CN1248632A

CN1248632A - Coal oxygen fused reduction iron-smelting method and apparatus

Info

Publication number: CN1248632A
Application number: CN 99122119
Authority: CN
Inventors: 殷瑞钰; 杨天钧; 刘浏; 吴启常; 干勇; 杨树德; 齐渊洪; 苗治民; 李尚诣; 肖兴国; 许志宏; 佟溥翘; 王久训
Original assignee: Beijing Iron And Steel Design And Research Institute Ministry Of Metallurgical Industry; Chengde Iron And Steel Group Co ltd; Central Iron and Steel Research Institute; University of Science and Technology Beijing USTB; Institute of Chemical Metallurgy CAS; Northeastern University China
Current assignee: Beijing Iron And Steel Design And Research Institute Ministry Of Metallurgical Industry; Chengde Iron And Steel Group Co ltd; Central Iron and Steel Research Institute; Institute of Process Engineering of CAS; University of Science and Technology Beijing USTB; Northeastern University China
Priority date: 1999-10-27
Filing date: 1999-10-27
Publication date: 2000-03-29
Anticipated expiration: 2019-10-27
Also published as: CN1073630C

Abstract

The invention relates to the field of direct reduction method for smelting molten iron. The coal-oxygen melting reduction ironmaking of the present invention is carried out in a pre-reduction shaft furnace and a final reduction iron bath furnace. Iron-containing materials are used as raw materials, and coal is used as energy and reducing agent. The pre-reduction adopts a medium reduction degree, and the metallization rate of the pre-reduced ore is 50-80%; the final reduction adopts a low secondary combustion rate, and the concentration of CO+H ₂ +CO ₂ +H ₂ O is ≥85%. During the whole reduction process, the ratio of indirect reduction to direct reduction is close to the theoretical optimal value of 7:3. The invention has the technical advantages of low energy consumption, high production efficiency, stable operation and little corrosion to the furnace lining.

Description

Coal oxygen smelting reduction iron-making method and device

The invention belongs to the field of smelting molten iron by a direct reduction method. It is mainly suitable for smelting molten iron directly with iron ore powder and coal powder.

The smelting reduction process is one important new metallurgical process and features that non-coking coal is used as the primary energy source and reductant, and iron oxide is reduced in molten state. It is the development direction of iron-making industry in the future, is known as the emerging iron-making process in the 21 st century, and is also an important field for competitive research and development of iron and steel industry in various countries at present.

In the prior art, the more well-known smelting reduction processes mainly include: the COREX process (CN1042185A), the DIOS process (CN1054446), the Hismelt process (CN07102252), the AISI process (CN1071202), the PJV process (CN86100138) and the like, and only the CPREX process realizes industrial production. Other processes are also in the industrial or pilot plant phase.

Most smelting reduction iron-making processes adopt: the two-step reduction process of pre-reduction and final reduction. Namely, the reduction process in which the upper pre-reduction is mainly based on indirect reduction reaction and the lower final reduction is mainly based on direct reduction. According to the degree of pre-reduction, various processes for smelting and reducing coal iron developed in the world at present can be divided into the following two major types:

(1) the process with high pre-reduction degree and low post combustion rate comprises the following steps: which is typically represented by the COREX process. The upper part of the COREX process adopts a shaft furnace for pre-reduction, and utilizes high-concentration (CO + H) generated by a final reduction furnace₂Not less than 95 percent) of the gas reduces the lump ore, the pellets and the sinter ore to the metallization rate not less than 90 percent, and then the lump ore, the pellets and the sinter ore enter a final reduction furnace to be melted and reduced into molten iron.

(2) The processes with low pre-reduction degree and high post-combustion rate, such as DIOS process, AISI process, Hismelt process and the like belong to the type. The method is basically characterized in that an iron bath (or slag bath) furnace with the characteristic of uniform mixing is adopted as a reactor in a final reduction furnace, FeO is directly reduced by utilizing C, and the heat generated by secondary combustion is directly reduced to the required heat. Therefore, the degree of pre-reduction of ores at the upper part of the process is lower, generally about 30 percent, and only Fe is used₃O₄Or Fe₂O₃Reducing the product to FeO; and then the molten iron is melted and reduced into molten iron in a final reduction furnace. In order to ensure the heat required for the final reduction, the post-combustion rate of the furnace gas (i.e. CO + H) is required₂O/CO+CO₂+H₂+H₂OThe coal consumption is more than or equal to 50-60 percent.

Because the COREX process mainly completes the reduction of the iron ore by gas-solid phase indirect reduction reaction, the consumption of the reducing gas is high, and the energy consumption is higher; and the production efficiency is low and the investment cost is high due to the limitation of low heat transferand mass transfer rate of the gas-solid reaction.

In various smelting reduction processes using a process route of high post-combustion rate and low pre-reduction degree represented by a DIOS process, the gas phase at the upper part of a final reduction furnace is required to have higher oxidation potential (high post-combustion rate), so that the reduction potential of slag and iron phase at the lower part is difficult to control. Therefore, the strong erosion of the furnace lining by the high-temperature high FeO slag cannot be avoided. At present, no process can reach the industrialized production condition.

Chinese patent ZL94115073.9 provides a smelting reduction iron-making method and apparatus, the patent uses cold-bonded carbon-containing pellets as raw material, uses non-coking coal as fuel and reducing agent; the smelting reduction adopts a two-step method of pre-reduction and final reduction, the pre-reduction is carried out in a separate shaft furnace, and the final reduction is carried out in a vertical iron bath furnace. The method can obtain molten iron with better performance, has high productivity and can reduce cost. The defects of the patent are as follows: the pre-reduction temperature is up to 1250 ℃, so that at the high temperature, the direct reduction process of directly participating in carbon is carried out in the pre-reduction stage, a large amount of heat needs to be absorbed, the temperature of the coal gas is reduced, the supply amount of the coal gas needs to be increased, the energy consumption is increased, and in addition, at the high temperature, the carbon in the pellets participates in the direct reduction reaction, so that the pellets are easy to be bonded, the furnace burden is not smooth to operate, and the reflow accident is caused.

The invention aims to provide a coal oxygen smelting reduction iron-making methodand a device thereof, which have low energy consumption, high production efficiency and low investment.

Aiming at the purposes, the coal oxygen smelting reduction iron-making method takes iron-containing materials as raw materials, takes coal as energy and reducing agent, adopts a two-step method of pre-reduction and final reduction to carry out smelting reduction, the pre-reduction is carried out in a pre-reduction shaft furnace, the final reduction is carried out in a final reduction iron bath furnace, in the final reduction process, coal dust and oxygen are injected into the final reduction iron bath furnace,

the pre-reduction adopts a medium pre-reduction degree, namely the metallization rate of the pre-reduced ore is 50-80%. The ratio of the metallization rates of indirect reduction and direct reduction is close to the theoretical optimal value of 7: 3 in the whole reduction process.

The temperature of the pre-reduction reaction is 750-:

the gas required for pre-reduction is provided by gas generated by oxy-combustion of coal, reduction of oxides, decomposition of coal, etc. in the final reduced iron bath. The coal gas generated by the final reduction iron bath furnace enters the pre-reduction shaft furnace through the coal gas conveying pipeline and the dust remover to carry out pre-reduction reaction.

The temperature of the pre-reduction ore when the pre-reduction shaft furnace discharges materials to thefinal reduction iron bath furnace is 800-,

the final reduction is carried out in a final reduction iron bath furnace, the upper part of the furnace is pre-reduced solid materials, the lower part of the furnace is a solid-liquid mixture, the indirect reduction reaction is continuously carried out on the pre-reduced ore which is still pre-reduced at the upper part of the final reduction iron bath furnace, the direct reduction reaction is carried out at the lower part of the furnace, and the reaction formula is as follows:

the reducing agent and heat required in the final reduction melting process are mainly supplied by coal powder sprayed into the final reduction iron bath furnace except carbon in the pellets. And simultaneously, oxygen is sprayed into the final reduction furnace, secondary combustion is generated due to the input of the oxygen, and the heat of the secondary combustion is transferred into the molten pool.

The final reduction adopts a lower secondary combustion rate,

CO+H₂/CO+H₂+CO₂+H₂O≥85％；

the final reduction temperature is controlled within the range of 1100 ℃ and 1600 ℃.

The pre-reduced raw materials of the invention comprise cold-bonded carbon-containing pellets, iron lump ores, common sinter ores and pellets.

The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a system diagram of a coal-oxygen smelting reduction ironmaking apparatus according to the present invention.

As shown in attached figure 1, the coal oxygen smelting reduction iron-making device comprises a raw material bin 1,

feeding systems

2 and 3, a pre-reduction shaft furnace 4, a final reduction iron bath furnace 5, a blanking pipe 6, an air locking valve 7, a gas pipeline 8,

cyclone dust collectors

9 and 14, an iron outlet 10, a slag outlet 11, a coal oxygen spray gun 12, compressors 23 and 24, a nitrogen conveying pipeline 17, a final reduction gas detection and temperature regulation device 13, a coal gas washing tower 15, a pressure regulating valve 20 and screw feeders 21 and 22. The pre-reduction shaft furnace 4 is connected with a final reduction iron bath furnace 5 through a feeding pipe 6 and an air locking valve 7; the coal-oxygen spray gun 12 is assembled on the lower furnace wall of the final reduction iron bath furnace 5, and the

cyclone dust collectors

9 and 14, the coal gas washing tower 15, the pressure regulating valve 20 and the final reduction coal gas detecting and temperature regulating device 13 are all arranged on a coal gas conveying pipeline; the screw feeder 22 is provided at the bottom of the pre-reduction shaft furnace 4, the screw feeder 21 is connected to the final reduced iron bath furnace 5, and the nitrogen gas feed pipe 17 is provided at the bottom of the final reduced iron bath furnace 5.

The whole coal oxygen melting reduction iron-making system comprising the pre-reduction shaft furnace 4, the final reduction iron bath furnace 5, the

feeding systems

2 and 3, the slag discharging system, the iron tapping system and the coal gas operation system is in a closed state.

An air locking valve 7 arranged in the blanking pipe 6 ensures that the pre-reduction shaft furnace 4 is in sealed connection with the final reduction iron bath furnace 5.

The working process of the coal oxygen smelting reduction iron making method comprises the following steps:

when the raw material uses carbon-containing pellets, the carbon-containing pellets preheated to 250-300 ℃ are uniformly added into the furnace through a distributing machine at the top of the shaft furnace through the

feeding systems

2 and 3 to the high-position storage bin 26 for pre-reduction. The pre-reduction temperature is 750-900 ℃, the metallization rate reaches 50-80 percent and the residual carbon content is 5-7 percent after 4-6 hours of reduction, the mixture is settled to the bottom of the pre-reduction furnace and is continuously discharged into a final reduction iron bath furnace through a water-cooling screw feeder 22, and the discharge temperature is 750-850 ℃. The pre-reduced carbon-containing pellets entering the final reduction iron bath furnace, the lump coal and the slagging auxiliary materials which are added in proportion are rapidly heated to about 1100 ℃ by the ascending furnace gas, and the pellets begin to generate self-reduction reaction. Because carbon directly reduces FeO and absorbs a large amount of heat, the temperature of the pellets is basically kept unchanged, and the metallization rate is rapidly increased to 85-90% within 20-25 min. Meanwhile, the added coal blocks are heated and vaporized to form broken coke. On the surface of the liquid slag-coke fluidized layer, the fully reduced carbon-containing pellets are rapidly melted and flow into the slag-coke layer to be finally reduced into molten iron under the stirring of high-temperature slag (about 1400 ℃).

At the lower part of the final reduction, the coal powder and the oxygen are continuously sprayed into the furnace through a water-cooling coal-oxygen spray gun 12, and the temperature of a reaction zone reaches 1550-. The furnace gas rising from the lower part of the hearth enters a solid packed bed to perform countercurrent heat exchange with the descending solid charging material after the temperature is reduced to about 1500 ℃ through the heat exchange between gas, solid and liquid, so as to maintain the self-reduction reaction of the carbon-containing pellets and gradually reduce the temperature to 1000 ℃ and 1100 ℃ to escape from the material layer. Further exchanging heat with the continuously added furnace burden, cooling to 950 ℃ and 1000 ℃ and discharging the furnace. After dust removal and temperature regulation, the temperature of the coal gas is controlled to be 900 ℃ and 950 ℃, and the coal gas is injected into the shaft furnace for prereduction. Through pre-reduction, the temperature of furnace gas is reduced to 350-40 DEGCO + H in furnace gas at 0 DEG C₂The concentration of (A) is 45-50% of the discharge. Discharging coalAfter the gas is dedusted and washed, the dust content is less than or equal to 30mg/Nm³When the temperature is reduced to room temperature, the gas is sent into a furnace gas storage tank, and the gas consumption per ton of iron is about 1100-³。

In the final-reduction iron bath furnace 5, the molten iron finally reduced is separated from the stationary iron slag layer of the slag at the bottom of the furnace, and is discharged through a tap hole 10 and a tap hole 11.

Compared with the prior art, the invention has the following advantages:

(1) and the energy consumption of the iron per ton is reduced by adopting a reasonable direct reduction-indirect reduction ratio.

(2) The solid filling layer of the short bed layer is adopted at the upper part of the final reduction iron bath furnace, so that the physical heat of coal gas can be fully utilized, the pre-reduction degree of the ore is improved, and the energy is saved. The oxidizability of the slag is also reduced.

(3) The characteristic of rapid self-reduction of the carbon-containing pellets at high temperature is utilized, the physical heat of furnace gas can be fully utilized, and the metallization rate of the pre-reduced pellets is improved.

(4) The lower shaft furnace pre-reduction degree (compared with COREX) is adopted, the production efficiency of the upper shaft furnace is improved, and the output gas output is reduced.

(5) The method adopts a rapid self-reduction process of the carbon-containing pellets at high temperature and fully stirred liquid slag-coke fluidized bed to carry out the final reduction reaction, thereby improving the melting rate of the pellets and the production rate of the final reduction iron bath furnace. Compared with the DIOS process, the production efficiency of final reduction can be improved by 1 time.

(6) The coal and oxygen injection process is adopted to carry out submerged combustion gas making in the liquid slag-coke fluidized bed, thereby reducing the dust content of the gas and ensuring the quality of the gas. It is suitable for different coal types, especially for high volatile coal gas making.

Examples

Three times of small-sized smelting reduction ironmaking thermal simulation tests are carried out by adopting the coal oxygen smelting reduction ironmaking device and the method thereof. The final reduction furnace used in the test had an internal diameter of 1.6m and a height of 4.5m, and the preliminary reduction furnace had an internal diameter of 1.5m and a height of 5.5 m. The iron yield per hour is designed to be 2T.The raw materials used in the test were carbon-containing cold-bonded pellets, and the chemical components of the iron ore concentrate powder used for the pellets are shown in table 1. The carbon distribution of the pellet is 8%. The reducing agent used is pulverized coal, and the chemical composition of the pulverized coal is shown in table 2. The carbon-containing pellets enter a pre-reduction furnace after being preheated, and the carbon-containing pellets after being pre-reduced for a certain time enter a final reduction furnace for final reduction. The pre-heating temperature, pre-reduction temperature and final reduction temperature of the carbonaceous pellets are shown in table 3. The energy consumption and corresponding indexes of the test are shown in table 4. Table 5 lists the chemical compositions of the molten irons obtained in the final reduction.

TABLE 1 examples chemical composition (wt%) of iron ore concentrate powder containing carbon pellets

TABLE 2 composition of raw coal used in examples (wt%)

Table 3 examples pre-reduction and final reduction process parameters

TABLE 4 energy consumption and corresponding index for the examples

Note: for comparison, the corresponding specifications for the CDERX process are also set forth in Table 4.

TABLE 5 examples chemical composition of final molten iron (wt%)

Claims

1. A coal-oxygen melting reduction ironmaking method, using iron-containing materials as raw materials, coal as energy and reducing agent, adopts the two-step method of pre-reduction and final reduction to carry out smelting reduction, and the pre-reduction is carried out in a pre-reduction shaft furnace. The final reduction is carried out in the final reduction iron bath furnace. During the final reduction process, pulverized coal is injected into the final reduction iron bath furnace, which is characterized in that:

(1) Pre-reduction adopts medium pre-reduction degree, that is, the metallization rate of pre-reduction ore is 50-80%;

(2) The temperature of the pre-reduction reaction is 750-900°C, and only the indirect reduction reaction between gas and iron-containing materials occurs in the pre-reduction.

(3) The temperature of the pre-reduction ore when the pre-reduction shaft furnace is discharged to the final reduction iron bath furnace is 800-850 ° C,

(4) The upper part of the final reduction iron bath furnace is the pre-reduced solid material, and the lower part is the solid-liquid mixture. The upper part of the final reduction iron bath furnace is still the pre-reduction ore to continue the indirect reduction reaction, and the lower part is the direct reduction reaction.

(5) The final reduction adopts a lower secondary combustion rate,

CO+H ₂ /CO+H ₂ +CO ₂ +H ₂ O≥85%;

(6) The final reduction temperature is controlled in the range of 1100-1600°C.

2. A coal-oxygen fusion reduction ironmaking device, comprising a pre-reduction shaft furnace (4), a final reduction iron bath furnace (5), a raw material warehouse (1), a feeding system (2, 3), a gas dust collector (9 , 14), feeding pipe (6) and gas delivery pipeline (8), it is characterized in that:

[1], including the pre-reduction shaft furnace (4), the final reduction iron bath furnace (5), the feeding system (2, 3), the tapping system, the slag tapping system and the gas operation system, including the entire coal-oxygen melting The reduction ironmaking system is in a closed state;

[2], a gas lock valve (7) is set in the feed pipe (6) for conveying materials from the pre-reduction shaft furnace (4) to the final reduction iron bath furnace (5), that is, the pre-reduction shaft furnace (4) is connected to the final reduction shaft furnace (4) The reduced iron bath furnace adopts sealed connection;

[3], more than 2 water-cooled coal-oxygen spray guns are installed on the lower furnace wall of the final reduction iron bath furnace (5);

[4] A gas scrubber (15) and a pressure regulating valve (20) are provided on the operating pipeline of the furnace top gas of the pre-reduction shaft furnace (4).