ECN publication
Gasash: Improvement of the economics of biomass/waste gasification by higher carbon conversion and advanced ash management
Published by: Publication date:
ECN Biomass, Coal and Environmental Research 1-6-2006
ECN report number: Document type:
ECN-C--06-038 ECN publication
Number of pages: Full text:
256 Download PDF  

Gasification of biomass and waste in circulating-fluidised-bed systems produces carbon-rich fly ash. How to deal with this fly ash in an economic way was the key question in the GASASH project. Landfill was not considered as an option, since it is prohibited in many countries due to the high calorific value of the fly ash. A parametric study showed that optimisation of the gasification process itself may decrease the amount of fly ash to some extent by increasing the carbon conversion and thus decreasing the carbon content in the fly ash. However, process optimisation will still not lead to a fly ash quality that allows utilisation options in building materials as developed for fly ash from pulverised-coal combustion. Direct utilisation of the fly ash appears to be limited to use as a (secondary) fuel or as filler in asphalt or asphalt-like products. For other utilisation options, after-treatment is needed, e.g., to lower the carbon content and to remove or immobilise contaminants like chlorine and heavy metals. Fly ash combustion tests at different temperature levels revealed that the resulting material can be used as (component in the manufacturing of) building materials. Leaching tests showed that several products comply with the lower limits of the Dutch Building Materials Decree, which means unrestricted use. Examples are synthetic basalt and heat-treated fly ash (as filler in cement). In general, consistency of quantity and quality is crucial for all forms of utilisation. Local factors strongly influence the technical and economic feasibility of various options. For the Netherlands, the most promising option is direct utilisation as secondary fuel, followed by utilisation as building material, directly in asphalt or after combustion in various building products.

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