1. Rotary spray drying desulfurization (SDA).
Rotary spray drying desulfurization technology (SDA) was first jointly developed by two companies in the United States and Denmark in the 70s of the 20th century. The process principle is that the lime slurry is atomized into fine droplets through a high-speed rotating atomization device, and after being sprayed into the absorption tower, on the one hand, it reacts chemically with SO2 in the flue gas to generate solid ash, and on the other hand, the flue gas transfers heat to the lime slurry to make it dry continuously, so the ash after the reaction will be discharged in a dry state. The desulfurization efficiency of this method can reach 80% 85%, which is known as the FGD technology in the 80s of the 20th century.
2. Semi-dry and semi-wet flue gas desulfurization technology
The semi-dry and semi-wet process is a desulfurization technology developed by the Chinese Academy of Environmental Sciences. This technology is based on the improvement of the semi-dry and semi-wet desulfurization device donated by Japan, and the desulfurization technology developed in line with the current situation of flue gas desulfurization in China. After the transformation, the process and technology investment is less, the land occupation is less, the cost is low, there is no corrosion, and the desulfurization ash can also be used to make bricks.
The process of semi-dry and semi-wet method is that the boiler flue gas is mixed with the desulfurizer (CAO and CA(OH)2) before entering the tower, and then enters the desulfurization tower, and the water mist is sprayed into the tower from the top of the tower, SO2, water and desulfurizer undergo a chemical reaction in the desulfurization tower, and the desulfurizer reacts with the aqueous solution of SO2 (i.e. sulfurous acid) to form calcium sulfite, and the calcium sulfite is oxidized to calcium sulfate, which can remove the SO2 in the flue gas.
3. Powder-granular spray bed semi-dry and semi-wet flue gas desulfurization
Powder-granular spray bed semi-dry flue gas desulfurization was developed by Japanese researchers in the 90s. The technical principle of this method is: the flue gas containing SO2 entering the spray bed is preheated by the preheater first, the desulfurizer is also mixed with water in advance, the desulfurizer is powdered, including limestone, slaked lime or other alkaline desulfurizer, the desulfurizer is sprayed into the bed from the top of the spray bed in the state of slurry, and is fully mixed with the spray particles from the bottom of the tower in the spray bed, and the spray particles are blown up by the flue gas containing SO2 sprayed from the bottom of the tower, showing a fluidized state.
The SO2 gas and the desulfurizer undergo a desulfurization reaction on the surface of the fluidized jet particles, and the drying process is completed at the same time. The product after the desulfurization reaction is a dry powder, and the product is blown out of the separator.
Subsequently, many Chinese scholars have conducted in-depth research on the flue gas desulfurization technology of the spray bed by improving the structure and form of the spray bed, studying different types of desulfurizers and additives, changing the particle size of the spray particles, and mixing particles of various particle sizes. Zhang Shaofeng et al. developed a rectangular spray bed with two nozzles, and studied the effects of additives, injection speed, bed height, and particle size on the desulfurization efficiency. The desulfurization efficiency of ammonia as the desulfurization agent is higher than that of calcium-based semi-dry flue gas desulfurization technology.