JPH0575928B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a method for controlling the amount of fuel supplied to the burner and the amount of acidity-containing gas for combustion when raising the temperature inside the furnace to a first set temperature by a burner. The present invention relates to a method for controlling temperature inside a furnace.

[Prior art]

Conventionally, as shown in Fig. 4, the amount of fuel supplied to the burner and the amount of oxygen-containing gas supplied for combustion are gradually increased at a nearly constant ratio suitable for combustion over the entire period of temperature rise from _t0 to _t2 . This suppressed the wastage of fuel caused by supplying excessive fuel considering the temperature inside the furnace.

[Problem that the invention seeks to solve]

However, since both the amount of fuel supplied and the amount of oxygen-containing gas supplied for combustion decrease at the beginning of temperature rise, the amount of high-temperature combustion gas generated decreases, and stirring in the furnace by high-temperature combustion gas becomes insufficient. The convection heat transfer efficiency to the object to be heated in the furnace deteriorates, and the overall thermal efficiency does not improve much, but rather causes problems in terms of heating performance.

Furthermore, in the early stages of temperature rise, even if you fine-tune the fuel supply amount using a valve and the combustion oxygen-containing gas supply amount using a damper to adjust the temperature, problems may occur due to the characteristics of the valve, damper, or controller. The rate of fluctuation in the supply amount of fuel and oxygen-containing gas for combustion becomes large, and there is a great risk that the temperature change in the furnace will greatly exceed the desired range, making it impossible or extremely difficult to accurately control the temperature inside the furnace.

An object of the present invention is to improve heating performance in the initial stage of temperature rise and to accurately and easily adjust the temperature inside the furnace, while making use of the conventional technical idea of suppressing fuel waste. .

[Means to solve the problem]

The characteristic means of the present invention is that when the temperature inside the furnace is raised to a first set temperature by a burner, the amount of fuel supplied to the burner is increased until the temperature inside the furnace reaches a second set temperature in the middle of heating. Initially, the first set temperature is maintained almost constant according to the second set temperature,
And after that, from the first set amount to the fifth set amount
The set amount is gradually increased, and the amount of combustion oxygen-containing gas supplied to the burner is gradually decreased from the second set amount to the third set amount at the initial stage of the temperature increase, and thereafter the third set amount is increased. The purpose is to gradually increase the amount from the amount to the fourth set amount, and its effects are as follows.

[Effect]

In other words, as shown in _{FIG .}
, the fuel supply amount is maintained at the first set amount Q ₁ corresponding to the state where the temperature inside the furnace reaches the second set temperature T ₂ corresponding to time t ₁ , and the oxygen-containing gas supply amount for combustion is maintained at the second set amount Q 1 . Gradually decrease the set amount Q ₂ to the third set amount Q ₃ to gradually raise the temperature of high-temperature combustion gas as the furnace temperature rises, and generate as large a quantity as possible to reduce the furnace temperature of high-temperature combustion gas. To suppress an increase in heat loss caused by exhaust gas becoming too high in temperature, and to efficiently convection heat an object to be heated by sufficient stirring in a furnace using a large amount of high-temperature combustion gas.

In addition, in order to adjust the temperature inside the furnace, it is possible to maintain a constant fuel supply amount without changing the calorific value, and instead change only the amount of combustion oxygen-containing gas, which is supplied in large quantities. To eliminate hunting and chattering in furnace temperature control, and to accurately and easily raise the furnace temperature as desired.

Then, from t ₁ to _{t 2} , both the fuel supply amount and the combustion oxygen-containing gas supply amount are gradually increased to bring the temperature inside the furnace to the first set temperature, which is the temperature increase target.
The amount is increased to the maximum amount Q ₄ or Q ₅ commensurate with the state of T ₁ to suppress heat loss due to excessively high temperature of high temperature combustion gas and maintain efficient convective heating by a large amount of high temperature combustion gas.

〔Effect of the invention〕

As a result, the temperature inside the furnace reaches the desired level from the start of combustion.
Until the temperature is raised to the set temperature, not only can fuel waste be minimized, but also the convection heating of the heated object can be carried out with good efficiency, and the overall thermal efficiency can be sufficiently improved. In addition, it has become possible to accurately raise the temperature in the furnace as specified and to reliably perform a good heat treatment.

〔Example〕

Next, examples will be shown.

First, the equipment used will be explained with reference to FIG.

A first pipe line 3 for supplying gas fuel and a second pipe line 4 for supplying combustion air are connected to the burner 2 of the heating furnace 1, and a pressure equalizing valve 5 and a first flow rate sensor _S1 are connected to the first pipe line. 3, and the damper 6 and the second flow sensor S ₂
is provided in the second pipe line 4, and a temperature sensor _S3 for detecting the temperature inside the furnace is provided in the heating furnace 1.

a programmer 7a for setting changes in furnace temperature;
The setting device 7 is provided with a determination means 7b that determines the control form based on the information from the programmer 7a and the temperature sensor _S3 , and a first controller that program-controls the damper 6 based on the information from the determination means 7b and the first flow rate sensor _S1 .
A second controller 10 includes a controller 8 and program-controls the damper 6 and the servo motor 9 using information from the determining means 8b and the first and second flow rate sensors S ₁ and S ₂ .
is provided, and through the rack and pinion mechanism 11, the tension spring 5a, and the rod 5b, so that the flow rate detected by the second flow sensor _S2 is maintained approximately constant by automatic operation of the servo motor 9 by the second controller 10. The opening of the valve body 5c of the pressure equalizing valve 5 is adjusted, and the force acting on the tension spring 5a is maintained constant at the set state.

The downstream side of the damper 6 and the first pressure chamber 5 of the pressure equalizing valve 5
d is connected by a pressure impulse pipe 12, and the downstream side of the valve element 5c is connected by a pressure impulse path 5g to a second pressure chamber 5f which is isolated from the first pressure chamber 5d by a first diaphragm 5e linked to the valve element 5c. The second diaphragm 5h that isolates the upstream side of the valve body 5c and the second pressure chamber 5f is connected to the valve body 5c.
The pressure from the impulse pipe 12 and the valve body 5 are
The air-fuel ratio is automatically maintained within a set range by the balance between the pressure on the upstream side of valve body 5c and the pressure on the downstream side of valve body 5c.

Next, a method for controlling the temperature inside the furnace will be explained.

As shown in Figure 2, the furnace temperature is set to the first set temperature.
In order to raise the temperature to _T1 , the correlation between the furnace temperature and time is set in the programmer 7a.

After igniting the burner 2, during the initial temperature rise period _t0 to _t1 until the temperature inside the furnace from the temperature sensor _S3 reaches the second set temperature _T2 during the temperature rise, the determining means 7b sends a signal to the second controller 10. The third
As shown in the figure, the gas fuel supply amount is adjusted to the second set temperature.
The first set amount Q ₁ corresponding to T ₂ is maintained almost constant by the action of the servo motor 9, and the combustion air supply amount is gradually changed from the second set amount Q ₂ to the third set amount Q ₃ by operating the damper 6. The temperature of the high-temperature combustion gas generated by the burner 2 is increased in proportion to the rise in the furnace temperature.

The furnace temperature from temperature sensor S ₃ is the second set temperature.
When T ₂ is reached, the first controller 8 is output from the determining means 7b.
and the second controller 10 to issue a stop command, and thereafter, during the temperature rising period t ₁ to _{t 2} until the furnace temperature from the temperature sensor S ₃ reaches the first set temperature T ₁ , the second controller 10 issues a stop command. As shown in Fig. 3, the combustion air supply amount is gradually increased from the third set amount _Q3 to the fourth set amount _Q4 by operating the damper 6, and the fuel supply amount is increased to the first set amount Q4.
Gradually increase the amount from Q ₁ to the fifth set amount Q ₅ by operating the pressure equalizing valve 5 through the impulse pipe 12, and increase the calorific value of the burner 2 while keeping the air-fuel ratio almost constant in proportion to the rise in furnace temperature. increase

The temperature inside the furnace determined by temperature sensor S ₃ is the first set temperature.
When T ₁ is reached, the first controller 8 operates the damper 6 to maintain the furnace temperature at a substantially constant temperature for a set time, or immediately closes the damper 6 completely and extinguishes the burner 2. I do things.

[Another example]

Next, another example will be shown.

To raise the temperature inside the furnace to the first set temperature T ₁ ,
The shape of the temperature rise curve can be selected appropriately, and
The set temperature T ₂ can be appropriately set depending on the convection heating characteristics of the object to be heated in the furnace.

First set amount Q ₁ and fifth set amount Q ₅ of fuel supply amount
can be appropriately selected according to the calorific value of the fuel, air ratio, and other requirements, and the second set amount Q ₂ third set amount Q ₃ and fourth set amount Q ₄ of the combustion air supply amount
can be selected depending on combustion stability, convective heating characteristics, air ratio, and other requirements. The end point of the initial temperature increase period t ₀ to _{t 1} may be set by a timer.

The type of fuel can be selected from various gas fuels such as city gas, natural gas, propane gas, various oils, and other suitable fuels.The type of burner 2 can be selected according to the type of fuel, furnace structure, and other conditions. You can choose appropriately.

Oxygen-enriched air, oxygen, or the like may be used instead of air, and these are collectively referred to as oxygen-containing gas for combustion.

The specific configuration for changing the fuel supply amount and the combustion oxygen-containing gas supply amount can be changed as appropriate, and the specific configuration of the setting device 7, the first and second controllers 8 and 10, and the program type for automatic control. , other specific forms of the automatic control means can be selected as appropriate, and furthermore, the amount of fuel supplied and the amount of oxygen-containing gas supplied for combustion may be artificially adjusted.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention,
FIG. 1 is a conceptual diagram of the equipment used, FIG. 2 is a graph showing changes in furnace temperature, and FIG. 3 is a graph showing changes in fuel supply amount and combustion air supply amount. FIG. 4 shows a conventional example and is a graph corresponding to FIG. 3. 2...Burna.

Claims (1)

[Claims] 1 The temperature inside the furnace is set to the first set temperature T ₁ by burner 2.
A furnace temperature adjustment method for adjusting the amount of fuel supplied to the burner 2 and the amount of oxygen-containing gas for combustion when raising the temperature to 2nd set temperature during heating
The initial temperature increase t ₀ to _{t 1} until reaching T ₂ is maintained almost constant at the first set amount Q ₁ commensurate with the second set temperature T ₂ , and thereafter, from t ₁ to _{t 2} 1st
The amount of oxygen-containing gas supplied to the burner 2 is gradually increased from the set amount Q ₁ to the fifth set amount Q ₅ , and from the second set amount Q ₂ to the third setting during the initial temperature increase period t ₀ to t _1. amount
A furnace temperature control method in which the temperature is gradually decreased to Q ₃ and then gradually increased from the third set amount Q ₃ to the fourth set amount Q ₄ from t ₁ to _{t 2} .