JPS602362B2 - Iron oxide direct reduction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direct reduction iron manufacturing method for producing metallic iron by solid reduction of iron oxide such as iron ore using a reducing gas, and particularly to a method for producing reducing gas with high efficiency.

Direct reduction steelmaking technology has been attracting attention as a small-scale steelmaking technology that has become a medium-sized technology in developing countries.

Among these, the Midrex method (U.S. Pat. No. 3,748,120, 37 I 123, 36
17227, etc.), Armco method (3558118, total 5
0616 etc.) Purofur method (3883123 39
48646, etc.) and the Nippon Steel method (4001010, etc.) are known. In these systems, a gas mainly composed of natural gas or the like is used as the reducing gas production gas, and this gas is reformed in a reforming furnace to become the reducing gas.

The reducing gas produced as a result of the reforming reaction in this reforming furnace is generally a considerably high temperature gas of 900 qo or more,
The temperature is too high for gas to be blown into a reduction furnace, especially a vertical reduction furnace. Therefore, the subordinates had no choice but to take measures such as adjusting the cooling of the high-temperature reducing gas produced in the reforming furnace using a gas cooler, or mixing the cooled reduction furnace exhaust gas to adjust the cooling. As a result of these cooling adjustment means, there is a problem that the head heat of the reducing gas is lost or the reducing ability of the reducing gas is deteriorated. Furthermore, in the case of hydrocarbons such as methane, when CO2 is used as an oxidizing agent, there is a problem of carbon precipitation, especially during the oxidation reaction, and this problem must also be solved in the production of reducing gas.

An object of the present invention is to provide a direct reduction iron manufacturing method including a new reducing gas production method that can solve the above-mentioned problems in the direct reduction iron manufacturing method.

More specifically, it is an object of the present invention to provide a method capable of solving the problem of carbon precipitation during a reforming reaction. Furthermore, it is an object of the present invention to provide a method capable of reducing and eliminating heat loss by effectively utilizing facial heat possessed by high-temperature teaching gas produced in a refining furnace. Furthermore, it is an object of the present invention to provide a method that can reduce the amount of reforming furnace equipment. The present invention achieves the above object by improving the direct reduction iron manufacturing method in which iron oxide is reduced to obtain metallic iron by blowing the reducing gas obtained by refining gas containing methane as the main component into a reduction furnace. The gas whose main component is methane to be reformed is divided into two parts, one of which is mixed with the reduction furnace exhaust gas and supplied to a reforming furnace filled with an externally heated catalyst.
The other part is heated and mixed with the above-mentioned high-flow reformed gas, and by using the heat of these mixed gases, it is blown into the reduction furnace in the presence of a catalyst. This is a direct reduction iron making method characterized by causing a reforming reaction which is an endothermic reaction, obtaining a cooling and regulated reducing gas through this reaction, and blowing this reducing gas into a reduction furnace.

In the method of the present invention, first, a gas whose main component is methane to be treated is divided into two parts, one of which is mixed with reduction furnace exhaust gas and supplied to a reforming furnace filled with an external heating type catalyst.

The reforming reaction of a gas whose main component is methane, such as natural gas, occurs as follows: C mountain 10 days 20 → CO + 3 days 2 C ratio 10 C02 → 2CO 12 days 2; There is a risk that carbon precipitation will occur due to the reaction of normal → 20C↓ for 2 days.

This reaction is influenced by component composition (partial pressure), temperature, etc. In the present invention, the problem of carbon precipitation is suppressed by changing the component composition. In contrast, the present invention suppresses carbon precipitation by changing the component composition (minutes). That is, in the present invention,
Rather than supplying all of the gas whose main component is methane to be reformed to the reforming furnace, it is divided into two parts and only one of them is supplied to the waste furnace, thereby reducing the waste gas from the reduction furnace. The purpose is to suppress the above reaction by reducing the partial pressure of methane gas in the mixed gas. Regarding this carbon precipitation, when natural gas (methane) is reused with an oxidizing agent of CO2, the change in carbon precipitation temperature due to the change in the ratio of CH4/(C020QO) is investigated using equilibrium theory calculations. , the F result shown in FIG. 1 is obtained.

Note that this result is a calculation result for a system in which C02 and H20 substantially coexist as oxidizing agents. This first
As can be seen from the figure, the carbon precipitation region in the reforming reaction expands toward the high temperature side as the CH4/(C02 Toka 20) ratio increases.

In the case of the present invention, since the hydrocarbon gas to be purified is divided into two and only one of them is supplied to the refurbishment reactor, the amount of hydrocarbon gas, such as natural gas (methane), is smaller than when the whole amount is supplied. Therefore, since the CH4/(C02 Toka 20) ratio is low, the carbon precipitation region does not spread much toward the high temperature side.
As will be described later, in the method of the present invention, the ratio (volume ratio) of C melon/(CO2 10 days 20) of the mixed gas supplied to the reforming furnace is preferably 0.35 to 0.55. Applying this to FIG. 1, it follows that carbon precipitation no longer occurs above about 670-715°C. Therefore, in the method of the present invention, even if the reforming reaction is carried out at a temperature as low as 750°, the problem of carbon precipitation is substantially eliminated.
Considering the speed of the reforming reaction, a higher temperature is preferable, but as mentioned above, the problem of carbon precipitation can be eliminated, so a high temperature of at most 90% is possible using a highly active catalyst.
Reducing gas can be generated by carrying out the reforming reaction at 50°C. Although preheating the mixed gas supplied to the reforming furnace is an effective means as an auxiliary means for suppressing carbon precipitation in the reforming reaction, in the case of the present invention, as mentioned above, the upper limit of the carbon precipitation temperature is low. The child heat temperature of the mixed gas is also 700 to 750q0
Relatively low temperatures below are sufficient. As described above, in the method of the present invention, a part of the gas containing methane as the main component to be further reformed is supplied to the reforming furnace, and the remaining gas containing methane as the main component is heated to produce the reformed gas coming out of the reforming furnace. The mixed gas is mixed with the purified high-temperature reformed gas, and the heat of these mixed gases is used to cause a reforming reaction while being blown into the reduction furnace.

In this synthetic reaction, it is not necessary to convert all of the CH4 in the mixed gas into reducing gas components.

In other words, it is effective to include a certain amount of carbon (for example, CO.1 to 0.3%) in the reduced iron as a heat source when melting and refining the reduced iron in a steelmaking furnace. It is desirable to include CQ in the reducing gas and carburize the reduced iron using this CIL. In the case of natural gas, the amount of carbon necessary for this carburizing is sufficient to be about 1 to 1 ol% relative to the reducing gas blown into the carburizing process. In this way, the reducing gas blown into the reduction furnace should contain C days, so the mixture gas of the high temperature reformed gas discharged from the reduction furnace and the heated gas whose main component is methane will be reduced. In the qualitative reaction, it is not necessary to convert all of the CH4; a partial reaction is sufficient.

This political reaction of the mixed gas is carried out using the heat possessed by the mixed gas itself.

The gas containing methane as a main component is preferably heated to 800 to 950°C in a heating furnace that shares a heating source with the reforming furnace. In addition, the reformed high-temperature reducing gas coming out of the reforming furnace does not act as an oxidizing agent even after the reforming reaction because the C ratio/(CQ Jubutsu 0) ratio of the mixed gas supplied to the political reactor is low. C02 and ratio O remain, and the qualitative reaction of the above-mentioned mixed gas proceeds using these C02 and H as oxidizing agents. Since this reaction utilizes the heat possessed by the mixed gas itself, it is performed in a non-ectothermic manner.

Further, in the reaction, it is preferable to carry out the reaction using a catalytic method rather than a non-catalytic method. That is, it is preferable to carry out the reaction using a non-exothermal catalyst system, and this reaction vessel is called an afterreactor. The distribution of the supply of gas containing methane as a main component to the reforming furnace and the supply to the heating furnace (therefore, the gas that leaves the heating furnace and is mixed with high-temperature teaching gas) is divided into two parts: It is desirable that the supply amount be 0.4 to 0.6.

Note that as the ratio of gas containing methane as the main component supplied to the heating furnace increases, the ratio of C ratio/(CQ + day 20) increases, and the carbon precipitation temperature range expands to the high temperature side, but as mentioned above. As shown in the figure, the modification in this area is only partial and is not a big problem. As mentioned above, the temperature of the heated methane-based gas and the high-temperature recycled gas discharged from the recycled furnace is between 800 and 950 degrees Celsius, as mentioned above, and this retained heat causes an endothermic reaction. The reaction progresses.

The temperature of the mixed gas drops by 50 to 20 ppm due to this reforming reaction, and the temperature of the mixed gas is adjusted to the temperature that was used as the temperature at which it was blown into the reduction furnace. It would be better if an auxiliary heater or cooler was provided midway to more accurately adjust the blowing temperature. Next, examples of the method of the present invention will be shown.

FIG. 2 is a diagram showing the process flow of the method of the present invention. In Fig. 2, 1 is a vertical reduction furnace, 2 is a political furnace, and 3 is a heating furnace, and the reduced exhaust gas a discharged from the vertical reduction furnace 1 is dedusted and cooled by a scrubber 4, and removed b. , after that, it is divided into two, and one becomes the fuel for the political reactor 2 and the reheating furnace 3, and the other b' is mixed with a part c of the natural gas from the natural gas 5, and becomes the mixed gas d, which is sent to the refining reactor 2. It will be buried. Reformed high temperature reducing gas e and other part of natural gas f
is mixed with the heated natural gas g heated in the heating furnace 1 3 on the exit side of the reformer, and this mixed gas h is mixed with the heated natural gas g heated in the heating furnace 1 3, and this mixed gas h is mixed with the after reactor 6 of the Higaiki Juku packed with a catalyst on the way to being blown into the reduction furnace. A reforming reaction is caused by the heat possessed by the mixed gas itself, and at the same time, cooling is adjusted by phosphorthermal reaction, resulting in a reducing gas j suitable for being blown into the vertical reduction furnace 1. As described above, according to the present invention, in the production of direct reduction reducing gas for iron making using the densification of a gas containing methane as a main component, it is possible to prevent and suppress carbon precipitation during the densification process. This is achieved by reducing the amount of hydrocarbon gas supplied to the oxidizing agent and lowering the content ratio with the oxidizing agent.As a result, it is possible to reduce the amount of reforming furnace equipment.

Furthermore, reducing gas, which is insufficient with just the high-temperature reformed gas produced in the above-mentioned reforming furnace, can be produced by effectively utilizing the heat possessed by the high-temperature teaching gas and mixing it with hydrocarbon gas heated in the heating Kenichi. It is possible to obtain the reducing gas necessary for injection into the reducing furnace by causing a cost reaction, and through this cost reaction (adjacent heat reaction), the temperature can be adjusted to a temperature suitable for use as a reducing gas for injection.
It is also possible to reduce heat loss.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between C ratio/(CQ+QO) and carbon precipitation temperature in a numerical reaction of natural gas (methane) by C02 Toka 20. FIG. 2 is a diagram showing the process flow of the present invention. 1
......Right reduction furnace, 2...Reforming furnace, 3.
...Heating furnace, 4...Scrubber, 5...Natural gas source, 6...After reactor. Figure 1 Figure 2

Claims (1)

[Claims] 1. In the direct reduction ironmaking method, in which the reducing gas obtained by reforming the gas whose main component is methane is blown into a reduction furnace and the iron oxide is reduced to obtain metallic iron, the gas whose main component is methane to be reformed is One half is mixed with the reduction furnace exhaust gas and supplied to the reformer to generate high-temperature reformed gas, and the other half is heated and mixed with the high-temperature reformed gas to release the heat contained in these mixed gases. A reforming reaction, which is an endothermic reaction, occurs in the presence of a catalyst while being blown into the reduction furnace, and through this reaction, the reducing gas is cooled and adjusted to a temperature suitable for being blown into the reduction furnace. Direct reduction method of iron oxide using iron oxide.