Steam Generation: Oper. Conds Tab

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab. The table also displays their default values and their generally acceptable range. Note that due to how the variables are used in the modeling equations, the range of acceptable values may be further reduced; for more details, see Steam Generation: Modeling Assumptions & Constraints.

Variable	Default Value	Range

○ Feed Stream Indicates the input port that is connected to the feedwater stream. If an input stream is already present at the selected port, then the button next to the selection is active. Click on the button to bring up the attached stream’s simulation dialog in order to provide its composition.	<None>	Dedicated Feedwater Stream
○ Fuel Stream Indicates the input port that is connected to the fuel stream. If an input stream is already present at the selected port, then the button next to the selection is active. Click on the button to bring up the attached stream’s simulation dialog in order to provide its composition.	<None>	Dedicated Fuel Stream
○ Air Stream Indicates the input port that is connected to the air stream. If an input stream is already present at the selected port, then the button next to the selection is active. Click on the button to bring up the attached stream’s simulation dialog in order to provide its composition.	<None>	Dedicated Air Stream
○ Excess Oxygen (%) The excess oxygen % of the air stream.	10.0	0-100
● Air Humidity (wt/wt of Dry Air) The fraction of water in the air stream expressed on a dry air basis.	0.0	Positive
● Total Heat in System (kcal/kg) The total heat in the furnace at the end of combustion expressed in units of energy per unit mass of fuel.	0.0	Positive
○ Ash Stream Temp. (^oC) The temperature of the ash stream.	250.0	Positive
○ Ash to Flue Gas (%) The percentage of entrained ash in the flue gas stream.	0.0	0-100
◙ Steam Pressure (bar) The pressure of generated steam.	45.0	Positive
◙ Steam Temperature (^oC) The temperature of generated steam.	99.97	Positive
● Required Heat (kcal/kg) The required specific enthalpy change of feedwater into steam.	0.0	Positive
○ Flue Gas Exit Temp. (^oC) The temperature of the flue gas outlet stream.	200.0	Positive
○ Overall Heat Losses (%) The fraction of total heat in system that is lost to the surroundings.	5.0	0-100
● Available Heat (kcal/kg) The net heat that is available for steam generation in the boiler, expressed in units of energy per unit mass of fuel.	0.0	Positive
● Fuel Requirement The mass of fuel required per unit mass of steam.	0.0	Positive
● Operating Throughput per Unit (kg/h) The mass flow rate of feedwater per equipment unit.	0.0	Positive

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

The following list describes the available specification choices in this tab; for more details on how these are implemented, see Steam Generation: Modeling Calculations.

•Adjust Feedwater Flow to Available Heat...

If you select this option, then you must specify the flow of the fuel stream, and based on this, the program will calculate the flow of the air stream so that it meets the excess air specification and the flow of the feedwater stream so that the heat required to convert feedwater into steam is equal to the available heat for steam generation in the boiler.

•Adjust Fuel Flow to Required Heat...

If select this option, then you must specify the flow of the feedwater stream, and based on this, the program will calculate the flow of the fuel stream so that the available heat for steam generation is equal to the heat required to convert feedwater into steam and the flow of the air stream so that it meets the excess air specification.