Biomass can be converted into gas through gasification. This gas is suitable for use in fuel cells, gas engines, gas furnaces and gas turbines. Gas from biomass gasifiers can also be upgraded into sustainable Substitute Natural Gas (SNG). SNG can replace conventional natural gas. The new ECN MILENA biomass gasifier produces a gas with a conversion efficiency of almost 100 percent. This 800 kW pilot gasifier, placed in November 2007, has a number of important advantages: the caloric value of the gas is high and there is no combustible matter in the ash.
The MILENA gasifier replaces the BIVKIN fluidised bed gasifier that was built in 1996 at ECN. According to Christiaan van der Meijden, ECN Project Leader, MILENA technology is very promising. “We are achieving the highest conversion efficiency of biomass to usable gas. The MILENA converts almost 100 percent of biomass, while the previous average was 95 percent.”
Removing Tar
The energy efficiency of biomass to usable gas is higher than other biomass gasifiers currently being developed, but MILENA gas does contain relatively high amounts of tar. Tar can cause problems during the gas cooling process. It fouls the installations and pollutes process water. OLGA technology, developed by ECN, can remove this tar from the gas and makes the gas suitable for use in gas furnaces, gas engines and gas turbines.
Bio-CNG
Van der Meijden: “The gas produced by the MILENA gasifier is also very suitable for catalytic conversion into Bio-SNG (Substitute Natural Gas). Bio-SNG can be injected in the natural gas grid to replace fossil natural gas. Compressed Natural Gas (CNG) is becoming increasingly popular as a transportation fuel, because of the low price and good environmental performance. Bio-SNG can be converted into Bio-CNG by compression. Bio-CNG is one of the most promising Bio-fuels for transportation. Overall efficiency is significantly higher for Bio-CNG than for “second generation” Bio-Diesel.
The development of MILENA technology started eight years ago. In 2002, the first research gasifier installation (30 kW capacity) was built on laboratory scale. In 2006, the MILENA was connected to the OLGA gas purification and SNG installation, and the entire system was tested extensively. Now, ECN is confident that the technology can be up scaled. This has been done and the 800 kW pilot will be taken in operation soon. MILENA gasification technology is the ongoing improvement of BIVKIN CFB technology. The latter technology has been applied commercially by HoSt BV, an engineering agency in the field of industrial energy conservation and the application of sustainable energy. HoSt BV, together with Klaas Zijlstra Metaalbewerking BV in Friesland, has also been involved in building the MILENA pilot installation.
Demonstration
If no problems arise with future assembly, the pilot installation will be made operational in the summer of 2008. Later that year, existing OLGA gas purification will be connected. We plan to have a conventional natural gas vehicle running on Bio-CNG in 2009. Preparations are underway to realise a 10 MWth demo, based on ECN MILENA and OLGA technology. The gas will be converted to SNG which can be injected into the gas network, or used as transport fuel (Bio-CNG).
Information:
More information on the MILENA gasifier technology is available on www.milenatechnology.com
Contact:
Christiaan van der Meijden
ECN Biomass, Coal & Environmental research
Tel. (+31) 224 - 564582
vandermeijden@remove-this-part-ecn.nl
