JPS5843302A - Method of controlling mixed pressure type waste heat recovery boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a method for controlling a mixed pressure type waste heat recovery boiler, and in particular, to prevent steaming of each low pressure and high pressure economizer, and to control the level of each low pressure and high pressure boiler drum. Focus on easy-to-implement control methods.

As a method of recovering the heat of various types of exhaust gas generated by gas turbine power generation, a waste heat boiler is placed in the exhaust gas stream to recover heat, but in this case, the heat recovery efficiency is increased. Therefore, a mixed pressure boiler with a high pressure boiler and a low pressure boiler is sometimes installed. Figure 1 shows an example of a mixed pressure boiler at Kakurai. In the figure, the boiler water in the deaerator 22 is supplied by a low pressure water supply pump. 21 to the main water supply pipe 45
After that, the temperature is raised in the low-pressure economizer 17 and then supplied to the low-pressure drum 12.

The canned water in the low pressure drum 12 is transferred to the downcomer pipe 14 and the evaporator 13.
The generated steam is sent from the drum 12 to predetermined equipment such as a low-pressure turbine as low-pressure steam. On the other hand, a portion of the canned water that has descended through the water pipe 14 is transferred to the high pressure water supply pipe 46. High pressure water pump 11. It reaches the high-pressure drum 2 via the high-pressure economizer 7. The canned water in the high-pressure drum z also circulates through the downcomer pipe 4 and the evaporator 3 in the same way as the canned water in the low-pressure drum 12, and the generated steam is transferred to the high-pressure drum 2. It passes through a superheater 1 and is supplied as high-pressure steam S to equipment such as a high-pressure turbine.

In this type of boiler, the flow rate of the water supplied to the low-pressure economizer 17 and the high-pressure economizer 7 is adjusted by the amount of water that passes through the main water supply pipe 45.
If the sa is softened and the water supply flow rate is reduced in response to a drop in boiler load, the pressure will be low.

Steaming occurs in each economizer 17 and 7 of j+:I pressure. In other words, since the amount of exhaust gas, which is the heating medium, passing through the valley boiler is always approximately constant, when the amount of feed water passing through decreases, the amount of heat absorbed per unit volume of the feed water increases, causing steaming. The passage of the upper gas-liquid mixture, which causes steaming in the coal burner, causes the heat exchanger tubes to receive a severe impact, resulting in so-called water hammer, which may damage the economizer. In addition, in order to prevent mutual interference between the boiler drums, the low pressure drum 12 is sometimes bypassed and a pipe 1147 is provided, but in this case, if steaming occurs in the low pressure economizer, the gas-liquid mixture Since the water directly flows into the high-pressure water supply pump 11, the problem of vibration damage due to cavitation of the pump 11 also occurs.

In addition, the high pressure drum 2 and the low pressure drum 12 are in communication via the downcomer pipe 14 and the high pressure water supply line: 46. The amount of water taken out from the can 12 changes and this appears as a level fluctuation in the low pressure drum 12.
'ru. In other words, mutual interference occurs between the two drums, making it extremely difficult to maintain the level of both drums at a constant level.

The purpose of this invention is to eliminate the above-mentioned problems and to control a mixed pressure type waste heat recovery boiler that does not cause steaming in each of the high-pressure and low-pressure economizers and prevents mutual interference between the high-pressure and low-pressure boiler drums. Our goal is to provide the following.

In short, this invention is a carbon economizer by making a part of the canned water supplied to each boiler drum via each economizer return to the deaerator, and adjusting the flow rate of water that passes through each economizer regardless of the boiler load. The present invention relates to a control method configured to prevent boiler drum steaming and to control the level of a boiler drum.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, the water supply inside the deaerator 22 is supplied to the main water supply pipe 45.
Low pressure water pump 21. Low pressure economizer 17 via flow meter 23
leading to. The feed water leaving the low-pressure economizer 17 flows into the low-pressure drum 12 through the flow control valve 15 whose opening degree is set by a control method described later, and circulates through the downcomer pipe 14 and the evaporator 13, and the generated steam becomes low-pressure steam. It is supplied to the low-pressure turbine as S work. 19 is a temperature detector that detects the temperature of the water supply at the outlet of the low-pressure economizer 17, and when the temperature of the water supply at the outlet is lower than the set value, the recirculation pump 18 supplies high-temperature canned water to the water supply at the inlet side of the economizer. Mix it in to adjust the temperature.

Next, if there is a risk that steaming will occur within the low-pressure economizer, the following control is performed. In order to prevent steaming inside the economizer, it is sufficient to increase the number of water supply lids that pass through the economizer so that the temperature at the outlet of the economizer is below the saturation temperature. A portion of the canned water in the low-pressure drum 12 is returned to the deaerator 22 to increase the amount of water that passes through the low-pressure economizer 17. In this case, the opening degree of the opening valve 20 is the water level gauge 1
6 and the signal from the temperature sensor 19, DM is performed so that more than the required amount of can water does not flow back into the deaerator 22.

Adjustment of this valve 20 not only prevents steaming within the low pressure economizer, but also controls the level within the low pressure drum 12 by receiving a signal from the water level gauge 16. 24 is a flow rate detector that detects the reflux amount.

On the other hand, a part of the water supply from the low-pressure economizer 17 is transferred to the pipe 48° high-pressure water supply pump 11. It reaches the high pressure economizer 7 via the flow meter 25. Thereafter, similarly to the low-pressure boiler, the flow rate is controlled by the flow control valve 5, and the steam flows into the high-pressure drum 2, circulates through the downcomer pipe 4 and the evaporator 3, and the generated steam flows into the drum 2. It passes through the superheater 1 and is supplied to the high pressure turbine as high pressure steam S2. Mixing of canned water into the economizer is carried out by the pump 8, and prevention of steaming and adjustment of the drum water level are carried out by adjusting the opening degree of the flow rate control valve IO based on signals from the water level gauge 6 and the temperature sensor 9. 26 is a flow rate detector that detects the feed water return amount on the high pressure boiler side.

Figure 3 shows in more detail the control method for preventing steaming in a low-E coal machine. In the figure, 51 is a gas turbine load signal transmitter.

52 is a drum pressure transmitter.
55 is a drum water level transmitter.

To the signal from the gas turbine load signal transmitter 51.

Therefore, the function generator 56 inputs the amount of water passing through the economizer that has been input in advance to the adder 60, and uses this as the preceding element of the a and i+ controls. The pressure drum pressure signal from the drum pressure transmitter 52 is input to the function generator 57, which calculates the saturation temperature at which the detected pressure is applied from the relational expression between the saturation pressure and the feed water temperature that has been input in advance. Specify a low temperature and input it into the setting device 58. The setting device 58 compares and calculates the temperature signal of the economizer outlet water supply from the transmitter 53 and the finger temperature to obtain a deviation value, and outputs a deviation value from the proportional and integrator 39.
The signal is inputted to the adder 60 via the adder 60, and the adder 60 issues a welfare signal to the constructor 63. In this case, the correction value is passed through the setting device 63.62. is input.

The controller 63 controls the opening of the flow rate control valve 20 using the proportional and integrator 649, either manually or automatically by the controller 64. (2) In order to adjust the drum water level, a drum water level target value is set in the signal memory 67, and the valve 20 is operated even if the drum water level rises from '' due to maladjustment of the valve or the like. That is, the signal generator 66 and the signal memory 67 add 'Si' L/ to the drum water level set value in the adder 68, and the set value and the actual drum water level measured by the transmitter 55 are added in the setter 69. Comparative calculations are performed, and the deviation value is numerically limited in the upper and lower limit setter 70 so as to limit the control box and enclosure, and manually inputted to the adder 60 as a correction value. Thereby, the opening degree of the valve 20 can be set from the viewpoints of both prevention of steaming and adjustment of the drum water level.

Similar control is performed on the high-pressure boiler side to prevent steaming and adjust the drum water level.

By implementing this invention, it is possible to effectively prevent steaming in each of the high pressure and low pressure new coal machines, and also to prevent mutual interference between the high pressure and low pressure drums.

[Brief explanation of the drawing]

Fig. 2 shows the system layer of a conventional mixed pressure waste heat recovery boiler, Fig. 2 is a system diagram of a mixed pressure waste heat recovery boiler showing the control method according to the present invention, and Fig. 3 shows a concrete example of the control of a low pressure boiler. FIG. 2... High pressure drum 7... High pressure economizer 10, 20... Flow control valve 12... Low pressure drum 17... Low pressure crystal Coal generator 22... Deaerator 51... Gas turbine load signal transmitter 52...
... Drum pressure transmitter 53 ... Coal generator outlet water supply temperature transmitter 54 ...
...Canned water return flow rate transmitter 55...Drum water level transmitter Patent attorney Oka Tagobe

Claims (1)

[Claims] 1. Supply water from the outlet of the low-pressure economizer to the low-pressure drum, and connect it to the high-pressure Nj
In the method of supplying coal field outlet water to the high-pressure drums, a portion of the canned water σ in the low-pressure and high-pressure drums is recycled to the deaerator in accordance with the temperature of the water supply at the outlet of the low-pressure and high-pressure economizers. A method for controlling a mixed-pressure waste heat recovery boiler, characterized in that the water supply temperature in each metering device is always kept below the saturation temperature to prevent steaming, and the water level in each drum is adjusted. 2. The mixed pressure type waste heat according to claim 1, characterized in that the return amount of canned water in each drum is determined based on the water level signal of each drum and the feed water temperature signal of each economizer outlet. Recovery boiler control method. 3. Patent No. 31, which is characterized in that a gas turbine load signal and a drum internal pressure signal are added as determining factors for the return amount of canned water in each drum. Heat recovery boiler control i, lit Jj method. 4. Patent nVI characterized in that the actual return amount measurement signal and drum water level set value are added as supplements + IE factors for determining the return amount of canned water in each drum. A method for controlling a mixed pressure waste heat recovery boiler according to scope 1.