JPH0830561B2 - Combustion control method corresponding to boiler load - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method corresponding to the load of a boiler during boiler operation.

[0002]

2. Description of the Related Art Normally, the control of steam pressure in a can in a boiler is performed by a signal from a pressure detector which detects the steam pressure in the can attached to the boiler. When the set value is reached, the burner of the combustion device is turned on or off. That is, the combustion of the burner is stopped when the steam pressure in the can exceeds the high set pressure, and the combustion of the burner is started when the low set pressure is cut off.

By the way, when the steam-using equipment that consumes the steam generated in the boiler is almost constant under normal load, the change in the steam pressure in the can is substantially sawtooth-like as shown in FIG. It becomes a cycle vapor pressure change curve. Where P ₁
Indicates a high set pressure, P ₂ indicates a low set pressure, and the solid line indicates burner O.
N, and the dotted line shows burner OFF, but in reality, the burner combustion start signal is output at point B intersecting with the low set pressure, but as shown in the combustion control time chart of the boiler in FIG. For example, the combustion of the burner is delayed for about 30 seconds to 45 seconds, so that the vapor pressure in the can starts rising at a point C below the low set pressure.

However, when the steam-using device consumes a larger amount of steam than usual, as shown in FIG. 2, the pressure drops steeper than usual from a high set pressure to a low set pressure.
[Short burner OFF time (t ')] Therefore, even if the burner combustion start signal is issued at point B'which intersects with the low set pressure, the reason why the steam pressure inside the can starts to rise again due to the above-mentioned time delay is C 'From the point. As described above, when the steam is consumed in a larger amount than usual, the steam pressure inside the can temporarily greatly decreases, and the load demand cannot be met. In addition, since the dryness of the generated steam is lowered due to the decrease of the steam pressure in the can, various problems occur and become a problem.

[0005]

In view of the above problems, the present invention detects the time from when the burner is turned on to when it is turned off, and based on the detected value, the burner is turned on next.
It is intended to provide a combustion control method corresponding to the load of a boiler, which predicts and controls the time until N is reached.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and turns on and off the burner based on a signal from a pressure detector that detects the steam pressure in the boiler can. In the control method, the burner is O
The time from N to OFF is detected, the time until the burner is turned ON is predicted based on the detected value, and when the predicted time exceeds a preset value, this time is exceeded. It is characterized in that the start of combustion of the burner is instructed earlier depending on the time.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 1, reference numeral 1 denotes a boiler, which is provided with a burner 2 for heating, and in which a blower 3 sends combustion air to the burner 2. A fuel supply line 4 is connected to the burner 2, and a fuel pump 5 and a fuel solenoid valve 6 are inserted in this line. Then, it is controlled by the combustion controller 8 based on the signal of the pressure detector 7 which detects the steam pressure in the can of the boiler 1. That is, when the steam pressure in the can exceeds the high set pressure, the combustion of the burner 2 is stopped, and when the low set pressure is cut off, the combustion of the burner 2 is started. Reference numeral 9 is a water level detector for detecting the water level in the boiler can. Based on the signal from this detector, an appropriate water level control device turns on the water supply pump 11 in the water supply line 10.
It is turned off to keep the water level in the can at a certain level.

In FIG. 2, if the high set pressure is set to P ₁ and the low set pressure is set to P ₂ , the combustion controller 8 issues a combustion stop command to the burner 2 at point A when the vapor pressure in the can reaches P _1. broth,
A command to start combustion of the burner 2 is issued at point B when the steam pressure in the can has dropped to P _2, but the actual steam pressure in the can is the pressure within the allowable pressure drop range at point C due to the time delay such as the above-mentioned pre-purge. It begins to rise above P ₃ . However, when the steam-using device consumes a larger amount of steam than usual, the time from when the burner 2 is turned on to when it is turned off becomes long,
On the other hand, the OFF time (t ₁ ) of the burner 2 becomes short (the pressure rising speed is slow). Therefore (pressure drop rate is fast), 'pressures just behind parts by out combustion command of the burner 2 at the point C' of the B pressure P ₂ substantially reduced to point, the pressure P ₃ of the pressure drop allowable range Will fall below.

Therefore, in the combustion control method of the present invention, the rate of rise (pressure gradient) with respect to the time from when the burner 2 is turned on to when it is turned off or when the vapor pressure in the can after the burner 2 is turned on is constantly maintained. Detected, and based on the detected value,
Next, when the combustion start command is issued to the burner 2 or the decrease rate (pressure gradient) of the steam pressure inside the can after the burner 2 is turned off is predicted, when the value exceeds a preset value, the normal Combustion controller 8 burner 2 earlier
Issue a command to start combustion. The command timing at this time is variably set according to the predicted decrease time (t) or decrease rate of the steam pressure in the can, and in the case of a short time or a steep slope, the burner 2 is set earlier. It is preferable to issue a command to start combustion to the steam generator, so that steam with stable steam pressure or dryness can be supplied.

The operation of the control method will be described in detail with reference to FIG. That is, in order to keep the decrease in the steam pressure in the can at the pressure P ₃ within the allowable range, after the predicted burner 2 is turned off, D which is earlier than the point B ′ at which the next command to start combustion is issued. At a point (advance by delay time due to pre-purge, etc.), if the burner 2 is instructed to start combustion, the steam pressure in the can can be limited to point C within the allowable pressure drop range of P ₃ .

[0011]

As described above, the present invention detects the time from when the burner is turned on to when it is turned off even when the load of the steam-using equipment consumes more steam than usual, and the detected value is detected. Based on the above, it is possible to predict the time until the burner is turned on next, and to command the start of burner combustion early so that the decrease in the steam pressure in the can stays within the allowable range. It is possible to prevent the abnormal decrease of the temperature and to supply high quality steam with stable pressure and dryness.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a boiler that implements a combustion control method of the present invention.

FIG. 2 is an explanatory diagram showing combustion control and a pressure change curve when the control method of the present invention is used.

FIG. 3 is an explanatory diagram showing combustion control and a pressure change curve when steam consumption is substantially constant under a normal load condition.

FIG. 4 is an explanatory diagram showing a time chart of boiler combustion control.

[Explanation of Codes] Boiler 2. Burner 7. Pressure detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-194103 (JP, A) Actual flat 4-63393 (JP, U) Actual flat 2-62203 (JP, U)

Claims (1)

[Claims] 1. A control method for turning on and off a burner 2 based on a signal from a pressure detector 7 for detecting the steam pressure in a can of a boiler 1, in which the burner is turned on and then turned off.
The time until the burner 2 is turned on is predicted based on the detected value, and when the predicted time exceeds a preset value, the time depending on the time is exceeded. The combustion control method corresponding to the load of the boiler, wherein the start of combustion of the burner 2 is instructed earlier.