Transportation systems for CO2––application to carbon capture and storage

Transportation systems for CO2––application to carbon capture and storage

Energy Conversion and Management 45 (2004) 2343–2353 www.elsevier.com/locate/enconman Transportation systems for CO2––application to carbon capture a...

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Energy Conversion and Management 45 (2004) 2343–2353 www.elsevier.com/locate/enconman

Transportation systems for CO2––application to carbon capture and storage Rickard Svensson a, Mikael Odenberger a, Filip Johnsson a

a,*

, Lars Str€ omberg

b

Department of Energy Conversion, School of Mechanical Engineering, Chalmers University of Technology, SE-412 96 Goteborg, Sweden b Vattenfall AB, SE-162 87 Stockholm, Sweden Received 27 August 2003; accepted 23 November 2003 Available online 24 January 2004

Abstract Commercialization of carbon capture and storage from fossil fuelled power plants requires an infrastructure for transportation of the captured carbon dioxide (CO2 ) from the sources of emission to the storage sites. This paper identifies and analyses different transportation scenarios with respect to costs, capacity, distance, means of transportation and type of storage. The scenario analysis shows that feasible transportation alternatives are pipelines (on and off shore), water carriers (off shore) and combinations of these. Transportation scenarios are given for different transportation capacities ranging from a demonstration plant with an assumed capacity of 200 MWe (1Mt/y of CO2 ) up to a system of several large 1000 MWe power plants in a coordinated network (40 Mt/y up to 300 Mt/y of CO2 ). The transportation costs for the demonstration plant scenario range from 1 to 6€/ton of CO2 depending on storage type and means of transportation. The corresponding figure for the coordinated network scenario with off shore storage is around 2€/ton of CO2 . Ó 2003 Elsevier Ltd. All rights reserved. Keywords: CO2 capture and storage; Transportation; Carbon systems

1. Introduction Both on a European and a global scale, there are large reserves of fossil fuels, e.g. the coal reserves are estimated to last several hundred years at the current production rate. Carbon capture and storage (CCS), i.e. capture and storage of carbon dioxide (CO2 ) emitted from large point *

Corresponding author. Tel.: +46-31-772-1449; fax: +46-31-772-3592. E-mail address: fi[email protected] (F. Johnsson).

0196-8904/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2003.11.022

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sources of emissions, has the potential of a significant and relatively quick response to the anticipated climate change at reasonable cost [1]. Successful commercialization of CCS could, therefore, serve as a bridge to a future during which generation from non-fossil energy sources can grow over time. In order for CCS to reach widespread commercialization, it is crucial to establish large scale demonstration projects, reduce capture costs, build infrastructures for transportation of the captured CO2 , establish an appropriate legal framework and reach acceptance by the public. Most research on CCS deals with capture technologies and storage possibilities (e.g. in connection to enhanced oil recovery (EOR) projects and in saline aquifers). Although capture represents the highest cost and storage is critical with respect to security and long time monitoring, still, there is a need to identify and structure transportation alternatives in order to analyse and evaluate future paths comprising CCS. Previous works on transportation of CO2 have investigated the costs and capacities for pipelines [2–6], but these investigations have not studied different transportation scenarios in order to evaluate paths for development of CCS systems. Other work has investigated the technological aspects for CO2 transportation by pipeline and by specially developed tank vessels at sea [7,8]. The risk and security issues related to pipeline transmission have also been investigated [9,10]. The aim of the present work is to identify and estimate costs for different transportation scenarios assuming that the CCS technology will develop from a demonstration plant with a size of 200 MWe to a cluster of several large 1000 MWe power plants. Details on the present investigation are given elsewhere [11].

2. Method The present work consists of a module based cost and capacity analysis, which gives the capacity and overall transportation cost per ton of CO2 for various distances for each means of transportation investigated. The work is based on technological, economical and logistic data from both the CO2 transportation industry and the liquefied petroleum gas (LPG) industry. A module in the system represents a specific means of transportation, e.g. pipeline or water carriers, for which the cost for utilization is calculated. The module costs were compiled for various combinations fulfilling the requirements of three different transportation scenarios (S1, S2 and S3), with respect to the amount to be transported, transportation distance and type of storage, i.e. on and off shore. The different combinations in the scenarios comprise an assumed development of the CCS technology from a European perspective, ranging from a demonstration plant to various options of large scale introduction of CCS. With respect to logistics, the scenarios have been established considering the requirements of handling CO2 , such as the need for intermediate storage. Thus, the scenarios correspond to a small scale ‘‘start up’’ case of 1 Mt/y of CO2 (S1), a large scale single source case of 10 Mt/y of CO2 (S2) and an evaluation of a fully developed and coordinated infrastructure with a capacity ranging from 40 to 300 Mt/y of CO2 (S3). Fig. 1 gives a schematic illustration of the three scenarios, and Table 1 lists the different scenarios with respect to combinations of transportation modules, transportation distance and capacity. It should be stated that the focus of the study is overall system solutions, rather than exact evaluation of technical details. It is difficult to perform more extensive and accurate cost estimations than performed in this work due to the fact that the alternatives investigated do not have

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S1. Small-scale start-up

Offshore disposal site

Onshore disposal site S2. Large -scale single-source

Offshore disposal site

Onshore S3. Coordinated network disposal site

Offshore disposal site

Fig. 1. Investigated scenarios.

Table 1 Module combinations evaluated in the different scenarios Amount [Mt/y of CO2 ]

Scenario

Module combinations

Distance [km]

S1-1

Pipeline on shore

110

1.0

S1-2

Railway Intermediate storage Water carrier

100

1.0

Pipeline on shore Intermediate storage Water carriers

100

S1-4

Pipeline on shore Pipeline off shore

100 500

1.0

S2-1

Pipeline on shore

110

10.0

S2-2

Pipeline on shore Intermediate storage Water carriers

100

10.0

S2-3

Pipeline on shore Pipeline off shore

100 500

10.0

S3-1

Pipeline network on shore Pipeline network off shore

230 550

40.0

S3-2

Pipeline network on shore Intermediate storage Water carriers

230

40.0

S1-3

500 1.0

500

500

500

any exact correspondence with existing logistics when it comes to volume and handling. Thus, economy of scale, limitations in the design of new systems and the lack of existing CCS systems make it difficult to perform exact cost calculations. The calculations are restricted to include only

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transportation costs, i.e. the costs included are for transportation, reloading and intermediate storage, whereas costs for bringing CO2 to conditions (pressure and temperature) suitable for transportation and storage are not included.

3. Transportation systems After the CO2 has been captured at the source of emission, the CO2 would have to be transported to the storage site. Such transportation will require a large scale infrastructure due to the large volumes to be handled. The transportation volumes of this work range from 1 to 2 Mt/y of CO2 , up to 300 Mt/y of CO2 as discussed above. 3.1. Existing CO2 transportation systems Several million tons of CO2 are transported annually, mainly in the USA, over long distances on shore in high pressure pipelines for use in the EOR industry [9]. Using CO2 in EOR projects has the advantage of adding a value to the CO2 , e.g. oil producers in the USA are willing to pay between 9 and 18US$/ton of ‘‘end of pipe’’ delivered CO2 [2]. Pipelines for off shore transportation of CO2 have not been applied yet but are technologically feasible [6], and a CO2 pipeline infrastructure off shore is investigated in the CO2 for EOR in the North Sea (CENS) project [5]. Other means of transportation that can be used are motor carriers, railway and water carriers. Experiences from these means of transportation are mainly found in the food and brewery industry, and the amounts transported are in the range of some 100,000 tons of CO2 annually, i.e. much smaller than the amounts associated with CCS. The transportation conditions for CO2 have many similarities to those for LPG [12], which is transported by water carriers, railway and motor carriers at a relatively large scale. Hence, experiences from the LPG industry could also be used in the establishment of a large scale CO2 transportation infrastructure. Thus, a great deal of the input data in the present work is based on LPG applications. For maximum throughput and to facilitate efficient loading and unloading, the physical condition with respect to pressure and temperature for the CO2 should be the liquid or supercritical/ dense phase. However, pipelines suffer from pressure drops along the transportation route, which can result in two phase flows and operational and material problems (e.g. cavitation) in components such as booster stations and pumps [13]. Hence, when utilizing pipelines, a stable condition is preferable, namely the supercritical/dense phase. This condition occurs at temperatures higher than )60 °C and pressures above the critical pressure of 7.38 MPa, giving a good margin for avoiding two phase flows. For the other means of transportation, i.e. motor carriers, railway and water carriers, which have constant pressure, liquid conditions are suitable. The density for CO2 approaches 1000 kg/m3 as liquid, as well as in the supercritical/dense phase. 3.2. Intermediate storage A pipeline has the advantage of providing steady state flow, i.e. a continuous flow from the emission source to the final storage site. The other means of transportation must include

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appropriate intermediate storage facilities to handle the reloading of CO2 , e.g. at harbours. There are two main technologies for intermediate storage of LPG, either underground in great rock and salt caverns or in large steel tanks above ground. At present, only the steel tank technology is used for CO2 , but both technologies can be applied. Existing rock caverns for LPG have storage capacities up to around 500,000 m3 LPG [14], which should approximately correspond to 500,000 tons of CO2 . Salt caverns have similar storage capacity of LPG, but are excluded in this work due to uncertainties with respect to the dissolution behaviour of CO2 . Steel tanks have storage capacities up to 3000 tons of CO2 [15]. Rock caverns within the LPG industry are constructed in two different ways, either as pressurised or as cooled caverns. If the caverns are intended for storage of CO2 , these techniques must be combined to create favourable conditions with respect to pressure and temperature for the CO2 . The cost for building a rock shelter depends mainly on the rock quality. Poor rock quality increases the need for lining and reinforcement of the rock, which increases costs [14]. 3.3. Safety and public acceptance CO2 is not toxic but can be fatal, due to asphyxiation, at concentrations exceeding around 10% by volume [10], levels that can be achieved at a discharge since CO2 is heavier than air and, hence, will tend to collect in depressions. Statistics from the EOR industry show that the risks for pipeline leakage are lower than for natural gas or hazardous pipelines [9], but to minimise risks, transportation of CO2 should be routed away from large centres of population. Another issue, which can indirectly affect the transportation, is the public opinion concerning storage of CO2 . On shore storage is believed to face difficulties with acceptance from the public, most likely as a Not In My Back Yard (NIMBY) problem, which means that even if the public (and perhaps thereby local authorities) might consider on shore disposal as legal and legitimate, they may still not want such facilities in their own neighbourhood. The concept of off shore disposal is considered to be safer, on the basis of leakage, than on shore and is, therefore, believed to be more easily implemented with the support of the public. However, on shore storage obviously enables storage near the emission source. As a comparison, off shore disposal requires a longer route and more complex and costly logistic infrastructure together with more expensive disposal facilities.

4. Transportation costs The capacity (Mt/y) and transportation cost (€/ton CO2 ) have been calculated for each means of transportation. Fig. 2 summarizes the results for the transportation alternatives included in this study, using a fictive transportation distance of 250 km and a depreciation time of 25 years at 5% interest rate [11]. The costs calculations in Fig. 2 do not include costs for intermediate storage. Such costs are exemplified in Table 2, which gives the costs for both steel tanks and rock caverns for two fictive cases (depreciation time 25 years at 5% interest rate) [11]. The evaluations of the scenarios are based on the results from the module based cost calculations and given as accumulated costs for each case investigated, with the combinations of means

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Fig. 2. Cost and capacity for transportation alternatives at 250 km.

Table 2 Compiled costs for intermediate storage

Steel tanks Rock cavern

Size [m3 ]

Investment cost [€]

Annual charge [€]

Throughput [Mt/y]

Specific cost [€/ton CO2 ]

3000 120,000

6,500,000 17,000,000

460,000 1,200,000

1.0 20.0

0.46 0.06

of transportation applied according to Table 1. Fig. 3 exemplifies the accumulated costs along the transported distance for the transportation combinations applied to Scenario 2, given as cost per ton of CO2 transported. Similar analyses have been performed for the other two scenarios, and the results are compiled in Fig. 4. Motor carriers are not included in the scenario analysis due to their high transportation costs and low capacity (see Fig. 2). It can be seen that the transportation costs for the demonstration plant scenario range from 1€/ton up to 18€/ton of CO2 depending on storage type and means of transportation, whereas the corresponding figure for the coordinated network scenario with off shore storage is around 2€/ton of CO2 .

5. Discussion Transportation of CO2 is technically possible by several means of transportation. However, when evaluating the economical figures, only three alternatives remain: pipelines (on and off shore) and water carriers (off shore) and combinations of these. 5.1. On shore Pipelines are the only remaining option for on shore transportation, due to the fact that railway and motor carriers are too expensive and lack capacity. To build CO2 pipelines on shore is, however, expensive, and the costs may also increase due to variations in local conditions, e.g. hilly terrain is estimated to result in 50% higher cost than for flat terrain, such as grassland [3,13].

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Fig. 3. Cumulated costs for Scenario 2––large scale single source.

Fig. 4. Specific cost comparisons from scenario analyses.

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Nevertheless, the experiences from CO2 pipeline transmission in the EOR industry shows that pipelines are cost-effective and reliable when large quantities of CO2 are to be transported, which is in line with the results from the costs analysis in this study. In summary, this makes pipeline the only alternative for on shore transportation. 5.2. Off shore Off shore, both water carriers and pipelines are competitive means of transportation and have, as can be seen in Fig. 2, a broad capacity spectrum. Nevertheless, these alternatives differ from each other, i.e. each alternative has its own most suitable use. Water carriers are more flexible than pipelines when it comes to adaptability of capacity and transportation route but have the disadvantage of requiring intermediate storage capacity and interfering with existing water carrier traffic at harbours [16]. Pipelines, on the other hand, have the advantage of being able to handle large quantities with less complex logistics due to the steady state flow, which also eliminates the need for intermediate storage. Pipelines do, however, require the development of new infrastructures, which means great capital investments. This highly affects the cost per ton of CO2 , especially for long distance small scale pipelines (see Fig. 4, bar S1-4). In summary, a future transportation system off shore should include both water carriers and pipelines, this to obtain flexibility and be able to handle large quantities of CO2 . 5.3. Scenarios The scenario analysis clearly shows that, as expected, on shore disposal near the location of the power station is preferable (see Fig. 4, bar S1-1 and S2-1). A short distance also enables transportation from small power stations (1 Mt/y of CO2 ) at a low specific cost. Relocation of fossil fuelled (especially lignite) power plants in order to achieve short transportation distance is, however, not likely. These power plants are situated near the fuel reserves and/or electricity consumers in order to minimise freight and transmission costs. In a future perspective, there will be three commodities to be considered, i.e. CO2 , electricity and fuel, and a CO2 infrastructure is both less expensive and less complex compared to the solid fuel and electricity transmission infrastructure because the CO2 can be transported at a steady state flow in a pipeline, whereas solid fuel transportation is mostly accomplished by railway and electricity transmission suffers from losses. From a European perspective, off shore disposal should be the first alternative in order to take advantage of early EOR opportunities and to reach acceptance by the public, the latter believed to be easier off shore. The ongoing CENS project has estimated the EOR capacities at the oil fields in the North Sea at 680 million tons of CO2 , and due to the fact that the fields have already reached a mature state, the injection of CO2 would have to start soon [5]. As can be seen in Fig. 4, the scaling effects are significant for CO2 transportation off shore (cf. bar S1-3 and S2-2, Fig. 4). Nevertheless, the total investment cost for a large scale test facility would be much larger than for a small scale project. Hence, the progress in a start up of CCS depends on whether investors find a large scale project interesting or not. For large power stations located far from disposal sites, a coordinated network is the only option left in order to create an economically defendable solution for transportation of CO2 .

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A single network is, however, believed to have an upper capacity limit, but not because of technical limitations. Considering that the fossil fuelled power industry within the European Union (EU) emits approximately 1 billion tons of CO2 annually [17], a realistic assumption may be to capture one third of this, i.e. about 300 million tons per year. Still, this amount of CO2 cannot be collected from a single source or local area but needs to be collected from power plants located all over the EU. Hence, a large network with this capacity leads to long transportation distances to the main trunk line, resulting in increased specific costs. Even if such a large scale network in a future perspective could be designed to be cost effective, there are other factors, mainly geological, that are to be considered, e.g. whether it is possible for a single disposal (e.g. the oilfields in the North Sea) to receive CO2 at this rate for a long period of time. It is, therefore, believed that a future large scale vision will consist of several transportation infrastructures, from suitable areas to contiguous disposal sites, with capacity and assembly similar to the two cases represented by Scenario 3 (see Fig. 4, bar S3-1 and S3-2). This also means that the transportation cost per ton of CO2 is expected to be the same as in Scenario 3. 5.4. Assumed vision for CCS A commercialization of CCS will mean that a transportation infrastructure must be developed and built over time. The marked bars numbered from 1 to 5 in Fig. 4, summarize how such a development, on the basis of the scenario investigation and the discussion above, may proceed. The progress of CCS starts with a small scale test facility with storage off shore and proceeds, via several large scale single sources with storage both on and off shore, to the establishment of several large scale networks. As can be seen, the costs for transportation will range from 1 to 6€/ton of CO2 and be around 2€/ton of CO2 for a large scale infrastructure with capacity from 40 Mt/y up to 300 Mt/y of CO2 . Before development of such an infrastructure can get started, there are many other issues beyond the scope of this work, which need to be investigated. A prerequisite is the establishment of appropriate legal frameworks for large scale CO2 transportation. In addition, a regulating framework for CO2 pipeline construction and safety must be established. In the long term vision for CCS, the infrastructure may consist of several coordinated networks with a total capacity of several hundred million tons of CO2 annually. Then, to be even more effective, these large scale networks can be linked together in a similar way as the pipeline grids for transportation of natural gas. This improves the flexibility of the networks and affects the economies of scale. Studies within the natural gas pipeline industry have also shown that there is much to gain by the establishment of trading markets for transportation capacities in pipelines [18], which, in the extension, lowers the costs and increases the capacity.

6. Conclusions At present, CO2 transportation is performed on and off shore by several means of transportation, motor carriers, railway, water carriers and pipelines, and all these alternatives can, in principle, be applied in a future large scale transportation system for CO2 , recovered from the fossil fuelled power industry. Nevertheless, considering the economical figures obtained in this

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work, three alternatives remain: water carriers (off shore), pipelines (on and off shore) and combinations of these. Off shore, the two means of transportation show similar cost per ton of CO2 transported, but each alternative has its own niche of application. This suggests that a combination of pipelines and water carriers is the most cost effective alternative for off shore transportation. The development of an infrastructure for CO2 transportation is expected to start with a small scale demonstration plant with a capacity of 200 MWe . On shore disposal near the point source location is, for such a test facility, the least expensive transportation alternative, with costs of about 1€/ton of CO2 . However, on shore storage may not be an option for a first demonstration project of this size, and if so, the present analysis shows that the transportation costs for off shore storage would be 6€/ton of CO2 when transported by water carriers. Further ahead, coordinated networks must be established in order to bring down the costs. For a large scale coordinated network, the transportation costs will be around 2€/ton. Hence, there is much to gain by establishing large scale systems. The latter figures should be compared with the economical target for cost effective methods for carbon avoidance of less than 20€/ton of CO2 as set by the European Climate Change Programme (ECCP) [19].

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