high temperature heat transfer fluid
high temperature heat transfer fluid
(OP)
I have a heat recovery application taking heat out of the exhaust of a turbine (930F) and using the heat in a Rankin cycle to generate power. I need a heat transfer media that can handle the high temperatures in the exhaust stream. My loop between the exhaust heat exchanger and the Rankin cycle equipment only needs 525F but I'm concerned about failsafe conditions and possibility the transfer media could approach the exhaust temp.
Does anyone know of a fluid the can operate up to 921F.
Does anyone know of a fluid the can operate up to 921F.





RE: high temperature heat transfer fluid
For higher temps you can consider molten salts
RE: high temperature heat transfer fluid
If this is the temperature needed from the heat recovery system then as mentioned above molten salt is the way to go.
We have large heat recovery systems using molten salt that operate in this temperature range that are used to preheat boiler feed water.
The critical temperature of Diphenyl based fluids is around 927F. This temperature is very critical because if these fluids are heated to this temperature in a closed vessel it will detonate.
We use Thermminol in the vapor state by using gas fired vaporizers that operate at 70 psig and 700F. There are some heat recovery systems that operate using these heating fluids.
RE: high temperature heat transfer fluid
Thanks for your response.
RE: high temperature heat transfer fluid
RE: high temperature heat transfer fluid
I worked on a project a number of years ago that used triethylene glycol in a HRSG on the exhaust of an LM6000 gas turbine. Worked fine. The system had a bypass stack so that the turbine could run independantly without heating up the coil too much. It wasn't unique in this regard, there are plenty of installations out there with bypass stacks. Lots of steam heat recovery boilers are out there with bypass stacks so that the gas turbine can be run without the steam system.
If you are really adverse to putting in a bypass stack, use steam and a once through style HRSG. Boil the HRSG dry when you don't need the waste heat. High water purity is key with this style boiler (probably cheaper to put the bypass stack than it is to do the water pruification).
Tim
RE: high temperature heat transfer fluid
The correct solution is as you indicated, a once thru HRSG. The max gas temp of 921 F implies the HRSG does not need to be incolnel , and a ferritic tubed OTSG will work OK, if the CTG is firing nat gas or LNG.
The water purifiers are likely not as costly as the bypass stack- these mini purifier skids are used in remote areas to supply the OTSG.
RE: high temperature heat transfer fluid
If so, it could be an elegant, compact solution. My concern would be the working fluid temperature limit, though.
Des Aubery
(www.adthermtech.com)
RE: high temperature heat transfer fluid
Back in 1990 , there was a replacement heat pipe airheater supplied in Maryland. Max fluegas temp = 750 F. The boiler started up after the new air heater was installed . Immediately after startup, the control room operator heard pop - pop- pop etc. The end caps of the individual heat pipe tubes were shot off the tubes like cannon shells, penetrated the casing of the boiler, flying around the plant. The plant was shut down pronto.
It seems the japanes mfr of the heat pipe tubes told the US boiler mfr ( in japanese notes) that these tubes contain water plus a corrosion inhibitor. The inhibitor breaks down to a series of child molecules above 700 F, yielding many more moles of vapor than originally expected, and a mcu higher heat pipe pressure. Unfortunately, the US boiler mfr does not read japanese. The pressure in the heat pipe tubes increased to 2-3 times the original design pressure, and the endcaps failed.
The ASME code then changed it rules, requiring each heat pipe tube to a have a relief valve or burst disk if used in section I or VIII service. That basically ended the US market for heat pipes.
Using a heat pipe results in a "indirect heat exchanger " arrangement, and the effectiveness of this is the product of the effectiveness of teh 2 sections. So if each section is 80% effective, the global effectiveness is 81%. So it is better in HRSG applications to use a direct heat exchanger using steam . Better cycle efficiency can be had if you use a ammonia water mixgture ( Kalina cycle), but it costs big bucks.
RE: high temperature heat transfer fluid
RE: high temperature heat transfer fluid
Des Aubery...
(adTherm Technology - www.adthermtech.com )
RE: high temperature heat transfer fluid
RE: high temperature heat transfer fluid