8.5 RESEARCH

8.5 RESEARCH

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RESEARCH


Oxy-fuel Fluidised Bed Combustion of Victorian Brown Coal
By Bithi Roy, PhD student, Energy, Fuels and Reaction Engineering Group, Department of Chemical Engineering, Monash University

The viability of Victorian brown coal as a future energy source will depend largely on the minimisation of its environmental impacts. This project investigates the applicability of a new technology using brown coal to produce electricity with fewer emissions, compared to conventional technologies.

In coal-fired power generation technologies, emission of CO2 is one of the major environmental challenges to be managed. Oxy-fuel based fluidised bed (Oxy-FB) combustion has emerged as a promising low-emissions technology due to its ability to produce concentrated capture-ready CO2 in flue gas.

Additional advantages of this technology include fuel flexibility, uniform temperature distribution, low NOx emissions, in-bed SO2 capture via sorbent addition and low air in-leakage. Oxy-FB technology in circulating fluidized bed (CFB) mode is currently being pioneered by Foster Wheeler at the 30MWth CIUDEN facility in Spain.

Despite the perceived advantages of Oxy-FB technology, nothing is known about its applicability for brown coal. My research project, supervised by A/Prof. Dr Sankar Bhattacharya, is an investigation of the suitability of Victorian brown coal for Oxy-FB combustion.
The broad aim of my project is to use a combined modelling and experimental approach to understand the combustion performance of Victorian brown coal under oxy-fuel fluidised bed conditions. The more specific aims of this project are:
  • To investigate fundamental combustion characteristics in a small laboratory scale reactor under well controlled operating conditions.
  • To design and construct a 10kWth (around 2kg/hr coal feed) multi-functional fluidized bed unit for operation in both oxy-fired and air-fired mode using a variety of coals (shown in Figure 1).
  • To conduct experiments on combustion characteristics of three Victorian brown coals to ascertain the combustion efficiency, conventional pollutant emissions (including N2O, SO3 and trace element emissions), sulphation characteristics, carbonation characteristics and agglomeration characteristics under Oxy-FB conditions.
  • To analyse the ash collected from different sections of the fluidised bed unit, using techniques such as Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Inductively Coupled Plasma – Atomic Emissions Spectrometry (ICP-AES) and Atomic Absorption Spectrometry (AAS).
  • To predict the compounds formed in both gas and solid phases using the thermodynamic equilibrium model FactSage.
  • To create a generic process model for Oxy-FB using the commercial engineering package Aspen Plus.

Figure 1: Fluidised bed rig

My project is progressing well and generating important new information on Oxy-FB combustion of Victorian brown coals. The major outcome at this stage is that the three tested brown coals combust very well under Oxy-FB conditions, with low emissions and no agglomeration. I have presented the results of my research at conferences and in peer-reviewed journals, with several new publications in progress.

Further research on Oxy-FB combustion at Monash University will extend the investigations to operation of the reactor in circulating mode and investigating the combustion performance and emissions of a range of coals, including other Australian brown and black coals. These will provide definitive guidance on the extent of gas clean-up required for CO2 capture, transportation and storage. We welcome industry involvement in our ongoing and future work.




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Bibliography:

  • Terry Wall and Sankar Bhattacharya, A scoping study on oxy-CFB technology, ANLECR&D report, 2012
  • Bithi Roy, Wei Lit Choo and Sankar Bhattacharya, Prediction of ash composition and agglomerating compounds formed during Oxy-CFB combustion of Victorian brown coals, CHEMECA Conference, Sydney, Australia, 2011.
  • Bithi Roy and Sankar Bhattacharya, Oxy-fuel combustion in a bench-scale fluidized bed using Victorian brown coal, The 38th International Technical Conference on Clean Coal & Fuel Systems, Clearwater, Florida, USA, 2013.
  • Bithi Roy, Wei Lit Choo and Sankar Bhattacharya, Prediction of distribution of trace elements under Oxy-fuel combustion condition using Victorian brown coals, Fuel 114 (2013) 135-142
  • Bithi Roy, Wei Lit Choo and Sankar Bhattacharya, Oxy-fuel fluidised bed combustion using Victorian brown coal: An experimental investigation, Fuel Processing Technology, In press, 2013




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