A method for upgrading low-grade iron ore

Abstract

A method for upgrading low-grade iron ore, comprising the following steps: 1) crushing and screening the low-grade iron-containing ore in sequence to obtain large-particle ore and small-particle ore; 2) roasting and modifying the large-particle ore to obtain a hot modified material; 3) cooling the hot modified material, and adding a reducing agent and the small-particle ore during the cooling process to perform a cooling and reduction treatment to obtain an iron-containing magnetic material; 4) subjecting the iron-containing magnetic material to sequential grinding and magnetic separation to obtain an iron concentrate. The present invention provides a method for upgrading low-grade iron ore, which separates the heating and reduction steps of the iron ore, thereby avoiding the ringing problem caused by local high temperatures caused by flame heating, while achieving precise control of the magnetization temperature and reducing atmosphere.

Description

Technical Field

[0001] The present invention relates to a quality improvement method, in particular to a quality improvement method for low-grade iron ore, and belongs to the technical field of steel metallurgy. Background Art

[0002] The use of high-yield pellets, along with blast furnace ironmaking and a shortened process using direct reduced iron (DRI) and scrap steel, represents a consensus in the iron and steel industry for reducing energy consumption and carbon emissions during steel production. my country's market for high-quality iron ore concentrate for pellet production is robust, and the outlook is promising. However, domestic iron ore resources are rapidly depleting, with high-quality ore becoming increasingly scarce. Furthermore, as mining continues at greater depths, the iron grade in lower deposits is gradually decreasing. Consequently, domestic iron ore resources, both in terms of quantity and quality, are no longer sufficient to support the scale and growth of the pellet industry.

[0003] my country's annual iron ore imports are primarily fine ore, which suffers from a wide variety of varieties, fluctuating properties, and declining quality. Most of it cannot meet the requirements of pellet production and can only be used as a sintering feedstock. To meet the development needs of my country's pelletizing industry, imported iron ore needs to be further sorted and upgraded to meet the requirements for pelletizing feedstock.

[0004] In terms of magnetic roasting-grinding and magnetic separation to improve the quality of low-quality iron ore, taking low-quality limonite as an example, limonite is a mixture of goethite, lepidocrocite, hydrogoethite, hydrolepidocrocite, hydrosilicon oxide, mud, etc., in which the iron minerals are finely embedded. Although the crystallization water can be removed and the mineral phase transformation of trivalent iron oxide to magnetite can be achieved during the magnetic roasting process, at the lower magnetic roasting temperature, the newly formed magnetite grains are difficult to grow and migrate and enrich, resulting in the iron-containing minerals after magnetic roasting still having a very fine embedded particle size, and it is difficult to dissociate from the gangue minerals during the grinding process, which ultimately leads to the low iron grade of the magnetic concentrate. Rotary kiln magnetization roasting is a common magnetization roasting method. During the magnetization roasting process in the rotary kiln, a certain amount of coal needs to be added to the material as a reducing agent. The material also needs to be heated to the reaction temperature by the kiln head flame. To maintain the stability of the flame, the temperature generally cannot be lower than 800℃. To prevent the iron oxides from being over-reduced to fusite and affecting the separation effect, the higher the temperature of the magnetization roasting process, the lower the suitable CO / (CO+CO2) ratio is, and the more difficult it is to control the CO partial pressure. In addition, the atmosphere in the kiln contains a large amount of residual oxygen, which reacts with the coal in the material layer after contact, releasing a large amount of heat, which can easily lead to local high temperature in the material layer. In the local high temperature part, not only will the iron oxides be over-reduced, but the large amount of FeO produced will also react with the high content of silicon in limonite to form low-melting-point silicate minerals, causing ring formation in the rotary kiln. At the same time, the iron transferred to the silicate will also reduce the iron recovery rate in the grinding process. Summary of the Invention

[0005] In response to the problems of the existing technology of iron ore with a wide variety of varieties, large fluctuations in properties, and continuously declining quality, as well as the immature magnetization roasting-grinding magnetic separation process for low-quality iron ore in the existing technology, which easily leads to ring formation and reduced iron recovery rate, the present invention proposes a method for upgrading low-grade iron ore. The iron-containing minerals are first roasted and modified to remove crystal water at high temperature to complete the transformation and aggregation growth of the iron minerals. The iron minerals are then reduced to magnetic materials during the cooling process. The heating and reduction processes of the conventional magnetization roasting process are distributed, solving the ring formation problem caused by the same cavity and heat in the conventional rotary kiln magnetization process.

[0006] According to the implementation scheme of this scheme, a method for upgrading low-grade iron ore is provided.

[0007] A method for upgrading low-grade iron ore, the method comprising the following steps:

[0008] 1) crushing and screening low-grade iron-containing ore in sequence to obtain large-size ore and small-size ore;

[0009] 2) roasting and modifying the large-size ore to obtain a hot-modified material;

[0010] 3) Cooling the hot modified material, and adding a reducing agent and small-particle ore during the cooling process to perform cooling and reduction treatment to obtain an iron-containing magnetic material;

[0011] 4) The ferromagnetic material is subjected to grinding and magnetic separation in sequence to obtain iron concentrate.

[0012] Preferably, the method further comprises: before the process is started, establishing a mathematical model for the total iron content of the iron concentrate based on the raw ore and the adjustment and control of parameters of each process, with the goal of ensuring that the total iron content of the iron concentrate meets the target requirement. Then, the actual operating parameters of each process are adjusted according to the mathematical model to ensure that the total iron content of the iron concentrate meets the target requirement.

[0013] Preferably, the mathematical model is as follows:

[0014]

[0015] Where, TFe mjk is the iron content in iron concentrate, %.

[0016] TFe myk is the iron content in the ore, %; α is TFe myk The power of, where 0≤α≤N g ; N g TFe myk The highest power of a gα TFe myk The coefficient of the αth power of .

[0017] Dmm is the grinding particle size, mm; β is D mm Power of; 0≤β≤N h ; N h D mm The highest power of a hβ D mm The coefficient of the βth power.

[0018] S mx is the pulp concentration during beneficiation, %; χ is S mx Power of; 0≤χ≤N i ; N i For S mx The highest power of For S mx The coefficient of the xth power of .

[0019] R mh is the amount of reducing agent, %; δ is R mh Power of; 0≤δ≤N j ; N j R mh The highest power of a jδ R mh The coefficient of the δth power.

[0020] Q mfl is the amount of powder added, %; ε is Q mfl Power of; 0≤ε≤N k ; N k Q mfl The highest power of a kε Q mfl The coefficient of the εth power.

[0021] T mcz is the magnetization termination temperature, °C; φ is T mcz Power of; 0≤φ≤N l ; N l T mcz The highest power of T mcz The coefficient of the φth power.

[0022] t mch is the magnetization time, min; γ is t mch Power of; 0≤γ≤N m ; N m t mch The highest power of a mγ t mch The coefficient of the γth power of .

[0023] T mgx is the modification temperature, °C; η is T mgxPower of; 0≤η≤N n ; N n T mgx The highest power of a nη T mgx The coefficient of the ηth power.

[0024] t mgx is the modification time, h; ι is t mgx The power of ; 0≤ι≤N o ; N o t mgx The highest power of a oι t mgx The coefficient of the ith power.

[0025] Among them, A, B, C, D, E, F, G, H, and I are the influence coefficients of various process parameters on the iron content in high-quality iron ore; the value range of A is 0.04-0.1, the value range of B is 0.05-0.13, the value range of C is 0.03-0.08, the value range of D is 0.11-0.15, the value range of E is 0.06-0.15, the value range of F is 0.1-0.15, the value range of G is 0.14-0.19, the value range of H is 0.10-0.15, and the value range of I is 0.11-0.17. The sum of A, B, C, D, E, F, G, H, and I is 1.

[0026] N g 、N h 、N i 、N j 、N k 、N l 、N m 、N n 、N o The value range is 1 to 5.

[0027] Preferably, the iron content of the low-grade iron-containing mineral is 30% to 65%.

[0028] Preferably, the low-grade iron ore includes any one or more of hematite, limonite, phosphite, siderite, goethite, specularite, red mud, iron-containing dust, copper slag, nickel slag, and iron-containing smelting slag;

[0029] Preferably, the particle size of the large-size ore is not less than 0.5 mm; the particle size of the small-size ore is less than 0.5 mm.

[0030] Preferably, the roasting modification is to use a modifier to perform any one or more of oxidation roasting, sodium roasting, potassium roasting, phosphorylation roasting, sulfuric acid roasting, and calcification roasting on the large-particle ore.

[0031] Preferably, the modifier includes any one or more of sodium salt, potassium salt, phosphate, sulfuric acid or sulfate, and calcium salt.

[0032] Preferably, the sodium salt includes sodium hydroxide, sodium carbonate, and sodium chloride; the potassium salt includes potassium hydroxide, potassium carbonate, and potassium chloride; the phosphate includes phosphorus pentoxide, phosphoric acid, sodium phosphate, and potassium phosphate; the sulfate includes potassium sulfate and sodium sulfate; and the calcium salt includes calcium oxide, calcium hydroxide, calcium carbonate, and calcium chloride.

[0033] Preferably, the mass of the modifier is (5%, 40%], preferably [10%, 20%] of the mass of the large-particle ore;

[0034] Preferably, the temperature of the calcination modification is 400-1300°C, more preferably 600-1100°C.

[0035] Preferably, the calcination modification time is 5 to 180 minutes, preferably 60 to 150 minutes.

[0036] Preferably, the cooling and reduction process is carried out in a dry slow-cooling porous reduction cylinder.

[0037] Preferably, the reducing agent is a solid reducing agent or a gaseous reducing agent, preferably any one or more of coal, biomass, coke, hydrogen, blast furnace gas, converter gas, and coke oven gas.

[0038] Preferably, the temperature when the reducing agent is added is 400-1000°C, preferably 600-900°C.

[0039] Preferably, the cooling rate during the cooling process is 2 to 10° C. / min, preferably 4 to 8° C. / min.

[0040] Preferably, the magnetization time is 5 to 60 minutes, preferably 30 to 50 minutes.

[0041] Preferably, the small-size ore accounts for 2% to 50% of the mass of the thermally modified material, preferably 5% to 20%.

[0042] Preferably, the mass of the solid reducing agent is 1% to 30% of the mass of the large-particle ore, preferably 2% to 15%; the gas-solid ratio of the gaseous reducing agent to the large-particle ore is 50 to 1000 kg / m 3 , preferably 300~900kg / m 3 .

[0043] Preferably, the grinding is any one of ball milling, vertical milling, rod milling and roller milling.

[0044] Preferably, the particle size of the ground ore is less than 325 mesh, accounting for more than 80%, and preferably less than 325 mesh, accounting for more than 90%.

[0045] Preferably, the pulp concentration during the magnetic separation is 20 to 70%, more preferably 25 to 50%.

[0046] Preferably, the actual operating parameters of each process are adjusted according to the mathematical model so that the total iron content of the iron concentrate meets the target requirements, specifically: according to the target value of the iron content in the high-quality iron ore, the grinding particle size, slurry concentration, reducing agent dosage, powder addition amount, magnetization termination temperature, magnetization time, modification temperature, and modification time are adjusted in sequence until the iron content in the high-quality iron ore reaches the target value; if the target value is still not reached after one round of adjustment, the adjustment and optimization are repeated until the iron content in the high-quality iron ore is not lower than the target value.

[0047] Preferably, the target value is an iron content of not less than 55% in high-quality iron ore, preferably not less than 65%.

[0048] Preferably, the reducing agent is a solid reducing agent;

[0049] The experiment was conducted to investigate the effect of various processes on the iron content in iron concentrate, with the following settings:

[0050]

[0051] According to the change of total iron content in the raw ore, the empirical fitting of formula (2) was performed to obtain the formula that the change of total iron content in the raw ore affects the total iron content of the iron concentrate:

[0052]

[0053] Similarly, set:

[0054]

[0055] According to the change of grinding particle size, the empirical fitting of formula (4) was performed to obtain the formula that the total iron content of iron ore affected by the change of grinding particle size is as follows:

[0056]

[0057] set up:

[0058]

[0059] According to the change of slurry concentration, the empirical fitting of formula (6) was performed to obtain the formula that affects the total iron content of iron concentrate based on slurry concentration:

[0060]

[0061] set up:

[0062]

[0063] According to the change of reducing agent dosage, the empirical fitting of formula (8) was performed to obtain the formula of the total iron content of iron ore affected by the change of reducing agent dosage:

[0064]

[0065] set up:

[0066]

[0067] According to the change of powder addition amount, the empirical fitting of formula (10) was performed to obtain the formula of the influence of the total iron content of iron ore based on the change of powder addition amount:

[0068]

[0069] set up:

[0070]

[0071] According to the change of magnetization termination temperature, the empirical fitting of formula (12) is performed to obtain the formula that the total iron content of iron ore affected by the change of magnetization termination temperature is:

[0072] TFe m6 =-0.0006T mcz +0.9139……(Equation 13)

[0073] set up:

[0074]

[0075] According to the change of magnetization time, the empirical fitting of formula (14) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of magnetization time:

[0076]

[0077] set up:

[0078]

[0079] According to the change of modification temperature, the empirical fitting of formula (16) was performed to obtain the formula that affects the total iron content of iron ore based on the change of modification temperature:

[0080] TFe m8 =4.06*10 -4 *T mgx +0.2415……(Equation 17)

[0081] set up:

[0082]

[0083] According to the change of modification time, the empirical fitting of formula (18) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of modification time:

[0084]

[0085] Preferably, the reducing agent is a gaseous reducing agent;

[0086] The experiment was conducted to investigate the effect of various processes on the iron content in iron concentrate, with the following settings:

[0087]

[0088] According to the change of total iron content in the raw ore, the empirical fitting of formula (2) was performed to obtain the formula that the change of total iron content in the raw ore affects the total iron content of the iron concentrate:

[0089]

[0090] Similarly, set:

[0091]

[0092] According to the change of grinding particle size, the empirical fitting of formula (4) was performed to obtain the formula that the total iron content of iron ore affected by the change of grinding particle size is as follows:

[0093]

[0094] set up:

[0095]

[0096] According to the change of slurry concentration, the empirical fitting of formula (6) was performed to obtain the formula that affects the total iron content of iron concentrate based on slurry concentration:

[0097]

[0098] set up:

[0099]

[0100] According to the change of reducing agent dosage, the empirical fitting of formula (8) was performed to obtain the formula of the total iron content of iron ore affected by the change of reducing agent dosage:

[0101]

[0102] set up:

[0103]

[0104] According to the change of powder addition amount, the empirical fitting of formula (10) was performed to obtain the formula of the influence of the total iron content of iron ore based on the change of powder addition amount:

[0105]

[0106] set up:

[0107]

[0108] According to the change of magnetization termination temperature, the empirical fitting of formula (12) is performed to obtain the formula that the total iron content of iron ore affected by the change of magnetization termination temperature is:

[0109] TFe m6 =-0.0002T mcz +0.7098……(Equation 25)

[0110] set up:

[0111]

[0112] According to the change of magnetization time, the empirical fitting of formula (14) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of magnetization time:

[0113]

[0114] set up:

[0115]

[0116] According to the change of modification temperature, the empirical fitting of formula (16) was performed to obtain the formula that affects the total iron content of iron ore based on the change of modification temperature:

[0117] TFe m8 =2.582*10 -4 *T mgx +0.4112……(Equation 27)

[0118] set up:

[0119]

[0120] According to the change of modification time, the empirical fitting of formula (18) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of modification time:

[0121]

[0122] Preferably, the method further comprises: 5) pumping unreacted reducing gas from the reduction process into the roasting and modification process for combustion to provide heat.

[0123] In the present invention, low-grade iron-containing minerals are crushed and then screened into large-size ore and small-size ore. The large-size ore is roasted and modified, and the resulting hot modified material is added to the screened small-size ore during the cooling process. The small-size ore and the hot modified material are gradually cooled. During the cooling process, the reducing agent reduces the iron oxides in the iron ore to magnetic iron oxides. The magnetic iron oxides are then ground and magnetically separated to obtain iron concentrate. The present invention separates heating and reduction, completing the material heating process during the roasting stage and magnetizing during the cooling process of the high-temperature material. This avoids the ringing problem caused by local high temperature caused by flame heating. At the same time, the addition of the reducing agent during the cooling process of the high-temperature material can achieve precise coordinated control of the magnetization temperature and the reducing atmosphere, avoiding the problem of difficult control of the reducing atmosphere in the reactor with the same cavity and heat during the conventional magnetization process.

[0124] In the present invention, since the existing conventional rotary kiln magnetization roasting process is generally at a low reaction temperature in order to prevent ringing and over-reduction of iron oxides in the kiln, at a lower reaction temperature, although the iron oxide can complete the removal of crystallization water and the magnetization process, the migration of iron oxide material points is difficult to achieve, and the iron oxide grains will not grow, which will cause the separation of magnetic materials and gangue minerals in the grinding process after magnetization to be more difficult. The present invention adopts a reaction temperature higher than that of conventional magnetization roasting in the roasting stage. During the roasting process, not only can the removal of crystallization water be completed, but the iron oxide can also achieve the transformation of the iron oxide crystal structure and microstructure under the action of high-temperature roasting, the iron oxide material points are more likely to migrate, and the grains can grow to a more ideal particle size requirement. Moreover, for special minerals, sodium, sulfation, phosphation, calcification and other reactions can be quickly completed at high temperature, promoting the growth of iron oxide grains. The magnetic mineral particles formed by the grown iron oxide after magnetization in the magnetization stage are larger, which is beneficial to subsequent grinding and separation, and improves the grade and recovery rate of the iron concentrate.

[0125] In the present invention, in view of the problem that in the existing conventional rotary kiln magnetization process, the coarse-grained and fine-grained ores are heated and reduced and magnetized at the same time, the fine-grained ores are more active and easily magnetized or even over-reduced, resulting in uneven magnetization. The present invention does not subject the fine-grained ores to high-temperature roasting, but directly adds them to the high-temperature material when the hot modified material is magnetized. The sensible heat of the hot modified material can be used to heat the fine-grained ores, and rapid magnetization can be achieved under a reducing atmosphere. The hot modified material directly undergoes a magnetization reaction, and the fine-grained ores are first heated and dehydrated to remove substances such as crystal water, and then a magnetization reaction occurs. This ensures that the fine-grained ores are not over-reduced, improves the overall magnetization uniformity of the material, and can improve the grade and recovery rate of the iron ore concentrate in the subsequent grinding process.

[0126] In the present invention, in order to make the iron content in the iron concentrate reach the target value, the influence of various parameters in different processes on the iron content in the iron concentrate is studied under the conditions of different reducing agents, and a mathematical model of the total iron content of the iron concentrate based on the adjustment and control of the original ore and various process parameters is proposed. By changing the various process parameters, the iron content in the iron concentrate is increased to reach the target value.

[0127] In the present invention, based on the influence of various process parameters on the iron content in the iron concentrate, the value range of the influencing factors of each process parameter (i.e., A, B, C, ..., I) is further calculated to obtain a calculation formula for the final iron content in the iron concentrate. The final iron content is estimated based on this formula and serves as a basis for changing the process parameters.

[0128] In the present invention, the process parameters are adjusted in sequence according to the grinding particle size, slurry concentration, reducing agent dosage, powder addition amount, magnetization termination temperature, magnetization time, modification temperature, and modification time. The adjustment principle is to adjust the grinding parameters first. When the grinding parameter adjustment fails to achieve the target, the magnetization parameters are adjusted. If the target still cannot be achieved, the modification parameters are adjusted.

[0129] In the present invention, based on application experience, the parameters such as the amount of modifier, roasting modification temperature and roasting modification time in the roasting modification process, as well as the amount of reducing agent and cooling rate in the reduction process are limited to ensure the stability of the overall process. During the application process, adjustments are made on the basis of the above parameter ranges to achieve refined control and increase the iron content in the iron concentrate.

[0130] In the present invention, unreacted reducing gas from the reduction process can be pumped into the roasting and modification process for combustion and heat generation, fully utilizing the waste heat. Furthermore, when the reducing agent is a gaseous reducing agent, the modified tail gas generated during the roasting process can be mixed with the gaseous reducing agent in a specific ratio to adjust the partial pressure of the gaseous reducing agent during the cooling process.

[0131] In the present invention, the process of mathematical model fitting is as follows:

[0132] When the reducing agent is a solid reducing agent,

[0133] The formula for the influence of the iron content in the raw ore on the iron content in the high-quality iron ore is:

[0134]

[0135] The experimental data are shown in the following table:

[0136] TFe content in the original ore / % TFe content in concentrate / % 30 55.34 40 60.11 50 65.35 60 69.18

[0137] Fitting the above data yields:

[0138]

[0139] Similarly, the effect of grinding particle size on the iron content in high-quality iron ore is expressed as follows:

[0140]

[0141] The experimental data are shown in the following table:

[0142] Grinding particle size / mm TFe content in concentrate / % 0.1 58.60 0.074 61.14 0.045 65.35 0.038 66.59

[0143] Fitting the above data yields:

[0144]

[0145] The formula for the effect of slurry concentration on the iron content in high-quality iron ore is:

[0146]

[0147] The experimental data are shown in the following table:

[0148] Slurry concentration / % TFe content in concentrate / % 10 55.21 20 57.36 30 59.24 40 63.24 50 65.35 60 66.01

[0149] Fitting the above data yields:

[0150]

[0151] The formula for the effect of reducing agent dosage on the iron content in high-quality iron ore is:

[0152]

[0153] The experimental data are shown in the following table:

[0154]

[0155]

[0156] Fitting the above data yields:

[0157]

[0158] The formula for the effect of powder addition on the iron content in high-quality iron ore is:

[0159]

[0160] The experimental data are shown in the following table:

[0161] Powder addition amount / % TFe content in concentrate / % 2 63.24 4 66.54 6 67.35 8 65.35 10 62.21

[0162] Fitting the above data yields:

[0163] The effect of magnetization termination temperature on the iron content in high-quality iron ore is as follows:

[0164]

[0165] The experimental data are shown in the following table:

[0166] Magnetization termination temperature / ℃ TFe content in concentrate / % 600 56.35 550 60.27 500 65.35 450 67.25 400 68.25

[0167] Fitting the above data yields:

[0168] TFe m6 =-0.0006T mcz +0.9139

[0169] The formula for the effect of magnetization time on the iron content in high-quality iron ore is:

[0170]

[0171] The experimental data are shown in the following table:

[0172] Magnetization time / min TFe content in concentrate / % 20 57.32 25 63.01 30 65.35 35 67.87 40 68.95

[0173] Fitting the above data yields:

[0174]

[0175] The effect of modification temperature on the iron content in high-quality iron ore is as follows:

[0176]

[0177] The experimental data are shown in the following table:

[0178] Modification temperature / ℃ TFe content in concentrate / % 700 52.35 800 56.53 900 60.98 1000 65.35 1100 68.24

[0179] Fitting the above data yields:

[0180] TFe m8 =4.06*10 -4 *T mgx +0.2415

[0181] The effect of modification time on the iron content in high-quality iron ore is as follows:

[0182]

[0183] The experimental data are shown in the following table:

[0184] Modification time / min TFe content in concentrate / % 10 58.34 20 63.24 30 65.35 40 67.57 50 68.14

[0185] Fitting the above data yields:

[0186]

[0187] Wherein, A, B, C, D, E, F, G, H, and I are the influence coefficients of each process parameter on the iron content in high-quality iron ore; the sum of A, B, C, D, E, F, G, H, and I is 1. For example, in the present invention, when the reducing agent is coke, in a preferred embodiment, the value of A is 0.09, the value of B is 0.06, the value of C is 0.07, the value of D is 0.12, the value of E is 0.08, the value of F is 0.13, the value of G is 0.16, the value of H is 0.13, and the value of I is 0.16.

[0188] In addition, when the reducing agent is a gaseous reducing agent,

[0189] The formula for the influence of the iron content in the raw ore on the iron content in the high-quality iron ore is:

[0190]

[0191] The experimental data are shown in the following table:

[0192] TFe content in the original ore / % TFe content in concentrate / % 30 53.49 40 59.23 50 65.14 60 68.03

[0193] Fitting the above data yields:

[0194]

[0195] Similarly, the effect of grinding particle size on the iron content in high-quality iron ore is expressed as follows:

[0196]

[0197] The experimental data are shown in the following table:

[0198] Grinding particle size / mm TFe content in concentrate / % 0.1 56.35 0.074 60.57 0.045 65.14 0.038 67.47

[0199] Fitting the above data yields:

[0200]

[0201] The formula for the effect of slurry concentration on the iron content in high-quality iron ore is:

[0202]

[0203] The experimental data are shown in the following table:

[0204]

[0205]

[0206] Fitting the above data yields:

[0207]

[0208] The formula for the effect of reducing agent partial pressure on the iron content in high-quality iron ore is:

[0209]

[0210] The experimental data are shown in the following table:

[0211] Reducing agent partial pressure / % TFe content in concentrate / % 10 56.32 20 60.24 30 65.14 40 67.35 50 68.21

[0212] Fitting the above data yields:

[0213]

[0214] The formula for the effect of powder addition on the iron content in high-quality iron ore is:

[0215]

[0216] The experimental data are shown in the following table:

[0217] Powder addition amount / % TFe content in concentrate / % 6 64.35 8 66.29 10 67.17 12 65.14 14 62.21

[0218] Fitting the above data yields:

[0219]

[0220] The effect of magnetization termination temperature on the iron content in high-quality iron ore is as follows:

[0221]

[0222] The experimental data are shown in the following table:

[0223] Magnetization termination temperature / ℃ TFe content in concentrate / % 500 60.68 400 62.77 300 65.14 200 66.57 100 69.02

[0224] Fitting the above data yields:

[0225] TFe m6 =-0.0002T mcz +0.7098

[0226] The formula for the effect of magnetization time on the iron content in high-quality iron ore is:

[0227]

[0228] The experimental data are shown in the following table:

[0229] Magnetization time / min TFe content in concentrate / % 20 56.68 30 62.57 40 65.14 50 67.28 60 68.35

[0230] Fitting the above data yields:

[0231]

[0232] The effect of modification temperature on the iron content in high-quality iron ore is as follows:

[0233]

[0234] The experimental data are shown in the following table:

[0235] Modification temperature / ℃ TFe content in concentrate / % 700 59.27 800 61.14 900 65.14 1000 66.98 1100 69.26

[0236] Fitting the above data yields:

[0237] TFe m8 =2.582*10 -4 *T mgx +0.4112

[0238] The effect of modification time on the iron content in high-quality iron ore is as follows:

[0239]

[0240] The experimental data are shown in the following table:

[0241] Modification time / min TFe content in concentrate / % 10 57.88 20 62.59 30 65.14 40 66.99 50 67.98

[0242] Fitting the above data yields:

[0243]

[0244] Wherein, A, B, C, D, E, F, G, H, and I are the influence coefficients of each process parameter on the iron content in high-quality iron ore; the sum of A, B, C, D, E, F, G, H, and I is 1. For example, in the present invention, when the reducing agent is hydrogen, in a preferred embodiment, the value of A is 0.05, the value of B is 0.11, the value of C is 0.04, the value of D is 0.13, the value of E is 0.13, the value of F is 0.12, the value of G is 0.17, the value of H is 0.12, and the value of I is 0.13.

[0245] In the present invention, all formulas in the present invention are obtained by fitting by the inventors based on experiments and engineering applications, and all calculations are numerical values converted according to prescribed units, and are obtained by substituting the converted numerical values into the formulas (after converting the units of each parameter, only the numerical values are substituted into the formulas for calculation, without substituting the units, and the units are only used to adjust the size of the numerical values).

[0246] Compared with the prior art, the present invention has the following beneficial effects:

[0247] 1. The present invention provides a method for upgrading low-grade iron ore, which separates the heating and reduction steps of the iron ore, avoiding the ring formation problem caused by local high temperature caused by flame heating, while achieving precise control of the magnetization temperature and reducing atmosphere.

[0248] 2. The present invention provides a method for upgrading low-grade iron ore, in which iron-containing minerals are processed separately according to particle size. The fine-grained material is not subjected to high-temperature roasting, but is directly added to the high-temperature material during the magnetization of the hot modified material, ensuring that the fine-grained material is not over-reduced and improving the overall magnetization uniformity of the material.

[0249] 3. The present invention provides a method for improving the quality of low-grade iron ore. The method studies the influence of various parameters in different processes on the iron content in high-quality iron ore, and improves the iron content in high-quality iron ore by changing various process parameters, thereby achieving refined control of each step. BRIEF DESCRIPTION OF THE DRAWINGS

[0250] Figure 1 The present invention provides a process flow chart of a method for upgrading low-grade iron ore using a solid reducing agent.

[0251] Figure 2 The present invention provides a process flow chart of a method for upgrading low-grade iron ore using a gaseous reducing agent. DETAILED DESCRIPTION

[0252] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0253] Example 1

[0254] A method for upgrading low-grade iron ore, the method comprising the following steps:

[0255] 1) 430.3 kg of iron-containing ore was ground and sieved to obtain 400.5 kg of large-size ore with a particle size of not less than 0.5 mm and 29.8 kg of small-size ore with a particle size of less than 0.5 mm;

[0256] 2) 400.5 kg of large-size ore was added to a rotary kiln, and 40 kg of sodium carbonate and 10 kg of calcium oxide were added to the rotary kiln. The temperature was raised to 1000° C., and the calcination modification was completed after reacting at 1000° C. for 60 minutes to obtain 433.4 kg of hot modified material;

[0257] 3) adding 433.4 kg of hot modified material to a dry slow cooling porous reduction drum, and adding 29.8 kg of small-particle ore and 24.7 kg of coke when the hot modified material and the small-particle ore are cooled and reduced at a rate of 5 ° C / min in a reducing atmosphere. After 40 minutes, the magnetization reduction is completed, and the magnetization termination temperature is 450 ° C, to obtain 457.3 kg of magnetic iron oxide;

[0258] 4) Grinding and magnetic separation of the obtained 457.3 kg magnetic iron oxide yielded 388.7 kg high-quality iron ore and 68.6 kg tailings.

[0259] (85% recovery rate)

[0260] Among them, experiments were conducted on the effects of different processes on the iron content in high-quality iron ore, and the relationship between each process parameter and the iron content in high-quality iron ore was obtained as follows:

[0261] In this embodiment, the reducing agent is coke. Under this operating condition, the value of A is 0.09, the value of B is 0.06, the value of C is 0.07, the value of D is 0.12, the value of E is 0.08, the value of F is 0.13, the value of G is 0.16, the value of H is 0.13, and the value of I is 0.16. Substituting equations (2) to (19) into equation (1) yields:

[0262] Among them, TFe myk is the iron content in the original ore, which is 31%; D mm is the grinding particle size, which is 0.05mm; S mx is the pulp concentration during beneficiation, which is 28%; R mh is the amount of reducing agent, which is 5%; Q mfl is the amount of powder added, which is 7%; T mcz is the magnetization termination temperature, which is 450℃; t mch is the magnetization time, which is 40 min; T mgx is the modification temperature, which is 1000℃; t mgx is the modification time, which is 60min.

[0263] According to the calculation, TFe mjk =65.29%, that is, the iron content in the iron concentrate meets the target requirement of 65%. In addition, the iron content in 388.7 kg of high-quality iron ore was tested and the result was 65.33%.

[0264] Example 2

[0265] A method for upgrading low-grade iron ore, the method comprising the following steps:

[0266] 1) 450.2 kg of iron-containing ore was ground and sieved to obtain 417.5 kg of large-size ore with a particle size of not less than 0.5 mm and 32.7 kg of small-size ore with a particle size of less than 0.5 mm;

[0267] 2) 417.5 kg of large-size ore was added to a rotary kiln, and 50 kg of sodium carbonate and 12.5 kg of sodium sulfate were added to the rotary kiln. The temperature was raised to 950° C., and the reaction was carried out at 950° C. for 110 minutes before calcination and modification were completed to obtain 452.2 kg of hot modified material;

[0268] 3) Add 452.2kg of hot modified material into the dry slow cooling porous reduction cylinder. When cooled to 700℃, add 32.7kg of small particle size ore. The flow rate is 0.753m 3 / min of hydrogen, so that the hot modified material and small-size ore were cooled and reduced at 6°C / min in a reducing atmosphere. The magnetization reduction was completed after 45 minutes, and the magnetization termination temperature was 430°C, and 478.3kg of magnetic iron oxide was obtained;

[0269] 4) Grinding and magnetic separation of the obtained 478.3 kg magnetic iron oxide to obtain 406.6 kg high-quality iron ore and 71.7 kg tailings.

[0270] Among them, experiments were conducted on the effects of different processes on the iron content in high-quality iron ore, and the relationship between each process parameter and the iron content in high-quality iron ore was obtained as follows:

[0271] In this embodiment, the reducing agent is hydrogen. Under this operating condition, the value of A is 0.05, the value of B is 0.11, the value of C is 0.04, the value of D is 0.13, the value of E is 0.13, the value of F is 0.12, the value of G is 0.17, the value of H is 0.12, and the value of I is 0.13. Substituting equations (20) to (28) into equation (1) yields:

[0272]

[0273] Among them, TFe myk is the iron content in the original ore, which is 31%; D mm is the grinding particle size, which is 0.05mm; S mx is the pulp concentration during beneficiation, which is 28%; R mh is the reducing agent dosage, which is 0.753m 3 / min;Q mfl is the amount of powder added, which is 7.2%; T mcz is the magnetization termination temperature, which is 430℃; t mch is the magnetization time, which is 45min; T mgx is the modification temperature, which is 950℃; t mgx is the modification time, which is 110 min.

[0274] According to the calculation, TFe mjk =62.21%, which does not meet the target requirement of 65% iron content in the iron concentrate. The grinding particle size is adjusted to 0.04mm, the pulp concentration is adjusted to 35%, and the hydrogen flow rate is adjusted to 0.55m 3 / min, the magnetization termination temperature was adjusted to 370℃, the magnetization time was adjusted to 55min, the modification temperature was adjusted to 1100℃, the modification time was adjusted to 90min, and TFe was calculated. mjk =65.17%.

[0275] The iron content of 399.2 kg of high-quality iron ore obtained after the process parameters were adjusted was tested and the result was 65.15%.

[0276] Comparative Example 1

[0277] A method for upgrading low-grade iron ore, the method comprising the following steps:

[0278] 1) 450.2 kg of iron-containing minerals were added to the rotary kiln, and 50 kg of sodium carbonate and 12.5 kg of sodium sulfate were added to the rotary kiln, and the temperature was raised to 950 ° C. After reacting at 950 ° C for 110 minutes, the roasting modification was completed to obtain 484.9 kg of hot modified material; then when the inside of the rotary kiln was cooled to 700 ° C, the flow rate was 0.753 m 3 / min of hydrogen, and after 45 min of reduction in a reducing atmosphere, the magnetic reduction was completed to obtain 472.5 kg of magnetic iron oxide;

[0279] 2) Grinding and magnetic separation of the obtained 472.5 kg magnetic iron oxide to obtain 401.2 kg iron ore and 71.3 kg tailings.

[0280] The iron content of 401.2 kg of iron ore was tested and the result was 54.72%. In addition, ring formation appeared inside the rotary kiln.

[0281] Comparative Example 2

[0282] 1) 450 kg of iron-containing ore was ground and screened to obtain 417.1 kg of large-size ore with a particle size of not less than 0.5 mm and 32.9 kg of small-size ore with a particle size of less than 0.5 mm;

[0283] 2) 417.1 kg of large-size ore was added to a rotary kiln, and 50 kg of potassium sodium carbonate and 12.5 kg of sodium sulfate were added to the rotary kiln, and the temperature was raised to 950° C. After reacting at 950° C. for 110 minutes, the calcination modification was completed to obtain 451.6 kg of hot modified material;

[0284] 3) Add 451.6kg of hot modified material into the reduction drum, first cool it to room temperature, then heat it to 700℃ and add 32.9kg of small-size ore, with a flow rate of 0.75m 3 / min of hydrogen, so that the hot modified material and small-size ore were cooled and reduced at 6°C / min in a reducing atmosphere. After 45 minutes, the magnetization reduction was completed, and the magnetization termination temperature was 430°C, and 475.0 kg of magnetic iron oxide was obtained;

[0285] 4) The obtained 475.0 kg magnetic iron oxide was ground and magnetically separated to obtain 399.1 kg iron ore and 75.9 kg tailings.

[0286] Among them, the iron content in 399.1 kg of iron ore was tested and the result was 45.29%.

Claims

1. A method for upgrading low-grade iron ore, characterized in that: The method comprises the following steps: 1) crushing and screening low-grade iron-containing minerals in sequence to obtain large-size ore and small-size ore; 2) roasting and modifying the large-size ore to obtain a hot-modified material; 3) Cooling the hot modified material, and adding a reducing agent and small-particle ore during the cooling process to perform cooling and reduction treatment to obtain an iron-containing magnetic material; 4) subjecting the ferromagnetic material to grinding and magnetic separation in sequence to obtain iron concentrate; Before the process is put into operation, a mathematical model for the total iron content of the iron concentrate is established based on the raw ore and the adjustment and control of the parameters of each process, with the goal of ensuring that the total iron content of the iron concentrate meets the target requirements. The actual operating parameters of each process are then adjusted according to the mathematical model to ensure that the total iron content of the iron concentrate meets the target requirements. The mathematical model is as follows: Where, TFe mjk is the iron content in iron concentrate, %; TFe myk is the iron content in the ore, %; α is TFe myk The power of, where 0≤α≤N g ; N g TFe myk The highest power of a gα TFe myk The coefficient of the αth power; D mm is the grinding particle size, mm; β is D mm Power of; 0≤β≤N h ; N h D mm The highest power of a hβ D mm The coefficient of the βth power; S mx is the pulp concentration during beneficiation, %; χ is S mx Power of; 0≤χ≤N i ; N i For S mx The highest power of a iχ For S mx The coefficient of the xth power; R mh is the amount of reducing agent, %; δ is R mh Power of; 0≤δ≤N j ; N j R mh The highest power of a jδ R mh The coefficient of the δth power; Q mfl is the amount of powder added, %; ε is Q mfl Power of; 0≤ε≤N k ; N k Q mfl The highest power of a kε Q mfl The coefficient of the εth power; T mcz is the magnetization termination temperature, °C; φ is T mcz Power of; 0≤φ≤N l ; N l T mcz The highest power of a lφ T mcz The coefficient of the φth power; t mch is the magnetization time, min; γ is t mch Power of; 0≤γ≤N m ; N m t mch The highest power of a mγ t mch The coefficient of the γth power; T mgx is the modification temperature, °C; η is T mgx Power of; 0≤η≤N n ; N n T mgx The highest power of a nη T mgx The coefficient of the nth power of t mgx is the modification time, h; ι is t mgx The power of ; 0≤ι≤N o ; N o t mgx The highest power of a oι t mgx The coefficient of the ιth power of ; wherein A, B, C, D, E, F, G, H, and I are the influence coefficients of each process parameter on the iron content in high-quality iron ore; the value range of A is 0.04-0.1, the value range of B is 0.05-0.13, the value range of C is 0.03-0.08, the value range of D is 0.11-0.15, the value range of E is 0.06-0.15, the value range of F is 0.1-0.15, the value range of G is 0.14-0.19, the value range of H is 0.10-0.15, and the value range of I is 0.11-0.17; the sum of A, B, C, D, E, F, G, H, and I is 1; N g 、N h 、N i 、N j 、N k 、N l 、N m 、N n 、N o The value range is 1 to 5.

2. The method according to claim 1, wherein: The iron content of the low-grade iron-containing mineral is 30% to 65%; and / or The particle size of the large-size ore is not less than 0.5 mm; the particle size of the small-size ore is less than 0.5 mm.

3. The method according to claim 1 or 2, characterized in that: The roasting modification is to use a modifier to perform any one or more of oxidation roasting, sodium roasting, potassium roasting, phosphorylation roasting, sulfuric acid roasting, and calcification roasting on the large-particle ore.

4. The method according to claim 1 or 2, characterized in that: The low-grade iron ore includes any one or more of hematite, limonite, phosphite, siderite, goethite, specularite, red mud, iron-containing dust, copper slag, nickel slag, and iron-containing smelting slag.

5. The method according to claim 3, wherein: The modifier includes any one or more of sodium salt, potassium salt, phosphate, sulfuric acid or sulfate, and calcium salt.

6. The method according to claim 5, characterized in that: The sodium salts include sodium hydroxide, sodium carbonate, and sodium chloride; the potassium salts include potassium hydroxide, potassium carbonate, and potassium chloride; the phosphates include phosphorus pentoxide, phosphoric acid, sodium phosphate, and potassium phosphate; the sulfates include potassium sulfate and sodium sulfate; and the calcium salts include calcium oxide, calcium hydroxide, calcium carbonate, and calcium chloride.

7. The method according to claim 3, wherein: The mass of the modifier is (5%, 40%) of the mass of the large-particle ore.

8. The method according to claim 7, wherein: The mass of the modifier is [10%, 20%] of the mass of the large-particle ore.

9. The method according to claim 1 or 2, characterized in that: The calcination temperature is 400-1300°C; and / or The calcination modification time is 5 to 180 minutes.

10. The method according to claim 9, characterized in that: The calcination temperature is 600-1100°C; and / or The calcination modification time is 60 to 150 minutes.

11. The method according to any one of claims 1-2, 5-8, and 10, characterized in that: The cooling and reduction process is carried out in a dry slow cooling porous reduction cylinder; and / or The reducing agent is a solid reducing agent or a gaseous reducing agent; and / or The temperature when the reducing agent is added is 400-1000°C; and / or The cooling rate of the cooling process is 2 to 10°C / min; and / or The magnetization time is 5 to 60 minutes; and / or The small-particle ore accounts for 2% to 50% of the mass of the thermally modified material.

12. The method according to claim 11, wherein: The reducing agent is any one or more of coal, biomass, coke, hydrogen, blast furnace gas, converter gas, and coke oven gas; and / or The temperature when the reducing agent is added is 600-900°C; and / or The cooling rate of the cooling process is 4-8°C / min; and / or The magnetization time is 30 to 50 minutes; and / or The small-size ore accounts for 5% to 20% of the mass of the thermally modified material.

13. The method according to claim 11, wherein: The mass of the solid reducing agent is 1% to 30% of the mass of the large-particle ore; the gas-solid ratio of the gaseous reducing agent to the large-particle ore is 50 to 1000 kg / m 3 .

14. The method according to claim 13, wherein: The mass of the solid reducing agent is 2% to 15% of the mass of the large-particle ore; the gas-solid ratio of the gaseous reducing agent to the large-particle ore is 300 to 900 kg / m 3 .

15. The method according to any one of claims 1-2, 5-8, 10, 12-14, characterized in that: The grinding method is any one of ball mill, vertical mill, rod mill and roller mill.

16. The method according to any one of claims 1-2, 5-8, 10, 12-14, characterized in that: The grinding particle size is less than 325 mesh accounting for more than 80%; and / or The ore pulp concentration during the magnetic separation is 20-70%.

17. The method according to claim 16, wherein: The grinding particle size is less than 325 mesh accounting for more than 90%; and / or The ore pulp concentration during the magnetic separation is 25-50%.

18. The method according to any one of claims 1-2, 5-8, 10, 12-14, and 17, characterized in that: The actual operating parameters of each process are adjusted according to the mathematical model so that the total iron content of the iron concentrate meets the target requirements. Specifically, according to the target value of the iron content in the high-quality iron ore, the grinding particle size, slurry concentration, reducing agent dosage, powder addition amount, magnetization termination temperature, magnetization time, modification temperature, and modification time are adjusted in sequence until the iron content in the high-quality iron ore reaches the target value; if the target value is still not reached after one round of adjustment, the adjustment and optimization are repeated until the iron content in the high-quality iron ore is not lower than the target value.

19. The method according to claim 18, wherein: The target value is that the iron content in high-quality iron ore is not less than 55%.

20. The method according to claim 19, wherein: The target value is that the iron content in high-quality iron ore is not less than 65%.

21. The method according to claim 18, wherein: The reducing agent is a solid reducing agent; The experiment was conducted to investigate the effect of various processes on the iron content in iron concentrate, with the following settings: According to the change of total iron content in the raw ore, the empirical fitting of formula (2) was performed to obtain the formula that the change of total iron content in the raw ore affects the total iron content of the iron concentrate: Similarly, set: According to the change of grinding particle size, the empirical fitting of formula (4) was performed to obtain the formula that the total iron content of iron ore affected by the change of grinding particle size is as follows: set up: According to the change of slurry concentration, the empirical fitting of formula (6) was performed to obtain the formula that affects the total iron content of iron concentrate based on slurry concentration: set up: According to the change of reducing agent dosage, the empirical fitting of formula (8) was performed to obtain the formula of the total iron content of iron ore affected by the change of reducing agent dosage: set up: According to the change of powder addition amount, the empirical fitting of formula (10) was performed to obtain the formula of the influence of the total iron content of iron ore based on the change of powder addition amount: set up: According to the change of magnetization termination temperature, the empirical fitting of formula (12) is performed to obtain the formula that the total iron content of iron ore affected by the change of magnetization termination temperature is: TFe m6 =-0.0006T mcz +0.9139……(Formula 13) set up: According to the change of magnetization time, the empirical fitting of formula (14) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of magnetization time: set up: According to the change of modification temperature, the empirical fitting of formula (16) was performed to obtain the formula that affects the total iron content of iron ore based on the change of modification temperature: TFe m8 =4.06*10 -4 *T mgx +0.2415……(Equation 17) set up: According to the change of modification time, the empirical fitting of formula (18) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of modification time:

22. The method according to claim 18, wherein: The reducing agent is a gaseous reducing agent; The experiment was conducted to investigate the effect of various processes on the iron content in iron concentrate, with the following settings: According to the change of total iron content in the raw ore, the empirical fitting of formula (2) was performed to obtain the formula that the change of total iron content in the raw ore affects the total iron content of the iron concentrate: Similarly, set: According to the change of grinding particle size, the empirical fitting of formula (4) was performed to obtain the formula that the total iron content of iron ore affected by the change of grinding particle size is as follows: set up: According to the change of slurry concentration, the empirical fitting of formula (6) was performed to obtain the formula that affects the total iron content of iron concentrate based on slurry concentration: set up: According to the change of reducing agent dosage, the empirical fitting of formula (8) was performed to obtain the formula of the total iron content of iron ore affected by the change of reducing agent dosage: set up: According to the change of powder addition amount, the empirical fitting of formula (10) was performed to obtain the formula of the influence of the total iron content of iron ore based on the change of powder addition amount: set up: According to the change of magnetization termination temperature, the empirical fitting of formula (12) is performed to obtain the formula that the total iron content of iron ore affected by the change of magnetization termination temperature is: TFe m6 =-0.0002T mcz +0.7098……(Equation 25) set up: According to the change of magnetization time, the empirical fitting of formula (14) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of magnetization time: set up: According to the change of modification temperature, the empirical fitting of formula (16) was performed to obtain the formula that affects the total iron content of iron ore based on the change of modification temperature: TFe m8 =2.582*10 -4 *T mgx +0.4112……(Equation 27) set up: According to the change of modification time, the empirical fitting of formula (18) was performed to obtain the formula that affects the total iron content of iron concentrate based on the change of modification time:

23. The method according to any one of claims 1-2, 5-8, 10, 12-14, 17, 19-22, characterized in that: The method further comprises: 5) pumping unreacted reducing gas in the reduction process into the roasting and modification process for combustion to provide heat.

Images