JPH0570824A - Method for removing soot in radiant tube - Google Patents

Abstract

PURPOSE:To simply remove soot even during operation by inserting a high air ratio combustion torch having the specific excess air ratio into a radiant tube clogged with the soot in the inner part and blowing combustion flame to the soot. CONSTITUTION:In the inner part of the radiant tube 1 set in a heat treatment furnace 9, the combustion of the burner 2 is executed, and the tube 1 is red- heated to heat a steel sheet. Then, in the case incomplete combustion happens because of shortage of the air for combustion in the burner 2 or in the case mixture becomes bad because of breakage of a burner nozzle 3, the soot 10 is stuck and piled in the inner part of the tube 1, and the inner part of the tube 1 is perfectly clogged very often. Then the torch 14 is inserted from an opening hole 11 at the inner part of the burner 2 and the high air ratio flame having >=1.5 the excess ratio is brought into contact with the soot 10 from this tip part 6, burnt and removed. In the case the air ratio is <=1.5, the combustion does not continue. Then the temp. of the soot becomes >=600 deg.C very often, but in this case, by inject-ing only the air from the torch 14, the soot can be burnt and removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing soot in a radiant tube.

[0002]

2. Description of the Related Art Radiant tube (hereinafter referred to as RT) heating is used in a continuous heat treatment furnace for steel strips.
Soot is often generated due to breakage of a combustion burner in the inside or shortage of combustion air, and soot is accumulated in the RT to block the RT. Conventionally, for a closed RT, the supply of fuel and air is stopped and the use of the burner is stopped. For this reason, when the number of the closed burners increases, the heating capacity decreases, which causes a problem that the heat treatment capacity decreases. On the other hand, for the blocked RT, remove the burner at the time of routine maintenance of the furnace
It was restored by scraping out the soot inside T using human power or a tool such as a hand drill, or replacing the entire RT if it was difficult.

[0003]

According to the present invention, the soot in the RT was conventionally removed when the furnace was stopped, but the soot can be easily removed even during the operation without stopping the furnace. A method for removing soot in a radiant tube is provided.

[0004]

Means for Solving the Problems The gist of the present invention is (1) In a radiant tube whose inside is blocked by soot, insert a high air ratio combustion torch with an excess air ratio of 1.5 or more into the radiant tube from outside the furnace. A method of removing soot in a radiant tube is characterized by spraying soot with a high-air-ratio combustion flame from the torch to incinerate and remove the soot. (2) In a radiant tube whose inside is blocked by soot in a high temperature state, an air injection torch is inserted from outside the furnace into the radiant tube, and air is blown from the torch to incinerate the soot. There is a method of removing soot in the radiant tube.

That is, the present inventors have found that the soot is the carbon content of the fuel carbonized and adhered to the inside of the RT, and soot is easily burnt and removed by self-combustion at a constant temperature and air supply. It focuses on that. Therefore, by applying this point, the inventors invented a method for easily incineration and removing even during operation.

The present invention will be described in detail below with reference to FIG. The RT1 is arranged in the heat treatment furnace 9, the radiant tube burner 2 is connected to the RT1, and combustion is performed inside the RT to heat the RT1 red and the steel strip. The RT burner 2 supplies an appropriate amount of fuel 4 and combustion air 5, mixes them at the tip of the burner nozzle 3, and burns them. At this time, when the combustion air is insufficient and an incomplete combustion state occurs, or when the burner nozzle 3 is damaged due to high heat or the like and the mixing becomes defective,
Carbide (soot) is deposited at the tip of the burner nozzle 3 and adheres and deposits inside the tube. And RT in extreme cases like 10
It often happens that the interior is completely blocked.

The present invention provides a method for removing this soot without shutting down the furnace. Specifically, in the burner 2 whose use has already been stopped due to soot,
The torch 14 is opened from the opening 11 attached to the rear of the burner 2.
Is inserted and the excess air ratio from the tip 6 of the torch 14 is 1.
A high air ratio flame of 5 or more is brought into contact with the soot 10 and incinerated and removed. The torch 14 is supplied with fuel 7 and air 8 for flame formation. Also, the opening 11 for inserting the torch
Is generally provided with an opening for inserting an ignition burner for igniting the burner, which can be used.

[0008] The RT closed with soot usually has a low temperature because the use of the RT burner is stopped, and soot is often 600 ° C or lower. Therefore, as described above, the soot is heated by the high air ratio flame from the torch and, at the same time, it is incinerated and removed by the unreacted oxygen in the flame. Here, the excess air ratio is 1.
When it is 5 or more, unreacted oxygen in the flame is present in an amount of 5% or more, and soot combustion progresses.

[0009] Next, after the soot combustion proceeds as described above, or when there are many sound RT around the RT closed by the soot and the heat from these keeps the furnace temperature high, Soot often reaches high temperatures of 600 ° C or higher. In such a state, soot can be incinerated and removed by ejecting only air from the torch. This enables economical removal without consuming extra fuel.

FIG. 2 shows a structural example of a torch for incinerating this soot. The fuel 7 and the air 8 are mixed and burned at the tip of the torch to form a flame. However, since the excess air ratio is as high as 1.5 or more, blowout is generally caused and it is difficult to form a flame.
As a countermeasure against this, by providing a flame holding cylinder like 8a, the mixture of the air and the fuel in the flame holding cylinder 8a maintains a stable state, and blowout does not occur. Further, if a blade tip such as 6a is attached to the tip of the torch and the blade is burned while excavating it in soot, the burning time can be greatly shortened.

[0011]

[Example] Radiant tube furnace of steel strip continuous heat treatment furnace 1) Tube diameter: 7 inches (inner diameter 175 mm), number 10
9 2) Fuel: coke oven gas (volume ratio of 85%) and mixed gas calorific value of butane gas (volume ratio 15%) = 7750kcal / Nm ³ theoretical air quantity = 8.2 nm ³ operating at -AIR / Nm ³ -GAS Completely blocked RT with soot accumulated in the middle tube
Has reached about 30% and the burner has stopped using because its use has stopped.

The soot removal method of the present invention was carried out at this RT. The soot removal work was carried out during the operation of the furnace, and the furnace temperature at the time of the execution was in the range of 500 to 800 ° C, although it varied depending on the position of the furnace. As shown in Table 1, when the excess air ratio is 1.5 or more, soot is removed by incineration, but when it is less than 1.5, incineration does not proceed. When the soot temperature was 600 ° C or higher, it could be incinerated with only air.

[0013]

[Table 1]

[0014]

EFFECT OF THE INVENTION Conventionally, the furnace was stopped and the RT was replaced. In this case, including the time of temperature decrease and temperature rise of the furnace,
Although it takes about 3 days to stop, the method of the present invention can remove soot efficiently without stopping the furnace, which is extremely effective for stable production.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of the present invention.

FIG. 2 is an explanatory view showing a torch used in the present invention.

[Explanation of symbols]

 1 Radiant tube 2 Burner 3 Burner nozzle 4,7 Fuel 5,8 Air 6 Torch tip 6a Blade edge 8a Flame holding tube 9 Heat treatment furnace 10 Soot 11 Opening

Claims (2)

[Claims] 1. In a radiant tube whose inside is blocked by soot, a high air ratio combustion torch having an excess air ratio of 1.5 or more is inserted into the radiant tube from outside the furnace, and a high air ratio combustion flame is burned from the torch. A method for removing soot in a radiant tube, which comprises spraying and removing the soot by incineration. 2. In a radiant tube whose inside is blocked by soot in a high temperature state, an air injection torch is inserted from outside the furnace into the radiant tube, and air is blown from the torch to incinerate the soot. Soot removal method in the radiant tube.