RotaCut®: Reliable protection against foreign matter and improved efficiency

Case Study - Biogas plant owned by Agrargesellschaft Gischau mbH, Kuhfelde, Mr. Schulz, (owner)


Pump damage due to foreign matter, insufficient gas yield from the biogas plant


Vogelsang RotaCut® 5000pro Compact XL

Mr. Schulz, Agrargesellschaft Gischau, says:

We run a 190 kW renewable resources biogas plant with an upright digester and post digester.
In addition to the 12 m3 liquid manure from cattle, approx. 4-5 t corn silage, 2 t dung and 2 t grass silage were being used each day on average.

The problem

The grass silage is quite long as it is also used to feed young cattle. Furthermore, we have a great deal of foreign matter, which means that the rotary lobes in the installed rotary lobe pumps were needing to be replaced approx. every 4 weeks due to damage caused by foreign matter. The achieved gas yield did not live up to our expectations either.

The solution

In order to optimize the plant, increase the gas yield and reduce the amount of damage caused by foreign matter, we use the RotaCut 5000pro Compact XL. The RotaCut was installed on the suction side in front of the rotary lobe pump. Since January 2011, the fresh liquid manure from cattle has first been passed through the RotaCut, before arriving in the digester. The transfer from the digester to the post digester is carried out via AutoBlubb (pneumatic overflow); however it does not always work reliably due to the high viscosity. Missing quantities are also pumped into the post digester via the RotaCut.

The situation at our biogas plant has been looking much better ever since. The gas yield was increased by 5-10%, which has enabled us to reduce the amount of corn silage by approx. 25%, thereby increasing the proportion of long-fibered materials. If the viscosity goes up as a result of this, we successfully compensate for it by circulating approx. one cubic meter of digester contents per hour via the RotaCut.

Overall, the organic suspension is now more flowable and the power consumption of the mixers is lower. The service time of the rotary lobes has multiplied; in August 2011 the rotary lobes installed in January were still in use.

Mentioned Vogelsang products

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