Seawater desalination is indeed a common method to obtain high-purity water for steam boilers. As industries and coastal power plants expand, the demand for stable, high-quality boiler feedwater continues to rise, and desalination has emerged as one of the most practical solutions for facilities located in water-scarce coastal regions.

Steam boilers are highly sensitive to water quality. Impurities such as dissolved salts, heavy metals, suspended solids and silica present in raw seawater pose severe threats to boiler operation. If inadequately treated, these contaminants will accumulate on heating surfaces to form hard scale, reduce heat transfer efficiency, increase fuel consumption, and even trigger localized overheating, tube rupture or serious boiler explosion. Meanwhile, dissolved ions can cause corrosion and pitting of boiler pipes, shorten equipment service life and bring frequent unplanned shutdowns. Ordinary freshwater treatment processes often struggle to meet the strict purity standards for boiler feedwater, especially when local freshwater resources are limited or of poor quality.

Following are the steps involved in the desalination process: Pretreatment: Seawater usually contains suspended solids, organic matter and algae, which need to be removed before desalination. Pretreatment steps may include filtration, flocculation and coagulation processes to remove these impurities. Reverse Osmosis (RO): The most common desalination method is reverse osmosis. During this process, seawater is passed under pressure through a semipermeable membrane that allows only pure water molecules to pass through, leaving dissolved salts and other impurities behind. The resulting product is called permeate. Post-treatment: After reverse osmosis, the permeate may still contain some impurities.

Combining reverse osmosis (RO) with electrodeionization (EDI) is a common method of desalination to obtain high purity water for steam boilers.

Electrodeionization (EDI): The RO permeate is then further purified by EDI.  EDI uses an electric field and an ion-selective membrane to remove any residual ions from the RO permeate. This is an ion exchange process in which positively and negatively charged ions are attracted to opposite poles and removed from the water. This helps achieve higher levels of purity. Post-treatment: After the EDI process, the water may undergo additional post-treatment to ensure its quality meets the requirements for steam boiler feed water.

Treated water is stored in tanks and distributed to steam boilers. It is very important to ensure proper storage and distribution systems to prevent any contamination of high purity water. Regular monitoring of water quality parameters such as conductivity, pH, dissolved oxygen and total dissolved solids is critical to maintaining the high levels of purity required for steam boiler operation. The combination of RO and EDI provides an efficient and reliable method for producing high purity water from seawater for use in steam boilers. However, factors such as energy consumption, maintenance and operating costs must be considered when implementing a desalination system using RO and EDI technologies.