It is required that the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage shall consist overwhelmingly of CO2Carbon dioxide. This is to ensure that the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage does not negatively affect the integrity of the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere site or transport facilities and to prevent any significant riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event to the environment or human health. The exact composition of the stream is highly dependent of the sourceAny process, activity or mechanism that releases a greenhouse gas, an aerosol, or a precursor thereof into the atmosphere and captureThe separation of carbon dioxide from other gases before it is emitted to the atmosphere processes used. The main issues associated with CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage composition are listed in Tab. 2-1.
Tab. 2-1: Main issues associated with selected incidental substances of a CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage (modified after DNV, 20102010 - DNVCO2QUALSTORE - Guideline for selection and qualification of sites and projects for geological storage of CO2see more). Component | Health & Safety | Pipeline capacity | Water solubility | Hydrate A solid compound containing water molecules combined in a definite ratio together with CO2, CH4 or similar gases as an integral part of the crystal formations | Materials | Fatigue | Fractures | Corrosion | Operations | Comment | CO2Carbon dioxide | X | X | X | X | X | X | X | X | X | Non-flammable, colourless, no odour; low toxicity,heavier than air in the gaseous state | H2O | | | | X | X | X | X | X | X | Non-toxic; condensable; forms acids with CO2Carbon dioxide, NOx and SOx, which have a corrosive impact on transport infrastructure | N2 | | X | X | | | | | | | Non-toxic; stable | O2 | | X | X | | | | | X | | Non-toxic | H2S | X | X | | | X | X | X | X | | Flammable, strong odour, extremely toxic at low concentrations | H2 | | X | X | | | | X | | | Flammable, non-condensable at pipeline operating condition; potential impact on transport infrastructure through embrittlement | SO2 | X | | X | | | | | X | | Non-flammable, strong odour, toxic; forms sulphuric acid with water | NO2 | X | | X | | | | | X | | Non-flammable, toxic; forms nitric acid with water | COCarbon monoxide | X | | X | | | | | | | Flammable, toxic | CH4 | | X | X | | | | | | X | Odourless, flammable | Amines | X | | | | | | | | | Potential occupational hazard, with corrosive impact | Glycol | X | | | | | | | X | | Potential occupational hazard | |
The three main transportation risks associated with impurities in the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage are: corrosion, gas hydrate A solid compound containing water molecules combined in a definite ratio together with CO2, CH4 or similar gases as an integral part of the crystal formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it, and pipeline flow characteristics. While some minor substances can be safely transported in pipelines, they might have a negative effect on their integrity.
Corrosion of pipelines may occur if there is too much water in the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage, since it may form acids that corrode the pipelines. The CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage composition could influence the choice of pipeline materials and thickness such as to ensure that safety requirements are met. Consideration of water concentration limits for pipeline corrosion is likely sufficient to address corrosion in other infrastructure components (pumps, valves, injectionThe process of using pressure to force fluids down wells tubing). CO2Carbon dioxide leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column through existing cracks could also lead to the acidification of water outside the pipe causing external corrosion. In addition to corrosion, water in a CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage can also increase the riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event for hydrate A solid compound containing water molecules combined in a definite ratio together with CO2, CH4 or similar gases as an integral part of the crystal formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it. Hydrates form at temperatures higher than the freezing point of water and its solid like property makes it a danger for pipelines (Carroll, 2003). Hydrates can form in liquids and gases, favourably in low temperatures and high pressure and are therefore mostly a concern for offshore operations. The main strategy for preventing hydrate A solid compound containing water molecules combined in a definite ratio together with CO2, CH4 or similar gases as an integral part of the crystal formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it is sufficient dewatering of the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage (DYNAMIS, 2007).
Oxygen in a CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage can also have corrosive effects in pipelines. In Enchanced Oil Recovery (EOREnhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means) another key riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event related to oxygen is that it reacts with oil and can cause overheating of injectionThe process of using pressure to force fluids down wells equipment (IEA GHGInternational Energy Agency – Greenhouse Gas R&D Programme, 2004; DYNAMIS, 2007). The DYNAMIS project report (2007) notes that it can be useful to place oxygen sensors in the injectionThe process of using pressure to force fluids down wells and production wells for EOREnhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means to ensure that these wells do not overheat. However, an early report in 1985 indicated that injectionThe process of using pressure to force fluids down wells of small amounts of O2 in EOREnhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means applications should not have significant impacts, and the main issue was corrosion (Taber, 1985). Taber (1985) also suggests that flue gas injectionThe process of using pressure to force fluids down wells with 1-2% oxygen and air injectionThe process of using pressure to force fluids down wells for in-situ combustion for EOREnhanced Oil Recovery: the recovery of oil additional to that produced naturally, achieved by fluid injection or other means takes place without serious corrosion problem, as long as there is sufficient dewatering. However, further research is necessary to assess the impact of O2 in CO2Carbon dioxide streams for storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere.
Long distance transportation of CO2Carbon dioxide is most efficient and economical in the liquid or supercritical(CO2) Conditions where carbon dioxide has some characteristics of a gas and some of a liquid states (DNV, 20102010 - DNVCO2QUALSTORE - Guideline for selection and qualification of sites and projects for geological storage of CO2see more). Getting to the supercritical(CO2) Conditions where carbon dioxide has some characteristics of a gas and some of a liquid fluid flow is made more difficult by the presence of non-condensable gases such as hydrogen (H2), argon (Ar), nitrogen (N2), oxygen (O2) and methane (CH4), as higher pressure is needed to convert CO2Carbon dioxide into the supercritical(CO2) Conditions where carbon dioxide has some characteristics of a gas and some of a liquid fluid (DYNAMIS, 2007). Models used need to predict the phase envelopes for the range of mixtures likely to be present. The cost of CO2Carbon dioxide purification is important for the total cost of CCSCarbon dioxide Capture and Storage as it affects many other parts such as transportation and storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere.
Acid gases can be transported safely in pipelines as long as the stream is sufficiently dehydrated, but interactions will occur with formation waterWater that occurs naturally within the pores of rock formations in the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere site. Of particular importance are the potential deterioration of wellboreThe physical hole that makes up the well, it can be cased, open, or a combination of both; open means open for fluid migration laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migration cement and other geochemical changes from acid interactions (chemical reactions and mineral dissolution and precipitation, along with related permeabilityAbility to flow or transmit fluids through a porous solid such as rock enhancements and clogging effects) with the fluids and rocks in the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it and heavy metal contamination of deep saline aquifers.
Some of the incidental substances found in the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage are toxic, such as COCarbon monoxide, NO2, SO2 and H2S, and may further influence the potential impacts of a pipeline leak or rupture (IPCCIntergovernmental Panel on Climate Change, 2005). Because low levels of H2S are tolerated by the human body quite wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids, H2S would mainly be a safety concern for the general public living along the pipeline route or workers who would be operating and maintaining the pipeline and pumping stations, where the concentrations of H2S from potential leakages could be higher.
When SO2 is inhaled it can cause immediate irritation in the throat and a sensation of tightness and difficulty in breathing. People with asthma are more sensitive to these health effects and could react to concentrations of SO2 below 1ppm (DYNAMIS, 2007). NO2 is a very toxic gas and exposure at low levels may result in unconsciousness or death. The SOx and NOx produced from air-combustion would be removed in post-combustion captureThe capture of carbon dioxide after combustion processes in order to achieve the longevity requirements of acid gasAny gas mixture that turns to an acid when dissolved in water (normally refers to H2S + CO2 from sour gas) removal and amineOrganic chemical compound containing one or more nitrogens in -NH2, -NH or -N groups solvents (Tzimas et al., 2007). If SOx and NOx are not removed from the CO2Carbon dioxide streams from oxyfuel combustion, oxy-fuel combustion will be the sourceAny process, activity or mechanism that releases a greenhouse gas, an aerosol, or a precursor thereof into the atmosphere of most of the SOx and NOx.
Amines used in post-combustion CO2Carbon dioxide captureThe separation of carbon dioxide from other gases before it is emitted to the atmosphere can be degraded to different harmful substances such as aldehydes, amides, nitrosamines, and nitramines, some of which have been found to be carcinogenic (Låg et al., 2009). Release of these substances to the air, drinking water or the aquatic ecosystems may need to be limited and several studies are underway to evaluate such effects (da Silva et al., 2013).
Small amounts of tracerA chemical compound or isotope added in small quantities to trace flow patterns substances can be added to the CO2 streamA flow of substances resulting from CO2 capture processes, or which consists of a sufficient fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long term geological storage for monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions and verifying the location and migrationThe movement of fluids in reservoir rocks of the CO2 plumeDispersing volume of CO2-rich phase contained in target formation. Although these substances are no serious health riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event in small amounts, the health impacts on operators should be considered (EPA, 2010).