Wide range of possibilities for thermochemical processes – We use high-temperature reactors to demonstrate processes in which chemical reactions take place at particularly high temperatures. To do this, we heat the reactors to over 500 degrees Celsius by irradiating them with concentrated natural or artificial sunlight. Our focus is on thermochemical cycles.
Such processes can be used, for example, to split hydrogen from water, produce synthesis gas and store solar energy in sulphur. Solar reforming, metal recycling and high-temperature electrolysis are further areas of application for high-temperature reactors.
In order to generate the necessary process temperatures from solar energy, point-focussing systems are required that concentrate the sunlight, focus it on a small area and can thus generate temperatures of over 1,000 degrees Celsius. To do this, a radiation receiver absorbs the concentrated radiation and converts it into heat. A detailed understanding of the physical and chemical processes within the reactor is essential for achieving the desired results and for a scalable design of the overall system. For example, our researchers investigate the kinetics of the reactions involved, the transport processes of atoms, molecules and ions in the gas phase and in solids as well as relevant heat transfer mechanisms and develop them further.
Cross-institute research
Fundamental investigations into these processes are carried out using numerical simulations and in the laboratory, including at the CeraStorE competence centre. There, researchers from the Institute of Future Fuels together with colleagues from the DLR Institutes of Engineering Thermodynamics and Materials Research are investigating the use of new ceramic materials for energy technology.
Some of the investigated processes consist of two reactions that differ in terms of temperature levels or gas atmosphere, among other things. We utilise two-chamber reactors (see figure above) to reproduce such processes using solar thermal technology. One example of this is the successive decomposition of sulphuric acid into sulphur trioxide and sulphur dioxide. Separation into two chambers makes it possible to select residence times and temperature levels according to the partial reaction.
Rotary kiln reactor for solar cement production
Filling the storage container with the raw material before starting a test in the simulator.
Another innovative concept for the realisation of thermochemical processes is the rotary kiln reactor. A sophisticated transport system continuously guides the particles through the reactor, where they absorb the solar heat supplied. We use these reactors for the thermal reduction of redox materials. As the reactor contains moving parts, it is a particular challenge to seal the reactor against the surrounding gas atmosphere.
Successful validation on a small scale is typically followed by a field test on a demonstration plant with a thermal output of several hundred kilowatts to one megawatt on a solar tower, for example at the DLR solar towers in Jülich or on CIEMAT's Plataforma Solar de Almería.
