Titanium’s superior corrosion resistance to seawater and high strength make it being the best materials for desalination industry in these years. There are two basic technology categories for desalination systems: membrane processes (primarily reverse osmosis) and thermal distillation (evaporation). Thermal distillation is broken out into three sub categories: multi-stage flash evaporation (MSF), multiple-effect evaporation (MED), and mechanical vapor compression (MVC). Titanium finds most of its applications in the thermal distillation category, used for tubing, valves and plate heat exchangers. By contrast, titanium has only limited use in reverse osmosis systems, primarily in pump heads.
Thermal distillation is the main desalination technology used in the Middle East. The world’s two largest thermal distillation desalination projects located in Saudi Arabia. The Ras Al-Khair MSF desalination plant, completed in 2014, required 6,000 metric tons of titanium, provided 1 million cubic meters per day (m3/day) of water to 3.5 million people in Saudi Arabia’s Riyadh region and additional 25,000 m3/day supply to Ma’aden Aluminum Complex. Thirty percent of this plant’s output were produced by reverse osmosis. The Yanbu 3 MSF plant, completed in March 2016, supplied 550,000 m3/day of water to nearly 2 million people in the industrial city of Yanbu and the nearby Medina region. Each desalination plant in Saudi Arabia used between 5,000 and 6,000 metric tons of titanium.Desalination is a moderate industrial growth market for titanium, with typical annual demand of around 500 metric tons.
For thermal desalination, MSF technology was specified for large outside-diameter (OD) tubing (above 40mm) and long tubes (above 20m). Tubes for MED are closer to power-generation tubes, with an OD of 25mm and length around 13m.Heat-transfer tubes are the heart of the MSF process, and that MSF plants typically offers a reliable, 40-year life span. MSF typically has an operating range of more than 110 C (230 F). Titanium is considered the best material for this technology in Saudi Arabia, competing against copper/nickel and aluminum/brass. As for MED, seawater is sprayed on the outside of titanium tubes and vapor is condensed inside the tube. As the name suggests, there are multiple stages of evaporation and condensation in the MED process. In MED, the feedwater preheaters and final condenser tubing are made from titanium. The operating range for MED is 65 to 75 C (150 to 170 F). For MFS, titanium can reach 0.7mm for tube walls, while in MED the goal is to achieve 0.4mm. All thermal desalination plants are combined with power plants when exhaust steam from the turbine is the source of energy for desalination. As a result, proper disposal of this flowback water is problematic. Thermal desalination can be used to clean up the flowback water, allowing it to be reused for another fracking project. It created a new market for desalination technology. Titanium is clearly the material of choice for this application.