CN108760983B - Coal face natural fire early warning method of graded composite index system - Google Patents
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Abstract
The invention provides a hierarchical compositionAccording to the coal face natural ignition early warning method of the index system, the reference values of the CO critical values of the goaf oxidation zone, the return air corner and the return air flow are obtained through test data, and meanwhile, the content of the CO of the goaf oxidation zone, the return air corner and the return air flow is actually measured to serve as the reference values of the CO critical values, so that the actual measurement result and the test measurement result are combined, and the critical values of the natural ignition CO of the goaf oxidation zone and the return air corner are determined through combination of the actual measurement result and the test measurement result. Thereafter, whether C is present in the further gob2H4And C2H2The gas is given an early warning level. The scheme provided by the invention can obtain the critical value of CO through comprehensive consideration of field measurement results and test results, and reasonably divides and forecasts the early warning level by combining different gas compositions, thereby accurately providing theoretical and application basis for the natural fire early warning of the coal face, and the method is effective and reliable.
Description
Technical Field
The invention relates to a natural fire early warning method for a coal mine, in particular to a natural fire early warning method for a coal face of a hierarchical composite index system.
Background
Coal spontaneous combustion is one of the main causes of coal mine fires. Coal mine fires not only cause serious coal resource waste, but also threaten the personal safety of underground operators, and the natural coal ignition prediction is that spontaneous combustion is judged according to signs and observation results appearing in the natural coal ignition process, and the development trend of spontaneous combustion is predicted and inferred, so that effective fire prevention and extinguishing measures can be taken timely, resource, equipment and even life loss is avoided, and safe production is guaranteed. The coal spontaneous combustion forecasting technology is mainly a mark gas analysis method, and is a method for identifying and forecasting the spontaneous combustion ignition state of coal according to characteristic parameters such as gas generated in the spontaneous combustion process of the coal, temperature change and the like, wherein the medium temperature is increased due to the fact that the contact oxidation heat storage of the mined loose residual coal and oxygen in the air is carried out.
The marker gas analysis method is to analyze CO and C2H4、C2H2The method is characterized in that gases generated in the spontaneous combustion temperature rise oxidation process of coal such as alkane-alkene ratio, alkane ratio and the like are used as indexes for judging the ignition state, and certain mathematical rules exist between the concentration and the speed of the generated gases in the oxidation temperature rise process, the ratio of specific gases and the temperature of the index gases. In the practical application process of the mine, the spontaneous combustion and ignition process of the coal is judged by monitoring or manually sampling the concentration of one or more marker gases through a beam tube, and the increase rate change characteristics of certain gas components or the ratio change rule among certain gas components can be used for prediction.
The coal mine safety regulations (2016 edition) stipulate: when the spontaneous combustion and spontaneous combustion coal layers are mined, spontaneous combustion ignition monitoring work must be carried out, a spontaneous combustion ignition monitoring system is established, the spontaneous combustion ignition identification gas and the critical value of the coal layers are determined, and a spontaneous combustion ignition prediction and management system is perfected. The critical value of the spontaneous combustion ignition mark gas is determined through experimental research, field test and statistical analysis according to specific conditions, and the limit value of the CO concentration in the wind flow specified in No. 135 of coal mine safety regulations is not more than 0.0024 percent and is an occupational health index and is not the critical value of spontaneous combustion ignition. At the present stage, no method capable of measuring the critical value of the spontaneous combustion ignition CO marker gas exists, the underground spontaneous combustion ignition condition cannot be forecasted, and efficient and safe production of a mine is not facilitated.
Disclosure of Invention
The invention aims to solve the technical problem that the accuracy of early warning the spontaneous combustion of coal on a coal face in the prior art is low, and further provides a method for early warning the spontaneous combustion by adopting a graded composite index system, which is suitable for coal mining work.
In order to solve the technical problem, the invention provides a coal face natural fire early warning method of a hierarchical composite index system, which comprises the following steps:
acquiring field data: collecting a gas sample of a goaf oxidation zone in a determination period as a first gas sample, and obtaining a first reference value a of a goaf oxidation zone critical value according to the content of CO in the first gas sample; collecting a gas sample of the return air corner in a measuring period to be used as a second gas sample, and obtaining a first reference value b of a return air corner critical value according to the content of CO in the second gas sample; collecting a gas sample at the return air flow in a measuring period to be used as a third gas sample, and obtaining a critical value c of natural ignition CO of the return air flow according to the content of CO in the third gas sample;
test data acquisition step: acquiring the CO generation rate of a coal body at a coal face when the temperature is T; obtaining a second reference value A of a critical value of the oxidation zone of the goaf according to the coal amount of the oxidation zone of the goaf, the space for containing gas and the CO generation rate, and obtaining a critical value A of the spontaneous ignition CO of the oxidation zone of the goaf according to the first reference value a of the critical value of the oxidation zone of the goaf and the second reference value A of the critical value of the oxidation zone of the goaf0(ii) a Obtaining a second reference value B of a return air corner critical value according to the quantity of the coal at the return air corner, the space for containing the gas and the CO generation rate, and obtaining a critical value B of the CO naturally ignited at the return air corner according to the first reference value B of the return air corner critical value and the second reference value B of the return air corner critical value0；
Early warning level determination: according to the concentration of CO in the oxidation zone of the goaf and the critical value A of CO naturally ignited in the oxidation zone of the goaf0Relation of (3), oxidation zone of goaf C2H4And C2H2Critical value B of content, return air corner CO concentration and return air corner spontaneous ignition CO0Relation of (1), corner of return air C2H4And C2H2The content, the concentration of the CO in the return air flow and the critical value c of the natural ignition CO in the return air flow are closedSystem and return air flow position C2H4And C2H2And determining the natural fire early warning level of the working face according to the content and sending early warning information corresponding to the early warning level.
Optionally, in the coal face natural fire early warning method of the hierarchical composite index system, the test data acquiring step includes:
obtaining a second reference value A of the critical value of the oxidation zone of the goaf according to the following formula:
the second reference value B of the return air corner critical value is obtained according to the following formula:
in the above formula, the first and second light sources are,
the permeability coefficient in the goaf is taken as the permeability coefficient; k is a radical of1The oxidation degree coefficient of the residual coal in the goaf oxidation zone is obtained; z1The width of an oxidation zone at the air return side of the goaf; y is1The width of the air inlet side oxidation zone is set; y is2The width of the heat dissipation belt at the air inlet side is the width of the heat dissipation belt at the air inlet side; k is a radical of2The oxidation degree coefficient of the heat dissipation zone residual coal in the goaf is determined;
the recovery rate of the working face is;CO(T) is the CO production rate of the coal body at a temperature T; l is the length of the working face; h is the thickness of the mined coal bed; qLeakage netThe air leakage rate of the working face is increased.
Optionally, in the coal face natural fire early warning method of the hierarchical composite index system, the test data acquiring step includes:
critical value A of natural ignition CO in oxidation zone of goaf0MAX (a, a); critical value B of natural ignition CO of return air corner0＝MAX(b，B)。
Optionally, in the above coal face natural fire early warning method of a hierarchical composite index system, the early warning level in the early warning level determining step includes four levels, where:
level i early warning level: concentration of CO in oxidation zone of goaf<A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a And, the return corner CO concentration<B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a And, the return air stream CO concentration<C, no gas C appears at the return air flow2H4And C2H2；
Level II early warning level: concentration of CO in oxidation zone of goaf>A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, no gas C appears at the return air flow2H4And C2H2；
Grade iii early warning level: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4Without the presence of gas C2H2(ii) a Or return corner CO concentration>B0Air C is present at the corner of the return air2H4Without the presence of gas C2H2(ii) a Or the CO concentration of the return air flow>C, gas C appears at the return air flow2H4Without the presence of gas C2H2；
Grade iv early warning level: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C is present at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, gas C appears at the return air flow2H4And C2H2。
Optionally, in the above coal face natural fire early warning method of a hierarchical composite index system, the early warning level determining step further includes: calling pre-stored plan information corresponding to the early warning level, wherein related personnel, communication modes of the related personnel and operations to be executed are recorded in the plan information; and sending the early warning level and the operation to be executed to related personnel according to the communication mode.
Optionally, in the coal face natural fire early warning method of the hierarchical composite index system, in the early warning level determining step, the CO generation rate of the coal body at the temperature T is obtained by the following method: collecting a test coal sample on the coal wall of the coal face; putting the test coal sample into a coal spontaneous combustion simulation test device, and determining the air supply flow, the heating rate and the gas sample collection interval time; and acquiring the CO generation rate of the coal body at the temperature T measured by the coal spontaneous combustion simulation test device.
Optionally, in the above coal face natural fire early warning method of the graded composite index system, the coal sample particle size of the test coal sample is less than 0.15mm, and the weight is 1 g; the air supply flow rate is 100 ml/min;
the temperature rise rate is 0.5 ℃/min within the temperature range of 25-80 ℃, the temperature rise rate is 1.0 ℃/min within the temperature range of 80-200 ℃, and the temperature rise rate is 2.0 ℃/min within the temperature range of 200-300 ℃; the interval time of gas sample collection is less than 20 min/time.
Optionally, in the coal face natural fire early warning method of the hierarchical composite index system, the field data acquisition step includes:
collecting a gas sample of a goaf oxidation zone in a measuring period as a first gas sample, and obtaining a first reference value a of a goaf oxidation zone critical value according to the content of CO in the first gas sample comprises the following steps: on each day within the assay cycle: taking a first gas sample from a bundle pipe embedded in a goaf along the direction of a roadway in a working face return air crossheading; measuring the content of CO in the first gas sample by using a gas chromatograph; taking the average value of the CO content in the first gas sample measured every day as a first reference value a of the critical value of the oxidation zone of the goaf;
collecting a gas sample of the return air corner in a measuring period to be used as a second gas sample, and obtaining a first reference value b of the return air corner critical value according to the content of CO in the second gas sample comprises the following steps: on each day within the assay cycle: collecting a second gas sample at the corner of the return air, and measuring the content of CO in the second gas sample by using a gas chromatograph; taking the average value of the CO content in the second gas sample measured every day as a first reference value b of the critical value of the return air corner;
acquiring a gas sample at the position of the return air flow in a measuring period as a third gas sample, and obtaining a critical value c of natural ignition CO of the return air flow according to the content of CO in the third gas sample comprises the following steps: collecting a third gas sample at the return air flow, and measuring the content of CO in the third gas sample by using a gas chromatograph; and taking the average value of the CO content in the third gas sample measured every day as the critical value c of the natural ignition CO of the return air flow.
Optionally, in the coal face natural fire early warning method of the graded composite index system, the measurement period is more than or equal to 30 days.
Compared with the prior art, the technical scheme provided by the invention at least has the following beneficial effects:
according to the coal face natural ignition early warning method of the grading composite index system, the reference values of the CO critical values of the goaf oxidation zone, the return air corner and the return air flow are obtained through test data, and meanwhile, the content of the CO of the goaf oxidation zone, the return air corner and the return air flow is actually measured to serve as the reference value of the CO critical value, so that the critical value of the natural ignition CO of the goaf oxidation zone and the critical value of the natural ignition CO of the return air corner are determined by combining the actual measurement result of a site and the test measurement result. Thereafter, whether C is present in the further gob2H4And C2H2The gas is given an early warning level. The scheme provided by the invention can obtain the critical value of CO through comprehensive consideration of field measurement results and test results, and reasonably divides and forecasts the early warning level by combining different gas compositions, thereby accurately providing theoretical and application basis for the natural fire early warning of the coal face, and the method is effective and reliable.
Drawings
Fig. 1 is a flowchart of a coal face natural fire early warning method of a hierarchical composite index system according to an embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be described below by way of example with reference to the drawings in the present embodiment. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description of the present invention, and do not indicate or imply that the device or assembly referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Wherein the terms "first position" and "second position" are two different positions.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, and the two components can be communicated with each other. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The embodiment provides a coal face natural fire early warning method of a hierarchical composite index system, as shown in fig. 1, including the following steps:
s1: acquiring field data: collecting a gas sample of a goaf oxidation zone in a determination period as a first gas sample, and obtaining a first reference value a of a goaf oxidation zone critical value according to the content of CO in the first gas sample; collecting a gas sample of the return air corner in a measuring period to be used as a second gas sample, and obtaining a first reference value b of a return air corner critical value according to the content of CO in the second gas sample; collecting a gas sample at the return air flow in a measuring period to be used as a third gas sample, and obtaining a critical value c of natural ignition CO of the return air flow according to the content of CO in the third gas sample; as described above, the longer the measurement period, the more accurate the result is, and preferably, the measurement period is 30 days or more, and for example, one month, forty-five days, or the like may be selected as the measurement period. The CO content value range under normal conditions is obtained by detecting the CO content conditions of the goaf oxidation zone, the return air corner and the return air flow in a longer period, and then the CO content value range is used as a reference value of the CO content of the three places, wherein the three places are most representative when in the coal face, so that the detection results of the marked gas at the three places can be used as early warning judgment standards. Specifically, a, b, c can be obtained in the following manner.
On each day within the assay cycle: taking a first gas sample from a bundle pipe embedded in a goaf along the direction of a roadway in a working face return air crossheading; measuring the content of CO in the first gas sample by using a gas chromatograph; taking the average value of the CO content in the first gas sample measured every day as a first reference value a of the critical value of the oxidation zone of the goaf; on each day within the assay cycle: collecting a second gas sample at the corner of the return air, and measuring the content of CO in the second gas sample by using a gas chromatograph; taking the average value of the CO content in the second gas sample measured every day as a first reference value b of the critical value of the return air corner; collecting a third gas sample at the return air flow, and measuring the content of CO in the third gas sample by using a gas chromatograph; and taking the average value of the CO content in the third gas sample measured every day as the critical value c of the natural ignition CO of the return air flow.
S2: test data acquisition step: acquiring the CO generation rate of a coal body at a coal face when the temperature is T; obtaining a second reference value A of a critical value of the oxidation zone of the goaf according to the coal amount of the oxidation zone of the goaf, the space for containing gas and the CO generation rate, and obtaining a critical value A of the spontaneous ignition CO of the oxidation zone of the goaf according to the first reference value a of the critical value of the oxidation zone of the goaf and the second reference value A of the critical value of the oxidation zone of the goaf0When the concrete implementation is carried out, the method can be selectedA calculation method is selected to calculate a critical value of the naturally-ignited CO in the goaf oxidation zone, for example, a weighting algorithm is used to set a weight value for the first reference value a of the goaf oxidation zone critical value and the second reference value a of the goaf oxidation zone critical value, and then a weighted average value of the two values is calculated0MAX (a, a); obtaining a second reference value B of a return air corner critical value according to the quantity of the coal at the return air corner, the space for containing the gas and the CO generation rate, and obtaining a critical value B of the CO naturally ignited at the return air corner according to the first reference value B of the return air corner critical value and the second reference value B of the return air corner critical value0In a specific implementation, a calculation method may be selected to calculate the critical value of the return-air corner spontaneous-ignition CO, for example, a weighting algorithm is used to set weight values for the first reference value B of the return-air corner oxidation zone critical value and the second reference value B of the return-air corner critical value, and then a weighted average of the two values is calculated0MAX (B, B); that is, when the critical value is selected, the larger data of the field measurement reference value and the test reference value is selected as the critical value, because after a large number of tests are compared, the difference between the CO content value measured on the field and the CO content value obtained by the test is not very large, the larger value between the two values is selected in consideration of not bringing great interference to the field working environment, the alarm is prevented from being frequently generated on the field, and in addition, the larger value of the two values is selected, and no potential safety hazard exists.
Above, the CO production rate of the coal body at the temperature T is obtained by:
collecting a test coal sample on the coal wall of the coal face; putting the test coal sample into a coal spontaneous combustion simulation test device, and determining the air supply flow, the heating rate and the gas sample collection interval time; and acquiring the CO generation rate of the coal body at the temperature T measured by the coal spontaneous combustion simulation test device. The above test process has related standards in the technical field of coal mining, and can be inquired, and can be carried out in the following modes during specific implementation: the granularity of the coal sample of the test coal sample is less than 0.15mm, and the weight of the test coal sample is 1 g; the air supply flow rate is 100 ml/min; the temperature rise rate is 0.5 ℃/min within the temperature range of 25-80 ℃, the temperature rise rate is 1.0 ℃/min within the temperature range of 80-200 ℃, and the temperature rise rate is 2.0 ℃/min within the temperature range of 200-300 ℃; the interval time of gas sample collection is less than 20 min/time. The coal spontaneous combustion simulation test device can be realized by adopting the existing products in the prior art.
Further, in the present embodiment, the second reference value a of the critical value of the goaf oxidation zone is obtained according to the following formula:
the second reference value B of the return air corner critical value is obtained according to the following formula:
in the above formula, the first and second light sources are,
the permeability coefficient in the goaf is taken as the permeability coefficient; k is a radical of1The oxidation degree coefficient of the residual coal in the goaf oxidation zone is obtained; z1The width of an oxidation zone at the air return side of the goaf; y is1The width of the air inlet side oxidation zone is set; y is2The width of the heat dissipation belt at the air inlet side is the width of the heat dissipation belt at the air inlet side; k is a radical of2The oxidation degree coefficient of the heat dissipation zone residual coal in the goaf is determined;
the recovery rate of the working face is;CO(T) is the CO production rate of the coal body at a temperature T; l is the length of the working face; h is the thickness of the mined coal bed; qLeakage netThe air leakage rate of the working face is increased.
The actual geographic environment parameters in the goaf can be obtained by means of field measurement or by means of looking up published documents.
S3: early warning level determination: according to the concentration of CO in the oxidation zone of the goaf and the critical value A of CO naturally ignited in the oxidation zone of the goaf0Relation of (3), oxidation zone of goaf C2H4And C2H2Critical value B of content, return air corner CO concentration and return air corner spontaneous ignition CO0Relation of (1), corner of return air C2H4And C2H2The content, the relation between the concentration of CO in the return air flow and the critical value C of the natural ignition CO in the return air flow, and the C at the return air flow2H4And C2H2And determining the natural fire early warning level of the working face according to the content and sending early warning information corresponding to the early warning level.
Specifically, the early warning level includes four levels, wherein:
the I-level early warning level is a security level and needs to meet the following requirements: concentration of CO in oxidation zone of goaf<A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a And, the return corner CO concentration<B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a And, the return air stream CO concentration<C, no gas C appears at the return air flow2H4And C2H2；
The level II early warning level corresponds to the oxidation state and needs to meet the following requirements: concentration of CO in oxidation zone of goaf>A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, no gas C appears at the return air flow2H4And C2H2；
A grade III early warning grade corresponding to an accelerated oxidation state, which needs to satisfy the following requirements: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4Without the presence of gas C2H2(ii) a Or return corner CO concentration>B0Air C is present at the corner of the return air2H4Without the presence of gas C2H2(ii) a Or the CO concentration of the return air flow>C, gas C appears at the return air flow2H4Without the presence of gas C2H2；
And IV-level early warning level, which corresponds to an open fire state and needs to satisfy the following requirements: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C is present at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, gas C appears at the return air flow2H4And C2H2。
According to the scheme, a calculation formula of natural ignition mark gas CO reference values of the goaf oxidation zone and the return air corner is provided, critical values of natural ignition mark gas CO at the goaf oxidation zone, the return air corner and the return air flow are determined, safety states, oxidation states, accelerated oxidation states and open fire states of the coal face are determined according to IV levels, early warning is carried out according to positions, corresponding fire prevention and extinguishing measures are taken, theories and application bases are provided for natural ignition early warning of the coal face, and the method is effective and reliable.
Preferably, in the above scheme, the early warning level determining step further includes:
calling pre-stored plan information corresponding to the early warning level, wherein related personnel, communication modes of the related personnel and operations to be executed are recorded in the plan information; and sending the early warning level and the operation to be executed to related personnel according to the communication mode.
The schedule information may refer to an example shown in table 1. Referring to table 1, a coal face natural ignition graded composite early warning system personnel emergency response suggestion table implements graded response measures.
TABLE 1 staff emergency response suggestion table of natural ignition grading composite early warning system for coal face
The contact information of each worker in the individual response part can be associated with the individual response part, and the contact information can be a telephone, a mailbox and the like. Once the early warning level is determined, the early warning level and the corresponding measures in the table can be directly sent to the contact way of the corresponding staff. Further, the method can further comprise the step of receiving operation feedback information of the staff to determine the result or effect of the staff after executing corresponding measures, and whether the potential safety hazard can be avoided, and the early warning level is prevented from changing to a higher level.
A specific example is provided below to illustrate the implementation of the above process:
collecting coal sample on coal wall of coal face, preparing test coal sample, placing the test coal sample into natural coal ignition test device, testing coal sample granularity<0.15mm, 1g in weight, determining the flow of air supply of 100ml/min, the heating rate of 0.5 ℃/min at 25-80 ℃, 1.0 ℃/min at 80-200 ℃, 2.0 ℃/min at 200-300 ℃, keeping the temperature of 2.0 ℃/min after 300 ℃, the gas sample collection interval time of 15 min/time, and obtaining the CO generation rate of the coal body at the temperature of T through testsCO(T) in mol.cm-3.s-1。
The method comprises the following steps of burying a beam tube in a working face return air gate along the roadway direction to a goaf to take a gas sample, measuring the average value of days of a natural ignition mark gas CO by using a gas chromatograph 40 days as a first reference value a of a goaf oxidation zone critical value 240ppm, measuring the average value of days of a natural ignition mark gas CO by using a gas chromatograph 40 days of a return air corner as a first reference value b of a return air corner critical value 57.6ppm, measuring the average value of days of a natural ignition mark gas CO by using a gas chromatograph 40 days of a return air corner at a return air position as a return air flow critical value c of the natural ignition mark gas CO as 18ppm, and calculating a formula according to the CO concentration in the goaf oxidation zone:
calculating a second reference value A of a critical value of the natural ignition oxidation mark gas CO in the oxidation zone of the goaf to be 224ppm, and according to a calculation formula of the concentration of the CO at the return corner:
and calculating the critical value second reference value B of the return air corner spontaneous ignition oxidation mark gas CO to be 56.6 ppm.
In the above formula:
in order to obtain the permeability coefficient in the goaf, the fully mechanized caving face is generally 0.5-0.7, and the median value is 0.6 in the embodiment; k is a radical of1Taking the oxidation degree coefficient of the residual coal in the oxidation zone of the goaf to be 0.4 and less than 1 (generally, taking 0.2-0.4 of the fully mechanized caving face); z1The width of an oxidation zone at the return air side of the goaf is expressed in m, and the actual measurement is 15 m; y is1The unit is m, and the actual measurement is 70 m; y is2The width of a heat dissipation belt at the air inlet side is m, and the actual measurement is 80 m; k is a radical of2Taking the oxidation degree coefficient of residual coal in the heat dissipation zone of the goaf to be 0.9 (generally taking 0.8-1 under the normal air leakage condition, and taking the coefficient to be less than 0.5 if the air leakage rate is less than 1 percent); z2The width of the heat dissipation zone of the goaf is m; actual measurement was 80 m;
taking 75/%, which is the recovery rate of the working face;CO(T) is the CO production rate (determined by coal spontaneous combustibility experiment) mol.cm of coal body at temperature T-3.s-1And tested to obtain 0.17mol.cm-3.s-1(ii) a L is the length of the working surface in m, which is not measured to be 240 m; h is the thickness of the mined coal bed, the unit is m, and the actual measurement is 6.1 m; qLeakage netFor the air leakage m of the working face3Min, actual measurement is 110m3Min, critical value A of natural ignition mark gas CO in oxidation zone of goaf0MAX (a, a) MAX (240, 224) 240ppm, critical value B of return air corner spontaneous ignition flag gas CO0＝MAX(b，B)＝MAX(57.6，56.6)＝57.6ppm。
According to the calculation results, when monitoring the goaf oxidation zone, the return air corner and the return air flow of the coal face, the coal face is graded as follows:
when the goaf is in the oxidation zone of CO concentration<240ppm, gas C therein2H4Not present, gas C2H2Not present and return corner CO concentration<57.6ppm of gas C2H4Not present, gas C2H2Not present and the return air stream CO concentration<18ppm of gas C2H4Not present, gas C2H2If the signal is not present, the signal is in a safe state and is defined as I level;
when the goaf is in the oxidation zone of CO concentration>240ppm of gas C2H4Not present, gas C2H2Not present, or return corner CO concentration>57.6ppm of gas C2H4Not present, gas C2H2Not present, or CO concentration of the return air stream>18ppm of gas C2H4Not present, gas C2H2The oxidation state is not appeared and is defined as II grade;
when the goaf is in the oxidation zone of CO concentration>240ppm of gas C2H4Appearance, gas C2H2Not present, or return corner CO concentration>57.6ppm of gas C2H4Appearance, gas C2H2Not present, or CO concentration of the return air stream>18ppm of gas C2H4Appearance, gas C2H2If not, the oxidation state is accelerated and is defined as III grade;
when the goaf is in the oxidation zone of CO concentration>240ppm of gas C2H4Appearance, gas C2H2Presence, or return corner CO concentration>57.6ppm of gas C2H4Appearance, gas C2H2Presence, or return air stream CO concentration>18ppm of gas C2H4Appearance, gas C2H2Appearing, and defining as IV grade.
The CO concentration monitored by the daily coal face goaf oxidation zone is 230ppm, and no C exists2H4、C2H2Gas appeared, and the return corner CO concentration is 56.6ppm, and no C2H4、C2H2Gas generationAnd the concentration of return air CO is 17.2ppm, and has no C2H4、C2H2Gas is present. Judging as I level, and in safe state, it is recommended to refer to I level response process in Table 1.
Wherein: and determining positions according to the classification states of the I level to the IV level, namely a safety state, an oxidation state, an accelerated oxidation state and an open fire state, carrying out early warning, and taking corresponding fire prevention and extinguishing measures.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A coal face natural fire early warning method of a hierarchical composite index system is characterized by comprising the following steps:
acquiring field data: collecting a gas sample of a goaf oxidation zone in a determination period as a first gas sample, and obtaining a first reference value a of a goaf oxidation zone critical value according to the content of CO in the first gas sample; collecting a gas sample of the return air corner in a measuring period to be used as a second gas sample, and obtaining a first reference value b of a return air corner critical value according to the content of CO in the second gas sample; collecting a gas sample at the return air flow in a measuring period to be used as a third gas sample, and obtaining a critical value c of natural ignition CO of the return air flow according to the content of CO in the third gas sample;
test data acquisition step: acquiring the CO generation rate of a coal body at a coal face when the temperature is T; obtaining a second reference value A of the critical value of the oxidation zone of the goaf according to the coal amount of the oxidation zone of the goaf, the space for containing gas and the CO generation rate, and obtaining natural emission of the oxidation zone of the goaf according to the first reference value a of the critical value of the oxidation zone of the goaf and the second reference value A of the critical value of the oxidation zone of the goafCritical value of fire CO A0(ii) a Obtaining a second reference value B of a return air corner critical value according to the quantity of the coal at the return air corner, the space for containing the gas and the CO generation rate, and obtaining a critical value B of the CO naturally ignited at the return air corner according to the first reference value B of the return air corner critical value and the second reference value B of the return air corner critical value0；
Early warning level determination: according to the concentration of CO in the oxidation zone of the goaf and the critical value A of CO naturally ignited in the oxidation zone of the goaf0Relation of (3), oxidation zone of goaf C2H4And C2H2Critical value B of content, return air corner CO concentration and return air corner spontaneous ignition CO0Relation of (1), corner of return air C2H4And C2H2The content, the relation between the concentration of CO in the return air flow and the critical value C of the natural ignition CO in the return air flow, and the C at the return air flow2H4And C2H2Determining the natural fire early warning level of a working face according to the content and sending early warning information corresponding to the early warning level;
the test data acquisition step comprises:
obtaining a second reference value A of the critical value of the oxidation zone of the goaf according to the following formula:
the second reference value B of the return air corner critical value is obtained according to the following formula:
in the above formula, the first and second light sources are,
the permeability coefficient in the goaf is taken as the permeability coefficient; k is a radical of1The oxidation degree coefficient of the residual coal in the goaf oxidation zone is obtained; z1The width of an oxidation zone at the air return side of the goaf; y is1The width of the air inlet side oxidation zone is set; y is2The width of the heat dissipation belt at the air inlet side is the width of the heat dissipation belt at the air inlet side; k is a radical of2To the heat dissipation of collecting space areaA coal oxidation degree coefficient;
the recovery rate of the working face is;CO(T) is the CO production rate of the coal body at a temperature T; l is the length of the working face; h is the thickness of the mined coal bed; qLeakage netThe air leakage rate of the working face is increased;
the early warning level determining step includes four levels, wherein:
level i early warning level: concentration of CO in oxidation zone of goaf<A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a And, the return corner CO concentration<B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a And, the return air stream CO concentration<C, no gas C appears at the return air flow2H4And C2H2；
Level II early warning level: concentration of CO in oxidation zone of goaf>A0Gas C does not appear at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C does not appear at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, no gas C appears at the return air flow2H4And C2H2；
Grade iii early warning level: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4Without the presence of gas C2H2(ii) a Or return corner CO concentration>B0Air C is present at the corner of the return air2H4Without the presence of gas C2H2(ii) a Or the CO concentration of the return air flow>C, gas C appears at the return air flow2H4Without the presence of gas C2H2；
Grade iv early warning level: concentration of CO in oxidation zone of goaf>A0Gas C appears at the oxidation zone of the goaf2H4And C2H2(ii) a Or, return corner CO concentration>B0Air C is present at the corner of the return air2H4And C2H2(ii) a Or, the CO concentration of the return air flow>C, gas C appears at the return air flow2H4And C2H2。
2. The coal face natural fire early warning method of the graded composite index system according to claim 1, wherein in the test data obtaining step:
critical value A of natural ignition CO in oxidation zone of goaf0MAX (a, a); critical value B of natural ignition CO of return air corner0＝MAX(b，B)。
3. The natural fire early warning method for the coal face of the graded composite index system according to claim 1, wherein the early warning level determining step further comprises:
calling pre-stored plan information corresponding to the early warning level, wherein related personnel, communication modes of the related personnel and operations to be executed are recorded in the plan information; and sending the early warning level and the operation to be executed to related personnel according to the communication mode.
4. The coal face natural fire early warning method of the graded composite index system according to any one of claims 1 to 3, wherein in the early warning level determination step, the CO production rate of the coal body at the temperature T is obtained by:
collecting a test coal sample on the coal wall of the coal face;
putting the test coal sample into a coal spontaneous combustion simulation test device, and determining the air supply flow, the heating rate and the gas sample collection interval time;
and acquiring the CO generation rate of the coal body at the temperature T measured by the coal spontaneous combustion simulation test device.
5. The coal face natural fire early warning method of the graded composite index system according to claim 4, characterized in that:
the granularity of the coal sample of the test coal sample is less than 0.15mm, and the weight of the test coal sample is 1 g;
the air supply flow rate is 100 ml/min;
the temperature rise rate is 0.5 ℃/min within the temperature range of 25-80 ℃, the temperature rise rate is 1.0 ℃/min within the temperature range of 80-200 ℃, and the temperature rise rate is 2.0 ℃/min within the temperature range of 200-300 ℃;
the interval time of gas sample collection is less than 20 min/time.
6. The coal face natural fire early warning method of the graded composite index system according to claim 4, characterized in that in the field data acquisition step:
collecting a gas sample of a goaf oxidation zone in a measuring period as a first gas sample, and obtaining a first reference value a of a goaf oxidation zone critical value according to the content of CO in the first gas sample comprises the following steps: on each day within the assay cycle: taking a first gas sample from a bundle pipe embedded in a goaf along the direction of a roadway in a working face return air crossheading; measuring the content of CO in the first gas sample by using a gas chromatograph; taking the average value of the CO content in the first gas sample measured every day as a first reference value a of the critical value of the oxidation zone of the goaf;
collecting a gas sample of the return air corner in a measuring period to be used as a second gas sample, and obtaining a first reference value b of the return air corner critical value according to the content of CO in the second gas sample comprises the following steps: on each day within the assay cycle: collecting a second gas sample at the corner of the return air, and measuring the content of CO in the second gas sample by using a gas chromatograph; taking the average value of the CO content in the second gas sample measured every day as a first reference value b of the critical value of the return air corner;
acquiring a gas sample at the position of the return air flow in a measuring period as a third gas sample, and obtaining a critical value c of natural ignition CO of the return air flow according to the content of CO in the third gas sample comprises the following steps: collecting a third gas sample at the return air flow, and measuring the content of CO in the third gas sample by using a gas chromatograph; and taking the average value of the CO content in the third gas sample measured every day as the critical value c of the natural ignition CO of the return air flow.
7. The coal face natural fire early warning method of the graded composite index system according to claim 6, wherein the measuring period is more than or equal to 30 days.
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