Mineral Resources and Mine Development

AIMS 2013

Pavlides A.Pavlides A.HristopulosHristopulos D.T.D.T.

Galetakis M.Galetakis M.Roumpos Ch.Roumpos Ch.

GEOSTATISTICAL ANALYSIS OF THE CALORIFIC VALUE AND ENERGY

CONTENT OF THE MAVROPIGI MULTI-SEAM LIGNITE DEPOSIT IN NORTHERN

GREECE

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PRESENTATIONPRESENTATION

Description of Mavropigi mineDescription of Mavropigi mine

Lignite energy content and geological ligniteLignite energy content and geological lignite

Estimation of Lower Calorific Value (LCV) with a Estimation of Lower Calorific Value (LCV) with a

geochemical equationgeochemical equation

Estimation of LCV with a regression linear modelEstimation of LCV with a regression linear model

Spatial estimation of the geological lignite energy contentSpatial estimation of the geological lignite energy content

Conclusions – suggestions for further studyConclusions – suggestions for further study

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MAVROPIGI MINEMAVROPIGI MINE

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MAVROPIGI MINEMAVROPIGI MINE Area 11 kmArea 11 km22 with extensive fault system with extensive fault system

Multi-Seam mineMulti-Seam mine

The mine is in operation sinceThe mine is in operation since 20022002 and has producedand has produced 51.851.8 Μ Μtt

of lignite till the end of 2012of lignite till the end of 2012

Average lignite production:Average lignite production: 8 Mt/Y8 Mt/Y

Estimated exploitable lignite reserves: 198 Mt, 146 Mt Estimated exploitable lignite reserves: 198 Mt, 146 Mt

remainingremaining

Estimated energy content: 350Estimated energy content: 350∙10∙106 6 MWhMWh

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GEOLOGICAL LIGNITEGEOLOGICAL LIGNITEThe Criteria used to determine if a layer is considered a The Criteria used to determine if a layer is considered a

geological lignite layer for this study are:geological lignite layer for this study are:

LCVLCV greater than 900 kcal/kggreater than 900 kcal/kg

Maximum contents in ash and COMaximum contents in ash and CO22 up to 55% up to 55%

No constraints on layer thicknessNo constraints on layer thickness

The criteria of geological lignite layers differ from the criteria The criteria of geological lignite layers differ from the criteria

of exploitable lignite layersof exploitable lignite layers

The criteria used are simplified in comparison with the PPC The criteria used are simplified in comparison with the PPC

criteriacriteria

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LOWER CALORIFIC VALUE AND LOWER CALORIFIC VALUE AND LIGNITE ENERGY CONTENTLIGNITE ENERGY CONTENT

Lignite is mainly used as fuel for power stationsLignite is mainly used as fuel for power stations

For such use the LCV (heat released/mass burned) is the For such use the LCV (heat released/mass burned) is the

dominant quality parameterdominant quality parameter

LCV shows intense variability within the depositLCV shows intense variability within the deposit

The LCV variability means that the quantity of the reserves The LCV variability means that the quantity of the reserves

can serve only as an indicator for the amount of contained can serve only as an indicator for the amount of contained

energyenergy

the lignite energy content (LEC) of a quantity of lignite is the the lignite energy content (LEC) of a quantity of lignite is the

LCV of the quantity multiplied by the mass of the lignite LCV of the quantity multiplied by the mass of the lignite

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ESTIMATION OF LCV ESTIMATION OF LCV

To estimate the LEC for all or part of the mine, LCV must be To estimate the LEC for all or part of the mine, LCV must be

known for the whole area investigatedknown for the whole area investigated

LCV is not measured for all core samples. Only 4416 core LCV is not measured for all core samples. Only 4416 core

samples have an LCV measurement out of 10208 core samples have an LCV measurement out of 10208 core

samples samples

The LCV for the remaining 5792 samples must be estimatedThe LCV for the remaining 5792 samples must be estimated

The first method is based on a geochemical equationThe first method is based on a geochemical equation

The second method is based on a regression model that links The second method is based on a regression model that links

LCV with measured quality parameters of the core samplesLCV with measured quality parameters of the core samples

Results are compared with the measured values of LCVResults are compared with the measured values of LCV

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GEOCHEMICAL EQUATION GEOCHEMICAL EQUATION Equation by RheinbraunEquation by Rheinbraun

Parameters of the equationParameters of the equation

Comparison of estimated and measured LCV

wcwleawcaawccalLCV )1()1()1(

ccal kcal/kg

w %

α %

ca kcal/kg

le %

cw kcal/kg

58005800 measuremeasuredd

measuredmeasured -437-437 27.527.5 -583-583

Pearson's ρ

Mean error (kcal/kg)

Mean abs error (kcal/kg)

Mean absolute relative error

0.8657 -71.54 104.38 0.085

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MULTIPLE LINEAR REGRESSION MULTIPLE LINEAR REGRESSION It is assumed that the LCV can be estimated from a linear It is assumed that the LCV can be estimated from a linear

equationequation

Parameters of the equation (kcal/kg)Parameters of the equation (kcal/kg)

Comparison of estimated and measured LCV

The LCV for the 5792 samples that miss it are estimated The LCV for the 5792 samples that miss it are estimated

using the linear regression model using the linear regression model

Pearson's ρ

Mean error (kcal/kg)

Mean abs error (kcal/kg)

Mean absolute relative error

0.9332 0.00 61.0 0.045

4321 aasacoawaLCV

α1 α2 α3 α4

-4114 -2470 -2727 4590

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LEC DENSITY LEC DENSITY To make easy estimations of the LEC for parts or the whole To make easy estimations of the LEC for parts or the whole

mine, a map of the estimated LEC per unit of surface area mine, a map of the estimated LEC per unit of surface area

(m(m22) or ) or LEC density LEC density will be createdwill be created

LEC density (Gcal/ mLEC density (Gcal/ m22) is the total energy content that would ) is the total energy content that would

be gained if all the geological lignite below a unit of surface be gained if all the geological lignite below a unit of surface

area is minedarea is mined

LEC density changes from part to part of the mine, based on LEC density changes from part to part of the mine, based on

the total lignite thickness and the LCV of the various lignite the total lignite thickness and the LCV of the various lignite

seams below the investigated unit of surface areaseams below the investigated unit of surface area

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DRILL-HOLE DATADRILL-HOLE DATA

Data comprise of the LEC density in 343 drill-holes calculated from the Data comprise of the LEC density in 343 drill-holes calculated from the

LCV of all the 10208 core samples of the drill-holes and the lignite LCV of all the 10208 core samples of the drill-holes and the lignite

thicknessthickness

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DATA STATISTICS DATA STATISTICS

Mean (Gcal/m2)

Minimum (Gcal/m2)

Maximum (Gcal/m2)

40.5 2.6 123.3

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SEMIVARIOGRAM SEMIVARIOGRAM

Experimental omnidirectional semivariogram fitted with the Experimental omnidirectional semivariogram fitted with the

exponential theoretical model with nugget effect. Distances are exponential theoretical model with nugget effect. Distances are

normalized and a linear trend has been removed (normalized and a linear trend has been removed (ρρ = 69.7%) = 69.7%)

r

ecr 1)( 20

c0 (Gcal/m2)

2

σ2 (Gcal/m2)

2

ξ

60.2 345.0 0.81

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OK OF LEC DENSITYOK OF LEC DENSITY

28∙106 MWh

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OK OF LEC DENSITYOK OF LEC DENSITY

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OK OF LEC DENSITY OK OF LEC DENSITY To validate the results, leave-one-out cross-validation was usedTo validate the results, leave-one-out cross-validation was used

LEC density (Gcal/ mLEC density (Gcal/ m22) estimated in a 30m x 30m grid) estimated in a 30m x 30m grid

LEC is greater in parts of the mine that have greater lignite LEC is greater in parts of the mine that have greater lignite

thicknessthickness

Using the estimated LEC density of the OK, the LEC for Mavropigi Using the estimated LEC density of the OK, the LEC for Mavropigi

mine is estimated at 300.4∙10mine is estimated at 300.4∙1066 Gcal or 349.1∙10 Gcal or 349.1∙1066 MWh MWh

Pearson's ρ

Spearman's r

Mean error

(Gcal/m2)

Mean abs error

(Gcal/m2)

Max abs error

(Gcal/m2)

0.86 0.87 -0.154 9.752 62.10

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CONCLUSIONS - SUGGESTIONSCONCLUSIONS - SUGGESTIONS The energy content of the geological lignite of Mavropigi The energy content of the geological lignite of Mavropigi

mine is estimated at mine is estimated at 349.1∙10349.1∙1066 MWh MWh

The LCV for drill holes that miss such a measurement is The LCV for drill holes that miss such a measurement is

estimated from other parameters using Rheinbraun’s estimated from other parameters using Rheinbraun’s

geochemical equation and a multiple linear regression modelgeochemical equation and a multiple linear regression model

While both methods give good estimations of the LCV, the While both methods give good estimations of the LCV, the

linear regression model gives a better estimationlinear regression model gives a better estimation

The effect of the depth as an independent parameter was The effect of the depth as an independent parameter was

investigated. It was concluded that its effects were already investigated. It was concluded that its effects were already

incorporated in the other parametersincorporated in the other parameters

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SUGGESTIONS FOR FURTHER SUGGESTIONS FOR FURTHER STUDYSTUDY

The estimated LCV along with other lignite parameters The estimated LCV along with other lignite parameters

could be used to make three-dimensional kriging estimate could be used to make three-dimensional kriging estimate

of the location of waste seams and geological lignite of the location of waste seams and geological lignite

seams. seams.

The LEC density of three dimensional cells (Gcal/ mThe LEC density of three dimensional cells (Gcal/ m33) could ) could

be estimated, further assisting in the mid-term planning for be estimated, further assisting in the mid-term planning for

individual sectors of the mineindividual sectors of the mine

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THANK YOU ! ! !THANK YOU ! ! !