JPH04214106A - Method of burning foamed liquid fuel and its method - Google Patents

Abstract

PURPOSE:To make the evaporation of the fuel easy and stabilize further the combustion by supplying air through a porous element to form foamed fuel uniformly, stabilizing the foaming property, and supplying the air required for complete combustion separately. CONSTITUTION:A wind box 7 for supplying the combustion air is provided outside a burner 4 that is positioned above an evaporation pan 3, and the liquid fuel is supplied to the upper section of a porous element 2 that is internally in contact with a foam forming device 1, and the fuel ascends in the state of foam that is a congregation of foams of small diameter by the air from a supply pipe 5 for the gas of foam formation. By the way the average diameter of the air pores in the porous element 2 that is provided below the recess 23 below the bottom face of the evaporation pan 3 is over 1mum and below 200mum. Accordingly the foams become a congregation of small foams by making the resistance of the gas for foaming small and limiting the superficial velocity through the porous element section 2, and it is possible to achieve a stable ignition and continuous combustion.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for foaming and burning liquid fuel, particularly light oil fuel (kerosene, light oil, etc.) for use in a wide range of applications from household kerosene stoves to industrial kilns, and a combustion apparatus for the same. It is something.

0002

BACKGROUND OF THE INVENTION Conventional combustion methods include either directly vaporizing liquid fuel and burning it, or splitting it into fine mist using a spray device and then burning it. In Japanese Patent Application Laid-Open No. 1-95205, the present applicant proposed a completely new liquid fuel foam combustion method that expands the range of variable combustion amount of liquid fuel and improves the drawbacks of the pot type and spray combustion methods.

Furthermore, in Japanese Patent Application Laid-Open No. 2-21106, the porous filter (element) used in the foam generator is made of a material having a surface property with a critical surface tension lower than that of the liquid fuel, thereby reducing combustion. We proposed a combustion device that prevents backflow of fuel when extinguishing a fire. Furthermore, in Japanese Patent Application Laid-open No. 2-259311, the present applicant has provided a combustor, an evaporation plate, and a foam generator in close proximity, supplies liquid fuel to the outside of a porous element in the foam generator, and supplies foam to the inside of the porous element. The present invention proposes a method and an apparatus for turning liquid fuel into foam by supplying a gas for use, significantly increasing the evaporation area of the fuel, and immediately combusting the fuel.

0004

[Problem to be Solved by the Invention] In such foaming combustion, if the amount of air from the gas supply pipe 6 is increased too much while keeping the fuel supply amount constant, the fuel may become droplets, resulting in unstable combustion. There is. The foaming combustion of liquid fuel depends on the average pore diameter of the porous elements that make up the foam generator and the superficial velocity of the foaming gas (the gas flow velocity calculated assuming that there is no porous element). Stability is greatly affected. The present invention provides a combustion method and apparatus that achieves uniformity and stabilization of foaming properties of foamy fuel, facilitates fuel evaporation, and achieves even more stable combustion. Here, the uniformity of foamy fuel means that the variation in the diameter of each bubble forming the foam (aggregation of bubbles) is small. Furthermore, stabilization of foamability means that the diameter of each bubble is small and the foaming ratio (volume of foam/volume of liquid) is stably large.

[0005]

[Means for Solving the Problems] The present invention provides a method for converting air into foam with an average pore size (opening) of 1 μm in the foaming combustion of liquid fuel.
As described above, after supplying liquid fuel through a porous element with a diameter of 200 μm or less and turning the fuel into foam consisting of an aggregate of bubbles with a small diameter, air necessary for complete combustion of the foamed fuel in a combustor is separately removed. It is a method of supplying and combusting it and a device that embodies the same, and the apparent velocity of the foaming gas passing through the porous element, that is, the superficial velocity, is 0.01 m/s or more and 1 m/s or less. It includes.

[0006] That is, the gist of the present invention is to
(1) The liquid fuel has an average pore diameter (opening) of 1 μm or more,
After supplying air through a porous element with a diameter of 200 μm or less to turn the fuel into foam consisting of an aggregate of air bubbles with a small diameter, air necessary for complete combustion of the foamed fuel in a combustor is separately supplied. This is a foaming combustion method for liquid fuel that is combusted, and if necessary, the apparent velocity at which the foaming gas passes through the porous element, that is, the superficial velocity, is reduced to 0.
．． 01 m/s or more and 1 m/s or less.

[0007] Furthermore, the present invention has an average pore diameter of 1 μm or more, 2 μm or more.
00 μm or less; a foam generator that connects a gas supply pipe to the porous element to form a foaming region; This is a liquid fuel foaming combustion device consisting of a combustor that supplies fuel to form a combustion zone, and if necessary, a porous element with a density of 4.0 to 6.0 gr/cm3.
The porous element is made of a ceramic body with a density of 2.0 to 5.0 gr/cm3 and an apparent porosity of 15 to 45%. The opening direction of the porous element is set horizontally to prevent obstruction of the foaming function due to soot and scale, and the opening direction of the porous element is set downward to prevent obstruction of the foaming function due to soot and scale, and the porous element has a ring-shaped shape. It's in what you're doing.

FIG. 1 is a longitudinal sectional view of a main part showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. Figure 3(a)(b)
) is a chart showing the relationship between the average pore diameter of the porous element and the ventilation resistance and the relationship between the ignition stability in the present invention. FIG. 5 is a chart showing the relationship between superficial velocity and expansion ratio in the present invention. 6 and 7 are longitudinal cross-sectional views of main parts showing other configuration examples of the foam generator related to the present invention, and FIG.
b) is a BB sectional view of FIG. 6(a).

[0009]

[Operation] The present invention will be explained below based on the drawings. Figure 1
2 shows an embodiment of the present invention, and is an explanatory diagram showing a main part thereof in a longitudinal section, and FIG. 2 is a sectional view taken along the line AA in FIG. 1. FIG. 1 is a foam generator, 2 is a porous element having a function of foaming fuel, and 3 is an evaporating dish. Reference numeral 4 denotes a combustor, and below the combustor 4, an evaporating dish 3 and a foam generator 1 for generating foam are disposed in series and close to each other below the evaporating dish 3.

[0010] The combustor 4 located above the evaporating dish 3 is provided with a wind box 7 on the outside thereof for supplying combustion air. The liquid fuel is supplied to the upper part of the porous element 2 which is inscribed in the foam generator 1, but since a gas represented by air is blown in advance from the foaming gas supply pipe 5 provided at the lower part, the fuel ( (kerosene, diesel oil, etc.) immediately foams and rises in a foamy state consisting of a collection of small-diameter air bubbles.

[0011] This foam is directly ignited by the ignition heater 13 to continue combustion. The liquid fuel used for combustion is usually kerosene, but light oil can also be used. These liquid fuels are supplied from a fuel tank 10 through a pump 11 and a fuel supply pipe 6. A flame stabilizer 9 pairs with the combustion ring 14 to stabilize continuous combustion, and is provided inside the combustor 4. 12 indicates a flame. The foam generator 1 is provided below the center of the evaporating dish 3. Inside the foam generator 1, a porous element 2 is provided below a recess 23 provided below the bottom surface of the evaporating dish. In the illustrated example, a gas supply pipe 5 for foaming is connected to the porous element 2 from below to form a foaming region a. The porous element 2 provided in this way plays an extremely important role in making the foamed fuel uniform and stabilizing the foamability. It is characterized in that it is 1 μm or more and 200 μm or less. Figure 3(a) shows the pressure loss in the ignition and extinguishing tests. Further, FIG. 3(b) shows the misfire frequency during ignition. All of these are based on experiments by the inventors. According to these tests, the average pore diameter of the porous element was 1μ.
It has been found that when it is less than m, the ventilation resistance of the foaming air increases and eventually clogging occurs. Furthermore, it has been found that if the diameter exceeds 200 μm, the diameter of the bubbles forming the foam becomes large as a whole, causing supply air to blow through, making it impossible to form stable foam.

Furthermore, according to experiments conducted by the present inventors, in order to increase the contact area between the fuel and the foaming air and bring the amount of fuel evaporation to the heating range necessary for ignition and combustion, it is necessary to It has been found that it is necessary to create foam with a foaming ratio of 5 times or more. However, even if the average pore diameter of the porous element is set appropriately, the expansion ratio changes depending on the type of fuel and temperature, as shown in Figure 4. .01m/s or more,
A range of 1 m/s or less is selected as an appropriate range.

That is, when the superficial velocity becomes less than 0.01 m/s, most of the bubbles remain in the liquid fuel and are separated, although the temperature of the liquid fuel varies, that is, the bubbles shown in FIG. Bubbles form in the separation zone, resulting in a lack of fuel vapor necessary for ignition and continued combustion at the type and temperature of fuel normally used. Furthermore, when the superficial velocity exceeds 1 m/s, a mass of gas blows through the liquid fuel, and stable bubbles are no longer formed, making ignition and continued combustion unstable.

Next, the specific structure of the porous element embodying the present invention will be described. Practical porous elements having an average pore diameter of 1 μm or more and 200 μm or less include, for example, porous sintered metals and ceramics. When using sintered metal for the porous element, the sintered body should have a density of 4.0 to 6.0 gr/cm3 and a porosity of 35 to 45%, and when using a ceramic body, the ceramic body should have a porosity of 35 to 45%. Density is 2.0~5.0gr
/cm3, and the apparent porosity is preferably 15 to 45%.

[0015] According to other experiments conducted by the present inventors, soot is produced due to long-term combustion or scale falls from a flame stabilizer, etc. In such cases, the porous element 2 is It is preferable to configure the foam generator with the openings facing sideways as shown in FIG. 6 or facing downwards as shown in FIG. 7. That is, in the example shown in FIG. 6, the porous element 2 is formed into a ring shape, and the foaming gas is supplied from the foaming gas supply pipe 5 in the tangential direction. According to these examples, since fuel soot and scale do not accumulate on the element, stable ignition and combustion can be continued.

As shown in FIG. 2, the foam generator, evaporating dish, and combustor according to the present invention are not limited to circular planes, and may include modifications such as square or rectangular planes. In either case, according to the configuration of the present invention, the amount of fuel supplied from the fuel supply pipe 6 and the amount of air supplied from the foaming gas supply pipe 5 are increased to increase the amount of foam produced,
By increasing the amount of air from the combustion air pipe 8, the amount of combustion can be easily increased, and its variable range is sufficiently wide.

[0017]

[Example] Examples and comparative examples in which combustion is performed in the following combustor with the same configuration as the embodiment shown in FIG. 1 will be described. The specifications of the combustor and foam generator used here are as follows.・Diameter x height of combustor
:Inner diameter 150mmφ×150mm ・
Diameter x height of foam generator: Inner diameter 40mmφ x 20mm・Diameter x thickness of porous element: Effective diameter 40m
mφ x 2mm (sintered metal and ceramic body) ・Evaporation dish inverted conical upper edge diameter x bottom diameter: Inner diameter
150mmφ×40mmφ・Flame holder
:The flame holder combustion test with a combustion ring consists of a long-term repeated continuous test in which the combustion is continued for 48 hours after ignition and extinguished, and the ignition test is repeated for 30 minutes after ignition, then extinguished, stopped for 15 minutes, and the test is repeated again. The fire extinguishing test was conducted separately.

In the long-term continuous test, a predetermined amount of air is supplied from the combustion air pipe 8 of the combustor 4, and then a predetermined amount of air is supplied from the foaming gas supply pipe 5 connected to the porous element 2 having a diameter of 40 mm. While supplying air, a predetermined amount of kerosene was supplied via the pump 11 to the upper part of the porous element 2 provided internally in the foam generator 1. Here, the kerosene immediately becomes foam and is ignited by the ignition heater 13, and after about 2 minutes, the air ratio and combustion amount are adjusted to a predetermined air ratio and combustion amount continues. after that,
After the combustion reached a steady state, CO, NOx, BR (soot), and aldehyde in the combustion exhaust gas were measured every 4 hours. The results are shown in Table 1 along with comparative examples.

[0019]

[Table 1]

As shown in Table 1, the present invention was good in all combustion characteristic values. These results mean that the foaming combustion of liquid fuel not only promotes evaporation of the fuel, but also greatly improves the uniformity of mixing the evaporated fuel and the combustion air.

[0021] Table 2 also shows the combustion characteristic values organized according to the average pore diameter (mesh opening) and superficial velocity of the porous element. This result also shows that the range of average pore diameter and superficial velocity range of the porous element shown in the present invention is effective. As shown in the comparative example in Table 1, even if the average pore diameter (opening) of the porous element is within the range of the present invention, if the superficial velocity deviates from the range of the present invention, the best combustion The condition was unobtainable.

[0022]

[Table 2]

[0023] In addition, the superficial velocity of the porous element has a large effect on the stability of ignition near the limit of opening, and
Even in long-term continuous tests, as shown in Table 2, it not only affects CO, NOx, and BR (soot) in the combustion exhaust gas, but also affects the extinguishing time shown in Figure 5. In all of these combustion test results, the superficial velocity of this porous element portion was within the appropriate range of 0.01 to 1 m/s.

[0024]

Effects of the Invention In the present invention, the average pore diameter (opening) of the porous element of the foam generator is optimally selected, so the ventilation resistance of the foaming gas can be reduced, and the superficial velocity of the porous element can be reduced. By limiting the amount, the generated foam becomes an aggregate of small bubbles with a diameter of 0.5 to 5 mm, achieving stable ignition and continuous combustion, which has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of essential parts showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIGS. 3(a) and 3(b) are charts showing the relationship between the average pore diameter of the porous element and the ventilation resistance and the relationship between the ignition stability in the present invention.

FIG. 4 is a chart showing the relationship between superficial velocity and expansion ratio in the present invention.

FIG. 5 is a chart showing the relationship between superficial velocity and extinguishing time in an example of the present invention.

FIG. 6(a) is a vertical cross-sectional view of essential parts showing another configuration example of the foam generator according to the present invention, and FIG. 6(b) is a vertical cross-sectional view taken along line BB in (a).

FIG. 7 is a vertical cross-sectional view of essential parts showing another configuration example of the foam generator according to the present invention.

[Explanation of symbols]

1 Foam generator 2 Porous element 3 Evaporating dish 4 Combustor 5 Gas supply pipe for foaming 6 Fuel supply pipe 7 Wind box 8 Combustion air supply pipe 9 Flame holder 10 Fuel tank 11 Pump 12 Flame 13 Ignition heater 14 Combustion ring

Claims (8)

[Claims] [Claim 1] The liquid fuel has an average pore diameter (opening) of 1.
After supplying air through a porous element with a size of µm or more and 200 µm or less and converting the fuel into foam consisting of an aggregate of air bubbles with a small diameter, air necessary for complete combustion of the foamed fuel in a combustor is separately supplied. A method for combusting liquid fuel into foam by supplying and combusting it. [Claim 2] The apparent velocity at which the foaming gas passes through the porous element, that is, the superficial velocity is 0.01 m/s.
The method for foaming and combustion of liquid fuel according to claim 1, wherein the combustion rate is 1 m/s or less. [Claim 3] Average pore diameter is 1 μm or more, 200 μm
a porous element as follows; a foam generator connecting a gas supply pipe to the porous element to form a foaming region;
A combustor for foaming and combusting liquid fuel, which comprises a combustor that is disposed close to the upper part of the foam generator and that supplies combustion air to the foamed fuel to form a combustion zone. 4. The porous element has a density of 4.0 to 6.0.
4. The liquid fuel foaming combustion apparatus according to claim 3, wherein the liquid fuel foaming combustion apparatus is made of sintered metal having a porosity of 0 gr/cm3 and a porosity of 35 to 45%. 5. The porous element has a density of 2.0 to 5.
4. The liquid fuel foaming combustion apparatus according to claim 3, which is constructed of a ceramic body having an apparent porosity of 0 gr/cm3 and an apparent porosity of 15 to 45%. 6. The liquid fuel foaming combustion device according to claim 3, wherein the opening direction of the porous element is oriented horizontally to prevent the foaming function from being impaired by soot or scale. 7. The liquid fuel foaming combustion device according to claim 3, wherein the opening direction of the porous element is directed downward to prevent obstruction of the foaming function due to soot and scale. 8. The liquid fuel foaming combustion device according to claim 6, wherein the porous element has a ring shape.