JPS5835321A - Oxygen controlling system for multi-fuel combustion - Google Patents

Abstract

PURPOSE:To effectively control the rate of residual oxygen to get an ideal rate, by finding the rate of residual oxygen to the mixing ratio of both fuel from a compensating coefficient to the mixing ratio of both fuel and a suitability value in the aspect of residual oxygen of both fuel, in an industrial combustion furnace in which two kinds of fuel are used. CONSTITUTION:When heavy oil and gas are mixed and burnt together, the flow rates of both oil and gas are detected by detectors 3 and 4, respectively, and a calorific value is compensated by compensators 6 and 7. Then, the mixing ratio of heavy oil to gas is found by a calculator 8, and a compensating coefficient to the mixing ratio is calculated by a function calculator 9. Both outputs from compensators 6 and 7 are added up by an adder 11, and a suitability value in the aspect of residual oxygen to the added value is calculated by a function calculator 10. Next, the rate of residual oxygen to the mixing ratio of both fuel is calculated by a multiplier 12 by multiplying the outputs from both function calculators 9 and 10, and the result is used as a setting value to a controller 14 to calculate the rate of oxygen. An air-fuel controller 16 is controlled by an output from the controller 14, by the intermediary of an arithmetic circuit 15 to compensate an air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen control device for co-combustion control in an industrial combustion furnace.

Oxygen control in the exclusive combustion control of industrial combustion furnaces has been established to some extent as an energy-saving measure, but for example, in the case of mixed combustion of gas and heavy oil, the ideal amount of residual oxygen is determined by each fuel, as shown in Figure 1. Since they are different, currently the curve for heavy oil, which has a higher amount of residual oxygen, is used as the set value for the oxygen control calculator. For this reason, the current situation is that the apparent combustion air tends to be excessive, resulting in energy loss.

In order to prevent this, a method of operating the engine by restricting the fuel to a constant mixture ratio may be considered, but the reality is that there is no degree of freedom and the operation is inconvenient.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide fuel A.

It is an object of the present invention to provide a control device in which the mixing ratio of B can be freely selected, and the ideal residual oxygen amount control can respond to changes in load with respect to the mixing ratio.

Taking the co-firing of heavy oil and gas as an example, since the ideal amount of residual oxygen for the load is different for heavy oil and gas, it is sufficient to depict this characteristic based on the mixing ratio. However, since it is a three-dimensional relationship between mixing ratio, load, and oxygen amount, this calf 1 has an infinite number of combinations, making it unsuitable as a control device.
If one of the characteristics is used as a basis and the relationship between the mixing ratio and the reduction rate is calculated or experimentally determined in advance according to the load for that curve, then it can be simply multiplied.
It becomes possible to determine the ideal amount of residual oxygen for a certain mixing ratio. This relationship holds true regardless of the combination or type of fuel.

FIG. 2 shows an example of a control circuit for co-firing according to the present invention. This example uses mixed combustion of heavy oil and gas. The heavy oil and gas used as fuel are detected by respective detectors 3 and 4, and the differences in their respective calories are corrected by coefficient units 6 and 7, and the values Fo and Fa converted to the same unit are calculated by calculators 8, It is calculated by the adder 11. In order to obtain the mixture ratio, the computing unit 8 uses the following formula as an example.

In this formula, there is no problem even if Fa is used in the molecule,
When burning mainly heavy oil, it is easier to use FO% in the molecule. When burning mainly gas, it is easier to use Fc in the molecule.

This is because the closer the value of α is to 1, the more the ideal residual oxygen amount curve can be used as the curve for each dedicated combustion. In equation (1), α=1 in case of heavy oil-only combustion, and α==0 in case of gas-only combustion.

On the other hand, the function calculator 10 stores an ideal residual oxygen amount curve for the load during heavy oil exclusive combustion, and calculates the oxygen amount for the load input from this curve.

In the example shown in this figure, μ is determined as a constant value with respect to α, but as can be seen from Figure 3, the curve against load is not always constant for heavy oil and gas. In order to accurately correct this, the multiplier 12 must be given a correction coefficient γ for the load shown in FIG.
need to be entered further. The results of these calculations are cascaded to an oxygen calculation controller 14, and the output thereof is input to a calculation circuit 15 that corrects and calculates the air-fuel ratio so as to achieve the oxygen concentration.

With the above configuration, the oxygen control for co-firing in the furnace is automatically maintained in an optimal state regardless of the fuel type/mixing ratio, contributing to energy saving.

Note that the function calculator 10 in FIG. 2 takes as an example a function calculator for the amount of oxygen with respect to the fuel flow rate; however, in the case of a boiler, the load steam amount is used, and in the case of a steel heating furnace, In the case of a soaking furnace, the output signal of the temperature controller is used on the horizontal axis.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing the oxygen control device for co-combustion according to the present invention, Fig. 2 is a diagram showing the relationship between load and ideal residual oxygen amount, and Fig. 3 is a diagram showing the ideal residual oxygen amount for each fuel type. It is a functional calculator that shows the ratio of quantities. 1...Oxygen detector, 2...Temperature detector, 3.4...
・Detection τ unit, 5...Square root operator, 6.7...Coefficient unit, 舆...Arithmetic unit, 9, 1o...Function operator, 11
. . . Adder, 12 . . . Multiplier, 13 . ...
Fuel oil regulator, 18... Fuel Figure 1 □ Kan 417 (Fuel) Figure 2 Figure 3

Claims (1)

[Claims] 1. After measuring the flow rate of each fuel A and fuel B and correcting the calories for each fuel, calculate the mixture ratio of fuel A and fuel B, and calculate the correction coefficient for the mixture ratio using a functional calculator. , this correction coefficient, and on the other hand fuel A and fuel B
Calculate the appropriate value of the residual oxygen amount for the total sum after calorie correction using another functional calculator, and multiply this value by the correction coefficient mentioned above to determine the residual oxygen amount for the mixture ratio of fuel A and fuel B. An oxygen control device for co-firing, characterized in that the amount of oxygen is calculated and the calculated value is used as a set value of an oxygen control controller.