Re: GAS-L: Gas "topping" turbines

[Peter Singfield <snkm@btl.net>]

At 10:12 AM 1/27/2001 -0200, you wrote:
>Peter,
>do you have information on the Kalina's (Ammonia) topping cicle? According
to an
>old Popular  Science, August 1986. It should be in use by now.
>Antonio
>

It is now being applied in many new large power plants around the world.


I did a quick research a few months back -- but only kept one PDF file --
and can't remember what the Url was where I found it.

Appended is a copy and paste of the beginning of that file -- minus the
excellent diagrams.

Search kalina or kalina cycle -- all kinds of info will pop up.

Peter singfield -- Belize

**********************************

EXERGY STUDY OF THE KALINA CYCLE
Göran Wall

University College of Eskilstuna/Västerås, Box 11, S-721 03 Västerås, Sweden.
and Chia-Chin Chuang and Masaru Ishida Tokyo Institute of Technology,
Research Laboratory of Resources Utilization 4259 Nagatsuta, Midori-ku,
Yokohama, 227 Japan

Presented at: 1989 American Society of Mechanical Engineers (ASME), Winter
Annual Meeting (WAM)

San Francisco, California
December 10-15, 1989

Published in:
R. A. Bajura, M. R. von Spakovsky and E. S. Geskin Eds., Analysis and
Design of
Energy Systems: Analysis of Industrial Processes, AES-Vol. 10-3, pp. 73-77,
ASME.
Abstract–Energy-Utilization Diagrams is a graphic method to describe the
exergy losses in industrial processes, i.e., improving the exergy use. 

We apply the method to a 3MW Kalina bottoming cycle. The Kalina cycle is
being developed as a competitive improvement of the Rankine steam cycle. By
using an
ammonia-water mixture as the working fluid and a condensing system based on
absorption refrigeration principles the Kalina bottoming cycle becomes
about 10% more efficient than the ordinary Rankine cycle.

The Energy-Utilization Diagram of the Kalina cycle is very tight. From this
we see that the cycle is very well optimized.

NOMENCLATURE
c Specific heat
e Exergy per unit mass
g Gibbs free energy per unit mass
h Enthalpy per unit mass
p Pressure; pc critical pressure
R Gas constant; Rm for mixture
s Entropy per unit mass
T Temperature; Tb bubble point; Td dew point; Tc critical point;
Ts saturation point for a pure component
u Energy per unit mass
v Volume per unit mass
X Ammonia mass fraction; X m for ammonia mol fraction
Density
Subscripts
f Saturated liquid
g Saturated vapor
l Subcooled liquid
m Mixture or mol fraction
v Superheated vapor
s Saturation
sol Solution
¥ Ideal gas

INTRODUCTION:

Energy-Utilization Diagrams (EUD) is an important engineering tool to
improve exergy
efficiency of energy conversion systems (Ishida and Zheng, 1986 and Ishida
et al., 1987).

The exergy losses of the system are shown by a graphical presentation which
gives a useful overall description of the process.

The use of mixtures as working fluids has opened new possibilities to
improve the
efficiency of power and refrigeration cycles with less costly equipment.
Mixtures may be an important substitute for CFC refrigerants, thus,
decreasing environmental problems.

The Kalina cycle, which use a ammonia-water mixture, may show 10 to 20% higher
exergy efficiency than the conventional Rankine cycle (Kalina, 1984 and
El-Sayed and
Tribus, 1985). The ammonia-water mixture boils at a variable temperature
unlike pure
water which boils at a constant temperature. Variable temperature boiling
permits the working fluid to maintain a temperature closer to that of the
hot combustion gases in the boiler, thus, improving the exergy efficiency,
a fact which has been well known among scientist and engineers. But there
was no practical, efficient way to condense the mixture back to a fluid for
recycling until the Kalina cycle was introduced.

By circulating the mixture at different compositions in different parts of
the cycle,condensation (absorption) can be done at slightly above
atmospheric pressure with a low concentration of ammonia, while heat input
is at a higher concentration for optimum cycle performance.

Figure 1 shows the simplified Kalina cycle (El-Sayed and Tribus, 1985a)
assumed in
this study. This is a bottoming cycle feed by exhaust gases (1, 2) to the
boiler. 

Superheated ammonia-water vapor (3) is expanded in a turbine to generate
work (4). 

The turbine exhaust (5) is cooled (6, 7, 8), diluted with ammonia-poor
liquid (9, 10) and condensed (11) in the absorber by cooling water (12,
13). The saturated liquid leaving the absorber is compressed (14) to an
intermediate pressure and heated (15, 16, 17, 18). 

The saturated mixture is separated into an ammonia-poor liquid (19) which
is cooled (20, 21) and depressurized in a throttle and ammonia-rich vapor
(22) is cooled (23) and some of the original condensate (24) is added to
the nearly pure ammonia vapor to obtain an ammonia concentration of about
70% in the working fluid (25). 

The mixture is then cooled (26), condensed (27) by cooling water (28, 29),
compressed (30), and sent to the boiler via regenerative feedwater heater
(31).

The mass flow circulating between the separator and the absorber is about 4
times that of the turbine, thus, causing some additional condensate pump
work. However, this loop makes possible the changes in composition between
initial condensation in the absorber and heat addition in the boiler. 

By changing the dew point of the mixture, the waste heat from the turbine
exhaust, which is lost in a Rankine cycle, can be used to dilute the
ammonia-water vapor with a stream of water, thus, producing a mixture with
a substantially lower concentration of ammonia which allows condensation at
a much higher temperature.

Usually thermodynamic properties of pure fluids and information of the
departure from ideal-solution is sufficient to derive mixture properties.
Stability, secondary reactions, safety, etc must, of course, also be
considered.
The Gasification List is sponsored by
USDOE BioPower Program http://www.eren.doe.gov/biopower/
and PRM Energy Systems http://www.prmenergy.com

Other Sponsors, Archives and Information
http://www.nrel.gov/bioam/
http://www.crest.org/renewables/gasification-list-archive
http://solstice.crest.org/renewables/biomass-info/gasref.shtml
http://www.crest.org/renewables/biomass-info/
http://www.crest.org/renewables/biomass-info/carbon.shtml