As a result of proposed new climate change legislation requiring carbon capture and sequestration (CCS) of atmospheric carbon dioxide (CO2) emissions, there has been increased interest in the development of carbon capture technology worldwide. CCS aims to reduce CO2 emissions to the atmosphere by capturing it from the emissions of large producers and storing it underground. One often overlooked component of the CCS process is the transmission of captured CO2 to sequestration sites. This anthropogenic, or man-made, CO2 presents unique challenges to transportation because of the inclusion of impurities in gas. Pure CO2 pipelines for Enhanced Oil Recovery (EOR) have a long history of operation in North America, but this technology must be adapted to anthropogenic CO2 uses. Other technologies can be adapted from the oil and gas industry. There are still challenges to be addressed, however, before anthropogenic CO2 pipeline technology can be considered mature. The aim of this project is to pinpoint areas of CO2 pipeline technology that still require development and provide a research roadmap to guide the development of anthropogenic CO2 technology to maturity.
The most significant challenges stem from the uncertainty about the properties of CO2 with impurities. Experimental evidence shows that even small amounts of certain impurities can appreciably change the properties of the CO2. Unfortunately, there is little experimental data about the properties of anthropogenic CO2. More experimental programs are necessary to characterize how impurities affect properties such as the density, viscosity, water solubility, speed of sound, and phase behavior. Engineers need useful data about these properties to perform design calculations and to operate the pipeline. This data can be used in thermodynamic and hydraulic relations to calculate fluid properties and predict behavior.
Similarly, Equations of State (EOS) must be developed to aid in understanding the behavior of anthropogenic CO2 at different conditions. Despite a recent surge of interest in the development of EOS models, current EOS is inadequate for modeling the characteristics of anthropogenic CO2 near the operating conditions. Due to the lack of operational experience for anthropogenic CO2 pipelines, it is important for engineers to have accurate models to understand the behavior of the fluid. The lack of an industry CO2 quality standard confounds the understanding the behavior of anthropogenic CO2. Each pipeline operator must develop independent quality specifications and base design calculations off of these compositional ranges. A universal standard would be useful to pipeline operators by standardizing the equipment, encouraging the creation of pipeline networks, and providing continuity in operating conditions and procedures between pipelines.
Many of the key equipment technologies can be adapted directly from natural gas or pure CO2 pipeline stations. CO2 booster pump stations have been operating for over forty years in North America. Major equipment such as pumps and valves has already been adapted for anthropogenic CO2 by forward-looking players in the industry. Many of the remaining challenges stem from the properties of CO2 and the effects of impurities present in anthropogenic CO2 streams. For example, the primary difficulty with metering technology is to determine the complex composition of the anthropogenic CO2 stream and calculate the flow properties. Information about other technologies such as hot welding procedures or pump station acoustics is proprietary and must be made part of the public domain. Still other equipment challenges are difficulties with current CO2 pipelines that do not have satisfactory solutions. These include corrosion prevention and fracture prevention.
Although CO2 pipelines have been in operation for over forty years in North America, most of the operational expertise developed during this time is proprietary. Because of the lack of operational experience in the public domain, procedures must be redeveloped and validated using flow loops and pipeline scale tests. Engineers need data about the effects of transients, intermittent operation, and emergency blow down on the pump station components. In addition, engineers must consider the effects of CO2 releases on the environment. Recent work has significantly advanced the understanding of CO2 release and dispersion modeling through small scale testing programs and analysis. More work is needed in the area of operations to ensure that anthropogenic CO2 pipelines are operated safely and efficiently.
Even with all the present challenges discussed, the state-of-the-art in anthropogenic CO2 pipelines and pump station components is rapidly advancing due to the surge of scientific interest in CCS.