Boiler

From SysCAD Documentation

Navigation: Models -> Energy Transfer Models

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Contents 1 General Description 1.1 Diagram 2 Inputs and Outputs 3 Model Theory 3.1 Assumptions and Limitations 4 Data Sections 4.1 Requirements 4.2 Results 5 Adding this Model to a Project

General Description

This is a very simple boiler model without regard to fuel type or feedwater heater type. The model will predict - based on the boiler feed water, the required drum pressure and the superheated steam conditions - the energy required by the boiler. This information can be used elsewhere to calculated / estimate the amount of fuel needed by the boiler.

Note: The Boiler & Combustion Project, which is distributed with SysCAD in the Examples folder, demonstrates the use of this model.

Diagram

The diagram shows the default drawing of the Boiler, with the required connecting streams. The unit will not operate unless all of the above streams are connected.

The physical location of the connections is not important; the user may connect the streams to any position on the drawing.

Inputs and Outputs

Label	Input /Output	No. of Connections		Description
		Min	Max.
FeedLiquor	In	1	1	The Boiler Feed Water.
SteamOut	Out	1	1	The superheated Steam Outlet.
Blowdown	Out	0	1	The boiler blow down.

Model Theory

The Boiler is designed to

1. Heat a stream of high pressure Boiler Feed Water to Saturated conditions at the specified Drum pressure.
2. A specified fraction of the saturated liquid is split off to blow down. A typical blow down is 2 to 8%.
3. The remaining liquor is heated to vapour at the specified outlet temperature and pressure (superheated steam).

The energy required to do the above divided by the boiler efficiency is reported as fuel energy required.

Assumptions and Limitations

1. The FeedLiquor (Boiler Feed Water) stream will contain water and is at a pressure higher than the Boiler Drum pressure.
2. The drum pressure must be higher than the outlet steam pressure.
3. All feed water will be evaporated to steam. Thus the outlet steam conditions specified must be at saturated or superheated conditions.

Data Sections

The default sections and variable names are described in detail in the following tables. The default Boiler access window may consist of 2 sections. This number may increase, based on user configuration.

1. The first section contains general information relating to the unit as well as a tick box for ShowQFeed.
2. 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. This is fully described in Common Data Sections.
3. Links tab, only visible in SysCAD 9.2, contains a summary table for all the input and output streams.
4. Audit tab - contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Class: Boiler - 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
On	Tick Box	If this option is deselected, the boiler will not be operational and thus all material will report to the blow down stream, if it is connected.
FinalTRqd	Input	The temperature required for the outlet steam. Note: this must be >= Saturation Temperature @ outlet pressure.
FinalPRqd	Input	The pressure required for the outlet steam. Note: This must be lower than or equal to the drum pressure.
DrumP	Input	The drum pressure. Note: Feed Water P > Drum P >= outlet P.
Blowdown	Input	The amount of boiler blow down. Note this will be ignored (assumed 0) if the physical blowdown connection is not present.
Efficiency	Input	This is the efficiency of the boiler. This value is used when calculating the energy required by the boiler.
ShowQFeed	Tick Box	Two additional tab pages (QFeed & Qm) will become visible, showing the properties of the combined feed stream.
Results
DrumT	Calc	Drum Temperature. This is the saturation temperature at the Drum Pressure.
HeatRqd1	Calc	The energy required for heating boiler feed water to Saturation Temperature at the Drum Pressure.
HeatRqd2	Calc	The energy required to evaporate all the preheated water (less boiler blow down) to the required outlet temperature and pressure.
TtlEnergyRqd	Calc	The Total energy required = HeatRqd1 + HeatRqd2
FuelEnergyRqd	Calc	This is the amount of fuel required to run the boiler = Total Energy Required / Boiler efficiency.
BlowDownQm	Calc	This is the mass flow of the boiler blow down.
FinalP	Calc	The boiler steam outlet pressure.
FinalT	Calc	The boiler steam outlet temperature.
SatT	Calc	The boiler steam outlet Saturation Temperature.
DegSuperHeat	Calc	This is the degree of superheat the steam outlet contains. Thus, the temperature above its saturation temperature.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

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

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

Insert into Project

Insert Unit

→

Heat Transfer

→

Boiler

See Insert Unit for general information on inserting units.