Study on Soot-fire Accident of Heat Recovery Plant of Diesel Ship and on its Countermeasures

柴油机船舶废气省煤器作为一种有效的余热回收装置，由于其受热面外结垢，一直受到各种问题的困扰。特别严重的是受热面熔毁事故，即“煤烟火灾”，是由沉积在受热面上的煤烟燃烧引起的。本项目可以明确煤烟火灾的发生机理，提出防治煤烟火灾的对策。1)成功地建立了煤烟燃烧的模拟模型，从而可以评估各种条件下煤烟燃烧引起的传热表面温度和热负荷的增加。2)揭示了由煤烟燃烧到煤烟火灾事故的过程机理。即发生烧灰*水侧换热面干涸*气侧换热面翅片温度迅速升高*翅片材料加速氧化导致翅片温度进一步升高*熔毁事故。3)根据所得结果，提出了提高废气省煤器可靠性的措施，成功地避免了煤火事故的发生。

Exhaust gas economizer of diesel ship, which is an effective recovery plant of waste heat, has been troubled by various problems due to outer foulings of its heating surface. Especially very serious one is the melt-down accident of heating surface, so called "soot-fire", induced by burning-up of soots deposited on heating surface. This project could have made clear the mechanism of soot-fire accident and proposed the countermeasures against the soot-fire.1) Simulation model of soot-burning could have been successfully developed and it has been made possible to evaluate the increase of heat transfer surface temperature and heat load due to soot-burning at various conditions.2) The mechanism of the process from soo-burning to soot-fire accident has been revealed. That is, occurence of soot-burning * dry-out of waterside heat transfer surface * rapid increase of temperature of gasside heat transfer surface fin * further increase of fin temperature due to accelerative oxidation of fin materials * melt-down accident.3) According to the obtained results, measures for improving the reliability of exhaust gas economizer could be porposed, and soot-fire accidents could have been avoided successfully owing to those measures.