Process Considerations for the Safe Process Considerations for the Safe Process Considerations for the Safe Process Considerations for the Safe Design of Sulphur Tanks and Design of Sulphur Tanks and Design of Sulphur Tanks and Design of Sulphur Tanks and

Collection SystemsCollection SystemsCollection SystemsCollection Systems

Ken Sourisseau, P. Eng.Shell Canada Energy

Figure 1Figure 1Figure 1Figure 1---- Simplified Claus ProcessSimplified Claus ProcessSimplified Claus ProcessSimplified Claus Process

Condenser

ClausReactor

Reheater

steam

steamTail Gas

Sulphur

Acid Gas

Air

WHBRF steamsteam

Figure 2Figure 2Figure 2Figure 2---- Liquid Sulphur HandlingLiquid Sulphur HandlingLiquid Sulphur HandlingLiquid Sulphur Handling

Pit DegassingPit DegassingPit DegassingPit Degassing

External DegassingExternal DegassingExternal DegassingExternal Degassing

Liquid Sulphur HazardsLiquid Sulphur HazardsLiquid Sulphur HazardsLiquid Sulphur Hazards

• Severe burns• Combustion product, SO2 is highly toxic• Production method results in H2S and

SO2 being dissolved in liquid– Degassing in storage creates explosive

vapours– Degassing in storage creates toxic

atmosphere

Mitigation of Personnel HazardsMitigation of Personnel HazardsMitigation of Personnel HazardsMitigation of Personnel Hazards

• Exposure to Toxic Vapour– Use of sulphur seal legs– Improvement in lookbox design– Elimination of lookboxes

• Exposure to Molten Sulphur– Proper tracing and steam supply– Packing glands for rod-out connections

Figure 3Figure 3Figure 3Figure 3Sulphur Seal LegSulphur Seal LegSulphur Seal LegSulphur Seal Leg

• Sulphur flow down centre pipe• Returns up annulus• Length of seal leg should

ensure blower deadhead cannot blow seal

• Proper heat tracing required on outside of return pipe

Figure 4 Figure 4 Figure 4 Figure 4 –––– Lookbox EvolutionLookbox EvolutionLookbox EvolutionLookbox Evolution

b) Newest Stylea) Second Generation

Figure 5 Figure 5 Figure 5 Figure 5 –––– Sulphur Sight GlassSulphur Sight GlassSulphur Sight GlassSulphur Sight Glass

Figure 6 Figure 6 Figure 6 Figure 6 ---- Inline Sulphur Site GlassInline Sulphur Site GlassInline Sulphur Site GlassInline Sulphur Site Glass

Figure 7 Figure 7 Figure 7 Figure 7 –––– Effective Heat TracingEffective Heat TracingEffective Heat TracingEffective Heat Tracing

Courtesy of Controls Southeast Inc.

Figure 8 Figure 8 Figure 8 Figure 8 –––– Heat Tracing Large PipeHeat Tracing Large PipeHeat Tracing Large PipeHeat Tracing Large Pipe

Figure 9 Figure 9 Figure 9 Figure 9 –––– Liquid Sulphur ViscosityLiquid Sulphur ViscosityLiquid Sulphur ViscosityLiquid Sulphur Viscosity

Liquid Sulphur Viscosity

0.001

0.010

0.100

1.000

10.000

100.000

120 130 140 150 160 170 180

Temperature (oC)

Vis

co

sit

y (P

a s

)

Figure 10 Figure 10 Figure 10 Figure 10 ---- Steam Ingress to Sulphur Steam Ingress to Sulphur Steam Ingress to Sulphur Steam Ingress to Sulphur RundownRundownRundownRundown

Prevention of Explosive AtmospheresPrevention of Explosive AtmospheresPrevention of Explosive AtmospheresPrevention of Explosive Atmospheres

• Sweep air required in rundown vessel• Degas liquid sulphur in pit or in external

degas vessel• In pit degas start-up concerns

– Increase air flow rate– Start degassing before pit is full

Storage Tank ConsiderationsStorage Tank ConsiderationsStorage Tank ConsiderationsStorage Tank Considerations

• Properly degassed sulphur should provide no problems, small H2S venting

• Proper heat tracing of roof and vents • Undegassed sulphur may create

explosive atmosphere in tank– Proper rim and centre vents recommended– Steam purge may create larger problem

Prevention of Pyrophoric DepositsPrevention of Pyrophoric DepositsPrevention of Pyrophoric DepositsPrevention of Pyrophoric Deposits

• Prevent formation by having oxidizing atmospheres

• Undegassed sulphur to rundown tanks creates a reducing atmosphere

• Steam purge creates wet conditions more conducive to pyrophoric deposits

• Pyrophoric deposits on tank roofs easily ignited when tank inbreathing

Prevention of CorrosionPrevention of CorrosionPrevention of CorrosionPrevention of Corrosion

• Keep surfaces hot to prevent water and/or sulphur deposition

• Use stainless steel for surfaces that can be uncovered of liquid sulphur

• Consider removal of sulphur tank heating coil in favour of external tank tracing