Economical evaluation

MAN B&W ME-C series for LNG Carriers. Economical evaluation

The operating costs and the additional income from the transport and sale of LNG for a 150,000 m3 LNG carrier is analysed, including an analysis of the fuel oil, lubricating oil and maintenance costs for both propulsion and electricity production under various operating conditions, comparing steam turbines with proposed configuration.
The analysis is based on state-of-the-art insulation of tanks, and thus BOG rate, and a traditional service speed of the vessel. 

An evaluation of the operating costs and the additional income from selling re-liquefied LNG shows that substantial economic benefits can be obtained. The outcome of the evaluation will depend on the actual project, i.e. voyage profile, service speed, economic factors, price of HFO and LNG, as well as of the boil-off rate.
The efficiency of the steam propulsion system (i.e. combined efficiency of boiler, steam turbine and reduction gear) will vary depending on steam pressure, condensation temperature and boiler cleaning intervals.
In any case, diesel engine propulsion offers significant economic savings for operator. 

Fig. 7. Voyage profile
The operating costs, calculated based on the Basic Data and a typical voyage profile as shown in Fig. 7, are indicated in the tables in the Appendix. Table 4 of this Appendix shows the final summary of the operating costs and indicates the potential for additional income.

Fig. 8. Operating costs for LNG carriers
In fig. 8 the result of the summary in Table 4 is visualized.
With the diesels plus reliquefaction plant, the BOG is replaced by HFO as the energy advantage of the diesels prevails. The additional sale of reliquefied BOG brings the large saving. This saving depends, of course, also on the price of LNG. Fig. 9 shows the optimum solution as a function of the LNG price and the Boil-off rate.

Fig. 9. Sensitivity to LNG price

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