RBCT Chief Executive Raymond Chirwa said in a statement on Monday the terminal's capacity would rise to 81 million tonnes by year-end from 76 million tonnes, and expand to 91 million tonnes a year in the first quarter next year -- a year later than initially targeted by RBCT.
The 1.2 billion rand ($160.2 million) expansion will consolidate Richards Bay's position as the single largest export coal terminal in the world.
"RBCT has embarked on technically commissioning Phase V on an upgraded and existing computer system, at the latest, by the end of the first quarter of 2010," Chirwa said.
"Coal is one of South Africa's strategic selling points. At RBCT we are committed to maintaining this position and playing our part in meeting customer demand in all of our markets."
Chirwa has previously said there was enough coal in South Africa and enough demand to justify the expansion, at least through the next decade. The expansion would also cater for emerging black-owned coal exporters.
The export terminal has been operating at less than its present capacity due to constraints on the rail network which transports coal from mines to the port.
South Africa is one of the world's major coal exporters, but regular train derailments and delays along the Richards Bay coal line have dented business confidence in Transnet Freight Rail's ability to meet international commitments.
Analysts say if South African state-owned logistics group Transnet does not deliver soon, the terminal could still be exporting around 60 million tonnes of coal despite the expanded export capacity.
RBCT shareholders include miners Anglo American , BHP Billiton, Xstrata , petrochemicals group Sasol and diversified mining group Exxaro.