|POSTGRADUATE RESEARCH UPDATES|
|In this edition of Perspectives on Brown Coal, Bayzid Kabir Kazi, PhD student from Monash University provides an update on his PhD research, which forms part of a larger project in conjunction with Kyushu University.|
|Right: High pressure DME synthesis reactor and ancillaries |
|Synthesis of Liquid Fuel following Gasification of Victorian Brown Coal|
|By Kazi Bayzid Kabir, PhD Student, Energy, Fuels and Reaction Engineering Group, Department of Chemical Engineering, Monash University|
|Victorian brown coal continues to be important as the cheapest energy source for the Victorian economy. However, due to the high propensity towards spontaneous combustion after drying, dried brown coal cannot be readily exported, and is therefore used locally, mostly for power generation. Upgrading and refining Victorian brown coal to liquid fuels, which can be used locally or exported, is one way of utilising this vast resource. |
|When considering liquid fuels production through gasification, Fischer-Tropsch liquids, methanol and Dimethyl ether (DME) are the major candidates. Fischer-Tropsch processes are widely used but have low energy efficiency and produce more greenhouse gases than methanol or DME. |
My PhD project, supervised by Assoc Prof Sankar Bhattacharya at the Department of Chemical Engineering at Monash University, focuses on production of DME from Victorian brown coal through gasification without the use of Fischer-Tropsch. This would significantly reduce the production of greenhouses gasses compared to standard techniques.
DME is a non-toxic, non-carcinogenic and non-corrosive compound that has been used as an aerosol propellant, refrigerant and precursor to many important chemicals. DME has similar properties to LPG, and is being promoted in Asia as a ‘synthetic natural gas’ for domestic use. It can also be used as a diesel substitute and in gas turbines for power generation.
While DME can in principle be synthesised from coal-derived fuel gas (consisting of CO and H2 including others), the majority of plants worldwide use natural gas as feedstock. Experimental investigation of DME production using fuel gas from gasification of Victorian brown coal has not been attempted.
|The fuel gas from brown coal will contain several contaminants, such as hydrogen chloride (HCl), ammonia (NH3), hydrogen cyanide (HCN) and even hydrogen sulphide (H2S) at various levels. The effect of these contaminants on the performance of the catalysts, and on the yield and selectivity of the DME from synthesis of brown coal derived fuel gas is unknown.|
|For assessing the possibility of DME production from Victorian brown coal, the following questions need to be answered:|
- What is the appropriate brown coal gasification scheme for the DME production? Can we do catalytic gasification at lower temperature to improve process efficiency?
- Is there any gas cleaning requirement prior to DME production?
- What will be the DME production pathway? Will it be once-through or recycled system? Will it be a poly-generation system?
- Can we use commercially available catalysts for syngas to DME production? If not, what modifications are needed?
- What are the appropriate process parameters (eg. temperature, pressure) for optimum production of DME?
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