Solvent analysis instrumentation options for the control and flexible operation of post combustion carbon dioxide capture plants
Buschle, William David
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Dispatchable low carbon electricity has been identified as a key requirement for low carbon electricity systems because these systems must provide reliable electricity services to an increasing portion of the world’s population while utilising an increasing share of nondispatchable assets such as renewable and nuclear generators. Fossil fuel generators can provide dispatchable low carbon electricity by leveraging post-combustion carbon capture technologies assuming post-combustion capture (PCC) plants can operate in a flexible and efficient manner. This thesis explores the connection between solvent analysis techniques and the optimal operation of PCC plants with a particular focus on process optimisation and control under flexible and transient conditions. The connection between solvent analysis measurements and PCC plant process control and optimisation strategies is established. An ideal set of analysis technique criteria is established for flexible post-combustion capture plants. Currently available solvent analysis techniques are surveyed and evaluated against the ideal set of criteria. Specific weaknesses of current techniques are highlighted and two novel solvent analysis techniques are introduced to address these weaknesses. The first provides continuous amine concentration and CO2 loading measurements at process flow conditions by inferring solvent chemical composition from physical properties. This method was evaluated by deploying an instrument prototype to a post-combustion pilot plant to continuously analyse solvent during a test campaign which simulated flexible plant operation. The measurement results were compared against industry standard solvent analysis techniques and the inferential technique was found to produce sufficient measurement accuracy and sensitivity while providing a faster, lower cost and more robust measurement technique. The second technique combines the strengths of several currently available CO2 loading techniques to measure CO2 gas evolved from an acidified solvent under vacuum conditions. The technique was found to provide superior measurement accuracy and sensitivity compared to currently available methods when measuring lab standard solutions. The integration of these novel analysis techniques into advanced process control systems is proposed and future method improvements are suggested.