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Blowdown system

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This topic contains 5 replies, has 2 voices, and was last updated by  Anonymous 8 years, 9 months ago.

  • Author
  • #2180

    Freddy Martinez

    Does anyone have any literature about Open and Closed Blowdown system? I would appreciate it a lot! Thank you.

  • #4838


    Hello everyone,

    I work at old Coker Unit and we are building new closed Blowdown system. We have some concerns regarding PSVs. Current PSV discharge upstream of the furnice is to our current open Blowdown system. Suggestion for the future is to discharge those PSVs to Main column bottom. We are afraid because of the pressure diference (35bar upstream of the furnice and 3 bar in the Main column).
    Does anyone have any experience with that? If yes, please share. We would appreciate it.

    Thank you!

  • #4814

    Claus Graf

    You might want to check page 69 of 131 (Question 48) in the document linked below:


  • #4772


    Thank you very much for your help.

    Best regards,

  • #4738


                                                            Coker Blowdown
         The Coker Blowdown System (CBD) is designed as an enclosed Blowdown System (not vented to the flare) to recover all available hydrocarbon and sour water associated with the current Coker Blowdown operations.  These activities would include:

    Cooling of the Coke Drums
    Steam test / warm-up of the Coke Drums
    Unit startups / shutdowns
    Relief Case Scenarios of heavy oil streams
         The CBD is designed to operate in an ambient temperature range of -30 degrees to 100 degrees.  The design flow rate is based upon maximum quenching of a Coke Drum and the simultaneous relief of 90F-2 (30,000 B/D at 550 degrees), or turned down to minimum.  The recovered products, Heavy Slop Oil (HSO), Light Slop Oil (LSO), Sour Water, and Blowdown Off Gas will be reprocessed in the Regular Coker, the Gas Plant or  sent to the Refinery Slops System or the Sour Water Plant.
         On the Regular Coker Drums, 90PSV-3 (north PSV on #1 Drum) and 90PSV-58 (south PSV on #2 Drum) are tied together and routed to the CBD 24 via a 14 header.  90PSV-54 (south PSV on #1 Drum) and 90PSV-56 (north PSV on #2 Drum) is routed to the CBD utilizing the existing 14 relief line.  Due to the increased back pressure on the system, two 6 PSVs (90PSV-67 on #1 Drum & 90PSV-68 on #2 Drum) have been installed at the coke drum nozzles and relieve into the existing relief line from the coke drums.  The PSVs on #3, #4, and #5 Drums are routed to the 24 CBD header via a 14 relief line.  As in the case of the Regular Coker, #5 Drum has an additional 6 PSV (87PSV-31) installed on the coke drum nozzle.
           The oil drain lines above each switch valve (3) discharge into the 14 Regular Coker Blowdown line.
         The 14 Blowdown Header is attached to a 24 header at the south edge of the abandoned 90E-22, Cooling Box.  The 24 header then turns west (toward the horseshoe) and then turns north toward the Regular Coker.  Directly downstream of the tie-in point there is a temperature element, 90TI-1960, that will be used to detect elevated temperature within the 24 Header.  The following streams connect to the 24 header in this order:

    The pumpout header from 87G-102A/B, Special Coker Charge Pumps
    The 14 relief line from 90PSV-3 and 90PSV-58
    The 14 relief line from 90PSV-54 and 90PSV-56
    The 14 relief line from 87PSVs-1,2,115 the Special Coker Drums (line turns north at this point)
    A 2 Heavy Slop Oil (HSO) nozzle
    Pressure Transmitter, 90PI-1230
    Temperature Transmitter 90TI-1860
    A 10 removable spool for cleaning of the header line
    A 3 Quench Water spray nozzle (removable)
    Temperature Transmitter 90TI-1900 (located on the bottom of the line)
    Temperature Transmitter 90TI-1590
         At this point, the 24 Header turns west and runs down the east/west pipe rack on the Regular Coker (north of 90F-1).  A Start-up fuel gas connection is installed on the header.  This connection is located on the elevated platform near the existing Isolation Butterfly Valves from both Cokers.  The 24 Header continues to the inlet of 90C-42, Quench Tower.  On the inlet to the Quench Tower, the following nozzles are installed:

    A 2 slop line used for clearing the HSO Coke Strainer and 90G-31, HSO Pumps
    A 8 Hot HSO Recycle Stream
    Temperature Transmitter 90TI-1870
    A 10 removable spool piece for cleaning of the header line
         There is an alternate relief line on the Special Coker 18 Flare Line.  On the vertical leg of the existing 18 Flare line, a hot tap has been made. The former 16 line from 90C-19, Blowdown Stack, has been removed from the Blowdown Stack, rerouted, and attached to the hot tap location on the 18 line to provide extra relief capacity.  The following new nozzles have been installed on the 16 Flare Header:

    90PSV-36 relief line from 90C-23, Sour Water Drum
    90C-118, Sour Water Skim Drum relief and vent line
    90G-5A Seal Pot and drain lines
    Fuel Gas purge
    87PSV-141 relief line from 87C-120, Special Coker Condensate Drum
    2 x 1 future connections
         All Blowdown streams enter into 90C-42, Quench Drum.  90C-42 is a 13 I.D. x 35 tall vertical vessel that is insulated.  The tower internals consist of 3 trays (Ring and Disc), seven spray nozzles, and a vortex breaker on the bottom outlet. On top of the vessel, there are three PSVs that relieve to the flare. There are two level transmitters on the tower as well as a Magnicator sightglass.  The Magnicator sightglass uses magnets that are attached to floats providing the following advantages:

    No portion of the glass is in contact with the process fluid
    There is a clear visual indication (no searching for an interface)
    No Jurgenson Valves are required.
    The top nozzles are purged with natural gas and the bottom nozzles are purged with Cool Distillate Seal Flush.
         The Quench Tower bottom temperature will be operated in the @ 400 degree range by using Heavy Slop Oil (HSO).  The HSO is circulated through 90E-39, HSO Recycle Heater, on temperature control and injected into the 24 CBD Header at the inlet of the Quench Tower.  Another slip stream of HSO is injected in the CBD 24 Header at the beginning of the Header to help keep the entire length of the header warm and free of waxy build-up during times when there is no/low flow in the header.  The HSO Recycle Heater, 90E-39, uses desuperheated 600# steam to heat the HSO. All of the HSO leaving the Quench Tower is routed through 90Y-31A/B, HSO Coke Strainers.  These strainers are equipped with a hot distillate flush and a 150# steam-out connection for clean-up of the strainers, and removable baskets (3 baskets with 1 as a spare) to collect any coke in the HSO stream.
         The Quench Tower top temperature is controlled @ 230 degrees by pumping Quench Oil (HSO) through the spray nozzles on the top of the Quench Tower. The cooled Quench is provided by pumping a slip stream of Hot HSO through 90E-33, Slop Oil Cooler. After the HSO has been cooled by 90E-33, the cooled HSO is either sent back to 90TV-1880, Quench Oil Temperature Controller or sent to Slop Oil through 90FV-0410, HSO to Slop Oil which is reset by 90LC-0641on the Quench Tower bottoms for level control of the Quench Tower. By keeping the tower top @ 230 degrees and a low operating pressure (1.5#), any free water will be flashed and carried out the top of the Quench Tower. The Quench Oil line to 90C-42 is also equipped with the following two lines:

    A 2 line where LSO (Light Slop Oil) can be routed during the winter months to help add traffic through the fans.
    A line for anti-foam injection in case of a foaming event.
         Any condensable hydrocarbon at the Quench Tower top should be knocked down into the bottoms. Any HSO in the bottom of the Quench Tower that is not used for 90E-39, Recycle Heater will be pumped to 90C-2, Regular Coker Fractionator, on level control. A maximum flow of 2000 b/d is injected in the black oil over the baffles line.  If for some reason the Quench Tower bottoms temperature falls below 300 degrees, a temperature switch will trip and not allow any HSO to be pumped into 90C-2, Fractionator through 90FV-0440.  This temperature switch is to prevent any free water to be pumped into the 600 degree bottoms on the Fractionator.  Any excess HSO that is not used as recycle, or is above the flow rate to the Fractionator, will be pumped to Slop Oil through 90FV-0410, HSO the Slop Oil. The HSO that is sent to Slop Oil will be cooled to < 190 degrees by 90E-33, HSO Slop Cooler. 
         All vapors leaving the Quench Tower Overhead flow to the inlet of 90E-37A/H, Quench Tower Condensers, to be cooled.  90E-37A/H consists of 8 banks of fans with 2 fans per bank for a total of 16 Fans.  Each bank has 2 fans, one fan is variable speed controlled and the second fan is variable speed controlled and reversible.  Each bank of fans has a top set of louvers, an internal set of louvers, and one side mounted (east side) set of inlet louvers that are all automated for temperature control.  The remaining set of side louvers (west side) are hand controlled.  Each bank of fans can be isolated from the remainder of the fans for maintenance or for cleaning by utilizing hot distillate flush and 150# steam that is piped into the inlet.  To aid in the winterization of the fans, there is a 150# steam coil under each bank of fans with a TI on the condensate temperature. If the temperature on the TI reaches @ 35 degrees, the steam trap will need to be bypassed or the condensate vented to the atmosphere for freeze protection.  After the process flow is cooled to @ 130 degrees, the vapor / liquid from the fans drop into 90C-37, Blowdown Settling Drum.
         90C-37, Blowdown Settling Drum is a horizontal drum that is 116 I.D. x 35 in length.  The drum is equipped with steam pads on the bottom 1/3 of the drum, & insulation, and one relief valve, 90PSV-37.  Normal operating temperature on the drum should be @ 130 degrees.  Internally, the drum is equipped with a 66 weir for separating the sour water from the LSO.  The sour water side of the weir is larger than the LSO side of the weir.  Both the sour water and LSO sides of the weir are equipped with vortex breakers on the bottom outlets.  The drum has two steam out connections, one for each compartment of the drum.  In addition to the vapor / liquid stream entering the drum, there are four other smaller streams:

    A sour water stream being recycled back to the inlet of the drum.
    A slip stream of LSO being recycle back during the summer months.
    A sour water return line from 90C-38, Gas Compressor Drum.
    A line from 90C-101, Compressor K.O. Drum, to drain liquid from the suction drum to the Settling Drum.
         The sour water side of the Settling Drum has two redundant level transmitters for the interface between the LSO and the sour water.  One of the level bridles is equipped with a Magnicator sightglass.  Normal maximum LSO level on the sour water side will be @ 12.  There are 2 level transmitters, with Distillate flush, that indicate the total level in the Drum.  The maximum total level in the Drum will be 86 (72%).  At this point, the LSO pump will auto stop to prevent pumping water into 90C-2, Fractionator.  Sour water flows to the suction of 90G-30A/B, Sour Water Pumps, after going through 90Y-30A/B, Sour Water Coke Strainers.  The pump will operate with one pump running at all times with a spillback of 150 gpm (5500 b/d) to the inlet of the Settling Drum to maintain a flow during idle times.  The spare pump will start on a high water leveling 90C-37, CBD Settling Drum and will auto stop on a low level in the Settling Drum.  90G-30A/B will also provide a stream of sour water to the 24 CBD Header to aid in the cooling process during a blowdown event or relief scenario.  This stream is injected into the header through a retractable spray nozzle with flow control by 90FV-0420, Quench Water Spray, after being filtered on the discharge piping by 90Y-107A/B, Quench Water Filters.  The amount of flow will be controlled by 90TI-1590.  This flow should be able to reduce the CBD Header temperature to @ 450 degrees during a blowdown or relief event, also the spare 90G-30 Pump will auto start whenever 90FV-0420, Quench Water Spray  valve is open to ensure proper flow rate to the spray nozzle. The suction, 90Y-30A/B, and discharge, 90Y-107A/B, filters are equipped with pressure differential instruments that will send a reading to the TDC.  90G-30A/B will also provide a sour water make-up for 90K-38A/B, CBD Gas Compressor, seal water system.  Any sour water that is not needed for the minimum flow, quench of the CBD Header, or seal water make up will be pumped to the Sour Water Plant on level control for processing.
         The Light Slop Oil (LSO) side of the Settling Drum has 1 level transmitter and 1 level Magnicator.  The oil in the LSO side of the Settling Drum flows to 90G-35A/B, Light Slop Oil Pumps.  One of the LSO pumps will be running continuously by recycling LSO back to the inlet of the Settling Drum (during the summer months) or to the Quench Tower top (during the winter months),  Any LSO not required for minimum flow will be pumped to 90C-2, Fractionator, through 90FV-0380 into the Rich Sponge Oil return line.  The flow, with a maximum flow rate of 350 B/D, ties into the return line downstream of 90LV-0110.  If the net production of LSO exceeds the 350 B/D maximum, the excess will be pumped to the Crude Tanks (2001, 2002, 2003 Tanks) via the Light Slop Header.  If there is not enough LSO to keep one of the 90G-35A/B pumps running, there is cold distillate make up available, on level control, through 90FV-0780 that will flow to the LSO side of the Settling Drum. 
         The vapor leaving the 8 outlet of the Settling Drum flows directly to the suction of 90K-38A/B, Coker Blowdown Gas Compressors.  90K-38A/B, Coker Blowdown Gas Compressors, are Nash Liquid Ring Compressors XL Vectra Series each capable of providing 100% capacity to operate the CBD System.  The Nash compressor is essentially a compressor and a pump combined.  The compressor is able to pump both liquid and gas at a very low suction pressure and at low rpms.  One compressor will operate continually with a spillback flow to the inlet of the 90E-37A/H Fans.  The suction pressure of the compressors will run between 1.5 psig, during idle periods, to 15 psig during the initial coke drum blowdown after switch.  Each compressor is equipped with interlocked automatic isolation valves on the Seal Water, suction valves, and discharge valves.  These automatic valves will close on 2 out of 2 (2 oo 2) voting on the following shutdowns on each individual compressor:

    Seal water temperature above 150 degrees
    Low seal water flow of < than 20gpm.
    High delta p of 25 psig between the suction and discharge pressure.
    The following conditions will trip both compressors (if running)

    High suction temperature (above 200 degrees)
    High level in 90C-37, Settling Drum (above 72%)
    High level in 90C-38, Blowdown Gas Compressor Drum (above 69%)
    Low suction pressure below .5 psig.  In this case the lag compressor will shutdown first
         The Nash Compressor has a continually supplied cool seal water stream that provides the liquid seal water at a temperature of < 180 degrees.  Seal water to the compressor is supplied by the water in 90C-38, Coker Blowdown Gas Compressor Drum, with make-up provided by a slip stream from 90G-30A/B, Sour Water Pumps.  The Seal Water flows through 90Y-38A/B, and then cooled by 90E-38A/B.  The cooled water is flow controlled by a flow orifice on the inlet line to each compressor.  The discharge from the Compressors is sent to 90C-38, Coker Blowdown Gas Compressor Drum, where the vapor and seal water are separated.  The vapor is then normally pressured to the inlet of 90C-10, Regular Coker Overhead Receiver.  An alternate destination for the vapor is the inlet of 90E-110, Regular Coker 1st Stage Spillback Cooler, for times when the Regular Coker is shutdown.
         Also being installed during this project is 90G-5A, Sour Water Pump, and 90C-118, Sour Water Skim Drum.  90G-5A pump is larger than the existing 90G-5 pump and will require a minimum flow of 30 gpm (1100 b/d) at idle times.  The minimum flow will be achieved by using 90FV-0800, Minimum Flow control valve.  The sour water export line from 90G-5 / 90G-5A will be rerouted to use the existing Blowdown Stack water line due to the increase in size, from 2 to 3. 90C-118, Sour Water Skim Drum will be installed for the purpose of skimming of hydrocarbon off of the level in 90C-23, Sour Water Drum (when needed).  The level in the Skim Drum will be pressure into the Flare Header with Refinery Fuel Gas.

  • #4620


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