Optimization of Brackish Water and Seawater Reverse Osmosis Desalination

CAMERON NardiniCyrus PocharaMariangel GarciaAdvisor: Dr. Mingheng Li Analysis of Brackish and Seawater Reverse Osmosis Desalination

Outline of PresentationReverse Osmosis Desalination OverviewMathematical ModelPlant Data/ResultsConclusionsDesalination Variablesk- pressure drop factorP- pressure difference across the membraneP0-feed pressure prior to pumpPpump- pressure increase across pumpQ- retentate flow rateQ0- feed flow rate 0- osmotic pressure change across the membrane entrance Lp- membrane hydraulic permeability Y0 - Product Water/Feed Water2 Pass RO system2nd Pass => Sea Water acts as Brackish (important to decide operating/design conditions)!FeedBrineBrinePermeatePermeate1st Pass Membranes2nd Pass Membranes2nd Pass necessary for SWRO.not required for BWRO2 Stage RO System

Reverse Osmosis DesalinationThe purpose of the reverse osmosis (RO) membrane system in the overall treatment process is to remove dissolved solids from the feedwater by forcing the feedwater through a semi-permeable RO membrane.

RO Membranes

dQ =-ALp (P 0 *(Q0/Q) )dx

(Volumetric Flow Rate of Change)

d(P) = - kQ2dx

(Pressure Rate of Change)

Normalized Specific Energy ConsumptionEnergy costs expensive for desalinationNormalized Specific Energy Consumption = NSECEnergy consumption per volume of produced permeate Our model can be evaluated to reduce NSEC

Where Yo is system level water recovery, N is the number of stages ( N 1 ) and erd is energy recovery efficiency of ERD (0 erd 1)ERD (Pressure Exchangers)

ERDs, How Do They Work?

Equation for effectiveness of ERD in energy reduction is PX Efficiency divided by Recovery. This implies ERD is only truly useful for SWRO. (Large recoveries in BWRO => small savings due to ERD)

Theoretical Energy Consumption Analysis

For optimization of swro and bwro processes Mathematical ModelNormalization dQ =-ALp (P 0 *(Q0/Q) )dx

Divide by Q0Rearrange to achieve:d(Q/Q0) = ( -ALp 0 /Q0)*((P/0)*(P0/P0) - Q0/Q ) dx

Now, letq = Q/Q0 = -ALp 0 /Q0p = P/P0 = 0 /P0

dq = -*(p/ 1/q)dx

d(P) = - **q2dx

Dimensionless Parameters

Operating Parameter - Changeable Design Parameters - Fixed 16SWRO vs. BWRO Parameters

Why the difference?Plant Data/Results

Westbasin Flow Chart

Umm Lujj Flow Chart

Ideal Conditions

Large Alpha by having a lesser inlet pressure than inlet osmotic pressure.Small Kappa by having large value of the inlet osmotic pressureLarge Gamma by having a larger osmotic pressure with a lower flow rate.Current ConditionsUmm Lujj SWRO 35% RecoveryAlpha = 0.52Gamma = 0.68Kappa = 0.31Westbasin SWRO 50% RecoveryAlpha = 0.38Gamma = 0.52Kappa = 0.535Umm Lujj BWRO 85% RecoveryAlpha = 0.11Gamma = 0.15Kappa = 1.5

Umm Lujj SWROWestbasin SWROUmm Lujj BWRONSEC Calculations With ERDUmm Lujj SWRO ERD = 86.67%

Westbasin SWRO ERD = 58.33%

Umm Lujj BWRO ERD = 7.55%

ConclusionsDifferences in BWRO and SWRO due to Osmotic Pressure differences implies different design and operating conditions should be used (high recovery for BWRO, low recovery for SWRO).Usage of an ERD will reduce NSEC significantly in SWRODesalination Facilities Can Be Profitable utilizing these energy reduction models.Properly optimizing design is crucial for future growth in this sector.