Power plants that can run on a variety of gaseous or liquid fuels reliably provide energy security in the event of fuel supply disruptions. Wärtsilä multi-fuel engines can switch fuels instantly while maintaining full output and efficiency. This flexibility gives it a significant advantage over gas turbines, which have lower availability and output when using fuel oils. Wärtsilä power plants can meet changing dispatch needs and respond quickly to changes in fuel availability thanks to fuel flexibility.
Energy security is still a major concern for many countries around the world. Potential threats include geopolitical instability, disruptions in fuel supply, and fluctuating fuel prices. Natural gas availability is increasing, owing primarily to global expansion of LNG supply infrastructure, but supply chain inflexibility and fluctuating prices are causing uncertainty. Fuel shortages, interruptions in supply, and price constraints, even if only temporary, pose significant economic and electric reliability risks. Some countries are now specifying multi-fuel capability for new power plants to mitigate fuel risk, recognizing that fuel flexibility is critical for ensuring a reliable source of electricity.
What is Fuel Flexibility?
The ability to burn a variety of fuels and switch fuels quickly during operation without reducing load or compromising power plant availability is referred to as fuel flexibility. Liquefied petroleum gas (LPG), crude oil, residual fuel oils (RFO), and distillate fuels such as light fuel oils (LFO), naphtha, and diesel are examples of liquid and alternative gaseous fuels that can be used for electric power generation. However, not all power plants are designed to run for extended periods of time on liquid fuels. When natural gas shortages force gas turbines to burn fuel oil as a backup, more inspection and maintenance are required, resulting in more frequent outages. Wärtsilä combustion engines are designed to burn a wide range of gaseous and liquid fuels without requiring additional maintenance or reducing availability, ensuring an efficient and reliable power supply around the clock.
While gas turbines are frequently advertised as having fuel flexibility, natural gas or liquefied natural gas (LNG) is used by approximately 90% of gas turbines worldwide due to its purity and ease of combustion. Only about 400 GE gas turbines in the world run on crude, naphtha, or heavy fuel oils. A number of Wärtsilä power plants were designed to run on liquid fuels, while natural gas infrastructure was built or expanded to meet both short-term and long-term power needs.
Wärtsilä combustion engines are designed to burn a wide range of gaseous and liquid fuels without requiring additional maintenance or reducing availability, ensuring an efficient and reliable power supply around the clock.
In addition to liquid fuels, Wärtsilä provides multi-fuel solutions that use LPG as fuel in conjunction with either diesel or gasoline. As an alternative fuel, consider liquid fuel or natural gas. Because of its widespread availability and low infrastructure costs, LPG is becoming an increasingly appealing fuel in power generation, particularly on islands and in smaller power systems.
Maintenance Concerns for Gas Turbines Powered by Oil
Because liquid fuels can contain water-soluble salts, high concentrations of heavy metals, and other impurities, they pose numerous challenges to gas turbines. Crude and residual oils are more viscous and have higher trace metal concentrations than distillates. Metals and salts abrade turbine blades and can form ash deposits, which cause fouling and corrosion in hot gas path components. Because combustion in gas turbines occurs continuously, the unit must be taken offline for inspection and maintenance. For gas turbines that run on fuel oil, a combination of fuel conditioning (cleaning, blending, heating, and pressurization) and more frequent maintenance cycles is required. Catalysts can be added to improve combustion, and heavy fuel oils (HFO) or crude can be blended with higher purity liquid fuels to meet sulfur, ash, and metals limits. For use in gas turbines, fuels containing vanadium or lead, which are oil-soluble and cannot be removed by washing or centrifuging, require corrosion inhibitors. Distillate fuels are generally thought to be relatively free of contaminants, but contamination during fuel transportation and delivery has resulted in corrosion in gas turbines.
Overhauling a gas turbine designed for natural gas to burn liquid fuels is expensive because it necessitates adjusting the firing temperature control, revising startup and shutdown procedures, and performing offline cleaning cycles to remove ash deposits. As a result, the gas turbine power plant’s availability is reduced. Explosion protection is frequently required for gas turbines because certain fuel oils contain volatile components with low flash points (such as naphtha). As a result, most gas turbines’ ability to run on liquid fuels is severely limited, both in terms of the characteristics of the fuel oils that can be used and the amount of time the turbine can run on such fuels.
Gas turbine liquid fuel options vary by manufacturer and model, with some gas turbines only able to use No. 2 distillate. To accommodate different fuels, multiple fuel delivery systems and combustors are used.
As a result, the gas turbine power plant’s availability is reduced. Explosion protection is frequently required for gas turbines because certain fuel oils contain volatile components with low flash points (such as naphtha). As a result, most gas turbines’ ability to run on liquid fuels is severely limited, both in terms of the characteristics of the fuel oils that can be used and the amount of time the turbine can run on such fuels.
Gas turbine liquid fuel options vary by manufacturer and model, with some gas turbines only able to use No. 2 distillate. To accommodate different fuels, multiple fuel delivery systems and combustors are used. The GE 7E and 9E gas turbines have an HFO package; the Siemens SGT-500 gas turbine can burn crude, HFO, and bio-oils; and Alstom has fuel oil capability on their GT24 and GT26 models.
Because Wärtsilä engines are not sensitive to metals or salts in fuel oils, fuel type has no effect on engine maintenance. To burn lower quality fuels such as HFO/RFO and crude, no corrosion inhibitors are required, and only minimal fuel conditioning (centrifugal separators and filters) is required. Because combustion occurs intermittently in combustion engines, with the expulsion of combustion products during the exhaust stroke, ash deposits are prevented from accumulating.
While ash-forming fuels (such as HFO) reduce gas turbine output by 4 to 5 percent when compared to natural gas operation, Wärtsilä multi-fuel engines maintain the same output and efficiency whether running on natural gas, LFO, or HFO. If the natural gas supply is cut off, a Wärtsilä multi-fuel power plant switches to a backup fuel oil instantly and maintains load without incurring any maintenance penalties. When routine maintenance is required, the modular architecture of Wärtsilä power plants enables an engine to be taken offline while the majority of plant output is maintained.
Wärtsilä dual-fuel (DF) engines use lean-burn combustion technology on gas and a standard diesel process on fuel oil. Wärtsilä DF engines have three parallel fuel delivery systems: a pilot fuel injection system, a liquid fuel supply system, and a gas admission system. The liquid backup fuel system enables the engine to switch from gas to liquid fuel operation automatically and instantly at any load. The tri-fuel delivery also enables instantaneous switching from LFO to HFO. The choice of Wärtsilä multi-fuel engine technology to help Jordan solve its energy supply problems was influenced heavily by fuel flexibility.
The 573 MW IPP3 plant, which is made up of 38 Wärtsilä 50DF engines that can run on natural gas, LFO, and HFO, is the world’s largest tri-fuel power plant, providing Jordan with dependable power.
While gas turbines require approximately 10 minutes to transition from baseload gas to fuel oil, Wärtsilä multi-fuel engines can do so instantly. Switching from liquid fuel to gas takes about 90 seconds with no load reduction. Wärtsilä multi-fuel engines have several advantages over gas turbines for flexible fuel solutions, including the ability to run on a variety of fuels without sacrificing power plant availability or incurring additional maintenance costs. Because a Wärtsilä power plant can ensure a secure power supply as fuel supplies change over time, this fuel flexibility saves money.
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