Exergoeconomic factor (f k )
Chapter 8: Conclusion
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may increase the work output of the simple cycle. It will help to burn the fuel more. To install an air compressor, spend approximately $380,000.00 investment is required, and which increases 3 to 4 MW more output.
In the air compressor (air compressor), the generated heat to produce compressed air is 2256 kWh/day. The percentage of waste heat to the environment is 361.01 kWh/day, for leakage 423.87 kWh/day, actuation is 92 kWh/day, and conveying & others is 1369.13 kWh/day.
The total Operating Cost of the cooling tower system is USD 177,769.87. It can be reduced by proper utilization of chemical dosing, changing the water treatment pipeline which is already damaged, reduce the excess use of raw water.
The Exergy balance of a thermodynamic system allows the determination of the Exergy destruction or the estimate of the energy losses due to actual transformations' irreversibility.
It leads to the quantitative measurement of the Exergy efficiency. The results show that the combustion chamber's efficiency is the lowest compared to that of the compressor and the expansion in the turbine because it is where the highest exergy destruction takes place in the simple cycle. For the combined cycle, the highest exergy destruction occurs in the combustion chamber, and the second-highest component is the HRSG. The combustion chamber's exergy destruction is 25MW and in HRSG is 9 MW, and the total exergetic efficiency in the combined cycle is 47.35% in the operating conditions. The change in ambient temperature has a direct impact on the exergy performance of the gas turbine.
Exergy destruction increases with air temperature increase, while the exergy efficiency decreases, and the plant's exergy efficiency and its units increase when the temperature decreases.
The exergetic analysis results identify the combustion chamber as the largest magnitude of overall exergy destruction, avoidable exergy destruction. By reducing the air-fuel ratio, and further preheating the combustion air, exergy destruction could be reduced in the combustion chamber. These results are helpful for future improvements for the plant. Additionally, the cost of products and cost formation is discussed. The plant owner may develop an opinion from these results and check the company’s economic policy. Exergy analysis of each of the component work can be done more briefly and using the exergy analysis tool to improve the plant's performance in our country.
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The plant's exergoeconomic analysis showed a lower cost of power compared to that of energy costing, which is due to the non-consideration of other cost factors involved in power production. It performs in terms of exergy cost and unit exergy cost. The exergoeconomic analysis results indicated that the combustion chamber was also the most cost-effective component to be improved due to a low cost of capital investment and high cost of exergy destruction.
Comparing the Fenchuganj Combined Cycle Power Plant with other plants also represents that the combustion chamber is the plant's highest exergy destruction component. The heat energy loss in the combustion chamber decreases with an increase in air mass flow rate. This implies that a high mass flow rate of air can minimize the combustion chamber's energy losses as this would introduce more air for combustion. The component with the highest exergy improvement potential is the combustion chamber.
This high improvement potential in the combustion chamber is due to the irreversibility of combustion and the large temperature difference between the air entering the combustion chamber and the flame temperature. These immense losses mean that a large amount of energy present in the fuel to generate useful work is wasted. Exergy improvement potential can be afforded in the combustion chamber by preheating the reactants and reducing the heat loss and the excess air entering the combustion chamber. The lower improvement potential in the air compressor, compared with the combustion chamber, is due to relatively heat loss from the air compressor through friction compared to the large temperature difference between the air entering the combustion chamber and the flame temperature. These results have made it possible to determine the critical points of the gas turbine system stating hierarchy on its components so that the measure is applied in the places where they will be most effective.
8.2 Recommendations for Future Works
Fenchuganj Combined Cycle Power Plant is a baseload gas-based power plant and running continuously. Plant’s standard economic life cycle is 20 years, and it is almost past 15 years.
Significant changes on that machine may not be economical and user friendly. However, some future works can be taken to maintain the plant efficiency with life cycle degradation
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and keep the plant available in desired capacity with the grid. Some recommendations to improve the plant performance are given below:
i. An Inlet air cooling system, designed with specific inlet air temperature can be installed to balance the inlet air temperature in the gas turbine. It will increase power production and reduce the cost of production.
ii. Installing an additional air compressor before the gas turbine air compressor will increase the airflow to the combustion chamber and reduce the Air compressor work in the gas turbine. By installing an additional air compressor, 2 to 4 MW capacity can be increased.
iii. A pre-heater could be introduced before the combustion chamber to reduce the rate of exergy destruction in the combustion chamber.
iv. the Exergy analysis of a combined cycle power plant with carbon capture utilization. This paper considers retrofitting an existing combined cycle power plant arrangement to get carbon dioxide from gas turbine exhaust and convert it into methane to run additional gas turbine for power augmentation. Here exergy analysis of the considered combined cycle estimates the exergy efficiency and exergy destruction of significant components. The study shows the comparative results for different power plants with and without carbon capture arrangement.
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