A containerised reverse‑osmosis (RO) desalination package is to be supplied for an unmanned gas platform in the North Sea by Salt Separation Services of Rochdale, UK.
The £ 1.1 million contract was placed for the F15-A well operated by Total E&P Nederland, the performance of which has been reduced by salt deposition. Seawater is to be treated and injected to the well riser to dissolve the salt.
Due to the fact that the platform is unmanned, the use of chemicals has been limited as far as possible. It has also been designed to operate automatically.
The innovative solution from Salt Separation Services includes:
· Over-sized prefiltration to improve filtration efficiency and reduce the frequency of disposable filter changes.
· Two-pass RO system with only one high pressure pump to reduce package footprint and weight, whilst also simplifying the process and controls.
· Recycling of second-pass RO concentrate back into first pass RO feed to dilute the influent seawater and increase the net overall recovery.
· Reduced first-pass RO recovery to remove the requirement for antiscalant dosing.
· RO arrays designed at low flux rates to reduce potential fouling.
· No clean-in-place system – thereby reducing package footprint, weight, complexity and cost. Due to the relatively low number of RO membrane elements (3 x 8 in and 3 x 4 in) a cost-benefit exercise identified that RO membrane replacement instead of RO membrane cleaning would be the most cost-effective solution.