GAS TURBIN POWER PLANT

Gas Turbine Power Plants
New Procedure for Increase of Efficiency & Power
Repowering of Existing GTPP developed bei TPT 

Existing Gas turbine power plant (GTPP)
GTPP in the whole consist of an air compressor, a gas turbine, gas turbine cooling system and generator (Fig. 028).
The gas turbine power plant offers low capital costs, quick installation, flexibility in fuel selection and low maintenance cost but low thermal efficiency and expensive demineralized cooling water.

Gas Turbine Air Cooling:
The problem of the gas turbine is particularly in the high temperature of the turbine blades. In order to bear the high temperatures, apart from the use of developed materials the turbine components are cooled additionally from the inside, by compressed and cooled cooling air.

Open cooling concept is used for cooling the compressed cooling air:
A part of the compressed air is removed on different pressure levels from the compressor and used for the cooling of combustion chamber and turbine blades. The extracted cooling air must be cooled down, before it used as cooling air in the turbine. After cooling of turbine components the cooling air is mixed in the turbine with the main gas flow.

Water Injection (quench cooler) is used in GTPP:
In gas turbine power plants usually the cooling air is cooled by water injection (Quench cooling) and be supplied as cooling air to the cooling system of the turbine. During such open air cooling with a water injection the previously demineralized water and its evaporation heat flow go lost with the turbine exhaust gases.

In particular in countries with dry regions it is to be found necessarily a new procedure with an effective cooling air cooling without a water consumption.

The research and the development of the gas turbine cycle led to a new procedure for the reduction of exhaust gas losses.




New Procedure for Gas Turbine Power Plants

"Procedure for increase the output and the thermal
efficiency of simple Gasturbine power plants"

     Publication Nr. EP 1 808 588, Date: 18.07.2007, Publication: pdf-file:
     Inventor: Y0ussef Mustafa (CH)
     Applicant: Thermal PowerTec Ltd, Zürich (CH)



1. Gas Turbine PP with Vacuum GT Expansion
The procedure concerns the increase of the power output and the thermal efficiency of gas turbine power plants. The gas in the turbine are expanded on a vacuum pressure, the gas are cooled by heat exchangers, which in a vacuum container are arranged, and compressed by a gas compressor on the atmospheric pressure. Furthermore the gas turbine cooling air is prepared without a water consumption. The cooling air is cooled by a water or a water-steam cycle, whereby the cooling circuit is connected with a heat exchanger in the cooling tower. The cooled air is led into the cooling system.

In the gas turbine the supplied heat flow is increased by reducing the pressure of the LP sequential combustion and the exhaust gas temperature is reduced by the gas expansion into the vacuum range. This lead to a low exhaust gas temperature, in order to achieve minimum exhaust gas losses. Thus the thermal efficiency (hth) of gas turbine plants can be increased by more than 0.06 (i.e. hth net >0.44) and the power output by more than 26%.

For a basis gas turbine plant with a net thermal efficiency of hth net = 0.384, the following Data are calculated:

Vacuum Pressure	Increased hth	hth net	Increased Output
0.60 [bar]	0.042	0.424	+22%
0.50 [bar]	0.052	0.434	+25%
0.40 [bar]	0.061	0.442	+27%
0.30 [bar]	0.065	0.447	+29%

In the gas turbine with vacuum expansion and sequential combustions the pressure of the LP combustion is reduced. The LP cooling air of the gas turbine taken from the air compressor by the corresbond pressure has a lower temperature and can be used, without cooling down. So only one gas turbine air cooler (HP air cooler) is necessary.


Construction of a GTPP with a vacuum gas turbine expansion
in order to benefit from the present new procedure the use of the vacuum gas turbine expansion can be implemented without a large expenditure. All necessary elements (vacuum gas turbine stage, gas compressor and gas cooling by means of water-steam cycles) are usual not complex parts in the power plant technology.

Expected profits in a 200 MW GTPP:
a) A power increase of 26% respectively 52 MW is expected. This can be evaluated with approx. 25 mil $. These will exceed the construction costs.

b) The increase of the thermal efficiency of 6 per cent points results for a power increase of approx. 26 MW without fuel cost. This can be evaluated with approx. 6 mil $/year.

c) With the new air cooling without a demineralized water consumption a saving of 1 mil $/year is to be expected.



2. Repowering of Existing GT Power Plants
Gas turbine plants can repowered purely in order to benefit from the increase of efficiency and power output even though they are far from the end of their design life. Repowering an existing GT power plant can be achieved by supplement of vacuum gas turbine stage and cooling system.
The equipment to repowering depends on technical and economic criteria:
Building and foundations, gas turbine and generator.

The following option is possible:
- Supplement of a separate vacuum gas turbine stage
- Arrangement of the gas turbine stage, a gas compressor and a Generator on a separate GT shaft
- Arrangement of a new cooling system with water/steam cycle and cooling tower.

Due to the cooling of exhaust gases and GT cooling air by the IP water-steam a steam flow rate is produced, which is separated from the water in the drum. A part this steam flow rate can be extracted and used for industrial purposes or for steam injection into the gas turbine (Fig. 029).