Condenser Types

The condenser is always considered to be a heat sink on tray one. Several options are provided for the condenser product(s) as described below. Note that condenser products correspond to products from the accumulator drum. For most columns there is a small pressure drop from the top tray of the column (tray two) to the accumulator drum.

Partial

Partial condensers correspond to an equilibrium stage, with both equilibrium liquid and vapor produced from the accumulator drum. Equilibrium liquid is always returned to tray two of the column model as reflux. The condenser may or may not have a liquid product withdrawn from the accumulator drum. A "fixed rate liquid draw" from tray one is used to represent the liquid product when both liquid and vapor products are desired for a partial condenser. The equilibrium vapor product is always defined as the column "overhead" product.

The condenser temperature is calculated, and must correspond to the dew point of the column overhead vapor product.

When a "fixed rate liquid draw" is used to represent a liquid product, inconsistencies can arise if the draw rate is not reasonable. To avoid such problems it is recommended that the condenser temperature be specified and the draw rate be calculated as a column variable. See Column Specifications and Variables for further information.

Bubble Temperature

The condenser temperature is computed such that the column top tray vapor (tray 2) is cooled to a bubble point liquid phase. Some liquid is returned to the column as reflux and some is withdrawn as product. The condenser liquid product is defined as the column "overhead" product.

Subcooled, Fixed Temperature

For this option the column top tray vapor (tray 2) is cooled below its bubble point or "subcooled". You must provide a value for the subcooled temperature. Note that for this option the condenser does not function as a theoretical tray, however it is still defined as tray number one for column set-up purposes. The subcooled liquid product is defined as the column "overhead" product.

PRO/II checks the condenser product to ascertain that it is truly a subcooled liquid at the defined temperature and pressure. If the product is not subcooled, the bubble point temperature is given in a message and a non-converged condition is flagged. It is your responsibility to revise the temperature or change the condenser type, as is appropriate.

The advantage of this condenser option is that a condenser temperature may be defined without using a column performance specification.

Subcooled, Fixed Temperature Drop

This condenser type is identical to the subcooled type described above except that the number of degrees of subcooling below the bubble point is provided instead of the subcooled temperature. For this case the liquid product bubble point is computed at the condenser pressure. The temperature is then reduced by the specified temperature drop for the reflux and liquid product.

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