Transcript TITLE

KHABAROVSK REFINERY
HYDROPROCESSING PROJECT
TROUBLESHOOTING
TRAINING COURSE
APRIL 29th – MAY 3rd 2013, MADRID, SPAIN
TROUBLESHOOTING / MITIGATION
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LOW SULPHUR RECOVERY
PRESSURE DROP ISSUE
The increase of pressure drops may be caused by two factors:
1) Increased flowrate through the plant
2) Plugging
Frequent inspection of the sulphur flow from the sulphur hydraulic seals, as
well as reading of the main burner inlet pressure, may give an early warning
before plugging by sulphur and/or ammonia salts might occur.
Note that, for what concerns pressure drop, Sulphur plant is capacity dependant.
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TROUBLESHOOTING / MITIGATION
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PRESSURE DROP ISSUE
In order to understand if the cause of pressure drop change is related to higher capacity
flow, it is defined the capacity ratio, R:
R=
Δ Pa/Fa2
Δ Pd/Fd2
where:
Δ Pa= actual thermal reactor inlet pressure
Δ Pd= design thermal reactor inlet pressure
Fa=
actual air flow rate to the thermal reactor
Fd=
design air flow rate to the thermal reactor
A sudden increase of R, in a chart displaying the capacity ratio versus time, means that
plugging might occur soon.
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TROUBLESHOOTING / MITIGATION
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CLAUS CATALYST PROBLEMS
Conversion in each reactor is directly related to the temperature increase
through the bed.
Temperature profile of each catalytic bed must be periodically controlled, in
order to avoid catalyst deactivation.
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TROUBLESHOOTING / MITIGATION
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CLAUS CATALYST PROBLEMS
If the flame is not stable, the reactions of conversion of H2S into sulphur may
be incorrect with operating problems in the downstream Claus reactors, which
may be exposed to the flow of process gas containing oxygen not reacted in
the main burner.
On the other hand, the hydrocarbons contained in the acid gas that are not
completely converted to CO and CO2 in the Claus burner may crack in the
Claus catalytic reactors forming soot which may plug the catalyst in short
time.
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TROUBLESHOOTING / MITIGATION
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CLAUS CATALYST PROBLEMS
Sulphur deposition
Catalyst deactivation
Carbon deposition
Sulphation
Sintherization
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TROUBLESHOOTING / MITIGATION
SULPHUR DEPOSITION
CAUSE: too close dew point approach of process gas from reactor
Catalyst deactivation can also occur when the reactor bed
temperature drops below the sulphur dew point of the process
gas.
ACTION: Increase process gas inlet temperature
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TROUBLESHOOTING / MITIGATION
CARBON DEPOSITION
CAUSE: Not complete hydrocarbon destruction in Thermal Reactor
A major deficiency of air at the main burner might result in
deposition of soot on the first catalyst bed (higher pressure drop
and less sulphur conversion).
ACTION: Check upstream units for excessive hydrocarbon breakthrough
or increase the ratio Combustion air/AAG
Soot is deposited on the catalyst and the sulphur produced is
brown or black. Soot can only be removed during a shutdown
period by replacing the catalyst.
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TROUBLESHOOTING / MITIGATION
SULPHATION
CAUSE: excess of air leading to more SO2 and consequent deactivation of
catalyst
A decrease of sulphur recovery is often caused by deactivation of
the catalyst due to sulphation.
The mechanism of sulphation is driven by the excessive partial
pressure of SO2, which bonds with alumina catalyst.
ACTION: Avoid H2S/SO2 ratio lower than 2; run 24hr at Reactors max temp
inlet.
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TROUBLESHOOTING / MITIGATION
SINTHERIZATION
CAUSE 1: Catalyst temperature higher than 400 °C
Burning of condensed Sulphur or deposited Carbon
CAUSE 2: Aging of catalyst
Life of catalyst
ACTION: Replace the catalyst
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TROUBLESHOOTING / MITIGATION
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TGT CATALYST PROBLEMS
HIGH TEMPERATURE ON THE BED
(temperature increase is strictly dependant on the SO2 content to Hydrog.R.)
CAUSE: High SO2 content in Tail gas
ACTION:High SO2 to TGT Reactor is caused by an incorrect run of upstream
Claus section; adjust the correct ratio air/acid gases to control the required
H2S/SO2 value
Note1: Temperatures higher than 420 °C could damage TGT catalyst;
Note2: In sulphided form, the TGT catalyst is strongly pyroforic.
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TROUBLESHOOTING / MITIGATION
TGT CATALYST PROBLEMS: look at the temperature rise!
2. Aging condition of the
catalyst (EOR)
outlet
3. First part of the catalyst is
deactivated (replacement ):
when the top of catalyst is
deactivated, the temperature
rise will move down to the
bed depth.
BED TEMPERATURE
CATALYST STATE
inlet
1. Reactions occur in the first
part of the bed height
1.FRESH AND ACTIVE
2.UNIFORM MILD DEACTIVATION
3.MILD DEACTIVATION FROM TOP DOWN
4.SEVERE UNIFORM DEACTIVATION
4. No conversion is reached
(catalyst replacement)
inlet
BED DEPTH
outlet
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TROUBLESHOOTING / MITIGATION
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HIGH H2S IN DEGASSING SULPHUR
CAUSE: Degassing Air/ Undegassed Liquid Sulphur ratio is too low
ACTION: Restore correct ratio
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PLUGGING OF HYDRAULIC SEALS
may cause sulphur plugging in condenser tubes
CAUSE:
a) Catalyst/refractory particles break trough
b) Corrosion products accumulation
c) Heating system malfunction
ACTION: Clean the hydraulic seals
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TROUBLESHOOTING / MITIGATION
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BLACK SULPHUR
CAUSE: Incorrect combustion of Hydrocarbon in Claus Thermal Reactor,
due to:
a) Air to fuel gas ratio too low (during fuel gas operation)
b) Presence of an abnormal content of heavy hydrocarbons in the feed
c) Combustion temperature in Thermal Reactor too low
ACTION: Sudden temperature changes should be avoided.
a. Adjust Air/ fuel gas ratio in order to not have sub-stoichiometric
combustion conditions in Thermal Reactor
b. Check operation of upstream units regarding hydrocarbons content
c. Check operation of upstream units regarding H2S concentration
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TROUBLESHOOTING / MITIGATION
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LEAKS
CAUSE: Damage of tubes or tubesheets of boilers and condensers
ACTION: replace damaged tubes
LEAKS CAN CAUSE:
1) Plugging due to sulphur condensation
2) Low steam production (the boiler water quality should be sampled
periodically to check the concentration of solids. The
concentration of solids can be adjusted by varying the blowdown rate)
3) Increase of pressure drops
4) Low boiler/condensers temperature
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TROUBLESHOOTING / MITIGATION
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HIGH H2S TGT Absorber
CAUSE:
a) Lean Amine feed temperature too high
b) Gas outlet temperature too high / Amine circulation rate too low
c) Reboiler steam rate too low
d) Poor Amine filtration
e) Degradation of Amine
ACTION:
a) Adjust lean amine temperature
b) Increase amine flowrate
c) Increase steam to amine ratio
d) Check Amine filters conditions
e) Check operating conditions of Reboiler
In order to restore a good Amine quality, bleed and make up Amine
solution (MDEA), if it’s necessary.
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TROUBLESHOOTING / MITIGATION
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HIGH H2S AT EXIT OF INCINERATOR
CAUSE:
Temperature in Thermal Incinerator too low.
ACTION: Increase combustion temperature by acting on fuel gas flowrate
to burner
- Adjusting fuel gas flowrate in the burner
- Check the ratio of fuel gas /combustion air
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TROUBLESHOOTING / MITIGATION
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LOW H2S IN THE AMINE ACID GAS (FROM ARU)
CAUSE:
a) Reboiler steam rate too low (high Acid gas loading in the lean amine)
b) Poor Amine filtration
c) Degradation of Amine
ACTION:
a) Increase steam to amine ratio
b) Check Amine filters conditions
c) Check operating conditions of Reboiler
In order to restore a good Amine quality, bleed and make up Amine
solution (DEA), if it’s necessary.
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TROUBLESHOOTING / MITIGATION
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HIGH H2S AND NH3 IN THE STRIPPED WATER (FROM SWS Unit)
CAUSE:
a) Reboiler steam rate too low
b) Reboiler temperature too low
ACTION:
a) Increase steam to sour water ratio
b) Increase stripper pressure
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GAS OUTLET TEMPERATURE TOO HIGH (FROM STRIPPER)
CAUSE:
a) Stripper pumparound flow too low
ACTION:
a) Increase stripper cooling water flowrate
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