Method for producing magnesium sulfite from boiler flue gas
The coal-based energy structure of the power industry will not change, and thermal power plants will still use coal as the main fuel for power generation. The flue gas emitted by industrial boilers in thermal power plants contains SO2, soot, HCL, HF, SO3, etc., which pollutes the environment very seriously. With the strengthening of environmental protection in my country, flue gas desulfurization technology has been applied and developed in China. At present, in the field of flue gas desulfurization, magnesium oxide has been widely promoted as a new desulfurizer. Wet magnesium flue gas desulfurization uses light calcined magnesium oxide as desulfurization absorbent, and fully contacts with SO2-containing flue gas in the desulfurization tower, and reacts to generate waste liquid saturated with magnesium sulfite, and the flue gas is desulfurized. The magnesium-based desulfurization unit has less investment, low operating cost, and good desulfurization effect, but its by-product waste liquid should not be directly discharged, and resource recovery is required.
In the current flue gas desulfurization process, magnesium sulfate fertilizer is usually produced by aeration of the waste liquid of magnesium desulfurization. Because the desulfurization waste liquid also contains a small amount of soot, HCL, HF, SO3, etc., and the composition is complex, the soot and SO2 in the flue gas are sent to the desulfurization tower together, and then enter the absorption liquid for desulfurization and dust removal, resulting in complex composition of the desulfurization waste liquid. Purity of by-products produced from waste liquids has an impact.
Using boiler flue gas to produce magnesium sulfite, the process flow is: 1. Grind magnesium oxide powder or magnesite ore into powder, mix with water to make absorbent slurry, and send it to the desulfurization tower; 2. Introduce boiler flue gas into flue gas The desulfurization pretreatment device is sprayed with circulating water to reduce the temperature of the flue gas, remove part of the soot and HCL, HF, SO3 components, and send it to the desulfurization tower; 3. In the desulfurization tower, SO2 in the flue gas reacts with the absorbent slurry, Generate MgSO3, control the temperature in the desulfurization tower at 50-55℃, and the pH value of the circulating slurry in the range of 5.0-6.8; 4. Send the desulfurization waste liquid to the sedimentation tank and centrifuge for separation and dehydration to increase the solid phase content to 50-70% 5. After drying with hot air, the finished product of dry magnesium sulfite is obtained.
This approach provides a new method for producing by-products of magnesium-based desulfurization, which is more convenient for the popularization of magnesium-based desulfurization technology. The magnesium sulfite product is calcined to produce sulfuric acid. It is suitable for the production of magnesium sulfite from boiler flue gas desulfurization waste liquid.
