Pre-combustion demonstration

Pre-combustion capture at HRL’s research gasifier, Mulgrave

The key objective is to reduce the technical risk and cost of pre-combustion capture projects for Victorian coal-fired stations with new coal burning technologies (IGCC, IDGCC).

The trials are to evaluate the technologies to identify the most cost-effective for application to HRL’s IDGCC power-generation technology. In this process the fuel, brown coal, is not burnt, but is dried and reacted at high pressure and temperature to form a synthesis gas. The carbon dioxide is captured, and the syngas is combusted to produce power. This project will also allow CO2CRC to leverage the existing research base of its capture activities in Victoria. Again, The University of Melbourne is responsible for developing solvent and membrane technologies while Monash University performs R&D on adsorbents.

In more detail, the program will:

• Identify and quantify the impact of realistic pre-combustion gas contaminants (H2S, CH4, CO) and water on each of the separation technologies’ performance,
• Identify and quantify the impact of pre-combustion gas temperature and concentration variations on the performance of the separation media and separation processes.
• Optimise process operating parameters
• Develop engineering solutions at a scale at which confidence can be established for full scale plant design and assessment.
• Assess the pre-combustion capture process and energy integration options
• Review the technical and economic viability of the commercial use of pre-combustion capture for new Victorian brown-coal power stations.

The technology found in the preliminary trials to be most cost-effective could then be subjected to further trials, including trials at plants which include extra steps to maximise the carbon dioxide capture. These steps involve further reacting the syngas with water to produce hydrogen and carbon dioxide. The carbon dioxide is captured and the hydrogen can be used in a gas turbine or a fuel cell to produce power.

Background for capture projects

Brown coal is the cheapest source of fossil fuel for power generation in Australia, but it produces the highest level of greenhouse gases when burned in conventional boilers in power plants. To ensure their viability in the longer term in the world, where greenhouse gas driven climate change is an accepted fact, we should be looking at ways of

Making coal burning more efficient 

It can be accomplished in many different ways, such as overall energy integration in the power plant and/or adopting new technologies. Coal gasification is one of the best methods of efficient burning at high pressure and temperature. Advanced technologies such as Integrated Gasification Combined Cycle (IGCC) and Integrated Drying Gasification Combined Cycle (IDGCC) will enable higher thermal efficiencies - up to 50% in the future. However, in the current carbon-constrained world, the viability of coal-fired plants can only be ensured if efficiency measures will be accompanied by the following activity.

Sequestration of the waste carbon dioxide

It involves capturing carbon dioxide from flue gases and then to compress and inject underground. Carbon dioxide can be captured from flue gases either after (post-) or before (pre-) combustion in a power station using a range of capture technologies as explained below. Pre-combustion capture is more suitable for plants having new coal burning technologies (IGCC, IDGCC).

1. Solvent absorption – when flue gas is passed through, liquid chemicals can absorb carbon dioxide and can then release it at elevated temperature in another vessel. So the same chemical can be used over and over again to perform the separation of carbon dioxide.
2. Adsorbents are solids that have the capacity to capture carbon dioxide on their surface, which can be reused in a cyclical process
3. Membranes like filters to separate one gas from another in a mixture. Membrane gas absorption (MGA) is a hybrid of membrane and solvent separation that seeks to exploit the advantages of both processes

Ultimately, the technical and economic viability of the commercial use of capture technologies for existing and new Victorian brown coal power stations will be reviewed and reported based on the R&D programs outlined below.