JPH07280256A - In-furnace pressure controlling method for burning furnace - Google Patents

Abstract

PURPOSE:To control an internal pressure of a furnace with excellent response by calculating a combustion exhaust gas amount from openings of a fuel flow control valve and an air flow control valve, and controlling an in-furnace pressure by a feed forward compensation based on the gas amount. CONSTITUTION:The method for controlling an internal pressure in a burning furnace comprises the steps of detecting a flow rate of fuel (air) to be supplied to the furnace 7 by a fuel (air) flowmeter 1 (4), comparing it with a flow rate previously set by a fuel (air) flow controller 2 (5), designating an opening of a fuel (air) flow control valve 3 (6) to a suitable value, and inputting designated values to an exhaust gas flow calculator 10. The calculator 10 calculates to predict a combustion exhaust gas amount, and applies an operation signal of an in-furnace pressure controller 11 by a feed forward compensation based on its calculated value. The controller 11 so controls a damper opening of an induced draft fan 9 and number of revolutions of a fan according to the signal and a signal of an in-furnace pressure gage 9 as to become suitable in-furnace pressure. Thus, the internal pressure in the furnace can be controlled with excellent response.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the internal pressure of a combustion furnace such as a boiler.

[0002]

2. Description of the Related Art Conventionally, in controlling the furnace pressure in a combustion furnace such as a boiler, the air flow rate control signal, which is a disturbance of fluctuations in the furnace pressure, is first used as a feedforward signal to directly control the exhaust gas induction fan, and then the state If there is a deviation between the set value and the actual value of the furnace pressure at, the furnace pressure control including the PID operation should be performed to make the deviation zero.
Feedback control worked, and the method of maintaining the furnace pressure at the set value was used.

However, in the above method, when the type of fuel changes and the internal pressure of the furnace changes greatly, there is a risk that control will not be possible. , For example, low-calorie gas BFG
In a pulverized coal burning boiler that burns by mixing (blast furnace by-product gas), the rate of change in combustion exhaust gas is large when BFG increases or decreases compared to when coal increases or decreases. Therefore, the pressure inside the furnace had to be controlled. Conventionally, as a furnace internal pressure control device for a boiler, Japanese Patent Laid-Open No. 63-65229 discloses predictive calculation of combustion exhaust gas amount from measured values of fuel supply amount and air supply amount, and controls internal furnace pressure by feedforward compensation. The technology is disclosed.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-63-65
The device disclosed in Japanese Patent No. 229 measures the supply amount of fuel and air from the signal of the flow meter, and therefore, when the flow amount of these supply amounts is controlled to change the supply amount, the response is delayed. This may make control difficult. Normally, when performing flow rate control, a flow rate control valve is provided after the flow meter, and the flow rate control valve is adjusted by comparing the measured value of the flow meter with the set flow rate value. Sex may deteriorate. It is an object of the present invention to provide a method for controlling the internal pressure of a combustion furnace such as a boiler with good responsiveness even when the supply amounts of fuel and air change and the fluctuation ratio of the combustion exhaust gas amount is large.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention calculates the amount of combustion exhaust gas from the opening of a flow control valve for fuel supplied to a combustion furnace and the opening of a flow control valve for air. A method for controlling the internal pressure of a combustion furnace, comprising controlling the internal pressure of the combustion furnace by feedforward compensation based on the combustion exhaust gas amount. Then, in the method of the present invention, it is preferable to control the flow rate control valve of the fuel and air supplied to the combustion furnace by PID control.

[0006]

The method of the present invention will be described with reference to the example of FIG. Fuel and air are introduced into the combustion furnace 7 and burned, the combustion exhaust gas is discharged through the induced draft fan 9, and the furnace pressure is measured by the furnace pressure gauge 8
And controls the damper opening of the induction fan 9 and the fan rotation speed according to an instruction from the furnace pressure control device 11 to control the furnace pressure.

The flow rate of the fuel supplied to the combustion furnace 7 is detected by the fuel flow meter 1 and compared with a preset flow rate by the fuel flow rate control device 2 to set the opening of the fuel flow rate control valve 3 to an appropriate value. And the input value is input to the exhaust gas amount calculation device 10. When supplying multiple fuels,
Such a circuit is provided for each fuel. Further, the flow rate of air is detected by the air flow meter 4, and the air flow rate controller 5
Compared with the preset flow rate, air flow control valve 6
The degree of opening is designated as an appropriate value, and the designated value is input to the exhaust gas amount computing device 10.

The exhaust gas amount calculation device 10 predictively calculates the amount of combustion exhaust gas, and feeds it as a control signal for the reactor internal pressure control device 11 by feedforward compensation based on the calculated value.
In the furnace pressure control device 11, the induction fan 9 is operated so as to obtain an appropriate furnace pressure by the operation signal and the signal from the furnace pressure gauge.
Controls the damper opening and fan speed.

Further, according to the present invention, as shown in FIG. 2, the instruction value of the fuel flow rate control device 2 is input to the exhaust gas amount calculation device 10 while controlling the fuel flow rate control valve 3 via the PID control device 12. Is preferred. In addition, 13 is a current-pressure converter. Further, in FIG. 2, it is preferable to similarly perform PID control on the air supply system. By such a method of the present invention, even if the fuel supply amount, the fuel type or the mixing ratio changes, and the fluctuation ratio of the combustion exhaust gas amount is large, the reactor internal pressure can be controlled with good responsiveness by the feedforward control. it can.

[0010]

EXAMPLE A combustion furnace 7 having a structure as shown in FIG.
The fuel is a mixture of pulverized coal and BFG, the supply amount of each is changed, and the combustion exhaust gas amount is 1000 Nm ³ / min / s.
The method of the present invention was carried out for the case where the rate of ec fluctuates rapidly. As a result, the time until the fluctuation of the furnace pressure settles is suppressed within 2 seconds when the method of the present invention is performed,
It was within 56 seconds in the conventional method.

[0011]

According to the method of the present invention, the fluctuation range of the internal pressure in the combustion furnace such as the boiler is reduced even when the fuel supply amount, the kind or mixing ratio of the fuel is changed, and the fluctuation ratio of the combustion exhaust gas amount is large. Can be suppressed. as a result,
Energy loss can be avoided as shown below.

First, the boiler of a steel mill plays a role of adjusting the energy balance of the entire steel mill.
Gas balance is one of them. Therefore, BFG
When a surplus occurs, it will be burned into the boiler, but if the speed at which the BFG combustion amount in the boiler can be increased is high, the amount of BFG that can be digested will be correspondingly large, combustion emission can be avoided, and energy loss will be eliminated.

When the boiler is required to reduce the steam load beyond its ability to follow, the load that cannot be followed up is dealt with by releasing the steam into the atmosphere or releasing it to the turbine condenser. Both of which lead to energy loss, but by the method of the present invention, the controllability of the pressure in the furnace is increased, so that the deceleration speed of the fuel supply amount can be increased,
The energy loss can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of the present invention.

FIG. 2 is a circuit diagram showing a preferred embodiment of the method of the present invention.

[Explanation of symbols]

 1: Fuel flow meter 2: Fuel flow rate control device 3: Fuel flow rate control valve 4: Air flow rate meter 5: Air flow rate control device 6: Air flow rate control valve 7: Combustion furnace 8: Furnace pressure gauge 9: Induction draft fan 10 : Exhaust gas amount calculation device 11: Furnace pressure control device 12: PID control device 13: Current-pressure converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshikatsu Narita 12 Nakamachi, Muroran City Nippon Steel Corporation Muroran Works

Claims (2)

[Claims] 1. A combustion exhaust gas amount is calculated from the opening degree of a flow rate control valve of fuel supplied to a combustion furnace and the opening degree of a flow rate control valve of air, and based on the combustion exhaust gas amount, the internal pressure of the furnace is compensated by feedforward compensation. A method for controlling the internal pressure of a combustion furnace, the method comprising: 2. The method for controlling the internal pressure of a combustion furnace according to claim 1, wherein the flow rate control valve for the fuel and air supplied to the combustion furnace is controlled by PID control.