Water is the basis of daily life and industrial development for all communities. Water desalination plants emerged as one of the most important alternatives to overcome the shortage of water resources especially in desertified countries like Libya. Boilers are the main part in thermal desalination plants which depends on steam as the working fluid to heat and evaporate the seawater. with a capacity of 80 tons/hr of superheated steam at 220℃ and 15bar. Due to operating conditions, there was a decrease in steam boilers productivity and low efficiency. Heavy black smoke in chimneys was also detected. This work investigates the performance of the above mentioned boilers to determine the actual causes of these negative results by comparing the design values with different operating readings data. The results show a decrease in the efficiency of the boilers for low loading rates, which is affected by the air/fuel ratio. The deviation of this ratio from the design values leads to low efficiency and the emergence of heavy smoke in the chimneys, which causes deposits on the boiler pipes reducing the effectiveness of heat exchanger and therefore the thermal efficiency. The study also shows that the long operation suspension of the boilers in the first years of its life, due to the lack of discharge network and electricity cutoffs resulted in bad effect on the pipes conditions. The last led to the pipes deterioration resulting in water leaks and thus low boilers evaporation rates.

No abstract

Mathematical thermodynamic modeling is used in desalination systems to obtain unknown values and predict various properties such as enthalpy or phase equilibrium. These models are useful to understand system behavior. Zuara desalination plant is a multi-effect evaporation plant without vapor pressure (MED) with three total units of 40,000 m3/day. A mathematical modeling of the desalination plant thermal components was performed to simulate and forecast the temperatures, mass flow rates, and the productivity of each cell of steam. The total productivity of the desalination unit and the performance rate in different operating conditions was also found. A Python program was used to solve the model equations. The obtained results show that the productivity of the system and the gain output ratio are directly proportional to seawater temperature and inversely proportional to plant load.

The flow of water within a pipeline system causes loss of energy due to friction effects. To overcome these losses, energy is added to the water through the pump. So, the right pump selection is important for providing the required flow rate. The first step to select a right pump for any pipeline system is calculating the performance curve of piping system, which is a graphical representation of the energy required to move a given flow rate through a piping system and is used to identify the characteristics of the system's pump. For this purpose, the system curve for the water pipeline connecting the main reservoirs of Zawia desalination plant to the sub-tanks in Harsha has been evaluated and represented graphically in H-Q curve of the selected pump. This water pipeline network consists of sets of pipes connected in parallel and series with a total length of 5 km. The system NPSHA at different water levels in the suction tank at the maximum system flow rate of 800 (m3/hr) has been calculated to ensure avoiding cavitations problem in the selected pump.

No abstract