oa South African Journal of Chemical Engineering - CFBC fuel flexibility : added value of advanced process optimization
A major advantage of circulating fluidized bed combustors (CFBC) is the high flexibility according to fuel type, composition and specific properties like particle size, moisture and morphology. On the other hand, flow and transport characteristics of large scale fluidized beds are far from ideal mixing conditions. Hence, fuel flexibility design for new or existing plants is a multi-parameter optimization problem with numerous aspects from storage and feeding equipment over optimum feeding location to the effect on fuel burn-out, emissions and wear. The combination of plant audits, specific measurements (e.g. primary air nozzle pressure drop as a measure for flow distribution and bed flow pattern) and the application of advanced computational fluid dynamics are presented in this contribution. Specific fuel flexibility challenges and solutions considering
- air staging,
- wear reduction and
- limestone injection for direct desulphurization
- coal/RDF mixture,
- up to 40% substitution of coal with wood pellets and/or wood chips and
- 100% biomass with different fuel specifications.
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