Waste Wood CHP Plants (2-4 MWe)

The development of the MILENA gasification technology for Bio Methane production has resulted in application of the technology for other applications as well.

Dahlman is offering commercial size Bio-CHP plants based on the MILENA gasification technology and OLGA tar removal technology.  The figure below shows the basic layout of the configuration. The biomass is converted into producer gas in the gasifier. After cooling and partial dust removal by a cyclone, the tars and the remaining dust are removed in the OLGA gas cleaning. The tar is recycled to the combustor section of the MILENA were it acts as fuel. A wet scrubbing system is used to remove most of the water, chloride and ammonia from the gas. The cleaned gas can be used in the gas engine to produce heat and electricity.

The electrical efficiency of Bio-CHP’s using gasification technology can vary significantly. The efficiency is strongly influenced by the type of biomass, water content of the biomass, scale of the installation, type of gasifier, type of gas engine, level of integration and emission limits. The figure below shows the calculated net electrical efficiencies for MILENA based Bio-CHP’s. The fuel is demolition wood with 20% moisture. The scale is based on the selection of two 2 MWe gas engines. Residual heat is used for district heating.

The left column shows the efficiency assuming the producer gas is fired in a gas engine (GE). Adding an Organic Rankine Cycle (ORC) increases the electrical efficiency significantly. A further increase can be achieved by integrating a biomass dryer. The right column shows the calculated efficiencies assuming wood with 40% moisture is dried to 20%. The MILENA gas engine (+ORC) combinations offers a significantly higher efficiency than combustion based processes at a typical scale of 3 – 10 MWe. Typical investment cost for this scale are 4000 €/kWe. For large scale applications CHP applications a gas turbine in combination with a steam cycle needs to replace the gas engines, to further increase overall efficiency and reduce specific investment costs.