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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)
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