JPS5921459B2 - Flare stack and its control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flare stack and a control method thereof, and its purpose is to reduce pilot fuel (pilot gas) consumption in a pilot burner attached to a flare stack main burner.

The purpose is to ensure that the main burner is ignited even though the main burner is light.

Flare stacks are used to safely burn and incinerate flammable and toxic process gases released from safety valves, etc. of plants at high altitudes in the atmosphere.

In addition, as a recent trend, ground flares are installed in order to prevent the visible flames, black smoke, and noise pollution generated from the flare stack, and ground flares are used alone until the amount of processed gas generated exceeds a certain value. I am trying to process it.

In such equipment, the pilot burner is required to be in an ignited state at all times in order to cope with a situation where toxic gas is suddenly released from a safety valve or the like in the plant.

Multiple pilot burners are installed around the main burner.

This is to ensure that the main burners can be ignited under all weather conditions and even if some of the pilot burners are damaged, which is important as repairs are difficult during plant operation. be.

However, keeping a plurality of pilot burners in the ignited state at all times in this way results in a huge amount of pilot gas consumed each year, which is often a problem as it goes against recent energy saving efforts.

The present invention has been made in view of the above, and embodiments thereof will be described below with reference to FIGS. 1 to 3.

1 is a flare stack, 2 is a ground flare, and the process gas is introduced into these by water seal drums 3,
This is done via 4.

That is, these water seal drums 3 and 4 consist of drums 3A and 4A filled with water, inlet pipes 3B and 4B inserted at a constant length L t t into the filled water, and outlet pipes 3c and 4c, The inlet pipes 3B and 4B are branched from a common conduit 5 extending from safety valves of plants, etc.
t t is set to the relationship L<A.

Therefore, the processing gas that has passed through the conduit 5 first breaks the water seal of the ground flare water seal drum 4 and is then sent to the ground flare 2.
When the flow rate reaches a certain level (more than the throughput of the ground flare 2), the water seal of the flare stack water seal drum 3 is broken and the water flows to the flare stack 1 side.

The outlet pipe 4C of the ground flare water seal drum 4 is a processing gas introduction pipe 6A for each burner (not shown) in each stage of the ground flare 2.

6B, 6C! are connected in a branched state.

The ground flare 2 has multiple stages of burners (three stages in the illustrated example).
The number of combustion stages of the burner is increased or decreased depending on the amount of processing gas introduced.

That is, the pressure detector 7 is installed in the processing gas introduction pipe 6A leading to the first stage burner and the processing gas introduction pipe 6B leading to the second stage burner.
A.

Automatic valves 8B and 80 are interposed in the processing gas introduction pipe 6B leading to the second stage burner and the processing gas introduction pipe 6C leading to the third stage burner.

Now, when the water seal of the water seal drum 4 is broken and the processing gas is introduced into the ground flare 2 side, the processing gas first flows through the processing gas introduction pipe 6A leading to the first stage burner and is combusted in the first stage burner.

When the amount of processed gas increases and exceeds the capacity of the first stage burner, this is detected by the pressure detector 7A, and the automatic valve 8B is opened in response to the signal.

Therefore, the process gas is combusted in the first stage burner and the second stage burner.

If the amount of gas to be processed further increases and exceeds the total capacity of the first and second stage burners, this is detected by the pressure detector 7B, and the automatic valve 8C is opened in response to the signal.

Therefore, the process gas is combusted in all the burners of the first, second and third stages.

When the amount of processing gas increases further and exceeds the capacity of the ground flare 2, the water seal of the flare stack water seal drum 3 is broken, and the processing gas in excess of the ground flare capacity flows to the flare stack 1.

The flare stack 1 has a main burner 9.

A plurality of pilot burners 10 are installed alongside the main burner 9, one of which is installed inside the main burner 9, and the rest are installed around the outside of the main burner 9 at equal angle intervals.

The internal pilot nozzle 10A is connected to an inlet pipe 11, and is also provided with an ignition pipe 12 and a device 1 for detecting the presence or absence of ignition, such as a thermocouple (not shown).

An on-off valve 13 is interposed in the pilot gas introduction pipe 11.

Similarly, a pilot gas introduction pipe 14 is connected to the outer pilot burner 10B, and an ignition pipe 15 is attached thereto.

An electric valve 16 is interposed in the pilot gas introduction pipe 14.

The base ends of the two ignition tubes 12 and 15 communicate with each other, and this portion communicates with a collecting pipe 19 of the pilot gas pipe 17 and the air pipe 18.

The ignition tubes 12, 15 have ignition devices 12A, 15A.

Further, electric valves 21 and 22 are interposed in the pilot gas pipe 17 and the air pipe 18.

23 is an automatic ignition control device, which controls the internal pilot burner IOA and the external pilot burner +10B.
between each other, and between the ground flare 2 side and flare stack 1
The operating conditions between the two sides are related.

Note that the internal pilot burner 10A is always in the ignition state.

In the above, when processing gas exceeding the ground flare capacity flows through the conduit 5, the excess breaks the water seal of the water seal drum 3 and flows into the flare stack 1, as described above, and flows into the internal pilot burner inside the main burner 9. It is ignited by the IOA and combusted by the main burner 9.

In this case, at the same time as the automatic valve 8C of the process gas introduction pipe 6C leading to the third stage burner of the ground flare 2 is opened, a signal from the pressure detector 7B causes the pilot gas introduction pipe 14 of the outer part pilot burner 10B to Electric valve 1 interposed in gas pipe 17 and air pipe 18 respectively
6.21.22 was opened and the ignition devices 12A, 15A
is activated.

Ignition pipe 12゜1 by opening electric valve 16.21.22
5, a gas-air mixture within the flammability limit flows and is ignited by the igniters 12A, 15A, thereby igniting the pilot gas ejected from the outer pilot burner 10B.

In order to ignite the outer pilot burner 10B, the processing gas in excess of the ground flare capacity is transferred to the flare stack 1.
completed by the time it flows into.

Therefore, the process gas ejected from the main burner 9 is ignited by both the internal pilot burner IOA and the external pilot burner 10B, and is performed safely and reliably.

When the internal pilot burner 10A extinguishes due to an unforeseen event (for example breakage) before the process gas enters the flare stack 1, this is detected by the thermocouple and the signal opens the electric valve 16, 21, 22, as described above. The outer pilot burner IOH is ignited in the following manner.

In this case, there will be no problem even if the internal pilot burner IOA is relit at the same time.

When the processing gas amount gradually decreases and reaches the ground flare capacity, the flare stack water seal drum 3 automatically shuts off the processing gas flow into the flare stack 1, and the three-stage burner of the ground flare 2 Upon receiving the closing signal of the automatic valve 8C interposed in the processing gas introduction pipe 6C,
The electric valve 16 is closed and the outer pilot burner 10B
extinguishes the fire.

In this embodiment, a case has been described in which the internal pilot burner 10A is one unit, but this may be a part (two or more) of the plurality of pilot burners 10 installed alongside the main burner 9. good.

As described above, according to the present invention, among the plurality of pilot burners attached to the main burner, some of them are installed inside the main burner and the rest are installed around the outside of the main burner. By using the burner for constant ignition and using the outer pilot burner for ignition in an emergency, pilot gas consumption can be significantly reduced compared to conventional ones.

Moreover, since the outer pilot burner is ignited when the internal pilot burner is extinguished, the main burner can be reliably ignited at any time.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the same,
FIG. 3 is an explanatory diagram of the same. 1... Flare stack, 2... Ground flare, 3... Water seal drum for flare stack, 4... Water seal drum for ground flare, 5...
... Conduit, 6A. 6B, 60... Processing gas introduction pipe, 7A, 7B.
...Pressure detector, 8B, 80 ... Automatic valve, 9 ... Main burner, 10 ... Pilot burner, IOA ... Internal pilot Burna,
10B...Outer pilot burner, 11,1
4...-Pilot gas introduction pipe, 12.15...
...Ignition tube, 12A, 15A...Ignition device, 16, 21, 22...Electric valve, 17...
... Pilot burner, 18 ... Air pipe, 1
9...Collecting pipe.

Claims (1)

[Claims] 1. A flare stack characterized in that among a plurality of pilot burners attached to a main burner, some of them are installed inside the main burner, and the rest are installed around the outside of the main burner. 2.In a flare stack installed around the outside of the main burner, with some of the multiple pilot burners attached to the main burner installed inside the main burner, and the remaining ones installed around the outside of the main burner, the pilot burner inside the main burner is always in the ignition state. Ok,
A flare stack control method characterized in that high-lot burners around the outside of the main burner are ignited by a detection signal when a pilot burner inside the main burner is extinguished.