JPS6014978B2 - Combustion control device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a control device for a combustion device such as a boiler.

FIG. 1 shows the relationship between the boiler combustion efficiency, that is, the thermal efficiency, the load, and the oxygen content in the exhaust gas.

As is clear from Figure 1, in order to control efficiency, it is sufficient to control the oxygen content in the exhaust gas.
Conventionally, the air-fuel ratio is controlled at a constant level throughout the entire combustion region, so there is a problem that the air amount cannot be automatically corrected in response to changes in fuel gas composition or changes in carbon monoxide (CO) amount. However, there is a problem in that it is impossible to accurately set the air-fuel ratio over a wide load range due to the thermal efficiency, drift, etc., and therefore the thermal efficiency cannot be controlled to a desired value. The present invention was made to solve these conventional problems, and an object of the present invention is to provide a combustion control device that can control thermal efficiency to a desired value (for example, maximum efficiency).

In order to achieve this object, the present invention includes a calculation circuit that receives a combustion load setting signal and calculates and outputs the oxygen content in exhaust gas that provides a predetermined thermal efficiency (for example, maximum efficiency);
A detector detects the actual oxygen content in the exhaust gas, and the amount of air supplied to the combustion device is controlled based on the output signal of this detector and the output of the arithmetic circuit, thereby controlling the amount of oxygen in the exhaust gas. and an oxygen amount control circuit for controlling the amount of oxygen.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Fig. 2 shows an embodiment of the boiler combustion control system according to the present invention, and this embodiment is roughly divided into a fuel flow rate control system, an air flow rate control system, and an oxygen content control system in exhaust gas. It is controlled so that it is maximized.

The fuel flow rate detector 2 is disposed in the fuel supply pipe 3 and detects the flow rate of fuel supplied to the boiler.

The fuel flow rate indicator controller 4 receives the boiler mass evening signal (boiler load setting signal) and the output signal of the fuel flow rate detector 2, and
It displays the fuel flow rate and controls the opening degree of the control valve 6 connected to the fuel supply pipe 3 to control the fuel supply amount to a set value. The oxygen content detector 8 is connected to the flue 9
It is installed in the exhaust gas and detects the oxygen content in the exhaust gas.

The oxygen content setting calculation circuit 10 receives the boiler mass signal and calculates and outputs the oxygen content in the exhaust gas that maximizes the thermal efficiency. Generally speaking, the efficiency of a combustor such as a boiler is determined by the oxygen content in the exhaust gas at the maximum efficiency point at a given load, as shown in Figure 1. The efficiency point is determined at a single point in the coordinates of the exhaust gas oxygen content and load, and although this relationship will vary from boiler to boiler, there is a unique relationship for each boiler. By determining the relationship between the oxygen content and the oxygen content, it is possible to determine the oxygen content of the exhaust gas that should achieve the highest efficiency depending on the boiler load. In response to the output of the content setting calculation circuit 10, the actual oxygen content is displayed, and an oxygen content control signal Y for maximizing thermal efficiency is output.

The converter 14 receives the boiler master signal, converts it into air equivalent, and outputs an air flow rate setting signal x. The multiplication/division calculator 16 corrects the air flow rate setting signal X in accordance with the oxygen content control signal Y so that the thermal efficiency is maximized, and outputs a corrected air flow rate setting signal. Air flow rate indicator controller 1
Reference numeral 8 indicates the opening of the flow rate regulating valve 22 provided in the air supply pipe 19 so that the thermal efficiency is maximized in response to the output signal of the air flow rate detector 20 provided in the air supply pipe 19 and the above-mentioned corrected air flow rate setting signal. This is to adjust the degree.

In the embodiment of FIG. 2 configured in this manner, the fuel flow rate indicating controller 4 controls the amount of fuel indicated by the boiler master signal to be supplied to the boiler.

On the other hand, the oxygen content setting arithmetic circuit 10 receives the boiler master signal and calculates the oxygen content in the exhaust gas that maximizes the thermal efficiency.
0 output and the output of the oxygen content detector 8, the computing unit 16 corrects the air flow rate setting signal x based on the oxygen content control signal Y, and outputs the oxygen content control signal Y. A flow rate setting signal is output, and the air flow rate indicating controller 18 receives this signal and adjusts the opening degree of the air flow rate regulating valve so that the thermal efficiency is maximized. Therefore, thermal efficiency is maximized. It goes without saying that by adding some ordinary control circuits to the above embodiment, it is possible to prevent the generation of black smoke when fuel increases suddenly, to improve thermal efficiency, and to prevent pollution.

In addition, in the above embodiment, the oxygen content in the exhaust gas is calculated by the calculation setting device to achieve the highest efficiency for a given load in the combustion control system. It is also possible to determine the load value for the content rate so as to obtain the highest efficiency.

Further, the present invention is not limited to maximizing thermal efficiency, but can control thermal efficiency to various values.

As is clear from the above description, the present invention calculates the relationship between the load of the combustion device, the oxygen content in the exhaust gas, and the thermal efficiency in advance, and determines the desired thermal efficiency (for example, the maximum thermal efficiency) according to the load setting signal. The oxygen content in the exhaust gas is determined by calculation, and the amount of air supplied to combustion equipment such as boilers is controlled based on the calculation results, so the thermal efficiency can be set to a desired value (for example, maximum efficiency). can do.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing an example of the relationship between the thermal efficiency of the boiler, the load, and the oxygen content in exhaust gas, and FIG. 2 is a control block diagram showing one embodiment of the combustion control device according to the present invention. 2...Fuel flow rate detector, 4...Fuel flow rate indicator controller, 6...Fuel flow rate control valve, 8...
...Oxygen content detector, 10...Arithmetic circuit for oxygen content setting, 12...Oxygen content indicating controller, 18...Air flow rate indicating controller, 20...
...Air flow rate detector, 22...Air flow rate adjustment valve. Groove 1 drawing 2 drawings

Claims (1)

[Claims] 1. A fuel flow rate indicating controller that controls the opening degree of a control valve disposed in a fuel supply pipe based on a boiler master signal and a fuel flow rate detection value from a fuel flow rate detector that detects the flow rate of fuel supplied to the boiler; an oxygen content setting arithmetic circuit that receives the boiler master signal and calculates the oxygen content in the exhaust gas that provides a combustion efficiency corresponding to the set load; and an output of the oxygen content setting arithmetic circuit and a flue. an oxygen content indicating controller that outputs an oxygen content control signal based on the installed oxygen content and the oxygen content in the exhaust gas from the detector;
a converter that receives the boiler master signal and outputs an air flow rate setting signal corresponding thereto; a multiplier/divider that outputs a corrected air flow rate setting signal from the air flow rate setting signal and the oxygen content control signal; An air flow rate indicating controller that adjusts the opening degree of the flow rate regulating valve of the air supply pipe based on a setting signal and an air flow rate detection value from an air flow rate detector disposed in the air supply pipe. Combustion control device.