Technology | December 2011
Carbon capture and storage: Technology implementation and certification
The challenge in assessing new power stations to evaluate their fitness for use of carbon capture and storage lies in balancing the technical and economic needs of this technology for each individual power station process, say Hans Christian Schröder and Walter Pfundt.
The implementation and certification of technologies for capturing and storing carbon dioxide is presenting plant owners or operators and political bodies with special challenges in ensuring their technologically safe, cost-effective and legally-compliant implementation. Our experts provide impartial support for carbon capture and storage (CCS) projects and assistance in the form of integrated system analysis, during which experts evaluate power stations for their possibility of integrating a suitable technology and for fitness for its use.
While solutions for cost-efficient implementation are being developed, the legal framework must be defined at the same time. These demands must be seen against the backdrop that the EU has agreed to cut its greenhouse gas emissions by at least 20 per cent by 2020 and even by 80 per cent by 2050, compared to its 1990 levels. The Intergovernmental Panel on Climate Change (IPPC), for example, recommends limiting global warming to a maximum of two degrees Celsius above pre-industrial levels to avoid devastating environmental impact. To reach this goal, third-party expert opinions, integrated risk assessment and safety strategies are becoming more vital. Technical mediators can assist in the implementation of legal requirements by providing third-party services.
Capture and storage methods
At present, there are three preferred approached to carbon capture and storage under development. These techniques capture carbon dioxide immediately before, during or after combustion. In addition to the three techniques, other alternatives are being researched. However, pre-combustion, oxy-fuel and post-combustion CCS are, at present, the techniques of choice and are expected to be available in the market in the next few years.
The maturity and feasibility of required technologies and the available storage capacities are two major factors to consider when assessing the chances of using CCS to keep greenhouse gas CO2 out of the atmosphere. According to initial, relatively rough estimates by experts, the global storage capacities currently range from 100,000 and 200,000 billion tonnes of CO2. If a reliable forecast of the potential for mitigating climate change is to be made, however, storage capacities need to be calculated more accurately.
The potential risks of integrating the technology into power station processes do not differ fundamentally from those in other industrial-scale plants and are considered manageable. Within the scope of CCS, the transport and storage of CO2 and the safety of geological reservoirs are the focus of interest. One of the major risks in CCS, and one that cannot be excluded, is the risk of leakage, i.e., the risk of CO2 escaping from storage sites with adverse effects on the direct environment (personal injuries, damage to property) and the climate. Another conceivable risk involves geochemical processes, e.g., the dissolution of carbonate overburdened by the carbon dioxide-water mixture, which forms carbonic acid. These geochemical processes involve the risk of leakage and present a risk for the stability of the storage site. Decisions on whether a specific site is suitable for CO2 storage should depend on the type of storage and be based on a case-by-case risk assessment.
Carbon capture and storage installations have a major impact on the operating strategy and costs of power generation. Therefore, to ensure the cost-effective generation of electricity, these technologies must be integrated seamlessly into the processes of a power station and the potential for optimising operating processes fully exploited. Depending on the type of technology used, it may cause a loss in efficiency and higher investment costs - disadvantages that must be compensated for as efficiently as possible. The new generation of coal-fired power stations represent one possibility. By increasing operating pressures and temperatures and applying new material concepts, the efficiency of a power plant can be improved to roughly offset the loss in efficiency caused by its use.
The cost of retrofitting an existing 800 MW power station with post-combustion CCS adds up to between 300 and 400 million Euros, i.e., almost half of the investment costs spent on the power station itself. These costs include:
For efficient energy generation, process and operations engineering must be tailored to the specific technical processes and the subsequent operation of the respective plant. An integrated approach also embraces maintenance and inspection programmes. These programmes must first be examined for their informative value and to ensure that they satisfy the integrated requirements of the complex system of a power station. Subsequently, plausibility and stresses occurring during operations are assessed. This customised approach ensures both safe and cost-effective operation.
- Flue gas desulphurisation
- Flue gas cooling
- Absorber (CO2 scrubbing)
- Heat exchanger
- Desorber (CO2 scrubbing)
- CO2 compressor (for transport)
Determination of total cost
Operating costs are a critical criterion to decide for or against a form of technology when planning a retrofit or new installation of such systems. These include all future expenses for operation, servicing and maintenance and the degree of plant availability. Also included are costs for the CO2 transport system and storage site. In this context, maintaining financial reserves for unexpected events during CO2 transport or storage is sensible.
An integrated cost-effectiveness analysis which considers the technological and geological parameters, the legal and corporate framework conditions and the total cost of ownership (TCO) is crucial to ensure its cost-effective integration in the long term. Examples include warranty costs and the subsequent cost of service contracts. Reliable determination of these costs and their optimisation is crucial for successful financial planning - from plant design, construction, installation and commissioning to actual operation.
Practical experience proves that the numerous interfaces between complex systems and component solutions frequently cause problems that may impact significantly on later operating philosophy and even the quality of the systems. To ensure the best possible operating philosophy and plant quality, support by an experienced partner is needed from design and construction to final approval before the system is taken into operation.
Third-party organisations assist in the systematic prevention of interface problems. Economic, technical, geological and legal risks must be assessed and controlled from the outset and problems solved in a way that leads to the desired results. Our experts provide integrated system analysis and support plant owners or operators in its implementation.
'Fit for carbon capture' certificate
New power stations must be assessed for the possibility of integrating a suitable technology and for their fitness for use of CCS. In this light, the key challenge is balancing the technical and economic needs of this technology for each individual power station process. As no generally valid definitions and criteria have been established so far, we have developed our own standard, which forms the basis of the 'Fit for Carbon Capture' certificate awarded by our power station specialists. The certification procedure builds on the documentation of technical facts and measures and offers improved planning certainty, higher investment security and wider public acceptance of plant-construction projects.
Prior to certification power plants must undergo an integrated analysis and audit, which involves the necessary technical documentation, including the process technology documentation of the power plant and possible CCS technologies and necessary liquefaction plant as well as the available approval document of the power plant. Furthermore, an assessment of the plant's prior documentation and analysis in relation to the individual CCS process technology is carried out.
After this has been done, experts coordinate all results with the plant owner or operator and evaluate the system-specific requirements as part of the retrofit measure for future operation of the power plant. Upon completion, the application documents are processed and submitted to the approval authority that evaluates them. Upon approval, the 'Fit for carbon capture' certificate can be issued.
The authors are Head of Power Plant and Energy Services and Technical Installations, Construction Supervision, TÜV SÜD Industrie Service GmbH. Views are personal.