Performance study of a pilot-scale low-temperature multi-effect desalination plant

A 30 t/d low-temperature multi-effect evaporation seawater desalination (LT-MED) system was designed based on the mathematical model, and the corresponding pilot device was constructed in Tianjin, China. Whole-process tests were carried out, and the effects of key operating parameters, including motive steam pressure, maximum operating temperature, temperature difference, spray density, non-condensing gas extraction method, and steam ejector flow, on desalination performance were analyzed. Results showed that the device successfully met product water design requirements; total dissolved solids were less than 5 mg/L. Water production initially increased as motive steam pressure increased, then stabilized when pressure exceeded 21% of the design value. Water production reached its maximum when heat transfer temperature difference and spray density ranged from 3 °C to 4 °C and from 240 L/(m h) to 300 L/(m h), respectively. Unlike in parallel mode, water production increased by 3.64% when vacuum pumping was operated in series mode. Water production and gain output ratio increased, and system energy consumption reduced when a thermo-vapor compressor was introduced. The results provide a useful reference for the design of other large-scale seawater desalination systems.