JPS5980706A - Operating method of preliminary reduction furnace with fluidized bed - Google Patents

Abstract

PURPOSE:To perform an operation which is stable for a long period of time without decreasing reduction rate in the stage of reducing preliminarily powder and granular ore with the high temp. waste gas generated from a melt reduction furnace as reducing gas by using gaseous hydrocarbon of a low temp. together as fluidizing gas and a reducing agent. CONSTITUTION:A part of gas contg. hydrocarbon such as CH3, C3H8 or the like is introduced 13, 13' respectively into a conduit 12 for the above-described high temp. reducing gas or near a supply port 8 for the reducing gas in a preliminary reduction furnace 1. On the other hand, a position of the gas contg. hydro-carbons corresponding to the amt. to remain after subtracting the amt. necessary for the preliminery reduction of Cr2O3 from total gas is supplied directly 9 to the fluidized bed 2 region of the furnace 1, and the operation of the furnace 1 is performed. The temp. of the reducing gas of a high temp. can be decreased effectively by increasing the flow rate of the gas contg. hydrocarbon to be supplied 12. However, in the case of reducing preliminarily hardly reducing Cr2O3, the rate of partial thermal crackng of hydrocarbon increases and there is possibilitythat the amt. effective for reducing Cr2O3 decreases. Therefore, it is possible to compensate some part (corresponding to the remaining part) with the amt. of the gas contg. hydrocarbon to be supplied directly into the bed 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating a fluidized pre-reduction furnace, in which high-temperature exhaust gas generated from a smelting reduction furnace is used as a reducing gas to prepare powdery ore containing metal oxides in a fluidized bed. We propose a new operating method that uses low-temperature hydrocarbon-containing gas as a fluidizing gas and reducing agent during preliminary reduction in a reduction furnace.

In recent years, the technology for producing ferroalloys has been that ore resources tend to be of lower grade and become finer minerals, so when smelting such ores, they are first agglomerated and then smelted using an electric furnace. Since it is common to
There was a problem in that the cost reached as high as 1/l, resulting in an extremely high cost.

Therefore, recently, the smelting reduction method has been attracting attention as a technology for producing ferrochrome and other ferroalloys that does not rely on electric power. For example, there is a method for directly producing ferroalloy from powdery ore using an apparatus that combines a fluidized bed pre-reduction furnace and a vertical smelting reduction furnace. This known method involves pre-reduction in a fluidized bed format using the high-temperature exhaust gas of a smelting reduction furnace as a source of reducing agent and heat necessary for the pre-reduction of metal oxide-containing ores. Since the ore can be used directly without agglomeration, it is possible to produce molten metal at a lower cost than the above-mentioned methods.

The main conditions necessary for the fluidized bed as a pre-reduction furnace in the above-mentioned known method are (1) easy heat supply to maintain the reaction temperature at which the required JK rate can be obtained, (2) local (3) Uniform and stable fluidization phenomenon can be obtained; (4) Short residence time. However, the required reduction rate can be obtained (using a multistage fluidized bed), and (5) there is less dust generated due to particles flying out of the fluidized bed.

However, generally speaking, the higher the temperature of the fluidized bed required for pre-reduction, the more difficult it is to maintain these various conditions, and moreover, the fluidized gas generated from the smelting reduction furnace contains a large amount of dust. If the operation method is
This increases the difficulty and requires the development of various new methods and devices.

In FIG. 1, a conventional device for preliminary reduction of powdery ore using a fluidized bed is not shown. The preliminary reduction furnace 1 is vertical and has a powder ore supply port 4 in its body, and a supply device 6 for supplying ore from an ore hopper 7 into the furnace is installed here. Further, a high temperature reducing gas supply port 8 is opened in the lower part of the furnace below a gas distribution plate (grate) 3 installed in the furnace to retain the ore. The above reducing gas is
High-temperature exhaust gas generated from a heating furnace, reducing gas generating furnace, or melting reduction furnace is used as a reducing agent and fluidizing gas. By introducing this reducing gas into the furnace, the powdery ore on the gas distribution plate 3 is fluidized, forming a fluidized bed 2, and fluidized reduction can be performed. Note that the illustrated reference numeral 9 is a reducing agent supply port that supplies a hydrocarbon-containing gas such as methane as a reducing agent. Further, the illustrated reference numeral 10 denotes a discharge pipe, and since the exhaust gas from the fluidized bed 2 discharged through this pipe contains a large amount of dust, the dust is removed by a cyclone 11. On the other hand, the pre-reduced ore is discharged from the discharge pipe 5 and transferred to the next process, such as a smelting reduction furnace.

Generally, the preliminary reduction temperature in a fluidized bed varies depending on the type and brand of ore, and is approximately 600 to 900 degrees Celsius for iron ore and 950 to 1100 degrees Celsius for chrome ore, and fluidization is inhibited by the stickiness of the reduced ore. The sintering limit temperature for iron ore is about 1000 to 1100℃, and for chromium ore it is about 120℃.
The temperature is about 50 to 1350°C.

By the way, in conventional pre-reduction processing, in order to maintain the reduction temperature necessary for pre-reduction using the sensible heat of the high-temperature reducing gas, it is necessary to introduce a high-temperature reducing gas. exceeds the above-mentioned sintering limit temperature, and in the vicinity of the reducing gas supply port 8 and gas distribution plate 3, the powdery ore is often overheated to a temperature exceeding the sintering limit temperature, resulting in the growth of sintered lumps and deposits. There were disadvantages in that the gas distribution plate 3 was clogged and the fluidization reaction was inhibited.

Furthermore, when exhaust gas generated from a smelting reduction furnace is used as the high-temperature reducing gas, the higher the temperature of the generated gas, the higher the dust content and the stronger the adhesion of the dust. It turns out there is a problem.

In order to solve the above-mentioned problems, it is sufficient to lower the introduction temperature of the reducing gas, but simply lowering the temperature will lower the reduction temperature and reduce the reduction rate. Therefore, the present invention overcomes the above-mentioned problems of the prior art by lowering the introduction temperature of the reducing gas without reducing the reduction rate. As an effective method for solving this problem, the present invention allows a part of the gas containing hydrocarbon fibers such as methane to merge into the reducing gas conduit 12 before reaching the reducing gas supply port 8, and in the conduit 12, high-temperature reducing gas is In addition to the preheating of the hydrocarbon-containing gas, the high-temperature reducing gas itself undergoes an endothermic reaction through partial thermal decomposition to lower its temperature, thereby solving the problems of the prior art described above at once. The details of the structure of the present invention will be explained below with reference to a diagram of a preferred embodiment shown in FIG.

The method of using a hydrocarbon-containing gas such as methane as a reducing agent in a pre-reduction furnace as in the present invention is particularly effective when reducing hard-to-reducible ores such as chromium ore. The reason for this is that the exhaust gas generated in the smelting reduction furnace in the next process is used as a reducing agent for preliminary reduction, and the main component of the generated exhaust gas is CO, so although this exhaust gas alone is effective in reducing Fe, it Since it is difficult to reduce ferrochrome, it becomes difficult to smelt ferrochrome, which is extremely uneconomical. However, when mixing hydrocarbon-containing gas such as methane with reducing gas, rcr20
This is because solid carbon, which is effective for the 3-reduction, is provided in the reducing agent, making it possible to carry out smooth preliminary reduction.

Therefore, the present invention is a method mainly consisting of introducing the hydrocarbon-containing gas into a pre-reduction furnace, and a part of the hydrocarbon-containing gas is fused into By merging the reducing gas into the exhaust gas generated by the reducing furnace before it reaches the supply port 8,
The endothermic reaction accompanying the thermal decomposition of the hydrocarbon-containing gas lowers the temperature of the high-temperature reducing gas, thereby eliminating the above-mentioned disadvantages caused by high temperatures.

The N2 diagram is a preferred embodiment of the present invention.
10 shows the same structure as a conventional pre-reduction furnace. In the preliminary reduction furnace 1 shown in FIG. 2, the present invention supplies a portion of the above-mentioned hydrocarbon-containing gas to a hydrocarbon-containing gas inlet in the high-temperature reducing gas conduit 12 or in the vicinity of the reducing gas supply port 8. 13° and 13' are connected and supplied, and on the other hand, an amount of the hydrocarbon-containing gas corresponding to the remaining amount required for the preliminary reduction of Cr2O3 is supplied to the carbonization furnace provided in the fluidized bed 2 area of the preliminary reduction furnace 1. The hydrogen-containing gas was supplied directly from the supply port 9 into the fluidized bed 2 to operate the preliminary reduction furnace.

By increasing the flow rate of the hydrocarbon-containing gas supplied to the high-temperature reducing gas conduit 12 generated by the smelting reduction furnace, it is more effective to lower the temperature of the high-temperature reducing gas. However, Cr, which is difficult to reduce,
In cases where 2O3 is pre-reduced, there is a risk that the degree of partial thermal decomposition of hydrocarbons will increase and the amount effective for reducing Cr2Q3 will decrease. In this regard, the present invention partially (
The remaining amount) can be supplemented by the amount of hydrocarbon-containing raw gas directly fed into the fluidized bed 2. However, the overall hydrocarbon content of the valve may increase, increasing the cost.

In this sense, it is necessary to balance the supply amounts of both, and it is preferable that the raw gas supply position to be supplied into the high-temperature reducing gas conduit 12 be close to the reducing gas supply port 8.

EXAMPLE The results of implementing the operating method of the present invention using the apparatus shown in FIG. 2 will be described below.

・Inner diameter of preliminary reduction furnace: 1.2m ・Ore: Sand chromium from the Philippines (average particle size 0.
2 mm> ・Supply u: 260
kg/hr・Exhaust gas ffl from smelting reduction furnace: 1960 N11l
/hr・Temperature of generated exhaust gas: 1380 ℃・Hydrocarbon-containing raw gas: Coke oven generated gas/high temperature reducing gas supplied to conduit m: 42Nm3/hr・Direct supply to fluidized bed: 57Nm”/hr・Mixed gas temperature at the high-temperature reducing gas supply port: 1190 °C In the example, the temperature at which the high-temperature reducing gas was introduced into the preliminary reduction furnace was able to be lowered to below the sintering limit temperature, so the temperature near the high-temperature reducing gas introduction port was It was possible to operate stably for a long time without the formation of sintered lumps or deposits.Moreover, the reduction rate of chromium was also good.

[Brief explanation of the drawing]

FIG. 1 is a route map of a conventional pre-reduction facility, and FIG. 2 is a route map of a pre-reduction facility of the present invention. 1... Pre-reduction furnace 2... Fluidized bed 3... Gas distribution plate 4... Powdered ore supply port 5... Pre-reduced ore discharge port 6... Supply device 7... Ore hopper 8...
・Reducing gas supply port 9...Hydrocarbon-containing gas supply port 10...Fluidized bed exhaust gas outlet 11...Zykron 12...Reducing gas conduit 1
3.13'...Hydrocarbon-containing gas supply port Patent applicant
Continued from page 1 of Kawasaki Steel Corporation ■Inventor: Tsutomu Fujita, 1 Kawasakicho, Chiba City, Kawasaki Steel Corporation, Chiba Works ■Inventor: Shunji Hamada, 1, Kawasakicho, Chiba City, Kawasaki Steel Corporation, Chiba Works

Claims (1)

[Claims] 1. While charging the granular ore into the fluidized bed pre-reduction furnace,
In the method of operating a pre-reduction furnace, the ore is pre-reduced by introducing a fluidizing reducing gas into the reactor to cause a fluidizing reaction. By mixing a portion of the gas into the high-temperature reducing gas supplied to the furnace, the temperature of the high-temperature reducing gas is lowered, and the remaining hydrocarbon-containing gas corresponding to the amount required for preliminary reduction of the above-mentioned granular ore is removed. A method for operating a fluidized bed pre-reduction reactor, characterized in that the pre-reduction reactor is directly introduced into a fluidized bed region within the reactor.