CO 2 Capture and Usage: Harnessing the CO 2 Content in Natural Gas for Environmental and Economic Gains

Abstract

power generation, as capable of contributing up to 19% in CO2 reductions (IEA 2008, page 69). These are not withstanding the assessment performed by IEA (2012) with respect to “high potential CO2 emissions” found with global “carbon reserves,” and thereby outlining the deployment of CCS as the major technology required for sustaining the projected demand on fossils. “The assessment has attributed almost 63% to coal, 22% to oil and 15% to gas in CO2 emissions potential locked in these reserves.” The case of CO2 in natural gas represents a typical scenario for a number of oil and gas companies faced with the enormous challenge of reduced energy level of sales gas making it subquality or when disposal by flaring increases the source of CO2 emissions to the atmosphere. However, the amount of natural gas flared globally has been shown to contribute approximately 1.2% of the global CO2 emissions, which is given to be more than one-half of the certified emissions reductions under the Kyoto Protocol (ICF International 2006). There are several technologies and techniques now available for separation of CO2 (or acid gases) from gas mixture, either as flue gas from power plants or from natural gas. In addition to deployment of these technologies, the captured or separated CO2 must be disposed of in such a manner as to prevent it from seeping back into the atmosphere. This is required to achieve the aims of the CDM from the use of fossil fuels. Among the fossil fuels, natural gas has been shown to contain the least amount of CO2 emitted per tonnage of fuel burnt as compared with coal and oil. In addition to the CO2 emitted during combustion, natural gas on production also contains a certain amount of impurities, including CO2 gas. The maximum level of CO2 permitted in natural-gas fuel is typically less than 3%. Hence, all natural gas is treated to remove the solids and free liquids and to reduce water-vapor content to acceptable levels and, especially, to meet pipeline specifications. Hence, natural gas must be purified through the removal of CO2 and other acid gases and impurities (where present) because these impurities can form acids in the presence of water to corrode pipelines and other equipment. In addition, higher concentrations of CO2 in natural gas reduce the heating value or energy level, which is below pipeline specifications, necessitating its removal before distribution to the end consumer. Natural gas has been a main source in meeting the world’s energy demand, contributing an estimated 23.81% in 2010 to the world energy supply mix (Rufford et al. 2012, page 123). This contribution is projected to increase because natural gas is considered the cleaner fossil fuel compared with coal and oil. The deployment of appropriate CO2-capture technology in processing natural gas stands to improve its value as the cleaner fossil fuel. In this paper, a brief review of related acid-gas separation processes will be reviewed and recommendations will be presented. Economic opportunities by use of the captured CO2 for additional revenue generation through EOR by CO2 flooding, as well as appropriate transportation and storage infrastructure, will be reviewed.