JP4870461B2 - Boiler and boiler combustion control method - Google Patents

Description

  The present invention relates to a boiler that adjusts a combustion amount in stages such as high combustion, medium combustion, low combustion, and combustion stop.

  In the case of a boiler that generates steam by burning with a combustion device, the amount of combustion is controlled based on the steam pressure value generated in the boiler. When the steam pressure value is lowered, the combustion amount is increased, and when the steam pressure value is increased, the combustion amount is decreased, thereby performing pressure control for keeping the steam pressure at a predetermined pressure. As the combustion amount control method, adjustment in stages such as three-position control of high combustion, low combustion, and combustion stop and four-position control in which medium combustion is added to the three-position control is widely performed.

  The four-position control is superior to the three-position control because, as described in Japanese Patent No. 2944080, the four-position control reduces the frequency of stopping combustion when the required steam amount is small. It can be done. In the case of 3-position control, high combustion is 100% combustion and low combustion is about 50% combustion, whereas in 4-position control, high combustion is 100% combustion and medium combustion is about 65%. As the combustion and the low combustion are approximately 30% combustion, the low combustion with the 4-position control has a smaller combustion amount than the low combustion with the 3-position control even with the same low combustion. Therefore, when the required steam amount is low, the frequency at which the combustion is stopped from the low combustion is reduced.

  Even in the three-position control, if the combustion amount is set to be small, for example, the combustion amount at low combustion is set to 30% of the high combustion, an effect of reducing the frequency at which the combustion is stopped from the low combustion can be obtained. However, even in such a case, since the control is performed with low combustion and high combustion, the pressure fluctuation range becomes large as compared with a four-position control boiler provided with medium combustion.

  In the case of the four-position control described in Japanese Patent No. 294080, the detected pressure value P, which is a detected value, is set to a preset high pressure value / middle pressure value / low pressure value (high pressure value> middle pressure). Value> lower pressure value) and the amount of combustion is determined. Combustion stops when the detected pressure value P is higher than the high pressure value, low combustion when the detected pressure value P is between the high pressure value and the intermediate pressure value, and the detected pressure value P is the intermediate pressure value and low pressure value. When the pressure is between, the combustion is medium, and when the detected pressure value P is lower than the low pressure value, the combustion is high. The detected pressure value P can be kept within a predetermined range by increasing the combustion amount as the detected pressure value P is lower and decreasing the combustion amount as the detected pressure value P is higher.

  When the amount of generated steam and the amount of steam used are balanced and the change in the detected pressure value P is gradual, the steam pressure value can be stabilized by controlling as described above. However, in the case of the above control in which the steps of high combustion → medium combustion → low combustion are employed, there is a case where a delay occurs in pressure recovery depending on conditions. When there is no steam accumulation immediately after the start of the boiler, or when there is a large demand for steam at the start of use of steam-using equipment, the steam pressure may drop significantly from the normal pressure (abrupt Generation of steam load). In this case, it is necessary to quickly return the steam pressure value to the normal pressure. However, in the case of four-position control in which the combustion amount is reduced from high combustion to medium combustion when the steam pressure value is recovered to the lower pressure value, the steam pressure is reduced. It may take some time to return.

  2 and 3 compare the steam pressure value in the combustion control according to the present invention with the steam pressure value in the conventional control described in Japanese Patent No. 294080 and the combustion state. The solid line indicates the steam pressure value when the control of the present invention is performed, and the broken line indicates the steam pressure value when the conventional control is performed. The solid line and the broken line are overlapped in many parts by making the slopes of the starting steam pressure, the required amount of steam, and the combustion amount the same, but are partially different due to the difference in control. In the figure, when the detected pressure value P is higher than the high pressure value P1, combustion is stopped, and when the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, low combustion, and the detected pressure value P is intermediate. When it is between the pressure value P2 and the low pressure value P3, it is set as medium combustion, and when the detected pressure value P is lower than the low pressure value P3, it is set as high combustion. The intermediate pressure value P2 and the high pressure value P1 have a difference between the pressure when the combustion amount is decreased and the pressure when the combustion amount is increased. At the intermediate pressure value P2, the pressure that decreases the combustion amount is the intermediate pressure value P2, the pressure that increases the combustion amount is the intermediate pressure value P2 ′ that is lower than the intermediate pressure value P2, and the high pressure value P1 The pressure that decreases the combustion amount is the high pressure value P1, and the pressure that increases the combustion amount is the high pressure value P1 ′ that is lower than the high pressure value P1. Here, the conventional control will be described in FIGS.

  In the case of FIG. 2, the steam pressure value starts from a state lower than the control range, and the initial combustion amount is high combustion. When there is no accumulation of steam immediately after the boiler is started, the steam pressure value is increased to a predetermined value by performing high combustion. In the case of high combustion, the steam pressure value increases rapidly due to the large amount of steam generated. When the steam pressure value becomes higher than the lower pressure value P3 at time A, the boiler reduces the combustion amount to the middle combustion. When the combustion amount is reduced from high combustion to medium combustion, the amount of steam generated is also reduced, so that the increase in the steam pressure value after time A is moderate. Therefore, the state where the pressure is higher than the lower pressure value P3 but lower than the middle pressure value P2 continues for a long time. When the steam pressure value reaches the middle pressure value P2 at time D, the combustion pressure is changed from the middle combustion to the low combustion, and therefore the steam pressure value is turned down. When the combustion amount is set to low combustion, the steam pressure value decreases, and when it becomes lower than the intermediate pressure value P2 'at time E, the combustion amount is set to medium combustion. Since the required steam amount and the generated steam amount are balanced after time D, the steam pressure value can be stabilized within a narrow range.

  In the case of FIG. 3, the steam pressure value starts from a high state, and the initial combustion amount is set to stop the combustion. Since the amount of steam used is small until time G, the steam pressure value has hardly decreased, but since the use of steam has started from time G, the steam pressure value has decreased. When the boiler has stopped combustion, it takes time to prepare for combustion, such as pre-purge, in order to resume the supply of steam. The period from time G to time H is a time for preparation for combustion, and during that period, steam cannot be supplied, so that the steam pressure value decreases rapidly. Combustion is started from time H, and since the steam pressure value at time H is lower than the lower pressure value P3, high combustion is performed. If the steam pressure rises by performing high combustion and the steam pressure value becomes higher than the lower pressure value P3 at time I, the boiler reduces the combustion amount to medium combustion. When the combustion amount is reduced from high combustion to medium combustion, the amount of steam generated also decreases, so that the increase in the steam pressure value after time I becomes gradual. Thereafter, when the steam pressure value reaches the middle pressure value P2 at time L, the combustion amount is changed from middle combustion to low combustion. Since the required steam amount and the generated steam amount are balanced after the time L, the steam pressure value can be stabilized within a narrow range.

In the case of the conventional control described in FIGS. 2 and 3, the steam pressure value can finally be stabilized, but the time until the steam pressure value reaches a sufficient value is relatively long. It has become a thing. If the recovery of the steam pressure value is delayed, the supply of steam will be insufficient during that time, so that a faster recovery of the steam pressure value has been desired.
Japanese Patent No. 294080

  The problem to be solved by the present invention is to achieve both improvement in operation efficiency and load followability in a boiler in which the combustion amount is changed in stages from high combustion, medium combustion, low combustion, and combustion stop.

  The invention according to claim 1 controls the combustion amount by detecting the steam pressure value and the combustion apparatus capable of changing the combustion amount in stages such as high combustion, medium combustion, low combustion, and combustion stop. In a boiler having a combustion control device, the combustion control device sets the detected pressure value P, which is a detected value of the steam pressure, to a preset high pressure value P1, medium pressure value P2, low pressure value P3 (high pressure value P3). Pressure value P1> middle pressure value P2> low pressure value P3), and the combustion amount is determined. When the detected pressure value P is higher than the high pressure value P1, combustion is stopped, and the detected pressure value P is high. When the pressure is between the pressure value P1 and the intermediate pressure value P2, the combustion is low, and when the detected pressure value P is lower than the low pressure value P3, the combustion is high, and the detected pressure value P is the intermediate pressure value P2 and the low pressure value P3. , The detected pressure value P is the middle pressure value P2. A combustion control device that performs medium combustion when the pressure is lower than the intermediate pressure value P2 from a high state, and performs high combustion when the detected pressure value P is lower than the low pressure value P3 from a state that is lower than the low pressure value P3. It is a boiler characterized by this.

  According to a second aspect of the present invention, in the boiler, the intermediate pressure value P2 has a difference between a pressure when the combustion amount is decreased and a pressure when the combustion amount is increased. When the decreasing pressure is the intermediate pressure value P2, the pressure that increases the combustion amount is set to the intermediate pressure value P2 ′ that is lower than the intermediate pressure value P2, and the detected pressure value P is lower than the intermediate pressure value P2. When the low pressure is higher than the intermediate pressure value P2, the combustion amount is changed from high combustion to low combustion, and the detected pressure value P is lower than the intermediate pressure value P2 'from the higher state than the intermediate pressure value P2'. The combustion amount is changed from low combustion to medium combustion, and when the detected pressure value P is lower than the low pressure value P3, the combustion control device maintains high combustion when the detected pressure value P becomes higher than the low pressure value P3. It is a featured boiler.

  The invention according to claim 3 controls the combustion amount by detecting the steam pressure value and the combustion device capable of changing the combustion amount in stages such as high combustion, medium combustion, low combustion, and combustion stop. In a boiler having a combustion control device, the combustion control device sets the detected pressure value P, which is a detected value of the steam pressure, to a preset high pressure value P1, medium pressure value P2, low pressure value P3 (high pressure value P3). Pressure value P1> middle pressure value P2> low pressure value P3), and the combustion amount is determined. When the detected pressure value P is higher than the high pressure value P1, combustion is stopped, and the detected pressure value P is high. When the pressure is between the pressure value P1 and the intermediate pressure value P2, the combustion is low, and when the detected pressure value P is lower than the low pressure value P3, the combustion is high, and the detected pressure value P is the intermediate pressure value P2 and the low pressure value P3. , The detected pressure value P is the middle pressure value P2. The boiler is characterized in that medium combustion is performed when the pressure is lower than the middle pressure value P2 from a high state, and high combustion is performed when the detected pressure value P is higher than the low pressure value P3 from a state lower than the low pressure value P3. This is a combustion control method.

  In the invention according to claim 4, in the combustion control method of the boiler, the intermediate pressure value P2 has a difference between a pressure when the combustion amount is decreased and a pressure when the combustion amount is increased, When the pressure that decreases the combustion amount is the intermediate pressure value P2, the pressure that increases the combustion amount is set to the intermediate pressure value P2 ′ that is lower than the intermediate pressure value P2, and the detected pressure value P is the intermediate pressure value. When the state is lower than the value P2 and higher than the intermediate pressure value P2, the combustion amount is changed from high combustion to low combustion, and the detected pressure value P is higher than the intermediate pressure value P2 ′ and the intermediate pressure value P2 ′. The combustion amount is changed from low combustion to medium combustion when lower, and high combustion is maintained when the detected pressure value P is lower than the lower pressure value P3 and higher than the lower pressure value P3. This is a boiler combustion control method.

  By carrying out the present invention, when the amount of steam used is small, the frequency of stopping combustion is reduced because combustion is performed with a small amount of combustion, and when the steam pressure value is low or when steam is used, the steam pressure value is reduced. In the case of a decrease, the time required to recover the steam pressure value can be shortened, so that both high operating efficiency and high load followability can be achieved.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a boiler for carrying out the present invention. At the upper part of the boiler, a combustion device 2 with a variable combustion amount for generating a downward flame is provided, and the flame is burned in the combustion chamber 3 in the center of the boiler. Combustion air used in the combustion device 2 is supplied by a blower 5 connected to the combustion device 2 through a blower passage. An air flow control device 8 for controlling the amount of air supplied from the blower 5 to the combustion device 2 is provided, and the air supply amount for combustion is adjusted by the air flow control device 8. A fuel supply control device 7 is also provided in the fuel supply pipe 4 that supplies fuel to the combustion device 2. The amount of fuel supplied to the combustion device 2 is also adjusted by the fuel supply control device 7. The boiler supplies water from the lower water supply pipe, takes out the steam from the upper steam pipe and sends it to the steam-using equipment, and is provided with a pressure detection device 1 for detecting the value of the steam pressure in the steam section. A combustion control device 6 connected to each of the pressure detection device 1, the blower 5, the air flow control device 8, and the fuel supply control device 7 is provided, and the combustion control device 6 controls the combustion of the boiler.

  The combustion control device 6 is set to change the combustion amount in accordance with the change in the steam pressure value. The amount of combustion is set in stages, and the amount of combustion is controlled at four positions, ie, high combustion, medium combustion, and low combustion, as well as combustion stop. When the combustion amount of high combustion is 100%, it is appropriate that medium combustion is 60% and low combustion is about 30%. The combustion control device 6 is set with a high pressure value P1, a medium pressure value P2, and a low pressure value P3 (high pressure value P1> middle pressure value P2> low pressure value P3). The amount of combustion in the combustion device 2 is changed in accordance with the change in the detected pressure value P, which is the detected value. The combustion control device 6 changes the combustion amount in the combustion device 2 by supplying fuel and combustion air in an amount corresponding to the combustion amount determined from the detected pressure value P.

  The combustion amount is set to stop combustion when the detected pressure value P is higher than the high pressure value P1, and when the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, the combustion is low and the detected pressure value P. If the pressure is lower than the lower pressure value P3, high combustion is assumed. When the detected pressure value P is between the intermediate pressure value P2 and the low pressure value P3, when the steam pressure value P is higher than the intermediate pressure value P2 and lower than the intermediate pressure value P2, intermediate combustion is performed. When the detected pressure value P becomes lower than the lower pressure value P3 from a state where the detected pressure value P is lower than the lower pressure value P3, high combustion is set.

  If the pressure value that increases the combustion amount and the pressure value that decreases the combustion amount are set to the same value, a phenomenon called hunting that alternately repeats the increase in the combustion amount and the decrease in the combustion amount occurs with a slight pressure fluctuation. Sometimes. If the amount of steam used is such that if the amount of combustion is increased, the steam pressure value will increase, and if the amount of combustion is decreased, the steam pressure value will be decreased. It will be necessary to re-change (revert). Therefore, the occurrence of hunting is prevented by providing a difference (differential) between when the combustion amount is increased and when the combustion amount is decreased. By making the pressure value that decreases the combustion amount higher than the pressure value that increases the combustion amount, the combustion amount is not changed until the difference pressure changes, so the increase and decrease of the combustion amount is repeated in a very short time This is no longer the case. Therefore, the intermediate pressure value P2 has a difference between the pressure when the combustion amount is decreased and the pressure when the combustion amount is increased, and the pressure that decreases the combustion amount is the intermediate pressure value P2. The pressure that increases the combustion amount is set to a middle pressure value P2 ′ that is lower than the middle pressure value P2. When the detected pressure value P is lower than the intermediate pressure value P2 and higher than the intermediate pressure value P2, the combustion amount is changed from high combustion to low combustion, and the detected pressure value P is higher than the intermediate pressure value P2 ′. When the state becomes lower than the middle pressure value P2 ′, the combustion amount is set to be changed from low combustion to medium combustion. Similarly, regarding the high pressure value P1, when the pressure that decreases the combustion amount is the high pressure value P1, the pressure that increases the combustion amount is the high pressure value P1 'that is lower than the high pressure value P1. When the detected pressure value P is lower than the high pressure value P1 and higher than the high pressure value P1, the combustion amount is changed from low combustion to combustion stop, and the detected pressure value P is higher than the high pressure value P1 ′. When the pressure value is lower than P1 ′, the combustion amount is set to be changed from the combustion stop to the low combustion.

  2 and 3 compare the steam pressure value in the combustion control of the present invention with the steam pressure value in the conventional control. The solid line indicates the steam pressure value when the control of the present invention is performed, and the broken line indicates the steam pressure value when the conventional control is performed. First, FIG. 2 will be described based on an example of the present invention control indicated by a solid line. Since the detected pressure value P is initially lower than the lower pressure value P3 in FIG. 2, the combustion control device 6 operates the boiler with high combustion, which is the largest combustion amount. The combustion control device 6 supplies fuel for high combustion by the fuel supply control device 7, and the air supply for high combustion is also supplied by the air flow control device 8 so that the combustion amount in the combustion device 2 is high combustion. To do. In the case of high combustion, since the amount of steam generated is large, the steam pressure value increases rapidly, and at time A, the detected pressure value P becomes higher than the lower pressure value P3. However, in the present invention, when the detected pressure value P is lower than the low pressure value P3 and becomes a pressure value between the middle pressure value P2 and the low pressure value P3, it is set to continue high combustion. Therefore, after the time A, the same high combustion as before is continued. In order to continue high combustion, the time required to increase the steam pressure value to the middle pressure value P2 is shortened.

  When the steam pressure value becomes higher than the intermediate pressure value P2 at time B, the combustion control device 6 decreases the combustion amount. When the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, since the low combustion is set, the combustion control device 6 skips the middle combustion from the high combustion to reduce the combustion amount to the low combustion. change. In the combustion control device 6, the fuel supply control device 7 supplies fuel for low combustion, and the air flow control device 8 also supplies low combustion air, thereby reducing the combustion amount in the combustion device 2 to low combustion. To do. Since the amount of generated steam decreases when the combustion is low, the detected pressure value P starts to decrease.

  Thereafter, since the detected pressure value P is lower than the middle pressure value P2 'at time C, the combustion amount is increased to medium combustion. In the combustion control device 6, the fuel supply control device 7 supplies the fuel for medium combustion, and the air supply control device 8 also supplies the air for medium combustion, thereby reducing the combustion amount in the combustion device 2 to medium combustion. To do. Since the amount of generated steam increases in the middle combustion, the detected pressure value P gradually increases. When the pressure range between the low pressure value P3 and the intermediate pressure value P2 is entered from the state lower than the low pressure value P3 due to the increase of the steam pressure, the combustion is set to high combustion, but this time from the intermediate pressure value P2 ′. Since the pressure range between the low pressure value P3 and the intermediate pressure value P2 ′ is entered from the high state due to the drop in the steam pressure, the combustion amount is assumed to be medium combustion.

  By performing the middle combustion, the steam pressure value increases, and at time D, the steam pressure value again becomes higher than the intermediate pressure value P2. Thereafter, the combustion amount is increased / decreased in accordance with the increase / decrease of the steam pressure value, and after time B, the steam pressure value can be maintained in the vicinity of the intermediate pressure value P2. In the case of the conventional control starting from the same pressure value, it was necessary to wait until time D for the steam pressure value to reach the intermediate pressure value P2, as described in the background art column. In the case of the control according to the present invention, the steam pressure value can be stabilized near the intermediate pressure value P2 at an early stage of time B. With the control according to the present invention, the steam pressure value is recovered earlier by the time difference between time B and time D. Has been able to.

  Next, a description will be given based on an example of the present invention control indicated by a solid line in FIG. FIG. 3 shows an example in which the steam pressure value is reduced by using steam. In FIG. 3, the steam pressure value starts from a high state, and the initial combustion amount is set to stop the combustion. Since the amount of steam used is small until time G, the steam pressure value has hardly decreased, but since the use of steam has started from time G, the steam pressure value has decreased. The period from time G to time H is a time for preparation for combustion, and during that period, steam cannot be supplied, so that the steam pressure value decreases rapidly. Combustion is started from time H, and since the steam pressure value at time H is lower than the lower pressure value P3, high combustion is performed. The steam pressure rises by performing high combustion, and the steam pressure value becomes higher than the lower pressure value P3 at time I. However, in the present invention, the detected pressure value P is lower than the lower pressure value P3 and the intermediate pressure is increased. When the pressure value is between the value P2 and the lower pressure value P3, it is set that the high combustion is continued. Therefore, the same high combustion is continued after the time I. In order to continue high combustion, the time required to raise the steam pressure value to the intermediate pressure value P2 is shortened, and at time J, the steam pressure value reaches the intermediate pressure value P2.

  When the steam pressure value becomes higher than the intermediate pressure value P2 at time J, the combustion control device 6 decreases the combustion amount. When the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, since the low combustion is set, the combustion control device 6 skips the middle combustion from the high combustion to reduce the combustion amount to the low combustion. change. In the combustion control device 6, the fuel supply control device 7 supplies fuel for low combustion, and the air flow control device 8 also supplies low combustion air, thereby reducing the combustion amount in the combustion device 2 to low combustion. To do. Since the amount of generated steam decreases when the combustion is low, the detected pressure value P starts to decrease. After time J, the required steam amount and the generated steam amount are balanced, so that the steam pressure value can be stabilized within a narrow range. In the case of the conventional control starting from the same pressure value, it was necessary to wait until time L for the steam pressure value to reach the middle pressure value P2, as described in the background art column. In the case of the control according to the present invention, the steam pressure value can be stabilized in the vicinity of the intermediate pressure value P2 at an early stage of time J. With the control according to the present invention, the steam pressure value is accelerated by the time difference between time J and time L. Can be recovered.

  When the steam pressure value becomes lower than a predetermined pressure, it is necessary to quickly return to the normal use pressure so as not to run out of steam in the steam using equipment. However, in the conventional control, a step of high combustion → medium combustion → low combustion is taken, and when the steam pressure value becomes the low pressure value P3, the combustion amount is changed from high combustion to medium combustion. It took time for the value to return to the intermediate pressure value P2. In the case of the conventional control indicated by the broken line, it is necessary to wait until the time D and the time L for the steam pressure value to reach the middle pressure value P2, as described in the background art section. It is late. According to the control of the present invention, when the previous steam pressure value is lower than the lower pressure value P3, the high pressure continues by high combustion even if the steam pressure value recovers to the lower pressure value P3. The time required for the value to recover to the intermediate pressure value P2 can be shortened. Even when the pressure value is the same between the lower pressure value P3 and the intermediate pressure value P2, if the previous steam pressure value is higher than the intermediate pressure value P2, intermediate combustion is performed. Therefore, the combustion amount is not increased more than necessary, and the steam pressure value can be stabilized when the pressure is stable in the vicinity of the intermediate pressure value P2.

Outline diagram of boiler implementing the present invention Explanatory diagram of changes in steam pressure and combustion state Explanatory diagram of changes in steam pressure and combustion state

Explanation of symbols

1 Pressure detection device 2 Combustion device
3 Combustion chamber 4 Fuel supply piping 5 Blower 6 Combustion control device 7 Fuel supply control device 8 Air flow control device

Claims (4)

In a boiler with a combustion device that can change the combustion amount in stages, such as high combustion, medium combustion, low combustion, combustion stop, and a combustion control device that detects the steam pressure value and controls the combustion amount,
The combustion control device sets the detected pressure value P, which is the detected value of the steam pressure, to the preset high pressure value P1, medium pressure value P2, low pressure value P3 (high pressure value P1> medium pressure value P2). > Combustion amount is determined by comparing with lower pressure value P3)
When the detected pressure value P is higher than the high pressure value P1, combustion is stopped. When the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, low combustion is detected, and the detected pressure value P is lower than the low pressure value P3. If it ’s low, it ’s high combustion.
When the detected pressure value P is between the intermediate pressure value P2 and the low pressure value P3, when the detected pressure value P is lower than the intermediate pressure value P2 from the state where the detected pressure value P is higher than the intermediate pressure value P2, A boiler having a combustion control device that performs high combustion when the detected pressure value P is lower than the lower pressure value P3 from the lower pressure value P3. In the boiler according to claim 1, the intermediate pressure value P2 has a difference between the pressure when the combustion amount is decreased and the pressure when the combustion amount is increased, and the pressure at which the combustion amount is decreased is medium. Assuming that the intermediate pressure value P2 is set, the pressure for increasing the combustion amount is set as the intermediate pressure value P2 ′ that is lower than the intermediate pressure value P2.
When the detected pressure value P is lower than the intermediate pressure value P2 and higher than the intermediate pressure value P2, the combustion amount is changed from high combustion to low combustion, and the detected pressure value P is higher than the intermediate pressure value P2 ′. When the state becomes lower than the intermediate pressure value P2 ′, the combustion amount is changed from low combustion to intermediate combustion, and when the detected pressure value P becomes lower than the low pressure value P3 and becomes higher than the low pressure value P3, high combustion is performed. A boiler characterized by having a combustion control device for maintenance. In a boiler with a combustion device that can change the combustion amount in stages, such as high combustion, medium combustion, low combustion, combustion stop, and a combustion control device that detects the steam pressure value and controls the combustion amount,
The combustion control device sets the detected pressure value P, which is the detected value of the steam pressure, to the preset high pressure value P1, medium pressure value P2, low pressure value P3 (high pressure value P1> medium pressure value P2). > Combustion amount is determined by comparing with lower pressure value P3)
When the detected pressure value P is higher than the high pressure value P1, combustion is stopped. When the detected pressure value P is between the high pressure value P1 and the intermediate pressure value P2, low combustion is detected, and the detected pressure value P is lower than the low pressure value P3. If it ’s low, it ’s high combustion.
When the detected pressure value P is between the intermediate pressure value P2 and the low pressure value P3, when the detected pressure value P is lower than the intermediate pressure value P2 from the state where the detected pressure value P is higher than the intermediate pressure value P2, A combustion control method for a boiler, characterized in that high combustion is performed when the detected pressure value P is lower than the low pressure value P3 from a state where the detected pressure value P is lower than the low pressure value P3. 4. The boiler combustion control method according to claim 3, wherein the intermediate pressure value P2 has a difference between a pressure when the combustion amount is decreased and a pressure when the combustion amount is increased, thereby reducing the combustion amount. When the intermediate pressure value P2 is the pressure to be increased, the pressure that increases the combustion amount is set as the intermediate pressure value P2 ′ that is lower than the intermediate pressure value P2.
When the detected pressure value P is lower than the intermediate pressure value P2 and higher than the intermediate pressure value P2, the combustion amount is changed from high combustion to low combustion, and the detected pressure value P is higher than the intermediate pressure value P2 ′. When the state becomes lower than the intermediate pressure value P2 ′, the combustion amount is changed from low combustion to intermediate combustion, and when the detected pressure value P becomes lower than the low pressure value P3 and becomes higher than the low pressure value P3, high combustion is performed. A combustion control method for a boiler, characterized in that it is maintained.

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