Distillation Glossary azeotrope A mixture that occurs when two or more components boil at the same temperature if the mixture is at a certain concentration. binary column Column which uses a feed mixture containing only two components. boiling range The span between the initial and the final boiling temperatures of a multi-component solvent. bottoms product The heavier components or high boilers distilled from a mixture. burping Vapor pressure becoming so great that it forces liquid up the column and out the overhead product line. Delta P The difference in pressure from the bottom of the column to the top of the column direct composition measurement When the percentages of components of a product are directly observed. distillation A process which separates the lighter and heavier molecules from a liquid mixture by exploiting the difference in the molecules’ boiling points. downcomer Downspouts that allow the liquid to drop to lower tray levels in the column as liquid overflows the weir. dumping Liquid on all the trays flowing through to the bottom of the column. emergency shutdown Procedure to rapidly shutdown a process if an emergency cannot be quickly remedied. energy balance The heat input to the column must be approximately equal to the heat removed from the column. entrainer A solvent that carries or pulls along another component in the distillation process. equilibrium State that occurs when the rate of vaporization is equal to the rate of condensation in a system. extractive distillation Process in which the entrainer pulls the heavier component of a mixture out of the column through the bottoms product. final boiling point The temperature where a natural material or fraction finishes boiling. flooding Excessive buildup of liquid in a column causing liquid to be entrained in the vapor rising through the column. forced reboiler Reboiler that uses a pump to circulate the bottoms liquid through the heat exchanger and back to the column. fractionation The use of a column to help separate the components of a mixture. idling procedures Procedures designed to suspend production in a column for a period of time, but the column continues to operate. indirect composition measurement When a measured variable is used as an indicator of product composition. initial boiling point The temperature when the first bubble of vapor is formed from a liquid mixture. kettle reboiler Reboiler that uses a weir to maintain the liquid level to cover the heated tube bundle. latent heat Heat input that causes a phase change without changing the temperature. long-term shutdown Process to safely maintain and prepare equipment and lines to remain unused for a long period of time. material balance The sum of all products exiting the column must be approximately equal to the feeds entering the column. multi-draw column Column which takes multiple product streams from locations along the height of the tower. overhead product The lighter components or low boilers distilled from a mixture. overloading A column operating above its maximum limits. packed columns Distillation columns which use various types of packing material to improve contact between the vapor and liquid. phase change Matter changing from one state to another. pre-startup procedures Procedures designed to ensure that the proper communications, equipment testing and commissioning have been completed prior to startup. process lag The time required for a change occurring in a process to reach a new equilibrium. process upsets Process variations falling outside the process control limits. reboiler Specialized term for a heat exchanger used in the bottoms system of a distillation column to provide heat to the system. reflux The overhead system returning a portion of the overhead product to the upper portion of the column. sensible heat Heat input that causes a change in temperature and that can be measured. shutdown procedures Procedures designed to stop the distillation process by gradually stopping the flow rates and cooling and heating sources. side-draw column Column which takes a product stream from a location along the height of the tower. startup procedures Procedures designed to bring the distillation process up to full operation. steady state operations The process variable values are within the process control limits and do not change significantly over time. structured packing Thin corrugated metal plates or meshes. temperature profiles The different temperatures at different locations in a distillation column. ternary azeotropes Azeotropes consisting of three components. thermosyphon reboiler Reboiler that uses natural circulation to move the liquid into the reboiler and back to the column. total pressure The sum of the vapor pressures for all the components in a mixture. tray columns Distillation columns which use trays to hold up the liquid to improve contact between the vapor and liquid.