CN112322891B - Finished pellet and preparation method thereof - Google Patents
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- CN112322891B CN112322891B CN202011091691.2A CN202011091691A CN112322891B CN 112322891 B CN112322891 B CN 112322891B CN 202011091691 A CN202011091691 A CN 202011091691A CN 112322891 B CN112322891 B CN 112322891B
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- 239000008188 pellet Substances 0.000 title claims abstract description 117
- 238000002360 preparation method Methods 0.000 title abstract description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 42
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 42
- 239000000920 calcium hydroxide Substances 0.000 claims abstract description 42
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims abstract description 42
- 235000011116 calcium hydroxide Nutrition 0.000 claims abstract description 42
- 239000000843 powder Substances 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 27
- 229910000281 calcium bentonite Inorganic materials 0.000 claims abstract description 25
- 229910052742 iron Inorganic materials 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims abstract description 21
- 238000005453 pelletization Methods 0.000 claims abstract description 18
- 239000011575 calcium Substances 0.000 claims abstract description 11
- 238000012216 screening Methods 0.000 claims abstract description 8
- 238000001035 drying Methods 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 9
- 238000002791 soaking Methods 0.000 claims description 9
- 238000010521 absorption reaction Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000007605 air drying Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 4
- 239000000084 colloidal system Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 15
- 239000000463 material Substances 0.000 abstract description 13
- 230000009286 beneficial effect Effects 0.000 abstract description 7
- 230000003647 oxidation Effects 0.000 abstract description 7
- 238000007254 oxidation reaction Methods 0.000 abstract description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 6
- 230000006872 improvement Effects 0.000 abstract description 6
- 239000011593 sulfur Substances 0.000 abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 abstract description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 4
- 230000001590 oxidative effect Effects 0.000 abstract description 4
- 229910052760 oxygen Inorganic materials 0.000 abstract description 4
- 239000001301 oxygen Substances 0.000 abstract description 4
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 abstract description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 17
- 230000035699 permeability Effects 0.000 description 10
- 239000002253 acid Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000003723 Smelting Methods 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 229910000278 bentonite Inorganic materials 0.000 description 3
- 229940092782 bentonite Drugs 0.000 description 3
- 239000000440 bentonite Substances 0.000 description 3
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical group O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- ONCZQWJXONKSMM-UHFFFAOYSA-N dialuminum;disodium;oxygen(2-);silicon(4+);hydrate Chemical compound O.[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[Na+].[Na+].[Al+3].[Al+3].[Si+4].[Si+4].[Si+4].[Si+4] ONCZQWJXONKSMM-UHFFFAOYSA-N 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 235000010755 mineral Nutrition 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910000280 sodium bentonite Inorganic materials 0.000 description 2
- 229940080314 sodium bentonite Drugs 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/242—Binding; Briquetting ; Granulating with binders
- C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/02—Roasting processes
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/2406—Binding; Briquetting ; Granulating pelletizing
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
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Abstract
The invention discloses a finished pellet, which comprises the following components in percentage by mass: 96.5 to 98.4 percent of iron ore powder and 0.1 to 0.5 percent of slaked lime1.5 to 3 percent of calcium bentonite, wherein Ca (OH) in the slaked lime 2 Mass fraction>88 percent. The invention also discloses a preparation method thereof, and the iron ore powder, the slaked lime and the calcium bentonite are uniformly mixed according to the proportion to obtain a mixture; and conveying the mixture to pelletizing, screening and roasting to obtain finished pellets. The specific surface area of the mixture can be improved by adding a small amount of slaked lime, so that the drop strength and the uniformity of granularity of the green pellets are improved, and the quality of the green pellets is improved; the improvement of the green pellet quality is beneficial to improving the circulation of hot air flow of a material layer and providing sufficient oxidizing atmosphere for the pellets in the roasting process, so that the FeO content of the finished pellets is reduced, a small amount of slaked lime plays a role in sulfur fixation, and the influence of the combination of sulfur and oxygen on ferrous oxidation is reduced.
Description
Technical Field
The invention relates to the technical field of pellet preparation, in particular to finished pellet and a preparation method thereof.
Background
The magnetite pellet is used as the raw material for blast furnace smelting, and the quality of the magnetite pellet has important influence on the blast furnace smelting process and the economy. 5500m manufactured by Jingtang corporation 3 The large blast furnace has high smelting strength and higher requirement on the quality of pellet ore. The FeO content is one of the important quality indexes of the pellet ore and has important influence on blast furnace smelting. Generally, the FeO content of the pellet ore is reduced by 1 percent, the coke ratio of the blast furnace is correspondingly reduced by 1 percent, the reduction of the FeO content is beneficial to the indirect reaction of the blast furnace, and the economic benefit is improved.
The production process of the pellet ore is a comprehensive process, and factors influencing the FeO content of the finished pellet ore are many and are mainly influenced by three factors of raw materials, pelletizing and roasting. The pelletizing process is one of the key links, mainly including the granularity and the green pellet quality of the green pellets, the too high proportion of the granularity of <5mm can directly influence the air permeability of a material layer, the oxygen content passing through the pellets in unit time is reduced, and the too high proportion of the granularity of >16mm can prolong the roasting time and influence the oxidation process. The air permeability and roasting atmosphere of the material layer can be influenced by too low falling of green pellets and too low compressive strength of the green pellets, and the FeO content is further influenced. Therefore, the improvement of the uniformity and quality of the green ball granularity is particularly important.
The added binder for producing the acid pellet is bentonite, and is restricted by high reduction expansion rate, some companies can only use calcium bentonite, the reduction expansion rate of the pellet can be reduced by using the calcium bentonite, but indexes such as water absorption rate of the calcium bentonite are far lower than those of sodium bentonite, so the green pellet quality is poor, the material layer of a roasting machine is poor in air permeability, and the pellets are not roasted fully and have high FeO content; the balling performance of the calcium bentonite is poorer than that of the sodium bentonite, the dropping frequency is lower, the wet return rate is higher, and the improvement of the productivity is restricted.
Therefore, how to prepare a finished pellet with low FeO content becomes a technical problem for those skilled in the art.
Disclosure of Invention
The invention aims to provide finished pellet ore and a preparation method thereof, which can greatly reduce the FeO content of the finished pellet ore.
In order to achieve the above object, the present invention provides a finished pellet, which comprises the following components by mass: 96.5 to 98.4 percent of iron ore powder, 0.1 to 0.5 percent of slaked lime and 1.5 to 3 percent of calcium bentonite, wherein Ca (OH) in the slaked lime 2 Mass fraction>88％。
Further, the water absorption of the calcium bentonite is >160, the blue absorption is >26, and the colloid value is >60.
Furthermore, the alkalinity of the finished pellet is 0.15-0.3.
The invention also provides a preparation method of the finished pellet ore, which comprises the following steps:
uniformly mixing iron ore powder, slaked lime and calcium bentonite to obtain a mixture;
conveying the mixture to pelletize to obtain green pellets;
screening the green pellets to obtain screened green pellets;
and roasting the screened green pellets to obtain finished pellets.
Furthermore, in the pelletizing, the rotating speed of a pelletizing disc is controlled to be 5-9 rpm/min, and the moisture content of green pellets is controlled to be 8-9%.
Furthermore, in the screening, the falling frequency of the screened green pellets is 6-9 times, and the compressive strength of the screened green pellets is more than 15N/pellet.
Furthermore, the granularity of the green balls obtained by sieving is 8-16 mm.
Further, the roasting specifically comprises: drying, preheating, roasting, soaking and cooling.
Further, the drying sequentially comprises forced air drying and air draft drying, wherein the forced air drying temperature is 280-350 ℃, and the time is 3-5 min; the temperature of the air draft drying is 300-400 ℃, and the time is 3-5 min.
Further, the preheating temperature is 500-1100 ℃, and the preheating time is 6-10 min; the roasting temperature is 1130-1250 ℃, and the roasting time is 6-10 min; the soaking temperature is 1100-1150 ℃, and the soaking time is 3-5 min; the cooling temperature is below 150 ℃, and the cooling time is 10-15 min.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the finished pellet ore and the preparation method thereof, on the basis of conventional bentonite addition, the specific surface area of a mixture can be improved by adding a small amount of slaked lime, so that the drop strength and the particle size uniformity of green pellets are improved, and the quality of the green pellets is improved; the improvement of the green pellet quality is beneficial to improving the circulation of hot airflow of a material layer and providing sufficient oxidizing atmosphere for the pellets in the roasting process, thereby reducing the FeO content of finished pellets. In addition, a small amount of slaked lime is added to play a certain role in sulfur fixation, and the influence of the combination of sulfur and oxygen on ferrous oxidation is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a method for manufacturing a finished pellet according to embodiment 1 of the present invention;
FIG. 2 is a graph showing the effect of reducing FeO content in a finished pellet provided in example 1 of the present invention.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be obtained by existing methods.
The embodiment of the invention provides a finished pellet, which has the following general idea:
in order to achieve the above object, the present embodiment provides a finished pellet, which comprises the following components in percentage by mass: 96.5 to 98.4 percent of iron ore powder, 0.1 to 0.5 percent of slaked lime and 1.5 to 3 percent of calcium bentonite, wherein Ca (OH) in the slaked lime 2 Mass fraction>88％。
The reason why 96.5% -98.4% of iron ore powder is as follows: too much or too little iron ore powder and improper binder proportion affect the quality of green pellets and finished pellets.
The calcium bentonite accounts for 1.5-3% of the following reasons: when the low pelletizing is added, the falling strength of the green pellets is too low, the damage condition may occur in the transfer process, and the plastic deformation is generated when the high green pellets are added.
The reasons for 0.1 to 0.5 percent of slaked lime are as follows: too high affects the alkalinity of the pellet ore, too little has no obvious effect. Wherein Ca (OH) in the slaked lime 2 Mass fraction>The reason for 88% is: ca (OH) 2 The mass fraction is too low, slaked lime is not completely digested, and the green pellets may be locally expanded to burst in the drying process of the roasting machine, so that the air permeability of a material layer is influenced, and the oxidation of FeO is not facilitated.
Therefore, the finished pellet provided by the invention has the advantages that the components have synergistic effect, the falling strength and the uniformity of granularity of the green pellets are improved, and the quality of the green pellets is improved; the improvement of the green pellet quality is beneficial to improving the circulation of hot airflow of a material layer and providing sufficient oxidizing atmosphere for the pellets in the roasting process, thereby reducing the FeO content of the finished pellets. In addition, a small amount of slaked lime is added to play a certain role in sulfur fixation, and the influence of the combination of sulfur and oxygen on ferrous oxidation is reduced.
As a preferred embodiment, the water absorption of the calcium bentonite is >160, the blue absorption is >26, and the colloid value is >60. The calcium bentonite satisfies the above conditions because: the indexes can not meet the requirements, thus affecting the drop strength of green pellets, reducing the roasting permeability and affecting the FeO content of finished pellets.
The granularity requirement of the iron ore powder is as follows: more than 85 percent of fine-grained iron ore powder smaller than 200 meshes (less than or equal to 0.074 mm);
according to another exemplary embodiment of the present invention, there is provided a method of manufacturing finished pellets, as shown in fig. 1, including:
s1, uniformly mixing iron ore powder, slaked lime and calcium-based bentonite to obtain a mixture;
s2, conveying the mixture to pelletize to obtain green pellets;
s3, screening the green pellets to obtain screened green pellets;
s4, roasting the screened green pellets to obtain finished pellets.
The specific surface area of the mixture can be improved by adding a small amount of slaked lime, and then the falling strength and the uniformity of the granularity of the green pellets are improved. The improvement of the green pellet quality is beneficial to reducing the falling loss in the belt conveying process and the powder entering the roasting machine, improving the circulation of hot air flow of a material layer, and providing sufficient oxidizing atmosphere for the pellets in the roasting process, thereby reducing the FeO content of finished pellets. By adding a small amount of slaked lime, the pelletizing performance of the pelletizing can be improved, the single-disc production capacity of the pelletizing disc is further improved obviously, and one less pelletizing disc can be used under the same yield; the wet return rate is reduced after the green ball quality is improved, the power consumption of the belt is reduced, the rotating speed of five fans is correspondingly reduced after the air permeability of a material layer of the roasting machine is improved, and the power consumption can be reduced while the problem of insufficient productivity is solved.
In the pelletizing, the rotating speed of a pelletizing disc is controlled at 5-9 rpm/min, and the water content of green pellets is controlled at 8-9%. The green pellets with too high water content are easy to be dried insufficiently after entering a roasting machine to generate burst, and the roasting air permeability is influenced.
In the screening, the falling times of the screened green pellets are 6-9 times, and the compressive strength of the screened green pellets is more than 15N/pellet. The transfer process may be broken when the falling frequency is too low, and green pellets are plastically deformed when the falling frequency is too high, so that the roasting air permeability is influenced, and the FeO is not reduced.
The granularity of the screened green pellets is 8-16 mm.
The roasting specifically comprises: drying, preheating, roasting, soaking and cooling; the drying sequentially comprises forced air drying and air draft drying, wherein the forced air drying temperature is 280-350 ℃, and the time is 3-5 min; the temperature of the air draft drying is 300-400 ℃, and the time is 3-5 min.
The preheating temperature is 500-1100 ℃, and the preheating time is 6-10 min;
the roasting temperature is 1130-1250 ℃, and the roasting time is 6-10 min;
the soaking temperature is 1100-1150 ℃, and the soaking time is 3-5 min;
the cooling temperature is below 150 ℃, and the cooling time is 10-15 min.
A finished pellet of the present application will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
Uniformly mixing iron ore powder, calcium bentonite and slaked lime according to a mass ratio of 97.8. For example, 485 tons of iron ore powder, 14 tons of calcium bentonite and 1 ton of slaked lime are added per hour and mixed evenly to form an ore powder mixture.
Pelletizing the mineral powder mixture in a disc pelletizer for 10 minutes, screening qualified balls with the size fraction of 8-16mm by using a roller screen after pelletizing is finished, and feeding the qualified balls into a roasting machine, wherein green balls smaller than 8mm and larger than 16mm are used as return materials and return to a mixture belt. The green pellets with qualified particle size are roasted by a belt roasting machine: the green pellets are first dried by blowing at 320 deg.c for 4 min, then dried by blowing at 350 deg.c for 4 min, preheated at 500-1000 deg.c for 6 min, roasted at 1190 deg.c for 7 min, soaked at 1130 deg.c for 2 min and then cooled at normal temperature to below 150 deg.c to obtain acid pellets.
Example 2
Iron ore powder, calcium bentonite and slaked lime are uniformly mixed into an ore powder mixture according to the mass ratio of 97.6 to 0.4, and then a proper amount of water is added to be uniformly mixed so as to adjust the moisture of the ore powder mixture to 8.5%. For example, 485 tons of iron ore powder, 13 tons of calcium bentonite and 2 tons of slaked lime are added per hour and mixed evenly to form an ore powder mixture.
Pelletizing the mineral powder mixture in a disc pelletizer for 11 minutes, screening qualified balls with the size fraction of 8-16mm by using a roller screen after pelletizing is finished, and feeding the qualified balls into a roasting machine, wherein green balls smaller than 8mm and larger than 16mm are used as return materials and return to a mixture belt. The green pellets with qualified granularity are roasted by a belt roasting machine: the green pellet is first air dried at 330 deg.c for 5min, then air dried at 360 deg.c for 5min, preheated at 500-1000 deg.c for 6 min, roasted at 1210 deg.c for 7 min, soaked at 1130 deg.c for 5min, and finally cooled with normal temperature air to below 150 deg.c to obtain acid pellet.
Example 3
In the embodiment, 98.4 percent of iron ore powder, 0.1 percent of slaked lime and 1.5 percent of calcium bentonite are adopted, wherein Ca (OH) in the slaked lime 2 Mass fraction of>88 percent. The rest is the same as in example 1.
Example 4
In the embodiment, 96.5 percent of iron ore powder, 0.5 percent of slaked lime and 3 percent of calcium bentonite are adopted, wherein Ca (OH) in the slaked lime 2 Mass fraction>88 percent. The rest is the same as in example 1.
Comparative example 1
In this comparative example, 97% of iron ore powder, 0.05% of slaked lime and 2.95% of calcium bentonite are added, wherein Ca (OH) is contained in the slaked lime 2 Mass fraction>88 percent. The rest is the same as in example 1.
Comparative example 2
97% of iron ore powder, 1% of slaked lime and 2% of calcium bentonite in the comparative example, wherein Ca (OH) in the slaked lime 2 Mass fraction>88 percent. The rest of the process was the same as in example 1.
Comparative example 3
97% of iron ore powder, 0.2% of slaked lime and 2.8% of calcium bentonite in the comparative example, wherein Ca (OH) in the slaked lime 2 The mass fraction is 85%. The rest of the process was the same as in example 1.
Comparative example 4
This comparative example contained no slaked lime and was otherwise the same as example 1.
Test example 1
For ease of comparison, the parameters of each group are listed as shown in table 1.
TABLE 1
The index of the acid pellets produced for each group is shown in table 2.
TABLE 2 index comparison of acid pellets with existing acid pellets in the examples
| Chemical composition | TFe | SiO 2 | CaO | FeO | Compressive strength | Basicity B2 |
| Example 1 | 66.14 | 3.19 | 0.58 | 0.6 | 2920 | 0.18 |
| Example 2 | 66.14 | 3.13 | 0.64 | 0.5 | 3045 | 0.20 |
| Example 3 | 66.81 | 2.48 | 0.38 | 0.59 | 2863 | 0.22 |
| Example 4 | 65.73 | 3.35 | 0.68 | 0.56 | 3084 | 0.20 |
| Comparative example 1 | 65.98 | 3.32 | 0.39 | 0.73 | 3021 | 0.12 |
| Comparative example 2 | 66.07 | 2.78 | 0.97 | 0.78 | 3062 | 0.35 |
| Comparative example 3 | 66 | 3.23 | 0.89 | 0.62 | 2914 | 0.28 |
| Comparative example 4 | 66.15 | 3.21 | 0.43 | 0.77 | 2912 | 0.13 |
From the data in table 2 it can be seen that:
in the comparative example 1, the slaked lime is 0.05 percent and is less than the range of 0.1 to 0.5 percent of the invention, and the defect that FeO is not obviously reduced exists;
in the comparative example 2, 1% of slaked lime, which is larger than the range of 0.1% to 0.5% of the present invention, has an increased alkalinity and is not favorable for the reduction of FeO;
in comparative example 3, ca (OH) 2 The mass fraction is less than or equal to 88 percent, which indicates that slaked lime is not completely digested, and the raw balls can be partially expanded to cause burst in the drying process of the roasting machine, thereby affecting the air permeability of a material layer and further being not beneficial to the oxidation of FeO.
Compared with the pellet of the comparative example 4, the pellet prepared in the example 1 has the FeO content lower by 0.2 percent and the alkalinity higher by 0.05 percent. The FeO content of the pellet prepared in the example 2 is lower by 0.3 percent, and the alkalinity is higher by 0.07 percent.
FIG. 2 is a diagram showing the actual effect of a finished pellet provided in example 1 of the present invention, and it can be seen from FIG. 1 that the FeO content of the finished pellet is greatly reduced.
Through one or more embodiments provided by the embodiments of the present invention, at least the following technical effects or advantages are achieved:
the specific surface area of the mixture can be obviously improved by adding a small amount of slaked lime, and further the green ball quality and the granularity uniformity are improved. After the falling strength and the compressive strength of the green pellets are improved, the conditions of breakage and deformation of the green pellets entering the roasting machine can be reduced, and the roasting atmosphere is favorably improved. After slaked lime is added, the grain size of 10-14mm is improved, which is beneficial to improving the air permeability of the material layer and the oxidation speed of FeO.
By adding a small amount of slaked lime, the single-disk production capacity of the pelletizing disk can be obviously improved, the proportion of 10-14mm size fraction is improved, the return ore rate is reduced, the rotating speed of five fans is reduced, the problem of insufficient capacity is solved, and the power consumption can be reduced.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (8)
1. The finished pellet is characterized by comprising the following components in percentage by mass: 96.5 to 98.4 percent of iron ore powder, 0.1 to 0.5 percent of slaked lime and 1.5 to 3 percent of calcium bentonite, wherein Ca (OH) in the slaked lime 2 Mass fraction>88％；
The water absorption rate of the calcium bentonite is more than 160, the blue absorption rate is more than 26, and the colloid value is more than 60;
the alkalinity of the finished pellet is 0.15-0.3.
2. A method for preparing a finished pellet as claimed in claim 1, wherein the method comprises:
uniformly mixing iron ore powder, slaked lime and calcium bentonite to obtain a mixture;
conveying the mixture to pelletize to obtain green pellets;
screening the green pellets to obtain screened green pellets;
and roasting the screened green pellets to obtain finished pellets.
3. The method for preparing finished pellets according to claim 2, wherein the rotation speed of the pelletizing disk is controlled to be 5-9 rpm/min and the moisture content of the green pellets is controlled to be 8-9%.
4. The method as claimed in claim 2, wherein the number of falling of the green pellets is 6-9, and the compressive strength of the green pellets is greater than 15N/pellet.
5. The method as claimed in claim 2, wherein the green pellets are sized to be 8-16 mm.
6. The method for preparing finished pellets according to claim 2, wherein the roasting specifically comprises: drying, preheating, roasting, soaking and cooling.
7. The method for preparing finished pellets as claimed in claim 6, wherein the drying includes forced air drying and air draft drying in sequence, the temperature of forced air drying is 280-350 ℃, and the time is 3-5 min; the temperature of the air draft drying is 300-400 ℃, and the time is 3-5 min.
8. The method for preparing finished pellets according to claim 6, wherein the preheating temperature is 500-1100 ℃ and the preheating time is 6-10 min; the roasting temperature is 1130-1250 ℃, and the roasting time is 6-10 min; the soaking temperature is 1100-1150 ℃, and the soaking time is 3-5 min; the cooling temperature is below 150 ℃, and the cooling time is 10-15 min.
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