JPS6333606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler reheat steam temperature control device.

Conventional boiler reheat steam temperature control (hereinafter referred to as RH temperature control)
This was done by increasing or decreasing the GR amount (abbreviated as GR amount), but since the amount was controlled by the opening of the inlet damper of the gas recirculation fan, there was a large response delay and control was extremely difficult. Rapid load changes and recent knowledge
It is difficult to follow changes in boiler combustion conditions in the NOx system (in-furnace denitrification method).

In particular, with the in-furnace denitrification method, the amount of GR required differs significantly depending on when it is used and when it is not used.
In addition, since operating terminals that have a large effect on RH temperature, such as burner tilt and O ₂ amount control, operate, it is difficult to control using conventional RH temperature control (GR amount control) alone.

In addition, the NOx reduction combustion method, which is a pollution control measure, cannot increase the GR amount due to the RH temperature limit, and there is a strong possibility that high NOx operation will be required.

An object of the present invention is to quickly stabilize RH temperature fluctuations caused by load changes that are difficult to follow with the conventional control device and fluctuations in boiler combustion conditions when in-furnace denitrification is used/not used.

In addition, intermediate load operation has been increasing in thermal power plants in recent years, and fast load changes are required. Until now, the speed of load changes has been dependent on the followability of steam temperature control in the boiler superheater and reheater. Given the limitations, the present invention aims to improve the followability of reheat steam temperature control.

Furthermore, in recent years, there has been a demand for anti-pollution measures, and it is thought that the use of the in-furnace denitrification method will increase. Therefore, the present invention aims to provide an improved reheat steam temperature control device for a boiler equipped with the in-furnace denitrification method. purpose.

For this reason, the boiler reheat steam temperature control device according to the present invention is installed by opening the downstream end of the gas recirculation duct that supplies low-temperature recirculation gas to the furnace wall located on the downstream side of the furnace combustion area. A gas recirculation fan is disposed in the middle of the gas recirculation duct, and a first damper whose opening degree is controlled based on the reheat steam temperature and load is disposed on the inlet side of the gas recirculation fan, and the gas recirculation fan is disposed in the gas recirculation duct. The present invention is characterized in that a second damper whose opening degree is controlled based on the reheated steam temperature and the load is disposed in the gas recirculation duct on the outlet side of the fan.

According to the present invention, by injecting low-temperature exhaust gas into the wake side of the furnace combustion area (upper part of the main burner wind box), low NOx operation and RH temperature control can be controlled separately without interrelation, and RH By adjusting the input amount of low-temperature exhaust gas, the temperature change in the exhaust gas that affects the temperature can be made faster, the RH temperature change can appear earlier, and the followability of the RH temperature control can be improved.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, 1 is a boiler furnace wall, 2 is a gas recirculation fan, 3 is a damper provided at the inlet of the gas recirculation fan 2, and 4 is a communication between the gas recirculation fan outlet and the furnace combustion zone 7 of the boiler. 6 is a duct branched from the duct 4 and connected to the downstream side of the furnace combustion area 7 or the outlet of the furnace above the furnace wall 1; 8 is a damper installed in the duct 6;

Figure 2 is a system diagram of a control device that controls the reheat steam temperature (RH temperature) by adjusting the opening degrees of the dampers 3 and 8, and 9 is the actual measured value of the RH temperature 1.
12 is a controller for damper 3, 13 is an adder, 14 is load 1
A function generator that transmits a damper opening degree according to 5, 1
6 is a controller for the damper 8, 17 is an adder, 18 and 19 are function generators that transmit the damper opening degree according to the load 15, 18 is for use when using the in-furnace denitrification method, 19
is for when the same is not used, and is switched by the switch 20. 21 is a control drive for the damper 3, and 22 is a control drive for the damper 8.

The flow rate of the low-temperature recirculation gas led from the boiler outlet flue is adjusted by the damper 3, and a part of it is sent to the furnace combustion zone 7 through the duct 4 via the gas recirculation fan 2.
The remainder is introduced through the duct 6 and damper 8 from above the furnace wall 1 into the downstream of the furnace combustion zone 7 or into the mixing section 5 at the furnace outlet. Here, it is mixed with the high temperature gas 23 generated in the furnace combustion zone 7 and flows to the convection heat transfer section of the boiler. The opening degrees of the dampers 3 and 8 are adjusted by the control device shown in FIG. 2, and the RH temperature is maintained at a set value.

In this case, the control adjustment of the damper 8 is performed using the same control system as that of the gas circulation fan inlet damper 3.
is set to follow relatively quickly.

Further, the damper 8 changes the program of the damper opening degree by switching the function generators 18 and 19 with the switch 20 at the timing when the in-furnace denitrification is used or not used.

Low-temperature recirculating gas (approximately 300℃) in the upper part of the furnace
is generated in the combustion zone 7 of the furnace, resulting in high-temperature exhaust gas 23 (approximately 1200℃).
temperature decreases and prevents the temperature of the superheater and reheater from rising.

In addition, if the temperature is to be increased, the amount of low-temperature recirculation gas input may be reduced.

As described above, since the exhaust gas temperature at the furnace outlet can be adjusted by adjusting the amount of low-temperature exhaust gas input into the furnace, RH temperature control can be quickly stabilized.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram showing an embodiment of the present invention;
FIG. 2 is a control system diagram. DESCRIPTION OF SYMBOLS 1... Boiler furnace wall, 2... Gas recirculation fan, 3... Damper, 5... Mixing section, 7... Furnace combustion zone, 8... Damper.

Claims (1)

[Claims] 1. A gas recirculation duct that supplies low-temperature recirculation gas to the furnace wall located on the downstream side of the furnace combustion area is installed with its downstream end open, and a gas recirculation fan is placed in the middle of the gas recirculation duct. , a first damper whose opening degree is controlled based on reheated steam temperature and load is disposed on the inlet side of the gas recirculation fan, and reheated steam is supplied to the gas recirculation duct on the outlet side of the gas recirculation fan. The second opening is controlled based on temperature and load.
A boiler reheat steam temperature control device characterized by having a damper arranged therein.