JPH04301021A - Method for preventing formation of stuck material to nozzle in fluidized reduction furnace - Google Patents

Abstract

PURPOSE:To improve the reduction efficiency of ores and the operability by introducing oxygen-incorporating gas into blown reducing gas into a fluidized bed reduction furnace, partially burning the reducing gas and raising the temp. of the reducing gas just before introducing to nozzles. CONSTITUTION:The circulating type fluidized bed reduction furnace 10 is constituted of a riser 3 and an outer 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. Introduction of inert carrier gas into the riser 3 is executed through an introducing tube 9, header 11 and permeabile nozzle supporting plate 12 and the introduction of the reducing gas is executed through an introducing tube 13, header 15 and nozzles 16. Then, air is introduced into the reducing gas through an introducing tube 17 and nozzles 18, and the reducing gas retained in the header 15 is partially burnt and the temp. is raised. By this method, the higher temp. reducing gas can be supplied into the fluidized bed reduction furnace 10 and the reducing efficiency 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 reduction generated during melt reduction in the subsequent process. A circulating type consisting of a fluidized bed (riser) equipped with a reducing gas introduction section that circulates the reactive gas, and a powder circulation fluidization section (downcomer) that circulates the powder via a cyclone outside of the fluidized bed (riser). There are fluidized beds and non-circulating fluidized beds in which the granular iron ore collected by the cyclone is not returned to the riser.

[0004] One of the problems when introducing the reducing gas generated in the smelting reduction furnace in this previous step and reducing the ore in the fluidized bed reduction furnace is that the reducing gas contains a large amount of metal fumes and dust. Therefore, there is a problem in that it precipitates and adheres to the inner surface of the nozzle, clogging the nozzle and hindering stable operation.

Conventionally, as a method to avoid problems caused by the formation of deposits, the reducing gas discharge nozzle is cooled to take advantage of the difference in thermal contraction rate between the metallic deposits and the refractory material constituting the nozzle. There is a method of preventing a drop in head pressure and blockage caused by the deposits by peeling the deposits from the inner surface of the nozzle and letting them fall.

[0006]

[Problems to be Solved by the Invention] However, this method of peeling off deposits by cooling requires cooling the introduced reducing gas, which not only causes a large heat loss but also reduces the temperature inside the fluidized bed reduction furnace. As a result, the reduction reaction rate of iron ore in the fluidized bed decreases, resulting in a decrease in the productivity of the fluidized bed reduction furnace.

The present invention aims to solve the problem of the formation of deposits in reducing gas injection nozzles by finding a means for suppressing the formation of deposits itself, rather than by treating the deposits after the deposition. It has a purpose.

[0008]

[Means for Solving the Problems] The present invention introduces an oxygen-containing gas into the blown reducing gas to cause partial combustion of the reducing gas, thereby increasing the temperature of the reducing gas passing through the nozzle from the temperature immediately before introduction into the nozzle. It is characterized by warming.

The oxygen-containing gas introduced into the reducing gas may be an oxygen-enriched gas or air.

[0010] Furthermore, the oxygen-containing gas for partial combustion is
The reducing gas may be introduced into the introduction reducing gas header formed below the fluidized bed, or may be introduced just before the blowing nozzle or near the inlet of the nozzle.

[0011]

[Effect] The dust and fumes in the reducing gas adhere to the inner wall of the nozzle hole when the reducing gas is cooled in the nozzle and the vaporized components contained in the reducing gas reach their respective precipitation temperatures and precipitate. The material that is deposited becomes a nucleus and grows. The present invention raises the temperature of the reducing gas by partially burning it, and maintains the temperature of the reducing gas in the nozzle higher than the temperature at the nozzle inlet, thereby maintaining the temperature higher than the precipitation temperature of fumes and dust in the gas, thereby removing deposits. Prevents formation and growth.

0012

EXAMPLES As an embodiment of the present invention, an example will be shown below in which air is introduced as an oxygen-containing gas into the header section of the circulating fluidized bed reduction furnace 10 shown in FIG.

In the figure, a circulating bed reduction furnace 10 consists of a riser 3 having an ore supply pipe 1 and a reduced ore discharge pipe 2, and an external particle circulation device 6 consisting of a cyclone 4 and a downcomer 5, each of which has a 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 an inert carrier gas introduction pipe to the riser 3, and the carrier gas from the introduction pipe 9 is once passed through the carrier gas header 1.
1 , from which it is ejected into the riser 3 via the breathable nozzle support plate 12 . The reducing gas introduced into the riser 3 through the reducing gas introduction pipe 13 from the melting reduction furnace (not shown) passes through the reducing gas header 15 located below the floor plate 14, and then passes through a large number of nozzles uniformly arranged on the floor plate 14 surface. 16 into the riser 3. Reference numeral 17 denotes an air introduction pipe through which air is introduced to partially combust the reducing gas remaining in the reducing gas header 15. A nozzle 18 that distributes and supplies air to each nozzle 16 is attached to the air introduction pipe 17 .

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

[0015] The conditions were: throughput of ore 20T/H, amount of reducing gas 42,000Nm3/H, temperature inside the header of reducing gas 900°C, and composition of reducing gas CO: 41.5.
%, CO2: 18.3%, H2: 17.0%, H2
O: 10.9%, N2: 12.1%.

[0016] 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 air introduction pipe 17 and a nozzle 18 were provided at the inlet of the reducing gas blowing nozzle of the equipment, and air was supplied as an oxygen-containing gas toward the nozzle inlet.

The reducing gas temperature is 900° C., which is well above the ignition temperature, and as soon as air is supplied from the nozzle 18, it ignites even without an ignition source, and a stable combustion state is obtained. The gas temperature can be raised above the reducing gas temperature at the inlet. FIG. 2 shows the results of measuring the temperature rise inside the nozzle of the reducing gas and the rate of deposition of deposits on the inner surface of the nozzle.

[0019] When the reducing gas temperature rose by 50 to 100°C, the effect of reducing deposits was significant. This is because the temperature of the reducing gas before implementation is such that alkali metal compounds are likely to precipitate.
00 to 900° C., and this is due to the combined effect of heating above this temperature range and lowering the partial pressure of impurity precipitation due to heating of the reducing gas.

For this reason, in the example, about 4000 Nm 3 /H of air was added as the oxygen-containing gas to raise the reducing gas temperature by about 100°C. As a result, the amount of adhesion was reduced to about 1/10 of that before implementation.

[0021] In the above embodiment, an example has been described in which the oxygen-containing gas introduction section for the introduced reducing gas is carried out in the reducing gas header section, but a direct combustion device may be used below the nozzle body. The point is that the temperature of the reducing gas passing through the nozzle should be higher than the temperature of the reducing gas introduced into the fluidized bed reduction furnace.

[0022]

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

(1) Nozzle clogging due to deposits from the introduced reducing gas can be prevented, and the operation of the fluidized bed reduction furnace itself can be stabilized.

(2) Since the reducing gas is not cooled but rather heated, the reduction efficiency is improved.

(3) The temperature of the reducing gas introduced into the fluidized bed becomes higher, the reduction reactivity becomes higher, and the production capacity is improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus implementing the method of the present invention.

FIG. 2 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 Carrier gas introduction pipe 10 Circulating fluidized bed reduction furnace 11 Carrier gas header 12 Nozzle support plate 13　Reducing gas introduction pipe 14 Floor bottom plate 15　Reducing gas header 16 Nozzle 17 Air introduction pipe 18 Nozzle

Claims (1)

[Claims] [Claim 1] Oxygen-containing gas is introduced into the reducing gas blown into the fluidized bed reduction furnace 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. A method for preventing the formation of nozzle deposits in a fluidized bed reduction furnace, characterized in that: