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MULANJE MOUNTAIN BAUXITE

June 02, 2021 / Grain W. P. Malunga
...
Minerals, Geology, Environment and Corporate Affairs Expert

ABSTRACT

MET-CHEM Canada Inc., on behalf of MIDCOR, carried out a feasibility study on the techno-economic  evaluation of the feasibility of setting up an integrated alumina/aluminium plant based on Mulanje mountain bauxite. The study was undertaken in 1993 through funds from African Development Bank.

The results of the 1993 feasibility study show that a combination of probable and indicated reserves of bauxite amounts to 25.6 million tonnes using a cut off grade of 30% Al2O3. An annual extraction of 580 thousand tonnes of bauxite will produce  200 thousand tonnes of alumina which in turn will produce 100 thousand tonnes of aluminium through the use of Bayer process in Alcan P-180 cells.

The capital cost estimate for the project is estimated at US$ 820 million with an Internal Rate of Return (IRR) 7.4% for alumina and 6.2% for aluminium. The corresponding payback periods are 15 and 17 years respectively.

1.0     INTRODUCTION

Mulanje mountain bauxite is situated about 70 kilometres east of Blantyre city. On its foot is situated Mulanje Boma (district headquarters). A Tarmac road connects Mulanje Boma to Blantyre and a rail line from Blantyre to Beira passes through Luchenza township about 30 kilometres west of the massif. A 66 Kv electric line is available from Nkula Hydroelectric Power Station. Telecommunication system is very good.

The low lying areas around Mulanje massif experience warm to hot and humid weather with an annual mean temperatures of about 220 C. Annual mean maximum temperatures reach as high as 350 C in November in the Phalombe plain. The coldest month is July when temperatures reach as low as 10.8 0 C at Mulanje Boma.

2.0     DEPOSIT DESCRIPTION

Mulanje bauxite is a residual product which resulted from the weathering of syeno-granitic rocks that form Mulanje massif. Six extensive bauxitic areas have been identified, but the best deposits are found on Lichenya and Linje plateaux.

The bauxite is mainly a trihydrate gibbsite which lies over kaolinite and has free quartz and geothite as the main contaminants. Some of the quartz is semi precious.

A feasibility study conducted by LONRHO showed that the two deposits on Lichenya and Linje (Figure 1)amount to 28.8 million tonnes within an average depth of 4.5 metres.

Table 1 shows the average analysis of the bauxite:

Table 1: Mulanje bauxite analysis

Al2O3 Free Quartz Combined Silica Fe2O3 TiO2 Kaolinite LIO
  43.3   13.3   2.2  14.2  1.8  < 5.0 28.8

The bauxite deposit exists in form of lenses which are located on the plateaux at an elevation between 1800 and 2000 metres.  The bauxite will be mined through the use of a front end loader and a backhoe hydraulic shovel will load it into articulated trucks.

The bauxite will then be hauled to a loading bay where it will be transported by a ropeway to an alumina plant about 600 metres below.

The proposed mining output has been set at 580 000 tonnes of bauxite (on dry basis) to produce 200 000 of alumina tonnes per year to meet an annual production of 100 000 tonnes of aluminium.

The bauxite will be processed to produce alumina and aluminium. Run of mine bauxite will be beneficiated to reduce the quartz content as well as reduce the quartz size to an undersized product below a 65 mesh size. Bayer process will be used to transform the bauxite into alumina.    The next stage will be alumina smelting producing 100 000 tonnes of aluminium sows per annum based on the Alcan P-180 cell.  The aluminium smelting will depend on the availability power inthe region of 15.3 kWh per kg of aluminium produced.  The present power supply in Malawi cannot meet this demand.

The main waste from the bauxite processing will be the tailings from beneficiation plant and the red mud from the Bayer process.  The red mud will be washed in high capacity wash thickeners to remove chemicals derived from the Bayer process.  The red mud and the tailings will then be pumped to a mud disposal area.

3.0     LABOUR AND INFRASTRUCTURE

The proposed labour for Mulanje bauxite is divided into mine and ropeway, alumina plant and alumina smelter as shown in the Table 2 below:

Table 2: Proposed labour for Mulanje bauxite

DEPARTMENT    STAFF    HOURLY  CONTRACT    TOTAL
Mine and Ropeway     14      77       91
Alumina plant    236     326    143    705
Smelter    169     300         46
Total    419     703    143   1265

The above table includes 26 expatriates in the alumina plant and 29 in the smelter. They are expected to be in Malawi for a  period of up to 4 years.

The plants and residential areas will be supplied with water from a dam in the Likabula river.

There is enough electricity to supply the alumina plant, but for the smelter more electricity will have to be sourced elsewhere. Suggestions have been made to import electricity through inter connector grid through Southern Africa Power Pool.

4.0     PROJECT SCHEDULE

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