Packed column hydraulics pressure drop

Packed fractional distillation columns run in the batch mode are often used for low-pressure drop vacuum separation. With a trayed column, the liquid holdup on the trays contributes directly to the hydraulic head required to pass through the column, and with twenty theoretical stages that static pressure drop is very high, e.g., as much as 100-200 mm Hg. 

Slowly ramp up to the target flow rate. This prevents hydraulic shock to the forming bed and therefore prevents uneven packing of the column. Adjust the pump speed to maintain a constant pressure drop over the resin bed. The operating pressure must never exceed the pressure limit of the column. Continue to flow pack at constant pressure until the resin bed stabilizes. 

Another parameter in the design of a packed column is the column diameter, which is determined on the basis of hydraulic considerations, such as pressure drop and flooding conditions. The hydraulic behavior of the column depends on the packing type and operating conditions. Correlations based on experimental data are available for calculating column packing hydraulics, and are discussed in this chapter. 

Having determined the column packing height on the basis of equilibrium calculations and whatever mass transfer correlations, the capacity of the column to handle the required vapor and liquid flows hydraulically must be checked. The specific items of concern in this regard are the pressure drop across the packing and the tendency of the column to flood. These are the considerations that determine the required column diameter. 

Site the Distillation Column. This includes the hydraulic aanlysis to establish operating mages, pressure drop, and mass transfer efficiency. The result is a set of dimensious, including columa diameter and height, number of actual trays (or height of packed bed), details of internal devices, and profiles of temperature and pressure. 

This FDPAK programme provides chemical engineers with a fast calculation the hydraulic parameters of any types of column internals (more than 200) and allows the user to assess the individual types of packings in terms of their maximum capacity, pressure drop and liquid hold-up. The experience of the past 20 years has shown that the programme is also suitable for teaching purposes at colleges and universities. 

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