مدل ساده شبیه سازی شده برای سیستم های اسمز معکوس برای نمک زدایی آب دریا

Desalination of seawater has been considered as one of the most promising techniques for supplying fresh water in the regions suffering water scarcity. Reverse osmosis (RO) is one of the major technologies for mid- and large-size desalination plants because it offers a means of producing high quality of water from seawater with lower energy consumption than other processes such as evaporation processes. In this study, RO systems for seawater desalination were theoretically investigated to provide insight into the optimum process design. A simple model based on the solution–diffusion theory and multiple fouling mechanisms was developed and used to analyze the performance of RO systems. The effect of recovery ratio and permeate flux on the efficiency of the whole RO system was investigated for a wide range of operating conditions. The model was also applied to optimize the design of RO process for low energy requirement and high boron removal.

Seawater desalination has been gaining popularity as a feasible option for potable water production, as available water sources are gradually depleting due to water scarcity as wellas quality deterioration [1,2]. High pressure reverse osmosis (RO) processes have been the technology of choice for seawater desalination in the US and many other countries in the world [3,4]. The market share of RO desalination was 43% in 2004 and is forecasted to increase up to 61% in 2015 [5]. This is because RO has manyadvantages including low energy requirements, low operating temperature, small footprint, modular design, and low water production costs. However, the performance of RO plants is quite sensitive to the quality of the feed water and plant operating conditions. This means that the availability of reliable RO models is of great importance for process design and operation [6, 7]. Unfortunately, it is difficult to obtain a rigorous mechanistic model of RO process, which accounts for several important operating factors such as permeate recovery, flux, feed temperature, concentration polarization, and fouling [8]. Although the membrane makers have developed several softwares to help possible customers to design an RO plant, they mainly focus on the performance analysis of some RO modules rather than the optimization of RO process in terms of energy consumption and product water quality.

In this work, RO systems for seawater desalination were theoretically investigated using a simple model based on the solution–diffusion theory and multiple fouling mechanisms. The following conclusions can be drawn from this work: C The predictions of our model were compared and verified with the predictions of ROSA 6.1 software. Although membrane manufacturers supply software for their own membrane products, our model presented in this work can be used in any type of RO membrane with small adjustments for model parameters, including water and salt transport constants. C Recovery ratio has to be optimized for low energy consumption and high solute rejection. Based on our calculation, the minimum specific energy for a SWRO plant with a capacity of 1,090 m3/d is 2.336 kWh/m3 at Rec = 51%, Javg = 14 L/m2-h, and T = 25EC. C Higher flux improves the solute rejection, but increases the specific energy consumption. Increasing the feed water temperature reduces the specific energy, but deteriorates the solute rejection. Energy recovery efficiency is an important factor affecting the specific energy consumption, especially at low recovery ratio. C Using our model, the optimum recovery and flux can be determine for a given condition of specific energy and boron concentration in permeate. Temperature is also an important factor affecting the optimization of SWRO system. C Depending on the fouling mechanism, boron rejection may be different even at the same fouling level.