Gasification

In thermochemical conversion by gasification, carbon carriers are converted into a gas containing H2 and CO at temperatures above 700 °C using a gasification agent. This synthesis gas is a basic chemical in the chemical industry and the starting point for a wide range of products. In addition to hydrogen and synthetic fuels, it can be used to produce the platform chemicals alcohols, paraffins, olefins and ammonia. The gasification process, which is usually carried out at high pressures for these applications, was originally developed primarily for the conversion of fossil fuels and used worldwide, but is attracting increasing interest for the material utilisation of waste due to its high flexibility.

Pyrolysis

In pyrolysis, carbon-containing waste is thermally decomposed into combustible gases, oils and solid residues at temperatures of approx. 400 - 600 °C in the absence of air. This requires the addition of heat and can be supported by the use of catalysts. It is an established thermochemical process for the production of oil and wax as well as waste treatment for the recovery of metal and fibres from composite materials. The use of waste-based pyrolysis oil in refinery processes as a substitute for naphtha is a favoured method for chemical recycling, particularly of used plastics.

Chemical recycling

Chemical recycling - also known as feedstock recycling - is based on the conversion of carbon-containing waste into chemical building blocks in order to produce new chemical products. This turns waste into resources in the sense of a consistent circular economy and carbon is incorporated into new products instead of being emitted as CO2, as is the case with waste incineration. In this context, we deal with the primary thermochemical conversion of various waste and residual materials through pyrolysis and gasification, including peripheral processes, as well as the technical, socio-ecological and economic evaluation of the entire process chain from feedstock to product. One focus is on the integration of electricity and hydrogen from renewable sources.

Sustainable hydrogen production

Hydrogen plays a central role in the realisation of a climate-neutral economy. The provision of hydrogen itself must be climate-neutral and therefore sustainable. This applies in particular to the hydrogen source and the provision of energy for the production process. Our research focusses on hydrogen production via electrothermal or thermochemical conversion processes. This includes the pyrolytic splitting of methane, which produces so-called "turquoise" hydrogen, and the gasification or reforming of biogenic waste and residual materials with subsequent maximisation of the hydrogen yield.

Hydrogen is a key element in the chemical structure of biomass. This means that biogenic energy raw materials represent a renewable hydrogen resource with high utilisation potential. Using the process of electrothermal or thermochemical gasification, these biomass structures can be broken down at high temperatures and molecular hydrogen can be obtained. If this is followed by a water-gas shift reactor, the hydrogen yield can be maximised and the resulting CO2 can be used as a point source for material use. This method of hydrogen production is particularly sustainable when biogenic residues and waste materials such as forest and wood residues, straw and agricultural waste, but also sewage sludge, fermentation and other residues are used.

Methane is an efficient hydrogen carrier and, in the form of natural gas, is highly available and has huge utilisation potential. When methane is heated to over 1000 °C, it is pyrolytically split into molecular hydrogen and carbon. The energy required for this can be realised both conventionally thermally and electrically via resistance heating or gas plasmas. The carbon is produced in solid form and can either be utilised for the production of soot, electrodes, etc. or stored with virtually no CO2 emissions. If methane pyrolysis is operated using electricity from renewable sources, the "turquoise" hydrogen produced is virtually CO₂-neutral.

CO₂-Neutral mobility

CO₂-neutral synthetic liquid fuels are a climate-friendly addition to electric and hydrogen mobility. Not only can they directly replace fuels from fossil sources, they can also be mixed with them in any ratio (drop-in capability). This enables a continuous transition to these synthetic fuels, including the utilisation of the existing infrastructure for distribution and sales. The current vehicle fleet can also continue to be used. A key area of application in the future will be in areas where electric and hydrogen mobility are reaching their limits. This applies in particular to the aircraft fleet, for which liquid fuels will continue to be indispensable in the near future. The focus of our research work is the synthesisation of "green" fuels based on methanol from laboratory to pilot scale, including catalyst and process chain evaluation.

The production of synthetic liquid fuels is possible in various ways. The primary step is the production of synthesis gas through thermochemical gasification. If biogenic energy sources are used for this, "green" fuels can be produced. An alternative to this is the utilisation of CO2 and electrolysis-based "green" hydrogen as synthesis gas, which is currently under development. Using Fischer-Tropsch synthesis, diesel and paraffin can be produced from the synthesis gas. Another efficient and flexible method is methanol synthesis. Methanol, a platform chemical that can already be used as a fuel itself, is then the starting point for further fuel syntheses, e.g. to produce petrol (MtG process) or dimethyl ether. However, synthetic fuels based on fossil fuels are already supplementing traditional petroleum-based fuels today.