High performance equipment for preventing pollution
Air pollution is one of the biggest challenges facing our customers on the journey to net zero. Emission limits for industrial pollutants like SOx, HCl, HF and particulate matter continue to tighten for power plants and industrial facilities worldwide. Heavy metal emissions, are a major concern as well.
Circulating Fluidized Bed Scrubbers (CFBS) are an efficient and flexible Flue Gas Cleaning (FGC) technology for removing a wide array of pollutants from flue gases from almost any combustion and industrial process. It’s suitable for a range of flue gas flow rates, from small industrial boilers to large power plants with capacities over 500 MWe.
The system uses an absorber chamber and baghouse. Flue gas with fly ash enters the bottom of the absorber, flowing upward through venturi to accelerate the gas causing turbulence flow. Recycled solids, reagents and water mix with the turbulent flue gas providing gas cooling, reactivation of ash and capture of pollutants.
The gas and solids enter the baghouse, where solids are captured and recycled back to the absorber to capture more pollutants. Reactive absorbents like sodium carbonates, hydrated lime, activated carbon or others can be added to target specific pollutants. It’s also possible to install a dry lime hydrator to produce hydrated lime on-site from lower cost quick lime.
The main tasks of the CFBS system are to:
- Remove Sulphur oxide gases (SOx) and other acid gaseous components (HCl, HF) from flue gas, using sorbent in the scrubber reactor (absorber)
- Cool down flue gases to optimal operating temperature with water spraying
- Save on hydrated lime consumption by recirculating the by-product including the calcium hydroxide in the loop from the fabric filter (FF).
Value for money and kind to the environment
- The semi-dry CFB scrubber technology uses up to 50% less water than wet flue gas desulfurization (FGD) units. Often power consumption is lower too.
- The excellent mixing properties, combined with long solids residence time of 20-30 minutes, minimizes sorbent consumption and accepts wide design range of flue gas parameters what improves fuel flexibility.
- In combination with CFB boilers, the semi-dry process takes advantage of the unreacted calcium of the fly ash, reducing or even eliminating the use of lime.
- Spraying water creates the optimal temperature for the process which means lime injection isn’t limited by the incoming flue gas temperature.
- The scrubber by-product is solid, eliminating the need for wastewater treatment. And it can be used as a cement additive, general aggregate (or landfilled).
- The investment costs for a CFB scrubber are often 25-50% lower than wet FGDs for the same plant size.
- Maintenance costs and needed annual downtime are very low because the technology uses practically dry material with low erosion and negligible corrosive properties. And it requires only easy-to-maintain auxiliaries.
Compact, scalable and efficient
- The CFB scrubber reduces SOx, particulate matter (PM10 and PM2.5), acid gases (HCl, HF), mercury (Hg) and organic compounds (dioxins and furans) emissions in the same unit.
- It is a proven technology on a large scale, with single-unit designs up to 500 MWe and for fuels with sulfur content above 4%. Multiple parallel venturis in the absorber bottom allow single designs for up to 800 MWe.
- The absorber is cylindrical and reaction residence time is provided by the unit height, which allows a compact footprint.
CFBS technology has been applied widely in power plants, steel mills, refineries, waste-to-energy plants, combined heat and power plants, and plants in many other industries. It is a very good solution to retrofit existing power plants currently operating a dedusting or FGC system, or with an electrostatic precipitator (ESP) – there’s no need to disassemble the existing ESP. And given the technology’s overall cost efficiency, it’s an attractive option for many organizations aiming to keep well within ever stricter emission limits.