JP6051952B2 - Fuel control method and fuel control apparatus for blast furnace gas fired boiler - Google Patents

Description

  The present invention relates to a method for controlling a fuel gas supplied from a blast furnace as a by-product gas to a steam generating boiler as a fuel, and an apparatus used for the control. The present invention relates to a method and apparatus for controlling fuel gas when it occurs.

  Conventionally, in steelworks, gas (blast furnace gas: BFG) obtained as a by-product gas from a blast furnace is sent to a boiler as fuel, and high-temperature and high-pressure steam obtained by the boiler is led to a turbine of a generator for power generation. That is, blast furnace gas-fired power generation is performed.

By the way, during the operation of the blast furnace, a phenomenon called so-called blow-through may occur.
Blowing is a phenomenon in which a part of the ore layer in the blast furnace causes fluidization or channeling, and a large amount of gas reaches the top of the furnace with a large amount of sensible heat without heat exchange or reaction with the charge. If such a blow-through occurs, the thermal energy of the blast furnace gas supplied to the boiler of the blast furnace gas-fired power generation facility (the amount of heat generated during combustion) increases rapidly, so the pressure in the boiler, steam temperature, And the like, the process value may fluctuate rapidly and greatly, resulting in an uncontrollable state, that is, a so-called trip state. And if it will be in a trip state, the operation of a blast furnace gas-fired power generation facility has to be stopped, and therefore the adverse effect on the inside and outside of the ironworks in that case becomes great. Specifically, when the power transmission to each factory in the steel works stops and there is a situation where the operation of each factory must be stopped, or when steam is sent from the power generation equipment to each factory in the steel works The air supply stops and the operation in each place is disturbed.

  From the above viewpoint, in blast furnace gas-fired power generation, the amount of heat generated by the blast furnace gas supplied to the blast furnace-fired boiler is prevented from abruptly increasing during the blast furnace blow-through, thereby minimizing the adverse effects of blow-through. It is strongly desired to suppress it.

  By the way, Patent Document 1, Patent Document 2 and the like have already been proposed as methods for preventing the amount of heat generated by the blast furnace gas supplied to the boiler from rapidly increasing when the blast furnace is blown through.

For example, Patent Document 1 estimates the blast furnace gas calorific value from the temperature of the blast furnace gas, further corrects the calorific value based on the blast furnace gas temperature and pressure, and guides the blast furnace gas to the boiler based on the corrected blast furnace gas calorific value. There has been proposed an apparatus for controlling fluctuations in the amount of blast furnace gas heat supplied to a boiler by controlling a flow rate control valve provided in a flow path. In addition, the blast furnace gas flow rate to the boiler in a 150 MW class power generation facility is extremely large, about 350,000 Nm ³ / h or more. To open and close such a large flow rate, a large butterfly valve with a valve body diameter of several meters or more is used. Is usually used.
In the apparatus of Patent Document 1, in order to suppress the amount of heat supplied to the boiler when the blast furnace gas heat generation amount suddenly rises due to the blow-through of the blast furnace, the blast furnace gas flow rate control valve to the boiler is suddenly and greatly closed. Need to work. However, when the flow of blast furnace gas at a large flow rate is suddenly closed by a large butterfly valve, a sudden draft change in the boiler or a sudden change in the amount of heat transferred to the heat transfer tube occurs, causing the blast furnace gas-fired power generation facility to trip. There is a risk.
Therefore, even if the method of Patent Document 1 is applied to actual operation, it has been difficult to reliably and stably prevent equipment trips when the blast furnace is blown through.

Patent Document 2 proposes that the fuel gas supplied to the boiler is switched from the blast furnace gas to the coke oven gas when the temperature of the blast furnace gas becomes abnormally high due to, for example, blow-through of the blast furnace.
However, it is practically difficult to secure a sufficient amount of coke oven gas comparable to the amount of blast furnace gas used in a large blast furnace gas-fired boiler because of the gas balance of the steelworks. In addition, since the absolute amount of coke oven gas obtained at ironworks is much less than that of blast furnace gas, when switching to coke oven gas when the temperature of the blast furnace gas rises abnormally, the amount of gas supplied to the boiler suddenly increases. Usually it decreases. In such a case, due to insufficient gas amount or insufficient heat amount in the boiler, there may be a sudden draft change in the boiler or a rapid change in the heat transfer amount to the heat transfer tube, causing the blast furnace gas-fired power plant to trip.
Therefore, it is difficult to apply the method of Patent Document 2 to actual operation at a steelworks, and even if it is applied to actual operation, the trip of equipment is reliably and stably prevented at the time of blowing through a blast furnace. It was difficult.

  As described above, a conventionally proposed method as a method for preventing the occurrence of a trip due to a sudden increase in the amount of heat generated by the blast furnace gas supplied to the boiler when the blast furnace is blown through. In fact, it is difficult to reliably and stably prevent the occurrence of trips, or a significant increase in cost has occurred, making it difficult to apply to actual steelworks.

Japanese Patent Publication No. 5-77926 JP 2008-2441048 A

  The present invention was made in the context of the above circumstances, and in a blast furnace gas-fired boiler that generates steam using blast furnace gas as fuel, such as a boiler for blast furnace gas power generation, a blast furnace blow-out occurs without causing a significant increase in cost. A fuel control method during blast furnace blow-through in a blast furnace gas-fired boiler, which can reliably and stably prevent a trip from occurring due to a sudden increase in calorific value of the blast furnace gas at the time, and It is an object to provide a device to be used.

As a result of various studies to solve the above-mentioned problems, the present inventor has noticed that a large amount of substantially non-flammable (non-exothermic) gas is discharged as exhaust gas from a blast furnace gas-fired boiler. Then, it was considered to dilute the blast furnace gas to be introduced into the boiler with the exhaust gas of the boiler when the blow-through of the blast furnace occurred.
That is, since a large amount of substantially non-flammable exhaust gas is inevitably discharged from a blast furnace gas-fired boiler, attention is paid to the fact that the use of the exhaust gas does not cause a significant increase in cost. Moreover, by appropriately determining the introduction position (mixing position for dilution) of the boiler exhaust gas into the blast furnace gas when a blast furnace blow-through occurs, the flow rate of gas supplied to the boiler is stabilized, thereby ensuring reliable and stable installation of the equipment. It has been found that trips can be prevented and the present invention has been made.

  In accordance with the method described in Patent Document 2, the fuel gas supplied to the boiler is changed from blast furnace gas to other than coke oven gas when the calorific value of the blast furnace gas becomes abnormally large due to blow-through of the blast furnace. It is also conceivable to switch to a high calorific value gas, for example natural gas (LPG). However, since natural gas (LPG) is expensive, in this case, the cost is significantly increased, which is not practical.

  Also, when the temperature of the blast furnace gas becomes abnormally high due to a blow-through of the blast furnace, it is not unthinkable to mix and dilute the blast furnace gas supplied to the boiler with nitrogen gas. Therefore, it is difficult to actually apply.

  In addition, even under normal conditions (no blow-through), a high calorific value gas such as coke oven gas or natural gas is mixed with the blast furnace gas as an auxiliary gas and supplied to the boiler. Although it is conceivable to reduce the flow rate, in this case also, the cost is increased and it is practically difficult to apply.

  On the other hand, if exhaust gas inevitably discharged from a boiler originally provided in a blast furnace gas power generation facility or the like is used, it becomes possible to avoid an increase in cost as in the case of each of the above methods. It is.

Basic aspects fuel control how put into the blast furnace gas fired boiler (first aspect) of the present invention, therefore,
A fuel control method for a blast furnace gas fired boilers you blast furnace gas and fuel,
A fuel supply step for guiding the blast furnace gas to the boiler via a fuel supply flow path;
A flow rate adjusting step for adjusting the supply amount of the high-pressure gas to the boiler using a flow rate adjustment valve provided in the fuel supply flow path;
An exhaust gas exhausting process for exhausting the boiler exhaust gas to the outside via an exhaust gas exhaust path;
The exhaust gas is introduced from the exhaust gas discharge passage to a position upstream of the flow rate adjustment valve in the fuel supply passage through the exhaust gas introduction passage, and mixed with the blast furnace gas in the fuel supply passage. An exhaust gas introduction process;
A state quantity detection step of detecting a state quantity of the blast furnace gas using a state quantity detection means provided at a position upstream of the connection position of the exhaust gas introduction flow path to the fuel supply flow path;
An exhaust gas introduction control step for controlling the introduction of the exhaust gas from the exhaust gas introduction channel to the fuel supply channel, provided in the exhaust gas introduction channel;
Have
When it is determined that a blast furnace blow-through has occurred based on the state quantity detected by the state quantity detection means, the operation of the exhaust gas introduction control means is performed according to the state quantity detected by the state quantity detection means. The exhaust gas is controlled and introduced into the fuel supply channel from the exhaust gas introduction channel .

In such a first aspect, since at the time of blast furnace blow is the calorific value of the blast furnace gas increases sharply, the exhaust gas of the boiler is substantially non-combustible, heat value is substantially zero, the state amount When it is determined that a blast furnace blow-through has occurred based on the state quantity detected by the detection means, the operation of the exhaust gas introduction control means is controlled according to the state quantity detected by the state quantity detection means, The blast furnace gas is thermally diluted by mixing the exhaust gas of the boiler with the blast furnace gas having an increased calorific value, and as a result, the calorific value of the gas introduced as fuel into the boiler is reduced. That is, a rapid increase in the amount of heat input to the boiler is mitigated, and a tripping state can be avoided.
In addition, the position where a part of the boiler exhaust gas is introduced into the fuel supply passage for guiding the blast furnace gas to the fuel supply port of the boiler at the time of blast furnace blow-off is set at a position upstream of the flow rate adjustment valve. Even when a blast furnace blow-through occurs, there is no need to greatly change the opening of the flow regulating valve. That is, at the time of blast furnace blow-through, the amount of heat generated by the blast furnace gas increases rapidly, but the blast furnace gas diluted before the amount of heat generated by the increased amount of blast furnace gas reaches the flow control valve. The adjustment of the opening (adjustment of the amount of gas supplied to the boiler) may or may not be performed.

  The flow rate adjusting valve for adjusting the amount of fuel gas supplied to the boiler is a large valve, for example, a large butterfly valve with a valve body diameter of several meters because the fuel gas flowing therethrough is a large flow rate. With such a large flow rate adjustment valve, it is difficult to finely adjust the flow rate.In particular, when the opening degree is suddenly changed greatly, it is not possible to finely adjust to an appropriate flow rate immediately. Have difficulty. Therefore, when the blast furnace gas is blown through, if the blast furnace gas is not diluted with the exhaust gas of the boiler, as already described with respect to Patent Document 1, the heating value of the gas to the boiler is controlled only by adjusting the flow rate of the blast furnace gas. In such a case, there is a risk that the facility will trip due to a sudden and large opening degree change of the large flow regulating valve. However, in the present embodiment, as described above, the adjustment of the flow rate adjustment valve (change in the opening degree) at the time of the blast furnace blow-through does not have to be performed or is negligible, so that such a situation does not occur. A stable operating state can be maintained.

The second fuel control how put in the blast furnace gas fired boiler aspect of the present invention is the method of the first aspect,
The state quantity detected by the state quantity detection means includes at least a calorific value and a flow rate of the blast furnace gas .

On the other hand, the 3rd aspect and the 4th aspect of this invention are about the apparatus used for implementation of the fuel control method at the time of blast furnace blow-by in a blast furnace gas-fired boiler.
That fuel control device that put the third aspect blast furnace gas fired boiler of the present invention,
In the fuel control system for blast furnace gas fired boilers using blast furnace gas as fuel,
A fuel supply flow path for guiding the blast furnace gas to the boiler;
A flow rate adjusting valve provided in the fuel supply path for adjusting the supply amount of the blast furnace gas to the boiler;
An exhaust gas discharge passage for discharging the exhaust gas of the boiler to the outside;
An exhaust gas introduction flow path that guides the exhaust gas from the exhaust gas discharge path to a position upstream of the flow rate adjustment valve in the fuel supply flow path, and mixes it with the blast furnace gas in the fuel supply flow path;
A state quantity detecting means provided at a position upstream of a connection position between the fuel supply passage and the exhaust gas introduction passage, and detecting a state quantity of the blast furnace gas;
An exhaust gas introduction control means for controlling the introduction of the exhaust gas from the exhaust gas introduction channel to the fuel supply channel, provided in the exhaust gas introduction channel;
Have
When it is determined that a blast furnace blow-through has occurred based on the state quantity detected by the state quantity detection means, the operation of the exhaust gas introduction control means is performed according to the state quantity detected by the state quantity detection means. The exhaust gas is controlled and introduced into the fuel supply channel from the exhaust gas introduction channel .
The fuel control apparatus for a blast furnace gas fired boiler according to the fourth aspect of the present invention is the fuel control apparatus for a blast furnace gas fired boiler according to the third aspect, wherein the state quantity detected by the state detection means is the amount of the blast furnace gas. It includes at least a calorific value and a flow rate.

  According to the fuel control control method at the time of blast furnace blow-through in the blast furnace gas-fired boiler of the present invention, it is possible to reduce the cost of equipment due to a rapid increase in the amount of heat generated by the blast furnace gas when the blast furnace blow-through occurs. The occurrence of trips can be reliably and stably prevented, and the operation of the blast furnace gas-fired boiler can be stabilized. Moreover, according to the fuel control apparatus for when the blast furnace is blown through in the blast furnace gas-fired boiler according to the present invention, the excellent fuel control method as described above can be applied to an actual steelworks easily and at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an overall configuration of an apparatus for carrying out a first embodiment of a fuel control method when a blast furnace gas is fired in a blast furnace gas-fired boiler in blast furnace gas power generation according to the present invention. It is a block diagram which shows the whole structure of the apparatus for enforcing 2nd Embodiment of the fuel control method at the time of blast furnace blow-by in the blast furnace gas fired boiler of this invention.

  Next, the fuel control method according to the first embodiment of the present invention will be described in detail with reference to FIG. 1 showing an example of an apparatus configuration for the implementation. In FIG. 1, a characteristic configuration portion in the present embodiment is surrounded by a broken line X. In other words, the portion not surrounded by the broken line X is a portion having a configuration substantially similar to the conventional one.

In FIG. 1, a boiler 10 includes a fuel supply port 10A for introducing fuel gas and an exhaust gas outlet 10B for discharging exhaust gas after combustion in the boiler to the outside of the boiler. Here, the fuel gas introduced into the boiler from the fuel supply port 10A is a blast furnace gas alone in a normal state (a state in which no blow-through occurs), and during the blast furnace blow-through, as described later, It becomes a mixed gas.
The specific configuration of the boiler 10, particularly the internal configuration thereof, may be the same as that of a blast furnace gas-fired boiler conventionally used for blast furnace gas power generation, and the details thereof are omitted.

  A fuel supply passage 12 made of a duct or the like is connected to the fuel supply port 10 </ b> A of the boiler 10. The fuel supply flow path 12 is branched from a blast furnace gas main pipe 14 through which blast furnace gas discharged from the top of the blast furnace (not shown) is passed, and guides the blast furnace gas to the fuel supply port 10 </ b> A of the boiler 10. A branch point from the blast furnace gas main pipe 14 to the fuel supply flow path 12 is indicated by a symbol P in FIG. In the middle of the fuel supply channel 12 (a position close to the boiler 10 in FIG. 1), a flow rate for adjusting the flow rate of the fuel gas flowing through the fuel supply channel 12 (and hence the total flow rate of the fuel gas supplied to the boiler 10). A regulating valve 16 is interposed.

  Further, an exhaust gas main pipe 18 for sending the fuel exhaust gas from the boiler 10 to the outside is connected to the exhaust gas outlet 10 </ b> B of the boiler 10. From the exhaust gas main pipe 18, an exhaust gas introduction flow path 20 for guiding the exhaust gas of the boiler 10 toward the fuel supply flow path 12 is branched. The exhaust gas introduction flow path 20 is connected to a position upstream of the flow rate adjustment valve 16 in the fuel supply flow path 12 (position closer to the branch point P). Therefore, as will be described later, the exhaust gas from the boiler 10 passes through the exhaust gas introduction flow path 20 and is located upstream of the flow rate adjustment valve 16 in the fuel supply flow path 12 (position close to the branch point P). Can be mixed with the blast furnace gas. The connection position of the exhaust gas introduction flow path 20 with respect to the fuel supply flow path 12, that is, the exhaust gas introduction / mixing position with respect to the blast furnace gas is indicated by the symbol Q for convenience in FIG.

  The exhaust gas introduction flow path 20 is provided with exhaust gas introduction control means 22 for controlling the state in which the exhaust gas is sucked from the exhaust gas main pipe 18 and introduced into the fuel supply flow path 12. Here, controlling the state in which the exhaust gas is introduced into the fuel supply passage 12 is performed by turning ON / OFF the introduction of the exhaust gas into the fuel supply passage 12 (mixing of the exhaust gas with respect to the blast furnace gas). It means that the amount of exhaust gas introduced (mixed amount) is adjusted. Specifically, in this embodiment, the exhaust gas introduction control means 22 includes a suction damper 22A, a blower 22B, and a serial connection from the exhaust gas main pipe 18 side toward the exhaust gas introduction point Q of the fuel supply passage 12. The discharge damper 22C is used.

  Furthermore, in order to detect the state quantity of the blast furnace gas led from the blast furnace gas main pipe 14 to the fuel supply flow path 12 on the upstream side of the exhaust gas introduction point Q in the fuel supply flow path 12 (side closer to the branch point P). The state quantity detection means 24 is provided. The state quantity detection means 24 is for detecting that a blow-through has occurred in the blast furnace and detecting the degree of the blow-through (the degree of increase in the amount of heat generated by the blast furnace gas).

  Here, as the state quantity of the blast furnace gas, basically only the calorific value and the flow rate may be used. However, in the actual calorific value detector, the calorific value is a value in a standard state (normal) at 0 ° C. and 1 atm. It is often configured to instruct and output as Regarding the flow rate, the blast furnace gas introduced from the blast furnace is usually in a steam saturated state by spraying water at the top of the furnace, but the flow rate detected by the state quantity detection means 24 is the standard state ( Normally, it is detected as a value in (normal). Therefore, in the present embodiment, the calorific value and flow rate in the standard state are converted and corrected to the calorific value in the actual gas state and the flow rate in the steam saturated state by the actual temperature and pressure of the blast furnace gas. In addition to the heating value and flow rate of the state, the temperature and pressure of the blast furnace gas are also detected at the same time.

Specifically, in this embodiment, the state quantity detection means 24 includes a calorific value detector 24A, a temperature sensor 24B, a pressure sensor 24C, and a flow rate detector 24D. The calorific value detector 24A is designed to instruct and output values in the standard state.
If the calorific value detector 24A and the flow rate detector 24D have functions for detecting and indicating the calorific value of the actual gas and the actual gas flow rate, the temperature sensor 24B and the pressure sensor 24C may be omitted. .

  The outputs of the calorific value detector 24A, the temperature sensor 24B, the pressure sensor 34C, and the flow rate detector 24D constituting the state quantity detection means 24 are sent to the calculation / determination device 26, and the result of determination by the calculation / determination device 26 is as follows. Based on the calculation result, the operation of each component (suction damper 22A, blower 22B, and discharge damper 22C) of the gas introduction control means 22 is controlled. That is, in the case of this embodiment, based on the detection result of the state quantity detection means 24, the start and stop of the blower 22B are controlled (thus turning on / off the exhaust gas to be introduced), and the suction damper 22A and the discharge damper 22C are opened. It is configured to control the degree (and thus to control the flow rate of the exhaust gas to be introduced).

  The arithmetic / judgment device 26 blows through the blast furnace when the calorific value of the blast furnace gas detected by the calorific value detector 24A (in this embodiment, the calorific value in the standard state) exceeds a predetermined threshold. It is determined that the blower 22B is activated. At the same time, the arithmetic / judgment device 26 calculates the calorific value and flow rate in the standard state detected by the calorific value detector 24A and the flow rate detector 24D of the actual temperature and pressure detected by the temperature sensor 24B and the pressure sensor 34C. Based on the value, the calorific value of the actual gas (the calorific value at the actual blast furnace gas temperature and pressure) and the actual gas flow rate are converted into the actual gas flow rate, and further, the suction damper 22A and the discharge damper 22C according to the actual gas calorific value and flow rate. The required opening is calculated, and the opening of the suction damper 22A and the discharge damper 22C is controlled thereby to control the amount of exhaust gas to be introduced.

In the apparatus configuration of the first embodiment shown in FIG. 1 as described above, the exhaust gas introduction point Q in the fuel supply flow path 12 is upstream from the flow rate adjustment valve 16 and from the installation position of the state quantity detection means 24. Downstream. Here, the distance L on the fuel supply flow path 12 from the installation position of the state quantity detection means 24 to the exhaust gas introduction point Q is preferably determined as follows.
That is, it is appropriate to determine the distance L so that the exhaust gas can be mixed with the blast furnace gas at the exhaust gas introduction point Q by the timing when the blast furnace gas reaches the exhaust gas introduction point Q from the state quantity detection means 24.

  Specific methods for setting the distance L include, for example, a detection time (particularly a calorific value measurement time) in the state quantity detection unit 24, a calculation / determination time in the calculation / determination device 26, and a start-up time of the blower 22B in the gas introduction control unit 22 Depending on the opening / closing time of the suction damper 22A and the discharge damper 22C, the flow rate of the blast furnace gas in the fuel supply flow path 12, and the like, from the state quantity detection means 24 until the timing when the blast furnace gas reaches the position of the exhaust gas introduction point Q It is desirable to determine the distance L so that the exhaust gas reaches the exhaust gas introduction point Q from the exhaust gas introduction flow path 20 (desirably before that timing).

  Incidentally, the calorific value measurement time in the state quantity detection means 24 is usually about several seconds, the calculation / determination time in the calculation / determination device 26 is 1 second or less, the start-up time of the blower 22B in the gas introduction control means 22, the suction damper 22A, The total opening and closing time of the discharge damper 22C is within several seconds, and even if these are combined, it is 10 seconds or less. On the other hand, the flow rate of the blast furnace gas in the fuel supply channel 12 is usually about 20 m / s at the maximum although it varies depending on the equipment. Therefore, if the distance L is set to about 200 m or more, the above timing condition can be sufficiently satisfied.

  Next, a specific control method in the first embodiment as described above will be described.

  During normal times, that is, while the blast furnace gas is not blown through and the blast furnace gas having a stable calorific value is supplied from the blast furnace gas main pipe 14, the suction damper 22A of the gas introduction control means 22 is closed, The blower 22B is set in a non-operating state. In this state, the blast furnace gas guided from the blast furnace gas main pipe 14 to the fuel supply flow path 12 is continuously supplied to the fuel supply port 10 </ b> A of the boiler 10 through the state quantity detection means 24 and the main flow rate adjustment valve 16. In the boiler 10, high-temperature and high-pressure steam is continuously generated by the combustion of the blast furnace gas. The high-temperature and high-pressure steam is sent, for example, to a turbine of a generator (not shown), and steady power generation is performed. Therefore, in normal times, blast furnace gas is used alone as the fuel gas of the boiler 10. The discharge damper 22C of the gas introduction control means 22 may be normally closed, but as described above, the suction damper 22A is closed and the blower 22B is non-operating as usual. Whether the discharge damper 22C is open / closed does not affect the operation state. Therefore, in the following description, it is assumed that the discharge damper 22C is normally open and only adjusts the opening degree when a blast furnace blow-off described later occurs.

The opening degree of the flow rate adjusting valve 16 is controlled by a control means (not shown) so that the calorific value of the gas introduced into the boiler 10 becomes an appropriate value. On the other hand, the state quantity detection means 24 is operated even during normal times so that the state quantity of the blast furnace gas led from the blast furnace gas main pipe 14 to the fuel supply flow path 12 is always detected. That is, the calorific value detector 24A always detects the calorific value (kcal / Nm ³ ) of the blast furnace gas in the standard state, and the temperature sensor 24B and the pressure sensor 34C are used to detect the actual temperature (° C.) and pressure ( mmAg.G) is detected, and the flow rate of the blast furnace gas introduced into the fuel supply passage 12 is detected by the flow rate detector 24D. These detection outputs are always input to the calculation / determination device 26.

The state quantity detected by the state quantity detection means 24 is set in advance to a threshold value preset in the calculation / judgment device 26, for example, the calorific value (kcal / Nm ³ ) of the blast furnace gas detected by the calorific value detector 24A. When the threshold value is exceeded, the calculation / determination device 26 determines that “blast furnace blow-through has occurred”.
Based on the calorific value (kcal / Nm ³ ), pressure (mmAg.G), temperature (° C.), flow rate (before correction) of the blast furnace gas measured by the state quantity detection means 24, the calculation / determination device 26 The actual gas calorific value (kcal / m ³ ) of the blast furnace gas and the actual gas flow rate (m ³ / h) of the blast furnace gas are calculated.

  Further, as described above, when it is determined that “blast furnace blow-through has occurred”, the blower 22B in the gas introduction control means 22 is activated and the suction damper 22A is opened. As a result, the exhaust gas from the boiler 10 enters the fuel supply flow path 12 at the position of the exhaust gas introduction point Q via the exhaust gas introduction flow path 20. That is, at the exhaust gas introduction point Q, the exhaust gas from the boiler 10 is mixed with the blast furnace gas, the blast furnace gas is diluted with the exhaust gas, and the diluted mixed gas passes through the flow rate adjustment valve 16 to the fuel supply port of the boiler 10. It will be in the state supplied continuously to 10A.

Then, the opening degree of the discharge damper 22C of the gas introduction control means 22 is controlled by a signal from the calculation / determination device 26 and introduced into the fuel supply passage 12 through the exhaust gas introduction passage 20 at the position of the exhaust gas introduction point Q. The exhaust gas flow rate (actual gas flow rate) is controlled. Specifically, the actual gas calorific value (kcal / m ³ ) of the mixed gas introduced into the boiler 10 is a normal value with no blast furnace blow-through (actual gas of the blast furnace gas introduced into the boiler 10 at normal times). The exhaust gas flow rate is controlled so as to coincide with the calorific value).

  Thus, even when it is determined that a blast furnace blow-through has occurred, the calorific value of the fuel gas introduced into the boiler 10 is maintained at the same value as in a normal state where there is no blast furnace blow-through, so that the amount of fuel gas introduced into the boiler 10 is maintained. It is possible to prevent a trip of the equipment from being caused by a sudden and large fluctuation of the calorific value.

  Further, mixing and dilution of the boiler exhaust gas into the blast furnace gas at the time of blast furnace blow-through is performed at a position upstream of the flow rate adjustment valve 16 (exhaust gas introduction point Q), so when the gas reaches the flow rate adjustment valve 16, The blast furnace gas has already been appropriately diluted with the boiler exhaust gas. Therefore, the flow rate adjustment by the flow rate adjustment valve 16 may not be performed, or even if it is adjusted, the adjustment is slight. That is, even when the blast furnace is blown through, it is not necessary to adjust the opening of the large flow rate adjustment valve 16 rapidly and drastically as a countermeasure against the increase in the heat generation amount of the blast furnace gas.

  Here, as already described, the blast furnace gas reaches the exhaust gas introduction point Q from the state quantity detection unit 24 at a distance L on the fuel supply flow path 12 from the installation position of the state quantity detection unit 24 to the exhaust gas introduction point Q. By determining that the blast furnace gas can be mixed with the blast furnace gas at the exhaust gas introduction point Q, the boiler without increasing the amount of generated blast furnace gas into the boiler exhaust gas even in the early stage of the blast furnace blow-off occurrence. 10 can be reliably prevented.

  Next, in the control method according to the first embodiment, the result of the trial calculation of the exhaust gas introduction amount (mixing / dilution amount of boiler exhaust gas into the blast furnace gas supplied to the boiler 10) when the blast furnace blow-through occurs is as follows. ) To 5) will be described in accordance with the trial calculation procedure.

  1) First, each condition shown in Table 1 was set as a precondition. In Table 1, BFG means blast furnace gas, and the specification values described as BFGOO are values for the blast furnace gas introduced from the blast furnace gas main pipe 14 to the fuel supply passage 12 in FIG. That is, various values to be detected by the state quantity detection means 24 are indicated. Further, in Table 1, as the “normal” specification value, a value typically obtained in a normal time without a blast furnace blow-through was set. In addition, as the specification value of “at the time of blast furnace blow-through”, an average value expected at the time of blast furnace blow-through was set based on the knowledge of the present inventors.

2) Volume conversion from the normal state (normal) to the saturated water vapor state (wet) was performed by the following equation (1).
10,332 / (10,332 + 250-573.2) × (273.15 + 35) /273.15=1.1646 (1)
Here, the value of 10,332 in the equation (1) means a value obtained by converting 1 atm to a water column height.
From this equation (1), it can be seen that if the standard state is converted to the saturated water vapor state, there is a volume increase of 1.1646 times, that is, about 16%.

3) The actual gas calorific value of the blast furnace gas in consideration of water vapor saturation was obtained by the following equations (2) and (3).
In other words, the actual gas calorific value of the blast furnace gas at normal time is
750 / 1.1646 = 644.0 [kcal / m ³ -wet] (2)
It becomes.
On the other hand, the actual gas calorific value of the blast furnace gas when a blast furnace blow-through occurs is
1,100 / 1.1646 = 944.5 [kcal / m ³ -wet] (3)
It becomes.

4) The mixing ratio of the exhaust gas amount required to reduce the actual gas calorific value of the blast furnace gas at the time of blast furnace blow-down to the actual gas calorific value of the blast furnace gas by mixing the boiler exhaust gas with the blast furnace gas is as follows: It is calculated by the following equation (4). Here, X is the exhaust gas amount ratio of the blast furnace gas to the actual gas flow rate. For simplicity, it was assumed that the exhaust gas was inert (completely non-combustible) and had the same temperature as the blast furnace gas.
944.5 / (1 + X) = 644.0 → X = 0.4666 (4)
Therefore, if the volume of the fuel gas supplied to the boiler is 1.4666 times that of the normal time (about 47% increase), the amount of heat generated by the fuel gas supplied to the boiler when the blast furnace is blown through is equivalent to that in the normal time. .

5) Further, as described above, the amount of exhaust gas required for the volume of the fuel gas supplied to the boiler to be 1.4666 times (about 47% increase) compared to the normal time is W [m ³ / h] is the blast furnace If the actual gas flow rate is Q [m ³ / h], the following equation (5) and equation (6) are obtained.
200,000 × 750 = 944.5 × Q → Q = 158,814 [m ³ / h]
... (5)
W = 158, 814 × 0.4666 = 74, 103 [m ³ / h] (6)

From the above, under the preconditions in Table 1, the fuel gas supplied to the boiler by setting the flow rate of the boiler exhaust gas mixed with the blast furnace gas to W = 74, 103 [m ³ / h] at the blast furnace blow-through. It can be seen that the calorific value of (a mixed gas of blast furnace gas and boiler exhaust gas) can be maintained at the same level as normal.

Further, based on the above calculation results, the equipment specifications necessary for ensuring the exhaust gas flow rate W = 74,103 [m ³ / h] at the time of blast furnace blow-through, especially the exhaust gas introduction flow path (duct) 20 and the exhaust gas The specification of the blower 22B of the introduction control means 22 can be roughly estimated as follows.

That is, assuming that the exhaust gas flow velocity is 20 [m / s], the diameter of the exhaust gas introduction flow path (duct) 20: φ [m] is given by the following equation (7).
74,100 / 3600 / {π × (φ / 2) ² } = 20 → φ = 1.15 [m]
(7)
The specification of the blower 22B of the gas introduction control means 22 is that if the maximum permissible air flow is Q: [m ³ / min] and the pressure loss is H, each has a 20% margin and the exhaust gas pressure is zero. Assuming that, the following equations (8) and (9) are obtained.
Q = 1,480 [m ³ / min] (20% margin) (8)
H = (250 + a + b + c) × 1.2 (20% margin) (9)
In equation (9), a is the duct pressure loss, b is the suction damper pressure loss, and c is the discharge damper pressure loss.

  FIG. 2 shows an example of a device configuration for implementing the second embodiment of the power generation fuel control method of the present invention. In FIG. 2, the same parts as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG.

  In the second embodiment, the state quantity second detection means 28 is provided between the flow rate adjustment valve 16 and the exhaust gas introduction point Q in the fuel supply flow path 12. The state quantity second detection means 28 includes a calorific value detector 28A, a temperature sensor 28B, a pressure sensor 28C, and a flow rate detector 28D, similarly to the state quantity detection means 24. The outputs of the calorific value detector 28A, the temperature sensor 28B, the pressure sensor 28C, and the flow rate detector 28D are sent to the second arithmetic unit 30, and the flow rate adjustment is performed based on the calculation result by the second arithmetic unit 30. The opening degree of the valve 16 is adjusted. The configuration of the other parts is the same as that of the first embodiment shown in FIG.

Also in the second embodiment, when the blast furnace is blown through, it is detected that the exhaust gas from the boiler 10 is mixed with the blast furnace gas supplied to the boiler 10 to dilute the blast furnace gas in the case of the first embodiment. Is exactly the same. The second embodiment is applied when it is desired to improve the accuracy of the control more than the control according to the first embodiment.
That is, the state quantity second detection means 28 detects the state quantity of the mixed gas after the blast furnace gas is diluted with the boiler exhaust gas when the blast furnace is blown through. Then, when the calorific value or flow rate of the mixed gas resulting from the mixing / dilution is out of the value that should be adjusted for some reason, the opening of the flow rate adjusting valve 16 is finely adjusted and sent to the boiler 10. The flow rate of the fuel gas (a mixed gas of blast furnace gas and boiler exhaust gas) can be readjusted.

  In each of the above embodiments, the discharge damper 22C of the gas introduction control means 22 is a parent-child type, that is, a large main damper with a small finely adjustable sub-damper from the viewpoint of controllability of the exhaust gas discharge flow rate. It is good also as a structure connected in parallel.

  Further, in each of the above embodiments, the boiler exhaust gas is mixed with the fuel supply flow path 12 at one location (exhaust gas introduction point Q) in the fuel supply flow path 12, but the fuel gas (blast furnace) supplied to the boiler 10 is used. From the viewpoint of controllability such as the mixing ratio of the gas and the mixed gas of the boiler exhaust gas), the boiler exhaust gas may be mixed into the fuel supply channel 12 at a plurality of different locations in the fuel supply channel 12. That is, the exhaust gas introduction points Q of the fuel supply channel 12 may be provided at a plurality of locations in the length direction of the fuel supply channel 12.

  In addition, a recirculation system may be installed in the blower 22B of the gas introduction control means 22 in order to secure the minimum flow amount.

  Although preferred embodiments of the present invention have been described above, the present invention is of course not limited to these embodiments. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.

  The fuel control method for blast furnace blow-through of the present invention is most suitable for a steam generating boiler for blast furnace gas-fired power generation, but it can of course be applied to a blast furnace gas-fired boiler for other uses.

DESCRIPTION OF SYMBOLS 10 Boiler 12 Fuel supply flow path 20 Exhaust gas introduction flow path 22 Exhaust gas introduction control means 24 State quantity detection means 26 Calculation / determination device

Claims (4)

A fuel control method for a blast furnace gas fired boilers you blast furnace gas and fuel,
A fuel supply step for guiding the blast furnace gas to the boiler via a fuel supply flow path;
A flow rate adjusting step for adjusting the supply amount of the high-pressure gas to the boiler using a flow rate adjustment valve provided in the fuel supply flow path;
An exhaust gas exhausting process for exhausting the boiler exhaust gas to the outside via an exhaust gas exhaust path;
The exhaust gas is introduced from the exhaust gas discharge passage to a position upstream of the flow rate adjustment valve in the fuel supply passage through the exhaust gas introduction passage, and mixed with the blast furnace gas in the fuel supply passage. An exhaust gas introduction process;
A state quantity detection step of detecting a state quantity of the blast furnace gas using a state quantity detection means provided at a position upstream of the connection position of the exhaust gas introduction flow path to the fuel supply flow path;
An exhaust gas introduction control step for controlling the introduction of the exhaust gas from the exhaust gas introduction channel to the fuel supply channel, provided in the exhaust gas introduction channel;
Have
When it is determined that a blast furnace blow-through has occurred based on the state quantity detected by the state quantity detection means, the operation of the exhaust gas introduction control means is performed according to the state quantity detected by the state quantity detection means. controlled, fuel control how put into the blast furnace gas fired boiler, which comprises introducing the exhaust gas to the fuel supply passage from the exhaust gas introduction flow path. 2. The fuel control method for a blast furnace gas-fired boiler according to claim 1, wherein the state quantity detected by the state quantity detection means includes at least a calorific value and a flow rate of the blast furnace gas.   In the fuel control system for blast furnace gas fired boilers using blast furnace gas as fuel,
  A fuel supply flow path for guiding the blast furnace gas to the boiler;
  A flow rate adjusting valve provided in the fuel supply path for adjusting the supply amount of the blast furnace gas to the boiler;
  An exhaust gas discharge passage for discharging the exhaust gas of the boiler to the outside;
  An exhaust gas introduction flow path that guides the exhaust gas from the exhaust gas discharge path to a position upstream of the flow rate adjustment valve in the fuel supply flow path, and mixes it with the blast furnace gas in the fuel supply flow path;
  A state quantity detecting means provided at a position upstream of a connection position between the fuel supply passage and the exhaust gas introduction passage, and detecting a state quantity of the blast furnace gas;
  An exhaust gas introduction control means for controlling the introduction of the exhaust gas from the exhaust gas introduction channel to the fuel supply channel, provided in the exhaust gas introduction channel;
Have
  When it is determined that a blast furnace blow-through has occurred based on the state quantity detected by the state quantity detection means, the operation of the exhaust gas introduction control means is performed according to the state quantity detected by the state quantity detection means. A fuel control apparatus for a blast furnace gas fired boiler, wherein the exhaust gas is controlled and introduced into the fuel supply passage from the exhaust gas introduction passage. The fuel control apparatus for a blast furnace gas fired boiler according to claim 3, wherein the state quantity detected by the state detection means includes at least a calorific value and a flow rate of the blast furnace gas.

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