OPERATING PROCEDURES
Custom Process Equipment, LLC4727 NW Evangeline ThwyCarencro, LA
70520Tel 337-896-3815
Fax 337-896-3816
www.cpe-llc.comINSTALLATION AND OPERATIONS MANUAL
INCLUDEPICTURE "cid:[email protected]" \*
MERGEFORMATINET
INSTALLATION, COMMISSIONING, AND OPERATING PROCEDURES
FOR
Khurmala Dome
Amine Contactor & Regeneration Section
Amine I, Gas Treatment Plant2013INDEX
SAFETY STATEMENT
BASIC COMPONENTS
SECTION I
INSTALLATION
SECTION II
OPERATION
SECTION III
START-UP & SHUTDOWN PROCEDURES
SECTION IV
MAINTENANCE
SECTION V
TROUBLESHOOTING
SECTION VI
DESIGN BASIS
SECTION VII
DocumentDoc. No.
P & ID12016-CPE-KAR AMINE #1- P&ID
Package GA DrawingsTROY to fill out
Cause & EffectTroy to fill out
Process Engineers Data BookCPE-12016-PED-1901
OPERATING PROCEDURESPRIVATE
******************************************************************************
WARNING - DANGER
EXPLOSIVE/HAZARDOUS GASES AND
LIQUID******************************************************************************
Work being performed on this equipment may expose you to
conditions, which can be hazardous and dangerous, as this equipment
or area may contain explosive, flammable or toxic gasses or
liquids. Keep all open flames at least 180 feet away.
This equipment must be serviced and operated by properly trained
and qualified personnel only.
Do not clean, service, repair, or attempt to perform any work
without relieving pressure and purging combustibles.
Check for unsafe conditions, and follow your company's safety
practices any time work is performed on this equipment.
If you have any questions, contact CPE prior to performing any
work on these units.
SECTION I
1.0BASIC COMPONENTS OF AN AMINE SWEETENING/REGENERATION
SYSTEM1.1Contactor (646-V-0101) & Inlet Scrubber (646-S-0101).
The contactor is a vertical tower with 20 2-pass BDH trays and the
inlet scrubber is a two phase vertical separator with vertical vane
pack. Please refer to drawings to see the contactor tower and inlet
scrubber.
1.2Heat Exchangers. Rich/Lean Amine heat exchanger supplied is a
plate and frame (646-E-0101). The Amine Thermosiphon Reboiler
(646-E-0102) is a shell and tube type BEM T.E.M.A class C heat
exchanger. The overhead reflux condenser (646-A-0101) and lean
amine coolers (646-A-0102A/B) are all forced draft coil type
exchangers.1.3Amine Booster, Amine Recirculation & Reflux Pumps
(646-P-0102A/B, 646-P-0103A/B/C & 646-P-0101A/B respectively).
The two by 100% capacity Booster pumps are electric motor driven
centrifugal pumps, one in operation and one in standby. The three
by 50% capacity amine recirculation pumps are variable speed
electric motor driven positive displacement pumps, two in operation
and one in standby. The two by 100% capacity reflux pumps are
electric motor driven centrifugal pumps, one in operation and one
in standby.1.4Still Column (646-V-0102). This column is a free
standing unit with thermosiphon reboiler (646-E-0102) mounted
directly to the vessels side wall. The column is randomly packed in
two sections, top (3)/bottom (23) both sections have Nutter RingTM
#1.5 packing and fluid distributors. See drawing for details. The
towers sump serves as the amine surge volume. 1.5Reflux Accumulator
(646-S-0103) & Reflux Condenser (646-A-0101). The condenser is
forced draft with automatic temperature controlling louvers. The
reflux accumulator is a vertical two phase separator with removable
mist extractor.1.6Hot Oil System: Expansion Tank (646-T-0101), Hot
Oil Circulation Pumps (646-P-0104A/B/C) & Direct Fired Heater
(646-H-0101). This system supplies a continuous stream of hot oil
(therminal 55) to the shell side of the still columns thermosiphon
reboiler. This sub system is a self-contained heat media loop was
provided by a third party and more information can be found in the
hot oil systems installation and operating manual. 1.7Amine Flash
Separator (646-S-0102). The amine flash separator is a three phase
bucket and weir type separator used to remove a substantial portion
of the acid gas liberated from pressure reduction taken by the
amine solution during the regeneration process. This vessel also
helps to separate and remove any liquid hydrocarbons which may have
condensed from the natural gas flowing through the contactor.
Excess liquid hydrocarbons carried over to the still column with
the amine solution may lead to erratic column behavior, foaming,
and premature fouling in the lean/rich amine exchanger, reboiler,
and column internals with marked decreases in overall system
efficiency. The levels are controlled by the bucket and weir
heights in conjunction with displacer type level controls.
1.8Lean Amine Particulate Filter (646-S-0104). This is a
cartridge type filter that removes solids from the amine.
1.9Lean Amine Carbon Filter (646-S-0105). This is a 10 % side
streamed activated carbon filter which aids in the removal of
organic contaminants and dissolved hydrocarbons from the amine.
2.0Lean Amine Polishing Filter (646-S-0106). This is a 10% side
streamed fine particulate filter and removes fine particles which
may carry over from the charcoal filter and/or accumulate in the
amine solution over time. SECTION II
2.0INSTALLATION
The proper installation of the gas sweetening and amine
regeneration system is imperative for successful operation. The
equipment must be installed level.
2.1Installation Instructionsa)Remove all shipping braces, flange
covers and protective guards. Inventory all parts.
b)Visually check the vessels, the couplings, nozzles, vessel
shells and accessory items to see that none have been damaged
during shipment. Report any damage as soon as possible.
c)Reinstall all components that were disassembled for shipment.
Refer to Package GA Drawings for details as well as the packing
list provided with shipment. Be sure that the still column contains
pall ring saddles that may have been shipped loose. Check level and
alignment of the vessels. If the contactors structured packing has
been removed for shipment, it should be reinstalled. The filter
elements must be installed in the lean amine stream downstream of
the lean amine coolers and upstream of the amine circulation pumps.
Ensure all pumps are properly lubricated. Please refer to Pumps
section of this manual for more details on installation, operation
and maintenance of these pumps.
d)Install ladders and walkway, which were removed using bolts
and grating clips. Also install vessel accessories, and all piping
items that were removed for shipment.
e)Check that all vessel accessories such as pressure gauges,
gauge glasses, relief valves, etc., are installed in proper
location. Refer to the drawings for nozzle locations, dimensions
and general description. In addition, you may refer to vendor
literature.
f)Check all instrument tubing for flattened areas or kinks.
Repair or replace before start-up.
g)Purge all instrument lines and start admitting instrument air
to the system. Check all instruments for proper operation and
stroke all control valves and shutdown valves. Be sure that all
control valves move freely and fail in the proper position.
h)Perform complete loop checks on all instruments and the entire
safety logic. The loop check procedure is of critical importance
and further steps of commissioning cannot proceed until this step
is totally completed.
i) After completion of the "Loop Checks", a piping system hydro
flushing is recommended. The initial flushing shall be carried out
prior to leak testing. For austenitic steelwork flushing can be
performed after pressure testing. Items of equipment that are
sensitive to damage during hydro flushing, shall be removed,
blocked off or isolated. Ball valves shall be flushed in fully open
position. All piping systems shall be flushed using high pressure
jet flushing equipment, such as rotating hose or rotating nozzle.
Water velocity shall be a minimum of l0 m/s. On systems where high
pressure jet flushing cannot be used due to complicated shapes
and/or long runs HVWF may be used. The flushing medium shall in
general be fresh water. When flushing stainless steel lines, the
chloride ion content shall be less than 200ppm.
j)After completion of hydro flushing, a complete pressure (i.e.,
leak) test of all of the equipment should be performed. We suggest
nitrogen should be used and all equipment should be brought to 95%
of design pressure, slowly, checking all areas for leaks.
k)IMPORTANT: Refer to filter and pump sections of this manual
for detailed installation and pre-commissioning checks which must
be performed on these items.
l)Calibrate all instrumentation and set levels in accordance
with alarm summaries.
m)Fill Procedure:
Before adding the amine solution or wash fluid, check all
openings, man ways, gauge cocks, etc. in reboiler, pumps, filters,
flash separator, contact tower air coolers, lean rich exchanger,
still column, reflux pumps and reflux accumulator making sure they
are secured by plugs or valves and are tight. Initial amine charge
or wash fluid fill is to be put into the still column sump via the
water makeup line. Have the operation management team prepare a
valve close/open check list utilizing the as-installed and walked
through P&ID during initial wash water fill before connecting
the sour gas feed. 1. Check that drain valves are closed2. Open all
control valve bypass lines3. Vent contact tower, flash separator,
still column and/or reflux accumulator4. Check for acid gas leaking
through vents
5. Bypass filters
6. Bypass main circulation pumps7. Close reflux accumulator
level control valve and bypass The reflux accumulator should be
filled separately and with make-up quality water8. Turn on power to
electric panels: all alarms and shutdown signals should be
operating correctly before continuing with the next steps.
9. Turn on amine fill pumps and slowly begin filling the system
with the amine solution10. Closely monitor the level gauge in still
column 646-V-??
11. Continue to fill the system until the set point level in
still column *&&* is achieved12. Turn on one of the amine
booster pumps13. Closely monitor level gauge (&*&) located
the rich amine section of amine flash separator (646-V-???)
14. Continue filling the system and running the amine booster
pump until the set point level of 646-LG-?? is achieved.
15. Turn off the booster pump and fill pump16. Check all liquid
levels, the reflux accumulator and liquid hydrocarbon bucket in the
amine flash separator are the only two levels that should visible
through level gauges.
17. By pass the reflux accumulator control valve and fill the
reflux accumulator via the top side 2 level gauge process
connection of LG-??? 18. Slowly fill the reflux accumulator until
the level set point is reached
19. Reconnect and tighten LG-??? to reflux accumulator
646-V-???
SECTION III3.0OPERATION3.1Definition
Sweetening is the process of removing acid gas from natural gas.
This section is only included to discuss the removal of CO2 and H2S
from natural gas by means of the tertiary amine
methyldiethanolamine (MDEA)
The amine sweetening Unit supplied has been designed and
fabricated to deliver a sweet gas composition in accordance with
the design conditions and product specifications supplied by the
customer. This section is intended to serve as a handbook and guide
to assist with the initial start-up and normal operation of the
unit. Not to replace the operating companies commissioning,
decomisioning or operating procedures.
A better understanding of the equipment and its application will
provide greater operation efficiency and make solving operating
problems easier. It is, therefore, the purpose of this manual to
explain the design, construction and operating characteristics of
the unit; however, it must be noted by the reader that no manual
can foresee all possible situations due to the myriad combinations
of pressure, temperature and operating conditions possible in
operations. The reader is, therefore, advised that the services of
a competent on-site technician during start-up and operation of the
unit is essential to prudent safe operation.
3.2Effect of Contact Conditions1)Temperature there are practical
limitations in using amine for acid gas absorption from the
standpoint of both absorption efficiency and operational cost. The
lower the temperature of contact, the greater the viscosity the
amine solution will be. As the viscosity of the solution increases,
the efficiency of contact decreases resulting in lower tray
efficiencies. Additionally, the amine sweetening process involves
both physical and chemical absorption and is driven primarily by
chemical absorption. As the amine solution contacts the sour gas
several chemical reactions take place, as in most controlled
chemical reactions temperature is critical. The two primary
reactions paths that take place are; Hydrogen sulfide reacts with
the MDEA solution to form R2NHCH4+ plus HS- and is believed to take
to take place instantaneously while Carbon dioxide reacts with the
MDEA solution to form R2NCH4+ plus HCO3- and is generally
considered to be the slower reaction since CO2 must form
bicarbonate with the water in the solution before reacting with the
tertiary amine. Both reactions are reversible and are in fact
reversed in the still columns reboiler during the regeneration
cycle. These reactions are exothermic and cause distinct
temperature profiles across the contact tower. This profile
reflects the rate of reactions and may prove to be a useful tool
when determining pinch points, optimizing lean/rich approaches and
advanced process trouble shooting techniques. The optimum lean
amine solution temperature depends on ambient temperatures, inlet
gas temperature and pressure, amine solution strength and lean
amine loadings. As a rule of thumb the amine solution is generally
held slightly above the inlet gas temperature 3-8 0C this helps to
reduce foaming and liquid hydrocarbons condensing out the natural
gas stream. Foaming in the contactor will lead to pronounced
reductions in absorption efficiency and high amine losses which
will carry over to the dehydration section of this gas process
facility. Amine carry over will inadvertently effect the downstream
dehydration process and should be mitigated prior to downstream
contamination. On the other hand, if the lean amine solution
temperature is excessively high, the higher vapor pressure of acid
gases in the amine solution will lead to poor reaction kinetics and
off spec product. Although this system is capable of meeting the
sweet gas product specification under an assortment of varying set
points and ambient temperatures it is advised that an experienced
operating company or engineering firm be consulted for proper
system optimization. 2)Pressure The contactors operating pressure
is dependent on the available sour gas pressure and is directly
related to the sour gas constituents partial pressure. The partial
pressure of acid gas affects the rate at which it reacts with the
amine solution. Generally the higher the partial pressure of acid
gas the faster the reaction rate, however practical considerations
such as down or upstream compressor stages and unit operations are
generally the governing elements. 3)Amine Concentration The amine
solution strength plays a significant role in the systems overall
performance and limitations. This system was designed considering
only a 50/50 solution of MDEA and water. Lower amine concentrations
will generally lead to increased reboiler duty and higher rich/lean
loadings. Although, slight adjustments to the amine solution
strength can result in increased efficiency, leaner products, and
lower corrosion rates it is suggested that this system be operated
at its design solution strength and adjustment only be made by
qualified experts. Note: the water used to dilute the amine
solution to its proper strength must be free of contaminates and
conform to the make-up water requirements provided in appendix
#.3.3How Does the Process Work?All continuous and regenerative
absorption processes have the same purpose, that is to remove
contaminants from contaminated gas streams , producing a continuous
gas stream with lower contaminants compositions, returning the
sorbent through a regeneration cycle, removing the contaminant from
the sorbent, leaving the lean sorbent to be pumped back to contact
the gas and repeating the process.
Now how does MDEA sweetening process work? First, refer to
P&ID place proper as built # here. Wet sour gas flows
vertically upwards into the absorber section of the contact tower
where it is contacted counter currently across twenty trays with
lean Methyl-Diethanol Amine (MDEA) Refer to vessel drawings for
details of internals. Sweet gas leaves the top of the absorber
tower through the outlet scrubber section while rich amine flows
from the contactor tower to the regeneration package. The pressure
of the amine solution is dramatically reduced via the contactors
level control valve and flows into the flash separator prior to
entering the lean/rich cross exchanger. Sour hydrocarbon vapors are
released from the amine as the pressure is reduced in the flash
separator and routed to incineration and/or flare. The vessel is
equipped with sufficient retention time to separate and remove any
light liquid phases that may develop, this light liquid phase
collects in the separators bucket and is routed to skid edge where
it is the operator responsibility to properly dispose of. Note:
Both the vapors and light liquids will be rich with acid gas
contaminants and must be disposed of in accordance to local or
national regulations. The heavy liquid phase (amine solution) is
routed to the lean/rich cross exchanger where it absorbs heat from
the lean amine stream. The heat absorbed by the rich amine stream
releases additional acid gasses from the solution and helps reduce
the still columns reboiler duty. However, this acid gas breakout
may lead to a complex two phase flow regime in the vertical piping
between the rich/lean cross exchanger and still column. Several
methods during the design of this system were used to predict and
control this regime by proper process piping, however all such
methods are inherently complex and lead only to close
approximations. The object of this design was to minimize slugging
to the still column which may disrupt the columns temperature
profile and may lead to erratic behavior. It is the operator
responsibility to analyze and mitigate any abnormal flow conditions
which may result from operating this system outside of its design
parameters, such abnormalities may include but not limited to:
excess fouling on the lean or rich side of the exchanger due to
improper maintenance, contaminated makeup water, excess amine
degradation products due to improper reboiler startup and/or
shutdown, etc. The rich amine solution enters the top of the still
column between the upper and lower sections of random packing where
it contacts the reflux stream flowing down the top section of
packing and travels through the lower packing section as it
contacts stripping vapors generated in the reboiler. Once the now
semi-lean amine exits the lower section of packing it collects on a
chimney tray and flows into the collection bucket of the
once-through vertical thermosiphon reboiler there it enter the
reboiler where it is partially vaporized and exits back into the
column below the chimney tray and into the reboilers collection
bucket spill over weir designed to maintain a constant liquid head
feeding the thermosiphon reboiler. Remember when calculating an
amine system reboilers required heat duty that it is the sum of the
sensible heat energy needed to bring the bottoms liquid to its
bubble point, the latent heat of vaporization energy associated for
the desired boil-up ratio and the heat necessary to break the
chemical bonds between the amine and acid gas. The now fully lean
amine flows over this spill over weir and into the still columns
sump, which also serves as the amines surge volume, during the
steady state operation of the regeneration system the level in this
towers sump will steadily decline as water is lost through the
still columns overhead. This rate has been predicted for the design
cases as depicted by the design basis of this system; however it is
the operators duty to determine the actual amount needed as well as
method of monitoring and adding makeup water to the system. This
process should be tailored to conform to the operators standard
practices. Lean Amine exits the column and enters the lean/rich
cross exchanger where it supplies heat to the rich amine entering
the still column as previously described. The lean amine then flows
to the amine booster pumps which supply the necessary suction head
pressure for the circulation pumps. After leaving the booster pump
the lean amine passes through the lean amine air coolers then
filtered the lean amine particulate and carbon filters. Upon
leaving the filters the lean amines pressure is elevated to
contactors operating pressure via the main circulation pumps and
returned to the contactor to complete its regeneration process.
3.4Amine Degradation & ContaminationOne of the biggest problems
connected with the operation of amine sweetening systems is amine
contamination degradation. This contamination usually results in
decreased performance, increased amine loss, and may result in
damage to the equipment. The most common source of contamination is
from slugs of heavy hydrocarbons, treating chemicals, saltwater,
drilling mud and dirt. The solid particles that enter the amine
are, in most cases, removed by the filter. Heavy hydrocarbons may
cause foaming with the resultant loss of amine through carryover.
This system includes an amine-hydrocarbon skimmer vessel. This is
the three phase flash separator (646-S-0102) which skims the
hydrocarbons off the amine. Amine degradation will usually occur in
the reboiler and results in the formation of amine salts, which are
toxic and corrosive. To limit the degradation of amine the reboiler
of this system has been design with specific circulation rates and
temperature of both the hot oil and amine. Operating outside of
these ranges is not advised and may lead to excess degradation of
the amine solution.3.5CorrosionThe sour gas processing service of
this system is an inherently corrosive one. Several mitigating
steps have been taken during the design of this system such as lean
and rich amine loadings, selective control valve and line sizing to
control velocity, excessive corrosion allowances where applicable,
industry specific material selections and vessel coatings for
specific regions of the process where acid gas may break out of the
amine solution, as well as minimal dead legs in piping. However, it
is ultimately the operators responsibility to properly monitor and
mitigate corrosion problems through proper maintenance and
operating procedures. The hot oil supply subsystem is also
susceptible to accelerated corrosion rates if oxygen is allowed to
contaminate the hot oil circulating in this subsystem. Please refer
to the hot oil (therminal 55) suppliers literature for more
information, and mitigating procedures.3.6 Alarm and Trip
Setting
Instrument TagUnitsOperatingSet Point
Complete only after
as-piped and walked through P&ID completed
SECTION IV4.0START UP & SHUT DOWN PROCEDURESStart up and
operation procedures depend on the particular application and type
of equipment and auxiliaries supplied. However, there are certain
generalities that usually apply which, with special procedures as
pointed out, should permit operation with a minimum of
difficulty.
Preliminary: operators should familiarize themselves with
literature for all instruments and controls, and study any
applicable flow sheets or drawings of the unit.
1.) Ensure that all Plant Check Out and Amine Unit Clean Out
procedures have been carried out and included at a minimum plant
controls logic, shutdown logic, electric systems, instrument air
systems, purging and leak checks, emergency systems, and charging
of all chemicals and lubricants. 2.) Block valves on sour process
gas should be initially closed.
3.) Turn on power to electric panels: all alarms and shutdown
signals must be operating correctly before continuing with the next
steps.
4.) Turn on the hot oil subsystem following the startup
procedure as given by the subsystems operations manual provided by
the third party vendor.
5.) Pressurize the amine flash tank using blanket gas
6.) Turn on all condenser fans, reflux pumps, booster and
circulation pumps.
7.) Allow time for the circulating hot oil to reach its set
point temperature.
8.) Open the sour process gas inlet slowly to pressurize the
contact tower and leave the sweet gas line valve closed; if
applicable divert to incinerator or flare, keep the gas flow rate
to no more than half the design flow rate. 9.) Check that the amine
solution concentration.
10.) Circulate the amine solution until the still overhead
condenser inlet temperature reaches its minimum operating
temperature or set point.11.) Open the sweet gas valve and slowly
increase the flow rate to its desired operating rate. While closely
monitoring the sweet gas outlet composition. 12.) Switch to fully
automatic mode. None of the safety shut downs should activate.
****NOTICE****
Amine Units are usually part of larger plants. Therefore the
start-up and commissioning of the amine unit should be synchronized
with other process and units within the entire gas treatment
facility. The following precautions should also be made aware to
operators and adhered to: A.) Make sure lean/rich cross exchanger,
lean amine air cooler, filters and pump suction lines are flooded,
bleeding air out of line should be done with extreme caution and
appropriately vented as necessary. Use bypass valve if
applicable.B.) Close all bypass valves (amine and hot oil where
applicable) around the pumps and heat exchangers C.) CAUTION ensure
that the reflux accumulator outlet is not restricted and operating
properly. BACK PRESSURE COULD RESULT IN PROCESS FAILURE, EQUIPMENT
DAMAGE AND PERSONAL INJURY. IRREGULAR PRESSURE CONTROL WILL LEAD TO
ERATIC REBOILER BEHAVIOR AND A DIFFICULT TO CONTROL PROCESS.
D.) Check pumps and motors (where applicable) for proper oil
level, alignment, condition of valves and seats, etc.E.) Adjust
instrument air supply regulators to maintain proper supply pressure
to shutdown and control valves.F.) Ensure all valves are in their
proper location, drain valves are closed, relief valve isolations
in accordance with the P&ID. Particularly ensure all lock open
valves are locked open and all locked closed valves are locked
closed.G.) If necessary to maintain minimum surge volume level and
or appropriate amine solution strength, add make-up water. CAUTION
SHOULD BE TAKEN, HOWEVER, THAT THE SURGE NOT BE FILLED TOO FULL.
AMINE WILL EXPAND AS IT COMES UP TO THE OPERATING TEMPERATURE
CAUSING THE SURGE VOLUME/STILL COLUMNS SUMP TO TRIP ON HIGH LEVEL.
Once levels and temperatures are properly established, there is
still room in the surge to accommodate absorber holdup and also
provide for several days normal operating losses.H.) CAUTION THIS
EQUIPMENT WILL HAVE HOT SURFACES. MOST ARE INSULATED BUT OPERATING
PERSONNEL MUST EXERCISE CAUTION.I.) Several hours may be required
to accumulate sufficient condensate for the oil level control to
activate in the amine flash separator. DO NOT ALLOW AMINE TO SPILL
INTO THE CONDENSATE BUCKET.
4.1Shutdown ProcedurePreliminary: check all temperatures,
pressures, levels and flow rates. This information may save time
returning the unit to operation.A.) Turn off gas to contactor
646-V-0101 if no bypass is in system
B.) Continue circulating amine while monitoring rich amine
loading until it matches the lean amine loading.
C.) Remove heat source, by following the shut down procedures of
the hot oil subsystem.D.) Disable makeup water supply and monitor
the reflux flow rate until no reflux flow is observed.E.) Stop
reflux pumps.F.) Turn off fans to reflux condenser.
G.) If draining is required allow the amine solution to
circulate until the temperature entering the lean amine air cooler
is approximately that of the exiting temperature. Otherwise
circulate until the temperature entering the lean amine air cooler
is under 100 0C. H.) Shut down the lean amine air cooler fans
I.) Turn off the circulation and booster pumps respectively.
J.) Bleed pressure off the absorber, if the system is to be down
for any extended period of time. USE CAUTION AND VENT IN ACCORDANCE
WITH PLANTS SOUR GAS VENTING PROCEDURES.K.) Turn off the blanket
gas to the flash separator and bleed off the amine flash tank, if
the system is to be down for any extended period of time. USE
CAUTION AND VENT IN ACCORDANCE WITH PLANTS SOUR GAS VENTING
PROCEDURES.
L.) Bleed pressure off the reflux accumulator, if the system is
to be down for any extended period of time. USE CAUTION AND VENT IN
ACCORDANCE WITH PLANTS SOUR GAS VENTING PROCEDURES.
M.) The Amine regeneration unit must be cooled down to ambient
temperature by natural cooling before any draining of the
system.
f)Standard maintenance procedures should apply to a unit being
taken out of service for an extended period of time. The absorber
and still column should be water-flushed with a caustic solution
rinsed and drained. The pumps should be cleaned and plungers coated
with a rust preventative. CAUTION ALWAYS DISCONNECT POWER SUPPLY
PRIOR TO SERVICING ELECTRICAL EQUIPMENT. DO NOT ALLOW SMOKING OR
OPEN FLAME AROUND GAS PROCESS EQUIPMENT.
4.2Operational Shutdown PhilosophyRefer To operational companys
standard practices. SECTION V5.0MAINTENANCE
5.1Preventive Maintenance
The best control of operating problems is to have an effective
maintenance program, not only for the equipment, but also for the
chemical.
A thorough checkout of an amine sweetening unit should be made
at least every 30-40 days to insure good operation.
Should a vessel require an internal inspection, a thorough
purging is recommended.
5.2Mechanical
5.2.1Pumps - Pump seals or O rings may need replacement or
adjustment. Strainer screens should be cleaned and/or replaced.
Consult the appropriate service bulletins for model specific
maintenance instructions and procedures.5.2.2Filters The
particulate and carbon filter elements should be replaced when the
differential pressures across the filters are ?? psi (?? BAR) for
carbon filters and ?? psi (?? BAR) for glycol filters. Filter
elements can be purchased either directly from the
vendor.5.2.3Temperature Controls - to insure that the fluid
temperature in the reboiler is below the degradation temperature
the controls must be in good working order.
5.2.4Level Controls and Control Valves - if not in good
operating condition, can cause an upset in amine flow. Any valves
and controls requiring lubrication should be properly lubricated at
selected intervals to assure best performance. Maintenance and
repair of valves and controls depends upon severity of service,
e.g. mud, sand, etc.
5.2.5Safety Valves - safety valves require periodic inspection
to assure the operator that the valves are not sticking and will
provide safety relief. Pressure testing is the approved method.
5.2.6Overhead Condenser - Refer to instruction manual in final
data books.
5.2.7Heat Exchangers:Tube Cleaning - Operating conditions
sometimes result in an accumulation of dirt on the outside surface
.This can be removed by directing compressed air, or a greaseless
solvent followed by a water spray through the tubes in a direction
opposite the normal flow. The inside of the tubes will require
periodic inspection and cleaning as necessary.
Plug Leaks - Should tapered plugs develop leaks, additional
tightening is normally all that is required. Thread dope may be
used if tightening alone is not sufficient. If shoulder type plugs
develop leaks, the gaskets should be replaced. TAPERED PLUGS THAT
ARE REMOVED FOR TUBE INSPECTION OR CLEANING SHOULD BE REPLACED IN
THE SAME HOLE.
Tube Leaks - Tube leaks can be of two types: (1) leaks in the
tubewall itself (usually corrosion) and (2) leaks in the tube to
tubesheet joint. In the first case, it is usually most practical to
plug both ends of the tube with the resulting loss in heat transfer
surface. When so many tubes have been plugged that performance is
affected, retubing will be necessary. If leaks develop in the tube
to tubesheet joints, re-rolling of the tube will be required. Care
must be used in selection of the proper tube expander for the size
and BWG of the tube being used. As with all rolled tube joints,
over-rolling must be avoided.
General - If it is ever necessary to contact us for service or
replacement parts, it is essential that the serial number or other
identifying data be obtained from the metal nameplate attached to
the exchangers. This is the only way to positively identify the
correct parts that may be required.
5.3Process5.3.1Check amine in the surge volume of the still
columns sump to always maintain a level in the gauge glass.
5.3.2Check filter cartridges. Filter cartridges should be
replaced after three months of initial operation. The used
cartridge elements should be visually inspected for accumulation of
contaminants and debris. Upon analysis, a minimum replacement
schedule should be determined. The carbon filters should be online
whenever the unit is operating and offline during cartridge
replacement.
5.3.3Take samples of amine and have these analyzed for
contaminants (salts, hydrocarbons, etc.), pH, foaming tendency and
color of amine, etc.
5.3.4Check levels, temperatures, pressures and flow rates
regularly. This information will help diagnose problems and prevent
shutdown.
5.3.5Check for leaks and repair as required.5.3.6the most
important item in any preventive maintenance program is to "keep
the system clean". When the amine is "dirty", the possibility of
plugging the absorber is greater, the efficiency of dehydration is
less, and glycol loss is enhanced.
5.4Periodic Shutdown and General Inspection
Every year or when required by operation, a shutdown and
complete inspection of the unit is desirable. This should include
but not be limited to:
5.4.1Cleaning of the reboiler. Remove any deposits.
5.4.2Clean the stripping column and clean or replace the packing
if deemed necessary.
5.4.3Clean the amine contact tower.
5.4.4Clean all heat exchangers.
5.4.5Clean, inspect and repair all valves and controls. Replace
damaged trim.
SECTION VI
6.0TROUBLESHOOTING
It is the responsibility of the operator in the field to quickly
identify and if possible, eliminate an operating problem. A delay
in correcting a malfunction can be very costly both in personnel
safety and damage to equipment.
The most obvious indication of an amine sweetening systems
malfunction is an off spec quality of the sweet gas or excessive
amine losses. In the majority of cases this is brought about by
insufficient amine circulation and/or high lean loadings. These two
factors can be due to a variety or contributing causes as listed
below.
In addition to mechanical causes, high product impurity may be
found due to existing operating conditions for which the equipment
was not designed. These conditions can sometimes be at least
partially alleviated by both changes in process condition and
mechanical operation.
6.1Common deviations, causes, consequences and actions are shown
below:6.3.1FiltersDeviationCauseConsequenceAction
Low differential pressure across filter Torn element.Open
bypass.Hydrocarbon Contamination.Foaming.
Filter material carry over.Confirm PLC and Field instruments
agree.
Close bypass. Replace element.
High or continuously rising differential pressure Across filter
Particle accumulation.
High liquid loadings.
Reduced Throughput. Hydrocarbon Contamination.
Foaming.Clean or replace dirty filters.
Sudden IncreaseLevel control failure.
Solid fouling.HC contamination.
Foaming.
Reduced throughput.
Clean or replace filter.
Mitigate level control failure
6.3.2Amine contactorDeviationCauseConsequenceAction
Low differential pressure across traysPossible tray damagePoor
efficiency.
Off spec product.Mechanical repair.
Gradual differential pressure increasePossible
fouling.Flooding.
Poor efficiency.
Capacity limit.
Off spec product.Cleanout.
Identify root cause.
Sudden differential pressure increaseFoaming.
Flooding.Poor efficiency.
Liquid carry over.
Plant upset.Reduce gas and/or liquid rates. Check relative inlet
temperatures. Check for hydrocarbon contamination and feed gas
liquid hydrocarbon entrainment.
Low gas flow rateUpstream process changeReduced amine
demand.
Potential for poor mass transfer due to contactor trays
weepingReduce amine flow. Supplement gas feed with clean or
recycled gas.
High gas flow rateUpstream process changeIncreased amine demand.
Possible jet flooding.Increase amine flow.
Low amine flow rateChange in supply pressure or pump control
malfunctionPotential off spec product.Check pumps and inlet sour
gas pressure
High amine flowChange in supply pressure or pump control
malfunctionIncreased utility consumptionAdjust conditions check
pump controls.
Amine contactor continuedDeviationCauseConsequenceAction
Low feed gas temperatureUpstream upset.
Change in ambient conditions.Reduced acid gas pickup.
Check instrument gauges. Monitor product spec for changes.
High feed gas temperatureUpstream upset.
Change in ambient conditions.Reduced acid gas pickup.
Check instrument gauges. Monitor product spec for changes.
Low lean amine temperatureUpstream upset.
Change in ambient conditions.Low rate of reaction due to higher
solution viscosity. Off spec product.Reduce lean amine cooling by
adjusting louvers (slowly while monitoring temp)
High lean amine temperatureUpstream upset.
Change in ambient conditions.Off spec product. Excessive
moisture in treated gas. And potential for downstream condensation
and corrosion/foulingIncrease lean amine cooling by adjusting
louvers (slowly while monitoring temp) and/or fan control.
Low lean amine/feed gas temperature differentialUpstream
upset.
Change in ambient conditions.Hydrocarbon condensation in
contactor. Foaming. Emulsification. Increase lean amine cooling by
adjusting louvers (slowly while monitoring temp) and/or fan
control.
Low rich amine loadingOver circulation.High utility
consumption.Reduce amine circulation rate.
High rich amine loadingUnder circulation.Off spec
productIncrease amine circulation rate.
High H2S in treated gasFlooding.
Foaming.
High lean amine loading.
Low amine solution strength.
Low circulation rate. Excessive amine degradation. Poor
contactor efficiency. Environmental non-compliance. Downstream
corrosion.Adjust process conditions as warranted.
6.3.3Amine Flash Separator
DeviationCauseConsequenceAction
High pressure Malfunctioning pressure control valve. Excessive
hydrocarbons in amine. Contactor foaming.Regenerator foaming.
Excessive acid gas breakout in rich/lean amine cross exchanger.
Correct contactor operation. Clean up amine.
Low pressureMalfunctioning pressure control valve.
Vessel vented to atmosphere or relief system. Blanket gas
malfunction.Amine may not flow to still column. Environment
contamination. Personal endangerment.Find and repair leak. Fix
blanket gas and/or pressure control valve.
High flash gas rateExcessive hydrocarbon carry over from
absorber. Foaming in still column.
Reduced acid gas absorption.Correct absorber operation.Clean up
amine.
High hydrocarbon bucket levelMalfunctioning level
control.Foaming in still column.
Reduced acid gas absorption.Fix level control.
High Amine bucket levelMalfunctioning level control.
Water leaking into the system. Excessive water makeup rates.
Over filled systemAmine carry over into gas system. Diluted amine
strength.Reduce makeup water rate.
Check amine strength.
Remove amine solution from system and correct solution
strength
Low Amine bucket levelDehydrating amine. Low makeup water rate.
High amine losses due to foaming in absorber or still column. Amine
leakFlash gas carry over into amine still column.Correct amine
solution strength. Find and repair leak. Correct absorber and/or
still column operations.
6.3.4Lean/Rich Amine Cross Exchanger
DeviationCauseConsequenceAction
High rich side outlet temperatureHigh hot oil temperature and/or
rate.
Flashing of acid gas in exchanger. Corrosion in exchangers and
outlet piping.Check amine flows. Lower hot oil rate or temp. check
for low lean loading.
Low rich side outlet temperatureExchanger foulingPoor still
column performance. High lean loading. Increased hot oil
demand.Check exchanger UA for design deviations and fouling. Check
rich side differential pressure.
High rich or lean side differential pressure.Exchanger clogged
or fouling.Poor still column performance. High lean loading.
Increased hot oil demand.Clean exchanger.
6.3.5Amine Regeneration Still
ColumnDeviationCauseConsequenceAction
Low pressureMalfunctioning pressure control. Loss of reboiler
heat source. Upset in flare.Determine cause. Check panel agrees
with instruments.
High or rising pressureDownstream upset. Failed pressure
control. Flooded accumulator. Excessive reboiler duty. Condenser
fouledDownstream unit shutdown. Unit shut down.Reduce reboiler
duty. Raise reflux temperature. Shut down and clean overhead lines
and condenser
Low differential pressure across packingPossible packing or
distributor damagePoor efficiency.
Off spec product.Mechanical repair.
Gradual differential pressure increasePossible
fouling.Flooding.
Poor efficiency.
Capacity limit.
Off spec product.Cleanout.
Identify root cause.
Sudden differential pressure increaseFoaming.
Flooding.Poor efficiency.
Liquid carry over.
Plant upset.Reduce gas and/or liquid rates. Check relative inlet
temperatures. Check for hydrocarbon contamination and feed gas
liquid hydrocarbon entrainment.
Gradual decline in rich amine flow Declining level in flash
drum. Cross exchanger fouling/plugging. Open drains and leaksLoss
of throughput and treating capability.Balance flows in and out of
system. Check contactor for foaming and amine losses or operational
upset. Check for maintenance activity. (filter change equipment
drains) check reflux and makeup water rates.
Amine Regeneration Still Column Continued
DeviationCauseConsequence Action
Sudden loss of rich amine feedGas blow by in amine flash
separator low level. Low pressure in amine flash separator. Lean
rich amine cross exchanger plugged. Loss of circulation. Low amine
inventoryFlash gas carry over to still column. Pump cavitation. Low
level in still column sump. Excessive reboiler skin temperatures
and amine degradation. Find and fix leak. Mitigate low level in
flash drum. Add amine and/or make water and check solution
strength. Mitigate circulation pumps problems. Check blanket gas
train. Check for amine degradation and remove amine salts and
reclaim amine if warranted. Check for liquid hydrocarbons carrying
over into the still column and flashing in the cross exchanger.
Low level in still column sumpInsufficient make up water rate.
Low amine inventory level. Amine leak. Amine carryover due to
contactor flooding and/or foaming. Increased amine degradation
products. Possible pump cavitation. High amine losses. Check makeup
water rates and solution strength. Add amine solution to inventory.
Correct contactor operation.
6.3.6Lean and Rich LoadingDeviationCause ConsequenceAction
High lean loadingInsufficient reboiler duty. Over circulating.
Fouled exchangers. Off spec solution strength. Leaking cross
exchanger. Caustic contamination. Off spec product. Excessive
corrosion rates. Increase reboiler duty. Decrease circulation.
Increase amine strength. Remove degradation products reclaim amine,
if warranted. Clean fouled exchangers. Check sodium levels.
Low Lean LoadingExcessive reboiler duty. Under circulating, Off
spec solution strength.Excessive utility usageLower reboiler duty.
Increase circulation.
High rich loadingUnder circulating. Excessive feed gas rates.
Feed gas composition change.High corrosion rates. High flash gas
rates.Increase circulation. Check feed gas rate and
composition.
Low rich loadingContactor flooding. Contactor loss of
efficiency. High solution strength. Low feed gas rate. Feed gas
composition change.Off spec product. Excessive utility
consumption.Correct contactor operation. Check solution strength.
Check feed gas rate and composition.
SECTION VII
7.0DESIGN BASIS
The design basis of the amine regeneration unit and contactor is
as follows:
CompositionFeed GasUnit
Methane(Mole Fraction, Total)68.9%
Ethane(Mole Fraction, Total)9.55%
Propane(Mole Fraction, Total)5.6%
i-Butane(Mole Fraction, Total)1.38%
n-Butane(Mole Fraction, Total)2.33%
i-Pentane(Mole Fraction, Total)1.25%
n-Pentane(Mole Fraction, Total)0.491%
CO2(Mole Fraction, Total)3.51%
H2S(Mole Fraction, Total)5.6%
C6+(Mole Fraction, Total)0.87652%
PropertiesFeed GasUnit
Temperature140oF
Pressure378.5Psig
Mass Flow154262lb/h
Specific Gravity0.882
Water Content 238lbm/MMSCF
Water Dew Point 122oF
Equipment Specification InputsSimulation Design Case Output
Requirements
DescriptionDesign SpecificationOperating-Case 1Design-Case 2
Reboiler Duty26.5 MMBTU/h24 MMBTU/h26.5 MMBTU/h
HEX Duty Lean/Rich Amine20.5 MMBTU/h18.7 MMBTU/h18.8 MMBTU/h
HEX Duty Lean Amine Return15 MMBTU/h13.76 MMBTU/h13.81
MMBTU/h
Stripping Column Reflux Condenser11.5 MMBTU/h8.04 MMBTU/h10.5
MMBTU/h
Circ. Pump Power Requirements150 hp141 hp141 hp
Circ. Pump Nominal Flowrate600 sgpm600 sgpm600 sgpm
Reflux Pump Power Requirements1 hp0.43 hp0.57 hp
Reflux Pump Nominal Flowrate32 sgpm14.8 sgpm19.4 sgpm
Booster Pump
Power Requirements30 hp25 hp25 hp
Booster Pump Nominal Flowrate600 sgpm600 sgpm600 sgpm
Abbreviation List:LT Level Transmitter
PT- Pressure Transmitter
TT Temperature Transmitter
PDZIT- Differential Pressure Transmitter
LAHH Level Alarm High HighLALL Level Alarm Low Low
LAH- Level Alarm High
LAL- Level Alarm Low
PAHH- Pressure Alarm High High
PALL Pressure Alarm Low Low
PAH- Pressure Alarm High
PAL Pressure Alarm Low
TAHH Temperature Alarm High High
TALL Temperature Alarm Low Low
TAH Temperature Alarm High
TAL Temperature Alarm Low
MDEA Methyl-Diethanol AminePAGE 2
