PROJECT DESCRIPTION
BACKGROUND
Organic solvents used in finishing processes are one of the main sources of Volatile Organic Compounds (VOCs) in the tanning industry. Abatement systems built in spray booths to capture powders, pigments and solvents soluble in water, fail to capture VOCs, which flow directly into the atmosphere as vapours. The limits on the emissions of VOCs in the tanning industry are set out in Directive 2010/75/EU on industrial emissions (integrated pollution prevention and control): 75 grams of VOC emitted per square metre of leather produced (for companies that consume more than 25 tonnes of solvent per year). More specific limits are also fixed by the VOC Paints Directive (2004/42/EC); these however are very high. While waiting for a long-term VOCs-free solution, it is important to innovate remediation and abatement processes and technologies to minimise the risk for public health, and in parallel, also recover precious raw materials from air emissions.
OBJECTIVES
The ReVoc4LIFE project aims to design and demonstrate the effectiveness of a full-scale pilot plant to improve the filtration system of spray booths used in the leather tanning process, minimising VOC emissions and recovering solvents contained in the VOCs to be reused in the tanning process. The pilot plant (reaching TRL9 by project end) is expected to reduce VOC emissions from 5,700 kg/year to 1,600 kg/year, and recover at least 2,400 kg of solvents annually. Furthermore, it will help reduce the water consumption of the process by 90%.
The specific objectives of the project are to:
1. Demonstrate the technical and economic effectiveness of the pilot plant over a period of 12 months, including conformity certification with CAPEX < €75,000, OPEX < €12,000/year, and investment payback within 5 years;
2. Increase in the VOC abatement efficiency of the conventional process from 50% (compliant with current regulatory limit) to 90%, with an improved treatment of water and an additional treatment of air, thanks to new adsorption filters, based on already available sintered granules (hereinafter KEU) produced by the pyrosintering of excess sludge from district wastewater treatment (which is considered as a waste);
3. Implement a circular re-use of the KEU for VOCs recovery and air filtering, avoiding the use of other filtering means. In particular, KEU, produced at a wastewater plant treating excess sludge, will be used as a VOCs adsorbent in the tannery’s air filters. The VOC-rich KEU will then be moved to a vacuum desorption plant, to extract and condensate the VOCs, allowing the exhaust KEU to be sent back to the wastewater plant for a complete regeneration;
4. Implement a circular re-use of VOCs in the tanning process, saving fresh solvents, needed to ensure desired surface characteristics of the painted leather. In particular, the soluble VOCs will be collected from the water (scrubbers) and removed by electro-oxidation while water-insoluble VOCs will be collected from the air and filtered out with the KEU granules and then recovered by stripping desorption and condensed for re-use;
5. Reduce water consumption thanks to the use of improved scrubbers to increase water-air surface and VOCs capture capacity, and in-flow water electro-oxidation to decontaminate water for closed loop re-use.
Through this, the project will contribute to the implementation of the following European policies: Industrial Emissions Directive (2010/75/EU); VOC Paints Directive (2004/42/EC); Directive 2008/50/EC on ambient air quality and cleaner air; the Circular Economy Action Plan (CEAP) of March 2020; the Water Framework Directive (2000/60/EC); and the Urban Waste Water Treatment Directive (91/271/EEC).
RESULTS
Expected results:
A full-scale pilot plant will be installed at BCN’s premises with the following impacts at project’s conclusion:
- Reduction of water use of 200 m3;
- Abatement of VOCs emission of 5,000 kg;
- Reduction of consumption of raw solvents of 4,000 kg.
Furthermore, the pilot plant includes 3 devices for VOCs abatement:
(1) VOCs scrubbers, able to reduce water consumption by more than 90%, with an increase of at least 20% in abatement efficiency compared to current systems that do not recover water;
(2) Air filters for absorption based on KEU, able to capture up to 90% of air VOCs compared to less than 55% of best available current abatement process;
(3) Solvent desorption unit based on vacuum stripping, able to recover up to 80% of VOCs, condensing them back into solvents, re-usable in the tanning process.
