Methanol Regeneration

 

A cost-efective system to help ensure the ow o deepwater production across extended distances has been developed by Paragon Engineering Services o Houston !he application o this system is ma"ing the newly announced #illiams $anyon Station pro%ect in the &ul o 'exico viable while helping to advance the industry(s deepwater development capability capability )sing a distillation process* Paragon has produced a system or the efective recovery and reuse o methanol as a hydrate inhibitor inhibitor +epending on the operating conditions* #illiams is expected to recover about ,-./0 o the chemical or re-in%ection using Paragon(s design application  !he methanol regeneration process process is expected to bring bring an estimated cost savings o 12/*///3day while successully producing the // ''c3d o gas rom deepwater subsea wells !he saving ma"es the pro%ect economically viable !he subsea wells are located in up to ,*4// t water depth* representing the &ul(s deepest subsea development to date Production is expected onstream by summer 4//4 5perators have used nominal amounts o methanol or many years to inhibit the ormation o hydrates* which can bloc" production ow in piping However* its use on the #illiams pro%ect represents an expanded application in terms o volume and importance to a deepwater pro%ect6 !he landmar" pro%ect calls or the efective storage* regeneration* and distribution di stribution o 7*.// b3d - or about  gallons3minute - o methanol

Project scope 8ewbuild acilities or $anyon Station call or a shallow-water platorm destined or 'ain Pass 9loc" 427:P in 4.. t water depth to accept deepwater production rom nine subsea wells in three ;elds6 Aconcagua* $amden Hills* and / degrees ? can cause hydrates to orm at the wellhead and in the pipeline ecovered ecover ed methanol plus ma"e-up - due to losses in the gas and hydrocarbon liDuid phases - is in%ected into each o the wells to efectively inhibit the ormation o hydrates and ensure gas ow throughout the entire system  !he ;rst step o the process process on the $anyon Station Station platorm involves separating the liDuids rom the gas through two* /0 high-pressure high-pressure separators !he condensate3water3methanol mixture is then separated into hydrocarbon and water phases in a three-phase low-pressure separator  !he water phase* which contains the bul" o the methanol* is urther processed to reduce the hydrocarbon concentration rom approximately 7*4// ppm to less than 4/ ppm !his low hydrocarbon concentration is achieved with high-eciency condensate coalescers A de-sanding hydrocyclone and a degassing vessel are installed upstream o the coalescers to ensure their proper operation  !he methanol3water mixture is then processed in the methanol rregeneration egeneration system consisting o methanol3water preheaters and a distillation column with a re-boiler* total condenser* and reux pumps !he methanol3water me thanol3water preheaters heat the methanol using the hot water distillation bottoms product !he methanol recovery process will have a design capacity o the 4*,/ b3d o inlet uids6 7*// b3d o methanol and 7*4/ b3d o water )pon regeneration* the methanol is .0 pure

Operational fexibility  !he methanol regeneration system is designed with operational exib exibility ility in mind ?irst* ?irst* multiple eed points are provided on the distillation column such that the eed location is optimiFed as the eed properties change throughout the lie o the ;eld Also* an automated recycle loop* which eeds distillation bottoms product bac" to the distillation column through a recycle cooler* allows the methanol regeneration system to stay online during operating conditions when no eed is coming rom the main process

 

Several steps were ta"en to mitigate corrosion and scale problems in the methanol regeneration system due to the potentially high dissolved solids content o the produced water and the presence o methanol !he methanol3water preheater plate pac" is titanium construction !he distillation column trays and valves and the re-boiler tubes are stainless steel construction 9oth the distillation column and the re-boiler have a special internal coating that will stand up to the high temperatures and the corrosive nature o the liDuid !he re-boiler design also includes provisions or cleaning the tubes in place Another design consideration or the methanol regeneration system is or the removal o hydrocarbons that may accumulate in the distillation column and decrease the methanol regenerating capacity due to increased vapor and liDuid ow ?irst* a s"im connection and interace level gauge are installed in the bottom o the column to remove any heavy hydrocarbons that may collect Second* a total liDuid draw tray is included in the column such that a three-phase separator may be installed at a uture date i accumulation o mid-range hydrocarbons in the column does occur occur

Schedule  !he #illiams $anyon Station Station design calls or a our our-pile* -pile* our-legged our-legged production platorm destined or 'ain Pass 9loc" 427 !he topsides production dec" is estimated to weigh =*// tons  !he %ac"et is scheduled scheduled or installation this summer B4//7C* with the dec" to ollow in the spring o 4//4 ?ollowing %ac"et installation* $anyon Express will begin installation and testing o the umbilical to ensure its operability operability !o !o acilitate the asttrac"  asttrac" process* #illiams reDuires a concurrent acilities design-and-build efort Paragon is designing the dec" using the =-+ Plant +esign 'anagement System BP+'SC to acilitate early resolution o design clashes and to improve operability and saety through better anticipation o haFards  !he engineering efort includes topsides system system design or compress compression ion and separation acilities* water treatment* instrumentation and utilities* including termination and connection o the power and control systems rom the umbilical bundle to the master control station or the subsea wells

Author W. Hickman Brown is a pro%ect manager with w ith Paragon Engineering Services He has more than 4 years o experience in the design3engineering o ofshore acilities and pipeline systems* much o it with 'obil* Superior* and Shell He holds a 9S'E rom 8ew 'exico State )niversity and a 'S in 5cean Engineering rom the )niversity o hode Gsland