CN111366686B - Method for judging coal mine spontaneous combustion area based on detection of C14 radioactive quantity - Google Patents
Method for judging coal mine spontaneous combustion area based on detection of C14 radioactive quantity Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 105
- 230000002285 radioactive effect Effects 0.000 title claims abstract description 95
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 70
- 230000002269 spontaneous effect Effects 0.000 title claims abstract description 69
- 238000001514 detection method Methods 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 39
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims abstract description 200
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims abstract description 100
- 235000017557 sodium bicarbonate Nutrition 0.000 claims abstract description 100
- 239000002002 slurry Substances 0.000 claims abstract description 43
- 238000005553 drilling Methods 0.000 claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 31
- 239000012153 distilled water Substances 0.000 claims description 30
- 238000002156 mixing Methods 0.000 claims description 20
- 239000000843 powder Substances 0.000 claims description 20
- 239000011812 mixed powder Substances 0.000 claims description 19
- 239000011259 mixed solution Substances 0.000 claims description 15
- 239000010881 fly ash Substances 0.000 claims description 14
- 238000003756 stirring Methods 0.000 claims description 13
- 238000000354 decomposition reaction Methods 0.000 claims description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 10
- 239000012047 saturated solution Substances 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 6
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims description 5
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 5
- 239000001569 carbon dioxide Substances 0.000 claims description 5
- 238000009837 dry grinding Methods 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- 238000002360 preparation method Methods 0.000 claims description 5
- 238000002372 labelling Methods 0.000 claims description 3
- 230000002265 prevention Effects 0.000 abstract description 3
- 238000011284 combination treatment Methods 0.000 abstract description 2
- 230000000694 effects Effects 0.000 abstract description 2
- 230000005764 inhibitory process Effects 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 31
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 7
- 229910052717 sulfur Inorganic materials 0.000 description 7
- 239000011593 sulfur Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 4
- 239000011435 rock Substances 0.000 description 4
- 230000001174 ascending effect Effects 0.000 description 3
- 238000009529 body temperature measurement Methods 0.000 description 3
- 238000004980 dosimetry Methods 0.000 description 3
- 229910052704 radon Inorganic materials 0.000 description 3
- SYUHGPGVQRZVTB-UHFFFAOYSA-N radon atom Chemical compound [Rn] SYUHGPGVQRZVTB-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000000700 radioactive tracer Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
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- 150000001875 compounds Chemical class 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 230000007774 longterm Effects 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
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- 238000000691 measurement method Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
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- 230000005855 radiation Effects 0.000 description 1
- 239000000941 radioactive substance Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000011895 specific detection Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/0055—Radionuclides
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- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/004—CO or CO2
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- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V9/00—Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00
- G01V9/007—Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00 by detecting gases or particles representative of underground layers at or near the surface
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Abstract
The invention discloses a method for judging a coal mine spontaneous combustion area based on detection of C14 radioactive quantity, which comprises the steps of firstly preparing radioactive sodium bicarbonate slurry; selecting a coal seam area with the coal seam spontaneous combustion tendency of easy spontaneous combustion and spontaneous combustion as a coal seam detection area, and then drilling a plurality of drill holes at equal intervals in the coal seam detection area; injecting the prepared radioactive sodium bicarbonate slurry into the drill hole, and then enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal body crack; and (3) judging the coal spontaneous combustion area: and extracting gas for each drill hole for multiple times, detecting the extracted gas by using a C14 detector at C14, drawing a change curve in a C14 radioactivity-time two-dimensional graph, and determining the spontaneous combustion condition of a coal seam detection area around the drill hole according to the change curve. The standard value is not required to be measured in the early stage, and radioactive sodium bicarbonate slurry is injected through drilling, so that whether spontaneous combustion and a spontaneous combustion range exist in a detection area can be accurately judged, meanwhile, an inhibition effect on a spontaneous combustion area can be realized, and the purpose of prevention and treatment combination is realized.
Description
Technical Field
The invention relates to a method for judging a coal mine spontaneous combustion area, in particular to a method for judging the coal mine spontaneous combustion area based on detection of C14 radioactive quantity.
Background
Mine fires are one of the main natural disasters of coal mines, and spontaneous combustion of coal is the main form of mine fires. In the coal mining process, the mechanical behavior of the coal rock mass is complex, and the fracture is continuously inoculated and expanded due to the occurrence of a large amount of broken coal rocks, so that oxygen supply conditions are provided for the oxidation reaction of coal. Spontaneous combustion fires not only cause economic property loss, but also seriously threaten coal mine safety production. In order to accurately and effectively manage the fire, the position of the spontaneous combustion initial fire area needs to be found accurately, and a targeted fire extinguishing scheme is formulated. Therefore, how to accurately position the fire source and judge the range of the self-ignition area has important significance for reasonably and effectively carrying out subsequent fire extinguishing work.
Existing useThe detection method for determining the coal mine fire area mainly comprises an earth surface temperature measurement method, a radon measurement method, a magnetic method and a drilling method, and various methods have obvious effects in actual application, but have some defects. The efficiency of a ground surface temperature measurement method is low, the temperature measurement work above a fire area is dangerous, and a deep fire area is probably free from abnormal heat in the ground surface; radon elements exist in surrounding rocks of coal beds in a radon measuring method, and the method is easily influenced by the properties of rock stratums in fire areas, and has weak anti-interference performance and larger error; when the magnetic method is used, the magnetic method is easily interfered by a plurality of factors such as a stray magnetic field of the earth, current, complex terrain in a mountainous area and the like, and has hysteresis; temperature measuring instruments used in the drilling method are poor in stability and sensitivity, areas with spontaneous combustion are difficult to accurately detect, a large number of drill holes are often required to be constructed to determine the fire area range, and a large amount of manpower, material resources and financial resources are consumed. At present, our country also presents a new method for detecting the fire zone of a coal mine, for example, the invention patent with the publication number of CN105588870A, entitled "a coal field fire zone detecting device and method based on sulfur isotope component ratio", detects the fire zone of a coal field by utilizing the isotope fractionation phenomenon of sulfur generated in the coal combustion process, and firstly, exploits the total sulfur in coal in the same non-spontaneous combustion area of the coal mine 34 S/ 32 Measuring S ratio as standard value, drilling hole in the area to be detected, collecting gas in the hole, and measuring sulfur content in the gas 34 S/ 32 The S ratio is compared with a standard value, and finally whether the spontaneous combustion condition exists around the drill hole is determined according to the comparison condition, the method has the advantages of convenience in operation and higher accuracy, but the method has the following defects: firstly, the measurement of the standard value at the early stage needs high accuracy, once the accuracy of the standard value cannot be ensured, the error of judgment caused by comparison between a subsequent measurement value and the standard value can be caused, but the measurement process at the early stage needs a plurality of links, so the accuracy of the standard value is difficult to ensure; secondly, because the isotope of the sulfur is calibrated, the method is not suitable for areas with less sulfur content in the coal bed; thirdly, the sulfur element composition substance detected by the method is SO 2 Gases, which are irritating and toxic gases, can be carcinogenic in long-term contact, and thus have an impact on the health of workers. Thus how to provideThe method can accurately judge the spontaneous combustion area of the coal mine without early-stage accurate measurement, and can be suitable for various different coal mines, and the problem to be solved in the industry is urgent.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for judging the spontaneous combustion area of a coal mine based on detection of C14 radioactive amount, which does not need to determine a standard value in the early stage, and can accurately judge whether spontaneous combustion exists in a detection area or not and the spontaneous combustion range by drilling and injecting radioactive sodium bicarbonate slurry, and can play a role in inhibiting the spontaneous combustion area and realize the purpose of prevention and treatment combination.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for judging a coal mine spontaneous combustion area based on detection of C14 radioactive quantity comprises the following specific steps:
A. preparation of radioactive sodium bicarbonate slurry:
(1) under the condition that the temperature is 30 ℃, firstly, injecting distilled water into a container, adding sodium bicarbonate powder into the distilled water, fully and uniformly stirring the distilled water and the sodium bicarbonate in a weight ratio of 1: 0.4 until the distilled water and the sodium bicarbonate are completely dissolved to prepare a saturated solution of the sodium bicarbonate;
(2) introducing carbon dioxide containing radioactive C14 into saturated solution of sodium bicarbonate, and reacting with sodium bicarbonate for 90min to obtain mixed solution;
(3) after the reaction is completed, the temperature of the mixed solution is reduced to cool and crystallize the mixed solution to prepare sodium bicarbonate solid with radioactivity C14;
(4) grinding the sodium bicarbonate solid prepared in the step (3) by using a ball mill in a dry grinding manner to form sodium bicarbonate powder with radioactive C14;
(5) mixing sodium bicarbonate powder with radioactive C14 with fly ash, mixing the sodium bicarbonate powder and the fly ash according to the weight ratio of 1-1.5: 0.5, and fully and uniformly stirring to form mixed powder; the fly ash can make the slurry have certain consistency to avoid too fast diffusion after injection;
(6) adding distilled water into the mixed powder to mix, mixing the mixed powder and the distilled water in a weight ratio of 1.5-2: 1, and fully and uniformly stirring to prepare radioactive sodium bicarbonate slurry;
B. determining the range of the coal seam detection area and drilling holes: the spontaneous combustion tendency of the coal bed is determined by using a known method (the spontaneous combustion tendency of coal is divided into 3 types of easy spontaneous combustion, spontaneous combustion and difficult spontaneous combustion by the existing classification method; when a production mine is mined, the spontaneous combustion tendency of all the coal beds is required to be identified for preventing and treating underground fire), the spontaneous combustion tendency of the coal bed is selected as a coal bed detection area, then a plurality of drill holes are drilled in the coal bed detection area at equal intervals in the longitudinal direction and the transverse direction, the interval is 50-100 m, and the volume in each drill hole is at least 3.5m 3 ；
C. Injecting radioactive sodium bicarbonate slurry: injecting the radioactive sodium bicarbonate slurry prepared in the step A into each drill hole by adopting a downhole movable grouting pump at the pressure of 2.5-3 MPa, and further enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal body crack;
D. and (3) judging the coal spontaneous combustion area:
firstly, after radioactive sodium bicarbonate slurry is injected into the drill holes for 3 hours, gas in each drill hole is extracted once;
secondly, extracting gas in each drill hole every 5 hours, continuing until each drill hole is extracted for 10 times, and labeling the extracted gas each time;
thirdly, detecting extracted gas by using a C14 detector for C14, detecting whether the gas extracted each time by each drill hole contains C14 radioactive elements, and if the gas does not contain C14 radioactive elements, indicating that radioactive sodium bicarbonate in the slurry is not heated and decomposed, thereby determining that spontaneous combustion does not occur in a coal seam detection area around the drill hole; if the radioactive element C14 exists, the radioactive content C14 is determined, the radioactive sodium bicarbonate in the slurry is decomposed by heat, and the detection result of each drill hole is drawn into a change curve in a C14 radioactive quantity-time two-dimensional graph, wherein the radioactive sodium bicarbonate starts to be decomposed when the temperature exceeds 50 ℃, the decomposition speed is higher along with the higher temperature, and the decomposition is complete when the temperature reaches 270 ℃;
the specific detection principle is as follows; since the spontaneous combustion of coal is the result of the formation of the critical point of the temperature rise of the oxidation reaction of the coal body, the temperature of the coal body is continuously increased along with the oxidation reaction before the spontaneous combustion of the coal, and the radioactive sodium bicarbonate injected into the detection area is not decomposed when the ambient temperature of the radioactive sodium bicarbonate does not exceed 50 ℃, so that CO with radioactive C14 is not generated 2 A gas; therefore, the C14 detector cannot detect C14 radioactive elements in the extracted gas, which indicates that the temperature of the coal body is lower than 50 ℃ at the moment, and the spontaneous combustion condition does not exist; decomposition begins when the ambient temperature of the radioactive sodium bicarbonate exceeds 50 ℃, the reaction is as follows:
NaHCO 3 →Na 2 CO 3 +H 2 O+CO 2 ↑
decomposition yields CO with radioactive C14 2 Gas and CO with radioactive C14 produced with higher temperature and faster decomposition rate 2 The more gas, therefore 14 The C detector can detect the radioactive content of C14 in extracted gas, and the higher the temperature of the coal body is, the higher the radioactive content of C14 is, so that the spontaneous combustion condition of a coal seam detection area can be determined by detecting the radioactive content of C14;
and fourthly, if the radioactive contents of C14 detected by two continuous gas extractions in any drill hole are within 600-1200 dpm/mmol, determining that spontaneous combustion occurs in a coal seam detection area around the drill hole.
Preferably, the plurality of bores are spaced apart by 80 m.
Preferably, the sodium bicarbonate and the fly ash are mixed according to the weight ratio of 1.2: 0.5 to prepare mixed powder; and the mixed powder and distilled water are mixed according to the weight ratio of 1.7: 1 to prepare the radioactive sodium bicarbonate slurry.
Compared with the prior art, the invention has the following advantages:
(1) by injecting sodium bicarbonate with radioactivity into the detection area, CO containing C14 generated by decomposition of sodium bicarbonate when coal spontaneous combustion occurs 2 Gases, with respect to CO containing C12, produced by oxidation of coal and spontaneous combustion 2 Gas and CO gas, C14, are radioactive and when diffused from the coal fractures and extracted from the boreholeWhether the gas in the drill hole contains C14 and the contained C14 radiation content is detected through a C14 detector, so that whether the coal seam detection area is spontaneously combusted or not and the spontaneous combustion area can be accurately positioned; according to the method, a standard value is not required to be measured in the early stage, so that the accuracy of judging the coal seam detection area can be effectively guaranteed;
(2) the selected radioactive C14 isotope belongs to a low-toxicity nuclide, C14 is used as a tracer for marking a compound, and the tracer is detected by a C14 detector, so that the method has the characteristics of simplicity, easiness in tracking, high sensitivity and accuracy, and cannot influence the health of workers, and the detection of a coal mine fire area is more accurate, efficient and safe.
(3) As the sodium bicarbonate can start to decompose at 50 ℃, the monitoring of the oxidation temperature rise stage before the spontaneous combustion of the coal is realized, and the decomposition speed is higher as the temperature is higher, the CO with the radioactive C14 is generated 2 The more gas, the C14 detector can detect the content of C14 in extracted gas, and the higher the temperature of the coal body is, the higher the content of C14 is, so the determination of the spontaneous combustion condition of a coal seam detection area can be realized by detecting the content of C14, the space temperature can be reduced by water generated in thermal decomposition, and CO generated can be reduced 2 The gas can dilute the oxygen concentration in the coal seam detection area, so that the spontaneous combustion of the coal body can be inhibited to a certain degree while the spontaneous combustion area is accurately positioned, and the purpose of prevention and control combination is finally achieved.
Drawings
FIG. 1 is a graph of C14 dosimetry data from a borehole tested using example 1;
FIG. 2 is a graph of C14 dosimetry data for a borehole measured using example 2;
FIG. 3 is a graph of C14 dosimetry data for a borehole measured using example 3.
Detailed Description
The present invention will be further explained below.
Example 1:
the specific steps of this embodiment are:
A. preparation of radioactive sodium bicarbonate slurry:
(1) under the condition that the temperature is 30 ℃, firstly, injecting distilled water into a container, adding sodium bicarbonate powder into the distilled water, fully and uniformly stirring the distilled water and the sodium bicarbonate in a weight ratio of 1: 0.4 until the distilled water and the sodium bicarbonate are completely dissolved to prepare a saturated solution of the sodium bicarbonate;
(2) introducing carbon dioxide containing radioactive C14 into saturated solution of sodium bicarbonate, and reacting with sodium bicarbonate for 90min to obtain mixed solution;
(3) after the reaction is completed, the temperature of the mixed solution is reduced to cool and crystallize the mixed solution to prepare sodium bicarbonate solid with radioactivity C14;
(4) grinding the sodium bicarbonate solid prepared in the step (3) by using a ball mill in a dry grinding manner to form sodium bicarbonate powder with radioactive C14;
(5) mixing sodium bicarbonate powder with radioactive C14 with fly ash, mixing the sodium bicarbonate powder and the fly ash according to the weight ratio of 1: 0.5, and fully and uniformly stirring to form mixed powder; the fly ash can make the slurry have certain consistency to avoid too fast diffusion after injection;
(6) adding distilled water into the mixed powder, mixing the mixed powder and the distilled water according to the weight ratio of 1.5: 1, mixing and fully and uniformly stirring to prepare radioactive sodium bicarbonate slurry;
B. determining the range of the coal seam detection area and drilling holes: the spontaneous combustion tendency of the coal seam is determined by using a known method, a coal seam area with the spontaneous combustion tendency of the coal seam being easy to spontaneously combust and spontaneously combust is selected as a coal seam detection area, then a plurality of drill holes with the interval of 100m are drilled in the coal seam detection area at equal intervals in the longitudinal direction and the transverse direction, and the volume of each drill hole is at least 3.5m 3 ；
C. Injecting radioactive sodium bicarbonate slurry: injecting the radioactive sodium bicarbonate slurry prepared in the step A into each drill hole by adopting an underground movable grouting pump at the pressure of 3MPa, and further enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal body crack;
D. and (3) judging the coal spontaneous combustion area:
firstly, after radioactive sodium bicarbonate slurry is injected into the drill holes for 3 hours, gas in each drill hole is extracted once;
secondly, extracting gas in each drill hole every 5 hours, continuing until each drill hole is extracted for 10 times, and labeling the extracted gas each time;
thirdly, detecting extracted gas by using a C14 detector for C14, detecting whether the gas extracted each time by each drill hole contains C14 radioactive elements, and if the gas does not contain C14 radioactive elements, indicating that radioactive sodium bicarbonate in the slurry is not heated and decomposed, thereby determining that spontaneous combustion does not occur in a coal seam detection area around the drill hole; if the radioactive element C14 exists, the radioactive content C14 is determined, the radioactive sodium bicarbonate in the slurry is decomposed by heat, and the detection result of each drill hole is drawn into a change curve (shown in figure 1) in a C14 radioactive quantity-time two-dimensional graph, wherein the radioactive sodium bicarbonate starts to be decomposed when the temperature exceeds 50 ℃, the decomposition speed is higher along with the higher temperature, and the decomposition is complete when the temperature reaches 270 ℃;
and fourthly, if the radioactive contents of C14 detected by two continuous gas extractions in any drill hole are within 600-1200 dpm/mmol, determining that spontaneous combustion occurs in a coal seam detection area around the drill hole.
Example 2:
the specific steps of this embodiment are:
A. preparation of radioactive sodium bicarbonate slurry:
(1) under the condition that the temperature is 30 ℃, firstly, distilled water is injected into a container, sodium bicarbonate powder is added into the distilled water, the weight ratio of the distilled water to the sodium bicarbonate is 1: 0.4, and the mixture is fully and uniformly stirred until the mixture is completely dissolved to prepare a saturated solution of the sodium bicarbonate;
(2) introducing carbon dioxide containing radioactive C14 into saturated solution of sodium bicarbonate, and reacting with sodium bicarbonate for 90min to obtain mixed solution;
(3) after the reaction is completed, the temperature of the mixed solution is reduced to cool and crystallize the mixed solution to prepare sodium bicarbonate solid with radioactivity C14;
(4) grinding the sodium bicarbonate solid prepared in the step (3) by using a ball mill in a dry grinding manner to form sodium bicarbonate powder with radioactive C14;
(5) mixing sodium bicarbonate powder with radioactive C14 with fly ash, mixing the sodium bicarbonate powder and the fly ash according to the weight ratio of 1.2: 0.5, and fully and uniformly stirring to form mixed powder;
(6) adding distilled water into the mixed powder, mixing the mixed powder and the distilled water according to the weight ratio of 1.7: 1, mixing and fully and uniformly stirring to prepare radioactive sodium bicarbonate slurry;
B. determining the range of the coal seam detection area and drilling holes: the spontaneous combustion tendency of the coal seam is determined by using a known method, a coal seam area with the spontaneous combustion tendency of the coal seam being easy to spontaneously combust and spontaneously combust is selected as a coal seam detection area, then a plurality of drill holes with the interval of 80m are drilled in the coal seam detection area at equal intervals in the longitudinal direction and the transverse direction, and the volume of each drill hole is at least 3.5m 3 ；
C. Injecting radioactive sodium bicarbonate slurry: injecting the radioactive sodium bicarbonate slurry prepared in the step A into each drill hole by adopting an underground movable grouting pump under the pressure of 2.5MPa, and further enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal body crack;
D. and (3) judging the coal spontaneous combustion area: the procedure was exactly the same as in example 1, and is plotted in FIG. 2.
Example 3:
the specific steps of this embodiment are:
A. preparation of radioactive sodium bicarbonate slurry:
(1) under the condition that the temperature is 30 ℃, firstly, distilled water is injected into a container, sodium bicarbonate powder is added into the distilled water, the weight ratio of the distilled water to the sodium bicarbonate is 1: 0.4, and the mixture is fully and uniformly stirred until the mixture is completely dissolved to prepare a saturated solution of the sodium bicarbonate;
(2) introducing carbon dioxide containing radioactive C14 into saturated solution of sodium bicarbonate, and reacting with sodium bicarbonate for 90min to obtain mixed solution;
(3) after the reaction is completed, the temperature of the mixed solution is reduced to cool and crystallize the mixed solution to prepare sodium bicarbonate solid with radioactivity C14;
(4) grinding the sodium bicarbonate solid prepared in the step (3) by a dry grinding mode by using a ball mill to form sodium bicarbonate powder with radioactivity C14;
(5) mixing sodium bicarbonate powder with radioactive C14 with fly ash, mixing the sodium bicarbonate powder and the fly ash according to the weight ratio of 1: 0.5, and fully and uniformly stirring to form mixed powder;
(6) adding distilled water into the mixed powder, mixing the mixed powder and the distilled water according to the weight ratio of 1.5: 1, mixing and fully and uniformly stirring to prepare radioactive sodium bicarbonate slurry;
B. determining the range of the coal seam detection area and drilling holes: the spontaneous combustion tendency of the coal seam is determined by using a known method, a coal seam area with the spontaneous combustion tendency of the coal seam being easy to spontaneously combust and spontaneously combust is selected as a coal seam detection area, then a plurality of drill holes with the interval of 50m are drilled in the coal seam detection area at equal intervals in the longitudinal direction and the transverse direction, and the volume of each drill hole is at least 3.5m 3 ；
C. Injecting radioactive sodium bicarbonate slurry: injecting the radioactive sodium bicarbonate slurry prepared in the step A into each drill hole by adopting a downhole movable grouting pump at the pressure of 3MPa, and further enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal body crack;
D. and (3) judging the coal spontaneous combustion area: the procedure was exactly the same as in example 1, and is plotted in FIG. 3.
From FIGS. 1 to 3, it can be seen that:
the data graph measured by the detection method of the embodiment 1 shows a trend of ascending first and then descending, and the peak value is 976 dpm/mmol;
the data graph measured by the detection method of the embodiment 2 shows a trend of ascending firstly and then leveling, and the peak value is 1189 dpm/mmol;
the data graph measured by the detection method of the embodiment 3 shows a trend of ascending first and then descending, and the peak value is 1556 dpm/mmol;
in the field of coal mines, the C14 detector is used for detecting whether gas contains C14 and the content of radioactive substances to judge the spontaneous combustion condition and range of the coal mine, and the detected data can be preferably stable and have certain regularity, so that the spontaneous combustion range of the coal mine can be accurately judged. Comparing the three data graphs, the data measured by the graph 2 has higher reliability and stability. Therefore, the overall scheme adopted in example 2 is the optimal scheme. Meanwhile, according to the data obtained by detection, when the emission of the C14 detected by extracting gas continuously twice in any drill hole is 600-1200 dpm/mmol, the spontaneous combustion of the coal bed detection area around the drill hole is judged, and the higher the spontaneous combustion temperature of the coal body is, the higher the slope of the obtained emission change diagram of the C14 is.
Claims (3)
1. A method for judging a coal mine spontaneous combustion area based on detection of C14 radioactive quantity is characterized by comprising the following specific steps:
A. preparation of radioactive sodium bicarbonate slurry:
(1) under the condition that the temperature is 30 ℃, firstly, injecting distilled water into a container, adding sodium bicarbonate powder into the distilled water, fully and uniformly stirring the distilled water and the sodium bicarbonate in a weight ratio of 1: 0.4 until the distilled water and the sodium bicarbonate are completely dissolved to prepare a saturated solution of the sodium bicarbonate;
(2) introducing carbon dioxide containing radioactive C14 into saturated solution of sodium bicarbonate, and reacting with sodium bicarbonate for 90min to obtain mixed solution;
(3) after the reaction is completed, the temperature of the mixed solution is reduced to cool and crystallize the mixed solution to prepare sodium bicarbonate solid with radioactivity C14;
(4) grinding the sodium bicarbonate solid prepared in the step (3) by using a ball mill in a dry grinding manner to form sodium bicarbonate powder with radioactive C14;
(5) mixing sodium bicarbonate powder with radioactivity C14 with fly ash, mixing the sodium bicarbonate powder with the fly ash according to the weight ratio of 1-1.5: 0.5, and fully and uniformly stirring to form mixed powder;
(6) adding distilled water into the mixed powder, mixing, and mixing the mixed powder and the distilled water in a weight ratio of 1.5-2: 1, and fully and uniformly stirring to prepare radioactive sodium bicarbonate slurry;
B. determining the extent of a coal seam detection zone and drilling a boreholeSetting: the spontaneous combustion tendency of the coal seam is determined by using a known method, a coal seam area with the spontaneous combustion tendency of the coal seam being easy to spontaneously combust and spontaneously combust is selected as a coal seam detection area, then a plurality of drill holes with the interval of 50-100 m are drilled in the coal seam detection area at equal intervals in the longitudinal direction and the transverse direction, and the volume of each drill hole is at least 3.5m 3 ；
C. Injecting radioactive sodium bicarbonate slurry: injecting the radioactive sodium bicarbonate slurry prepared in the step A into each drill hole by adopting an underground movable grouting pump under the pressure of 2.5-3 MPa, and then enabling the radioactive sodium bicarbonate slurry to enter a detection area through a coal crack;
D. and (3) judging the coal spontaneous combustion area:
injecting radioactive sodium bicarbonate slurry into the drill holes for 3 hours, and extracting gas in each drill hole once;
secondly, extracting gas in each drill hole every 5h, continuing until each drill hole is extracted for 10 times, stopping extracting, and labeling the extracted gas for each time;
thirdly, detecting extracted gas by using a C14 detector for C14, detecting whether the gas extracted each time by each drill hole contains C14 radioactive elements, and if the gas does not contain C14 radioactive elements, indicating that radioactive sodium bicarbonate in the slurry is not heated and decomposed, thereby determining that spontaneous combustion does not occur in a coal seam detection area around the drill hole; if the radioactive element C14 exists, the radioactive content C14 is determined, the radioactive sodium bicarbonate in the slurry is decomposed by heat, and the detection result of each drill hole is drawn into a change curve in a C14 radioactive quantity-time two-dimensional graph, wherein the radioactive sodium bicarbonate starts to be decomposed when the temperature exceeds 50 ℃, the decomposition speed is higher along with the higher temperature, and the decomposition is complete when the temperature reaches 270 ℃;
and fourthly, if the detected C14 radioactive contents of the gas extracted for two times continuously from any drill hole are all within 600-1200 dpm/mmol, determining that the spontaneous combustion condition occurs in the coal seam detection area around the drill hole.
2. The method for determining the spontaneous combustion zone of a coal mine based on the detection of the emission of C14 of claim 1, wherein the plurality of boreholes are spaced apart by 80 m.
3. The method for judging the spontaneous combustion region of a coal mine based on the detection of the radioactivity of C14, according to claim 1, wherein the mixed powder is prepared by mixing sodium bicarbonate and fly ash in a weight ratio of 1.2: 0.5; and the mixed powder and distilled water are mixed according to the weight ratio of 1.7: 1 to prepare radioactive sodium bicarbonate slurry.
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