Preliminary status note: Thermal biomass conversion technologies ...

2.2. Fluid bed gasification
2.2.1. Short description of technology
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In fluid bed gasifiers a fluidized bed of sand is used to obtain stable temperature and mixing conditions in
the reactor. Fluidized biomass gasification reactors often operate in the range of 800 to 950°C. The reactors
appear in many different designs and sizes. Reactors are used for both small scale plants using internal
combustion gas engines to produce electricity and large scale units that can be applied for synthesis gas
production. Most fluid bed gasifiers do not operate well on alkali rich biomasses that may cause de-­‐
fluidization of the bed.
2.2.2. Global status of technology development
Because of the limited time to write this note a status is not provided in this case.
2.2.3. Danish strong positions and facilities
The only Danish developed fluid bed gasifier is the Low Temperature Circulating Fluid Bed gasifier
(PYRONEER). The concept was originally invented by Peder Stoholm and further development of the gasifier
has been conducted by DONG energy and DTU Risø. The PYRONEER has been designed specifically to gasify
biomass resources with high contents of low melting ash compounds that has proven difficult to convert in
other processes – e.g. straw, manure fibers, sewage sludge, organic waste etc. The process is based on
separate pyrolysis and gasification reactors with a suitable heating medium circulating to transfer heat
from the gasification process to the pyrolysis. The temperature is kept below the melting point of the ash
components – i.e. max process temperatures around 700-­‐750 °C. In this way sintering and de-­‐fluidization is
prevented. The design of the plant ensures that the fuel ash can be removed in a solid phase from the
gasifier. The gas produced on the gasifier contains relatively high tar content and will initially be utilized as
fuel in a power plant boiler. There presently exist a 500 KWth plant at Risø and a 6 MWth pilot plant is
operated by DONG in Kalundborg. The 6 MWth PYRONEER plant will be gasify straw and supply the process
gas to Unit 2 of the 1000 MW coal fired power plant Asnæsværket. Operation will begin in March 2011, the
project will finish in 2013, and if successful it will be succeeded by a full scale plant.
The PYRONEER is a highly scalable concept, with potential plant sizes of 5-­‐100 MW depending on the fuel.
Desired fuel characteristics include small particle size (3-­‐4 mm) and limited water content (< 30 wt%).
Successful operation on two different types of straw, chicken manure, two types of pig manure, two types
of degassed manure from biogas plants and one type of wood have been carried out on a small scale
PYRONEER gasifier at the Technical University of Denmark. These fuels had ash content as high as 44 wt%dry
and a high content of potassium, chlorine and phosphorous.
To increase the future usability of the PYRONEER process gas, a new project called Gasolution has recently
been initiated by a consortium. The aim is to develop new gas cleaning and upgrading techniques that will
reduce the content of tar and dust particles in the gas, and make it usable for synthesis or direct production
of electricity.