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Picking the Right Materials for Desalination

by Jan 11, 2017News, Products

Desalination is an important emerging process to bring fresh water to more and more parts of the world. As new processes emerge, we get the opportunity to explore newer and less corrosion-prone materials, meaning that desalination units last longer and work better.

The earliest desalination involved multi-stage flash, in which water is evaporated and then condensed in a series of flash chambers. Historically, these desalination tanks were made with shell materials that included mild steel or mild steel with a linking of copper-nickel, clad steel or stainless steel. Newer construction often includes solid duplex stainless steel instead.

Because of the risk of scaling with multi-stage flash, newer distillation processes have been created. In the new process, low temperature multi-effect distillation (LT-MED), distillation occurs under vacuum using lower temperatures, typically between 60 and 70 degrees Celsius. The lower temperatures involved means that less energy is used; however, this is a process that takes more time. The large surface areas needed can also mean higher fabrication costs. Over time, these distillation units have gone from being made with mild steel to being made with stainless steel shells with either titanium or copper-nickel tubes.

In the third most common desalination process, reverse osmosis is used. This process was first investigated in lab settings in the 1950s and came into commercial use in the 1970s. By the beginning of the 21st century, over 15,000 reverse osmosis plants were in operation. This filtering process is based on the principle of osmotic pressure; however, instead of osmosis causing particles to become fully dispersed, high pressure causes the opposite to happen. Selective membranes allow some materials through while keeping others behind. Water is pushed through the membranes of a filter while salt is prevented from moving through with it. Because of the high pressure put on piping, stronger materials are called for. Duplex steel, superduplex or alloys like 904L are used. 

As more areas deal with pressures such as drought and growing populations, more desalination processes will be needed. By picking the materials that are ideal to fabricate desalination units that are able to stand up to the rigors of processes such as sea water reverse osmosis, you can create items that are resistant to pitting, corrosion and other kinds of wear. There are more materials than ever that can help you balance effectiveness and durability with economy. 

Great Plains Stainless Steel has a wide range of options available, including strong and corrosion-resistant duplex stainless steel. Our highly knowledgeable staff can work with you to find the options that fit your needs the best. Get in touch today to discuss the right materials for your next project.