Cost and energy needs of RO-ED-crystallizer systems for zero brine discharge seawater desalination

Abstract

A zero brine discharge seawater desalination concept integrating reverse osmosis (RO), electrodialysis (ED) and crystallizer into a single system (REC) is presented. Analytical models were used to optimize parameters and minimize water production costs. Parameters varied were: the ratio of seawater to RO brine in the ED diluate channel, ED current density, ED diluate outlet salinity, electricity and salt prices, and RO recovery by adding high pressure RO (HPRO). Using only RO brine instead of only seawater in the ED diluate channel reduced water production costs by 87% from 27 to 3.5 $/m 3 while increasing salt production costs 26% from 135 to 170 $/tonne-salt. The former was best for brine minimization, and the latter for salt production.Optimizing ED current density reduced REC costs by another 14% to 3.0 $/m 3 while increasing specific energy consumption 26% to 12.7 kWh e /m 3 , corresponding to a Second Law efficiency of 18%. Adding an HPRO stage was uneconomical as it increased specific costs 21%. A salt price of 104.5 $/tonne-salt will justify the cost of adding an ED-crystallizer. REC systems may be economically feasible in parts of the Middle-East. Producing other products such as Mg(OH) 2 or Br 2 may further improve economics. , "Cost and energy needs of RO-ED crystallizer systems for zero brine discharge seawater desalination," Desalination, online

Techno-economic analysis of ion concentration polarization desalination for high salinity desalination applications

“…When other parameters are set constant, the CE decreases with the salt removal ratio because 273 higher ion removal requires a higher current density and thus thicker ion depletion layers, which 274 cause undesirable phenomena, such as leakage of desalination, loss of membrane perm-selectivity 275 or water splitting, reducing the performance of ICP desalination ( Fig. 1(b)) (Nayar et al, 2017). 276…”

“…The 413 optimal water cost is $21.7/m 3 , which corresponds to $95/tonne salt produced. Adding the 414 crystallization cost of approximately $40/tonne of salt (Nayar et al, 2017), the total salt production 415 cost from the ICP-crystallizer is $135/tonne salt. The cost of brine concentration by multi-stage 416 ICP desalination is about twice of the brine concentration cost by electrodialysis (concentration 417 from 35 g/kg to 200 g/kg), which is around $60/tonne salt (Nayar et al, 2017).…”

“…Adding the 414 crystallization cost of approximately $40/tonne of salt (Nayar et al, 2017), the total salt production 415 cost from the ICP-crystallizer is $135/tonne salt. The cost of brine concentration by multi-stage 416 ICP desalination is about twice of the brine concentration cost by electrodialysis (concentration 417 from 35 g/kg to 200 g/kg), which is around $60/tonne salt (Nayar et al, 2017). The large gap in the 418 cost from the two processes is most likely to stem from that the recovery in ICP desalination is 419 limited to 50% at each stage, whereas the recovery in ED is much higher.…”

Brackish water desalination for greenhouse agriculture: Comparing the costs of RO, CCRO, EDR, and monovalent-selective EDR

“…For brackish water desalination, alternatives to conventional RO include: a novel variant of RO that operates in a semi-batch fashion called closed circuit reverse osmosis (CCRO) [10][11][12][13]; a membrane based electricity driven process called electrodialysis reversal (EDR) [14][15][16][17]; and a variant of EDR called monovalent-selective electrodialysis reversal (MS-EDR) [18][19][20][21][22] which uses MS-EDR membranes to selectively remove monovalent ions (see Fig. 2).…”

Energy Savings in Desalination Technologies: Reducing Entropy Generation by Transport Processes

“…Altmann et al [11] have assessed primary energy efficiency for a wide variety of desalination plants. Second-law analysis has also been applied to zero-liquid discharge desalination systems [12,13].…”