Zimbabwe Green Fields ethanol
The TGM planetary gearbox and WEG motor at Green Fuel in Zimbabwe. image: Green Fuel

Green Fuel’s ethanol facility in Chisumbanje, Zimbabwe is expanding its mill operations with a new high-pressure boiler to increase energy recovery.

Electrical and instrumentation engineering and project management services company Zest WEG will supply a TGM planetary gearbox with a WEG variable speed drive (VSD) and WEG medium voltage motor for the latest mill expansion at the plant.

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Leandro Magro, steam turbines manager at Zest WEG, said the equipment is destined for the new sugar cane crushing mill #6 at Green Fuel’s state-of-the-art ethanol facility in south-eastern Zimbabwe. The plant produces high-grade anhydrous ethanol, with a high-pressure boiler and TGM steam turbine generator set to increase energy recovery. This will allow the plant to not only be self-sufficient in its energy needs but also generate excess electricity.

The ethanol project employs more than 3,000 people in its agricultural and industrial operations and its ethanol product not only produces less greenhouse gas emissions than unleaded petrol but can be sold more cheaply.

Localised assembly to assist Zimbabwe’s ethanol production

“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,” explained Magro.

The volume and quality of cane being brought in from the fields to the mill vary during the harvesting season – usually from April to October or November – so the rate of crushing in the mill needs to be adjustable. Thus the specified motor had to be able to facilitate speed variations.

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.

While the gearbox is manufactured and assembled in Brazil, the electrical motor will be assembled in South Africa by Zest WEG. Delivery will take place by the end of 2020 and 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,” said Magro.

As a producer of anhydrous ethanol, The Green Fuel Ethanol Project is one of Africa’s first indigenous suppliers of biofuel on a large scale.