Zest WEG is supplying a TGM planetary gearbox with a WEG variable speed drive (VSD) and a WEG medium voltage motor for a mill expansion by Green Fuel, Zimbabwe’s leading producer of renewable fuel.

According to Leandro Magro, steam turbines manager at Zest WEG, the equipment is destined for the new sugar cane crushing mill #6 at Green Fuel’s state-of-the-art ethanol facility at Chisumbanje in south-eastern Zimbabwe. The plant 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.

Green Fuel’s ethanol project – awarded National Project status by Zimbabwe’s government for its economic contribution – reduces the country’s reliance on imported petroleum products. It also produces less greenhouse gas emissions than unleaded petrol, and can be sold significantly cheaper. The company employs over 3,000 people in its agricultural and industrial operations.

“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,” says Magro. “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 constant 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 the beginning of its operation. During its plant expansion from 2017 to 2018 we supplied a planetary gearbox, motor and VSD for mill number 1,” he says. “Our current contract is for a second expansion, where Zest WEG will supply similar equipment to mill #6.”

While the gearbox is 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 11kV to the required motor voltage of 3.3kV. Delivery will take place by year-end, although the high efficiency motor will be supplied earlier from WEG in Brazil. Installation of the equipment on site will be conducted in early 2021, over a period of 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 that everything is running optimally,” Magro says. “Using several production facilities around the world, Zest WEG provides its customers in Africa an integrated solution that combines the highest quality of equipment with our in-depth industry expertise.”