$90m to Help Burn More Brown Coal

From The Age.
The whole La Trobe valley is a tough area for policy makers. The funds mentioned above will go to a range of projects, broadly aimed at getting more money out of the brown coal in Victoria.
As we know by now, brown coal is not that terrific a fuel source over all. In decreasing purity, coal can be classified as metallurgical coal, which is used in making steel and is almost all exported; black coal, which is chemically similar to metallurgical coal, but with higher levels of silicates (which becomes ash) and maybe some sulphur and other contaminants. At the bottom is brown coal, which has blessedly low ash, but can contain up to 60% water. This is the problem with brown coal. The water is chemically bonded (ie the coal doesn’t feel wet) so is really hard to remove. What mostly happens is the water heats in the boiler and then goes up the flu as steam. So, for a tonne of coal, 600kg of water goes into the boiler as well, then the energy derived from the remaining 400kg of coal is divided between evaporating the water, and driving the powerplant. This energy loss significantly lowers the cycle efficiency of brown coal plants, both in terms of carbon efficiency and thermal efficiency. Consider these ballpark figures; carbon intensity for a good black coal plant is getting down to about 0.8 tonnes of CO2 emitted, per MWh of electricity produced. Henceforth this will just be known as t/MWh. A bad brown coal generator emits at closer to 1.4t/MWh, almost twice the emissions. Then on thermal cycle efficiency, a good black coal generator would approach 35% (comparison of coal energy in and electricity out) while an old brown coal would be closer to 25%. There are some design differences between the two plants, but that embodied water is the main drag on efficiency.

The water also makes brown coal surprisingly unstable. Underground it sits there happily because there’s no oxygen. But once it’s been dug up and put in a pile, it starts to oxidise and will combust if left long enough. This means first of all it’s almost impossible to export without processing, but also that the mines require incredible amounts of water to stop them catching on fire. Hazelwood’s energy use in the mine, most of which is used to pump water to suppress fires, was enough to put them in the top 300 energy using companies in Australia.
So that’s all the bad stuff about brown coal. The good stuff is that the resource in the La Trobe is quite possibly the cheapest fuel source in the world. While Qld black coal deposits might involve a 10m thick coal seam with 100m of overburden, Victorian mines I have visited have more like a 100m thick coal seam, with 10m of overburden. Analysts suggest the Hazelwood mine alone could meet Victoria’s energy needs for 300 years. The lure for policy makers is pretty obvious; dig up prosperity!

So, there will need to be some tough decisions made there soon. There are about 75,000 people in the La Trobe. There are also 4 MAJOR powerplants each with 400+ full time staff, plus the contracting specialists that move between plants. Beyond this there are other industries reliant on brown coal to some other degree; Energy Brix makes brown coal briquettes, used in bbqs, as a start-up fuel for the brown coal plants and to drive thermal processes in the dairy industry. There is a company there drying timber with brown coal. What is the role for government here then? Pretend nothing is wrong and try to buy a technological solution? Or make a conscious decision to change the status quo and start working towards it? It seems they’re taking the first option for the moment at least.


About evcricket

Extreme gardener, engineer and bird nerd. View all posts by evcricket

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