Low Energy Desalination Demonstration Unit Results

Transcription

1 Low Energy Desalination Demonstration Unit Results SIWW July By: R. Knauf, T. LeTourneau, K. H. Ng, R. Fu, L. S. Liang, M. Shaw

2 The Desalination Challenge In August, 2007, the Singapore Environment & Water Industry Development Council (EWI) offered a Challenge Ideas sought to produce drinking water from seawater at an energy value of 1.5 kwh/m 3 or less Siemens R&D was announced the sole winner in June, 2008 from 35 proposal submissions The Siemens Project officially commenced on 01 October 2008 The project to culminate with 50 m 3 /d Demonstration Plant in Singapore by October, 2011 Slide 2

3 Successful Demo Unit Start-up: Dec 2010 Pilot Unit - Singapore Results Actual seawater treated to drinking water quality standard achieved (26 months) Greater than 50% reduction of energy from existing best available technology ( kWh/m 3 ) At start-up, pilot achieving 1.85 kwh/m 3 (inclusive of pumping, pretreatment, desalting, and post-treatment) Demo constructed of commercially available ion exchange membranes EWI Challenge focused solely on energy consumption not capital costs Slide 3

4 Electrodialysis (ED) & Continuous Electrodeionization (CEDI) Water is not forced through a membrane Salt ions are transferred through Ion Exchange Membranes ED CEDI Slide 4

5 Overall Flow Schematic 100μm Disk Filters Ultra Filtration Desalination Post Treatment Slide 5

6 Desalting Flow Schematic ED Dilute Series Flow ED Concentrate Parallel Flow CEDI 3 Parallel Modules Overall recovery rate = 30% Slide 6

7 Contributing Factors to Power Consumption Electrical Resistance R cm = cation exchange membrane R d = fluid in the dilute compartment R am = anion exchange membrane R c = fluid in the concentrate compartment Current i = current density I e = i ΔA ΔA = area of membrane element Donnan Potential Voltage ac 2RT ln a d ΔΦ = zf R = universal gas constant T = absolute temperature z = valence (=1 for NaCl) F = Faraday s constant (96,500 amp-sec/equiv) a d = activity in dilute a c = activity in concentrate V = i ΔA (R am+r d+r cm+r c) + ΔΦ Total Power = V i ΔA + pumping power + electrode losses + other losses Slide 7

8 Process Model Sensitivity Analysis Energy vs. Current Density Energy vs. Water Recovery kwh/m 3 kwh/m Pretreatment Desalt pumpage Desalt deionization Pretreatment Desalt pumpage Desalt deionization Current density (A/m 2 ) Water recovery (%) Conditions: 3 stages, velocity = 0.50 cm/sec, recovery = 35%, membrane resistance 2.80 ohm-cm 2, spacer thickness = 0.38 mm, pump efficiency = 0.75 Conditions: 3 stages, velocity = 0.50 cm/sec, current density = 20 A/m 2, membrane resistance = 2.80 ohmcm 2, spacer thickness = 0.38 mm, pump efficiency = 0.75 Slide 8

9 Process Control SCADA Interface DC Power Controllers Slide 9

10 Total Power Consumption Power 2 kwh/m Operating hours Average power consumption = 1.81 kwh/m 3 Accumulated running hours = 1600 Power consumption = desalination power + pumping power + electrode losses and other inefficiencies Slide 10

11 Conductivity Data Feed ms/cm 25 5 ms/cm Feed water conductivity Product water conductivity Product Operating hours Average seawater conductivity = 43.5 ms/cm or ~ 32,000 ppm TDS Average product water conductivity = 0.96 ms/cm or ~500 ppm TDS Slide 11

12 Module Resistance ED 3 35 Ohms CEDI ED Stage-1 ED Stage-2 ED Stage-3 CEDI 10 5 ED 2 ED Operating hours Module resistance stable. Resistance fluctuations due to variation in product water quality and current. CEDI resistance is lower due to resins in dilute compartments Slide 12

13 System Flowrate Reject Flowrate (LPM) Product/Dilute Reject/Concentrate Product Operating hours System flowrate was allowed to fluctuate, thus keeping the pressure drop constant. Total system pressure drop= 1.5 bar Slide 13

14 Water Quality Parameter WHO Guideline Seawater (Avg.) Product (Avg.) Conductivity (ms/cm) TDS (ppm) <600 32, Chloride (ppm) <250 15, Sulfate (ppm) <250 2,200 ND Boron (ppm) < Aluminum (ppm) < Copper (ppm) < Iron (ppm) < Manganese (ppm) < Fluoride (ppm) < Sodium (ppm) - 8, Calcium (ppm) Potassium (ppm) Magnesium (ppm) - 1, E. Coli (cfu/100 ml) <1 <1 <1 Slide 14

15 Ion Exchange Membrane Evaluation Parameter Area Resistance (ohmcm 2 ) Transport No. Thickness (μm, wet) Water Content (%) AEM CEM Existing Membrane Technology Challenges Expensive (> 10x commercial acceptance) Higher energy consumption (high resistance) Not manufacturing-friendly (brittle) Not feasible for commercial ED product Status of New Siemens Desal Membranes New formulations developed, patents filed Successful production trial completed Superior performance characteristics New R&D pilot line producing samples Slide 15

16 Technology Scale-up Plate & Frame Spacer Demo Module design has numerous challenges Plate & Frame design required rubber spacer less than 0.4 mm thick difficult to manufacture Flow ports large enough to minimize headloss were needed for low energy Large flow ports are prone to cross leakage and current leakage - inefficiencies Large flow ports require cap material to support netting Flow channel required proper distribution Stack is reliant upon very large clamping force for sealing Membrane utilization is less than 70% Plate & Frame system design is costly Slide 16

17 Technology - to - Product Transition Module Production Next-Generation Module Design Status of new Siemens ED module New design optimizes operating & capital costs High IEM utilization; low pressure drop Easily automated assembly process Eliminates leakage potential Eliminates need to clamping force sealing Challenges of new Siemens ED module Design for highest efficiency (current, membrane) Materials (stable, low cost, corrosion-resistant, functional) Validate system costs Development of production automation Slide 17

18 Technology - to - Product Transition Field Testing Demonstration Plant Technology Feasibility Reference Plants Commercial Module Design Example Demonstrate feasibility of Technology Attempt to achieve all-inclusive target energy value of 1.5kWh/m 3 Determine pre- and post-treatment needs Determine operational characteristics of ED/CEDI process on actual seawater Obtain long-term performance data on membrane and system materials Demonstrate Product performance Obtain economic confirmation on design & construction at commercial flow rates Gain customer feedback Obtain operational data on membrane life & cleaning frequencies, energy consumption Reference plants for potential customer visits Slide 18

19 Customer Impact? Energy Capital Balance Other Value Adds kwh/m m 2 /(m 3 /h) Energy Consumption Membrane Area Required 500 Low energy consumption Low pressure pumps, piping, valves, fittings Low vibration, low noise levels Less Pretreatment, Less Post-treatment Less corrosion concerns with non-metal piping Chlorine tolerant components Improved finished water quality Improved safety No maximum feedwater salinity Current Density, A/m 2 0 Slide 19

20 Thank You Slide 20