District heating from biomass
Bad Mergentheim site in Germany has been generating environmentally friendly heat and electricity from regional biomass for over a decade. The increasing demand in the district heating network at the site must be covered.

Stadtwerk Tauberfranken GmbH – Bad Mergentheim site

More output, more efficiency – with existing technology

Bad Mergentheim site in Germany has been generating environmentally friendly heat and electricity from regional biomass for over ten years. The natural heat power plant on the outskirts of the town covers the heating requirements of around 2,000 buildings with regional wood chips. In order to meet the increased demand in the now significantly expanded district heating network, a concept was developed together with Kablitz and NESS Wärmetechnik to increase the efficiency of the existing plant – without requiring additional space or long approval procedures by the authority.

Project goals & advantages

Sustainability is a huge topic

In a brief study, Richard Kablitz GmbH investigated the potential for increasing the output and flexibility of the existing plant. The aim was to cover the increasing heat demand with minimal investment and without new construction areas. Targeted efficiency measures enabled operating costs and CO2 emissions to be reduced and plant output to be significantly increased. The conversion was implemented quickly and economically thanks to intelligent planning.

What does the customer say about the project?

Julian Bullmann | Head of heat generation and -distribution at Stadtwerk Tauberfranken GmbH

“Thanks to the successful efficiency improvements in the existing building and the excellent cooperation with our partners Richard Kablitz GmbH and NESS Wärmetechnik GmbH, we were able to sustainably increase the heat output from regenerative biomass for Bad Mergentheim. This project is a strong example of how the efficient use of resources, security of supply and climate protection can go hand in hand – in line with our goals at Stadtwerk Tauberfranken.”

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1)Requirements analysis and planning

Efficiency instead of new construction

Increasing energy consumption in the municipal utilities‘ district heating network resulted in growing pressure to the Stadtwerk Tauberfranken. The proportion of gas-based heat supply increased – an ecological and economic disadvantage. Instead of investing in a new heat generator, the idea was to exploit the existing performance potential of the biomass cogeneration plant. Together with the original installer, Kablitz, and NESS Wärmetechnik, a concept was developed to specifi cally increase the efficiency of the existing plant.

2)Technical solution & implementation

30% more district heating output

After analyzing the maximum firing capacity, a concept was developed to increase the district heating capacity by around 30 %. The existing conveyor technology offered sufficient reserves. Sensors, actuators and air flow were optimized for the higher fuel throughput and different load cases. An ash circulation system with cyclone separation improves the burnout of wet fuels.

To increase efficiency, the return temperature in the thermal oil system was lowered and a hot water economizer was installed. This reduced the exhaust gas temperature from 210 °C to 130 °C – with the recovered heat being fed directly into the district heating system. This increased the usable energy and increased the overall efficiency – without any structural expansion.

3)Planning & construction

Efficiency restructuring in record time

A detail project plan and time schedule was developed based on existing documents. The installation was carried out in two stages during planned shutdowns outside of the heating period. All installations were carried out in just 20 days of total downtime and the system was successfully commissioned in October 2023. The short project duration between submission of the tender and commissioning demonstrates the high feasibility of such efficiency measures
in existing buildings.

4)Realization during operation

+2 MW district heating through precise 3D planning

Despite the limited space available in the existing building, the district heating output of the biomass plant was increased by around 2 MW at a manageable cost. The boiler roof was opened up for the disassembly and reassembly of the large components. Continuous 3D planning enabled precise preparation and minimized the downtime of the plant. Preliminary work without plant downtime was completed in advance, so that after just four weeks of a cold combustion chamber, the conversion including commissioning was completed – and it was “fire free” again. In addition, the specific energy consumption was lowered, the security of supply increased and the need for fossil fuels significantly reduced – a complete success for efficiency, cost-effectiveness and climate protection.

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