9.5 RESEARCH

9.5 RESEARCH

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RESEARCH


Pilot-Scale Oxy-Fuel Combustion of Victorian Brown Coal Update
By Dr Lian Zhang, ARC Future Fellow, Department of Chemical Engineering, Monash University

Oxy-fuel combustion is a process of burning coal in the mixture of high purity oxygen and recirculated flue gas (RFG) to deliver a CO2-rich gas stream that is ready for direct storage/sequestration. It has the potential to be more cost-effective than existing subcritical brown coal-fired boilers coupled with CO2 capture by amine solvents.

In Australia, commissioning trials of a pilot-scale 30MW black coal oxy-fuel boiler are under way at the Callide A power station in central Queensland. In the USA, the FutureGen 2.0 project is committed to commencing a 200MW full-scale oxy-fuel plant during 2014-18.

On 9 December, 2013 the UK government announced approval of a Front End Engineering Design (FEED) contract project for the deployment of oxy-fuel combustion technology with a gross output of 426 MW. Ninety per cent of all CO
2 produced is to be captured and transported by pipeline for permanent storage deep beneath the floor of the North Sea.

Through these demonstration and industrial scale projects, oxy-fuel combustion technology is aiming for international commercialisation by 2020.

Monash University has been a leader of research in the oxy-fuel combustion of Victorian brown coal since 2007. Our current project, funded by ANLEC R&D and BCIA, targeted the total system check, lab-scale result verification and process integration via the combustion of Victorian brown coal, either fully dried or wet, in a 3MWth pilot-scale facility during 2011-13.

The project involves collaboration with a Chinese boiler manufacturer (Shanghai Boiler Works Co Ltd), three local power generators (EnergyAustralia and GDF SUEZ Australian Energy (Hazelwood and Loy Yang B)), and two international research institutes (Chubu University, Japan and Shanghai Jiao Tong University, China).

From the two-year pilot-scale experiments, we have successfully confirmed the following advantages of oxy-fuel combustion technology for Victorian brown coal:


  • A stable combustion of both dried and wet (~40wt% moisture) coals in 27-30 per cent O2 balanced by recirculated flue gas, as demonstrated in Figure 1.
  • A purity of no less than 80 per cent vol for CO2 to be achieved with approximately five per cent air leakage in the pilot-scale boiler, see Figure 2. Through the CO2 Processing Unit (CPU) installed downstream on an oxy-firing boiler, the CO2 concentration prior to storage could be improved to 95-99 per cent. The reduction of flue gas amount by 30 per cent in furnace was also confirmed.
  • The extremely low concentrations for corrosive SO3 and NOx in flue gas, requiring less/no further purification when compared with black coal oxy-firing plant.
  • Demonstration of a smooth change-over (less than 30 minutes) between air versus oxy-firing modes.

Figure 1. Wet brown coal combustion in air versus oxy-firing

Figure 2. Brown coal oxy-firing flue gas composition, vol%

Apart from these successful experimental investigations, detailed process flowsheeting was also conducted to assess the net efficiencies for the integration of oxy-firing technology with coal drying and super-critical steam conditions.

The oxy-firing plant for Victorian brown coal could deliver a net efficiency of approximately 28 per cent (LHV based) with CPU inclusive, which is comparable and even slightly better than the existing Victorian power plants (see Figure 3).


Figure 3. Net Efficiency LHV based for oxy-firing of brown coal in 600MWth supercritical steam boiler integrated with internal/external dryer


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