A demand for the reduction in GHG emissions from the worldwide community has seen the energy industry pressured to address its contribution to this dilemma. In recent decades there has been a push toward research into technologies that would provide energy at an affordable price while keeping with GHG emission standards, which are rising as fast technological developments will allow.
Solvent technologies are considered to be the first large scale CO2 capture technology to be employed in an attempt to curb CO2 emissions. However, the energy consumption of this process is still too high to be economically attractive to the industry. The method of pH Swing as proposed by Norsk Hydro, in theory, has the ability to cut this energy consumption considerably. This thesis has explored this possibility in an attempt to verify it.
The method of pH swing, as it relates to CO2 capture using solvent technologies, has been investigated resulting in an experimental procedure which simulates this process. The choice of reagents used in experimentation was based on previous work done on pH swing (Perumal 2005); taking these recommendations into consideration, MEA was used as a solvent and the pH agents to be used in testing were Suberic, Phthalic and Oxalic acids.
Running experimentation with varying pH parameters, it was possible to find trends that would be relevant to verifying this theory. It was noticed that with a greater swing in pH a larger quantity of CO2 was released; there was also a significant decrease in the evaporation of solvents during heating of the system. These were the first favorable signs in verifying the pH swing theory and were confirmed with energy analysis. A significant decrease in regeneration energy per unit CO2 was found due to pH swing; greater pH swing corresponded with greater energy savings.
Although the validity of the pH swing theory has been proven, much work is still required to verify if this process is sustainable in industry application. Further research will need to be conducted on the dynamics of the chemical reaction, crystallisation properties of the pH agents in MEA(aq), corrosion effects on the system and optimisation of parameters in maximising energy efficiency.
An interesting anomaly observed during the testing of pH swing was the immediate release of large amounts of CO2, initiated by the introduction of the pH agent to the CO2 rich solvent. Essentially CO2 was released without any addition of energy to the system; this effect seemed to escalate with the amount of acid added. Analysing this phenomenon was outside the scope of this thesis and was not considered in energy analysis. However, validating that CO2 is released, without solvent degradation, has the potential to make this already efficient process more appealing to the energy industry; such a possibility warrants further research.