JPH05215301A - Controller for waste-heat steam generating facility - Google Patents

Abstract

PURPOSE:To reduce the variation of a level, and to enable improvement in thermal efficiency and stable operation by additionally inputting the signal of a waste-heat flow rate to a control valve in a feed forward manner when the increase rate of the waste-heat flow rate reaches a specified value or more. CONSTITUTION:A temperature detector 131 and a flow rate detector 132 are installed to a waste-gas feed line 5 to a waste heat boiler 1. A heat flow rate computing element 133 computes a waste-heat flow rate Q taken into the waste heat boiler 1 from outputs from the temperature detector 131 and the flow rate detector 132. An output from the heat flow rate computing element 133 is time-differentiated by a conversion rate computing element 134, and transmitted over a signal limiter 136. The signal limiter 136 is added to a control signal from a flow rate controller 123 in a feed forward manner when an input reaches a specified value or more. Accordingly, the quantity of feed water to a boiler drum 115 is increased, and the variation of a level in the drum is reduced.

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 (waste gas boiler).

[0002]

2. Description of the Related Art Waste heat sources used in conventional waste gas boilers often have a variable waste heat flow rate. 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. A waste heat boiler 1 for waste gas is provided. Waste heat boiler 1 coal-saving pipe 11
A water supply line 6 is connected to 3 via a water supply flow rate detector 111 and a control valve 112. The outlet of the superheater tube 117 is connected to the steam supply line 7 via the steam flow detector 118.
Connected to. Further, the 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 arithmetic unit (adder) 122 via 21. The output of the steam flow rate detector 118 is sent to the control valve 112 via the calculator 122 and the flow rate control device 123. Further, the output of the water supply flow rate detector 111 is sent to the flow rate adjusting device 123.

In the figure, 4 is a bypass damper and 114 is an evaporation pipe.

[0006] In the above, the feed water flow rate setting signal corresponding to the generated steam flow rate (output of the steam flow rate detector 118) is calculated by the output signal of the adjusting device 121 for controlling the drum liquid level to be constant. The value added by the device 122 is input to the feed water flow rate control device 123 as a set value. Further, the output signal from the water supply flow rate detector 111 is input to the flow rate adjusting device 123. The flow rate control device 123 outputs a control signal 123s to the control valve 112 to control the control valve 112 so that the flow rate becomes a set value.

[0007]

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 reverse response phenomenon (for example, when the waste heat heat flow rate increases) However, there is a drawback that the feed water flow rate becomes insufficient due to this phenomenon during the period in which the drum liquid level first increases even though the generated steam amount increases. Further, since it is a feedback control system, it also has a drawback of delaying the response of the water supply flow rate.

Due to these drawbacks, when the waste heat heat flow rate changes,
There was a problem that the fluctuation of the drum liquid level was large.

[0009]

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

That is, the waste heat is provided with a feed water flow rate detector and a control valve provided in the water supply line of the waste heat boiler, and a flow rate control device which receives the output of the feed water flow rate detector and outputs a control signal to the control valve. In the control device for steam generating equipment, the temperature detecting means and the flow rate detecting means provided in the waste gas supply pipe of the waste heat boiler, and the heat for receiving the output of the temperature detecting means and the flow rate detecting means and calculating the heat flow rate of the waste gas. Input the output of the flow rate calculator, the change rate calculator that calculates the change rate by receiving the output of the heat flow calculator, and the output of the change rate calculator,
A signal limiter that outputs when its input is above a predetermined value,
An arithmetic unit for receiving the output of the signal limiter and performing an arithmetic operation on the output of the flow rate controller.

[0011]

In the above means, the heat flow rate calculator receives the temperature of the waste gas from the temperature detecting means and the flow rate of the waste gas from the flow rate detecting means, and calculates the heat flow rate of the waste gas. This heat flow rate signal is time-differentiated by the change rate calculator and sent to the signal limiter. The signal limiter outputs to the arithmetic unit when the input is equal to or more than a predetermined value. The arithmetic unit adds the output from the signal limiter to the output of the flow rate control device and sends it to the control valve.

Therefore, when the amount of waste gas supplied is greatly increased, the signal output from the signal limiter is feedforwardly added to the control signal from the flow rate control device. The control valve increases the opening by this signal to increase the supply of water to the waste heat boiler. By increasing the flow rate of water supplied to the waste heat boiler, the reverse response of the liquid level in the boiler is mitigated, and fluctuations in the liquid level are mitigated. In addition, the responsiveness of the water supply flow rate is also improved.

[0013]

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

In FIG. 1, a temperature detector 131 and a differential pressure type flow rate detector 132 are provided in the waste gas supply line 5 to the waste heat boiler 1.
Is provided. These outputs are sent from the heat flow calculator 133 to the signal limiter 136 via the change rate calculator 134.

A calculator 137 is provided between the flow rate control device 123 and the control valve 112. The output of the signal limiter 136 is input to the calculator 137.

FIG. 2 shows a block diagram of the above-mentioned overall control.

In the above, the temperature detector 131 detects and outputs the temperature of the waste gas. Further, the flow rate detector 132 detects the differential pressure and calculates and outputs the flow rate of the waste gas by the equation (1).

[0018]

[Equation 1]

The heat flow calculator 133 is the temperature detector 1
From the outputs of 31 and the flow rate detector 132, the waste heat heat flow rate Q taken into the waste heat boiler 1 is calculated by the equation (2).

[0020]

[Equation 2]

The output of the heat flow rate converter 133 is time-differentiated by the change rate calculator 134 and sent to the signal limiter 136. The signal limiter 136 outputs when the input is a predetermined value or more.

Further, the computing unit 137 is the flow rate adjusting device 12
The signal from the signal limiter 136 is added to the control signal from 3 and sent to the control valve 112.

Therefore, when the amount of waste gas supplied is greatly increased, the signal output from the signal limiter 136 is added to the control signal from the flow rate controller 123 in a feedforward manner. The control valve 112 increases the opening degree by this signal, and accordingly increases the amount of water supplied to the boiler drum 115.

In this way, by increasing the water supply flow rate to the drum 115, the reverse response of the liquid level in the drum is alleviated (since the water supply temperature is lower than the temperature of water in the drum (saturated steam temperature), As a result, the temperature of water in the drum decreases, the volume of water in the drum contracts, and the effect of alleviating the increase in the liquid level (reverse response phenomenon) when the heat flow rate of waste heat increases is generated. Fluctuations in the liquid level in the drum when the heat flow rate increases are reduced / improved. The responsiveness of the water supply flow rate is also improved.

In order to understand these functions and effects, a behavior diagram of process quantities is shown in FIG. 3 (a) in comparison with the case of the conventional example shown in FIG. 3 (b). From the figure, it can be seen that the rapid response of the drum liquid level is improved and the fluctuation of the drum liquid level is significantly reduced.

Although the differential pressure type is used for the flow rate detector 132 in the above, a direct type turbine meter or the like may be used.

Although the density γ of the gas is set to be constant, the degree to which the density depends on temperature and pressure is relatively large.
In some cases, the temperature and pressure may be corrected according to the equation (3).

[0028]

[Equation 3]

Similarly, since the specific heat also changes somewhat depending on the temperature, it may be corrected in some cases.

As described above, the following effects can be obtained. (1) The controllability of the liquid level is improved while reducing the reverse response phenomenon of the liquid level in the drum. (2) The liquid level of the boiler drum is stabilized by increasing the flow rate of the water supply. (3) Due to the increase in the quick response (preceding) feed water flow rate, the natural circulation rate of the water in the evaporation pipe increases as the temperature of the can water in the boiler drum decreases, and the thermal efficiency improves. (Increase in absorption rate of waste gas heat quantity in the evaporation pipe section due to increase in natural circulation rate (increase in boiler thermal efficiency)) (4) As a result of (3) above, a rapid rise in waste gas temperature leading to the coal-saving pipe is prevented ( Steaming prevention with coal-saving pipes).

[0031]

As described above, according to the present invention, when the increase rate of the waste heat heat flow rate is equal to or greater than the predetermined value, this signal is additionally input to the control valve in a feedforward manner. Therefore, the liquid level inverse response phenomenon of the waste heat boiler when the waste gas greatly increases is mitigated, the fluctuation of the liquid level is reduced, and the thermal efficiency is improved and stable operation is performed.

[Brief description of drawings]

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

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

FIG. 3 is an explanatory diagram of a function and effect of the same embodiment.

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

[Explanation of symbols]

 1 Waste Heat Boiler 4 Bypass Damper 5 Waste Gas Supply Line 131 Temperature Detector 132 Flow Rate Detector 133 Heat Flow Rate Calculator 134 Heat Flow Rate Calculator 137 Calculator 111 Water Supply Flow Rate Controller 112 Control Valve 115 Boiler Drum 116 Liquid Level Detection Vessel 118 Steam flow rate detector 121 Liquid level controller 122 Calculator 123 Flow rate control device

Claims (1)

[Claims] 1. Waste heat comprising a feed water flow rate detector and a control valve provided in a water supply line of a waste heat boiler, and a flow rate control device which receives an output of the feed water flow rate detector and outputs a control signal to the control valve. In the control device for steam generating equipment, the temperature detecting means and the flow rate detecting means provided in the waste gas supply pipe of the waste heat boiler, and the heat for receiving the output of the temperature detecting means and the flow rate detecting means and calculating the heat flow rate of the waste gas. A flow rate calculator, a change rate calculator that receives the output of the same heat flow rate calculator and calculates a change rate, and a signal limiter that inputs the output of the change rate calculator and outputs when the input is a predetermined value or more, A controller for waste heat steam generation equipment, comprising: a calculator that receives the output of the signal limiter and performs an addition operation on the output of the flow rate controller.