Distillation Modeling CHEN 4470 Process Design Practice Dr

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Distillation Modeling CHEN 4470 – Process Design Practice Dr. Mario Richard Eden Department of

Distillation Modeling CHEN 4470 – Process Design Practice Dr. Mario Richard Eden Department of Chemical Engineering Auburn University Lecture No. 14 – Design of Overhead Condensers and Air-cooled HX February 26, 2013 Material Developed by Dr. Jeffrey R. Seay, University of Kentucky - Paducah

Overview • Purpose of Overhead Condensers – • Provide reflux flow to the top

Overview • Purpose of Overhead Condensers – • Provide reflux flow to the top of a column and acts as an additional theoretical stage above the trays/packing Types of Condensers – – – Knock-back reflux Total condenser Partial condenser Proper condenser design is critical to the optimum operation of a column!

Knock-Back Condenser • This design is easy to operate, but difficult to achieve precise

Knock-Back Condenser • This design is easy to operate, but difficult to achieve precise control. • Condenser will be larger due to the bi-directional traffic on the process side. 2 Phase Flow Region • Condenser can be in the vertical or horizontal position. Horizontal – Process on the shell side. Vertical – Process is on the tube side. • Elevation is critical.

Partial Condenser Vapor Distillate • Used when vapor product is required, or if non-condensible

Partial Condenser Vapor Distillate • Used when vapor product is required, or if non-condensible gases are present in the overhead product. • Controlling the vapor stream split can be challenging. • Condenser can be in the vertical or horizontal position. Horizontal – Process on the shell side. Vertical – Process is on the tube side. Liquid Distillate • Elevation is not critical.

Total Condenser • Total condensers are used when no non-condensable gases are present. •

Total Condenser • Total condensers are used when no non-condensable gases are present. • As with other condensers, vertical or horizontal operation is possible. • Elevation is not critical for a total condenser. • Subcooling of the reflux can be a problem with overhead condensers, especially with vertical designs. Liquid Distillate

Condenser Design • Considerations – The overhead condenser is often a critical part of

Condenser Design • Considerations – The overhead condenser is often a critical part of the control concept of a column – Because distillation is based on VLE principles, the overhead condenser can be used to control the temperature and pressure in the column – A later lecture will present some control concepts and strategies for overhead condensers – Condensers in series can also be used to optimize utility consumption

Condensers in ASPEN Plus

Condensers in ASPEN Plus

Air-Cooled Heat Exchangers • Typical Air-Cooled Condenser Tube Detail Design Equations: Air-cooled HX are

Air-Cooled Heat Exchangers • Typical Air-Cooled Condenser Tube Detail Design Equations: Air-cooled HX are primarily used when no other cooling utilities are available on site Note: The surface area, A, includes the area of the fins! C and m are parameters based on the size of the fin.

Air-Cooled HX Design • Design Considerations – – • Natural convection in turndown cases

Air-Cooled HX Design • Design Considerations – – • Natural convection in turndown cases Changing ambient air conditions Effect of precipitation on operation of unit Possibility of water-hammer inside tubes Possible Control Parameters – – – Air flow across the tube bank Position of louvers on top of the unit Liquid level inside the tubes

Other Business • Next Lecture – February 28 – – • Integration of design

Other Business • Next Lecture – February 28 – – • Integration of design and control part I SSLW 322 -340 Individual Team Assignments – – – Will be assigned over next two week period Choose one from the project description or Email me two sentences describing what you would like to investigate and I will respond with the ”official” problem statement.