Exxonmobil refinery Rotterdam orders multiple domes from CTS:
As part of a program reducing refinery emissions CTS was contacted in 2006 to support a design review for several ExxonMobil tanks, and to study options to reduce emissions of volatile organic carbons from these tanks. CTS presented an approach where installing aluminium domes would significantly reduce emissions from external floating roof tanks being converted to internal floating roof tanks.
Storage tank emissions and their volume largely depend on direct exposure of floating roofs to sun radiation (heating up the tank contents), and the wind speed directly above the floating roof. As aluminium domes shield the formerly external floating roof from direct sun radiation the temperature of the product stored in tanks equipped with an aluminium dome roof goes down significantly. Right now API is conducting a temperature survey to express this effect correctly in emission calculations.
Second aspect contributing to tank emissions is the wind speed, and aluminium domes eliminate wind influence on former external floating roofs as well. This also reduces emissions, as the evaporation of hydrocarbons and chemicals increases when wind disperses vapours, and reduces when wind effects are not significant.
| Emission aspects ExxonMobil RAP tanks: |
| Description: |
Emissions per annum: |
Emission reduction (%): |
| Emissions for reference fixed roof tank (BREF Storage tanks 2005, IPPC) |
20,513 kgs |
0 |
| Emissions for tank with external floating roof, double seal |
1,708 kgs |
91.7% |
| Emissions for tank with internal floating roof, double seal |
184 kgs. |
99.1% |
The domes distributed by CTS even do allow further improvements to tank configurations, and multiple domes have been installed that are sealed off and fitted with P/V vents (pressure vacuum vents, only opening at certain internal under- or overpressure). Using a dome with a P/V-vent will reduce breathing losses from tanks (typically introduced by the temperature difference between day and night). One major aspect in selecting CTS as a dome supplier on the tanks involved was the fact that CTS introduced vapour tight domes, and also has offered the opportunity to install aluminium domes that could be converted to pressurized domes in later stages. This as ExxonMobil also wants to have the opportunity to reduce emissions even further in the near future, if required.
Apart from reducing emissions the aluminium dome will shield the floating roof and its appurtenances which also will reduce the maintenance requirements for the external floating roof as coating and materials are not exposed to weather conditions.
Per the end of 2007 one ExxonMobil tank was satisfactorily converted, and the other tanks will follow in due time.
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