Presentation on theme: "KHABAROVSK REFINERY HYDROPROCESSING PROJECT TROUBLESHOOTING APRIL 29th – MAY 3rd 2013, MADRID, SPAIN TRAINING COURSE."— Presentation transcript:
KHABAROVSK REFINERY HYDROPROCESSING PROJECT TROUBLESHOOTING APRIL 29th – MAY 3rd 2013, MADRID, SPAIN TRAINING COURSE
2 TROUBLESHOOTING / MITIGATION 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.
3 TROUBLESHOOTING / MITIGATION 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= 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. Δ Pa/Fa 2 Δ Pd/Fd 2
4 TROUBLESHOOTING / MITIGATION 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.
5 TROUBLESHOOTING / MITIGATION CLAUS CATALYST PROBLEMS If the flame is not stable, the reactions of conversion of H 2 S 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 CO 2 in the Claus burner may crack in the Claus catalytic reactors forming soot which may plug the catalyst in short time.
7 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
8 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.
9 TROUBLESHOOTING / MITIGATION SULPHATION CAUSE: excess of air leading to more SO 2 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 SO 2, which bonds with alumina catalyst. ACTION: Avoid H 2 S/SO 2 ratio lower than 2; run 24hr at Reactors max temp inlet.
10 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
11 TROUBLESHOOTING / MITIGATION TGT CATALYST PROBLEMS HIGH TEMPERATURE ON THE BED (temperature increase is strictly dependant on the SO 2 content to Hydrog.R.) CAUSE:High SO 2 content in Tail gas ACTION:High SO 2 to TGT Reactor is caused by an incorrect run of upstream Claus section; adjust the correct ratio air/acid gases to control the required H 2 S/SO 2 value Note1: Temperatures higher than 420 °C could damage TGT catalyst; Note2: In sulphided form, the TGT catalyst is strongly pyroforic.
12 TROUBLESHOOTING / MITIGATION BED DEPTH BED TEMPERATURE CATALYST STATE 1.FRESH AND ACTIVE 2.UNIFORM MILD DEACTIVATION 3.MILD DEACTIVATION FROM TOP DOWN 4.SEVERE UNIFORM DEACTIVATION TGT CATALYST PROBLEMS: look at the temperature rise! 1.Reactions occur in the first part of the bed height 2.Aging condition of the catalyst (EOR) 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. 4.No conversion is reached (catalyst replacement) inletoutlet inlet outlet
13 TROUBLESHOOTING / MITIGATION HIGH H 2 S IN DEGASSING SULPHUR CAUSE: Degassing Air/ Undegassed Liquid Sulphur ratio is too low ACTION: Restore correct ratio 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
14 TROUBLESHOOTING / MITIGATION 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 H 2 S concentration
15 TROUBLESHOOTING / MITIGATION 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 blow- down rate) 3)Increase of pressure drops 4)Low boiler/condensers temperature
16 TROUBLESHOOTING / MITIGATION HIGH H 2 S 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.
17 TROUBLESHOOTING / MITIGATION HIGH H 2 S 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
18 TROUBLESHOOTING / MITIGATION LOW H 2 S 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.
19 TROUBLESHOOTING / MITIGATION HIGH H 2 S AND NH 3 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 GAS OUTLET TEMPERATURE TOO HIGH (FROM STRIPPER) CAUSE: a)Stripper pumparound flow too low ACTION: a)Increase stripper cooling water flowrate