Reaction Subsystem- Major Equipment, How it works, Controlling, & Shut Down

Question 1

What are the 3 subsystems of the 634 HDS?

Answer 1

Reaction Subsystem, Stipper Subsystem, Hydrogen Compression Subsystem

Question 2

Overall, what happens in the Reaction Subsystem?

Answer 2

undesirable sulfure and nitrogen compounds in the feed stream are converted to hydrogen sulfide and ammonia. Olefins and aromatics in the feed are saturated with hydrogen.

Question 3

Why are the feed filters important?

Answer 3

They remove solids from the feed stream which could foul the catalyst beds in the reactor.

Question 4

What does an increasing differential pressure across the in-service filter indicate?

Answer 4

The filter media is plugging and must be replaced. If the differential pressure is excessive, the stand-by filter is placed in service and the in-service filter is taken out of service

Question 5

The natural gas blanket on the Feed Surge Drum Prevents _________ from entering the drum and provides sufficient suction pressure for the Reactor Fresh Feed Pumps.

Answer 5

Oxygen

Question 6

The Target Outlet temperature for the Reactor Feed heater (F1) is ________ F

Answer 6

665 F

Question 7

What is the normal control mode for the Feed Surge Drum pressure (pc0001)?

Answer 7

Local

Question 8

What can happen if the fresh feed flow (as indicated by FT0003 A/B/C) drops below 1070 BPH?

Answer 8

Low- Low (2oo3 voting) The SIS interlock is activated which initiates a shutdown of the Reactor feed heater.

Question 9

The potential effects of a low combined hydrogen flow to the fresh feed (FI0016) are ________ ______ and insufficient hydrogen for desired ______, resulting in off-spec product.

Answer 9

catalyst deactivation, reactions

Question 10

The potential effects of a high reactor outlet temperature are premature _________ of the catalyst and loss of _________ of the recycle hydrogen stream.

Answer 10

deactivation, purity

Question 11

What is the high pressure alarm setpoint on the unit pressure controller (PC0007) _________ -psig?

Answer 11

907 psig

Question 12

A low hot flash drum level can allow high-pressure gas to flow to the Product Stripper resulting in damage to the tower’s _________ and the possibility of lifting PSVs.

Answer 12

tray’s

Question 13

The potential effect of a high Hot Flash Vapor Air Coolers outlet temperature is a decrease in the __________ of the recycle Hydrogen

Answer 13

purity

Question 14

The Reactor Feed Heater high coil pressure alarm activates at _________-psig.

Answer 14

980 psig

Question 15

The SIS will trip the Reactor Feed Heater on a low-low fuel gas pressure of _______

Answer 15

2%

Question 16

What happens if the SIS detects a low current of 20 amps to the Forced Draft Fan motor?

Answer 16

After a 30 decond delay, the SIS interlock is activated to switch the heater to natural draft.

Question 17

What are the process variables on the Reactor Feed Heater that are equipped with triple redundant instrumentation.

Answer 17

Feed flow (FT3A/B/C), Hydrogen flow (FT16A/B/C), Fuel gas pressure (PT5134A/B/C), Furnace pressure (PT5131A/B/C)

Question 18

If the SIS initiates a trip of the heater due to a high or low furnace pressure, the heater is switched to _________ ________ mode prior to the actual trip.

Answer 18

natural draft

Question 19

What action does teh DCS take if the SIS trips the Reactor Feed Heater due to either Low Feed flow or Low Hydrogen Flow?

Answer 19

The DCS will automatically override the signal from termperature controller TC1 and place teh fuel gas pressure controller (PC5134) in manual with a minimum fire output of 10% to prevent coking of the heater tubes.

Question 20

If the SIS automatically switches the Reactor Feed Heater from Balanced draft to Natural Draft, what actions must occur to prevent an eventual complete trip of the heater?

Answer 20

Within 30 seconds of trip to natural draft, both transmitters on the stack damper and forced draft air door much show >50% open to avoid an SIS trip of the heater. After 30 minutes, one transmitter on each damper must indicate >30% open to avoid a heater trip.

Question 21

What are the three circumstances under which the Reactor Feed Heater SIS can be bypassed?

Answer 21

Startup, Maintenance, and Emergency

Question 22

The ___________ use fiber filter elements to remove particulates from the gas oil. The filtered feed exits to the feed surge drum

Answer 22

Feed Filters 634 D1001/D0006B

Question 23

The ____________ is a holding tank for feed to the unit. It provides surge capacity to operate for 30 mins without receiving feed. It also serves as a reservoir to provide steady feed flow to the reactor fresh feed pumps.

Answer 23

Feed Surge Drum 634D0001

Question 24

The ____________ is an electric motor-drivin pump. The _____________ is a turbine driven pump that uses 550-psig steam to drive teh turbine. Medium pressure steam (125-psig) exhausts from the turbine. The pumps increase the pressure of the feed stream to 730-psig. The increased pressure allows the feed stream to join the combined hydrogen stream

Answer 24

Reactor fresh feed pumps 634P0001

Question 25

The _____________ use Hot Flash Drum vapor flowing through the exchanger tubes to preheat the fresh feed flowing on the shell side.

Answer 25

Hot Flash Vapor/Fresh Feed Exchangers 634E0053A-D

Question 26

The ____________ uses Hot Flash Drum Vapor flowing through the exchanger tubes to heat the combined hydrogen gas stream flowing on the shell side. The heated hydrogen mixes with the heated feed before teh combined feed stream enters the reactor feed/product stripper bottoms exchangers.

Answer 26

Hot Flash Vapor/Hydrogen Gas Exchanger 634E0054

Question 27

The _______________ use product stipper bottoms flowing on the shell side to heat the reactor feed flowing through the exchanger tubes before the feed enters the reactor feed/reactor effluent exchanger.

Answer 27

Reactor Feed/ Product Stripper Bottoms Exchangers 634E0051 A/B

Question 28

the _______________uses reactor effluent on the tube side to heat the reactor feed before it enters the reactor feed heater.

Answer 28

reactor feed/reactor effluent exchanger 634 E0052

Question 29

The _______________ is a refinery fuel gas-fired heater that raises the temperature of the feed before it enters the reactor. The reactor feed heater is a balanced-draft heater equipped with an air preheater for energy conservation.

Answer 29

Reactor feed heater 634F0001

Question 30

The___________ is a centrifugal fan that provides high velocity ambient air to the reactor feed heater as combustion air, which improves air/fuel mixing for the small burners in the heater

Answer 30

Forced draft fan 634N0011

Question 31

The ______________ is equipped with a rotating drum charged with ceramic elements that transfers heat from the hot heater flue gas to the ambient air from the Forced Draft Fan prior to the air entering the reactor feed heater.

Answer 31

Air preheater 634E0001

Question 32

The _____________ is a centrifugal fan taht draws the hot flue gas out of the reactor feed heater convection section and through the air preheater. The fan then discharges the flue gas back into the heater stack from which it is vented to the atmosphere.

Answer 32

Induced Draft Fan 634N0001

Question 33

The _________ utilizes two beds of catalyst to treat the unit feed. The catalyst used in the reactor is Nickel Moly catalyst and cobalt moly. In the reactor, the sulfur and nitrogen compounds in the heated feed are saturated with hydrogen and converted by an exothermic reaction to hydrogen sulfide (H2S) and Ammonia (NH3). Hydrogen gas is used as quench for temperature control between the two beds.

Answer 33

HDS Reactor 634R0001

Question 34

The ____________ separates the cooled reactor effluent stream into a hydrocarbon liquid stream and vapor stream. Hydrocarbon liquid is released from the bottom of the vessel to the product stripper in the Stripping Subsystem. The vapor exits the top of the drum and is cooled in the hot flash vapor/fresh feed exchangers and the hot flash vapor/hydrogen gas exchanger.

Answer 34

Hot Flash Drum 634D0002

Question 35

The ____________ inject high-pressure wash water into the hot flash vapor stream as it leaves the hot flash vapor/hydrogen gas exchanger. The water injection removes ammonia and ammonia salts from the proces stream.

Answer 35

Condensate Water Injection Pumps (Wash Water Pumps) 634P0013 A/B/C (Also supply 633 and 635 HDS units)

Question 36

The _______________ are two banks of air coolers that cool the hot flash drum vapor by heat exchange with ambient air.

Answer 36

Hot Flash Vapor Air Coolers 634E0001A/B

Question 37

The ____________ separates the cooled stream from the Hot Flash Vapor Air Coolers into hydrocarbon liquid, sour water, and vapor streams. The Hydrocarbon liquid stream is released to the product stripper in the stripping subsystem and the sour water exits the bottom of the drum to the sour water stripper in SRC. The vapor flows from the top of the drum to the recycle Gas Contactor in the Hydrogen compression subsystem.

Answer 37

Cold Flash Drum 634D0003