OVERWIEW OF IN-PIT CRUSHING & CONVEYING TECHNOLOGY IN OPEN PIT MINES

Abstract

The conditions under which contemporary surface mining operations is carried out obviously becoming increasingly complex. In such complex conditions, the optimization of haulage systems as the technological phase with the largest share in the total operating costs, is very important from the aspect of achieving profitability of the mining project. In a large number of cases, the application of traditional haulage systems with trucks (as the most dominant type of haulage in open pit mines) does not lead to a reduction in costs, but they are constantly increasing. In such cases, it is necessary to find suitable alternatives, among which continuous mining systems such as In-Pit Crushing and Conveying (IPCC) systems stand out. The use of these systems provides significant benefits in terms of reducing operating costs, labor costs, risk reduction, dependence on tires and fuels as well as in reducing of CO2 emissions. The essence of this paper is to compare and review the various types of IPCC systems, present the advantages and disadvantages among them and in comparison with other types of haulage, as well as to emphasize the importance of implementing IPCC systems in open pit mines. The paper is part of a broader study related to the possibility of application the IPCC system in the Songun copper mine (Iran).

Full text

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OVERWIEW OF IN-PIT CRUSHING & CONVEYING TECHNOLOGY IN
OPEN PIT MINES
Ali Nasirinezhad1, Dejan Stevanović2, Dragan Ignjatović2, Petar Marković2
1 National Iranian Copper Industries Co., Ahar, IRAN
2 University of Belgrade, Faculty of Mining and Geology, Belgrade, SERBIA,
dejan.stevanovic@rgf.bg.ac.rs, dragan.ignjatovic@rgf.bg.ac.rs, petar.markovic@rgf.rs
Abstract: The conditions under which contemporary surface mining operations is carried out obviously becoming
increasingly complex. In such complex conditions, the optimization of haulage systems as the technological phase
with the largest share in the total operating costs, is very important from the aspect of achieving profitability of the
mining project. In a large number of cases, the application of traditional haulage systems with trucks (as the most
dominant type of haulage in open pit mines) does not lead to a reduction in costs, but they are constantly increasing.
In such cases, it is necessary to find suitable alternatives, among which continuous mining systems such as In-Pit
Crushing and Conveying (IPCC) systems stand out. The use of these systems provides significant benefits in terms of
reducing operating costs, labor costs, risk reduction, dependence on tires and fuels as well as in reducing of CO2
emissions. The essence of this paper is to compare and review the various types of IPCC systems, present the
advantages and disadvantages among them and in comparison with other types of haulage, as well as to emphasize
the importance of implementing IPCC systems in open pit mines. The paper is part of a broader study related to the
possibility of application the IPCC system in the Songun copper mine (Iran).
Keywords: In Pit Crushing and Conveying, IPCC, open pit mining, haulage, optimization, costs saving
1. INTRODUCTION
One of the basic tasks of mining exploitation is to select the appropriate mining method that best suits the
unique characteristics of mineral deposits, with the aim of achieving the lowest possible costs and
maximizing profits. Basically, extraction of minerals from the ground is mainly done by surface and
underground mining methods. Although many factors such as the depth, size and shape of the ore body
influence the choice of mining method, statistically mining engineers traditionally tend to use the surface
method in as many cases as possible. Nowadays, more than 90% of minerals are extracted by surface
methods (open-pit mining, strip mining method). The most important reasons for this are related to better
utilization of the deposit, as well as significant mining rate that can be achieved by surface method [1].
In surface mines, loading and hauling have always been a significant part of capital and operating costs
with a share of 65-70% of the total. In this sense, the optimization of the loading and hauling system can
have a significant impact on the mining economy [2]. In most surface mines, a combination of Trucks and
Shovels are most used technology for loading and hauling materials. The flexibility and controllability of
this systems have made them more practical [3]. When the mines get deeper or expand in size, unloading
destinations are becoming more and more distant and the length of transport as well as the height
difference between loading and unloading point, are increasing. All this causes, a reduction in the
economic benefits of Trucks and Shovels systems.
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The first thought in solving this problem is to change the strategy and move from surface to underground
method of mining. Usually, this transition from surface to underground method, implies a significant
change in technology and has a big effect on production and economy of the mining project. Given the
risk of not achieving business objectives during and after this transition, most of mining companies try to
delay this important change as much as possible by using some alternatives solutions. Mainly, there are
two solutions, the first of which involves the purchase of more capacitive equipment (larger dump trucks
and larger shovels), and the second which involves the use of systems consisting of a crusher and a
conveyor belts.
The first solution has the advantage of reducing the number of employees for the same mass of raw
material, but the space for equipment operation, potential road changes, increased dilution, the use of
bigger blasting pattern and the costs themselves must be considered. The second option provides more
benefits (most importantly lower operating costs for material transport) but requires the addition of a
crushing plant, because the blasted material due to granulation cannot be conveyed without previous
crushing. Using an in-pit crusher, a combination of track mounted mobile crusher, with mobile and fixed
conveyor belts, make it more competitive in compared to first method. This combination is called In-Pit
Crushing & Conveying (IPCC) System. [4, 5].
This paper is part of a broader study related to the possibility of applying the IPCC system in Songun
copper pit mine (Iran) and provides overview of IPCC system design, advantages and disadvantages of
using the system, and emphasizes the importance of IPCC system implementation in open pit mines.
2. DESCRIPTION AND CLASSIFICATION OF IPCC SYSTEMS
In the technological sense, an IPC system performs feeding, crushing, conveying and discharging system
[5, 6] and it can be used as a part of hauling and dumping operations in mines. This system is usually be
supported by a system of Shovel (or Shovel & Trucks) for loading in the beginning. Error! Reference
source not found. shows a schematic view of IPCC system in open pit mines. The basic task of the
crusher is to provide the appropriate granulation of the material necessary for conveyor feeding. This size
is in most cases less than 20% of the width of the conveyor belt. Based on the high impact energy of the
larger particles and the interconnection of the larger particles at the material transfer point between the
two conveyors, the granulation of the material should be less than 350mm [7]. IPCC systems can be used
for both waste and ore materials. In first case (for waste material) the conveyor is connected to spreader
which conducts material dumping. In case of ore material, conveyor can be connected with stackers
(stockpile formation) or can transport material directly to the processing plant. Since these systems have
two basic parts, a crusher and a conveyor, their categorization is usually based on the characteristics of
these two parts [8].
Figure 1. Schematics of IPCC System

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2.1.
Classification of IPCC Systems based on Crusher
The IPCC system comprises a combination of feeding, crushing, conveying, and discharging systems.
The most commonly used categorization implies a division according to the type of crusher, on the basis
of which IPCC systems can be divided into three types[5-7, 9]:
1.
Fixed crusher & conveyer (FIPCC),
2.
Semi mobile crusher & conveyer (SMIPCC)/Semi fixed crusher & conveyer (SFIPCC) and
3.
Fully mobile crusher & conveying (FMIPCC).
Each concept has its own corresponding material flow compared to the traditional Shovel-Truck system
(ST), which are presented in Error! Reference source not found. [10].
Shovel Truck Operation (ST)
Fixed Crushing Plant Concept or Semi Fixed/Semi Mobile
Fully Mobile Crushing Plant Concept
Figure 2. Operating parts of IPCC systems [10]
The crusher in the FIPCC system can be placed out or inside of pit limits and is not moved for a period of
15 years or longer (usually till the end of mining operations). They are mainly built on the concrete
structure and fed by trucks. Figure 3 shows an example of a fixed crushing station.
Figure 3. Crusher type in FIPCC system

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In SMIPCC systems, crusher unit works close to the mine front compared with FIPCC systems and helps
to reduce number of necessary trucks. They are usually located on a box-shaped steel structure and fed by
mining trucks and designed for a period of one to ten years, after which they should be moved to a new
location, closer to active part of pit.
SFIPCC systems are very similar to the SMIPCC systems, with the difference that their relocation is not
so frequent. In the mine design process, the relocation period of the SFIPCC system should be longer than
five years (Figure 4) [5, 6].
Figure 4. Crusher type in SMIPCC/SFIPCC systems
The FMIPCCs are mounted on a steel platform and are self-propelled by wheels and crawlers. These
systems are directly fed by shovel (loader/dragline) and can move simultaneously with the progress of
active benches. For this reason in terms of reducing operating costs, it has significantly greater potential
than other types of IPCC systems (Figure 5) [5, 6, 8]. A complete comparison between different types of
IPCC systems are shown in Error! Reference source not found. [6, 8].
Figure 5. FMIPCC Systems

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Table 1. Comparission of different IPCC systems
IPCC Crushing Options
FIPCC
SMIPCC/SFIPCC
FMIPCC
Lifetime (Year)
>15
1-10 / >5
By Face Advance
Structure
Concrete
Steel
Steel
Fed By
Truck
Truck
Shovel/Dragline
Capacity (t/h)
<12,000
<12,000
<10,000
Truck Number
Intermediate
Low
None
Crusher Type
Any
Any
(Sizer & Jaw) / Double Roll Crusher
Unit Crushing Cost
Lower
Intermediate
Higher
One of the newest innovative technology that is developed by MMD supplier (Mining Machinery
Developments) in 2019, is using continuous mining and existing truck fleet together without the need to
install capital-intensive conventional conveyers. This company has used a fully mobile surge loader
(FMSL) that is a part of FMIPCC system for loading of trucks. System increases the productivity of
shovel up to 50 % and accuracy in loading of trucks up to 98 %. Figure 6 shows typical truck and shovel
mining operation incorporating the FMSL. This solution draws upon MMD’s experience in Colombia
some 16 years ago, as well as a more recent in-pit sizing & conveying (IPSC) installation in China [11].
Figure 6. Typical truck and shovel mining operation incorporating the FMSL
2.2.
Classification of IPCC Systems based on Conveyer
Classification of conveyers in mining is based on their mobility. In that sense, conveyers can be divided
into Fully-mobile, Portable, Shiftable, Semi-fixed and fixed conveyor belt [12].
Fully-mobile conveyor belt is capable of changing its location through the mining operation continuously.
This type is generally used in combination with the FMIPCC systems. The main fully mobile conveyor
contains belt wagon, bridge conveyors, and horizontal conveyors (Figure 7).
Portable conveyor belts are like the fully mobile conveyor belts, i.e. this conveyor belt also can
continuously move while extraction, but using tires instead of crawlers (Figure 8) [9].
Shiftable conveyor belts are constituted from several shiftable conveyor modules, each four to six meters
long. These modules are installed on a steel sleeper, which is concocted to the steel rail. This steel rail
allows the whole system can be shifted by pipe laying dozers without dismantling the modules [13]. This
type of conveyor belts are usually used with the SMIPCC or FIMIPCC systems (Figure 9) [9, 12].

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Figure 7. Fully mobile conveyor belt
Figure 8. Portable conveyor belt
Figure 9. Shiftable conveyor belt
Semi fixed conveyor belt is occasionally relocated whenever it is needed. It is constituted from portable
modules of length four to six meters, which are installed on the concrete sleepers (Figure 10).

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Figure 10. Semi fixed conveyor belt
Finally, fixed conveyor belts are types of conveyors which should not be relocated along with the mine’s
life. It is typically installed outside the pit and works with a fixed crusher station (Figure 11) [6, 9, 10, 12].
Figure 11. Fixed conveyor belt
3. PROS AND CONS OF IPCC SYSTEMS
IPCC systems offer many advantages when compared to Shovel-Truck alternatives. The main reason for
the implementation of an IPCC System is the optimization of material transport around and out of the pit
on its way to the waste dump or processing plant. Advantages of belt conveyor haulage as compared to
the Shovel-Truck System include the following:
•
Placing the crusher in the pit reduces cost by shortening the haulage distance between the loaders
and crushing plant.
•
Operating costs associated with fuel, tires, and lubricants are reduced.
•
Labor costs are reduced.
•
Compared with truck haulage, safety risks are reduced.

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•
Dependence on the availability of fuel is greatly reduced.
•
Dependence on rubber tires is greatly reduced.
•
Conveyors can handle a slope of up to 30°, versus approximately 10-12% for trucks.
•
Conveyors can easily cross roads, railways, waterways, and other obstructions.
•
With the reduction of haulage costs, lower-grade ore bodies can be mined economically.
•
CO2 emissions are greatly reduced.
•
Downhill conveyors can produce regenerative electrical power instead of , as is the situation with
trucks braking.
•
Conveyors are more energy efficient than trucks.
•
Conveyors require less skilled labor for maintenance than trucks.
•
IPCC equipment can achieve maximum operational availability because of greater independence
from weather conditions such as fog, rain, snow, and frost.
•
The cost of haulage road maintenance is significantly reduced by using conveyors.
•
Continuous flow of material can be maintained by using conveyors.
The principal drawbacks of belt conveyor haulage as compared to truck haulage are the following:
•
Short-term flexibility is reduced.
•
Capital costs are higher.
•
Capacity increments are easier to achieve with trucks compared to large IPCC systems.
•
In mines where ore blending is important, truck flexibility provides additional benefits.
•
Lump size is limited. Sometimes it is necessary to crush the blasted ore or waste.
•
During the maintenance process, production can be reduced to zero by shutting down the entire
system
•
The production of the IPCC system is dependent on how it is loaded [6, 14].

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In additional different type of IPCC systems have own pros and cons they are described in Error!
Reference source not found. [9]:
Table 2. Advantages and disadvantages of the IPCC systems
System
Advantages
Disadvantages
FIPCC
1. Traditional plants can simply be modified in
order to be used as in-pit crushers.
2. Reducing maintenance costs because there is no
need for an apron feeder.
3. High crushing chamber capacity
4. Reducing capital costs mainly because of the
limited capability of mobility
5. Reduced maintenance costs because of a better
crushing in the upper portion of the chamber and
decreased localized abrasive wear
6. Higher capacity and finer product size due to the
weight of the ore column above the crusher
1. Concrete design cannot be relocated
2. Structural steel usually cannot be moved.
If it is not the case, a considerable sub-
structure is needed to support the plant for
relocation
3. Overall height is more significant because
of the higher dump point bench level
4. Large retaining wall
5. Long bench strikes and width in mine plan
SFIPCC
1. Traditional plants can be simply modified in
order to be used as in-pit crushers
2. Reducing maintenance costs because there is no
need for an apron feeder
3. High crushing chamber capacity
4. Reducing capital costs mainly due to the limited
capability of mobility
5. Increased long-term flexibility due to limited
capability of moving, which allows for future
modifications.
6. Reduced maintenance costs due to a better
crushing in the upper portion of the chamber and
decreased localized abrasive wear
7. Higher capacity and finer product size due to the
weight of the ore column above the crusher
1. Only the crusher as part of the whole plant
is mounted on a steel base
2. The balance of the station depends on
adequate construction design. Greater overall
height is due to the higher dump point bench
level.
3. Long bench strikes and width in mine plan
SMIPCC
1. Traditional plant configuration
2. Low bench height for dumping ore
3. Reduced truck queue time
4. Improved control of oversize material fed to the
crusher
5. Reduced crusher downtime due to the bridging of
large lumps
6. High flow of crushing chamber
7. Reduced capital costs due to the limited degree of
mobility
8. Increased long-term flexibility due to the ability
to move the complete station intact,
9. Reduced maintenance costs due to cleaning of the
apron feeder, the greater amount of crushing in the
upper portion of the chamber, and decreased
localized abrasive wear when compared to indirect
feed designs
10. Greater capacity and finer product size due to
the weight of the ore column
1. Large and heavy structure requiring large
transporters for moving
2. Greater overall height due to the higher
dump point bench level, which requires
extensive bench-retaining walls
3. Long bench strikes and width in mine plan
FMIPC
1. Elimination of truck transport
2. Reduced number of stuff
3. Avoidance of high truck maintenance costs
4. Reduction of mine traffic
5. Increase in the overall safety
1. Increased total capital costs
2. Increased maintenance costs associated
with adding an apron feeder
3. Increased maintenance costs associated
with the crusher from using an apron feeder
4. Long bench strikes and width in mine plan

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4. THE MINIMUM CONDITIONS FOR USING IPCC
Although using IPCC in a mine is related to economical, technical, environmental, safety and social
perspectives, there are some general consensus for initial selection. The most fundamental parameters for
using IPCC are:
•
The mine life should be longer than 10 years
•
The production should be more than 10 Mtpa (preferably closer to 25 Mtpa)
•
The electricity prices ($/kWh) should be lower than 25% of unit diesel prices ($/L) [15] (in some
researches less than 40 %) [8]
•
Haulage distance should be more than 10 km (more than 25 minutes of truck cycle time) [5]
And using IPCC is more recommended in these situations:
•
Rocks should be low comprehensive strength
•
Waste development is constrained
•
Brown field projects (when truck cycle time becomes excessive)
•
Vertically advancing operations (when difference altitude of mine and destination becomes
higher) [5, 15]
•
No more than three types of material
•
Workforce issues prevail
•
Reducing of carbon dioxide and dust emissions is important [8]
5. CONCLUSION
As said before, in the cost structure of mining project, Loading and Hauling operation, participate with
the largest percentage. In the initial development stages of the mining project, these operations are mainly
performed by a Truck and Shovel system. In large mining projects, whose lifespan is measured in
decades, benefits from Truck and Shovel system are greatly undermined by deepening and widening of
the pit limits. The potential transition to underground mining method, can be delayed by introduction of
IPCC systems. It provides benefits by reduction in operation costs, labor costs, safety risk, fuel & tire
consumption, and CO2 emission. Additionally, it can increase capacity of productions, which in
conditions of declining deposits grade can be especially important.
IPC systems occur in several different forms (FMIPPC, SMIPCC, SFIPCC and FIPCC) and each form
has its own unique set of characteristics. Knowledge of these characteristics is of key importance, first of
all in the decision making process whether to introduce a IPCC system and later for the selection of the
optimal type of the IPCC system for a specific mining project. The introduction of the IPCC system
requires significant technological, organizational, and economic changes in the mining project and any
possible mistakes made during the implementation of the IPCC system are costly and difficult to
eliminate.
Recognizing the importance of the everything mentioned above, this paper offers an overview of existing
IPCC system technologies, basic characteristics and minimum conditions for their application, as well as
the advantages and disadvantages of specific types. The paper was created as part of a broader study on
the possibility of using the IPCC system in the Songun open pit (Iran), but the conditions for the
application of the IPCC system, listed in this paper, are generally applicable in open pit mining practice.

92
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