There are several ways to improve the operating characteristics of gas turbines, and those few extra percentage points of operating efficiency are critical to optimizing the value of an installation. Owners and operators are looking for cost-effective ways to enhance gas turbine operability, improve efficiency, acquire additional output, and extend the life of their existing equipment in the current economic context. The regulatory process for approving new power sources is more time-consuming and rigorous than ever before, making minor turbine upgrades to existing equipment a more appealing choice.
Many things can be done to maintain a turbine running efficiently. Detail-oriented observation and trends of operating data might reveal deteriorating turbine performance. There are various monitoring solutions available to help with this endeavor. Some are intended to warn of impending failures (for example, bearing vibration), preventing costly forced downtime. Other devices are designed to track the performance of a turbine or a power plant over time. Remote monitoring centers can provide any or both functions.
Degradation and Recovery of Turbine Efficiency
A gas turbine’s performance can degrade in a variety of ways over time. Some can be repaired or mitigated while the system is running, while others necessitate extensive maintenance during a shutdown. Clogged inlet filters, filthy compressor blades, broken compressor, and turbine blading, excessive clearances between casings and moving compressor or turbine blades, and sub-optimal combustor tuning are all major causes of turbine efficiency loss.
Cleaning and maintenance of the inlet filter
Maintaining the inflow filtering system properly is critical to the overall health of the turbine. Inlets that are not properly maintained can cause compressor blade breakage, unclean, fouled compressor blades, and excessive pressure drop over the filters (with the resultant loss in turbine efficiency).
Periodic checks of the clean side of the filters should be undertaken, looking for “light leaks” and debris that is or could become loose and enter the compressor.
Some turbines incorporate a reverse air ‘puff’ cleaning mechanism for the filters that use the compressor to discharge air (after cooling it) to reverse flow filters for a brief moment in order to dislodge particles imprisoned on the filthy side of the filter. One of the most significant disadvantages of this technique is that the vast majority of pollutants are pulled back into the filters after the short puff, necessitating numerous repetitions of the procedure to considerably lower inlet filter differential pressure. When the turbine is turned down, the plant air system can be used to puff the filters. This procedure dramatically minimizes the amount of time and air used in the cleaning process.
Regular compressor cleaning is critical for sustaining turbine output and efficiency. Dirty compressor blades can cause significant performance deterioration, especially if the gas turbine is located in or near an industrial area.
Compressor cleaning can be done while the unit is running (online) or while it is turned off (offline). Some turbines, particularly those with low NOx combustors, prohibit the use of detergent during turbine operation. These turbines are typically washed online once a day for a few minutes. When the unit can be turned off, a more thorough wash is performed, utilizing detergent and repeated rinse cycles.
Input conditioning, or lowering the inlet air temperature, is a popular approach for increasing gas turbine production. There are three well-known strategies for increasing output: fogging, evaporative cooling, and chilling.
Fogging involves injecting atomized water downstream of the inlet filters into the inlet air stream. The mechanism precisely regulates the amount of water injected to guarantee that no huge droplets of water enter the compressor.
After the filtration system, evaporative cooling equipment is put in the inflow ducting. The system comprises of an airstream media bank that is constantly wetted by one or more water pumps. As the incoming air travels through the media, part of the moisture is absorbed and heat is lost (through water evaporation), resulting in cooler, denser air. This thick air is then introduced into the compressor. With cooler, denser air, the turbine can create higher output power while improving turbine efficiency.
Chilling the incoming air stream is an efficient method of increasing air density and thereby increasing turbine output. The chiller, which is normally a huge mechanical refrigeration machine, is adjusted to give the compressor a controlled inlet air temperature. The chiller guarantees that the compressor inlet temperature does not exceed a specified target temperature regardless of the ambient air temperature.
Peak firing a gas turbine (beyond the OEM design limit) is another alternative for increasing output, but the higher maintenance demands placed on combustion and turbine components make this economically possible only on rare occasions.
Improving Emissions Compliance
Emissions compliance is a constant concern for operational facilities, with the regulations becoming increasingly demanding over time. The EU big machine directive, for example, requires NOx. CO emissions to be fewer than 20 ppm for all plants larger than 20 MW. A similar initiative in the United States is pushing for all non-attainment zone plants to be upgraded to the best possible retrofit technology.
Compliance with emissions standards is not only beneficial for the environment, but it also helps to avoid costly fines. Gas turbine combustion systems are typically ‘adjusted’ twice a year, once before the summer and once before the winter. Each tuning session is intended to optimize the turbine for the forthcoming season. While ensuring that there are no excessive emissions, excessive combustor dynamics, or flame loss (due to lean blowout).
Gas Turbine Control System
The gas turbine control system can improve safety and Security. While enhancing efficiency with the use of a turbine control system. Manufacturers like GE Speedtronic and Woodward netcon design and generate control systems for gas and steam turbines. General Electric control system component examples include IS215UCVEH2A, IS200VAICH1D, IS200VVIBH1C, IS220PDIOH1A, etc.
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