JPS5844722B2 - Sankatetsugan Yuzairiyou Okangensuruhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the complete or partial reduction of a powdered material containing iron oxide mixed with ground solid carbonaceous material at a temperature below the melting point of iron.

Solid carbonaceous material refers to coke obtained from carbon-containing fuel and reducing agents, such as anthracite, coal or oil.

Powder material containing iron oxides means iron ore concentrate, calcined iron sulfide or other materials containing iron oxides
It refers to particles with a particle size of up to m.

It has already been proposed to reduce iron oxide-containing powder materials mixed with powdered solid carbonaceous materials, for example in rotary furnaces or in fluidized beds of the usual type.

The present invention does not use the usual type of fluidized bed, but instead uses a so-called circulating fluidized bed.

Regarding the presence conditions of circulating fluid, please refer to the Chemical Engineering Progress (CHEM, ENGINEERI).
NGPROGRESS) (February 1971) No. 6
See Vol. 7, No. 2, pp. 58-63.

Most previous attempts to utilize fluidized bed technology to reduce materials containing iron oxides have used conventional fluidized bed technology; There were difficult problems due to keeping the gas in place.

Efforts to increase efficiency in such processes by increasing reaction temperatures have resulted in sticking problems;
That is, small particles of material in the fluidized bed agglomerate into larger particles that clump together and eventually make flow impossible.

By using a circulating fluidized bed, the contact time can be increased, the tendency to sticking being much smaller due to the active internal circulation of the material.

Adhesion increases with increasing temperature, degree of metallization and fineness of the fluidized bed material, and as the content of turbulent gangue, total pressure and addition of pulverized diluent (e.g. coke) increases. Decrease.

A powdered material containing iron oxide mixed with a powdered solid carbonaceous material is mixed with a circulating fluidized bed in which the carbonaceous material is partially combusted with a gas containing molecular oxygen introduced as a fluidizing gas. An experiment was conducted in which the reduction was carried out on the floor.

By adding solid, finely divided carbonaceous material, the risk of sticking is reduced and the temperature can be increased, thus increasing the reaction rate.

However, if the gas containing molecular oxygen is blown into the bottom of the reactor through the distributor for fluidization, there is also a tendency in this case to agglomerate in the distributor, possibly due to local overheating.

The present invention relates to a method for reducing a pulverulent material containing iron oxide mixed with a pulverized carbonaceous material in a circulating fluidized bed while completely avoiding adhesion between particles, and an apparatus for implementing this method. be.

According to the present invention, a circulating fluidized bed of pulverized material containing iron oxide mixed with pulverized carbonaceous material is maintained in a vertically elongated reaction zone.

This circulating fluidized bed is maintained by feeding it with appropriate flows of pulverized material containing iron oxide, pulverized solid carbonaceous material and optionally liquid carbonaceous material together with molecular oxygen-containing gas.

The mixture of gas and solid material exits the reaction zone and is separated;
The solid material is then returned to the reaction zone.

The pulverized material containing iron oxide is fed to the fluidized bed for less than 1 hour,
Preferably it has a particle size of 0.5 mm or less.

The pulverized solid carbonaceous material fed may be coke breeze, anthracite dust or coal dust, but must have a particle size of less than 3 mm, preferably less than 1 u.

The reaction zone can be considered divided into an upper part, a lower part and a middle part.

In the method of the invention, a finely divided iron oxide-containing material, a carbonaceous material and a molecular oxygen-containing gas are supplied to the intermediate section.

Partial combustion of the carbonaceous material in this section generates the heat necessary for this process.

Coking and gassing of the carbonaceous material occurs in the upper part of the reaction zone, as well as reduction of carbon dioxide formed during combustion with carbon and water to produce hydrogen gas and carbon monoxide.

Some reduction of the iron oxide-containing material also occurs here.

This reaction occurs stably at temperatures of 850-10,000G.

The flow of solid carbonaceous material is controlled so that there is always a sufficient amount in the bed to prevent interference with fluidization due to agglomeration.

The dissolved gas is discharged from the top, mixed with solid material from the floor.

The solid material is separated from the gas and returned to the intermediate section.

It has been found that the ability of solid carbonaceous materials to prevent sticking is dependent on the temperature and the nature of the iron oxide containing material.

It has been found that when using conventional iron ore concentrate at a temperature of 900° C., the weight ratio between solid carbonaceous material (coke) and concentrate in the reaction zone must be at least 0.5:1. .

A portion of the discharged gas is further subjected to dust separation to remove most of the CO2 and H2O it contains and is returned to the reaction zone so that the amount of solid material in the reaction zone remains constant.

The overall transport of solid material is countercurrent to the gas introduced into the lower part.

Transfer of heat from one section of the reaction zone to the lower section is maintained primarily by internal circulation of materials in the reaction zone.

The discharged solid material consists of coke and fully or partially reduced iron oxide, and is preferably cooled below the Curie temperature of the iron and substantially coke-free and substantially iron-free coke. Divided into parts.

Cooling is suitably accomplished by feeding the material through a conventional fluidized bed formed of the material itself with built-in cooling surfaces.

Gases containing molecular oxygen are suitably used as coolants and are then preheated.

It is desirable to control the flow of air mixed with a gas containing molecular oxygen, such as perhaps CO2 and/or H2O, to meet the heat demand to maintain the desired temperature in the circulating bed.

This heat is generated by partial combustion of carbonaceous material.

Additionally, all or part of the heat can be supplied indirectly from an external heat source, such as a nuclear reactor.

In this case, the heat can be transferred by means of hot gas to the heating active surfaces installed in the reaction zone.

In order to prevent the generation of excessive heat per unit volume of the reaction zone, which gives rise to the risk of local overheating and some degree of agglomeration of the bed material, the flow of the molecular oxygen-containing gas is preferably , which are introduced at several points at several levels in the middle part of the reaction zone.

The solid carbonaceous material is suitably fed into the middle part of the reaction zone in several jets, preferably with the aid of reducing gas and/or neutral gas blowing through nozzles.

However, for carbonaceous materials with such a low volatile content, e.g. anthracite, it is possible to use molecular oxygen-containing gases, e.g. air, in which case it is preferable not to preheat to prevent local overheating. .

For this purpose, depending on the shape of the blowout nozzle,
A gas flow rate that accounts for 10-30% of the gold deposit on the carbonaceous material may be required.

Furthermore, the carbonaceous material can also be introduced via a relatively small auxiliary reaction zone separate from the reaction zone, in which the fluidized bed is maintained with the aid of a partial flow of molecular oxygen-containing gas.

In this case, gases and materials are conducted from the auxiliary reaction zone via a common pipe into the middle part of the reaction zone.

Some partial combustion of the carbonaceous material occurs in the auxiliary reaction zone, and agglomeration around the distributor opening therefore results in a shorter residence time of the carbonaceous material there (
This means that only a few particles can be burned to ash).

When the concentration decreases and local overheating occurs, agglomeration and agglomeration easily occur.

Some of the solid carbonaceous materials may be replaced by liquid carbonaceous materials, such as petroleum.

In this case it is preferred to spray it in the form of multiple jets into the middle part of the reaction zone.

The so-called atomization of the oil, which is associated with complete combustion, is not necessary.

Relatively rough oil dispersions are sufficient, which are obtained when the oil is fed as a partial stream via a pipe together with a non-oxidizing gas.

A volume ratio of ioo:i is suitable for the gas and oil used.

If an auxiliary reaction zone is used, it is preferably fed with oil, and the level at which it is fed should be 0.5 m above the bottom of the distributor for the molecular oxygen-containing gas.

The exhaust air from the reaction zone can be used, at least in part, to preheat the iron oxide-containing feedstock by direct contact.

This part of the exhaust gas is then recycled to the lower part of the reaction zone after removing most of the CO2 and H20 contents in a known manner and is used as fluidizing and reducing gas in the lower part of the reaction zone. .

A substream of the exhaust gas substantially free of CO2 and H2O is suitable for use as fluidizing gas in the cooling and magnetic separation of the material discharged from the lower part of the reaction zone.

By operating the entire process above atmospheric pressure (eg 1-10 atm), the size of the equipment can be reduced considerably.

The heat content (physical and chemical) of the exhaust gas is suitably used to generate electrical energy, with which the reduced iron-containing material, for example, is melted and possibly finally reduced.

Illustrated embodiments of the method and apparatus according to the invention will now be further described.

This embodiment includes a vertically long reactor 1,
Its upper part 2 constitutes the upper part of the reaction zone, the central part 3 of the reactor constitutes the middle part of the reaction zone and the lower part 4 of the reactor constitutes the lower part of the reaction zone.

A cyclone 5 is connected to the upper part 2 of the reactor and is provided with a return line 6 leading to the central part 3 of the reactor.

This zone also has one or several inlets for carbonaceous material 7.

The molecular oxygen-containing gas is fed into the central part 3 of the reactor in a number of sub-streams via nozzles 8, while the recycled sub-streams of the gas are passed through suitable distributors 9 to the lower part 4 of the reactor.
supplied to

The treated solid material is delivered to the outlet 10 in the lower part of the reactor.
is discharged through, is cooled in a cooler 11 and reaches a magnetic separator 12 where it is separated into a substantially coke-free iron portion 13 and a substantially iron-free coke portion 1.
It is divided into 4.

The gas 15 (preferably air) containing molecular oxygen is 1
6, it is blown out to a cooler 11, where it is preheated, and then further passed through a pipe 17 to a nozzle 8.

The cooler 11 is preferably of the conventional fluidized bed type with built-in cooling elements, through which the molecular oxygen-containing gas is conducted for preheating.

Some (e.g. 50%) of the exhaust exiting the exhaust pipe 18 from the cyclone 5 is directed to a venturi device 19 where it collects iron oxide-containing powder material (e.g. concentrate 20) possibly mixed with coke returned from the magnetic separator. Preheat.

The gas and material stream is then sent to a cyclone 21 and then to a microcleaning cyclone 22 where the solid material is separated and preferably returned to the central part of the reactor via return line 6.

The gas cleaned from the solid material is passed along line 23, with indirect cooling at 24, possibly by boiling water, and passes through a heat exchanger 25 into an absorption column (scrubber) 27, where it is substantially free of CO2. and H2O is removed.

Cooling with boiling water is necessary to prevent the temperature in the heat exchanger from becoming too high for the materials used.

H2O can be removed by direct or indirect cooling.

For example, the CO2 can be washed away using alkaline solutions, in which case steam 28 from boiler 24 can be used to regenerate these solutions.

If the pressure in the system is high enough, the CO2 can be washed away with water.

The bulk of the gas coming from the scrubber driven by compressor 29 is heat exchanged at 25 with the gas entering the scrubber and is introduced into the lower part 4 of the reactor as fluidizing and reducing gas.

This creates a strongly reducing zone through which the solid material passes before being discharged.

Due to the small gas flow, this part of the reactor suitably has a smaller diameter than the upper part.

The partial stream 31 of the gas, excluding CO2 and H2O, is transferred without heat exchange to the cooling device 11 for the discharged solid material.
It is used as a fluidizing working gas in the magnetic separator 12 and is sent via 32 and 33 into the lower part of the reactor.

The remainder of the exhaust from cyclone 5 may be used as fuel in the thermal power generation section, possibly with a coke fraction diverted from the magnetic separation operation, with the remainder of the coke stream possibly being an iron oxide-containing feedstock. The reactor is recycled and/or used as a reducing agent in the melt reduction process for the iron fraction from the magnetic separation operation.

Below, representative examples of the gist and aspects of the present invention are listed.

1. A circulating fluidized bed is formed in a vertically long reaction zone by feeding it with appropriate amounts of each of the finely divided iron oxide-containing material, the finely divided solid carbonaceous material and possibly the liquid carbonaceous material and the molecular oxygen-containing gas. , separating the gas and solid materials coming out of the reaction zone, returning the solid materials to the reaction zone, and supplying the iron oxide-containing micronized material, carbonaceous material and molecular oxygen-containing gas to the middle section of the reaction zone. The feed flow of the carbonaceous material is controlled so that there is always sufficient coke in the bed to prevent interference with fluidization due to sticking, and the gases and solid materials leaving the reaction zone are withdrawn from the top and the solid material is separated from the gas and returned to the middle part of the reaction zone, and a portion of the exhaust gas is fed to the lower part of the reaction zone as a fluidizing and reducing gas after separation of the dust and removal of most of the contained CO2 and H2O. , and removing the solid material containing completely or partially reduced iron oxide from the lower part of the reaction zone.

2, characterized in that the flow of molecular oxygen-containing gas, possibly mixed with CO2 and/or H2O, is controlled to meet the thermal requirements for maintaining the desired temperature in the reactor. the method of.

3. Cooling the solid material removed from the lower portion of the reaction zone below the Curie temperature of the iron and magnetically separating it into a substantially coke-free iron portion and a substantially iron-free coke portion. The first item characterized by: or 2
The method described in Section 9.

4. Process according to claim 30, characterized in that a part of the recycled gas substantially free of CO2 and H2O is used as fluidizing working gas in the magnetic separation.

5. Solid carbonaceous material is introduced into an auxiliary reaction zone separate from the reaction zone, where it is fluidized with the help of a partial stream of molecular oxygen-containing gas and partially combusted, after which the gas and solid materials are 1. is introduced into the middle part of the reaction zone. 49. The method according to any one of items 49 to 49.

6, characterized in that the carbonaceous material is blown into the middle part of the reaction zone with a non-oxidizing gas, possibly as a branch flow. 42. The method according to item 41.

7. The method according to any one of the preceding items, characterized in that the molecular oxygen-containing gas is introduced into the intermediate part of the reaction zone in a plurality of sub-streams.

8. The solid material withdrawn from the lower portion of the reaction zone has a built-in cooling surface formed by the material itself and is substantially free of CO2.
2. Process according to any of the preceding clauses, characterized in that the cooling is carried out by passing the recycle gas, free of H2 and H2O, through a fluidized bed.

9. The method according to item 80, characterized in that a molecular oxygen-containing gas is used as a coolant.

10. Part of the exhaust air from the circulating fluidized bed is used in direct contact with the iron oxide-containing feedstock for preheating the material and then recycled to the lower part of the reaction zone after removing most of its CO2 and H2O. The method according to any one of the preceding items, characterized in that:

11. The method according to any one of the preceding items, characterized in that the entire process is carried out at atmospheric pressure or higher.

12, characterized in that the heat content (physical and chemical) of the exhaust gas is used for the generation of electrical energy,
The method described in any one of the above items.

13. A substream of the coke fraction from the magnetic separation is recycled to the reaction zone, possibly mixed with iron oxide-containing materials, and the coke residue is used for other purposes, such as in the smelting reduction stage for the iron fraction from the magnetic separation operation. Process according to any one of the preceding clauses, characterized in that it is used as a reducing agent and/or as a fuel in a thermal couplant.

14, connecting a cyclone 5 to its upper part 2, a return line 6 leading to its central part 3, an inlet lower for carbonaceous material and an inlet 8 for molecular oxygen-containing gas, from the cyclone 5 to the reactor; a line 23 for conveying the exhaust air to a scrubber 27 for removing CO2 and H2O from the gas via line 30 for recycling the gas to the lower part 4 of the reactor, and a solid material provided in the lower part of the reactor. 11. Apparatus for carrying out the method according to claim 10, characterized in that it is a vertically elongated reactor 1 with an outlet 10 for.

[Brief explanation of the drawing]

The accompanying drawings illustrate one embodiment of the method and apparatus according to the present invention. 1... Reactor, 5, 21, 22... Cyclone, 6... Return pipe, 7... Carbonaceous material, 8... ... Nozzle, 9 ... Distributor, 10 ... Outlet, 11 ... Cooler,
12... Magnetic separator, 13... Iron part, 14... Coke part, 15... Molecular oxygen-containing gas, 17...・Pipe, 18...
...Exhaust pipe, 19...Venturi device, 2
0... Concentrate, 24... Boiler, 25
... Heat exchanger, 27 ... Absorption tower (scrubber), 29 ... Compressor, 30,3
2,33...Pipe line.

Claims (1)

[Claims] 1 Micronized material containing iron oxide in a vertically long reaction zone,
Micronized solid carbonaceous material and molecular oxygen-containing gas are supplied to maintain a circulating fluidized bed in the reaction zone, with sufficient coke in the bed at all times to prevent interference with fluidization due to sticking. The feed flow of carbonaceous material is controlled such that the gas and solid material leaving the reaction zone are withdrawn from the upper part, the solid material is separated from the gas and returned to the middle part of the reaction zone, and a portion of the exhaust gas is removed as dust. is supplied to the lower part of the reaction zone as a fluidizing and reducing gas after separating and removing most of the contained CO2 and H2O,
and removing a solid material containing fully or partially reduced iron oxide from the lower part of the reaction zone,
A method of reducing iron oxide-containing micronized materials mixed with carbonaceous materials.