Plasma Route for Cheap Hydrogen
Hydrogen as a fuel is a critical antidote to global warming; burning Hydrogen produces only water. However, nascent Hydrogen is not available in nature. Water is two atoms of Hydrogen to one atom of oxygen, 11% hydrogen by mass. Methane, a significant component of natural gas, has four hydrogen atoms for one of Carbon, 25% by mass.
Steam Methane Reforming (SMR) produces the Hydrogen used worldwide in fertilisers, oil refining and chemicals industries. First, high-pressure steam at elevated temperatures of 700°C–1,000°C, reacts with Methane in the presence of a nickel catalyst, and the products are Hydrogen, carbon monoxide, and carbon dioxide. Subsequently, in the “water-gas shift reaction,” the carbon monoxide and steam react using a catalyst to produce hydrogen along-with carbon dioxide. Following this, a process called “pressure-swing adsorption,” filters out carbon dioxide and other impurities, leaving essentially pure so-called blue Hydrogen.
The SMR process produces 9 to 12 tonnes of CO2 per tonne of Hydrogen because the released carbon atoms combine with oxygen in the air readily. If the process runs without air, Methane will dissociate into Hydrogen and solid Carbon. Heating natural gas without adding air, a process called pyrolysis, produces Hydrogen and Carbon, as was shown in 1977 by the Norwegian company Kværner (now Aker Solutions). They built a commercial-scale methane pyrolysis facility based on plasma torch technology in 1997.
The microwave-assisted plasma pyrolysis technology developed by James J. Strohm, George L. Skoptsov, Evan T. Musselman, Kurt W. Zeller of H Quest in Pittsburgh uses microwave energy to convert Methane into a plasma state. Methane gets dissociated into Hydrogen and lighter hydrocarbon molecules in the methane plasma. A series of reactions that create solid Carbon or petrochemical compounds such as acetylene or ethylene follow. The process synthesises different forms (allotropes) of Carbon that differ according to how the atoms arrange themselves. These include graphite, Carbon black, graphene sheets, and Carbon nanotubes. Carbon Black is a raw material for tyres, printing inks, reinforced plastics and batteries. Graphite finds use in pencils and arc welding. Graphene, a one-atom-thick film of Carbon, is priced at roughly $175 per kg, while carbon nanotubes can fetch up to $2,300/kg. Hydrogen made by this process is “turquoise hydrogen”. There are no commercial turquoise hydrogen plants in operation. The carbon co-products are so expensive that Hydrogen is almost free.
Microwave ovens in the kitchen use a Magnetron type electron tube to produce microwaves — a form of high-frequency electromagnetic radiation at 2.45 GHz (2.45 billion oscillations per second) and above. In the plasma process, microwaves at 2.4GHz cause the few naturally occurring free electrons to vibrate rapidly, causing them to collide with Methane molecules and dissociate them into lighter hydrocarbons and Hydrogen. This process of ionisation frees more electrons, causing a chain reaction that eventually converts Methane into plasma, a soup of electrons and ions.
Microwave discharges belong to the group of warm plasmas. It can operate in an extensive pressure range: from the atmospheric pressure ( 1 bar) to down to a thousandth of a bar. The gas temperature can quickly rise to above 3,000 K at atmospheric pressure.
Because of the power limit of Magnetrons, H Quest reactors are modular, small-scale units sized according to the project requirement. As a result, the world’s first large-scale plasma-based Hydrogen factory could cut the cost of Hydrogen by 20%. H Quest plans to set up a pilot project capable of producing 250 kg of turquoise Hydrogen and 750 kg of Carbon black per day in the next couple of years. A larger commercial project, projected to cost $3m-5m to build, will come up within three years, which produces one tonne of Hydrogen and three tonnes of speciality carbon black daily. The first focus will be on Carbon black as the co-product in the early plants because the production process is simple. However, ethylene may be the product in future plants.
H Quest’s process of making Hydrogen from natural gaswithout the burden of CO2 is sure to revolutionise the fast-growing Hydrogen sector. It may completely replace the Steam Methane Reform process and allow the hydrogen economy to develop at speed. Setting up the plants at the site of methane sources like fossil-fuel facilities that routinely flare natural gas can solve the problem of methane leakage in transportation. In addition, using biogas instead of fossil gas can make the Hydrogen and carbon-based co-products Carbon negative.
Because renewable electricity can power microwave generation, extracting Hydrogen from natural gas using microwave plasma technology can be entirely Carbon negative. Microwave plasma technology is appropriate for modular, small-scale, low-cost plasma reforming plants, making the industry more efficient, effective, flexible and competitive.
The present research focuses on how to relate the process parameters with the carbon product forms, which will allow selective production of specific carbon allotropes and tailor their Physico-chemical properties. The hope is to lead to future hydrogen technologies that could revive the demand for natural gas and coal, thereby diversifying potential feedstocks carrying Hydrogen.
The process could also stimulate the demand for Hydrogen and associated technologies, infrastructure to enable hydrogen energy deployment, and domestic natural gas to manufacture Hydrogen and synthetic carbon products. The spectrum of the plasma-derived products is vast: activated Carbon, plastics and graphite electrodes for steel and aluminium smelting. The other problem is that The market for Carbon products limits h Quest’s market size. The carbon black market requires 14 million tonnes of the stuff each year.
H Quest’s microwaves process requires substantially less electricity than the electrolytic process of splitting water molecules to release Hydrogen. The specific energy requirement is well below the US DoE benchmark of 60 g(H2)/kWh. Key employees and a handful of early investors own the US company, generating funds from research grants. The company says that they’re looking to partner closely with the existing industry. And according to H Quest, they sell the means of achieving sustainability and decarbonisation goals.
