JP2004093121A - Flare stack and method for replacing gas in fuel gas pipe using the flare stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flare stack capable of low calorie fuel gas combustion, eliminating possibility of diffusing environmentally hazardous gas into atmosphere, and eliminating the necessity of a huge processing expense. <P>SOLUTION: The flare stack 11 comprises a tubular combustion chamber with one end opened, a fuel blowing nozzle and an oxygen-containing gas blowing nozzle, with their nozzle injection openings on the inside surface of the combustion chamber. A tubular flame burner 12 having an approximate tangent direction of the inner surface of the combustion chamber, coincident to the injection direction of the fuel blowing nozzle and the oxygen-containing gas blowing nozzle is arranged. The fuel gas diffused through a diffusing pipe 13 is made combustion by air supplied by air piping before being diffused into atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a flare stack for burning combustible components in a gas before releasing the gas into the atmosphere.

In the repair work on the fuel pipe, the fuel gas remaining in the pipe is replaced with air before the work is performed, but before replacing the fuel gas with air, the fuel gas is first replaced with nitrogen or the like. At that time, the emission rate or amount of the fuel gas is suppressed so that the landing concentration of the combustible component contained in the fuel gas to be replaced does not exceed a certain value.

However, if it is not possible to limit the emission rate or amount of the fuel gas to a certain value or less, a combustion device such as a flare stack is provided to burn combustible components in the fuel gas and then I am trying to do it.

The conventional burner used in such a flare stack is a baffle type burner that blows out a flame generated by burning fuel from the tip of the burner (for example, see Non-Patent Document 1). In such a burner, the fuel supplied by the fuel passage and the combustion air supplied by the air passage are ejected from the nozzle forward of the burner, and a turbulent flow field is generated by the ejected air and the fuel. Is formed.

Therefore, since the combustion flame also becomes turbulent, partial extinction occurs. Since such partial quenching causes combustion instability, the combustion is hydrodynamically and thermally controlled according to the heat value and combustion rate specific to the fuel so that such a phenomenon does not occur as much as possible. The nozzle is designed such that the nozzle flow velocity is optimized so as to perform the operation stably.

Thus, the fuel for which the nozzle was designed is burned stably, but the combustion becomes unstable with other fuels.

Further, since the combustion reaction is always performed in a flame having a certain volume, the time required for the reaction is also increased, and the time margin for generating NOx and soot is increased. Then, since there are local high-temperature portions and low-temperature portions, NOx is likely to be generated in the high-temperature portions and soot is likely to be generated in the low-temperature portions.
Iron and Steel Handbook Third Edition Vol. 3, Chapter 5, Section 3, Section 1 Figure 5.33 (p126)

However, the flare stack having the conventional baffle type burner has the following problems.

Since a baffle type burner is used, it is necessary to use a high calorie fuel as a fuel to maintain stable combustion. The fuel gas diluted by the above is extremely low in calories and poor in combustibility, and cannot be burned as it is.

Therefore, there is no other way but to release it to the atmosphere over time or to burn it using auxiliary fuel and then to the atmosphere so that the landing concentration does not exceed a certain value. For this reason, when the gas is directly emitted, environmentally undesirable gas is emitted into the atmosphere. When the fuel is burned using an auxiliary fuel, a large processing cost is required.

The present invention has been made to solve the above-mentioned problems of the prior art, and can burn even low-calorie fuel gas diluted with nitrogen without requiring auxiliary fuel, An object of the present invention is to provide a flare stack that does not emit environmentally unfriendly gas into the atmosphere and does not require a large processing cost, and a method for replacing gas in a fuel gas pipe using the flare stack. .

A flare stack according to the present invention includes a tubular combustion chamber having an open end, a fuel injection nozzle having a nozzle injection opening opened on an inner surface of the combustion chamber, and an oxygen-containing gas injection nozzle. And a tubular flame burner in which the injection direction of the oxygen-containing gas injection nozzle coincides with the substantially tangential direction of the peripheral surface of the combustion chamber.

The gas replacement method in the fuel gas pipe according to the present invention is a method using the flare stack having the above configuration.

(4) In the flare stack according to the present invention, since the tubular flame burner is disposed, the range of adjustment of the combustion amount is wide, and one burner can cope with a high range of combustion amount. Also, extremely low calorie and poorly combustible gas, such as combustible gas diluted by nitrogen discharged when the inside of the pipe is replaced with nitrogen, can be burned.

For this reason, if the flare stack of the present invention is used and the gas discharged when the inside of the pipe is replaced with nitrogen is burned, even if the discharged gas is a low calorie and poorly combustible gas, Since the combustion can be performed without supplying the auxiliary fuel, the unnecessary gas can be released into the atmosphere at a low processing cost without polluting the environment.

燃料 Fuel refers to gaseous fuel, liquid fuel that has been gasified in advance, liquid fuel that has been atomized with air or vapor, fine solid fuel that is pneumatically pumped with nitrogen, or the like.

Oxygen-containing gas refers to a gas that supplies oxygen for combustion, such as air, oxygen, oxygen-enriched air, and a mixed gas of oxygen and exhaust gas.

According to the present invention, unnecessary gas can be released into the atmosphere at low processing cost without polluting the environment.

The best mode for carrying out the present invention will be described with reference to the drawings. FIGS. 1A and 1B are explanatory diagrams of a tubular flame burner arranged in a flare stack of the present invention, wherein FIG. 1A is a configuration diagram of a tubular flame burner, and FIG. FIG.

This tubular flame burner has a tubular combustion chamber 1, one end of which is an open end and serves as a discharge port for combustion exhaust gas. A long slit is formed at the other end along the tube axis direction, and a nozzle 2 that is connected to the slit and separately blows a fuel gas and an oxygen-containing gas is provided.

The nozzle 2 is provided substantially in a tangential direction on the inner wall surface of the combustion chamber 1, and a swirling flow is formed in the combustion chamber 1 by blowing the fuel gas and the oxygen-containing gas. Further, the nozzle 2 has a flattened tip portion and a reduced opening area, so that the fuel gas and the oxygen-containing gas are blown at a high speed. 3 is a spark plug.

In the burner having the above configuration, when the mixture of the fuel gas and the oxygen-containing gas blown from the nozzle 2 to form a swirling flow is ignited, the gas in the combustion chamber 1 is stratified by centrifugal force due to the density difference. Gas layers with different densities are formed on both sides of the flame. That is, high-density combustion exhaust gas having a low density exists on the axial center side of the combustion chamber 1 having a low swirl speed, and unburned gas having a high density exists on the inner wall side of the combustion chamber 1 having a high swirl speed. Become.

Further, near the inner wall, the flame cannot stay near the inner wall because the speed toward the center is higher than the flame propagation speed. Therefore, the flame is generated in the combustion chamber 1 in a tubular shape. Reference numeral 4 denotes a tubular flame. In addition, since unburned low-temperature gas exists in the vicinity of the inner wall of the combustion chamber in a boundary layer state, the wall surface of the combustion chamber 1 is not heated to a high temperature by direct heat transfer. Then, the gas in the combustion chamber 1 flows to the downstream side while swirling. During this time, the gas on the inner wall side sequentially burns, moves to the axial center side, and is discharged from the open end.

バ ー The burner with the above configuration has the following advantages. Since combustion can be performed even under a condition in which the fuel gas component is extremely lean or slow, the stable combustion range of the burner itself is widened.

(4) The amount of harmful substances such as NOx is small due to the small variation in the temperature of the combustion exhaust gas, the generation of local high-temperature parts during combustion, and the extremely short reaction time.

Since the reaction time is extremely short and a local low-temperature region cannot be formed, the residual amount of unburned components such as hydrocarbons is not very small, and the generation of soot is suppressed.

FIG. 2 is a diagram showing an embodiment of the flare stack of the present invention. The tubular flame burner 12 as described above is disposed in the flare stack 11, and the combustion chamber of the tubular flame burner 12 is supplied with a fuel gas that diffuses into the atmosphere through a radiation pipe 13. At the same time, air for combustion is supplied by the air pipe 14, combustion of the fuel gas diluted with nitrogen before emission is performed, and the combustion exhaust gas is emitted to the atmosphere.

The flare stack may be of a type that is always connected to the emission tube, or may be a portable type that is connected to the emission tube whenever necessary.

In the flare stack of the present invention, since the gas that has become unnecessary as described above can be burned without using an auxiliary fuel, the emission of the unnecessary gas is performed at low cost and without polluting the environment. Can be.

When repairing coke oven gas pipes installed in factories, etc., replace coke oven gas remaining in the pipes with nitrogen gas in order to prevent an explosion accident. I do it. As described above, when the coke oven gas in the pipe is replaced with the nitrogen gas, the gas is diffused by the gas diffusion pipe 16 provided in the middle of the coke oven gas pipe 15 as shown in FIG. The emission speed is adjusted based on the measurement result of the landing concentration around the gas emission tube 16.

In the present embodiment, the flare stack 17 of the present invention was installed at the tip of the gas diffusion tube 16, and the combustion air was supplied by the compressed air piping 18 installed nearby. In the case of this embodiment, at the start of gas emission by nitrogen replacement, since the coke oven gas is filled in the piping, the flare stack 17 can be easily ignited by the ignition torch. . Further, a flame detector 19 is provided on a burner of the flare stack 17, and an alarm device 20 is activated by a signal from the flame detector 19 when the flame is misfired.

Thus, it is possible to safely dissipate and burn until fuel (coke oven gas) is diluted and becomes a flame-retardant gas by nitrogen replacement.

(4) After the flammability of the fuel becomes poor and the flame detector 19 indicates misfire, the control is switched to the conventional landing concentration management.

FIG. 4 shows the calorific value of the fuel in the pipe when the fuel (coke oven gas) is dissipated while completely burning the flare stack of the present invention in which the tubular flame burner is arranged as described above. FIG. 6 is a diagram showing the change over time of the conventional flare stack in comparison with a conventional flare stack in which baffle type burners are arranged.

In the case of dissipating by the conventional flare stack, the combustible range is a range from the initial calorific value of the fuel in the pipe of 4600 kcal / Nm ³ to 1000 kcal / Nm ³ , whereas the range of the present invention is as follows. When dissipating with a flare stack, the combustible range expands from the initial calorific value of the fuel in the pipe of 4600 kcal / Nm ³ to 600 kcal / Nm ³ .

For this reason, in the past, the calorific value of the fuel was naturally dissipated from 1000 kcal / Nm ^3, but in the flare stack of the present invention, the calorific value of the fuel was naturally dissipated from 600 kcal / Nm ^3. In the present invention, the concentration has changed like the straight line A, but in the present invention, it changes like the straight line B. Therefore, the time until the end of the emission is about half of the conventional one, and the working time can be saved. It can be seen that most of the coke oven gas which has been emitted without being burned can be burned, which is very effective in preventing environmental pollution.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the tubular flame burner arrange | positioned at the flare stack of this invention, (a) is a block diagram of a tubular flame burner, (b) is the AA arrow line view of (a). It is a figure showing an embodiment of a flare stack of the present invention. FIG. 3 is a diagram illustrating a method of dispersing a coke oven gas using the flare stack of the present invention. 5 is a graph showing a change over time in a calorific value of fuel in a pipe.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Nozzle 3 Spark plug 4 Tubular flame 11 Flare stack 12 Tubular flame burner 13 Dispersion tube 14 Air piping 15 Coke oven gas piping 16 Gas diffusion tube 17 Flare stack 18 Compressed air piping 19 Flame detector 20 Alarm apparatus

Claims (2)

A tubular combustion chamber having an open end, a nozzle for fuel injection and a nozzle for oxygen-containing gas injection having a nozzle injection opening opened on the inner surface of the combustion chamber, wherein the fuel injection nozzle and the oxygen-containing gas injection nozzle A flare stack comprising a tubular flame burner whose injection direction is substantially coincident with a tangential direction of a peripheral surface of a combustion chamber. A method for replacing gas in a fuel gas pipe using the flare stack according to claim 1.

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