|
Once the proper geometry was determined, it became necessary to find a way to retard the alkaline scaling of seawater on the heat transfer surfaces. It was known that alkaline scale was a function of both operating temperature and feedwater pH. It was thought that operating the plants under a vacuum would aid in retarding the rate of scale formation. This, however, necessitated the physical size of the plants grow larger. It also posed additional operational difficulties (such as air in leakage) while not effectively preventing scale formation.
MECO developed what is known today the M3C evaporator design. The design principles include operation at a positive pressure utilizing less vapor volume and a smaller evaporator. This allows for the use of a higher grade of material (90/10 copper nickel) than typically available in vacuum plants. In addition, this design eliminates the maintenance problems and ancillary equipment associated with a vacuum plant.
The issue of alkaline scale formation was overcome through the development of a MECO-patented process known as TARGA. The TARGA system for alkaline scale abatement in seawater desalination plants is widely used all over the world today allowing MVC plants to operate continuously with on-stream cleanings and uninterrupted water service.
|
