DAHLMAN MILENA Gasifier

INFO
GASIFICATION MILENA GASIFIER
Overview Renewable energy, energy efficiency  Product gas is diluted with combustion flue
and energy independence are hot topics nowadays. gas (CO2, H2O);
An energy source, with a large potential is biomass.  Product gas is diluted with nitrogen in case air
Biomass is generally considered as one of the most is used as oxygen supply.
important renewable energy sources. Biomass is The latter can be solved by using an oxygen/steam
the only renewable carbon source! mixture instead of air, but this will increase the
Another important energy source is waste. plants costs and decrease the efficiency.
Landfilling waste is limited and will be abolished in Product gas from air blown gasification has an
a lot of regions. Mass incineration of waste is energy value up to 6 MJ/Nm3 (150 Btu/scf) after tar
unpopular and has a low energy efficiency. Waste is removal and water condensation, good enough for a
partly fossil (plastics) and partly biogenic (e.g. gas engine but too low for a gas turbine.
wood, paper, leather, cotton). Hence utilising waste
is not only solving our waste related problems, it Principle of the MILENA gasifier MILENA is
also contributes to our renewable energy mix. an indirect gasifier, meaning that the pyrolysis and
combustion reactions are separated. Main
Gasification of biomass & waste advantage of this process is that the MILENA has a
Gasification of biomass and waste opens the full separate flue gas exhaust, hence the product gas is
potential of this valuable carbon source. not diluted with the N2 present in air. After tar
Combustion is still used more nowadays, but removal and water condensation, the MILENA
gasification has more potential. Cleaning product gas has an energy value up to 20 MJ/Nm 3
gasification product gas is more efficient than (500 Btu/scf), well within specification for a gas
cleaning combustion flue gas. Once the product gas turbine.
is cleaned, it can be used in efficient combined
cycle power stations. Moreover, the product gas
can also be upgraded by catalytic conversion into
gaseous and liquid fuels like substitute natural gas,
hydrogen or Fisher Tropsch diesel.
Principle of gasification Gasification can be

defined as the thermal conversion of carbon rich
fuels into a syngas or product gas. Syngas contains
hydrogen, carbon monoxide and also carbon
dioxide and water. Product gas contains syngas as
well as hydrocarbons like methane. Biomass and
waste is normally gasified at temperatures in the
The 800 kW MILENA pilot at ECN
range of 700-900°C (1300-1700°F). At these
temperatures the solid fuel is vaporised and
converted to the gaseous components of product
gas. In the absence of oxygen this process is called
pyrolysis. Pyrolysis is an endothermic process, it
needs an energy source to maintain the
temperature level. In a gasifier reactor a controlled
amount of oxygen is fed, which combusts part of
the fuel, therewith supplying the energy for the
gasification process. An efficient process with some
disadvantages:
 Gasification does not have a full carbon
conversion, normally this is 90-95%;
Design of a 12MW MILENA gasifier island
INFO
MILENA process Solid fuel (biomass or waste) Because of the volatilization; the product gas, sand
enters the system in the central riser (red). A small and char flow upwards through the riser into the
amount of steam or air is also injected in the riser to settling chamber. In this settling chamber the
fluidise the hot sand (catalytically active bed majority of the solids (sand, ash & char) are
materials like olivine can also be used). Using the separated from the product gas. Raw product gas
energy of the hot sand biomass reacts into three (containing gaseous tars) is flowing to downstream
basic products: equipment.
 Solids (char) The solids collected in the settling chamber flow
 Condensables (tars) under influence of gravity to the combustion
 Product gas chamber (green). In this combustion chamber the
(mainly H2, CO, CH4, C2H4, CO2, & H2O) char fraction burns, heating up the sand after which
the hot sand flows back to the riser completing the
cycle.
MILENA-OLGA: clean & efficient In MILENA

the combustion process is optimised resulting in
100% carbon conversion, boosting gasifier efficiency
and minimizing ash volume. The product gas is
concentrated and can therefore be cleaned
efficiently. Most important cleaning step is the tar
removal. Tars are known as the Achilles heel of
biomass and waste gasification. Tar related
problems form a major issue in efficient use of
product gas. ECN and Royal Dahlman also developed
the OLGA technology which efficiently removes tar
and is fully integrated with the MILENA process.
Tars and char are removed from the product gas
and recycled to the MILENA’s combustor reactor
where the energy is used for the gasification
process.
MILENA a patented process MILENA is an

invention of the Energy research Centre of the
Netherlands (ECN). ECN is one of the leading
institutes in the world for research & development
of gasification technology. ECN & Royal Dahlman
cooperated in the development of MILENA. Royal
Dahlman is licensee for the MILENA technology.
Features Benefits
Full carbon conversion Leads to a high cold gas efficiency
100% carbon to gas ratio Carbon free ash, reduction in waste
High cold gas efficiency, >80% chemical energy 5-10% higher than direct air blown gasifiers
transfer to tar free product gas Better use of a valuable carbon source
Separate flue gas exhaust High quality heat recovery
classic, commercially proven flue gas treatment Easy collection of carbon free ash
No dilution of the product gas N2 free gas suitable for SNG (CH4) production
and still using ambient air as oxygen source Smaller downstream process, less capex
High product gas energy value Suitable for a gas turbine combined cycle
3
Up to 20 MJ/Nm (500 Btu/scf) Smaller compressors, less parasitic load
WWW.DAHLMAN.NL | T. +31 (0)10 599 1111 | E. DAHLMAN@DAHLMAN.N L MAY 2013

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INFO

GASIFICATION MILENA GASIFIER

Principle of gasification Gasification can be

MILENA-OLGA: clean & efficient In MILENA

MILENA a patented process MILENA is an

WWW.DAHLMAN.NL | T. +31 (0)10 599 1111 | E. DAHLMAN@DAHLMAN.N L MAY 2013

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