Published on May 29, 2024
The electro-bioreactor for industrial scale
Electrochemical and electro-biotechnological processes take place primarily at the interface between the electrode and the surrounding solution. In order to achieve high conversion rates, the ratio of electrode surface area to solution volume must be maximized. Particle electrodes in the form of fixed or fluidized bed electrodes offer not only a large surface area but also the advantage that the biocatalysts required for the reactions, e.g. enzymes or microorganisms, can be fixed to the particles of the electrode. This prevents the expensive biocatalysts from being washed out during continuous process control. In addition, the close proximity of the electrochemical and biocatalytic reactions results in short material transport paths and therefore accelerated reaction kinetics.
Solid basis, limited scaling
Established electrochemical reactors based on fixed-bed electrodes or stacks of electrode plates, expanded metal meshes or carbon fabrics have proven their worth on a laboratory scale, but are only scalable to a limited extent for large-scale industrial applications due to their design. The possible operating time of electrochemical reactors with fixed biocatalysts is often limited to a few days to a few weeks at most. Clogged fixed-bed electrodes, deactivated biocatalysts or electrode particles that have exhausted their function are just some of the problems. As a result, reactions must be stopped and the electrode particles or plates and the biocatalysts fixed to them must be replaced regularly. As the reactor diameter increases, the resulting electron transport paths between the working and counter electrodes also increase and the voltage losses become too high for economical operation.
Another problem with scaling is the efficient cooling of large reactors. External, uniform and constant cooling of the entire reactor is complex and temperature regulation inside the reactor is sluggish. The circumstances described lead to functional losses and therefore to insufficient efficiency in upscaling.
Industrial companies therefore have a need for particle electrode reactors that are characterized by optimized charge transport and thus fast reaction kinetics, uniform cooling and electrode particle exchange without interrupting reactor operation.
Design with interweaving
Researchers at KIT have developed a reactor type that solves the described disadvantages of the state of the art through a special design. What is new is the three-dimensionally interwoven arrangement and design of the particle electrode chamber as well as the design of the counter-electrode chamber. The arrangement of the counter electrode inside the particle electrode minimizes the electron transport paths and makes them more uniform in the particle electrode chamber. The design of a uniform arrangement of membrane-encased, hollow cylindrical counter electrodes, placed inside a common, fluidized particle electrode, promises less energy loss and enables internal cooling. This arrangement also allows the diameter of the particle electrode to be scaled as required with constant charge transport paths. The electron transport paths can therefore be kept short even in large reactors and the system is industrially scalable without any loss of efficiency. The technology also solves the need for an electrochemical reactor type that allows the electrode particles or catalyst carriers to be replaced quickly and easily. The complete replacement can be carried out within a few minutes without dismantling the reactor housing and the partial replacement can even be carried out during operation.
Perspective of industrial electro-(bio)technological production of chemical base materials
The new design enables the construction of modular, scalable particle electrode reactors for the first time. These have great potential for the use of sustainably generated electrical energy for the production of chemical raw materials that can be used in biotechnological processes. One example is the electrochemical conversion of CO2 into organic compounds such as formic or acetic acid. Another example is the electroenzymatic reduction of CO2 to methanol. The latter requires reactor volumes of up to many cubic meters for the production of biofuels.
An initial prototype on a liter scale was produced as part of a collaborative project. The aim of the industrial partner is to produce renewable methanol using an electroenzymatic multi-stage process. To this end, the reactor type is to be scaled up to an industrial scale in the future.
The collaboration in this first cooperation project concerns the application area of reactions with direct electroenzymatic charge transfer. For other, purely electrochemical applications, for example, the KIT researchers are looking for further industrial partners.
comments about this article
No comments