A New Way to Think About Saltwater Filtration Systems

Clean drinking water is a daily necessity – and there is simply not enough of it. Shortages of drinking water impact the survival of the world’s population because nearly 50 percent of all potable water is used by industry and agriculture.

According to the United Nations, nearly 700 million people do not have access to clean water globally. This figure is estimated to rise to 1.8 billion during the next ten years. One method for rapidly increasing the amount of fresh water is to extract it from seawater through a process called desalination. Together, wire mesh and wire cloth play an absolutely critical role in creating new supplies of fresh water.

Desalination by the Numbers

The International Desalination Association (IDA) indicates there are approximately 18,426 desalination plants located in 150 countries, supplying water to nearly 300 million people. Most of these are in the extremely dry climates of the Middle East. However in the U.S., drought-inflicted California has also added desalination to its water generating portfolio with the largest plant in the Western Hemisphere. These are three examples of the world’s largest desalination facilities.

• Carlsbad, California plant – 50 million gallons daily
• Sorek plant, Israel – over 165 million gallons daily, with nearly 50 percent of all water in Israel generated by desalination
• Ras Al Khair plant, Saudi Arabia – 192 million gallons daily

Power consumption and wastewater brine are two issues that affect all desalination plants.

How it Works

There are several different methods of desalination. Two of the main processes – highly simplified here – are seawater reverse osmosis (SWRO) and multistage flash desalination (MSF).

• SWRO – Salt water is forced under high pressure through a semipermeable membrane of very thin plastic sheets. The membrane pores are incredibly small, which allows water molecules to squeeze past, but not salt.
• MSF – Salt water is heated and caused to repeatedly boil by being forced into smaller and smaller chambers under pressure. The resulting steam passes through wire mesh demisters and condenses into fresh water which is collected.

Demystifying Demisters

Demisters using wire cloth and mesh, separate and capture liquid in the vapor stream during MSF desalination. The demister mats consist of several layers of wire mesh, each staggered relative to the next. These mats are placed horizontally facing the stream of vertically rising vapor. As the vapor rises, droplets land on the mesh wires, merging into larger drops that drip down to the bottom layer. Since the wire mesh presents very little vapor resistance, this enables production of distilled water with extremely low salinity.

Wire mesh demister performance depends on many variables including:

• Number of support grids – Since the wire mesh is not rigid, it must be supported on suitable grids with a high percentage of free passage.
• Velocity of water vapor – Separation efficiency, which is influenced by the specific wire mesh surface area, improves with increasing flow velocity.
• Wire diameter and packing density – Wire diameter generally ranges between 0.1 mm and 0.5 mm.
• Pad thickness – The demister pad is between 100 and 150 mm deep in most applications. If the vapor contains very fine droplets, much deeper pads or multiple layers are required.
• Wire mesh material – Wire mesh filters must be sturdy, have constant permeability, high corrosion resistance, and high thermal stability.

The Last Drop

Clearly, desalination is a critically important source of fresh water for the world. A proven, scalable technology, desalination also depends on the properties of wire mesh and cloth during the MSF process.

Newark Wire Cloth, a recognized leader in the wire cloth industry, manufactures off-the-shelf and custom woven wire cloth for any and every application. It has specialized in the fabrication of wire cloth parts and assemblies for the past 105 years. Contact us today to discuss how wire cloth can help create water for the world in your next desalination project or application.