Methane plasmalyser saves costs in hydrogen production

Bürkert process control valves have already proven their reliability in many hydrogen applications. For example, Graforce uses them in methane plasma electrolysers, which produce hydrogen and solid carbon at a high yield and comparatively low cost.

Hydrogen has huge energy potential and is not only found in water. It is a component of many organic and inorganic compounds in industrial waste water, liquid manure, plastics and gases. Graforce provides plasma electrolysers that produce hydrogen from energy-rich chemical compounds in residual materials – with significantly lower production costs and higher yields.

Green hydrogen – energy for the future

The high energy content of hydrogen means it is considered an important enabler in the energy transition and a ‘green’ alternative to petrol, diesel etc. Not only can it be burned directly in the conventional way, but it can also be used for the electrochemical production of electricity and heat. The energy-rich gas is suitable for powering vehicles, ships and even aeroplanes. Instead of particulate matter, nitrogen oxides or other air pollutants, only water vapour is produced as exhaust gas.

CO₂-free power and heat generation

However, when hydrogen is produced by electrolysis, i.e. splitting water into hydrogen and oxygen using electricity, the production process is energy-intensive and, therefore, expensive. “The average cost per kilogramme of hydrogen is between EUR 6 and 9”, says Kai Dame, development engineer at Graforce GmbH. “However, hydrogen is much more tightly bound in water than in other chemical compounds. This is why our plasmalysers require significantly less energy, because they extract the hydrogen not from water, but from other energy-rich chemical compounds. For example, hydrogen is only weakly bound in organic or natural gas. This means that just 10 kWh of energy is enough to extract 1 kg of hydrogen and 3 kg of elemental carbon from 4 kg of biogas or natural gas. The costs fall to an average of just EUR 1.5 to 3 per kilogramme of hydrogen.”

Graforce’s methane plasmalysers generate a high-frequency voltage field from solar or wind energy in order to split methane into its molecular components hydrogen (H2) and carbon (C). Each plasmalyser system has a capacity of up to 500 kW or 550 Nm³ (standard cubic metres) of hydrogen per hour and can be expanded on a modular basis. CO₂-free heat and power generation is possible in combination with a hydrogen CHP (combined heat and power unit) or an SOFC (solid oxide fuel cell). The solid carbon can be used as an industrial raw material, for example for the production of steel, carbon fibres and other carbon-based structures. For example, one such methane plasmalyser was put into operation at a cavern storage facility near Linz in April 2023.

The core components of the plant are two reactors in which the plasmalytic splitting of the methane takes place. The plant also has a separator for separating the two product streams of hydrogen and solid carbon, equipment for recovering the process heat and buffer storage for the hydrogen produced. This is delivered to a compressor station at a pressure of 500 mbar and then compressed to a pressure of 25 bar. The plant, which is around 25 metres high, is integrated into the operator’s overall plant using interfaces for control technology, media flow and compressed air and produces 50 kg of hydrogen per hour.

Graforce’s methane plasmalysers generate a high-frequency voltage field from solar or wind energy in order to split methane into its molecular components hydrogen (H2) and carbon (C).

Hydrogen-resistant process fittings

To ensure that hydrogen and carbon can be produced safely and to a high quality in the methane plasmalysis plant, a large number of process fittings are required. However, hydrogen applications are challenging here because the hydrogen atom has the smallest mass, so it is very volatile. As hydrogen is also a flammable and potentially explosive gas, all components that come into contact with it must meet high tightness specifications. On top of this, it has the unwanted property of diffusing into metals and changing the material properties, which can result in embrittlement or corrosion.

The Berlin start-up company found what it was looking for in Bürkert’s product portfolio. Today, almost 50 process valves in nominal diameters DN 15 to DN 65 with pneumatic actuators are used in the plasmalysis plant, for example the pneumatic angle seat and globe valves (Type 2000 and Type 2012) on the hydrogen and carbon lines. Their high reliability ensures a long service life with minimal pressure drop. Process control systems with Type 8802 positioners and ball valves with pneumatic rotary actuators (Type 8805) are used on the reactors.

Around 50 process valves are used on the hydrogen and carbon lines. Process control systems with positioners and ball valves with pneumatic rotary actuators are used on the reactors.

Control is performed via the Type 8652 AirLINE valve islands. “Their compact dimensions mean they were easy to install in the control cabinets in the immediate vicinity of the process”, adds Dame. Bürkert could also have supplied suitable control cabinets, but Graforce decided to build its own. “With our systems, we want to keep things in-house as much as possible; perhaps we will utilise this option later on in another project”, adds Dame.

Short communication channels and fast delivery

There were several reasons for opting for Bürkert process control valves. Bürkert has a great deal of expertise in hydrogen applications and the materials used fulfil the special requirements of this area of application. There is no risk of embrittlement or leaks.

Graforce is now also using Bürkert valves in another of its plants. A wastewater plasmalyser that has been in operation for some time has been converted to solenoid valves with a dual coil and Kick and Drop electronics in order to reduce waste heat and power consumption. The coil is initially overexcited by a high voltage pulse in order to generate the high pulling force required to open the valve. After a few milliseconds, the electronics integrated in the compressed coil switch to an energy-saving holding mode. As a result, the valves consume up to 80% less energy than conventional solutions.