Hydrogen-Fueled Gas Turbines: An Overview
Once produced, hydrogen can be used as a fuel for power generation. Because gas turbines can run on hydrogen, they can be used in a variety of industrial applications such as steel mills, refineries, and petrochemical plants.
The Hydrogen Story
There are differences between hydrogen and natural gas that must be considered in order to use hydrogen correctly and safely in a gas turbine. Aside from changes in combustion properties; the impact on all gas turbine systems and the overall balance of the plant must be considered. In a power plant with one or more hydrogen-fueled turbines, fuel accessories, bottoming cycle parts, and plant safety systems must be replaced. Due to the inherent fuel flexibility of gas turbines, they can be designed to run on green hydrogen or similar fuels as a new unit, or they can be modified after years of operation on conventional fuels such as natural gas. The extent to which a gas turbine must be modified to run on hydrogen is determined by the gas turbine’s initial configuration and overall plant balance, as well as the required hydrogen concentration in fuel.
Hydrogen can be produced using a wide range of feedstocks and chemical processes. A few examples include algae photosynthesis, natural gas steam methane reforming, crude oil partial oxidation, coal gasification, and water electrolysis. The sections that follow will discuss steam methane reforming and electrolysis as potential hydrogen-generation pathways for energy production.
Methane Reforming Using Steam
The majority of hydrogen produced today is the result of steam methane reforming. A large portion of this hydrogen is used to produce ammonia for fertilizers or petrochemicals. In this process, natural gas (methane) is reacted with water and heat to produce H2 and CO2 via two reactions.
Water electrolysis is a well-known method for producing hydrogen. For every mole of water used in this reaction, one mole of hydrogen and one-half mole of oxygen are produced. Using the molecular weights of the individual components, each gram of water would yield 0.11 grams of hydrogen and 0.89 grams of oxygen. (Note how the total mass does not change.) In other words, if no losses occur during the electrolysis process, 1 gram (1 kg) of hydrogen requires 9 grams (9 kg) of water. Using this knowledge, it is possible to calculate the amount of water required to support the power to hydrogen principle.
Renewable Energy for Hydrogen Production
To support the idea of producing hydrogen through electrolysis using renewable energy, a significant amount of carbon-free electricity would be required (also known as the power to hydrogen). The good news is that the global push for carbon-free energy has resulted in an unprecedented increase in renewable energy output, as evidenced by renewable energy generation statistics. The amount of electricity generated in Europe by renewables such as wind and solar has increased from 12.6 terawatt hours (TWh) in 1990 to more than 570 TWh in 2016.
Hydrogen Combustion Evolution
For many years, coal-burning heat was used to boil water, superheat the steam, and then extend it through a turbine/alternator to generate electricity. The Rankine Cycle is a traditional power generation method.
Another method for generating electricity was to burn natural gas in compressed air, then direct the hot combustion products through a power turbine, using the shaft power to drive both the compressor and the generator, a process known as the Gas Turbine arrangement (Brayton Cycle). Increasing steam and producing additional electricity in a turbine/alternator using hot exhaust gases can generate additional energy. This combination is known as a Combined Cycle Gas Turbine (CCGT).
After environmental damage to trees and land was linked to sulfur dioxide (SO2) emissions from power plants’ coal flue gas. The first option was to scrub SO2 from the flue gas, while the second was to gasify the coal to produce synthetic gas (Syngas, a mixture of carbon monoxide and hydrogen). Syngas is fed into a gas turbine, which burns similarly to natural gas.
The sulfur species will be removed from the syngas using petrochemical-specific chemical processes. This operation was known as the Integrated Gasification Combined Cycle (IGCC). Because the fuel gas properties varied, different combustion arrangements for the Gas Turbines were required.
Meanwhile, the production of NOx has raised health and environmental concerns. In coal-fired power plants, low-NOx burners and selective catalytic reduction were used. Low-NOx burners were developed by gas turbine manufacturers for older models. It used water or steam injection (so-called “wet” systems), and then “dry” versions for modern machines that used staged or lean premix combustion techniques (so-called “Dry Low Emission,” or DLE burners).
Getting Ready for the Hydrogen Society
MHPS, a joint venture between Mitsubishi Heavy Industries and Hitachi, has been especially vocal about its efforts to comply with Japan’s plans to become a “hydrogen society,” which were announced in the aftermath of the Fukushima Daiichi nuclear plant meltdown in 2011. The government-industry collaboration will be divided into three phases: first, it plans to expand its existing fuel cell initiative to help lower hydrogen and fuel cell prices; second, it plans to introduce large-scale hydrogen electricity production and hydrogen supply infrastructure; and finally, it plans to provide a zero-carbon supply system in the manufacturing process.
MHPS has tested 29 gas turbine units with hydrogen content ranging from 30% to 90%, totaling over 3.5 million operating hours since 1970. One of the most difficult challenges for the company was reducing the high NOx emissions associated with hydrogen combustion without sacrificing performance. MHPS wanted to reduce the risk of combustion oscillation and “flashback” (backfire) in higher hydrogen mixtures because hydrogen has a faster flame than natural gas.
Control system for Gas Turbines
The gas turbine control system helps technical professionals by adding security improvements. It is in the area of lowering fuel emissions by properly indicating insecure operations. Turbine control systems cover excessive fuel emissions, fuel control, and vibration monitoring. Turbine control system parts include IS200TBCIH1B, IS215UCCAM03A, etc.
The Hydrogen Gas Turbine’s Future
The challenge with hydrogen gas turbines is that they must function without sacrificing performance, startup times, or NOx emissions. This is accomplished by developing combustor designs that make greater use of the hydrogen in natural gas.
Gas Turbines will be able to meet the market’s needs as the hydrogen economy develops over the next decade without compromising today’s high-performance standards in terms of emissions, response, and productivity.
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