Dry digestion in the LARAN® plug-flow digester
This patented dry digestion process was developed as a continuous, thermophilic or mesophilic process for the anaerobic treatment of richly structured substrates with a dry matter (DM) content from 15 to 50%, and has been in successful use for over 15 years.The digestion principle is based on a horizontal plug flow through a horizontal vessel (LARAN® plug-flow digester) with solely local mixing of the substrate by way of agitators.
A compact design and robust construction characterise the digester, which can either be cast in situ or made up from prefabricated concrete elements.
The digester is equipped with agitators which are arranged transversely to the flow direction and prevent uncontrolled sedimentation or the formation of swimming layers. The overlapping arrangement of the agitators guarantees targeted local mixing of the substrate, optimum release of the gas bubbles and reliable transportation of sediments to the digester discharge. The agitator drives operate intermittently and thus with very low energy consumption.
All components, such as feed unit, agitator drives, digestate discharge and gas system, are easily accessible from outside for easy maintenance.
The input material is fed into the digester in a semi-continous way by way of a compact feed unit. If necessary, the optimum DM content can also be adjusted at the same time. At the end of the process, the digestate is discharged together with sediments via the wear-resistant STRABAG vacuum discharge system.
In addition to the treatment of richly structured waste with high dry matter content, such as biowaste, green waste or household waste, this process is suitable above all for the mono- or co-digestion of richly structured energy crops or agricultural waste products (manure etc.).
Process characteristics and benefits
- Patented process, industrially approved over 15 years High specific biogas yield through plug-flow characteristics
- Continuous biogas production due to own continuous feeding system High operating reliability through multiple, individually driven and robust agitators with short shafts Local mixing allows control of scum and sedimentation layers and
- Transport of sediments to the discharge unit of the digester
- Unique and wear-resistant STRABAG vacuum discharge system
- Heating elements in the walls and floor allow secure heat transfer
- Flexible application of different substrates with variable DS content
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