Divided-flow treatment method for secondary sludge of converter in iron and steel enterprise

Abstract

The invention provides an iron and steel enterprise converter secondary sludge split-flow treatment method, and relates to the technical field of slag metallurgy, the method comprises the following steps: classifying waste steel used by an iron and steel enterprise converter according to the zinc content, and classifying and using the waste steel according to the characteristics of products produced in each converter workshop; the zinc element in the waste steel is subjected to split-flow treatment through the secondary sludge of the converter; the converter secondary sludge with lower zinc content is directly returned to be sintered for use, and the converter secondary sludge with higher zinc content is used for producing metallized pellets and recycling zinc oxide powder in a rotary hearth furnace. According to the method, the waste steel is classified by taking the zinc content as a classification index so as to obtain the converter secondary sludge with different zinc contents, the sludge is recycled in an enterprise through different purpose planning of the sludge with different zinc contents, and the technical effects of reducing the zinc load of a blast furnace, efficiently recycling the zinc element and improving the economic benefit of the converter secondary sludge are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of slag metallurgy, and in particular to a method for diverting and treating secondary sludge from a converter in a steel enterprise. Background Art

[0002] Converter secondary sludge is a byproduct of wet dust removal of coal gas during converter steelmaking production. It contains elements such as iron, calcium, magnesium and carbon, and has a fine particle size. The proportion of converter secondary sludge particles smaller than 5μm accounts for more than 70%; however, the viscosity of the converter secondary sludge after dehydration is high, and it is difficult to transport and handle. Converter secondary sludge is mainly composed of oxides formed by oxidation of iron, calcium, silicon, phosphorus and other elements in metallurgical raw materials, as well as impurities brought in during the steelmaking process, eroded and detached furnace lining materials, etc. At the same time, the scrap steel ratio in the converter smelting process of various steel enterprises is gradually increasing. There are a large number of zinc-containing scrap steels such as galvanized automobile plates, home appliance plates, and color steel tiles in the scrap steel, resulting in more and more zinc elements entering the converter. According to statistics, more than 90% of the zinc in the converter workshop comes from scrap steel, and the zinc element is very volatile to form zinc vapor. In the air, the zinc vapor is oxidized into small zinc oxide particles, which are captured by the converter's flue gas recovery (OG) system and enter the converter gas. Then, after wet gas dust removal, it enters the converter secondary sludge. About 85% of the zinc in the converter system enters the converter secondary sludge. If the converter sludge is all sintered and used, it will cause the blast furnace phosphorus load to exceed the standard seriously. Therefore, a rotary hearth furnace is established for dezincification of the converter secondary sludge, but the rotary hearth furnace has limited production capacity and cannot completely balance the digestion of the converter secondary sludge.

[0003] At present, there are generally two ways to treat converter sludge, one is to return it for sintering, and the other is to use it for dezincification in a rotary hearth furnace. Patent application CN115572828A discloses a method for treating converter sludge, including drying and disintegrating, mixing, pelletizing, drying, and roasting and reduction; in the converter sludge, the mass percentage of CaO is >7%, the mass percentage of SiO2 is <3%, the mass percentage of T.Fe is >45%, and the binary basicity of the converter sludge is >4; in the mixing step, the converter sludge and the carbon-containing raw material are evenly mixed into a mixture with a binary basicity >2.5, the ratio of the number of atoms of elemental carbon in the mixture to the number of atoms of oxygen contained in the iron-containing oxide is 0.6-0.9, the mass percentage of CaO is >8%, and the drying temperature is <350°C; the dry balls are sent into a rotary hearth furnace for roasting and reduction to obtain metallized pellets, and the secondary zinc oxide powder is recovered from the flue gas system of the rotary hearth furnace, the roasting temperature is 1200-1350°C, and the roasting time is >8min. The above scheme partially solves the technical problems of difficult treatment and low recycling rate of converter sludge in the prior art, but is limited to the process of treating converter secondary sludge in a rotary hearth furnace, and does not include other treatment processes for converter secondary sludge. At the same time, the sludge is not diverted according to the zinc content. Summary of the invention

[0004] The purpose of the present invention is to provide a method for diverting and treating converter secondary sludge in a steel enterprise, so as to realize the recycling of converter secondary sludge within the steel enterprise, reduce the zinc load of the blast furnace caused by sintering converter secondary sludge with a higher zinc content, and at the same time recover the zinc element to the maximum extent, thereby improving the economic benefits of converter secondary sludge.

[0005] To achieve the above-mentioned purpose, the present invention proposes the following technical scheme: a method for diversion treatment of converter secondary sludge in a steel enterprise, wherein scrap steel used in the converter is classified according to the zinc content, and the classified scrap steel is combined in different proportions and used in different converter workshops to make the zinc content of the converter secondary sludge in each converter workshop different, and then part of the sludge with lower zinc content in the produced converter secondary sludge is used for sintering, and part of the sludge with higher zinc content is used for the rotary hearth furnace.

[0006] Furthermore, the classification of scrap steel used in the converter according to zinc content includes: dividing the scrap steel used in the converter into five categories of scrap steel according to zinc content, and the zinc contents of the five categories of scrap steel are, in order, by weight percentage: ordinary scrap steel 0.4-0.6%, crushed material 1.0-1.2%, high-quality scrap steel 2.1-2.3%, clean scrap steel 2.1-2.3% and other scrap steel 0-0.1%.

[0007] Furthermore, the converter workshop includes a first converter workshop, a second converter workshop and a third converter workshop, the first converter workshop is used for producing carbon steel, the second converter workshop is used for producing alloy steel, and the third converter workshop is used for producing special tool steel.

[0008] Furthermore, in terms of weight percentage, the scrap steel ratio used in the first converter workshop is 60-70% ordinary scrap steel, 0-5% crushed material, 0-3% high-quality scrap steel, 0-3% clean scrap steel and 20-30% other scrap steel.

[0009] Furthermore, in terms of weight percentage, the scrap steel ratio used in the second converter workshop is 25-35% of ordinary scrap steel, 0-3% of crushed material, 0-10% of high-quality scrap steel, 45-55% of clean scrap steel and 0-10% of other scrap steel.

[0010] Furthermore, in terms of weight percentage, the scrap steel ratio used in the third converter workshop is 55-65% of ordinary scrap steel, 20-30% of crushed material, 0-3% of high-quality scrap steel, 5-15% of clean scrap steel and 0-10% of other scrap steel.

[0011] Furthermore, when the zinc content of the converter secondary sludge produced by the first converter workshop does not exceed 2% by weight, it is directly added for sintering; when the zinc content of the converter secondary sludge produced by the first converter workshop exceeds 2%, it is returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder.

[0012] Furthermore, the zinc content of the converter secondary sludge produced by the second converter workshop is not less than 9.5% by weight, and it is returned to the rotary hearth furnace for dezincification to produce metallized pellets and recover zinc oxide powder.

[0013] Furthermore, the zinc content of the converter secondary sludge produced by the third converter workshop is not less than 5.5% by weight, and the sludge is returned to the rotary hearth furnace for dezincification to produce metallized pellets and recover zinc oxide powder.

[0014] Furthermore, when the converter secondary sludge is used for sintering, the addition ratio is 3-5% by weight; when the converter secondary sludge is used for producing metallized pellets and recovering zinc oxide powder in a rotary hearth furnace, the addition ratio is 55-70% by weight, and the zinc load of the rotary hearth furnace mixture is 4.5-6.5%.

[0015] It can be seen from the above technical solutions that the technical solutions of the present invention have the following beneficial effects: The invention provides a method for shunting secondary sludge of a converter of a steel enterprise, and relates to the technical field of slag metallurgy. The method classifies scrap steel used in the converter of the steel enterprise according to zinc content, and classifies the scrap steel into common scrap steel (Zn%=0.4-0.6%), crushed material (Zn%=1.0-1.2%), high-quality scrap steel (Zn%=2.1-2.3%), clean scrap steel (Zn%=2.1-2.3%) and other scrap steel (Zn%=0-0.1%), so that each converter can use the scrap steel according to its product classification in the subsequent process; and then the classified scrap steel is combined in different proportions and used in the first to third converter workshops to produce products that meet the production requirements of each workshop and produce converter secondary sludge with obvious differences in zinc content, and then the part of the converter secondary sludge with a zinc content of no more than 2% can be directly added for sintering, and the part with a zinc content of more than 2% can be returned to the rotary hearth furnace for dezincification, metallized pellets can be produced and zinc oxide powder can be recovered, so as to finally realize the shunting treatment of zinc elements in scrap steel through the converter secondary sludge and improve the recovery rate of new elements. The present invention uses zinc content as a classification index to classify scrap steel and thereby obtains converter secondary sludge with different zinc contents. By planning different uses of sludge with different zinc contents, the converter secondary sludge can be recycled within the enterprise, thereby achieving the technical effects of reducing the zinc load of the blast furnace, efficiently recovering the zinc element, and improving the economic benefits of the converter secondary sludge.

[0016] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0017] The foregoing and other aspects, embodiments and features of the present invention will be more fully understood from the following description. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or will be learned from the practice of the specific embodiments according to the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0019] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular form of "a", "an" or "the" and similar words do not indicate a quantity limitation, but indicate the existence of at least one. "Include" or "comprises" and similar words mean that the elements or objects appearing before "include" or "comprises" include the features, wholes, steps, operations, elements and / or components listed after "include" or "comprises", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.

[0020] Based on the fact that the scrap ratio of each steel enterprise gradually increases during the converter smelting process, and the current complex sources of scrap steel have caused the zinc content of scrap steel to gradually increase; during the converter smelting process, the zinc element is very easy to volatilize to form zinc vapor, and then be oxidized into small zinc oxide particles, which are then captured and processed by the OG system and enter the converter secondary sludge; when the converter secondary sludge is used for sintering, it will cause the blast furnace phosphorus load to seriously exceed the standard, and then the existing technology adopts the establishment of a rotary hearth furnace for dezincification treatment of converter secondary sludge, but the production capacity of the rotary hearth furnace is limited and cannot completely balance the digestion of the converter secondary sludge. Therefore, the present invention proposes a method for diverting and treating the converter secondary sludge of a steel enterprise, aiming to solve the above problems, by classifying the scrap steel used in the converter according to the zinc content, and using it in different converter workshops, so as to promote the difference in the zinc content of the converter secondary sludge of each workshop, and then the part of the sludge with lower zinc content in the produced converter secondary sludge is used for sintering, and the part of the sludge with higher zinc content is used for the rotary hearth furnace; that is, the amount of converter secondary sludge consumed by sintering is reduced, while the zinc load of the rotary hearth furnace is increased, and the recovery rate of zinc element is improved.

[0021] Specifically, in the method for diverting secondary sludge from the converter of a steel enterprise, the scrap steel used in the converter is classified according to the zinc content, including: dividing the scrap steel used in the converter into five categories of scrap steel according to the zinc content, and the zinc contents of the five categories of scrap steel are, in order, by weight percentage: ordinary scrap steel 0.4-0.6%, crushed material 1.0-1.2%, high-quality scrap steel 2.1-2.3%, clean scrap steel 2.1-2.3% and other scrap steel 0-0.1%; the converter workshop includes the first converter workshop, the second converter workshop and the third converter workshop, wherein: the first converter workshop is used to produce carbon steel, such as carbon structural steel, high-quality carbon structural steel and carbon tool steel, and the scrap steel ratio used is 60-70% for ordinary scrap steel, 0-5% crushed material, 0-3% high-quality scrap steel, 0-3% clean scrap steel and 20-30% other scrap steel; the second converter workshop is used to produce alloy steel, such as low-alloy structural steel, alloy structural steel and alloy tool steel, and the scrap steel ratio used is 25-35% ordinary scrap steel, 0-3% crushed material, 0-10% high-quality scrap steel, 45-55% clean scrap steel and 0-10% other scrap steel; the third converter workshop is used to produce special tool steel, such as bearing steel, electrical steel, spring steel and free-cutting structural steel, and the scrap steel ratio used is 55-65% ordinary scrap steel, 20-30% crushed material, 0-3% high-quality scrap steel, 5-15% clean scrap steel and 0-10% other scrap steel.

[0022] In the above converter workshops, the zinc content of the converter secondary sludge produced by the first converter workshop is usually no more than 2% by weight. The converter secondary sludge with a zinc content of no more than 2% is directly added for sintering, and the addition ratio of the converter secondary sludge is 3-5%; however, when the zinc content of the converter secondary sludge produced by the first converter workshop exceeds 2%, it is directly returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder. By weight percentage, the zinc content of the converter secondary sludge produced by the second converter workshop is not less than 9.5%, and it is returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder; by weight percentage, the zinc content of the converter secondary sludge produced by the third converter workshop is not less than 5.5%, and it is returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder; when the converter secondary sludge is used in the rotary hearth furnace to produce metallized pellets and recover zinc oxide powder, its addition ratio is 55-70% by weight, and the zinc load of the rotary hearth furnace mixture is 4.5-6.5%.

[0023] The method for treating secondary sludge from a converter in a steel enterprise disclosed in the present invention will be further specifically introduced below in conjunction with specific embodiments.

[0024] Example 1 The scrap steel used in the converter of the steel enterprise is divided into ordinary scrap steel (Zn%=0.51%), crushed material (Zn%=1.14%), high-quality scrap steel (Zn%=2.2%), clean scrap steel (Zn%=2.2%) and other scrap steel (Zn%=0.05%) according to the zinc content; in terms of weight percentage, the first converter workshop produces carbon structural steel, and the scrap steel ratio is ordinary scrap steel (65%), crushed material (5%), high-quality scrap steel (2%), clean scrap steel (0%) and other scrap steel (28%), producing converter secondary sludge. The zinc content is 1.85%; the second converter workshop produces alloy tool steel, and the scrap steel ratio is ordinary scrap steel (30%), crushed material (0%), high-quality scrap steel (5%), clean scrap steel (50%) and other scrap steel (15%), and the zinc content of the production converter secondary sludge is 10.54%; the third converter workshop produces electrical steel, and the scrap steel ratio is ordinary scrap steel (60%), crushed material (25%), high-quality scrap steel (0%), clean scrap steel (10%) and other scrap steel (5%), and the zinc content of the production converter secondary sludge is 5.85%.

[0025] The first converter workshop produces converter secondary sludge with low zinc content due to the addition of low-zinc scrap steel, which is directly added for sintering with an addition ratio of 3%, and the corresponding blast furnace production is stable. The second and third converter workshops produce converter secondary sludge with high zinc content due to the addition of scrap steel with high zinc content. The rotary hearth furnace is returned to dezincify, metallized pellets are produced and zinc oxide powder is recovered. The proportion of rotary hearth furnace converter secondary sludge is 60%, and the zinc load of the mixed material is 5.48%. The production of the rotary hearth furnace is stable, and the dezincification rate is 88.59%.

[0026] Example 2 The scrap steel used in the converter of the steel enterprise is divided into ordinary scrap steel (Zn%=0.51%), crushed material (Zn%=1.14%), high-quality scrap steel (Zn%=2.2%), clean scrap steel (Zn%=2.2%) and other scrap steel (Zn%=0.05%) according to the zinc content; in terms of weight percentage, the first converter workshop produces carbon tool steel, and the scrap steel ratio is ordinary scrap steel (70%), crushed material (0%), high-quality scrap steel (0%), clean scrap steel (0%) and other scrap steel (30%), producing converter secondary sludge. The zinc content is 1.46%; the second converter workshop produces alloy structural steel, and the scrap steel ratio is ordinary scrap steel (30%), crushed material (0%), high-quality scrap steel (5%), clean scrap steel (55%) and other scrap steel (10%), and the zinc content of the production converter secondary sludge is 11.14%; the third converter workshop produces spring steel, and the scrap steel ratio is ordinary scrap steel (55%), crushed material (30%), high-quality scrap steel (0%), clean scrap steel (10%) and other scrap steel (5%), and the zinc content of the production converter secondary sludge is 6.08%.

[0027] The first converter workshop produces converter secondary sludge with low zinc content due to the addition of low-zinc scrap steel, which is directly added for sintering with an addition ratio of 3%, and the corresponding blast furnace production is stable. The second and third converter workshops produce converter secondary sludge with high zinc content due to the addition of scrap steel with high zinc content. The rotary hearth furnace is returned to dezincify, metallized pellets are produced and zinc oxide powder is recovered. The proportion of rotary hearth furnace converter secondary sludge is 60%, and the zinc load of the mixed material is 5.97%. The production of the rotary hearth furnace is stable, and the dezincification rate is 88.26%.

[0028] Example 3 The scrap steel used in the converter of the steel enterprise is divided into ordinary scrap steel (Zn%=0.51%), crushed material (Zn%=1.14%), high-quality scrap steel (Zn%=2.2%), clean scrap steel (Zn%=2.2%) and other scrap steel (Zn%=0.05%) according to the zinc content; in terms of weight percentage, the first converter workshop produces high-quality carbon structural steel, and the scrap steel ratio is ordinary scrap steel (60%), crushed material (5%), high-quality scrap steel (3%), clean scrap steel (2%) and other scrap steel (30%), producing converter secondary sludge. The zinc content is 2.12%; the second converter workshop produces alloy structural steel, and the scrap steel ratio is ordinary scrap steel (30%), crushed material (0%), high-quality scrap steel (5%), clean scrap steel (55%) and other scrap steel (10%), and the zinc content of the production converter secondary sludge is 11.14%; the third converter workshop produces special steel products, and the scrap steel ratio is ordinary scrap steel (55%), crushed material (30%), high-quality scrap steel (0%), clean scrap steel (10%) and other scrap steel (5%), and the zinc content of the production converter secondary sludge is 6.08%.

[0029] The zinc content of the secondary sludge produced by the first converter workshop is 2.12%. Because the zinc content is greater than 2%, it is no longer used for sintering, but returned to the rotary hearth furnace for dezincification. The second and third converter workshops produce secondary sludge with a higher zinc content due to the high zinc content of scrap steel added. It is returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder. The proportion of secondary sludge in the rotary hearth furnace is 60%, and the zinc load of the mixed material is 4.68%. The production of the rotary hearth furnace is stable, and the dezincification rate is 89.99%.

[0030] The invention divides the scrap steel currently used in the converter into ordinary scrap steel, crushed material, high-quality scrap steel, clean scrap steel and other scrap steel according to the zinc content, and uses them in different converter workshops according to the types of steel produced by them and in different proportions, so as to meet the production requirements of each workshop and classify the zinc-containing scrap steel for use, thereby causing differences in the zinc content of the converter secondary sludge in each workshop; according to the zinc content of the converter secondary sludge, the part with a content lower than 2% is directly added for sintering, and the part with a content higher than 2% is reused in the rotary hearth furnace, so as to solve the problem of serious excessive phosphorus load of the blast furnace caused by the high zinc content of the converter secondary sludge during sintering, and at the same time increase the zinc load of the rotary hearth furnace, thereby improving the recovery rate of the zinc element; the converter secondary sludge diversion treatment method of the invention realizes the balanced digestion of the converter secondary sludge.

[0031] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for treating secondary sludge from a converter in a steel enterprise, characterized in that: Scrap steel used in converters is classified according to zinc content. The classified scrap steel is combined in different proportions and used in different converter workshops to make the zinc content of converter secondary sludge in each converter workshop different. Part of the converter secondary sludge with lower zinc content is used for sintering, and part of the sludge with higher zinc content is used for rotary hearth furnace.

2. The method for treating secondary sludge from a converter in a steel enterprise according to claim 1, characterized in that: The classification of scrap steel used in the converter according to zinc content includes: dividing the scrap steel used in the converter into five categories of scrap steel according to zinc content, and the zinc contents of the five categories of scrap steel are, in order, by weight percentage: ordinary scrap steel 0.4-0.6%, crushed material 1.0-1.2%, high-quality scrap steel 2.1-2.3%, clean scrap steel 2.1-2.3% and other scrap steel 0-0.1%.

3. The method for treating secondary sludge from a converter in a steel enterprise according to claim 2, characterized in that: The converter workshop includes a first converter workshop, a second converter workshop and a third converter workshop. The first converter workshop is used for producing carbon steel, the second converter workshop is used for producing alloy steel, and the third converter workshop is used for producing special tool steel.

4. The method for treating secondary sludge from a converter in a steel enterprise according to claim 3, characterized in that: In terms of weight percentage, the scrap steel ratio used in the first converter workshop is 60-70% ordinary scrap steel, 0-5% crushed material, 0-3% high-quality scrap steel, 0-3% clean scrap steel and 20-30% other scrap steel.

5. The method for treating secondary sludge from a converter in a steel enterprise according to claim 3, characterized in that: In terms of weight percentage, the scrap steel ratio used in the second converter workshop is 25-35% ordinary scrap steel, 0-3% crushed material, 0-10% high-quality scrap steel, 45-55% clean scrap steel and 0-10% other scrap steel.

6. The method for treating secondary sludge from a converter in a steel enterprise according to claim 3, characterized in that: Calculated by weight percentage, the scrap steel ratio used in the third converter workshop is 55-65% ordinary scrap steel, 20-30% crushed material, 0-3% high-quality scrap steel, 5-15% clean scrap steel and 0-10% other scrap steel.

7. The method for treating secondary sludge from a converter in a steel enterprise according to claim 4, characterized in that: Measured by weight percentage, when the zinc content of the converter secondary sludge produced by the first converter workshop does not exceed 2%, it is directly added for sintering; when the zinc content of the converter secondary sludge produced by the first converter workshop exceeds 2%, it is returned to the rotary hearth furnace for dezincification, producing metallized pellets and recovering zinc oxide powder.

8. The method for treating secondary sludge from a converter in a steel enterprise according to claim 5, characterized in that: Measured by weight percentage, the zinc content of the converter secondary sludge produced by the second converter workshop is not less than 9.5%, and it is returned to the rotary hearth furnace for dezincification to produce metallized pellets and recover zinc oxide powder.

9. The method for treating secondary sludge from a converter in a steel enterprise according to claim 6, characterized in that: Measured by weight percentage, the zinc content of the converter secondary sludge produced in the third converter workshop is not less than 5.5%, and it is returned to the rotary hearth furnace for dezincification to produce metallized pellets and recover zinc oxide powder.

10. The method for treating secondary sludge from a converter in a steel enterprise according to claim 7, characterized in that: When the converter secondary sludge is used for sintering, the addition ratio is 3-5% by weight; when the converter secondary sludge is used in the rotary hearth furnace to produce metallized pellets and recover zinc oxide powder, the addition ratio is 55-70% by weight, and the zinc load of the rotary hearth furnace mixture is 4.5-6.5%.