Towers piping arrangement

Pipe still (pipestill) a still in which heat is applied to the oil while being pumped through a coil or pipe arranged in a suitable firebox the distillation tower in a refinery. 

A symmetrical piping arrangement between the draw-off and reboiler inlet nozzles and between the reboiler outlet and return connection on the tower is preferred for equal flow in the reboiler circuit. Nonsymmetrical arrangements may also be... 

Lines interconnecting exchangers with other process equipment can run just above the required headroom or about on the same level as the yard piping. Reboiler line elevations are determined by the draw-off and return line nozzles on the tower. Symmetrical reboiler piping arrangements — between the tower draw-off and reboiler inlet nozzles and between reboiler outlets and return... 

Tower piping should be arranged with sufficient flexibility to accommodate tower growth and to allow interconnection to equipment during regular operating conditions. Exhibits 10-53 and 10-54 show typical overhead vapor line and pump suction arrangements. 

For finite flow rates of heavy liquid, hi will decrease, i.e., the interface will rise. This piping arrangement is not directly applicable to control of the extraction tower shown in Fig. 12.8, because of the variable pressure drop encountered in the packing and discharge line. 

A few towers with very low liquid flow rates have been set up with pipe downcomers arranged for liquid flow in the same direction on successive trays. On the other hand, it is much simpler mechanically to provide reversed flow of liquid on adjacent trays. 

If the plant has only one acid circulation tank, then all the exit streams from the towers get mixed. Separate add pumps or a common acid pump can supply acid to the towers through separate cooling arrangements. These are in the form of trombone coolers (rows and columns of Cl pipes over which water spray trickles down) having more cooling area for DT than FAT. 

Relief valves are usually furnished as part of the reactor piping. system and should be located in accordance with the arrangements shown in Chapters 5 (Drums) and 10 (Towers). 

The vapor outlet is usually a vertical nozzle located on the top head of the tower. It is usually a single nozzle, but in certain cases (e.g., towers with very large diameters), more than one nozzle is specified. On large-diameter vapor lines, the vessel connection could be butt-welded instead of flanged. In addition, the vent and relief valve could be located on the top head instead of attached to the overhead piping. Exhibit 10-32 shows a typical top head arrangement. 

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