Project
Flowchar

Idea behind FlowChar is to combine two processes:

Renewable heat and power
generation from
the syngas produced through
biomass gasification

Clean water production using
flow-electrode capacitive
deionisation (FCDI)
of brackish or sea water

FLOWCHAR
– learn more about the project

Inspiration

The development of the power, heat, and desalinated water polygeneration system based on renewable resources and aligned with the principles of a circular economy.

What motivates us?

To achieve net-zero emissions and mitigate climate
changes, we must rely on the sustainable energy
production. Meanwhile, depletion of clean water reserves calls for efficient and affordable technologies for water purification and wastewater treatment.

Potential application of polygeneration systems

Combined energy and clean water production could be used in a variety of remote locations where grid connection is difficult. This solution would be particularly suitable for the agricultural sector that produces a substantial amount of waste biomass and has a large water demand.

Locating such systems close to brackish or sea water would allow for biomass utilisation and clean water production on site, eliminating the environmental impact of transport, which is in line with the distributed generation policy, while respecting the principles of the circular economy by implementing the closed cycle of energy and water production.

1^st process
Biomass
gasification

The process of thermochemical conversion of biomass feedstock (e.g. forest or agricultural residues) into calorific gas that can be combusted for heat and power generation, or transformed further into chemicals in a biorefinery.

The process begins with the release of the volatile compounds from the feedstock, creating a mixture of gaseous and condensable products. Meanwhile, the remaining carbonaceous matter reacts with the provided gasifying agent, such as O₂, CO₂, or steam. This way, additional carbon is converted from the solid state into combustible gas, while the surplus of the residual material, called char, develops a highly porous structure.

2^nd process
Flow-electrode capacitive deionisation

Capacitive deionisation can be used for water desalination, where the ionic contaminants are removed from the feed due to the electrical potential difference applied to the two electrodes.

The applied voltage charges the electrodes and attracts the cations and anions from the feedwater. Clean water is collected at the outlet of the cell, while the ions are retained on the surface of the electrodes, forming the electrical double layer. The sorption step is followed by desorption, when ions are released by reversing electrodes charge. In consequence, a stream of concentrated salt solution is obtained.

Flow-electrode capacitive deionisation is a recently developed approach to the classical CDI. Instead of the solid electrode, the conductive slurry of carbon particles flows through the dedicated channels. Thus, the adsorbed ions are constantly removed from the cell, allowing for the continuous operation.

Why integrate gasification with FCDI?

We believe that the application of the otherwise surplus or useless by-products of each of these processes has the potential to improve the effectiveness of the other one.

By-products:

Gasification char

Biomass gasification creates calorific gas used for heat and power generation. Meanwhile, the surplus solid residue called char accumulates in the reactor. Char is abundant and highly nonhomogeneous, however, potentially useful as an alternative for commercial activated carbons due to its well-developed surface area and good electrical capacitance.

Sodium

Capacitive deionisation of brackish or sea water involves the removal of sodium ions via their adsorption on the surface of the charged electrodes, the regeneration of which generates waste in the form of salt brine. However, sodium has also a well-documented ability to catalyse the thermochemical conversion of carbon, e.g. during biomass gasification.

WORK PACKAGES

Questions and challenges

What if...?

What if we could use the gasification char as the material for flow electrodes in the desalination cell so that it would capture Na⁺ ions?
What if we could direct the char saturated with Na⁺ back to the gasification process, thus enhancing the biomass conversion?

The feasibility of this concept requires answers to three fundamental questions:

Can biomass gasification provide the char that meets the requirements for the flow electrode material?
How well will this char perform during the water desalination?
Will the Na-saturated char improve the biomass gasification process?

The scope of the FlowChar project is to verify each of these questions via a dedicated work package.

WP 1

Char preparation and analysis

WP leader:

Agnieszka Korus

The objective of this work package is to prepare biomass gasification char that can be utilised as a flow electrode for the purpose of water desalination.