Manufacture Of Magnesium Oxide From Sea Water Mineral Processing Plant 0.4-30t/h Capacity

The feedstock is slaked lime (calcium hydroxide) and purified sea water. These have to be produced from the raw materials, which are limestone, fresh water and sea water. The limestone and fresh water are used to produce the calcium hydroxide, which is then reacted with the purified sea water to produce magnesium hydroxide.

About 1000 tonnes of limestone are used each day. The limestone is very pure calcium carbonate (over 98%), and is crushed and washed before being heated in a lime kiln to form quicklime (calcium oxide):

CaCO3 → CaO + CO2

This reaction is carried out in a rotary kiln at 1500 o C. Fresh water is then added to the quicklime to produce slaked lime (calcium hydroxide):

CaO + H2O → Ca(OH)2

About 150 million litres of sea water is used each day. The sea water is taken from the Boyne estuary for about 8 hours each day, and is stored in a large reservoir, where sand and other solid impurities settle out. It is then pumped through underground pipelines to the Premier Periclase plant, four miles upstream.

In a similar manner as with the fresh water, the sea water is acidified with sulfuric acid and passed downwards through a tower against a rising current of air which strips off carbon dioxide. The sea water then undergoes further clarification to remove excess sand and other particles by a settling process.Rate and product yield (temperature and pressure variables, catalysts etc.) Catalysts, or pressures other than atmospheric pressure, are not required for any of the reactions involved in the Premier Periclase process. There are no reversible reactions involved, so no compromises in relation to striking a balance between reaction rates and product yields are needed. In the reaction of sea water with calcium hydroxide:

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MgCl2 + Ca(OH)2 → CaCl2 + Mg(OH)2

conditions have to be chosen which will result in the production of large crystals of magnesium hydroxide, which will settle and filter more easily. To do this, the following is done:

• Dilution of the incoming sea water with spent sea water

• Seeding with a heavy slurry of magnesium hydroxide.

The reaction, which is a very rapid one, is carried out in large tanks (circular, and about 30 metres in diamete