Stainless steel for the seawater desalination industry

摘要

Water is no doubt one of the most important chemical compounds for mankind's life on Earth, second to oxygen, and the importance of proper handling and managing of water resources was established already by the Roman Empire. Its water commissioners (curators aquarum) and engineers established patterns for seeking out water sources, for transport, treatment, distribution and management that, together with technology updates, are followed to this day. There is a lot of water on the earth, around 1.4 million km~3, but more than 97% of it is salty, leaving about 2.5% as fresh water. Of this latter fraction, about 70% are frozen in polar icecaps and glaciers. Much of the rest lies deep underground in aquifers, essentially beyond human reach. The consequence is that all life depends on less than one percent of the total water on our planet. Interestingly, even this small fraction is believed to be adequate to support all life on Earth. However, it is not evenly distributed throughout our planet, either temporally or spatially. Besides, mankind has during the 20th century, by the industrial revolution, by the urbanisation of population and by poor management, to a large extent destroyed the available resources. Lakes and rivers have been used as recipients for waste from municipalities and industries, and aquifers have been overexploited resulting in penetration by seawater in some cases. However, the need for more and above all, better water for the world has resulted in increased awareness of the problems created and a variety of remedies have been taken in terms of legislation, management and engineering technologies. Municipal wastewater is being taken care of by wastewater treatment plants. Industrial effluents have been reduced, either by increased recycling of the effluents or by more thorough cleaning before being emitted. Distribution networks for potable water are being modernised to reduce spill from leakage and even in houses the water distribution systems are updated. These measures are still just not enough for certain parts of the world, i.e. in arid areas where fresh water just does not exist. In some such areas, however, there is seawater available and freshwater can be generated from this source by desalination, which will be the main subject of this presentation also including materials of construction.