ENEL experience of seawater desalination plants

Abstract

ENEL is Italy's main electrical energy producer with an installed thermal capacity of over 35,000 MW. For the production of both industrial and demineralized waters in coastal power plants, desalination processes (MSF and VC evaporators and seawater RO) are widely used. As far as MSF evaporators concerns, 28 units are operating: the capacity of each unit ranges between 25 and 100 t/h for a total capacity of about 1,500 t/h of desalinated water. MSF evaporators have been installed since late seventies up to now, optimizing time by time and case by case design parameters (construction materials, in particular) and operating conditions. Presently, 20% of the MSF units are acid-conditioned and 80% are operated with commercial organic scale inhibitors. To define a list of recommended products, pilot tests are in progress at the Piacenza Central Laboratory of ENEL. As far as VC evaporators concerns, 3 units have been installed since 1980, with a capacity of 20 t/h each. For solving problems during operation, some modifications have been made to the materials of the tube bundles, to the coatings of tube shells, and to the steam compressors. As far as seawater RO plants concerns, beyond one very small unit (3 t/h) already in operation for the production of potable water, 4 units are under construction or commissioning for industrial water production: the capacity of each unit ranges between 20 and 150 t/h for a total capacity of 270 t/h of desalinated water. To define, case by case, the optimal pretreatment technology's pattern and to test the various types of seawater membranes, the Piacenza Central Laboratory has under advanced commissioning a containerized SWRO pilot plant with a capacity of 2 t/h.