Low temperature heat recovery methods in power generation

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Waste heat capture driving a secondary turbine.
Quoting only repeated graphs of Web.
350 megawatt turbine, Steam temperature +550* Celius- 175 bar. Rising from + 100* Celius 1 bar.
CO2 is 10,000 bar. Rising from +32* Celius 74 bar.
The great thing about CO2 is that it produces it own cooling upon release. This quality of Co2 is now being exploited as refrigerant R744.

Therefore at the point of liquid exit a cool gas can enter to fill the vaccum left by the liquid cast out. By turbine rotation that cool gas can be brought into contact with a heat source causing gas expansion which in itself provides a drive force. The hot gas by turbine rotation is brought down to the point where the liquid cooling tank ajoins. Gas being gas always seeks to rise in a liquid. So at this point the hot gas exits the vane and cool liquid fills the vane. The hot gas having travelled through the cool liquid arrives in cool state at the top of the cooling tank. This cool gas then replaces the cool liquid being flung out. The process repeats.

akpowerThe designers take utmost care for heat recovery from fuels while designing power plant equipments as well as preservation of it for maximum utilization .With advent of better heat insulation materials,better heat transfer materials in heat exchangers,precious little heat is wasted outside thermal cycle. However any heat having temperature more than atmospheric temperature is a loss. What are methods available to recover this low temp.heat in a Thermal Power Plant?

Consider 10,000 m3 of water 1 cm above ground level and 10 m3 of water 10 m above ground level. Both have the same potential energy. However, the second law of thermodynamics shows that the energy recovery from the 10 m high source will be higher than the one from the lower level. This is because of the former having a higher availability. Likewise, recovering heat from a thermal source near ambient will be less efficient. It is currently not worth the cost of recovery.

Hello Bioramani
Please consider this to drive a 350 megawatt steam turbine one needs a steam force of 175 bar which must be at heat of +550* Celisus. That means another +550* Celisus is going up the stack as the steam will only absorb half the available heat. Notably cooling of steam requires its temperature to be reduced to +100* to return to liquid. Co2 is liquid at +32* Celisus an 74 bar and gas of 10,000 bar force at +100* Celsius, therefor 9926 bar or roughly 110,000 megawatts extra to the already 350 meagwatts. As only +225*C can be obsorbed out the stack +550*C that is a tottal is extra ouput of a little over an extra 220,00 megawatts. This being based upon the Toshiba turbine/generator Tarong Qld. Co2 phase graphs are web available. To exploit this phenomomin one needs utilise a DaS valve and a hydro turbine to cope with Supercritical Co2 behaving as liquid though being a gas. Peter

The OP refers to existing thermal plants in India (presumably).

Hello Bioramani

The OP is direct data from Tarong Power Station Qld Australia. 240 tonne Coal per hour creating +550*C steam temperature -175 bar to a Toshiba Tururbine/generator. Peter

Mr. Bioramani has rightly pointed out. My query was about recovery of heat with low temperature but above atmospheric temp. Economics of method will depend upon quantity of heat being lost / recovered. It may be heat exchanger, secondary fluid , but mostly static in nature.

Co2 also known as refrigerant R744 expands to cold gas "Eintein" all fidges. That known as the restrictor blocking the high energy flow is replaced by turbine giving same effect. The gathering of heat source is constant 6 foot below ground level. Pitch or Bitumen best heat sink, and steel wool best in heat collector. The efficiency of no cost adds another dimension.

akpowerMr. Bioramani has rightly pointed out. My query was about recovery of heat with low temperature but above atmospheric temp. Economics of method will depend upon quantity of heat being lost / recovered. It may be heat exchanger, secondary fluid , but mostly static in nature.

This report may trigger some ideas:
#-Link-Snipped-#

Hello Bioramani,

Thank you for the most interesting link. I fully agree there is scope for improvement in Coal fed power stations. However our work is not with Coal but Green Fuels as such provides the neccessary heat when other drive lquid/gas is employed as opposed to water/ steam. One of the improvements when using Co2 as the driver is that internal boiler heating can be achieved by having flame within the liquid itself, by use of screw compresser. The ignition gasses having a higher pressure need to return to liquid allows them to be tapped of at cooling.

DaS EnergyHello Bioramani,

Thank you for the most interesting link. I fully agree there is scope for improvement in Coal fed power stations. However our work is not with Coal but Green Fuels as such provides the neccessary heat when other drive lquid/gas is employed as opposed to water/ steam. One of the improvements when using Co2 as the driver is that internal boiler heating can be achieved by having flame within the liquid itself, by use of screw compresser. The ignition gasses having a higher pressure need to return to liquid allows them to be tapped of at cooling.

Thanks for the info on supercritical CO[SUB]2[/SUB]. My only involvement with this was for extracting spice oleoresins from raw tropical spices. Live and learn.

Hello Bioramani,

Thank you for your comment, though your sounds the more exciting feild.

One other interesting thing with Co2 is that when contained in a cylinder with bottom heat above +33* Celius the Co2 at the top of the cylinder turns into Dry-Ice -40* Celsius. Cook the meat at the bottom and freeze the beer at the top, a most eccentic gas.