JPH0351766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for reducing ore, particularly iron ore, using a fluidized bed reactor.

(Prior Art) The most widely used process for obtaining molten iron by reducing iron ore is a method using a blast furnace. However, in order to maintain stable operations in the blast furnace steelmaking process, high-quality agglomerate ore and coke are required, and problems have been pointed out such as increased costs for producing these and restrictions on raw material selection. .

As one means of solving these issues,
Research and development of the smelting reduction process, which reduces iron ore while heating and melting it using the partial oxidation heat of coal, has been decreasing. For example, in Japanese Patent Application No. 59-184056, iron ore, coal, and oxygen-containing gas are charged into a fluidized bed reactor, and the reaction is allowed to proceed to obtain iron ore and chir. , a steelmaking process characterized in that briquettes obtained by mixing and agglomerating coal supplied from another system are charged into a top-bottom blowing converter type reactor, and the pre-reduced ore is melted and reduced. The law is shown.

Regarding the preliminary reduction process, for example, in Belgian Patent No. 826521, carbonaceous material is gasified by a partial combustion reaction with oxygen using a circulating fluidized bed, a part of it is turned into a char, and the carbonaceous material generated in this reaction is A process for reducing iron ore with gas is disclosed. Furthermore, Japanese Patent Application Laid-Open No. 51-99671 discloses a method of suppressing reoxidation of reduced ore particles in the oxidation region by devising the shape of the reactor.

However, regarding the gas flow rate in the reaction tower,
Chemical Engineering Progress67, 58–63
(1971) and Japanese Patent Application Laid-Open No. 51-99671, the gas flow rate is determined solely from the viewpoint of transporting particles, and the gas and carbon substances introduced into the reaction tower are generated by the reaction with O ₂ . The efficiency with which this gas is utilized for reduction is not necessarily guaranteed.

Originally, a fluidized bed reaction tower reacts reactants in a dilute bed, and therefore has the drawbacks of lower productivity per volume and poor gas utilization efficiency compared to a packed bed type reaction tower. In particular, the circulating fluidized bed has a large amount of gas passing through it, and this tendency is remarkable.

For this reason, the present inventors proposed in Japanese Patent Application No. 61-73754 a method for improving productivity by blowing reducing gas into the reactor even from the middle.

However, in the reduction of ore using such a fluidized bed, there is a problem that the degree of oxidation of the exhaust gas is lower than that in a moving bed type reactor with a high particle packing density.

In other words, in order to circulate ore, the gas flow rate in the reaction tower needs to be higher than the terminal velocity of the particles, and as a result, as a result of operating at a void ratio of about 0.85 or more, the number of particles that come into contact with each other in one path is reduced. This means that it is difficult to obtain a sufficient gas utilization rate, which in turn leads to poor productivity.

(Problems to be Solved by the Invention) The present invention provides ores which are collected from the flue gas discharged from the fluidized bed reduction furnace and charged into the fluidized bed reduction furnace again via a descending connecting pipe. In the circulating fluidized bed reduction method, the pressure difference between the upper and lower part of the particle movement bed in the downflow pipe is adjusted, and the reducing gas at a speed below the fluidization start speed of the ore is passed through the downflow pipe. It is characterized by carrying out a reduction reaction.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram of an apparatus to which the method of the present invention is applied;
FIG. 2 is an explanatory diagram of the conventional method.

In FIG. 1, reference numeral 2 denotes a reaction tower for reducing the ore 1. At its lower part, a charging port 16 for the ore 1 and a discharge port 17 for the finished product 10 are provided, and a connecting pipe 18 connected to the cyclone 3 is provided above. It is provided.
Note that 8 is an exhaust port provided in the cyclone 3.

Further, this cyclone 3 is provided with an upper descending communication pipe 14, a hopper 4, a lower descending communication pipe 15, a pneumatic valve 6, etc. in series, and the pneumatic valve 6 is connected to the lower end of the reaction column 2. ing.

Reference numeral 11 denotes a pressure impulse pipe that connects the upper part of the reaction column 2 and the hopper 4, and a pressure control valve 1 is installed in the middle.
3 is provided. 12 is a differential pressure gauge inserted between the hopper 4 and the lower end of the reaction column 2.

Further, in FIG. 2, reference numeral 5 indicates a descending communication pipe provided between the hopper 4 and the pneumatic valve 6;
is the feeder gas inlet.

In the conventional circulation type fluidized reactor as shown in FIG. 2, the reducing gas blown into the reaction tower 2 rises while reducing the ore in the reaction tower 2,
After going through cyclone 3 and being separated into solid and gas,
It is discharged from the exhaust port 8 as exhaust gas.

On the other hand, the granular ore recovered by Cyclone 3 is
It is returned to the reaction tower 2 through the hopper 4, the down-connecting pipe 5, and the pneumatic valve 6, where it undergoes a reduction reaction again. In this case, there is usually a pressure loss commensurate with the hold-up of particles in the height direction within the reaction tower 2, with the highest pressure at the bottom, and the pressure gradient inside the reaction tower is also larger at the bottom. Due to the pressure difference or the pressure difference that also takes into account the pressure loss in the cyclone 3, the ore flowing down the descending connecting pipe 5 is prevented from blowing through the reducing gas in the reaction tower from the descending connecting pipe 5 in the direction of the cyclone 3. The descending connecting pipe 5 is made to have a required length so that a particle seal can be achieved.

The present invention allows the ore reduction reaction to occur even in the descending connecting pipe portion of the conventional method. In other words, inside the descending connecting pipe,
Since the ore particles come down as a moving layer with a lower porosity than in the reaction tower, the reaction is also allowed to proceed in the descending connecting pipe by flowing an appropriate amount of reducing gas into this part.

Therefore, in the present invention, the descending connecting pipe is connected to the upper descending connecting pipe 1 between the cyclone 3 and the hopper 4.
4 and a lower descending communication pipe 15 between the hopper 4 and the pneumatic valve 6, and sealing between the reaction column 2 and the upper descending communication pipe 14 that communicates with the cyclone 3, This is characterized in that the reduction reaction is carried out in the lower descending communication pipe 15 located below.

That is, in the present invention, not only the ore is reduced in the reaction tower 2 as in the conventional method, but also
Since a pressure pipe 11 is provided between the upper part of the reaction tower 2 and the hopper 4 provided below the upper descending communication pipe 14, the pressure control valve 13 provided in the pressure pipe 11 is adjusted to prevent the cyclone 3 and When the differential pressure with the hopper 4 is adjusted, the ore particles in the upper descending communication pipe 14 are
This serves to provide an appropriate seal between the cyclone 3 and the hopper 4.

On the other hand, a part of the reducing gas flows into the lower descending communication pipe 15 via the pneumatic valve 6 due to the pressure difference between the lower part of the reaction tower 2 and the hopper 4, and the ore particles in the communication pipe 15 are reduced. be done. At this time, the amount of reducing gas flowing into the lower descending communication pipe 15 can be adjusted by adjusting the pressure control valve 13.

In addition, the flow rate of the reducing gas flowing into the lower descending communication pipe 15 prevents the fluidization of ore particles in the pipe and the blow-through of ore particles and gas to the cyclone 3, thereby reducing the cyclone recovery efficiency and the circulation rate controllability. In order to avoid deterioration etc., it is necessary to keep the ore fluidization start speed below.

In this case, the start of fluidization can be detected by the pressure gradient in the height direction of the lower descending communication pipe. That is, at a gas flow rate below the start of fluidization, the gas flow rate and the pressure gradient are approximately proportional, but after the start of fluidization, the pressure gradient does not depend on the gas flow rate and exhibits a substantially constant value, so it can be determined.

In this way, in the present invention, the reduction reaction proceeds not only in the reaction tower but also in the lower downcomer pipe, thereby improving productivity. In particular, in the lower descending communication pipe, since ore particles are descending in a filled state, the relative ratio of ore amount/gas amount becomes large, and it is possible to obtain a gas utilization rate close to an equilibrium state.

(Example) Iron ore with iron content of 68% with a target preliminary return rate of 60%
10t/m ² hr was charged into the reaction tower, and the composition and temperature of the inlet gas were H ₂ 15%, CO 82.5%, H ₂ O 0.5%,
Iron ore was reduced by injecting gas at 10,500 Nm ³ /m ² hr under the conditions of 2.0% _CO 2 and 900°C.

The productivity of the method of the present invention and the conventional method are shown in comparison in FIG. The horizontal axis is the ratio of the gas distributed to the lower descending communication pipe out of the total blown reducing gas, and the vertical axis is the relative productivity when the productivity of the conventional method is set as 100.

In the case of the method of the invention, approximately 4.4
% productivity improved.

(Effects of the Invention) As explained above, the present invention can improve productivity by reducing ore also in the descending communication pipe, and its effects are significant.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the present invention, FIG. 2 is an explanatory diagram of the conventional method, and FIG. 3 is a graph showing the effects of the present invention. 2: Reaction tower, 3: Cyclone, 11: Impulse tube,
12: Differential pressure gauge, 13: Pressure control valve, 14: Upper descending communication pipe, 15: Lower descending communication pipe.

Claims (1)

[Scope of Claims] 1. In a circulating flow reduction method for ores in which ore accompanying exhaust gas discharged from a reaction tower is recovered and charged into the reaction tower again via a downlink pipe, The ore is characterized in that the pressure difference between the upper and lower part of the particle movement layer is adjusted, the reducing gas is passed through the descending communication pipe at a speed lower than the fluidization start speed of the ore, and a reduction reaction is carried out in the descending communication pipe. Circulating flow reduction method. 2. Divide the descending communication pipe that connects the inlet and outlet sides of the reaction tower into an upper descending communication pipe and a lower descending communication pipe, and further divide the exit side of the reaction tower and the outlet end of the upper descending communication pipe. 1. A circulating flow reduction device for ores, characterized in that a pressure control pipe is provided between the pipes, a pressure control valve is provided in the middle of the pressure pipe, and differential pressure gauges are provided above and below the lower descending communication pipe.