JPH06159603A - Control device for waste heat steam generator - Google Patents

Abstract

PURPOSE:To provide a control device capable of reducing the occurrence of reverse response phenomena with regard to the liquid level in a drum of a waste heat boiler. CONSTITUTION:The title device is provided with a temperature detector 131 for detecting the temperature of waste gas fed to a waste heat boiler 1, a flow rate detector 132, a heat flow rate calculator 133 to which the outputs of both the temperature detector and the flow rate detector are inputted, a means 134 for calculating the rate of heat flow change to which the output of the heat flow rate calculator is inputted and a signal limiter 136 which receives the output of the means 134 and transmits an operation signal to a bypass regulating valve 112 when the output of the means 134 exceeds a set point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for waste heat steam generation equipment applied to a waste heat steam generator (waste gas boiler).

[0002]

2. Description of the Related Art A conventional waste gas boiler generally receives heat from a waste heat source whose waste heat flow rate varies greatly. For example, the heat flow rate of the clinker cooler exhaust gas from a cement plant is a process in which the clinker cooler waste gas heat flow rate may rapidly increase due to the clinker cooler in the rotary kiln sometimes causing a large amount of clinker to enter the clinker cooler. Can be said. From the viewpoint of maximum utilization of waste heat, steam is generated corresponding to the total heat flow of waste heat.

A conventional example will be described with reference to FIG. Waste gas a is introduced into the waste heat boiler 1. A bypass line is provided between the inlet and outlet of the waste heat boiler 1, and a bypass damper 4 is attached in the middle of the bypass line.

A superheat pipe 117, a main steam pipe 114, and a coal saving pipe 113 are arranged in the waste heat boiler 1. Superheated tube 117
Is connected to the upper part of the boiler drum 115. The outlet is also connected to the steam supply line 7 having the steam flow rate detector 118. The inlet and outlet of the steam pipe 114 are connected to the lower portion and the upper portion of the boiler drum 115, respectively. The inlet of the coal-saving pipe 113 is a control valve 112, the feed water flow rate detector 11
It is connected to the water supply line 6 having 1. The outlet is connected to the lower part of the boiler drum 115. Boiler drum 115
Is provided with a liquid level detector 116.

The output of the liquid level detector 116 is the liquid level adjusting device 1.
It is sent to the adder 122 via 21. Further, the output of the steam flow rate detector 118 passes through the adder 122 and the flow rate controller 12
Sent to 3. Further, the output of the water supply flow rate detector 111 is sent to the control valve 112 via the flow rate control device 123.

In the above, the liquid level adjustment of the boiler drum 115 is performed as follows.

The steam flow rate detector 118 detects the steam flow rate generated by the boiler and outputs a signal for setting the feed water flow rate corresponding thereto. The liquid level adjusting device 121 receives the output of the liquid level detector 116 that detects the liquid level of the boiler drum, and outputs a signal for setting the feed water flow rate that makes the liquid level of the drum constant. The adder 122 inputs these outputs, adds them, and sends a feed water flow rate setting signal to the flow rate controller 123. The flow rate adjusting device 123 further receives the output of the water supply flow rate detector 111 that detects the water supply flow rate to the boiler, and sends an operation signal to the control valve 112 so that the water supply flow rate becomes the water supply flow rate set value. The control valve 112 opens and closes according to the input to adjust the water supply amount.

In this way, the liquid level of the boiler drum is adjusted to be constant.

[0009]

In the above-mentioned conventional apparatus, when the waste heat heat flow rate taken into the waste gas boiler greatly changes (increases), the drum liquid level of the waste gas boiler changes greatly (at first, the reverse response phenomenon of the boiler). As a result, the liquid level of the drum rises and the liquid level of the drum lowers in spite of the increase in the amount of generated steam.

Further, there is a drawback that the response of the feed water flow is delayed due to the feedback control.

[0011]

The present invention takes the following means in order to solve the above problems.

That is, the steam flow rate detector provided in the steam supply line of the waste heat boiler, the liquid level detector of the drum of the waste heat boiler, and the feed water flow rate detector provided in the water supply line of the waste heat boiler. And a control valve for controlling the liquid level in the drum so that the liquid level in the drum is constant, in a controller for a waste heat steam generation facility, which is branched from the downstream side of the feed water flow rate detector and is connected to the drum and is a bypass control valve. With a bypass line, a temperature detector and a flow detector for waste gas to the waste heat boiler, a heat flow calculator that receives the output of the temperature detector and the flow detector, and an output of the heat flow calculator. A heat flow rate change rate calculator for receiving and a signal limiter for receiving an output of the heat flow rate change rate calculator and sending an operation signal to the bypass control valve when the input exceeds a predetermined value are provided.

[0013]

In the above means, the heat flow rate calculator receives the outputs of the temperature detector and the flow rate detector which detect the temperature and flow rate of the waste gas supplied to the waste heat boiler, calculates and outputs the heat flow rate. . The heat flow rate change rate calculator calculates and outputs the change rate of the input. The signal limiter sends an operation signal to the bypass control valve when the input exceeds a predetermined value. The bypass control valve opens and closes according to the input, and feeds water directly to the boiler drum.

In this way, for example, when the amount of waste gas suddenly increases, the heat flow rate change rate exceeds the predetermined value. Then, the bypass control valve is opened to feed water directly to the drum in a feedforward manner.

Then, just before the steam generation amount starts to increase, the feed water flow rate increases. Moreover, since the water temperature of this increased water supply is low, the temperature of the water in the drum of the boiler drops,
The volume of water contracts, and the increase in the drum liquid level when the waste gas heat flow rate increases is mitigated. That is, the reverse response phenomenon is reduced.

Therefore, it is possible to reduce or improve the fluctuation of the liquid level in the drum when the waste heat heat flow rate increases. The responsiveness of the water supply flow rate is also improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. It should be noted that the parts described in the conventional example are denoted by the same reference numerals and the description thereof is omitted, and the parts relating to the present invention will be mainly described.

In FIG. 1, a bypass line 120 is provided from the downstream side of the feed water flow rate detector 111 to the outlet of the economizing pipe 113. In the bypass line 120, the bypass control valve 13
7 is provided.

Waste gas supply line 119 to the waste heat boiler 1
A temperature detector 131 and a flow rate detector 132 are provided in the. The outputs of the temperature detector 131 and the flow rate detector 132 are sequentially sent to the bypass control valve 137 via the heat flow rate calculator 133, the heat flow rate change rate calculator 134, and the signal limiter 136.

In the above, the heat flow rate calculator 133 calculates and outputs the waste heat heat flow rate Q of the waste heat source taken into the waste heat boiler 1 by the equation (1) from the outputs of the temperature detector 131 and the flow rate detector 132. .

Q = C · T · W (1) where C: specific heat W: flow rate (mass flow rate) T: temperature heat flow rate change calculator 134 calculates the absolute value of the input change rate, and signal limiter 136. Send to. Signal limiter 136
Transmits an input signal to the bypass control valve 137 when the input exceeds a predetermined reference value. The bypass control valve 137 is operated in the opening direction in response to the input, and the drum 115
The direct water supply flow to is increased.

As a result, for example, when the waste gas heat flow rate greatly increases, the feed water flow rate to the waste heat boiler is feedforwardly increased before the steam flow rate generated from the waste heat boiler 1 increases. For this reason, the water temperature in the boiler drum 115 is lowered, so that the reverse response phenomenon of the boiler drum liquid level is reduced.

Further, the shortage of the feed water flow rate via the coal saving pipe 113 during the reverse response is compensated, and the liquid level of the boiler drum 115 is maintained at a constant value.

FIG. 3 (a) shows a conventional example of changes in the drum liquid level when the waste heat heat flow rate changes in this embodiment (FIG. 3).
(B)). From the figure, it can be seen that the change in the drum liquid level has been greatly improved.

In FIG. 1, the flow rate is detected by the differential pressure type,
Although the device is calculated by the formula (2), it may be calculated by the formula (3) using an insertion type turbine meter or the like.

W = K√ (γ · Δp) (2) where K: coefficient, γ: density, Δp: differential pressure W = γ · β · S (3) where γ: density β: cross-sectional area S: Velocity Since the density γ of gas is relatively large depending on temperature and pressure, it may be necessary to correct it depending on temperature and pressure.

Although the specific heat of the equation (1) changes to some extent depending on the temperature, it is necessary to correct it when strict control is performed.

As described above, when the change of the waste heat heat flow rate is large, the following effects can be obtained. (1) Improvement of controllability of drum liquid level of a waste heat boiler, which is provided as a result of reduction of reverse response phenomenon of liquid level. (2) Stabilize the waste heat boiler drum liquid level by increasing the flow rate of water supply. (3) Prompt response (preceding) Increasing the natural circulation rate of the water inside the evaporation pipe due to the decrease in the boiler water temperature in the boiler drum due to the increase in the feed water flow rate (increasing the absorption rate of the waste gas heat quantity in the evaporation pipe section due to the increase in the natural circulation rate (boiler thermal efficiency Increase)). (4) As a result of the above (3), the temperature of waste gas reaching the coal-saving pipe is prevented from rising rapidly (preventing steaming in the coal-saving pipe).

[0029]

As described above, according to the present invention, when the waste heat heat flow rate largely changes, water is fed to the drum of the waste heat boiler by feedforward bypass. Therefore, the reverse response phenomenon of the liquid level is reduced, and the controllability of the drum liquid level is improved. Further, since the water is supplied in a feedforward manner, the drum liquid level is stabilized.

[Brief description of drawings]

FIG. 1 is an overall configuration system diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a control device of the embodiment.

3 (a) and 3 (b) are explanatory views of the operation of the embodiment and the conventional example.

FIG. 4 is an overall configuration system diagram of a conventional example.

[Explanation of symbols]

 1 Waste Heat Boiler 4 Bypass Damper 115 Drum 131 Temperature Detector 132 Flow Rate Detector 133 Heat Flow Rate Calculator 134 Heat Flow Rate Change Calculator 136 Signal Limiter 137 Bypass Control Valve

Claims (1)

[Claims] 1. A steam flow rate detector provided in a steam supply line of a waste heat boiler, a liquid level detector of a drum of the waste heat boiler, and a feed water flow rate detector provided in a water supply line of the waste heat boiler. And a control valve for controlling the liquid level in the drum so that the liquid level in the drum is constant, in a controller for a waste heat steam generation facility, which is branched from the downstream side of the feed water flow rate detector and is connected to the drum and is a bypass control valve. With a bypass line, a temperature detector and a flow detector for waste gas to the waste heat boiler, a heat flow calculator that receives the output of the temperature detector and the flow detector, and an output of the heat flow calculator. Waste heat comprising a heat flow rate change rate calculator for receiving and a signal limiter for sending an operation signal to the bypass control valve when the input of the output of the heat flow rate change rate calculator exceeds a predetermined value Control device for steam generator Place