KR20200000656A - Method for recycling industrial byproduct - Google Patents

Abstract

According to the present invention, an industrial byproduct discharged from a Fe-Si process is mixed with metal oxides and used as a reducing agent and a basicity control agent in a carbothermal reduction process. By using the industrial byproduct as a subsidiary material for recovering the metal oxides, a resource recycling utilization process is established, and operation cost reduction and energy saving effects can be provided.

Description

Recycling method of industrial by-products {METHOD FOR RECYCLING INDUSTRIAL BYPRODUCT}

The present invention relates to a method for thermal reduction of pellets, briquettes and bricks by utilizing C, SiC, Si and SiO ₂ contained in industrial by-products as reducing agents and basicity controlling agents.

Currently, a process of reducing metal with carbon as a reducing agent is most commonly known as a rotary kiln and RHF (ROTARY HEARTH FURNACE). Among them, a process of reducing metal by a typical carbon heat reduction method in a rotary kiln is a Waelz process, which recovers Zn from steel by-products. To reduce ZnO in oxide form to Zn, carbon-containing coal, pulverized coal and coke are used as reducing agents. It also uses CaO and SiO ₂ -containing ores for refractory protection of rotary kilns.

RHF processes also include FASTMET and FASTEMELT. This is a process for recovering Fe and valuable metals from steel by-products. In this process, carbon-containing coal, pulverized coal, and coke are used to reduce metals in the form of oxides, and basicity is managed by using CaO and SiO ₂ -containing ores to protect RHF refractory and increase reduction efficiency.

The present invention provides a method for recycling industrial by-products by securing C, SiC, and Si, which serve as reducing agents in the carbon heat reduction process, and SiO ₂ added for basicity control, from industrial by-products.

According to an embodiment of the present invention, preparing the by-products for reducing and basicity of the industrial by-products containing C, SiC, Si and SiO ₂ discharged from the Fe-Si manufacturing process; Preparing a mixture by mixing the subsidiary materials with a metal oxide-containing raw material, wherein the subsidiary materials in the mixture are mixed so as to have a content of 1 to 20 wt%; A pellet manufacturing step of adding a binder to the mixture and forming a pellet by pressure molding; And it provides a method for recycling industrial by-products comprising the carbon thermal reduction of the pellets.

The secondary material may be slag, dust or sludge.

The _secondary raw material may include C 10 to 30% by weight, SiC 20 to 40% by weight, SiO ₂ 20 to 60% by weight, Si 10 to 30% by weight.

The secondary raw material may have a water content of 1 to 10% by weight.

The secondary raw material may have an average particle size of 30 to 150㎛.

The mixture may have a basicity in the range of 1.0 to 2.0.

The binder may be at least one selected from water glass, rosin powder, and bentonite.

The metal oxide may be an oxide of at least one metal selected from Mn, Cr, Fe, Zn, Ni, and Cu.

According to the present invention, by replacing the raw material used as a reducing agent and basicity control agent in the carbon heat reduction process with industrial by-products, it establishes a resource circulation utilization process, and provides an operation cost savings and energy savings.

1 is a graph showing the reduction rate of Fe oxide according to basicity.
2 is a ternary state diagram showing a change in melting point according to the basicity of FeO.
3 is a schematic diagram of pellets and RHF internal refractory erosion according to basicity.
Figure 4 is a graph showing the CO and CO ₂ reduction temperature by the Ellinggam diagram.
Figure 5 shows the reduced carbon steel dust using industrial by-products discharged from the Fe-Si manufacturing process.
Figure 6 is a graph analyzing the particle size of the industrial by-products discharged from the Fe-Si manufacturing process.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a method for recycling industrial by-products utilizing the industrial by-products discharged from the Fe-Si manufacturing process as a side material of the carbon heat reduction process. By-products generated in the Fe-Si process are used to replace the reducing agents used in the existing RHF process, and the by-products also serve as basicity control agents. If the basicity is used as a control agent can be used to replace the existing silica sand or silica 100%.

According to an aspect of the present invention, the method comprising the steps of preparing the industrial by-products containing C, SiC, Si and SiO ₂ discharged from the Fe-Si manufacturing process as a feedstock for reducing and basicity control; Preparing a mixture by mixing the sub-raw materials with a metal oxide-containing raw material, wherein the content of the reducing agent and the basicity controlling agent in the mixture is 1 to 20% by weight; A pellet or briquette manufacturing step of preparing a pellet or briquette by adding a binder to the mixture and pressing-molding the binder; And carbon heat reducing the pellets or briquettes.

A representative process of the carbon heat reduction process is FASTMET, which reduces metal oxides in dust form based on RHF. The metal oxides may be steel by-products, automobile by-products, other ferroalloy by-products, or metal-containing ores, and may be, for example, one or more selected from scales, sludges, and dusts. In addition, as a secondary raw material of the carbon heat reduction process, a reducing agent, a basicity controlling agent and the like.

Industrial by-products that can be used as a feedstock of the carbon heat reduction process in the present invention may be dust discharged from the Fe-Si manufacturing process. Fe-Si is used in steel processing, and C (Carbon) is used as a reducing agent to produce Fe-Si. Dust generated at this time depends on the location of dust collection, but contains a large amount of C, SiC, Si, SiO ₂ and the like.

The subsidiary material is included in an amount of 1 to 20% by weight based on the mixture of the metal oxide and the subsidiary material. When the content of the secondary raw material is less than 1% by weight, the amount of C to reduce the metal oxide is insufficient to reduce the metal oxide or the high base may cause the melting point of the metal oxide to increase due to the operation, and 20 wt% If it exceeds, residual C which is not used for reduction may reduce the strength of the pellets after reduction, or may erode the RHF internal refractory material by a low base group, that is, an acidic atmosphere.

In addition, the sub-material includes C 10 to 30% by weight, SiC 20 to 40% by weight, SiO ₂ 20 to 60% by weight, Si 10 to 30% by weight. When the content of each component is out of the above range, especially when the C and Si content is less than 10% can not act as a reducing agent, when the composition of SiO ₂ is less than 20% basicity can not act as a control agent, carbon heat reduction It is not preferred as an auxiliary material of the process.

The water content of the secondary raw material is preferably 1 to 10% by weight. If the moisture content of the subsidiary material is less than 1% by weight, secondary dust may occur during the by-product transport and management process, and if it exceeds 10% by weight, it may be difficult to use as an operation raw material.

In addition, in order to mix the subsidiary materials with the metal oxide in the carbon heat reduction process and to assemble in pellet or briquette form, the average particle size of the sub raw material should be kept smaller than the metal oxide, and the average particle size of the sub raw material is preferably 30 to 150 μm. . As shown in FIG. 6, the average particle size of the by-products discharged from the Fe-Si process is in the above range, and due to these characteristics, the carbon nano-reduction process, particularly the RHF process, can be optimally utilized, and the metal reduction rate and the strength of briquettes are excellent. Do.

Dust generated in converters and electric furnaces includes Fe or other metals in the form of oxides. The metal oxide is reduced by the carbon heat reduction process when a mixture of the additives including the reducing agent and the basicity controlling agent in the metal oxide is added to the RHF process. Figure 1 shows the experimental results of measuring the reduction rate according to the basicity of the two by-products of the dust (including sludge) containing a metal oxide. In the case of Fe oxide as shown in Figure 1, since the basicity shows the maximum reduction rate in the range of 1.0 to 2,0, the basicity of the mixture should be adjusted to the range of 1.0 to 2.0.

2 is a ternary state diagram (FeO—SiO 2 —CaO) showing a melting point change according to the basicity of Fe oxide. The lower the melting point is, the higher the reduction efficiency of the Fe oxide is. In the case where the metal oxide is a dust containing a metal oxide generated in the steel process, a large amount of CaO is contained. As such, since the melting point of the metal oxide such as Fe oxide is changed depending on the basicity, an optimum reduction effect can be obtained by controlling the basicity to 1.0 to 2.0 by using a by-product generated in the Fe-Si process for the high base metal oxide.

Figure 3 is a schematic diagram showing the state of the pellet and the RHF internal refractory according to the basicity of the mixture. If the basicity of the mixture is less than 1.0, since the acidic components are relatively high, the internal refractories of RHF may be eroded. If the basicity exceeds 2.0, briquettes may react with basic refractory (CaO refractories) at the bottom of the RHF to cause fusion. Due to fusion, the refractory thickness increases during self-lining and increases the load on the equipment, so there is a problem in that defects or DRI product ejection do not occur.

Meanwhile, the reducing agent in the present invention may be one or more selected from a carbon-based reducing agent, a silicon-based reducing agent and an aluminum-based reducing agent, but is not limited thereto. As the carbon-based reducing agent, for example, one or more selected from coke, coal, and graphite may be used, and the silicon-based reducing agent may use one or more selected from Ferro-Si powder and Si powder, and the aluminum-based reduction Zero can use at least 1 type selected from Al-Si alloy powder and Al powder.

In particular, in the present invention, industrial by-products C, SiC, Si, and SiO _{2 which} are discharged from the Fe-Si manufacturing process are used as reducing agents, and the SiC is dissociated into Si and C to primarily reduce metal oxides to reduce SiO ₂ and Generates CO. Since SiO ₂ generated at this time plays a role of the basicity controlling agent, SiC may simultaneously play the role of a reducing agent and a basicity controlling agent. When the SiC is used, the cost is lower than that of other conventional reducing agents, and the amount of use thereof is small, thus reducing manufacturing costs.

The amount (mol) of the reducing agent blended in the present invention may be 0.5 Х [O] or more and 1.5 Х [O] or less. If the amount of the reducing agent is less than 0.5Х [O], the oxygen reduction rate is low, there is a risk that a good valuable metal can not be obtained, whereas, if the amount of reducing agent exceeds 1.5 Х [O], a large amount of energy is required when reducing the solid phase due to excessive reducing agent In addition, the remaining reducing agents that do not participate in the reaction may react with each other to interfere with the reduction of the metal oxide. Here, [O] means the amount of oxygen (mol) contained in the valuable metal-containing metal oxide mixed with subsidiary materials.

On the other hand, the binder may be used one or more selected from water glass, rosin powder and bentonite. When using the binder as described above, there is an additional advantage that can be reused as slag flux when secondary by-products are generated in the carbon heat reduction process.

The content of the binder in the mixture is preferably 0.5 to 3% by weight based on the content of the valuable metal-containing metal oxide mixed with the crude agent. When the content of the binder is less than 0.5% by weight, the mixture containing sludge, dust, and the like having a small particle size may not be formed in briquettes or may be crushed due to its weak strength during operation. Since a very dense structure is formed during reduction, the oxygen-based gas generated by the reduction may not be released to the outside, and the oxygen-based gas may remain inside the briquettes.

Thus, the average circular equivalent diameter of the briquettes produced is preferably 0.5 to 3 cm. If the average circular equivalent diameter of the briquettes is less than 0.5 cm, there is a risk of briquetting and brittleness during operation. On the other hand, if the average diameter of the briquettes exceeds 3 cm, energy transmission for reduction to the inside of the briquettes is not performed when the solid phase is reduced, that is, Since briquette internal temperature is low, there exists a possibility that reduction may not fully occur.

Next, the briquettes are reduced in solid phase. The solid phase reduction of the briquettes is preferably performed by using a Rotary Hearth Furnace (RHF).

The solid phase reduction step is performed to precipitate the valuable metal in the form of briquettes in the form of Fe-X (where X denotes the valuable metal). In this step, the setting of the reduction temperature is important, which is contained in the briquettes. The valuable oil may vary depending on the type of metal. When steelmaking by-products contain Fe and Ni, the steelmaking by-products contain Fe and Ni, and the steelmaking by-products contain Fe, Ni and Cr. Because.

4 is an elling feeling diagram for explaining the reduction temperature of the metal oxide. Referring to FIG. 4, in the case of Ni, the reduction temperature is 200 to 400 ° C., and in the case of Cr, the reduction temperature is 1,200 to 1,600 ° C. For Fe it is known to those skilled in the art that the reduction temperature is from 1,000 to 1,400 ° C. The difference in the reduction temperature as described above is because the oxidation degree of each element is different.

In the present invention, the step of reducing the briquettes in solid phase may be performed at 1,200 to 1,300 ° C. Typically, the RHF operating temperature is 1,200 to 1,300 ° C. Here, if there is a material that reduces at high temperatures such as Cr, the reduction efficiency is low. However, in the case of mixing the crude agent as described above, Cr can also be efficiently reduced at the above temperature, thereby reducing the reduction efficiency. In the present invention, the metal is reduced at a high temperature such as Cr to reduce the crude material at 1,200 to 1,270 ° C.

On the other hand, the solid phase reduction step may be performed for 15 to 30 minutes. If it is less than 15 minutes, the primary reduction occurs and the generated CO gas should be secondary reduced, but the reduction is not effective because the secondary reduction does not occur due to a short time. If it exceeds 30 minutes, the pellet or briquette will remain in RHF for a long time, and the intensity of pellet or briquette will fall.

Example

Hereinafter, an Example is given and this invention is demonstrated more concretely. The following examples are intended to illustrate the present invention in more detail, and the present invention is not limited thereto.

Example 1

A mixture having a basicity of 2.0 is prepared by mixing industrial by-products containing 24 wt% of C, 27 wt% of SiC, 28 wt% of Si, and 21 wt% of SiO ₂ with Fe oxide discharged from the steelmaking process. . The content of the industrial by-product relative to the mixture is 3% by weight, and 1% by weight of bentonite relative to Fe oxide is added to the mixture to form pellets by pressure molding. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

2. Example 2

A mixture having a basicity of 1.8 is prepared by mixing Fe oxide discharged from the steelmaking process with industrial by-products containing 24% by weight of C, 27% by weight of SiC, 28% by weight of Si and 21% by weight of SiO ₂ from the Fe-Si manufacturing process. . The content of industrial by-products is 5% by weight, and 1% by weight of bentonite is added to Fe in the mixture, followed by compression molding to prepare pellets. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

3. Example 3

A mixture having a basicity of 1.5 is prepared by mixing Fe by an industrial by-product containing 24% by weight of C, 27% by weight of SiC, 28% by weight of Si, and 21% by weight of SiO ₂ and Fe oxide from the steelmaking process. . The content of industrial by-products relative to the mixture is 8% by weight, and 1% by weight of bentonite relative to Fe oxide is added to the mixture to form pellets by pressure molding. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

4. Example 4

A mixture having a basicity of 1.0 is prepared by mixing the industrial by-products containing 24% by weight of C, 27% by weight of SiC, 28% by weight of Si and 21% by weight of SiO ₂ with Fe oxide discharged from the steelmaking process. . The content of the industrial by-products relative to the mixture is 10% by weight, and 1% by weight of bentonite relative to Fe oxide is added to the mixture to form pellets by pressure molding. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

5. Comparative Example 1

A mixture having a basicity of 1.5 is prepared by mixing the valuable metal-containing metal oxide discharged from the steelmaking process with silica and fine coal. The content of silica sand in the mixture is 2.5% by weight, the content of pulverized coal is 8% by weight, and 1% by weight of the binder is added to the mixture with respect to Fe oxide. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

6. Comparative Example 2

Pellets are prepared in the same manner as in Example 1, except that the basic acidity of the mixture is 0.5, including 22 wt% of the industrial by-product. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

7. Comparative Example 3

A pellet is prepared in the same manner as in Example 1 except that the basic acidity of the mixture is 2.3 by weight, including 0.5% by weight of industrial by-products. The prepared pellets are reduced in solid phase at 1,240 ° C. through RHF.

Experimental Example

The composition of the thermally reduced briquettes in the Examples and Comparative Examples is shown in Table 1 below.

Melting point Composition after reduction (wt%) When manufacturing 1ton of DRI
Subsidiary Cost
(Won / ton) T-Fe M-Fe Si Example 1 1,390 72 61 1.5 300 Example 2 1,370 74 63 3.0 500 Example 3 1,310 73 65 4.5 800 Example 4 1,270 71 61 6.0 1,000 Comparative Example 1 1,340 72 61 4.3 11,200 Comparative Example 2 1,250 67 55 7.2 2,000 Comparative Example 3 1,420 65 52 0.7 50

In Table 1, T-Fe means all the Fe composition in the metal Fe, Fe oxide and Fe compound, M-Fe means metal Fe, Si means Si composition of Si and Si compound.

As shown in Table 1, the lower the basicity in Examples 1 to 4 it can be seen that the lower the melting point of the Fe oxide.

The mixture of Comparative Example 1 has the same basicity as Example 3, but a large amount of secondary raw materials should be used compared to Example 2, and the composition after reduction, that is, T-Fe, M-Fe, and Si, From the inferiority, it can be seen that the reduction rate is lower than that in Example 3. On the other hand, compared with Example 4 using the same amount of sub-materials it can be seen that the cost reduction effect of the industrial by-products discharged from the Fe-Si manufacturing process of the present invention is large.

In addition, in Comparative Example 2, the pellet was manufactured using 22% by weight of industrial by-products, but in this case, the basicity of the mixture was too low, so that the refractories of RHF were eroded and the reduction rate of Fe oxide was reduced. In Comparative Example 3, 0.5 wt% of the industrial by-product can be inferred that the prepared pellet is fused by a reaction with a basic refractory (CaO refractory) at the bottom of the RHF to lower the reduction rate of the Fe oxide.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations can be made without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

Claims (9)

Preparing C, SiC, Si, and SiO ₂ containing industrial by-products discharged from the Fe-Si manufacturing process as sub-materials for reducing and basicity control;
Preparing a mixture by mixing the subsidiary materials with a metal oxide-containing raw material, wherein the subsidiary materials in the mixture are mixed so as to have a content of 1 to 20% by weight;
A briquette manufacturing step of inserting a binder into the mixture and pressing to form briquettes; And
Recycling the industrial by-products comprising the step of thermally reducing the briquettes. The method of claim 1, wherein the subsidiary material is slag, dust or sludge. The method of claim 1, wherein the _secondary material comprises 10 to 30% by weight of C, 20 to 40% by weight of SiC, 20 to 60% by weight of SiO ₂ , and 10 to 30% by weight of Si. The method of claim 1, wherein the secondary raw material has a water content of 1 to 10% by weight. The method of claim 1, wherein the secondary raw material has an average particle size of 30 to 150㎛. The method of claim 1, wherein the mixture has a basicity of 1.0 to 2.0. The method of claim 1, wherein the binder is at least one selected from water glass, rosin powder, and bentonite. The method of claim 1, wherein the binder content is 0.5 to 3% by weight relative to the metal oxide. The method of claim 1, wherein the metal oxide is an oxide of at least one metal selected from Cr, Ni, Zn, and Mn.

Images