According to Alastair Gerrard, managing director of Zest Energy, the plant will begin producing electricity during the first quarter of 2017, with an initial capacity of 12,5 MW from an installation of seven 2 200 kW diesel generators.
“The isolated location of the Balama mine – over 250 km west of Pemba in northern Mozambique – means that while the operation does have access to power from the national grid this will need to be supplemented to ensure an adequate supply for full plant demand,” Gerrard says. “We are therefore required by the customer to ensure 100% availability, and have consequently designed the plant with substantial standby capacity to allow for maintenance and repairs without affecting the continuous supply.”
He says the plant, which was the largest footprint project yet tackled by Zest Energy, would initially run with seven 2 200 kW generators; six running and one on standby, and would later be expanded to include eleven generators, of which two will be standby units.
Equipment for the extensive scope of supply has been sourced from various companies within the Zest WEG Group, locally and worldwide. The containerised power generators include WEG alternators with automatic voltage regulation systems, as well as motorised louvres, generator auxiliary systems, and fuel and lube tanks. To cool the engines, a horizontal-type radiator system, rated for 50°C ambient temperature, was manufactured in South Africa and each radiator includes 10 WEG 3 kW fan motors positioned in two cooling banks of five fans each.
“One of the challenges of the mine environment is the presence of graphite dust, which is highly conductive and must not be allowed to enter the power generation units,” Gerrard says. “For this reason, a filter system was designed that could accommodate the high volumes of moving air required to cool the engines, while also requiring as little maintenance as possible.”
Once again, a local solution was designed, in the form of a custom-engineered, self-cleaning cartridge type ventilation and pressurisation fan unit, comprising four WEG 7.5 kW fan motors.
To feed diesel to the generators, Zest Energy will install a 30 000 litre intermediate fuel tank to draw from the customer’s bulk fuel storage system with a duplex fuel filtration and circulation system as well as all interconnecting piping, valves, pumps and fittings within the power plant area.
A local fuel connection point within the plant area will also be installed as a contingency, should bulk fuel supply not be available. To comply with environmental regulations, a bunded fuel and oil area will be constructed, with and oil-water separation system.
“There are also various systems we will provide for plant auxiliary power requirements and for plant earthing and lightning protection, as well as cabling, terminations, racking and supports to all plant electrical equipment,” Gerrard says. “Through our member companies in the Zest WEG Group, we are able to give our customer a single point of contact for the range of services we are providing, while project managing and quality controlling every aspect of the power plant.”
