Integrated Drive Systems have boosted efficiency in fan application by 23 percent

The Best Available Technology for the combined processing of sludge and solid waste

Marie-Isabelle de Lobkowicz, marketing executive with Siemens Belgium, reports on the completion of a major drive train project Siemens recently accomplished in Belgium.

Doel, a town in the Belgian province of Oost-Vlaanderen is home to the Sleco plant, Europe’s largest fluidized bed incineration plant. This type of plant generates electricity with a steam turbine powered by the combustion of sludge and waste. The Sleco plant processes more than 580,000 tons of household and similar commercial waste per year. Recently, a capacity increase of the plant’s three fluidized bed incinerators was carried out. It revealed that the speed of the air condenser fans needed to be adjusted in order to meet actual cooling requirements. To accomplish this, the existing drive trains had to be replaced by stronger devices.

After approaching various suppliers for an offer, the plant operator, SVEX, finally awarded the contract to Siemens, after it had turned out that the Integrated Drive Systems approach made it possible to offer all the components from a single source. This is a huge advantage for the customer – from contacts management to servicing and scheduling and all the way to technical advice.

The new installation required a motor speed of 1,200 rpm, so our experts chose a 60 Hz Simotics AC motor. This turned out to be the best solution in terms of both size and cost. The gearboxes were dimensioned with a service utilization factor of 2, which means that it is suitable for providing twice the rated torque. This was considered necessary to guarantee a reliable installation, because the wind load on the fan shafts on the particular type of fans used at Sleco can be very high.

To ensure that system downtime was kept to a minimum, the installation of the drive trains had to follow a very tight and precise schedule. The fluidized beds are stopped for servicing purposes every four years, and as this servicing was due, there was a three-day working window. During this time, all cabling had to be connected and the first motors and gearboxes installed, so that the first fluidized bed incinerator and its turbine could be returned to service after three days.

Thanks to precise project management and the perfect integration of all Integrated Drive Systems components, this goal was accomplished without significant problems.

Measurements that were carried out a week after the complete restart of the new Sinamics drives showed that the air condensers’ capacity had increased by 23 percent – well in excess of the 20 percent that were projected. This means that the total profitability of the project is higher than predicted.

With our Integrated Drive Systems approach we were able to provide a uniform solution comprising components that interact seamlessly. The outstanding efficiency of the new drive trains ensures that the investment will have paid for itself within only two years. Moreover, the customer benefits from the added advantage that all components are from a single supplier and that there is a single point of contact for all drive train issues.