Kalina Cycle 1

[bonzoboy]

Years ago, I heard of this novel cycle, supposedly that would improve plant efficiency. In a nutshell, what is the Kalina Cycle, and why (if its an improved design) has it not had much impact on power world (I don't know of anyone who is using it, nor have I seen anyone write a specification to require it).

Any comments?

 

[davefitz]

The Kalina cycle uses a binary mixture of NH3 and H2O as the working fluid, in lieu of steam. This binary mixture boils at a varying boiling temperature, allowing one to minimize the rate of entropy increase during the boiling process. The gradient in boiling temp vs NH3 content may also be used to advantage in the exhaust of the turbine.

The kalina cycle has its best applications in low temp service, such as geothermal wells. One of its patents also applies to gas fired combined cycle plants ( HRSG's) , and this patent was purchased by GE maybe 10 yrs ago. One such HRSG was built, but apparently it is not considered to be economically competitive in this market.

The problems with the kalina cycle as applied to high temp - high pressure cycles include:
a) nitriding of the alloy steel superheater tubes, at temps above 950 F
b) complicated distillation columns required to recombine the turbine exhaust into the binary mixture used in the heat exchangers
c)cycle proposals seem to be based on zero frictional pressure drop and zero temperature differences in the main process components, and it is pretty expensive to meet such requirements.