BCIA’s annual program of postgraduate research scholarships is part of our commitment to strategic investment in skills development to secure the scientific, engineering and trades expertise required for the development of new low-emissions brown coal technologies.

To date, BCIA has awarded six research scholarships to PhD candidates at top-ranking Australian universities. In the last edition of Perspectives on Brown Coal, Adam Rady from Monash University provided an update on his project titled ‘Evaluation of Victorian Brown Coal as Fuel for Direct Carbon Fuel Cells (DCFC)’.

This month, Alicia Reynolds, a BCIA scholarship recipient from Monash University provides the following update on her project: 'Understanding the Effects of Post-Combustion CO2
Capture on the Environment'.

Understanding the Effects of Post-Combustion CO2 Capture on the Environment

By Alicia Reynolds, Monash University PhD Candidate and BCIA Research Scholar

Globally, brown coal-fired power stations are an important source of reliable, secure and affordable electricity. CO2 Capture and Storage (CCS) is one of the technologies that is currently being developed to reduce CO2 emissions and associated environmental consequences, while also maintaining energy security and reliability. Both the International Energy Agency and the Intergovernmental Panel on Climate Change have identified CCS as an important technology for reducing anthropogenic greenhouse gas emissions in the medium term. Research teams around the world are working together to maximise the efficiency, effectiveness and safety of the technologies available for capture, transport, utilisation and storage of CO2.

The most matured technology for separating CO2 from flue gases generated by coal-fired power station is Post-Combustion Capture (PCC) by chemical absorption in aqueous amines. This process was originally patented in the 1930s and is an established process for separating acid gases (including CO2) from natural gas. More recently, a number of pilot plants established around the world have demonstrated that chemical absorption with aqueous amines is suitable for separating CO2 from flue gas generated by coal-fired power stations. A significant advantage of this PCC technology is that it can be retrofitted to brown coal-fired power stations.

One major complication is that oxygen, SOx, NOx and residual fly ash present in coal-fired power station flue gases are capable of degrading aqueous amines solvents. Four main degradation pathways have been identified in laboratory experiments: reactions with SOx to form corrosive, heat-stable salts, oxidative degradation, carbamate polymerisation and thermal degradation. These reactions reduce the efficiency of the aqueous amine solvent and create a challenge for waste solvent treatment that needs to be effectively managed.

While many of the solvents currently used for PCC are also safely used as stabilisers in cosmetics, anti-corrosion agents in boiler water and for industrial gas treatment, it is important that any potential risks to the environment are identified and mitigated before PCC is widely deployed for capturing CO
2 from coal-fired power stations. To ensure that PCC is deployed safely, the following questions are being addressed by researchers worldwide:

  • What compounds are likely to be emitted to the atmosphere in the CO2 depleted flue gas? What treatment and monitoring techniques will be needed to ensure CO2 depleted flue gas is safe to emit to atmosphere?
  • How often will the aqueous amine solvent need to be regenerated or replaced? What opportunities exist to safely reuse or recycle spent solvent?
  • Is waste water produced during PCC harmful to the environment? How should the water be treated to ensure safe discharge to the environment?

My project aims to complete two important steps towards ensuring the environmental safety of PCC. Firstly, robust analytical methods for monitoring chemical reactions and products in amine solvents will be developed. The analysis of trace components is challenging because most samples contain water and higher levels of amines. Therefore, none of the established standard methods for water or soils are directly applicable. Developing, validating and publishing robust methods for trace level organics analysis will facilitate investigations into the degradation of different PCC systems world-wide.

Secondly, I will use these methods to characterise the changes in solvent and waste water samples from CSIRO’s pilot plant at Loy Yang power station in the Latrobe Valley. I will also seek to understand how the known degradation reaction pathways and rates in the pilot plant compare with laboratory experiments. In addition, I will investigate the possibility of catalytic degradation in the presence of brown coal fly ash and metal ions resulting from corrosion. I will also screen the samples for potentially toxic or environmentally sensitive compounds.

The close proximity of Loy Yang power station to our analytical laboratory at the Gippsland campus of Monash University mean that samples can be gathered, transported and analysed very quickly. This will minimise degradation or transformation of the sample prior to analysis. Working closely with CSIRO has enabled us to design a sampling plan for investigation of long-term degradation of solvent, accumulation of metals from corrosion and changes in the solvent during each CO
2 capture cycle.

The development of CCS is truly a global effort and communicating our findings with researchers worldwide is an important aspect of this project. One review paper has been published in
Environmental Science & Technology and a number of conference presentations are planned. The results of my PhD project will support efforts to develop improved solvent management practices to ensure that PCC of CO2 from coal-fired power stations is as safe and beneficial as possible.

BELOW: CSIRO Post-Combustion Capture plant on site at Loy Yang Power.

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