烧焦对Cr25Ni35乙烯裂解炉管锰铬尖晶石薄膜的影响

Effect of coke decoking on manganese-chromium film in Cr25Ni35 ethylene cracking furnace tube

在保留内表面的前提下切割Cr25Ni35工业裂解炉管,得到5 mm×5 mm×3 mm的试样。使用原位涂层抑制结焦技术对试样进行处理,在炉管内表面生成锰铬尖晶石薄膜,再经结焦实验后,分别采用850℃空气、850℃空气/水蒸气混合气、900℃空气对结焦试样进行烧焦及再次结焦实验,通过SEM及EDS分析了烧焦处理前后试样的结焦量变化、表面形貌及元素组成变化。同时,也考察了急冷处理对试样结焦量、表面形貌和元素组成的影响。实验结果表明,850℃空气烧焦和急冷处理后试样的结焦量下降,850℃空气/水蒸气混合气烧焦和900℃空气烧焦对Cr25Ni35试样的结焦量影响不大;850℃空气烧焦、850℃空气/水蒸气混合烧焦、急冷处理和900℃空气烧焦都明显改变了Cr25Ni35原位涂层试样的表面形貌;850℃空气烧焦和850℃空气/水蒸气烧焦后,难以通过Cr25Ni35试样表面的元素变化判断对结焦量的影响,而急冷处理和900℃空气烧焦导致Cr25Ni35试样表面的元素变化有利于产生结焦。

The Cr25Ni35 samples of 5 mm×5 mm×3 mm were cut from industrial cracking furnace tube on the premise of retaining the inner surface.A layer of manganese chromium spinel film was formed on the inner surface of the sample by in-situ coating to inhibit coking.After coking experiments,the samples were treated with air at 850℃,air plus steam at 850℃or air at 900℃to docoke.Then coking experiments were carried out on the samples again.The changes of coking amount,surface morphology and element composition of samples before and after decoking were investigated by SEM and EDS,and the effect of decoking on manganese-chromium spinel film on Cr25Ni35 tube was studied.In addition,the effect of quenching treatment on the coking amount,surface morphology and element composition of the samples were also investigated.The results show that decoking with air at 850℃and quenching decreased the coking amount,while decoking with air plus steam at 850℃and decoking with air at 900℃had less effect on the coking amount of samples.The surface morphology of samples were obviously changed by decoking with air at 850℃and 900℃,decoking with air plus steam at 850℃and quenching.It was difficult to judge the effect of the element changes on the coking amount of samples after decoking with air and with air plus steam at 850℃,while the element changes might lead more coking after decoking with air at 900℃and quenching.