Hydrogen Compression System in HDS Unit #3

• Hydrogen is essential for the operation of the #3 HDS Unit.
• The Compression 1 and 2 System has two four-cylinder reciprocating compressors.
• These compressors compress recycle and make-up hydrogen streams.
• The compressed streams are then fed to the Reaction and Separation System.
• Recycle hydrogen, separated from the reactor effluent, undergoes one stage of compression.
• This compression ensures the required hydrogen partial pressure in the Distillate HDS Reactors.
• Increasing hydrogen partial pressure in the reactors enhances sulfur and nitrogen removal.
• Higher hydrogen partial pressure leads to increased hydrogen consumption.
• It also increases hydrogen saturation and reduces coke formation.
• Make-up hydrogen compensates for hydrogen consumed during the reactions.
• Hydrogen is lost both in the liquid phase and during equipment purging to maintain unit pressure.
• The Compression 1 and 2 System compresses make-up hydrogen from the Reformer Hydrogen Header in two stages.
• This make-up hydrogen is supplied to the Reaction and Separation System to compensate for hydrogen losses.

Recycle Hydrogen Flow

• Sweetened recycle hydrogen from the #3 HDS Absorber (13PV-2306) is sent to the Recycle Hydrogen Knock Out (KO) Drum (13PV-2314).
• 13PV-2314 slows down hydrogen flow, allowing liquids to separate to prevent compressor damage.
• Recycle hydrogen gas, free of entrained liquid, exits the top of the Recycle Hydrogen KO Drum and goes to the H2 Compressor Recycle Suction Snubber West/East (13PV-2350/2360).
• Suction snubbers (13PV-2350/2360) or pulsation dampers compensate for pressure variations to prevent pulsation in the compressor suction line.
• During start of a shutdown, nitrogen can be sent through 13PV-2314 and relieved to the atmosphere via the Eductor (13ED-101).
• 180 psig steam can be sent to 13ED-101 to create a pressure drop, drawing nitrogen gas into the eductor perpendicular to the steam flow.
• The steam and nitrogen combine and flow through 13ED-101 to a silencer.
• The eductor is a venturi nozzle using high-pressure steam as motive fluid to draw nitrogen gas from 13PV-2314 to the atmosphere.
• The combined steam and nitrogen stream exits the eductor to a silencer to muffle noise from venting high-pressure gas.
• Remaining liquid in the steam and nitrogen stream is removed from the silencer and sent to a drain.
• Recycle hydrogen flows into the "1L" Cylinder on each of the #1/#2 Distillate Hydrogen Compressor West/East (13C-101/102).
• Compressors 13C-101/102 increase the pressure of recycle and make-up hydrogen using pistons.
• One of the four cylinders on Compressors 13C-101/102 compresses recycle hydrogen in a single stage.
• Increasing recycle hydrogen gas pressure maintains the needed hydrogen partial pressure in the Distillate HDS Reactors West/East (13PV-2301/2302).
• Compressed recycle hydrogen exits the "1L" Cylinder to the H2 Compressor Recycle Discharge Snubber West/East (13PV-2351/2361).
• Discharge snubbers 13PV-2351/2361 prevent pulsation and vibration in the compressor discharge line.
• A portion of the compressed recycle hydrogen is supplied to the Feed/Effluent Exchanger (13EX-2331) upstream of the Distillate HDS Reactors.
• The remaining compressed recycle hydrogen flows through the shell side of the Recycle Make-Up Cooler (13EX-2338), cooled by cooling water.
• 13EX-2338 removes the "heat of compression" to reduce temperature and increase compressor efficiency.
• Cooled recycle hydrogen, regulated by spillback control valve PV-217, is sent to the Recycle Hydrogen Knock Out (KO) Drum (13PV-2314) inlet.
• PV-217 provides a minimum and constant flow to the compressors, preventing surging.
• Sour water separated in 13PV-2314 is routed to the SWS Collection Drum (14PV-2402) and the Amine Decanter (13PV-2307).
• Sour water from 13PV-2314 can be drained off and discarded.
• Sour water is collected to be recovered and reused throughout the refinery

Make-Up Hydrogen Flow

• Make-up hydrogen from the Reformer Hydrogen Header enters the First Stage Make-Up Knock Out (KO) Drum (13PV-2312).
• 13PV-2312 slows down make-up hydrogen flow and allows liquids to separate to prevent compressor damage.
• Make-up hydrogen, free of entrained liquid, exits the top of the First Stage Make-up KO Drum and is sent to the H2 Compressor 1st Stage Make-Up Suction Snubber West/East (13PV-2352/2362).
• The suction snubbers (13PV-2352/2362) or pulsation dampeners, compensate for pressure variations to prevent pulsation in the compressor suction line.
• Make-up hydrogen flows into the "2R" Cylinder on each of the #1/#2 Distillate Hydrogen Compressors West/East (13C-101/102).
• Three of the four cylinders on Compressors 13C-101/102 compress make-up hydrogen gas in two stages.
• The pressure of the make-up hydrogen gas must be increased so it can be supplied upstream of the Feed/Effluent Exchanger (13EX-2331) in the #3 HDS Reaction and Separation System.
• Compressed make-up hydrogen enters the H2 Compressor 1st Stage Make-Up Discharge Snubber West/East (13PV-2353/2363).
• Discharge snubbers 13PV-2353/2363 prevent pulsation and vibration in the compressor discharge line.
• Compressed make-up hydrogen flows through the shell side of the Interstage Make-Up Cooler (13EX-2337), cooled by cooling water.
• 13EX-2337 removes the "heat of compression" generated during the first stage, reducing the temperature of the make-up hydrogen.
• Compressed and cooled make-up hydrogen is sent to the Interstage Suction Make-Up KO Drum (13PV-2313).
• 13PV-2313 slows down the make-up hydrogen flow and allows any entrained liquids to separate to prevent compressor damage in the second stage of compression.
• Make-up hydrogen gas, free of entrained liquid, exits the top of 13PV-2313 and is split into three streams.
• A portion of the make-up hydrogen exiting 13PV-2313 is routed, on pressure control, to the Feed Preheaters (22EX-2503 and 27EX-2503) in the 1 and 2-Hydrogen Units.
• It can also be sent to the inlet of 13PV-2312 for return to the compressor, regulated by spillback control valve PV-226.
• Make-up hydrogen gas is directed through PV-226 to provide a minimum and constant flow to the compressors, preventing surging.
• The remaining compressed make-up hydrogen is split into two streams sent to the H2 Compressor 2nd Stage Make-Up Suction Snubber West/East (13PV-2356/2366 and 13PV-2354/2364).
• Suction snubbers 13PV-2356/2366 and 13PV-2354/2364 prevent pulsation and vibration in the suction line to the "4R" and "3L" Cylinders respectively.
• Make-up hydrogen flows into the "4R" and "3L" Cylinders on the #1/#2 Distillate Hydrogen Compressor West/East (13C-101/102) for further compression.
• The "4R" and "3L" Cylinders operate in parallel, doubling the capacity of the compressors.
• Compressed make-up hydrogen exits the "4R" and "3L" Cylinders to the H2 Compressor 2nd Stage Make-Up Discharge Snubber West/East (13PV-2357/2367 and 13PV-2355/2365).
• Discharge snubbers 13PV-2357/2367 and 13PV-2355/2365 prevent pulsation and vibration in the second stage discharge lines.
• The compressed make-up hydrogen streams from the "4R" and "3L" Cylinders combine and route upstream of the Feed/Effluent Exchanger (13EX-2331).
• Make-up hydrogen is supplied to compensate for hydrogen loss during desulfurization.

Fuel Gas Flow

• Fuel gas from the High Pressure Fuel Gas KO Drum (5PV-1613) in the Reformer Unit is routed to the Fuel Gas KO Drum (13PV-2311).
• 13PV-2311 slows down fuel gas flow and allows any remaining liquid to separate to prevent it from entering the burners of the Reactor Charge Heater (13HT-101).
• Fuel gas, free of entrained liquid, is routed to the burners of 13HT-101 in the #3 HDS Reaction and Separation System as fuel.

Sour Water Flow

• Sour water separated from hydrogen gas in the First Stage Make-Up KO Drum (13PV-2312) and the Interstage Suction Make-Up KO Drum (13PV-2313) is routed to the SWS Collection Drum (14PV-2402) and the Amine Decanter (13PV-2307) on level control.
• The combined sour water stream is also combined with the separated sour water from 13PV-2311 and the drain line from the Alternate Stripper Feed Header.
• Sour water is collected to be recovered and reused throughout the refinery.
• Sour water from knock out drums 13PV-2311, 13PV-2312, and 13PV-2313 can also be drained off and discarded.

This lesson explores the hydrogen compression system within the #3 HDS Unit. It details the two four-cylinder reciprocating compressors used for compressing recycle and make-up hydrogen streams. The compressed streams are then fed into the Reaction and Separation System to be used in the removal of nitrogen and sulfur.