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CONTROL AND INVENTORY OF WATER PONDS IN TAILINGS EMBANKMENTS THROUGH

PHENOMENOLOGICAL MODELLING

Dr. Christian Goñi

Universidad de Concepción

ABSTRACTABSTRACT

The conventional technology of mineral processing plants, consider the recovery ofwater from tailings dams, through the formation of ponds and groundwaterinfiltration or seepage.

The formation of ponds involved several complex phenomena such as evaporation, seepage, sedimentation, compression, pipeline, dam topology, etc. To quantify theavailable water in time, has set a goal to develop a dynamic model of the inventoryof water in the lagoon. To do this, we used phenomenological modeling techniquesand the development of numerical schemes using the finite volume resolution.

The result was a dynamic simulator software of the lagoon, whose estimated areaand volume of ponds are successfully validated by information collected fromplants.

We conclude that the simulator can estimate the water availability for a given time horizon, from initial conditions of the pond, tailings, water recycling and physicalcondition of the dam

Dr. Christian Goñi , [email protected]

The problem of water recycling by treating The problem of water recycling by treating tailingstailings

The deposition of tailings into a dam allows the sedimentation of these generating a flow of water which then drains into the lower zones of the dam forming parasitic ponds. The water accumulated in these ponds is then transported to the mining operations, to achieve recovery of this.

The formation process of the pond is complex, involving several dynamic phenomena such as water transport, sedimentation, evaporation, infiltration and compaction of the tailings. Because of this, knowledge of the inventory of water over time is a mystery to solve for the efficient management of water recovery.

The aim of this study was to construct a physical model that accounts for the variation of water in the formation of pond. Thus, it is possible to predict water availability in the time, given the initial conditions of the dam and tailings deposition horizon.


Some examples of ponds in tailings dams


Example artificial pond for water recovery

Artificial pond


Lagoon

Tails


Tails

Channeling

Pond


Deposition of tails

Basic elements of a tailings pond

water drains through the surface of the tailings into the lower areas, to accumulate in the form of ponds


Lagoon

Slope(gravitational water drainage)

Channelingphenomena

Artificial pondFor waterrecovery

Lagoon (pond) formation


MODELINGMODELING THETHE PHENOMENOLOGYPHENOMENOLOGY

Physical Phenomena• The physical phenomena considered in the formation of the pond (or

lagoon) are as follows :

– Tails and water transport (Convective and Diffusive Flux)

– Sedimentation tails (Hindered sedimentation model)

– Channeling (Empirical model for assays in laboratory)

– Runoff surface (Model and assays)

– Evaporation pond (Model and assays)

– Compression soil (Model and soil‐test)

– Seepage ( Conservation laws for water)

– Pond formation (Conservation laws)


Conceptual model of the dynamics of water flowTransport tails andwater channeling

TASK


Parameters and variables in process


Evaporation rate modelling

Dry

Wet

Channeled

Water pond

according to the type of surface evaporation has different formulation in terms of linear speed and exposed area

flow corresponds to greater evaporation

( ) ( )eQ A t e t= ⋅

0 00, ,soile

KQ if t t Q Qt∞

⎛ ⎞= > ≠ +⎜ ⎟⎝ ⎠


Typical rate evaporation in ponds


InfiltrationVertical unsaturated flow of moisture in soil can be described physically by the equationpartial derivatives of Richards (1931), combination of unsaturated flow equation of Darcy-Buckingham and the continuity or mass conservation

1HKt z zθ∂ ∂ ∂⎛ ⎞= +⎜ ⎟∂ ∂ ∂⎝ ⎠

Richards equation:

( )infv k h H= − ∇Darcy - Buckingham:

However, developing a pattern of granular material to simulate the flow of infiltration in a tailings. The results were better.


Green – Ampt Model infiltration in soils


Infiltration modelingModeling of water infiltration through the porous soil under the pond, was performed by applying discrete particles for tailings under pond . It is considered a given thickness of infiltration

This allowed us to construct a proper boundary condition for the flow of infiltration in the lagoon

Soil sample like granular set


Modeling of the tails sedimentation

( )

( ) ( )

2

18

1

sed

n

v v f

d gv

f

φ

ρμ

φ αφ

∞

∞

=

Δ=

= −

The tailings particles sediment under a regime hindered and laminar flow conditions. Reynolds considered around 10 - 1000.

important is the viscosity of the mixture water - tailings ( ), , . .f d C Qμ φ=


Modelling “Channeling”

Channeling is the phenomenon of surface water runoff sediment through the tailings

( ), , ,...channelv f roughness thickness inclinated=

{ }, ,μ ρ τ•Viscosity•Density•Surface tension•Roughness•Thickness•Inclinated level soil•Perimeter pond


Modeling of the topography of the dam

A topographic mapping from a tailings dam, it generated a three-dimensional geometric model. Then, depending on the altitude of tailings filling identifies the lower area where the lake was formed.

dam pondΩ = Ω ΩU


Contour diagram of the tailings dam

Boundary embankment

Interior levels contour


Example contour for tailings damDatabase (x,y,z)

Pos-processing in MATLAB


ExampleExample ofof pondpond


ManuallyManually constructionconstructionofof perimeterperimeter pondpond

SIMULATIONSSIMULATIONS

point of pumping and water recycling

CASE I. Tails with high fines


DepositionsDepositions tailstails pointspoints((settingsetting forfor useruser))

pondpond

Some physical parameters


values given by the user

Tab for water recovery flow (given for the user)

Physical properties of soil and water

Parameters of simulation


ResultsResults ofof simulationsimulation


Case I: Case I: ResultsResults forfor pondpond estimationsestimations


Case I: Case I: ResultsResults forfor flowsflows involvedinvolved


Case I: Case I: FlowsFlows ((feedersfeeders) ) inputinput forfor thethe useruser


Case Case IIII: : ResultsResults forfor pondpond estimationsestimations


Case Case IIII: : ResultsResults forfor flowsflows involvedinvolved


Case Case IIII: : FlowsFlows ((feedersfeeders) ) inputinput forfor thethe useruser

A tool for simulation and calculation has been obtained from the dynamic modeling of water flow between the lagoon and the tailings dam. It’s possible include information of plant such as measurable fed tailings flows, percentage of solids, water pumping rates and deposition program.

The simulator is able to determine the dynamic evolution of the volume of the lagoon as well as the maximum depth and surface area of this

You can program the tailings deposit according to water availability estimates obtained with the simulator developed

The simulator can maintain control of tailings deposition scheduling with plant information

The simulator can simuling diffrents soil types (high fines, clays, etc.)

CONCLUSIONSCONCLUSIONS


FINFIN

s9!14!20 christian goni

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