JPH02169902A - Boiler steam temperature control device - Google Patents

Abstract

PURPOSE:To perform the continued steam temperature control even when either one of feed water or fuel is manually controlled by distributing the water/fuel ratio signal for the added fuel and feed water based on the boiler operating condition, judgment by the operator, malfunction signal of control device, mode condition of automatic or manual and control signal in accordance with the temperature changing condition. CONSTITUTION:The water/fuel ratio signal 43 is distributed to the feed water compensation water/fuel signal 33 and the fuel compensation water/fuel signal 34. The distribution ratio is set such that the load change which requires the temperature changed reduction most can properly be met, and that the temperature control is premeditated just in case the rate of temperature change is going to be greater, judging from the steam temperature forecast. A manual controller 28 is provided so that the setting may be changed at will depending on the operating conditions. Further, when the feed water (fuel) is switched to the manual mode signal 29, the feed water and fuel compensation water/fuel signals 33, 34 are generated by means of the water/fuel ratio distribution coefficient circuit 33 and the distribution circuit 32 so that the remaining fuel (feed water) may be able to compensate the water/fuel ratio 100% under the automatic mode.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a command signal (hereinafter referred to as water-fuel ratio The present invention relates to a once-through boiler in which steam temperature is controlled by a boiler steam temperature control device.

[Conventional technology]

In the conventional device, as shown in FIG. 3, the temperature is controlled by adjusting the amount of fuel based on the water-fuel ratio.

As shown in Figure 4, a once-through boiler is equipped with a boiler feed pump (
The boiler feed water flow rate 7 is measured between B F P) and the energy saver (ECO), and the SH spray water is branched to 1
Water is injected between the secondary SH and the secondary SH by the SH spray valve 14 to perform temporal temperature control.

On the other hand, the fuel flow rate from the fuel pump (FOP) to the burner 15 is measured by the fuel operation end 11.

In a once-through boiler of such a system, steam temperature control of the boiler is performed as follows.

That is, as shown in FIG. 3, the unit or boiler load control device 1 outputs a boiler master signal 6 requesting water supply and fuel, the boiler master signal 6 and the water supply flow rate 7 are compared, and the water supply controller 12 controls the water supply operation. Edge 1
Adjust the opening and rotation speed in step 3.

At the same time, the boiler master signal 6 is summed with the water-fuel ratio signal 5, which is the output of the temperature controller 4, which works to keep the temperature constant by comparing the steam temperature set value 2 and the steam temperature signal 3, and becomes the fuel quantity command 8. The opening of the fuel operation end 11 is adjusted by the fuel controller 10 in comparison with the fuel amount 9.

However, as can be easily inferred from the system shown in Figure 4, the steam temperature in a once-through boiler is determined by the ratio of the fuel that provides heat and the feed water that absorbs heat and exits as steam. Despite these characteristics, temperature control was performed only by fuel as shown in Figure 3, and no consideration was given to temperature effects due to changes in the amount of water supplied.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not give sufficient consideration to the operating speed of the operating end of the water supply and fuel, and the difference in dynamic characteristics of the steam temperature that changes after the amount of water supply and fuel changes. There was a problem in suppressing fluctuations.

In addition, if the fuel control system becomes manual or malfunctions, there is no operating end to automatically control the temperature (SH spray contributes to temperature control, but it only has a -temporal effect, so it is dependent on ), the load change had to be made very slowly or the load had to be operated at a constant value, which was inconvenient.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to
To provide a boiler steam temperature control device that can continue steam temperature control even if either fuel is operated manually.

[Means to solve the problem]

The above purpose is to adjust the water-fuel ratio signal to fuel and water supply according to conditions such as boiler operating status, operator judgment, control device abnormal signals, automatic/manual operation mode, and control signals according to temperature fluctuations. This is accomplished by distributing the addition to .

In addition, when the fuel or water supply system goes into manual mode or an abnormality occurs in the control device, by adjusting the boiler master signal mentioned above to the amount of fuel or water supply on the abnormal side,
By using the abnormal side as a base and following the normal side, steam temperature control becomes possible, and restrictions on load change operation (such as the need to keep the load change rate extremely slow) are alleviated.

[Effect]

By automatically or arbitrarily selecting the distribution ratio in each case as shown below, the water/fuel ratio signal changes the fuel/feed water ratio that governs the steam temperature appropriately. Temperature fluctuations during operation are expanded, and high load change rate operation is not hindered.

(1) When the load changes, the water supply command is corrected based on the water-fuel ratio by taking advantage of the rapidity of the change in water supply amount.

(2) When the temperature change rate is large according to the steam temperature prediction, the water supply distribution of the water-fuel ratio is strengthened.

(3) The water-fuel ratio distribution ratio can be controlled arbitrarily by the operator.

(4) When the water supply is manual, the water-fuel ratio command is given to the 100% fuel system, and when the fuel is manual, the water-fuel ratio command is given to the 100% water supply system. The same operation will be performed when each control system has an abnormality.

〔Example〕

An embodiment of the invention is shown in FIG.

Among boiler control devices, load control device (or circuit) 2
The boiler master command 22 outputted from the boiler master command 22 becomes a common base demand signal for water supply and fuel.

The boiler (or possibly turbine inlet) steam temperature 23 is compared to a set point 24 and entered into a temperature controller 25 .

The temperature controller 25 operates to eliminate temperature deviation and outputs a water-fuel ratio signal 43.

The water-fuel ratio distribution ratio circuit 31 includes output signals from a load change detector 26, a steam temperature prediction device 27, a manual operation device 28, a water supply control manual mode signal 29, a fuel control manual mode signal 30, etc.
is input, and the water-fuel ratio distribution ratio suitable for each state is determined in advance as a result of operation adjustment, and the distribution ratio is output to the circuit 32.

In the water-fuel ratio distribution circuit 32, the water-fuel ratio signal 43 is divided proportionally according to this distribution ratio to obtain a feed water correction water-fuel ratio signal 33 and a fuel correction water-fuel ratio signal 34.

The feed water correction water-fuel ratio signal 33 is added to the boiler master command 22 to become the water feed command 35. After comparison with the feedback value from the feed water flow rate transmitter 36, the water feed controller 37 changes the water feed operation end 38 so that the deviation becomes zero. temperature control.

On the other hand, the fuel correction water-fuel ratio signal 34 also receives the boiler master command 2.
2 to obtain a fuel command 39. After comparison with the feedback value from the fuel flow signal 40, the fuel controller 41 changes the fuel operating end 42 to perform temperature control so that the deviation becomes zero.

In addition, the water supply flow rate signal 36. The fuel flow rate signal 40 is input to the load control device circuit, and the flow rate signal on the manual mode side is selected and output as the boiler master.

When both fuel and water supply are automatic, a signal created by the load control operation is output.

From the characteristics of the once-through boiler, the evaporation amount and steam temperature of the boiler,
The pressure depends on the boiler inputs, such as feed water and fuel. Therefore, steam temperature fluctuation control is essential to achieving high load change rates, which is an important issue for intermediate-load operation plants that have been required in recent years. Simply put, it is twice as effective, and in cases where there is a delay in fuel change, such as in a coal-fired boiler, it can be seen that using water supply with quick response is more effective in suppressing temperature fluctuations.

Based on the above considerations, the water-fuel ratio signal 43 is distributed to the feed water correction water-fuel ratio signal 33 and the fuel correction water-fuel ratio signal 34, respectively, but what is important here is that the distribution ratio is appropriate. Therefore, in order to set the distribution ratio for the time of load change when temperature fluctuation suppression is most needed, and when the rate of temperature change is likely to increase based on steam temperature prediction, the setting is made in advance with consideration given to temperature change.

Furthermore, depending on the operating state, changing the distribution ratio based on the judgment of the operator may be more helpful in stabilizing the temperature, so a manual operating device 28 is provided so that the distribution ratio can be changed at will. Furthermore, when the water supply (fuel) becomes the manual mode signal 29, the remaining fuel (water supply) is configured with a water-fuel ratio distribution ratio circuit 33 and a distribution circuit 32 so that the water-fuel ratio is automatically corrected to 100%. /Fuel correction water-fuel ratio signal 33.34 is obtained.

Feed water/fuel flow signal input to load controller 36.4
0 means that when either water supply or fuel is controlled manually, the signal is replaced with the boiler master command 22, and the automatic fuel/water supply control automatically continues temperature control based on the manual flow rate. Enables stable steam temperature characteristic operation.

Another embodiment of the invention is shown in FIG.

In this embodiment, the water-fuel ratio correction to the water supply is performed by a temperature controller 4 configured with proportional and/or differential operation of steam temperature.
4, and the aforementioned water-fuel ratio distribution ratio is 1. on the water supply side only.
This is a method that automatically or arbitrarily sets the percentage of the fuel effect to be smaller than 0.

The advantages of this embodiment are that the temperature controllers 25 and 44 are independent, making it easy to avoid temperature interference due to changes in fuel and water supply, and since only the water supply side temperature correction gain is changed,
The advantage is that it is easy to add to conventional circuits.

〔Effect of the invention〕

According to the present invention, each of the water supply and fuel operation terminals can be operated at an appropriate ratio for steam temperature control, so it is effective in suppressing steam temperature fluctuations during load fluctuations, and an improvement in the load change rate can be expected.

In particular, in cases such as coal boilers where fuel measurement accuracy is insufficient and errors are likely to occur in the feed water/fuel ratio, the use of feed water has the effect of making it easier to absorb errors, and also reduces the delay in coal change. By utilizing water supply response,
It has the effect of improving water-fuel ratio control responsiveness. As a result, temperature stability is enhanced.

In addition, when the fuel control is manual, the boiler master command is used as the fuel, so it is easier to balance the water supply and fuel ratios, and the temperature is more stable than in the past.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a boiler temperature control device according to an embodiment of the present invention, Fig. 2 is a system diagram of the same according to another embodiment, and Fig. 3 is a temperature side '4ffll device according to a conventional example. phylogenetic diagram,
Figure 4 is a schematic diagram of a once-through boiler system. 21... Load control device, 22 31... Water-fuel ratio distribution circuit, 3 33... Water supply correction water-fuel ratio signal, ratio signal, 39... Fuel command, 4 4.3... Water-fuel ratio signal . ... Boiler master command, 2 ... Water-fuel ratio distribution circuit, 34 ... Fuel correction water salt 0 ... Fuel flow signal, Fig. 2

Claims (1)

[Claims] In a boiler steam temperature control device that controls the boiler steam temperature by the ratio of the amount of fuel supplied to the boiler and the amount of water supplied, the ratio between the amount of fuel and the amount of water supplied is determined by using the temperatures of the boiler outlet, boiler middle section, turbine inlet, etc. as feedback. The boiler steam temperature is characterized by being able to arbitrarily change the distribution of command signals to the fuel amount control system and the water supply amount control system, and further comprising a control means for automatically changing the distribution when the control device is abnormal. Control device.