GANGPUEnvironmental Technology

Flue Gas Desulfurization & Denitrification

Boiler Flue Gas FGD and SCR Retrofit

Indonesia2023Thermal Power Plant

Wet limestone-gypsum desulfurization tower with SCR reactor and wet electrostatic polishing added to an existing coal fired boiler flue gas train.

Flue gas desulfurization tower and SCR reactor at a coal fired power plant

Original condition

The problem on site

The boiler had to keep running while the retrofit was built, the site had limited space behind the existing ESP, and the added system resistance exceeded the original induced draft fan margin.

Engineering approach

What we designed and built

  1. 01Designed a compact tower layout with the absorber and slurry tank arranged to fit the available plot, using a steel structure shared with the existing duct supports.
  2. 02Placed the SCR reactor in high dust arrangement upstream of the FGD to use the existing temperature window without reheating.
  3. 03Used three spray layers with a low pressure drop demister to keep total resistance within the upgraded fan capability.
  4. 04Retrofitted the induced draft fan and circulation pumps with medium voltage VFDs so the plant can follow load changes.
  5. 05Phased construction around planned outages, with bypass damper arrangement for start-up and maintenance.

Measured results

Before and after commissioning

Values recorded on this project under its own operating condition. Results at another plant depend on fuel, material, load profile and the local standard in force.

Before and after measurements for Boiler Flue Gas FGD and SCR Retrofit
ItemBeforeAfter
Flue gas volume treatedExisting ESP only780,000 m³/h full train
SO₂ removalNo desulfurization stage96% removal at rated load
NOx removalCombustion control only88% removal with SCR at 2 layers
Fan power after retrofitOriginal ID fan marginID fan upgraded with VFD to cover added resistance

Outcome

How the system runs now

The full train now handles 780,000 m³/h of flue gas. SO₂ and NOx removal rates measured during the performance test reached 96% and 88% at rated load, and outlet values are recorded by the plant CEMS. Final compliance is judged against the local emission limit and actual fuel quality.

Site records

Fabrication, erection and commissioning

Flue gas desulfurization tower and SCR reactor at a coal fired power plant
Flue gas desulfurization tower and SCR reactor at a coal fired power plant
Limestone gypsum desulfurization tower with multiple spray layers
Limestone gypsum desulfurization tower with multiple spray layers
Installation of honeycomb catalyst modules inside an SCR reactor
Installation of honeycomb catalyst modules inside an SCR reactor
Wet electrostatic precipitator used for fine particle polishing at a power plant
Wet electrostatic precipitator used for fine particle polishing at a power plant

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