Barometric Condenser

From SysCAD Documentation

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Contents 1 General Description 1.1 Diagram 2 Inputs and Outputs 3 Model Theory 3.1 Reference 4 Flowchart 5 Data Sections 5.1 Requirements 5.2 Results 5.3 Flash Train Macro Model 6 Adding this Model to a Project 7 Hints and Comments

General Description

This is a direct contact cooler. The unit has separate water and steam inlets, and mixture and vapour outlets. In most situations the vapour line is connected to a steam ejector.

There are two operational modes:

1. As a stand-alone unit, or
2. As part of a Flash Train.

The operational mode is decided by the overall configuration of the flowsheet in which the unit is located. If the Barometric Condenser is correctly connected to other units such as Heat Exchangers and Flash Tanks, the model may become part of the entire Flash Train. The user does not have to specify whether the unit is part of a Flash Train, SysCAD will do this automatically. Refer to Flash Train for the rules governing this behaviour.

The model mixes the inlet streams, rejects heat lost to atmosphere, and performs any reactions, if specified, before flashing the incoming streams. The unit calculates the temperature, composition and flow rate of the exit streams. All of the liquid is pumped from the mixture outlet. The non-condensable vapours and excess steam exit via the vapour outlet at flash pressure.

The user may specify reactions, which must occur in the unit. The Barometric Condenser will combine all of the incoming streams to form a homogeneous mixture before carrying out the reactions.

An Environmental Heat Loss may also be included in the unit. This allows the user to specify a heat loss, or gain, between the unit and the environment.

Note: The Evaporation Project, which is distributed with SysCAD in the Examples folder, demonstrates the use of this model in a SysCAD project.

Diagram

The diagram shows the default drawing of the Barometric Condenser, with the required connecting streams. The vapour connection allows for the removal of non-condensable as well as any excess steam. The user does not have to connect a stream to the vapour outlet.

The physical location of the connections is not important; the user may connect the streams to any position on the drawing. When the user inserts a Barometric Condenser into a flowsheet, he may choose a different drawing from a pull down menu.

Inputs and Outputs

Label	Input / Output	No. of Connections		Description
		Min	Max
Steam	In	1	1	The steam inlet.
Water	In	1	1	The liquid or slurry inlet
Mixture	Out	1	1	The outlet, containing the cooling water and condensed steam.
Vapour	Out		1	Vent for non-condensable and excess steam.

Model Theory

The unit is configured to achieve Vapour:Liquid equilibrium at a required pressure using the saturated steam calculations. At this stage, only two phase flash calculations are handled in SysCAD. Any solids that may be in the cooling stream entering the unit are ignored in the flash calculations. However, the enthalpy balance does include the solids. The temperature and amount of material which changes phase is calculated using an adiabatic flash routine¹.

The unit will attempt to condense the steam at the user defined flash pressure. The equilibrium point of the unit will be that of saturated steam plus any Boiling Point Elevation equations that may be associated with the liquor.

Reference

Coker, A.K., Equilibrium flash calculations quickly computed on PC, Oil & Gas Journal, Jan 14, 1991.

Flowchart

The following shows the sequence of events if sub model options are switched on. See next heading for more information.

Data Sections

The default sections and variable names are described in detail in the following tables. The default Barometric Condenser access window may consist of a number of sections, which may change, based on user configuration.

1. The first tab contains general information relating to the unit.
2. RB - Optional tab, only visible if the Reactions are enabled.
3. EHX - Optional tab, only visible if the EnvironHX is enabled.
4. QProd - The pages associated with the product flow show the properties of the mixed output stream as the product before separation to outlet streams of the unit.
   • This is after all sub-models models, but before flow splits.
5. The Info section contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
6. Links tab, only visible in SysCAD 9.2, contains a summary table for all the input and output streams.
7. Audit tab - contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Class: BaroCond The first tab page in the access window will have this name.

Tag / Symbol	Input / Calc	Description/Calculated Variables / Options
Common First Data Section
Requirements
Rqd_Flash_Press	Input	The required Flash pressure of the unit. This field is only visible if the Barometric condenser is NOT part of a flash train.
ApproachTemp	Input	This field is only visible if the unit is part of a Flash Train. The approach temperature of the unit. This number defines the inefficiency of the unit. If the approach temperature is 0°C, then all of the liquid will be used to condense the incoming steam and the final temperature is at the saturation point. If the approach temperature is X, then some of the liquid is not used for condensing the steam and the final temperature is X°C lower than the saturated temperature.
Reactions	List	This can be used to switch on the Reaction Block (RB). If this is 'On' then the associated page, RB becomes visible and may be configured. Note: The user does not have to configure a reaction file, even if this block is checked.
EnvironHX	List	This can be used to switch on Environmental Heat Exchanger (EHX). If this is 'On' then the associated page, EHX may become visible and may be configured. Note: The user does not have to configure an environmental heat exchange, even if this block is checked.
Results
Cond_Press	Calc	The working pressure of the unit
Cond_Temp	Calc	The temperature at which the mixture leaves the unit. This will be at, or below, the saturated temperature at the required Flash Pressure.
Flash Train Macro Model Note: Extra fields are visible if the unit is part of a Flash Train. These fields are described below. Please refer to Flash Train.
SuctionP	Calc	The pressure on the steam inlet to the Barometric Condenser.
QRqd	Calc	The calculated mass flow of steam required by the Barometric Condenser.
QCond	Calc	The amount of steam condensed by the Barometric Condenser.
MinSatPress	Calc	The minimum saturated pressure of steam that could satisfy the heating requirements of the Barometric Condenser.
FlashTrain	Display	A unique tag assigned to the flash train by SysCAD. Each unit in the flash train will have the same tag in this block.
FlashTearBlock	Display	Displays the name of the tear block that is part of the Flash Train.
FlashTrainEqp	List	This contains a list of all of the equipment tags in this flash train. For example, if this is Barometric Condenser 1 connected to Flash Tank 2, then the list would be as follows: BarometricCondenser_1 Flash_Tank_2

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

	DLL:	HeatXch1.dll	→	Units/Links	→	Heat Transfer: Barometric Condenser
or	Group:	Energy Transfer	→	Units/Links	→	Heat Transfer: Barometric Condenser

See Project Configuration for more information on adding models to the configuration file.

Insert into Project

Insert Unit

→

Heat Transfer

→

Barometric Condenser

See Insert Unit for general information on inserting units.

Hints and Comments

1. The unit will flash to the required pressure if there is insufficient cooling water to condense all of the steam. If there is enough cooling water to condense all of the steam and also to cool it, the exiting temperature will be below the saturated temperature.