CN114687721B - Microwave degassing method for coal bed of high-gas mine - Google Patents
Microwave degassing method for coal bed of high-gas mine Download PDFInfo
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- CN114687721B CN114687721B CN202210251633.4A CN202210251633A CN114687721B CN 114687721 B CN114687721 B CN 114687721B CN 202210251633 A CN202210251633 A CN 202210251633A CN 114687721 B CN114687721 B CN 114687721B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
Abstract
The invention discloses a microwave degassing method for a coal seam of a high-gas mine, and aims to effectively solve the problem of damage to a coal seam roof caused by microwave transitional injection. Before coal mining operation, drilling an extraction borehole in a roadway of a working face to the middle part of the coal mining working face, and measuring the distance from the extraction borehole to a coal seam roof; then, the first waveguide tube and the extraction tube which are provided with the antenna are placed in an extraction drill hole, and the extraction drill hole is plugged; drilling a coal core on the coal bed by using sampling equipment; performing microwave heat injection anti-reflection simulation on the coal core by using a microwave heating simulation system; continuously collecting the water temperature by using a temperature sensor, obtaining a real-time heating curve of the water by using a computer, and setting the time corresponding to an inflection point of the sharp change of the heating curve as heating time; and opening the first microwave generator, injecting microwaves into the coal seam around the extraction drill hole for heat injection and permeability increase, extracting gas by using the extraction pipe, and closing the first microwave generator when the set heating time is reached.
Description
Technical Field
The invention belongs to the technical field of coal seam mining, and particularly relates to a microwave degassing method for a coal seam of a high-gas mine.
Background
The content of gas (the main component is methane) in a coal seam of a high-gas mine needs to be reduced through an extraction link before coal mining operation. The microwave heating technology has the essential properties of selective heating and volume heating, so that the heating process is efficient, environment-friendly and easy to control, and the microwave heating technology is considered to have greater application potential in the field of coal seam degassing. When the coal bed is irradiated by microwaves, the microwaves are mainly absorbed by pore water in the coal rock [1], the moisture after the microwaves are absorbed is continuously heated and finally vaporized, the process not only promotes the enhancement of the thermal motion of methane molecules, but also helps the methane molecules break away and absorb and convert into a free state [2]; steam pressure generated by the steam can also destroy the original pore structure of the coal rock and communicate with adjacent pores, and a channel [3] is opened for the migration of the subsequent coal bed gas.
The heat injection and permeability increasing effects of microwaves on the coal bed are mainly realized by taking pore water in the coal as a carrier, the microwave heat injection permeability increasing coal bed has a time effect in consideration of vaporization and evaporation of water, the microwave energy absorbed by the coal bed can be continuously reduced along with heating, the microwave injection time in the existing microwave heat injection permeability increasing coal bed method is determined according to experience, when the coal body is completely dehydrated, if the microwaves are continuously injected, only a small part of the continuously injected microwaves are absorbed by the coal bed, most of the remaining microwaves penetrate through the coal bed to act on a rock top plate, so that the heat damage of the rock top plate is caused, the top plate is easy to fall off, and the casualties are caused.
In conclusion, there is a need for improvement of the existing microwave heat injection permeability-increasing coal seam method.
Reference to the literature
[1]Marland,S.,Merchant,A.,Rowson,N.Dielectric properties of coal[J].Fuel,2001,80(13):1839-1849.
[2] Analysis of characteristics of coal desorption and adsorption of gas under the action of alternating electric field sound field [ J ]. China mining industry, 2005,14 (5): 70-73.
[3] Li Hao, lin Bo quan, hong Ying, etc. under the microwave radiation, the characteristic of the structural evolution of the coal pore crack is [ J ]. The university of Chinese mining, academic newspaper, 2017,46 (6): 1194-1201.
Disclosure of Invention
The invention mainly aims to provide a microwave degassing method for a coal seam of a high-gas mine, and aims to effectively solve the problem of damage to a coal seam roof caused by microwave transitional injection.
Therefore, the microwave degassing method for the coal bed of the high gas mine provided by the invention comprises the following steps:
drilling an extraction borehole in a roadway of a working face to the middle of the coal working face before coal mining operation, and measuring the distance d from the extraction borehole to a coal seam roof;
then, placing the first waveguide tube and the extraction tube which are provided with the antenna into an extraction drill hole, and plugging the extraction drill hole, wherein the first waveguide tube is connected with a first microwave generator outside the extraction drill hole;
drilling a coal core with the length d on the coal bed by using sampling equipment;
performing microwave heat injection anti-reflection simulation on the coal core by using a microwave heating simulation system; the microwave heating simulation system generates microwaves with the same power as the first microwave generator, the microwaves are injected from one end of the coal core, and the microwaves are absorbed by water from the other end of the coal core;
continuously collecting the water temperature by using a temperature sensor, and obtaining a real-time heating curve of the water by using a computer, wherein the time corresponding to an inflection point of the heating curve with rapid change is T;
and opening the first microwave generator, injecting microwaves into the coal seam around the extraction drill hole for heat injection and permeability improvement, extracting gas by using the extraction pipe, closing the first microwave generator when the heating time reaches T time, and stopping heat injection and permeability improvement on the coal seam.
Specifically, the microwave heating simulation system comprises a second microwave generator, a second waveguide and a water tank;
one end of the second waveguide tube is in butt joint with a microwave emitting port of the second microwave generator, and the other end of the second waveguide tube is in butt joint with a wave-transmitting plate of the water tank;
a hollow waveguide cavity is formed in the second waveguide tube, and the coal core is installed in the waveguide cavity in a matching mode.
Specifically, the wave-transmitting plate is a polytetrafluoroethylene plate.
Specifically, a pressure relief valve, a temperature sensor and a pressure gauge are arranged on the water tank.
Specifically, the second microwave generator includes a shielding case, a magnetron arranged in the shielding case for generating microwaves, and a PLC controller for controlling the operation of the magnetron.
Compared with the prior art, the invention at least has the following beneficial effects: the method comprises the steps of performing microwave heat injection anti-reflection simulation on a coal core through a microwave heating simulation system, continuously collecting water temperature by using a temperature sensor, obtaining a real-time heating curve after water absorbs microwaves through a computer, and taking time corresponding to an inflection point as microwave heating time for actual microwave anti-reflection of the coal bed on the basis of the characteristic that the heating curve has an obvious inflection point before and after the coal bed is completely dehydrated, so that the heat damage to rocks on a top plate of the coal bed caused by microwave transitional injection can be avoided on the premise of ensuring the effective anti-reflection of the coal bed.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a microwave degassing design for a coal seam provided by an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a microwave heating simulation system provided by an embodiment of the present invention;
wherein: 1. a housing; 2. a magnetron; 3. a PLC controller; 4. a second waveguide; 5. a coal core; 6. a wave-transmitting plate; 7. a water tank; 8. a temperature sensor; 9. a pressure gauge; 10. a pressure relief valve; 11. and (4) a computer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
Referring to fig. 1 and 2, a microwave degassing method for a high gas mine coal seam provided by an embodiment of the invention includes:
drilling an extraction borehole in a roadway of a working face to the middle of the coal working face before coal mining operation, and measuring the distance d (m) from the extraction borehole to a coal seam roof;
then, placing the first waveguide tube and the extraction tube which are provided with the antenna into an extraction drill hole, and plugging the extraction drill hole by using a plug, wherein the first waveguide tube is connected with a first microwave generator outside the extraction drill hole;
drilling a coal core 5 with the length dm and the diameter 50mm on a coal bed by using sampling equipment;
performing microwave heat injection anti-reflection simulation on the coal core 5 by using a microwave heating simulation system; wherein, the microwave which is generated by the microwave heating simulation system and has the same power as the first microwave generator is injected from one end of the coal core 5, and is absorbed by water from the other end of the coal core 5;
continuously collecting the water temperature by using a temperature sensor 8, and acquiring a real-time temperature rise curve after the water absorbs the microwaves by using a computer 11; wherein, the time corresponding to the inflection point of the temperature rising curve with rapid change is counted as T;
and opening the first microwave generator, injecting microwaves into the coal seam around the extraction drill hole for heat injection and permeability increase, extracting gas by using the extraction pipe, closing the first microwave generator after the heating time reaches T time, and stopping heat injection and permeability increase of the coal seam.
The principle of the invention is as follows: the method is based on the characteristic that the temperature rise curve can be changed rapidly before and after the coal core 5 is completely dehydrated, the time corresponding to the inflection point of the heating curve is used as the optimal heating time of the microwaves when the coal layer with the thickness of d m from the top plate is heated in the actual degassing process of the coal bed microwaves, and the heating time is controlled at the time corresponding to the inflection point of the heating curve, so that not only can effective permeability improvement be ensured, but also the phenomenon that the heat loss of the top plate of the coal bed is damaged due to the fact that the rocks are injected in a transition mode can be avoided.
Referring to fig. 2, in practical application, the microwave heating simulation system includes a second microwave generator, a second waveguide tube 4 and a water tank 7, one end of the second waveguide tube 4 is butted with a microwave emitting port of the second microwave generator, the other end of the second waveguide tube is butted with a wave-transmitting plate 6 of the water tank 7, a hollow waveguide cavity is formed in the second waveguide tube 4, a coal core 5 is installed in the waveguide cavity in a matched manner, a pressure release valve 10, a temperature sensor 8 and a pressure gauge 9 are arranged on the water tank 7, the temperature sensor 8 is electrically connected with a computer 11, the second microwave generator includes a shielding shell 1, a magnetron 2 arranged in the shielding shell 1 and used for generating microwaves, and a PLC controller 3 for controlling the work of the magnetron 2. The wave-transmitting plate 6 is a plate through which the microwaves can pass but are not absorbed, and the material of the wave-transmitting plate can be polytetrafluoroethylene, because polytetrafluoroethylene is an excellent wave-transmitting material, the energy of the microwaves passing through the wave-transmitting plate is not basically lost, and the wave-transmitting plate can be made of other materials.
In this embodiment, the coal core drilled during the experiment is placed in the waveguide tube to be heated, a part of the microwaves emitted by the microwave source is absorbed by the coal sample, the rest of the microwaves pass through the wave-transmitting plate to be absorbed by the water in the water tank, the temperature sensor continuously collects the water temperature, and the computer obtains the real-time temperature rise curve. In the initial stage of microwave heating, most microwaves are absorbed by the coal core, so that the temperature curve of water is slowly increased, when the coal core is completely dehydrated, the microwaves are almost completely absorbed by the water, so that the temperature curve is rapidly changed, and the time corresponding to the change inflection point of the heating curve is the reasonable microwave heating time t when the coal bed with the thickness of d m is heated Superior food 。
In addition, if the total energy of the microwave is defined(W General assembly ) The microwave absorption energy (W) is the sum of the energy output in a certain time Suction device ) The microwave dissipation energy (W) is the sum of the energy absorbed by the coal and rock in a certain time Consumption unit ) Is the change of the internal energy of the water tank within a certain time.
Then W General assembly ＝Pt；W Consumption unit ＝Q Water (W) ＝cmΔT＝cm(f(t)-T 0 )；
According to the conservation of energy within a graduated microwave heating system, W Suction device ＝W General assembly -W Consumption of
Then the energy utilization efficiency phi of the microwave can be calculated when the coal bed is completely dehydrated Superior food ＝(W General (1) -W Consumption unit )×100％/W General assembly ＝1-cm(f(t Superior food )-T 0 )×100％/Pt Superior food ；
In the formula: p is microwave power, W; t is heating time s; c is the specific heat capacity of water, J/(kg. K); m is the mass of water in the water tank, kg; t is 0 The initial temperature of water, DEG C.
According to the method, the microwave heating simulation system is used for performing microwave heat injection permeability-increasing simulation on the coal core, the temperature sensor is used for continuously collecting water temperature, a real-time heating curve after water absorbs microwaves is obtained by a computer, and based on the characteristic that the heating curve has an obvious inflection point before and after the coal bed is completely dehydrated, the time corresponding to the inflection point is used as the microwave heating time for actual microwave permeability increase of the coal bed, so that on the premise that the effective permeability increase of the coal bed is guaranteed, the heat damage to the rock on the top plate of the coal bed caused by the transitional injection of microwaves can be avoided.
Any embodiment disclosed herein above is meant to disclose, unless otherwise indicated, all numerical ranges disclosed as being preferred, and any person skilled in the art would understand that: the preferred ranges are merely those values which are obvious or representative of the technical effect which can be achieved. Since the numerical values are too numerous to be exhaustive, some of the numerical values are disclosed in the present invention to illustrate the technical solutions of the present invention, and the above-mentioned numerical values should not be construed as limiting the scope of the present invention.
Meanwhile, if the invention as described above discloses or relates to parts or structural members fixedly connected to each other, the fixedly connected parts can be understood as follows, unless otherwise stated: a detachable fixed connection (for example using bolts or screws) is also understood as: non-detachable fixed connections (e.g. riveting, welding), but of course, fixed connections to each other may also be replaced by one-piece structures (e.g. manufactured integrally using a casting process) (unless it is obviously impossible to use an integral forming process).
In addition, terms used in any technical solutions disclosed in the present invention to indicate positional relationships or shapes include approximate, similar or approximate states or shapes unless otherwise stated. Any part provided by the invention can be assembled by a plurality of independent components, or can be manufactured by an integral forming process.
The above examples are merely illustrative for clearly explaining the present invention and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Nor is it necessary or exhaustive for all embodiments. And obvious variations or modifications are intended to be within the scope of the present invention.
Claims (4)
1. A microwave degassing method for a coal seam of a high-gas mine is characterized by comprising the following steps:
drilling an extraction borehole in a roadway of a working face to the middle of the coal working face before coal mining operation, and measuring the distance d from the extraction borehole to a coal seam roof;
then, placing the first waveguide tube and the extraction tube which are provided with the antenna into an extraction drill hole, and plugging the extraction drill hole, wherein the first waveguide tube is connected with a first microwave generator outside the extraction drill hole;
drilling a coal core (5) with the length d on the coal seam by using sampling equipment;
performing microwave heat injection anti-reflection simulation on the coal core (5) by using a microwave heating simulation system; wherein, the microwave which is generated by the microwave heating simulation system and has the same power as the first microwave generator is injected from one end of the coal core (5) and is absorbed by water from the other end;
continuously collecting the water temperature by using a temperature sensor (8), and obtaining a real-time heating curve of the water by using a computer (11), wherein the time corresponding to an inflection point of the heating curve with rapid change is T;
opening a first microwave generator, injecting microwaves into the coal seam around the extraction drill hole for heat injection and permeability increase, extracting gas by using an extraction pipe, closing the first microwave generator after the heating time reaches T time, and stopping heat injection and permeability increase of the coal seam;
the microwave heating simulation system comprises a second microwave generator, a second waveguide tube (4) and a water tank (7);
one end of the second waveguide tube (4) is in butt joint with a microwave emitting port of the second microwave generator, and the other end of the second waveguide tube is in butt joint with a wave-transmitting plate (6) of the water tank (7);
a hollow waveguide cavity is formed in the second waveguide tube (4), and the coal core (5) is installed in the waveguide cavity in a matching mode.
2. The microwave degassing method for a high gas mine coal seam according to claim 1, wherein: the wave-transmitting plate (6) is a polytetrafluoroethylene plate.
3. The microwave degassing method for a high gas mine coal seam according to claim 1, wherein: and a pressure relief valve (10), a temperature sensor (8) and a pressure gauge (9) are arranged on the water tank (7).
4. The microwave degassing method for a high gas mine coal seam according to claim 1, wherein: the second microwave generator comprises a shielding shell (1), a magnetron (2) arranged in the shielding shell (1) and used for generating microwaves and a PLC (programmable logic controller) used for controlling the magnetron (2) to work.
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| WO1984003021A1 (en) * | 1983-01-25 | 1984-08-02 | Deryck Brandon | Apparatus and method for heating, thawing and/or demoisturizing materials and/or objects |
| CN105525901A (en) * | 2015-12-29 | 2016-04-27 | 中国矿业大学 | Coal seam hydrofracture strengthening permeability increasing method based on microwave irradiation |
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|---|---|---|---|---|
| US4256944A (en) * | 1979-04-09 | 1981-03-17 | Deryck Brandon | Apparatus and method for thawing materials stored in gondola-type containers |
| CN103698411B (en) * | 2013-12-25 | 2015-06-17 | 辽宁工程技术大学 | Device and method for improving coal bed gas desorption efficiency with microwaves |
| CN106812512A (en) * | 2017-03-02 | 2017-06-09 | 新疆大学 | Low-permeability water-bearing coal seam reservoirs microwave steam explosion is anti-reflection drop absorbing method |
| WO2019132041A1 (en) * | 2017-12-28 | 2019-07-04 | 国際環境開発株式会社 | Heat-generating device and use thereof |
| CN110578549B (en) * | 2019-07-23 | 2021-05-04 | 华北科技学院 | Electric explosion and seismic fracturing cooperated microwave heat drive gas extraction system and method |
| CN110985110B (en) * | 2019-12-18 | 2021-06-25 | 中南大学 | High-gas tight coal seam pumping and injecting integrated system and method |
| CN112780243B (en) * | 2020-12-31 | 2022-03-29 | 中国矿业大学 | Integrated reinforced coal seam gas extraction system and extraction method |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1984003021A1 (en) * | 1983-01-25 | 1984-08-02 | Deryck Brandon | Apparatus and method for heating, thawing and/or demoisturizing materials and/or objects |
| CN105525901A (en) * | 2015-12-29 | 2016-04-27 | 中国矿业大学 | Coal seam hydrofracture strengthening permeability increasing method based on microwave irradiation |
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