ONSHORE AND OFFSHORE TRANSPORT PROCESS DESIGN FOR CARBON DIOXIDE SEQUESTRATION IN A MARINE GEOLOGICAL STRUCTURE

摘要

In response to climate change, the Kyoto Protocol, and the need to reduce greenhouse gas emissions, researchers are looking to marine geological storage of CO_2 as one of the most promising options. Marine geological storage of CO_2 involves the capture of CO_2 from major point sources (such as a power plant) and the transport of CO_2 to storage sites in marine geological structures such as a deep sea saline aquifer. Since 2005, we have developed relevant technologies for marine geological storage of CO_2. Those technologies include possible storage site surveys and basic designs for CO_2 transport and storage processes.To design a reliable CO_2 marine geological storage system, we devised a hypothetical scenario and used a numerical simulation tool to study its detailed processes. The process of transport CO_2 from the capture sites to the storage sites can be simulated with a thermodynamic equation of state. We compared and analyzed the relevant equation of state, including the Benedict-Webb-Rubin-Starling (BWRS), Peng-Robinson (PR), Peng-Robinson-Boston-Mathias (PRBM) and Soave-Redlich-Kwong (SRK) equations of state. To evaluate the predictive accuracy of the equation of state, we compare the results of numerical calculations with experimentalreference data. In a supercritical state (above 31.1°C and73.9bar), which corresponds to the thermodynamic conditions of CO_2 reservoir sites, the BWRS, PR, and PRBM equations of state showed a good predictive capability. On the other hand, the SRK equation of state showed a high error rate of 300% in the supercritical state. This paper analyzes the major design parameters that are useful for constructing onshore and offshore CO_2 transport systems. On the basis of a parametric study of the hypothetical scenario, we suggest relevant variation ranges for the design parameters, particularly the flow rate, diameter, temperature, and pressure. Using the hypothetical scenario, we also studied how the thermodynamic conditions of CO_2 affect on the fluid flow behavior and thermal characteristics of a pipeline transport system.In summary, this paper presents our analysis and deductions of the major design parameters that are useful for constructing onshore and offshore CO_2 transport systems.