khabarovsk refinery hydroprocessing project normal operation april 29th – may 3rd 2013, madrid,...

KHABAROVSK REFINERY HYDROPROCESSING PROJECT

NORMAL OPERATION

APRIL 29th – MAY 3rd 2013, MADRID, SPAIN

TRAINING COURSE

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NORMAL OPERATION

The purpose of this section is to give a general explanation of the main parameters that the operator shall check during normal operation.

Process variables, that determine a good operation of the Unit, play a different role depending upon the type of operation.

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CLAUS SECTION

PROCESS VARIABLES NORMAL OPERATION

AIR/ACID GAS RATIO

TEMPERATURE IN

THERMAL REACTOR

CLAUS REACTORS

STEAM PRODUCTION PRESSURE

FEEDSTOCK VARIATIONS INCOMPOSITION

PRESSURE

TEMPERATURE

PRESSURE PROFILE

NORMAL OPERATION

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NORMAL OPERATIONCLAUS SECTION- MAIN PARAMETERS

CORRECT QUANTITY OF DEMI WATER/LP CONDENSATE (0.15 m3/h) TO THE AMINE ACID GAS SCRUBBER

CORRECT H2S/SO2 RATIO IN THE CLAUS TAIL GAS

CORRECT CLAUS REACTORS INLET TEMPERATURE (240 AND 206 °C)

CORRECT OPERATION OF PIPING AND EQUIPMENT HEATING SYSTEM

CORRECT FLUSHING OF INSTRUMENTS AND EQUIPMENT WITH NITROGEN AND AIR

QUALITY OF UTILITIES ACCORDING TO THE DESIGN BASIS

CORRECT STEAM PRESSURE AND BLOW-DOWN FLOWRATE IN THE CLAUS WHB AND SULPHUR CONDENSERS

LIQUID SULPHUR PRODUCTION (FLOW) FROM EACH HYDRAULIC SEAL

SULPHUR DEGASSING SYSTEM OPERATION

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NORMAL OPERATIONCLAUS SECTION

OPERATION WITH TWO ZONES IN THERMAL REACTOR

SPLIT THE FLOW OF AAG BETWEEN 1ST AND 2ND ZONE DURING OPERATION WITH SWS (SINGLE ZONE OPERATION WHEN AAG IS THE ONLY FEED)

MONITOR THE TEMPERATURE IN THE FIRST ZONE ESPECIALLY DURING OPERATION WITH SWS (ADIABATIC FLAME TEMPERATURE AROUND 1450°C)

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TGT SECTION


TEMPERATURE IN

HYDROGENATOR REACTOR (INLET AND OUTLET)QUENCH TOWER OUTLET

CLAUS TAIL GAS COMPOSITION

H2 EXCESS FROM QUENCH TOWER (MIN. 2.5% vol.)

PROCESS WATER FLOWRATE AND pH

TAIL GAS SO2 CONTENT DOWNSTREAM HYDROGENATION REACTOR

NO SO2 CONTENT IN EFFLUENT GAS FROM QUENCH TOWER ALLOWED IN NORMAL OPERATION WHEN TAIL GAS IS TREATED IN AMINE ABSORBER

NORMAL OPERATION

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REDUCTION REACTOR TEMPERATURE AT SOR: INLET 280°C - OUTLET 310°CAT EOR: INLET 320°C - OUTLET 350°C

CLAUS TAIL GAS COMPOSITION

INSTRUMENTATION AND LINES PURGING SYSTEM OPERATION BY INERT GAS

PIPING AND EQUIPMENT HEATING SYSTEM OPERATION

HYDROGEN EXCESS AFTER QUENCH TOWER (MIN. 2.5% vol.)

TAIL GAS TEMPERATURE FROM QUENCH TOWER

SOUR WATER FROM QUENCH TOWER FLOW RATE AND pH

SO2 CONTENT IN EFFLUENT GAS FROM QUENCH TOWER

SOUR WATER FILTERS PRESSURE DROP

AMINE SOLUTION IN TGT ABSORBER (10 m3/h NORMAL)

NORMAL OPERATIONTGT SECTION – MAIN PARAMETERS

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AMINE SECTION


LEAN AMINE LOADING

LEAN AMINE SOLUTION

CONCENTRATION

TEMPERATURE (LEAN AMINE TO ABSORBER)

EFFICIENCY OF LEAN/RICH HEAT EXCHANGER

PRESSURE DROPS THROUGH FILTERS

NORMAL OPERATION

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LEAN AMINE LOADING (STEAM / AMINE RATIO IN THE REBOILER)

LEAN AMINE SOLUTION QUALITY AND CONCENTRATION (50% BY WT.)

TEMPERATURE OF LEAN AMINE SOLUTION SENT TO ABSORBER (42°C MAX.)

AMOUNT OF AMINE SENT TO FILTERING SYSTEM



CONCENTRATION AND TEMPERATURE OF ACID GAS FROM REFLUX DRUM

NORMAL OPERATIONAMINE SECTION – MAIN PARAMETERS

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INCINERATOR SECTION

INCINERATOR FLUE GAS

TEMPERATUREOXYGEN CONTENT

TAIL GAS COMPOSITION

INCINERATOR OPERATION


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NORMAL OPERATIONINCINERATOR SECTION- MAIN PARAMETERS

INCINERATOR CHAMBER TEMPERATURE (650°C) TO GUARANTEE THERMAL CONVERSION OF SULPHUR COMPOUNDS

O2 CONTENT IN FLUE GAS (2% vol. minimum on wet basis)

TAIL GAS COMPOSITIONTail gas fed to the Incinerator comes from TGT Section or directly from Claus Section (in case of TGT by-pass)

• PIPING HEATING SYSTEM OPERATION

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AMINE REGENERATION SECTION (ARU)


RICH AMINE FLOWRATE TO REGENERATOR

DEA SOLUTION

CONCENTRATION

TEMPERATURE

REGENERATOR PRESSURE

NORMAL OPERATION

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RICH AMINE FLOWRATE (STEAM / AMINE RATIO IN THE REBOILER)

DEA SOLUTION QUALITY AND CONCENTRATION (25% BY WT.)

TEMPERATURE OF LEAN DEA SOLUTION SENT TO B.L. (55°C MAX.)

AMOUNT OF AMINE SENT TO FILTERING SYSTEM



FLOWRATE OF REFLUX TO THE REGENERATOR

NORMAL OPERATIONARU SECTION – MAIN PARAMETERS

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SOUR WATER STRIPPER SECTION (SWS)


SOUR WATER FLOWRATE TO STRIPPER

SOUR WATER CHARACTERISTICS

CONCENTRATION OF H2S AND NH3

TEMPERATURE

STRIPPER PRESSURE

NORMAL OPERATION

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SOUR WATER FLOWRATE (STEAM FLOWRATE TO REBOILER)

POLLUTTANT CONCENTRATION IN THE SOUR WATER

STRIPPER PRESSURE / TEMPERATURE

EFFICIENCY OF FEED/BOTTOM HEAT EXCHANGER

FLOWRATE OF PUMPAROUND TO THE STRIPPER

NORMAL OPERATIONSWS SECTION – MAIN PARAMETERS

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ROUTINE OPERATIONUTILITIES

VERIFY SUITABILITY OF SYSTEMS, OPERATION AND CORRECT VALUES OF OPERATING PARAMETERS FOR:

STEAM AND STEAM CONDENSATE SYSTEM OPERATION

FUEL GAS MOLECULAR WEIGHT AND NETWORK SYSTEM

PIPING AND EQUIPMENT HEATING SYSTEM OPERATION

NITROGEN AND INSTRUMENT AIR NETWORK SYSTEM OPERATION

BOILER FEED WATER NETWORK SYSTEM OPERATION

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GENERAL PRECAUTIONSOPERATION ACTIONS

Compile daily record book

Check instruments for:

- Maintenance- Periodic readings to be recorded- Unrealistic values

Monitor catalyst activity through bed temperature profiles

Avoid sudden temperature changes

Control liquid carry-over and content of hydrocarbons and ammonia in feeds

Schedule frequency of sampling and analyses

Perform periodic laboratory analyses to check proper working of on-line analysers

Observe refractory color from burner sight glasses

Check burners for flame quality and temperature

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CORRECTIVE ACTION FOR ABNORMAL CONDITIONS

ACID GAS FEED LOAD VARIATION

ACID GAS FEED COMPOSITIONVARIATION

No modifications of the normal operating parameters are necessary during turndown operation for both Claus and TGT sections.

Load variations should be as smooth as possible to avoid plant upset and shut-down.

Acid gas composition variations can produce a remarkable effect on the plant operation and/or on sulphur recovery efficiency.

Hydrocarbons

Hydrocarbons have several negative effects on the acid gas; the first is the difficulty in burning hydrocarbons if they are present in massive quantities, the second is the effect of dilution of the process gas with the consequent sulphur efficiency decreasing.

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A further negative effect is the consumption of combustion air according to the rates described.

It is important to note that while the H2S combustion requires about 0.5 mol O2/mol H2S, the minimum combustion (partial oxidation) requirement of hydrocarbons :

1.5 mol O2/mol CH4

2.5 mol O2/mol C2H6

3.5 mol O2/mol C3H8

4.5 mol O2/mol C4H10



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The maximum tolerance of hydrocarbons for the correct and safe acid gas combustion can be calculated according to the following system:


CH4 2 X % CH4 in the acid gas +

C2H6 8 X % C2H6 in the acid gas +

C3H8 50 X % C3H8 in the acid gas +

C4H10 100 X % C4H10 in the acid gas = ∑

∑ < % H2S in the acid gas


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If the resulting from the operation is less then the H2S percentage in the acid gas, the hydrocarbons contained in the acid gas can be easily tolerated (note that the Thermal Reactor effluent temperature should be always higher than 1000 °C to ensure the hydrocarbons complete destruction).

In case the hydrocarbons content in the acid gas exceeds the tolerance calculated as per the above system, some carbon can be formed during the acid gas combustion with the consequence of catalyst plugging and fouling.



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In addition, note that the carbon formation can also be caused by deficiency air operation, even if the hydrocarbons content in the acid gas is within the tolerance limit.

The hydrocarbons contained in the acid gas feedstock is largely acceptable; the presence of C4+ hydrocarbons at concentrations exceeding 0.9% is the limit of acceptability to avoid risks of uncompleted hydrocarbons combustion in the Thermal Reactor.



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Ammonia

Ammonia in the acid gas has the negative effect of requiring additional process air for the combustion (0.75 molO2/molNH3) and therefore diluting the process gas.

Non-destroyed ammonia can form deposits of solid salts (ammonium sulphate, ammonium bisulphate, ammonium sulphides) at the low temperature points of the plant, such as at the sulphur condensers outlets.

The maximum molar ratio of ammonia in the fed gas to the Thermal Reactor is:

mol NH3 / (mol NH3 + mol H2S) = 0.25



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The unit has been designed to treat an acid gas stream (acid gas from amine regeneration and acid gas from SWS) with an NH3 content of about 35% mol.

The crucial operation parameter for the ammonia destruction is the adiabatic flame temperature, which has never to drop below 1420 °C.

The unit is provided with a two zones thermal reactor which allows to modify the temperature of combustion of the gas containing ammonia as necessary by by-passing a part of the amine acid gas not containing ammonia to the thermal reactor second zone.

Higher is the by-pass, higher shall be the temperature of the first zone. Note that the max allowable by pass has never to exceed the 25% of the quantity of the amine acid gas.



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Carbon Dioxide Carbon dioxide plays the role of diluting process gas and of producing COS and CS2 during the acid gas combustion. The production rate of COS and CS2 is proportional to the concentration of CO2 and hydrocarbons in the feed acid gas.

Steam

Steam present in the acid gas acts as a diluting agent.Note that the increasing of the rate of the acid gas diluting agents implies, in addition to the sulphur recovery efficiency decreasing, the lowering of the plant capacity due to the inevitable increase of the pressure drops of the system.



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Acid gas fed to SRU is normally free from liquids; it is anyway possible, for upsets of the Amine and SWS units, that some liquid is present (water, amine solution and perhaps hydrocarbons).

Amine Acid Gas Scrubber and SWS Acid Gas Separator are provided upstream the combustor burner and all the entrained liquids are separated and transferred outside the SRU battery limits by pumps.

In case of impossibility in removing liquids from the acid gas separators, very high-level switches shall shut down the unit.


ENTRAINED LIQUID

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The effect of liquid entrained to the burner is to create disturbance to the acid gas flame and the sudden evaporation in the combustion chamber with the risk to damage the Thermal Reactor refractory lining. A long-term effect of entrained liquid (H2O) may be also the corrosion of the acid gas piping lines. The amine acid gas and the SWS acid gas lines are traced/jacketed as a protection against condensation of steam and to avoid precipitation of solid salts, which could plug the lines. Tracing/Jacketing facilities shall be maintained in operation in all seasons.

ENTRAINED LIQUID


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FUEL GAS Fuel gas pressure much lower than normal shall cause the

Incinerator shut‑down and consequently the SRU shut‑down; this is necessary in order to prevent lack of flame to the Incinerator Burner in case of Fuel gas network failure; a pre‑alarm of low and high Fuel gas pressure in control room shall inform the operator.

Variation of fuel gas composition has not practical effects on the Incinerator operation, provided that the system operates on automatic control.


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On the other side, fuel gas variations in composition would be quite important for the combustion operation during plant heating up.

For this reason it is necessary that any variation of the Fuel gas feed composition is anticipated to the operator, which shall change the combustion parameters accordingly.

Note that an incorrect (not stoichiometric) operation during fuel gas combustion, in plant heating up stages could be dangerous due to the possibility of carbon formation (oxygen deficiency) and to the presence of excess oxygen in the flue gas.


FUEL GAS

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Low-pressure steam is used to heat all the parts of sulphur plant containing liquid sulphur in order to avoid solidification. All plant components containing liquid sulphur are heated with steam at a temperature not exceeding 160 °C, because at this temperature liquid sulphur starts becoming very viscous.LS steam is used for tracing/heating purposes.

The steam heating for “sulphur” services is provided essentially to maintain the sulphur at liquid state or to avoid (or minimize) the condensation of the sulphur at vapour state; it is therefore extremely important that the heating system is always well efficient.

We suggest checking the “sulphur” service heating efficiency at least daily.

The heating in non‑sulphur services is essentially provided in order to avoid water or liquid condensation in vessels or piping lines, so preventing corrosion.


LP STEAMUSES

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DEA FLOWVARIATION

SOUR WATER COMPOSITIONVARIATION

If the amount of products to be absorbed by the amine in the Absorption Section increases, the circulating amine solution flowrate shall increase proportionally and the saturated steam flowrate to the Reboiler shall be increased.

If the amount of pollutants (H2S and NH3) in the sour water increases, it shall be necessary to increase the pressure (and therefore the temperature) in the Stripper.

HydrocarbonsHydrocarbons cause fouling of the heat exchanger: it can be controlled by checking that the Slop Oil Pump works properly.

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RomeRome

Viale Castello della Magliana 75Viale Castello della Magliana 7500148 - Italy00148 - Italy

Ph. +39 06 602161Ph. +39 06 602161Fax +39 06 65793002Fax +39 06 65793002

[email protected] – [email protected] – www.tecnimontkt.it

THANK YOU FOR THE ATTENTION

khabarovsk refinery hydroprocessing project normal operation april 29th – may 3rd 2013, madrid,...

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