JP6087141B2 - Boiler with combustion equipment - Google Patents

Description

  The present invention relates to a boiler having a combustion device, and more particularly to a boiler that can increase or decrease the amount of combustion, and that performs a predetermined ignition sequence at the start of combustion.

  As described in Japanese Patent Application Laid-Open No. 2004-353978, in a boiler having a combustion device, the amount of fuel supplied to the combustion device and the amount of air supplied for combustion are adjusted to adjust the combustion amount. ing. For boilers that set the combustion amount in stages, perform three-position combustion control with high combustion, low combustion, and stop, and four-position combustion control with high combustion, medium combustion, low combustion, and stop. . In the low combustion of the three-position combustion control, the turndown ratio is often about 2: 1 by setting the fuel supply amount to about half that of the high combustion. In a four-position combustion combustion boiler, the low combustion ratio is made smaller and the turndown ratio is set to 7: 1 or the like.

  In the boiler, the amount of combustion is determined according to the steam load. In the case of three-position combustion control, the steam pressure is set in three stages, combustion stops if the pressure value is higher than the high set pressure value, low combustion if the pressure value is between the high set pressure value and the low set pressure value, If the pressure is lower than the lower set pressure value, control is performed so that high combustion occurs. At this time, if the pressure value that increases the combustion amount and the pressure value that decreases the combustion amount are set to the same value, the increase in the combustion amount and the decrease in the combustion amount are frequently repeated with slight pressure fluctuations. A differential is set for the pressure value. For example, the pressure value to change from low combustion to combustion stop is 0.80 MPa, the pressure value to change from combustion stop to low combustion is 0.78 MPa, the pressure value to change from high combustion to low combustion is 0.70 MPa, from low combustion The pressure value to be changed to high combustion is set to 0.68 MPa. Similarly, in the case of four-position combustion control, control is performed by setting in four stages.

   The ignition sequence when starting the operation of the boiler is as shown in FIG. FIG. 4 shows a boiler that performs three-position combustion control. The fuel supply amount is adjusted by the first electromagnetic valve and the second electromagnetic valve, and the combustion air supply amount is adjusted by the position of the damper. The first solenoid valve is a shut-off valve that is controlled by full opening and full closing, and the second solenoid valve is a flow rate adjusting valve that is controlled by full opening and half opening. When the first solenoid valve is fully open and the second solenoid valve is half open, the fuel supply amount is low combustion, and when both the first and second solenoid valves are fully open, the fuel supply amount is high. Supply amount. The adjustment of the combustion air supply amount by the damper is a low combustion supply amount in the low combustion position and a high combustion supply amount in the high combustion position.

  The ignition sequence is started in response to a high combustion demand at time a, and is first performed from a pre-purge in which only the blower is operated to ventilate the interior of the furnace. In the pre-purge, it is necessary to feed a predetermined amount of air, and the damper is changed to the high fuel position because the larger opening degree can supply more air. The pre-purge ends at time c, and an ignition operation is performed from time c. Since ignition is performed with low combustion, the damper is set to the low combustion position before time c, and the air supply amount is reduced to the low combustion amount. From time c, the igniter is operated and the pilot solenoid valve is opened to start pilot combustion. Then, at the time d, the first electromagnetic valve is opened and low combustion is started by supplying fuel for low combustion. Since the combustion demand is high combustion, the combustion amount is changed from low combustion to high combustion after ignition, but it is held at low combustion during the flame stabilization time after ignition, and the combustion demand is reduced to the combustion amount. Change after the flame stabilization time has expired. At time e when the flame stabilization time ends, the damper position is changed to the high combustion position, and the second electromagnetic valve is opened to change to high combustion.

  The change of the combustion amount is performed by changing the fuel supply amount and the combustion air supply amount, and the fuel supply amount can be changed instantaneously because it is performed by opening and closing the electromagnetic valve. However, since the change of the combustion air supply amount is performed by changing the damper position or the rotational speed of the blower, a certain amount of time is required. Therefore, when the combustion amount is changed, the balance between the fuel amount and the air amount is temporarily lost, and combustion may become unstable. In particular, if the combustion amount is changed immediately after ignition and combustion is not stable, there may be a problem such as the flame blowing out, so do not change the combustion amount immediately after ignition. The amount of combustion is changed after the predetermined flame stabilization time has ended.

  As described above, when starting combustion from a state where combustion has been stopped, even if the combustion command is high combustion, the target combustion amount is not reached unless the flame stabilization time after the start of combustion ends. Can not do it. Therefore, the state where steam supply is insufficient continues during that time, and there is a case where a delay occurs in load following. In particular, in a boiler with a large turndown ratio, when it is desired to supply steam at a high combustion rate of 100% combustion, it is necessary to maintain a low combustion rate of 15% combustion until the end of the flame stabilization period. The shortage of will increase.

JP 2004-353978 A

  The problem to be solved by the present invention is to provide a boiler having improved followability to a load.

The invention according to claim 1 is a boiler having a combustion device, wherein the combustion amount is set in four-position combustion control stepwise by high combustion, medium combustion, low combustion, and stop, and combustion is performed according to a load. In a boiler that switches the amount, the ignition sequence is set to the medium combustion ignition sequence that ignites with medium combustion and the low combustion ignition sequence that ignites with low combustion. It is characterized in that it is ignited by a combustion ignition sequence and is ignited by a low combustion ignition sequence when a low combustion demand is required.

  Since combustion is performed with the required combustion amount immediately after ignition, followability with respect to the load is improved, and it is possible to prevent the steam supply amount from being insufficient. Moreover, since the combustion amount is not changed immediately after ignition, combustion stability can be maintained high.

Flow diagram of boiler implementing the present invention Time chart showing ignition sequence in boiler implementing the present invention Time chart showing ignition sequence in boiler implementing the present invention Time chart showing the ignition sequence of a conventional boiler

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of a boiler implementing the present invention, FIGS. 2 and 3 are time charts showing an ignition sequence in a boiler implementing the present invention, and FIG. 4 is a conventional boiler for comparison. 3 is a time chart showing an ignition sequence. 2 shows a case where a high combustion ignition sequence is executed, and FIG. 3 shows a case where a low combustion ignition sequence is executed.

  The boiler is provided with a combustion chamber 1 in the center and a combustion device 2 in the upper part of the combustion chamber 1, and by burning a flame in the combustion chamber 1, the water pipe 3 provided around the combustion chamber is heated, The can water is evaporated to generate steam. A fuel supply pipe 4 is connected to the combustion device 2, and the fuel supply pipe 4 is branched into a main burner and a pilot burner on the way. A pilot solenoid valve 13 is provided in the middle of the fuel supply pipe for the pilot burner, and a first solenoid valve 5 and a second solenoid valve 6 that are fuel quantity adjusting devices are provided in the middle of the fuel supply pipe for the main burner. The pilot solenoid valve 13, the first solenoid valve 5, and the second solenoid valve 6 are connected to the operation control device 7, and the amount of fuel supplied to the combustion device 2 by operating each device by the operation control device 7. To automatically control.

  The combustion device 2 performs combustion using the fuel supplied through the fuel supply pipe 4 and the combustion air supplied from the blower 9 connected to the combustion device 2. The fuel supply amount by the first solenoid valve 5 and the second solenoid valve 6 is the low combustion supply amount by fully opening the first solenoid valve 5 and half-opening the second solenoid valve, and the first solenoid valve 5 and the second solenoid valve 5. The two solenoid valves 6 are both fully open so that the high combustion supply amount can be adjusted, and the high combustion supply amount is about twice the low combustion supply amount. The amount of combustion air supplied from the blower 9 to the combustion device 2 is adjusted by a damper 11 provided in the middle of the blower passage. The damper 11 is set with a high fuel position, a low fuel position, and a fully closed position, and air with a low combustion supply amount during low combustion and a high combustion supply amount during high combustion is supplied. The blower 9 and the damper 11 are also connected to the operation control device 7, and are automatically controlled by the operation control device 7. Low combustion by supplying low combustion fuel and combustion air, and high combustion fuel And high combustion by supplying combustion air.

  Further, a wind pressure switch 10 for detecting that combustion air is being supplied and a steam pressure detecting device 8 for detecting the steam pressure in the boiler are provided, and the wind pressure switch 10 and the steam pressure detecting device 8 are used. The detection result is also output to the operation control device 7. In the operation control device 7, the combustion amount of the boiler is determined based on the steam pressure value detected by the steam pressure detection device 8. When the steam pressure value is lower than the high combustion set value, the boiler is operated at high combustion. When the steam pressure value is higher than the high combustion set value but lower than the combustion stop set value, the boiler is operated at low combustion. When the steam pressure value is higher than the combustion stop set value, the combustion of the boiler is stopped.

  The operation control device 7 is set with a low combustion ignition sequence for starting combustion with low combustion and a high combustion ignition sequence for starting combustion with high combustion. The operation control device 7 selects an ignition sequence to be used based on the combustion request at the start of combustion. In the low combustion ignition sequence, the combustion air supply amount is set as the low combustion supply amount before ignition, and ignition is performed while supplying the low combustion fuel. The high combustion ignition sequence is performed before the ignition. The combustion air supply amount is set as a high combustion supply amount, and ignition is performed while supplying high combustion fuel. If the combustion request at the start of combustion is low combustion, a low combustion ignition sequence is executed, and if it is high combustion, a high combustion ignition sequence is executed.

  The boiler operation control will be described with reference to the drawings. FIG. 2 shows a case where a high combustion ignition sequence is performed. In the figure, the boiler starts from a state where combustion is stopped, each device is stopped, and a damper and a fuel valve are closed. When there is a combustion request for high combustion at time A, the operation control device 7 selects and executes an ignition sequence for high combustion. First, the pre-purge of the combustion chamber 1 is started by changing the damper from the fully closed position to the high combustion position and starting the operation of the blower. When the damper is in the high combustion position, a high combustion air amount is supplied to the combustion chamber.

  However, since a sufficient air volume cannot be obtained immediately after the start of the operation of the blower, the pre-purge time is not counted, and the time after time B when the wind pressure switch 10 detects that the predetermined wind pressure is reached is set as the pre-purge time. Until a predetermined pre-purge time elapses from time B, the air in the combustion chamber 1 is ventilated by supplying only air to the combustion chamber 1 so that safe ignition can be performed.

At time C, the pre-purge is finished and the ignition operation is started. At this time, the pilot solenoid valve 13 is opened and the operation of the igniter 12 is started, but the first solenoid valve 5 and the second solenoid valve 6 are closed. When fire is generated by the igniter 12 in a state where air is being supplied and the supply of pilot fuel is started, a pilot flame is generated and combustion starts.
When the ignition trial time elapses after starting the operation of the igniter 12, the operation of the igniter 12 is stopped, and the first electromagnetic valve 5 and the second electromagnetic valve 6 are opened at the time D when the pilot-only time has elapsed.
Since the supply amount of combustion air is a supply amount for high combustion, and the supply amount of fuel is also a supply amount for high combustion, combustion is performed at high combustion as requested by combustion from time D. Since combustion is started with the combustion amount as required, it is not necessary to change the combustion amount until the combustion amount changes, and it is stable because the combustion amount does not change immediately after ignition. Combustion can be performed. Thereafter, since the combustion demand has changed from high combustion to low combustion, the damper is changed from the high combustion position to the low combustion position, and the second electromagnetic valve 6 is closed halfway to change the combustion amount to low combustion. When the combustion amount is changed, the balance between fuel and air is temporarily lost. However, if the combustion is stable, the combustion amount can be changed without any problem.

  FIG. 3 shows a case in which a low combustion ignition sequence is performed. Initially, it is the same as FIG. 2, and the boiler starts from a state where combustion is stopped. When there is a combustion request for low combustion at time E, the operation control device 7 selects and executes an ignition sequence for low combustion. For low combustion, first, the damper is changed from the fully closed position to the high combustion position, and the operation of the blower is started to start supplying air to the combustion chamber 1. The time after the time F when it is detected that the wind pressure switch 10 has reached a predetermined wind pressure is set as the pre-purge time. Until a predetermined pre-purge time elapses from time F, the air in the combustion chamber 1 is ventilated by supplying only air to the combustion chamber 1 so that safe ignition can be performed.

  In the low combustion ignition sequence, since ignition is performed with low combustion, the damper position is changed to the low combustion position during the pre-purge, and the air supply amount is set for low combustion. When pre-purge is completed at time G, an ignition operation is performed. At this time, the igniter 12 and the pilot solenoid valve 13 are opened, but the first solenoid valve 5 and the second solenoid valve 6 are closed. When fire is generated by the igniter 12 in a state where air is being supplied and the supply of pilot fuel is started, a pilot flame is generated and combustion starts. When the ignition trial time has elapsed since the start of the operation of the igniter 12, the operation of the igniter 12 is stopped, and the first electromagnetic valve 5 is opened at the time H when the pilot-only time has elapsed. Even when the second solenoid valve is controlled to close, the second solenoid valve is in a half-open state, and fuel for low combustion is supplied. Since the supply amount of combustion air is a supply amount for low combustion, and the supply amount of fuel is also a supply amount for low combustion, combustion is performed from time H with low combustion as required by combustion.

  FIG. 4 shows an example of conventional control for comparison. 4 is the same as FIG. 2 at the beginning, and the boiler starts from a state where combustion is stopped. When there is a combustion request for high combustion at time a, the operation control device 7 executes an ignition sequence. In the conventional control, there is only one ignition sequence, and the ignition sequence is not selected based on the combustion request. Even if the combustion demand is high combustion, combustion is started at low combustion, and after the combustion starts, the combustion is changed from low combustion to high combustion.

  Also in this case, first, the damper is changed from the fully closed position to the high combustion position, and the operation of the blower is started to start the supply of air to the combustion chamber 1. The time after time b when the wind pressure switch 10 detects that a predetermined wind pressure has been reached is defined as a pre-purge time. Until a predetermined pre-purge time elapses from time b, the combustion chamber 1 is ventilated by supplying only air to the combustion chamber 1 so that safe ignition can be performed.

  Since ignition is performed with low combustion, the damper position is changed to the low fuel position during the pre-purge, and ignition is performed when the pre-purge ends at time c. At this time, the opening operation of the pilot electromagnetic valve 13 and the operation of the igniter 12 are started, but the first electromagnetic valve 5 and the second electromagnetic valve 6 are closed. The pilot solenoid valve 13 is opened, the ignition trial time has elapsed since the start of the operation of the igniter 12, and the first solenoid valve 5 is opened at a time d after the pilot-only time has elapsed. When fuel supply for low combustion is started to the main burner while pilot combustion is being performed by the pilot burner, a flame is generated in the main burner and combustion starts. Since the supply amount of combustion air is a supply amount for low combustion and the supply amount of fuel is also a supply amount for low combustion, combustion at low combustion is performed from time d.

  Ignition is performed with low combustion, but since the combustion demand is high combustion, the combustion amount is changed to high combustion after the end of the ignition sequence. However, if the amount of combustion is changed at a time immediately after ignition and combustion is not stable, there is a risk that problems such as the flame blowing out may occur. Therefore, it does not change to high combustion immediately after ignition, maintains low combustion until time e when the flame stabilization time elapses, and then changes to high combustion. To change to high combustion, change the damper position from the low fuel position to the high fuel position, change the combustion air supply amount to high combustion, and open the second solenoid valve to increase the fuel supply amount for high combustion. It is done by changing to.

  In the conventional control, there is only one ignition sequence. When the combustion amount at the time of ignition and the combustion amount of the combustion request are different, the ignition sequence is changed to the combustion amount of the combustion request after completion of the ignition sequence. In this case, if the combustion amount is changed immediately after ignition, the combustion becomes unstable, so that a stable flame can be set by setting a flame stabilization time and delaying the change of the combustion amount. However, in the present invention, since a plurality of ignition sequences are set and ignition is performed with the combustion demanded combustion amount, combustion is performed with the combustion demanded combustion amount at the time of ignition. In the conventional control, it took time until the required combustion amount was reached, and there was a case where the supply of steam was insufficient. Therefore, the combustion amount is not changed immediately after ignition, so that stable combustion can be performed.

  Although the case of the three-position combustion control has been described in the above embodiment, the same applies to the four-position combustion control. If high-combustion, medium-combustion, low-combustion and stop four-position combustion control is used, a high-combustion ignition sequence that ignites with high combustion, a medium-combustion ignition sequence that ignites with medium-combustion, and a low-combustion ignition sequence that ignites with low-combustion Set it. Then, based on the combustion request at the start of combustion, a high combustion ignition sequence is executed for a high combustion request, a medium combustion ignition sequence is executed for a medium combustion request, and a low combustion ignition sequence is executed for a low combustion request. By performing ignition with a combustion amount as required by the combustion, the followability to the load is enhanced.

  Further, when a shock is generated due to thermal expansion at the time of ignition when ignited with high combustion, it may be ignited with medium combustion when demanding high combustion and when demanding medium combustion, and may be ignited with low combustion when demanding low combustion. When the combustion demand is high combustion, it is possible to balance the reduction of shock at the time of ignition and the improvement of load followability by igniting with medium combustion that is larger than low combustion but smaller than high combustion. In this case, the amount of steam supplied will be insufficient because it will be ignited by medium combustion with a smaller amount of combustion than that of high combustion, but the amount of steam supplied will be larger than when ignited with low combustion, Supply deficiencies can be reduced.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Combustion device 3 Water pipe 4 Fuel supply piping 5 1st solenoid valve
6 Second solenoid valve 7 Operation control device 8 Steam pressure detection device 9 Blower 10 Wind pressure switch 11 Damper 12 Igniter 13 Pilot solenoid valve 14 Steam pressure detection device

Claims (1)

It is a boiler with a combustion device, and the combustion amount is set as four-position combustion control in stages with high combustion, medium combustion, low combustion, and stop, and the combustion amount is switched according to the load. In the boiler, the intermediate combustion ignition sequence that ignites with medium combustion and the low combustion ignition sequence that ignites with low combustion are set as the ignition sequence. A boiler having a combustion device characterized by being ignited by a low combustion ignition sequence when a low combustion demand is required .

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