Document Lpy178EGJEKG90VZyrMmgJmkX

summer . POWERFAX 1 93i ses throughout the system due to frictional resistance or static head to a minimum. Extremely high boiling fractions cannot be distilled commercially in a dry system because the ab solute pressure required to accom plish the distillation is not com mercially practical. Dry distilla tion is therefore limited in its ap plication to those products which may be distilled at commercially obtainable pressures, with operat ing temperatures well below the cracking range for the particular product in question. In any vacuum distillation proc ess the number of overhead or ex ternal condensers required is de termined by the number of over head cuts or fractions desired. Dry distillation systems, operating at extremely low absolute pressures, are usually suitable for recovering only one or two fractions; for in order to recover a greater number of fractions, the equipment re quired, even though designed with extreme care, would impose a suf ficient pressure drop to prevent securing the necessary absolute pressure at the point of injection to accomplish vaporization. The flow diagram illustrates a typical dry distillation system. The charging stock is received hot from a previous processing operation and enters the pipe still of the vacuum unit, where it is heated. Pancake coils are . employed in the tower to keep down the num ber of trays required in order to keep the pressure loss at a mini mum. All of the vapors enter a single overhead condenser in which they are almost completely con densed and partially cooled. The distillate removed from this con denser is further cooled in a sepa rate water-cooled exchanger, and a portion of-the cold reflux'is pumped back to the top of the tower for control purposes. The non-condensable gases, plus a small amount of saturated hydro carbon vapors, pass through a small water-cooled gas cooler and subsequently to the suction of the steam jet ejector. The steam jet ejector is of the three-stage type, employing barometric inter-con densers between stages. Experience with dry distillation systems indicates that it is not commercial to attempt to secure absolute pressures at the point of vaporization appreciably below 8 to 10 mm. Within certain limits, however, which depend to some extent on the temperature of the water supply and pressure of the steam available, the lower the ab solute pressure at which the sys tem is operated, the better will be the overall economy of the unit. There are fewer dry systems in actual use in this country than wet systems, although the former are far more economical in most instances where they are appli cable. as qooJ in. KANSAS CITY as it was in LOUISVILLE his eluott-bidoway Tengine-generator unit has traveled about the country a little bit for the National Candy Company. The unit was originally in stalled in 1922 in the F. A. Menue factory of the National Candy Company at Louisville, Kentucky. After seven years of continuous operation, it stood idle for a while due to the discontinu ance of the Menne factory. The management, however, re membering the good perform ance of the unit, moved it early in 1931 to the Kansas City, Missouri factory of the National Candy Company, where it is again dem- onstrating its reliability and per formance capabilities! The pho tograph shows the unit as installed at Kansas City. It is a four-valve engine direct-connected to a 125kw., 3-wire generator. (231 y>:: CRIMDEBN00000382