Vapour Recovery Systems worldwide

Recovery of hydrocarbon vapours produced by the storage and handling of oil based products and other volatile organic components is increasingly gaining momentum versus combustion of the vapours. Debit to this are of course the elevated price of crude oil and its derivatives, environmental issues like the reduction of CO2 emissions and last but not least the operational cost of enhanced combustion or incineration, due to the consumption of large amounts of assist gas (propane) to facilitate combustion of vapours from inerted liquid bulk carriers.

CarboVac is one of the major suppliers of Vapour Recovery Systems worldwide, providing an innovative and reliable technology based on adsorption on activated carbon, regeneration of the activated carbon by vacuum and recovery of the desorbed vapours preferably in one of the products stored on the terminal. The system is fully flexible regarding throughput and concentration variations from 0 to 100% of the design values. The system does not need peak shaving devices such as gasholders. Usually the pressure developed in the product carrier is sufficient to transport the vapours through the activated carbon beds. In case not enough pressure is available we install a ventilator in the outlet of the VRU to assist the vapour flow.

CarboVac was formed by the members of the vapour recovery department of Symex SA, who went bankrupt in 2005. The technology developed by CarboVac is the most energy efficient one available on the market today and provides numerous advantages compared to the technologies supplied by others. The use of frequency controlled dry screw vacuum pumps allow for an optimal adjustment of the required vacuum capacity to the mass of hydrocarbons to be recovered. The process is fully automatic and controlled by PLC. The process parameters are visualized by a PC based supervision system which keeps records of all events of interest for the end user. The operational parameters of the system can be accessed via a secured internet connection (VPN) to anywhere in the world to assist operators in fault finding and to optimize operational conditions. The system enables full modulation of the regeneration process of the activated carbon and together with a unique way of distribution of the vapours through the carbon beds the carbon life time is quasi infinite.

CarboVac vapour recovery systems are in use on all types of liquid product storage and loading facilities and for a large diversity of applications. Most recent projects of interest are VRU’s put in operation on large marine loading facilities for the loading of light fuels, bio-fuels, pure benzene, oxygenates, aromatics and crude oil with loading capacities ranging from 1000 up to 14 000 m3 of product loaded per hour. The recovery efficiencies targeted are in the range of 99% recovery. The standard emission levels of a CarboVac VRU are around 1 g of hydrocarbons per m3 product loaded. A lower emission level, as is currently envisaged in Holland and although technically not a problem, will drastically increase the energy consumption of the unit and therefore have a negative effect on the environment, due to secondary emissions from the electrical power plant in the form of rest hydrocarbons, COx, SOx and NOx (Environmental Balance Dilemma). Benzene and other aromatics are very well removed from the vapour mixture, resulting in standard emission less than 1mg/m3.
Methane however is difficult to remove and is usually excluded from the emission requirement.

CarboVac VRU’s are in operation in diverse climatological circumstances. In Russia the units are operating at extremely low ambient temperatures of -40°C, whereas in the Middle East, Australia and Africa the high ambient- and product storage temperatures in the summer of up to +50°C  need to be catered for. The design of a VRU for hot climates also needs to take special care for sun radiation on metal surfaces and the occurrence of sand storms.

The recovered product from most oil based fuels consists mainly of light hydrocarbons (for example 10% C3, 35% C4, 40% C5, 10% C6, some aromatics and others). The vapour pressure of this mixture at ambient temperature may be as high as 4 bar abs. The recovered vapours are usually (and most simply) re-absorbed in one of the products of the terminal. For this a simple scrubber type of column is used connected to one or two of the storage tanks. At reasonable turnover of the product in storage tank the increase of vapour pressure of the product will be negligible. Usually the product with the highest daily throughput is used as absorbents. The efficiency of the scrubber drops with increase of the vapour pressure and temperature. In extreme cases it might be necessary to cool the product.

Recently a VRU for the recovery of gasoline vapours at the truck loading facility of WOQOD in Qatar was put in operation. The specification of the product used for absorption is such that at extreme ambient temperature and maximum RVP of the product in summer the maximum limit for the vapour pressure could not be guaranteed. Cooling water is not (usually) available on site. CarboVac installed an air cooled chiller system with cold recovery to cool the absorbents to the top of the scrubber during peak summer conditions. By recovering the cooling energy in a 2 stage heat exchanger system, the energy consumption of the chiller system can be reduced by more than 60%.

CarboVac is willing to assist her potential customers early on in the project phase to develop the best solution for any typical application without any obligation.