JPS5844115B2 - How to suppress combustion gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suppressing the generation of harmful components in combustion gas, and in particular to a method for reducing nitrogen oxides in combustion gas and at the same time reducing the generation of harmful components due to the reduction measures. The present invention relates to a method for simultaneously reducing unused carbon.

It is well known that various S and N compounds contained in the exhaust gas of heat engines such as boilers, diesel, and gas turbines that use fossil fuels such as coal and heavy oil cause environmental pollution. For this purpose, flue gas desulfurization equipment has been put into operation and is producing considerable results.

Also, N compounds (mainly oxides of NO, No2, etc., usually called NOx).

), research has been conducted on treatment methods using catalysts and NH3 injection, or directly injecting NH3 into high-temperature combustion gas at around 1000°C to directly decompose NOx, and some have reached the stage of practical application. ing.

NOx treatment (denitrification) is difficult even if highly pure so-called clean fuels such as natural gas and hydrogen are used, because as long as air is used as the oxygen source, the nitrogen in the air is oxidized in the high-temperature combustion gas. It is difficult to control the occurrence.

(In the case of point desulfurization, no S oxides are generated unless the fuel contains S compounds).

For this reason, studies are being conducted on a denitration method using a catalyst as described above, and a method of denitration by injecting NH3 into high-temperature gas and causing it to react directly with NOx.

However, in methods that use catalysts, the soot and dust components contained in the exhaust gas adhere to the catalyst surface and weaken its action, making it impossible to maintain its effectiveness over a long period of time.
It is a big economic burden because it needs to be replaced frequently.

In addition, with the method of directly injecting NH3 into high-temperature gas, the injection equipment is large and difficult to install in an existing plant, which increases construction costs, and because it is directly injected into high-temperature gas, there is a risk of damage to the equipment. It has drawbacks such as being large and requiring a lot of maintenance.

Therefore, very recently, attempts have been made to suppress the generation of NOx by injecting into fuel an additive in which lower-grade iron oxides are suspended in light oil or the like.

This principle is based on, for example, the following NOx production reaction N2+
02 → 2NO (1) N2 + 202 → 2NO2 (2) Replace 02 with lower iron oxide (e.g. Fed, Fe3
o4) to suppress the production of NOx.

However, even when this method was actually applied, the NOx reduction effect as theoretically achieved was not achieved, and the effect was poor.

Since the method of reducing NOx using additives as described above is theoretically superior, the present inventor has conducted intensive research into ways to improve the practicality of the method, and has found that the method of reducing NOx in the environment where NOx is generated is We learned that the effect of the additives mentioned above doubles when the In addition to adding an additive suspended and dispersed in fuel to the fuel, the amount of excess oxygen in the combustion gas is reduced to 1.3
% or less (see Japanese Patent Application No. 152850/1982).

In this way, in this method, the amount of excess oxygen in the combustion gas is reduced to 1.
Low excess oxygen combustion is required, controlled to 3% or less.

However, in general, a sufficient amount of oxygen is required for complete combustion of the fuel.

Therefore, in the above method, the amount of oxygen required for complete combustion of the fuel tends to be insufficient, and there is a risk that combustion may be partially incomplete and unburned carbon may be generated.

As a result of intensive research into a method for simultaneously suppressing the generation of carbon when suppressing the NO warning using the above method, the inventors found that the above additive was added with alkaline earth under the above conditions of excess oxygen in the combustion gas. It was discovered that the addition of similar metal compounds and seed oxides promotes the combustion of unburned carbon, and based on this knowledge, the present invention was completed.

That is, the present invention provides: 1 or more types of iron and lower oxides of iron, and an amount of 25
An additive made by suspending and dispersing one or more alkaline earth metal compounds having a weight of φ or less in hydrocarbons using a surfactant is added to the fuel, and the amount of excess oxygen in the combustion gas is reduced by 13
2. A method for suppressing the generation of harmful components in combustion gas, characterized by controlling the generation of harmful components to less than 25% of the amount of 2.
An additive made by suspending and dispersing one or more alkaline earth metal compounds and one or more oxides with a weight of φ or less in hydrocarbons using a surfactant is added to the fuel, and the excess in the combustion gas is The gist of the present invention is a method for suppressing the generation of harmful components in combustion gas, which is characterized by controlling the amount of oxygen to 1.3% or less.

The additives used in the present invention are Fe00H and FeO.

A lower oxide of iron such as Fe s 04 and one or more types of iron (hereinafter referred to as basic additives), and an amount of Ca(OH) of 25φ or less 2. CaO, CaC
O3゜Mf(OH) 2. MS'0. MfCO3,Ba
(OH) 2. Bad.

One or more alkaline earth metal compounds such as BaCO3 are suspended and dispersed in hydrocarbons using a surfactant, or the above basic additives and the above alkaline earth metal compounds in an amount not more than 25% by weight of the above basic additives are added. one or more of the following and MnO, Mn3O
4. It can be obtained by suspending and dispersing one or more Mn oxides such as Mn2O3, MnO2, and Mn207 in hydrocarbons using a surfactant.

In this case, the upper limit of the amount of alkaline earth metal compound or alkaline earth metal compound and protrusions added is set to the above basic additives, since too much will promote the generation of S oxides and N oxides. If the weight is too low, the effect of addition will be lost, but since the amount of unburned carbon is affected by the amount of oxygen during combustion, the lower limit is not particularly limited and can be adjusted as appropriate depending on the amount of oxygen during combustion. Set.

As the surfactant, any one of cationic, anionic, and nonionic surfactants can be used, but nonionic surfactants that are not affected by the polarity of the medium are generally used.

Although light oil is used as the hydrocarbon, other fuels such as heavy oil, crude oil, and kerosene may also be used.

The additive obtained as described above is added to the fuel, and the amount of excess oxygen in the combustion gas is so low as to be 1.3 or less (e.g., the amount of excess oxygen is 0.3 to 1). In addition, in the present invention, the reason why the amount of excess oxygen in the combustion gas is set to 1.3% or less is that if more excess oxygen exists, the amount of oxygen in the additive This is because lower oxides of iron and/or iron are consumed by free oxygen and cannot react with the oxygen in formulas (1) and (2) above, which are involved in NOx production.

If the present invention is carried out while observing the above conditions, not only will the reduction in NOx become more remarkable, but also the generation of unburned carbon will be completely eliminated, and the following effects will also be obtained.

In other words, heavy fuel oil contains corrosive substances such as V2O5゜Na2SO4 as impurities, and although these impurities are not corrosive in the solid state, when they become molten (liquid) they can severely corrode metals. be.

When heavy oil is burned, these impurities become low-melting point compounds (melting point 600-650°C) in the heavy oil ash and are absorbed into the boiler furnace wall tube (
Adhesive at surface temperature of 500-650°C.

Incidentally, the combustion gas temperature is 800 to 1600°C.

When the additive of the present invention is added to the furnace under such conditions, the alkaline earth metal compounds and the oxides become high melting point compounds (MgO: mp2800'c, Bad:
mp 1920°C2Cab: mp 2570°C, M
nO2: mpl 650'C), combines with the above-mentioned low melting point compounds to raise their melting point, and also acts on the low melting point compounds that have already stuck to the furnace wall tubes, creating a paste-like It is assumed that the liquid is sprinkled like grains of sand on top of the substance that is attached to it), causing a chemical reaction and raising its melting point.

As the melting point increases, it tends to solidify, which reduces corrosivity.
In addition, the adhesion to the furnace wall tube decreases.

Therefore, cleaning becomes easy and it is also possible to prevent damage to the heat transfer surface.

As described above, the present invention can be said to be an extremely useful flue gas pollution prevention technology with low equipment costs and operating costs, and can be advantageously applied to general boilers, incinerators, heavy oil, gas, coal combustion furnaces, etc. .

FIG. 1 shows an example in which the present invention is applied to a heavy oil combustion device.

In the figure, 1 is a combustion tank, 2 is a combustion pump, 3 is a burner, 4 is a combustion furnace, 5 is a blower, 6 is an additive tank, 7 is an additive pump, and 8 is a gas extraction duct.

Fuel (heavy oil) is sent from a fuel tank 1 to a burner 3 using a fuel pump 2, and can be injected into a combustion furnace 4 lined with refractory material. This is done by operating the blower 5 and pressurizing the Er-8KIvtJi with air.

A portion of the pressurized air is branched off and sent into the combustion furnace 4 for complete combustion.

NOx reducing agent of the present invention (i.e., lower iron oxide or iron)
The additive, which is dispersed in light oil, is stored in a tank 6 and can be injected into the fuel by an additive pump 7 as needed.The additive is completely combusted together with the fuel in the combustion furnace 4, and NOx is removed. It is designed to perform a reduction reaction.

The amount of N oxides, S oxides, and unburned carbon in the combustion gas can be determined by extracting the gas from a duct 8 connected to the tip of the combustion furnace 4, and extracting N oxides,
It is now possible to measure the amount of S oxide and unburned carbon.

The following examples were performed using the apparatus described above.

Example 1 Additives include iron 1 (weight), Fe0OH, and Fe3
A basic additive in which 5% (by weight) of O4 is dispersed in heavy oil with 2% (by weight) of a nonionic surfactant is used, and this basic additive is added to heavy oil CJISK 2205 No. 1.
Type 1 heavy oil, 80.3% (heavy oil)], 1/10 of that
Continuous injection was performed at a rate of 0.00 (volume).

As a combustion condition, the amount of excess oxygen in the combustion gas is set to 0.3 to 2.
N in the gas extracted from duct 8 when changed to 0%
The amount of Ox, SO3, and unburned carbon were measured, and the results are summarized in FIGS. 2 and 3.

In addition, in FIGS. 2 and 3, the amount of excess oxygen on the horizontal axis is based on the measured value of the amount of 02 in the gas extracted from the duct 8.

This means that, theoretically, the amount of excess oxygen in the combustion gas is equal to the amount of excess oxygen in the gas extracted from duct 8, unless air is mixed in due to leakage before reaching duct 8. It is based on

In Figure 2, curves 1 and 3 are the data on NO consumption and S03 amount when no basic additive is used, but even in this case, the smaller the excess oxygen amount, the more
It is recognized that the NOx amount and SO3 amount tend to decrease.

This is because the amount of oxygen in the combustion atmosphere is small, so combustion takes a long time and the combustion temperature does not become excessive.
This is thought to be because the O3 production reaction is suppressed.

Curves 2 and 4 are the data on the amount of NO and SO3 when the basic bath caloric agent is injected, respectively.
On the high excess oxygen content side, that is, in the presence of 1.5 to 20% excess oxygen, as shown in the figure, there is not much of a reduction effect on NOx and SO3, and in particular, the reduction effect on NOx is extremely small, reducing injection costs. When you think about it, it is no exaggeration to say that it is not effective industrially.

In the presence of a low excess oxygen amount, both NOx and S03 decrease, with NOx in particular decreasing significantly, and N
Great effect in suppressing Ox generation.

In fact, remarkable effects can be obtained with an excess oxygen amount of 12 to 1.3%, preferably 1% or less.

In Figure 3, curve 5 is curve 6 when no basic additive is used.
is the data on the amount of unburned carbon when the basic additive is injected, but in any case, the amount of unburned carbon produced tends to increase as the amount of excess oxygen decreases, especially when the amount of excess oxygen is 0. This tendency becomes remarkable when it becomes 9% or less.

Example 2 As additives, Ca01% (
weight) + Ba01% (weight) + Mg01% (weight) in the above basic additives Fe1% (weight) + Fe00H5 (
weight) + 1/9 weight ratio compared to Fe3045 (weight)
This additive was continuously injected into the heavy oil used in Example 1 at the same ratio as in Example 1.

The amount of NOx in the gas extracted from the duct 8, SO3 when the amount of excess oxygen in the combustion gas is set to 0.6 as the combustion condition
The amount of unburned carbon and the amount of unburned carbon were measured, and the results are shown in FIG.

In Figure 4, curve 1 is data on S03 amount, and curve 2 is NOx data.
Curve 3 is data on the amount of unburned carbon.

As is clear from this figure, the amount of unburned carbon decreases considerably even at low excess oxygen amounts, and the amount of NOx and S
Since the amount of 03 is not so large, it can be seen that the effect of the above-mentioned carbon additive on reducing unburned carbon, NOx, and SO3 is remarkable.

It is assumed that this is because the basic additive suppresses the generation of NOx, and the alkaline earth metal compound promotes combustion and reduces the amount of unburned carbon.

However, as shown in the figure, when the amount of alkaline earth metal compound added increases, it tends to promote the generation of NOx and SO3, so in reality it is less than 2/8, preferably 1/9.
Example 3 Additives used in Example 1 include Ca01% (wt) + Ba01% (wt) + Ca01% (wt) + Mn
Oo, 3% (by weight) of Fe1 in the above basic additives
% (weight) + Fe00H5% (weight) + Fe3045 (weight) at a weight ratio of 1/9 to 9/1, and this additive was added to the heavy oil used in Example 1. Continuous injections were made at the same rate as 1.

The amount of NOx in the gas extracted from duct 8 when the excess oxygen amount in the combustion gas is set to 0.4% as the combustion condition, S03
The amount of unburned carbon and the amount of unburned carbon were measured, and the results are shown in FIG.

In FIG. 5, curve 1 is data on the amount of S03, curve 2 is data on NO usage, and curve 3 is data on the amount of unburned carbon.

As is clear from this figure, it can be seen that almost the same effect as in Example 2 can be obtained with the additive containing Mn oxide.

[Brief explanation of the drawing]

Figure 1 is a flow sheet for explaining the embodiments of the present invention, Figures 2 to 5 are charts for showing the effects of the present invention, Figures 2 and 3 are effects of the presence or absence of basic additives, The figure shows the effect of the basic additive + alkaline earth metal compound, and Figure 5 shows the effect of the basic additive + alkaline earth metal compound + Mr + oxide.

Claims (1)

[Claims] 1. One or more types of iron and lower oxides of iron, and an amount of 25
An additive made by suspending and dispersing one or more alkaline earth metal compounds having a weight of φ or less in hydrocarbons using a surfactant is added to the fuel, and the amount of excess oxygen in the combustion gas is reduced by 1.
A method for suppressing the generation of harmful components in combustion gas, characterized by controlling the generation of harmful components to 3% or less. 2. One or more types of iron and lower oxides of iron, and the amount of 25
One or more alkaline earth metal compounds and Mn
It is characterized by adding to the fuel an additive made by suspending and dispersing one or more oxides in hydrocarbons using a surfactant, and controlling the amount of excess oxygen in the combustion gas to 1.3% or less. A method for suppressing the generation of harmful components in combustion gas.