Process Description
Simtronics’ Oil Terminal simulation includes the following processing systems commonly found in oil terminal facilities:
- Crude Oil Well & Pipeline
- Crude Oil Receiving & Stabilization section
- Crude Oil Degasser & Slop Tank
- Vapor Recovery Unit
- Condensate Recovery Unit
- Crude Oil Storage and Export section
- Condensate Storage and Export Section
- Oily Water System (OWS)
- Dissolved Air Flotation (DAF) Unit
- Fuel Gas System
- Hot Oil System
- Closed Drain System
- High Pressure (HP) Flare System
- Low Pressure (LP) Flare System
- Instrument Air System
All these process and utility sections are fully integrated, and, therefore, the Oil Terminal simulation enables realistic and comprehensive training for operators to master startup, normal shutdown, and emergency shutdown operations. The simulated oil well can be varied in its characteristics to impact conditions throughout all the process units. The fully integrated Oil Terminal simulation also allows operators to master storage tank management and off-spec situations. A rich set of faults is provided to permit training for response to a wide variety of operational problems.
A full range of operations can be learned and practiced on the Oil Terminal simulator. These include normal, startup, shutdown, and emergency shutdown procedures.
The rest of this manual describes the simulated Oil Terminal process and provides detailed operating procedures and exercises for training.
Oil Terminal Overview
The Oil Terminal simulation consists of the following processing and utility sections/units:
- Oil Well & Pipeline
- Stabilization Section
- Vapor Recovery Unit
- Condensate Recovery Unit
- Degasser & Slop Oil Tank
- Crude Storage & Export
- Condensate Storage & Export
- Oily Water System
- Dissolved Air Flotation System
- Fuel Gas System
- Hot Oil System
- Closed Drain System
- HP Flare System
- LP Flare System
- Instrument Air System
Crude oil produced by a well is transported by pipeline to the Oil Terminal. The crude oil is stabilized in the Stabilization Section by heating the oil and successively depressuring it in two stages to release associated gas. The crude oil is also washed with water in the Electrostatic Desalter situated between the two depressuring stages. This removes most of the salts compounds contained in the crude oil from the well. Warm Stabilized crude oil is used to preheat crude oil from the pipeline before being sent to the Crude Storage and Export section.
The released gas from the Stabilization section is compressed, cooled and exported to a gas pipeline in the Vapor Recovery Unit (VRU). A portion of the produced gas is used as fuel gas within the Oil Terminal. The cooling of the compressed gas produces a significant flow rate of condensate which is sent to the Condensate Recovery Unit (CRU).
The Condensate Recovery Unit stabilizes the condensate from the VRU by first depressuring the liquid to release volatile gases. The condensate is then heated in the Condensate Stabilizer column which further releases volatile gases from the condensate. These volatile gases are returned to the VRU for compression and cooling. The condensate from the Condensate Stabilizer is further cooled and depressured to atmospheric pressure before being pumped to the Condensate Storage and Export section.
The Degasser & Slop Oil Tank Section processes crude oil diverted from the feed pipeline and off-spec stabilized crude oil. Crude oil is first depressured in the Degasser which flashes off volatile gases and sends them to the VRU for recovery. The Slop Oil Tank is used to store any crude oil processed in the Degasser. The Slop Oil Tank has pumps so the crude can be processed in the Stabilization section as needed. Normally, this section is not processing any crude oil. However, oil recovered in the Oily Water section and any liquids separated in the HP and LP Flare systems are sent to the Slop Oil Tank.
In the Crude Storage & Export Section, stabilized crude oil is pumped from the Crude Storage Tanks and exported to a crude oil pipeline.
In the Condensate Storage & Export Section, stabilized condensate is pumped from the Condensate Storage Tank and exported to a condensate pipeline.
In the Oily Water System, separated process water from the Stabilization Section and the Condensate Recovery Unit are settled in a series of tanks and sumps to allow most of the oil dispersed in the water to coalesce and separate into an immiscible phase that floats on the water. The water is then sent to the Dissolved Air Flotation (DAF) Unit to remove the last amounts of oil still dispersed in the water. The separated oil is collected and pumped to the Slop Oil Tank.
The Dissolved Air Flotation (DAF) Unit treats water produced by the Oily Water System using an added flocculant to promote coalescing of the remaining oil in the water. The coalesced oil droplets are brought to the surface of the DAF Basin using circulating water saturated with a small flow of ambient air. The air-saturated water is injected back where the flocculated water enters the basin. Small air bubbles form because the pressure is lower in the basin than in the Air Saturator Tank. The small air bubbles help lift the coalesced oil to the top of the basin where it is skimmed off. Clarified water from the DAF Basin is then sent to the DAF Surge Tank and pumped to discharge facilities at battery limits. The float oil from the DAF Basin is recovered in the DAF Float Tank and pumped back to a sump in the Oily Water System.
The other sections of the Oil Terminal are utilities that are fully integrated with the oil, gas, condensate and water processing sections described above.
The Fuel Gas System distributes gas taken from the VRU to various equipment in the Oil Terminal and to the other utilities.
The Hot Oil System circulates and heats a commercially produced heat transfer oil for heating:
- Feed crude oil to the Stabilization Section
- Oil from the Slop Oil Tank for stabilization and dewaxing
- The Condensate Stabilizer Reboiler
The Closed Drain System collects any drained liquid from process units in the Oil Terminal, flashes the liquid and sends any produced vapor to the LP Flare System. Collected liquid is pumped to the Slop Oil Tank.
The HP Flare System and LP Flare System collect vented gases and pressure safety valve releases from equipment in the Oil Terminal. The HP Flare System handles releases from equipment that operates at high pressure while the LP Flare System handles all the other releases. Both systems are outfitted with liquid KO drums and pumps to return any collected liquids to the Slop Oil Tank. Any collected gases are sent to flare stacks for combustion prior to release to atmosphere.
The Instrument Air System provides dry compressed air to the pneumatic control valves in the Oil Terminal. In case of a low air supply pressure, control valves will move to their air-fail position.
Oil Well & Pipeline
Oil Well
Crude oil, along with associated gas and water, is produced from the Oil Well that provides the production for feed to the Oil Terminal via the oil pipeline. The Oil Well is outfitted with an engineered wellhead assembly at the surface, which consists of a set of valves to isolate and control the flow from the well. This wellhead assembly is commonly referred to as a “Christmas Tree”. The wellhead assembly includes an emergency shutdown isolation valve (ESDV) and a production choke valve to manually control the well’s flow and to reduce the line pressure. The pressure at each wellhead is indicated on the instrumentation.
Pipeline
Crude oil from the oil well flows via pipeline to the Stabilization section.
Stabilization Section Overview
Crude oil from the oil well flows via pipeline to the Stabilization section. The design flow rate of crude oil into the Oil Terminal is 50.0 MBPD. Crude oil is preheated using warm stabilized crude in Crude/Crude Exchanger E-101 and using circulating utility hot oil in Crude Oil Heater E-102. The warm crude oil is then depressured in 1ST Stage Separator D-201 to release associated gas from the crude oil. Removing the associated gas stabilizes the crude oil so it can be more safely transported to crude oil refineries via pipeline, rail cars, and tanker ships. A large portion of water in the crude oil from the pipeline is separated and removed in D-201 and sent to the Oily Water System. The gas separated in D-201 is sent to the Vapor Recovery Unit after cooling in E-201 1ST Stage Offgas Cooler.
The crude oil from the 1ST Stage Separator D-201 is washed with desalter water in Electrostatic Desalter D-211 to remove salt compounds. This improves the desirability of the crude oil as an oil refinery feedstock. The residual water in the crude oil from D-201 and wash water are electrostatically separated from the crude oil and sent to the Oily Water System.
The crude oil from D-211 is further depressured in 2ND Stage Separator D-221 to release more gas from the crude oil. Any residual amounts of water leaving the Electrostatic Desalter D-211 are separated and removed in D-221 and sent to the Oily Water System. The gas separated in D-221 is sent to compressors in the Vapor Recovery Unit.
Stabilized crude oil from the 2ND Stage Separator D-221 is pumped to the Crude/Crude Exchanger E-101 by Stabilized Crude Pumps P-221A/B and then to the Crude Oil Storage Tanks. The design flow rate of stabilized crude produced by the Oil Terminal is 43.6 MBPD.
Vapor Recovery Unit Overview
Offgas from the 2ND Stage Separator D-221 flows to a header supplying Vapor Recovery Compressors K-301A/B. Two offgas streams from the downstream Condensate Recovery Unit also recycle back into this header. One is a smaller stream of flash gas produced by depressuring condensate generated by the Vapor Recovery Unit in LP Condensate Separator D-321. The second, larger stream is gas produced from heating the generated condensate in the Condensate Stabilizer T-331.
The Vapor Recovery Compressors K-301A/B are electric motor-driven and increase the pressure of these lower pressure gas streams so that condensate containing heavier hydrocarbon compounds will be condensed in the Compressor Aftercoolers E-305A/B that follow the compressors. E-305A/B are air cooled heat exchangers.
Cooled gas/condensate from E-305A/B combines with offgas from 1ST Stage Separator D-201 and is sent to 1ST Stage Discharge Separator D-311 to separate out the condensate. A portion of the gas leaving D-311 is used as fuel gas in the Fuel Gas System. The balance of the gas is sent to a metering unit prior to flowing into the gas pipeline at battery limits. Condensate collected in D-311 is sent to LP Condensate Recovery Separator D-321 in the Condensate Recovery Unit.
Condensate Recovery Unit Overview
Light hydrocarbon condensate from 1ST Stage Discharge Separator D-311 in the Vapory Recovery Unit is modestly depressured in LP Condensate Recovery Separator D-321. This produces a small stream of flash gas which is recycled to the Vapor Recovery Compressors K-301A/B. Any liquid water produced with the condensate from the Vapor Recovery Unit separates out and is collected in the boot of D-321 and then sent to the Oily Water System. The condensate is normally sent to the Condensate Stabilizer T-331 which operates at a modestly lower pressure than D-321.
Condensate Stabilizer T-331 is outfitted with a kettle-type reboiler that uses circulating hot oil to generate vapor from condensate reaching the base of T-331. The vapor from Stabilizer Reboiler E-331 is returned to the bottom tray of T-331 and contacts cooler condensate feed flowing onto the top tray of T-331. This produces an overhead vapor stream of light gas which is recycled back to the Vapor Recovery Compressors K-301A/B. Like with crude oil stabilization, the removal of these light gases stabilizes the condensate making it safer for storage and transportation. This light gas stream recirculates around the Vapor Recovery Unit and the Condensate Recovery Unit until the lighter components exit in the gas leaving the 1ST Stage Discharge Separator D-311 and the heavier components leave in the condensate leaving the Stabilizer Reboiler E-331.
Hot stabilized condensate from the overflow collection sump of Stabilizer Reboiler E-331 is cooled in Condensate Cooler E-332 which is an air-cooled heat exchanger.
The cooled condensate from E-332 is collected in Atmospheric Condensate Recovery Separator D-341 which operates at atmospheric pressure. A very small flow of flash gas is normally produced in D-341. This gas is sent to the Low Pressure Flare Header to be burned before venting to atmosphere. The collected condensate is pumped to the Condensate Storage Tank T-501 by Condensate Recovery Pumps P-341A/B.
Degasser & Slop Oil Tank Overview
Crude oil diverted from the crude oil pipeline and/or off-spec crude oil from the outlet of Crude/Crude Exchanger E-101 flow into the Degasser D-111 which is a large drum that depressures the diverted crude oil. Offgas gas produced by flashing of crude oil in D-111 is sent to the 1ST Stage Discharge Separator D-311.
Partially stabilized crude oil from D-111 is sent to Slop Oil Tank T-121 which operates slightly above atmospheric pressure. Offgas gas produced by T-121 is sent to the LP Flare Header to be combusted before being vented to atmosphere. Oil and water will separate in T-121. Slop Oil Pumps P-121A/B are used to pump crude oil to either the Crude/Crude Exchanger E-101 in the Stabilization section or to Slop Oil Heater E-111.
Slop Oil sent to E-111 is warmed using circulation utility hot oil and returns to the Degasser D-111. Warming the oil and circulating it through D-111 and back to T-121 helps minimize the possibility of the precipitation of waxy compounds in the equipment. Warming also helps flash more gas off to the Vapory Recovery Unit in D-111.
Slop Water Pumps P-123A/B are used to pump separated water from T-121 to the Oily Water System.
Crude Storage & Export Overview
Cooled, stabilized crude oil from Crude/Crude Exchanger E-101 is sent to the Crude Storage Tanks T-401 & T-402. Crude is pumped from T-401 & T-402 by Crude Export Pumps P-411A/B to the Crude Meter Skid A-421 which precisely measures the crude oil flow rate being sent to the Crude Oil Pipeline at battery limits. A minimum flow recycle line from the discharge of P-411A/B protects the pumps from potential mechanical damage during low export flow operation. The recycle flow can also be used to minimize stratification within the Crude Storage Tanks.
Instrumentation
Basic Controls
Process-side Instrumentation
The process feed flow is controlled by flow controller FIC-101. Flow to the east and west passes can be adjusted by varying the positions of valves HIC-101E and HIC102W respectively. Process inlet temperature is indicated by TI-101. Process outlet temperature is controlled by TIC-102 which modulates fuel flow to the burners. East and west pass outlet temperatures are indicated by TI-102E and TI-102W respectively. East and west pass crossover temperatures are indicated by TI-101E and TI-101W respectively
Fuel Gas Instrumentation
Fuel flow to the burners is controlled by temperature controller TIC-102 which is cascaded to fuel flow controller FIC-201. Fuel flow to the east and west burners can be adjusted by varying the positions of valves HIC-201E and HIC-201W respectively. Fuel inlet temperature is indicated by TI-201.
Flue Gas Instrumentation
Temperatures in the east and west radiant cells of the furnace are indicated by TI301E and TI-301W respectively. Bridge wall temperature is indicated by TI-302. Stack inlet and outlet temperatures are indicated by TI-303 and TI-304 respectively.
The draft in the east and west radiant sections of the furnace is indicated by PI301E and PI-301W respectively. Bridge wall draft is indicated by PIC-302. Stack draft is indicated by PI-303.
The stack damper position is controlled by HIC-301.
Volume percent oxygen in the stack gas is indicated by AIC-301.
The oxygen concentrations (volume %) of the flue gas in the east and west cells are indicated on AI-302E and AI-302W, respectively. The carbon monoxide concentrations (PPM) of the flue gas in east and west cells are indicated on AI-303E and AI-303W, respectively. The combustibles/hydrocarbon concentration (PPM) of the flue gas in east and west cells are indicated on AI-304E and AI-304W, respectively.
Advanced Controls
Combustion Air Instrumentation
Air flows into the plenums serving the east and west burners can be trimmed by varying the positions of the respective air dampers HIC-301E and HIC-301W.
The ambient air temperature and pressure is indicated by TI-300 and PI-300 respectively.
The BURNER-E and BURNER-W switches act as both igniters and flame indicators.
Note: These switches are not identified by tag on the main process schematic but are accessible on the simulator just above their respective burner assembly.
The draft in the furnace is controlled by bridge wall pressure controller PIC-302. The output of PIC-302 is cascaded to the setpoint of stack damper position controller HIC-301. Adjusting the stack damper position changes the flow of flue gas up the stack which, in turn, affects the draft in the fired heater. Normally, HIC-301 is in cascade mode and PIC-302 is in automatic mode.
The output of stack O2 controller AIC-301 is cascaded to the setpoints of both combustion air damper controllers HIC-301E and HIC-301W. If desired, differences between the east and west air flows are made by adjusting the ratio setting of HIC301E or HIC-301W. Normally, HIC-301E and HIC-301W are in cascade mode and AIC-302 is in automatic mode.