The Robuschi ROBOX energy screw compressors for the low pressure range deliver considerable energy savings in comparison to the rotary lobe blowers which are widely used in wastewater treatment plants. The direct drive with permanent magnet motor reduces energy consumption by up to 30%. Additional savings of 30% can be achieved by using the "Smart Process Control" control system.
Gardner Denver development engineers have managed to considerably reduce the energy costs for the aeration of sludge tanks in wastewater treatment plants.
The ROBOX energy series is the first to consistently utilise the possibilities of gearless, direct drive technology with permanent magnet motors. The advantage of these synchronous motors is that they offer excellent controllability within a large speed range while maintaining a high level of efficiency.
The low power consumption of these electric motors- better than IE4 - and the integration of the control technology in the overall "wastewater treatment plant" system results in energy benefits in comparison to the blowers that were previously used in this area with conventional three-phase asynchronous motors, which drive the compressor screws via gears.
With these new compressors, it is possible to reduce the high energy costs for generating blow air for the biological treatment stage, in which bacteria break down the organic components of the wastewater, by around 30% in comparison to the rotary lobe blowers which are normally used. This means that owners of wastewater treatment plants in communal or industrial areas can breathe easy, as they rank as one of the largest energy consumers and more than 40% of their overall energy requirement is due to the sludge tanks. Here, there is enormous potential for reducing costs and increasing efficiency which can be tapped with the ROBOX energy technology.
The fact that the drive of the oil-free, proven Robuschi screw compressor block with patented rotors now works directly, i.e. without belt and gear, through the permanent magnet motor technology brings twofold benefits: the optimum ratio between the delivery rate and pressure, which the rotors generate, enables the high level of efficiency to be maintained from low to high speeds.
The new drive covers the large speed range with high efficiency, and the fluctuating air volume requirement in the settling basin - even or especially for low volume flows -can therefore be precisely controlled. The drive control unit, a frequency converter, is decentrally housed in an integrated and air conditioned electrical control cabinet.
In addition to the aforementioned 30%, users of ROBOX energy screw compressors can also benefit from even further energy saving potential. The "Smart Process Control" control system lowers the energy requirement even further in practice by around 20 to 30%, by ensuring that only the required amount of compressed air or blow air is provided. This is achieved by analysing the oxygen data acquired during the treatment process, i.e., by intelligently linking to the process control system of the wastewater treatment plant
Its compact design is another plus point. In comparison to the ROBOX SCREW series with conventional drive, the space required has been reduced by approximately 1/3. This is an important factor when it comes to equipping existing wastewater treatment plants and other plants with energy-saving compressor and blower technology. The ROBOX energy screw compressors are controlled via an operating unit with touchscreen. The intuitive menu structure is user-friendly and parametrisation can be carried out conveniently via Ethernet or Internet. This means that it also meets the requirements for online remote diagnostics and continuous plant monitoring.
The newly developed series, whose advantages have been documented in tough practical tests, has been launched with four sizes. The systems with motor powers of 34, 50, 84 and 135 kW achieve a delivery volume of 1,030 to 4,250 m3/h over a pressure range of 250 to 1,000 mbar (g).