JPS5921908A - Low nox gas burner for radiant tube - Google Patents

Abstract

PURPOSE:To reduce the production of NOX, by installing an annular or tubular fuel gas nozzle, and primary and secondary air nozzles within a radiant tube. CONSTITUTION:In order to perform primary combustion after a fuel gas is first mixed with the primary air, of which the quantity is smaller than a theoretical air amount, by means of the primary air nozzle 8, a reducing range is formed at the initial combustion range, and the secondary combustion is effected with the secondary air to perform a so-called 2-stage combustion. In that case, the secondary nozzle 9 consists of two or more nozzles, such as main and auxiliary nozzles 9a, 9b, or long and short nozzles, or a nozzle and a mere opening, and since the secondary air is jetted in a condition that the air is divided into plural ranges within a tube 1, a change in an O2 concentration within the section of the tube is produced, whereby thick and thin fuel combustion is conducted in the secondary combustion. This enables reducing of production of NOX.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a radiant tube river bottom NOx that reduces NOx by simplifying the structure and enables a wide turndown.

In gas burners, methods such as a two-stage combustion method and an exhaust gas circulation method are conventionally known as means for reducing NOx.

However, since the space in a radiant tube burner is limited, when adopting the two-stage combustion method, it is not possible to form a large reduction combustion region, and it is difficult to achieve sufficient low NO.
It is not possible to achieve

Furthermore, even when the exhaust gas circulation method is adopted, since space is limited, exhaust gas must be supplied to the burner from outside through piping, which complicates the structure of the burner itself.

On the other hand, since conventional radiant tube burners are designed to perform slow combustion at the time of design, they have the disadvantage that combustion performance deteriorates when the burner is turned down.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology, and by arranging the air nozzle, gas nozzle, and pilot burner disposed inside the radiant tube in a special manner, it is possible to significantly reduce NOx and The purpose is to provide a radiant tube river bottom NOx that can reduce down to a level greater than before.

Next, the present invention will be explained with reference to drawings which are one embodiment.

In the figure, 1 is the radiant tube, 2 is the furnace wall, and 3 is the radiant tube.
is a svarna according to the present invention that is incorporated into the end of the radiant tube 1.

In the burner 3 described above, a pilot burner 4 is located in the center of the tube 1, and a constant air nozzle 5 is arranged around it to blow out air equivalent to about 1 to 10 times the maximum amount of combustion air. . Further, a fuel gas nozzle 6 is disposed on the outer periphery of the constantnia nozzle 5, and a primary air nozzle 8 is further disposed on the outer periphery, and the fuel gas is ejected from the ejection hole 7 to the upstream side of the opening of the primary air nozzle 8. The air is mixed with primary air in advance and then ejected into the tube 1. However, the arrangement of the primary air nozzle 8 and the fuel gas nozzle 6 may be reversed.

Reference numeral 9 denotes a secondary air nozzle arranged outside the primary air nozzle 8, and in the figure, two main nozzles (v9a) protruding from the position 180 and an opening on the upstream side from the opening of the main nozzle 9a are shown. It consists of a secondary nozzle/l/91).

In other words, 10 to 50% of the total combustion air supplied is directed to the primary air nozzle 8, and the remaining air is directed to the secondary air nozzle 9 at a distance of 11f. Note that 10 is a combustion air supply port.

In the gas burner 3, the fuel gas is first mixed with primary air of less than the theoretical air amount in the primary air nozzle 8, and then subjected to primary combustion. Therefore, after forming a reduction region in the initial combustion area, the fuel gas is mixed with primary air in the primary air nozzle 8. It burns and performs what is called a two-stage combustion. In this case, the secondary air nozzles 9 are the main and sub nozzles 9λ, 9b.
Or, it consists of two or more nozzles, such as long and short nosles, or a nozzle and a simple opening, and the secondary air is ejected in the tube 1 in a divided state into the rear area, so there is no 0 in the cross section of the tube.
Since the concentration of NOx varies, the secondary combustion performs concentrated combustion, contributing to NOx reduction.

Further, in parallel with this, the downstream combustion exhaust gas is recirculated upstream and mixed with the secondary air due to the sliding movement of the secondary air 11f, so that the exhaust gas is circulated at the same time.

In addition, in the embodiment, since the fuel gas and the primary air are mixed in advance in the primary air nozzle 8 as described above, the
Thermal NO
Generation of x is suppressed. Therefore, the two-stage combustion, concentrated combustion, and exhaust gas circulation greatly reduce the generation of NOx. In addition, as mentioned above, if the fuel gas and primary air are mixed in advance, the miscibility is good, so when using butane, propane, etc. as the fuel gas,
Even when using a fuel gas with a large molecular chain, fuel can be supplied at a lower supply pressure than before.

Fuel: LNG, Furnace temperature: 920℃, Combustion air/! 14
A comparison of the burner described above and a conventional two-stage combustion method burner under the conditions of temperature = 400°C and residual 0222 ratio shows that the burner of the present invention has a larger lumen than the conventional burner, as shown in Figure 3. ] was found to reduce the production of NOx.

Also, since constant air is ejected from the center of burner 3, by turning down the burner,
Even if the flow velocity from each nozzle decreases and the miscibility with the fuel decreases, the initial mixing can be maintained particularly well. As a result, good turndown can be achieved with low excess air operation up to 1 near.

Furthermore, since the pilot burner 4 is located at the center of the burner, the momentum of the combustion exhaust gas allows the flame to maintain its straightness even if one burner is turned down as described above.
The low excess air operation can be further ensured, and the temperature distribution of the radiant tube 2 can be maintained uniformly.

It goes without saying that the present invention is not limited to the above configuration, and that the secondary air nozzles may be a plurality of nozzles all having the same shape.

As is clear from the above explanation, according to the present invention, the present invention has a simple structure in which an annular or tubular fuel is placed in a radiant tube with a snorzzle, primary air nozzle, and secondary air nozzle. Since concentrated combustion and exhaust gas circulation are performed simultaneously, it is possible to significantly reduce NOx even in a radiant tube with limited space.

In addition, since the pilot burner and constant air nozzle are located in the center, not only the flame travels straight, but also the fuel gas and air mix well, making it possible to perform a wide turndown. .

[Brief explanation of the drawing]

Figure 1 shows the bottom NOx for the radiant tube according to the present invention.
2 is a schematic diagram for explaining the burner, FIG. 2 is a front view, and FIG. 3 is a comparison diagram comparing the NOx reduction between the burner of the present invention and a conventional low NOX/<-suto. 1...Radiant tube, 3...Burner, 4...
- Nonoirotpurana, 5...Constant air nozzle, 6...Fuel gas nozzle, 8...Primary air nozzle, 9 (9a, 9b)...Secondary air nozzle. Patent applicant: Chugai Roko Kogyo Co., Ltd. Representative: Patent attorney: Aohaku Ao and 2 others

Claims (1)

[Claims] +11 11] A pilot burner at the center, a constant air nozzle on its outer periphery, a primary air nozzle or gas nozzle on its outer periphery, and a gas nozzle or gas nozzle on its outer periphery.
A radiant tube riverbed NOx svarna characterized by having secondary air nozzles arranged at the outermost periphery in the above order within the tube. (2) The bottom NOx for the patented radiand tube, which is characterized by dividing the secondary air nozzle into several pieces, is a svarna. The bottom NOx for the radiant tube according to the scope of the patent claim @Claim 1 or Item 2 is characterized in that the NOx is premixed with the secondary x anosle. The low NO for radiant tube according to any one of claims 1 to 3, characterized in that:
x Gas burner.