JPS60100635A - Method for reforming granular material from iron ore powder utilized for thermal cracking of heavy gravity oil - Google Patents

Abstract

PURPOSE:To provide large crushing strength to a titled granular material with a method for preheating said material in a grate kiln by heating the material to a prescribed temp. in a preheating temp. then passing air in a calcination chamber and heating up the granular material. CONSTITUTION:The carbon-stuck iron ore powder byproduced in the stage of producing light oil and cracked gas by thermal cracking of residual heavy gravity oil with iron ore powder as a heat medium are molded to a briquette shape. The briquettes are passed through a preheating stage and thereafter reduced iron is produced with the carbon thereof as a reducing agent. The briquettes 15 are continuously supplied into the traveling grate 18 of a grate kiln 14 consisting of a preheating chamber 16 and a calcination chamber 17 in succession thereto in the above-described preheating stage of the process for producing said granular material. Then, the briquettes 15 are heated to 600-700 deg.C by the high temp. gas from a hot stove or burner 20 in the chamber 16 while the briquettes are carried, then the carbon in the briquettes is allowed to burn of itself by the air from a fan 27 in the chamber 17 to attain 1,000-1,300 deg.C by which the briquettes are calcined.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves bringing heavy residual oil into contact with iron ore powder in a heated fluidized state and thermally decomposing it to produce light oil and cracked gas. In a method for producing reduced iron by forming iron magnet powder adhering to a briquette into a briquette and then using the carbon of the briquette as a reducing agent, this invention relates to an improvement in the preheating process, particularly in the case of using a grate kiln. It is something.

Currently, the blast furnace-converter method, which is widely used as a steel manufacturing method, reduces iron ore to produce iron. First, pig iron containing excess carbon is obtained in a blast furnace, and then the carbon is converted into silicon, Since steel is produced by oxidizing and removing phosphorus and other substances, the efficiency is low, and there is also a problem that there is a worldwide shortage of highly coking coal, which is used as a raw material for blast furnace coke.

In response, a method has been developed in which iron ore is brought into contact with a reducing agent in a solid state, reduced to a reduction rate of 90% or more to obtain reduced iron, which is then melted and refined in an electric furnace to produce steel. . This method has advantages over the above-mentioned blast furnace-converter method, such as there is no waste in principle due to excessive reduction and oxidation of carbon, accompanying silicon, and phosphorus, and it does not require strong coking coal. There is.

In addition, industrial tests have also been carried out on the use of reduced pellets with a reduction rate of 70 to 90% as a raw material for whole blast furnaces to help save fuel coke and improve productivity.

However, the reason these methods are not widely used worldwide is that the reducing agents and raw materials used to produce reduced iron, such as coal, natural gas, and other carbons, are not widely used worldwide.

This is because hydrogen gas and carbon oxide gas sources are unevenly distributed on the earth, and there are only a limited number of areas where this can be carried out economically. Therefore, the emergence of inexpensively available reducing agents or reducing methods has been highly anticipated for the development of efficient direct iron manufacturing methods and the rationalization of iron manufacturing technology.

On the other hand, with the depletion of petroleum resources, high-quality light crude oil is gradually becoming a waste of human resources, and heavier crude oil has now become the trend of the times. In order to extract as much light oil as possible, which is in high demand, from such heavy oil, the heavy oil is lightened by catalytic cracking, hydrogen cracking, etc., and when the cracked components are fractionated, the light oil is Vacuum distillation is used to obtain a large amount. Attempts to extract more light fractions in this way have resulted in the residual oil becoming heavier and worse, and the effective use of such heavy residual oil has become a new problem. I ended up picking it up.

In order to simultaneously satisfy the above-mentioned demands for rationalization of steelmaking technology and demands for effective use of heavy residual oil, heavy residual oil is catalytically cracked in a fluidized bed pyrolysis furnace for iron ore powder to produce light oil and cracked gas. Recently, a method has been developed and is being industrialized in which carbon-incorporated granules, that is, carbon-containing briquettes, are produced from iron ore powder to which by-product carbon is attached, and the briquettes are reduced in a q-tally kiln reduction furnace. However,
One of the important technical problems encountered in such a method is the problem of imparting strength to the carbonaceous material-incorporated granules.

That is, when reducing briquettes in a h'60-tally kiln type reduction furnace, the briquettes are given sufficient strength to withstand the transfer and abrasion of the kiln, for example, a crushing strength of at least about 15 kg, and the briquettes are granulated in the kiln. Decrease in the yield of pulverization of materials.

It is necessary to prevent a decrease in operational stability due to the formation of kiln rings, etc.

As such an attempt, a method has already been proposed in which raw briquettes formed by a briquetting machine [are introduced into a preheater such as an i-great kiln and preheated to 600 to 900°C; according to this method, 4.4 with raw briquettes
The crushing strength was Kg/@ after preheating: Ll, ? The result was only that the number increased to KV, which was far from the value of at least about 15 as described above.

Therefore, an object of the present invention is to impart a high crushing strength to a carbonaceous-incorporated granule, ie, a briquette, made of iron ore powder used for heavy oil pyrolysis. Another object of the invention is to obtain highly prereduced briquettes. Another object is to provide Briquella which has high porosity and excellent reducibility in a reduction process.

The ultimate purpose of the present invention is to increase the yield and operating rate in the reduction process, as well as to facilitate maintenance of the equipment and improve productivity.

The above purpose is to form carbon-adhered iron ore powder, which is a by-product when producing light oil and cracked gas by thermally decomposing heavy residual oil using iron ore powder as a heat medium, into briquettes, and after a preheating process, to In the preheating step of the method for producing reduced iron using carbon from the briquettes as a reducing agent, the briquettes are supplied to a great kiln consisting of a preheating chamber and a subsequent firing chamber; After heating to 1,000 ~
This is achieved by a method for modifying granules made from iron ore powder used in heavy oil thermal decomposition, which is characterized by raising the temperature to -, 300°C.

Before explaining in detail the features and aspects of the method of the present invention,
Regarding the reduced iron production method using heavy residual oil to which the present invention is applied,
The process will be outlined with reference to sheet 70 in FIG.

First, iron ore powder crushed to an appropriate particle size is fed into an iron ore heating furnace (1), where it is sufficiently heated and then passed through a pipe (
2) to the fluidized bed pyrolysis furnace (3) to form a fluidized bed.

On the other hand, the preheated heavy residual oil is supplied to the fluidized bed pyrolysis furnace (3), where it comes into contact with hot iron ore particles and is thermally decomposed, partially reducing the iron ore particles and at the same time producing by-products from the pyrolysis. Carbon attaches to iron ore particles. The iron ore particles coated with carbon pass through the pipe (4) from the fluidized bed pyrolysis furnace (3) and return to the iron ore heating furnace (1), and some of the attached carbon is combusted to heat the iron ore. Contribute. Thus, an iron ore circulation circuit is formed between the fluidized bed pyrolysis furnace (3) and the iron ore heating furnace (1).

Light oil, which is a pyrolysis product of heavy residual oil, is taken out from the top of the fluidized bed pyrolysis furnace (3) and sent to a rectification separation system (not shown).
O, #0. The decomposed gas is sent to a gas reforming furnace (6) along with water vapor and carbon dioxide through a pipe (5), where it is denatured into a reducing gas consisting of hydrogen and carbon monoxide by the action of an L-based catalyst. The reducing gas is dehydrated while passing through the cooler (7), heated again in the gas heater (8), and then desulfurized in the desulfurization tower (9) and used as a reducing agent in shaft furnaces (00), etc. Ru.

Superheated steam is supplied to the iron ore heating furnace (1) from a lower pipe (11), and the iron ore powder is fluidized and controlled at an appropriate temperature. In addition, in the fluidized bed pyrolysis furnace (3), as mentioned above, 01 to C4
For example, in the case of methane gas (a), the following reaction occurs with water vapor and carbon dioxide gas in the furnace, producing a reducing gas consisting of carbon oxide and hydrogen. .

OH, →O-1-2H2・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・(1) (Carbon by-product) OH, + H20→Co + 3kl?・・・・・・・・・
・・・・・・(2) OH,, -1-co2→200 +
2H2・・・・・・・・・・・・(3) Furthermore, due to the action of this reducing gas, iron ore particles become hematite (
03Fe203 + Co is partially reduced from Fe2O3) to magnetite (Fe, 04), and at the same time, carbon by-produced by the above formula (1) adheres to the iron ore particles.
→2F@,O,+co□,,=-,,(4)3Fe2
03 + H2→2Fe304 + HlO...==
(5) The above-mentioned by-product carbon-adhered iron ore is sent to the iron ore heating furnace (1) as described above, and a part of it is taken out through the pipe (b) and sent to the granulation process.

The outline of the heavy oil pyrolysis process to which the method of the present invention is applied is as described above, and the raw material heavy residual oil to which the present invention is applied is as follows: Since there is no need to suppress it, poor quality vacuum distillation residues such as those used in the fluid coking method can also be used, as well as solvent dehydrator extraction residues.

Pyrolysis residual oil, catalytic cracking residual oil, heavy gas oil, vacuum gas oil, and feedstock oils used in the B'OO process can all be used, and oily substances obtained from coal, oil shale, etc. can also be used. It is possible. However, in any case, it is preferable that the adhesion of by-product carbon to the iron ore is 10 to 20% by weight. It is necessary to adjust the decomposition temperature etc. appropriately.

If the amount of adhering by-product carbon is less than the above, self-combustion will not take place sufficiently in the briquette firing process described below, and if it is too much, the quality of the reduced iron will deteriorate, which is undesirable in any case.

Next, the preheating step of the carbonaceous material-incorporated granules, which is an important part of the method of the present invention, and the granulation step and reduction step that are directly related thereto will be described.

The by-product carbon-coated iron ore particles obtained by the above-mentioned heavy oil pyrolysis process are charged into a kneader at a predetermined rate, and heavy residual oil is added as a binder at a predetermined mixing ratio, that is, to the carbon-coated iron ore particles. It is preferably kneaded while adding at a ratio of 3 to 0% by weight.

If the amount of heavy residual oil blended is less than this, not only will the crushing strength of the raw briquettes obtained in the next process decrease and the yield will decrease, but also the porosity will decrease and the inside of the briquettes will be sufficiently reduced. I feel separated. On the other hand, if the amount of heavy residual oil blended is too large, both the crushing strength and yield of the briquettes tend to decrease. When kneading the above mixture, the heavy residual oil is solid at room temperature. Since it is a highly viscous substance, in order to mix it thoroughly, it must be heated at an appropriate temperature above the softening point of the heavy residual oil, i.e. 10
It is preferable to add the mixture in a molten state by heating it to a temperature higher than 150° C., and to perform the kneading operation while heating and maintaining the mixture in the mixer at the same temperature.

Furthermore, even though heavy residual oil is in a molten state, it has extremely high viscosity and high surface tension, so the mixing operation involves applying compressive force to the mixture using rollers, etc., and at least kneading it. It is important to carry out the heating for 3 to 5 minutes to allow the heavy residual oil to sufficiently penetrate between each iron ore particle, so that the surface of each particle is substantially coated with the heavy residual oil.

The heated and kneaded mixture is sent to a briquetting machine (13) shown in FIG. 1 while still being heated, and is formed into green briquettes of a predetermined shape. Many known pressure molding machines can be used as the briquetting machine (13), but in particular, a forced-pressing machine that is a double roll type with mold pockets on the surface and equipped with a twin screw feeder is applicable. Formulas of the above formula are preferred and can generally be molded into a good briquette at a temperature of about 100 DEG C. or higher and a molding pressure of 130 to 150 degrees Celsius.

The size and shape of the briquettes can be arbitrarily designed. Although it is preferable to have a small size in order to receive sufficient reduction action in the next reduction process, considering that reduced iron is added into the steel bath through the slag layer during steelmaking, it is necessary to have a certain size, and usually, It is preferable to have a maximum diameter of about 20 mm x 15 mm, and a shape with rounded corners, that is, an almond-nut shape, in order to avoid a decrease in yield due to powdering.

The raw briquettes molded as described above are returned to the mixer after being sieved to remove molding defects and molding waste, and only qualified products are sent to the grate kiln 0, which is a breheater, and subjected to a preheating process. The present invention has its greatest feature in this preheating step.

FIG. 2 is a flowchart of the preheating step in the method of the present invention. Great kiln θ for carrying out the preheating process→
The apparatus comprises a preheating chamber 06) and a firing chamber αη which is connected to the preheating chamber 06), and an endless belt-shaped traveling grate (2)) extends through both chambers.

The traveling grate (2)) consists of a grate-like or net-like band made of heat-resistant material such as metal or ceramics,
It is driven by the sprocket wheel ((9) from the preheating chamber side toward the firing chamber.

The preheating chamber (16) is equipped with a pipe C711 that injects gas heated by a hot blast furnace or a burner ψ@ from below to above the traveling grate (E) if necessary, and an air collection hopper provided at the top. @ is connected by a duct (29) to an exhaust chimney (24) via an exhaust fan (23).

On the other hand, in the firing chamber 07) there is a traveling grate (2)).
Piping for injecting gas from above to below (2
0 is applied, and air is passed through the pipe 0 by a blower (27). In addition, an air collection hopper (marked with 2) is installed at the bottom of the traveling grate (2) in the firing chamber θη.
The high temperature gas collected here is connected to the heated gas injection pipe (2+) via a pipe @ and is reused.

Traveling grade 0) upper hebricket (15) of great kiln 04) configured as above? When the briquettes are continuously fed and placed, the briquettes (■) are first heated in the preheating chamber (16) while being transported by the traveling grate Q8), and heated to 600 to
7oo"c. This heating temperature has an important meaning in relation to the next firing temperature; if it goes below the above range, a sufficient firing temperature will not be obtained; on the other hand, if it is too high, On the contrary, it results in wasted burning of the interior carbon material, and in any case, it is impossible to impart sufficient crushing strength and preliminary reduction rate to the briquettes.

As a heat source at the start of operation, waste heat from a rotary kiln or a grate kiln, which is the next reduction process, is used. The next reduction method is the shaft furnace method.

In the case of the smelting reduction furnace method, a hot blast furnace or burner 00) is required.

1. Once stable operation has started, the heat source for the preheating chamber is entirely covered by the waste heat from the firing chamber supplied from the piping (29).

The briquettes (1,5) heated to 600-700°C in the preheating chamber (16) are then carried into the firing chamber (17).

In the firing chamber (7), fresh air is ventilated downward through the piping (26) by the blower (27), and the carbon in the briquettes is combusted by itself due to the presence of oxygen in the air.1. ○OO~
Firing is carried out by bringing the temperature to 1°300°C. Although the amount of air conveyed varies depending on the firing conditions, it has been experimentally confirmed that a volumetric velocity of 40 to 170 Nm per minute per Lm is sufficient to maintain the firing temperature within the above range. Ta.

Furthermore, if it is desired to shorten the firing time, this can easily be done by increasing the amount of air flow.

The temperature increase in the briquette layer described above is due to self-combustion of the internal carbon material, that is, attached by-product carbon, accompanied by a significant exothermic reaction as shown in the following equation.

0 + O, →002 + 97.000 Kcal
/ Kmol ・−1−−−(6)a+V2o,,−
>a○+29,400 Kca, l/Kmol-=
- (7) Such a calcination process gives the briquettes a crushing strength of at least 15 to 9/hard and at least 25%
and a porosity of at least 40%. These values (d) show a tendency to increase as the firing temperature rises, and in the examples described below, when the firing temperature reaches 1200°C, the crushing strength is 34 KLjA, the solid reduction rate is 6 Co%, and the porosity is 55%. ＜Indicated the power value.

The above-mentioned reforming of briquettes involves CQ produced by combustion of carbon on the outer periphery of briquettes through the reaction of formula (6) above;
The carbon inside the briquettes reacts (-
As a result of producing CO gas, the inside of the briquette becomes at a partial pressure of CO gas, which is thought to occur through the reaction of equation (9) below.

0 + Co2 = 2C! 0・・・・・・・・・・・・
・・・・・・・・・・・・・・・(8) Fe203+ 3C
O-2Fe + 3CO2.=-=-- (9) That is, the reduction of iron oxide to iron progresses rapidly, and the accompanying fusion of the reduced irons causes the pressure a strength to increase significantly. In addition, as the temperature increases, the consumption of carbon and the removal of oxygen by reduction of iron oxide become more active, and as a result, the porosity also increases, resulting in a high reducibility in the subsequent reduction step.

The fired briquettes obtained by the method of the present invention in step 1- are then subjected to the next step, the reduction step.

As shown in Fig. 1, the reduction process is carried out using the shaft furnace method α0).

A rotary kiln method (3G or smelting reduction method C31) can optionally be applied depending on the situation. The reducing agents used in each of these methods are as follows.

(b) Shaft Furnace Method As already mentioned with reference to Figure 3, a fluidized bed pyrolysis furnace (3
) to the C1-C4 hydrocarbon gas generated from H2O.

A gas reforming furnace (6
) to produce a reducing gas consisting of H2 and Co, which is used as a reducing agent after dehydration and desulfurization. For example, in the case of methane gas, the reaction in the reforming furnace (6) is as shown in equations (2) and (3) above.

(b) The residual carbon in the rotary kiln pre-reduced briquettes and the exterior carbon material are used as reducing agents. However, when the amount of residual carbon is small, a slightly larger amount of exterior carbon material is required than in the conventional carbon material merging method.

(c) Melting reduction method Solid carbon such as A oil coke and coal are applied.

Among the above reduction methods, the rotary kiln method, which can take full advantage of the features of the briquettes modified by the method of the present invention, will be explained in some detail below.

The briquettes whose crushing strength and preliminary reduction rate have been increased by the preheating step of the method of the present invention are charged into a rotary kiln (2)), and 20 to 50% by weight of carbon based on the weight of the briquettes is heated in an external device in a reducing gas atmosphere. Lower, 800-1,
It is reduced by heating to a temperature of 300°C, preferably 1,100 to 1,200°C. If the reduction temperature exceeds the above range, it should be avoided because it not only leads to a rise in operating costs due to wasteful consumption of thermal energy, but also tends to cause briquettes to become powder and form kiln rings.

As the exterior carbon material, for example, coke with a particle size of about 5 to 10 Wn is used at the above-mentioned ratio, preferably 30 Wn, to the weight of the briquette.
It is used in an amount of ~40% by weight. If the amount of exterior carbon material is too small, the reduction rate will decrease, and as the amount of exterior carbon material increases, the reduction rate will increase, but conversely, the reduction contribution rate of interior carbon material will decrease, so use more than necessary should be avoided. It is.

It is suitable that the occupancy rate of the substances in the rotary kiln, that is, the ratio of the briquettes and the exterior carbon material to the kiln internal capacity, is about 15 to 20%. Heating is performed by operating the main burner and a shell burner installed on the rotary kiln jacket, and it takes about 1 hour to raise the temperature from the preheating temperature to the specified reduction temperature, and then maintain that temperature for another 1 hour. Ru. The waste heat from the rotary kiln can be used for the preheating process as described above.

An example of the composition of the reducing gas in the above reduction step is N2:
Co: Co2=75:5:20 or P(10/(PQO+Pco2)=0.2-
--<10), but when the value of the α0) formula is increased to O26, the reduction rate further improves, but on the other hand, the reduction contribution rate of the interior carbon material decreases, and the reduction The residual amount increases.

In the above-mentioned reduction process, the briquettes are reduced to a metallization rate of iron and a reduction rate of 90% or more.

The fired briquettes pre-reduced by the method of the present invention are
Because of its high preliminary reduction rate and high reducibility derived from its large porosity, high-rate reduction can be easily carried out in a relatively short time by any of the above-mentioned reduction methods. Especially when applying the rotary kiln method, kiln transfer,
Powdering of briquettes due to abrasion is minimized,
This method has the remarkable effect of preventing a decrease in yield and the formation of kiln rings, achieving stable operations, and significantly improving operating rates and productivity. In addition, preheating in the method of the present invention can be performed by using the waste heat of the subsequent rotary kiln at the time of start-up, and by using the waste heat of firing during stable operation, so there is no increase in energy costs and less operation is required. Another advantage is that it can be implemented at low cost.

The above-mentioned excellent functions and effects of the method of the present invention will be further described with reference to the following Examples, Reference Examples, and Comparative Examples.

The crush strength and porosity in Examples and Comparative Examples were determined as follows.

(1) Crushing strength Using a Shimadzu R8g type universal strength testing machine, apply a compressive load to one briquette at a specified pressurizing speed, and calculate the crushing strength value of the briquette as the load at the moment the briquette breaks <bye. , 20 granules were destroyed and their average value was expressed.

(2) Porosity Calculated from the true specific gravity and apparent specific gravity of the briquette sample using the following formula.

PC%) = (S -5A)
B (approximately 1.5 cc) was made into an almond-nut shape.

Comparative Example 5 parts by weight of heavy residual oil was added to 95 parts by weight of iron ore powder with 13.6% by-product carbon attached, which was extracted from the fluidized bed pyrolysis furnace of the heavy residual oil pyrolysis equipment that does not utilize iron ore powder, as shown in Fig. 1. The mixture was mixed as a binder to produce raw briquettes.

Iron ore from Rio Doce (Brazil) was crushed in a ball mill, coarse particles were removed, and the iron ore was heated and dried at 150°C before use. However, the particle size of the iron ore powder used as the fluidized bed in the fluidized bed pyrolysis furnace was -325mesh 60%, and the heavy residual oil used was in the column of the vacuum distillation equipment currently used in commercial production. The bottom oil is Daqing crude oil. The properties of the heavy residual oil are as follows.

[Physical properties]

Specific gravity (1574℃) o, 927a Viscosity (centistokes) 343 (at 75℃) 120 (a
t 100℃) Softening point (℃) 40.6 [Elemental analysis value] 0: 8'7.0% H: ], 22.3%: 0.39% S: 0.22% [Industrial analysis value] ASH : 0.03% V/M : 92.51% Bl (++7.46%) The briquetting conditions and properties of the raw briquettes were as follows.

[Brikerating conditions]

Kneading time: 5.0 minutes Kneading temperature: 80℃ Molding pressure: 1soKy/crd [Physical properties of raw briquettes] Apparent specific gravity: 2'75 f/aa True specific gravity: 3.90 f/cc Porosity: 29.49% Crushing strength: 4.4Kg/piece [Chemical composition of raw briquettes] T, Fθ: 55.47% FeO19,09% M-ret: 0.09% 0' 13.00% 0,07'7 % The sample was charged into the Briquera Trapot grate furnace described above, and a preheating test was conducted based on the conventional method using four types of heat patterns as shown in FIG. 3, assuming preheating using waste heat from the rotary kiln. Table 1 shows the preheating conditions and the properties of the obtained briquettes.

(Hereinafter, blank space) As shown in Table 1, the crushing strength of briquettes subjected to the conventional preheating process is 1.8 to 6.8 to 9, and the strength decreases as the preheating temperature increases. In the case of about 850°C (Experiment A, PH-2), it shows a very low value of 1.8 kg. When this material was subjected to a known reduction process in a rotary kiln, the granules were considerably powdered in the kiln, resulting in a decrease in yield and the formation of lumps or kiln rings as shown in Figure 4. This caused a problem in operations.

Example: 3 kg of briquettes produced in the above comparative example were charged into a pot grate furnace so that the sample layer height was olff+.
Preheat the burner from below the grate and bring the sample layer temperature to 6.
After the temperature was set at 00°C to 700°C, the burner was extinguished and air was ventilated downward to self-combust the carbon in the briquettes and sinter them.

In addition, the air flow rate is 42, 86, 125 Mrr per minute?
/rr? It was changed to three levels.

FIG. 5 is a diagram showing a heat pattern during preheating and firing. In an experiment in which air was blown at 125 Nm''/rn' per minute, the temperature at the bottom of the sample layer increased to 125 Nm''/rn' in 9 minutes.
The temperature reached 0°C.

Table 2 shows the preheating and firing conditions and the properties of the briquettes after firing.

(Hereinafter, blank space) The diagram in Figure 6 shows the firing temperature, reduction rate of fired briquettes,
It shows the relationship between crushing strength and porosity.

As is clear from the figure, the reduction rate increases as the firing temperature increases, and at a firing temperature of 1,200°C, the reduction rate increases by 6.
A return rate of 1% was obtained. This degree of reduction is 1 or less because CO2 produced by the combustion of carbon on the outer periphery of the briquette reacts with the carbon inside the briquette to generate COf, creating a high CO partial pressure inside the briquette. , it is confirmed that this is caused by the above-mentioned formula (9), since the cross section of the sample briquette was observed, and it was confirmed that the reduction was proceeding from the inside.

Similar to the behavior of the reduction rate, the crushing strength increases as the firing temperature increases, and when fired at 1,200°C, it shows a high strength of 34 kg.

The porosity increases as the temperature increases, as carbon consumption and oxygen removal through reduction become more active.

The amount of carbon consumed is 9% when the firing temperature is 1,000°C.

10.5%, l for 1100℃, 1 for 200℃
It was 0.7%.

The above experimental results demonstrate that the preheating firing method according to the present invention significantly improves the strength and enables high prereduction by utilizing the total carbon content in the briquettes as a heat source and reducing agent.

Reference Example: Covering of fired briquettes produced by the method of the present invention! In order to evaluate performance including originality, reduction experiments were attempted using a rotary kiln and a simulator.

The reduction conditions include reduction temperature 1. ．． 335℃, reduction time 20 minutes, external coal content 40% by weight, kiln rotation speed 10
It was carried out in r, p, m.

In addition, N2 near 5% was used as a gas for atmosphere adjustment.

A mixed gas of 0.002: 15% and Co: 1.0% was circulated for 15η.

Table 3 shows the properties of the preheated preheated by the conventional method and the preheated prequent fired at 1,200° C. by the method of the present invention, which were used in this experiment.

FIG. 7 is a graph showing a comparison of changes over time in the reduction rate and powdering rate of the two briquettes.

Comparing the two methods in terms of the reduction time required to obtain a reduction rate of 90% or more as a raw material for electric furnace steelmaking, it is found that the reduction time required for the conventional method is 10%.
Compared to 0 minutes, in the case of the method of the present invention, the time can be shortened to 60 minutes, making it possible to significantly improve productivity.

However, in the case of the conventional method, pulverization during reduction begins actively from the early stage of reduction, reaches a maximum value of 55% pulverization rate at 60 minutes of reduction time, and then apparently decreases as reduction progresses. This apparent reduction in the powdering rate is due to the fact that once powdered material is exposed to a high temperature atmosphere, it welds with the nearby briquettes and the exterior carbon material, resulting in agglomerated materials as shown in Figure 4. This is to generate.

On the other hand, the pulverization rate of briquettes by the method of the present invention is significantly reduced, and even in the maximum case through the reduction process,
It is only within 0%.

From the above results, it can be concluded that the briquettes pre-reduced by the method of the present invention have excellent reducibility compared to briquettes produced by the conventional method, have very little powdering during reduction, and are extremely good briquettes. confirmed.

[Brief explanation of the drawing]

Figure 1 is a flow sheet showing an overview of the reduced iron production method using heavy residual oil applying the method of the present invention, Figure 2 is a flow chart of the preheating step in the method of the present invention, and Figure 3) (B) (C) Figures 4(a) and 4(b) are diagrams of the four types of heat patterns in the preheating process according to the conventional method, Figures 4(a) and 4(b) are morphological diagrams of the agglomerates produced by pulverizing briquettes in the rotary kiln, and Figure 5
The figure is a diagram showing the heat pattern during preheating and firing according to the method of the present invention, and Figure 6 shows the relationship between the firing temperature during firing according to the method of the present invention and the reduction rate, crushing strength, and porosity of the fired briquettes. FIG. 7 is a diagram comparing and comparing the changes over time in the reduction rate and powdering rate in the reduction process of briquettes obtained by the conventional method and the method of the present invention. (1)・・・・・・Iron ore heating furnace, (2)・・・・・・
·Piping. (3)...Fluidized bed pyrolysis furnace, (4)...
····Piping. (5)...Piping, (6)...Gas reforming furnace. (7)・・・・・・Cooling! , (8)... Gas heater. (9)...Desulfurization tower, α0)...Shaft furnace. (11)・・・・・・Downward piping, (b)・・・・・・
··Piping. (1B)・・・・・・ Briquerating machine. 0→・・・・・・Great kiln, α5）・・・
...briquettes. (16)... Preheating chamber, a7)... Firing chamber. (to))...Traveling Great. (Hot blast stove or burner, /2D...)
·····Piping. (2 Thirst...Air collection hopper, (23)...
...Exhaust fan. C(a)・・・Exhaust chimney, Q■・・・・・・
·duct. (2e...Piping, (2)...Blower, (2 mark...Hopper. (29)...Piping, (To)・・・・・・・・・
Rotary kiln method. can・・・・・・-melting reduction method. 6th figure

Claims (1)

[Claims] ■. Carbon-adhered iron ore powder, which is a by-product when producing light oil and cracked gas by thermally decomposing heavy residual oil using iron ore powder as a heat medium, is formed into a briquette shape and subjected to a preheating process. After that, in the preheating step of the method for producing reduced iron using the carbon of the briquettes as a reducing agent, the briquettes are supplied to a great kiln consisting of a preheating chamber and a subsequent firing chamber. After heating to °C,
Continue to blow air in the firing chamber for 1,000 to 13,000 yen.
A method for modifying granules from iron ore powder used for heavy oil pyrolysis, characterized by bringing the humidity to a temperature of ℃. 2. The air flow rate is 40% per minute per minute.
A method for modifying granules from iron ore powder used for heavy oil pyrolysis according to claim 1, which is carried out at a volumetric rate of 1'7 ONrn''. 8. The briquettes have a weight of at least 10 A method for modifying granules made from iron ore powder used for thermal decomposition of heavy oil according to claim 1 or 2, which contains carbon in the amount of carbon.4. 4. A method for modifying granules made from iron ore powder used in heavy oil pyrolysis according to any one of claims 1 to 3, wherein hot air is effectively used to heat a preheating chamber.