A cost analysis
of the transport
surrounding
underwater
mining
ME2110 Literature research
by
J. van Kampen
Student number: 1359177
Project duration: March 1, 2017 – July 26, 2017
Supervisors: Dr. ir. D. L. Schott, TU Delft, supervisor W. Ma MSc, TU Delft
Summary
In this report, some insight into the transportation of minerals collected by deep sea mining is given. The aim of the report is to find a mathematical relation between the components that make up the transportation cost. This is done by posing a main question:• Which factors determine the cost of the transport related to deep sea mining and how are they
re-lated to each other mathematically?
Additionally four sub questions are posed in order to answer the main question. They are: • How can the transport in a deep sea mining operation be divided?
• What factors can be considered capital expense and what factors can be considered operational
ex-pense?
• How are capital expenditure and operational expenses related in a deep sea mining operation? • To what extent can the transport of a deep sea mining operation be detailed beforehand?
The transport is divided into three parts. The vertical transport, which consists of minerals being trans-ported from the ocean floor to the production support vessel. The horizontal transport, which contains all the transport of minerals from the PSV to the port of choice. And finally the logistics that support the entire operation and ensure that it runs as smoothly and efficiently as possible.
The capital expenditure of transport of a DSM operation are mainly the purchase of a number of bulk carriers. Though this is only one part of the total expenses, according to [23] and [22], this purchase should be estimated at $ 495 million to $ 600 million. Whereas [21] estimates the total vertical transport CAPEX at $ 50 million. The CAPEX of the logistics were assumed to be negligible since the transport of the supplies would be conducted by the bulk carriers used for the horizontal transport.
The operational expenses proved harder to qualify and quantify. This is due to the fact that there are far more factors that play a role in the operational expenses. The factors that were discussed in all three parts of the transportation problem, explicitly or implicitly, were energy consumption and production rate. This is because they lie at the basis of the operational expenses of the transport of minerals and are closely related to one another.
The OPEX and CAPEX are linked to each other by several factors, one being the production rate which was mentioned earlier. This is because a higher production rate leads to a higher yield, this needs to be stored, first on the PSV, next on a bulk carrier and finally in a port before it can be transferred to a processing plant. This means that factors like production rate determine the size of the operation. Thus influencing not only the OPEX but also the CAPEX. Due to the fact that several factors influence both the OPEX and the CAPEX of the operation, it can be complex to find the optimal configuration of the DSM operation. It also means that there is no standard best solution for any operation and a new considerations have to be made for each operation. This is due to the complexity and the scale of the operation.Due to the fact that there are several unknown factors surrounding any DSM operation it seems wise to keep in mind that the cost estimate of any component, including the transport, can be be off by a considerable margin.
The factors that are found to be of influence on the transport costs are the location of the DSM operation because it influences the time it takes to travel to the port, thus influencing the fuel consumption for horizon-tal transport and the wages that have to be paid to the crew on the bulk carrier. Likewise depth had a similar contribution to the vertical transport cost.
A second factor that was found is the production rate that the DSM operation needs to be financially sound. iii
iv
This factor influences the energy consumption of every transport component. It determines the energy con-sumption and the scale of the vertical transport, it determines the scale of the bulk carriers and the number of bulk carriers that are required. The production rate also influences the logistics, since an increasing pro-duction rate leads to an increased burden on the components reducing their service lifetime expectation.
The way everything ties together is by looking at the Equation 3.2 and expanding it even further. This can be done by looking at each component and filling in these components. This is done by looking at the factors that each component depends on. The function that is obtained is:
Tr anspor t cost = fC APE Xver t i c al(h,Qs) + fOPE Xver t i c al(h,Qs)
+ fC APE Xhor i zont al(d , v,Qs) + fOPE Xhor i zont al(d , v,Qs)
+ fC APE XSur f acel og i st i c s(d ,Qs, Ef) + fOPE XSur f acel og i st i c s(d ,Qs, Ef)
In this Equation, h is the vertical transport distance [m], Qsis the production rate [kg/s], d is the distance
that the vertical transport needs to sail in order to reach the PSV [m] and Efis the energy in the form of fuel
that has to be brought from the mainland to the PSV [J]. These factors all relate to a certain price. Since the total transport cost is linked to the way that the operation is run, coming up with a single equation for all DSM operations seems impossible. The closest one can get is taking a general equation like the one above and filling in the terms that they think are vital for their specific operation. This, together with a number of conditions and demands can be put in several simulation in order to find a way of transporting the minerals that is best suited for the operation.
Contents
1 Introduction 1
2 The process of deep sea mining 3
2.1 Working on the ocean floor . . . 3
2.2 Transporting minerals to the surface . . . 5
2.3 The Production Support Vessel . . . 5
2.4 Transshipment from the PSV to the Supply Vessel. . . 5
2.5 The Supply Vessel . . . 6
2.6 Components of interest to the transport . . . 6
3 How to asses the costs 9 3.1 Examining the cost of DSM transport . . . 9
3.2 Vertical transport . . . 10
3.3 Transshipment between the PSV and the Supply Vessel . . . 10
3.4 The horizontal transport . . . 10
3.5 Surface logistics . . . 11
4 Operational expenses of vertical transport 13 4.1 The energy consumption of a continuous line bucket. . . 13
4.2 The energy consumption of a pipe lifting system . . . 14
4.3 Case study by Van Wijk . . . 15
5 Operational expenses of horizontal transport 19 5.1 Location . . . 19
5.2 Choice of port. . . 19
5.3 Transshipment of minerals . . . 20
5.4 Production rate and storage capacity . . . 20
5.5 Fuel consumption of the transport vessels . . . 20
5.6 Crew wages and benefits . . . 21
5.7 Repairs and maintenance . . . 23
6 Operational expenses of surface logistics 25 6.1 Fuel . . . 25
6.2 Key spare parts . . . 25
6.3 Crew and various consumables . . . 26
6.4 Waste . . . 26
7 Capital expenditure of the transport of minerals 27 7.1 The capital expenditure of vertical transport . . . 27
7.2 Capital expenditure of the horizontal transport and logistics . . . 28
7.3 The CAPEX and OPEX of a DSM operation . . . 28
8 The total transport cost 29 8.1 A general equation . . . 29 8.2 Limitations . . . 29 9 Conclusion 31 10 Recommendations 33 Bibliography 35 v
1
Introduction
The demand for minerals is ever increasing. The growth of the smart industry, among others, means that minerals like copper and manganese are in high demand [16]. One of the areas that are rich with these min-erals is the bottom of the ocean [29]. Here manganese nodules can be found in large amounts. However, getting them to the surface and to the mainland proved to be difficult. This literature research aims to give some insight into how the transport can be organized and which factors play a role in the eventual transport cost.Since 2009, the Canadian company Nautilus Minerals has been mining in the ocean near Papua New Guinea for seafloor massive sulfides [7]. This indicates that, even though the circumstances seem difficult, it is feasible to mine for minerals at great depths. The mining that Nautilus Minerals does takes place at approximately 1600 meters depth, at roughly 20 km from the coast. Relatively close to the coast in relatively shallow water. The location of the Solwara mining site is shown in Figure 1.1.
Figure 1.1: Location of the Solwara 1 mining site [14]
2 1. Introduction
The location and depth of the Solwara mining site raises the question to what extend transport costs have an impact on the exploitation of a mining site. Since the site is located close to shore, travel time between the site and the shore for example, is negligible. This literature research focuses on the transport costs of under-water mining. The main question of this literature research is:
• Which factors determine the cost of the transport related to deep sea mining and how are they
re-lated to each other mathematically?
In order to answer the main question, four sub-questions are proposed: • How can the transport in a deep sea mining operation be divided?
• What factors can be considered capital expense and what factors can be considered operational
ex-pense?
• How are capital expenditure and operational expenses related in a deep sea mining operation? • To what extent can the transport of a deep sea mining operation be detailed beforehand?
These questions all serve a different purpose, the first one aims to cut up the problem in several smaller problems that will be more manageable. The second question divides the problem even further as it looks to the assets that are needed in a mining operation and the costs that have to be made. The third question aims to shed some light on the relations between the assets and the costs. Finally the fourth question raises the notion that a complex undertaking like a deep sea mining operation may not be fully known before the operation starts.
This report consists of several chapters, which all relate to a part of the transportation surrounding deep sea mining. First a brief overview of the working process is given. The second chapter examines the cost associated with the transport briefly. The following three chapters, three four and five, give insight into the operational expenses of the transport of a deep sea mining operation. The sixth chapter contains a look on the capital expenditures of a deep sea mining operation and the transport specifically. A seventh chapter explores the relations between the factors that were found to have influence on the transport cost. The report will end with a conclusion and a recommendation for further research based on the literature that was found.
2
The process of deep sea mining
Transporting minerals from the bottom of the ocean and getting them to port, where they can be processed, is a complex process. In order to get a better understanding of how deep sea mining (DSM) works, this Chapter will explain the process, the components involved and finally list the components that are of interest in the transport of the minerals.2.1. Working on the ocean floor
Figure 2.1: Illustration of the working principle of DSM [15]
The first step in the mining process is the search for interesting minerals to mine. The minerals that are most often searched for are manganese, copper, cobalt and nickel [23]. The minerals are located with the help of
4 2. The process of deep sea mining
a Remotely Operated Vehicle (ROV), which can take samples from the ocean floor. When the samples prove lucrative, the mining site can be developed further. According to [22] samples should have a cut off grade of 1.8 % for nickel and copper and should have a cut off abundance of 5 kg/m2, for the mining site to be devel-oped. This means that the amount of nickel and copper should be high enough to be mined eventually and also the amount of soil that can be mined should be high enough to ensure a sufficient yield.
Figure 2.2: Auxiliary cutter used in the Solwara project [15]
The minerals that are located on the ocean floor, are mined using three different vehicles. First the Auxil-iary Cutter (AC), shown in Figure 2.2, works the seabed to prepare it for the Bulk Cutter (BC), shown in Figure 2.3. Th AC separates the unwanted soil from the mineral rich layers. When this is finished the BC follows the AC and grinds up the minerals. This makes sure that the minerals are of transportable size.
Figure 2.3: Bulk cutter used in the Solwara project [15]
After the BC is done with the minerals they are ready to be picked up. This is done by the Collecting Machine (CM), shown in Figure 2.4. The CM collects the piled up minerals and starts with the process of refining the minerals. This reduces the amount of slurry that needs to be transported and thus decreases the energy that is needed to transport the material to the surface. The CM is connected to a flexible hose. The flexible hose ensures that the CM has room to move around over the ocean floor. The flexible hose is the first part of the vertical transport.
2.2. Transporting minerals to the surface 5
Figure 2.4: Collecting machine used in the Solwara project [15]
2.2. Transporting minerals to the surface
After the minerals are collected, they are transported trough a flexible hose. The slurry is pumped up by a number of pumps, attached to the vertical transport system up to the Production Support Vessel(PSV).
Another common way of transporting minerals to the surface is with the use of a Continues Line Bucket (CLB), this is a line bucket that is lowered from the PSV into the ocean. Then, at a specific depth, the end of the flexible hose comes out above the CLB. The buckets get filled and are brought to the surface, where they are unloaded in the PSV.
2.3. The Production Support Vessel
The Production Support Vessel (PSV) is the location from which the mining operation is conducted. The PSV stores the mined minerals, it processes the slurry and holds all the equipment and spare parts. The PSV also provides housing and locations for recreation for the crew, such as gyms and recreation rooms. The PSV should also contain a kitchen, a mess room and a sickbay, among others. To summarize, the PSV should contain everything to successfully conduct a DSM operation and also house everything for the crew to work and live in the middle of the ocean.
Figure 2.5: Illustration of the Production Supply Vessel with the Supply Vessel [15]
2.4. Transshipment from the PSV to the Supply Vessel
The transshipment of the minerals from the PSV to the supply vessel can be done in several ways. For example using cranes, using regular conveyors, or a pipe conveyor. A conveyor or pipe conveyor can be suspended from the PSV over the supply vessel, that way the minerals are transported from the PSV to the supply vessel. An example of a pipe conveyor can be found in Figure 2.6.
6 2. The process of deep sea mining
Figure 2.6: Illustration of a pipe conveyor [11]
The pipe conveyor works in a similar way as a regular conveyor. With the exception that the belt is forced in a circle by the idlers to create closed loop. This shields the minerals from the elements. In the schematic picture above, the belt is loaded in the upper right corner, the minerals are transported in the lower left corner and in between these points the idlers force the conveyor belt into a circle.
2.5. The Supply Vessel
When the PSV is empty, the supply vessel can return to the port. When the supply vessel arrives at the port, the vessel will be unloaded. Furthermore, the supply vessel can also be used for the logistics. This consists of everything that the PSV needs to continue operation. For example, fuel, replacement parts, food and water, and a new crew. The time it takes for the supply vessel to make a round trip and the time it takes for the PSV to fill up and consume its supplies is critical for a good planning.
2.6. Components of interest to the transport
In order to zoom in on the transport of minerals in a deep sea mining operation the following components that are examined in greater detail:
• The flexible hose and rigid pipe
• The transshipment between the PSV and the supply vessel • The transport across the surface
• The logistics to support the operation
2.6. Components of interest to the transport 7
From the items of the list, the flexible hose and the rigid pipe are considered vertical transport. The trans-shipment of the minerals, as well as the transport to the port is considered horizontal transport and every-thing that has to be brought to and taken from the PSV in order to keep the operation running is considered logistics. A schematic overview of these components can be seen in Figure 2.7. These components will be evaluated in order to see how their capital expenditure and operational expenses are built up. The compo-nents of the operational expenses, like energy consumption, are investigated in order to see their impact on the total transport cost. Furthermore, the capital expenditure is looked into as well, to come up with a clear picture of how the transport cost is made up.
3
How to asses the costs
In order to asses the cost build up of the transport, this Chapter provides insight into the different compo-nents that make up the final cost. This will be done for the four items that were listed in the previous chapter. This chapter gives insight into how the costs are build up for each of those items.3.1. Examining the cost of DSM transport
The cost of the transport can be assessed at various levels. At the highest level it is only one component, simply transport cost. However, this level is not sufficient in order to give insight into the transport cost. Therefore one needs to zoom in at the transport cost. When this is done, looking at Chapter 2, one way of looking at the transport cost can be split according to equation 3.1.
Tr anspor t cost = T Cver t i c al+ T Chor i zont al+Csur f acel og i st i c s (3.1) In this formula, TCverticalis the transport cost of the vertical transport, TChorizontalthe cost of horizontal
transport and Csurface logisticsthe cost of all the logistics. Although this is an improvement, it is still an equation
that needs further refinement.
In order to zoom in further at the transport cost, the distinction between capital expenditure and opera-tional expenses is made. According to [8] capital expenditures (CAPEX) are the funds that a business uses to purchase major physical goods or services to expand the company’s abilities to generate profits. In the case of DSM the PSV, the collecting vehicles and the bulk carrier among others can be considered CAPEX. Opera-tional expenses (OPEX) are the costs that result from the basic business operations. An example of OPEX is the wages for the crew, the fuel cost for the various systems and the costs of unloading the bulk carrier among others. When these concepts are applied to equation 3.1, this equation can be expanded to equation 3.2.
Tr anspor t cost = C APE Xver t i c al+ OPE Xver t i c al +C APE Xhor i zont al+ OPE Xhor i zont al +C APE XSur f acel og i st i c s+ OPE Xsur f acel og i st i c s
(3.2)
This expansion of 3.1 leads to a more detailed view at the transport costs. However, this is still not refined enough. The examples of CAPEX and OPEX in the previous paragraph need to be fleshed out and exam-ined thoroughly. This is done by examining every component of equation 3.2 and zooming in on them even further.
This means that every component needs to be analyzed in order to gain insight into the transport cost. Chapter 4 zooms in on the cost build-up of vertical transport, Chapter 5 looks at the cost build-up of the hor-izontal transport and Chapter 6 looks at the cost build-up of the logistics. This is done by examining what the components, studied in the Chapters, contain, from material to energy consumption and investments.
When looking at the process of DSM the cost of the transport is quite clear. Getting the minerals from the ocean floor to the surface requires pumps, pipes and a hose. The pumps need to be driven, which requires energy. The service lifetime of the pumps and the pipes and hose determine the write off costs and together with the energy cost, these two components determine the cost of the vertical transport. The number of pipes
10 3. How to asses the costs
and hoses can be increased to increase the transport capacity. Increasing the number of pipes does increase the complexity of the operation and also increases the cost of the vertical transport [21].
The next step in the transport is the transshipment of the minerals from the PSV to the bulk carrier. This can be done with a pipe conveyor as suggested by [12], the cost build up of this process is similar to the cost build up of the vertical transport. This process uses a certain number of pipe conveyors with a certain service lifetime. This service lifetime determines the write off cost of the component and together with the energy cost of the pipe conveyor this determines the transport cost of the transshipment of the minerals.
After the minerals are loaded into the bulk carrier, they can be shipped to shore. The cost build up of the transport of the minerals from the PSV to the shore is also made up of investment costs and operational cost. The unloading of the bulk carrier is the final step in the transport process. The choice of harbor can be a factor of interest, if the nearest harbor has higher fees or is less efficient than a harbor further removed from the mining site, the best option should be chosen.
The last part of the transport is the logistics, the logistics can be assessed based on the service life of all the components, and the energy demands of the all the components. The assumption is that when any one component is broken, or at the end of its service life, a new component should be present at the PSV in order to keep the interruptions as short as possible. The second part of the surface logistics is everything that is consumed on the PSV. This can be energy, food and supplies for the crew and the crew itself.
3.2. Vertical transport
The vertical transport consists of the flexible hose, the rigid pipes and the pumps that move the slurry through the pipes [12]. The characteristics of this system, the capacity of the pumps and the diameter of the pipes, determine the amount of slurry that can be transported to the surface. The cost of the vertical transport can be divided in two categories, operational expenditure and capital expenditure. The capital expenditure for the vertical transport consists of the purchase costs of the components that are needed. In this case the pumps, the pipes and the flexible hose among others. Operational expenditure of the vertical transport consists of the energy consumption of the system.
3.3. Transshipment between the PSV and the Supply Vessel
It is suggested by [12] that the transshipment of the minerals between the PSV and Supply Vessel is done with the help of a pipe conveyor, or a set of pipe conveyors. However, there are other ways to transfer the minerals from the PSV to the supply vessel. For example, a regular conveyor, bulk cranes on the PSV or floating bulk cranes on ships alongside the PSV. These different types of transshipment have different advantages and disadvantages. However, to reduce spilling the best choice is the pipe conveyor. Since this mode of transshipment seals the minerals from the elements, spilling can reduced in comparison with a regular, open, conveyor. It also ensures a steady regular stream of minerals, instead of the cranes which always drop their entire load at once, possibly damaging the loading bays of the bulk carrier.
The CAPEX for the transshipment are the pipe conveyor system, the steel frame the pulleys the engine and, of course, the belt. The OPEX of the transshipment is the energy that is consumed during the transshipment operation.
3.4. The horizontal transport
The horizontal transport will be conducted by bulk carrier. The number of bulk carriers depends, among others, on the magnitude of the operation, the production rate and the distance that the PSV is removed from the port. If only one bulk carrier is used, the shipping capacity or dead weight tonnage, should be large enough to cover the storage capacity of the PSV. Also the distance needs to be taken into account, since the bulk carriers will have a finite velocity. The time it takes for a round trip needs to be taken into account when the distance increases. Furthermore, the bulk carriers need to be loaded and unloaded, they need to be fueled and maintained if necessary. All these actions take time and have to be kept in mind when an approximation for the scale and number of carriers needs to be made.
The CAPEX of the horizontal transport are the investment that need to be made in order to purchase a bulk carrier or bulk carriers. The OPEX of the horizontal transport consists of several components. The main
3.5. Surface logistics 11
component is the fuel cost, for the main engine as well as the auxiliary engines, next there is crew wages, port and canal fees, maintenance and repair cost among others.
3.5. Surface logistics
The logistics are evaluated based on the life expectancy of the components. Since the operation needs to run continuously, the spare parts need to be brought to the PSV in time to be replaced. This means that every critical component should have at least one spare located on the PSV. However, the surface logistics entail more than just spare parts. Everything that is needed in order to keep the DSM operation running as smoothly as possible will have to be brought in from the main land. This means that fuel has to be shipped in, again main engine as well as auxiliary engine fuel needs to be shipped. However, exploring renewable energy sources in the form of wind, solar or even wave energy might be an interesting option to reduce the cost of the fuel transport.
Since the crew on the PSV needs to be replaced at the end of their shift, at regular intervals a new crew needs to be brought in to keep the operation going. Expanding on that, the crew needs to eat and drink, they need basic household items, like soap and other cleaning materials. Safety gear needs to be available and, if broken, replaced. But also the tools and fasteners that are consumed during operation need to be brought onto the PSV. This means that everything that is needed, needs to be shipped to the DSM location. After the consumables are finished, the waste, that cannot be processed on the PSV, need to be transported back to shore.
Since the PSV is visited at regular intervals by a bulk carrier, it stands to reason that the bulk carrier can transport the supplies that are needed to keep the operation going. This means that room and capacity needs to be reserved on the bulk carrier to make the transport of supplies and waste possible.
Looking at everything that a DSM operation and, especially, an entire crew of a PSV consumes between visits of the bulk carrier is a complex task and perhaps a general number needs to be introduced in order to quantify the "small" orders. When looking at the CAPEX of the logistics, the bulk carrier needs to be adapted so that it can service as a supply vessel as well as a bulk carrier. This means additional costs arise when the purchase of the bulk carrier needs to be made. The OPEX of logistics are similar to the OPEX of the horizontal transport, since the horizontal transport facilitates the logistics that support the DSM operation.
4
Operational expenses of vertical transport
The vertical transport of the minerals is the transportation of minerals from the ocean floor to the PSV. The minerals are gathered by the collecting vehicle and transported from the ocean floor through a flexible hose, the hose ensures that the mining vehicle has room to move around, and then through a pipe system or a continuous line bucket system to the PSV. The vertical transport depends on several factors like depth, pro-duction rate and transportation mode.4.1. The energy consumption of a continuous line bucket
One of the transport modes is the continuous line bucket system. It works by lowering a line of buckets down in the water. After descending to its lowest point, the buckets are lifted back up again. The principle is shown in Figure 4.1.
Figure 4.1: A schematic overview of the continuous line bucket system [13]
The energy consumption of a continuous line bucket system is given by [13]. The energy that is needed to run a continuous line bucket system is calculated by the following equations:
Ecu= Qs· g · H · (1 −ρl ρs) +Qs· g · h (4.1) Ec t= 3600 · P (4.2) η =Ecu Ec t (4.3) Et on= Ec t Qs (4.4) In these equations, Ecuis the useful energy consumption [J/h], Ectis the total energy consumption [J/h],
Qsis the solid mineral production rate [ton/h],ηcis the continuous line bucket systems efficiency and Eton
is the energy consumption lifting per tonnage mineral [J/ton] or [kWh/ton]. Using these equations, one can calculate the required energy that is needed to use a continuous line bucket system.
14 4. Operational expenses of vertical transport
4.2. The energy consumption of a pipe lifting system
The pipe lifting system is another way of transporting minerals to the surface. The pipe lifting system consists of a series of pipes and pumps that transport the slurry, containing the minerals, to the surface. An overview of what the pipe lifting system looks like can be seen in Figure 5.1. The energy consumption of a pipe lifting system is given by [12]. The equations that are used are:
PR= Pmai n+ Psubor d i nat e (4.5)
Pmai n= PF+ PD= λ h Dp 1 2(ρlClv 2 l + ρsCsv2s) + hg (ρm− ρi) (4.6) Psubor d i nat e= PI+ PV= (ξf+ ξh(h)) 1 2(ρlClv 2 l + ρsCsv 2 s) (4.7)
In these equations PRis the required pressure that has to be supplied by the pumps [Pa]. Pmainis the main
influencing aspect of the pressure loss [Pa]. Psubordinateis the subordinate influencing aspect of the pressure
loss [Pa]. PIis the pressure loss caused by the fluid inlet and acceleration [Pa]. PVis the pressure loss caused
by the valves [Pa]. PFis the pressure loss caused by the friction [Pa]. PDis the pressure loss caused by the
difference between the mixture and the ocean water [Pa]. vsis the mineral solid velocity [m/s]. vlis the liquid
velocity [m/s].ξf is the pressure loss factor.ξhis the valve pressure loss factor.λ is the friction loss factor. h is the mining depth [m]. Dpis the pipe diameter [m]. Cland Csare the volume concentrations of the ocean
water and the solids respectively.
With the help of these equations, the required number of pumps can be calculated. This can be done with the following equation:
Np=
PR
αfPP
(4.8) In this equation Npis the number of pumps that is required andαf is the Stepanoff factor. The equations give insight into the material that is needed in order to transport the minerals to the surface.
The energy consumption of the transport is directly related to the operational expenses of the transport. The useful energy consumption of a vertical centrifugal lifting system is given in Equation 4.9 and the total energy consumption is given in Equation 4.10.
[H ]Er p= (1 −ρl ρs )Qmg H (4.9) [H ]Er t= Np vmApPR ηh(aw)Np (4.10) From equation 4.9 it can be seen that the useful energy consumption depends on the ratio between the density of the liquidρland solidρsparts, the volume flow Qm, the gravity constant g and the height, H, that
needs to be traversed. The total energy consumption depends on Npwhich is the number of pumps, vmis the
velocity of the mixture, Apis the diameter of the pipe, Pris the required pressureηhis the dynamic efficiency and awis the work ability factor.
A greater mining depth means a greater distance and a greater water pressure to overcome. This trans-lates to a greater energy consumption of the vertical transport system. This means that increasing the mining depth, increases the transport cost of the operation. The increasing energy cost, however, is not the only component that adds to the increasing cost of vertical transport, the number of pumps also increases. This is stated by [12], the number of pumps is directly related to the pressure difference. A greater mining depth has another consequence that is not directly related to the energy consumption. As stated by [13] the a continu-ous line bucket system cannot function a depths greater than a 1000 meters. This is due to the fact that the winch force that is needed to keep the buckets turning increases to unacceptable heights. This means that the continuous line bucket system can only be used in relatively shallow waters.
According to [18] the production that a DSM operation needs to attain is 2,4 million tonnes per year. This comes down to a production rate of 77 kg/s. When this number is put into Equation 4.9m and assuming a mining depth of 2000 meters, a solid, stone, density of 2600 kg/m3and a liquid, water, density of 1000 kg/m3[26] the useful energy consumption would come down to 929,7 kW. Per day this equates to 22312 kWh
4.3. Case study by Van Wijk 15
Figure 4.2: A schematic overview of the vertical transport described by [28]
or 22,3 MWh. This equates to just over 13 barrels of oil each day [9]. This is only the useful energy consump-tion related to the producconsump-tion rate. The efficiency of the system is not taken into account. A more detailed case study, discussed in the next Section, explores the energy requirement of a vertical transport system to a greater extent.
4.3. Case study by Van Wijk
In 2016, [28], conducted a master thesis on the flow that is needed for vertical transport of minerals in a DSM operation. In a case study, the stability of the flow is calculated. The case study evaluates the situation described in Figure 5.1. Although the case study looks at the stability of vertical transport, data on the energy consumption can also be extracted.
The case study looks at manganese mining in the Clarion Clipperton Zone. Here the water is several kilometers deep. The seawater temperature is relatively constant at about 5◦C. The values that are used in the case study are listed in Table 4.1. The design parameters are given in Table 4.2.
Parameter Description Value
H Water depth 5000 m
ρf Density water 1025 kg/ m3
µf Dynamic viscosity water 1,7·10-3Pa s
ρs Density solids 2500 kg/m3
¯
s Average dry solids production 111 kg/s smax Maximum dry solids production 150 kg/s
Table 4.1: Values used in the case study of [28]
Furthermore the vertical transport system that is used in the case study is also described. It uses a 14" = 356 mm pipe in the vertical transport. This is based on the maximum particle diameter d100= 125mm, the
particle size distribution is given in Figure 4.3. The minimum bulk velocity that is required is 3,6 m/s, based on the particle size distribution and the settling velocity. However, to ensure that the desired production rate of 111 kg/s is achieved, the bulk velocity is increased to vbulk4 m/s. The bulk density isρbul k = 1200 kg/m3.
16 4. Operational expenses of vertical transport
To overcome the static pressure and the wall friction in the pipe a pressure ofPpe,f= 103,6 bar is needed.
Figure 4.3: Particle size distribution used by [28]
The case study uses 12 pumps, distributed over 6 booster stations. This means that every pump needs to deliver at least pe,f = (103,6/12)· (1025/1200) = 7.37 bar of water pressure to maintain the required flow.
However, this the nominal required pressure, to be safe a higher pressure is suggested. This pressure is based on the idea that the minimum bulk velocity should be attained even if two pumps malfunction. The mini-mum bulk velocity is equal to 3,6 m/s which comes down to a total pressure drop ofPpe,f= 99,85 bar. The
minimum required pressure per pump to ensure stable flow with 10 pumps is pe,f= (99,85/10)· (1025/1200) =
8,53 bar. This pressure is deemed sufficient to ensure a stable vertical transport.
Parameter Specification
Internal diameter D 356 mm
Pump pressure pe,f(min., nom., safe) 7,1 bar, 7,4 bar, 8,6 bar
Bulk velocity ¯vm 4 m/s Minimum velocity ¯vm,mi n 3,6 m/s Slurry densityρm 1200 kg/m3 Volume fraction of solids cv 0,12
Table 4.2: Specifications of the vertical transport system used in the case study of [28]
Using these values, [28], comes to a steady state pressure of approximately 120 bar after 1400 seconds as can be seen in Figure 4.4 and a hydraulic power of 5 MW after 1400 seconds as can be seen in Figure 4.5. This gives another indication of the power consumption of the vertical transport.
4.3. Case study by Van Wijk 17
Figure 4.5: The hydraulic power delivered by the pumps as described by [28]
The case study gives insight into the energy consumption of the vertical transport. To put the numbers into perspective, a constant energy consumption of 5 MW equates to 120 MWh per vertical transport system. This comes down to approximately 70 barrels of oil each day for each vertical transport system [9]. Since this is only the hydraulic power and not the power that is consumed by the pumps, due to the pump efficiency, the estimate of 120 MWh per vertical transport system is likely to low. However, these numbers do give some insight into the operational expenses of the vertical transport, the current price of a barrel of oil is $ 47,89 [19]. If this type of fuel would be used for the vertical transport, this would equate to $ 3500. Any loss of energy is not taken into account in this calculation.
5
Operational expenses of horizontal
transport
The horizontal transport of the minerals consists of bringing the minerals from the PSV to the mainland. The scale of the horizontal transport depends on the production rate of the operation and the location of the mining site.One of the most important factors is whether or not the minerals are extracted from the silt at the PSV or if that is done at the main land [2]. This section will give some insight in how the cost of the horizontal transport is built up.5.1. Location
The location of the mining site is an influence on the transport cost. Since the energy consumption of the transport increases when the distance increases, the cost increases as well. The location of the mining site is one of the components that is of influence on the cost of horizontal transport. The further a supply ship has to travel the higher the cost.
The main criterion of the horizontal transport is that the PSV is visited often enough so that the produc-tion can run continuously. The frequency of the visits depends on the producproduc-tion rate of the PSV and its storage capacity. A higher production rate leads to a higher frequency of visits. Something similar applies to the storage capacity, a lower storage capacity leads to a higher frequency of visits. While this may not be a problem for mining sites like Solwara 1, which is located relatively close to shore [14]. For mining operations in the middle of the ocean with distances over several thousand kilometers, the time it takes to reach the PSV is something to take into account. The design speed of a bulk carrier is approximately 14 knots [27] or 25.92 km/h. This means that a bulk carrier, disregarding the extra time it takes to accelerate and decelerate the ship, can travel approximately 620 km per day. This means that when the mining site is located at 2500 km from the port of choice, the transport vessel will have to sail four days to reach the PSV, and another four days to return to the port. This means that the round trip alone, will take eight days. The time it takes to load and unload the cargo and the materials needed to continue the operation at the PSV is not taken into account.
5.2. Choice of port
Given the travel speed of a bulk carrier, choosing the right port can be critical in reducing the time a round trip to the PSV takes. EMO, the largest bulk transshipment company in the port of Rotterdam, has a throughput capacity of sixty million tons [4]. In a news update dating from 2014 EMO states that it can unload a 375.000 tonnes of iron ore from the Vale China in approximately four days [3], this comes down to 93.750 tonnes of iron ore per day. If one assumes that the mining operation uses a Panamax size bulk carrier, 55.000 dwt -80.000 dwt [27], unloading would take a day, if the same unloading speed is attained, which seems unlikely due to time losses at the beginning and end of the unloading phase. If docking, undocking and loading the transport ship with new consumables for the PSV is taken into account, the process can easily take up a few days. This time is based on the assumptions that the transport vessel can be serviced immediately when arriving at the port. Choosing a port with a sufficient handling time can be critical in reducing the transport cost. A different port, or even a different transshipment company can influence the transport cost.
20 5. Operational expenses of horizontal transport
5.3. Transshipment of minerals
The transshipment of material between the PSV and the bulk carrier is done by pipe conveyor. The pipe conveyor is selected because it shields the minerals from the elements and is a flexible component [12]. The forces that act on the pipe conveyor can be calculated by:
F = Fm+ Fb (5.1)
In which F is the total force on the idlers, Fmis the force caused by the material and Fbis the force caused
by the belt. In order to come to an energy equation, [12] uses the following equations.
My= 2 Z c 0 Z a −b(y)x · σ(x, y)d xd y (5.2) F0= MyRl (5.3) Eh= n · F0· vb· 3600ηp (5.4)
In theses equations, Myis the torque of the conveyor idler [Nm], Rlis the idler radius [m],σ(x, y) is the
pressure distribution at the deformation area [Pa], c is the width of the idler contact area on the belt [m], a is the front edge line coordinate of the deformation area [m], -b(y) is the end edge line coordinate of the deformation area [m]. Ehis the horizontal pipe conveyor energy consumption [J/h], vbis the conveyor speed
[m/s], n is the number of idlers in the conveyor,ηpis the efficiency of the pipe conveyor. These equations can be used to quantify the amount of energy that a pipe conveyor, used to transship the minerals from the PSV to the bulk carrier, needs.
5.4. Production rate and storage capacity
As stated in Section 5.1 the production rate and storage capacity of the PSV has a direct influence on the amount of trips that have to be made. Shutting down the PSV because it has reached its maximum storage capacity, seems inefficient. Therefore the choice of the size of the transport vessel depends on the production rate and the storage capacity. According to [18] a DSM operation would need a production of 2,4 mt/year to be commercially viable. This comes down to a production of 6.575 tonnes per day. If the Panamax size bulk carrier, mentioned in the previous Section is used, a round trip cannot take longer than twelve days. This would mean that the PSV should have a storage capacity of at least 80.000 dwt.
5.5. Fuel consumption of the transport vessels
The operating cost of the horizontal transport is strongly connected to the fuel consumption of the transport vessels. The fuel consumption depends on several factors, the size of the transport vessel, the speed of the vessel and the number of vessels among others. All these factors can be influenced in order to lower the fuel consumption. Of course, the fuel consumption of the support vessels is not the only component that determines the cost of the horizontal transport.
The main objective of the horizontal transport is to make sure that the DSM operation can keep working continuously. The horizontal transport has to make sure that the PSV is visited frequently enough so that the PSV will not run out of storage space. That means that the production rate along with the storage space on the PSV determine the frequency of the visits of support vessels.
According to [1] the operating cost of a 110 000 dwt bulk carrier, in 1985, were made up of the components listed in Table 5.1.
5.6. Crew wages and benefits 21
Component %
Crew wages and benefits 16,5 Victualling and stores 2,7 Maintenance and repair 7,8
Insurance 4,6
Administration and sundries 2,4 Port and canal dues 10,0
Fuel costs 53,5
Commissions 2,5
Total 100
Table 5.1: Insight into operating cost [1]
Although this data is over thirty years old, it provides some insight into the contribution of fuel cost on the total operating cost. The fuel cost of a ship, according to [1], comes down to:
F uel cost = (MEconsump t i onx M Epr i ce + ASconsumpt i onx AFpr i ce) x DS + APconsumpt i onx AFpr i cex DP (5.5) In Equation 5.5 MEconsumptionis the main engine fuel consumption, MEpriceis the price of the main
en-gine fuel, ASconsumptionis the auxiliary fuel consumption at sea, DS is the number of days at sea, APconsumption
is the auxiliary fuel consumption in port and DP is the number of days in port.
The fuel price for both the main engine fuel and the auxiliary fuel can fluctuate, and the number of days at sea and in port can change as well. The consumption of both the main engine fuel and the auxiliary fuel is dependent on many factors. Among others, these can be the route, the ocean current and the weather. However, these are factors that the mining company does not have influence over. The factor that can be influenced is the way that the support vessel operates, an empirical relationship between the speed of the vessel and the fuel consumption of the engine. The empirical relationship states that the third power of the speed is a good approximation. This means that reducing the speed of the ship with 20%, reduces the fuel consumption with 50% [20].
All these factors combined lead to a complex consideration. As stated in Section 5.1 and Section 5.4, when one Panamax size bulk carrier is used, that sails at approximately 620 kilometer per day, based on the pro-duction of 6.575 tonnes per day, a round trip cannot last longer than twelve days. This means, assuming three days for unloading, loading, refueling and maintenance, that a PSV cannot be further removed from the port than 4,5 days sailing or 2790 kilometer. If the distance is smaller, the travelling speed can be lowered in order to save fuel. However, if the distance is larger, at least one of the factors need to be changed. The size of the transport vessel can be changed, this would lead to an increased storage capacity as well, the production can be lowered, or the number of ships can be changed.
Having only one bulk carrier to service the PSV is a dangerous undertaking. If the bulk carrier would need extensive repairs, it will be taken out of service. This leads to an increased time between visits, since the repair time needs to be added to the travel time. Depending on the distance that the bulk carrier has to travel between the PSV and the port that time may not be available. This means that, even though the travel time would be attainable for just one ship, the operation would need more than one bulk carrier. The number of visits to the PSV can be increased if the number of bulk carriers is increased. This means that the PSV could have a higher production rate and still be visited often enough.
5.6. Crew wages and benefits
The second biggest cost component according to [1] is the wages and benefits that are given to the crew. This comes down to 16,5% of the total operating cost. However, this data comes from 1985. At that time automa-tion and the digital revoluautoma-tion did not have the impact that it has today. This means that the size of the crew has diminished since 1985. Another source, [24], claims that the size of the crew in the early 1980’s would be around 28 for an ocean going vessel, whereas modern vessels can operate with a crew of only 17. It even states that tests are conducted in order to decrease the size of the crew even further to less than 10. However,
22 5. Operational expenses of horizontal transport
it also states the size of the crew is limited by the law of some countries.
According to [24] the crew cost for a five year old 160.000 DWT carrier is $544.000 per year or $45.344 per month. This only covers the direct wages and employment related cost for a crew of 20. A detailed explana-tion of the crew wages can be found in Table 5.2. Per year another $119.000 has to be added to cover travel cost, support, insurance and victualling. Furthermore, management cost that apply to the crew also needs to be incorporated. This leads to a total crew cost of $663.000 per year. Whereas a crew for a twenty year old ship of the same size would have a bigger crew and thus more crew cost. According to [24] this comes down to $57.362 per month or $688.000 per year for a crew of 28, the added wages and other crew cost are specified in Table 5.3 and Table 5.4. This Assuming that the additional cost increases linearly this leads to an additional cost $167.000, bringing the total crew cost to $855.000 per year.
5.7. Repairs and maintenance 23
Rank Note Basic Allowances Bonus Provident Total 2007 Total 1993 Increase %
Master India 1.967 3.933 300 35 6.235 3.644 171
Chief officer 1.294 3.206 200 35 4.735 3.025 157
Second officer 1.077 1.773 - 35 2.885 2.338 123
Third officer 1.030 1.320 - 35 2.385 1.650 145
Radio officer radio officer no longer required in 2007 1.650 0
Chief engineer 1.760 3.990 300 35 6.085 3.575 170
First assistant engineer second engineer 1.294 3.206 200 35 4.735 3.025 157
Second assistant engineer third engineer 1.077 1.773 - 35 2.885 2.338 123
Bosun Philippines 670 649 - 182 1.501 1.521 99
Five assistant bosuns 558 542 - 171 6.353 6.479 98
Three oilers 558 542 - 171 3.812 3.888 98
Cook/std chief cook 670 649 - 182 1.501 1.596 94
Std second cook 558 542 - 171 1.271 1.296 98
Messman 426 378 - 158 962 1.071 90
Total crew for a modern ship: 20 45.344 37.094 122
Table 5.2: Crew wages for a crew of 20 on a modern ship [24]
Rank Note Basic Allowances Bonus Provident Total 2007 Total 1993 Increase %
Third assistent engineer India 1.030 1.320 - 35 2.385 1.650 145
Electrician Electrical officer 1.077 1.832 - 35 2.935 2.338 126
Assistant bosun Philippines 558 542 - 171 1.271 1.296 98
Oiler 558 542 - 171 1.271 1.296 98
Total crew for a 10 year old ship: 24 53.205 43.673 122
Table 5.3: Crew wages for a crew of 24 on a 10 year old ship [24]
Rank Note Basic Allowances Bonus Provident Total 2007 Total 1993 Increase %
Two ordinary seaman Philippines 426 378 - 158 1.925 2.142 90
Oiler 558 542 - 171 1.271 1.071 119
Messman 426 378 - 158 962 1.071 90
Total crew for a 20 year old ship: 28 57.362 47.956 120
Table 5.4: Crew wages for a crew of 28 on a 20 year old ship [24]
The numbers that were mentioned in the previous Section are not set stone. A large part of the crew cost is determined by the nationality of the crew and the flag under which the ship is sailing. This means that a ship with a European crew, sailing under a French flag would have higher crew cost than an African or Asian crew sailing under the flag of Singapore. Another factor that influences crew cost is the exchange rates between currencies. This only applies when the revenue is made in a currency different from the one where the cost and wages are paid in. Al these factors lead to some interesting opportunities to keep the crew cost as low as possible.
5.7. Repairs and maintenance
To ensure that any ship keeps operating as smoothly as possible, repairs and maintenance are critical. This ensures that the ship is out of operation as little as possible. According to [24] the repair and maintenance cost is around 14% of the total operating cost. Which is significantly higher than the 7,8% that is given by [1]. However, in both cases it is a cost factor to take into consideration, and if the difference between the sources is an indication of a trend, the repair and maintenance costs are an even bigger factor in the future. [24] splits the repair and maintenance cost in three parts:
• Routine maintenance: Includes the maintenance of the hull and structure of the ship, but also the engines and auxiliary equipment. Routine maintenance has to cover everything that ensures a safe trip for the crew and ship. The routine maintenance cost tend to increase as the ship ages.
• Breakdowns: These are mechanical failures, outside of the routine maintenance, that lead to additional cost. Often this work is done by an external contractor which can lead to high costs. Due to the nature of the repair work the ship is often taken out of service. This increases the repair costs since it means that the ship cannot create any revenue.
24 5. Operational expenses of horizontal transport
• Spares: Replacement parts for any component that needs to be replaced. This can be due to routine maintenance or breakdowns. The cost of these components can be directly related to the cost of the repairs.
The total repair cost per year is estimated by [24] to be $164.000 for a five year old ship, whereas a twenty year old ship will have a far higher repair cost, up to $393.000. Another indication that the age of a ship has a huge impact on the operating cost of a ship.
6
Operational expenses of surface logistics
The logistics of DSM is everything that needs to be brought to and taken from the PSV in order to keep the operation going, for example, fuel, spare parts, and workers. In order to quantify the logistics, the service life of the components is evaluated. Since everything that is used needs to be transported from the mainland, evaluating service life gives an indication of the scale of the logistics. The consumables can be brought to the PSV in two ways. Either the bulk carriers, that relieve the PSV of its minerals, carry the consumables, or designated ships are purchased to supply the PSV with everything it needs.6.1. Fuel
The energy that is consumed, but cannot be generated on site with the help of renewable sources, has to be shipped in. This would be in the form of ship fuel and has to be brought in by the bulk carrier. The fuel that has to be brought in is fuel for the main engine and the auxiliary engines. This is most likely in the form of fuel oil and diesel oil [27].
However, it might be worth investigating how the demand for fuel can be lowered with the help of renew-able energy sources. A common option is to use wind energy at sea [17]. Although these parks are currently situated in relatively shallow waters, it might be an interesting option to generate power at the PSV location. Other types of renewable energy sources are solar power [6], ocean power [5] and ocean wave energy [25].
Using one or several ways to generate power at the PSV could reduce the demand for fossil fuels that have to be shipped in. It seems highly unlikely that every way of generating renewable energy is suited for a deep sea mining operation, but if the energy needs grow out of proportion it might be worth wile to investigate this option.
6.2. Key spare parts
The parts that are crucial for the operation to continue as smoothly as possible need to be kept in stock at the PSV. This can be a part that breaks regularly or a part that is hard to fabricate and has a long delivery time. The parts that are necessary for maintenance should be available. The life time expectancy of every part should be kept in mind to keep the operation running continuously. When production is increased while still using the same equipment, the operation puts a higher demand on the equipment. This leads to breakdowns hap-pening more often and this should be taken into account when the amount of spare parts that need to be shipped in are ordered.
The tools that are used to maintain the DSM operation will break at regular intervals and stopping the mining operation because a power tool is not available or the right fastener has just run out, is not acceptable. Therefore, a sufficient supply should always be kept in stock on the PSV. This, along with everything else needs to be shipped in.
26 6. Operational expenses of surface logistics
6.3. Crew and various consumables
A new crew needs to be shipped in at regular intervals to replace the crew that ends their shift. This has to be done along with everything that the new crew consumes. Food and water being the most vital. However, food and water is not sufficient, since everything that the crew consumes during their shift needs to be brought in. From toilet paper to soap and from safety gear to medicines.
Everything that is hard to classify, or just too small to take into account from a transport point of view, should still be taken into consideration. However, due to the complexity of a DSM operation, it is impossible to account for everything that has to be brought in. Therefore an extra variable needs to be introduced which gives some room to the estimates. An illustration of how this could work is given in Figure 6.1
Figure 6.1: A list of items transported from the port to the PSV in a bulk carrier to conduct surface logistics
6.4. Waste
All the previous sections dealt with things that need to be brought to the PSV. Although this can be quite a col-lection of items and consumables, it seems unlikely that it will not fit on a 80.000 dwt bulk carrier. Assuming that the bulk has the same density as manganese, 7430 kg/m3[26], but assuming a bulk density of just over half that, the total cargo space would come down to at least 20.000 m3. This would seem large enough to ship in all the consumables, spare parts and the fuel for the engines. Also the weight of everything that needs to be shipped in will not be a problem. Since the manganese will have a higher density than most of the items that are shipped in. Thus, if the maximum volume is not exceeded, it is highly unlikely that the maximum weight is exceeded.
However, everything that is consumed and from which the waste cannot be processed at the PSV needs to be returned to the port. This could be anything from food containers and oil barrels to broken tools and equipment. Not to mention the crew that has been replaced. All these components need to be shipped to shore along with the minerals that have been mined. This means that the removal of waste reduces the maximum amount of manganese that can be shipped from the PSV back to the port. An illustration of this is given in Figure ??
Figure 6.2: A list of items transported from the PSV to the port in a bulk carrier to conduct surface logistics
It seems from this analysis that when looking at the logistics, the removal of various components from the PSV, will be more cumbersome than the delivery of the same components. This means that when the bulk carriers will be used in as supply vessels, the design of those bulk carriers need to take into account the needs that arise due to the logistics of a DSM operation.
7
Capital expenditure of the transport of
minerals
In order to conduct a deep sea mining operation, several investments have to be made. The components all have to be developed and produced which is a highly technical challenge. This, together with the scale of the operation makes it hard to come up with estimates on the purchase price of the components. However, there have been attempts to do just that. In this chapter, estimates on the capital expenditures of the DSM operation are discussed. These are based on [21], and [23], [22] and [13].7.1. The capital expenditure of vertical transport
The vertical transport of a DSM operation consists of several components. These are, starting at the collecting vehicle, the flexible hose, a buffer station, the rigid pipes and the pumps. This assumes that a pipe lifting system, PLS, is used. Which, as stated in Chapter 4, is necessary when the mining depth exceeds 1000 m [13], since a continuous line bucket, CLB, has a limited depth at which it can operate. This is due to increasing forces on the winch.
When the operation is conducted in shallow water, a continuous line bucket is a viable option. The CLB consists of several buckets, chains to connect them, a winch to power the system and a weight to keep the chains under tension. When a mining vehicle has to move over the ocean floor instead of the buckets dredging up mineral rich soil, a flexible hose and a transfer system between the hose and the buckets need to be added. [13] uses a similar equation to Equation 3.2 to come up with the capital expenditure of a CLB and a PLS. They are given in Equation 7.1 and 7.2
Mp,t= Msv+ 5 · l2· rb· nc· ρb· Mm,c· (1 + ²1) (7.1)
Mp,t= Msv+ π · lp· (r12− r22) · np· ρp· Mm,p· (1 + ²2) (7.2)
In these Equations, Mp,tis the total capital expenditure of the transport system Msvis the purchase cost
of the support vessels, l and lpare the lengths of the chains and the pipe respectively, rbis the radius of the
bucket, ncis the number of buckets, Mm,cis the metal price of the metal used in the bucket and²1is the
bucket price factor to simplify the manufacturing fees. r1and r2are the external and internal radii of the
pipes, npis the number of pipes,ρp is the density of the metal used to manufacture the pipe and Mm,pis
the corresponding metal price.²2is the pipe manufacturing factor. Msvis the purchase price of the support
vessels.
Some assumptions on the scale of investments have also been made. [21] estimates the entire purchase cost for the vertical transport system are $50 million. In this estimation a PLS is assumed to be used and a mined amount of 2,76 million tonnes poly metallic nodules per year. This equates to 7900 tonnes per day, assuming 350 days of operation per year. When this is expressed in kg/s production rate would be 91,25 kg/s. This means that the estimates are the same order of magnitude as the case study by [28] and the number mentioned by [18].
28 7. Capital expenditure of the transport of minerals
7.2. Capital expenditure of the horizontal transport and logistics
As stated in Chapter 5 the horizontal transport will be conducted by one or several bulk carriers acting as shipping vessels. The number of bulk carriers depend on several factors, like distance, production rate, stor-age space and travel speed, among others. This means that the capital expenditure of the vertical transport is equal to the purchase price of the bulk carriers. The estimate that [22] and [23] comes up with is $ 495 million up to $ 600 million for three bulk carriers acting as supply vessels. However, in [23] and [22] an assumption of 1,5 million tonnes of nodules mined per year is made. This equates to 4300 tonnes per day or 49 kg/s. This is significantly lower than [28], [18] and [21], all these sources assume a production rate which is roughly twice as high as [23] and [22]. This means that, the capital expenditure of the horizontal transport might be signif-icantly higher as well. Although it should be noted that the production rate is only one of the components that determine the number of bulk carriers.
7.3. The CAPEX and OPEX of a DSM operation
[23], [22] and [21] all give an estimate on the capital expenditure and the operational expenses of the entire DSM operation. All though this is somewhat out of the scope of this literature research the data does give insight into to scale of the total investments that have to be made. Therefore they are included here.
According to [23] and [22] the total capital expenditure for a 20 year during DSM operation comes down to $ 1,9 billion and operational expenses of $ 10,0 billion. This is specified in Table 7.1. As stated in the previous section, it should be noted that [23] and [22] expect a production rate of 1,5 million tonnes per year, which is lower than other sources expect.
Item CAPEX OPEX (for 20 years) Total
Mining system $ 550 million $ 2 billion $ 2,55 billion Ore transfer $ 600 million $ 3 billion $ 3,6 billion Processing plant $ 750 million $ 5 billion $ 5,75 billion Total $ 1,9 billion $ 10 billion $ 11,9 billion
Table 7.1: CAPEX and OPEX as given by [23] and [22]
[21] also gives an estimate for the capital expenditure of a deep sea mining operation. The horizontal transport and the material needed for logistics is not taken into account here. The values are given in Table 7.2
Item CAPEX Total
Year 1 2 3 4 5 6 7 8 9 10
Vessel $ 450 million 0 0 0 0 0 0 0 0 0 $ 450 million
Vertical transport $ 50 million 0 0 0 0 0 0 0 0 0 $ 50 million
Buffer $ 25 million 0 0 0 0 0 0 0 0 0 $25 million
Mining vehicle $ 50 million 0 0 0 0 0 0 0 0 0 $ 50 million Power generator $ 50 million 0 0 0 0 0 0 0 0 0 $ 50 million Controls $ 25 million $ 25 million 0 0 0 0 0 0 0 0 $ 50 million Other $ 10 million $ 25 million $ 15 million 0 0 0 0 0 0 0 $ 50 million
Vessel $ 450 million 0 0 0 0 0 0 0 0 0 $450 million
Total $ 660 million $ 50 million $ 15 million 0 0 0 0 0 0 0 $ 725 million
Table 7.2: CAPEX of a DSM operation as given by [21]
The values of [21] and [23] and [22] are somewhat different, whereas [21] comes to a total CAPEX of $ 725 million, [23] and [22] come to a total CAPEX of $ 1,9 billion. This difference can be attributed to the fact that [23] and [22] take the entire system into account, including the horizontal transport, whereas [21] only looks at the PSV and all its components. Excluding then the ore transfer from [23] and [22], the total CAPEX comes down to $ 1,3 billion instead of $ 725 million, which is almost half the total capital expenditure. The different data can be due to different mining operations having different needs and different corresponding costs. However, the huge different in estimates, can also indicate the complexity of estimating the entire capital expenditure of a deep sea mining operation.
8
The total transport cost
In the previous chapters the transport cost, that surround a deep sea mining operation, were explained. It started with a simple Equation 3.1, which was expanded to Equation 3.2. In the next chapters, the compo-nents of Equation 3.2 were examined even further, starting at the bottom of the ocean. The first step in the transport process is the vertical transport from the ocean floor to the surface. Next step is the transshipment between the PSV and the bulk carriers and the horizontal transport that is conducted by the same bulk carri-ers. The last part of the transport consists of the logistics that support the operation. Finally some light was shed on the capital expenditures that are needed to run a deep sea mining operation. This chapter will give an explanation on how these factors are related to one another.8.1. A general equation
If one takes a look at Equation 3.2, it can be seen that the equation consists of 6 components. The components are the CAPEX and OPEX of the vertical transport, the CAPEX and OPEX of the horizontal transport and the CAPEX and the OPEX of the logistics.
Tr anspor t cost = C APE Xver t i c al+ OPE Xver t i c al +C APE Xhor i zont al+ OPE Xhor i zont al +C APE XSur f acel og i st i c s+ OPE XSur f acel og i st i c s
(3.2 revisited)
Although Equation 3.2 gives insight into how the transport cost can be calculated, it does not show any de-pendencies between the components. This means that the equation does not give a detailed enough picture to zoom in on the transport cost.
Tr anspor t cost = fC APE Xver t i c al(h,Qs) + fOPE Xver t i c al(h,Qs)
+ fC APE Xhor i zont al(d , v,Qs) + fOPE Xhor i zont al(d , v,Qs)
+ fC APE XSur f acel og i st i c s(Qs, Ef) + fOPE XSur f acel og i st i c s(Qs, Ef)
(8.1)
In this Equation, h is the vertical transport distance [m], Qsis the production rate [kg/s], d is the distance
that the vertical transport needs to sail in order to reach the PSV [m] and Efis the energy in the form of fuel
that has to be brought from the mainland to the PSV [J].
8.2. Limitations
However, this still does not capture the complexity to its full extend. For example, if the production rate Qs
increases all the components of Equation 8.1 change, in fact all the components increase. But the conse-quences of this increase are complex. The number of bulk carriers that are used might increase, this leads to an increase in CAPEXhorizontalbut also to an increase in OPEXhorizontal, since the size of the crew increases the
wages will increase as well and since the number of bulk carriers increases the fuel cost will increase as well. This does not mean that the increase is linear, far from it. As stated by [1], the speed of a ship is related to the fuel consumption of the ship. The empirical relation states that the fuel consumption is related to the third power of the speed such that if the speed is reduced with 20%, the fuel consumption is reduced with almost
30 8. The total transport cost
50%. Meaning that if the deep sea mining operation uses two ships that can sail at 80% of their design speed, it consumes only a fraction more than one ship sailing at full speed, all the while increasing the transport capacity of the horizontal transport. Other cost, like wages, will develop linearly. Two ships means two crews to man those ships, which lead to double the wages. However, not all crew cost has to develop linearly, as it seems inefficient to increase the overhead cost at the same pace as the crew wages.
When taking on a deep sea mining project, these factors need to be taken into account. When the desired production rate is specified consequences arise for the transport, the energy consumption and the overall scale of the project. When the location of the project is known, the port, that is best suited, needs to be identified and the distance that has to be traversed has consequences for the transport, like the number of ships, the size of the ships and the speed of the ships. All and all, there is no one formula that captures the complexity of an entire deep sea mining operation. To find the optimal solution for such a problem, a list of conditions and demands needs to be drafted and several simulation need to be run. This way not only the cheapest, but also the most reliable, way to design the transport of minerals can be found.
