JPS63113209A - Combustion method for low temperature liquefied fuel gas - Google Patents

Abstract

PURPOSE:To improve the combustion efficiency of liquefied natural gas, by a method wherein primary air is mixed in low temperature liquefied gas, by a method wherein primary air is mixed in low temperature fuel gas for evaporation to produce a mixing flow, and secondary air is mixed to atomize fuel liquid drops for ignition and combustion. CONSTITUTION:Primary air is introduced through a pipe 3 to an LNG nozzle 10 as it is swirled, and the primary air is accelerated by means of a swirl vane 4 to introduce it to a premixing chamber 6. LNG is mixed with swirled air in the premixing chamber 6, and the primary air is evaporated to produce a mixing flow of LNG, LNG liquid drops, and the primary air. The mixing flow is injected in a combustion chamber 7 where it is mixed and dispersed in secondary air introduced through a secondary air feed pipe 5. The mixture is ignited by means of a pilot burner, not shown. This constitution enables efficient combustion of liquefied natural gas to generate high temperature energy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method of burning and utilizing low-temperature liquefied fuel gas as an energy alternative to petroleum. In particular, the present invention relates to a method for efficiently burning liquefied natural gas to obtain high temperature energy.

[Prior art]

Liquefied natural gas (hereinafter referred to as LNG) was first used in large quantities industrially in 1969, when it was introduced from Alaska as a clean energy source. One of the reasons for introducing this NG is
It was used as a high-calorie gas fuel for household use, and the other was in response to social demands for pollution-free thermal power plants located in large cities. Furthermore, LNG has been well-received as a stable energy source even during the several oil shocks since 1971.

As a result, from a national perspective, LNG has come to be given a place alongside nuclear power and coal as an energy source that replaces petroleum. For example, there are plans to supply 44 million people with LIIIG electricity by fiscal 1985. Are standing.

If you look at the power source mix for the same fiscal year: oil, nuclear power, and coal at 49 million KV, 48 million KL, and 21 million KW, respectively, you can understand the relative importance of LNG.

However, the oil crisis made people widely aware of the importance of energy, and energy conservation efforts were made everywhere.
The industrial structure has changed to one that consumes less energy. In particular, over the past few years, total energy demand has been decreasing continuously, and the energy elasticity of GNP has become negative. As a result, the price of oil has dropped surprisingly, and combined with the appreciation of the yen, securing crude oil is no longer as urgent as it once was.

Due to its nature as a primary energy source, LNG is also prone to oversupply, and this trend is expected to increase, especially as LNG has potential supply destinations around the world, including Savarin and Canada.

However, in reality, when using LNG, since it is a liquid at a low temperature of -160℃,
Both the LNG import and export sides require large capital investments.
rTake or
There is a PayJ clause and the contract period is 15~
It has been going on for a long time of 20 years.

In other words, while the price of LNG does not rise easily, it is also difficult for it to fall, and we need to utilize it accordingly.

Looking at the status of natural gas usage around the world, 1. Outside of Japan, there are overwhelmingly many countries that use it as gas through pipeline transportation. For example, in the United States in 1978, LNG
1 billion Nm1/year, pipeline transportation is 263
It is Nri'/year. Speaking of Japan, this year it was 154.
All of the 11 million tons of natural gas was supplied as LNG. Therefore, L
The challenge for Japan is to find a way to utilize NG not as gaseous natural gas, but as liquid LNG, and to make it a reality.

[Problem to be solved]

As is well known, LNG is a low-temperature liquefied gas containing methane (C114) as its main component and having a boiling point of about -162°C. This is currently used as city gas and fuel for power generation, but all of it is vaporized and heated before being used in gas form. In other words, although it is imported into Japan as LNG, it reverts back to natural gas when it is used. Demand for LNG is expected to reach 31 million tons in fiscal 1988, but only about 6 million tons of this is essentially needed as city gas.

Isn't there a big loss in the process here? In fact, seawater is used as a heating source during this vaporization, and expensive materials such as aluminum and stainless steel are used for the equipment, creating a large cost burden when using LNG.

Furthermore, there is the problem of recovering cold energy that is wasted into seawater. Countermeasures have now been implemented such as air liquefaction separation, carbon dioxide gas liquefaction (solidification), and cryogenic storage.

In particular, air separation has a high cooling heat utilization efficiency because its usage temperature is close to the boiling point of LNG, and has already become the mainstream method in this field.

However, in these cases, demand cannot be expected to be sufficient to match the amount of LNG cold heat that can be supplied, and since it is inherently difficult to transfer cold heat, it is necessary that the LNG be located adjacent to a power plant or LNG terminal. , there are extremely large restrictions on location. LNG cold thermal power generation, which overcomes these drawbacks and has no problem with demand, has also been commercialized through technological development. However, at present, there are economic difficulties and there are doubts about further progress. In other words, the vaporization equipment is still L.
The cost accounts for a significant portion of NG usage.

The present invention has been made in an attempt to solve the above-mentioned problems in the use of LNG. In particular, in the prior art, LNG was vaporized and heated before being used as an ignition material, but if we consider the essence of LNG, it would be costly to burn LNG in its liquefied state. By omitting the need for vaporization equipment, LNG becomes more economical and easier to handle.Furthermore, by using it as a liquid, it can also be used in aircraft, ships, and automobiles as a high-energy-density fuel. It is clear that That is, the present inventors have confirmed that LNG is useful not only as natural gas, but that even greater technical advantages arise when it is used as a liquid. Therefore, the present inventors focused on the characteristics of LNG as a liquid and conducted research to develop an efficient combustion method for it.
The present invention has been accomplished.

[Means for solving problems]

That is, according to the present invention, 1. In a method of combusting low temperature liquefied fuel gas, a flow of primary air or oxygen is mixed with a stream of low temperature fuel gas in a liquefied state to vaporize a portion of the liquefied fuel gas and to form droplet particles of the liquefied fuel gas. Forming a mixed flow of the vapor of the liquefied fuel gas and the secondary air or oxygen, and jetting this mixed flow into the secondary air or oxygen flow to further atomize the droplet particles and ignite and burn them. It is characterized by A method is provided in which low-temperature liquefied fuel gas is directly combusted as a liquid without using vaporization equipment.

Hereinafter, the present invention will be described in detail using LNG as a representative low-temperature liquefied fuel.

The structure of the present invention is, firstly, that LNG is used directly without passing through vaporization equipment, unlike in the past.

Compared to natural gas in its vaporized state, LNG
Since it has a density 00 times higher, if it is burned as it is, a large energy density can be obtained, making it particularly useful as a power source for transportation. Second, combustion air or oxygen (hereinafter referred to as ``oxygen'') is introduced into the LNG liquid stream.

(also simply called air) is introduced as secondary air or oxygen. The amount of secondary air is in the range of 2 to 55 VO Q'A, more preferably 5 to 40 VO 0% of the theoretical air amount important for complete combustion. This is because if the amount exceeds this range, the concentration may fall below the excessively concentrated flammable limit concentration, and in some cases, there is a risk that an explosion phenomenon may occur.

On the other hand, when the amount is less than this range, combustion occurs simply by diffusion, resulting in a decrease in combustibility. In addition to the chemical aspects of combustion, this introduction of secondary air also aids in the atomization of the LNG due to the relative velocity difference between the liquid and gas streams.

Furthermore, since LNG is at its boiling point, introducing air will promote adiabatic vaporization. However, simply introducing secondary air does not atomize the LNG and do not secure enough surface area for combustion.As a third means, a premixture of LNG droplets and primary air is injected into the nozzle. The amount of secondary air is 1.01 to 1.10 times the theoretical air amount minus the large air amount mentioned above. is desirable. This amount of secondary air is large compared to the amount of primary air, so L
It is suitable for atomizing and burning NG.

Next, the present invention will be explained with reference to the drawings. The drawing is a system diagram of a combustion apparatus for carrying out the combustion method of the present invention.

In the drawings, reference numeral 10 indicates an LNG/secondary air mixer (burner), and the whole has a double pipe structure consisting of an outer pipe l and an inner pipe 2 as an LNG supply pipe (nozzle), and the outer pipe l is provided with a primary air supply pipe 3 having an opening 11 that penetrates its peripheral wall and allows secondary air to flow out in the circumferential direction, and a swirl vane 4 is provided on the outer surface of the tip of the inner pipe 2. There is.

LNG is supplied to the inner tube 2 in a liquid state, and secondary air is supplied from the supply tube 3 into the outer tube 1. The primary air introduced in the circumferential direction through the opening of the supply pipe 3 is accelerated by the swirl vane 4 and sent to the premixing chamber 6, where it is mixed with the LNG flowing out from the tip of the inner pipe 2.

In this premixing chamber 6, LNG is made into coarse particles due to the relative speed difference with the primary air flow, and a portion of the LNG is vaporized by the sensible heat of the primary air, resulting in LNG droplet particles and LNG.
A mixed stream of NG vapor and primary air is formed. This mixed flow is ejected into the secondary mixing chamber 7 from the tip of the outer tube 1, and is diffused and mixed into the secondary air supplied from the secondary air supply pipe 5. By ejecting this mixed flow into the secondary air, the LNG droplets are further atomized and burned while forming a flame 8 within the combustion chamber a. Note that 9 indicates the combustion chamber wall.

〔effect〕

According to the combustion method of the present invention, LNG is burned in a liquid state without being vaporized, so it is first of all economical, and conventional vaporization equipment can be completely eliminated.
Its economic efficiency is obvious. Until now, vaporization equipment was
It is the core equipment at LNG terminals and has been required to have extremely high reliability.

It also needed to have the ability to follow load fluctuations in power generation equipment, which is the demand side, as well as operational stability and safety. Furthermore, since the fluids to be handled range from low-temperature liquids to gases, advanced technology has been required, including the use of materials with excellent low-temperature properties and the prevention of droplet entrainment due to unstable boiling. In addition, since these materials often use seawater as a heat source, it has been required to give sufficient consideration to corrosion resistance. These technical and economic problems are solved at once by the present invention.

According to the method of the present invention, since combustion is based on the atomization of liquid, the fuel energy density is 600 times greater than that of natural gas, and the amount of combustion per unit volume is overwhelmingly large, so the combustion chamber is large. The size is extremely small compared to that of a gaseous combustion chamber.

To burn liquid fuel, generally, fluid atomizing by adding steam or the like, or mechanical atomizing by dispersing liquid from the outer periphery of a rotating body by centrifugal force, is used. In the method of the present invention, since LNG is a liquid that easily vaporizes, LNG is used as a part of the combustion air as primary air, rather than as a pressure source like steam.
By mixing LNG with G, there is an advantage that primary particleization of LNG is easily performed. Moreover, this premix is
Since it is carried out at the upper limit of the flammability limit concentration of LNG, it has the great advantage of being carried out safely.

Combustion of LNG partially mixed with combustion air means that the LNG as a whole is converted into a gas/liquid mixed fluid and then combusted in secondary air. It has excellent ignitability even with low temperature fluids of −100° C. or lower, and it is possible to easily obtain a stable flame. In addition, since the combustibility is good, the overall amount of combustion air is very close to the theoretical amount, which is practically 1-1.
Complete combustion is possible with 0% excess air.

Such a small excess air ratio has the advantage of reducing the size of particles that produce NOx, which is a component of air pollution, and the burner used in the method of the present invention essentially becomes a low NOx burner. More proactively, the NOx generated can be further reduced by installing a self-made means of circulating exhaust gas using the fluid energy generated when LNG evaporates in the combustion chamber as it rapidly receives indoor radiant heat. is also easy.

Another advantage of the present invention is that LNG can be advantageously used not only as a fuel for power generation, but also as a fuel for transportation, taking advantage of its high energy density. LNG
Although it was considered as a fuel for automobiles, one of the reasons why it was not put into practical use is not only the problem of the fuel tank, but also the conventional idea that the engine would have to inhale vaporized gas. This resulted in a decrease in output. However, according to the present invention, since LNG is injected as a liquid, the energy density is high and there is no such problem. You can make an engine. The method of the invention can also be applied to aircraft gas turbines. Since LNG is maintained at almost normal pressure, the container can be made of lightweight metals such as aluminum and titanium, which are conventionally used in aircraft, and these aircraft metals can be stored at temperatures as low as -160°C. Its toughness makes its use extremely convenient. In particular, when an aircraft is cruising, the temperature is low at high altitude, so the LNG tank is at a low temperature (-50°C).
℃ or less), which has the advantage that gasification of LNG due to heat loss is minimized. Of course, minor measures will be necessary, such as processing the LNG gas generated on the ground with a gas turbine and using it for air conditioning. In any case, by using the method of the present invention that utilizes the high-density energy characteristics of LNG, including for ships,
It becomes possible to use LNG as a power source for transportation vehicles.

Further, the method of the present invention is similarly applicable to other low-temperature liquefied fuel gases such as LPG in addition to LNG.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 LNG was combusted using the combustion equipment system shown in the drawings.

That is, g/H is added to LNG 160 in tube 2 (inner diameter 10 mm
) was introduced from. Most of this tube 2 was kept cool with ordinary cold insulating material, but the burner section had a double tube structure (the annular space was evacuated) to avoid evaporation of the LNG. −
Large air 50ON/H has a temperature of 20℃ and a pressure of 400mm.
H2O was introduced through tube 3 (inner diameter 150 mm). This-
The large air is introduced into the LNG nozzle 10 in a swirling manner, is further accelerated by the swirling vane 4, and is then introduced into the premixing section 6.
was introduced to. The LNG is mixed with the swirling air in the premixing section 6, and is made into coarse particles due to the relative speed difference with the air flow.
Some of it was vaporized by the sensible heat of the air. L of premixing section
Since the NG supply pipe (nozzle) 2 is made of ceramic together with the swirling blades 4 that extend outward from it, freezing due to moisture in the air can be virtually ignored on the outside thereof.

The premixed LNG/N low/compound is then injected into the combustion chamber 7, mixed and diffused into the secondary air 180ONm/II introduced from the secondary air supply pipe (inner diameter 300mm) 5,
When this was ignited by a pilot burner (not shown), a stable flame 8 was formed. The open end of the secondary mixing chamber 7 protruded into the combustion chamber a by about 500 mm from the combustion chamber wall 9, so that the secondary air and the LNG particles were sufficiently mixed.

[Brief explanation of the drawing]

The drawing is a system diagram of a combustion device for implementing the present invention. l...Outer pipe, 2...LNG supply pipe, 3...-large air supply pipe, 4...swivel vane, 5...secondary air supply pipe, 6...premixing chamber, 7... Secondary mixing chamber, 8... Flame, 9... Combustion chamber wall, a... Combustion chamber.

Claims (1)

[Claims] (1) In a method of burning low-temperature liquefied fuel gas, a flow of primary air or oxygen is mixed with a flow of low-temperature fuel gas in a liquefied state to vaporize a portion of the liquefied fuel gas, and the liquid of the liquefied fuel gas is A mixed flow of the droplet particles, the vapor of the liquefied fuel gas, and the primary air or oxygen is formed, and this mixed flow is jetted into the secondary air or oxygen flow to further atomize the droplet particles, and ignite and burn them. A method for directly burning low-temperature liquefied fuel gas in its liquid state without using vaporization equipment.