With the continuous improvement of environmental protection requirements, flue gas desulfurization towers have become an essential equipment for coal-fired power plants and industrial boilers. However, in the flue gas desulfurization process, due to various reasons, the desulfurization tower will have fouling, resulting in a decrease in desulfurization efficiency and an increase in equipment resistance, which seriously affects the normal operation and service life of the equipment. Therefore, it is of great significance to study the causes of fouling of flue gas desulfurization tower and put forward corresponding countermeasures to improve the desulfurization efficiency and service life of the equipment.
Types of scale and the causes of its formation.
1.Calcium sulphate scale.
Calcium sulfate scale is one of the most common scales in flue gas desulfurization towers, which is mainly formed by the precipitation and deposition of calcium sulfate crystals in gypsum slurry. In the limestone-gypsum desulfurization process, the pH value of gypsum slurry is generally controlled at 52~5.6, at this time, the solubility of calcium sulfate is the smallest, and it is easy to precipitate and deposit. In addition, impurities such as calcium carbonate and calcium sulfite in the slurry will also promote the formation of calcium sulfate scale.
2.Magnesium sulphate scale.
Magnesium sulphate scale is mainly formed by the presence of excessive magnesium ions in the slurry in the absorption tower. In the wet desulfurization process, due to the limited solubility of the absorbent, the concentration of magnesium ions in the slurry will gradually increase, and when it reaches a certain concentration, it will precipitate and deposit to form magnesium sulfate scale.
3.Calcium carbonate scale.
Calcium carbonate scale is mainly formed by the reaction of carbon dioxide in flue gas with calcium hydroxide in the slurry. In the limestone-gypsum desulfurization process, due to the limited solubility of limestone, the concentration of calcium hydroxide in the slurry will gradually decrease, and when it reaches a certain concentration, it will react with the carbon dioxide in the flue gas to form calcium carbonate scale.
Effects of fouling and countermeasures.
1.Reduce the efficiency of desulfurization.
The formation of the scale layer will hinder the contact between the flue gas and the desulfurizer, reduce the mass transfer efficiency, and thus lead to the reduction of the desulfurization efficiency.
2.Increase device resistance.
The formation of the scale layer will increase the resistance of flue gas flow, which will lead to an increase in the power consumption of equipment such as fans and an increase in operating costs.
3.Shorten the life of your equipment.
The formation of the scale layer will cause corrosion and wear and tear on the equipment, shortening the service life of the equipment.
4.Countermeasures against calcium sulfate scale.
Select the appropriate desulfurization process, control the pH value of the slurry, add antiscalants, etc.
5.Countermeasures against magnesium sulfate scale.
Choose a highly soluble absorbent, control the concentration of magnesium ions in the slurry, add antiscalants, etc.
6.Countermeasures against calcium carbonate scale.
Choose high-purity limestone, control the concentration of calcium carbonate in the slurry, add scale inhibitors, etc.
In summary, the main causes of fouling in flue gas desulfurization towers include the formation of scales such as calcium sulfate, magnesium sulfate and calcium carbonate. In order to prevent and remove scaling, measures such as selecting a suitable desulfurization process, controlling the pH value of the slurry, and adding antiscalants can be taken. Through these measures, the desulfurization efficiency can be effectively improved, the equipment life can be extended, and the operating cost can be reduced.