JP2011240250A - Method for preventing ignition in mill and device for preventing ignition in mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ignition inside a mill.SOLUTION: The ratio of the oxygen content rate and/or the hydrogen content rate to the carbon content rate in the mixed coal obtained by mixing coal A with coal B are calculated beforehand as analytical values. The amounts of the coal A and coal B to be supplied to the mill 5 are adjusted respectively on the basis of measured results of the concentrations of carbon monoxide and/or carbon dioxide in a gas at an outlet of the mill 5 and the analytical value so as to vary the ratio, which is the ratio of the oxygen content rate and/or the hydrogen content rate to the carbon content rate in the mixed coal to be supplied to the mill 5, the ratio being in the same type as the analytical value.

Description

  The present invention relates to an ignition prevention method and an ignition prevention apparatus for a pulverizer that pulverizes a solid fuel serving as a boiler fuel.

  A solid fuel pulverized by a pulverizer is supplied to a boiler using the solid fuel as fuel together with the air for conveyance.

  In Japan, bituminous coal, which has a high ignition temperature, is used as boiler fuel, so much attention has not been paid to ignition in a pulverizer. Rather, some of the early pulverized coal combustion boilers are provided with a system for supplying an inert gas (such as water vapor) and a rupture disk (rupture disk) as a countermeasure after a fire has occurred.

  On the other hand, in the United States, especially in the United States, many fires and explosions were experienced in the crusher in the 1980s by using low-grade coal produced in the West. In the future, there will be more opportunities to use low-grade coal, that is, low-ignition coal, subbituminous coal, modified brown coal (UBC), etc. in Japan. Need to prevent.

  In Patent Document 1, biomass is quantitatively supplied to a coal supply pipe that supplies coal to a pulverizing mill for pulverizing coal, thereby stabilizing the ratio of the amount of coal supplied to the pulverizing mill and the amount of biomass fuel. In addition, a coal / organic fuel mixed pulverization apparatus that prevents the ignition of biomass and thus stabilizes the operation state of the pulverization mill is disclosed.

  Further, Patent Document 2 compares the mill inlet temperature measurement value of the mixed air with the mill inlet temperature set value, and if the mill inlet temperature measured value is equal to or higher than the mill inlet temperature set value, the mill outlet temperature setting A mill device that continues to control the mill outlet temperature while reducing the value while preventing ignition accidents due to excessive rise of the mill inlet temperature and a coal-fired boiler facility equipped with the same are disclosed.

  Patent Document 3 discloses a roller mill device that controls the mill inlet temperature in accordance with the supply amount of the object to be pulverized, thereby reducing the change in the mill outlet temperature and preventing the pulverized coal from igniting. ing.

  In Patent Document 4, the temperature in the heated air pipe and the coal pulverizer is measured, and the temperature and the supply amount of the air supplied to the coal pulverizer are controlled to eliminate the possibility of ignition. A temperature control device is disclosed.

  In Patent Document 5, the raw coal moisture is obtained from the mill inlet temperature and the amount of coal supplied to the mill, and the mill outlet temperature is set to the raw coal moisture by setting the mill outlet temperature according to the raw coal moisture. As an optimum value according to this, a mill outlet temperature control method that prevents ignition is disclosed.

  Further, Patent Document 6 discloses a pulverized coal that prevents a pulverized explosion by switching a carrier of pulverized coal from air to an inert gas when a smoldering or smoldering combustion state of pulverized coal is detected in a pulverized bottle. A combustion method is disclosed.

JP 2004-347241 A JP 2006-102666 A JP-A-4-244246 JP-A-56-152750 JP-A-63-315158 JP-A 63-267814

  However, at present, there is no operation index for solid fuel having a low ignition temperature, which has not been assumed so far. For this reason, it is not known what operating conditions, specifically, what inlet / outlet temperatures and fuel supply amount should be used to operate the pulverizer. Therefore, it is desired to obtain operating conditions for safely operating the pulverizer and prevent ignition in the pulverizer.

  The objective of this invention is providing the ignition prevention method and ignition prevention apparatus of a grinder which can prevent the ignition in a grinder.

  The method for preventing ignition of a pulverizer in the present invention is a method for preventing ignition of a pulverizer that pulverizes solid fuel, and the ratio of oxygen content and / or hydrogen content to carbon content in one or more types of solid fuel. Is determined in advance as an analytical value, and the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer is measured. Based on the measurement result of the concentration and the analytical value, the pulverizer The ratio of the oxygen content and / or the hydrogen content to the carbon content in the one or more types of solid fuel to be supplied, and supplied to the pulverizer so as to change the ratio of the same kind as the analysis value. The supply amount of the one or more types of solid fuel is adjusted.

  According to the above configuration, if a solid fuel having a low ignition temperature is used in a pulverizer that pulverizes the solid fuel while hot air (conveying air) is supplied, there is a risk that the heated fuel may ignite in the pulverizer. is there. And if the oxidation reaction of the fuel which is a precursor of ignition occurs in the pulverizer, carbon monoxide and carbon dioxide are detected in the gas at the outlet of the pulverizer. Therefore, in order to prevent ignition in the pulverization, in the pulverizer, the oxidation reaction of fuel, which is a sign of ignition, does not occur, that is, in the gas at the outlet of the pulverizer, carbon monoxide and carbon dioxide. Need to be detected.

  Here, the ignition temperature of one or more types of solid fuels decreases as the ratio of the oxygen content and / or the hydrogen content to the carbon content in one or more types of solid fuels increases. This is considered to be because as the ratio of the oxygen content and / or the hydrogen content to the carbon content increases, volatile components such as combustible gas are easily released at a low temperature, and ignition is likely to occur. Therefore, if the supply amount of one or more kinds of solid fuel supplied to the pulverizer is adjusted so that the ratio of the oxygen content and / or the hydrogen content to the carbon content is low, the pulverizer is supplied. The ignition temperature of one or more kinds of solid fuels becomes high, and the oxidation reaction of the fuel, which is a sign of ignition, hardly occurs in the pulverizer.

  However, simply reducing the ratio of oxygen content and / or hydrogen content to carbon content and increasing the ignition temperature of one or more solid fuels supplied to the pulverizer is inexpensive. The supply of solid fuel with a low ignition temperature cannot be increased. In order to reduce the cost, it is necessary to increase the supply amount of the solid fuel that is inexpensive and has a low ignition temperature as much as possible without causing ignition in the pulverizer.

  Therefore, when the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer is measured, if no carbon monoxide or carbon dioxide is detected, an oxidation reaction of fuel, which is a precursor of ignition, has occurred. Therefore, based on the analytical value obtained in advance, the ratio of the oxygen content and / or the hydrogen content and the carbon content in the solid fuel, the ratio of the same kind as the analytical value becomes high, that is, The supply amount of one or more types of solid fuel supplied to the pulverizer is adjusted so that the ignition temperature of the solid fuel is lowered. Specifically, the ignition temperature of one or more types of solid fuel is lowered by increasing the supply amount of the solid fuel having a lower ignition temperature. As a result, the supply amount of the solid fuel that is inexpensive and has a low ignition temperature increases, so that the cost can be reduced.

  On the other hand, if carbon monoxide and / or carbon dioxide is detected as a result of measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer, the oxidation reaction of fuel, which is a sign of ignition, is detected. Therefore, based on the analytical value obtained in advance, the ratio of oxygen content and / or hydrogen content to carbon content in the solid fuel, the ratio of the same kind as the analytical value becomes low That is, the supply amount of one or more types of solid fuel supplied to the pulverizer is adjusted so that the ignition temperature of the solid fuel becomes high. Specifically, the ignition temperature of one or more kinds of solid fuels is increased by reducing the supply amount of the solid fuel having a lower ignition temperature. This reduces the amount of solid fuel that is cheap and has a low ignition temperature, but the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer, and carbon monoxide and carbon dioxide in the gas at the outlet of the pulverizer Will not be detected. Therefore, even if solid fuel having a low ignition temperature is used, ignition in the pulverizer can be prevented, and disasters such as fire and explosion of the pulverizer can be prevented.

  In the method for preventing ignition of a pulverizer according to the present invention, the solid fuel may be at least one of coal and biomass fuel. According to the above configuration, low cost and low ignition temperature coal and biomass fuel can be used in place of high grade coal such as bituminous coal with high ignition temperature and low cost while preventing ignition in the crusher. Can be achieved.

  The ignition preventing device for a pulverizer according to the present invention is an ignition preventing device for a pulverizer that pulverizes solid fuel, and adjusts the supply amount of one or more types of solid fuel supplied to the pulverizer. Means, concentration measuring means for measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer, oxygen content and / or hydrogen content and carbon in the one or more solid fuels One or more types of the one or more kinds supplied to the pulverizer based on the storage means for storing the ratio with the content rate as an analysis value, the measurement result of the concentration measurement means, and the analysis value stored in the storage means A control means for controlling the supply amount adjusting means so as to change the ratio of the oxygen content and / or the hydrogen content and the carbon content in the solid fuel, the same kind of ratio as the analysis value; It is characterized by having .

  According to said structure, as above-mentioned, supply_amount | feed_rate of the 1 or more types of solid fuel supplied to a grinder so that the ratio of oxygen content rate and / or hydrogen content rate, and carbon content rate may become low. If adjusted, the ignition temperature of one or more types of solid fuel supplied to the pulverizer becomes high, and the oxidation reaction of fuel, which is a sign of ignition, hardly occurs in the pulverizer.

  Therefore, when the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer is measured, if no carbon monoxide or carbon dioxide is detected, an oxidation reaction of fuel, which is a precursor of ignition, has occurred. Therefore, based on the analytical value obtained in advance, the ratio of the oxygen content and / or the hydrogen content and the carbon content in the solid fuel, the ratio of the same kind as the analytical value becomes high, that is, The supply amount of one or more types of solid fuel supplied to the pulverizer is adjusted so that the ignition temperature of the solid fuel is lowered. Specifically, the ignition temperature of one or more types of solid fuel is lowered by increasing the supply amount of the solid fuel having a lower ignition temperature. As a result, the supply amount of the solid fuel that is inexpensive and has a low ignition temperature increases, so that the cost can be reduced.

  On the other hand, if carbon monoxide and / or carbon dioxide is detected as a result of measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer, the oxidation reaction of fuel, which is a sign of ignition, is detected. Therefore, based on the analytical value obtained in advance, the ratio of oxygen content and / or hydrogen content to carbon content in the solid fuel, the ratio of the same kind as the analytical value becomes low That is, the supply amount of one or more types of solid fuel supplied to the pulverizer is adjusted so that the ignition temperature of the solid fuel becomes high. Specifically, the ignition temperature of one or more kinds of solid fuels is increased by reducing the supply amount of the solid fuel having a lower ignition temperature. This reduces the amount of solid fuel that is cheap and has a low ignition temperature, but the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer, and carbon monoxide and carbon dioxide in the gas at the outlet of the pulverizer Will not be detected. Therefore, even if solid fuel having a low ignition temperature is used, ignition in the pulverizer can be prevented, and disasters such as fire and explosion of the pulverizer can be prevented.

  In the ignition prevention device for a pulverizer according to the present invention, the solid fuel may be at least one of coal and biomass fuel. According to the above configuration, low cost and low ignition temperature coal and biomass fuel can be used in place of high grade coal such as bituminous coal with high ignition temperature and low cost while preventing ignition in the crusher. Can be achieved.

  According to the ignition prevention method and the ignition prevention device of the pulverizer of the present invention, as a result of measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the pulverizer, carbon monoxide and carbon dioxide are detected even a little. In this case, the ratio of the oxygen content and / or the hydrogen content to the carbon content in the solid fuel based on the analysis value, which is the same ratio as the analysis value, that is, the solid fuel The supply amount of one or more types of solid fuel supplied to the pulverizer is adjusted so that the ignition temperature becomes high. As a result, the fuel oxidation reaction, which is a precursor to ignition, does not occur in the pulverizer, so even if solid fuel with a low ignition temperature is used, ignition in the pulverizer is prevented and disasters such as fire and explosion of the pulverizer are prevented. Can be prevented.

It is the schematic which shows the ignition prevention apparatus of a grinder. It is the schematic which shows a pulverized coal ignition test apparatus. It is a figure which shows the relationship between the molar ratio of oxygen content rate and carbon content rate, and ignition temperature. It is a figure which shows the relationship between the molar ratio of hydrogen content rate and carbon content rate, and ignition temperature. It is a figure which shows the relationship between the molar ratio of oxygen content rate and hydrogen content rate, and carbon content rate, and ignition temperature.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following embodiment, description will be given using coal as the solid fuel, but the solid fuel is not limited to this, and may be biomass fuel, sludge carbide, or the like, and coal, biomass fuel, sludge carbide, etc. More than one species may be used.

(Configuration of crusher ignition prevention device)
As shown in FIG. 1, the pulverizer ignition prevention device 10 according to this embodiment is a coal supply amount adjustment device (supply) that adjusts the supply amounts of coal A and B supplied from the coal hoppers 1 and 2 to the mixer 4. (Amount adjusting means) 3a, 3b, a concentration measuring device (concentration measuring means) 7 for measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer 5, and a calculator for controlling the coal supply amount adjusting devices 3a, 3b, respectively. (Storage means, control means) 11. The concentration measuring device 7 may measure the concentration of carbon dioxide in the gas at the outlet of the pulverizer 5, or may measure the concentrations of carbon monoxide and carbon dioxide.

  Coal hoppers 1 and 2 hold two types of coals A and B, respectively. The coal A held by the coal hopper 1 and the coal B held by the coal hopper 2 have different molar ratios (O / C ratios) between the oxygen content and the carbon content, as well as the hydrogen content and carbon. The molar ratio (H / C ratio) with the content and the molar ratio ((O + H) / C ratio) between the oxygen content, the hydrogen content, and the carbon content are different from each other. The mixer 4 mixes two types of coal A and B supplied from the coal hoppers 1 and 2. The supply amount of coal A supplied from the coal hopper 1 to the mixer 4 is adjusted by the coal supply amount adjusting device 3a, and the supply amount of coal B supplied from the coal hopper 2 to the mixer 4 is adjusted to the coal supply amount. It is adjusted by the device 3b.

  The pulverizer 5 pulverizes the mixed charcoal mixed by the mixer 4 into pulverized coal. The crusher 5 is supplied with conveying air (hot air) for conveying pulverized coal. By this conveying air, the pulverized coal in the pulverizer 5 is conveyed to the pulverized coal burner 8 while being dried. Here, from the measurement result of the ignition temperature of the pulverized coal described later, in order to prevent the pulverized coal from igniting, it is preferable that the temperature of the conveying air (hot air) at the inlet of the pulverizer 5 is set to 200 ° C. or less. The concentration of carbon monoxide in the gas at the outlet of the pulverizer 5 is measured by the concentration measuring device 7. The pulverized coal burner 8 burns pulverized coal. The boiler 9 recovers heat by burning pulverized coal.

  Here, if coal having a low ignition temperature is used for the pulverizer 5, there is a risk that heated fuel (pulverized coal) may ignite in the pulverizer 5. In the pulverizer 5, if an oxidation reaction of fuel that is a sign of ignition occurs, carbon monoxide and carbon dioxide are generated, and the carbon monoxide is detected by the concentration measuring device 7. Therefore, in order to prevent ignition in the pulverizer 5, it is necessary to prevent the oxidation reaction of fuel, which is a sign of ignition, from occurring in the pulverizer 5, that is, in the gas at the outlet of the pulverizer 5. It is necessary to prevent carbon oxide and carbon dioxide from being detected.

  If high grade coal such as bituminous coal having a high ignition temperature is used, carbon monoxide and carbon dioxide are not detected in the gas at the outlet of the pulverizer 5. This is because the temperature at which the fuel starts the oxidation reaction is much higher than the temperature of the conveying air (hot air) supplied to the pulverizer 5.

  The computing unit 11 stores in advance the coal properties such as the oxygen content rate, the hydrogen content rate, and the carbon content rate of coal A and coal B as analysis data (analytical value), and the O / C ratio of the mixed coal. Is stored as analysis data (analysis value). Further, the measurement data (measurement result) of the carbon monoxide concentration in the gas at the outlet of the pulverizer 5 measured by the concentration measuring device 7 is input to the calculator 11. The computing unit 11 uses the mixing ratio of the coals A and B as a parameter, and the O / C ratio of the mixed coal supplied to the pulverizer 5 based on the measurement data from the concentration measuring device 7 and the analysis data. The coal supply amount adjusting devices 3a and 3b are respectively controlled so as to change. Thereby, supply_amount | feed_rate to the mixer 4 of coal A and B is each changed. Note that the H / C ratio of the mixed coal is stored in the computing unit 11 as analysis data (analytical value), and the computing unit 11 uses the mixing ratio of the coals A and B as a parameter to measure from the concentration measuring device 7. Based on the data and the analysis data, the coal supply amount adjusting devices 3a and 3b may be controlled so as to change the H / C ratio of the mixed coal supplied to the pulverizer 5. Moreover, you may use (O + H) / C ratio instead of O / C ratio and H / C ratio.

  Here, the ignition temperature of mixed coal (pulverized coal) falls, so that O / C ratio of mixed coal (pulverized coal) becomes high. This is considered to be because the higher the O / C ratio, the easier it is to release volatile components such as combustible gas at low temperatures, and the easier it is to ignite. Therefore, if the supply amounts of coal A and B supplied to the pulverizer 5 are adjusted so that the O / C ratio is lowered, the ignition temperature of the pulverized coal increases, and the igniter predicts the ignition in the pulverizer 5. This makes it difficult for the oxidation reaction of the fuel to occur. The same applies to the H / C ratio and the (O + H) / C ratio.

  However, simply lowering the O / C ratio, H / C ratio, and (O + H) / C ratio to increase the ignition temperature of the mixed coal supplied to the pulverizer 5 is inexpensive and the ignition temperature is low. The supply of low coal cannot be increased. In order to reduce the cost, it is necessary to increase as much as possible the supply amount of low-cost and low-ignition temperature coal to the extent that ignition does not occur in the pulverizer 5.

(Operation of crusher ignition prevention device)
Next, the operation of the pulverizer ignition prevention apparatus 10 having the above-described configuration, that is, the pulverizer ignition prevention method will be described.

  The two types of coal A and B supplied from the coal hoppers 1 and 2 are mixed by the mixer 4 and supplied to the pulverizer 5 as mixed coal. The supply amount of coal A supplied from the coal hopper 1 to the mixer 4 is adjusted by the coal supply amount adjusting device 3a, and the supply amount of coal B supplied from the coal hopper 2 to the mixer 4 is adjusted to the coal supply amount. It is adjusted by the device 3b.

  The mixed coal is pulverized into pulverized coal by the pulverizer 5, and is conveyed to the pulverized coal burner 8 while being dried by the conveying air. The pulverized coal is burned by the pulverized coal burner 8, and the heat generated by the combustion is recovered in the boiler 9. The concentration of carbon monoxide in the gas at the outlet of the pulverizer 5 is measured by the concentration measuring device 7. The measurement data (measurement result) of the carbon monoxide concentration in the gas at the outlet of the pulverizer 5 measured by the concentration measuring device 7 is input to the calculator 11.

  The computing unit 11 stores in advance the coal properties such as the oxygen content rate, the hydrogen content rate, and the carbon content rate of coal A and coal B as analysis data (analysis value), and the O / C ratio is the analysis data. It is stored as (analysis value). The calculator 11 changes the O / C ratio of the mixed coal supplied to the pulverizer 5 based on the measurement data from the concentration measuring device 7 and the analysis data, using the mixing ratio of the coals A and B as a parameter. Thus, the coal supply amount adjusting devices 3a and 3b are respectively controlled. Thereby, supply_amount | feed_rate to the mixer 4 of coal A and B is each changed.

  Specifically, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer 5, if no carbon monoxide is detected, the fuel oxidation reaction, which is a precursor of ignition, has not occurred. 11 controls the coal supply amount adjusting devices 3a and 3b based on the analysis data (O / C ratio) obtained in advance, so that the O / C ratio of the mixed coal becomes high, that is, the mixed coal The supply amounts of coal A and B supplied to the pulverizer 5 are adjusted so that the ignition temperature is lowered. Specifically, the ignition temperature of mixed coal is lowered by increasing the supply amount of coal having a lower ignition temperature. Thereby, since the supply amount of coal which is cheap and has a low ignition temperature increases, the cost can be reduced. When carbon monoxide is not detected, the O / C ratio of the mixed coal may not be changed by not controlling the coal supply amount adjusting devices 3a and 3b.

  On the other hand, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer 5, if any carbon monoxide is detected, an oxidation reaction of fuel, which is a sign of ignition, has occurred. 11 controls the coal supply amount adjusting devices 3a and 3b based on the analysis data obtained in advance, so that the O / C ratio of the mixed coal becomes low, that is, the ignition temperature of the mixed coal becomes high. Next, the supply amounts of coal A and B supplied to the pulverizer 5 are adjusted. Specifically, the ignition temperature of the coal mixture is increased by reducing the supply amount of coal having a lower ignition temperature. As a result, the supply amount of coal that is inexpensive and has a low ignition temperature is reduced, but in the pulverizer 5, the oxidation reaction of fuel, which is a sign of ignition, does not occur, and carbon monoxide is contained in the gas at the outlet of the pulverizer 5. It will not be detected. Therefore, even when coal having a low ignition temperature is used, ignition in the pulverizer 5 can be prevented, and disasters such as fire and explosion of the pulverizer 5 can be prevented. An H / C ratio or an (O + H) / C ratio may be used instead of the O / C ratio.

  Further, as described above, biomass fuel may be used as the solid fuel. And, by using low-cost coal and biomass fuel with low ignition temperature instead of high-grade coal such as expensive bituminous coal with high ignition temperature, it is possible to reduce costs while preventing ignition in the crusher 5. Can do.

  Note that a threshold value may be provided for the carbon monoxide concentration measured by the concentration measuring device 7. The threshold value is a carbon monoxide concentration when the fuel (pulverized coal) is ignited in the pulverizer 5 and is several tens of ppm. Then, when the carbon monoxide concentration measured by the concentration measuring device 7 is sufficiently close to the threshold value, the pulverizer 5 is set so that the O / C ratio of the mixed coal becomes low, that is, the ignition temperature of the mixed coal becomes high. The supply amount of supplied coals A and B is adjusted. Further, when the carbon monoxide concentration is sufficiently far from the threshold value, the O / C ratio of the mixed coal is increased, that is, the pulverizer 5 is passed through the mixer 4 so that the ignition temperature of the mixed coal is lowered. The supply amount of supplied coals A and B is adjusted. When the carbon monoxide concentration is sufficiently far from the threshold value, the O / C ratio of the mixed coal need not be changed.

  In this way, by setting the threshold value for the carbon monoxide concentration and controlling the coal supply amount adjusting devices 3a and 3b, while preventing the ignition in the pulverizer 5, the low-cost and low-ignition temperature coal is targeted. You can use it to reduce costs.

(Relationship between O / C ratio, H / C ratio and (O + H) / C ratio and ignition temperature)
Next, the relationship between the O / C ratio, H / C ratio, (O + H) / C ratio and ignition temperature in one or more types of solid fuel will be described. In order for the computing unit 11 to control the coal supply amount adjusting devices 3a and 3b, respectively, the O / C ratio, the H / C ratio and the (O + H) / C ratio in one or more kinds of solid fuels and the ignition temperature It is necessary to grasp the relationship in advance. Therefore, the ignition temperature of pulverized coal obtained by pulverizing pulverized coal using one or more of three types of coals A, B, and C with different O / C ratio, H / C ratio, and (O + H) / C ratio was investigated. did. For this investigation, a pulverized coal ignition test apparatus 21 shown in FIG. 2 was used. Table 1 shows the coal properties of three types of coals A, B, and C.

  The pulverized coal ignition test apparatus 21 includes a cylindrical vertical reaction tube 22 having an inner diameter of φ25 mm × 700 L, a pulverized coal feeder 23 for supplying a predetermined amount of pulverized coal into the cylindrical vertical reaction tube 22, and an outer periphery of the cylindrical vertical reaction tube 22. , A gas supply line 25 for supplying a mixed gas heated in the cylindrical vertical reaction tube 22, a receiving container 27 provided below the cylindrical vertical reaction tube 22, and a cylindrical vertical type A carbon monoxide concentration meter 26 provided at the lower part of the reaction tube 22 and a rupture disk 29 provided above the cylindrical vertical reaction tube 22 are provided.

  The atmospheric temperature inside the cylindrical vertical reaction tube 22 can be raised substantially uniformly along the vertical direction of the cylindrical vertical reaction tube 22 by the heater 24 from room temperature to about 400 ° C. Here, the temperature increase rate of the atmospheric temperature inside the cylindrical vertical reaction tube 22 is adjusted to about 5 ° C./min.

  In addition, thermocouple insertion ports are provided at eight locations along the longitudinal direction on the side surface of the cylindrical vertical reaction tube 22, and sheath K thermocouples 28 having an outer diameter of 1 mm are respectively connected to these thermocouple insertion ports. Inserted. These sheath K thermocouples 28 enable measurement of the ambient temperature on the central axis inside the cylindrical vertical reaction tube 22.

  The gas supply line 25 includes a mixing chamber 31 that mixes nitrogen gas (a gas having a lower oxygen partial pressure than air) and air to form a mixed gas, an oxygen concentration meter 32 that measures the oxygen concentration in the mixed gas, And a heater 33 for heating the mixed gas. The rupture disk 29 is normally closed, and is opened when the inside of the cylindrical vertical reaction tube 22 becomes high pressure.

  Here, in order to perform the test under the same conditions as the pulverizer 5, several test conditions were provided. That is, pulverized coal whose moisture content was adjusted in the range of 4.0 to 5.0% in advance was used as test conditions. As test conditions, the proportion of pulverized coal having a particle size of 75 μm or less was set to 80% or more. As test conditions, the Air / Coal ratio (ratio of the amount [L / min] of the heated mixed gas supplied to the cylindrical vertical reaction tube 22 and the amount [g / min] of coal supply) is 1.7. It was. Further, as a test condition, a residence time in which the pulverized coal stayed in the cylindrical vertical reaction tube 22 was set to about 6 seconds. Further, it was assumed that the pulverized coal particles move in the cylindrical vertical reaction tube 22 at the same speed as the mixed gas. Further, it was assumed that the pulverized coal did not adhere to the inside of the pulverizer 5 and stayed there.

  The fixed amount of pulverized coal supplied from the pulverized coal feeder is dropped into the cylindrical vertical reaction tube 22 by its own weight. A heated mixed gas is supplied from the gas supply line 25 into the cylindrical vertical reaction tube 22. In the cylindrical vertical reaction tube 22, the pulverized coal and the mixed gas are heated to the same temperature. Thereafter, the pulverized coal falls out of the system from the lower flange portion 22 a of the cylindrical vertical reaction tube 22 and is stored in the receiving container 27.

  If the pulverized coal rises to a temperature at which the pulverized coal ignites within the residence time in which the pulverized coal stays in the cylindrical vertical reaction tube 22, the carbon monoxide concentration meter 26 installed at the lower portion of the cylindrical vertical reaction tube 22 is increased. Detects an increase in carbon oxide concentration. The test was repeated while changing the atmospheric temperature in the cylindrical vertical reaction tube 22 with the heater 24, and the cylinder vertical length at the time when the carbon monoxide concentration in the gas at the outlet of the cylindrical vertical reaction tube 22 became 30 ppm or more was measured. The average value of the atmospheric temperature in the type reaction tube 22 was calculated as the ignition temperature of the pulverized coal. Note that the ignition temperature of the pulverized coal may be calculated by measuring the concentration of carbon dioxide in the gas at the outlet of the cylindrical vertical reaction tube 22.

  The measurement result of the ignition temperature of pulverized coal using the molar ratio (O / C ratio) between the oxygen content and the carbon content of coal as a parameter is shown in FIG. Moreover, the measurement result of the ignition temperature of pulverized coal which made the molar ratio (H / C ratio) of the hydrogen content rate and carbon content rate of coal a parameter is shown in FIG. Furthermore, the measurement result of the ignition temperature of pulverized coal which made the molar ratio ((O + H) / C ratio) of the oxygen content rate and hydrogen content rate, and carbon content rate of coal a parameter is shown in FIG. From the measurement results of the ignition temperature of pulverized coal, it can be seen that the ignition temperature of pulverized coal decreases linearly as the O / C ratio, H / C ratio, and (O + H) / C ratio increase. This is presumably because the higher the O / C ratio, H / C ratio, and (O + H) / C ratio, the easier it is to release volatile components such as flammable gas at low temperatures and the easier it is to ignite. Therefore, controlling the O / C ratio, the H / C ratio, and the (O + H) / C ratio in the solid fuel is based on operating conditions for safely operating the pulverizer 5 from the viewpoint of ignition in the pulverizer 5. It is considered to be. Moreover, from the measurement result of the ignition temperature of pulverized coal, in order to prevent the ignition of pulverized coal, it is understood that the temperature of the conveying air (hot air) at the inlet of the pulverizer 5 is preferably 200 ° C. or less. .

(Modification of this embodiment)
The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

  For example, the control of the coal supply amount adjusting devices 3a and 3b by the computing unit 11 is not limited to the above-described one. Even if the concentration measuring device 7 does not detect the carbon monoxide concentration, one type is supplied to the pulverizer 5 so that the O / C ratio in the solid fuel becomes low, that is, the ignition temperature of the solid fuel becomes high. Even if the supply amount of the above solid fuel may be adjusted or the concentration measuring device 7 detects the carbon monoxide concentration, if the value is less than the threshold value, the O / C ratio in the solid fuel becomes high. That is, the supply amount of one or more types of solid fuel supplied to the pulverizer 5 may be adjusted so that the ignition temperature of the solid fuel becomes low. In short, the supply amount of one or more types of solid fuel supplied to the pulverizer 5 may be adjusted within a range where ignition does not occur in the pulverizer 5. The same applies to the H / C ratio and the (O + H) / C ratio.

1, 2 Coal hopper 3a, 3b Coal supply amount adjustment device (supply amount adjustment means)
4 Mixer 5 Crusher 7 Concentration measuring device (concentration measuring means)
8 Pulverized coal burner 9 Boiler 10 Ignition prevention device of pulverizer 11 Calculator (storage means, control means)
21 Pulverized Coal Ignition Test Equipment 22 Cylindrical Vertical Reaction Tube 23 Pulverized Coal Feeder 24 Heater 25 Gas Supply Line 26 Carbon Monoxide Concentration Meter 27 Receiving Container 28 Sheath K Thermocouple 32 Oxygen Concentration Meter 33 Heating Heater

Claims (4)

A method for preventing ignition of a pulverizer for pulverizing solid fuel,
The oxygen content in one or more kinds of solid fuels and / or the ratio of the hydrogen content and the carbon content are determined in advance as analytical values,
Measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the grinder;
Based on the measurement result of the concentration and the analysis value, a ratio of oxygen content and / or hydrogen content and carbon content in the one or more types of solid fuel supplied to the pulverizer, A method for preventing ignition of a pulverizer, wherein the supply amount of the one or more types of solid fuel supplied to the pulverizer is adjusted so as to change a ratio of the same type as the analysis value.   The method for preventing ignition of a pulverizer according to claim 1, wherein the solid fuel is at least one of coal and biomass fuel. An ignition prevention device for a pulverizer for pulverizing solid fuel,
A supply amount adjusting means for adjusting a supply amount of one or more kinds of solid fuel supplied to the pulverizer;
Concentration measuring means for measuring the concentration of carbon monoxide and / or carbon dioxide in the gas at the outlet of the grinder;
Storage means for storing an oxygen content and / or a ratio of a hydrogen content and a carbon content in the one or more solid fuels as an analysis value;
Based on the measurement result of the concentration measuring means and the analysis value stored in the storage means, the oxygen content and / or hydrogen content and carbon in the one or more types of solid fuel supplied to the pulverizer Control means for controlling the supply amount adjusting means so as to change the ratio of the content ratio and the same kind of ratio as the analysis value;
An ignition prevention device for a pulverizer characterized by comprising:   The said solid fuel is at least 1 sort (s) of coal and biomass fuel, The ignition prevention apparatus of the grinder of Claim 3 characterized by the above-mentioned.

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