(discontinuous phase) are captured by the tight media, where they are retained until they come into contact with additional hydrocarbon droplets and coalesce into larger droplets. Once these droplets grow larger than approximately 1 mm, they force their way through the media as very large droplets. These droplets readily
To SRU
Demonstration vessels
Endur
Envision
Fouling
Additional energy cost
Charge pumps (at Tank farm)
Stripped sour water
Hydrocarbon
Figure 1 Simplified process flow diagram of Torsep installation
With matched particulate removal from solid separators upstream (prefilters), the emulsion separator elements generally remain in service for six months to one year, possibly longer. Performance evaluation The system was installed on a rental basis to demonstrate its effectiveness to the customer. The design parameters for sour water service were based on an operating flow rate of 440 gpm (600 gpm max), at a temperature of 75-105ºF, pressure of 140 psig, and design viscosity and density of 0.8 cp and 1.0, respectively. The system could handle a maximum of 600 gpm inlet flow, but the customer’s sour water system operated at only 440 gpm. A process flow diagram of the system is shown in Figure 1 . The equipment configuration installed at the refinery is shown in Figure 2 . The system was started in February 2019 and has operated nearly continuously since then. The only time the system has been bypassed is for cleaning and element changeout. As shown, the system was installed with one solid separator and one emulsion separator; therefore, during changeout of the elements in either vessel, both vessels were put into bypass. In an optimised installation, it is advised to have two solid separators so that when changing out those filters, the emulsion separator does not have to be put into bypass. The performance evaluation criteria for the system were:
rise through the water phase and collect in the boot at the top of the vessel on the opposite side of the inlet. The hydrocarbon exits through the nozzle at the top of the boot, while the water exits from the nozzle at the bottom. A baffle over the outlet helps ensure the longest possible separation time for the hydrocarbon droplets to rise to the top of the vessel, rather than be drawn out with the water flow. The residence time is typically of the order of seconds rather than minutes and is dependent on the media velocity, as well as the densities and viscosities of the two fluids. The emulsion separator elements offer the following benefits: u Applicability : The coalescing separator elements will meet a broad range of physical and chemical resistance requirements while allowing very high-efficiency separation of aqueous/hydrocarbon or hydrocarbon/aqueous dispersions. v Long online life : Without particulate fouling, the elements are merely reclassifying liquid droplets, and will have extraordinarily long online life. w Ergonomic: The liquid-liquid coalescing vessels are preferentially oriented horizontally, eliminating the need for expensive ladders and platforms, while making it easy for operators to replace elements. x Lower capital cost : Since the coalescer is a single-step process, with liquid disengagement occurring once large droplets are created, the pressure vessel size is reduced by an order of magnitude relative to conventional corrugated plate or other coalescing devices.
• Impact on heat exchanger fouling. • Amount of hydrocarbon recovered. • Filter changeout frequency.
Refining India
19
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