Prediction and control method for oxidation spontaneous combustion of coal dynamically retained in coal bucket

Abstract

The invention relates to the technical field of fire coal safety, in particular to a prediction and prevention method for oxidation spontaneous combustion of coal dynamically retained in a coal bucket. Comprising the steps of determining spontaneous combustion index rules of coal retained in a coal hopper at different accumulation speeds; establishing a multi-field coupling numerical simulation model, and determining the temperature change and distribution rule in the continuous retention and accumulation process of the coal in the coal bucket and the concentration change rule of O2 and CO in the coal bucket according to a numerical simulation result; setting temperature monitoring points according to a range change rule of the highest temperature area, and performing monitoring by taking a temperature value corresponding to the highest temperature area as a monitoring early warning value; and predicting the oxidation spontaneous combustion risk in the dynamic retention process of the coal in the coal bucket by combining the O2 concentration reduction rule, the CO concentration increase rule and the highest temperature of the coal retained in the coal bucket. According to the method, coal oxidation spontaneous combustion prediction and prevention under the dynamic accumulation condition are achieved, safe operation of the coal bucket can be guaranteed, and the heat value consumed by coal due to oxidation spontaneous combustion can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of coal burning safety, and in particular to a method for predicting and preventing oxidation and spontaneous combustion of dynamically retained coal in a coal hopper. Background Art

[0002] During the long-term coal transportation process, coal particles are easily retained and accumulated in the coal hopper. Long-term accumulation leads to an increase in the height of the retained coal. Under the induction of the wind flow in the coal hopper, after a certain period of time, the retained coal is prone to slowly oxidize and release heat to reach a state of spontaneous combustion. The retention, accumulation and oxidation of coal will not only cause the coal in the coal hopper to be in danger of fire and explosion, but also reduce the calorific value of the coal due to long-term slow oxidation.

[0003] The spontaneous combustion of coal is a relatively slow process and is not easy to detect in advance. The traditional method of judging the spontaneous combustion of coal in the raw coal hopper is mainly to manually conduct multi-point temperature measurement and appearance inspection on the hopper wall on a regular basis. However, this judgment method has a long interval and high labor cost, and it is difficult to achieve real-time monitoring.

[0004] The Chinese utility model patent with the authorization announcement number CN204745419U discloses a coal spontaneous combustion warning and fire prevention system for raw coal hoppers, which includes: a CO sensor, a smoke detector, and one or more of a plurality of temperature sensors, wherein the CO sensor is located at the top of the raw coal hopper to detect the concentration of CO at the top of the raw coal hopper, the smoke detector is located at the top of the raw coal hopper to detect the concentration of smoke at the top of the raw coal hopper, and a plurality of temperature sensors are located on the outer wall of the raw coal hopper at the point where spontaneous combustion is easy to occur, and are used to detect the temperature of the point where spontaneous combustion is easy to occur in the raw coal hopper; a CO2 gas cylinder connected to a first stop valve to provide CO2 gas; a controller connected to the CO sensor, the smoke detector, one or more of a plurality of temperature sensors, and the first stop valve to control the opening and closing of the first stop valve to connect or disconnect the CO2 gas cylinder according to the information of the CO sensor, the smoke detector, and one or more of a plurality of temperature sensors. The system can automatically warn and inertate the fire when spontaneous combustion occurs in the coal stored in the raw coal hopper. However, during the coal stacking process, the oxygen consumption, gas generation and heat release laws of the coal retained in the coal hopper are different at different stacking speeds. This scheme cannot predict spontaneous combustion under dynamic stacking conditions.

[0005] In order to solve this problem, a method for predicting and preventing oxidation and spontaneous combustion of dynamically retained coal in the coal hopper is urgently needed. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, the purpose of the present invention is to provide a method for predicting and preventing oxidation and spontaneous combustion of coal dynamically retained in a coal hopper, thereby ensuring the safe operation of the coal hopper and reducing the calorific value consumed by the oxidation and spontaneous combustion of the coal.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper, comprising the following steps:

[0008] S1: Conduct experiments on the spontaneous combustion law of coal oxidation under the condition of dynamic accumulation of coal in the coal hopper, and determine the spontaneous combustion index law of the coal retained in the coal hopper under different accumulation speeds;

[0009] S2: Establish a multi-field coupling numerical simulation model based on the multi-field coupling numerical simulation method;

[0010] S3: introducing the spontaneous combustion index law of the retained coal obtained in step S1 into the multi-field coupling numerical simulation model established in step S2, and combining the multi-field coupling conditions to carry out numerical simulation results of coal oxidation temperature rise, gas consumption and gas generation in the dynamic retention and accumulation process of coal in the coal hopper;

[0011] S4: Determine the temperature change and distribution law during the continuous retention and accumulation of coal in the coal hopper based on the numerical simulation results, and determine the change law of O2 and CO concentration in the coal hopper;

[0012] S5: According to the temperature change and distribution law in the process of continuous retention and accumulation of coal, determine the temperature value of the highest temperature area and the change law of the range of the highest temperature area in the process of coal retention;

[0013] S6: Set temperature monitoring points according to the range change rule of the highest temperature area, and monitor with the temperature value corresponding to the highest temperature area as the monitoring warning value;

[0014] S7: Based on the decreasing pattern of O2 concentration, increasing pattern of CO concentration and the maximum temperature of coal retained in the coal hopper, the risk of oxidation and spontaneous combustion during the dynamic retention process of coal in the coal hopper is predicted.

[0015] The present invention is further configured as follows: before conducting the experiment on the law of spontaneous combustion of coal oxidation, the dynamic accumulation conditions of the coal hopper are measured, including the coal accumulation rate of the coal hopper, the wind pressure difference between the coal hopper feed port and the coal hopper discharge port, and the air intake flow rate of the discharge port.

[0016] The present invention is further configured as follows: the spontaneous combustion index law includes oxygen consumption rate, gas generation rate and heat release rate.

[0017] The present invention is further configured as follows: the gas generation rate includes a CO generation rate and a CO2 generation rate.

[0018] The present invention is further configured as follows: Step S2 specifically comprises: using COMSOL software to construct a geometric physical model of the coal hopper, adopting multi-field control for the geometric physical model of the coal hopper, including five complex fields of free and porous medium flow field, solid and fluid heat transfer field, porous medium reaction field, dilute material transfer field, and deformation geometry, to establish a multi-field coupling numerical simulation model.

[0019] The present invention is further configured to: control the temperature and heat flow direction as coupling conditions between the free and porous medium flow field and the solid and fluid heat transfer field;

[0020] The gas basis and reaction temperature providing heat generation are used as coupling conditions for solid and fluid heat transfer fields and porous media reaction fields;

[0021] Controlling gas composition, consumption and production gas volumes as coupling conditions for porous media reaction field and dilute species transfer field;

[0022] The coupling conditions between the dilute material transfer field and the free and porous media flow field are as follows:

[0023] Using deformed geometry as coupling condition for free and porous media flow fields, solid and fluid heat transfer fields, porous media reaction fields, and dilute species transport fields;

[0024] The deformation geometry is the coal accumulation rate and coal accumulation height of the coal hopper.

[0025] The present invention is further configured as follows: in step S3, the temperature, gas concentration and coal accumulation height are used as dependent variables, and the transient solver MUMPS is used to solve the multi-field coupling numerical simulation model.

[0026] The present invention also relates to a method for preventing and controlling oxidation spontaneous combustion of coal dynamically retained in a coal hopper, wherein the above-mentioned method for predicting oxidation spontaneous combustion of coal dynamically retained in a coal hopper is used to predict the risk of oxidation spontaneous combustion, and the following steps are further included after step S7:

[0027] S8: When the coal trapped in the coal hopper reaches a risk state of spontaneous combustion, cooling liquid is injected into the highest temperature area of ​​the coal hopper.

[0028] The present invention is further configured as follows: the cooling liquid is liquid CO2.

[0029] In summary, the beneficial effects of the above technical solution of the present invention are as follows:

[0030] Based on the different oxygen consumption, gas generation and heat release laws of the coal retained in the coal hopper at different stacking speeds and heights, the present invention establishes a multi-field coupling numerical simulation model for prediction, thereby realizing the prediction and prevention of coal oxidation and spontaneous combustion under dynamic stacking conditions. This can not only ensure the safe operation of the coal hopper, but also reduce the calorific value consumed by the coal due to oxidation and spontaneous combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0032] Figure 1 Schematic diagram of the variation of oxygen consumption rate of coal retained in the coal hopper with temperature in the embodiment;

[0033] Figure 2 Schematic diagram of the variation of CO generation rate of the coal retained in the coal hopper with temperature in the embodiment;

[0034] Figure 3 Schematic diagram of the variation of CO2 generation rate of coal retained in the coal hopper with temperature in the embodiment;

[0035] Figure 4 Schematic diagram of the change of the upper limit of heat release rate of coal retained in the coal hopper with temperature in the embodiment;

[0036] Figure 5 is the multi-field coupling condition of the multi-field coupling numerical simulation model in the embodiment;

[0037] Figure 6 Schematic diagram of the temperature distribution in the coal hopper when the coal accumulation in the coal hopper reaches different heights in the embodiment;

[0038] Figure 7 The O2 concentration distribution in the coal hopper when the coal accumulation in the coal hopper reaches different heights in the embodiment;

[0039] Figure 8 The CO concentration distribution in the coal hopper when the coal accumulation in the coal hopper reaches different heights in the embodiment. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, other similar embodiments obtained by ordinary technicians in the field without making any creative work should all fall within the scope of protection of the present invention.

[0041] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0042] Embodiment 1:

[0043] like Figure 1-Figure 8 As shown in the figure, a preferred embodiment of the present invention is a method for predicting the oxidation and spontaneous combustion of coal dynamically retained in a coal hopper, comprising the following steps:

[0044] S1: Conduct an experiment on the spontaneous combustion law of coal oxidation under the condition of dynamic accumulation of coal in the coal hopper to determine the spontaneous combustion index law of the coal retained in the coal hopper under different accumulation speeds, including oxygen consumption rate, gas generation rate and heat release rate. The gas generation rate includes CO generation rate and CO2 generation rate.

[0045] Before conducting the experiment on the spontaneous combustion law of coal oxidation, the dynamic accumulation conditions of the coal hopper were measured, including the coal accumulation rate of the coal hopper, the wind pressure difference between the coal hopper inlet and the coal hopper outlet, and the air inlet flow rate at the outlet.

[0046] In this implementation, taking the coal accumulation thickness of 10 cm and the upper and lower wind pressure difference of 20 Pa as an example, the spontaneous combustion index law of the coal retained in the coal hopper is determined. The oxygen consumption rate, CO generation rate, CO2 generation rate, and heat release rate upper limit are as follows: Figure 1-Figure 4 shown.

[0047] S2: Establish a multi-field coupling numerical simulation model based on the multi-field coupling numerical simulation method;

[0048] like Figure 4 As shown, the geometric physical model of the coal hopper is constructed using COMSOL software, and multi-field control is adopted for the geometric physical model of the coal hopper, including five complex fields: free and porous medium flow field, solid and fluid heat transfer field, porous medium reaction field, dilute material transfer field, and deformation geometry, to establish a multi-field coupling numerical simulation model.

[0049] In this embodiment, the coal hopper includes three discharge ports at the lower end, each with a simplified width of 0.6m, and an upper end as a feed port, with a total width of 9m and a total height of 10m.

[0050] Controlling temperature and heat flow direction as coupling conditions between free and porous media flow fields and solid and fluid heat transfer fields;

[0051] The gas basis and reaction temperature providing heat generation are used as coupling conditions for solid and fluid heat transfer fields and porous media reaction fields;

[0052] Controlling gas composition, consumption and production gas volumes as coupling conditions for porous media reaction field and dilute species transfer field;

[0053] The coupling conditions between the dilute material transfer field and the free and porous media flow field are as follows:

[0054] Using deformed geometry as coupling condition for free and porous media flow fields, solid and fluid heat transfer fields, porous media reaction fields, and dilute species transport fields;

[0055] The deformation geometry is the coal accumulation rate and coal accumulation height of the coal hopper.

[0056] S3: The spontaneous combustion index law of the retained coal obtained in step S1 is introduced into the multi-field coupling numerical simulation model established in step S2, and the numerical simulation results of coal oxidation temperature rise, gas consumption and gas generation in the dynamic retention and accumulation process of coal in the coal hopper are carried out in combination with the multi-field coupling conditions; the temperature, gas concentration and coal accumulation height are taken as dependent variables, and the transient solver MUMPS is used to solve the multi-field coupling numerical simulation model.

[0057] S4: Determine the temperature change and distribution law during the continuous retention and accumulation of coal in the coal hopper according to the numerical simulation results, and determine the change law of O2 and CO concentration in the coal hopper; in this embodiment, take the daily coal accumulation thickness of 10cm and the upper and lower wind pressure difference of 20Pa as an example, and the distribution laws of the temperature, O2 concentration and CO concentration in the coal hopper after 30, 50, 70 and 90 days of accumulation are as follows: Figure 6-Figure 8 shown.

[0058] in, Figure 6 Figure a shows the temperature distribution in the coal hopper when the coal accumulation height reaches 3m; Figure 6 Figure b shows the temperature distribution in the coal hopper when the coal accumulation height reaches 5m; Figure 6 Figure c shows the temperature distribution in the coal hopper when the coal accumulation height reaches 7m; Figure 6 Figure d shows the temperature distribution in the coal hopper when the coal accumulation height reaches 9m.

[0059] Figure 7 Figure a shows the O2 concentration distribution in the coal hopper when the coal accumulation height reaches 3m; Figure 7 Figure b shows the O2 concentration distribution in the coal hopper when the coal accumulation height reaches 5m; Figure 7 Figure c shows the O2 concentration distribution in the coal hopper when the coal accumulation height reaches 7m; Figure 7 Figure d shows the O2 concentration distribution in the coal hopper when the coal accumulation height reaches 9m.

[0060] Figure 8 Figure a shows the CO concentration distribution in the coal hopper when the coal accumulation height reaches 3m; Figure 8 Figure b shows the CO concentration distribution in the coal hopper when the coal accumulation height reaches 5m; Figure 8 Figure c shows the CO concentration distribution in the coal hopper when the coal accumulation height reaches 7m; Figure 8 Figure d shows the CO concentration distribution in the coal hopper when the coal accumulation height reaches 9m.

[0061] S5: According to the temperature change and distribution law in the process of continuous retention and accumulation of coal, determine the temperature value of the highest temperature area and the change law of the range of the highest temperature area in the process of coal retention;

[0062] S6: Set temperature monitoring points according to the range change rule of the highest temperature area, and monitor with the temperature value corresponding to the highest temperature area as the monitoring warning value;

[0063] S7: Based on the decreasing pattern of O2 concentration, increasing pattern of CO concentration and the maximum temperature of coal retained in the coal hopper, the risk of oxidation and spontaneous combustion during the dynamic retention process of coal in the coal hopper is predicted.

[0064] According to the above steps, predictions are made according to different dynamic accumulation conditions to obtain the spontaneous combustion risk status under different dynamic accumulation conditions, and targeted predictions and prevention measures are carried out.

[0065] When the coal temperature rises to 70℃, it is the critical temperature point of the initial oxidation stage and the oxidation exothermic stage of coal. At this time, the spontaneous combustion process of coal oxidation is accelerated, oxygen is consumed rapidly, and the slow oxidation of coal produces CO. Therefore, the intersection of the three trend intervals of coal temperature rising to above 70℃ under dynamic stacking conditions, oxygen is consumed rapidly, and CO is continuously produced with gradually increasing concentration is regarded as the coal reaching a spontaneous combustion risk state.

[0066] In this embodiment, the dynamic accumulation conditions are set as a daily coal accumulation thickness of 10 cm and an upper and lower wind pressure difference of 20 Pa. After the coal is accumulated to 5 meters, the maximum temperature of the coal exceeds 70°C. After the coal is accumulated to 3 meters, oxygen is rapidly consumed. After the coal is accumulated to 3 meters, the CO concentration gradually increases. The intersection of the above conditions is taken, that is, after the coal is accumulated to 5 meters, the maximum temperature of the coal exceeds 70°C, and oxygen is rapidly consumed. The interval in which the CO concentration gradually increases is a spontaneous combustion risk state.

[0067] Embodiment 2:

[0068] The present invention also relates to a method for preventing and controlling oxidation spontaneous combustion of coal dynamically retained in a coal hopper, wherein the above-mentioned method for predicting oxidation spontaneous combustion of coal dynamically retained in a coal hopper is used to predict the risk of oxidation spontaneous combustion, and the following steps are further included after step S7:

[0069] S8: When the coal trapped in the coal hopper reaches a risk state of spontaneous combustion, liquid CO2 is injected from the highest temperature area of ​​the coal hopper to cool down and extinguish the fire. Specific measures and flow rates can be formulated based on actual conditions on site.

[0070] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for predicting oxidation and spontaneous combustion of dynamically retained coal in a coal hopper, characterized in that: The following steps are involved: S1: Conduct experiments on the spontaneous combustion law of coal oxidation under the condition of dynamic accumulation of coal in the coal hopper, and determine the spontaneous combustion index law of the coal retained in the coal hopper under different accumulation speeds; S2: Establish a multi-field coupling numerical simulation model based on the multi-field coupling numerical simulation method; S3: introducing the spontaneous combustion index law of the retained coal obtained in step S1 into the multi-field coupling numerical simulation model established in step S2, and combining the multi-field coupling conditions to carry out numerical simulation results of coal oxidation temperature rise, gas consumption and gas generation in the dynamic retention and accumulation process of coal in the coal hopper; S4: Determine the temperature change and distribution law during the continuous retention and accumulation of coal in the coal hopper based on the numerical simulation results, and determine the change law of O2 and CO concentration in the coal hopper; S5: According to the temperature change and distribution law in the process of continuous retention and accumulation of coal, determine the temperature value of the highest temperature area and the change law of the range of the highest temperature area in the process of coal retention; S6: Set temperature monitoring points according to the range change rule of the highest temperature area, and monitor with the temperature value corresponding to the highest temperature area as the monitoring warning value; S7: Based on the decreasing pattern of O2 concentration, increasing pattern of CO concentration and the maximum temperature of coal retained in the coal hopper, the risk of oxidation and spontaneous combustion during the dynamic retention process of coal in the coal hopper is predicted.

2. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 1, characterized in that: Before conducting the experiment on the spontaneous combustion law of coal oxidation, the dynamic accumulation conditions of the coal hopper were measured, including the coal accumulation rate of the coal hopper, the wind pressure difference between the coal hopper inlet and the coal hopper outlet, and the air inlet flow rate at the outlet.

3. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 1, characterized in that: The spontaneous combustion index rules include oxygen consumption rate, gas generation rate and heat release rate.

4. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 3 is characterized in that: The gas generation rate includes the CO generation rate and the CO2 generation rate.

5. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 1, characterized in that: Specifically, step S2 uses COMSOL software to construct a coal hopper geometric physical model, and adopts multi-field control for the coal hopper geometric physical model, including five complex fields: free and porous medium flow field, solid and fluid heat transfer field, porous medium reaction field, dilute material transfer field, and deformation geometry, to establish a multi-field coupling numerical simulation model.

6. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 5, characterized in that: Controlling temperature and heat flow direction as coupling conditions between free and porous media flow fields and solid and fluid heat transfer fields; The gas basis and reaction temperature providing heat generation are used as coupling conditions for solid and fluid heat transfer fields and porous media reaction fields; Controlling gas composition, consumption and production gas volumes as coupling conditions for porous media reaction field and dilute species transfer field; The coupling conditions between the dilute material transfer field and the free and porous media flow field are as follows: Using deformed geometry as coupling condition for free and porous media flow fields, solid and fluid heat transfer fields, porous media reaction fields, and dilute species transport fields; The deformation geometry is the coal accumulation rate and coal accumulation height of the coal hopper.

7. The method for predicting oxidation and spontaneous combustion of coal dynamically retained in a coal hopper according to claim 6, characterized in that: In step S3, the temperature, gas concentration and coal accumulation height are taken as dependent variables, and the transient solver MUMPS is used to solve the multi-field coupling numerical simulation model.

8. A method for preventing and controlling oxidation spontaneous combustion of coal dynamically retained in a coal hopper, wherein the risk of oxidation spontaneous combustion is predicted by using a method for predicting oxidation spontaneous combustion of coal dynamically retained in a coal hopper according to any one of claims 1 to 7, characterized in that: After step S7, the following steps are also included: S8: When the coal trapped in the coal hopper reaches a risk state of spontaneous combustion, cooling liquid is injected into the highest temperature area of ​​the coal hopper.

9. The method for preventing and controlling the oxidation and spontaneous combustion of the coal dynamically retained in the coal hopper according to claim 8, characterized in that: The cooling liquid is liquid CO2.

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