JPH04301022A - Method for introducing reducing gas into fluidized bed reduction furnace - Google Patents

Abstract

PURPOSE:To inprove the reducing efficiency of ores and the operability by mixing combustion gas into exhaust gas, heating and raising the temp. at the time of introducing the exhaust gas from a smelting reduction furnace into a fluidized bed reduction furnace as reducing gas. CONSTITUTION:The circulating type fluidized bed reduction furnace 10 is constituted of a riser 3 and an external part particle circulating device 6, and the upper part with a circulating introducing tube 7 and the lower part with a connecting tube 8, are connected, respectively. The exhaust gas from the smelting reduction furnace is injected into the riser 3 as the reducing gas through an introducing tube 9, header 11 and permeable nozzles in a supporting plate 12. Then, a burner 13 using LPG gas as fuel is provided in the vicinity of an introducing hole in the introducing tube 9, and the combustion gas is injected in the header 11 to raise the temp. of reducing gas. By this method, the generation of stuck material into the inside face of the nozzle is suppressed and the high temp. reducing gas is uniformly blown in the fluidized bed reduction furnace 10, and the reduction efficiency of ores and the operability are improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to equipment for reducing iron ore using a fluidized bed reduction furnace.

0002

BACKGROUND OF THE INVENTION The smelting reduction method is attracting attention as an alternative to the conventional method of producing hot metal using a blast furnace. This method has been developed with the aim of producing hot metal at low cost by using fine ore, steam coal, and omitting the coking process. In addition, in order to effectively utilize the reducing power and heat of the exhaust gas generated in the smelting reduction furnace, a method has also been developed in which the raw ore is preheated and pre-reduced by supplying it to the fluidized bed reduction furnace as a fluidized gas.

[0003] As such a fluidized bed reduction device, Japanese Patent Application Laid-Open No. 1982
As disclosed in JP-A-269283 and JP-A-1-111807, there is a fine ore input part on the side, a carrier gas introduction part for forming a fluidized bed near the bottom, and a A circulating fluidized bed consisting of a fluidized bed (riser) equipped with a circulating introduction section for reducing gas, and a powder circulation fluidization section (downcomer) for circulating powder via a cyclone outside of the fluidized bed (riser). There are various types, such as a non-circulating fluidized bed in which the granular iron ore collected by a cyclone is not returned to the riser.

One of the problems with this fluidized bed reduction apparatus is that the reducing gas from the smelting reduction furnace contains a large amount of metal fume and dust, so when it is introduced into the fluidized bed from the nozzle, it is It may precipitate and adhere to the inner surface of the nozzle, lowering the head pressure or, in severe cases, clogging the nozzle, resulting in a situation where the operation must be stopped.

Conventionally, as a method to avoid problems caused by fume adhesion to the nozzle, the nozzle is cooled and the adhered material is removed from the nozzle inner surface by utilizing the difference in thermal contraction rate between the adhering fume and the nozzle base material. A method has been proposed in which the material is peeled off from the surface and allowed to fall. In addition, as another method, oxygen-containing gas is introduced into the blown reducing gas to partially burn the reducing gas, and the temperature of the reducing gas passing through the nozzle is raised from the temperature immediately before introduction into the nozzle. It is also possible to consider a method of preventing the precipitation of vaporized metal in the reducing gas, which becomes the core of formation.

This latter method of preventing deposition by partial combustion of the reducing gas proactively prevents the formation of deposits compared to the stripping method by cooling the nozzle, and also does not cause a decrease in the temperature of the reducing gas. There is an advantage.

[0007]

[Problems to be Solved by the Invention] However, since this method of introducing oxygen-containing gas is carried out by partially burning the reducing gas, reducing gases such as CO and H in the reducing gas are inevitably consumed, and the As a result, the reactivity is reduced and the ore reduction efficiency is reduced.

[0008] The problem to be solved by the present invention is to find a method for reducing the formation of deposits due to an increase in the temperature of the reducing gas without reducing the reducing ability of the reducing gas itself.

[0009]

[Means for Solving the Problems] The present invention is characterized in that when introducing exhaust gas from a smelting reduction furnace into a fluidized bed reduction furnace, high-temperature combustion gas from a combustion burner is blown into the introduced exhaust gas before the introduction.

[0010] This can be carried out by providing a burner near the reducing gas inlet of the fluidized bed reduction furnace. This burner can also be of a partial combustion type that generates reducing gas. This partial combustion type is suitable for increasing the reducing ability of the reducing gas. Furthermore, when installing this burner, it is preferable to install a device for removing solids in the gas in the piping on the upstream side of the reducing gas inlet, and furthermore, using a water-cooled cyclone as the device for removing solids can be expected to be even more effective. .

[0011]

[Action] Since the combustion gas formed by the burner itself has reducing properties, even if the temperature of the reducing gas mixed with it rises, its reducing properties will not be diminished, and the reducing gas temperature will increase. Therefore, the reduction reaction rate increases.

Furthermore, the components of the reducing gas introduced into the fluidized bed can be freely adjusted, and the components of the exhaust gas that has passed through the fluidized bed can also be freely adjusted, making it possible to adjust the reducing ability of the exhaust gas.

Furthermore, by providing a water-cooled cyclone in the upstream piping of the reducing gas inlet, impurities in the reducing gas can be precipitated and removed, thereby purifying the reducing gas and further reducing the formation of deposits on the inner wall surface of the nozzle hole. do.

[0014]

[Example] As an embodiment of the present invention, an example in which the present invention is applied to a circulating fluidized bed reduction furnace will be shown below.

In FIG. 1 showing the first embodiment, a circulating fluidized bed reduction furnace 10 includes an ore supply pipe 1 and a reduced ore discharge pipe 2.
riser 3 with cyclone 4 and downcomer 5
The riser 3 and the external particle circulation device 6 are connected at the upper part by a circulation introduction pipe 7 and at the lower part by a connecting pipe 8. 9 is a reducing gas introduction pipe to the riser 3, and the reducing gas from the introduction pipe 9 is once passed through the gas header 1.
1 , from which it is ejected into the riser 3 via the breathable nozzle support plate 12 . And gas header 1
1 is provided with a burner 13 that uses LPG gas as fuel, and the combustion gas of this burner 13 is sent to the gas header 1.
1, the temperature of the reducing gas is raised. Furthermore, the degree of reduction of the combustion gas can be adjusted by adjusting the amount of LPG gas and introduced oxygen. Note that the heating fuel is not limited to LPG, and may be other gaseous fuels or liquid fuels.

FIG. 2 shows an example in which a cyclone 14 is installed in the reducing gas introduction path from the melting reduction furnace. by this,
The reducing gas introduced from the inlet pipe 9 is purified by removing a considerable amount of impurities to prevent the formation of deposits, and
By adding and blending high-temperature combustion gas by the burner 13, it is possible to heat the reducing gas passing through the reducing gas nozzle and supply a reducing gas that meets the operating conditions of the fluidized bed reduction furnace in which the partial pressure for precipitation of impurities is reduced. can.

The present invention was carried out using the apparatus shown in FIG.

The conditions were as follows: ore throughput 20T/H, reducing gas amount 42,000 Nm3/H, reducing gas temperature in the header approximately 900°C, gas composition CO: 41.5%, C
O2: 18.3%, H2: 17%, H2O: 10
．． 9%, N2: 12.1%.

At this time, the average rate of dust adhesion to the inner surface of the nozzle was about 17.5 μm/H. With this device,
In areas where a large amount of deposits were generated, troubles such as nozzle clogging occurred after several hundred hours.

An LPG burner was installed on the side wall of the reducing gas header of the fluidized bed reduction furnace to heat the reducing gas, and the rate of deposits on the inner surface of the nozzle was investigated. The results are shown in FIG.

When the reducing gas is heated to raise its temperature, the effect is small when the temperature rise is about 50°C, but when the temperature rises above that, the deposits decrease rapidly, and the temperature rises by about 10°C.
The amount of adhesion decreased to 1/10 with a temperature increase of 0° C., and there was no further effect even if the reducing gas temperature was further increased. This is because the temperature of the reducing gas before implementation was 800 to 900° C., where alkali metal compounds and the like tend to precipitate, resulting in a large amount of precipitated matter. By heating this reducing gas, we were able to move out of this large amount precipitation temperature range, and due to the combined effect of lowering the partial pressure of impurity precipitation due to the heating of the reducing gas, we were able to significantly reduce the precipitation and adhesion of impurities.

[0022]

[Effects of the Invention] The present invention provides the following effects.

(1) The formation of deposits that cause nozzle clogging can be reduced, and the operation of the fluidized bed reduction furnace can be stabilized.

(2) Since the reducing gas components can be adjusted arbitrarily, there is no reduction in the reduction rate.

(3) Production capacity is improved because the components and temperature of the reducing gas introduced into the fluidized bed can be adjusted depending on the condition of the ore.

[Brief explanation of drawings]

FIG. 1 shows an example of an apparatus in which the method of the present invention is implemented in a circulating fluidized bed reduction furnace.

FIG. 2 shows an example in which a cyclone device is installed in the reducing gas introduction path in the example of FIG.

FIG. 3 is a diagram illustrating the effects of the present invention.

[Explanation of symbols]

1 Ore supply pipe 2 Reduced ore discharge pipe 3 Riser 4 Cyclone 5 Downcomer 6 External particle circulation device 7 Circulation introduction pipe 8 Connecting pipe 9 Reducing gas introduction pipe 10 Circulating fluidized bed reduction furnace 11 Gas header 12 Nozzle support plate 13 Burner 14 Cyclone

Claims (1)

[Claims] 1. A method for introducing reducing gas, which is exhaust gas from a smelting reduction furnace, into a fluidized bed reduction furnace, in which a combustion burner is provided near the introduction port, and the combustion gas is mixed with the introduced exhaust gas, thereby reducing the introduced exhaust gas. A method for introducing reducing gas into a fluidized bed reduction furnace characterized by heating.