(153b) Emerging Technology in Clean Energy.

Carbon Dioxide (CO₂) emission has raised major environmental concerns in the last 20 years and scientists are trying to find alternative green energy sources which can replace the pollution-causing fuels being used at present. In addition, efforts channeled towards mitigating the amount of CO₂ present in the atmosphere have resulted in a technology which is deemed essential to make the transition to clean energy and it is called Carbon capture and storage (CCS). In combination with CCS, fossil fuel usage has the potential to fuel industrial growth while simultaneously mitigating CO₂ emissions. To capture CO₂, various chemicals like amine-based solvents are used. Currently, only monoethanolamine (MEA) has been adopted in commercialized process for carbon capture from flue gas stacks in several post-combustion plants. This process has one significant drawback. The MEA must be regularly refilled and re-packed to make up due to losses in the process. Solvent degradation and high volatility are the reasons which cause these losses. Being a corrosive solvent, the recovery of MEA which takes place after capturing the CO₂ necessitates a high amount of energy.

These drawbacks of MEA based CO₂ capture from the fossil fuel fired fuel gas stack can be rectified by the application of Industrial hydroxides like sodium Hydroxide, Ammonium Hydroxide etc. As per the extent research, the absorption capacity of CO₂ in a NaOH solution is greater when compared to that of MEA. One research has shown that the theoretical amount of MEA and NaOH to capture a ton of CO₂ is 1.39 and 0.9 tons, respectively. Furthermore, NaOH and other hydroxides are available in replete amounts and at an affordable rate as compared to MEA. However, when compared to MEA, NaOH cannot readily be reconverted or regenerated back to its original form post-capture of CO₂. This is primarily due to the byproduct of the reaction between CO₂ and NaOH, which is NaHCO₃, a compound that shows good solubility in aqueous medium. At a temperature of 333K, it decomposes into Na₂CO₃, H₂O and CO₂. Na₂CO₃ is thermally very stable and starts decomposing (to give Na₂O) at temperatures close to 1100K. NaOH’s direct source is Na₂O, however, this apparent drawback of NaOH serves our purpose well.

Our purpose is to use the NaOH directly for flooding and oil recovery in depleted reservoirs post capture of CO2, removing any need for NaOH recovery. NaOH is often used as an alkali in Alkali-surfactant-polymer (ASP) flooding to produce a conducive environment for micelle formation. With injection of CO₂ laden NaOH, not only can the CO₂ be sequestered downhole much easily but the presence of CO₂ in form of bubbles can help in the production of extra oil due to alteration of the oil miscibility. NaOH can be further substituted with other hydroxides as permitted by the oilfield conditions and parameters to not only enhance CO₂ capture but also improve oil recovery from depleted oil fields.