The Effect of Reverse Osmosis Brine Recycling by Employing Adsorption Desalination System Essay

Intake, pretreatment and disposal cost of reverse osmosis desalination plant represent about 25% of total cost per cubic meter of permeate product. The present study investigates the effect of reverse osmosis brine recycling by employing adsorption desalination system. The adsorption-desalination system produces dual useful effects namely producing high quality potable water and generating cooling effect. Reverse osmosis sea water desalination using cellulose triacetate membrane -hollow fine module design- was simulated by engineering equation solver. The brine leaving reverse osmosis system was fed to adsorption desalination system. The adsorption desalination is driven by a heat source such as solar energy. The adsorption desalination system has been simulated by MATLAB program. Results show that system recovery increases and system permeate concentration decreases by using the new combination. In addition to system performance improvements, a cooling effect is generated and can be utilized.
Considering feed flow rate is constant and the calculations are based on seawater temperature of. shows one module of proposed RO system.
Osmotic pressure can be calculated by the following equation.
Water recovery and salts rejection are two parameters used to evaluate RO performance and are defined as
The following equation defines the rate of water passage through a semi-permeable membrane.
P_average and _average are the average hydraulic and osmotic pressures on the feed side and are given by
The following equation defines the salt through the membrane.
Values of Kw and Ks are taken from manufacturer manuals. The salinity of permeate is calculated by the following equation. Substituting Eq. and Eq. into Eq.
The transient uptake by the silica gel can be obtained using linear driving force kinetic equation as
Energy balance equation for the adsorbent bed can be expressed by
The outlet temperature of the water from each heat exchanger is estimated using log mean temperature difference method and it is given by,
The energy balance in the evaporator is expressed as
The heat of evaporation, desorption, and the condensation energy rejected at the condenser are given by
The energy balance in the evaporator is expressed as
The heat of evaporation, desorption, and the condensation energy rejected at the condenser are given by
The cycle is analyzed using key performance parameters namely specific cooling power (SCP), specific daily water production (SDWP) and the coefficient of performance (COP).
Applying mass and salt balance
AD system recovery is given by
The overall system recovery is given by Eq.
Adsorbent bed heat transfer area
Condenser heat transfer area
Evaporator heat transfer area
Aluminum specic heat
Cupper specic heat
Chilled water specic heat
Water specic heat vapor phase
Water specic heat liquid phase
Silica gel specic heat
Cooling/heating water ow rate
Chilled water ow rate
Bed heat exchanger n weight(Al)
Condenser heat exchanger tube weight(Cu)
Bed heat exchanger tube weight(Cu)
Evaporator heat exchanger tube weight(Cu)
Weight of silica gel in each bed
Liquid water in side evaporator initially
Average radius of silica gel particle
Chilled water inlet temperature
Heat transfer coefcient of bed
Condenser heat transfer coefcient
Evaporator heat transfer coefcient