Efficient and cost-effective RDF-fired heat and power plant for paper factory Vrancart
High efficiency at small scale
Large scale RDF-fired heat and power plants often struggle with total efficiency, as a significant portion of heat is released unnecessarily. The primary goal for the Vrancart project was to demonstrate that a smaller 15 MWt unit could be designed for a lower investment cost per MWt than a conventional 100 MWt plant, while achieving a significantly higher total efficiency by fully utilizing the heat for local processes. Due to its high efficiency, significant savings are achieved not only in electricity purchases but also in gas cost savings. This results in payback periods of 2 to 4 years, depending on waste processing costs, gas and electricity costs in the country concerned.
A critical feature for achieving high availability is the innovative staged combustion system, which minimizes fouling and corrosion. Flue Gas Recirculation (FGR) is used under the grid and at two stages above the grid, reducing the O₂ content in the flue gas to 4-6%. This effectively halves the energy loss in the flue gas compared to an air-blown furnace for dry fuels. FGR maintains low temperatures on the grid, which prevents ash melting, reduces entrainment and mineral evaporation, and ensures a longer lifetime for grid elements. Furthermore, a unique throat/venturi design and double-gas turning ensure optimal O₂/flue gas mixing and high temperatures at the top of the furnace, resulting in CO emissions below measuring levels.
Modular design meets advanced combustion
HoSt leveraged its 30+ years of thermal technology experience to integrate several key features. The 15 MWt plant is engineered for an exceptional total efficiency of up to 90%. By capturing and utilizing all heat in the Vrancart production process, the installation maximizes energy output, a major benefit over the low efficiencies of large-scale plants.
A key innovation is the patented standing boiler design, positioned adjacent to the furnace rather than suspended above it (the conventional method). This standardized, modular approach reduces building height and expensive foundations, eliminates the need for a costly steel structure to suspend the boiler, and shortens on-site assembly time to just one week, reducing construction costs and time.
Months of continuous operation
The optimal combustion conditions and boiler design proved to be effective. The Vrancart waste incinerator ran from the end of October until the beginning of July with very limited fouling. It required no cleaning other than the normal operation with soot blowers, confirming the high-availability goals of the project.
For high fuel flexibility, the plant can process waste with a caloric value between 9 and 16 GJ/ton. This versatility requires the fuel to be prepared by shredding it to 200 mm and homogenizing it via a buffer system.