JPS6255048B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a radiant tube burner, and in particular aims to improve the air-fuel ratio balance to reduce the fuel consumption rate, and to prevent local overheating of the radiant tube to extend its durable life. This is an attempt to propose development results based on the development results.

Radiant tube burners are used to indirectly heat steel plates and other materials in heat treatment furnaces, etc. In order to improve combustion performance, this type of burner generally uses a primary gas ejected from the burner nozzle with fuel gas, such as M gas, at the tip of the burner. The structure is such that the mixture is mixed with air and combusted, and the unburned content is completely combusted by secondary air introduced into the radiant tube.

This type of conventional burner requires a supply of primary air under high pressure to ensure the flow rate of the primary air ejected from the small-diameter burner nozzle, so cold air is used, and the secondary air is usually supplied by a heat exchanger, especially a radiant tube. Hot air was used through a requipulator using waste gas from the air.

Because the primary air and secondary air are separate systems in this way, air-fuel ratio control in response to fluctuations in combustion conditions is performed only on the secondary air, which has a large flow rate, and the primary air is excluded from actual air-fuel ratio control, so it must be strictly controlled. In this sense, proportional control with a constant air-fuel ratio was not achieved, and since the primary air was cold air, the combustion efficiency was poor. Although it is possible to install a device to proportionally control the primary air and measure thermal aeration, the number of radiant tubes is as large as a normal plate normalizing furnace, about 140 per unit. , there are disadvantages associated with huge costs.

Furthermore, in conventional burners, the primary air has a high pressure and a significant jet velocity, so most of the fuel gas is burned in a short time, resulting in a short flame, which results in local overheating of the radiant tube near the tip of the burner. In addition to deformation and other disadvantages, the normalizing furnace has the disadvantage of having to replace the radiant tube at a rate of approximately 30% per year.

In view of these problems, it is an object of the present invention to reduce the fuel consumption of the radiant tube burner and to extend the life of the radiant tube.

In this invention, inside the radiant tube,
Mainly consists of an inner and outer double cylinder, with the inner cylinder used for the fuel supply system, and the annular gaps between the inner and outer cylinders and between the outer cylinder and the radiant tube used for the primary and secondary air supply systems, respectively. The burner bodies are arranged concentrically, and an air supply port is provided in the outer cylinder to connect the primary air supply system to the secondary air supply system and a common preheated air intake port, and This is a radiant tube burner with an opening orifice arranged around an outer cylinder.

FIG. 1 illustrates a preferred embodiment of the present invention, particularly a modified burner which is a conventional burner.

In the figure, 1 is a radiant tube, and 2 is a burner body. The burner body 2 is attached to the inside of the radiant tube 1 by a flange 3 at one end so as to be concentrically arranged.

The burner body 2 mainly consists of a double cylinder consisting of an inner cylinder 4 and an outer cylinder 5. The inside of the inner cylinder 4 is used as a supply system 6 for fuel, for example, M gas, and the inner cylinder between the inner cylinder 4 and the outer cylinder 5 is The annular gap is used as a primary air supply system 7,
The outer annular gap between the outer cylinder 5 and the radiant tube is used for the secondary air supply system 8.

The primary air supply system 7 is conventionally connected to the burner main body 2.
A cold air high-pressure pipe (not shown) is connected to a ventilation hole 9' drilled in the body wall of the end piece 9, but in this invention, this ventilation hole 9' is connected to a blind plate or a blind plug. On the other hand, an air supply port 11 facing and communicating with the preheated air intake port 10 of the burner body 2 is bored in the outer cylinder 5 and opened to the primary air supply system 7.

In this way, the secondary air supply system 8 shares the primary air supply system 7 and the preheated air intake port 10.
An orifice 11' is arranged around the outer cylinder 5 toward the direction. This orifice 11' is prepared in the form of a plug with holes of various inner diameters, and one suitable for combustion conditions is selected and replaced as appropriate.

In addition, 12 in the figure is an end tube fixed to the tip of the inner cylinder 4,
13 is a fuel gas injection nozzle drilled in the bottom wall;
Reference numeral 14 designates a primary air jet nozzle formed in the peripheral wall of the end portion of the end tube 12, reference numeral 15 designates a flow guide tube connected to the outer cylinder 5, and reference numeral 16 designates a flow guide collar having an enlarged diameter at the tip of the flow guide tube 15.

The inventors conducted numerous experiments and found that the length of the burner's frame depends on the hole diameter of the orifice 11'; making it smaller will make the flame shorter, and making it bigger will make it longer. The frame has been made long enough to almost match the length of the tube, and in this state, the amount of air is smaller than in the conventional burner operation described above, that is, the excess air given by the ratio of the amount of air used to the theoretical amount of air. ratehoヾ
At 1.05, it was confirmed that complete combustion occurred within radiant tube 1 and a stable flame was obtained.

Next, regardless of changes in the total amount of air introduced into the preheated air intake port 10, the ratio between the flow rate of primary air jetted from the air jet nozzle 14 and the flow rate of secondary air jetted from the orifice 11' remains approximately the same. It has also been confirmed that it can be controlled in a constant manner and in this way produces a stable frame under any operating conditions.

For comparison, in an experiment in which the frame length was adjusted by changing the aperture of the air jet nozzle 14, it was found that not only was it extremely difficult to adjust the frame length, but it was also difficult to adjust the frame length by increasing the aperture of the nozzle 14. When trying to lengthen the burner, the mixing of the primary air with the fuel gas tends to be poor, resulting in incomplete combustion, and compared to conventional burners, it requires a larger amount of air, making it difficult to put into practical use due to combustion efficiency. It was hot.

The present invention simply closes the primary air inlet of a conventional radiant tube burner and instead communicates the primary air supply system with the secondary air supply system and a common preheat air intake. By simply installing an orifice in the outer cylinder and installing an orifice in the secondary air supply system, as described below, the effect of significantly reducing fuel consumption and extending the life of the radiant tube is achieved. is realized.

1 Effect of reducing fuel consumption (1) The primary air becomes hot air instead of the conventional cold air.

(2) Proportional control is also applied to the primary air,
In other words, since the ratio of the primary air flow rate and the secondary air flow rate can be kept constant and balanced, and the primary air flow rate and the secondary air flow rate follow fluctuations in the total air flow rate, incomplete combustion does not occur.

(3) A stable flame can be obtained even when the amount of air is reduced compared to that in conventional burners, for example, the excess air ratio is about 1.05, and low O ₂ operation is advantageously possible.

2. Extending the life of the radiant tube (1) The frame is longer, the surface temperature distribution of the radiant tube becomes more uniform, and the peak temperature decreases, preventing local overheating near the burner tip and reducing deformation due to high-temperature creep. do.

According to the results of an actual furnace test in a normalizing furnace at a plate factory, the fuel consumption with M gas is reduced by 20 to 30% compared to conventional radiant tube burners, and there is no deformation of the radiant tubes due to local overheating. It became.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the invention. 1... Radiant tube burner, 2... Burner body, 4... Inner cylinder, 5... Outer cylinder, 6... Fuel system, 7... Primary air supply system, 8... Secondary air supply system, 10...Preheated air intake, 1
1... Air supply port, 11'... Orifice.

Claims (1)

[Claims] 1 Inside the radiant tube, there are two main cylinders: inner and outer cylinders, and the inner cylinder is used for the fuel supply system.
The burner bodies are arranged concentrically, and the annular gaps between the inner and outer cylinders and between the outer cylinder and the radiant tube are used as primary and secondary air supply systems, respectively, and the primary air supply system is connected to the secondary air supply system. A radiant tube burner in which an air supply port communicating with a common preheated air intake is provided in the outer cylinder, and an orifice opening toward the secondary air supply system is arranged around the outer cylinder.