Requirement of Electrical Power in Smelters for Primary Aluminium

Hi Friends,


We all know that production of aluminium from calcined alumina in Aluminium is a power intensive process. On an average, the efficient aluminium producers are consuming about 13.5 MWh to 15.5 MWh of electrical power per tonne of aluminium. Most of the technology suppliers are putting efforts to minimise the specific electrical power consumption. But it appears that we have to travel a long way to bring down the electrical power requirement close to theoretical power requirement of about 9.53 MWh per tonne of aluminium.


For arriving at the theoretical power requirement, I have simply followed the Faraday's law of electrolysis as step by step described here under:

1. Atomic mass of aluminium = 27 gram / mole,
2. Valency of aluminium = 3,
3. Electro-chemical equivalent of aluminum, z = 27/3 = 9 grams.
4. The mass of aluminium deposited on electrode on paasage of one coulomb of charge is termed as Electrochemical equivalent.
5. For production of 1 tonne of aluminium per hour, m = 1 tonne = 1000,000 grams, t = 1 hour = 60 x 60 seconds = 3600 sec., z = 9.
6. Let i amperes of current is required.
7. Hence as per Faraday's Law of Electrolysis, m = z.i.t/F
8. or, 1000,000 = 9 x i x 3600/96500
9. Therefore, i = (1000, 000x 96500) /(9 x 3600) = 2978395 amperes.
10. Let the voltage across electrodes = 3.2 v.
11. Hence electrical power required = i x v /1000,000 MWh = (2978358 x 3.2) / 1000, 000 = 9.53 MWh/t of aluminium metal.
12. Taking 10% extra for inefficiencies, power required = 1.10 x 9.53 = 10.5 MWh/ tonne of aluminium.

The above calculation signifies that there is tremendous scope for reduction in electrical power consumption at least by 25 to 30% from present level in aluminium smelters.

Regards.

Kunwar Rajendra

Overall Material Balance for Typical Alumina Refinery

Hi Friends,

Developing material and thermal energy balance is a bit complicated as it involves calculations for individual unit operations and unit processes for Alumina refinery taking into account the physical and chemical changes during processing. However, in simple format, I have presented here the overall material balance for a typical 1.5 Mtpa Alumina refinery.


Regards.


Kunwar Rajendra

World Bauxite Reserves & Production

Hi Friends,


Bauxite Reserves in World:

As per the latest published literatures and data available on public domain, the total Bauxite reserves in the World is around 39930 Million tonnes (Mt). Countrywise reserves are tabulated below-

1. Guinea: 8600 Mt
2. Australia: 7900 Mt
3. Vietnam: 5600 Mt
4. India : 3290 Mt
5. Brazil : 2500 Mt
6. Jamaica : 2500 Mt
7. China : 2300 Mt
8. Greece: 650 Mt
9. Guyana : 900 Mt
10. Kazakhastan : 450 Mt
11. Rusia : 250 Mt
12. Suriname : 600 Mt
13. Venezuela : 350 Mt
14. USA : 40 Mt
15. Other countries:4000 Mt

From above mentioned data, it is evident that Guinea stands at no.1 and accounts for about 21.5 % of total reserves in the World where as Australia, Vietnam and India has got the reserves of 19.8%, 14% and 8.2 % respectively. With respect to Bauxite qualitywise, India has the best quality bauxite having high alumina content, low silica content and moderate iron content. Vietnam stand at no.2 on quality of Bauxite in the World. Majority of Bauxite in India and Vietnam are gibbsitic in nature with reasonably high extraction efficiency which will attribute in lower production cost of alumina. Though Guinea has huge Bauxite reserves but the quality wise inferior compared to those of other countries.

World Production of Bauxite:

In 2007, World production of Bauxite was 213 Million tonnes (Mt) which was over 10.3% higher than 2006 production of 193 Million tonnes. Countrywise production of Bauxite in World for ten leading coutries in 2007 are given below-

1. Australia: 62.4 Mt
2. Brazil : 25.5 Mt
3. India: 23.1 Mt
4. Chnia: 21.6 Mt
5. Guinea: 18.5 Mt
6. Jamaica: 14.6 Mt
7. Russia: 6.1 Mt
8. Surinam: 5.3 Mt
9. Venezuela: 5.0 Mt
10. Kazakhastan: 4.9 Mt.

The total production of Bauxite in 2010 in the World  is estimated at around 215 Million tonnes as against 201 Million tonnes in 2009.


Concluding Remarks:

Austalia continued to remain as the leader in production of Bauxite for over three decades. The production during 2007 was mainly from five mines namely Huntly, Weipa, Gove, Willodale and Mt. Saddleback. In 2006, Huntly was the single largest mine in the World with Bauxite production of over 18 Million tonnes.

Brazil was the 2nd largest producer of Bauxite in 2007 leaving India, China and Guinea at 3rd , 4th and 5th position in Bauxite production. The majority of Bauxite deposits in China are owned by CHALCO and are Diasporic in nature with high silica content. Thus Bayer process combine with sinter process is adopted for recovery of alumina at high temperature and pressure.

In Guinea, there are three principal producers of Bauxite namely CBG, ACG and CBK. The Government formed Aluminium Company of Guinea (ACG) operates Bauxite mine for Alumina refinery in Fria. RUSAL has majority stake in ACG.

Though Vietnam stands at 3rd position with respect to Bauxite reserves in the World after Guinea and Australia but it has only one Alumina refinery owned by SBCC, Government of Vietnam. This plant is over 60 years old and has the honour of smallest Alumina refinery in the World and even today this plant is being operated efficiently. The 2nd Alumina refinery in Vietnam, Tan Rai Alumina plant of 600,000 tpa alumina production capacity is under execution with investment of around US$ 460 million. The plant is owned by Hanoi based Vinacomin. This plant is being erected by a chinese company under EPC contract and is expected to be commissioned by end of 2011.


Regarding specifications of Bauxite suitable for various applications along with implications on process and profitability shall be covered in forthcoming articles.

Regards.

Kunwar Rajendra