  h ours . ▁ ▁The ▁sh ale ▁oil ▁yield ▁varied ▁from ▁ 8 0 % ▁to ▁ 8 5 % ▁of ▁Fischer ▁ass ay . ▁ ▁Adv antages ▁and ▁dis adv antages ▁The ▁advantage ▁of ▁the ▁N T U ▁ret ort ▁process ▁was ▁simple ▁design , ▁simple ▁operation , ▁and ▁limited ▁need ▁for ▁external ▁fuel . ▁It ▁was ▁suitable ▁for ▁processing ▁of ▁wide ▁variety ▁of ▁oil ▁sh ales . ▁The ▁dis adv antage ▁of ▁this ▁process ▁was ▁a ▁batch ▁mode ▁of ▁operation ▁not ▁allowing ▁continuous ▁ret ort ing , ▁and ▁therefore ▁having ▁small ▁capacity ▁being ▁labor ▁extensive ▁at ▁the ▁same ▁time . ▁The ▁process ▁also ▁had ▁a ▁relatively ▁low ▁oil ▁yield ▁and ▁it ▁required ▁cool ing ▁water . ▁ ▁See ▁also ▁ ▁Al berta ▁Ta ci uk ▁process ▁ ▁Pet ros ix ▁ ▁K iv iter ▁process ▁ ▁Gal oter ▁process ▁ ▁T OS CO ▁II ▁process ▁ ▁F ush un ▁process ▁ ▁Super ior ▁mult im iner al ▁process ▁ ▁References ▁ ▁Category : O il ▁sh ale ▁technology ▁Category : F u els ▁infrastr ucture ▁in ▁the ▁United ▁States ▁Category : P et role um ▁in ▁the ▁United ▁States <0x0A> </s> ▁Robert ▁Doc at ▁( fl . ▁ 1 5 5 3 ) ▁was ▁an ▁English ▁politician . ▁ ▁He ▁was ▁a ▁Member ▁( MP ) ▁of ▁the ▁Parliament ▁of ▁England ▁for ▁Hel ston ▁in ▁March ▁ 1 5 5 3 . ▁ ▁References ▁ ▁Category : Year ▁of ▁birth ▁missing ▁Category : Year ▁of ▁death ▁missing ▁Category : M