JPS5928606B2 - Method for producing reduced iron powder through pyrolysis of heavy oil - Google Patents

Description

Detailed Description of the Invention The present invention not only pyrolyzes heavy oil to produce light oil and cracked gas, but also utilizes the by-product carbon produced during the pyrolysis to reduce iron ore and produce reduced iron powder. The purpose of the present invention is to improve the reaction efficiency and simplify the manufacturing process by reducing the powder as a powder using a rotary kiln reduction furnace.

Originating from the problem of depletion of petroleum resources, there has recently been a great deal of interest from various quarters in the technology of pyrolyzing heavy oil to produce light oils such as gasoline and diesel oil. Various uses of carbon and other resources are being discussed.

Conventionally, there has been a fluid coking method in which by-product coke during the thermal decomposition of heavy oil is extracted as a product, and this method is widely used. It decomposes thermally as a medium, and powder coke does not act as a catalyst.
Since it is used simply as a heat and fluid medium, it does not deactivate even if by-product coke is deposited, and therefore, heavy oil is easy to treat. It is used in the production of feedstock oil for the fluid catalytic cracking method (FCC method), which is known as a method for lightening oil.
Compared to the King method, this method has advantages such as being a completely continuous process and having a higher yield of decomposition products.

However, on the other hand, due to the above-mentioned usage conditions, the product coke has the disadvantage that it is not suitable for purposes other than fuel in terms of quality.

In light of recent trends and the current state of technology,
Focusing on the more effective use of carbon (coke) that is produced as a by-product in the fluidized contact or thermal decomposition of heavy oil, such as the FCC method or fluid coking method mentioned above, reducing agents for producing reduced iron have attracted attention as a way to utilize it, and rationalization has been developed. A method for extracting light oil and obtaining reduced iron using a process has been developed.

In response to these circumstances, the present applicant has been conducting various research for some time, and first used iron ore particles instead of silica/alumina particles and powder coke in the fluidized pyrolysis of heavy oil, and developed a fluidized bed. We proposed a rational method for supplying heated iron ore particles, which serve as a heat source for a pyrolysis furnace, and a number of further advanced methods.

The present invention further provides, as part of these methods, the use of the iron ore in the form of powder, and the production of light oil and cracked gas by thermally decomposing the heavy shaft in a fluidized bed pyrolysis furnace that maintains the powder in a fluidized state. In addition, the present invention provides a new and more preferable thermal reduction means in the method for producing reduced iron powder by reducing iron ore using the by-product carbon generated during the thermal decomposition, and At the time of decomposition, the by-product carbon is attached to iron ore powder particles and extracted from the fluidized bed pyrolysis furnace,
The method is characterized in that the resulting carbon-adhered iron ore powder is supplied in powder form to a rotary kiln-type reduction furnace for thermal reduction.

Here, the rotary kiln method has the advantage of being a direct steelmaking method that can use solid reducing agents such as coal and coke powder, and can be used in a wide range of ore particle sizes, as well as being capable of reduction at fairly high temperatures. It has the advantage that the produced reduced iron has excellent reoxidation resistance.

This rotary kiln method has a long history, and has been operated for a variety of purposes, including the production of raw materials for steelmaking and the treatment of ducts generated within steelworks, using solid reducing agents suited to local conditions.

The SL/RL method utilizes such a rotary kiln, in which iron ore is granulated in a pelletizer, then preheated in a traveling grade, and then transferred to the rotary kiln, but at the same time, fixed reducing agents such as coal and coke breeze are mixed in. Heavy oil, gas, pulverized coal, etc. are used as the main burner raw materials.

This method is usually called the carbon sheathing method because it is transferred to a kiln and mixed with the sheathed carbon grains for reduction.
There are various methods such as the carbon material interior method and the carbon material merging method.

However, what is common to all other methods except the oxidation pellets 1 to reduction method is the problem of pulverization in the kiln and during the reduction process.

If the pulverization is significant, not only will a large amount of ore escape from the kiln inlet in the airflow, but powdered iron will adhere to the bricks in the high-temperature parts of the kiln, forming so-called rings, which will cause major problems in operations.

According to the applicant's experiments, a typical example of the change in strength inside the kiln in the carbon material sheathing method and the combined method is that even if the preheated pellets have a constant strength, the strength decreases in the first half of the kiln, and then , it has been found that it improves again.

The reason for this is due to the use of a rotary kiln.
The crystal structure at the stage of change to magnetite changes from hexagonal (lattice constant a-5, 42) to cubic (cubic, a).
= 8.38 people),
This is also promoted by the increase in voids due to oxygen escape and carbon consumption during reduction.

At the New Zealand Steel Company, titanium-containing iron ore powder was once granulated and heated using the carbon material sheathing method shown in the above representative example, and then reduced in a kiln. I had some concerns, so I took the plunge and removed the preheating grade, and by supplying iron ore powder (100 to 200μ) with controlled particle size directly to the kiln together with the exterior carbon material and performing reduction, I was able to achieve smooth operation. reported that it was obtained.

The method of the present invention having the above-mentioned characteristics is thus similar to the suggestions of the New Zealand Steel Company, but it also requires measures to further increase the reduction efficiency and prevent the phenomenon of adhesion within the kiln. This is what I learned.

Hereinafter, specific embodiments of the present invention will be described further based on the accompanying drawings.

The figure is a flow sheet showing an example of the manufacturing method of the present invention.
For example, Conradson carbon 5-30 ratio, specific gravity 0.90
Heavy oil such as vacuum distillation residual oil of ~1.10 is stored, and is preheated in a preheating furnace 2 to a temperature below 400°C at which thermal decomposition does not occur, and then passed through a pipe 11 into a vertically cylindrical fluidized bed. The heavy oil is supplied to the pyrolysis furnace 4 and is catalytically cracked by the iron ore powder that is supplied from the piping 14 and is in a fluid state within the pyrolysis furnace 4, and 70 to 90% of the supplied heavy oil is from the top of the pyrolysis furnace 4. Piping 1
6 and sent to a known rectification separation system 5 where it is separated into respective fractions such as cracked gas, gasoline, light gas oil, etc., and the heavy fraction is taken out of the system as residual oil. It has become.

In order to fluidize the iron ore powder in the pyrolysis furnace 4, high-temperature steam is separately supplied to the pyrolysis furnace 4 from a pipe 21, and these iron ore powder and steam are fed into the pyrolysis furnace 4 at a temperature of 400. The supply is controlled in the amount and temperature necessary to form a fluidized bed at ~630°C.

In this case, it is of course possible to partially reduce the iron ore at this stage by raising the pyrolysis temperature to 630°C or higher, but it is generally disadvantageous thermally to raise the pyrolysis temperature in this way. Therefore, preferably the above temperature range is adopted.

The superficial velocity in the pyrolysis furnace 4 is generally 30 crrL/sec.
Thereafter, the furnace is operated at a pressure of 2 kg/m or less, and as mentioned above, approximately 70 to 90% of the heavy oil is sent from the top of the furnace as a decomposition product to the separation system via piping 16, and the remaining approximately 10 to 30% of the heavy oil
The carbon becomes a by-product carbon, which adheres to the iron ore powder and is discharged from the pipe 15 to the rotary kiln, which is the next process.

On the other hand, the iron ore powder to be supplied to the fluidized bed pyrolysis furnace 4 is crushed or pulverized in advance to the extent that it will not be scattered in the gas flow at the inlet of the kiln and stored in the hopper 7. The ore heater 3 is then heated to 500°C or higher, usually 600°C to 700°C, by high-temperature exhaust gas of approximately 800 to 1100°C supplied from a rotary kiln reduction furnace 6, which will be described later, through piping 20. It is fed to the fluidized bed pyrolysis furnace 4 through a pipe 13.

Since the decomposition reaction in the pyrolysis furnace 4 is usually an endothermic reaction, a sufficient amount of heat must be supplied to the furnace 4.
Moreover, since this amount of heat is mainly the amount of heat carried into the furnace by the iron ore powder, a portion of the by-product carbon-adhered iron ore powder extracted from the pyrolysis furnace 4 is preferably 90% or more. is returned to the ore heater 3 through the piping 14 and reheated, and then returned to the pyrolysis furnace 4 through the piping 13 described above.
An arrangement is made to form a circulation circuit for iron ore powder to be supplied to the pyrolysis furnace 4 to increase the amount of heated iron ore powder supplied to the pyrolysis furnace 4.

In the above case, although it depends on the type of heavy shaft, pyrolysis temperature, or type of iron ore, the amount of heat in the high-temperature exhaust gas alone is generally insufficient to heat the iron ore. Supply air as shown by the arrow in the figure,
Either burn some of the by-product carbon attached to the iron ore to make up for the lack of heat, or use a separate burner (not shown) to burn it.
Fuel such as heavy oil or gas is supplied and combusted to generate high-temperature combustion gas, which is supplied to the ore heater 3 through piping to replenish the insufficient amount of heat, or furthermore, there is a considerable amount of CO in the high-temperature exhaust gas. Since it contains gas, it is possible to combust it in advance in an exhaust gas combustor (not shown) to turn it into a higher-temperature gas and supply it to the ore heater 3. It is a preferred embodiment to use them in appropriate combinations.

In particular, when burning part of the carbon adhering to the surface of the iron ore powder in the heater 3, the amount of air supplied to the combustor etc. may be reduced to some extent, although the air supply system is not shown. By making it excessive, it is also possible to replace the air supply with the piping arrow.

Furthermore, the supplied air also has the role of burning exhaust gas from the reduction furnace.

As the ore heater 3, a fluidized bed type one is used like the pyrolysis furnace 4 as shown in the figure, but it is not limited to this, and any device that can continuously heat the iron ore powder can be used. Layered and other structures may also be used at any time.

In this way, the surface of the iron ore powder is coated with the by-produced carbonaceous material, but this carbon-adhered iron ore powder is subsequently mixed with an exterior carbonaceous material through the pipe 22 as necessary, and subjected to rotary kiln type reduction. Transfer to a furnace and heat and reduce.

The Rochley kiln type reduction furnace 6 is usually heated by burner combustion of heavy oil, gas, coal, etc., and the gas phase inside the kiln is filled with CO2CO2°H2O as combustion exhaust gas.

On the other hand, in the solid phase, carbon-adhered iron ore powder is F e O+ CO= F , e + CO2 (2) C
It is necessary to cause a reaction consisting of +C02=2CO (3>), and therefore an atmosphere with a high CO gas concentration must be maintained.

What should be noted here is that the reducing gas is gas obtained by separating cracked gas from the pyrolysis products discharged from the pyrolysis furnace 4 and reforming it in a gas reforming furnace, for example, the desulfurization equipment 10. be.

This gas is blown into the rotary kiln from pipe 17 through pipe 19, but since the surface of the iron ore powder in the furnace is coated with carbon, it is possible to reach a temperature of over 900°C, and the cracked gas is In the furnace, which is maintained in a reducing atmosphere of 800 to 1200°C in conjunction with high temperature, the carbonaceous material on the powder surface reacts as follows: Fe2O3+3C→2Fe+3CO, and the iron ore is reduced to an iron grade of 85 to 9.
It becomes reduced iron of about 5 ratio, and the subsequent rotary cooler 8
, and is sent out as reduced iron powder through briquettes 9.

Note that H2-H2O in Fe-0-based materials.

The equilibrium relationship with C0-CO2 gas needs to be maintained above a certain value as described above in order to proceed with the reduction of iron oxide and generate metallic iron.

Therefore, the solid phase in the rotary kiln is desired to be exhausted by the burner, but one of the roles of the exterior carbonaceous material in the carbonaceous packaging method is to provide CO gas as a reducing agent, and the other is to remove acid gas from the gas phase. The goal is to block the migration of into the solid phase.

Although it cannot be disputed that this requires a considerably large amount of exterior carbon material relative to the Fe-0 material, in the method of the present invention, the periphery of each iron oxide in the iron ore powder is covered with carbon material. Therefore, the iron ore powder during the reduction reaction is not directly exposed to the gas phase, making it possible to reduce the blending amount of the exterior carbon material to the necessary minimum.

In order to make the reaction in the rotary kiln effective, the total amount of the carbonaceous powder mixed through the pipe 22 and the carbonaceous material in the carbon-coated iron ore powder sent out from the fluidized bed pyrolysis furnace should be adjusted to reduce the iron ore. It is desirable that the amount be in excess of the theoretical amount required.

Furthermore, it is most industrially advantageous for the amount of by-product carbon adhering to the iron ore powder to be in the range of 2 to 20 times the carbon adhering iron ore powder.

The average particle size of the carbon-attached iron ore particles is extremely small, 50 to 100μ, and therefore the reduction reaction proceeds quickly, so the residence time of the iron ore particles in the kiln is significantly shortened compared to the conventional pellet reduction method. It takes about 15 to 40 minutes.

As a method for managing the residence time in the kiln, the following Warner equation is well known.

t: Residence time in the kiln (minutes) D: Inside diameter of the kiln (m) N: Kiln rotation speed (rpm) L: Kiln length (m) f: Raw material compression coefficient (K1.0) θr: Raw material repose angle (degrees) θS: Kiln inclination angle (degrees) In the above equation, flθr is a raw material characteristic and D7L is a value determined by the kiln, so the residence time t is N, θ
It will be constantly managed by S.

Therefore, in the present invention, the residence time (1) is 15 to 4
The above-mentioned N and θS will be managed so that the time will be 0 minutes, and in particular, θS will be managed so that the value in the conventional pellet method is reduced.

Next, as the raw material oil to which the method of the present invention is applied, it is also possible to use low-quality vacuum distillation residual oil, such as that used in the fluid coking method, since there is essentially no need to suppress carbon by-products in the pyrolysis process. , other heavy oils include solvent deasphalt extraction residual oil, pyrolysis residual oil, catalytic cracking residual oil, heavy gas oil,
Vacuum gas oil, other fluid coking method and FCC
All feedstock oils used in the process can be used, as well as oily substances obtained from coal, oil sands, shale, etc.

In addition, the iron ore used in the present invention includes various iron ores that are used as ordinary raw materials for iron making, and examples of constituent minerals include magnetite, hematite, pyrite, pyrrhotite, magnetite, magnetite, etc. According to other classifications, Kiruna
Type, Taberg type, Ma-gnitnaya type, Bil bao type, Laterite type, A1go type
ma type, Lake 5upper type, C11nto
Examples include n-type, Minette-type, etc., and it goes without saying that any of them can be used in the present invention, although there may be some changes in composition.

As explained above, the method of the present invention is a method in which the thermal decomposition of heavy oil in a fluidized bed and the reduction of iron ore using the by-product carbon resulting from the thermal decomposition are carried out in a rotary kiln state in a powdered state. The features of this method can be summarized as follows.

(1) Since the iron oxide or reduced iron powder is individually coated with carbonaceous material and is not directly exposed to gaseous oxidizing gas, the atmosphere in which reduction progresses is high. (2) Point (1) above It has the advantage that exterior carbonaceous material is not necessary, or even if it is necessary, only a very small amount is required.

(3) Iron ore is a powder and is smaller in size than ores or pellets, so it conducts heat quickly and has good heat transfer efficiency.

(4) As mentioned above, since the surface is coated with carbonaceous material, mutual adhesion and ring formation do not occur at all even in the rotary kiln.

(5) Since there is no granulation process or preheater, the reduced iron manufacturing process is simplified and practical.

Thus, the method of the present invention can process heavy oil and iron ore in large quantities in one process, and can produce reduced iron with high efficiency without producing by-products with low load value. It is a method that can quickly respond to current trends and is expected to be industrialized.

[Brief explanation of drawings]

The figure is a flow sheet showing an example of the method of the present invention. 1...Oil tank, 2...Preheating furnace, 3...
...Ore heater, 4...Fluidized bed pyrolysis furnace, 5
... Rectification separation system, 6 ... Rotary kiln.

Claims (1)

[Claims] 1. Fluidized bed pyrolysis furnace 4 that maintains iron ore powder in a fluidized state.
In the method of pyrolyzing heavy oil to produce light oil and cracked gas, and reducing iron ore using by-product carbon generated during pyrolysis to produce reduced iron powder, the method comprises: At the time of thermal decomposition, the by-product carbon is attached to iron ore powder particles and extracted from the fluidized bed pyrolysis furnace 4, and the obtained carbon-adhered iron ore powder is supplied in a powder state to a rotary kiln type reduction furnace 6, A method for producing reduced iron powder through thermal decomposition of heavy oil, the method comprising producing reduced iron powder by heating. 2. An ore heater 3 is provided to preheat the iron ore powder to be supplied to the fluidized bed pyrolysis furnace 4, and a part of the carbon-adhered iron ore powder extracted from the fluidized bed pyrolysis furnace 4 is heated to the ore heater 3. A method for producing reduced iron powder through thermal decomposition of heavy oil according to claim 1, which comprises returning the oil to reheating. 3 Production of reduced iron powder with thermal decomposition of heavy oil as described in claim 2, in which a part of carbon attached to iron ore particles is burned in the ore heater 3 and used for heating the iron ore powder. how to. 4. A method for producing reduced iron powder through thermal decomposition of heavy oil as set forth in claim 2, in which high-temperature exhaust gas from the rotary kiln-type reduction furnace 6 is supplied to the ore heater 3 and used for heating iron ore powder. . 5. A claim in which carbonaceous powder is supplied together with carbon-adhered iron ore powder into the rotary kiln-type reduction furnace 6, and the total amount of the adhering carbon and carbonaceous powder is in excess of the theoretical amount necessary for iron ore reduction. A method for producing reduced iron powder through thermal decomposition of heavy oil according to any one of items 1 to 4. 6 Claims 1 to 5, wherein the iron ore heating temperature in the rotary kiln type reduction furnace 6 is 800 to 1200°C.
A method for producing reduced iron powder through thermal decomposition of heavy oil according to any one of the preceding paragraphs. 7. Reduced iron powder with thermal decomposition of heavy oil according to any one of claims 1 to 6, wherein the amount of by-product carbon attached to the iron ore powder is 2 to 20% wt of the carbon-attached iron ore powder. How to manufacture.