Thanks to two new Aerzen Turbo Blowers an industrial sewage treatment plant now works with highest energy efficiency in the Netherlands – inspite of the large capacity utilisation bandwidth from 50 up to 100 percent.
Between beginning of August and March the Aerzen customer produces approx. 9.000 tons of potato starch per week. With the production of starch as well as during its further process- ing a lot of waste water accumulates which is immediately prepared in a sewage treatment plant on the company site. In three activated sludge tanks the oxygen content is determined via sensors. In case of falling below the setpoint value, oxygen is fed in and the process air production activated via a pressure sensor.
For more than 20 years the process air-production has been effected at the customer first of all by Aerzen Positive Displacement Blowers Type GMb 16f13 with a max. power of 5.000 Nm3/h each. As the motors could be driven with two speeds, the conditions standstill, 50 and 100 percent were possible. In the meantime two units have been dismantled and replaced by two Aerzen Positive Displacement Blowers of series Delta Blower. “When we then planned the modernisation of our process air-production, we originally wanted to install two new positive displacement blowers of the already existing type GM 90S. However, at that time, Aerzener Maschinenfabrik has recommended to choose two new AT-urbo Blowers and to connect them with the two existing positive displacement blowers”, explains the production engineer. “The results of the calculations convinced us. The investment has already amortized via the energy costs in less than five years.”
Now a new AT-Turbo Blower of Type AT 300-0,8 produces the base load with a max. power of 10.000 Nm3 per hour, a smaller Turbo Blower of type AT 150-0,8, the peak load with a max. power of 5.000 Nm3 per hour. In case of further increasing requirement the two older positive displacement blowers are switched in addition. All units are speed-controlled and driven with a constant pressure of 0,6 bar. “Our waste water-introduction quantity fluctuates significantly depending on production and consequently also the processair-requirement. Therefore the installed capacity is fully utilised.“We do not maintain any reserves. In case of emergency an Aerzen rental machine replaces the failed capacity“, assures the production engineer. The described case of application shows that the process-air-requirement of a sewage treatment plant can be produced with highest possible energy efficiency, especially, if it can be realized with different machine types and power by a design concept. They can be defined as ideal base- and peak load units acc. to their constructive properties. Consequently the physical advantages of a flow machine (high energy efficiency in design point) can be ideally combined with the advantages of positive displacement machines (high controllability and good efficiency also in partial load operation).
