氧化钙在油基钻屑热脱附中的协同作用

Synergistic effect of calcium oxide in thermal desorption of oil-based drilling cuttings

为了解决油基钻屑热脱附过程中所存在的能耗高、过度裂解改变油品性质和二次污染等问题,采用自主研发的动态电磁加热脱附实验装置,将氧化钙(CaO)作为添加剂与油基钻屑混合进行协同热脱附处理,考察了掺混CaO对反应工况、产物分布及性质的影响,分析了冷凝油与不凝气组分的变化特征。研究结果表明:①添加5%左右的CaO,可将脱附温度降低25℃,使回收油和不凝气产率分别提高9.0%和127.9%,使残渣含油率降低62.5%,并且减少了冷凝水的产量;②CaO催化促进了钻屑中油分裂解断链,增加了自由基碎片重新聚合的概率,提高了C19~C22化合物的产量,在一定程度上保持了基础油的性质;③不凝气中CH4、H2含量分别增加了12.1%和18.4%,吸收固定了CO2,提高了不凝气热值。结论认为:①CaO与油基钻屑协同热脱附有利于优化反应条件,提高不凝气热值,改善回收油品性质,是节能降耗、增加产品附加值的有效途径;②CaO对油基钻屑热脱附具有催化长链烃裂解和促进结焦积碳的双重作用,因而需要结合实际情况确定最佳的掺混比例。

There still exists such problems as high energy consumption,qualitative alterations of the recovered oil caused by excessive cracking as well as secondary pollution produced in the process of thermal desorption of oil-based drilling cuttings.In this regard,a self-developed dynamic electromagnetic heating desorption experimental device was adopted with CaO as an additive being co-pyrolyzed together with oil-based drilled cuttings.The effects of adding CaO were investigated on working conditions and properties of products and the characteristics of recovered oil and noncondensable gases were also analyzed.The following experimental results were obtained.First,when 5%CaO is added.the desorption temperature drops by 25℃,yielding rates of oil and non-condensable gas increase by 9.0%and 127.9%,respectively,the oil content of residue decreases by 62.5%and the condensed water yield is reduced.Second,CaO catalysis promotes oil splitting and chain breaking in drilling cuttings,increases the possibilities of reaggregation for free radicals and the yield rates of compounds C19-C22,which to a certain extent makes the properties of the base oil maintained.Third,the content of CH4 and H2 in the non-condensable gas increased by 12.1%and 18.4%,respectively,which absorbed and fixed CO2 and improved the calorific value of the non-condensable gas.In conclusion,the synergistic thermal desorption of CaO and drilling cuttings contributes to the optimization of working conditions,the increase of the calorific value of non-condensable gas,the improvement of recovered oil properties,which provides an excellent approach to energy-saving,cost-reducing and additional value-enhancing of products.Besides,CaO has the dual function of catalyzing long-chain hydrocarbon cracking and promoting coking and carbon deposition on the thermal desorption of oil based drilling cuttings.Therefore,the optimal mixing ratio should be determined according to the actual situation.