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INTERTANKOINTERTANKOInternational Association of Independent Tanker OwnersInternational Association of Independent Tanker Owners

Safe Transport, Cleaner Seas, Free CompetitionSafe Transport, Cleaner Seas, Free Competition

A Report upon

Increased Effectiveness ofCRUDE OIL WASHING

(CRUCLEAN)

CRUCLEAN ProjectObjectives and Deliverables

• By use of the sludge data from CRUCOGSA examine the impact pressure from a COW machine during operation.

• Undertake alternative impact pressure measurements with differing nozzles and differing delivery pressures.

• Optimise COW Machine operational criteria to increase washing effectiveness and reduce the evolution of VOC from wash stock.

CRUCLEAN ProjectExample of Sludge Yield Stress

CRUCLEAN ProjectMeasurement Record

min:s

6:50 6:55 7:00 7:05 7:10

300,00

250,00

200,00

150,00

100,00

50,00

0,00

13,00

12,00

11,00

10,00

9,00

8,00

7,00

120,0

100,0

80,0

60,0

40,0

20,0

0,0

Trigger Impact force Feed pressure Feed flow

CRUCLEAN ProjectJet Appraisal

CRUCLEAN ProjectObservations – Operating

Pressure

• Irrespective of nozzle size the operating pressures currently required (8 kg/cm2) produce an impact pressure well in excess of the Yield Stress of typical sludge.

• Conclusion – operating pressure can be reduced.

CRUCLEAN ProjectAssessment of impact area

• The direct impact area for one cycle of an existing COW machine is approx 7.6%. (this excludes “splash zone” and therefore reduced impact pressure)

• By increasing nozzle size from the current 30 mm to 45 mm, the impact area is increased to 30.5% for one cycle of the machine.

CRUCLEAN ProjectNozzle Flow Rates

• By increasing the flow rate into the cargo tank the final blend of sludge and COW stock will decrease to more flow/pumpable viscosities.

• Flow rate into the cargo tank is determined as a function of either delivery pressure and/or nozzle size.

CRUCLEAN ProjectVapour Generation

• Vapour generation during washing has two primary consequences:– Loss of solvent that will dissolve sludge– Generate VOC gases that will be displaced to

atmosphere during loading of next cargo.

• In order to decrease vapour generation a maximum operating pressure of 5 bar should be observed.

CRUCLEAN ProjectInterim Conclusions

• In order to increase effectiveness of a COW operation and reduce VOC emissions– the nozzle pressure should be reduced to below

5 bar (roughly kg/cm2) and;– the COW machine nozzle should be increased

to a size compatible with the tank size (jet reach)