used during fire extinguishment 4th Foam Seminar

Transcription

1 Design of a mobile posttreatment unit for the water used during fire extinguishment 4th Foam Seminar July 2009 Bolton, United Kingdom Dr. Martial Pabon E. I. DuPont de Nemours International SA Copyright DuPont Safety & Protection Be Sure

2 2 Work done in collaboration with - Dr. Romain Severac E. I. dupont de Nemours France SAS - Isabelle Deguerry E. I. dupont de Nemours France SAS Laboratory of electrochemistry, membrane and electromembrane processes (Ecole centrale centrale de Paris) Pr. Mohamed Rakib Dr. Estelle Coualier Mr. Clément Baudequin

3 Update on DuPont products The C6 based products that are being developed to replace C6-C8 products may require in most cases a foam reformulation. Forafac 1157N is based on C6 and C8 telomers. Forafac 1157 is based on C6 telomers. These two products were placed simultaneously on the market in the early 70s. Capstone TM 1157 is a me too product of Forafac DuPont is developing a C6 version of Forafac 1157N aiming at keeping the fluorine level in Fire Fighting foams in the same range for similar performances.

4 Water treatment: Outline 4 Type of effluent and typical volume to treat Final goal of our study Pilot effluent Analytical methods Pretreatment process (Electrocoagulation) Treatment process (Reverse Osmosis)

5 Life cycle to set up FFF Manufacturers CaF 2 Fluorinated surfactant for FFF FFF concentrates Incineration Recovery of the fluorinated surfactant Fire fighting: Rafineries,, Airports, Chem plants, End users Effluents treatment Effluents collection Extinguish the fire

6 Type of effluent and typical volume to treat Element present into the aqueous effluent generated by the extinction of a large class B fire: Water Gasoline, diesel, kerozene, Components of fire fighting foams Hydrocarbon surfactants Or Hydrolyzed protein Fluorinated surfactant Co-solvents like butylcarbitol Anti-freezing agents like ethylene glycol or propylene glycol. Handling issues: Gasoline or diesel particles are dispersed into the effluent (effluent heterogeneity) The effluent foams easily Ranges of effluent volumes to treat: Buncefield s fire (Dec 2005): 20 MM liters Missouri s fire (Jan 2005): 4.2 MM liters Effluent generated in Norway (May 2009): 1.7MM liters

7 Final goal of our study Identify existing effluent/water treatment technologies that could be used to Remove surfactants from water Remove specifically fluorinated surfactants from water Induced breakdown of fluorinated molecules Generate data on identified technologies At the lab scale At the pilot scale Evaluate the feasibility Time of treatment Cost Design for the construction of a mobile unit that can treat several million liters of effluent after a fire event.

8 8 Pilot effluent Raw pilot effluents production: Extinguishment of 2L heptane fires 6% synthetic AFFF. 3% AFFF composition: Compound mass (%) Dipropylene glycol methyl ether 10% Sodium octyl sulfate 8% Alkyl propionate 2.4% Octyl glucoside 2% Demineralized water 72.6% Perfluorinated surfactant 5% Diethanolamine 50% ph 7.5

9 9 Pilot effluent Pilot effluents were obtained after discarding the upper heptane phase and the oil/water interface from raw pilot effluents. Only the aqueous phase was kept. Raw pilot effluent Pilot effluent Heptane Heptane emulsified in water Aqueous phase Pilot effluent characteristics : turbidity 30 NTU, perfluorinated surfactant 115 ppm

10 Analytical methods Back up slide 10 l Turbidity measurements Hach 2100 AN Turbidimeter l HPLC-ELSD l Eclipse Zorbax XDB-C8 analytical column (Agilent Technologies, 4.6mm 150 mm, 5 µm particle size) l Mobile phase: methanol:water 70:30, flow rate: 0.5 ml/min l Knauer K-501 HPLC pump (Eurosep Instruments) l Rheodyne valve, 40 µl loop, 35 C oven l Evaporative Light Scattering Detector: T nebulization=50 C, T evaporation=70 C, Attenuation=2, P(N 2 )=1.5 bar

11 11 Analytical methods HPLC system and ELSD schema LOD: 1.4 ppm

12 Analytical methods Pilot effluent chromatogram: Back up slide 12 Non separated hydrocarbon surfactants Perfluorinated surfactant Limit of detection for perfluorinated surfactant: 1.4 ppm

13 Electrocoagulation Back up slide 13 EC is a water treatment process that can be used to remove l foodstuff and oil wastes, dyes, suspended particles. l chemical and mechanical polishing waste, organic matter from landfill leachates. l synthetic detergent effluents, mine wastes and heavy metals. Flow rates : from 70 L/h to 30 m³/h Total aluminum maximal concentration admited in drinking water: 0.2 ppm Aluminum concentration after electrocoagulation and floc removal: <5 ppm

14 Electrocoagulation principles 1 In situ introduction of Al 3+ ions by aluminum anode electrodissolution, H 2 generation at the cathode. At ph 6-9: aluminum hydroxide monomers and polymers generation. 14

15 Electrocoagulation principles 2 Destabilization of dissolved and suspended matter, adsorption on the floc 15

16 Electrocoagulation principles 3 Floc flotation with the help of H 2 bubbles 16

17 Electrocoagulation principles Back up slide 17 A large part of the floc is removed from the core solution by flotation. However, electrocoagulation has to be followed by a floc segregation step : press, band or rotative filtration, decantation hydrocycloning, centrifugation (flow rates > 1-2 m³/h)

18 Electrocoagulation laboratory material Back up slide l L and 2-5 L electrocoagulation cells: 18

19 Electrocoagulation laboratory material l Pilot effluent electrocoagulation, 3L, 1 A 19 Initial 1h Initial pilot effluent, 30 NTU* Electrodes Dark initial floc Clear final floc *NTU: Nephelometric Tubidity Units 30 min: end of the dark initial floc. Minimal pretreatment time.

20 Copyright DuPont Electrocoagulation Back up slide laboratory material Press filtration In press filtration, the filtering media is the cake formed by retained particles. 3-5 L of electrocoagulated pilot effluent did not contain enough suspended matter to form a filtration cake. Hence, press filter was covered by a 2 mm CaCO3 cake to better its initial efficiency. => To treat 4.5 m³/h, 6 m² of filter are required. 20

21 Pilot effluent pretreatment results l Turbidity removal Back up slide 21 Minimal electrocoagulation time to remove suspended matter and turbidity by filtration was found to be 30 min, for 3L at 1 A, hence 600 Coulomb/L. After 30 min, the turbidity of every filtrated solution was <1 NTU. *NTU: Nephelometric Tubidity Units

22 Pilot effluent pretreatment results l Perfluorinated 22 surfactant removal Electrocoagulation was able to reduce perfluorinated surfactant concentration from 115 ppm to 31 ppm in 30 min for 3L at 1 A (600 C/L). Controlling and keeping ph optimal during electrocoagulation could lead to better perfluorinated surfactant removals.

23 Pilot effluent pretreatment results 23 Total aluminum in pretreated pilot effluent: Before floc removal: 100 ppm After floc removal: <5 ppm For the pretreatment of 10 6 L: 100 kg of Aluminum and KWh are required. 1 ton of Aluminum: 1700$ 1KWh : in France

24 24 Treatment processes Available processes: l Electrocoagulation with ph control l Nanofiltration l Reverse osmosis l Adsorption l Ion exchange Tested process : Reverse osmosis

25 25 Reverse Osmosis l Principle: RO is a membrane process that is often used for water. It works by using pressure to force a solution through a membrane, retaining the solute on one side and allowing the pure solvent to pass to the other side. Ultrapure water generation by reverse osmosis : Feed Flow: 100 m3/h Permeate Flow: 80 m3/h Energy consumption: kwh Specific energy: 2,9 3,25 kwh/m3

26 26 Reverse Osmosis Principles

27 Reverse Osmosis Back up slide 27 Material Millipore ProScale nanofiltration/reverse osmosis pilot, 5L tank Osmonics SG1821C-28D polyamide reverse osmosis membrane, 0.37 m² Operating conditions Pump speed: 20 Hz Transmembrane pressure: 20 bar

28 28 Reverse Osmosis Millipore ProScale pilot

29 Reverse Osmosis results Artificially concentrated model effluent, full recycle mode Model pretreated effluent: Dilution of a synthetic AFFF base to 23 ppm of perfluorinated surfactant. Artificial concentration: Back up slide Successive addings of base components amounts to double model effluent concentration. Achieved artificial concentration factor: 18 (23 to 417 ppm of perfluorinated surfactant). 29

30 Results Copyright DuPont Reverse Osmosis results 30 Concentration factor: CF = C/Ci Flux: 60% of initial water flux at CF=18 (reversible fouling) Perfluorinated surfactant: not detected in permeate (LOD: 1.4 ppm), some moderate adsorption was observed at low concentration. At high concentrations it was smaller than the measurements error.

31 Reverse Osmosis results Pretreated pilot effluent, 5L Back up slide 31 Same order of magnitude for permeability regarding concentration

32 Reverse Osmosis results Pretreated pilot effluent, 5L 32 A Surfactants not detected in permeates (LOD = 1.4 ppm) Permeates surface tensions (25 C): 72.4 and 72.2 mn/m (demineralized water: 71.4 mn/m, 24.9 C) B C

33 Reverse Osmosis results Pretreated pilot effluent, 5L Back up slide 33 Expected fluorinated surfactant in retentate (ppm) Measured fluorinated surfactant in retentate (ppm) Difference (mg) Difference (%) Beginning of full recycle A 27 ± 5 20 ± 1 41 ± 6 26% B 31 ± 3 34 ± 2 Insignificant C 62 ± 8 46 ± 2 33 ± 11 25% Moderate fluorinated surfactant adsorption

34 Back up slide Characterization of the treated water (After electrocoagulation followed by Reverse osmosis) With HPLC-ELSD Surfactants not detected in permeates - (LOD = 1.4 ppm) Surface tension measurements Deionizer water, 24.9 C => Surface Tension = 71.4 mn/m 1st permeate phase conc., 25.0 C => Surface Tension = 72.4 mn/m 2nd permeate phase conc., 25.0 C => Surface Tension = 72.2 mn/m

35 Reverse Osmosis results 35 Neither perfluorinated nor hydrocarbon surfactants were detected in RO permeates (cf. LODs) Membrane area needed to treat 4.5 m³/h: 400 m² at 20 bar (can be decreased by increasing pressure)

36 36 Post-treatment Unit Current process diagram

37 Post-treatment Unit Back up slide 37 Potential process 1 diagram Concentrated retentates could be sent to incineration. If sufficiently concentrated, they could be reused.

38 38 Post-treatment Unit Potential process 2 diagram Sending the retentate back to electrocoagulation to discard surfactants through the floc could reduce or even avoid reverse osmosis membranes washing. In addition, operating pressures should be lower.

39 Conclusion Electrocoagulation and reverse osmosis are technologies available at the large scale. The identified process gives a residual concentration below 1.4 ppm. Cost in use: (to treat 10MM L = m 3 in 3 month) Coagulation* less than 0.5$/ m 3 Reverse Osmosis*: 1 KWh/m 3 (in France two years ago /KWh). Next steps: Refine the measurement on residual levels. Assess financial model. * Equipment fix cost for electrocoagulation: in the range of $ ** Equipment fix cost for Reverse osmosis: in the range of $

40 Thank You. Contact Information Dr. Martial Pabon Tel: martial.pabon@che.dupont.com Isabelle Deguerry Tel: Isabelle.deguerry@fra.dupont.com