Magnesium oxide desulfurization process

Magnesium oxide desulfurization process

System process diagram

working principle
The magnesium oxide wet desulfurization process (abbreviation: magnesium desulfurization) is similar to the lime-gypsum desulfurization process. It uses magnesium oxide (MgO) as raw material, and is slaked to generate magnesium hydroxide (Mg(OH)2) as a desulfurizing agent. An economical desulfurization system. In the absorption tower, the absorption slurry is contacted and mixed with the flue gas, and the sulfur dioxide in the flue gas is chemically reacted with the magnesium hydroxide in the slurry to be removed, and the reaction product is a mixture of magnesium sulfite and magnesium sulfate. If the forced oxidation process is adopted, the reaction product is a magnesium sulfate solution, which is dehydrated and dried to form magnesium sulfate crystals.
reaction process
1. Maturation
MgO+H2O→Mg(OH)2.
2. Absorption
SO2+H2O→H2SO3
H2SO3+H2O→H2SO4
3. Neutralization
Mg(OH)2+H2SO3→MgSO3+2H2O
Mg(OH)2+H2SO4→MgSO4+2H2O
Mg(OH)2+2HCL→MgCL2+2H2O
Mg(OH)2+2HF→MgF2+2H2O
4. Oxidation
2MgSO3+O2→2MgSO4.
5. Crystallization
MgSO3+3H2O→MgSO3·3H2O
MgSO4+7H2O→MgSO3·7H2O
System composition
The desulfurization system is mainly composed of flue gas system, absorption tower system, magnesium hydroxide slurry preparation system, concentration tower system, by-product treatment system, waste water treatment system, public system (process water, compressed air, accident slurry tank system, etc.), electrical control system composed of several parts.
Process characteristics
1. Good reactivity and high desulfurization efficiency
The reaction intensity of wet desulfurization depends on the dissolved alkalinity of alkali metal ions of the desulfurizer. Since the dissolved alkalinity of magnesium ions is hundreds of times higher than that of calcium ions, magnesium-based desulfurizers have a desulfurization reaction ability that is dozens of times higher than calcium-based desulfurizers. Industrial practice has proved that magnesium-based desulfurizers can achieve higher desulfurization efficiency than calcium-based desulfurizers, reaching more than 99%. At the same time, the amount of spray water required for magnesium-based desulfurization is only equivalent to 1 % of calcium-based desulfurization that achieves the same desulfurization efficiency. /3, the power consumption is also greatly reduced.
2. High operational reliability
Due to the high solubility of magnesium-based desulfurization products, the solid suspended solids are loose crystals, which are not easy to deposit. Therefore, there are no scaling, agglomeration, clogging and other phenomena that exist in calcium-based wet desulfurization systems, and the operation is reliable and maintenance is easier. .
3. Low cost
Due to the high reaction intensity, the height of the magnesium-based spray reaction absorption tower is only about 2/3 of that of the calcium-based desulfurization tower. Therefore, the cost of the main equipment for the magnesium-based desulfurization is significantly lower than that of the calcium-based absorption tower. At the same time, since the molecular weight of magnesium oxide (40) is 73% of calcium oxide (56) and 40% of calcium carbonate (limestone, with a molecular weight of 100), the magnesium oxide required to remove the same amount of sulfur dioxide is more than calcium-based It is much less, and Mg0 is supplied in powder form, and the desulfurization agent supply system is also greatly simplified compared with calcium-based desulfurization, which reduces the cost of the system.
The comparison shows that the cost of magnesium oxide desulfurization equipment is generally 10-15% lower than that of the limestone/gypsum method.
4. Low operating cost
Since the power consumption of the magnesium-based process is about half lower than that of the limestone/gypsum method, and the investment is lower, although the cost of the desulfurizer is higher, the comprehensive desulfurization cost is generally about 10-15% lower than that of the limestone/gypsum method.
5. High economic benefits of by-product recovery
A direct by-product of magnesium-based processes is magnesium sulfite, which is oxidized to form magnesium sulfate. The actual output of the desulfurization process is a magnesium sulfite by-product containing a small amount of magnesium sulfate. Only the forced oxidation produces by-products whose main component is magnesium sulfate. Both desulfurization by-products have market utilization value, and their treatment and utilization forms should be "adapted to local conditions", depending on the comparison of technology and economy and the feasibility in specific projects.