Desulphurization – Dry System

With the CRANFOS CFB Absorber, you can maximize emission control with high efficiency, low cost, and zero water waste!

The dry desulphurization process, based on the circulating fluidized bed (CFB) principle, operates at a temperature of approximately 75/85°C, typically using hydrated lime for the combined absorption of SO2, SO3, HF and HCl. This process transforms the aforementioned gases into a dry product that is collected in the easy-to-use CRANFOS Bai-Press 10™ bag filter.

The absorber, installed before the Bai-Press 10™ Bag Filter, is an empty vertical gas duct, with venturi-type elements located at its base, which will allow the formation of the fluidized bed mixture with hydrated lime, recirculated desulfurization products and combustion ash.

Within the circulating fluidized bed, the solids are distributed along the entire height of the absorber. The average velocity of solids is much lower than the average velocity of the gas, the difference in velocity is called “sliding velocity”.

This sliding speed between the combustion gases and the solids is the fundamental criterion for the transfer of heat and mass inside the circulating fluidized bed absorber.

This allows water to be injected directly into the fluidized bed and the absorption temperature to be controlled independently of the lime feed quantity. The absorption product, which mainly consists of calcium sulphite (CaSO3 x ½ H2O), calcium sulphate (CaSO4 x ½ H2O), limestone (CaCO3) and fly ash, is separated from the downstream cleaning gas in the CRANFOS Bai-Press 10™ Bag Filter.

Bai-Press 10TM Advanced Dry Desulphurization: Superior Removal of SO₂, SO₃, and HCl!

Most of the product collected in the Bag Filter is recirculated back to the absorber through fluidized troughs, which allows for an extension of the solids retention time of the sorbent. This makes it possible to reduce the Ca/S molar ratio of the process.

• Ca(OH)2 + SO2 ↔ CaSO3 . ½ H2O + ½ H2O
• Ca(OH)2 + SO3 ↔ CaSO4 . ½ H2O + ½ H2O
• CaSO3 . ½ H2O + ½ O2 ↔ CaSO4 . ½ H2O
• Ca(OH)2 + 2 HCl ↔ CaCl2 + 2 H2O
• Ca(OH)2 + 2 HF ↔ CaF2 + 2 H2O
• Ca(OH)2 + CO2 ↔ CaCO3 + H2O

Advantages of CFB ABSORBER

In the CFB Absorber, water and hydrated lime injection are performed separately, so that the Ca(OH)2 injection rate is controlled solely by the pollutant load at the equipment inlet and the desired emission reduction, without being limited by the temperature or moisture content of the flue gas. As a result, the CFB Absorber can be operated to achieve emission reduction for a wide variety of fuels, including sulfur-rich coals.

• Low investment and maintenance costs;
• Simple, proven and reliable technology;
• Dry feeding of absorbents;
• In addition to the high removal of SO2, efficient removal of HCl/HF is also possible;
• Total removal of SO3;
• Dry final product;
• Absorption temperature about 20 to 30 C above the dew point of water;
• Does not require reheating of clean gas;
• There is no need for pre-dedusting;
• No water waste;
• No special equipment inside the absorber;
• No special materials – just carbon steel;
• No rubber coatings in interior areas;
• There is no need to apply corrosion protection;
• High efficiency in the use of absorbents due to powder recirculation;
• Possibility of operating with reduced loads through the installation of the clean gas recirculation system, keeping the system flow rate constant, even with the boiler operating at low load.

For more information, please consult our Process Engineering team.