View source for TEG Regenereation

=Introduction=

At FNNPF the sweetened gas from the process train is dehydrated with a triethylene glycol (TEG) solution as described in [[TEG Dehydration]]. In the process building, gas is dehydrated in a TEG contactor to below 4 lb/mmscf water content sales specification.


==Overview==

[[File:TEGRegenOverview.png|center|]]

Figure 1 illustrates a complete overview of the TEG dehydration and regeneration process. Treated wet gas from the sweet gas scrubber flows to the TEG dehydration unit and flows upwards through the TEG contactor. The wet gas contacts lean TEG flowing downwards across trays in contactor and has its water removed by the TEG which leaves the bottom of the contactor as rich TEG. The now dry gas leaves the top of the contactor and delivered to sales. The rich TEG now must be regenerated in the following equipment process flow - each segment of this overview process is discussed in more detail within the module.

'''Condensing/Reflux Coil:''' rich TEG from the contactor flows through the regenerator reflux coil where it is heated by the TEG off-gas leaving the regenerator to about 112F. The now warm rich TEG flows through the contactor level control valve. This level control valve reduces the pressure of the rich TEG which assists in the flashing off any gases in the TEG flash drum.

'''TEG Flash Drum:'''rich TEG enters this drum where through volume increase and pressure decrease any entrained gases are flashed off. The flashed off gases flow to the HP Flare. Pressure in the TEG Flash Drum is maintained by the LP Fuel gas supply.

'''Filtration:''' the rich amine from the TEG flash drum is then filtered through TEG particulate filters to remove any entrained solids. After the particulate filters a manually adjusted slip stream of the rich TEG is sent through the carbon filter which removes any heavy hydrocarbons or other TEG degradation products. The flow from the carbon filter then rejoins the main flow of rich TEG from the particulate filters.

'''Heat Exchanger:''' after filtration the rich TEG is heated further in a plate flow heat exchanger by cross flow heat exchange with hot lean TEG (about 3000F) from the regenerator. From the heat exchanger the now hot TEG flows through the flash drum level control valve. This level control valve not only maintains the level in the flash drum but also reduces the pressure of the rich TEG prior to entering the regenerator.

'''Regeneration:''' the rich TEG enters the regenerator column section which is located between two packed columns. The rich TEG contacts the hot vapour rising from the regenerator reboiler. This contact results in removal of most of the water from the TEG before it enters the reboiler section of the regenerator. The rich TEG then enters the re-boiler where most of the remaining water in the rich TEG is boiled off by a steam coil heated by medium pressure (390 psi) steam. This steam maintains the lean TEG in the reboiler at 400F. The packed section of the regenerator contacts the liquid that is condensed by the condensing/reflux coil with the vapour leaving the regenerator. This contact minimizes any TEG losses that may be vented from the regenerator top to the TEG off-gas incinerator.

'''Stripper:''' the hot lean TEG leaves the regenerator and enters the stripping column where it is contacted with fuel gas preheated within the regenerator reboiler section. The fuel gas contacting the TEG removes any final traces of water and flows out the top of the stripper back into the regenerator reboiler section to be vented with the hot reboiler vapours. The hot lean TEG then flows back through the lean/rich exchanger where it is cooled to 2030F and then to the TEG Accumulator

'''Accumulator:''' The TEG accumulator provides the surge capacity for the TEG charge pumps. Lean TEG from the accumulator is supplied to the suction of the TEG charge pumps driven by variable speed electric motors. These variable speed motors control the amount of required TEG flow back to the contactor via the lean TEG cooler.

'''Lean TEG Cooler:''' this cooler is an aerial cooler with two fans – one fan is driven by a variable speed motor and the other is a fixed speed motor. Lean TEG flows through the cooler tube bank and is cooled to 105F (check) by the air flowing across the outside of the tube banks. The TEG then enters the TEG contactor and the process is repeated.

'''Incineration of TEG Off-Gas:''' the TEG incinerator incinerates any off-gas from the TEG regenerator. A TEG knock out drum is located between the TEG regenerator and the TEG incinerator to capture any liquids carried over from the regenerator. The incinerator uses fuel gas along with the fuel gas in the regenerator off-gas to incinerate the off-gas. The maximum top temperature of the incinerator is 1800F and removes 99.9% of any organic compounds present.

'''TEG Drain Tank:''' the TEG drain tank captures any liquids from the TEG closed blow down system. Any liquids drained to this tank are pumped back to the inlet of the particulate filters.

'''TEG Storage''' pure TEG is stored in the TEG storage tank. From this tank TEG is pumped into the accumulator to make-up for any losses in the system. Before any addition concentration tests of the TEG system should be done to ensure the required concentration of TEG (99.5%) is maintained at the TEG contactor inlet.


=Operator Responsibilities=

To ensure that the TEG dehydration and regeneration process is correctly meeting process specifications, routine area operator responsibilities in the TEG regeneration process include:
*monitoring and recording process temperatures, pressures, and levels
*verifying that process controllers are maintaining set point operations
*monitoring TEG flash drum, accumulator, regenerator boiler, and drain vessel liquid levels via sight glasses and transmitters
*monitoring differential pressure across the TEG filter and TEG drain vessel filter
*monitoring TEG pump operation
*blowing down float columns and sight glasses to avoid internal buildup. Whenever blowing down level-switch equipped float columns, co-ordinate your activities with the control room operator to avoid low-level alarms and shutdowns.
*monitoring for signs of leakage at valves and flanges
*responding promptly to alarms to avoid insufficient TEG regeneration
*confirming heat tracing operation
*troubleshooting process upsets and alarms
*shutting down equipment in preparation for maintenance

Specific area operator responsibilities are described with each section of this module. The area operator works with the control room operator to investigate and rectify the cause of the alarms to prevent damage to equipment, personnel, or the environment.


=TEG Regenerator Safety Issues=

<u>'''Important:'''</u> For confined space safety entry precautions and the requirements for safety backup personnel, refer to:
*the safety training you completed during your FNNPF orientation
*SET West’s confined space/ initial entry permitting safety procedures

Around the TEG regeneration process operations described in this module, the area operator must remain vigilant for potential hazards.