Boosting efficiency of activated carbon treatment at a waste treatment facility
Activated carbon is a widespread and highly efficient treatment for emissions from the waste management sector. DESOTEC has the expertise and equipment necessary to ensure that filtration set-ups are always optimised to enable customers to remain in compliance in the most efficient, cost-effective and sustainable way possible, as this case study from Italy illustrates.
Key takeaways
- DESOTEC can carry out full industrial tests rapidly to demonstrate that our solutions meet a client’s needs.
- By using filters in series, companies can be assured of meeting even very low emissions limits at all times.
- Filter design can make all the difference to the efficiency of an activated carbon solution.
The challenge
This Italian company manages hazardous waste from industrial sources at one of its sites. This includes the preparation of plastic waste for incineration or other forms of disposal.
The plastic shredding process releases emissions containing solvents and volatile organic compounds (VOCs), mainly xylene, styrene, toluene and ethyl acetate. Concentration levels are usually around 300 mg/ m³, but peaks sometimes surpass 1g/ m³.
The company has to comply with a very low limit of 20 mg/ m³ of VOCs. Therefore, the emissions are extracted to a dust filter and a fixed activated carbon filter for treatment.
However, the company had to exchange the nine tonnes of carbon every three weeks, and often found the filter had a breakthrough, especially when VOC peaks occurred. . In addition, emptying and refilling fixed filters is a messy process involving a lot of staff hours and downtime.
This inefficiency was mainly due to the design of the fixed filter, with poor air distribution in the filter bed. Additionally, it was filled with a mineral carbon grade that was not well suited to the task.
Therefore, the company began exploring more efficient alternatives. One option was to install a regenerative thermal oxidiser (RTO); however, such installations are major investments, and energy consumption would be high at this site due to its discontinuous operations.
DESOTEC already worked with this company at some of its other Italian sites. Following a webinar that we gave about RTOs compared with our mobile activated carbon filtration solutions, the client contacted us for a solution.
The solution
We recommended two of our largest filter models, the AIRCON V-XL, which requires installing a simple base.
The client decided first to test our solution with two AIRCON H filters, which do not require a base. They contain a total of six tonnes of renewable microporous carbon – the optimal grade for this type of application.
It was simple for the client to modify the piping to bypass the existing fixed filter and send the air flow of 25 000 m³/ h instead to the two mobile filters.
They are placed in series, with the second adsorbing molecules only when the first becomes saturated or when there is a peak in concentration levels.
This set-up is more efficient, as it means that companies can allow the first filter to become fully saturated before exchanging it, while remaining in compliance with the 20 mg/ m³ limit.
When the first filter is exchanged, the second filter is moved into first place and a new filter placed downstream.
The results
Tests show that the mobile filters adsorb roughly double the amount of solvents and VOCs as the old fixed filter. Their loading capacity is around 18%, compared with 9% for the fixed filter.
The filters need to be exchanged roughly once a month – a simple process that requires minimal production downtime.
On the basis of these tests, the client gave the go-ahead for permanent bases to be installed for two larger AIRCON VL models in the next phase of the project. These will allow a longer time between exchanges, further improving efficiency.
After exchange, the filters are transported by DESOTEC to our facilities, where the spent carbon is emptied, sampled and sorted.
It is then thermally treated, destroying the adsorbed VOC and solvent molecules. The carbon is then reactivated for reuse, cutting the customer’s costs and improving circularity.
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Our unique service
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VOCs and Solvents
It’s vital to reduce VOCs and solvents in air emissions to protect occupational health, maintain air quality, and avoid contributing to climate change. -
Waste and wastewater management
Sustainable air and water purification for waste management and recycling to protect our environment and control odours.