JPS6214616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the temperature inside a continuous heating furnace.

For example, walking beam furnaces are known as continuous heating furnaces. An example of the structure of a walking beam furnace is one in which a fixed beam and a moving beam are provided in the furnace, and the moving beam is moved in a rectangular shape to move the object to be heated while being placed alternately on the fixed beam and the moving beam. , combustion chambers are provided above and below the beam, and the object to be heated is heated from its upper and lower surfaces. The beam consists of a skid that supports the object to be heated and posts that support the skid, and these are water-cooled. Therefore, compared to the upper zone, the lower zone inside the furnace has more heat lost due to skid cooling, post cooling, etc., and heat radiated from the hearth opening, so the combustion efficiency (the amount of heat input and the amount of heat transferred to the heated object) is lower than that in the upper zone. The ratio to the amount of heat generated) is significantly inferior. In a conventional furnace, the combustion efficiency was 76.7% in the upper zone and 42.9% in the lower zone.

Therefore, in the past, based on the idea that the furnace temperatures in the upper and lower zones should be equal, the amount of combustion in the lower zone was increased to compensate for the decrease in furnace temperature in the lower zone.

In this conventional method, in order to maintain the upper and lower zones at the same furnace temperature and evenly heat the upper and lower surfaces of the object to be heated,
The lower zone required approximately 1.8 times more fuel input than the upper zone.

Therefore, the present invention does not increase the amount of combustion by focusing on the lower zone where combustion efficiency is poor (rather than eliminating the temperature difference between the upper and lower zones), but on the contrary, it starts from the upper zone where combustion efficiency is high. The purpose of the present invention is to provide a method for controlling the temperature inside a continuous heating furnace, which improves the combustion efficiency of the entire furnace by increasing the amount of heat transferred to the heated object. Therefore, the feature is that in a continuous heating furnace where heat sources are provided at the upper and lower parts of the furnace, and the object to be heated passes through the middle part, the heat quantity of the upper heat source is larger than that of the lower heat source. The upper zone of the internal atmosphere is set to a higher temperature than the lower zone, and the amount of heat transferred from the upper zone to the heated object is actively increased.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

What is shown in FIG. 1 is an outline of equipment used for carrying out the present invention, and a walking beam furnace 1 is illustrated as an example. This furnace 1 has a preheating chamber 2, a heating chamber 3, and a soaking chamber 4 in series, and includes a walking beam device 5 therein. The object to be heated 7 is placed on the skid 6 of this apparatus 5, and the object to be heated 7 moves from the preheating chamber 2 to the soaking chamber 4 approximately at the vertical center of the furnace. The walking beam device 5 is cooled by cooling water. Gas burners 8 are provided in the upper and lower parts of the furnace 1, respectively, to form an upper combustion chamber 9 and a lower combustion chamber 10. 11 is a furnace atmosphere temperature detection device, and 12 is a heated object temperature detection device, each of which is of a thermocouple type. In the illustrated example, these devices 11, 12 are provided only in the upper band, but of course they are also provided in the lower band. And these temperature detection devices 11, 12,
The fuel control devices 13 are connected by a control device 14 such as a computer, and the fuel supply is automatically controlled so that the temperature of the atmosphere in the furnace reaches an optimum set point. Of course, the optimum set point will also be determined taking into account other requirements such as from waste gas sampling.

In addition, 15 is a requipator, 16 is a damper, and 17 is a chimney.

In the example of the present invention, using the above equipment, the temperature inside the furnace was set as shown in FIG. That is, the furnace temperature in the upper zone was set to be 30°C higher than the standard furnace temperature, and the furnace temperature in the lower zone was set to be 50°C lower than the standard temperature. The standard set temperature at this time was the current average furnace temperature.

As a specific means for obtaining the above temperature difference, fuel control of the upper burner 8 and the lower burner 8 was performed. That is, the upper and lower zone temperature detection devices 11,
12 as variable input data, and the material of the heated object, fuel composition, set furnace temperature, etc. as fixed input data, the control device 14 calculates the optimum value for fuel supply and controls the fuel control device 13. be. By increasing the amount of heat input into the upper zone, which has better combustion efficiency, we aimed to improve the combustion efficiency of the entire furnace.

FIG. 3 is a graph showing the amount of fuel used, and shows the conventional normal heating and the temperature difference heating according to the present invention. As is clear from this graph, the average fuel consumption for normal heating was 2678Nm ³ /Hr, but for temperature difference heating the average fuel consumption was 2678Nm 3 /Hr.
2089Nm ³ /Hr, the fuel source unit was reduced by 2.2% compared to the conventional one.

In addition, due to the temperature difference heating, distortion such as downward warping of the heated object did not occur, and there was no difference in rolling properties in subsequent rolling operations.

Next, conventional normal heating and the temperature difference heating according to the present invention will be compared by numerical calculation.

(1) Preconditions (a) Combustion efficiency of upper and lower zones of heating furnace Upper zone: 76.7% Lower zone: 42.9% (b) Charging temperature of heated materials for normal heating 650℃ 〃 〃 Extraction temperature 1230℃.

(c) Charge temperature of heated object for temperature difference heating: 650℃ 〃 〃 Extraction temperature Top surface 1260℃ Bottom surface 1200℃ shall be.

(d) The steel type of the heated object shall be medium carbon steel (C; 0.4% or less).

(2) Calculating the required heat input (a) For normal heating The heat content at 1230℃ is 183.5Kcal/Kg The heat content at 650℃ is 85.1Kcal/Kg The heat input in the upper zone is (183.5−85.1) ÷ 0.767 = 128.3Kcal/Kg Lower zone heat input is (183.5-85.1) ÷ 0.429 = 229.4Kcal/Kg Calculated heat input ratio close to the upper/lower heat input ratio in the actual furnace of 0.54 (ratio of upper heat input to lower heat input) In order to
Assuming that 50% of the heat is input from the upper zone and 50% of the heat is input from the lower zone, the required heat input for normal heating is (128.3 x 0.5) + (129.4 x 0.5) = 17.89 Kcal/Kg.

(b) In the case of temperature difference heating The heat content at 1260℃ is 188.34Kcal/Kg The heat content at 1200℃ is 178.7Kcal/Kg The heat input in the upper zone is (188.34−85.1) ÷ 0.767 = 134.6Kcal/Kg Lower zone The amount of heat input is (178.7−85.1) ÷ 0.429 = 218.2Kcal/Kg In the results of temperature difference heating in the above example,
The heat input ratio at the bottom was 2.28. Therefore, assuming that the calculated heat input ratio is also adjusted accordingly, as shown in FIG. 4, 79% of the upper part of the object to be heated 7 receives heat from the upper zone, and 21% of the lower part receives heat from the lower zone. Therefore, the required heat input from the upper and lower zones in that case is (134.6×0.79) + (218.2×0.21) = 152.2Kcal/Kg.

(3) Therefore, the unit heat consumption is 178.9-152.2/178.9×100=1
It will be reduced by 5%.

There is a difference between the above calculation result of 15% and the actual low energy consumption rate of 22%, but this is due to the rough patterning model used to simplify calculations. It should be noted that the present invention is not limited to the above-mentioned embodiments, but can also be employed in a walking house furnace or the like, and the heat source may be an oil burner, electric heat, or the like.

In view of the effects of the embodiments and calculations of the present invention, the present invention exhibits extremely excellent effects in reducing fuel consumption and improving combustion efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of equipment used in an embodiment of the present invention, FIG. 2 is a diagram showing a heat pattern according to the present invention, and FIG. 3 is a fuel consumption amount according to a conventional example and the present invention. FIG. 4 is an explanatory diagram of a calculation example. 1... Continuous heating furnace, 7... Heat target, 8... Heat source.

Claims (1)

[Claims] 1. In a continuous heating furnace in which heat sources are provided at the upper and lower parts of the furnace, and the object to be heated passes through the middle part, the heat quantity of the upper heat source is larger than that of the lower heat source so that the upper zone of the furnace atmosphere is higher than the lower zone. A method for controlling the temperature inside a continuous heating furnace, which is characterized by actively increasing the amount of heat transferred from the upper zone to the heated object.