KR20030013057A - Ironmaking process for using sludge drying by off gas of fluidized bed for iron reduction - Google Patents

Abstract

PURPOSE: An ironmaking process to recycle waste sludge in smelting reduction process is provided, which is characterized in that waste sludge is dried by off gas from fluidized bed reduction furnaces, thus reduce manufacture cost. CONSTITUTION: In an ironmaking facility comprising one or more fluidized bed reduction furnaces(2,3,4) for reducing iron ore fines charged as forming a fluidized bed, a melter-gasifier(1) for manufacturing hot metal by melting and reducing the reduced iron fines after receiving reduced iron fines from a final reduction furnace(2) in the fluidized bed reduction furnaces(2,3,4), and a cyclone(9) for circulating particulate ore in the flue gas by collecting off gas of the melter-gasifier(1) and supplying the particulate ore removed flue gas into reduction gas of the fluidized bed reduction furnaces(2,3,4) through a reduction gas pipe(5), wherein the final reduction furnace(2) is connected to the melter-gasifier(1) through an iron charging pipe(7), the cyclone(9) is connected to a powder injection unit(15) for injecting molten and agglomerated particulate ore into the melter-gasifier(1), and the powder injection unit(15) is connected to a powder storage tank(12), the ironmaking method for recycling sludge by using off gas of the fluidized bed reduction furnaces comprises the steps of storing the dried sludge into a sludge storage bin(205) after first drying sludge; injecting flue gas of the fluidized bed reduction furnaces(2,3,4) to a pneumatic conveying pipe(206) one end of which is connected to the one side of the powder storage tank(12), and the other end of which is connected to the sludge storage bin(205); and pneumatic conveying the sludge into the powder injection unit(15) as finally drying the first dried sludge using flue gas after supplying the first dried sludge into the pneumatic conveying pipe(206).

Description

Ironmaking process for using sludge drying by off gas of fluidized bed for iron reduction}

The present invention relates to a method for manufacturing molten iron for recycling sludge in a molten reduction process, and more particularly, to manufacture molten iron for recycling sludge in a molten gas furnace by drying the sludge with the use of exhaust gas from a fluidized-bed reduction furnace as a transport gas. It is about a method.

The Finex process (FINEX process), which is one of the melt reduction processes currently successfully developed in Pohang Steel, is composed of three stage fluidized bed furnaces (2, 3, 4) as shown in FIG. The gas used for the flow of the iron ore in the fluidized bed furnace (2. 3, 4) is supplied from the molten gasifier (1). The temperature of the flue-gas discharged through the three stage reactor is approximately 680 ° C and the pressure is 1.7 bar.

At present, a large amount of sludge is generated in various processes, including about 150 tons of sludge generated in the Korex process, a kind of melt reduction process. As a result of building a clean production system around the world, minimizing industrial wastes and recycling in factories, Pohang Steel is also recycling 94% of all by-products. However, in terms of actual contents, 45% of the sludge is buried in the dumping site.

Therefore, a method of injecting the generated sludge into the Korex melt gasifier 1 is being examined, and as shown in FIG. 1, the dried sludge is charged into the powder storage tank 12 in a separate drying process through the powder injecting device 15. A method for recycling in the melt gasifier 1 has been studied. In particular, as shown in Table 1, the sludge generated in the melt reduction process has a high iron content (36.7%), which can be said to be of great value for recycling.

Chemical composition (% by weight) Water content T.Fe SiO ₂ Al ₂ O ₃ CaO MgO Zn Mn P S C Etc 38-42% 36.70 6.96 2.69 5.75 1.60 0.065 0.090 0.139 0.950 26.58 Remainder

The sludge in Table 1 has a high moisture content of 40%, so a drying process is required to recycle it. Therefore, after drying in an independently installed rotary kiln dryer, it is transported, and then supplied to the powder storage tank 12 for recycling. However, in order to dry the sludge in the rotary kiln to the required level in the melt gasifier, a considerable process load is generated and the cost thereof is also a obstacle to the use of the sludge.

An object of the present invention is to provide a method for manufacturing molten iron while reducing the cost required for sludge drying by drying the sludge with its depletion while utilizing the exhaust gas of the fluidized bed reduction furnace as the feed gas of the sludge.

1 is a schematic diagram of a melt reduction process for recycling sludge

Figure 2 is a schematic diagram of a molten iron manufacturing method for drying and recycling the sludge using the exhaust gas in accordance with the present invention

* Explanation of symbols for the main parts of the drawings *

1 ..... Melt Gasification Furnace 2 ..... Final Reduction Furnace

3, 4 ...... Reserve Reactor 5 ..... Reducing gas pipe

6 ..... flue gas conduit 7 ..... iron ore flow chart

8 ..... HBI Manufacturing Equipment 9 ..... Cyclone

10, 11 ..... storage tank 12 ..... powder storage tank

13 ..... Balancing tank for powder blowing 14 ..... Powder weighing extraction device

15 ..... Extraction device

201 ..... Sludge Storage Tank 202 ..... Dryer (Rotary Kiln)

203 ..... sludge sorter 204 ..... crusher

205 ..... Sludge Reservoir 206 ..... Pneumatic Tube

The molten iron manufacturing method of the present invention for achieving the above object, at least one fluidized bed reduction reactor (2, 3, 4), configured to reduce the charged iron ore while forming a fluidized bed,

A molten gasifier (1) configured to receive molten reduced iron from the final reduction furnace (2) in the fluidized-bed reduction furnace to produce molten iron by melting reduction;

The exhaust gas of the melt gasifier 1 is collected, and the fine ore in the exhaust gas is circulated to the melt gasifier 1, and the exhaust gas from which the fine ore is removed is reduced through the reducing gas pipe 5. Including a cyclone (9) for supplying a reducing gas of

In the fluidized bed final reduction reactor (2), the final reduced direct reduced iron (DRI-Direct Reduced Iron) is transferred to a hot briquetted iron (HBI) manufacturing facility (8) through an ore flow conduit (7), where the HBI is manufactured and melted. Charged into the gasifier (1), the cyclone (9) is connected in a dust communication relationship with the dust blowing device (13) for collecting the fine ore in the molten gasifier (1) and re-injected into the molten gasifier (1) In the molten iron manufacturing method using the molten iron manufacturing equipment is configured to be connected to the powder storage tank 12 in a powder blowing relationship,

First drying the sludge and storing the sludge in a sludge storage bin,

Injecting the exhaust gas of the fluidized-bed reduction paths (2, 3, 4) into a pneumatic pipe having one end connected to one side of the powder storage tank 12 and the other end connected to the sludge storage bin,

And supplying the primary dried sludge to the pneumatic tube and conveying it to the powder blowing device 15 while finally drying the exhaust gas.

Hereinafter, the present invention will be described in detail with reference to FIG. 2 as an example.

In the present invention, while using the exhaust gas exhausted by using the reduced gas of the iron ore in the fluidized-bed reduction reactor (2, 3, 4) as the pneumatic conveying gas of the primary dried sludge, the first dried sludge as its dedication. Finally dry. Of course, if the initial water content of the sludge is low, it is also possible to transfer the drying to the exhaust gas directly without the first drying process.

The sludge recycled in the present invention can be any sludge which has high iron content and a certain amount of moisture and needs drying, and a representative example is Corex sludge. As seen in Table 1, Corex sludge has a T.Fe of 30% or more and a water content of 38-42%.

In FIG. 2, the most preferred method of utilizing the exhaust gas is to supply some of the exhaust gas to the primary dryer to use the dry gas as well as to utilize the rest of the exhaust gas as the pneumatic gas.

In order to dry while utilizing the exhaust gas as the sludge pneumatic gas, it is preferable to connect one end of the pneumatic pipe to one side of the powder storage tank 12 and the other end to the sludge storage bin 205. Therefore, if an independent dryer such as rotary kiln is connected to the molten process equipment and installed, the primary drying sludge can be used immediately without transport.

According to the present invention, a method of blowing sludge into a molten gasifier while drying the sludge will be described. First, the sludge of the sludge storage tank 201 is dried in a drier. Dryers typically use rotary kilns. At this time, by using a part of the exhaust gas in the dryer for heat supply to reduce the cost of the rotary kiln process. Supply of flue gas is good to supply 30-60% of flue gas. If the amount of exhaust gas is less than 30%, if the cost savings in the rotary kiln are not significant, more than 60% limits the amount of gas to be used in the pneumatic gas.

The first drying of the sludge should be within 5 ~ 10% of moisture. The reason for this is that if the water content is less than 5%, the process load is increased in the rotary kiln, and if it is more than 10%, the load in the conduit is too heavy.

As described above, the fine particles of the first dried sludge are discharged to the sludge storage bin 205, and the granulated particles are crushed and discharged to the sludge storage bin 205. Sludge screening is preferably based on 1 mm.

The primary dried sludge of the sludge storage bin is supplied to the pneumatic pipe 206 in which the exhaust gas is blown into the pneumatic gas. At this time, the sludge conveyed to the sludge storage bin 205 is adjusted to be injected is supplied to the pneumatic tube 206. The first dried sludge in the pneumatic tube is finally dried. In this invention, it is preferable to maintain the flow velocity of the gas blown into a pneumatic pipe at 5-15 m / s. The reason is that when the gas flow rate is less than 5 m / s, the fraction of particles in the air pipe increases significantly, which makes the operation and operation of the air pipe difficult, and conversely, when the gas flow rate is greater than 15 m / s, It is not preferable because the pressure applied to the pressure increases, and the wear on the particles and the pneumatic tube is severe. This gas flow rate is set to allow operation in the dilute phase. In order to transport the sludge in the conduit, it is easy to operate and operate in a dilute phase in which the volume ratio of the total solid particles is at most 5%.

The sludge conveyed during final drying according to the present invention may be considered to be directly blown into the powder burner 15 of the molten gasifier 1, but is preferably supplied to the powder storage tank 12.

According to the present invention, the sludge throughput is 100-200 ton / day when the sludge is blown into the melt gasifier using the flue-gas of the fluidized-bed reduction reactor.

The present invention will be described in more detail with reference to the following examples.

EXAMPLE

Correx sludge of Table 1 above was dried in the rotary kiln of FIG. At this time, 45% of the exhaust gas from the preheating furnace 4, which is one of the fluidized-bed reduction reactors, was supplied as a dry gas of the rotary kiln furnace. Table 2 shows the characteristics of the exhaust gas of the preheating furnace 4.

Flue gas composition CO: 20%, H ₂ : 21%, CO ₂ : 20%, N ₂ : 39% Temperature and pressure in flue gas 680 ° C, 1.7kgf / ㎠ Flow rate of exhaust gas discharged 8000 ~ 9000Nm ³ / hr

The primary dried sludge was sorted on the basis of 1 mm, crushed at least 1 mm, discharged to the sludge storage bin 205 and then supplied to the transport pipe 206. Table 3 shows the size, flow velocity and pressure drop in the tube.

Pneumatic Tube Size Inner diameter: 0.10m, height: 20.0m Gas Velocity in Pneumatic Tube 5 ~ 15m / sec Pressure drop in the air line 0.06 ~ 0.10kgf / ㎠

In the treatment process as described above, the moisture change of the initial sludge was measured and the results are shown in Table 4.

Sludge throughput 100 ~ 200ton / day Moisture Content of Initial Sludge 38-42 wt% Moisture content after drying in rotary kiln 5 ~ 10wt% Moisture Content after Drying in Pneumatic Tube Less than 3wt%

As can be seen from Table 4, it can be seen that while drying the sludge by using the flue gas of the fluidized-bed reduction furnace can be dried at the same time, the cost can be reduced by about 30% compared to the conventional drying method.

As described above, according to the present invention, by minimizing waste generated by recycling the exhaust gas of the fluidized-bed reduction furnace to the drying and conveying gas of the sludge, there is a useful effect that can greatly reduce the drying cost of the sludge.

Claims (4)

One or more fluidized-bed reduction reactors (2, 3, 4) configured to reduce charged iron ore while forming a fluidized bed, A molten gasifier (1) configured to receive molten reduced iron from the final reduction furnace (2) in the fluidized-bed reduction furnace to produce molten iron by melting reduction; The exhaust gas of the melt gasifier 1 is collected, and the fine ore in the exhaust gas is circulated to the melt gasifier 1, and the exhaust gas from which the fine ore is removed is reduced through the reducing gas pipe 5. Including a cyclone (9) for supplying a reducing gas of The fluidized bed final reduction path (2) is connected to the molten gasifier (1) in the ore communication relationship through the ore charge pipe (7), the cyclone (9) is dissolved and agglomerated particulate ore in the molten gasifier (1) In the method of manufacturing molten iron using the molten iron manufacturing equipment which is connected to the dust blowing device 15 to be blown in a dust communication relationship, the powder blowing device 15 is connected to the powder storage tank 12 in a powder blowing relationship, Primary drying the sludge and storing the sludge in the sludge storage bin 205, Blowing the exhaust gas of the fluidized-bed reduction paths (2, 3, 4) into a pneumatic pipe (206) having one end connected to one side of the powder storage tank (12) and the other end connected to the sludge storage bin (205), Sludge using the flue gas of the fluidized-bed reduction reactor, characterized in that it comprises the step of supplying the primary dried sludge to the pneumatic pipe 206 and the final drying in the flue gas to the powder blowing device 15 Recycling iron manufacturing method. The method of claim 1, wherein the primary drying of the sludge, Drying the water content of the sludge in the range of 5-10%, Selecting the dried sludge, the fine particles are discharged to the sludge storage bin 205, granulated particles are crushed into fine particles and discharged to the sludge storage bin 205, 30 ~ of the exhaust gas of the fluidized bed reduction reactor A method of manufacturing molten iron for recycling sludge using exhaust gas of a fluidized-bed reduction furnace, comprising 60% of the first drying step as a dry gas. The molten iron manufacturing method of claim 1, wherein the sludge is Corex sludge having a T.Fe of 30% or more and a water content of 38 to 42%. 4. The molten iron manufacturing method according to any one of claims 1 to 3, wherein the air conduit 206 transports the sludge at a gas flow rate of 5-15 m / s. Way.