Pellet using high-sulfur high-ferrous concentrate and preparation method thereof

Abstract

The present application aims at solving the problems in the prior art of preparing pellets from high-sulfur and high-ferrous concentrate, and provides a method for producing high-quality pellets from iron concentrate with sulfur content of 0.7% or more and FeO content of 30% or more. The pellets prepared from high-sulfur and high-ferrous iron concentrate according to the present application are composed of the following raw materials in terms of mass percentage: high-sulfur and high-ferrous iron concentrate 98.5%-99.0%, and sodium-based bentonite 1.0%-1.5%. The pellets are prepared after drying, preheating and roasting. According to the different oxidation rules of FeO and sulfur, the preheating and roasting system is reasonably divided, and the hindering effect of sulfur removal on the oxidation of FeO in the pellet roasting process is reduced.

Description

Technical Field

[0001] This invention belongs to the field of pellet technology, and specifically relates to a pellet using high-sulfur, high-ferrous concentrate and its preparation method. Background Technology

[0002] With the continuous exploitation of iron ore resources and the decreasing availability of rich ore, iron ore suitable for pellet production is becoming increasingly scarce. To reduce pellet production costs, domestic steel companies have shifted from relying solely on imported concentrates to increasingly using relatively inexpensive domestic concentrates to replace some of the imported high-quality iron concentrates. These measures have broadened the sources of iron concentrates used in pellet production, resulting in a greater variety and more complex properties. In particular, in recent years, high-sulfur (S content > 0.7%) and high-ferrous (FeO > 30.0%) concentrates have begun to be used in pellet production. These ores differ significantly in composition from ordinary magnetite. When the S content in the iron concentrate exceeds 0.5%, some sulfur exists as sulfate, which is difficult to remove through conventional roasting. Furthermore, the oxidation and removal of sulfides hinders the oxidation of FeO in the pellets. When the FeO content exceeds 30.0%, the adverse effects of sulfur removal on the pellets become even more pronounced, leading to a different roasting thermal regime compared to conventional magnetite. In order to make more rational use of this special iron concentrate in the pelleting industry, and also to improve energy conservation and environmental protection, it is necessary to study the pelleting production process of high-sulfur and high-ferrous iron concentrate, so as to make more effective use of this iron concentrate resource.

[0003] Domestic research institutions and universities have also studied how to effectively utilize domestically produced high-sulfur, high-ferrous magnetite concentrates. For example, Ni Lu of Xinyu Iron & Steel Group Co., Ltd. used pelletizing to process magnetite concentrate with a sulfur content of over 0.8%, but the specific quality of the pellets was not detailed. Yang Dabing et al. of Wuhan University of Science and Technology studied the roasting and desulfurization of high-sulfur, high-alkalinity magnetite concentrate pellets in Inner Mongolia. Their study pointed out that high sulfur content hinders the oxidation of ferrous iron. However, the iron concentrate they used differed significantly from the iron concentrate used in this study. Their iron concentrate had only 28.45% ferrous iron and 1.24% silica, which greatly reduced the rate of fir olivine formation. Moreover, their preheating and roasting times were relatively long, at 22 min and 13 min respectively. Professor Guo Yufeng et al. of Central South University also conducted pelletizing research on high-sulfur magnetite concentrate, but their research was limited to pelletizing and green pellet drying, without studying the roasting of the pellets.

[0004] Some patents also describe methods for preparing pellets using high-sulfur iron ore. For example, patent application number CN201110179774 describes a process for producing pellets using high-sulfur ore and sulfuric acid slag. Half of the raw material is sulfuric acid slag, the iron concentrate has a relatively low ferrous content, the preheating temperature is relatively high, ranging from 1000 to 1100℃, and the roasting temperature is as high as 1310℃. The sulfur content of the finished pellets is all above 0.015%.

[0005] In summary, based on currently available information, there are not many methods for producing pellets from high-sulfur, especially high-ferrous iron concentrate. Therefore, given the shortage of high-quality iron concentrate, further research is needed on using relatively inexpensive high-sulfur, high-ferrous iron concentrate to produce pellets. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the preparation of pellets from high-sulfur, high-ferrous iron concentrate in the prior art. This invention provides a method for producing high-quality pellets from iron concentrate with a sulfur content of 0.7% or higher and an FeO content of 30% or higher. Based on the different oxidation characteristics of FeO and sulfur, this invention rationally divides the preheating and roasting processes, reducing the hindering effect of sulfur removal on FeO oxidation during pellet roasting.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] The present invention provides a pellet of high-sulfur, high-ferrous iron concentrate, which is composed of the following raw materials in the following mass percentages on a dry basis: 98.5% to 99.0% high-sulfur, high-ferrous iron concentrate and 1.0% to 1.5% sodium-based bentonite; and is obtained after drying, preheating and roasting.

[0009] Among them, the sulfur content of high-sulfur, high-ferrous iron concentrate is above 0.7% by mass, and the FeO content is above 30% by mass.

[0010] Furthermore, the pellets produced using high-sulfur, high-ferrous concentrate have a specific surface area of ​​1500–1800 cm². 2 / g.

[0011] Furthermore, the sodium-based bentonite used in the above-mentioned pellets made from high-sulfur, high-ferrous concentrate is metallurgical grade 1 sodium-based bentonite.

[0012] The present invention provides a method for preparing pellets using high-sulfur, high-ferrous concentrate, specifically comprising the following steps:

[0013] Step 1: Raw Material Preparation

[0014] High-sulfur, high-ferrous iron concentrate is crushed using a high-pressure roller mill to reduce its specific surface area to 1500–1800 cm². 2 / g;

[0015] Step 2: Mix ingredients and form into balls

[0016] The high-sulfur, high-ferrous iron concentrate obtained in step one is mixed with sodium-based bentonite in a dry weight ratio, and the total moisture content of the material is controlled to be 7.5-8.5% of the dry weight of the high-sulfur, high-ferrous iron concentrate and sodium-based bentonite. After the material is mixed evenly, it is pelletized on a disc pelletizer to obtain green pellets.

[0017] Step 3: Preheating and roasting

[0018] After drying the raw pellets obtained in step two, they are preheated and roasted. The preheating is divided into two stages: the first stage preheating temperature is 830-870℃, and the second stage preheating temperature is 930-970℃. The preheated pellets are obtained under the condition that the total preheating time is 10-14 minutes. Then, they enter the roasting stage, which is divided into two stages: the first stage roasting temperature is 1200-1230℃, and the second stage roasting temperature is 1250-1280℃. The roasted pellets are obtained under the condition that the total roasting time is 11-12 minutes.

[0019] Furthermore, in the above-mentioned pellets made from high-sulfur, high-ferrous concentrate and their preparation method, in step two, the green pellets have the following strength parameters: drop strength ≥ 5.0 times / pellet, compressive strength ≥ 10.0 N / pellet.

[0020] Furthermore, in the above-mentioned pellets made from high-sulfur and high-ferrous concentrate and their preparation method, in step three, the preheated pellets have a compressive strength ≥ 500 N / pellet, the roasted pellets have a compressive strength ≥ 2500 N / pellet, and the pellets contain TFe ≥ 65.0%, S ≤ 0.008%, and FeO ≤ 0.5%.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. The raw material in this invention is high-sulfur, high-ferrous iron concentrate. Based on the different oxidation patterns of FeO and sulfur, the preheating and roasting processes are rationally divided to reduce the hindrance effect of sulfur removal on FeO oxidation during pellet roasting.

[0023] 2. In this invention, the preheating and roasting temperatures of the pellets are relatively low, and the roasting time is relatively short.

[0024] 3. The pellets obtained by this invention have a strength of over 3000 N / pellet, a grade of TFe ≥ 65.0%, and relatively low S and FeO contents, with S ≤ 0.008% and FeO ≤ 0.5%. Detailed Implementation

[0025] Example 1

[0026] A method for preparing pellets using high-sulfur, high-ferrous concentrate specifically includes the following steps:

[0027] Step 1: Raw Material Preparation

[0028] The main chemical components of the raw materials in Example 1 are shown in Table 1:

[0029] Table 1. Test results of main chemical components of raw materials

[0030]

[0031] After high-pressure roller milling, the iron concentrate has a -200 mesh content of 95.95% and a specific surface area of ​​1780 cm². 2 / g. The bentonite used has a 200 mesh content of 98.10%, and its physicochemical properties are shown in Table 2.

[0032] Table 2. Test results of physicochemical properties of sodium-based bentonite

[0033]

[0034] Step 2: Mix ingredients and form into balls

[0035] The high-sulfur, high-ferrous magnetite and sodium-based bentonite prepared in step one were mixed according to the dry weight ratio, with 99.0% high-sulfur, high-ferrous concentrate and 1.0% sodium-based bentonite. The total moisture content of the material was controlled to be 8.0% of the dry weight of the high-sulfur, high-ferrous concentrate and sodium-based bentonite. The mixture was then pelletized on a disc pelletizer to obtain green pellets for the test. The green pellets had a drop strength of 5.4 times / pellet and a compressive strength of 13.2 N / pellet.

[0036] Step 3: Preheating and roasting

[0037] After drying the green pellets obtained in step two, they were preheated and calcined in a horizontal tube furnace. The preheating was divided into two stages: the first stage preheating temperature was 850℃ for 10 minutes, and the second stage preheating temperature was 950℃ for 4 minutes. Under these conditions, preheated pellets were obtained with a compressive strength of 560 N / pellet. The preheated pellets were then calcined in two stages: the first stage calcination temperature was 1200℃ for 8 minutes, and the second stage calcination temperature was 1250℃ for 3 minutes, resulting in calcined pellets. The main chemical composition and compressive strength of the calcined pellets under these conditions are shown in Table 3 below.

[0038] Table 3. Main Chemical Components and Properties of Pellets

[0039]

[0040] Example 2

[0041] A method for preparing pellets using high-sulfur, high-ferrous concentrate specifically includes the following steps:

[0042] Step 1: Raw Material Preparation

[0043] The main chemical components of the raw materials and the physicochemical properties of bentonite in Example 2 are the same as in Example 1.

[0044] After high-pressure roller milling, the iron concentrate has a -200 mesh content of 93.22% and a specific surface area of ​​1640 cm². 2 / g.

[0045] Step 2: Mix ingredients and form into balls

[0046] The high-sulfur, high-ferrous magnetite and sodium-based bentonite prepared in step one were mixed in a weight ratio based on dry weight, with the high-sulfur, high-ferrous concentrate comprising 98.9% and sodium-based bentonite 1.1%. The total moisture content of the materials was controlled to be 8.5% of the dry weight of the high-sulfur, high-ferrous magnetite concentrate and sodium-based bentonite. The mixture was then pelletized on a disc pelletizer to obtain green pellets for the experiment. The green pellets exhibited a drop strength of 5.7 times / pellet and a compressive strength of 12.6 N / pellet.

[0047] Step 3: Preheating and roasting

[0048] After drying the green pellets obtained in step two, they were preheated and calcined in a horizontal tube furnace. The preheating was divided into two stages: the first stage preheating temperature was 850℃ for 10 minutes, and the second stage preheating temperature was 950℃ for 4 minutes. Under these conditions, preheated pellets were obtained with a compressive strength of 530 N / pellet. The preheated pellets were then calcined in two stages: the first stage calcination temperature was 1200℃ for 8 minutes, and the second stage calcination temperature was 1250℃ for 3 minutes, resulting in calcined pellets. The main chemical composition and compressive strength of the calcined pellets under these conditions are shown in Table 4.

[0049] Table 4. Main Chemical Components and Properties of Pellets

[0050]

[0051] Example 3.

[0052] A method for preparing pellets using high-sulfur, high-ferrous concentrate specifically includes the following steps:

[0053] Step 1: Raw Material Preparation

[0054] The main chemical components of the raw materials and the physicochemical properties of bentonite in Example 3 are the same as those in Example 1, as shown in Tables 1 and 2.

[0055] After high-pressure roller milling, the iron concentrate has a -200 mesh content of 94.02% and a specific surface area of ​​1590 cm². 2 / g.

[0056] Step 2: Mix ingredients and form into balls

[0057] The high-sulfur, high-ferrous magnetite prepared in step one was mixed with sodium-based bentonite according to the dry weight ratio, with 98.7% high-sulfur, high-ferrous concentrate and 1.3% sodium-based bentonite. The total moisture content of the materials was controlled to be 7.5% of the dry weight of the high-sulfur, high-ferrous concentrate and sodium-based bentonite. Then, the mixture was pelletized on a disc pelletizer to obtain green pellets for the test. The green pellets had a drop strength of 5.2 times / pellet and a compressive strength of 13.4 N / pellet.

[0058] Step 3: Preheating and roasting

[0059] After drying the green pellets obtained in step two, they were preheated and calcined in a horizontal tube furnace. The preheating was divided into two stages: the first stage preheating temperature was 850℃ for 10 minutes, and the second stage preheating temperature was 950℃ for 4 minutes. Under these conditions, preheated pellets were obtained with a compressive strength of 520 N / pellet. The preheated pellets were then calcined in two stages: the first stage calcination temperature was 1230℃ for 8 minutes, and the second stage calcination temperature was 1270℃ for 3 minutes, resulting in calcined pellets. The main chemical composition and compressive strength of the calcined pellets under these conditions are shown in Table 5.

[0060] Table 5. Main Chemical Components and Properties of Pellets

[0061]

[0062] Example 4

[0063] A method for preparing pellets using high-sulfur, high-ferrous concentrate specifically includes the following steps:

[0064] Step 1: Raw Material Preparation

[0065] The main chemical components of the raw materials and the physicochemical properties of bentonite in Example 4 are the same as in Example 1, as shown in Tables 1 and 2.

[0066] After high-pressure roller milling, the iron concentrate has a -200 mesh content of 93.4% and a specific surface area of ​​1510 cm². 2 / g.

[0067] Step 2: Mix ingredients and form into balls

[0068] The high-sulfur, high-ferrous magnetite prepared in step one was mixed with sodium-based bentonite in a weight ratio of 98.5% and 1.5% respectively. The total moisture content of the materials was controlled to be 8.0% of the dry weight of the high-sulfur, high-ferrous magnetite concentrate and sodium-based bentonite. The mixture was then pelletized on a disc pelletizer to obtain green pellets for the test. The green pellets had a drop strength of 5.6 times / pellet and a compressive strength of 14.1 N / pellet.

[0069] Step 3: Preheating and roasting

[0070] After drying the green pellets obtained in step two, they were preheated and calcined in a horizontal tube furnace. The preheating was divided into two stages: the first stage preheating temperature was 850℃ for 10 minutes, and the second stage preheating temperature was 950℃ for a total preheating time of 4 minutes. Under these conditions, preheated pellets were obtained with a compressive strength of 510 N / pellet. The preheated pellets were then calcined in two stages: the first stage calcination temperature was 1230℃ for 8 minutes, and the second stage calcination temperature was 1280℃ for 3 minutes, resulting in calcined pellets. The main chemical composition and compressive strength of the calcined pellets under these conditions are shown in Table 6 below.

[0071] Table 6. Main Chemical Components and Properties of Pellets

[0072]

Claims

1. A method for preparing pellets using high-sulfur, high-ferrous concentrate, characterized in that, Specifically, the following steps are included: Step 1: Raw Material Preparation High-sulfur, high-ferrous iron concentrate is crushed using a high-pressure roller mill to reduce its specific surface area to 1500-1800 cm². 2 / g; Step 2: Mix ingredients and form into balls The high-sulfur, high-ferrous iron concentrate obtained in step one is mixed with sodium-based bentonite in a dry weight ratio, and the total moisture content of the material is controlled to be 7.5-8.5% of the dry weight of the high-sulfur, high-ferrous iron concentrate and sodium-based bentonite. After the material is mixed evenly, it is pelletized on a disc pelletizer to obtain green pellets. The weight ratio of high-sulfur, high-ferrous iron concentrate to sodium-based bentonite is: 98.5%~99.0% high-sulfur, high-ferrous iron concentrate and 1.0%~1.5% sodium-based bentonite; wherein, the high-sulfur, high-ferrous iron concentrate has a sulfur content of more than 0.7% by mass and an FeO content of more than 30% by mass. Step 3: Preheating and roasting After drying the raw pellets obtained in step two, they are preheated and roasted. The preheating is divided into two stages: the first stage preheating temperature is 830~870℃, and the second stage preheating temperature is 930~970℃. The preheated pellets are obtained under the condition that the total preheating time is 10~14min. Then, they enter the roasting stage, which is divided into two stages: the first stage roasting temperature is 1200~1230℃, and the second stage roasting temperature is 1250~1280℃. The roasted pellets are obtained under the condition that the total roasting time is 11~12min.

2. The method for preparing pellets using high-sulfur, high-ferrous concentrate according to claim 1, characterized in that, In step two, the raw balls have the following strength parameters: drop strength ≥ 5.0 times / ball, compressive strength ≥ 10.0 N / ball.

3. The method for preparing pellets using high-sulfur, high-ferrous concentrate according to claim 1, characterized in that, In step three, the preheated pellets have a compressive strength ≥ 500 N / pellet, the roasted pellets have a compressive strength ≥ 2500 N / pellet, and the pellets contain TFe ≥ 65.0%, S ≤ 0.008%, and FeO ≤ 0.5%.

4. The method for preparing pellets using high-sulfur, high-ferrous concentrate according to claim 1, characterized in that, Sodium-based bentonite is a first-grade sodium-based bentonite for metallurgical use.

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