Basic research on application of LNG fuel to Japanese Tuna Longline Fishing Vessel and Fish Carrier

In this paper, we present some results of our recent research on application of LNG fuel to Japanese tuna fishing vessel and fish carrier which must be cleared the new SOx regulations of MARPOL convention. As the regulation to emission of SOx and PM will be tighten from January 2020, commercial vessels has been responding to this regulation hiring low sulfur fuel or a scrubber. However, it is difficult for relatively small vessels like fishing vessels to install a scrubber or to hire expensive fuel. One of the possible solutions is applying LNG fuel to fishing vessels. Considering various conditions, we designed a concept of a tuna fishing vessel and a fish carrier. To reduce the total running cost of those vessels, we investigated the possibility of usage of coldness of LNG. Refrigerators consume much power, but if one can use the low temperature of the fuel, then the running cost should be reduced. To investigate this possibility, we simulated a supposed fish refrigeration room temperature changing flow rate of refrigerant in the pipe. From simulations we found it is effective to use LNG coldness for rapid refrigeration. We also developed a refrigeration test bench which uses nitrogen gas (-196°C) flow instead of LNG as refrigerant. Using this test bench, we examined the temperature at several points of a horse mackerel. Through these simulations and experiments, we found cold LNG gas flow can lower the refrigerator temperature very rapidly and effectively. From our estimation, this might reduce the annual running cost for refrigeration around 200,000USD compared to a traditional diesel power generator. Although further investigation such as IGF code adaptability should be examined, we developed the conceptual designs of two vessels and refrigeration system and will explain them in the paper.