KR20020051307A - Method for producing cementite - Google Patents

Abstract

PURPOSE: A method for producing cementite with reduced free carbon and pulverization of iron ore is provided, in which a trace amount of sulfurated hydrogen is added in a reactive gas mainly composed of hydrogen and carbon monoxide during reduction and carburization. CONSTITUTION: In a producing method of cementite by charging iron ore in fluidized bed reactor, the present method is characterized in that a reactive gas of which the gas portion of H2 and CO is higher than 85% and the ratio of H2/CO is between 1 and 3 is added with sulfurated hydrogen in such a manner that the activity of FeS become 0.1-0.5 and then the reactive gas is introduced into a fluidized bed reactor to react with iron ore at 600-800°C for 2-4 hours.

Description

Method for Producing Cementite {Method For Producing Cementite}

The present invention relates to a method for producing cementite used as raw materials for steelmaking, and more particularly, to a method for producing cementite used as raw materials for steelmaking in a fluidized bed reactor.

In recent years, blast furnace operations have been aiming at low-silicon operations from the viewpoint of quality improvement and economical efficiency in the subsequent steelmaking process. As a typical process of such an operation mode, a method of blowing powdered iron source such as iron oxide powder or reduced iron powder together with pulverized coal is shown in Japanese Patent Application Laid-Open No. 57-137402.

The powdered iron sources such as iron oxide powder and reduced iron powder are thus reduced in the blast furnace to be reduced to the metal state and react with molten iron in the blast furnace during the reduction to react with 2 (FeO) + Si = 2Fe + (SiO ₂ ). This lowers the silicon in the molten iron. When the blast furnace is stable, the amount of iron ore charged from the top can be reduced by the amount of powdered iron source taken from Punggu.

In general, iron ore charged from the top of the road is hardened in order to maintain the air permeability of the furnace. Therefore, using an inexpensive powdered iron source for iron ore that requires pretreatment may also help improve the economic efficiency of the blast furnace operation.

The powdered iron source blown from the tuyere is melted by reducing melting in the race way area where the coke turns and burns.

For the reduction melting, the calorific value is adjusted in advance by raising the blowing temperature or increasing the kx ratio.However, the pulverized iron source can reduce the required calorie due to the high preliminary reduction rate, so that the amount of blown can be increased by The amount of iron ore can be further reduced.

Cementite is an pulverized iron source with a preliminary reduction rate of 100%, and contains 6.7% of carbon and thus is an ideal pulverized iron source effective as an alternative raw material for pulverized coal.

In addition, since it is chemically stable even when stored in the yard, it does not cause change due to oxidation or heat generation, and there is no adhesion and blockage in transportation by gas, so it is an excellent powdered iron source in this respect.

In the future, the technique of blowing a large amount of cementite in the blast furnace blast furnace is expected to be an essential technology for reducing the manufacturing cost. Therefore, it is necessary to develop a method for producing this material with high purity and stability.

However, in the conventional cementite production method, as shown in Japanese Patent Application Laid-Open No. 6-100918, using methane, hydrogen, carbon monoxide, carbon dioxide, and nitrogen, the reaction temperature is 600 to 700 ° C., and the reaction time is 30 minutes to 4 hours. I am doing it.

In addition, the ratio of (carbon monoxide + carbon dioxide) in the mixed gas is set at 15 to 30%.

However, the manufacturing method is not only difficult to apply in a region where natural gas is not mass produced because the main carbonization reaction is dependent on methane, and the decomposition of chronic cementite generated during the carbonization reaction and the generation of free carbon and Carbonization is difficult to avoid.

Therefore, in the case of the manufacturing method, it is difficult to obtain a product having a high carbonization rate, and also has a problem of providing a cause of equipment trouble due to a decrease in product error rate due to free carbon and carbonization and an increase in load of a gas cleaning equipment connected to a fluidized bed facility. have.

MEANS TO SOLVE THE PROBLEM The present inventors carried out research and experiment in order to solve the above-mentioned all the problems of the prior art, and based on the result, the present invention proposes the present invention. The purpose of the present invention is to provide a method for stably obtaining high purity cementite without generating free carbon and carbonization in a fluidized bed reactor.

1 is a schematic view showing an example of a bubble-type fluidized bed reactor to which the present invention can be applied.

2 is a schematic view showing an example of a high-speed circulating fluidized bed reactor to which the present invention can be applied.

Explanation of symbols on the main parts of the drawings

1, 11. . . Reactor 2, 12. . . Cyclone

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention provides a method for preparing cementite by charging iron ore into a fluidized bed reactor,

The reaction gas was added to the fluidized bed reactor to add H ₂ and CO to 85%, the H ₂ / CO composition ratio is 1 to 3, and the hydrogen sulfide was added so that the activity of iron sulfide (FeS) was 0.1 to 0.5. The present invention relates to a method for producing cementite by reacting the reaction gas with iron ore under a reaction temperature of ˜800 ° C. and a reaction time of 2 to 4 hours.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Cementite is produced through the following reaction.

When supplying the reaction gas to the iron ore charged in the fluidized-bed reduction furnace, iron iron ore and hydrogen and carbon monoxide react first to produce metal iron, as shown in Equation (1) below.

2Fe ₂ O ₃ + 3CO + 3H ₂ = 4Fe + 3CO ₂ + 3H ₂ O

Next, metal iron and carbon monoxide react to produce cementite as shown in the following formula (2).

6Fe + 2CO = 2Fe ₃ C + O ₂

The cementite produced as described above is unstable and precipitates free carbon by decomposition reaction as shown in Equation (3), which causes a part of metal iron (or cementite) to be differentiated and dusted. Sulfur components in the added hydrogen sulfide adhere to the cementite surface to inhibit the cementite decomposition reaction occurring at the surface.

Fe ₃ C = 3Fe + C

In the present invention, the reaction gas preferably has a sum of H ₂ and CO of 85% or more and a H ₂ / CO composition ratio of 1 to 3, because the sum of H ₂ and CO is 85% or less, or H ₂ / If the CO composition ratio is greater than 3 or less than 1, the carbonization reaction rate is lowered.

Hydrogen sulfide should be contained in the reaction gas so that the activity of iron sulfide (FeS) is 0.1 to 0.5.

When the hydrogen sulfide is added so that the iron sulfide activity (a _FeS ) is less than 0.1, the possibility of decomposition of Fe ₃ C and the appearance of free carbon increases, and when it is added to more than 0.5, the rate of reduction and carbonization reaction only decreases. In addition, the proportion of sulfur contained in the product increases.

The activity of iron sulfide is defined as the partial pressure ratio of hydrogen sulfide and hydrogen in the equilibrium state of Fe / FeS, that is, the relative ratio of partial pressure of P _{H 2 O} / P _{H 2} .

Table 1 below shows the ratio of P _{H 2 O} / P _{H 2} at the Fe / FeS equilibrium at each temperature.

Temperature (℃) 600 700 800 (P _H2S / P _H2 ) x 10 ⁴ 4.75 11.9 24.2

The reaction gas of the present invention may contain less than 15% of carbon dioxide (CO ₂ ) and nitrogen gas (N ₂ ).

In addition, in this invention, it is preferable to set reaction temperature as 600-800 degreeC, and reaction time as 2 to 4 hours.

When the reaction temperature is less than 600 ℃ or the reaction time is less than 2 hours, the cementite is not produced sufficiently, when the reaction temperature exceeds 800 ℃ or the reaction time exceeds 4 hours, cementite is decomposed to free carbon Is generated or sulfur is accumulated on the surface, and high-quality cementite cannot be obtained.

In the case of preparing cementite according to the present invention, since the temperature is low as 600 to 800 ° C., the metal iron produced by the reaction of the following Chemical Formulas (1) and (2) does not cause sticking, and therefore, It does not cause a problem in the discharge of the fluidized bed reactor by this.

The raw material particle size may be a particle size used in a normal fluidized bed reactor.

In addition, the fluidized bed reactor that can be applied to the present invention as shown in Figure 1 is a bubble-type fluidized bed reactor disclosed in Japanese Patent Laid-Open No. 57-32351 or high-speed published in Japanese Patent Laid-Open No. 62-228877 as shown in FIG. Circulating fluidized bed reactors;

In Fig. 1 and Fig. 2, numerals 1 and 11 represent reactors and 2 and 12 represent cyclones.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

The iron ore having a particle size as shown in Table 2 is charged to a fluidized bed reactor as shown in Table 2 below to react the iron ore and the reaction gas under the reaction gas and reaction time conditions as shown in Table 2 to produce cementite, product cementite content (%), Product iron content (%), product iron oxide content (%), product carbon content (%), product sulfur content (%), product yield (%) and free carbon generation (o, x) And the results are shown in Table 2 below.

Inventive Example 1 Inventive Example 2 Inventive Example 3 Comparative example Fluidized Bed Reactor Temperature (℃) Reaction Pressure (atm) Gas Composition H ₂ (%) CO (%) CO ₂ (%) N ₂ (%) CH ₄ (%) a _FeS (-) Bubble type625166223900.5 High speed circulation type Bubble type750145455500.1 Bubble type Reaction time (hr) Raw material particle size (mm) 2.50.1-1.0 3.50.1-1.5 3.00.1-1.5 8.00.1-1.0 Product Cementite Content (%) Product Iron Content (%) Product Iron Oxide Content (%) Product Carbon Content (%) Product Sulfur Content (%) Product Reality (%) Glass Carbon Emission (o, x) 91546.00.0397x 90555.90.0298x 90555.90.0197x 8210812.50.00582o

As shown in Table 2, in the case of Inventive Examples 1, 2 and 3 according to the present invention it can be seen that the cementite content of the product is more than 90% and there is no generation of free carbon.

On the contrary, in the case of the comparative example deviating from the present invention, it can be seen that the cementite content of the product is 90% or less and that free carbon is generated, thereby lowering the product yield.

As described above, the present invention suppresses the generation and carbonization of free carbon by adding carbon monoxide and hydrogen as the main components and reducing the amount of hydrogen sulfide as the reducing gas during the reduction and carbonization of spectroscopy in a fluidized bed reactor. There is an effect that can be obtained stably with a high real yield.

Claims (1)

In the method for preparing cementite by charging iron ore into a fluidized bed reactor, The reaction gas was added to the fluidized bed reactor to add H ₂ and CO to 85%, the H ₂ / CO composition ratio is 1 to 3, and the hydrogen sulfide was added so that the activity of iron sulfide (FeS) was 0.1 to 0.5. A process for producing cementite, wherein the reaction gas and iron ore are reacted under a reaction temperature of ˜800 ° C. and a reaction time of 2 to 4 hours.