Iron ore beneficiation technology

(1) Magnetic separation ore

1, single magnetic iron ore, mainly magnetite metamorphic deposition. Most of the iron minerals in the ore are magnetite, mainly composed of fine-grained inlays; the gangue minerals are mainly silicate minerals such as quartz or amphibole. Some have more iron silicates. The ore dressing production history is the longest. Due to the simple ore composition, weak magnetic separation is often used.

For large and medium-sized magnetic separation plants, when the grinding particle size is larger than 0.2 mm, a section of grinding magnetic is used first; when less than 0.2 mm, two-stage grinding magnetic separation is used. If coarse tailing can separate qualified tailings, phase grinding magnetic separation is used. In the water-deficient areas, dry-type grinding dry magnetic separation is used, and the magnetite-rich ore or lean magnetite is depleted. The gangue is generally removed by dry magnetic separation. The former obtains massive ore-rich ore; Choose to obtain concentrate. In order to obtain high-grade concentrates, magnetite concentrates can be treated by reverse flotation or shock sieves. In order to improve the recovery rate, it can be further recycled by considering processes such as tailings re-election.

At present, there is no reasonable utilization route for iron silicate. Therefore, iron silicate in ore does not emphasize recycling in ore dressing. Although iron ore can be recovered by the beneficiation method, since the iron grade in the iron-containing silicate mineral is low, the total concentrate grade will be greatly reduced, which is economically unreasonable. Generally speaking, when the charge contains a certain amount of iron silicate, it does not affect the large and medium-sized blast furnace, and the iron in the iron silicate is not lost from the slag; but in the small blast furnace, due to the iron silicate during the smelting process. It is an endothermic reaction with a low melting point. If a certain amount of iron silicate is contained in the charge, the furnace temperature is lowered to make the furnace condition not smooth, and the slag is run.

2, a multi-metal containing magnetite ore, mainly skarn sulfide-containing magnetite ore and a few magmatic apatite-containing magnetite ore, the ore particles in the form of a magnet (2 to 0.2 mm) to fine disseminated, pulse there silicate stone or carbonate minerals, frequently with calendar Polygonum iron, cobalt, brass or mineral pyrite and apatite. Such ores also have more ore dressing production practices. Generally, a weak magnetic separation and flotation combined process is adopted, that is, iron is recovered by weak magnetic separation, and sulfide or apatite is recovered by flotation. The principle process is divided into weak magnetic separation-flotation and flotation-weak magnetic separation. The two processes have different orientations of magnetite and sulfide. In the previous process, the continuous body mainly enters the iron concentrate; The latter process mainly enters the sulphide concentrate. Therefore, under the same grinding particle size, the post-floating magnetic process can obtain a sulfide concentrate with a lower sulphide content and a sulphide concentrate with a higher recovery rate.

Depleted ore can also be removed by dry magnetic separation, and then finely screened. Such ores are often self-fluxing and care should be taken to maintain the self-fluxing properties of the concentrate. There are high-containing, magnesium and some were isomorphic occur in the magnetite, iron difficult to separate by mechanical processing methods.

(2) Weak magnetic iron ore

1. Single weak magnetic iron ore, including hematite ore, siderite ore, limonite ore (mirror iron)-cementite ore of sedimentary metamorphic, sedimentary, hydrothermal and weathered deposits Wait. This type of ore dressing production practice is less, due to the variety of minerals, a wide range of inlaid grain size, the use of mineral processing methods are also more, the commonly used methods can be divided into two;

(1) Magnetization roasting magnetic separation or parallel flow with reselection, flotation, and strong magnetic separation. Roasting magnetic separation is one of the effective methods for selecting fine particles to fine particles (<0.02 mm) weak magnetic iron ore. When the minerals in the ore are complex and it is difficult to obtain good indicators by other methods, magnetization roasting magnetic separation should be used. 75~20mm lump ore has long-term production experience in shaft furnace reduction roasting; less than 20mm powder ore magnetization roaster has less practice. At present, fine ore is often selected by strong magnetic separation, re-election, flotation line method or joint process.

(2) Re-election, flotation, strong magnetic separation or a joint process. Flotation is also one of the commonly used methods for sorting fine particles to particulate weak magnetic iron ore. There are two principle processes of positive flotation and reverse flotation. The former applies to quartz hematite ore that does not contain easy-flowing gangue, and the latter applies to ore that is easy to float, and has production practices.

Re-election and strong magnetic separation are mainly used to select coarse particles (20~2 mm) and medium-grain weak magnetic iron ore. Due to these two methods, in recent years, there has been great progress in technology, and China has begun to use it. In the selection of fine-grained weak magnetic iron ore. The re-election of coarse and very coarse (>20 mm) ore is usually carried out by heavy medium or jigging; the medium to fine ore is treated by a liquid film re-election method such as a spiral concentrator, a shaker, a fan-shaped chute and a centrifugal concentrator. The strong magnetic separation of coarse and medium-grain ore is usually a dry induction roller type strong magnetic separator; the fine ore is usually a strong induction medium with strong induction medium. At present, because the fine magnetic ore concentrate of fine-grained ore is not high in grade, and the re-election unit has low processing capacity, it often forms a combined process of strong magnetic-re-election, discards a large number of qualified tailings with strong magnetic separation, and then re-selects further Handle strong magnetic concentrates to improve grade.

The application of the above various methods varies with the type of ore. Sedimentary metamorphic hematite ore, iron ore is mainly hematite, gangue is mainly quartz; mirror iron-siderite ore, iron mineral is mainly from siderite of mirror iron ore, gangue has quartz, jasper , barite and iron dolomite. These ores are all fine-grained, industrially using magnetic roasting magnetic separation or flotation methods, and methods such as strong magnetic separation and re-election are being studied.

Sedimentary braided hematite ore-ironite ore, iron minerals are mainly hematite and siderite, gangue has chlorite, quartz, and some calcite . Iron minerals are often embedded in micro-particles, which are closely symbiotic with the gangue and have a scorpion-like structure, which is difficult to dissociate. It is generally underground mining and is often depleted by surrounding rock. This type of ore is more difficult to choose. If it is rich ore or self-fluxing ore, the gangue is removed by heavy medium, jigging or dry magnetic separation to obtain a block-shaped finished ore. If it is richer ore, Commonly used roasting magnetic separation method, sometimes the block gangue is removed before roasting magnetic separation. As for the lean granule ore, even if roasting magnetic separation is used, the concentrate grade is difficult to reach more than 50%, and it is considered to remove the surrounding rock. Other high-grade concentrate ore mining or research direct reduction and other methods of combined metallurgy. Such ores are often higher aluminum-containing, iron ore concentrate should be noted that the silica to alumina ratio; self-fluxing or alkaline ores should be noted that the self-fluxing holding concentrate.

The hydrothermal quartz hematite ore and hematite-limonite ore are often unevenly embedded, and the combined processes of re-election, strong magnetic separation, and flotation are often used.

The accumulation of weathered deposits and the accumulation of limonite ore, containing more mud, generally adopts the re-election method, that is, the jigging and centrifugal concentrator are selected after washing, and the re-election-strong magnetic separation process can also be adopted. [next]

2. Polymetallic weak magnetic iron ore, mainly hydrothermal or sedimentary hematite or siderite containing phosphorus or barium sulfide. Such ores generally recover iron minerals by re-election, flotation, strong magnetic separation or a combination thereof, and recover phosphorus or sulfide by flotation.

The hydrothermal type apatite-containing hematite ore and copper-containing sulphur iron ore can be floated.

Sedimentary phosphorus-containing hematite ore, phosphorus in the state of colloidal phosphorus, although it can be separated from iron by flotation, it is often difficult to integrate phosphorus concentrate, and the iron recovery rate is much reduced. It can be considered to remove the large-grained gangue, smelt the high-phosphorus pig iron, and then recover the steel slag phosphate fertilizer.

The iron cap of weathered deposits contains limonite ore of non-ferrous metals, often accompanied by copper, arsenic , tin and other accompanying fractions without separate minerals. It is difficult to separate from iron by beneficiation method, and chlorination roasting is being studied. Red earth type nickel- chromium- cobalt-molybdenite-bearing medium, with no separate minerals, and methods such as roasting ammonia leaching and separation magnetic separation are under study.

(3) Magnet - Chi (Ring) Iron Ore

1. Single magnet-red (Ring) iron ore, mainly depositing metamorphic hematite-magnetite ore and diamond-iron ore. The iron minerals in the ore are magnetite and hematite or siderite, which are mostly fine-grained; the gangue is mainly quartz, and some contain more iron silicate. The proportion of magnets in the ore varies, from the surface of the deposit to the depth of the deposit. There are two common methods for this type of ore:

(1) Weak magnetic separation combined with reselection, flotation, and strong magnetic separation. The series process of recovering magnetite by weak magnetic separation and recovering weak magnetic iron mineral by re-election, flotation or strong magnetic separation has been used more recently. This is because weak magnetic separation of magnetite is far more economical than other methods, and most mines will gradually switch from processing magnets - hematite to magnetite. In this process, weak magnetic separation-flotation, flotation-weak magnetic separation and weak magnetic separation-reselection have been used for production; weak magnetic separation-strong magnetic separation and weak magnetic separation-strong magnetic separation-reselection are also Building a factory. Through production practice, the weak magnetic separation-flotation process tends to put the flotation before the weak magnetic separation, the production is more stable and easy to operate and manage; for the weak magnetic separation-re-election process, it tends to change to weak magnetic separation. - Strong magnetic or weak magnetic selection - strong magnetic selection - reselection process.

(2) Magnetization roasting magnetic separation or parallel flow with other methods. Similar to the magnetization roasting magnetic separation of a single weak magnetic iron ore, but in the parallel flow of magnetization roasting magnetic separation and other beneficiation methods, the fine ore is combined with weak magnetic separation and other methods. This parallel process has production practices. In addition, the series process of roasting magnetic separation and other methods has been studied, that is, the roasting magnetic separation concentrate is selected by flotation, re-election or rotating magnetic field magnetic separation to further improve the concentrate grade, which has not been used yet. produce.

The micro-embedded magnet-hematite ore is not easy to obtain good results by general beneficiation methods, and methods such as selective flocculation desilting and flocculation flotation are being studied.

2. Containing multi-metal magnets - Chi (Ring) iron ore, belonging to this type of ore, skarn-type sulphide-containing iron ore and hydrothermal phosphorus, sulfur or rare earth iron ore. The iron minerals in the ore are mainly magnetite and hematite or siderite, medium to fine grain inlay; gangue minerals are silicate and carbonate minerals or fluorite; the formation is divided into apatite and yellow iron. Mines, chalcopyrite and rare earth minerals. The ore dressing method of such ore is the most complicated in iron ore. Generally, the combined process of weak magnetic and other methods is adopted, that is, magnetite is recovered by weak magnetic separation; weak magnetic iron is recovered by re-election, flotation or strong magnetic separation. Minerals and flotation are used to recover companion fractions. Weak magnetic separation-flotation-strong magnetic separation, weak magnetic separation-strong magnetic separation-flotation and weak magnetic separation-re-election-flotation processes are being studied. For rare earth-containing mixed iron ore, when hematite is used as a large amount in iron ore, there is also a reduction roasting magnetic separation-flotation process, reduction roasting magnetic selection of iron minerals, and rare earth minerals after reduction roasting Flotation has improved the indicator.

In recent years, I have conducted comprehensive research on useful components such as me and non-ferrous metals in sulfuric acid slag. The ore dressing method is similar to natural iron ore and varies with the degree of oxidation of iron minerals. The black or brown black slag can be weak magnetic separation or weak magnetic separation-re-election method; the red slag is considered to be roasting magnetic separation or re-election; if it is difficult to be treated by the beneficiation method, various direct reduction methods can be used. For the useful components such as non-ferrous metals in the sulfuric acid slag, the chlorinated sulfuric acid was studied for comprehensive recovery by means of roasting and leaching, and chlorination volatilization.