JP2577409Y2 - Furnace heating controller - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus for a combustion furnace, and more particularly to a furnace temperature control apparatus having a furnace temperature control.

[0002]

2. Description of the Related Art In a conventional furnace temperature control system, when a temperature rise control is started to raise the temperature of a furnace at the time of furnace startup, a set value of the furnace temperature control is adjusted to a temperature rise rate corresponding to a temperature rise schedule. Program control is performed so that it rises with.

The furnace temperature control output is cascaded to a fuel flow rate control loop and an air flow rate control loop to control the furnace temperature by controlling the burner combustion amount.

At this time, air-fuel ratio control is performed so as not to cause abnormal combustion, and stable control accuracy is compensated by double cross limit control.

The setting of the air ratio is corrected by low load correction based on the fuel flow rate and exhaust gas O ₂ control.

[0006]

[Problems to be Solved by the Invention] Recent combustion furnaces are excellent in heat retention, and the furnace temperature often rises excessively even in the MIN combustion just before the turndown of the main burner. There is a defect that it is difficult to control the furnace temperature according to the heating rate and the control accuracy is poor.

An object of the present invention is to provide an in-furnace heating control apparatus in which the control accuracy of furnace temperature control during heating is improved in order to solve the disadvantages of the prior art.

[0008]

According to the present invention, there is provided a heating program circuit for program-controlling a set value at the time of startup of a furnace at a heating rate corresponding to a predetermined heating schedule at the time of startup and heating of the combustion furnace. A steady-state set value circuit controlled by a furnace temperature steady-state set value corresponding to a predetermined operation base after the completion of the temperature rise of the combustion furnace; and either the output of the steady-state set value circuit or the output of the temperature rise program circuit. A first switching circuit for selecting one of them, and a fuel flow control circuit and an air flow control circuit which are connected to the output circuit of either the steady-state set value circuit or the temperature raising program circuit via the first switching circuit. A furnace temperature control circuit that outputs a furnace temperature setting signal to the furnace and a furnace temperature setting signal output from the furnace temperature control circuit are input, and the amount of air to be blown into the combustion furnace during startup and temperature rise is set in advance. Cascade air volume A constant circuit, a change rate limiting circuit that limits the rate of change of the air amount setting signal output from the cascade air quantity setting circuit, a start-up heating of the combustion furnace completed,
A heating completion processing circuit for detecting that the operation has entered a steady state;
One of the output of the heating completion processing circuit and the output of the rate-of-change limiting circuit is selected, and a second switching circuit connected in conjunction with the first switching circuit is connected to the second switching circuit. An air ratio correction circuit that is connected to one of the output circuits of the temperature increase completion processing circuit or the rate-of-change limiting circuit and that outputs a fuel-air ratio correction value; and an air ratio correction output value of the air ratio correction circuit and A furnace internal temperature control system comprising: a furnace internal temperature control circuit; and a double limit control circuit for limiting any of the internal furnace temperature set output values for safety.

[0009]

In the in-furnace temperature raising control device of the present invention, the furnace temperature startup set value is program-controlled at a heating rate corresponding to a predetermined heating schedule when the combustion furnace is started up and heated. After the completion of the temperature rise, control is performed with the furnace temperature steady state set value corresponding to the predetermined operation base, and either the output of the steady state set value circuit or the output of the temperature rise program circuit is selected, and the first switching is performed. Connected to the output circuit of either the steady-state set value circuit or the temperature rise program circuit through the circuit, outputs the furnace temperature setting signal to the fuel flow rate control circuit and the air flow rate control circuit, and outputs from the furnace temperature control circuit The furnace temperature setting signal is input, the amount of air to be blown into the combustion furnace at the time of startup and temperature rise is preset, the rate of change of the air amount setting signal output from the cascade air amount setting circuit is limited, and the combustion furnace Completes startup and heating Detecting that the motor has started to rotate, selects one of the output of the temperature increase completion processing circuit and the output of the rate-of-change limiting circuit, and connects the second switching circuit in conjunction with the first switching circuit; Connected to one of the output circuits of the temperature raising completion processing circuit or the rate-of-change limiting circuit via the second switching circuit;
A fuel / air ratio correction value is output, and a safety limit is applied to both the air ratio correction output value of the air ratio correction circuit and the furnace temperature set output value of the furnace temperature control circuit.

[0010]

Next, an embodiment of the present invention will be described. In FIG. 1, reference numeral 1 denotes a temperature raising program circuit for program-controlling a set value at the time of furnace temperature rise at a temperature rising rate corresponding to a predetermined temperature rising schedule at the time of temperature rise of the combustion furnace. A steady-state set value circuit, which is controlled later by a furnace temperature steady-state set value corresponding to a predetermined operation base, and 1b selects one of the output of the steady-state set value circuit 1a and the output of the temperature raising program circuit 1. The switching circuit 2 is connected to the output circuit of either the steady-state set value circuit 1a or the temperature raising program circuit 1 via the switching circuit 1b, and is connected to the fuel flow control circuit 7 and the air flow control circuit 8 to set the furnace temperature. A furnace temperature control circuit 12 for outputting a signal, a furnace temperature setting signal output from the furnace temperature control circuit 2, and a cascade air amount for presetting an air amount to be blown into the combustion furnace when the temperature rises and rises. Setting circuit 13 is a rate-of-change limiting circuit for limiting the rate of change of the air quantity setting signal output from the cascade air quantity setting circuit 12, and 14 is a rate-of-change detecting that the startup of the combustion furnace has been completed and the steady-state operation has been started. The temperature completion processing circuit 1c selects one of the output of the temperature increase completion processing circuit 14 and the output of the rate-of-change limiting circuit 13 and is connected in conjunction with the switching circuit 1b, and 11 is the switching circuit 1c. An air ratio correction circuit which is connected to an output circuit of either the temperature increase completion processing circuit 14 or the change rate limiting circuit 13 and outputs a fuel / air ratio correction value. This is a double limit control circuit that limits safety for both the corrected output value and the in-furnace temperature setting output value of the in-furnace temperature control circuit 2. On the heating schedule In the furnace temperature raising control in which the setting value of the furnace temperature control loop is program-controlled at a predetermined heating rate, the furnace temperature control loop and the air ratio setting loop are cascade-connected during furnace temperature raising, and the AIR blows into the furnace. Means for controlling the rate of the amount to suppress the furnace temperature from increasing excessively with respect to the heating rate, and means for disconnecting the cascade connection when the heating is completed to return to an operation-based proper air ratio. It is a temperature control device.

In this embodiment, a cascade control of a furnace temperature control output and an air ratio setting loop is added.

When the heating is started, the furnace temperature control executes a program control according to a heating schedule and simultaneously outputs a setting output to an air ratio setting loop.

Then, a means for disconnecting the cascade connection when the temperature rise is completed and once returning to the operation-based air ratio value is added. Thereafter, air ratio intervention by the operator is possible. At the start of heating, the air ratio setting can be operated by the furnace temperature control output, so if the furnace temperature control accuracy deteriorates due to the furnace temperature overspeed during the furnace temperature program control, the air By changing the ratio, AI
An excessive amount of R can be added to provide a cooling effect.

[0014]

According to the present invention, the furnace temperature control loop and the air ratio setting loop are cascade-connected to each other during the temperature rise and are blown into the furnace.
A means for controlling the rate of IR amount to suppress an over-speed rise of the furnace temperature with respect to the heating rate, and a means for disconnecting the cascade connection at the time of completion of the heating and returning to an operation-based proper air ratio. The control accuracy of the internal temperature rise control can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an in-furnace heating control apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heating program circuit 1 b, 1 c switching circuit 2 furnace temperature control circuit 3 double cross limit control circuit 11 air ratio correction circuit 12 cascade air amount setting circuit 13 change rate restriction processing circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A heating program circuit for program-controlling a setting value of a furnace temperature rising at a heating rate corresponding to a predetermined heating schedule when the temperature of the combustion furnace is raised, and completion of the heating of the combustion furnace A steady-state set value circuit controlled by a furnace temperature steady-state set value corresponding to a predetermined operation base later, and a second step of selecting one of the output of the steady-state set value circuit and the output of the temperature raising program circuit 1 switching circuit and the first
Furnace temperature control for outputting a furnace temperature setting signal to the fuel flow rate control circuit and the air flow rate control circuit by being connected to the output circuit of either the steady-state set value circuit or the temperature raising program circuit through the switching circuit of A cascade air amount setting circuit for inputting the in-furnace temperature setting signal output from the in-furnace temperature control circuit and presetting the amount of air to be blown into the combustion furnace at the time of the start-up and heating; A rate-of-change limiting circuit that limits the rate of change of the air amount setting signal output from the air amount setting circuit, and a temperature-raising completion processing circuit that detects that the combustion furnace has been started up and temperature-raised and has entered steady operation. A second switching circuit for selecting one of the output of the temperature increase completion processing circuit and the output of the rate-of-change limiting circuit, and connecting the second switching circuit in conjunction with the first switching circuit; Via the switching circuit An air ratio correction circuit that is connected to one of the output circuits of the temperature increase completion processing circuit or the rate-of-change limiting circuit and that outputs a fuel-air ratio correction value; and an air ratio correction output value of the air ratio correction circuit and An in-furnace temperature raising control device comprising: a double limit control circuit for imposing safety restrictions on any of the in-furnace temperature set output values of the in-furnace temperature control circuit.