n System composition

The CFB-FGD (Circulating Fluidized Bed Flue Gas Desulfurization Technology) process is a novel dry desulfurization process first proposed by LURGI in the late 1980s. The CFB-FGD desulfurization system consists of an absorbent addition system, an absorption tower, a recirculation system, an automatic control system, and an on-line monitoring system. See the process flow chart for details.

n Process flow diagram

 n Technological process

The flue gas enters the absorption tower from the lower air distribution plate of the fluidized bed, and is fully mixed with the slaked lime particles. SO₂, SO₃ and other harmful gases such as HCl and HF react with the slaked lime to form CaSO₃·1/2H₂O, CaSO₄·1/2H₂O and CaCO₃. The reaction product is carried by the flue gas from the upper part of the absorption tower, separated by the dust remover, and the separated solid ash is sent back to the circulating bed absorption tower through the air chute, and the ash slag circulation amount can be adjusted according to the load. The recycling of the absorbent prolongs the desulfurization reaction time and improves the utilization of the desulfurizing agent. Process water is sprayed through the nozzle into the lower part of the absorption tower to increase the humidity of the flue gas and reduce the temperature of the flue gas, so that the reaction temperature is as close as possible to the dew point temperature, thereby improving the desulfurization efficiency.

n Key Features

1) The process is simple, the system equipment is small, the investment is low, and the by-products can be comprehensively utilized.

2) The system has a small footprint and flexible layout, which is suitable for occasions where the site is in short supply.

3) The absorbent is recirculated multiple times in the reactor to prolong the contact time of the absorbent with the flue gas and increase the utilization rate of the absorbent.

4) The system does not have corrosion problems and does not require corrosion protection.

5) The desulfurization efficiency is related to the characteristics of the dry powder of the desulfurizer sprayed；when the sodium-based desulfurizer is used, it can reach to 80%.