source purification involves softening, filtering, and desulfurizing / dechlorinating tap water to remove calcium and magnesium ions and harmful impurities, obtaining high-purity feedwater to ensure stable operation of the subsequent system. The purified water is converted into saturated steam in a high-temperature boiler, and then superheated at 200-250°C through steam-water separation and superheating. During this process, the characteristic that gas solubility decreases with increasing temperature is utilized to achieve preliminary removal of dissolved oxygen. The superheated steam is then passed through a palladium-based catalyst fixed bed, where residual oxygen and hydrogen undergo a catalytic reaction at high temperature to generate water, thereby reducing the oxygen content in the steam to ≤0.0001 mg / L (ppb level), fundamentally eliminating the risk of combustion and explosion. The resulting deoxygenated superheated steam is injected into low-permeability coal seams. Through its triple synergistic mechanism of "thermal modification and permeability enhancement, thermal desorption promotion, and drying and lockout reduction," the gas desorption and seepage efficiency is significantly improved, achieving safe and efficient mining. This invention is particularly suitable for gas extraction from easily self-igniting coal seams, and is significantly superior to traditional displacement technologies in terms of both safety and overall benefits.

[0020] Specifically as follows:

[0021] (1) This invention systematically couples the thermal displacement advantage of superheated steam with the safety advantage of deep oxygen reduction, employing a "two-step deoxygenation" process (high-temperature physical oxygen reduction combined with palladium-based catalytic conversion) to achieve a maximal reduction in oxygen content in steam, and effectively mitigates the water-locking effect by utilizing the dryness of superheated steam. Specifically, it is manifested as follows:

[0022] Water softening and purification: The incoming water is softened and impurities are removed, with a focus on reducing the content of calcium and magnesium ions to prevent scaling in equipment, and removing impurities such as sulfur and chlorine to avoid poisoning of subsequent catalysts, thus providing a basic guarantee for the long-term stable operation of the system.

[0023] Superheated steam preparation and preliminary deoxygenation: Utilizing the physical law that "gas solubility decreases with increasing temperature", saturated steam is further heated to 200-250℃ to form superheated steam. During this process, dissolved oxygen escapes due to the high temperature, achieving preliminary deoxygenation and effectively reducing the load on subsequent catalytic units.

[0024] Palladium-based catalytic adsorption for deep deoxygenation: Under high temperature conditions, residual oxygen in superheated steam is passed through a Pd-based catalyst bed and reacts with introduced hydrogen to produce water. No other impurities are introduced during the process, and the oxygen content can be reduced to the ppb level (≤0.0001 mg / L), fundamentally eliminating the risk of coal seam oxidation and gas explosion.

[0025] Oxygen-reduced superheated steam injection and displacement: By rationally controlling the injection pressure and flow rate, the deeply oxygenated superheated steam can be uniformly infiltrated into the coal seam, simultaneously exerting a triple synergistic effect of thermally modifying the coal body structure, thermally promoting gas desorption, and drying to reduce water-locking effect, thereby achieving a significant improvement in gas extraction efficiency.

[0026] (2) The deoxygenated superheated steam of the present invention achieves efficient gas displacement in coal seams through the following triple synergistic mechanism:

[0027] Thermal modification and permeability enhancement: The high-temperature heat carried by superheated steam can effectively thermally modify the coal body, improve its original pore structure, enhance the overall permeability of the coal seam, and create favorable conditions for gas migration.

[0028] Heat-induced desorption: After heat is transferred to the coal matrix, the coal seam temperature rises. According to Langmuir adsorption theory, the temperature rise will significantly reduce the adsorption capacity of methane on the coal surface, thereby promoting the desorption of adsorbed gas into free gas.

[0029] Drying and reducing water lock-in: As a drying medium, superheated steam can absorb and carry out some of the liquid water in the coal seam, effectively alleviating the "water lock-in effect" caused by moisture in the pore throat and improving the seepage efficiency of free gas.

[0030] Finally, the desorbed free gas is extracted through the production well under pressure, and high-purity methane products can be obtained through subsequent gas-water separation and purification processes.

[0031] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects:

[0032] This invention provides a method for safely and efficiently displacing coal seam gas using deoxygenated superheated steam, achieving significant improvements in safety, displacement efficiency, system stability, and environmental friendliness. Specifically:

[0033] Safety is maximized: Through a two-stage deoxygenation process of "preliminary deoxygenation by superheating + deep deoxygenation by palladium-based methods," the oxygen content in the steam can be reduced to ≤0.0001 mg / L. This concentration is not only far below the minimum oxygen concentration required to initiate coal oxidation (0.5%, approximately 5000 mg / L), but also significantly lower than the explosive oxygen concentration threshold of methane-air mixtures (12%). This eliminates the risk of spontaneous combustion of coal seams and gas explosions at the source, completely resolving the core safety hazards of traditional displacement technologies.

[0034] Significantly improved displacement efficiency: The deoxygenated superheated steam simultaneously exerts a triple synergistic effect in the coal seam, namely "thermal modification and permeability enhancement, thermal promotion of desorption, and drying and lockout reduction," greatly improving the gas desorption rate and seepage efficiency. This technology is particularly suitable for easily spontaneously combustible, medium- to high-permeability coal seams, and has good adaptability and promotional value.

[0035] The system operates stably and reliably: the influent pretreatment unit effectively prevents scaling and catalyst poisoning; the system is equipped with pressure stabilization control and online monitoring devices to ensure continuous stability of steam parameters. The catalyst has regeneration capabilities, extending its service life and supporting long-term continuous and stable operation of the unit.

[0036] Environmentally friendly: No chemical agents are added throughout the process, and the only product of the deoxygenation reaction is water. There is no wastewater or waste residue discharge, which meets the requirements of green mining and clean production and has good environmental benefits. Attached Figure Description

[0037] Figure 1 This is a system diagram illustrating the safe and efficient displacement of coalbed methane using deoxygenated superheated steam, as described in this invention.

[0038] 1-Softener; 2-Precision filter; 3-Desulfurization and dechlorination device; 4-Water flow regulating valve; 5-Water level controller; 6-Industrial boiler; 7-Safety valve; 8-Cyclone steam-water separator; 9-Steam regulating valve I; 10-Tube superheater; 11-Steam regulating valve II; 12-H2 injection device; 13-Pd / Al2O3 supported catalyst; 14-Oxygen concentration analyzer; 15-Palladium-based catalyst fixed bed; 16-Superheated steam injection control system; 17-Pressure regulating valve; 18-Sealer; 19-Coal seam floor; 20-Directional coal seam; 21-Coal seam roof; 22-Extraction pipe; 23-Steam emitter; 24-Recovery pipe; 25-Steam injection pipe; 26-Gas extraction borehole; 27-Injection borehole.

[0039] Terminology Explanation

[0040] Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0041] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0042] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0046] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0047] General Method

[0048] S1 water source softening and impurity removal

[0049] Tap water first enters softener 1 (containing cation exchange resin), where it undergoes an ion exchange reaction (2R-SO3H+Ca). 2 + →(R-SO3)2Ca+2H + Remove Ca 2+ Mg 2+To prevent subsequent scaling in the boiler and pipes, the water hardness at the softener 1 is 0.02 mmol / L. After standing for 48 hours to remove impurities, the water then enters the precision filter 2 (the filter element is made of polypropylene pleated material, with a filtration accuracy of 0.1-1μm) to further remove suspended particles, colloids, and microorganisms, preventing blockage of the boiler heating tubes. The suspended solids in the water are 0.08 mg / L. Finally, the water enters the desulfurization and dechlorination unit 3 (the upper layer is ZnO desulfurizing agent, and the lower layer is columnar activated carbon), where ZnO reacts with sulfates in the water (ZnO + SO42-). 2- +2H + →ZnSO4+H2O), activated carbon adsorbs residual chlorine (Cl2+C→C-Cl+HCl), controlling the sulfur and chlorine content in the effluent and preventing poisoning of the subsequent palladium-based catalyst. The sulfur content in the effluent from the desulfurization and dechlorination unit is 0.0007 mg / L, and the chlorine content is 0.003 mg / L.

[0050] S2 wet saturated steam generation

[0051] Purified water is pumped into industrial boiler 6 (horizontal water-tube structure, rated pressure 0.5-10MPa, rated temperature 151-311℃) via a variable frequency feedwater pump. The boiler pressure can be adjusted according to the coal seam depth. The boiler is equipped with an electrode-type water level gauge to monitor the water level in real time and automatically replenish water to prevent dry burning. A spring-loaded safety valve (with an opening pressure of 1.05 times the rated pressure) is also installed to prevent overpressure risks. The purified water is heated to saturation temperature inside the boiler by natural gas combustion or electric heating to generate saturated wet steam containing liquid water, with a steam output of 12m³. 3 / h.

[0052] S3 Dry Saturated Steam Purification

[0053] Saturated wet steam enters the cyclone steam-water separator 8 (made of stainless steel) tangentially. The separator has a built-in spiral guide plate that guides the steam to rotate at high speed along the inner wall. Liquid water is thrown to the inner wall of the separator under centrifugal force and flows along the wall to the bottom drain (equipped with a steam trap) for discharge. The top outlet outputs dry saturated steam with a dryness of ≥99.5%, which avoids liquid water entering the superheater and causing "liquid slugging" (pipeline vibration or damage), and at the same time lays the drying foundation for subsequent superheating.

[0054] S4 superheated steam preparation for preliminary deoxygenation

[0055] Dry saturated steam enters steam regulating valve I 9, maintaining the pressure consistent with the boiler pressure, and then flows into tubular superheater 10. Tubular superheater 10 uses "high-temperature flue gas heating" to heat the dry saturated steam to 200-250℃, forming superheated steam. During this process, according to Henry's Law, the solubility of oxygen in the steam decreases significantly with increasing temperature, completing preliminary deoxygenation, and reducing the steam oxygen content to 0.005 mg / L.

[0056] S5 Palladium-based catalytic adsorption deoxygenation

[0057] Superheated steam enters the palladium-based catalyst fixed bed 15 (diameter 0.3-0.8m, height 1.5-3m, material 316L stainless steel) via steam regulating valve II11. The bottom of the fixed bed is supported by a quartz sand layer, and the middle is filled with a Pd / Al2O3 supported catalyst 13. Simultaneously, the H2 injection device 12 (including an H2 storage tank, pressure reducing valve, and proportional valve) injects hydrogen into the fixed bed based on data from an online oxygen analyzer. The proportional valve precisely controls the molar ratio of H2 to O2 in the steam to be 2.1:1-2.5:1. Under superheated conditions of 200-250℃, the Pd catalyst surface exhibits strong adsorption activity, which can dissociate O2 into active oxygen atoms. H2 dissociates into active hydrogen atoms ( The two react rapidly to produce H2O ( The generated water flows out along with the superheated steam. An online laser oxygen concentration analyzer 14 is installed at the fixed bed outlet to monitor the steam oxygen content in real time. The outlet oxygen content is 0.00008 mg / L. If the oxygen content is too high, the proportional valve is automatically triggered to increase the H2 injection rate. If the standard is still not met after adjustment, the system is shut down for maintenance. In addition, a catalyst regeneration interface is provided on the side of the fixed bed. When the catalyst activity decreases, hydrogen is introduced for regeneration, reducing the poisoned Pd active sites and extending the catalyst's service life.

[0058] S6 Coal Seam Displacement Injection

[0059] Oxygen-reduced superheated steam is injected into the target coal seam through the injection well (casing material of stainless steel, with pressure regulating valve and check valve at the wellhead) of the superheated steam injection control system 16. The injection pressure is 4.2 MPa, which is higher than the original coal seam pressure of 0.7 MPa. The injection flow rate is adjusted according to the coal seam permeability (10-12 m³ / s). 3 The deoxygenated superheated steam emitted by the steam emitter 23 continuously heats the coal seam. Under high temperature and displacement, the coal seam desorbs a large amount of gas. The gas flows through the fractures to the gas drainage borehole 26 and is then drained through the gas drainage pipe.

[0060] Example 1

[0061] Coal seam parameters: Coal seam No. 3 in a certain mining area, depth 800m, original pressure 3.5MPa, original moisture content 6%, original gas content 12m³. 3 / t, prone to spontaneous combustion (spontaneous combustion tendency class II).

[0062] Method implementation steps:

[0063] S1 water source softening and impurity removal

[0064] Tap water first enters softener 1 (containing cation exchange resin), where it undergoes an ion exchange reaction (2R-SO3H+Ca).2 + →(R-SO3)2Ca+2H + Remove Ca 2+ Mg 2+ To prevent subsequent scaling in the boiler and pipes, the water is allowed to stand for 48 hours to remove impurities. The hardness of the water from softener 1 is 0.02 mmol / L. It then enters precision filter 2 (filter element is made of polypropylene pleated material, filtration accuracy 0.5 μm) to further remove suspended particles, colloids, and microorganisms, preventing blockage of the boiler heating tubes. The suspended solids in the water are 0.08 mg / L. Finally, it enters desulfurization and dechlorination unit 3 (upper layer is ZnO desulfurizing agent, lower layer is columnar activated carbon), where ZnO reacts with sulfates in the water (ZnO + SO42-). 2- +2H + →ZnSO4+H2O), activated carbon adsorbs residual chlorine (Cl2+C→C-Cl+HCl), controlling the sulfur and chlorine content in the effluent and preventing poisoning of the subsequent palladium-based catalyst. The sulfur content in the effluent from the desulfurization and dechlorination unit is 0.0007 mg / L, and the chlorine content is 0.003 mg / L.

[0065] S2 wet saturated steam generation

[0066] Purified water is pumped into industrial boiler 6 (horizontal water-tube structure, rated pressure 4MPa, rated temperature 250℃) via a variable frequency feedwater pump. The boiler pressure can be adjusted according to the coal seam depth. The boiler is equipped with an electrode-type water level gauge to monitor the water level in real time and automatically replenish water to prevent dry burning. A spring-loaded safety valve (with an opening pressure of 1.05 times the rated pressure) is also installed to prevent overpressure risks. The purified water is heated to saturation temperature inside the boiler by natural gas combustion or electric heating to generate saturated wet steam containing liquid water, with a steam output of 12m³. 3 / h.

[0067] S3 Dry Saturated Steam Purification

[0068] Saturated wet steam enters the cyclone steam-water separator 8 (made of stainless steel) tangentially. The separator has a built-in spiral guide plate that guides the steam to rotate at high speed along the inner wall. Liquid water is thrown to the inner wall of the separator under centrifugal force and flows along the wall to the bottom drain (equipped with a steam trap) for discharge. The top outlet outputs dry saturated steam with a dryness of 99.7%, which avoids liquid water entering the superheater and causing "liquid slugging" (pipe vibration or damage), and at the same time lays the drying foundation for subsequent superheating.

[0069] S4 superheated steam preparation for preliminary deoxygenation

[0070] Dry saturated steam enters steam regulating valve I9 ​​to maintain the pressure consistent with the boiler pressure, and then flows into tubular superheater 10. Tubular superheater 10 uses "high-temperature flue gas heating" to heat the dry saturated steam to 280℃ (superheat 30℃). During this process, according to Henry's Law, the solubility of oxygen in the steam decreases significantly with increasing temperature, completing preliminary deoxygenation, and reducing the oxygen content of the steam to 0.005 mg / L.

[0071] S5 Palladium-based catalytic adsorption deoxygenation

[0072] Superheated steam enters the palladium-based catalyst fixed bed 15 (0.5m in diameter, 2m in height, made of 316L stainless steel) via steam regulating valve II11. The bottom of the fixed bed is supported by a quartz sand layer, and the middle is filled with a Pd / Al2O3 supported catalyst 13. Simultaneously, the H2 injection device 12 (including an H2 storage tank, pressure reducing valve, and proportional valve) injects hydrogen into the fixed bed based on data from an online oxygen analyzer. The proportional valve precisely controls the molar ratio of H2 to O2 in the steam to be 2.2:1. Under a superheated environment of 250℃, the Pd catalyst surface exhibits strong adsorption activity, which can dissociate O2 into active oxygen atoms. H2 dissociates into active hydrogen atoms ( The two react rapidly to produce H2O ( The generated water flows out along with the superheated steam. An online laser oxygen concentration analyzer 14 is installed at the fixed bed outlet to monitor the steam oxygen content in real time. The outlet oxygen content is 0.00008 mg / L. If the oxygen content is too high, the proportional valve is automatically triggered to increase the H2 injection rate. If the standard is still not met after adjustment, the system is shut down for maintenance. In addition, a catalyst regeneration interface is provided on the side of the fixed bed. When the catalyst activity decreases, hydrogen is introduced for regeneration, reducing the poisoned Pd active sites and extending the catalyst's service life.

[0073] S6 Coal Seam Displacement Injection

[0074] Oxygen-reduced superheated steam is injected into the target coal seam through the injection well (casing made of stainless steel, with a pressure regulating valve and a check valve at the wellhead) of the superheated steam injection control system 16. The injection pressure is 4.2 MPa, which is higher than the original coal seam pressure of 0.7 MPa. The injection flow rate is adjusted according to the coal seam permeability (12m). 3 The deoxygenated superheated steam emitted by the steam emitter 23 continuously heats the coal seam. Under high temperature and displacement, the coal seam desorbs a large amount of gas. The gas flows through the fractures to the gas drainage borehole 26 and is then drained through the gas drainage pipe.

[0075] Implementation results: After 60 days of continuous injection, the coal seam temperature rose to 85℃, gas desorption increased by 45%, and the gas production of the production well increased from 0.6 m³ / s. 3 / d increased to 3.2m 3 / d, no signs of coal seam oxidation (CO concentration <5ppm), no risk of explosion.

[0076] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A method for safe and efficient displacement of coal seam gas by superheated steam under oxygen reduction, characterized in that, The application relates to a method for preparing and purifying superheated steam, which comprises the following steps: Step 1: water source softening and impurity removal: tap water is treated into purified water through softening, precision filtration and desulfurization and dechlorination treatment, the upper layer of a desulfurization and dechlorination device is ZnO desulfurization agent, and the lower layer is columnar activated carbon; Step 2: superheated steam preparation and preliminary oxygen removal: purified water is heated at high temperature, steam-water separation, superheating treatment to obtain superheated steam, the steam-water separation refers to that liquid water is separated from saturated wet steam through the centrifugal action of a spiral guide plate to obtain dry saturated steam with a dryness of greater than or equal to 99.5%, and the superheating treatment refers to that dry saturated steam is heated to 200-250 DEG C through a pressure stabilizing valve and a tubular superheater to form superheated steam, and the oxygen content of the steam is reduced to 0.005 mg / L; Step 3: deep oxygen removal through palladium-based catalytic adsorption: superheated steam is subjected to catalytic oxygen removal to obtain reduced-oxygen superheated steam; Step 4: reduced-oxygen superheated steam injection and displacement: the reduced-oxygen superheated steam is injected into a coal seam to realize gas extraction.

2. The method of claim 1, wherein, The softening treatment uses cation exchange resin to adsorb Ca 2 + , Mg 2+ of the water source, and the hardness of the effluent is 0.02 mmol / L.

3. The method of claim 1, wherein, The precision filtration refers to that impurities are removed through a precision filter after water is left to deposit for 48 hours, and the suspended solids in the effluent are 0.08 mg / L; the filter core of the precision filter is polypropylene folding material, and the filtering precision is 0.1-1 mu m.

4. The method of claim 1, wherein, The desulfurization and dechlorination treatment adopts ZnO desulfurization agent adsorption and columnar activated carbon adsorption in a desulfurization and dechlorination device to obtain purified water, the sulfur content is 0.0007 mg / L, and the chlorine content is 0.003 mg / L.

5. The method of claim 1, wherein, The high-temperature heating is realized by using an industrial boiler with a rated pressure of 0.5-10 MPa and a rated temperature of 151-311 DEG C, and the high-temperature heating generates saturated wet steam containing liquid water, and the steam output reaches 12 m 3 / h; and the industrial boiler is of a horizontal water-fire tube structure.

6. The method of claim 1, wherein, The spiral guide plate is arranged in the cyclone type steam-water separator.

7. The method of claim 1, wherein, The heating medium of the tubular superheater is high-temperature flue gas or electric heating wire.

8. The method of claim 1, wherein, The catalytic oxygen removal refers to that the molar ratio of H2 to O2 in steam is accurately controlled to be 2.1:1-2.5:1 through a proportional valve, reduced-oxygen superheated steam is obtained through Pd / Al2O3 supported catalyst catalysis under a superheated environment of 200-250 DEG C, and the oxygen content is reduced to 0.00008 mg / L.

9. The method of claim 8, wherein, The Pd / Al2O3 supported catalyst is arranged in a palladium-based catalyst fixed bed; a quartz sand supporting layer is arranged at the bottom of the palladium-based catalyst fixed bed, and the Pd / Al2O3 supported catalyst is filled in the middle part.

10. The method of claim 8, wherein, The injection pressure of the injection coal seam is higher than the original pressure of the coal seam, and the injection flow is 10-12 m 3 / h, the oxygen-reduced superheated steam emitted by the steam emitter continuously heats the coal seam, a large amount of gas is desorbed from the coal seam under the high temperature and displacement, the gas flows to the gas extraction borehole through the fissure, and the gas extraction is performed through the gas extraction pipe.

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