スートファイア (排ガスエコノマイザメルトダウン事故) の発生機構

抄録

The mechanism of soot-fire accident of exhaust gas economizer in diesel ship is investigated in this report. This is the second report following the first one, in which the process of soot-burning of exhaust gas economizer was studied by a simulation model. According to the soot-burning simulation, temperature of heat transfer surface seldom reaches its melting point only by soot-burning. So it is difficult to consider that soot-fire is occurred only by heat released by the soot-burning. It has been reported the oxidative heat of tube materials might be another heat source. The experiments, therefore, are carried out in order to measure the rate of oxidation of tube materials, and reveal that there is a possibility that the oxidative heat might be another heat source when the oxidation rate is accelerated by the high temperature steam atmosphere and the“break-away”oxidation. Accordingly it is made clear the soot-fire is occurred by a series of events, that is, burning of soots deposited on finned tubes, waterside dry-out of the finned tubes induced by the soot-burning, sudden degradation of waterside heat removal due to the dry-out, rapid increase of fin temperature, and further increase of the fin temperature due to oxidation of iron, and finally melt-down of the heat transfer surfaces.