Tarong Power stealing water from Wivenhoe Dam

[Darren E]

stevem,
I'm no expert, but I think it might have to do with the build-up of contaminants in the water, and their detrimental effect in the boilers (scaling, etc).
In the cooling towers, large volumes of "pure" water are evaporated, increasing the concentration of Ca, Na, etc. in the remaining water.
This is not to say that a purifying process such as RO (reverse osmosis) could not be used.

[stevem]

Thanks Darren, the boiler used at work used town water as its source and required regular maintence and repairs on pipes and the like due to corrosion and build up of deposits.

Still it may be a good option for using recycled sewage as an alternative source with the methods used that you suggested.

[Darren E]

stevem,
Recycled sewerage effluent is so pure that I still think it's best use is for domestic drinking water, not industrial. However, due to the social/political hurdle of the public conception of drinking "poo" I concede that industrial use is a good start.

But our power stations could do a lot better than their current performance with respect to water. The steam cycle requires that the process water is cooled after it emerges from the turbines. This is done by evaporative cooling - allowing massive quantities of water to evaporate in cooling towers.

However, they could take a separate stream of impure water (grey water, stormwater, seawater) and use it to cool the process water in a series of heat exchangers. This would immediately reduce or eliminate the need for evaporative cooling.

Then, the impure water stream, which has been heated with "free" waste energy, could be very cheaply purified, using either flash distillation (if it's hot enough) or RO (which becomes more efficient as temperature increases).

So there is a two-fold gain. Reduced consumption of water in the power station, and cheap water purification powered by free waste energy.
This technology exists today. They do it in Dubai. If our state government invested some money researching and implementing this technology, we really could lay claim to being the "smart state".

[stevem]

Darren the jury is still out in my book for using sewage as drinking water, however you never cease to amaze me with that practical and innovative solution. The technical details are way above my head but you deserve a gold medal for your last post.

[Darren E]

I haven't been able to find much technical info about the Dubai process.
There is this link to the Jebel Ali Power and Desalination Station.

http://www.lahmeyer.de/e/units/ge/ps_ge4_e_230300_jebel_ali_2004_03.pdf

1400 MW power, and 140 MIGD water desalination.
(140 MIGD = 636 ML/day = 232 GL/year - over 3 times the predicted yield from Traveston Dam).

[Rev Watt]

Luv it
Lets do it, as power is one thing we already suffer from not enuf of.
It also saves the Mary!
Darren maybe you should use your engineering talents more than wixing up merds!
_________________
Everyone who drinks this water will be thirsty again, but whoever drinks the water I give him will never thirst. John 4:13f

[Darren E]

Thanks stevem and Rev Watt.

Something I meant to add earlier (but had lost the piece of paper I wrote it down on):

Tarong power station consumes 28.2 GL of water per year (i.e. nearly half the yield expected from Traveston Dam). [Based on 2003/2004 data from Tarong Energy website].
It's power capacity is 1400 MW, i.e. the same as the Dubai power station referenced above.
Tarong produces roughly 1/4 of Queensland's electricity, so the total water consumption associated with electricity generation must be in excess of 100 GL/year. That's a lot of water!
If you look at the cost:yield equation for the proposed dam (>$2B for 70 GL/year) that should mean a lot of money to throw at improving the water efficiency at coal fired power stations.

[stevem]

Fact sheet from Tarong Energy