KR20010018743A - An apparatus for controlling the water level of drum in heat recovering - Google Patents

Abstract

PURPOSE: A water level controlling device for a drum of a back heat recovering boiler is provided to improve stability and heat efficiency of the back heat recovering boiler system by uniformly maintaining a water level in a vapor drum by controlling an opening degree of a water supply flow controlling valve by computing and applying an input heat capacity of the boiler based on an output load of a gas turbine. CONSTITUTION: A water level controlling device for a drum of a back heat recovering boiler includes an operating part(210) for computing a change ratio of input heat capacity of the back heat recovering boiler by receiving an output load of a gas turbine, a drum water level operating part(220) for computing a drum water level set value by receiving the output load of the gas turbine, an adder(230) for adding the drum water level set value to a vapor flow value and adding the change ratio of the input heat capacity to the added drum water level set value and the vapor flow value, and a comparator(240) for comparing an output value from the adder and a water supply flow value to output a driving signal of a water supply flow controller.

Description

An apparatus for controlling the water level of drum in heat recovering

The present invention relates to an apparatus for controlling a power generation system for recovering and using an array generated in a gas turbine of a combined cycle power plant. In particular, a heat supply flow controller is calculated by calculating heat input of an array recovery boiler based on the output load of the gas turbine. The present invention relates to a drum level control device for an array recovery boiler, which improves the stability of the array recovery boiler system and improves thermal efficiency by maintaining a constant water level in the steam drum by controlling the water supply flow rate by applying the preceding signal.

In general, the combined cycle power plant uses a gas turbine to recover the heat generated from the power plant and turns the steam turbine through the boiler to increase power efficiency. As such, a power generation system using an array recovery boiler for driving a steam turbine is disclosed in FIG. 1.

1 is a view showing the configuration of a general heat recovery power generation system, as shown, the heat recovery system 20 and the heat recovery boiler 20 for recovering and heat-exchanging the arrangement of the gas turbine (10) It consists of the steam turbine 30 which generate electric power using the steam heat exchanged by 20. In particular, the above power generation system drives the gas turbine 10 and heat the waste gas discharged through the heat recovery boiler 20 to drive the steam turbine 30, which will be described in detail below.

The heat recovery boiler 20 has a coke 21 for first heating the water introduced through the water supply pipe 40 and a saturated steam heated by the coke 21 to flow into the steam drum 50. The evaporator 22 which converts into a state, and the superheater 23 which converts this steam water into a superheated steam state, and supplies it to the steam turbine 30 are provided. The superheated steam output in this way is sent to the steam turbine 30 to drive the steam turbine 30 to produce power. In this figure, reference numeral 60 denotes a water supply flow rate detector for detecting the amount of water flowing into the steam drum, reference numeral 61 denotes a drum level detector configured to detect the drum level, which is configured outside the drum level, and reference numeral 62 denotes a steam turbine. It is a steam flow detector for detecting the steam flow rate.

The control of the drum water level installed in the boiler 20 in the combined power plant mainly based on the gas turbine 10 as described above is controlled by adjusting the opening degree of the water supply flow rate control valve 70, the most in the normal operation of the equipment. It is one of the important parts. Therefore, the control system as shown in Fig. 2 is constructed to control the drum level.

2 is a block diagram showing a drum level control apparatus of a conventional heat recovery boiler. As shown, the drum level LT is input to the comparator 100 and is input to the drum level controller 102 in comparison with the set value. The proportional term and the integral term are calculated and output to the adder 104. In addition to the value output from the drum level controller 102, the adder 104 is weighted and input through the multiplier 106. This drum level controller 102 is composed of a proportional integral controller.

The values input to the adder 104 are added and output to the comparator 108. In this case, the water supply flow rate FT is input to the comparator 108 and compared with the value input from the adder 104. The comparison value output to the comparator 108 is input to the water supply flow rate controller 110 to multiply the error by a gain to output a control signal of the water supply flow rate control valve 70 to control it. Of course, the water supply flow rate controller 110 is also configured as a proportional integral controller, the automatic / manual switch 112 is provided between the water supply flow rate controller 110 and the water supply flow rate control valve 70, the water supply flow rate control valve 70 It can be controlled automatically or manually.

As mentioned above, the control of the drum level of the waste heat recovery boiler is composed of a control circuit based on the drum level, steam flow rate, and water supply flow rate. Such a control system can operate in a steady state. However, in general, the heat recovery boiler frequently starts and stops, so that the load of the gas turbine drops or rises rapidly. In this case, the drum level drops or rises rapidly due to the sudden change in the heat input of the heat recovery boiler. It is happening. As such, the conventional heat recovery power generation equipment is frequently started and stopped repeatedly. Therefore, the conventional control method has a disadvantage in that the stability is low.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks, by calculating the heat input of the heat recovery boiler based on the output load of the gas turbine and applying it as a preceding signal of the water supply flow controller. The present invention provides a drum level control device for a waste heat recovery boiler that improves the stability of the waste heat recovery system and improves thermal efficiency by maintaining a constant water level in the steam drum.

1 is a view showing the configuration of a general heat recovery power generation system,

2 is a block diagram showing a drum level control apparatus of a conventional heat recovery boiler;

Figure 3 is a block diagram showing a drum level control apparatus of the heat recovery boiler according to the present invention.

* Code descriptions for the main parts of the drawings

202: multiplier 210: heat input rate calculation unit

212: first function generator 214: change rate calculator

220: drum water level calculation unit 222: second function generator

224: comparator 226: drum level controller

230: adder 232: first adder

234: second adder 240: comparator

250: water supply flow controller 252: automatic / manual switch

260: water supply flow control valve

Drum level control apparatus of the heat recovery boiler according to the present invention for achieving the above object by using the drum water level, steam flow rate, water supply flow value in the heat recovery boiler to drive the steam turbine by utilizing the waste heat of the gas turbine An apparatus for controlling a drum level by controlling a water supply flow rate controller for driving a water supply flow rate control valve, the apparatus comprising: an input heat change rate calculation unit configured to receive an output load of a gas turbine and calculate and output a heat input change rate of the heat recovery boiler; A drum level calculator which receives the gas turbine output load and calculates and outputs a drum level set value; An adder which adds the drum water level set value and the steam flow rate value, and adds the input heat change rate to the value; And a comparator for outputting a drive signal of the water supply flow rate controller by comparing the output value from the adder with the water supply flow rate value.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram showing the drum level control apparatus of the heat recovery boiler according to the present invention.

As shown in the drawing, the apparatus receives an input load TT of a gas turbine and inputs a heat input change rate calculating unit 210 for calculating and outputting a heat input change rate of the heat recovery boiler and a gas turbine output load TT. A drum level calculator 220 for calculating and outputting the drum level set value, and adding the drum level set value and the steam flow value, and adding the heat input change rate to the value again, and the adder above. And a comparator 240 for outputting a drive signal of the water supply flow rate controller 250 for controlling the water supply flow rate control valve 70 by comparing the output value from the output value 230 with the water supply flow rate value.

The heat input change rate calculating unit 210 uses the output load TT of the gas turbine as an input value and outputs the heat input of the heat recovery boiler corresponding to the first function generator 212 and the first function generator 212. The change rate calculator 214 calculates and outputs the rate of change of the heat input amount by using the heat input amount of the output heat recovery boiler as an input value.

The drum water level calculating unit 220 receives the gas turbine output load TT and outputs a steam drum level target value, and a steam drum level target value of the second function generator 222 and the current steam drum level target value. A first comparator 224 for comparing and outputting drum level values, and a drum level controller 226 for receiving an output value of the first comparator 224 and calculating and outputting a proportional term and an integral term for an error.

In addition, the adder 230 includes a first adder 232 for adding a value output from the drum level controller 226 and a weighted steam flow rate value, a value outputted from the first adder 232, and a change rate calculator. And a second adder 234 which adds and outputs a heat input change rate output from 214.

This will be described in more detail below and the operation of the apparatus will be described.

The output load TT of the gas turbine is input to the first function generator 212. The first function generator 212 outputs a heat input amount of the heat recovery boiler corresponding to the gas turbine output load TT as an input value. The heat input amount of the heat recovery boiler thus output is input to the change rate calculator 214 to calculate the change rate according to time and multiply it by a predetermined gain.

The gas turbine output load TT is also input to the second function generator 222 to output the steam drum water level target value. The steam drum water level target value is input to the first comparator 224 to output a comparison value with the current value of the drum water level. The comparison value is input to the drum level controller 226 to compare the gain with respect to the error deviation, time integration, and output the result to the first adder 232. In addition to the value output from the drum level controller 226, the first adder 232 is weighted and input through the multiplier 202. The drum level controller 226 is configured as a proportional integral controller. In this way, the values input to the first adder 232 are added to the second adder 234 to be added to the heat input change rate calculated by the change rate calculator 214. The output of the second comparator 240 is compared with the input water supply flow rate. The value output to the second comparator 240 is input to the water supply flow rate controller 250 so as to control and output the control signal of the water supply flow rate control valve 70 by reflecting a proportional and integral gain in the error. Of course, the water supply flow rate controller 250 is also configured as a proportional integral controller, and an automatic / manual switch 252 is provided between the water supply flow rate controller 250 and the water supply flow rate control valve 70 to supply the water supply flow rate control valve 70. ) Can be controlled automatically or adjusted manually.

As described above, the drum level control apparatus of the heat recovery boiler according to the present invention calculates the heat input of the heat recovery boiler based on the output load of the gas turbine and applies it as a preceding signal of the water supply flow controller to supply the water supply flow rate. By regulating the opening of the control valve, the water level in the steam drum is kept constant, thereby improving the stability of the heat recovery boiler system and improving the thermal efficiency. In particular, when the load of the gas turbine changes, this signal is inputted to the water supply flow controller as a preceding signal, so that even if the load of the gas turbine changes suddenly, the reverse response characteristic of the drum level of the heat recovery boiler can be alleviated, so that the amount of change in the drum level is reduced. This has the advantage of reducing the stability. In addition, it is possible to control the level of the drum stably without installing various sensors, so there is no additional cost burden and has economic advantages.

Claims (4)

In the heat recovery boiler that drives the steam turbine by utilizing the waste heat of the gas turbine, the drum water level controller controls the water level flow control valve that drives the water supply flow rate control valve using the drum level value, steam flow rate value, and water supply flow rate value. In A heat input change rate calculating unit which receives an output load of a gas turbine and calculates and outputs a heat change rate of the heat recovery boiler; A drum level calculator which receives the gas turbine output load and calculates and outputs a drum level set value; An adder which adds the drum water level set value and the steam flow rate value, and adds the input heat change rate to the value; And And a comparator for comparing the output value from the adder with the water supply flow rate and outputting a drive signal of the water supply flow rate controller. The method of claim 1, wherein the heat input change rate calculating unit is a first function generator for outputting the heat input of the heat recovery boiler corresponding to the output load of the gas turbine as an input value, the output from the first function generator And a change rate calculator for calculating and outputting a change rate of the heat input amount by using the heat input amount of the heat recovery boiler as an input value. 3. The drum water level calculating unit according to claim 1 or 2, wherein the drum water level calculating unit receives a gas turbine output load and outputs a steam drum water level target value, and the steam drum water level target value of the second function generator and the present value. A first comparator for comparing and outputting drum level values, and a drum level controller for receiving the output value of the first comparator and comparing the gains with respect to error deviations and time-integrating the output; Drum level control device of boiler. 4. The heat generator according to claim 3, wherein the adder comprises: a first adder for adding a value output from the drum level controller and a weighted steam flow rate value; a value output from the first adder and an input heat amount output from the change rate calculator; A drum level control apparatus for an array recovery boiler, characterized by comprising a second adder for adding and outputting a rate of change.