Analysis of ISO-Tank Wall Physical Exergy Characteristic : Case Study of LNG Boil-off Rate from Retrofitted Dual Fuel Engine Conversion

Abstract

Ministry of Transportation of the Republic of Indonesia has conducted a feasibility study for conversion plans with the use of 60% LNG fuel on its 3200 DWT passenger ship using LNG ISOtank type T75 size 20 feet (1 TEU), but only limited to economical study. To verify that the conversion plan is really profitable, analysis of physical exergy characteristics i.e. the rate of exergy transfer and destruction through tank wall due to heat transfer, boil-off rate and boil-off gas from stored LNG is conducted by a closed system exergy balance approach with specified shipping conditions parameters, using the empirical equations of the literature and physical model of the three tank options offered, designed using COMSOL Multiphysics 5.1. The results show a positive correlation between exergy destruction rate with BOR and BOG values, depending on the total thermal resistance value R tot due to material variation of shell and insulation of tank wall affecting the value of heat leak on the inner and outer surface of the tank wall. Quality scale is presented to summarize the analysis parameters that can be measured by cost, i.e. the exergy cost and operating costs required by forced vaporizer to achieve the required BOR.

Performance Analysis of Combined Cycle with Air Breathing Derivative Gas Turbine, Heat Recovery Steam Generator, and Steam Turbine as LNG Tanker Main Engine Propulsion System

“…One of the factors that influence the level of efficiency of gas transportation using LNG tankers is the propulsion system used. Currently, LNG tankers in the world generally still use a steam turbine with boilers that use fuel from boil-off gas [15][16][17][18]. Several alternative propulsion systems have been developed by engineers to increase the efficiency value of the main engine driving LNG tankers, such as the dual-fuel diesel engine (DFDE) [19] and the combined cycle [20][21][22].…”

Study on the LNG distribution to mobile power plants utilizing small-scale LNG carriers

“…The term boil-off gas in Table 4 is an LNG cargo in the form of liquid which changes phase to gas due to environmental influences. LNG tank insulation is designed in such a way as to keep LNG cargo at the temperature of around -160 ° Celsius at atmospheric pressure, but due to the heat from the environment, the penetration into the tank causes the temperature of the charge to rise, and change the phase to gas [ 37 ]. This gas from phase change then used as fuel from the LNG Tanker.…”

Study on the Performance Analysis of Dual Fuel Engines on the Medium Speed Diesel Engine

“…The development of a dual-fuel diesel engine was started there in 1987 by Wartsila with the first concept of gas diesel engine, and the first dual-fuel engine was introduced in 1995 [18]. The selection of the insulation type of ISO-tanks for the boiled of gas is important issues in the use of dual fuel engine conversion [19]. Dual fuel engine technology can be used as fuel and also diesel at the same time and also in rotation mode on this machine, which can be done without loss of power or speed on the machine [20].…”