What are the steps of magnesium

The flue gas of the boiler is sent to the precooling section of the absorption tower by the induced draft fan. After cooling to the appropriate temperature, the flue gas enters the absorption tower and reacts with the absorption slurry under the reverse flow,


Magnesium oxide desulfurization


Magnesium oxide desulfurization


Remove sulfur from flue gas. A mist eliminator is installed on the top of the absorption tower to remove the small droplets carried in the clean flue gas. The clean flue gas is discharged into the chimney after the moisture in the flue gas is reduced by the demister. Dust and dirt are attached to the demister, resulting in blockage of mist eliminator and increase of system pressure loss. It is necessary to wash water pumps with mist eliminator to provide industrial water for spray cleaning of mist eliminator.


Absorption process


The main reactions in the absorption process are as follows:


Mg(OH)2 + SO2 → MgSO3 + H2O


MgSO3 + SO2 + H2O → Mg(HSO3)2


Mg(HSO3)2 + Mg(OH)2 → 2MgSO3 + 2H2O


The absorption liquid which has absorbed the sulfur content falls into the bottom of the absorption tower. The main process of the bottom of the absorption tower is oxidation and circulation.


oxidation process


A large amount of compressed air is forced to be supplied to the slurry at the bottom of the tower by the aeration blower, so that MgSO3, which causes chemical oxygen demand, is oxidized to MgSO4. The chemical reactions at this stage are as follows:


MgSO3 + 1/2O2 → MgSO4


Mg(HSO3)2 + 1/2O2 → MgSO4 + H2SO3


H2SO3 + Mg(OH)2 → MgSO3 + 2H2O


MgSO3 + 1/2O2 → MgSO4


Cycle process


The absorption liquid falling into the bottom of the tower is transported to the upper absorption area of the absorption tower through the slurry circulating pump. The pH value of the absorption solution at the bottom of the tower is adjusted by the automatic injection of 20% magnesium hydroxide slurry, and the pH value is controlled in chain with the acid-base meter. When the pH value of the slurry at the bottom of the tower is lower than the set value, the magnesium hydroxide slurry is automatically added to the bottom of the absorption tower through the transfer pump. Under the action of the bottom agitator, the slurry is evenly mixed. When the pH reaches the set value, the magnesium hydroxide slurry is stopped. 20% magnesium hydroxide solution is produced by heating water with magnesium oxide powder, or directly using magnesium hydroxide. Because the magnesium oxide powder is not pure and the solubility of magnesium hydroxide is very low, the aged slurry is very easy to deposit. Therefore, the mixer and magnesium hydroxide solution delivery pump must be continuously running to avoid precipitation at the bottom of pipeline and absorption tower.