(376bw) A Novel FO-MED Hybrid System for MED Brine Further Concentration

Authors: 
Yang, Y., East China University of Science and Technology
Sun, Y., East China University of Science and Technology
Yu, J., East China University of Science and Technology

A Novel FO-MED Hybrid System for MED Brine Further
Concentration

Ye Yang (speaker) , Yuzhu Sun*, Jianguo
Yu*

State Key Laboratory of Chemical
Engineering, College of Chemical Engineering, East China University of Science and
Technology, Shanghai 200237, China

Abstract

Multi-effect distillation (MED) is one of the most common
thermal desalination processes. However, MED brine disposal is still an
inevitable problem. In this paper, forward osmosis (FO) process was integrated into
multi-effect distillation (MED) process for brine further concentration, as
shown in Figure 1.The feasibility of FO for LT-MED brine was studied in
experiments, and the result showed that CaCO3 scaling not only caused flux
decline, but also reduced the forward salt rejection remarkably at lower
temperature due to cake-enhanced concentration polarization (CECP) as figure 2
shows. The membrane scaling was almost reversible under simple physical
cleaning, which was explained by the interaction of
scaling ions with membrane interface using radial distribution function (RDF)
via Materials Studio software. Besides, the effects of operating condition on flux and
rejection were investigated to improve FO performance, and it was found that
the flux was linearly increased with temperature in premise of thermal
stability. The
influence of flow rate was lower than that of temperature. Based on above
operational characteristics, a FO-MED hybrid system was proposed to improve the
performance of existing traditional LT-MED system as shown in Figure 3. The
Aspen Plus simulation results showed that this hybrid system had higher
concentration factor (CF) of 2.67, greater gained output ratio (GOR) of 7.68,
as well as lower specific area (SA) of 198, which was a bridge linking thermal
seawater desalination and resource utilization of brine.

Figure 1 Schematic diagram of MED-FO hybrid system

Figure 2 Forward salt rejection during membrane scaling at 25 degree and 40 degree

Figure 3 Aspen Plus flow sheet of FO-HT-MED system for LT-MED brine
further concentration