CN100410170C - A kind of method of preparing iron carbide with iron concentrate powder - Google Patents

Abstract

The invention belongs to a method for preparing iron carbide (Fe ₃ C), in particular to a method for preparing iron carbide with iron concentrate powder. The technical solution adopted in the present invention is: add vanadium-containing oxides as additives to the iron concentrate powder in an amount of 1% to 5% of the weight of the iron concentrate powder, mix them with appropriate amount of water to make pellets, and drying the pellets; then putting the dried pellets into a furnace at a temperature of 800-900° C. for sintering for 10-20 minutes, taking them out and cooling to room temperature. Finally, react with the mixed gas at a temperature of 700-800°C. When the mixed gas is CH ₄ -H ₂ , the reaction is 30-50 minutes; when the mixed gas is CO-H ₂ or H ₂ -CO-CO ₂ , the reaction is 90-180 minutes. After the reaction, the reaction was rapidly cooled to room temperature with an inert gas. The invention has the characteristics of fast reaction speed, high conversion rate, good stability and no increase of sulfur-containing impurities.

Description

A kind of method of preparing iron carbide with iron concentrate powder

1. Technical field

The invention belongs to a method for preparing iron carbide (Fe ₃ C), in particular to a method for preparing iron carbide with iron concentrate powder.

2. Technical background

As a direct reduced iron product that appeared in the 1970s, iron carbide has attracted widespread attention due to its unique physical properties, chemical properties and production conditions: 1. It has attracted the attention of metallurgists due to its outstanding advantages and can be used as a substitute for steel scrap 2. As a steelmaking raw material, compared with the iron blast furnace production process, the production temperature of iron carbide is relatively low, and the by-product of its production process is mainly water. The main product iron carbide is solid and stable, easy to transport and store, Therefore, the production process of iron carbide, as an alternative process of the traditional blast furnace ironmaking process, has great advantages in energy consumption, environmental protection and economy; 3. The unique electromagnetic properties of iron carbide can be used as information materials and electromagnetic shielding Materials; 4. Iron carbide can be used as hydrogen storage material.

For the above reasons, people have been devoting themselves to the research on the preparation of iron carbide. The main preparation principle of iron carbide is to react with iron ore with reducing gas (such as H ₂ -CH ₄ ) containing carburizing gas under certain conditions to prepare iron carbide.

1. Using CH ₄ -H ₂ mixed gas to produce iron carbide. Studies have shown that in the temperature range of 650~950°C, the best operating conditions are: the ratio of CH ₄ : H ₂ is 40:60, and the temperature is 750°C. Under these conditions, most of the iron ore will be transformed within 45 minutes. Formation of iron carbide (Fe ₃ C) [Nakagawa Dai, Takeaki Murayama, Yoichi Ono, ほか.セメンタィトの结合に和ぼす铁鉱の实验の影响. Materials and Proseス, 1994, 7: 85], [Nakagawa Dai, Murayama Takeaki , Yoichi Ono, ほか. セメンタィトの结合に and ぼすガス composition and temperature の influence. Materials and proseス, 1995, 8: 109], [Nakagawa Dai, Takeaki Murayama, Yoichi Ono. CH ₄ -H ₂ mixed ガスにょるァイァンカ一バィドのManufacturing. Iron and Steel, 1996, 82(4): 261]; another study showed [Ni Hongwei, Cang Daqiang, Jiang Junpu. The influence of reaction temperature and atmosphere on the preparation process of iron carbide. Iron and Steel Research. 1999 , No.6:22-25]: Iron ore powder reacts with H2-CH4 mixed gas. When the temperature is 700°C and the gas percentage is 50-80% H ₂ +20-50% CH ₄ , iron carbide is more It is formed early and can maintain a fast conversion rate in the early stage, but in the later stage of the reaction, the conversion of iron carbide is slow, and the decomposition reaction of iron carbide is prone to occur; when the temperature is 500 ° C, 600 ° C, the percentage of mixed gas is 30 When ~50% H ₂ +50 ~ 70% CH ₄ , a higher conversion rate of iron carbide can be obtained, but the conversion of iron carbide starts later and is slow.

2. Use CO-H ₂ mixed gas to reduce iron ore. Studies have shown [Wang Guanghui, Jiang Maofa, Ma Qiang. Research on Iron Carbide. Steelmaking. 1997, Vol(12): 22-23]: CO-H ₂ series gas is difficult to obtain iron carbide directly from iron ore reduction, adding an appropriate amount Although iron carbide can be produced in the range of 550-950 ° C after the sulfur-containing gas (such as H ₂ S), the conversion rate of iron carbide is low, and the impurity sulfur is brought into the product.

3. Using H2-CO-CO2 mixed gas to prepare iron carbide. At 550-700°C, H ₂ -CO-CO ₂ mixed gas can produce iron carbide from iron ore [Wang Guanghui, Jiang Maofa. Experimental research on the production of iron carbide by reducing iron ore with COREX tail gas. Iron and Steel. 1998, Vol .33, No.1:18-21], reacted for 4 hours under the conditions of 700 ℃ and reducing gas composition of 20% H ₂ +60% CO + 20% CO ₂ , the conversion rate of iron carbide can reach up to 94.02%. According to this method, although a relatively ideal iron carbide conversion rate has been obtained, the conversion is too slow.

Although a high conversion rate of iron carbide can be obtained on a laboratory scale, the slow conversion rate and low yield of iron carbide are still urgent problems to be solved. CIRCOFER) process (also iron carbide process) developed by Lurgi Company in Germany. After preheating, the iron concentrate powder first participates in the reaction in the circulating fluidized bed. The metallization rate of the obtained product can reach 80%, and then undergoes the second stage reaction , The metallization rate can reach more than 93%. The direct reduction equipment with an annual output of 500,000 tons of this process was put into operation in Trinidad and Tobago in 1994 in the factory of Nucor Corporation of the United States. However, due to many problems in the production process, the production could not be stabilized. Industrial production was stopped in 1999 [World Metal Bulletin, November 23, 2001: Summary of new technologies for direct reduced iron production in the world]. In 1995, Grabke Hans Jurgen et al. found that sulfur has an effect on the stability of iron carbide [Grabke, Hans Jurgen et al.: Effect of sulfur on the stability of cementite, SteelResearch, 66(1995): 254]. Later, Lin Zhaoer from Nagoya Institute of Technology found that adding a small amount of H ₂ S to the H ₂ -CH ₄ mixed gas can inhibit the precipitation of free carbon and increase the yield of iron carbide [Hayashi et al.: Iron Carbide Synthesis by Reaction of Iron Ore with H ₂ -CH ₄ Gas Mixtures Containing Traces of Sulfur, ISIJ Int., 37(1997) 16, 345], but sulfur will poison the catalyst in the process of reforming natural gas as reducing gas, and will also bring impurity sulfur into the product , its application is limited.

3. Contents of the invention

The purpose of the present invention is to provide a method for preparing iron carbide from iron concentrate powder with fast reaction speed, high conversion rate, good stability and no increase of sulfur-containing impurities.

In order to achieve the above purpose, the technical solution adopted in the present invention is to add vanadium-containing oxides as additives to iron concentrate powder, and the vanadium-containing oxides are either V ₂ O ₅ , V ₂ O ₃ , or V ₂ The mixture of O ₅ and V ₂ O ₃ is added in an amount of 1% to 5% of the weight of the iron concentrate powder; after mixing, add an appropriate amount of water to make pellets, then dry the pellets, and then dry the dried pellets Put the dough into a furnace at a temperature of 800-900°C for sintering for 10-20 minutes, take it out and cool it to room temperature; finally react with a mixed gas at a temperature of 700-800°C, and react for 30-30 minutes when the mixed gas is CH ₄ -H ₂ 50 minutes, when the mixed gas is CO-H ₂ or H ₂ -CO-CO ₂ , the reaction is 90-180 minutes, and after the reaction, use an inert gas to quickly cool to room temperature.

The mixture of V ₂ O ₅ and V ₂ O ₃ is a mixture of the two in any ratio.

The weight percentage of the iron concentrate powder is as follows: the total iron content is not less than 64%, the sulfur content is less than 0.04%, and the _TiO2 is less than 0.5%; the particle size of the iron concentrate powder is below 80 mesh.

The mixed gas is either CH ₄ -H ₂ , CO-H ₂ , or H ₂ -CO-CO ₂ ; the volume percentage of the mixed gas CH ₄ -H ₂ is 60-80% H ₂ + 20-40% CH ₄ , the volume percentage content of the mixed gas CO-H ₂ is 60-85% CO+15-40% H ₂ , the volume percentage content of the mixed gas H ₂ -CO-CO ₂ is 10-30 %H ₂ +50-70% CO+10-20% CO ₂ .

Due to the adoption of the above technology, the present invention has the characteristics of fast reaction speed, high conversion rate, good stability and no increase of sulfur-containing impurities.

4. Description of drawings

Fig. 1 is the comparative schematic diagram of the present invention and no additive;

Figure 1 is a schematic diagram of the comparison between _TiO2 as additive and no additive.

5. Specific implementation

Embodiment 1 A method for preparing iron carbide with iron concentrate powder, the chemical composition of the concentrate powder is as shown in the table. For iron ore concentrate powder with particle size below 80 mesh, add industrial V ₂ O ₅ as an additive according to 2% to 4% of the weight of iron ore concentrate powder, mix the two evenly; add an appropriate amount of water and use a pelletizing machine to make 8mm ~ 10mm pellets are then dried. Put the pellets into a high-temperature furnace at 800-900° C. for sintering for 10-15 minutes, then take them out and cool to room temperature, and the preparation of the pellets is completed.

Chemical Composition of Iron Concentrate

composition T.Fe FeO SiO₂ CaO MgO S weight% 67.05 0.81 1.89 0.89 0.11 0.033

Iron carbide preparation method: after the temperature of the reaction vessel rises to 700-800°C, feed nitrogen into the reaction vessel to drive away the air in the vessel, put the pellets into the reaction vessel, and after the temperature stabilizes, feed the reaction gas (70% H ₂ +30% CH ₄ ), after reacting for 30-35 minutes, change to nitrogen gas and quickly cool to room temperature.

The obtained product was analyzed by Mössburg otogram, and the conversion rate of Fe ₃ C in the product was 96.0%.

Example 2

The iron ore powder raw material and preparation process are the same as in Example 1, the additive is a mixture of 60% V ₂ O ₅ +40% V ₂ O ₃ by weight, and the additive amount is 2.0% to 4.5% of the weight of the iron ore powder. The reaction gas is H ₂ -CO-CO ₂ , and its volume percentage is 10-30% H ₂ +50-70% CO+10-20% CO ₂ . After reacting with the pellets for 120 to 150 minutes, nitrogen gas was passed through and cooled to room temperature rapidly.

The obtained product was analyzed by Moossburg otography, and the conversion rate of Fe ₃ C in the product was 95.0%.

Example 3

This embodiment is a comparative example.

The iron ore powder raw material and the preparation process are the same as in Example 1, adding V ₂ O ₅ and TiO ₂ respectively, and the other without adding any additives. The addition amounts of V ₂ O ₅ and TiO ₂ are both 1-2% of the weight of the iron ore powder. The results are shown in Figure 1 and Figure 2. The stage of increasing weight loss rate in the figure is the reduction of iron ore. From Figure 1 and Figure 2, it can be seen that the use of additives V ₂ O ₅ or TiO ₂ and no additives have no obvious effect on the reaction rate of this stage. In Figure 1 and Figure 2, after the weight loss reaches the maximum value, the product begins to increase in weight, and this stage is the carbonization stage of iron. It can be seen from Figure 1 that compared with no additives, the carbonization rate can be greatly increased after adding 1% V ₂ O ₅ , and in contrast to Figure 2, the addition of 2% TiO ₂ reduces the carbonization rate of iron. Within the same reaction time (30 minutes), the conversion rates of iron carbide in the products with 1% V ₂ O ₅ , no additives, and 2% TiO ₂ were 96%, 84.8%, and 73.2%, respectively. Adding only 1% _V2O5 can increase the conversion rate of iron carbide by more than 10%, _and the reaction rate is also improved.

Claims (4)

1. A method for preparing iron carbide with iron concentrate powder is characterized in that vanadium-containing oxides are added as additives in iron concentrate powders, and vanadium-containing oxides are either V ₂ O ₅ or V ₂ O ₃ , Or a mixture of V ₂ O ₅ and V ₂ O ₃ , the amount of which is 1% to 5% of the weight of the iron concentrate powder; after mixing, add an appropriate amount of water to make pellets, then dry the pellets, and then The dried pellets are sintered in a furnace at a temperature of 800-900°C for 10-20 minutes, taken out and cooled to room temperature; finally react with a mixed gas at a temperature of 700-800°C, and the mixed gas is CH ₄ -H ₂ The reaction time is 30 to 50 minutes, and the reaction time is 90 to 180 minutes when the mixed gas is CO-H ₂ or H ₂ -CO-CO ₂ . After the reaction, the reaction is rapidly cooled to room temperature with an inert gas. 2. The method for preparing iron carbide from iron concentrate powder according to claim 1, characterized in that the mixture of V ₂ O ₅ and V ₂ O ₃ is mixed in any ratio of the two. 3. The method for preparing iron carbide with iron concentrate powder according to claim 1, characterized in that the weight percentage of the iron concentrate powder is: the total iron content is not less than 64%, and the sulfur content is less than 0.04% %, TiO ₂ is less than 0.5%; the particle size of iron concentrate powder is below 80 mesh. 4. The method for preparing iron carbide with iron concentrate powder according to claim 1, characterized in that the mixed gas is either CH ₄ -H ₂ , CO-H ₂ , or H ₂ -CO- CO ₂ ; the volume percentage of the mixed gas CH ₄ -H ₂ is 60-80% H ₂ +20-40% CH ₄ , the volume percentage of the mixed gas CO-H ₂ is 60-85% CO+15- 40% H ₂ , the volume percentage content of the mixed gas H ₂ -CO-CO ₂ is 10-30% H ₂ +50-70% CO+10-20% CO ₂ .

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