JPS59145438A - Control system of heating furnace - Google Patents

Abstract

PURPOSE:To improve the heat efficiency of entire system for thereby realizing a systematic relationship between the heat efficiency and a total flow rate, by increasing the flow rate passing through a channel having the greatest heat efficiency and by controlling the flow rate of respective main channel before branched off by the adjustment of pump r.p.m. CONSTITUTION:An arithmetic and control unit 6 continuously monitors the temperature of respective channel of outlet side heating furnace 4 by the signal of temperature detecting devices T1-T4. The final temperature of fluid after heating is detected by a temperature detector T5 provided at a main channel downstream of confluences. An arithmetic and control unit 5 is adapted to calculate the difference DELTAFV in the opening amount of control valves V1-V4 to verify whether the difference falls within a prescribed allowance. In an event of the difference being smaller than the prescribed allowance, a channel Tmax is selected to take a remedial action. The remedial action is to further increase the opening amount of the control valve of channel Tmax for thereby increasing the flow rate of fluid passing therethrough. Since the opening amount of respective control valves is continuously monitored by the arithmetic and control unit 5 even while the remedial action of valve opening amount is being taken, a control unit C1 can be fed with such a preset value as to keep a consistent total flow rate. In consequence, a control unit C2 receiving the input from the control unit C1 functions to maintain the consistent total flow rate by adjusting the r.p.m. of pump 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace control system that improves overall thermal efficiency by increasing the flow rate of a channel with higher thermal efficiency than that of other channels.

In a heating furnace control system that divides fluid into multiple channels and heats the fluid through a heating furnace, a flow rate controller is installed in each channel, and each controller has a target value set based on its thermal efficiency. being driven.

By the way, if the heating furnace is operated for a long period of time, there will be differences in dirt etc. inside the tubes of each flow path, and the thermal efficiency will differ from the initial setting. Therefore, a large amount of fluid often passes through channels with poor thermal efficiency, which is not desirable in terms of effective use of combustion energy.

The present invention has been made in view of the above points, and improves the thermal efficiency of the entire system by increasing the flow rate of the channel with the highest thermal efficiency among the flow channels, and also increases the total flow rate to the main flow channel before branching. This system realizes a heating furnace control system that organically links thermal efficiency and total flow rate by controlling the rotation speed of cascaded pumps controlled by an installed flow rate controller.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is a tank in which fluid is stored. 2 is a steam turbine pump, 3 is a governor, R□ is a rotation speed detector that detects the rotation speed of pump 2, Fl is a flow rate detector that detects the fluid flow rate, and cl is a flow rate indication adjustment that receives the output of the flow rate detector. C2 is a rotational speed controller which receives the output of the rotational speed detector R□ and provides a drive signal to the governor 3. pump 2
The outlet is branched into four channels, and a flow rate controller is installed for each channel. C3 to C6 are flow rate controllers provided for each flow path, and F2 to F5 are flow rate detectors provided for each flow path, the outputs of which are entered into controllers 03 to C6, respectively. ■□ to F4 are il1 control valves driven by controllers 03 to C6. A valve opening signal of the control valve is input to an arithmetic and control device (described later).

4 is a heating furnace, and the fluid is heated while passing through the heating furnace. In the figure, the combustion system of the heating furnace is omitted.

T1 to T4 are temperature detectors provided for each flow path on the exit side of the heating furnace 4, T5 is a temperature detector that detects the temperature of the flow path where the four flow paths merge to form one main flow path; Ml to M
5 is a temperature indicator that indicates the output of each temperature sensor.

5 is a first arithmetic and control device which performs various calculations and controls in response to the outputs of the flow rate detectors F2 to F5 and also provides a set value to the flow rate indicating controller C; 6 which receives the outputs of the temperature detectors T-T; 5 is a second arithmetic and control device that performs various calculations and controls. As these arithmetic and control devices, for example, microcombeaters are used. The arithmetic and control units 5 and 6 are connected to each other and exchange signals.

The operation of the device configured as described above will be explained as follows.

The arithmetic and control device 6 constantly monitors the temperature of each flow path on the outlet side of the heating furnace based on signals from temperature detectors T1 to T4. The final temperature of the fluid after heating is detected by a temperature sensor T5 installed in the main flow path after the merging, and a control signal that keeps the final temperature of the five fluids constant is sent from the arithmetic and control unit 6 to the heating to the furnace combustion control system (not shown). Arithmetic control unit H
6 is the maximum temperature Tma of the heating furnace outlet temperature of each flow path
Select x and the smallest one Tm1n. After that, Tma
Calculate the difference ΔT between x and Tm1n. When this difference ΔT is within the predetermined tolerance ΔTs, the current operating state is continued.

On the other hand, when the difference ΔT between Tmax and Tm1n becomes larger than the allowable deviation ΔTs by (3), the arithmetic and control unit 5 calculates the opening difference ΔFV of the control valves v1 to v4. ΔFV is the maximum opening FVmax
It is determined as the difference between FVmin and the minimum opening degree FVmin. It is checked whether the opening degree difference ΔFV obtained in this way is smaller than a predetermined tolerance, and if it is smaller, the TmaxO flow path is selected. Then, when the unit opening degree α% for correction is added to the operation output MV of the control valve of the flow path at Tmax, it is checked whether it is smaller than the allowable operation amount (allowable opening degree) MVmax. Take corrective action for the first time. The corrective action is to further open the control valve of the Tmax flow path to increase the flow rate of liquid passing through it. Therefore, the arithmetic and control device 5 gives a correction value α to the controller of the Tmax l path. As a result, the liquid flow rate in the TmaX channel increases, and the heating furnace is operated efficiently.

Note that if (Mv+α) becomes larger than the allowable opening degree MVmax, the valve cannot be opened any further. Therefore, this time, the Tm1nO flow path is selected, and the lower limit tolerance MVm1n is obtained by subtracting α from the valve opening degree MV of the flow path.
Determine whether it is greater than When it is determined that the flow rate is large (4), the control valve for that flow path is closed.

This closes the control valve, thereby increasing the flow rate in the remaining channels. Therefore, since the flow rate increases when the valve opening degree of the 'rmax flow path is almost fully open, the same effect as when opening the valve to increase the flow rate can be obtained. Even during such a valve opening correction operation, the arithmetic and control unit 5 constantly monitors the valve opening of each control valve, so it is necessary to give a set value to the controller C□ that will keep the total flow rate constant. I can do it. Therefore, C1
The controller 02 receiving the output controls the rotation speed of the pump 2 to maintain a constant total flow rate. That is, it is possible to perform control in which thermal efficiency and total flow rate are organically linked. FIG. 2 is a flowchart showing the control sequence. Such a sequence is constantly returned.

In the above description, the case of four channels was explained as an example, but the number of channels does not need to be limited to this and may be any number as long as it is plural.

As described in detail above, according to the present invention, the flow rate of the channel with the highest thermal efficiency is increased to improve the thermal efficiency of the entire system, and the total flow rate is divided by calculating the flow rate for each channel. To realize a heating furnace control system that organically links thermal efficiency and total flow rate by determining the flow rate for each previous main flow path and controlling the rotation speed of a pump installed in the main flow path before branching. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a flowchart showing an operation sequence. 1...Tank, 2...Pump, 3...Governor, 4
...Heating furnace, 5,6...Arithmetic control unit, R□...
Rotation speed detector, F□~F5...Flow rate detector, 01~C
6...Adjusting needle, M1~M5...Temperature indicator, T1~
T5...Temperature detector.

Claims (1)

[Claims] In a method of dividing fluid into multiple flow paths and heating them in a heating furnace, the temperature at the outlet of the heating furnace is detected for each flow path, the flow path with the maximum thermal efficiency is selected, and the flow rate flowing through that flow path is increased. A heating furnace control system characterized by adjusting a control valve and controlling the flow rate of a main channel before branching by the rotational speed of a pump.