Extraction of Biorecalcitrant Petroleum Extraction of Biorecalcitrant Petroleum Hydrocarbons from Contaminated Soil Hydrocarbons from Contaminated Soil

Using Supercritical Fluid Extraction (SFE)Using Supercritical Fluid Extraction (SFE)

Gavin Cheng, Selma E. GuigardGavin Cheng, Selma E. GuigardCivil & Environmental Engineering, University of AlbertaCivil & Environmental Engineering, University of Alberta

Julie RoyJulie RoyImperial Oil ResourcesImperial Oil Resources

October 15, 2004October 15, 2004

OutlineOutline

•• IntroductionIntroduction•• Supercritical Fluid ExtractionSupercritical Fluid Extraction•• ObjectivesObjectives•• Materials and MethodsMaterials and Methods•• Progress and ResultsProgress and Results•• Future WorkFuture Work

IntroductionIntroduction

•• Issue: Issue:

Flare pits were once commonly used to store and Flare pits were once commonly used to store and burn disposed petroleum hydrocarbons (PHCs) burn disposed petroleum hydrocarbons (PHCs) and other oilfield wasteand other oilfield waste

Migration of some of these compounds may Migration of some of these compounds may contaminate the surrounding environment.contaminate the surrounding environment.

Current remediation methods are not able to Current remediation methods are not able to remediate these sites effectively and efficiently.remediate these sites effectively and efficiently.

IntroductionIntroduction

(Alberta Environment, 2001)(Alberta Environment, 2001)

Flare PitFlare Pit

•• Earthen pitsEarthen pits

•• 30,000 in Alberta30,000 in Alberta

•• Decades old (20Decades old (20--30 years)30 years)

•• Operation of flare pits Operation of flare pits banned in 1996banned in 1996

•• Both active and inactive Both active and inactive sites require remediationsites require remediation

ContaminantsContaminants

•• PHCs and heavy metalsPHCs and heavy metals•• Crude bitumen, liquid Crude bitumen, liquid HCsHCs, ,

process chemicals, and waste process chemicals, and waste waterwater

•• From upstream oil and gas From upstream oil and gas operationsoperations

Tars, waxesTars, waxesF4 (C34 to C50)F4 (C34 to C50)

LubricantsLubricantsF3 (C16 to C34)F3 (C16 to C34)

DieselDieselF2 (C10 to C16)F2 (C10 to C16)

GasolineGasolineF1 (C6 to C10)F1 (C6 to C10)

RangeRangeFractionFraction

CCME (2001)CCME (2001)

Current Remediation MethodsCurrent Remediation Methods

•• Excavation / LandfillingExcavation / Landfilling–– transportation, solid waste disposal, waste transportation, solid waste disposal, waste

of natural resourcesof natural resources•• Thermal TreatmentThermal Treatment

–– destroy natural organics, variable results, destroy natural organics, variable results, high costhigh cost

•• Bioremediation and CompostingBioremediation and Composting–– slow process, not effective for certain soilsslow process, not effective for certain soils

Supercritical Supercritical FluidFluid

RegionRegion

Pres

sure

(M

Pa)

Pres

sure

(M

Pa)

Temperature (Temperature (EEC)C)

SolidSolid Critical PointCritical Point

GasGas

LiquidLiquid

7.387.38

31.131.1

Supercritical FluidSupercritical Fluid

Supercritical FluidSupercritical Fluid

•• COCO22 has critical point of 31has critical point of 31ooC and 7.4 C and 7.4 MPaMPa

•• NonNon--toxic, nontoxic, non--flammable, chemically flammable, chemically inert, low cost, readily availableinert, low cost, readily available

•• High diffusivities, low viscosities and High diffusivities, low viscosities and zero surface tensionszero surface tensions

•• rapid and effective matrix penetrationrapid and effective matrix penetration

Supercritical Fluid ExtractionSupercritical Fluid Extraction

•• Used extensively in food and other Used extensively in food and other industrial sectorsindustrial sectors

•• Rapid and effective matrix penetration Rapid and effective matrix penetration and hence better extraction than and hence better extraction than conventional solvent extractionconventional solvent extraction

•• Previous studies showed promising Previous studies showed promising resultsresults

Supercritical Fluid ExtractionSupercritical Fluid Extraction

•• 95% diesel fuel removal from 95% diesel fuel removal from contaminated soil (Lee and contaminated soil (Lee and GongawareGongaware, , 1997)1997)

•• Complete removal of CComplete removal of C2020 to Cto C3838 HCsHCs at at 15MPa and 4015MPa and 40ooC (LopezC (Lopez--Avila et al. 1992)Avila et al. 1992)

•• 7070--100% recoveries of aromatic fractions 100% recoveries of aromatic fractions from crude oil in clayeyfrom crude oil in clayey--sandy soil at sandy soil at 22.7MPa and 8022.7MPa and 80ooC (C (MorselliMorselli et al. 1999)et al. 1999)

Supercritical Fluid ExtractionSupercritical Fluid Extraction

•• PilotPilot--scale tests have shown that SFE can scale tests have shown that SFE can remove PCBs from contaminated sediments for remove PCBs from contaminated sediments for $150 to $450 per $150 to $450 per tonnetonne

•• Economic analysis suggests that SFE for soil Economic analysis suggests that SFE for soil remediation will range from $60 to $300 per remediation will range from $60 to $300 per cubic meter cubic meter

•• The technology may be competitive if the cost is The technology may be competitive if the cost is less than $200 per less than $200 per tonnetonne under certain under certain circumstancescircumstances

ObjectivesObjectives

•• Investigate the use of labInvestigate the use of lab--scale SFE to scale SFE to extract PHCs from flare pit soils with extract PHCs from flare pit soils with supercritical carbon dioxidesupercritical carbon dioxide

•• Identify the operating conditions that Identify the operating conditions that produce the highest extraction efficiencies produce the highest extraction efficiencies across soils and hydrocarbon fractions.across soils and hydrocarbon fractions.

MaterialsMaterials

MaterialsMaterials

•• Flare pit soil samplesFlare pit soil samples

56005600

800800

900900

FP2FP2

28002800

400400

150150

FP1FP1

Alberta Tier 1Alberta Tier 1

3400034000

6400064000

1900019000

10.4710.47

5.675.67

LoamLoam

14.1214.12

43.9443.94

41.9441.94

FP2FP2

1200012000

1700017000

33003300

3.313.31

3.2493.249

SandSand

4.274.27

0.170.17

95.5795.57

FP1FP1

F4 (CF4 (C3434--CC5050) mg/kg) mg/kg

F3 (CF3 (C1616--CC3434) mg/kg) mg/kg

F2 (CF2 (C1010--CC1616) mg/kg) mg/kg

Petroleum Hydrocarbon Content (PHC)Petroleum Hydrocarbon Content (PHC)

Sodium Adsorption Ratio (SAR)Sodium Adsorption Ratio (SAR)

Electrical Conductivity (EC) (Electrical Conductivity (EC) (dS/mdS/m))

Soil TypeSoil Type

Clay (<2Clay (<2µµm) (%w)m) (%w)

Silt (2Silt (2--5050µµm) (%w)m) (%w)

Sand (>50Sand (>50µµm) (%w)m) (%w)

Particle Size DistributionParticle Size Distribution

PARAMETERPARAMETER

MaterialsMaterials

•• SFE apparatusSFE apparatus•• GC/FID (Varian 3800)GC/FID (Varian 3800)

MethodologyMethodology

•• Contaminated soil sample is mixed with Contaminated soil sample is mixed with SC COSC CO22 at defined conditions in at defined conditions in stainless steel extraction vessel in stainless steel extraction vessel in extended time duringextended time during staticstatic mode mode

•• Continuous flow of SC COContinuous flow of SC CO22 carries the carries the extracted PHCs from soil matrix to the extracted PHCs from soil matrix to the outlet duringoutlet during dynamicdynamic modemode

MethodologyMethodology

•• Extracted PHCs separate from SC COExtracted PHCs separate from SC CO22upon change in extraction conditions upon change in extraction conditions and contaminants are collectedand contaminants are collected

•• Cleaned soil sample is extracted again Cleaned soil sample is extracted again using using SoxhletSoxhlet extraction to obtain the extraction to obtain the residual PHC contentresidual PHC content

•• The concentrated extract is analyzed by The concentrated extract is analyzed by GC/FID to determine the residual PHCs GC/FID to determine the residual PHCs in the cleaned soil samplein the cleaned soil sample

MethodologyMethodology

•• Extraction ConditionsExtraction Conditions

10103030SC COSC CO22 flow rate (flow rate (mLmL/min)/min)

11.0 / 160011.0 / 160024.1 / 350024.1 / 3500Pressure (MPa / Pressure (MPa / psipsi))

40408080Temperature (Temperature (ooCC))

LowLowHighHighLevelLevel

ParameterParameter

Results (FP 1)Results (FP 1)

777798989595Equivalent Removal to meet Alberta Tier 1 Hydrocarbon guidelinesEquivalent Removal to meet Alberta Tier 1 Hydrocarbon guidelines

2424505099994646101015.115.18080

626291919999838316166060

62628383100100797915.515.56060

565652529595626214.614.66060

363644449999515113.913.96060

4343393998985151

1010

13.113.16060

81819898100100939324.124.14040

46469595999979792020

16.116.14040

75759898100100919124.124.14040

727296969797898921.321.34040

696994949696878716.216.24040

636392929999848414.814.84040

535381819898747412.912.94040

4242868694947373

1010

11.111.14040

46469292979777775516164040

55558989979780801116.116.14040

28002800400400150150Alberta Tier 1 Hydrocarbon guidelines (residential land use) (Alberta Tier 1 Hydrocarbon guidelines (residential land use) (ppmppm))

1200012000170001700030003000Initial PHC content (Initial PHC content (ppmppm))

F4% removalF4% removalF3% removalF3% removalF2% removalF2% removal% Extraction% ExtractionFlow (ml/min)Flow (ml/min)Pressure (MPa)Pressure (MPa)Temp.(oCTemp.(oC))

Results (FP 2)Results (FP 2)

838399999595Equivalent Removal to meet Alberta Tier 1 Hydrocarbon guidelinesEquivalent Removal to meet Alberta Tier 1 Hydrocarbon guidelines

282880801001007171101024.124.16060

404095959999828224.124.14040

282879799999696915.415.44040

1414696998986262

1010

14.714.74040

56005600800800900900Alberta Tier 1 Hydrocarbon guidelines (residential land use) (Alberta Tier 1 Hydrocarbon guidelines (residential land use) (ppmppm))

340003400064000640001900019000Initial PHC content (Initial PHC content (ppmppm))

F4% F4% removalremoval

F3% F3% removalremoval

F2% F2% removalremoval% Extraction% ExtractionFlow (ml/min)Flow (ml/min)Pressure (MPa)Pressure (MPa)Temp.(oCTemp.(oC))

ResultsResults

•• Extraction efficiency is directly related to the Extraction efficiency is directly related to the solvent densitysolvent density

•• Higher Pressure increases removal Higher Pressure increases removal efficiencyefficiency

•• Higher Temperature decreases removal Higher Temperature decreases removal efficiencyefficiency

•• Best extraction conditions at 24.1 MPa and Best extraction conditions at 24.1 MPa and 4040ooCC

ResultsResults

•• The effect of SC COThe effect of SC CO22 flow rate on removal flow rate on removal efficiency is not significant efficiency is not significant

•• Higher SC COHigher SC CO22 flow rate yield faster flow rate yield faster extractionextraction

•• Soil type affects extraction efficiencySoil type affects extraction efficiency

4040959599998080LoamLoam

818198981001008989SandSand

F4% removalF4% removalF3% removalF3% removalF2% removalF2% removal% Extraction% ExtractionSoil TypeSoil Type

Future WorkFuture Work

•• Evaluate the effect of static and Evaluate the effect of static and dynamic extraction mode which is dynamic extraction mode which is related to solubility and related to solubility and desorptiondesorptionkineticskinetics

•• Evaluate parameters such as Evaluate parameters such as temperature, pressure, SC COtemperature, pressure, SC CO22 flow flow rate, moisture content, mixing, and soil rate, moisture content, mixing, and soil typetype

•• Potential pilotPotential pilot--scale experimentsscale experiments

ConclusionConclusion

•• Flare pits are hazardous to the environmentFlare pits are hazardous to the environment•• Preliminary results show SFE is a potential Preliminary results show SFE is a potential

treatment technology to remove PHCs from treatment technology to remove PHCs from soilsoil

•• Analysis from literature suggests that SFE Analysis from literature suggests that SFE for soil remediation can be cost effective for soil remediation can be cost effective

•• More engineering design and economic More engineering design and economic analysis are needed to advance the analysis are needed to advance the technologytechnology

AcknowledgementsAcknowledgements

•• Imperial Oil Imperial Oil •• Staff at Imperial Oil Resources Staff at Imperial Oil Resources •• TechnicalTechnical staff at the University of staff at the University of

AlbertaAlberta•• Vaishalie NagpalVaishalie Nagpal

Questions ?Questions ?