Extractive Metallurgy of Molybdenum (Mo)

In The Earth, Molybdenum is found as Molybdenite (MoS2), Jordisit (MoS2), Drisdallite (Mo(Se,S)2).

Figure 1. Molybdenite (MoS2)

Figure 2. Jordisite (MoS2)

Figure 3. Drysdallite (Mo(Se,S)2)

-->

Many products flow from the mining and processing of ores containing molybdenite (MoS₂), including:

1. Chemical Mo products

Used in catalysts, polymer compounding, corrosion inhibitors, and high-performance lubricant formulations, these include pure molybdic oxide and molybdates, and lubricant grade MoS₂.

2. Meltstock products

Used as alloy additions to iron, steel, nickel, and titanium alloys, these include technical Mo oxide, ferromolybdenum, and Mo metal pellets.

3. Mo metal products

These include powder, Mo metal and Mo-base alloy mill products, and products fabricated from them such as LCD Screen, Air Plane Avionics etc.

Most of molybdenum used in stainless steel industry. Molybdenum is a ferrite former, so corrosion resistivity is very high.

-->

Before used, concentrate from flotation should be freed of sulfide which is done by roasting:

MoS₂ + 3 ½ O₂ = MoO₃ + 2 SO₂

MoS₂ + 3 O₂ = MoO₂ + 2 SO₂

Reaction in roasting occurs with heat evolution, process is carried out at 590-620 ^oC in Multiple hearth furnace.

Figure 4.

-->Production of Molybdenum Products

Figure 5. Roasting Plant

The next process for Chemical Mo dan Mo metal can be shown in Figure 6.

Figure 6. Production of Molydenum Chemical

-->

Ferromolybdenum (FeMo) producted by aluminothermic reaction:

MoO₂ + FeO + 2 Al = FeMo + Al₂O₃

This is a spontaneous reaction until 2000 ^oC with KMnO₄ as an ignition, phase diagram of Fe-Mo can be shown in figure 7.

Figure 7. Phase Diagram of Fe-Mo

-->

Ferromolybdenum (FeMo)

FeMo can be used in any melting or refining unit to produce Mo-containing steel or cast iron. It is frequently used as ladle addition to achieve accurate final adjustment of composition. In steels with low Mo content (usually no more than 0.2% Mo) like High Strength Low Alloy (HSLA) steel, all of the Mo is added as FeMo.

FeMo typically contains 65 – 75% Mo and a maximum of 0.5% Cu.

The product is produced in size ranges between:

0 and 10 mm, and 10 mm on the low side and several maximum size limits between 20 and 100 mm. It is available as powder for special applications like welding electrodes.

Figure 8. Ferromolybdenum


Figure 9. Ferromolybdenum Plant

-->

Packaging is normally in steel drums or big bags.

Product standards include:

ASTM A132-04 Standard Specification for Ferromolybdenum

DIN 17561, 2004-02, Ferromolybdän

Proses Pengolahan Bijih Timah (Sn)

Bijih timah di Indonesia ditemukan pada sabuk pulau Sumatera dalam bentuk Kasiterit (SnO₂). Proses pengolahan bijih timah sebenarnya cukup sederhana, hanya saja akan sedikit kesulitan dalam proses pemurniannya. Kesulitan itu disebabkan karena pengotor besi yang nilai kesetimbangannya hampir sama dengan timah.

Figure 1. Bijih Kasiterit (SnO₂)

Sebagaimana dengan bijih yang lainnya, proses benefisiasi bisa dilakukan dengan melakukan pengkonsentrasian secara gravitasi untuk meningkatkan kadar SnO₂ dalam bijih. Setelah kadar meningkat, bisa dilakukan reduksi (peleburan) SnO₂ sehingga terjadi reaksi berikut:

SnO₂ + CO = SnO + CO₂

SnO + CO = Sn + CO₂

Kesetimbangan fasa logam dan fasa terak adalah sebagai berikut:

Jila [a_Sn] = 1, maka :

Kesetimbangan untuk reduksi besi oksida sebagai berikut:

Berdasarkan kesetimbangan tersebut didapatkan:

Dari data termodinamika, K_Sn tidak terlalu jauh berbeda dengan K_Fe sehingga kemungkinan pembentukan Fe terjadi. Di samping itu Fe dapat larut dalam Sn, bahkan akan membentuk senyawa intermetalik sehingga sangat menurunkan kualitas logam Sn.

Figure 2. Binary Phase Diagram Of Fe-Sn

Sebaliknya, jika diinginkan dihasilkan Sn dengan kemurnian tinggi maka akibatnya kehilangan Sn (sebagai SnO dalam terak) akan membesar. Oleh karena itu peleburan timah umumnya dilakukan lebih dari satu tahap agar dapat dicapai hasil yang optimal, yaitu memproduksi timah dengan kemunian tinggi tanpa kehilangan yang besar.