Oil and gas production from wellheads at shale formations generates toxic vapors during initial stabilization of flow between the producing wells and transportation to refinery or at processing facilities. Other important source of toxic vapors is during the temporary storage of oil in condensate storage tanks. Emission of toxic gases during tank venting is known to contribute significantly to toxic vapor emissions (TVEs) released into the environment as losses which are primarily classified as breathing, working and flash losses. This research is focus on the design and testing of a thermal swing adsorption system to capture and recover vapors released into the environment through tank venting.
A bench scale thermal-swing adsorption (TSA) systems was designed and operated at temperature 77ºF and 110ºF to capture and recover toxic vapor release from crude oil and condensate storage tanks. Benzene, toluene, ethylbenzene, and xylene isomers (BTEX) are examples of toxic vapor emitted from storage tanks which represent 9.97% of the mixture of crude oil and condensate sample obtained at a well site (API is 54.2). BTEX adsorption onto a commercially available granular activated carbon was studied at different gas flow rate ranging from 1 sLpm to 6 sLpm, after which the bed was regenerated.
Experimental breakthrough curves for the vapor stream containing 1,000 ppmv BTEX resulted in adsorption capacities for toluene, benzene, m, p-xylene, o-xylene and ethylbenzene on the activated carbon of 215 ± 7 mg/g, 183 ± 5 mg/g, 56 ± 2 mg/g, 9 ± 2 mg/g and 3 ± 0.3 mg/g, respectively with overall liquid recoveries of 30-35% at 77ºF. Different from existing TSA systems, the bench scale TSA system developed has one adsorber and operated for continuous treatment of the TVE in four different phases namely; adsorption, desorption, regeneration with nitrogen and liquid recovery. Most of the BTEX vapor (>90%) was removed during the adsorption phase of the TSA cycle and before breakthrough started to occur which is an indication that the bench scale TSA setup was effective for the removal of TVEs.