JPH0633373B2 - Iron oxide for fuel additive and method of using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an additive for coal and petroleum-based fuels and a method for using the additive.

[Conventional technology]

Since the ratio of fuel cost to operating cost is high in a prime mover such as a boiler and a gas turbine, practical use of petroleum-based low-quality fuels such as asphalt, petroleum coke, residual oil in petrochemicals, and by-product oil is being promoted. These fuels are LN
G and light oil are not only cheaper than general heavy oil, but also have high calorific value and can be diverted by simple modification of existing equipment, so demand is expected to grow significantly in the future.
In addition, heavy oil containing a large amount of S (sulfur), V (vanadium), and Na (sodium) with high viscosity, called orinocotar from Venezuela, is also used as a fuel from a long-term energy perspective. Can be considered.

However, these petroleum-based low-quality fuels are stable because they have (1) a large amount of fixed carbon and a small amount of volatile components, (2) a high ignition temperature and a slow burning rate, compared to light oil and general heavy oil. There are drawbacks such that the combustion state cannot be obtained and a large amount of unburned carbon is contained in the combustion gas.

As a method of compensating for these drawbacks, (1) increase combustion air. (2) Solid fuel such as petroleum coke is pulverized to increase the contact area with the combustion air. (3) For asphalt and tars, increase the preheating temperature and atomize the particles during spray combustion to increase the contact area. (4) Methods such as developing burners that meet this purpose are being implemented.

However, these improvement measures have the following problems and cannot be said to be sufficient measures.

That is, (1) The increase in combustion air not only lowers the boiler efficiency, but also promotes the production of NOx and SO ₃ in the combustion gas, causing environmental pollution and sulfuric acid dew point corrosion. The miniaturization of (2) has a limit to the capacity of the crusher, and a large equipment cost is required for fine crushing. Further, the increase in the preheating temperature of (3) leads to energy consumption, and it is not easy to improve and develop the burner of (4), and at present, a complete burner has not been developed.

In view of the above situation, there have been cases where a method of adding compounds such as Ba, Mn, Ce, Cu, and CO to the fuel has been adopted and research has been conducted on the combustion improver (combustion accelerator). However, these metals belong to heavy metals and have problems of pollution, and they are not economical.

The present inventors have previously proposed, as Japanese Patent Application No. 60-244155 "fuel additive", a method of preventing many obstacles caused by combustion by adding iron oxide to a fuel.

As iron compounds, FeO, Fe ₃ O ₄ , Fe ₂ O ₃ , FeOOH, Fe (OH)
Inorganic substances such as ₃ , FeCO ₃ , FeSO ₄ , FeCl ₂ , Fe (NO ₃ ) ₂
It is classified into organic ones such as iron octylate, iron naphthenate, iron stearate, iron complexate, iron formate, and iron methacrylate.Each compound undergoes a process of being oxidized or decomposed in a high temperature combustion region. Eventually, they are suspended in the combustion gas as Fe ₂ O ₃ particles.

In general, the inorganic iron compound is often added to the fuel in the form of fine powder, and the organic iron compound is often used in a state of being dissolved in an aqueous solution or the fuel. Regarding the dispersion in fuel and the uniform distribution in combustion gas, organic iron compounds are much more advantageous, but they are expensive. The current situation is that the number is decreasing.

Under such circumstances, "Japanese Patent Application No. 60-244155" proposes the use of fine iron oxide (at least 1 μm).
Although the purpose has been met for the time being, the demand for fine and highly reactive iron oxide additives is strong, and not only for the petroleum-based low-quality fuels but also for coal fuels. On the contrary, the appearance of an effective iron oxide is desired.

Furthermore, the properties required for this type of inorganic iron compound are that it disperses evenly in an aqueous solution or fuel, and that the pump power for transporting these is small, and that the pump part and burner nozzle also wear. What is not expected is expected.

[Problems to be solved by the invention]

The present invention, when using iron oxide that is low in operating costs even when continuously used for a long period of time, has the following drawbacks when using a conventional iron oxide, that is, poor uniform dispersion in an aqueous solution and a fuel, If a large amount of iron oxide is added to these, the viscosity will increase, so a large amount of power is required when injecting into the fuel pipe, and the iron oxide added to the aqueous solution or fuel will not be stored during long-term storage. When a part of it settles at the bottom of the container, it becomes muddy and sticks, and it is difficult to re-disperse.It is expected to be improved when the conventional iron oxide is injected into the fuel. The following problems, namely, improvement of combustion promotion effect of fuel, improvement of suppression effect of NOx generation amount in combustion gas, and electrostatic precipitator (hereinafter EP) of dust contained in combustion exhaust gas Improvement of collection efficiency, further in the boiler furnace If 硝用 catalyst is placed not only does not adversely affect the catalyst function, the mechanism of action of such to improve the function is to improve the current situation is not sufficient.

[Means for solving problems]

The present invention is (1) a fuel additive characterized by comprising fine iron oxide, the shape of which is a plate or a ring having a through hole in the center of the plate, (2) a plate and a ring oxide A fuel additive characterized by mixing iron into a Mg compound, and (3) a plate-like or cyclic iron oxide as a water slurry or an oil slurry mixed into petroleum-based and coal fuels This is how to use the additive.

[Action]

(1) Improvement of action mechanism by refining iron oxide When iron oxide is added to fuel, it is generally regulated by weight content, but if the particle size is different, the surface area and the number of particles are large. There will be a difference. For example, assuming that the surface area of iron oxide particles having a diameter of 44 μm is 1, the surface area becomes 2.2 times as large as the same weight of iron oxide particles is pulverized to 20 μm, and the same surface area becomes 4.4 times 2 times.
It increases 22 times in μm and 88 times in 0.5 μm. Again 4
Assuming that the number of iron oxide particles of 4 μm is 1, the number of particles pulverized to 20 μm is 11, 10 particles of 85 μm, 2 particles of 10,600 particles, and 0.5 μm of 681,000 particles. (However, these calculations assume that the shape of the particles is a sphere.) When the iron oxide is made into ultrafine particles in this manner, the surface area as well as the number of particles is dramatically increased even with the same added weight. The increase in surface area has the effect of promoting the chemical reaction on the iron oxide surface, and the increase in the number of particles significantly increases the chances of contact with unburned carbon suspended in the combustion gas, resulting in coarse particles of iron oxide. Compared with this, the reaction opportunity is physically increased.

(2) Shape and action mechanism of iron oxide particles Although iron oxide particles are generally called ultrafine particles, many of them have a needle-like shape. Even if such particles are added to the fuel together with the dispersant, vibration during transportation is applied, or if they are stored for a long period of time, the particles will entangle with each other to form coarse particles. Then, there is a phenomenon in which it settles on the bottom of the container. In this way, particles in which coarse particles are entangled with each other do not return to the original fine particles even when mechanically stirred, and eventually, coarse iron oxide particles are used. Will be the same as. For this reason, it may cause sedimentation in the fuel pipe and wear damage to the fuel pump and the burner chip.

Since the iron oxide particles of the present invention are ultrafine particles,
In addition to the effect of (1), it exhibits the following extremely useful function.

That is, since the iron oxide particles have a plate shape without an acute angle, the pump and the burner chip are not worn even if a large amount is added to the fuel. In addition, since the particles do not entangle with each other, secondary coarse particles are not formed, there is no sedimentation phenomenon, and if the addition amount is the same, the effect on the viscosity of the fuel oil is small and the transportation power is small. Will be completed.

In addition, iron oxide having a through hole in the center of the plate-like particles (hereinafter referred to as “ring iron oxide”) allows fuel to pass through the through-holes, further improving the function of the plate-like particles described above, and burning. Even after that, since the combustion gas component passes through the through holes, various chemical reactions occurring on the iron oxide surface are significantly accelerated.

The above-mentioned plate-like and cyclic iron oxide particles are described in "Carpentry Test News" vol.29 (1985) No. 11 published by Kogakuin Osaka Industrial Research Institute.

5 and 6 show electron micrographs of plate-like and cyclic iron oxide particles of the present invention, and FIG. 7 shows commercially available acicular iron oxide particles.

〔Example〕

(Example 1) The composition and characteristics of a fuel additive using the plate-shaped and cyclic iron oxide of the present invention will be described.

When Used as Oil Slurry An example of producing a fuel additive using the iron oxide of the present invention is shown below.

If this composition is well stirred with a stirrer having four blades, it becomes a fuel additive for oil slurry. An oil slurry containing iron oxide containing iron oxide of the present invention produced in this manner and another commercially available iron oxide are added in the same amount to prepare an oil slurry of 20 ° C.
The viscosity of iron oxide and the stability of iron oxide in oil slurry were investigated. Stability was investigated by mixing well, stirring 100 ml in a glass tube having a scale, and leaving it still for 1 to 3 months to compare the amount of supernatant formed with the amount of iron oxide deposited on the bottom. First
The table shows these results, the viscosity of the oil slurry containing the commercially available iron oxide of the comparative example, the viscosity is very high even if the iron oxide is fine particles, the handling is difficult. I understand. In this respect, the granular oxide of Fe ₃ O ₄ has a lower viscosity. However, the stability was poor, and almost all of it settled to the bottom after 30 days. In this respect, the stability of needle-shaped iron oxide was far better than that of granular iron oxide.

On the other hand, the plate-like and cyclic iron oxides of the present invention have low viscosities, and even when they are allowed to stand for one month, no sedimentation of particles is observed and good stability is exhibited.

Then, as a result of allowing the slurry containing the acicular iron oxide of the present invention to stand for 3 months, a small amount of sedimentation phenomenon was observed from the acicular iron oxide of C and the iron oxide slurry of the present invention, but other comparative examples were All were found to have a large amount of sedimentation and poor stability. Next, with respect to the iron oxide of the present invention and the acicular iron oxide slurry of C and D that were left standing for 3 months, the glass tube was moved up and down several times (5 to 6 times).
When the iron oxide that had reversed and precipitated was redispersed and allowed to stand for one month again, it was found that the sedimentation phenomenon of the acicular oxide was accelerated and the stability was poor. It is considered that this is because even if the acicular iron oxide was fine, once settled, the particles became entangled with each other to form apparently large particles, which accelerated the settling rate. It was confirmed that the point-plate-shaped and ring-shaped oxides did not become entangled as apparent from the shape, and maintained stability for a long period of time.

When used as water slurry The following is an example of the composition when the iron oxide of the present invention is used as a water slurry.

After stirring as well as when producing the oil slurry,
The viscosity of the water slurry and the stability of the slurry were compared with those of the same amount of acicular iron oxide added. The method of the comparative test was the same as that of the oil slurry, but in the case of the water slurry, the characteristics of the iron oxide slurry of the present invention were extremely good as compared with those of the needle-like shape after standing for 1 month, and thus 3 months. No tests such as standing and subsequent re-stirring were performed.

Table 2 shows the test results when the water slurry was prepared. As with the oil slurry, it was found that the viscosity of the slurry was low and it was extremely stable even when left standing for one month. In particular, it was found that the water slurry of cyclic iron oxide has excellent properties.

From the above results, it was found that the plate-like and cyclic iron oxides of the present invention are extremely promising as a fuel additive not only in oil slurry but also in water slurry state.

(Example 2) Using the oil slurry composition shown in Example 1, the wear characteristics of two types of iron oxide of the present invention and a commercially available acicular iron oxide with respect to metal materials were investigated. The wear characteristics were investigated by investigating Al alloy castings type 2 B (JIS H 52
Immerse a 4-blade propeller with a diameter of 80 mm made of Al-Cu-Si) in AC2A of 02 and rotate it 300 times for 1 minute.
A 0-hour continuous test was conducted. After that, take out the propeller,
The wear characteristics of iron oxides having different shapes were evaluated from the change in appearance and the change in weight before and after the test. In this test, the propeller rotation speed was kept constant, so the viscosity of the oil slurry containing iron oxide of the present invention was low and it rotated easily, but in the oil slurry of the needle-shaped iron oxide of the comparative product, the same rotation speed was obtained in the former case. Needless to say, it required a great deal of power compared to.

Table 3 shows the results. In oil slurries containing plate-shaped and ring-shaped iron oxide, almost no shape change was observed in the appearance even with an Al alloy propeller, and the surface of the piper was lightly polished. However, the needle-shaped iron oxide oil slurry caused numerous scratches on the propeller surface. Such a difference in appearance also appears in the change in the weight of the propeller, and the weight reduction of the iron oxide slurry of the present invention was extremely small, whereas the weight loss of the comparative iron oxide slurry was small. The wear amount of 20 times or more was confirmed.

(Embodiment 3) FIG. 1 shows an example in which the iron oxide of the present invention is added as a water slurry into a boiler fuel and dispersed in the boiler furnace along with the combustion of the fuel. Fuel is sprayed from the fuel tank 1 through the pipe 2 into the boiler furnace 4 by the fuel pump 3 and burned. The hot gas after combustion exchanges heat with the boiler heat transfer tube, passes through the air preheater 5, and the electric dust collector 6 removes the solid matter (dust) in the gas, and is discharged from the chimney 7 to the outside. .
On the other hand, the combustion air is heat-exchanged from the position 8 by the air preheater 5 to raise the temperature, and is injected into the furnace as combustion air through the fuel burner.

When the iron oxide of the present invention is used in a water slurry state, an iron oxide slurry (50%) having a higher concentration than the chemical composition shown in Example 1 is prepared and stored in the water slurry tank 13.
On the other hand, water is injected from the industrial water storage tank 9 through the pipe 10 into the fuel pipe through the pump 11, but at that position, two series of water slurry pipes 12 are provided so that water can be injected either before or after the fuel pump 3. There is. The water slurry of iron oxide passes from the storage tank 13 through the pipe 14, and is injected by the pump 15 into the water pipe 10 by the water pipe 15. Therefore, it is injected into the fuel from this injection position. Water slurry of iron oxide particles is present in the pipes up to this point. The water slurry concentration can be automatically controlled by the pump 15 and the pump 11 according to the fuel consumption amount. It is also possible to send iron oxide particles from the pump 15 to the water storage tank 9 through the pipe 16 to form water slurry having a predetermined concentration in the water storage tank and inject it into the fuel.

In the iron oxide water slurry storage tank 13, an air blowing pipe 17
Is included and is ready for operation as needed.

Test conditions Boiler under test: Evaporation amount 600t / h Fuel: Commercial C heavy oil (S: 2.5%, V: 30pp
m, Na: 20 ppm) Injected iron oxide (A) Ultra-fine plate-like iron oxide of the present invention (hereinafter A iron oxide particles) (B) Ultra-fine cyclic iron oxide of the present invention (hereinafter B iron oxide particles) (C) Commercially available ultrafine acicular iron oxide (hereinafter referred to as C iron oxide particles) (D) No injection Performance comparison item Dust amount in the exhaust gas from the air preheater 5 and unburned carbon amount contained in it Efficiency SO ₃ , N in exhaust gas at the position of the air preheater 5 inlet
Ox amount Table 4 shows the above test results with 100 measured values without injection.
Is shown as the ratio. (Note that iron oxide Fe ₂ O ₃
The injection amount into the fuel was set to be 100 ppm, but actually it was in the range of 80 to 210 ppm. The amount of dust and the amount of unburned carbon in the dust are decreased by the injection of iron oxide, and it can be seen that the dust collection efficiency is improved accordingly. Generally, the efficiency of the electrostatic precipitator is extremely effective when the electric resistance of soot and dust is about 10 ⁵ to 10 ⁸ Ωcm.
It is considered that the effect of lowering the resistance value of unburned carbon having a large electric resistance value appeared. The decrease in SO ₃ and NOx is caused by the injected iron oxide adhering to the combustion furnace wall tube, increasing its radiation absorption rate and lowering the maximum temperature in the combustion region, which reduces the amount of activated oxygen generated. However, it is considered that the oxidation of SO ₂ → SO ₃ and the generation of thermal NOx were suppressed.

Thus, the injection of iron oxide showed a very effective action, but it was confirmed that the effect of the plate-like and cyclic iron oxide of the present invention was further improved.

The reason for this is that iron oxide is fine particles, and it is evenly dispersed in the fuel and has a plate shape and an annular shape, so it makes good contact with gas components and fuel components and adheres to the furnace wall tube. Even so, it is considered that it exists in a stable state, rarely exfoliates and falls off, and exerts a function peculiar to iron oxide for a long period of time.

(Embodiment 4) FIG. 2 shows an outline of a boiler injected with an oil slurry containing iron oxide according to the present invention.

The asphalt storage tank 21 maintains fluidity,
The steam heating device 22 is installed, and the piping for guiding this to the boiler is also provided with the same kind of heating mechanism. Asphalt is heated to 180 to 230 ° C., and injected into the boiler 4 by the pump 33 and burned. The oil slurry passes from the storage tank 24 through the pipe 25 and the injection pump 26.
Is injected into the outlet side of the fuel pump 33 by the pipe 27.

The air preheater 5, the electrostatic precipitator 6, and the chimney 7 provided in the gas passage discharged from the boiler are the same as those in FIG. 1, and the combustion air 8 passes through the air preheater 5 for combustion. Used as air to burn fuel.

Test conditions Test boiler: Evaporation rate 180t / h Fuel: Asphalt (S: 3.2%, V: 50
0ppm, Na: 100ppm) 70% to C heavy oil (S: 1.8
%, V: 63 ppm, Na: 17 ppm) 30% mixture Iron oxide injected; A iron oxide particles, B oxide particles and C iron oxide particles which were the same as those used in Example 3 were used, and an oil having the following composition A slurry was prepared and tested.

Machine oil J-9 (trade name of Idemitsu Kosan Co., Ltd.) 160 g Petroleum-based calcium sulfonate 3 g Sorbitan monooleate 3 g Iron oxide 57 g Performance comparison item: Same as Example 3 Table 5 shows the results of this Example. Injecting iron oxide into asphalt gave the same effect as injecting into C heavy oil. Further, it was confirmed that the iron oxides of the plate-like and ring-like ones of the present invention were more excellent than those of the conventional needle-like crystals.

(Example 5) Fig. 3 shows an example in which the iron oxide of the present invention is applied to a boiler burning petroleum coke. Petroleum coke storage tank 3
The coke discharged from No. 1 is crushed into a predetermined particle size by a mill 32, passed through an air preheater 5, and heated to an air pipe 33.
Is introduced into the boiler furnace 4 via. On the other hand, it is also introduced into the boiler 4 from the C heavy oil storage tank 37 by the pump 38 through the pipe 39.

A predetermined amount of oil slurry containing iron oxide is injected from the storage tank 34 into the C heavy oil pipe 39 through the pipe 36 by the metering pump 35, and the combustion air sucked from the boiler furnace 4 from the combustion oil 8 Coke and heavy fuel oil C are being burned in the boiler furnace. The equipment of the apparatus until the combustion gas emitted from the boiler is discharged from the chimney is the same as that shown in FIGS. 1 and 2.

Test conditions Test boiler: Evaporation rate 180t / h Fuel: Commercial petroleum coke (S: 4.2%,
V: 670ppm, Na: 60ppm) 60% to C heavy oil (S:
(1.8%, V: 40 ppm, Na: 10 ppm) 40% mixed together.

Injected iron oxide: The same amount as in Example 3 was injected into heavy oil by using the one used in Example 4.

Performance comparison item: same as in Example 3 Table 6 shows the test results. As is clear from this result, the iron oxide of the present invention exhibited extremely excellent performance even for a boiler burning petroleum coke.

When the iron oxide of the present invention was mixed in powder form with petroleum coke powder, it was also tested, and it was confirmed that the same effect as when the iron oxide was injected into C heavy oil was obtained. However, it was found that it is practically difficult to control the injection amount of iron oxide powder by this method, and it is inferior to the oil slurry type in terms of powder transportation and handling.

(Example 6) Corrosion of the oxide of the present invention generated on the gas side of a heavy oil combustion boiler (for example, accelerated oxidation corrosion by V, Na and S compounds contained in combustion ash in a superheater tube of a boiler) received,
In addition, the SO ₃ contained in the exhaust gas is used as a measure against Mg compounds (Mg (OH) ₂ , M
An example in the case of being added to gCO ₃ , MgO) will be described.

The boiler used was the same as that shown in FIG. 2, and the heavy oil C was put in the asphalt storage tank 21, and the mixed oil slurry of iron oxide and Mg (OH) ₂ was put in the iron oxide oil slurry tank 24. The composition of the iron oxide oil slurry was the same as that used in Example 4 and was adjusted so that the weight of Fe ₂ O ₃ in Mg (OH) ₂ was 2%. Mg (OH) ₂ has a particle size of 0.1 μm of 80% of the whole and the remaining 20% has a particle size of 0.7 to 1.2 μm.

The composition of the Mg (OH) ₂ oil slurry is as follows.

The test conditions in this example are as follows.

Test boiler: Same as in Example 4 Fuel: C heavy oil (S: 1.8%, V: 63 ppm, N
a: 17ppm) Type of additive used Additive injection amount: Mg / V = 1.
It was injected into the fuel at a ratio of 5 (weight ratio).

Performance investigation item Measurement of melting point of Devogit adhering to the boiler heat transfer tube Measurement of NOx and SO ₃ amounts in exhaust gas (test result) Table 7 shows the case where the test additive was injected over 6 months. The results are shown. Injecting only Mg (OH) ₂ surely raises the melting point of the divodyt on the heat transfer tube and suppresses the corrosiveness of S, V, and Na compounds contained in the divodyt, but the injection period is long. Then, there is a drawback that the amount of NOx in the exhaust gas increases. The cause of this is that white MgO {Mg (OH) ₂ is overheated to become MgO} covers the surface of the fire wall tube and becomes a white furnace wall tube, so the radiation absorption heat decreases and the combustion area is in a high temperature state accordingly. This is because the generation of thermal NOx increased as a result of maintaining the above.

On the other hand, when iron oxide is included, whitening due to MgO is suppressed and the above phenomenon is suppressed. In particular Mg (OH) ₂ containing iron oxide of the present invention is more effective than that of adding acicular oxide, since the amount added is less Mg (OH) ₂
The effect of increasing the melting point of the deposit can be used as it is.
Staining of thermal NOx is completely achieved by coloring. It was found that plate-like and cyclic iron oxides are more effective than needle-like ones for coloring MgO because they are finer than acicular iron oxides and have a function as a flat plate. Again SO
₃ The effect is well recognized for the amount generated.

(Example 7) Fig. 4 shows an outline of a boiler in which iron oxide of the present invention is mixed with coal fuel. The coal is made into a fine powder and is put into the boiler furnace 41 and burned, and the high-temperature combustion gas passes through the superheaters 42, 42 ', 42 ", the reheaters 43, 43', and the economizer 44, Preheater 5 exchanges heat with air,
Smoke is exhausted from the chimney 7 to the outside through the electric dust collector 6.
Reference numeral 8 is a combustion air intake portion, which is heated by the air preheater 5 and used for combustion of coal. Reference numeral 49 in the boiler furnace indicates a flow of combustion gas, and 40 indicates a coal ash take-out portion.

Test conditions Test boiler: Evaporation amount 600t / h Fuel: Coal shown in Table 8 was used. The chemical composition of the combustion ash of this coal is shown in Table 9.

Injected iron oxide: same as in Example 3. However, when iron oxide was added, the addition amount of iron oxide sprinkled on the coal powder as the water slurry of Example 1 was adjusted to a ratio of 300 to 500 ppm (based on the amount of coal), but actually 200 to 10
It was in the range of 00 ppm.

Performance Comparison Items The test results are summarized in Table 10 which is the same as in Example 3. In this example, the measured value in the case of no addition was set as 100 and shown as the ratio. As is clear from these results, the iron oxide of the present invention was found to have the same effect in the case of a boiler using petroleum-based fuel. That is, even if needle-shaped iron oxide is injected, the combustion of coal is promoted, the amount of unburned carbon in the exhaust gas is reduced, the generation of SO ₃ and NOx is suppressed, and the electric dust collection efficiency is improved. It is recognized that the effects of plate-shaped and cyclic iron oxides are further improved.

The electric resistance of coal ash is generally high, and it is usually difficult to collect it as compared with petroleum fuel ash, but the injection of iron oxide mixes iron oxide with low resistance into the coal ash, and It is considered that the catalytic action oxidizes SO ₂ in the exhaust gas into SO ₃ , which adheres only to the surface of the iron oxide powder, lowering the resistance value of the coal ash and improving the efficiency of the electrostatic precipitator.
The decrease in NOx and SO ₃ generation due to iron oxide injection is considered to be due to the same mechanism as described in the examples of petroleum-based fuels.

[Advantages of the Invention] The present invention has the following drawbacks when conventional iron oxides are used when using iron oxide, which has a low operating cost even when continuously used for a long period of time, namely, uniform dispersion in an aqueous solution and a fuel. Poor performance, because adding a large amount of iron oxide to these increases the viscosity, so a large amount of power is required when injecting into the fuel pipe, and the iron oxide added to the aqueous solution or fuel may not be used for a long time. When a part of it settles on the bottom of the container during storage, it has the effect of improving handling defects such as sticking as a mud and making it difficult to re-disperse. When injected into a fuel cell, the following problems are expected: improvement of the combustion promotion effect of fuel, improvement of the effect of suppressing the amount of NOx generated in combustion gas, and collection of dust contained in combustion exhaust gas. Improved collection efficiency with dust collectors Furthermore, when a denitration catalyst is installed in the boiler furnace, not only does this catalyst function not be adversely affected, but the function is improved.

[Brief description of drawings]

1 to 4 are diagrams showing a flow adopted in the embodiment of the present invention, FIGS. 5 to 7 are electron micrographs of iron oxide crystals, and FIG. 5 is a plate crystal used in the present invention. 6 shows the same ring-shaped crystal, and FIG. 7 shows the conventional iron oxide needle-shaped crystal.

Claims (3)

[Claims] 1. A fuel additive comprising fine iron oxide and having a plate-like shape or an annular shape having a through hole in the center of the plate-like shape. 2. A fuel additive comprising tabular and cyclic iron oxides mixed in an Mg compound. 3. A method of using the above-mentioned additive, which comprises mixing plate-like or cyclic iron oxide as water slurry or oil slurry into petroleum-based and coal fuels.