NCEDA Project Workshop February 6, 2013

Transcription

1 NCEDA Project Workshop February 6, 2013 Silica Removal from groundwater for Reverse Osmosis water recovery enhancement and waste brine volume reduction Victoria University Institute for Sustainability and Innovation

2 Participating Organizations and Personnel Victoria University Peter Sanciolo Nicholas Milne Stephen Gray Origin Energy Eddy Ostarcevic Mark Beighton Greg Peril Minara Resources/Hatch Engineering Kelvin Taylor Mark Mullet University of Texas El Paso Anthony Tarquin Thomas Davis

3 Project Deliverables and Outcomes Project Deliverable A full literature review Written reports on laboratory outcomes for Origin and Minara Resources water samples Written report on process designs and preliminary costs - Minara Resources Industry workshops to communicate outcomes Project outcomes Identified knowledge gaps in the area of silica scale mitigation to be written up as journal article PhD on silica chemistry initiated Demonstrated the effectiveness of: silica removal by adsorption for silica scale mitigation in RO treatment of coal seam gas water and mining groundwater low ph RO operation as a silica scale mitigation method for mining groundwater Favourable results have prompted: larger scale research on silica removal by adsorption consideration of low ph RO as a water management option in mining operations Performed a preliminary costing of silica removal and low ph operation as silica scaling mitigation processes for a mining operation Communication of project outcomes to the community

4 Silica Concentration (mg/l) Introduction: Scaling in Reverse Osmosis Process 1200 Expected concentrate silica concentration for a feed water containing 74 mg/l silica Water Recovery Limit Water Recovery (%) Without scale formation With scale formation at 200 mg/l solubility limit Consecutive doubling of silica concentration at 50%, 75%, 87.5%, 93.75% Scaling occurs at silica solubility limit Water recovery is limited by scale formation Solubility limit is sensitive to solution conditions

5 Literature review highlights R. Sheikholeslami et al. Desalination 139 (2001) 83-95

6 Option 1: Remove the silica Literature review highlights Mitigation of silica scaling in RO processes Alkaline precipitation in the presence of Ca and/or Mg Metal ion addition (Fe(III), Al(III)) Electrocoagulation using sacrificial Fe or Al electrode Adsorption onto metal oxides or hydroxides Fe(III) Hydroxide Cobalt hydroxide Nickel hydroxide Goethite Gibbsite Alumina Seeded precipitation Ion exchange Option 2: Operate RO under conditions where solubility of silica is higher Remove all Ca and Mg and operate RO at high ph Operate RO at low ph

7 RO Concentrate Studies: Introduction Salt laden water is a by-product of the gas production process ~ 150 GL/yr from QLD basins Origin has capacity to treat 32 ML/day (~12 GL/y) at its current operations The recovery of low-salt water by reverse osmosis is limited to ~80% by silica scale formation Achievement of 95% water recovery equates to a waste volume that is ¼ of the current waste volume

8 Irrigation area : Evap. pond area ratio Area (ha) Area (ha) RO Concentrate Studies: Introduction Benefits of achievement of higher water recoveries for 32 ML/d (11,680 ML/y) of CSG water: e.g.: at 80% RO water recovery 9,344 ML/y of irrigation water => can irrigate 1,557 ha for one year at 6 ML/ha/y irrigation requirement 2,336 ML/y waste brine => need ha at 10 ML/ha/y evaporation rate => Irrigation area : Evaporation pond area Ratio = 6.7 Irrigation area (ha) Water recovery (%) Evaporation pond Area (ha) Water recovery (%) Irrigation area : Evaporation pond area Ratio Water recover (%)

9 RO Concentrate Studies RO concentrate composition : Parameter Sample 1 Site 1 Sample 2 Site 1 Sample 1 Site 2 ph Conductivity (ms/cm) SiO 2 (ppm) ICP B (ppm) ICP Ca (ppm) ICP Fe (ppm) ICP Mg (ppm) ICP Total Organic Carbon (ppm) Total Inorganic Carbon (g/l) Total Dissolved Solids (g/l) Test brines were highly carbonated, therefore Option 2 not considered practicable (All adsorption tests performed at native ph of 9.3)

10 Silica removal by adsorption, RO Brine: Adsorbent screening trials Option 1: Silica removal (by adsorption) Trial adsorbents: Adsorbent Type Particle Size Range Other Details Activated Alumina mesh ( µm) Standard, unpromoted Activated Alumina mesh( µm) Standard, unpromoted Activated Alumina -48 mesh(<300µm) Standard, unpromoted Activated Alumina mesh( µm) Enhanced Activated Alumina mesh( µm) Enhanced Activated Alumina 15 µm Silica removal resin Anion exchange resin Silica Gel mesh 60 Å pores Silica Gel mesh 100 Å pores Pre-adsorption treatments: Ion exchange to remove hardness Activated carbon treatment to remove organics

11 Silica removal by adsorption, RO Brine: Effect of ion exchange treatment * on Ca and Mg concentration Characterization of primary RO concentrates before and after softening using ion exchange Component Site 1 Site 2 Before After Before After SiO B Ca Fe Mg

12 Silica Concentration (mg/l) Silica removal by adsorption, RO Brine: Effect of ion exchange treatment on silica removal by adsorption Screening of adsorbents After adsorption - softened After adsorption - raw Silica removal by absorption before and after softening, Site 1 Brine Sample 2, 2 g/l, 25⁰C

13 Silica Concentration (mg/l) Silica removal by adsorption, RO Brine: Effect of ion exchange treatment on silica removal by adsorption Screening of adsorbents After adsorption - softened After adsorption- raw Silica removal by absorption before and after softening, Site 2 brine sample, 2 g/l, 25⁰C

14 Silica removal by adsorption, RO Brine: Effect of AC treatment* on organic content, Size exclusion chromatography results, Site 1, Sample 1, before and after AC treatment 220 nm Before AC treatment 254 nm 220 nm After AC treatment 254 nm * Coconut shell activated carbon, 7.5 g/l, 3 days contact time

15 Silica removal by adsorption, RO Brine: Sample to sample variability, organic carbon 220 nm Site 1 Sample nm 220 nm Site 1 Sample nm

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17 Results Summary Silica removal by adsorption, RO Brine : Adsorbent screening with and without pre-treatments Removal of Ca and Mg and organics does not improve silica removal by adsorption Activated alumina is able to reduce silica concentration without pretreatment to remove hardness and organics

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20 Silica Concentration (mg/l) Results Summary Silica removal by adsorption, RO Brine Silica removal by adsorption onto activated alumina is favoured by: high temperature high adsorbent dose For Site 1 primary 80% water recovery RO concentrate brine, 45 mg/l residual silica concentration can be achieved Overall water recovery of 96% may be possible: Expected increase in silica concentration for a feed water containing 45 mg/l silica Water Recovery (%) Overall water recovery = *20 = 96% Without scale formation With scale formation at 200 mg/l solubility limit

21 Irrigation area : Evap. pond area ratio Results Summary Silica removal by adsorption, RO Brine Irrigation area : Evaporation pond area Ratio Water recover (%) 80% water recovery evaporation pond area = 1/7 of irrigation area 96% water recovery evaporation pond area = 1/40 of irrigation area irrigation area Evaporation pond area

22 Concentration (mg/l) Silica removal by adsorption, RO Brine: Regeneration of activated alumina First regeneration, after first loading Second regeneration, after second loading Third regeneration, after third loading Batch Regeneration Steps Silica Aluminium Silica and aluminium concentrations during regeneration of AA1 adsorbent, 25⁰C, 2% NaOH

23 Silica Desorbed (%) Silica removal by adsorption, RO Brine: Regeneration of activated alumina First regeneration, after first loading Second regeneration, after second loading Third regeneration, after third loading Batch Regeneration Steps Silica desorption during regeneration of AA1, 25⁰C, 2% NaOH

24 Adsorbent lost (%) Silica removal by adsorption, RO Brine: Regeneration of activated alumina 10 First regeneration, after first loading Second regeneration, after second loading Third regeneration, after third loading Batch Regeneration Steps Adsorbent loss (as Al 2 O 3 ) during regeneration of AA1, 25⁰C, 2% NaOH

25 Silica removal by adsorption, RO Brine: Regeneration of activated alumina Silica loading rate, silica desorption rate and adsorbent loss rate data, 2% NaOH, 25 C Loading- Regen.Cycle Silica Loading Rate (mg/g/load step) Silica Desorption Rate (%/regen. step) Adsorbent Loss Rate (%/regen. step) Max. Min. Ave. Max. Min. Ave. Max. Min. Ave. 1 st nd rd

26 Results Summary Silica removal by adsorption, RO Brine Adsorbent regeneration Regeneration of activated alumina is possible using 2% NaOH, at 25 Deg.C Silica loading rate and silica desorption after 3 loading-regeneration cycles similar to during first loading and regeneration Adsorbent loss of approximately 6% per regeneration cycle Further optimisation required

27 Minara Resources RO concentrate studies: Introduction Minara Resources nickel mines use large quantities of groundwater (26 ML/day) Available groundwater needs to be desalted Salts interfere with downstream processing Salts corrode process equipment The recovery of low-salt water by reverse osmosis is limited to ~60% by silica scaling Achievement of 95% water recovery equates to a waste volume that is 1/8 of the current waste volume and 1.6 times as much usable water

28 Minara Resources RO concentrate studies Effect of low ph at high RO water recoveries Permeate flux Silica, Ca and Mg concentration Scale composition FTIR SEM-EDX Silica removal by adsorption

29 Minara RO Concentrate Composition

30 Low ph RO scaling study, Minara RO Brine Flat sheet membrane equipment used in low ph RO study

31 F/F0 Low ph RO scaling study, Minara RO Brine Permeate flux as function of water recovery Water recovery (%) ph 3.1, No antiscalant ph 3.1, 4 mg/l antiscalant Native ph, No Antiscalant Poly. (ph 3.1, No antiscalant) Poly. (ph 3.1, 4 mg/l antiscalant) Poly. ( Native ph, No Antiscalant)

32 F/F0 Low ph RO scaling study, Minara RO Brine Permeate flux as function of water recovery Water recovery (%) ph 3.1, No antiscalant, repeat ph 3.1, No antiscalant, repeat Native ph, No antiscalant, ph 3.1, 4 mg/l antiscalant, repeat ph 3.1, 4 mg/l Antiscalant, Repeat 2, Native ph, No antiscalant, Repeat 3, Native ph, No Antiscalant, Repeat 4, Native ph, No Antiscalant, Repeat ph 3.1, 4 mg/l Antiscalant

33 F/F0 Low ph RO scaling study, Minara RO Brine Permeate flux as function of water recovery Water recovery (%) ph 3.1, No antiscalant, repeat ph 3.1, No antiscalant, ph 3.1, 4 mg/l antiscalant, Repeat 2, Native ph, No antiscant, Repeat 3, Native ph, No Antiscalant, Repeat 4, Native ph, No Antiscalant, repeat ph 3.1, 4 mg/l antiscalant Poly. (ph 3.1, No antiscalant, ) Poly. (repeat ph 3.1, No antiscalant, ) Poly. (ph 3.1, 4 mg/l antiscalant, ) Poly. (Repeat 2, Native ph, No antiscant, ) Poly. (Repeat 3, Native ph, No Antiscalant, ) Poly. (Repeat 4, Native ph, No Antiscalant, ) Poly. (repeat ph 3.1, 4 mg/l antiscalant )

34 Silica Concentration (mg/l) Low ph RO scaling study, Minara RO Brine Silica concentration as function of water recovery Water recovery (%) No scaling silica concentration Native ph, No antiscalant ph 3.1, No Antiscalant ph 3.1, No Antiscalant Native ph, No Antiscalant ph mg/l Antiscalant ph 3.1, 4 mg/l Antiscalant Native ph, No Antiscalant Native ph, No Antiscalant Native ph, No Antiscalant

35 Calcium Concentration (mg/l) Low ph RO scaling study, Minara RO Brine Calcium concentration as function of water recovery Water recovery (%) No Scaling Ca Concentratiion Native ph, No antiscalant ph 3.1, No Antiscalant ph 3.1, No Antiscalant Native ph, No Antiscalant ph mg/l Antiscalant ph 3.1, 4 mg/l Antiscalant Native ph, No Antiscalant ph 3.1, 4 mg/l Antiscalant Native ph, No Antiscalant Native ph, No Antiscalant

36 Magnesium Concentration (mg/l) Low ph RO scaling study, Minara RO Brine Magnesium concentration as function of water recovery Water recovery (%) No Scaling Mg Concentratiion Native ph, No antiscalant ph 3.1, No Antiscalant ph 3.1, No Antiscalant Native ph, No Antiscalant ph mg/l Antiscalant ph 3.1, 4 mg/l Antiscalant Native ph, No Antiscalant Native ph, No Antiscalant Native ph, No Antiscalant ph 3.1, 4 mg/l Antiscalant

37 Low ph RO scaling study, Minara RO Brine FTIR of membranes Seen in IR spectra of quartz and calcite (CO2 adsorption) FTIR of Membranes 830 cm -1, Si-O stretch? 410 cm -1, O-Si-O bend? Wavenumber (cm -1) Unused Membrane Native ph ph 3

38 Low ph RO scaling study, Minara RO Brine SEM of membranes Unused membrane Membrane after native ph flat sheet scaling experiment Membrane after ph 3 flat sheet Scaling experiment

39 Low ph RO scaling study, Minara RO Brine EDX analysis of membranes Energ Element y (kev) Cl C Ca Ca O Na Mg Si P P S S Cl Cl Ca Ca Unused membrane Membrane after native ph flat sheet scaling experiment Membrane after ph 3 flat sheet scaling experiment

40 Results Summary Low ph RO scaling study, Minara RO Brine Operation of RO at ph 3 minimises silica scale formation Higher soluble silica at high recoveries Higher permeate flux at high recoveries Estimated achievable water recovery = 94% (= *40) FTIR data suggested the presence of silica and possibly carbonate on the native ph fouled membrane SEM images confirm that: Flux decrease at native ph is due to scaling Low ph operation minimises silica scale formation EDX data confirm that the scale formed at native ph contains silicon, calcium, magnesium and oxygen

41 Silica Concentration (mg/l) Silica removal by adsorption, Minara RO Brine Effect of ph on silica adsorption/precipitation Effect of ph, 2 g/l adsorbent, 15 minutes contact time, ambient temperature ph AA1 (15) AA2 ( ) No Adsorbent SG(100A) IX

42 Calcium Concentration (mg/l) Silica removal by adsorption, Minara RO Brine Effect of ph on calcium adsorption/precipitation 350 Effect of ph, 2 g/l adsorbent, 15 minutes contact time, ambient temperature ph AA1 (15) AA2 ( ) No Adsorbent SG(100A) IX

43 Magnesium Concentration (mg/l) Silica removal by adsorption, Minara RO Brine Effect of ph on magnesium adsorption/precipitation 250 Effect of ph, 2 g/l adsorbent, 15 minutes contact time, ambient temperature ph AA1 (15) AA2 ( ) No Adsorbent SG(100A) IX

44 Silica Concentration (mg/l) Silica removal by adsorption, Minara RO Brine Effect of adsorbent dose on silica adsorption Residual Silicon concentration after AA1 (15) treatment, 15 minutes contact time Adsorbent Dose (g/l) 45 Deg.C 35 Deg.C 20 Deg. C

45 Silica Concentration (mg/l) Silica removal by adsorption, Minara RO Brine Effect of contact time on silica adsorption 250 Effect of Contact time and temperature, AA1 (15) g/l adsorbent, 20 deg. C Time (minutes) 2 g/laadsorbent, 45 Deg.C 10 g/l adsorbent, 20 Deg.C 10 g/l adsorbent, 45 Deg.C

46 Results Summary Silica removal by adsorption, Minara RO Brine Estimated achievable water recovery, residual silica concentration = 16 mg/l Silica Concentration (mg/l) 400 Expected water recovery after 10 g/l, AA1 (15) treatment of RO Concentrate, 45 Deg.C, 60 minute contact time treatment Maximum Silica concentration Water recovery (%) Overall water recovery = *40 = 96%

47 Design and costing of alternative silica scale mitigation technologies Capital and operating expenditure estimates for treatment of Minara s Murrin operation Low ph, batch-wise sea-water RO (SWRO) treatment of RO concentrate Interstage high ph silica precipitation and removal using sedimentation. Interstage silica removal using activated alumina adsorbent at ambient temperature Interstage silica removal using activated alumina adsorbent at 45 C CAPEX ($M) OPEX ($/kl of permeate) $2.5 $0.8 $4.0 $2.0 $2.7 $6.2 $2.2 $6.2

48 Summary and Conclusions Coal Seam Gas Water High buffering capacity of tested CSG water prevents low ph RO operation Adsorption investigated Estimated water recovery achievable for tested CSG water = 96% Using 1 g/l adsorbent at 35 C Regeneration of adsorbent is possible Using 2% NaOH, at 25 C Silica loading /desorption after 3 cycles was similar to during first loading Adsorbent loss of approximately 6% per regeneration cycle Further optimisation of regeneration process required

49 Summary and Conclusions Groundwater from Mining Operation Low buffering capacity allows consideration of three treatment options: Low ph RO operation Silica removal by adsorption Silica removal by precipitation Estimated water recovery achievable for groundwater using Low ph RO = 94% low ph RO at 85% water recovery, on RO concentrate from 60% water recovery treatment of groundwater Adsorption/precipitation estimated water recovery achievable for groundwater = 96% 10 g/l adsorbent at 45 C, with a contact time of 60 min 20 g/l adsorbent at 20 C, with a contact time of 60 min Precipitation at ph 10.7 Preliminary costing for mining operation Low ph RO treatment most economically favourable (low capex low opex) Precipitation at ph 10.7 (high capex low opex) Adsorption at high temp (low capex- high opex)

50 Thank You

51 Results Summary Silica removal by adsorption, Minara RO Brine Estimated achievable water recovery, residual silica concentration = 42 mg/l Silica Concentration (mg/l) 500 Expected water recovery after 10 g/l AA1 (15) treatment of RO Concentrate, 20 Deg. C, 60 minute contact time treatment Maximum Silica concentration Water recovery (%) Overall water recovery = *40 = 90 %

52 Results Summary Silica removal by adsorption, Minara RO Brine Estimated achievable water recovery, residual silica concentration = 109 mg/l Silicon Concentration (mg/l) Expected water recovery after 5 g/l AA1 (15), 20 Deg. C, 15 minute contact time treatment Maximum Silica concentration Water recovery (%) Overall water recovery = *40 = 71%