Improving Steam Turbine Power Generation Efficiency
According to global statistics, energy supply has shown a steady increase in the past few years. However the available energy generation plants are not sufficient to produce the required power. Therefore, we need to invest more in the construction of new power generation plants or seek alternative forms of energy generation. Therefore, in order to remain competitive, it is important for power generation companies and private power operators to seek ways of optimizing existing plants in order to improve efficiency and reliability, as well as to reduce the cost of plant operations and maintenance. This article depicts an overview of a preliminary study on the optimization of the design of the steam turbine. This was done with a special focus on the last stage low-pressure turbine blades because the design parameters of this component exhibit an influence on the efficiency of power generation from the steam turbine electric power generating system.
The turbomachery and turbine energy generation system
The prominent forms of energy used in the industrial process for heating are electricity, directfire heating, and steam. Heating using electricity basically involves the use of heating elements (normally resistors) which convert the electrical current flowing through them to heat energy. For direct-fire heating, hot gases from a burner transfer their heat energy to the system. Steam, which is the most commonly used form of energy for process heating, is also used for pressure control, and mechanical drive, and is sometimes directly injected into the process as a source of water for process reactions. Steam is often used compared to other sources of energy for heating because of its performance advantages which include non-toxicity, ease of distribution, high heat capacity, and low running and set-up cost. Turbomachinery generally transfers energy between a fluid and a rotor. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid. The overall efficiency of the simple steam power plant is generally lower than that of other power plants such as hydro, diesel, and nuclear power plants.
Efficiency improvements in steam turbine power plants
In the last three decades, engineers and designers have done several research, simulations, and experimentations on turbine systems to make industrial steam turbines more efficient and reliable. These works have led to the improvement and the design of more powerful, efficient, and reliable steam turbines and the development of new materials and manufacturing processes. During the past years, the steam turbine inlet temperatures have been increased further to improve the efficiency of the steam plant, especially, with recent designs having up to 620 °C inlet temperatures that can still be increased in the near future. This increment makes the review of the heat transfer characteristics of the materials chosen for the design of the turbine and most especially the turbine blades important and necessary. In addition, the structural integrity of all rotating components, mainly the rotor and the shaft,t is a key factor for the successful, efficient, and reliable operation of any turbomachinery.
The energy cycle for the steam power turbine system
Steam power plants are assumed to follow this ideal thermodynamic cycle for the explanation of their basic processes. It involves two isentropic and two isobaric processes. However, for practical operation, the working fluid is reheated and made to run through another turbine before going to the condenser.
The turbine blade is the most important element in the steam power generation system as it transmits the pressure energy from the steam to the rotor. Turbine blades can be classified based on their interaction with the steam as impulse or reaction blades. It is important to note that turbine blades are not exactly the same throughout the section of the steam turbine. Steam turbines are designed with multi steam expansion stages, which are basically high, intermediate and low pressure stages
Turbine Control system
Improving the efficiency of steam turbine power generation involves sophisticated turbine control systems that play a pivotal role in optimizing performance. These systems utilize advanced algorithms and real-time data analytics to monitor and adjust various parameters such as steam flow, temperature, pressure, and rotational speed. By precisely controlling these factors, turbine control systems can maximize energy output while minimizing fuel consumption and emissions.
Modern turbine control systems integrate predictive maintenance capabilities, allowing for early detection of potential issues and proactive maintenance scheduling. This proactive approach not only improves reliability and uptime but also extends the lifespan of critical components, reducing overall operational costs. Global suppliers, such as WOC, offer GE Speedtronic components for your Speedtronic system. These companies provide OEM Speedtronic and GE Excitation replacement parts, including models like IS200TBAIH1CED, IS200TBCIH2BBC, and IS200WROBH1ABA.
Factors affecting efficient steam power turbine blade design
The LP, which is also the last stage, turbine blade is characterized by a number of issues due to the length of its blades. These issues, among others, include large centrifugal stress, low rigidity, and high Mach number flow. The overall thermal efficiency of the steam turbine as well as its size and total power output significantly depend on the last stage blades, the reason for which designing an optimal range of last stage blades is important. The life span of the turbine blades is influenced by a number of parameters. Unlike blades of a compressor, turbine blades experience harsh forces acting within its environment ranging from high operating temperatures to high varying blade load. Other factors affecting the life span of the turbine blade include flow mismatch during water and steam ejection at the extraction ports, partial or imperfect vacuum, water injection, incorrect steam conditions, presence of impurities in the steam, etc
A Practical Overview: The Egbin Power Plant, Nigeria
For a practical overview, this paper examines the steam power turbine system for electric enery generation at the Egbin thermal power plant, Nigeria. The plant is located at Ikorodu, Lagos State, Nigeria. The plant, which has six turbine stations, was commissioned in 1987. Each individual station operates on a reheat-regenerative cycle and can be fired using either gas or heavy oil. The construction of the plant commenced in 1984 under the supervision of the Japanese and French contractors with most of the equipment, including the Hitachi turbine being used at the plant, were sourced from Japan. The budget estimate of the plant was about 1 billion USD at that time while the life span of the plant was estimated at 25 years. According to, efficiency of the plant was averaged at 34.67% under the review period of 2000 to 2010. However, in 2016, the plant recorded an overall efficiency of 29% based on the output/input method of calculation. This shows a significant drop in the efficiency of the power station, and thus, necessitates the needs for reviewing the system for improvement possibilities. In this study, the analysis for improvement being proposed is being carried out on the turbine blade. To improve the efficiency of the blade rows, the flow pattern of individual stage will need to be redesigned considering all the fluid forces acting on the end-wall contour of the steam turbine and the blade profile.
Summary
Improving the efficiency of steam turbine power generation is crucial for meeting global energy demands sustainably. By implementing advanced materials, optimizing design through computational modeling, and enhancing operational strategies, significant efficiency gains can be achieved. These improvements not only reduce environmental impact by lowering emissions but also enhance the economic viability of power generation. Investing in research and development in this area is essential for realizing a future where clean, efficient energy plays a central role in powering our world.
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