【作者】 李梦丽；

【导师】 王威强；

【作者基本信息】 山东大学 ， 化工过程机械， 2008， 硕士

【摘要】 国内1995年和2005年各发生了一起层板包扎尿塔爆破事故,前一起事故原因报告未公布,后一起事故分析报告公布的原因争议很大。全国尚有约400台同类型尿塔在运行,找到事故真正原因,杜绝此类事故发生意义重大。后起事故前后全国有多台层板包扎尿塔因层板严重开裂报废,报废一台塔直接经济损失约500万元,后一起爆破事故原因分析认为也是由层板开裂引起,所以应尽快找出层板开裂原因及与爆破关系,避免重大损失再次发生。作者对尿塔内物料发生化学爆炸的可能性进行了分析,对可能发生化学爆炸的情况进行了计算并与事故能量进行了对比研究,发现化学爆炸能量小于引发完好简体开裂需要的能量,更不能单独由化学爆炸引发尿塔爆破。不排除在层板已有多层开裂的情况下,事故可能由化学爆炸引起,但事故现场应该有化学爆炸痕迹。但是在国内的两起事故中,没有任何化学爆炸痕迹,而“爆沸”(又称“平衡破坏型蒸汽爆炸”)产生的能量与事故能量吻合。对爆口层板做金相试验,发现爆破前应力腐蚀已经造成所有的强度层层板开裂。所以事故原因是强度层层板因为应力腐蚀开裂无法承受工作压力而发生了尿塔“爆沸”。其它层板严重开裂的尿塔如果其开裂未被发现,后果不堪设想。对其中一台爆破尿塔和另外两台报废尿塔进行了逐层解剖,对全国范围内层板严重开裂的尿塔进行了调研总结,总结了尿塔的开裂规律:自外至内严重开裂型、自内至外严重开裂型、混合严重开裂型和轻度开裂型。通过尿塔开裂的宏观特征和截取试样的金相分析,判断层板的开裂原因是碱应力腐蚀。从材料、应力、介质三方面分析了引起尿塔应力腐蚀开裂的要素,阐明了尿塔碱脆的机理和出现四种不同开裂形式的原因。在查明开裂原因的基础上,提出了防止尿塔应力腐蚀的措施,对于保证层板包扎尿塔的安全运行意义重大。更多还原

【Abstract】 Two multilayed urea reactors exploded in 1995 and 2005 in China respectively. The accident cause report of the former was not announced, and the latter was quite disputable. There are about 400 urea reactors under operation, so it is of important significance to find the real accident causes and put an end to such accidents. Many urea reactors were disabled by the reason of severe cracking of layers before and after the latter accident. The direct economic loss of disabling one urea reactor is about 500 million, and the latter accident cause by accident investigation were thought to be the cracking of layers, therefore, reasons for layers cracking and relationship between layers cracking and urea reactor exploding should be found as soon as possible to avoid such heavy losses from happening again.The author have analyzed possibilities of chemical explosion of urea reactor materials, calculated energy of chemical explosion in certain cases that chemical explosion may occur, compared with the accident energy, then draw a conclusion that chemical explosion energy is smaller than the energy that rip one intact shell section .Furthermore, chemical explosion alone can not make urea reactor exlplode. At the same time, chemical explosion may cause the accident when many of the layers cracks severely. There was not any chemical explosion trace in the two domestic urea reactor accidents. The energy from boiling liquid expanding vapor explosion (BLEVE for short) is equivalent with the accident energy. According to metallographic experiment of the ripped layers in accident, it was found that Stress Corrosion Cracking ("SCC" for short) had been on all the strength layers before the reactor exploded. Hence, the accident cause is that strength layers can not withstand working pressure and BLEVE happened because of SCC in layers. If reactors were not found in which layers had cracked severely, the consequences would be disastrous.Through layer by layer anatomy of one of the explosion reactors and two other disabled reactors and investigation of reactors with severe cracking of layers all over China, layer cracking rules have been summed up: severe cracking from outside to inside; severe cracking from inside to outside; mixing severe cracking; slight cracking. The reason for layers cracking is SCC based on macro-characteristics of reactors cracking and metallographic experiment of samples. The author analyzed factors which caused reactor SCC from materical, stess, media and clarified mechanism of reactor caustic embrittlement and reasons for four cracking rules. On the base of finding out reasons for cracking, methods of preventing reactors from SCC have been put forward, which have great significance for insure urea reactor safe operating.更多还原