Colloidal clay gelation: relevance to current oil sands operations

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https://doi.org/10.4224/12745807

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Colloidal clay gelation: relevance to current oil sands operations

Mercier, P. H. J.; Ng, S.; Moran, K.; Sparks, B. D.; Kingston, D. M.; Kotlyar, L. S.; Kung, J.; Woods, J. R.; Patarachao, B.; McCracken, T.

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– Colloidal Clay Gelation –

Relevance to Current Oil Sands Operations

P.H.J. Mercier *, S. Ng, K. Moran, B.D. Sparks, D.M. Kingston, L.S. Kotlyar, J. Kung, J.R. Woods, B. Patarachao, T. McCracken

*[email protected]

8th _{World Congress of Chemical Engineering}

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Topics for the talk

Review of earlier research in colloidal clay gelation

• Water holding capacity of MFT (mature fine tailings) • Flocculation and gelation of ultrafine/clay suspensions • Nature of ultrafines and clays in oil sands

Part 1

Part 2 Application to current commercial operations

• Reduced segregation of solids and bitumen in gravity separation vessel (GSV)

• Development of markers for “problem ores” and for identification and quantification of ultrafines content

Part 3 Concluding remarks

•New ERCB regulation Directive 074 specifying

performance criteria for reduction of MFT/fluid tailings •Predicting extent of MFT formation by monitoring

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before agitation

after agitation

Settling Behaviour of Mature Fine Tailings (MFT)

~3 wt%

ultrafines

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Kotlyar, Sparks et al. (1992) AOSTRA J. Res. 8(1):55-61

Diluted

MFT

pond water distilled water Na-pyro solution

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Dispersing agents

Flocculating agents

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Reaction limited flocculation Diffusion limited flocculation ultrafines suspensions settle to nearly same solids concentration (~3% wt%) more rapid water release for recycle favoured by fast flocculation

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in situ

_{measurement of gelation rate}

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115 ppm Na+ 460 ppm Na+ _{960 ppm Na}+ distilled water fast aggregation dispersed slow aggregation

Kotlyar, Sparks & Schutte (1996) Clays & Clay Minerals 44(1):121-131 ultrafines concentration and water chemistry

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water chemistry and ultrafine/clay flocculation behavior Clay particles in Salt-free environment Cations Na+_{, Ca}2+ Time

Small flocs formed by aggregation of Individual particles

Space spanning cluster

(gel)

Two conditions are necessary for an aqueous suspension to form a thixotropic gel:

-- critical amounts of ultrafines (3wt%) or clays (10-15wt%) AND

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Transmission Electron Microscopy of Ultrafines

500 nm

mostly phyllosilicates

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XRD Measurements

illite 001 kaolinite 001

high intensities

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XRD-derived Marker combining

Phyllosilicates Mineralogy and their Size Distributions

For a waste unit sample, this data representation showed that:

-- the illite/kaolinite XRD peak area ratio

increases as average clay mineral thickness decreases

(i.e., the clays in this oil sands are more-and-more illite-rich as the particle size gets smaller)

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XRD patterns for delaminated illite

and kaolinite calculated with Debye’s formula

Mercier et al. (2008) Petroleum Science and

Technology 26: 307-321

The calculations assumed a particle with 6 nm diameter and a thickness t comprising one composite layer.

XRD Analysis of Smallest Size-Fraction in a Waste Unit Sample

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Part 2

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Segregation and non-segregation comparison 0.5% ultra-fines 5.7% fines 12.2% bitumen 1.8% ultra-fines 16.6% fines 8.7% bitumen Water to oil sands ratio 0.7 Water to oil sands ratio 2.0

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PSV No Gel

Low ultra-fines and salt content (Bitumen can separate) Conditioning

(dispersion of clays) PSV Gel

High ultra-fines and salt content (No bitumen separation)

Effect of Ultrafines and Clays on GSV Performance

PSV

Bitumen

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Pilot Test

BEU Tests

Comparison of total solids content with ultrafines concentration

in the middlings zone of BEU and Pilot tests

Process failure required

plant shutdown

GOC = gel onset concentration

(minimum conc. producing noticeable thickening of suspension)

2.9 wt% ultrafines

13 wt% fines

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Processability marker for ultrafines content in oil sands ore

anomalous samples

ultrafines content of oil sand ores

not a simple function of fines content

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10 Regionally-Distributed Oil Sands

Samples from Syncrude

Marine (5 samples) Estuarine (5 samples) Poor Recovery Good Recovery Expectation

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Bitumen Recovery vs. Clays Content (Process Water A = Constant Caustic)

estuarine

marine

Clays content appears useful as potential processability marker.

Although not enough clays are present to possibly cause gelation in GSV, the clays content might be sufficient to induce slurry thickening.

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ultra-thin clay

mineral content

by XRD

ultra-fines

concentration

without

time-consuming

separation of this

component

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Summary

1) Earlier research on settling of MFT and ultrafine/clay suspensions revealed that:

-- MFT always contains ~3wt% ultrafines

-- aqueous suspensions with 3wt% ultrafines readily form gels if enough flocculating cations are present

=> Ultrafine gels can therefore account for 100% of the water holding capacity of MFT

2)

Recent applications to current oil sands operations have demonstrated that:

-- the ultrafines content of an ore may be responsible for reduced segregation of bitumen and solids in a GSV -- ultrafines content may therefore represent an indicator

for both bitumen recovery and extent of MFT formation

-- recent XRD developments for analyzing clay minerals in oil sands may make the determination of this parameter easier

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Part 3: Concluding remarks

New regulation from Alberta ECRB Directive 074, effective September 2009, will impose future tailings performance criteria and requirements for oil sands mining schemes.

This regulation requires the reduction of fluid tailings and their conversion into trafficable deposits.

As such, the application of this directive will effectively place stringent limits on the amount of MFT which can be produced by oil sands operators.

In this light, we expect that predicting the extent of MFT formation will be important and achievable by monitoring the ultrafines content of ores.

Our recently developed XRD-based methodology shows potential to reach this objective.

Based on our earlier work in this field, we believe that the ultrafines content of an oil sands sample represents the ore property that is most relevant to explain MFT formation.

The physical limitations inherent to aqueous suspensions of ultrafines should therefore be taken into account in dealing with fluid tailings management.