Abstract
This paper presents the improved design of a 25 MW gas turbine power plant at Omoku in the Niger Delta area of Nigeria, using combined cycle application. It entails retrofitting a steam bottoming plant to the existing 25 MW gas turbine plant by incorporating a heat recovery steam generator. The focus is to improve performance as well as reduction in total emission to the environment. Direct data collection was performed from the HMI monitoring screen, log books and manufacturer’s manual. Employing the application of MATLAB, the thermodynamics equations were modeled and appropriate parameters of the various components of the steam turbine power plant were determined. The results show that the combined cycle system had a total power output of 37.9 MW, made up of 25.0 MW from the gas turbine power plant and 12.9 MW (an increase of about 51%) from the steam turbine plant, having an HRSG, condenser and feed pump capacities of 42.46 MW, 29.61 MW and 1.76 MW respectively. The condenser cooling water parameters include a mass flow of 1180.42 kg/s, inlet and outlet temperatures of 29.8°C and 35.8°C respectively. The cycle efficiency of the dry mode gas turbine was 26.6% whereas, after modification, the combined cycle power plant overall efficiency is 48.8% (about 84% increases). Hence, SIEMENS steam turbine product of MODEL: SST-150 was recommended as the steam bottoming plant. Also the work reveals that a heat flow of about 42.46 MW which was otherwise being wasted in the exhaust gas of the 25 MW gas turbine power plant could be converted to 12.9 MW of electric power, thus reducing the total emission to the environment.
Highlights
Energy is a basic requirement for human existence, and a driving force of civilization as almost all of our everyday activities and productive processes involve energy in one form or another [1]
3) MATLAB software was used to model the standard thermodynamic relations and equations for the analysis of the turbo-machinery components of the gas turbine to determine the heat energy rejected in the exhaust gas of the existing plant so as to ascertain the corresponding power that can match with the exhaust gas temperature (EGT). 4) Determination of a suitable capacity of a heat recovery steam generator (HRSG). 5) From the relevant design calculations, the capacities of other components of the proposed steam turbine system were determined
Iterations 1, 3 & 7 show that as the saturation pressure increases from 20 bar - 40 bar and HRSG stack temperature increases from 170 ̊C - 190 ̊C, the steam turbine net power output increases by 13.2% and the combined cycle overall efficiency increases by 6.2%
Summary
Energy is a basic requirement for human existence, and a driving force of civilization as almost all of our everyday activities and productive processes involve energy in one form or another [1]. The economic development and living standard of any society is a function of the availability and accessibility of electrical power to her. The acknowledgement of the importance of increasing access to commercial electricity is fundamental for the future and sustainable development of any society [2]. The increased world population and the quest to improve living conditions as well as global economic growth have resulted in a continuous increase in energy demand [3]. Accommodating the projected increase in energy demand must be approached with caution as it is generally accepted that human activities such as burning of fossil fuels involved in energy systems are the main sources of acid rain and greenhouse gases which are the major contributor to global climatic change [4]. Yadav [5] in his work, observed that one of the greatest challenges facing humanity during the twenty-first century is that of giving everyone on the planet access to safe, clean and sustainable energy supplies
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