CASE3

Calcium oxide plays the following important roles in thermal power plants:

1、 Desulfurization effect

1. Removing sulfur dioxide: Burning fossil fuels such as coal in thermal power plants produces a large amount of sulfur dioxide (SO ₂), which is a major atmospheric pollutant. Calcium oxide (CaO) can react with sulfur dioxide to produce solid substances such as calcium sulfite (CaSO3) and calcium sulfate (CaSOx), effectively removing sulfur dioxide from flue gas. For example, in a flue gas desulfurization system, calcium oxide is made into a slurry and sprayed into the flue or absorption tower to fully contact and react with sulfur dioxide in the flue gas, achieving the purpose of desulfurization. Through this method, the sulfur dioxide emissions from thermal power plants can be greatly reduced, reducing pollution to the atmospheric environment.

2. Improve desulfurization efficiency: Calcium oxide has high reactivity and can quickly react with sulfur dioxide. Meanwhile, by adjusting the dosage and reaction conditions of calcium oxide, the desulfurization effect can be optimized and the desulfurization efficiency can be improved. For example, controlling factors such as pH value, temperature, and particle size of calcium oxide in the slurry can make the desulfurization reaction more complete and achieve higher desulfurization rates.

2、 Denitrification process

1. Auxiliary denitrification: Although calcium oxide itself has limited removal effect on nitrogen oxides (NO ₓ), it can assist in the denitrification process in some cases. For example, in selective catalytic reduction (SCR) denitrification systems, calcium oxide can react with some acidic substances in the flue gas to reduce their toxic effects on the catalyst, thereby improving the activity and denitrification efficiency of the catalyst. In addition, calcium oxide can also regulate the acidity and alkalinity of flue gas, creating more favorable conditions for denitrification reactions.

2. Reduce ammonia escape: In the SCR denitrification process, it is usually necessary to inject ammonia gas (NH3) as a reducing agent. However, if there is an excess of ammonia, it can cause ammonia to escape and cause secondary pollution to the environment. Calcium oxide can react with escaping ammonia to produce substances such as ammonium sulfate and ammonium nitrate, thereby reducing the risk of ammonia escape.

3、 Solid waste treatment

1. Solidified fly ash: The fly ash generated by thermal power plants contains a large amount of heavy metals and harmful substances. If not handled properly, it can cause serious pollution to the environment. Calcium oxide can react with heavy metal ions in fly ash to generate stable compounds, thereby achieving solidification treatment of fly ash. For example, after mixing calcium oxide with fly ash and undergoing certain treatment processes, heavy metal ions in fly ash can be stably fixed in solid substances, reducing their leaching toxicity and facilitating subsequent landfill or comprehensive utilization.

2. Treatment of desulfurization gypsum: The desulfurization gypsum generated during the desulfurization process needs to be treated and utilized. Calcium oxide can react with impurities in desulfurization gypsum to improve its purity and quality. Meanwhile, calcium oxide can also regulate the acidity and alkalinity of desulfurization gypsum, making it more suitable for production in fields such as building materials. For example, by mixing calcium oxide with desulfurization gypsum and calcining it, high-quality building gypsum products can be obtained.

4、 Other functions

1. Adjusting water quality: In the water treatment system of thermal power plants, calcium oxide can be used to regulate the acidity, alkalinity, and hardness of water. For example, adding an appropriate amount of calcium oxide to water can increase its pH value, converting bicarbonate ions into carbonate ions, which then combine with calcium and magnesium ions to form precipitates and reduce the hardness of the water. This can reduce scaling and corrosion of pipelines and equipment, and improve the operational efficiency and reliability of water treatment systems.

2. Auxiliary combustion: In some special cases, calcium oxide can be added to the boiler as an auxiliary fuel or additive to improve combustion efficiency. For example, mixing calcium oxide with coal for combustion can promote the combustion reaction of coal, lower the ash melting point, reduce slagging, and improve the thermal efficiency of the boiler.

In short, calcium oxide plays an important role in thermal power plants, helping them achieve energy conservation, emission reduction, and environmental protection goals through desulfurization, denitrification, solid waste treatment, and water quality regulation.