原油脱钙剂作用机理及其脱钙效果

通过对不同化学剂诸如EDTA钠盐、六偏磷酸钠盐、盐酸和RPD作为原油脱钙剂时对原油脱钙的试验研究,分析了原油脱钙剂的作用机理。结果表明,在原油脱钙过程中,脱钙剂与原油中石油酸钙的作用类似于复分解反应,原油中的环烷酸钙转化为环烷酸钠或环烷酸。不同化学剂与原油中钙之间存在化学计量关系,EDTA钠盐和六偏磷酸钠盐类化学剂在络合脱除原油中钙的同时会使原油中钠离子增加。RPD新型脱钙剂避免了钠盐化学剂的缺点,对新疆克拉玛依九区稠油、北疆原油及苏丹稠油等不同性质高钙原油,在剂钙质量比为4.0时脱钙率达90％以上。原油脱钙后,原油中的石油酸钙盐转化生成石油酸组分,不给原油引入新的有害杂质。

THE EFFECTS OF DECALCIFYING AGENTS ON CRUDE OIL DECALCIFICATION AND ITS ACTION MECHANISM

Through experimental study of various decalcifying agents, such as disodium EDTA, tetrasodium EDTA, sodium hexametaphosphate, hydrochloric acid and RPD, for crude oil decalcification , the action mechanism was analyzed. It was indicated that the reaction between the chemical reagent and calcium species of crude oil might be similar to that of ion exchange reaction at oil/ water interface, and the calcium naphthenate in the crude oil was converted to sodium naphthenate or naphthenic acid. The amount of calcium removed was equal to the stoichiometic increment of sodium specie or total acid number. When using sodium EDTA and sodium hexametaphosphate as decalcifying agents, the sodium ion might increase during the calcium removal. The new RPD decalcifying agent could avoid the above deficit. The sodium removal rate of RPD for different high calcium-containing crude oils, such as viscous crude oils from No. 9 district of Karamayi Oilfield, Northern Xinjiang and Sudan, was higher than 90% at an agent to calcium ratio of 4. 0. The calcium naphthenate existed in crude oil was transformed into naphthenic acid without introducing any new detrimental impurities during decalcification.