JPS63113210A - Combustion device for low temperature liquefied fuel gas - Google Patents

Abstract

PURPOSE:To enable LNG to be used as liquid fuel, by a method wherein a burner is formed with a liquid injection nozzle, a primary gas/injection nozzle, and a secondary gas/nozzle, and a flame stabilizing cylinder is situated on the downstream side. CONSTITUTION:If LNG is fed through a conduit 4 to a liquid injection nozzle 1, it is injected at high speed. Primary air is introduced through a feed pipe 5 to a primary gas/injection nozzle 2, and the LNG is mixed with primary air in a premixing chamber (a). In this case, the LNG is crushed by friction with air to produce a spray flow. In this case, an LNG streamline is reduced by primary air and is injected in a secondary gas/injection nozzle 3. After the LNG is mixed with secondary air, fed through a feed pipe 6, in a secondary mixing chamber (c), the mixture is ignited by a pilot burner 7. Flame is held in a high density state by means of a flame stabilizing cylinder 8. This constitution enables the LNG to be used as liquid fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a combustion device for low-temperature liquefied fuel gas.

[Prior art]

Liquefied natural gas (LNG) is already 2,000 to 3,000 yen per year.
In particular, in the electric power industry, as part of energy diversification, it has come to be used on the same scale as oil and coal.

LNG is an abundant resource worldwide, and since it is made of almost pure methane, it does not contain harmful sulfur compounds and is an advantageous fuel for environmental protection.

However, although LNG is said to be a liquid, it actually
Because it is kept in tanks at an extremely low temperature of 60°C, its handling is difficult compared to other thermal power generation fuels. LNG evaporates very easily and has a low temperature, so conventionally it was vaporized, and the temperature was even lower than 0°C.
These are the ones I have used above. Therefore, if you look at it from the heated side.

Although it was said that LNG was being used, there were no particular problems because it was actually using a gas whose main component was methane as fuel. Gaseous fuel has the characteristics of being much easier to handle and more controllable than liquid or solid fuels.

However, from the perspective of this fuel supplier, LNG
Since it is a liquid, it is necessary to provide vaporization equipment to use it as a gaseous fuel. Moreover, LNG is 116
Since it is kept at an extremely low temperature of 0°C, bringing it to room temperature not only requires an enormous amount of heat, but also requires expensive low-temperature materials for vaporization equipment, and requires technical consideration to prevent freezing. be. More specifically, the open rack vaporizer (ORV) uses seawater as a heat source, and the submerged compass John vaporizer (SMV) uses combustion gas as a heat source.
) are mainly used, the former being mainly used for base load and the latter for emergency use. An intermittent fluid vaporizer using propane as a heat medium is also used in the − part. In any case, there is no difference in the fact that it requires equipment costs to produce gaseous fuel.

Furthermore, when seawater is used as a heat source, there are concerns that large amounts of cold energy will be dumped into the seawater, causing changes to the sea ecosystem, and algae and shellfish will sometimes grow on the seawater side of the vaporization equipment. Problems have also been pointed out, such as the need to take great care to ensure the reliability of the equipment.

Generally speaking, combustion is the process by which fuel vapor, whether gaseous, liquid, or solid, ultimately reacts with oxygen. Therefore, it is clear from the combustion of kerosene, coal, wood, etc. that although gas supply has the advantage of simplifying the combustion process, it is not limited to this. There are also devices that burn it. In contrast to these conventional fuels, LN
G has two major differences. One of them is 116
The other reason is that it is at an extremely low temperature of 0°C, and it evaporates very easily.For example, the critical temperature of methane is -82°C, so it does not exist as a liquid at temperatures higher than this.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion device that can essentially handle LNG as a liquid fuel, taking into consideration the physical characteristics of LNG as described above.

〔composition〕

According to the present invention, in a combustion device for directly burning low-temperature liquefied fuel gas in a liquid state, (i) a liquid jet nozzle that coarsens the low-temperature liquefied fuel gas; (ii) a tip portion of the liquid jet nozzle; a primary air/liquid injection nozzle which surrounds and has a primary air or oxygen supply pipe in its wall and a cylindrical gas retaining member at its tip; .

Secondary air for ignition with secondary air or oxygen supply pipe on the wall/
There is provided a low-temperature liquefied fuel gas combustion device, comprising: a combustion burner comprising a liquid injection nozzle; and (iv) a flame-holding cylinder located downstream of the combustion burner.

Next, an embodiment of the combustion apparatus of the present invention will be described with reference to the drawings.

The drawing shows a detailed illustration of the present invention, and the combustion burner used in the present invention includes a liquid jet nozzle 1 that coarsens LNG, and a primary gas/liquid that surrounds the tip of the liquid jet nozzle 1. It consists of an injection nozzle 2 and a secondary air/liquid injection nozzle 3 for ignition that surrounds the tip of the injection nozzle 2. An LNG supply conduit 4 is connected to the rear end of the liquid jet nozzle 1, and the blowing air/liquid injection nozzle 2 has a primary air or oxygen (hereinafter also simply referred to as air) supply pipe 5 on its wall; A cylindrical gas holding member 10 is disposed at the tip of the nozzle, and a secondary air supply pipe 6 is disposed on the wall of the secondary air/liquid injection nozzle 3 for ignition. A pilot gas burner 7 that opens near the tip of the secondary air/liquid injection nozzle 3 for ignition is also provided.

On the downstream side of the gas burner, there are openings at both ends surrounding the flame formed by the ignition injection nozzle 3.

A flame cylinder 8 is provided. Note that 9 indicates the combustion chamber wall.

In order to burn LNG using the combustion device of the present invention, LNG
G is supplied as a liquid to the liquid jet nozzle l through the conduit 4, and is jetted from its tip at a high jet velocity. - Secondary air is introduced into the primary air/liquid injection nozzle 2 through its supply tube 5 and travels towards the tip of the nozzle as indicated by the arrow. - The tip space of the blowing air/liquid injection nozzle 2 forms a premixing chamber a of LNG and primary air. In this premixing chamber a, the LNG jet is mixed with the surrounding primary air flow, but the LNG jet is pulverized by the frictional force with the air at that time and converted into a spray flow. However, here, the LNG injection pressure is 2 to 7.
Since it is relatively small (kg/ciG), the LNG is only coarsened. When this coarsening occurs, LNG evaporates rapidly, the flow path expands, and the relative velocity tends to decrease, but due to the action of the primary air flow around the LNG flow, the LNG streamline shrinks. be converted into Also, L
Since NG easily evaporates, the tip of liquid jet nozzle 1 is
As shown in the figure, an enlarged throat can also be used to prevent paper locking. In this case as well, the LNG streamline is reduced by the action of the primary air flow and the contraction throat of the blowing air/liquid injection nozzle 2 . The jet stream consisting of a mixture of LNG coarse particles and primary air is held for a certain period of time in a gas holding zone b consisting of a cylindrical gas holding member 10 connected to the tip of the blowing air/liquid injection nozzle 2, and then Secondary air is injected into the secondary air/liquid injection nozzle 3 for ignition, which is introduced through the supply pipe 6.

In the gas retention zone b, good mixing of secondary air and evaporated LNG is achieved, and the atomization of LNG coarse particles is promoted.

The LNt particulate group injected at high speed from the primary air/liquid injection nozzle 2 into the tip space C (secondary mixing chamber) of the secondary air/liquid injection nozzle 3 for ignition is mixed with secondary air here, and the first is ignited by the pilot burner 7, and after the start of combustion is heated mainly by radiant heat transfer from the flame, combustion is maintained. In this case, the ignition zone is a position downstream of the primary gas/liquid injection nozzle 2 where the jetting speed and the combustion speed are in equilibrium.

- Since the LNG particles and the primary air are well mixed in the gas holding zone b of the blowing air/liquid injection nozzle 2, the combustion immediately downstream of the ignition zone is a premixed flame. However, since the amount of secondary air is 2 to 40 voQ% of the theoretical air amount, and the LNG concentration is on the higher side outside the flammable limit concentration of 5 to 15 vo, 0%, the flame front automatically propagates. There is no danger. This is because combustion occurs as LNG and oxygen diffuse into a high-temperature flame front.

When combustion begins immediately downstream of the primary air/liquid injection nozzle 2, the LNG microdroplets evaporate rapidly, bending the LNG microdroplet stream upward and increasing the diffusion rate of the secondary air-mobile oxygen. LNG vapor escapes upward at a greater velocity.

As a result, combustion stability is lost. Therefore, in the present invention, a flame-holding tube 8 is disposed downstream of the nozzle 3 in order to maintain the main flame flow in a high-density state.

By arranging this flame-holding cylinder 8, the flame is held within the flame-holding cylinder for a required distance. In addition, by arranging this flame-stabilizing tube, the combustion exhaust gas is induced by the gas flowing inside the flame-stabilizing tube at high speed, and circulates as shown by the arrow 20, so that the high-temperature flame is contained inside the flame-stabilizing tube. functions occur. This function suppresses flame turbulence caused by rapid evaporation of LNG, allowing stable combustion to continue. In this case, the secondary air/liquid injection nozzle 3 shown in FIG. 2 may have an enlarged throat that responds to the flow of LNG vapor, and in combination with the flame stabilizing tube 8, it may have the effect of stabilizing the flame. can. Furthermore, this circulating flow of exhaust gas also serves to prevent the combustion temperature from locally increasing abnormally, and therefore has the secondary effect of reducing the generation of thermal NOx during combustion.

〔effect〕

A feature of LNG is that it has a low temperature of -160°C, which can lead to the problem of freezing in some cases. In the device of the present invention, this possibility exists only in the external part of the LNG jet nozzle.

Other parts of the LNG jet nozzle are kept above room temperature due to the radiant heat during combustion, so there is no risk of this happening.
are usually made from austenitic stainless steel tubes, so when primary air is flowed outside of them, the moisture in the air can solidify due to the cold heat and stick to the itching surface. However, since ice is a non-conductor to heat, it stops growing once it reaches a certain thickness and does not pose any particular problem to operation. In particular, if you want to be safe in this regard, you can cover the outside of the LNG jet nozzle 1 with a heat insulating material such as glass foam, or form the nozzle itself with ceramics, or even more proactively embed a heating wire. Measures can be taken such as keeping the surface above 0°C. At this time, some of the LNG inside the nozzle may vaporize slightly due to the heat, but the vapor becomes bubbles and immediately exits from the nozzle tip into a wider space, so it does not interfere with operation. On the contrary, since the apparent flow velocity of the jet flow is increased, there is also the advantage that the atomization of LNG is promoted.

Although low-temperature LNG tanks are kept sufficiently cool, the generation of boil-off gas (BOG) is unavoidable due to external heat input and fluctuations in the liquid level. A general liquid fuel burner has a difficulty in disposing of this BOG, but in the apparatus of the present invention, this BOG can be easily disposed of by sending it into the blowing gas/liquid injection nozzle 2.

This is because inside this nozzle 2, the gas is in a continuous phase, and the pressure is not as high as in the liquid continuous phase. Of course, BOG can be kept in a gas tank and used as pilot burner fuel, or as burner fuel exclusively for gaseous fuel. Moreover, the device of the present invention.

In addition to LNG, the present invention can also be applied to other low-temperature liquefied fuel gases, such as LPG. .

〔Example〕

Examples of the apparatus of the present invention will be shown below, but various changes and modifications can be made as necessary, and the present invention is not limited to these examples.

LNG was branched from a cold-insulated pipe made of Example SO5304 and burned in the apparatus of the present invention shown in the drawings at a flow rate of 1 and 200 kg/Fl. In this case, the pressure gauge attached to the LNG conduit 4 showed 4.5 kg/cJG. The tip diameter of the LNG jet nozzle 1 is 7 mm+, and the large air amount for the LNG jetted from the nozzle 1 is 2.15 ON rri.
'/H. - The tip diameter of the blowing gas/liquid injection nozzle 2 is 200++ ua, and the length of the gas holding zone b is 300 ua.
++v+, and atomized LNG flows from its tip.
It could be seen from the side glass attached to the side that the jet was flying out with air. It was ignited with a pilot burner, and secondary air was immediately introduced at a rate of 11,0 OONrrl'/H to continue combustion. The diameter of the opening of the secondary silver/liquid injection nozzle 3 was 500 mm, and it was located 800 mm downstream from the tip of the blowing air/liquid injection nozzle 2.

On the other hand, the flame-holding tube 8 has an inner diameter of 1,000 mm and a length of 6,000 mm.
It was made of 0mm refractory material. By using such a combustion device, it was possible to supply LNG in liquid form at low temperatures and achieve good combustion. NOx al
According to the ff constant, it was 40 to 60 ppm on a capacity basis. Exhaust gas circulation using flame-holding tubes was effective in reducing this.

[Brief explanation of the drawing]

1 and 2 are detailed explanatory views of the present invention. 1...LNG jet nozzle, 2...-Blow air/liquid injection nozzle, 3...Secondary silver/liquid injection nozzle, 4...LNG
Inlet part, 5...-large air supply pipe, 6... secondary air supply pipe, 7... pilot burner, 8... flame-holding tube,
9... Furnace wall, lO... Cylindrical gas holding member.

Claims (1)

[Claims] (1) In a combustion device for directly burning low-temperature liquefied fuel gas in a liquid state, (i) a liquid jet nozzle that coarsens the low-temperature liquefied fuel gas; (ii) surrounding the tip of the liquid jet nozzle; A primary air one-liquid injection nozzle having a primary air or oxygen supply pipe on the wall and a cylindrical gas holding member at the tip; (iii) surrounding the tip of the primary air one-liquid injection nozzle;
Secondary air for ignition 1 having a secondary air or oxygen supply pipe on the wall
A combustion device for low-temperature liquefied fuel gas, comprising: a combustion burner consisting of a liquid injection nozzle; and (iv) a flame-holding cylinder located downstream of the combustion burner.