Member press release – Suma – When energy demand leads the way: Reliable agitation technology for biogas plants
At a biogas plant near Krefeld, Germany, the daily feed rate varies between 35 and 80 tonnes in order to match gas production to energy demand. Suma’s central mixer Z-Mix ensures reliable plant operation.
Biogas plants were originally designed with combined heat and power units for the continuous generation of electricity and heat. As the existing Renewable Energy Sources Act (EEG) feed-in tariff periods in Germany come to an end, many operators are seeking viable business models for the future and are often turning to market-oriented electricity and heat production. A plant in the west of Germany is already controlling its gas production via an adjusted substrate feed and is balancing out short-term fluctuations using a gas storage facility.
Variable feed rates place demands on the agitation technology
Depending on the forecast, between 35 and 80 tonnes are fed into the digester each day, the composition of which depends on the availability of the feedstocks. These include slurry, manure and waste products from vegetable cultivation, in particular potato and onion residues. Before being put into the tank, the input material is shredded and diluted with the recirculate. The highly variable quantity and characteristics of the substrate pose a major challenge for mixing within the digester. The demand-driven approach requires a high degree of flexibility – both in plant operation and in the biology within the fermenter. Plant technology is needed that can reliably manage changing process requirements. This is exactly what our Z-Mix is designed for: it remains efficient ev
en under varying conditions and ensures stable plant operation’, says Dominik Stimmelmayer, Team Leader Application Support at Suma.
Process stability and maximum operational reliability
For the 20-metre-high steel digester, which is 18 metres in diameter and has a maximum volume of 4,489 m³, the tank manufacturer selected Suma’s Z-Mix central mixer, which was designed to meet the specified requirements using CFD simulations. The flow-optimised paddles generate powerful vertical mixing and ensure a high circulation rate throughout the entire tank volume. The consistent temperature distribution, monitored by several installed sensors, indicates a high degree of homogenisation without layer formation.
The 30 kW agitator is operated via a frequency converter at a rated rotational speed of 14 revolutions per minute in continuous operation. Suma has developed this type of agitator specifically for large fermenters and offers it in various sizes for tanks up to approximately 10,000 m³.
Reserves for the future
With the planned increase in the manure proportion, the dry matter content will rise from the current 8 per cent to 10 per cent. To ensure reliable mixing even under these more demanding conditions, the performance range, material selection and components of the central mixer have been chosen accordingly.
Furthermore, the drive, bearings and seal are accessible from the outside to enable inspection and maintenance
work to be carried out with minimal effort, without having to open the tank.
As a further step in the development process, the integration of a fuel cell into the operator’s plant design is intended. This will enable the use of the produced biogas to be even more flexible in future and better adapted to the demands of the energy market. The combination of demand-driven operation and high-performance agitation technology creates the conditions for stable and cost-effective plant performance, even under changing conditions in the digester.
-ENDS-
Notes to editor
About SUMA
SUMA Rührtechnik GmbH, headquartered in Sulzberg, Germany, has been developing and manufacturing high-grade agitators since 1957 for the biogas, agricultural, wastewater and industrial sectors. As a specialist in innovative agitation technology, SUMA offers customized solutions and is committed to the highest levels of quality, efficiency, and durability. A complementary range of pumps and comprehensive services round out the product portfolio. With more than 130,000 agitators installed in over 66 countries and an export share of two-thirds, SUMA has grown into an internationally successful company. The organization has multiple locations in Europe, North and South America, as well as Asia. For more information about SUMA, visit www.suma.de/en.
Contact:
Katharina Kuisle | Phone: +49 8376 / 92131 93 | Email: KuK@suma.de
SUMA Rührtechnik GmbH | Martinszeller Str. 21 | 87477 Sulzberg / Germany
