Pilot Plant Experts

DME Clean Energy Pty. Ltd. (DMECE) intends to develop a new opportunity for the struggling Australian brown coal industry.  The company has asked Unitel to design an enhanced process for making DME from brown coal mined in the State of Victoria.  With a prevailing price of $7 per ton for brown coal, the underlying economics of this business are exceptionally attractive. 

To begin with, DMECE plans to build and operate a demonstration plant that will use Latrobe Valley brown coal to make one ton per day of DME.  The project will be implemented in collaboration with HRL Limited and the demo plant will be integrated downstream of HRL’s existing coal gasifier in Mulgrave.  Following the successful completion of its demo program, DMECE intends to build multiple 150 tons/day DME plants in the State of Victoria.  The first such unit will probably be located in Yallourn Valley. 

The process design proposed by Unitel is based upon the one-step method for the direct conversion of synthesis gas into DME, as distinguished from the conventional indirect approach that involves the dehydration of methanol.  The four key features that set Unitel’s design apart from other direct methods are:

Reactor design

To date, proponents of the direct process have used either a slurry or fixed bed reactor for the core synthesis step.  Studies at Unitel show that a fluidized bed is much better suited for the efficient production of DME than either the slurry or fixed bed reactors. 

The superior efficiency of the fluidized bed results from the elimination of diffusional limitations resulting in a yield-effectiveness factor close to one.  This is achieved because the equilibrium shifts to more favorable conditions as the product diffuses from the dense phase to the bubble phase. 

Catalyst 

After reviewing several formulations, Unitel has selected a highly robust catalyst that has been specially optimized for fluidized bed reactions. 

Liquid sorbent for separating carbon dioxide   

Our process uses a special liquid sorbent, wherein sequential pressure drops enable the separation of the various products in a carefully calibrated manner: 

• Carbon dioxide
• Purge stream containing hydrogen, carbon monoxide and methane
• DME, methanol and water

Methane reduction

Our process achieves methane reduction by diverting the purge stream into a) the gasifier as a direct secondary feed, or b) a catalytic auto-thermal reformer to convert the methane into hydrogen and carbon monoxide before re-injection into the gasifier. 

Engagement:  C, B, D, O.  Status – ongoing.