HCurve Column Internal Stream Evaluation Data

Heating/Cooling Curve for Column Internal Streams

For columns and side columns, heating/cooling curves may be generated for reboiler, condenser and pumparound heater/cooler internal streams. Both isothermal and fixed-enthalpy calculations can be performed, and additionally you can specify the pressure range over which the curves have to be generated. The appropriate tray conditions for generating the curve are retrieved by PRO/II automatically.

Note : Heating/Cooling curves cannot be generated for tray side heaters (heaters which directly heat a tray). Also, for each column entry in the Heating/Cooling Curve Main Window, PRO/II will perform only one type of calculation. If multiple curve types are required for the same unit, you have to select the column entry multiple times and select different curve types.

Usage

From the Heating/Cooling Curve Main Window, select the desired column in the unit operation selection table. Push the corresponding Enter Data button to display this window.

Evaluation Condition

Select the desired column attachment from the Heater list box. You can then select either an isothermal or fixed-enthalpy Flash Calculation type. You may also optionally enter the Starting Pressure and Ending Pressure if you desire to override the default pressure range. If the ending pressure is not entered, it defaults to the starting pressure.

Curve for Condenser

The first flash point calculation for the condenser stream is performed at the thermodynamic state of the vapor stream entering the condenser. The last flash point on the curve is thermally defined by the duty on the condenser calculated in the column solution. The pressure drop is set to zero, in which case the curve is generated at the same pressure (feed pressure) by varying the temperature. However, you can set a pressure range by entering the desired starting and ending pressures to vary both pressure and temperature for the curve calculations.

Curve for Reboiler

The first flash point calculation for the reboiler stream is performed at the thermodynamic state of the product from the bottom tray. The last flash point on the curve is thermally defined by the duty on the reboiler calculated in the column solution. The pressure drop is set to zero, in which case the curve is generated at the same pressure by varying the temperature. However, you can set a pressure range by entering the desired starting and ending pressures to vary both pressure and temperature for the curve calculations.

Curve for Pumparounds

The first flash point calculation for the pumparound heaters/coolers is performed at the thermodynamic state of the liquid or vapor in the tray from which the stream is drawn for pumparound operation. The last flash point on the curve is thermally defined by the duty on the pumaround heater/cooler calculated in the column solution. The final pressure is set at the return tray pressure. You can override this pressure range by supplying your own starting and ending pressures.

Report Options

You can request the results printout to contain additional data such as Liquid Activity Coefficients, K-Values, etc., by selecting the appropriate options. These selections will apply only to the curve for which you are entering the evaluation data. The first of these options (liquid activity coefficients, etc.) will produce meaningful results only if a liquid-activity K-value method is chosen in the thermodynamic data section of input.

Number of Evaluation Points

The temperature, pressure and enthalpy ranges are divided equally into the number of evaluation points where flash calculations are performed. The default value is eleven. Note that the first evaluation point is at the inlet or the initial conditions.

$image\SML_LINE.gif$