JPS63192811A - Method for reducing iron ore - Google Patents

Abstract

PURPOSE:To drastically reduce fluctuation of product reduction rate by heat-exchanging waste gas of an ore reduction furnace into reduced iron through a gas holder after cooling, dewatering and decarboxylation and blowing into the ore reduction furnace by mixing it with high temp. gas of coal gasifying furnace. CONSTITUTION:The waste gas from the ore reduction furnace 11 is in order introduced to a hot cyclone 17, cooling dehumidifier 20 and decarboxylation equipment 22, to execute dust removal, cooling dewatering and decarboxylation and to make it high reducing gas having rich CO and H2 and it is introduced to the gas holder 27 for preventing pressure variation. The circulated waste gas in the gas holder 27 is sent to the heat-exchanger 13 by a blower 24 and heat-exchanged to the reduced iron discharged from the ore reduction furnace 11 and sent to a piping 10. On the other hand, in the coal gasifying furnace 1, oxygen-contained gas is blown through packing zone part 4 of coal ash at the lower part, and the high temp. gas generated by gasifying the coal is sent to the piping 10 after removing the dust by the hot cyclone 8 and mixed with the circular waste gas from the heat exchanger 13 and used for reduction of ore by blowing into the ore reduction furnace 11. In this way, fluctuation of the gas blowing into the ore reduction furnace 11 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing reduced iron in which iron ore is reduced in an ore reduction furnace using reducing gas produced by a coal gasification furnace.

[Conventional technology]

A method of reforming gas in a coal fluidized bed gasifier and using it to reduce iron ore in an ore reduction furnace was published in Japanese Patent Publication No. 60-2316.
It is disclosed by No. 2. This method cools the exhaust gas from the ore reduction furnace, removes moisture and CO2, and then branches this gas into three systems. The first system boosts the pressure and blows it into a fluidized bed of coal, and the second system A part of the reducing furnace exhaust gas is combusted and heated, and this is mixed with the third system and mixed with the generated gas from the coal fluidized bed gasifier to determine the composition of the generated gas from the coal fluidized bed gasifier. Iron ore is reduced by adjusting the temperature and injecting it into an ore reduction furnace.

In this method, the exhaust gas from the ore reduction furnace is cooled, dehydrated, and decarboxylated and then branched into three systems, so the gas path is complex and requires sophisticated control equipment, which requires a large amount of work in the exhaust gas circulation system. There was a defect that required equipment costs.

Furthermore, with this method, fluctuations in the amount of gas in each system directly appear as fluctuations in the temperature and composition of the reducing gas blown into the ore reduction furnace, resulting in fluctuations in the quality of the reduced iron product, that is, fluctuations in the reduction rate. There was a serious defect that caused this.

In other words, when the amount of exhaust gas circulated to the coal gasifier increases, the temperature of the coal gasifier decreases, resulting in a decrease in the temperature of the generated gas, and furthermore, coal gasification does not proceed smoothly and the oxidizing components H2O and CO2 increases. Furthermore, since the amount of H2 and CO-rich gas in the second and third systems to be mixed with the generated gas has decreased, the temperature and reducing power of the gas blown into the ore reduction furnace have significantly decreased. The reduction rate of the produced reduced iron is significantly reduced.

On the other hand, when the amount of exhaust gas circulated to the coal gasifier decreases, the result is completely opposite to the above, and the reduction rate becomes equal to or higher than the target value.

As described above, this method is inherently a process in which it is difficult to control the quality of the product.

Furthermore, the third defect of this method is that the sensible heat of the reduced iron discharged from the ore reduction furnace and the sensible heat of the coal ash discharged from the coal gasification furnace cannot be used effectively, and the carbon remaining in the ash cannot be used effectively. The problem is that coal consumption increases because it cannot be gasified.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is the above-mentioned deficiencies of the conventional method, and its purpose is the following three points.

(1) Eliminate the complexity of the ore reduction furnace exhaust gas circulation system and simplify it to reduce equipment costs.

(2) To prevent fluctuations in the product reduction rate due to fluctuations in the circulating amount of ore reduction furnace exhaust gas.

(3) Effectively utilize the sensible heat of reduced iron and coal ash,
Furthermore, by gasifying the carbon content remaining in coal ash, coal consumption can be significantly reduced.

[Means for solving problems]

The present invention is characterized in that the following technical measures are taken in a method of reducing iron ore in an ore reduction furnace using high-temperature generated gas generated in a fluidized bed coal gasifier.

(a) When gasifying coal with oxygen-containing gas in a fluidized bed coal gasifier, a bed filled with coal ash is formed in the lower part of the fluidized bed gasifier, and the fluidized bed gas is passed through the bed filled with ash. Gasification is performed by blowing oxygen-containing gas or oxygen into the furnace.

(b) After the ore reduction furnace exhaust gas is cooled, dehydrated, and decarboxylated, it is heated by exchanging heat with the reduced iron discharged from the ore reduction furnace via a gas holder for preventing pressure fluctuations.

(c) The heated exhaust gas is mixed with the gas generated from the coal gasifier and blown into the ore reduction furnace.

[Effect]

The configuration of the present invention will be explained based on the drawings. FIG. 1 is a process flow diagram of the present invention.

Exhaust gas from the ore reduction furnace 11 passes through a duct 16 and is removed by a hot cyclone 17. The removed dust is returned to the ore reduction furnace 11 through the pipe 18. On the other hand, the dust-removed exhaust gas passes through the duct 19 and reaches the cooling dehumidifier 20, where it is cooled and dehumidified.

Further, the exhaust gas is decarboxylated by a decarboxylation equipment 22 via a pipe 21 to become a gas rich in CO and H2 with high reducing power, and enters a gas holder 27 for preventing pressure fluctuations. The purpose of providing a gas holder to prevent pressure fluctuations is to absorb pressure fluctuations caused by fluctuations in the ore reduction furnace and coal gasification furnace, making it easier to maintain a constant amount of circulating gas and at the same time converting the gas into coal. Even if the temperature and gas composition of the gas generated from the furnace fluctuate, the amount of circulating gas can be quickly adjusted, making it easy to obtain the desired temperature and composition of the gas blown into the ore reduction furnace. It is.

In other words, in the method disclosed in Japanese Patent Publication No. 60-23162, there is no buffer equipment in the ore reduction furnace exhaust gas circulation system that can adjust the gas amount, so it is not easy to adjust the amount of circulating gas in each system. When contrasted with the disadvantage that the composition and temperature of the blown gas tend to fluctuate, the effect of providing the gas holder for preventing pressure fluctuations in the present invention can be clearly understood.

The circulating exhaust gas that has entered the gas holder is pressurized slightly by the blower 24, and then exchanges heat with the reduced iron discharged from the ore reduction furnace through the extraction pipe 12 in the heat exchanger 13, receiving the sensible heat of the reduced iron.
Next, it is mixed with the generated gas from the coal gasifier through the pipe 26 in the middle of the pipe 10, and is blown into the ore reduction furnace 11. The effect of introducing the dehydrated and decarboxylated circulating exhaust gas rich in reducing gas into the heat exchanger 13 is that the sensible heat of the reduced iron can be effectively used and the reduced iron can be cooled without using an inert gas and without reoxidizing it. The point is beyond debate.

The amount of circulating exhaust gas to be mixed with the gas generated from the coal gasifier 1 is determined by measuring the temperature and gas composition of the gas generated from the coal gasifier 1 in the duct 9, and further measuring the temperature of the circulating exhaust gas in the pipe 26. The blower 24 is adjusted to determine the desired blowing gas composition and temperature of the ore reduction furnace by measurement.

In addition, if the desired amount of gas blown into the ore reduction furnace cannot be obtained by simply adjusting the amount of the circulating exhaust gas, adjust the amount of oxygen-containing gas or oxygen supplied to the coal gasifier 1 to obtain the desired amount. Generates ore reduction furnace injection gas.

In this process, iron ore is cut out from a hopper 14 and charged into an ore reduction furnace 11 via a charging pipe 15 to become reduced iron, and this high temperature reduced iron passes through a discharge pipe 12 to a heat exchanger. 13 and is cooled without being reoxidized by the circulating exhaust gas rich in reducing gas, and then passed through the discharge pipe 29 and stored in the storage container 30.

On the other hand, the fluidized bed coal gasifier 1 is operated as follows.

Raw material coal is cut out from the hopper 31 and supplied to the coal gasifier l through the conduit 6. A packed bed section 4 is provided in the lower part of the coal gasifier 1 in which coal ash is aggregated and partially welded to increase the particle size and form a packed bed of lumped ash. The oxygen-containing gas or oxygen for coal gasification is supplied from the lower part of the packed bed section 4 to the oxygen-containing gas or oxygen supply stage @2.
The reason why the packed bed section 4 is provided here and the oxygen-containing gas is blown in from the lower part of the bed section 4 is to transfer the sensible heat of the coal ash to gas in the packed bed section 4. This is because the carbon content remaining in the ash can be completely gasified without being completely gasified in the fluidized bed section, and the remarkable effect that the supplied coal can be almost completely gasified can be exhibited. The lumped coal ash is cooled with oxygen-containing gas in the packed bed section 4 and then discharged by the discharger 5.

The high temperature gas generated in the coal gasifier 1 is transferred to the duct 9
After passing through the hot cyclone 8 and removing dust, the gas passes through the duct 1O and is mixed with the circulating exhaust gas coming from the duct 26, and then blown into the ore reduction furnace 11. The dust containing a large amount of coal removed by the hot cyclone 8 is returned to the gasifier 1 via the circulation pipe 7 again, and the coal can be effectively gasified.

〔Example〕

A test plant with a reduced iron production capacity of 10 t/d and having the process flow shown in Figure 1 was used to produce coal with an ash content of 14% by weight and a volatile content of 32% by weight, T, and Fe of 67% by weight.
Average particle size: 12 mm c7) Brazilian ore, iron ore was reduced based on the method of the present invention using oxygen as the oxygen-containing gas. In the example of the bow, a fluidized bed type ore reduction furnace was adopted. Table 1 shows the operational results along with a comparative example of the conventional method.

According to the method of the present invention, it is clear that the coal consumption rate and oxygen consumption rate can be significantly reduced, and the reduction rate of the product can be stabilized.It is also advantageous in terms of equipment because there is only one circulation system for the ore reduction furnace exhaust gas. Become.

Table 1 [Effects of the Invention] According to the method of the present invention, the ore reduction furnace exhaust gas system can be simplified to one system, which is advantageous in terms of equipment, and furthermore, it is possible to prevent fluctuations in the gas blown into the ore reduction furnace. As a result, it is possible to significantly reduce the fluctuation range of the product return rate.

Furthermore, the carbon content remaining in the coal ash can be effectively gasified, and the sensible heat of the ash and the apparent reduced iron of the product can also be effectively used in the process, reducing the coal consumption rate and oxygen consumption rate. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a process flow diagram for producing reduced iron by reducing iron ore, which explains the present invention in detail. ■...Fluidized bed coal gasifier? ... Oxygen-containing gas or oxygen supply device 3 ... Oxygen-containing gas or oxygen supply pipe 4 ... Filled bed section 5 ... Discharge machine 6 ... Coal supply pipe 7 ... Dust return tube 8
... Hot cyclone 9.10 ... Generated gas duct 11 ... Ore reduction furnace 12 ... Reduced iron discharge pipe 1
3.--Heat exchanger 14.. Ore hopper 15.
...Ore supply pipe 16...Exhaust gas duct 17...
・Hot cyclone 18...Dust return pipe 19.21.23...Exhaust gas duct 20...Cooling dehumidifier 22...Decarboxylation equipment 24
...Blower

Claims (1)

[Scope of Claims] 1. A method for reducing iron ore in an ore reduction furnace using high-temperature gas generated in a fluidized bed coal gasification furnace, including: (a) oxygenating coal in a fluidized bed coal gasification furnace; For gasification, a packed bed of coal ash is formed in the lower part of the fluidized bed gasifier, and an oxygen-containing gas or oxygen is blown into the fluidized bed gasifier through this ash packed bed to convert the coal. (b) After the ore reduction furnace exhaust gas is cooled, dehydrated, and decarboxylated, it is heated by exchanging heat with the reduced iron discharged from the ore reduction furnace via a gas holder to prevent pressure fluctuations; (c) A method for reducing iron ore, characterized in that the heated exhaust gas is mixed with gas generated from the coal gasifier and blown into an ore reduction furnace.