Issue link: https://geospatial.trimble.com/en/resources/i/1415432
62 Spring 2019 KI-impregnated carbon is extremely selective towards H 2 S and allows for very high efficiency, removing more than 99.9% of H 2 S. KI is not consumed during this process and acts as a catalyst for the chemical destruction of H 2 S into elemental sulfur (in solid state), which builds up on the pores of the activated carbon, clogging them over time and making the diffusion of molecules into the pores almost impossible. When this happens, the activated carbon is exhausted and must be replaced. Such carbon beds can be designed to accommodate for the desired or convenient replacement period (from 6 months to 2 years). Case studies All of these methods of effectively controlling VOC emissions resulting from crude oil loading have been used by AEREON in applications within the storage and distribution industry. One project in the Far East involved unloading sweet crude oil into a storage cavern from sea-going ships and subsequent ship loading from the cavern. The cavern provides a fixed large storage volume, which is not vapour balanced (i.e. there is not a floating roof ). As such, during loading operations, vapours are displaced and must be sent to vapour control treatment. The design loading rate, from a single ship loading or unloading, is 11 000 m 3 /hr. During ship loading, from the dock where the ship is moored, vapours are moved by two 50% centrifugal blowers to two 50% VRU trains; each VRU discharges the exhaust vapours into a single VCU. During crude unloading from ship to cavern, vapours are moved from the cavern to the two VRUs by means of over-pressure. This solution has been operational since 2009 (Figure 3). Intermediate and alternative operational cases are possible during maintenance and emergency, as shown in the process sketch of the adopted configuration (Figure 4). A more recent case study concerns an application in Europe, involving ships loading sour crude. The design loading rate is 6000 m 3 /hr from a maximum of two ships loading simultaneously. The vapour control solution engineered and put in place is summarised in the following configuration (Figure 5): Three blowers (two 50% and one spare) to move the vapours from the ship tankers through the system. Two 50% twin carbon adsorption VRUs. Two upstream sacrificial carbon beds (one operational and one spare) per VRU to remove H 2 S. Both VRUs discharge exhaust vapours in a single common VCU. Alternative operational cases are not possible because of the stringent emission requirements of the industrial area where the unit has been installed. This unit (Figure 6) was installed in 2018 and recently started up. Conclusion VOC emissions from crude oil loading operations at storage and distribution terminals have a significant impact worldwide. Traditional vapour control technologies applied to crude oil are not always effective at controlling VOC emissions, thus setting the basis for further technological developments. One solution lies in H 2 S removal using a sacrificial bed and a combination of recovery and combustion, a process that has been successfully carried out at two loading applications worldwide. Figure 6. 3D model of the vapour control plant installed in Europe. Figure 5. Process scheme of a vapour control solution installed in Europe. Figure 4. Process scheme of a vapour control solution installed in the Far East.