Paper details

Title:

The Low Temperature CFB Gasifier -100 KWth Tests on Straw and New 6 MWth Demonstration Plant

Author(s):

Stoholm, P., Cramer, J., Krogh, J., Nielsen, R.G., Sander, B., Ahrenfeldt, J., Henriksen, U.B.

Document(s):

Abstract:

The novel “Low Temperature Circulating Fluidised Bed” (LT­CFB) gasifier is briefly described together with results from first gasification and gas cleaning tests with a new 100 kWth LT­CFB test plant located at the Technical University of Denmark (DTU). Plans for a new 6 MWth demonstration plant are also presented. A first and still major purpose of the LT­CFB gasifier is “indirect” co­firing of difficult biomass and waste fuels at coal fired power plants. In this case simple hot gas cleaning prior to the boiler can be based on just a hot secondary cyclone, i.e. cooling of the product gas is avoided. The necessary fuel flexibility is achieved by designing the gasifier in a way that allows for good char conversion in spite of typically keeping the char gasification temperature at only around 750°C. High retention of e.g. K, P and Cl in the separated bio­ash is possible due to an even lower gas exit temperature from the gasifier (~650°C). Furthermore, a low tar dew point as well as a low content of PAHs in the separated ash are achieved due to initially pyrolysing the bio­fuel at low temperature and retention time. Evidence for all of these advantages as well as a first scale up have been established by erecting and testing a first 50 kW and a 500 kW LT­CFB plant. The test fuels have mainly been high alkaline wheat straw, hen manure, pig manure, biogas residue fibers and residue fibers from a food processing industry using citrus shells and seaweed. During the reported first 100 kW tests, again only ordinary silica sand and no additives was used as bed material, and in spite of that, no agglomeration problems occurred. Gas cleaning was for the first time performed by not only dynamic ash separation in a cyclone but thereafter also by cooling and filtration of the gas in a bag filter. By operating the bag filter at around 300°C a relatively low cost glass fiber type of filter bag could be applied and potential problems due to tar condensation in the cooler and filter could be avoided. The reported first tests with this type of extended gas cleaning system indicate that it will be possible to produce an essentially dust free but still tarry gas, which can be utilized for co­firing very high shares of bio­and waste fuels in not just coal fired boilers but also in boiler plants designed only for oil and natural gas. Moreover, many other applications are possible. Funding for a new 6 MW LT­CFB demonstration plant has been secured and this plant will be commissioned at a DONG Energy owned Danish coal fired power plant in the beginning of 2011.

Keywords:

biomass, circulating fluidised bed (CFB), conversion, gasification, waste, co-firing

Topic:

Thermochemical conversion - Gasification for power and CHP and polygeneration

Subtopic:

Gas cleaning (session 2)

Event:

18th European Biomass Conference and Exhibition

Session:

OA10.4

Pages:

619 - 623

ISBN-13:

978-88-89407-56-1

ISBN-10:

88-89407-56-5

Paper DOI:

10.5071/18thEUBCE2010-OA10.4

Price:

FREE