Improving The Economic Efficiency Of Biogas Installations

The reason for their popularity is the relatively low energy consumption compared to high specific speed units with small propellers.

As the flow-off velocities of the medium cause lower losses on low specific speed agitators with large propellers, these are significantly more efficient from the point of view of energy consumption. Numerous empirical tests conducted by the pump manufacturer have shown the ratio of the generated axial thrust to the amount of power consumed to be best on this particular design. In biogas installations equipped with this agitator type thus far, the agitators are executed with a propeller measuring 2.5 m on diameter.

The Amaprop is placed in the centre of the basin which speeds up mixing of the fresh substrate with the fermentation medium. With the agitator in this position, the propeller thrust prevents the so-called teacup effect, i.e. an accumulation of dirt in the middle of the basin. A further advantage of the Amaprop in this position is that the agitator produces an energy-efficient circular flow which stops the dirt deposits forming a layer that either floats on the surface or sinks to the bottom of the basin. With this arrangement, more gas is produced than with discontinuously running high specific speed agitators producing uncontrolled mixing results.

For the rare event of over-acidification due to inconsistent feeding or excessive temperature fluctuations in either the primary or secondary fermenter, the system can be complemented with an additional agitator type Amamix. With its 16 kW motor rating and an 800 mm propeller diameter, the Amamix can be relied upon to stabilize the medium after a short period of operation. Because of their robust design, agitators only have to be serviced after 16,000 hours of operation or every other year.