Gasification is an old technology and dates back to mid 1800, where it was used to produces gasses for heating and lighting. When oil became available the interest in coal gasification declined. However, during the oil crisis in the 70's the technique became "hot" again.

There are three basic types of reactors, which are used for gasification.

• The moving bed reactor
• The fluidized bed reactor
• The entrained flow reactor

Within these types a lot of different operating modes exist, such as updraft, downdraft, slagging, non-slagging etc. These technologies are described in any good gasification textbook. What one will not find there is information about the MILENA gasification technology.

The development of the MILENA started close to the finishing of another succesful gasification technology BIVKIN. The BIVKIN is a circulating fluidized bed reactor which due to the straight forward technology makes it useful for a large range of different types of biomass.

For the development of a route to bioSNG the efficiency is very important. A higher efficiency can be obtained by going to 100% fuel conversion, which was not possible with the BIVKIN. When considering an indirect gasification, where char is burned separately and heat is transported to the gasification zone, the 100% fuel conversion becomes possible. Two important examples in this field are the Battelle gasifier, which uses two reactors, one to combust and one to gasify. The second example is the Güssing gasifier, which is an FICFB (Fast Internally Circulating Fluidized Bed).

Indirect gasification means that the combustion and gasification are separated. The gasification of biomass always results into three basic products.

1. Solid (char)
2. Liquid (tars)
3. Gas (mainly CH₄, C₂H₄, CO₂, CO and H₂)

The char is internally recycled to the combustor with the bed material. In the combustor the char is burned with an excess of air and heating the bed material. The bed material is recycled back to the riser, where the gasification takes place. This ingenious design virtually removes nitrogen (only present in the combustor) from the product gas. The hot bed material provides the energy for the gasification reactions resulting in the three basic products.

In this process the 100% fuel conversion is obtained by recycling cyclone ashes (containing carbon) and tars (removed from the product gas) to the combustor or riser.

The MILENA technology started on a lab scale 25 kW gasifier, but in 2007 the construction of a pilot plant was started. At the end of 2007 a 800 kW indirect gasifier will be operational at the ECN site in Petten.

After the successfull operation of the 800 kW pilot gasifier, the next step would be a demo plant of 10 MW. This demo facility will not be constructed on ECN ground, because the site in Petten is not suitable for this kind of size plants. The idea for this demo is that it will start producing gas for a gas boiler. This will prove that the gasifier works. In the next phase the 10 MW MILENA will be coupled to OLGA for removal of tars and the gas can now be used in a gas engine. The last phase will be a complete gas cleaning section with gas upgrading, resulting in SNG at gas grid specifications.

The development and results of these different steps (1 MW, 10 MW, 100 MW and 1GW) will be reported on this website.