(A) General ferrochrome ore industry requirements listed in Table 1 and 2, which is a requirement blocks:
Smelting ferrochrome alloy with high-grade ore (or ore) industrial index 1
grade | Cr 2 O 3 content, % | Ferrochromium ratio | Contains P% | With S% | Containing SiO 2 % | Applicable conditions | |
Cr 2 O 3 | Cr 2 O 3 | ||||||
(FeO) | TFe | ||||||
I | ≥50 | >3 | >3.85 | - | - | <1.2 | For ferrochrome nitride |
II | ≥45 | ≥2.5~3 | ≥3.2~3.85 | <0.03 | <0.05 | <6 | Medium and low carbon and micro carbon ferrochrome |
III | ≥40 | ≥2.5 | ≥3.2 | <0.07 | <0.05 | <6 | Electric furnace carbon ferrochrome |
IV | ≥32 | ≥2.5 | ≥3.2 | <0.07 | <0.05 | <6 | Blast furnace carbon ferrochrome |
Note: 1. The blast furnace carbon ferrochrome is not less than 20 mm and not more than 75 mm;
2. The smelting ferrochrome alloy in electric furnace is not more than 60~40 mm (all powder or concentrate powder can be used);
3. The block size of chromite ore for refractory materials is 50~300 mm.
Industrial indicators for chromite ore for refractory materials Table 2
grade | chemical composition,% | use | ||
Cr 2 O 3 | SiO 2 | CaO | ||
I | >35 | <8 | <2 | Used as a natural refractory |
II | >30~32 | <11 | <3 | Manufacturing magnesium chrome brick and chrome brick |
Note: 1. Block size requirement: 50~300 mm;
2. There is no >5~8 mm stone in the ore.
Chromite ore for chemical chromium salts: 
A small amount of SiO 2 .
A small amount of SiO 2 . Chromite for diabase cast stone: Cr 2 O 3 >10~20%; SiO 2 <10%.
(2) Influence of harmful impurities in chrome ore on smelting
1. Sulfur and sulfur When smelting ferrochrome alloy, 10% enters the alloy. The alloy requires S<0.02~0.03%. Its harmfulness is the same as that of iron making.
2, phosphorus , in the smelting of ferrochrome alloy, 40 ~ 60% into the alloy, the alloy requires P <0.04 ~ 0.07%. Its hazard is the same as in iron making.
3, silica, ferrochrome alloy allows silicon content of 1.5 ~ 5%, the presence of SiO 2 in the raw material has little effect on the alloy, but its content is too high, it is necessary to add a large amount of limestone , maintain the appropriate alkalinity, and thus slag When the amount is increased, the amount of chromium carried in the corresponding slag is also increased, which affects the recovery rate of chromium.
4. The content of MgO in magnesia, ore (or concentrate) is more than 10%, the melting point of slag is increased during smelting, the viscosity is increased, and the power consumption is much. If the amount of limestone is used to cause high alkalinity slag and dilute the proportion of MgO, then the amount of slag is large, and the amount of chromium carried in the corresponding slag is also large, which affects the recovery rate of chromium.
(3) Calculation method of ferrochrome ratio
The ferrochrome ratio refers to the ratio of Cr 2 O 3 to FeO in chromite ore or its concentrate.
The chromite ore used for smelting ferrochrome alloys is an important indicator in addition to the Cr 2 O 3 grade, which is a measure of quality. Because of the low ferrochrome ratio of ore or concentrate, even if the grade of Cr 2 O 3 is high, it is difficult to produce high-grade ferrochrome.
The chromite ore or its concentrate used for smelting ferrochrome alloy contains iron minerals such as magnetite in addition to chromite ore. Therefore, all iron in ore or concentrate is often converted into oxidation. After the ferrous iron, calculate the ferrochrome ratio, ie
The above formula is more troublesome in practical application. Can it be calculated directly by TFe, that is, the ratio of Cr 2 O 3 to TFe is the ratio of ferrochrome to iron, which is based on iron of chromite ore or its concentrate, which is more than Cr. 2 O 3 is easy to reduce, and first enters the ferrochrome alloy, so it can be tried, but it should be pointed out that the ratio of ferrochrome listed in some existing books is calculated according to the above formula, such as using Cr 2 O 3 and TFe When the ratio is ferrochrome ratio of chromite ore or its concentrate, some data in some books should be converted and used. Otherwise an error will occur.
(4) Comprehensive recovery of accompanying components in chrome ore
Chromium deposits often associated with a platinum group (platinum, palladium, iridium, osmium, ruthenium and germanium) cobalt, titanium, vanadium, nickel and other elements. When the platinum content is greater than 0.2~0.4 g/ton, the cobalt content is greater than 0.02%, and the nickel is greater than 0.2%, comprehensive recovery should be considered. The surrounding rock has serpentine than peridotite and is a high-quality raw material for the production of calcium magnesium phosphate. In the shallow part of the ultrabasic rock mass, there is sometimes an amorphous magnesite that is leaching and is also a good raw material for refractory materials. Attention should be paid to comprehensive recycling.
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