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Manejo de Residuos y RelavesLa disposicin segura y efectiva de residuos presenta desafos ambientales ytcnicos. Las condiciones de cada proyecto son nicas, por esta raznimplementamos diseos especficos de instalaciones de depsito de rocas yalmacenamiento de relaves con el fin de proporcionar soluciones econmicas

apropiadas a las condiciones especficas del sitio y que al mismo tiempo proveanproteccin ambiental y seguridad a largo plazo.

Knight Pisold cuenta con una amplia experiencia en seleccin de sitio, diseo,asistencia con la obtencin de permisos, servicios de apoyo a la construccin ,monitoreo operacional y cierre de las instalaciones de almacenamiento de rocaestril y relaves para una vasta variedad de condiciones ssmicas y climticas endistintos lugares del mundo.Caracterizacin de DesmonteEl conocimiento profundo de la geologa de los yacimientos, mineraloga,geoqumica e hidroqumica es importante para asegurar que las operacionesmineras se desarrollen de manera segura para el medio ambiente. La optimizacinde las operaciones mineras, el entendimiento de temas ambientales, losprocedimientos de solicitud de permisos y el planificacin del cierre y rehabilitacinde las minas son componentes crticos para el xito de un desarrollo minero.

Nuestra capacidad y experiencia en la caracterizacin de desmonte, pruebas delaboratorio y de campo, modelos numricos y la aplicacin prctica de estrategiaspreventivas han sido utilizadas en muchos desarrollos de proyectos minerosexitosos en varia de sus etapas, desde el desarrollo inicial hasta la operacin decierre.

Manejo de RelavesKnight Pisold ha trabajado en el diseo de instalaciones de manejo de relaves enms de 400 proyectos mineros alrededor del mundo. Tenemos una ampliaexperiencia con todo tipo de sistemas de manejo de relaves y hemos sidopioneros en el desarrollo de tecnologas alternativas de manejo de relaves talescomo sistemas subacuticos, sistemas subareos drenados, disposicin derelaves espesados / ultra espesados / en pasta y sistemas de "apilamiento enseco" para relaves. Knight Pisold ha establecido una relacin slida de trabajocon grupos especializados, los que proveen apoyo para el diseo de espesantesde relaves, plantas filtrantes, tuberas para pulpa y plantas de relaves en pasta demanera de proporcionar diseos completos y globales, as como experienciaoperacional para el manejo de relaves.

Tuberas y Estaciones de BombeoUn manejo sensato y de costo eficiente de la pulpa es un importante componenteen la mayora de los proyectos mineros. La seleccin de tuberas y de las bombasdebe ser adaptada al rango de las condiciones previstas de flujo, de presiones yde los materiales durante la vida til del proyecto. Knight Pisold tiene ampliaexperiencia en el manejo y operacin del transporte de pulpas incluye relaves,concentrados y arenas cicloneadas.

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Dry Stacking of Tailings (Filtered Tailings)

Figure 1: The La Coipa dry stack facility in Chile (Courtesy Anglo

American De!s"ana)

#ntroductionDewatering tailings to higher degrees than paste produces a filtered wet (saturated) and

dry (unsaturated) cake that can no longer be transported by pipeline due to its low

moisture content. These filtered tailings are normally transported by conveyor or truck,

deposited, spread and compacted to form an unsaturated tailings deposit (Davies and

Rice 2 !). This type of tailings storage produces a stable deposit usually re"uiring no

retention bunding and is referred to as #dry stack$. %igures ! and 2 show the &a 'oipa dry

stack tailings facility in 'hile.

typical moisture content of less than 2 is achieved by using a combination of belt,

drum, hori*ontal and vertical stacked pressure plates and vacuum filtration systems

(+artin, Davies et al. 2 2). The term #dry cake$ or #dry stack$ is not entirely correct as the

tailings have a moisture content several percent below saturation. owever, this

terminology has been adopted by regulators and designers (Davies and Rice 2 !).

Figure $: Dry stacking of tailings from a con%eyor at La Coipa&

Chile (Courtesy Anglo American De!s"ana)

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Advantages and Disadvantages&ike with thickened and paste tailings, the mechanical dewatering process compared to

conventional slurry deposition increases costs. -roducing wet and dry cake further

increases this cost particularly if high throughputs are re"uired. owever, some of the

many advantages to using dry stacking of tailings are 'an be used in areas where water conservation is critical and any water loses can

/eopardise plant performance. Risks of catastrophic failure and tailings runout as associated with conventional

storage facilities are eliminated if the facility is operated as intended. Dry stacking is suited to areas of high seismic activity as the construction of

retention embankments is prevented. 0uitable where there is limited construction material available to develop a

conventional retention impoundment. -rogressive rehabilitation is possible, spreading the cost of closure over a longer

time period when compared to conventional storage facilities. igher rates of rise can be achieved due to the high dense state of the placed

tailings when compared to conventionally deposited tailings. ccess by mechanical

e"uipment to provide spreading and compaction is also advantageous. %or cold climates, dry stacking prevents pipe free*es and frosting problems with

conventional impoundments. 1roundwater contamination through seepage is virtually eliminated.

%iltered tailings allow better recovery of dissolved metals and process chemicals(e.g. gold and cyanide).

Dry stack facilities are also easier to close and rehabilitate, re"uire a smaller footprint

compared to other surface tailings storage options (i.e. higher density), can be utilised in

aggressive environments (e.g. undulating and steep terrain) and generate better regulator

and public perceptions of tailings storage (Davies and Rice 2 !).

Figure ': Dry stacking of tailings using truck transportation (

on *ngels)

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0ome of the disadvantages to dry stack tailings are as follows igh capital and operating costs associated with modern filtration technology

(power, maintenance) that render other tailings storage options more economic to develop. nly really suited to low throughput operations (currently around 2 , tpd) due to

e"uipment costs and operational management of a large filtration plant. 3pstream diversion systems re"uired to prevent inundation of the dry stack facility. 0urface contour management re"uired to prevent accumulation and easy removal

of surface water (i.e. precipitation events) to prevent ponding and erosion of the stack

through channelised runoff flow channels. 4o option to store water within a dry stack facility. conventional tailings facility,

designed to store water, can provide a mining operation with a buffer (e.g. storm water

storage) to maintain operations during dry months of the year. 5idation of sulphides in the tailings can create high concentrations (but low

volume) of seepage water. +ay not be practical for some ore types. Detailed geochemical

testing is re"uired. Dust generation is a common problem in arid climates and can occur relatively

"uickly after tailings disposal due to the low moisture content of the placed material. dry stack installation in a high rainfall environment can create day to day

management problems for trafficability of haulage and compaction e"uipment. 0easonal

fluctuations are an important consideration in the design of a dry stack facility.

owever, it should be noted that the economics associated with implementing tailings

filtration systems have decreased rapidly over the last 6 years. This is mainly due to theincrease in capacity of modern filtration systems (e.g. increased filtration area of hori*ontal

filtration belts) and operational optimisation such as minimised blinding of filter cloths.

+au,ite -esidue (red mud)The alumina industry produces bau5ite residue (red mud) as a by7product of the refining

process. Red mud storage facilities are often referred to as dry stack facilities, even

though the tailings are commonly discharged into the facility by pipeline deposition. 8n

reality this is conventional tailings storage (high rate thickened or paste), but the term 9dry

stacking9 refers to the final product based on the methods used to promote sedimentation

and release of water within the facility and thus drying and strength gain. Due to the fine

nature of the tailings properties, flocculation addition and mechanical disturbance are

commonly used techni"ues, which increase overall operational costs.

0ome low throughput alumina operations filter their tailings to produce a wet cake and thus

9dry stack9 the tailings. This is the common definition of dry stack tailings or filtered tailings

placement.

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Data!ase of Dry Stack Facilities in .peration(#/ D*0*L. 2*/T)

The following table is based on a literature review of dry stack facilities currently in

operation from information available in the public domain. ny modifications or additions to

this table should be sent via the contact form .

MINE/PROJECT &

LOCATION

ORE

TYPE THROUGHPUT (TPD)

FILTRATION

TECHNOLO

GY

COMMENTS

Alamo Dorado,Mexico

silver/gold 4,000 Vacuum BeltRecovery of 97. ! sodium cya"ide

#$e%site&

$31$ on *ngels 4 To !e reproduced !y permission only

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