JPH02101316A - Combustion control method for burning furnace - Google Patents

Abstract

PURPOSE:To automatically control the fuel feed rate so as to obtain a constant air-fuel ratio by a method wherein fuel is sent to a fuel control equalizer valve through a fuel differential pressure control equalizer valve, and the fuel differential pressure control equalizer valve is controlled according to the outlet pressure of the fuel control equalizer valve. CONSTITUTION:Air is supplied to a burner 1 through an air temperature control valve V1, and a fuel control equalizer valve V2 is brought into action by a fuel control pressure Px which is taken between the burner 1 and the air temperature control valve V1 to control the fuel feed rate to the burner 1. Fuel is supplied through a fuel differential pressure control equalizer valve V4 to the fuel control equalizer valve V2. The fuel differential pressure control equalizer valve V4 is controlled according to the outlet pressure P4 of the fuel control equalizer valve V2. By this constitution, a desired air-fuel ratio can be kept constant by automatic control over the entire operation range from the high temperature region to the low temperature region, so that ease of operation and combustion efficiency are improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a combustion control method for a firing furnace, etc.

(Prior Art) Generally, in a firing furnace or the like, it is necessary to supply air and fuel to a burner at a required constant air-fuel ratio. Therefore, as shown in FIG. 2, as a conventional combustion control method for firing furnaces, etc., an air temperature control valve v1 is provided in the air supply pipe 2 to the burner I, and an adjustable fuel supply pipe is provided in the fuel supply pipe 3. A control pressure equalization valve v2 and a manual valve v3 are provided, and the fuel control pressure is supplied from the air supply pipe section 2a between the air temperature control valve V and the burner 1 to the fuel control pressure equalization valve v2 through a pilot pressure pipe 4. For example, when increasing the temperature of the firing furnace using a combustion control system configured to supply Px, open the air temperature control valve V in response to a temperature increase command and send air to the burner 1. Air 2 in air supply pipe section 2a
The next pressure rises, and the fuel control pressure Px is introduced from the pipe section 2a through the pilot pressure pipe 4 to the fuel control pressure equalizing valve v2, thereby adjusting the amount of fuel supplied according to the change in the amount of air supplied to the burner. It's changing.

As shown in FIG. 3, the fuel control pressure equalizing valve V has an upper and lower wing case 11 and a diaphragm case 12 airtightly connected with a diaphragm 10 in between, and a valve body 13 is fixed to the diaphragm case 12 to control the fuel supply. A passage 16 between the inlet 14 and the outlet 15 of the valve body 13 connected to the line 3
A valve seat 17 is provided on the valve body 1 , which cooperates with the valve seat 17 .
8 is attached to the diaphragm 10 and held in the closed position by an adjustable spring 19, and the fuel control pressure PX is introduced into the spring case 11 via the pilot pressure line 4.
This causes the valve body 18 to be in the open position, and the amount of fuel supplied to the burner 1 is increased or decreased in accordance with the increase or decrease in the secondary air pressure P2. Therefore, the pressure equalization valve for fuel control v
2 is sent to the burner 1 at a secondary fuel pressure P, and the amount of fuel supplied to the burner 1 increases in accordance with the increase/decrease in the secondary air pressure, raising the temperature.

(Problem to be Solved by the Invention) However, in the method of controlling fuel using the pressure equalizing valve described above, if the differential pressure between the fuel source pressure P3 and the fuel secondary pressure P on the inlet side of the pressure equalizing valve differs, As shown in Figure 5, the flow rate differs even with the same valve opening, and as shown by the broken line curve A in Figure 7, the amount of fuel cannot be reduced in the low opening range of the air temperature control valve V, and the amount of fuel cannot be reduced in the low temperature range. It is difficult to control the air-fuel ratio in the low temperature range, and the air-fuel ratio cannot be kept constant at a predetermined value, and it rises above the predetermined value.As a result, not only is smoke and soot generated intensely, but the furnace temperature also decreases. There is also the problem of the fire going out. As described above, in the conventional method, it was impossible to automatically control the fuel supply amount in proportion to the air supply amount in a low temperature range, so conventionally a manual valve V was used.

The source pressure P3 of the fuel is adjusted by operating the furnace, which makes it difficult to operate the furnace, and there is a problem that combustion control cannot be performed fully automatically and efficiently over the entire temperature range.

An object of the present invention is to provide a method for automatically controlling the flow rate of fuel so that a constant air-fuel ratio can be obtained even in a low temperature range by solving the above-mentioned problems.

(Means for Solving the Problems) According to the present invention, air is supplied to a burner such as a kiln through an air temperature control valve V, and the fuel is controlled by being taken out between the burner and the temperature control valve V. In a combustion control method for a firing furnace, etc., in which the fuel control pressure equalization valve v2 is operated by the pressure PX to control the amount of fuel supplied to the burner, the fuel control pressure equalization valve v2 is operated via the fuel differential pressure control pressure equalization valve v4. It is characterized in that fuel is sent and the pressure equalizing valve V for fuel differential pressure control is controlled by the pressure on the outlet side of the fuel controlling pressure equalizing valve v2.

(Function) According to the present invention, the population side pressure P of the fuel control pressure equalizing valve v2
The differential pressure between the temperature control valve V and the outlet pressure P4 becomes constant with respect to the full opening of the temperature control valve V, as shown by the solid line B in FIG. Unlike the conventional method shown by the broken line curve A in FIG. The automatically controllable combustion range according to the present invention is substantially directly proportional to that of the conventional automatically controllable combustion range a. Through automatic control, it is possible to perform combustion at a predetermined required air-fuel ratio.

(Example) An embodiment of the method of the invention will be explained with reference to FIG.

In a firing furnace with a capacity of 100 i, the combustion control device shown in Figure 1 is used to raise the temperature inside the furnace from 100°C to 250°C in the low temperature range of 100°C to 500'C. The opening degree of the temperature control valve ■1 was controlled to 15%, and the primary air pressure P1 of the combustion air was set to the secondary air pressure P2.
As a result, air was supplied to each burner at a flow rate of 220 Im'/hr, kerosene was supplied at a flow rate of 201 Im'/hr, the required air-fuel ratio was maintained constant, and the temperature inside the furnace was raised to 250'C.

FIG. 4 shows the detailed structure of the pressure equalizing valve v4 for fuel differential pressure control used in the method of the present invention. In the illustrated valve ν4, upper and lower valve bodies 21 and a spring case 22 are airtightly connected with a diaphragm 20 in between. The bridge 2 is mounted on a yoke 25 that is supported against fluid pressure within the diaphragm 21 and is attached to the diaphragm 20.
6 is attached to the fuel supply pipe 3, and a fuel control equalizing valve v
A valve body 31 is attached to a valve seat 30 provided in a passage 29 between an inlet 27 and an outlet 28 of the valve body 21 connected on the upstream side of the valve body 21.
is seated by the bridge 26, and the outlet side pressure P4 of the fuel control pressure equalizing valve v2, that is, the fuel secondary pressure, is introduced into the spring case 22 through the inlet 32, and the opening degree of the valve is increased or decreased by the differential pressure. The fuel is passed from the port 27 to the outlet 28 through the fuel supply pipe 3 to the fuel control pressure equalizing valve V,
It is configured to be sent to

(Effects of the Invention) According to the present invention, it is possible to keep the required air-fuel ratio constant and automatically control combustion over the entire range from a low temperature range to a high temperature range, thereby facilitating operation in a kiln. , combustion efficiency can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a combustion control system implementing the combustion control method according to the present invention, Fig. 2 is a schematic diagram of a conventional combustion control system, Fig. 3 is a vertical cross-sectional view of a pressure equalization valve for fuel control, and Fig. 4 is a vertical cross-sectional view of the pressure equalization valve for fuel differential pressure control, and FIG. 5 is the fuel source pressure P at various opening degrees of the air temperature control valve v1 according to the conventional control method.
6 is a graph showing the relationship between the differential pressure between 3 and secondary fuel pressure P4 and the outlet flow rate of the pressure equalizing valve for fuel control.
A graph showing the relationship between the opening degree and the differential pressure (P4-P3), Figure 7 shows conventional method A and method B of the present invention. It is a graph which shows the relationship between the opening degree of the temperature control valve v1 of : and the amount of fuel supplied to the burner. 1...Burner 2...Air supply pipe 3...
・Fuel supply pipe 4...Pilot pressure pipe V,...
・Air temperature control valve v2...Fuel control pressure equalization valve v3...Pressure equalization valve for fuel differential pressure control Fig. 2L~ Fig. 5 - Differential pressure (P4-Pa) Fig. 6 ■ Opening degree! 00%

Claims (1)

[Claims] 1. Air is supplied to a burner such as a firing furnace through a temperature control valve V_1, and the fuel control pressure equalization valve V_2 is operated by the fuel control pressure P_x taken out from between the burner and the temperature control valve V_1, and the air is supplied to the burner. In a combustion control method for a firing furnace, etc., in which the amount of fuel is controlled, fuel is sent to a fuel control pressure equalization valve V_2 via a fuel differential pressure control equalization valve V_4, and this fuel pressure difference control pressure equalization valve V_4 is used for fuel control. A combustion control method for a firing furnace, etc., characterized in that the control is performed by the outlet side pressure of a pressure equalizing valve V_2.