活性氧化铝和分子筛对C3F7CN/CO2及其过热分解产物的吸附特性

Adsorption Characteristics of Activated Alumina and Molecular Sieves for C3F7CN/CO2 and Its Decomposition By-Products of Overheating Fault

近几年提出的环境友好型气体绝缘介质全氟异丁腈(C3F7CN),在介电特性和环保方面表现良好,具有替代SF6气体的可能性。探究常用吸附剂对绝缘介质C3F7CN及其分解产物的吸附特性,可为实际设备中吸附剂的选择提供参考。在过热实验基础上,对比分析γ-Al2O3和分子筛(3A、4A和5A)对绝缘介质C3F7CN和缓冲气体CO2及其混合气体分解产物的吸附特性。C3F7CN/CO2混合气体在650℃下的过热分解产物主要为CO、CF4、C2F6、C2F4、C3F8、C3F6、i-C4F10、CF3CN、CNCN和C2F5CN等。实验结果表明:γ-Al2O3和分子筛对缓冲气体CO2及分解产物CO和全氟碳类气体的吸附能力较弱,但能有选择地吸附腈类气体。其中,四种吸附剂均能有效吸附腈类气体CNCN,但只有γ-Al2O3和5A分子筛能有效吸附CF3CN气体,γ-Al2O3吸附速率大于5A分子筛。此外,γ-Al2O3能吸附绝缘介质C3F7CN,故不适合用于以C3F7CN混合气体作为绝缘介质的电力设备中。

The heptafluoro-isobutyrontrile(C3F7CN)is an environmentally friendly gas-insulating dielectric.It performs well in dielectric properties and environmental protection,which has the potential to replace SF6 gas.Exploring the adsorption characteristics of common adsorbents for insulating medium C3F7CN and its decomposition by-products can provide reference for practical equipment.In this paper,the overheating experiment was carried out,and the gas decomposition by-products were qualitatively detected by gas chromatography-mass spectrometry(GC/MS).The adsorption characteristics of insulating media C3F7CN,buffer gas CO2 and decomposition by-products by γ-Al2O3,3A,4A and 5A molecular sieves were studied quantitatively.The results show that the decomposition by-products of C3F7CN/CO2 mixture at 650℃ are CO,CF4,C2F6,C2F4,C3F8,C3F6,i-C4F10,CF3CN,CNCN,C2F5CN,etc.3A,4A and 5A molecular sieves andγ-Al2O3 do not adsorb CO and perfluoroalkane gases,but they have selective absorption of nitrile fluorocarbons.Wherein,they all can effectively adsorb decomposition gas CNCN;only γ-Al2O3 and 5A molecular sieve can adsorb CF3CN gas,and the adsorption rate of γ-Al2O3 is the fastest.In addition,γ-Al2O3 can adsorb C3F7CN,then with long-term adsorption it will reduce the content of C3F7CN.Therefore,γ-Al2O3 is not suitable for using in C3F7CN mixed gas insulated power equipment.