Popvlar Science Monthly 



387 



CmVM DltTiLLMJtS 



Fi2. 2. How Pennsylvania Crude Oil Is Refined 

 B — Steam Still D— Agitator F — Chilling Tank H — Wax Sweater 



C — Steam and Fire Still E— Fuller's Earth Filter G— Wax Filter Press K— Air Drying Tank 



pass up through alternate boxes and 

 air-cooled tubes, where products of 

 different boiling points are simultaneous- 

 ly condensed and thus automatically 

 separated into groups. The lightest 

 l^roducts pass completely through the 

 tower and flow in vapor form to a water 

 cooled condensing coil, where all light 

 hydro-carbons condensable without the 

 application of pressure, are liquefied and 

 separated from the remaining \apors, 

 which arc further treated at a compressor 

 plant, for the separation of very light 

 hydro-carbons from the "fixed" gases. 

 Of the remaining vapors, the heaviest 

 condense upon striking the first air- 

 cooled tubes, and the lightest upon 

 striking the last tubes. Intermediate 

 jiroducts, lying between the light and 

 lieav>' ends, condense in ihe intermediate 

 tubes, depending upon their respective 

 boiling point. The vapors liquefying in 

 different sections of the aerial condenser 

 fall back into corresponding collector 

 pans, whence each is led by wav' of a 

 separate water-cooled coil to the storage 

 tanks, called "running tanks." The 

 liquids reco\'ercd in the collector pans 

 are still at a temperature above their fire 

 points, and it is necessary to cool them 

 down to prevent spontaneous ignition. 



when they come into contact with air in 

 the running tanks. 



Distillation continues until a residue 

 (crude cylinder stock), of about 15 per 

 cent, remains, when the fires are drawn 

 and the remaining oil is pumped from the 

 still through a cooler into a running 

 tank. 



The quantit>' and quality of products 

 obtained from this first separa.lion de- 

 pend upon the method of distillation 

 employed and from the base or "family" 

 to which the crude petroleum belongs. 

 This description, however, only concerns 

 Pennsylvania crude oil of paraffin base. 

 High quality oils are obtained when the 

 sep;xration is made by distilling under 

 vacuum or by the use of fire in combina- 

 tion with steam injection. Due to the 

 mixture of (jil and water vapors in fire 

 and steam distillation, oil vapors pass 

 over at lower temperatures than were 

 fire used alone. This prevents the occur- 

 rence of any serious "cracking" of the 

 heavier products. 



Second Stage — Separation and 

 Finishing of First Groups 



The prime object of subjecting the 

 group-distillates from the running tanks 

 to different processes is to further 



