JP5385849B2 - Crusher ignition prevention method and ignition prevention device - Google Patents

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 according to the present invention is a method for preventing ignition of a pulverizer that pulverizes solid fuel, and supplies air and a gas having a lower oxygen partial pressure than the air as a mixed gas to the pulverizer. , Measuring the carbon monoxide concentration and the oxygen concentration in the gas at the outlet of the pulverizer, respectively, based on the measurement result of the carbon monoxide concentration and the oxygen partial pressure calculated from the measured oxygen concentration, A supply amount of a gas having a lower oxygen partial pressure than that of the air supplied to the pulverizer is adjusted so as to change the oxygen partial pressure in the mixed gas supplied to the pulverizer.

  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, the carbon monoxide concentration is detected in the gas at the outlet of the pulverizer. Therefore, in order to prevent ignition in the pulverization, the carbon monoxide concentration is detected in the gas at the outlet of the pulverizer so that the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer. It is necessary not to be done.

  Here, the lower the oxygen partial pressure in the mixed gas supplied to the pulverizer, the higher the ignition temperature of one or more types of solid fuel. This is considered to be because as the oxygen partial pressure in the mixed gas supplied to the pulverizer is lower, the solid fuel is less likely to be oxidized and less likely to ignite. Therefore, if the supply amount of the gas having a lower oxygen partial pressure than the air supplied to the pulverizer is adjusted so that the oxygen partial pressure in the mixed gas supplied to the pulverizer becomes lower, the gas was supplied to the pulverizer. 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.

  That is, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer, if any carbon monoxide concentration is detected, the fuel oxidation reaction, which is a precursor of ignition, is taking place. Based on the oxygen partial pressure calculated from the oxygen concentration, the oxygen partial pressure in the mixed gas supplied to the pulverizer is lower, that is, the ignition temperature of the solid fuel is higher than the air supplied to the pulverizer. Also adjust the supply amount of gas with low oxygen partial pressure. Specifically, the ignition temperature of the solid fuel is increased by increasing the supply amount of the gas whose oxygen partial pressure is lower than that of air. Thereby, the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer, and the concentration of carbon monoxide is not detected in the gas at the outlet of the pulverizer. 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.

  In the method for preventing ignition of a pulverizer according to the present invention, the gas having a lower oxygen partial pressure than air may be at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. According to the above configuration, the oxygen partial pressure in the mixed gas supplied to the pulverizer is suitably changed by supplying at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas to the pulverizer. Can be made.

  Further, the ignition preventing device for a pulverizer according to the present invention is an ignition preventing device for a pulverizer for pulverizing solid fuel, the air supply means for supplying air to the pulverizer, and the mixed gas mixed with the air. Gas supply means for supplying a gas having a lower oxygen partial pressure than the air to the pulverizer so as to be supplied to the pulverizer, and a gas supply having a lower oxygen partial pressure than the air supplied to the pulverizer Gas supply amount adjusting means for adjusting the amount, carbon monoxide concentration measuring means for measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer, and oxygen for measuring the oxygen concentration in the gas at the outlet of the pulverizer The mixture supplied to the pulverizer based on the concentration measurement means, the measurement result of the carbon monoxide concentration measurement means, and the oxygen partial pressure calculated from the oxygen concentration measured by the oxygen concentration measurement means gas So as to change the oxygen partial pressure, and having a control means for controlling the gas supply amount adjusting means.

  According to the above configuration, as described above, the supply amount of the gas having a lower oxygen partial pressure than the air supplied to the pulverizer is set so that the oxygen partial pressure in the mixed gas supplied to the pulverizer becomes lower. If adjusted, the ignition temperature of one or more kinds of solid fuel supplied to the pulverizer becomes high, and the oxidation reaction of the fuel, which is a sign of ignition, hardly occurs in the pulverizer.

  Therefore, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer, if any carbon monoxide concentration was detected, the fuel oxidation reaction, which is a precursor of ignition, was taking place. Based on the oxygen partial pressure calculated from the oxygen concentration, the oxygen partial pressure in the mixed gas supplied to the pulverizer is lower, that is, the ignition temperature of the solid fuel is higher than the air supplied to the pulverizer. Also adjust the supply amount of gas with low oxygen partial pressure. Specifically, the ignition temperature of the solid fuel is increased by increasing the supply amount of the gas whose oxygen partial pressure is lower than that of air. Thereby, the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer, and the concentration of carbon monoxide is not detected in the gas at the outlet of the pulverizer. 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.

  In the ignition preventive device for a pulverizer according to the present invention, the gas having a lower oxygen partial pressure than air may be at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. According to the above configuration, the oxygen partial pressure in the mixed gas supplied to the pulverizer is suitably changed by supplying at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas to the pulverizer. Can be made.

  According to the ignition prevention method and the ignition prevention device of the pulverizer of the present invention, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer, if the carbon monoxide concentration is detected even a little, the measured oxygen Based on the oxygen partial pressure calculated from the concentration, the oxygen partial pressure in the mixed gas supplied to the pulverizer becomes lower, that is, the ignition temperature of the solid fuel becomes higher than the air supplied to the pulverizer. Adjust the gas supply amount with low oxygen partial pressure. 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 oxygen partial pressure 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 includes an air supply device (air supply means) 12 that supplies air for conveyance (air) to the pulverizer 5, and an oxygen partial pressure higher than that of air. Gas supply device (gas supply means) 13 for supplying a low gas to the pulverizer 5, an air supply amount adjusting device 14 for adjusting the supply amount of air supplied to the pulverizer 5, and the pulverizer 5 A gas supply amount adjusting device (gas supply amount adjusting means) 15 for adjusting a supply amount of a gas having a lower oxygen partial pressure than air, and a carbon monoxide concentration for measuring a carbon monoxide concentration in the gas at the outlet of the pulverizer 5 Measuring device (carbon monoxide concentration measuring means) 7, oxygen concentration measuring device (oxygen concentration measuring means) 6 for measuring the oxygen concentration in the gas at the outlet of the pulverizer 5, air supply amount adjusting device 14 and gas supply amount Control each adjustment device 15 Calculator has a (control means) 11, a.

  Coal hoppers 1 and 2 hold two types of coals A and B, respectively. 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 pulverizer 5 is supplied with transfer air (hot air) for transferring pulverized coal from the air supply device 12. 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.

  A gas having a lower oxygen partial pressure than air is supplied from the gas supply device 13 to the pulverizer 5. The gas having a lower oxygen partial pressure than air is at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. The conveying air from the air supply device 12 and the gas having a lower oxygen partial pressure than the air from the gas supply device 13 are supplied to the pulverizer 5 as a mixed gas in which both are mixed.

  The carbon monoxide concentration in the gas at the outlet of the pulverizer 5 is measured by the carbon monoxide concentration measuring device 7. The oxygen concentration in the gas at the outlet of the pulverizer 5 is measured by the oxygen concentration measuring device 6. 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. And if the oxidation reaction of the fuel which is a precursor of ignition occurs in the pulverizer 5, the carbon monoxide concentration measuring device 7 detects the carbon monoxide concentration. 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 the carbon oxide concentration from being detected.

  If high grade coal such as bituminous coal having a high ignition temperature is used, the concentration of carbon monoxide is 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 calculator 11 includes the measurement data (measurement result) of the carbon monoxide concentration in the gas at the outlet of the pulverizer 5 measured by the carbon monoxide concentration measuring device 7 and the pulverizer 5 measured by the oxygen concentration measuring device 6. Measurement data (measurement result) of the oxygen concentration in the gas at the outlet is input. The calculator 11 calculates the oxygen partial pressure from the measurement data of the oxygen concentration. The computing unit 11 uses the oxygen partial pressure as a parameter, and based on the measurement data from the carbon monoxide concentration measuring device 7 and the oxygen partial pressure calculated from the oxygen concentration measured by the oxygen concentration measuring device 6, The air supply amount adjusting device 14 and the gas supply amount adjusting device 15 are respectively controlled so as to change the oxygen partial pressure in the mixed gas supplied to the pulverizer 5. Thereby, the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is changed.

  Here, the ignition temperature of the pulverized coal increases as the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 decreases. This is considered to be because the pulverized coal is less likely to be oxidized and less likely to ignite as the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is lower. Therefore, if the supply amounts of the carrier air supplied to the pulverizer 5 and the gas having a lower oxygen partial pressure than the air are adjusted so that the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is lowered, respectively. The ignition temperature of the mixed coal (pulverized coal pulverized by the pulverizer 5) supplied to the pulverizer 5 becomes high, and the oxidation reaction of fuel, which is a sign of ignition, hardly occurs 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 carbon monoxide concentration in the gas at the outlet of the pulverizer 5 is measured by the carbon monoxide concentration measuring device 7. The oxygen concentration in the gas at the outlet of the pulverizer 5 is measured by the oxygen concentration measuring device 6. Measurement data (measurement result) of the carbon monoxide concentration in the gas at the outlet of the pulverizer 5 measured by the carbon monoxide concentration measuring device 7 and oxygen in the gas at the outlet of the pulverizer 5 measured by the oxygen concentration measuring device 6. The concentration measurement data (measurement result) is input to the calculator 11.

  The calculator 11 calculates the oxygen partial pressure from the measurement data of the oxygen concentration. The computing unit 11 uses oxygen partial pressure as a parameter, and oxygen in the mixed gas supplied to the pulverizer 5 based on the measurement data from the carbon monoxide concentration measuring device 7 and the calculated oxygen partial pressure. The air supply amount adjusting device 14 and the gas supply amount adjusting device 15 are controlled so as to change the partial pressure. Thereby, the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is changed.

  Specifically, as a result of measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer 5, if any carbon monoxide concentration is detected, an oxidation reaction of fuel, which is a sign of ignition, is occurring. Therefore, the computing unit 11 is configured so that the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is reduced based on the calculated oxygen partial pressure, that is, the ignition temperature of the pulverized coal is increased. The supply amount of the carrier air supplied to the gas and the supply amount of the gas having a lower oxygen partial pressure than the air are adjusted. Specifically, the ignition temperature of pulverized coal is raised by relatively increasing the supply amount of gas having a lower oxygen partial pressure than air. As a result, the oxidation reaction of fuel, which is a sign of ignition, does not occur in the pulverizer 5, and the carbon monoxide concentration is not detected in the gas at the outlet of the pulverizer 5. 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.

  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.

  Further, by supplying at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas to the pulverizer 5 as a gas having a lower oxygen partial pressure than air, the mixed gas supplied to the pulverizer 5 The oxygen partial pressure of can be suitably changed. A part of the exhaust gas from the boiler 9 may be used as the gas having a lower oxygen partial pressure than air.

  In addition, you may provide a threshold value in the carbon monoxide density | concentration which the carbon monoxide density | concentration measuring apparatus 7 measures. 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. When the carbon monoxide concentration measured by the carbon monoxide concentration measuring device 7 is sufficiently close to the threshold value, the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is lowered, that is, the ignition temperature of pulverized coal. Is adjusted so that the supply air supplied to the pulverizer 5 and the supply amount of gas having a lower oxygen partial pressure than air are adjusted. On the other hand, when the carbon monoxide concentration is sufficiently far from the threshold value, the supply air supplied to the pulverizer 5 and the supply amount of the gas having a lower oxygen partial pressure than the air are not changed. When the carbon monoxide concentration is sufficiently away from the threshold value, the pulverizer 5 is set so that the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 increases, that is, the ignition temperature of the pulverized coal decreases. The supply amount of the carrier air supplied to the gas and the supply amount of the gas having a lower oxygen partial pressure than the air may be adjusted.

  Thus, even if the threshold value is provided for the carbon monoxide concentration and the air supply amount adjusting device 14 and the gas supply amount adjusting device 15 are controlled, ignition in the pulverizer 5 can be prevented.

(Relationship between oxygen partial pressure and ignition temperature)
Next, the relationship between the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 and the ignition temperature will be described. In order for the computing unit 11 to control the air supply amount adjusting device 14 and the gas supply amount adjusting device 15, the relationship between the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 and the ignition temperature is grasped in advance. It is necessary to keep. Then, the ignition temperature of the pulverized coal which grind | pulverized this using 1 type (s) or 2 or more types of 3 types of coal A, B, C from which a property differs was investigated. 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. While changing the oxygen partial pressure of the mixed gas supplied into the cylindrical vertical reaction tube 22 and changing the atmospheric temperature in the cylindrical vertical reaction tube 22 with the heater 24, repeated tests were performed to obtain a cylindrical vertical reaction tube. The average value of the atmospheric temperature in the cylindrical vertical reaction tube 22 at the time when the carbon monoxide concentration in the gas at the outlet of 22 became 30 ppm or more was calculated as the ignition temperature of the pulverized coal.

  The measurement result of the ignition temperature of pulverized coal using the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 as a parameter is shown in FIG. From the measurement result of the ignition temperature of the pulverized coal, it can be seen that the ignition temperature of the pulverized coal increases linearly as the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 decreases. This is considered to be because the pulverized coal is less likely to be oxidized and less likely to ignite as the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is lower. Therefore, controlling the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is considered to be an operating condition for safely operating the pulverizer 5 from the viewpoint of ignition in the pulverizer 5. 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 air supply amount adjusting device 14 and the gas supply amount adjusting device 15 by the computing unit 11 is not limited to the above-described one. Even if the carbon monoxide concentration measuring device 7 does not detect the carbon monoxide concentration, the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is reduced, that is, the ignition temperature of the solid fuel is increased. The carrier air supplied to the pulverizer 5 and the supply amount of the gas having a lower oxygen partial pressure than the air may be adjusted, respectively, or even if the carbon monoxide concentration measuring device 7 detects the carbon monoxide concentration, If the value is less than the threshold value, the conveying air supplied to the pulverizer 5 so that the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 is increased, that is, the ignition temperature of the solid fuel is lowered. The supply amount of the gas having a lower oxygen partial pressure than air may be adjusted. In short, as long as ignition does not occur in the pulverizer 5, the supply air supplied to the pulverizer 5 and the supply amount of gas having a lower oxygen partial pressure than air may be adjusted.

  In addition, the calculator 11 controls the air supply amount adjusting device 14 that adjusts the supply amount of the conveying air supplied from the air supply device 12 to the pulverizer 5, but the calculator 11 is configured to control the air supply amount. The structure which does not control the adjustment apparatus 14 may be sufficient. A gas that adjusts the supply amount of gas having a lower oxygen partial pressure than the air supplied from the gas supply device 13 to the pulverizer 5 while keeping the supply air supply amount supplied from the air supply device 12 to the pulverizer 5 constant. Even if the calculator 11 controls only the supply amount adjusting device 15, the oxygen partial pressure in the mixed gas supplied to the pulverizer 5 can be changed. In this case, the air supply amount adjusting device 14 is unnecessary.

1, 2 Coal hopper 3a, 3b Coal supply amount adjustment device 4 Mixer 5 Crusher 6 Oxygen concentration measuring device (oxygen concentration measuring means)
7 Carbon monoxide concentration measuring device (carbon monoxide concentration measuring means)
8 Pulverized coal burner 9 Boiler 10 Ignition prevention device of crusher 11 Calculator (control means)
12 Air supply device (air supply means)
13 Gas supply device (gas supply means)
14 Air supply amount adjusting device 15 Gas supply amount adjusting device (gas supply amount adjusting 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 (6)

A method for preventing ignition of a pulverizer for pulverizing solid fuel,
Supplying air and a gas having a lower oxygen partial pressure than the air to the pulverizer as a mixed gas;
Measure the carbon monoxide concentration and oxygen concentration in the gas at the outlet of the pulverizer,
Based on the measurement result of the carbon monoxide concentration and the oxygen partial pressure calculated from the measured oxygen concentration, the oxygen partial pressure in the mixed gas supplied to the pulverizer is changed. A method for preventing ignition of a pulverizer, comprising adjusting a supply amount of a gas having a lower oxygen partial pressure than the air supplied to the pulverizer.   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.   The method for preventing ignition of a pulverizer according to claim 1 or 2, wherein the gas having a lower oxygen partial pressure than air is at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. . An ignition prevention device for a pulverizer for pulverizing solid fuel,
Air supply means for supplying air to the pulverizer;
Gas supply means for supplying the pulverizer with a gas having a lower oxygen partial pressure than the air so as to be supplied to the pulverizer as a mixed gas mixed with the air;
A gas supply amount adjusting means for adjusting a supply amount of a gas having a lower oxygen partial pressure than the air supplied to the pulverizer;
Carbon monoxide concentration measuring means for measuring the carbon monoxide concentration in the gas at the outlet of the pulverizer;
Oxygen concentration measuring means for measuring the oxygen concentration in the gas at the outlet of the pulverizer;
The oxygen in the mixed gas supplied to the pulverizer based on the measurement result of the carbon monoxide concentration measuring means and the oxygen partial pressure calculated from the oxygen concentration measured by the oxygen concentration measuring means. Control means for controlling the gas supply amount adjusting means so as to change the partial pressure;
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 4 characterized by the above-mentioned.   The ignition prevention device for a pulverizer according to claim 4 or 5, wherein the gas having a lower oxygen partial pressure than air is at least one of nitrogen gas, carbon dioxide gas, water vapor, and combustion exhaust gas. .

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