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

船舶废气省煤器作为一种有效的余热回收装置，由于受热面外部结垢，一直受到各种问题的困扰。尤其严重的是，由于受热面上沉积的烟尘烧毁而导致的受热面熔毁事故，即所谓的“烟尘火灾”。通过本课题的研究，可以明确烟尘燃烧事故的机理，并提出预防烟尘火灾的对策。1)成功地建立了烟尘燃烧的仿真模型，为研究各种工况下烟尘燃烧引起的换热表面温度升高和热负荷增加提供了可能。2)揭示了烟尘燃烧到烟尘火灾事故的过程机理。即发生烧黑*水侧换热表面干涸*气侧换热表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*熔融事故。3)根据研究结果，提出了提高废气省煤器可靠性的措施，成功地避免了烟尘火灾事故。

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.