Capture and recovery of vapor emissions from a painting facility with an electrothermal-swing adsorption system

Hazardous air pollutants (HAPs) are subject to Maximum Achievable Control Technology standards as specified in Title III of the Clean Air Act Amendments of 1990. There were 5.8×10 ⁸ kg of anthropogenically-generated HAPs released to the atmosphere in 2001. Reduction in HAP emissions can be achieved by capture and recovery with activated carbon fiber cloth (ACFC) using an electrothermal-swing adsorption (ES A) technology. The ESA system consists of two vessels, each containing 2 kg of ACFC, that operate alternatively on a continuous basis. While one of the vessels is adsorbing vapors, the other one is undergoing regeneration. The system runs in a series of continuous adsorption/desorption cycles. A pilot-scale ESA system was evaluated at a painting facility to assess its technical feasibility. Gaseous emissions from the painting facility contained 80-380 ppmv of organic vapors during painting operations. Some of those vapors were HAPs, such as toluene, methyl ethyl ketone, and xylene. The removal efficiency before the occurrence of breakthrough was 99.5 % (± 0.2 %). The liquid recovery efficiency per regeneration cycle was 56 % (± 3 %) of the amount of vapors adsorbed on the ACFC. The energy required to regenerate the adsorbent per unit mass of adsorbed vapors and per unit mass of recovered condensate were 4.3 kJ/g (± 0.3 kJ/g) and 7.6 kJ/g (± 0.2 kJ/g), respectively. Other parameters that were evaluated include the adsorption capacity of the ACFC (0.19 grams of adsorbate per gram of adsorbent) and pressure drop across the adsorption vessel (5-9 in H ₂O) at typical operating conditions. The ESA system was shown to be a promising technology to capture and recover dilute organic vapors from realistic gas streams in the field and to comply with environmental regulations.