JPH04301169A - Combustor - Google Patents

Abstract

PURPOSE:To reduce the soot in the exhaust to be exhausted after combustion effectively and easily. CONSTITUTION:In a first heat exchanger 9, gas oil as fuel is heated by the exhaust heat exhausted from a combustion chamber of an engine main frame 1 to vaporize methane gas. The methane gas is introduced to a second heat exchanger 33 with the steam generated by a steam generating machine 11, and is heated again by the exhaust heat, and thereafter, the methane gas is reformed into hydrogen and carbon monoxide through the catalyst 45. This reformed gas is supplied to the above-mentioned combustion chamber through an intake pipe 5 to accelerate combustion and reduce the quantity of soot produced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus in which air and fuel are supplied to a combustion chamber and combusted, and the combustion gas is discharged from the combustion chamber as exhaust gas.

0002

[Prior Art] Generally, combustion gas, alcohol fuel, and biomass fuel are burned in internal combustion engines, gas turbines, industrial boilers, power generation boilers, water heaters, high-temperature gas furnaces, etc. that use fossil fuels such as oil and coal. If the soot contained in the exhaust gas of combustion gas is released into the atmosphere as it is, it will cause environmental pollution and is undesirable.

For example, in the case of a diesel engine, light oil or alcohol-mixed fuel is injected into the compressed air in the combustion chamber to generate a mixture of air and fuel, which is then ignited spontaneously. In order to achieve proper combustion, it is essential to create a uniform air-fuel mixture throughout the combustion chamber, and it is extremely difficult to create such a uniform air-fuel mixture. The generation of a non-uniform air-fuel mixture means that there are places where there is a local lack of air (or oxygen). In this air-deficient state, fuel particles are thermally decomposed in the high-temperature gas in the absence of oxygen, and the hydrogen contained in the fuel is selectively and quickly combusted, leaving only carbon, and the fine particles are bonded to each other. It becomes soot. This soot is released into the atmosphere along with exhaust gas and causes pollution, so regulations are becoming stricter.

Conventionally, measures to remove soot include (1) improving combustion by generating a swirling flow of air to uniformly mix air and fuel spray within the combustion chamber;

(2) Combustion is improved by improving fuel injection pumps and combustion injection nozzles.

(3) Lean combustion.

(4) Soot discharged from the combustion chamber is collected using a filter made of ceramic or the like in the middle of the exhaust system, and the collected soot is periodically combusted with high-temperature gas (generated by a heater). There are other methods.

As a method of using a filter, for example, Japanese Utility Model Application No. 61-181814 discloses that a combustible substance having a lower reaction temperature than light oil is placed upstream of the filter at a time when the filter is regenerated when soot has accumulated and at a specified exhaust temperature. Techniques are disclosed for dispensing and combusting the collected soot when it is present in the area.

[0009]

[Problems to be Solved by the Invention] However, with these methods, there is a limit to the soot reduction effect achieved by improving combustion, and a large amount of reduction cannot be expected. Although this decreases, nitrogen oxides (NOx) increase, and there is a risk that the limit of the NOx regulation value will be exceeded. In addition, the method of collecting soot with a ceramic filter involves periodically flowing high-temperature gas through the ceramic filter, which may cause damage, and if the ceramic filter becomes clogged with soot, the exhaust pressure increases and engine performance decreases. Therefore, there is a problem in that removal work must be carried out frequently.

[0010] Accordingly, an object of the present invention is to efficiently and easily reduce soot in exhaust gas discharged after combustion.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a combustion apparatus in which air and fuel are supplied to a combustion chamber and combusted, and the combustion gas is discharged from the combustion chamber as exhaust gas. , the combustion chamber is configured to supply at least one of hydrogen gas and carbon monoxide gas.

0012

[Operation] By supplying at least one of hydrogen gas and carbon monoxide gas to the combustion chamber in addition to air and fuel, the amount of hydrogen or carbon monoxide in the combustion chamber is increased. When burned in this state, combustion is promoted and the remaining amount of carbon contained in the fuel is reduced, reducing the amount of soot generated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a combustion apparatus showing an example in which the present invention is applied to a diesel engine. Engine body 1
A fuel pipe 3 into which light oil flows as fuel and an intake pipe 5 into which air flows are connected to the combustion chamber. One end of an exhaust pipe 7 through which exhaust gas burned and exhausted in the combustion chamber flows out is also connected to the combustion chamber. Heat radiating portions 7a and 7b in the middle of the exhaust pipe 7 are arranged inside the first heat exchanger 9 and the steam generator 11, respectively, and the other end is open to the atmosphere. A control valve 13 is provided in the exhaust pipe 7 between the first heat exchanger 9 and the steam generator 11, and a temperature sensor 15 is provided in the first heat exchanger 9, which are connected to a control circuit 17. The amount of exhaust gas flowing to the heat radiation portion 7a is controlled.

Between the first heat exchanger 9 and the fuel pipe 3, there is a fuel branch pipe 19 for supplying part of the fuel to the first heat exchanger 9;
and a fuel return pipe 21 that returns the used fuel to the fuel pipe 3.
are connected to each other. A flow rate sensor 23 and a control valve 25 are respectively installed in the fuel branch pipe 19, and these are connected to a control circuit 27 and controlled so that a desired amount of fuel is supplied to the first heat exchanger 9. The steam generator 11 includes a pipe 29 for supplying water into the steam generator 11.
is connected.

One end of an exhaust branch pipe 31 is connected to the middle of the exhaust pipe 7 between the engine body 1 and the first heat exchanger 9. A heat radiating portion 31a in the middle of this exhaust branch pipe 31 is disposed within the second heat exchanger 33, and the other end is open to the atmosphere. A control valve 35 is provided in the exhaust branch pipe 31 between the second heat exchanger 33 and the exhaust pipe 7, and a temperature sensor 37 is provided in the second heat exchanger 33.
The amount of exhaust gas flowing to the heat radiation portion 31a is controlled. The second heat exchanger 33 and the steam generator 11 are connected by a steam pipe 41 so that the steam generated in the steam generator 11 is introduced into the second heat exchanger 33.

The first heat exchanger 9 and the second heat exchanger 33 are connected through a gas pipe 43, and methane gas and small amounts of propane and ethane gas, which are evaporated by heating diesel oil with exhaust heat, are transferred to the second heat exchanger 9 and the second heat exchanger 33.
It is designed to be introduced into a heat exchanger 33. Also, the second
A catalyst 45 is housed in a portion of the heat exchanger 33 opposite to the communicating portion of the gas pipe 43 . The catalyst 45 is made of nickel, ruthenium, platinum, or the like, and in this example, an inexpensive nickel catalyst is coated on a mixed carrier of ceramic and resin.

The side of the second heat exchanger 33 where the catalyst 45 is provided and the intake pipe 5 are connected through a reformed gas pipe 47, and the methane gas etc. introduced into the second heat exchanger 33 is converted into water vapor. Hydrogen gas and carbon monoxide gas, which are produced by mixing with the hydrogen gas and reforming through the catalyst 45, are introduced into the combustion chamber of the engine body 1. This reformed gas pipe 47 is provided with a fan 49 that feeds the reformed gas toward the combustion chamber.

Next, the operation of the combustion apparatus constructed as described above will be explained.

Light oil and air are supplied to the combustion chamber of the engine body 1 through the fuel pipe 3 and the intake pipe 5 and are combusted, and the combustion gas flows out into the exhaust pipe 7 as high-temperature exhaust gas. When the exhaust gas passes through the heat radiation part 7a in the first heat exchanger 9, the light oil introduced from the fuel branch pipe 19 is heated by this exhaust heat (200 to 250°C), and remains in the light oil. Evaporate methane gas and small amounts of propane and ethane gas. The used light oil after these gases have evaporated is returned to the fuel pipe 3 through the fuel return pipe 21, and is supplied to the engine body 1 as part of the fuel. Evaporated methane gas and the like are introduced into the second heat exchanger 33 through the gas pipe 43.

On the other hand, water is supplied to the steam generator 11 through a pipe 29, and the water is heated by the heat of the exhaust gas flowing through the heat radiation part 7b via the heat radiation part 7a of the exhaust pipe 7, and steam is generated. This water vapor is supplied through the steam pipe 41 into the second heat exchanger 33 into which the methane gas is introduced, and the two are mixed. This mixed gas is heated to 300 to 400°C by the heat of the exhaust gas passing through the heat dissipation portion 31a from the exhaust branch pipe 31, and in this state, the catalyst 45
pass through. At this time, the mixed gas is chemically changed into hydrogen gas and carbon monoxide gas and reformed. The chemical formula in this case is as follows.

CH4 +H2 O→3H2 +CO Hydrogen gas and carbon monoxide gas obtained by reforming flow out into the reformed gas pipe 47, are forcibly sent to the intake pipe 5 by the fan 49, and are sent to the engine body along with air. 1 combustion chamber, where it is compressed. Light oil from the fuel pipe 3 is injected into this compressed air just before the compression top dead center of the piston, but since the combustion chamber contains more hydrogen and carbon monoxide, it is in a state where it is easy to burn. As a result, the amount of residual carbon is small, and soot generation is suppressed. Additionally, the combustion rate of hydrogen is generally about 1 that of diesel oil.
It is extremely fast, 0 times faster, and the flame is stable at high temperatures, so even if cold fuel spray is injected here to cool the flame, little soot will be generated.

The above-mentioned device uses the thermal energy of the exhaust gas and the catalyst 45 to heat and evaporate methane gas contained in light oil, which is the fuel, and introduces hydrogen and carbon monoxide into the intake system. Since it uses on-board reforming, there is no need to supply energy from the outside, and there is no need to prepare a high-pressure cylinder for supplying hydrogen, making it possible to efficiently and reliably achieve soot reduction effects. Further, since no filter is provided in the exhaust passage, an increase in exhaust pressure and a decrease in engine output due to this can be avoided.

FIG. 2 shows the relationship between the hydrogen addition rate to the intake system and the corresponding soot concentration in the exhaust gas. Here, a single-cylinder 4-stroke diesel engine is used, and the rotation speed is 2.
The soot concentration was measured at 500 rpm and an output of 7.5 PS. This soot concentration is determined by a method that detects the degree of contamination by shining light onto the filter of a smoke meter that collects soot. According to this, the soot concentration was 10% and 9.5% when 1% and 2% hydrogen was added, respectively, which was significantly reduced compared to 38% when no hydrogen was added (0%). I understand that.

FIG. 3 shows the relationship between the crank angle (compression top dead center is 0 degrees) and the combustion chamber pressure at an intake negative pressure of 73 mmHg at the engine inlet and an intake air temperature of 24° C. in the single-cylinder four-stroke diesel engine. 2% by volume relative to intake air
A comparison is shown between the case where hydrogen is added (dashed line) and the standard state where no hydrogen is added (solid line). According to this, the pressure in the combustion chamber near compression top dead center is higher when hydrogen is added, the ignition delay period is shorter, the combustion period is shortened, and combustion is completed quickly within the early crank angle of the expansion stroke. This also results in increased output, improved thermal efficiency, and prevention of incomplete combustion.

FIG. 4 shows that a reformed gas of hydrogen and carbon monoxide is produced using the apparatus of FIG.
．． The broken line shows the relationship between the crank angle (compression top dead center at 0 degrees) and the combustion chamber pressure when the above-mentioned single-cylinder four-stroke diesel engine is operated in a state containing 0.05%. The solid line is the case without hydrogen. The operating conditions are a rotation speed of 2500 rpm and an output of 7.5 PS. Here, the amount of hydrogen added is small, but this is because the exhaust gas is cooled before it flows into the second heat exchanger 33 and has a hydrogen content of about 300 to 350%.
This is because the water flowed in at a temperature of ℃. Therefore, in order to increase the amount of hydrogen added, measures such as keeping the exhaust branch pipe 31 warm may be taken.

In the above embodiment, hydrogen and carbon monoxide are supplied to the combustion chamber, but only hydrogen or only carbon monoxide may be supplied to the combustion chamber. Also,
Although the explanation is given using a diesel engine as an example, the explanation is not limited to this, but it also applies to gas turbines, industrial boilers, power generation boilers, water heaters, and high-temperature gas furnaces that use fossil fuels such as oil and coal, as well as alcohol fuels and biomass fuels. The present invention may be applied to a combustion device.

[0028]

[Effects of the Invention] As explained above, according to the present invention, at least one of hydrogen gas and carbon monoxide gas is supplied to the combustion chamber to which air and fuel are supplied for combustion. , the content of hydrogen or carbon monoxide in the combustion chamber is increased, combustion is promoted, the amount of carbon remaining in the fuel is reduced, and the amount of soot generated can be efficiently reduced. Further, since no filter is provided in the exhaust passage, an increase in exhaust pressure and a decrease in engine output due to this can be avoided.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a correlation diagram between hydrogenation rate and soot concentration.

FIG. 3 is a correlation diagram between the crank angle and the pressure in the combustion chamber when 2% hydrogen is added and when it is not added.

FIG. 4 is a correlation diagram between the crank angle and the pressure in the combustion chamber when the combustion apparatus of FIG. 1 is used, with and without the addition of reformed gas.

[Explanation of symbols]

1 Engine body 3 Fuel pipe 5 Intake pipe 7 Exhaust pipe 9 First heat exchanger 11 Steam generator 33 Second heat exchanger 47 Reformed gas pipe

Claims (1)

[Claims] 1. A combustion device in which air and fuel are supplied to a combustion chamber and combusted, and the combustion gas is discharged from the combustion chamber as exhaust gas, wherein at least hydrogen gas and carbon monoxide gas are present in the combustion chamber. A combustion device characterized by supplying either one of them.