Biogas plants with LARAN® mixed digester
This wet digestion technology is based on use of the simple and cost effective LARAN® mixed digester and can be implemented as a mesophilic or thermophilic process, either as single digestion or in a two-stage configuration with a combination of main digester and post-digester.The LARAN® mixed digester is the preferred system for agricultural products, such as easily digestable silages or simple-to-handle liquids such as manure or process wastewater with high organic load. Alternatively, it can also be installed as a post-digester or process wastewater storage facility downstream of a main digester of a different type, e.g. a dry digestion.
The vessel is usually designed with diameters up to 30 metres, which provides a total volume of approx. 4,000 m³ in combination with a typical height of approx. 6 metres. Larger digesters are possible where required. The vessels can be mode of reinforced concrete (monolithic or prefabricated) or steel (welded or bolted plate) and are usually covered with a membrane roof serving as a gas holder.
Mixing is done with conventional, commercially available agitators, whose number and size can be varied according to the digester volume and feedstock. For certain applications, the predominantly horizontal mixing achieved with the agitators can be supplemented or even replaced with a special STRABAG system for vertical mixing.
With suitable waste inputs, such as process wastewater with high organic load and no significant unsuspended solids, a STRABAG system for biomass retention can be integrated into the LARAN® mixed digester to shorten the usually necessary retention time and thereby significantly reduce the digester volume.
Process characteristics and benefits:
- Standardised, simple and cost effective design
- Vessel volumes and materials can be adapted to the project and site conditions
- Use of widely proven and commercially available components for mixing, heating and gas dome
- Possibilities for process optimisation by incorporating STRABAG systems for vertical product mixing and biomass retention, if necessary
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