Green Fuel’s state-of-the-art ethanol facility at Chisumbanje in southeastern Zimbabwe uses the latest technology to produce high-grade anhydrous ethanol, with a high-pressure boiler and a TGM steam turbine generator set increasing energy recovery. This allows the plant to be self-sufficient in its energy needs, and to generate excess electricity. South African company Zest WEG is supplying a TGM planetary gearbox with a WEG variable speed drive (VSD) and a WEG medium voltage motor for the latest mill expansion at the plant.

Leandro Magro, Steam Turbines Manager at Zest WEG, says the equipment is destined for the new sugar cane crushing mill #6 at the facility.

Green Fuel is Zimbabwe’s leading producer of renewable fuel. Its ethanol project – awarded National Project status by Zimbabwe’s government for its economic contribution – reduces the country’s reliance on imported petroleum products. Ethanol produces a lower level of greenhouse gas emissions than unleaded petrol, and can be sold at significantly cheaper prices. The company employs over 3 000 people in its agricultural and industrial operations.

Supplying ethanol plant expansion in Zimbabwe

The TGM planetary gearbox and WEG motor at Green Fuel in Zimbabwe.

Magro says, “The engineered gearbox for this project is custom-built by TGM in Brazil, a WEG Group company, and is supplied with a WEG VSD and WEG electric motor as a package. The components in this solution are designed to deliver the specific torque required to crush the cane to the customer’s specifications, reliably and efficiently.”

The output speed of the gearbox in operation is usually between five and seven revolutions per minute. To deliver the required rotating force, a 750 kW, 3 300 V WEG motor was specified, with a WEG VSD to facilitate speed variations. The volume and quality of cane being brought in from the fields to the mill varies during the harvesting season – usually from April to October or November – so the rate of crushing in the mill needs to be adjustable.

The TGM third-generation planetary gearbox is designed specifically for sugar cane mills, where torque variations are always a factor and robust construction is required. The bearings are designed to achieve more than 100 000 hours of operation. This means the equipment can run for up to 10 years before any major service intervention is required.

“WEG has supplied efficient and reliable equipment to Green Fuel since it began operating. In its 2017/2018 plant expansion we supplied a planetary gearbox, motor and VSD for mill number 1,” Magro says. “Our current contract is for a second expansion, where Zest WEG will supply similar equipment to mill number 6.”

While the gearbox is being manufactured and assembled in Brazil, the WEG VSD with integral transformer will be assembled in South Africa by Zest WEG. The transformer will step down power from 11 kV to the required motor voltage of 3.3 kV. Delivery will take place by year-end, although the high efficiency motor will be supplied earlier from WEG in Brazil, and installation of the equipment will be done in early 2021, over about two weeks. Zest WEG will be involved in the installation supervision and commissioning, which includes the required tests before the start-up.

“We also assist with the start-up of the equipment at the beginning of the crushing season, to ensure everything is running optimally,” Magro says.

“Using production facilities within the group and around the world, Zest WEG provides its customers in Africa with integrated solutions that combine the highest quality of equipment with our in-depth industry expertise.”

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