Case study: Optimizing a dry FGD system for a thermal power plant

Context & problem

A dry desulfurization system injects sorbent into the flue gas ahead of the dust filter and must balance two conflicting requirements: low pressure loss and high removal efficiency. In the base design, poor gas–solid mixing reduced the removal efficiency, while uneven flow and several turning points increased the pressure loss, forcing the ID fan to run close to its limit.

Approach

Four steps: engineering calculations on the base design → building quantitative assessment criteria → CFD analysis of the base design → proposing and verifying improvement options on the same model.

Model: multi-species + turbulence + Lagrangian particle tracking; calibrated against the design data.
Three main analyses: recirculation zones; sorbent residence-time distribution; pressure loss per section.

Results

Gas–solid mixing efficiency improved by 50%; the residence-time distribution narrowed considerably around the target value.
System pressure loss down 15%; flow uniformity into the dust filter improved by 12%.
4 weeks from diagnosis to a settled optimal option.
After installation the client confirmed the model predicted the pressure to within ~5% — reliable enough to be used directly for ID fan selection.

Value

The retrofit decision rested on quantitative evidence rather than trial and error on site, reducing both the risk of the fan investment and the long-term operating cost. The validated model became the assessment tool for later adjustments.

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