CARVOC
CARVOC is the acronym of the R&D project titled “Innovative eco-friendly activated carbon filters for harmful vapors and gases VOC purification”. It is an european project that has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) managed by REA-Research Executive Agency.
Project execution was from December 2012 to May 2015. During these 30 months, different tests at laboratory and pilot scale have been undertaken to achieve project objectives. At the beginning of the project it was estimated a project budget of 1,496,654 €. European Commission gave a funding of 1,187,000 €.[1]
Concept
CARVOC wants to solve the social, environmental and economic problem that represents the emission of VOC (volatile organic compounds) to the atmosphere. Thus, project CARVOC aims to reduce global air pollution, reducing air emissions of harmful volatile organic compounds (VOC) emitted by industries by development of activated carbon filters from agroindustrial waste (hemp shives).
Hemp (Cannabis sativa) was considered the most suitable waste because it represents a sustainable crop with beneficial environmental characteristics. Hemp shives are a suitable feedstock, produced as a waste in hemp fibre extraction. It has advantages for the preparation of activated carbons mainly due to the large amounts of hemp residues generated and its high carbon content. Different methods, for the activation of the residues, has been used for preparing activated carbons with a suitable porous texture for gas and vapour phase pollutant abatement. Moreover, the most frequent and harmful VOC have been selected. Then, adsorption tests have been carried out with the selected VOC, to determine the adsorption capacity of the activated carbons towards those compounds.
| Compound | Formula | Chemical family | Justification |
|---|---|---|---|
| Toluene |  |
BTEX | High toxicity and abundance (chemical industries) |
| Acetone |  |
Ketone | Involved in food and chemical industries |
| Propanol |  |
Alcohol | Involved in breweries |
| n-hexane |  |
Alkane | High abundance (chemical industries) |
| Butyraldehyde |  |
Aldehyde | Involved in waste treatments and disposal |
| Methanethiol |  |
Sulfur compound | Involved in waste treatments, disposal and wastewater treatment plants |
| Dichloromethane |  |
Chlorinated | High toxicity and abundance (chemical industries) |
| Butyric acid |  |
Volatile fatty acid | Olfactory nuisance |
| Triethylamine |  |
Amine | Olfactory nuisance Involved in chemical industries |
| Ethyl acetate |  |
Ester | Solvent use |
| Hexene | - | Alkene | High abundance (chemical industries) |
In CARVOC, the Small and Medium Enterprises (SME) have benefited from the R&D conducted by the Research and Technological Development performers (RTD). From the R&D activities, activated carbon filters with improved structural and functional features have been obtained. These activated carbons tailor-made for the purification of VOC can outperform most commercial carbons. Moreover, CARVOC helps to reduce the current 26% activated carbon imports rate by producing a competitive activated carbon made of EU-born hemp wastes.
CARVOC is an interdisciplinary project involving aspects related to valorisation of natural waste, gas treatment systems for the VOC purification, development of activated carbons from natural waste, carbonaceous materials, VOC abatement, VOC adsorption and development of different forms of synthetic carbon and filter systems.
Objectives
Project Consortium distinguish between scientific and technological objectives.
Scientific objectives
The scientific objectives of the project are:
- To get a better understanding about the influence of the different experimental conditions, especially the different activating agents, on the physical form, porosity and/or porosity distributions of the activated carbons prepared from hemp fiber residues. This was achieved by a systematic study of the impact of the different activation conditions on the porosity of the prepared samples.
- To increase the understanding of the effect of scaling up the preparation procedures of the activated carbons in their final properties. This goal was achieved comparing the properties of the activated carbons prepared at laboratory scale (g), and by using industrial equipment (kg).
- To achieve a better understanding of the optimum agglomeration conditions to prepare agglomerated activated carbons with similar porous textures than the original ones (less than 20% porosity loss after agglomeration) and having good mechanical properties. This objective was achieved exploring how the experimental agglomeration conditions affect the porous texture and mechanical properties of the prepared activated carbons.
- To demonstrate the potential for producing activated carbon monoliths from hemp and their comparison to phenolic resin derived monolithic carbons.
- Get a global approach of the anthropogenic sources of volatile organic compounds by screening the industrial emissions of VOC in Europe so that the research program targets the actual compounds involved in atmospheric pollutions.
- Increase the understanding of the adsorption process and especially the relationship between the properties of the activated carbons and their abilities to remove the VOC. For that purpose, the adsorbents must be fully characterized (physical structure, chemical composition, functional surface groups) and the kinetics and equilibrium studies are necessary for a comparison of the different adsorbents. From the previous selection of VOC (pure and in mixtures), the best activated carbons will be determined and other pathways toward higher efficiencies would be enlightened.
- Enhance knowledge in the field of air treatment by combining the adsorption with the absorption process in order to remove poorly adsorbed VOC. Possibly, some VOC would not adsorb onto the activated carbons. In those particular cases, the absorption process is another option that will be carried out for a complete VOC removal.
- Demonstrate that efficient regeneration of the newly developed carbons is feasible (steam, hot nitrogen or electrothermal regeneration) as this is critical for the use of these materials in commercial VOC treatment systems.
Technological objectives
The technological aim of the project regarding the activated carbon and filtering systems sectors is the development of a new activated carbon (from hemp) for VOC/TIC abatement with new and better adsorption properties and acceptable regeneration properties compared to the current activated carbons.
The specific technological objectives of CARVOC project are:
- To prepare optimum activated carbons (at gram scale) to retain organic compounds.
- To demonstrate that this can be extended to kilogram scale to allow realistic process evaluation and to use this to understand the commercial potential of the materials.
- Development of an activated carbon based on hemp wastes to obtain an activated carbon filter to be used in a filtering system. The activated carbon developed must have a high capacity to adsorb harmful VOC that are emitted by the European industries that use organic solvents in their production processes.
- To establish the required experimental activation conditions to prepare activated carbons from hemp fiber residues with the desired porosity and/or pore size distributions (microporous activated carbons with specific surface areas above 1000 m2/g) to retain the desired organic compounds at different concentration ranges and/or experimental conditions.
- To establish and develop the optimum experimental conditions to prepare agglomerated activated carbons from the previous materials.
- To guide industrial partners towards the optimum activation and agglomeration conditions to prepare the final activated carbon filters to be used for the organic compounds’ adsorption.
- To trigger the design of an industrial filtering system using a numerical model especially developed for the adsorption of VOC onto activated carbons. From the experimental data obtained during the adsorption study, the numerical simulation of the adsorption process is enabled using adsorption models that were developed from previous works. The model would be used and its predicting abilities will be assessed for a variety of VOC and adsorbents. Consequently, the model might be improved to describe the adsorption with a greater accuracy. The objective will then be to run numerous tests, in various conditions, to determine the best operating conditions (flow rates, concentrations, regeneration mode) and to ensure the best efficiencies of the filtering system at a minimum cost. Likewise, the simulation tool enables the prediction of the temperature profiles inside the bed as well as the cost of the regeneration of the filter. Hence, an economic survey is considered. Within this the demonstration of effective regeneration will be critical.
- To allow the design of new and more cost effective personal protection devices suitable to be used by the general public and the emergency services based on either monolithic or carbon fibre based adsorbents.
The challenge
- To solve the social, environmental and economic problem that represents the emission of VOC to the atmosphere.
- To develop innovative activated carbon filters based on activated carbons produced from agricultural wastes, capable of adsorbing VOC emitted by highly pollutant industries.
- To develop improved and cost effective VOC filtering material for mask and industrial filtering purposes for VOCs.
- To increase the value of hemp which represents a sustainable crop with beneficial environmental characteristics.
Results
Final project results have been achieved thanks to all project partners works:
- Activated carbon as filtering material made of hemp. Competitive Activated Carbons (ACs) where obtained using the residues from hemp industry by means of chemical activation. The production strategy optimised in CARVOC allows high yield (40-50%) and a well-developed porosity (>1,500 m2/g). The production parameters influencing the micropore-to-mesopore ratio were identified, enabling the preparation of tailor-made absorbents. The suitable equipment to scale-up the production of ACs to the kg and Ton scale was successfully identified and repeatability of lab-scale results was validated.
- Evaluation of the compatibility of the new adsorbent(s) with main organic solvent gases and vapor (VOC) to be purified. The removal of 10 relevant pollutants originated by chemical and food & beverage industries were evaluated. A benchmarking study revealed similar efficiency of the hemp-derived AC in comparison to those commercially available. An in depth analysis with 3 molecules of different nature (toluene, hexane and propanol) shown that the retention capacity for the innovative ACs was higher than for commercial Steam Activated Coal. The correlation between the more relevant carbon parameters and the performance was established with a theoretical model.
- VOC recovery is critical for the economic viability of particular industrial sectors using large amount of volatile solvents. Such is the case of paint manufacturers, industrial printing and laboratories of chemical synthesis. A preliminary evaluation of VOC recovery was performed in a purpose-made pilot filter during CARVOC project. As a result, a set of detailed instructions was provided to adapt the innovative ACs for the particular specification of this application were both hardness and thermal stability are of great importance.
- Industrial filtering systems with the new activated carbon filter. Industrial filters with an EU based AC have proved feasible in CARVOC Project. The strategy for AC conformation was successfully developed at the lab-scale by using cellulose as a binder. Pellets of AC with sufficient hardness to be used in large filters were obtained. In addition, one SME involved in CARVOC has developed a Pilot Activation Plant that can reproduce the characteristics of ACs previously developed at lab-scale. The large output capacity of the pre-industrial facility enables full-scale demonstration in large industrial filters for VOC abatement.
- Personal protective equipment with the new activated carbon filter. Advanced conformation strategies were developed by CARVOC partners in order to manufacture carbon monoliths with an intricate channel structure, using hemp waste as a precursor. A careful selection of the binder and thorough optimization of the conditions allowed to obtain monoliths of Activated Carbon with excellent mechanical properties. Such methodology has been suggested as a renewable alternative to petroleum derived resins, currently used as precursors for advanced conformation.
Participants
The 7 partners of CARVOC are:[1]