PORTABLECRAC. PORTABLE SOLUTION FOR THE ELECTROCHEMICAL REGENERATION OF ACTIVATED CARBON
In 2017, the global activated carbon market accounted for 4 billion dollars and the demand trend shows an exponential growth in the oncoming years.
Currently, both the water and the chemical sectors require large quantities of activated carbon for the elimination of certain water pollutants. During the filtration process, as water flows through the carbon, the contaminants get adsorbed until a saturation point is reached. Then, a carbon replacement or a regeneration is required. When saturation happens in facilities with small volume of carbon, the preferred option is to extract it, dispose it in a landfill or incinerate it, and replace the filter media with virgin carbon. However, in bigger facilities is more common to regenerate the carbon thermally. Both practices require laborious extraction, transport and carbon losses with significant environmental and economic impacts.
The critical point for the EU is the high cost of the process, which becomes even more expensive given that Europe imports around 80% of the domestic consumption of activated carbon. Nowadays, the most widespread activated carbon regeneration technique is thermal regeneration. In spite of being able to reduce costs up to 50%, the treatment has a high cost, mainly associated with energy consumption and the need for external services.
In order to improve the operational flexibility of the process and achieve a significant reduction of environmental and economic impacts, Portablecrac proposes an ambitious alternative: in situ regeneration of activated carbon by electrochemical treatment. When a voltage is applied between two electrodes in a compartment filled with exhausted carbon and acidic electrolyte, the porous material is polarized, modifying the adsorption equilibrium of the retained species. In this way, the desorption of most of the contaminants and a significant recovery of the initial properties of the activated carbon is achieved. It is an environmentally and economically beneficial technology, capable of regenerating spent activated carbon in small, medium and large industries. Currently, there are no portable solutions that offer this service.
The Portablecrac project, funded by the European Program Horizon 2020, is structured in three technical phases of work. Firstly, prototypes will be designed and adapted for the regeneration of carbon, which in a second stage will be technically and economically validated. Furthermore, there will be an investigation carried out to determine the best treatment for the electrolyte in order to either reuse it or discharge it legally. The compact and portable nature of the equipment will allow the demonstration and integration of the technology in existing installations and other industrial scenarios.
During the execution of the project, it is intended that the electrochemical technology evolves from its operation in discontinuous mode to continuous mode; thus, the optimal scaling of the prototypes will be achieved to meet the needs of potential users.
THE PROJECT’S STRUCTURE
Three different prototypes will be developed in order to adapt to the customer’s regeneration needs.
- Batch prototype. 100 kg capacity of activated carbon in discontinuous operation. The prototype consists of two compartments, with their respective electrodes, separated by an ionic membrane. This design is recommended for facilities with low regeneration needs.
- Vertical prototype of fixed/mobile carbon bed with fixed electrodes. Vertical cylindrical reactor with the option to operate in continuous or discontinuous mode. Focused to meet the regeneration needs of medium-sized facilities.
- Prototype of bands with moving carbon bed. Based on the principles of sludge electric dewatering technology by band filter, this prototype, which operates in continuous mode, is proposed. The electrification of the bands is combined with the dosage of pulverized electrolyte. It will offer service to facilities with greater regeneration needs.
The described prototypes depend on the current that can be supplied, either by a conventional source or directly by a renewable energy source. Once the current is set to meet the established current density, the electrical voltage depends on the distance between the electrodes and the electrolyte concentration. The electrolyte, composed of 0.5M sulfuric acid , is recirculated at a flow rate for the desired residence times. Optimal treatment times vary between 1 – 4 hours.
The automation of the process provides total control of the regeneration in each of the prototypes. Thus, it will be possible to scale the amount of activated carbon to be regenerated, modify the process times and vary the electric current to be applied.
Technical and economic validation
The technical validation will take into account several aspects:
- Correct operation of the prototype according to its technical and functional specifications
- Assessment of the electrochemical regeneration efficiency
- Ensure the compatibility of the prototype with the current operating conditions in the chemical and water industries
- Evaluation of operational and environmental risks
Additionally, a complete feasibility study, which will identify and quantify the expected economic benefits, will be carried out. Based on the technical results and the analysis of the life cycle cost, the equipment will undergo an economic validation:
- Assessment of the consumables availability in order to ensure a minimum supply.
- Estimation of the cost associated with the possible adjustments required
- Profitability analysis against the economic margin of improvement
- Ecodesign development in prototypes, exploring the proper use of resources with the least possible impact on the society and the environment.
Initially, Portablecrac will allow the regeneration of saturated activated carbon in water treatment plants and chemical industries in Spain and Portugal. Subsequently, the results will be transferred to different industries in the rest of Europe with similar needs.
In order to achieve the zero-waste discharge a system to treat active carbon regeneration effluents is being designed, so that organic and inorganic pollutants are degraded or stabilized prior to their final disposal.
Accordingly, the AC regeneration process proposed by PORTABLECRAC is very versatile allowing both the regeneration of AC when exhausted and the transformation of contaminants.