Reaction Block (RB)

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Related Links: Reaction Editor, Reaction Block - Extents, Reaction Block - HOR & Energy, Reaction Block - Other, Reaction Block - Solving Reactions, Reaction File (RCT) Text Format, Reaction Block Energy Balance

Contents

General Description

Many SysCAD models have the facility to allow the user to enable chemical reactions in the unit. If a unit has this facility, the first access window will have a field called 'Reactions'. To enable the reactions, change the status of the field from 'Off' to 'On' and SysCAD creates a reaction block for the model. If the Reaction Block is part of an Evaluation Block (EB) then the user may change the evaluation sequence relative to other sub-models by selecting On-Sequence1, On-Sequence2, etc. (refer to Evaluation Block for more information).

In dynamic mode, units which have the facility for surge may allow reactions as part of a Content Evaluation Block (CEB). This allows the user to have the reactions occur on the content or surge of the unit and is referred to as a Content Reaction Block (CRB).

Once reactions are switched 'On', an RB or CRB tab will appear as shown above.

The user may then access the RB tab and click on the 'Edit_RCT' button, as shown below:

Image:EditReactions.JPG


SysCAD will start the reaction editor (The editor used by SysCAD will have been set in the Tools/General Options/Global tab page. See Reaction Editor) to edit a text file, with the extension .rct. The reaction file will have the same name as the unit - in the case shown here it will be called 'Neutralisation.rct'.

This file is read into the unit and SysCAD solves the reactions.

Location of Reaction Files

  • All reaction files used in a project must be stored within the project in a folder called Reactions.
  • SysCAD automatically creates this folder when you start a new project or upgrade an older project to SysCAD 9.2.
  • You may check the location and names of all reaction files in a project by accessing the Project Window - Files List.

Solving Reactions

Reactions within a single reaction block may be solved sequentially or simultaneously. By default the reactions will be solved sequentially, which is the recommended method. Please refer to Solving Reactions for more information.

Reaction File Format

Chemical reactions are defined in a text file.

The recommended method of editing reaction files is to use the SysCAD Reaction Editor. However, any text editor can be used to edit or view these reactions (see Reaction File (RCT) Text Format). The reaction filename must have the extension .rct.

NOTE: The reaction file must contain at least one reaction. Sources, sinks and heat exchange can not be used in isolation without at least one reaction.

Reaction Block Options and Features

  • A reaction may proceed in the forward direction only, or may be a reversible reaction, refer to Reaction Directions for more information.
  • There several methods for specifying the extent of a reaction, refer to Reaction Block - Extents for more information.
  • A reaction block can also have sources, sinks and/or heat exchange defined. Refer to Reaction Block - Other for more information.

Data Sections

A description of the variables on the access page is given here.

  • When the user adds a reaction block to a unit, SysCAD creates the RB tab.
  • When a reaction file is loaded into the unit, SysCAD creates at least one additional tab, R1. Depending on the number of reactions specified within the reaction file, there may be more than one of these tabs. The additional sections will be numbered Rn, where n is the number of the first reaction on that page. For example, if the reaction file contains 5 reactions, the first 3 may appear on the R1 page, then the next page will be labelled R4.


RB Section

Tag / Symbol Input / Calc / Options Description
RB...
On Tick Box Used to enable the reaction file. The default is On.
RCT_Name Input The user may type in the name of the required reaction file, or if the user leaves this field Blank and clicks on the Edit_RCT button, SysCAD will create a reaction file with the same name as the unit.
RCT_Path Display The full path of the reaction file is displayed here.
AutoReload Tick Box This enables the automatic reloading of the reaction file if it has been changed. The user then does not have to click on the 'ReLoad' button each time a change is made to the reaction file.
Load State Output A number of possibilities exist here. Before a reaction file is entered, this field will state 'No Reactions'. Once the reaction file is entered it will have either 'OK', if all is well, or an error message if there is a problem. The message will depend on the error.
Error Output If there is an error with the RCT file, this will give the line number of the error, and a brief message describing the error.
Edit RCT Button Opens the reaction file in the editor defined in the General Options (Please see Setting the Reaction Editor for more information on selecting the editor. The default editor is Notepad, but we recommend using the SysCAD Reaction Editor).
Reload RCT Button Manually reloads the reaction file after changes are made.
Browse RCT Button The user can browse for the reaction file by clicking on this button.
Notes Input The user may type in notes related to the reactions. This field can be accessed in the same way as all other fields, i.e. it may be added to Excel reports, to be read or set. This field is available in SysCAD 9.2.
Overrides
StdSpecieModel Tick Box If user is using a non-standard species model, e.g. Bayer model, then selecting this box will force the reaction block to calculate values using the Standard Species Model. (If the user IS using the Standard Model, then this will have no effect)
OverrideHtDil Tick Box If this option is enabled then the reaction energy will NOT include any Heat of Dilution effects (this is NOT recommended), ie. the reactions will not take any dilution or concentrating effects into account. This is only relevant IF the project includes any species that have Heat of Dilution data entered in the database. See Heat of Dilution in Reaction Energy Calculations for more information.
OverridePP Tick Box If this is enabled then user can choose the Partial Pressure override method used when calculating the enthalpy of gaseous species used in the reaction block energy calculations. If this is disabled, then the reaction calculations are carried out using the feed partial pressure to calculate the enthalpy of gaseous species. This is only relevant if Steam and other gases are present in the Reaction Block. See Partial Pressure of Gases in Reaction Energy Calculations for more information. If this is enabled an additional group of RB.VapourHf tags will be visible.
IgnoreLockup Tick Box This option is only available in SysCAD 9.2 Build 132 or later. This option allows the user to ignore the LockUp functionality, if it has been enabled. Normally, lockup is specifically enabled so that the 'locked up' portion of a specie will NOT react. However, it can also be used to emulate a portion of a specie as some quality, such as Fines, or orginating from a different source. In this case, the user may require the locked up portion to react, in which case this 'Ignore Lockup' tickbox must be enabled.
IgnoreEnergyBalance Tick Box This option is only available in SysCAD 9.2 Build 132 or later. This option allows the user to switch off the Energy Balance within the reaction block. This would result in less work for SysCAD and hence increases the solver speed. This may be used where reporting of the energy terms such as the HOR is not important and/or the final temperature of the product is to be forced. The overall Energy Balance of the model is maintained by the reporting the energy override on the Audit page. See Ignore Energy Balance Option for more information. If this is enabled an additional group of RB.ProductTemp tags will be visible.
RB.ProductTemp... These fields are only visible if the IgnoreEnergyBalance option has been selected (only available in SysCAD 9.2 Build 132 or later).
Method FeedT The feed temperature will be maintained.
DeltaT The product temperature = Feed temperature + DeltaT.
UserT The product temperature is forced to a user specified value.
Reqd.DeltaTemp Input This field is only visible if the DeltaT method is selected. This is the user specified required temperature difference between the RB feed and RB product temperatures. A positive number indicates an increase in temperature while a negative number indicates a decrease in temperature.
Reqd.UserTemp Input This field is only visible if the UserT method is selected. This is the user specified required product temperature.
Visibility(the ExtraInfo field is NOT visible if the IgnoreEnergyBalance option has been selected)
ExtraInfo Remove All No additional energy values will be displayed.
User Defined Info Overall and individual reaction energy values (such as heat of reaction) are displayed at a User Defined temperature and pressure (@UsrDef).
Feed Info Overall and individual reaction energy values (such as heat of reaction) are displayed at Feed temperature and pressure (@Fd).
Product Info Overall and individual reaction energy values (such as heat of reaction) are displayed at Product temperature and pressure (@Pr).
Feed & Product Info Overall and individual reaction energy values (such as heat of reaction) are displayed at Feed and Product temperature and pressure (@Pr).
Reference Info Overall and individual reaction energy values (such as heat of reaction) are displayed at the reference temperature (0°C) and pressure (101.325 kPa) (@Ref).
All Extra Info Overall and individual reaction energy values (such as heat of reaction) are displayed at all four sets of temperatures and pressures defined above.
ChangeVars List Remove All -- no additional fields will be displayed.
Mass -- extra fields will be displayed at the end of each individual reaction, detailing the mass conversion of each reactant and product.
Molar -- extra fields will be displayed at the end of each individual reaction, detailing the molar conversion of each reactant and product.
All -- extra fields will be displayed at the end of each individual reaction, detailing the mass and molar conversions of each reactant and product.
Settings
ExtentType List This list box allows the user to set the error tracking methods for the current RB block. NB, for simultaneous reactions, user should change this to All_Target. If user want to set the options on individual reactions, select either of the two default options, Strict or Target, then set the desired option for each reaction in the Extent.Type field.
All_Strict -- error tracking is switched on for all reactions.
All_Target -- error tracking is switched off for all reactions.
Strict -- error tracking can be switched on or off for each individual reaction, with the default being on.
Target -- error tracking can be switched on or off for each individual reaction, with the default being off.
CnvTolerance Input The convergence tolerance for the reaction solver. Generally, the user should not have to alter this value. However, if the solution is difficult, the user may set this to a larger number to improve the speed of the solution.
MaxIters Input The maximum number of iterations of the reaction solver.
CnvTTolerance Input The convergence tolerance for the temperature solver. Generally, the user should not have to alter this value. However, if the solution is difficult, the user may set this to a larger number to improve the speed of the solution.
MaxTIters Input The maximum number of iterations of the temperature solver.
UsrDefT Input This field is only visible if the ExtraInfo list box is set to 'User Defined Info' or 'All Extra Info'.
The user defined temperature for the reactions. The default is 25°C. This temperature is for display purposes only, it does not affect the calculated results. The displayed values affected will be under Tag.RB.dH@UsrDef fields and the xxxx.@UsrDef fields under each individual reaction.
UsrDefP Input This field is only visible if the ExtraInfo list box is set to 'User Defined Info' or 'All Extra Info'.
The user defined Pressure for the reactions. The default is atmospheric. This pressure is for display purposes only, it does not affect the calculated results. The displayed values affected will be under Tag.RB.dH@UsrDef fields and the xxxx.@UsrDef fields under each individual reaction.
RB.VapourHf... (these fields are only visible if the OverridePP option has been selected)
Method List There are several methods available to the user for calculating/setting the partial pressure used when calculating the enthalpy of gaseous species to be used in the reaction block calculations. Use of the different methods will not change the amount of material reacted or the final temperature of the stream. It will only change where the energy is reported between the HOR for an individual reaction and the Work term. Refer to Partial Pressure of Gases in Reaction Energy Calculations for more information.
TotalPressure -- The partial pressure used will be the total feed pressure.
FeedPP -- The partial pressure used will be the feed partial pressure (this is identical to not using the Partial Pressure Override).
ProductPP -- The partial pressure used will be the product partial pressure.
EnviroPPFrac -- The partial pressure used will be the environmental fraction of the gas (as defined on the Plant Model-Environment page) multiplied by the total pressure.
UserDefinedPPFrac -- The partial pressure used will be the user defined fraction of the gas multiplied by the total pressure.
UserDefinedPP -- The partial pressure used will be the user defined partial pressure.
PP.Rqd.H2O(g) Input This field is only visible if the UserDefinedPP method is selected. This is the user specified required partial pressure of steam used when calculating the enthalpy of gaseous species to be used in the reaction block calculations.
PP.Used.H2O(g) Calc This is the partial pressure of steam used when calculating the enthalpy of gaseous species to be used in the reaction block calculations, based on what the user has selected for the method.
PP.Feed.H2O(g) Calc This is the partial pressure of steam in the feed.
PP.Prod.H2O(g) Calc This is the partial pressure of steam in the product.
PPf.Rqd.H2O(g) Input This field is only visible if the UserDefinedPPFrac method is selected. This is the user specified required partial pressure fraction of steam used when calculating the enthalpy of gaseous species to be used in the reaction block calculations.
PPf.Used.H2O(g) Calc This field is only visible if the EnviroPPFrac or UserDefinedPPFrac method is selected. This is the partial pressure fraction of steam used when calculating the enthalpy of gaseous species to be used in the reaction block calculations.
PPf.Feed.H2O(g) Calc This field is only visible if the EnviroPPFrac or UserDefinedPPFrac method is selected. This is the partial pressure fraction of steam in the feed.
PPf.Prod.H2O(g) Calc This field is only visible if the EnviroPPFrac or UserDefinedPPFrac method is selected. This is the partial pressure fraction of steam in the product.
Work.Feed Calc The HOR for H2O(g)@PPFeed –> H2O(g)@PPUsed. Obviously if there is no H2O(g) in the feed then this term is zero.
Work.Product Calc The HOR for H2O(g)@PPUsed –> H2O(g)@PPProd. Obviously if there is no H2O(g) in the product then this term is zero.
Results
RunState Output This reports run time messages for the reaction file.
Feed.T Calc The temperature of the feed material to the reaction block.
Rct.Feed.T Calc The temperature of the feed material prior to any reaction occuring but after any adjustments to enthalpies of species has been made.
Rct.Prod.T Calc The temperature of the product material after all reactions have taken place but prior to any heat exchange and automatic phase changes have been applied.
Prod.T Calc The temperature of the product material after all reactions, heat exchange and automatic phase changes have occurred.
Press Calc The pressure of the reaction block. Reactions are carried out at a constant total pressure.
Iters Calc The number of iterations required on the last step of the model run to achieve convergence.
TIters Calc The number of iterations required on the last step of the model run to achieve temperature convergence.
NoOfReactions Calc The number of reactions in this reaction block.
SysCAD calculates the following Energy values for the overall reaction block at up to 5 different Temperatures and Pressures. Values at 0°C and 1 atmosphere (101.325 kPa), dH@0, are always displayed. The user may choose to also display the following values by selecting one or all in ExtraInfo: dH@Fd - the values at Feed conditions, dH@Pr - the values at Product conditions,dH@Ref - the values at Reference conditions (0°C and 1 atmosphere (101.325 kPa) (excluding partial pressures), and dH@UsrDef - the values at the User defined conditions.
Nett Calc The overall enthalpy change in the reaction block. This includes all reactions, any heat exchange specified within the RCT file and the enthalpy of any material added (Sources) or lost (Sinks) in the reaction file. A positive number denotes sensible heat gain.
Rct Calc The overall Heat of Reaction for ALL reactions in the Reaction Block. A Negative number denotes an exothermic result.
Work Calc The sum of the energy required to change steam from its feed partial pressure to the partial pressure used in the reaction block calculations and the energy required to change steam from the partial pressure used in the reaction block calculations to the product partial pressure.
HtDiln.Specie Calc The enthalpy change due to Heat of Dilution of the specified specie (for example HtDiln.H2SO4(aq)) If the user has chosen to Override the Heat of Dilution then this value will be 0.
HX Calc Energy supplied or removed from the unit using the HeatExchange method. A positive number means energy ADDED to the system.
Source Calc The Energy added to the unit due to the addition of any material via the RB Source. A positive number means energy ADDED to the system.
Sink Calc The Energy removed from the unit due to the removal of the material via the RB Sink. A negative number means energy REMOVED from the system.

Individual Reactions

Tag / Symbol Input / Calc / Options Description
There will be one block displayed here for each reaction specified in the rct file.
On Tick box Allows the individual reaction be switched on/off.
Reaction Output This displays the actual reaction in the reaction file. This is a standard tagged object and hence it can be copied and pasted and used in reports, etc.
Sequence Display Format of information display: [Sequence Number] ([number] of [total number] of reactions solved simultaneously).
For Example:
  1. If a single number is displayed this means the reaction is sequential and the number stands for the order in which it is reacted.
  2. If the field displays something like this: 2 (1 of 3 Sim), then it means the reaction will solve in sequence 2, and it is part of a set of 3 simultaneous reactions.
State Display Shows the status of the individual reaction.
TypeID Display The method by which the reaction is controlled, e.g. Fraction, FinalConc, etc.
Extent.Desc Display The method by which the reaction is controlled and the species that is used for the control. For example: Fractional Extent: FeSO4(aq) means that the user defines the fraction of FeSO4(aq) (which is a Reactant) that must react.
Extent.Type Strict The unit will display a warning if the Achieved extent does NOT match the required extent.
NB, for simultaneous reactions, user should change this to Target. See also Hints and Comments.
Target The unit will NOT display a warning if the achieved extent is different from the required extent, i.e. the required extent is a target only, it is not essential that it is achieved.
<Default> The individual reaction will use the overall Extent Type (Strict or Target) specified in Settings on the main RB tab.
Extent.Specie Display Shows the species that is used for the extent control.
The following fields will change depending on the Extent type chosen for the reaction in the reaction file (the user cannot change the extent type in the Access Window). Each type is described individually.
Notes:
  1. For each type the required extent may be the value specified in the reaction file (Rct), or the user may change the extent in SysCAD (Set), in which case the field background colour will change to Yellow. If '*' is entered here, default value as specified in the reaction file will be used.
  2. If any specie is a Reactant and it has LockUp, then the locked up portion is NOT be available for reaction, unless Ignore Lockup has been enabled. In this case the Achieved or Actual results are based on the unlocked portion only.
1. Fractional Extent:
Extent (Rct/Set) Input The required Extent of the reaction, either the value typed in on the reaction file (RCT) or overridden in the access window (Set).
Extent.Achieved Calc The actual reaction extent achieved, based on availability of unlocked reactants. See also Hints and Comments.
2. Final Conc: Species(phase)
Conc.Required (Rct/Set) Input The final concentration of the specified species after this reaction, either the value typed in on the reaction file (RCT) or overridden in the access window (Set). The concentration will be measured at either the user specified temperature (Conc_MeasTemp) or FinalT.
Conc.MeasTemp Display The user specified temperature. If '*' is present, it means user has not specified a temperature and the concentration will be given at Final Temperature.
Conc.Actual (@ T) Calc The actual concentration of the species after this reaction step at Conc_MeasTemp. Note: if more reactions are present after this, the concentration of the species in the outlet stream may differ due to further reactions.
Conc.Final (@ T) Calc The final concentration of the species after ALL reactions have taken place. This concentration may differ from what the user has specified.
3. Molar or Mass Ratio
Ratio.Required (Rct/Set) Input The required ratio, either mass or molar, of the product to the reactant. The value is either typed in on the reaction file (RCT) or overridden in the access window (Set).
Ratio.Actual Calc The actual ratio of the product to the reactant after the current reaction has been solved. Note: if more reactions are present after this, the ratio of the compounds in the outlet stream may differ due to further reactions.
Ratio.Final Calc The actual ratio of the product to the reactant after ALL reactions have been solved.
4. Equilibrium
K.Required (Rct/Set) Input The required equilibrium constant, k, of the reaction, either the value typed in on the reaction file (RCT) or overridden in the access window (Set).
K.Actual Calc The equilibrium constant after the current reaction has been solved. Note: if more reactions are present after this, the equilibrium constant in the outlet stream may differ due to further reactions.
K.Final Calc The actual equilibrium constant calculated by the solver after ALL reactions have been solved.
5. Final Fraction This can be either Mass or Molar fraction of all phases or of the species phase.
Fraction.Required (Rct/Set) Input The final fraction remaining of the specified compound after this reaction, either the value typed in on the reaction file (RCT) or overridden in the access window (Set).
Fraction.Actual Calc The actual fraction remaining of the compound after this reaction step. Note: if more reactions are present after this, the final fraction of the compound in the outlet stream may differ due to further reactions.
Fraction.Final Calc The final fraction of the compound remaining after ALL reactions has taken place. This fraction remaining may differ from what the user has specified.
ExtentError Calc The difference between what is required as defined by the user and what is achieved. Notes:
  1. If the reaction is part of a simultaneous set of reactions, then the required extent might not be achieved individually.
  2. The Extent Error is calculated after the reaction step, NOT at the final conditions.
ReactingMoles / mlXfer Calc The number of moles of the specified species which are reacted. In the case of the equilibrium constant, this will be the first reactant.
See Hints and Comment for extra note.
ReactingMass / msXfer Calc The mass of the specified species which are reacted. In the case of the equilibrium constant, this will be the first reactant.
See Hints and Comment for extra note.
The following 3 fields are only visible if the user has enabled the Heat of Reaction Override in the reaction file.
HoRRefT Display The temperature for the HOR specified by the user in the reaction file.
HoRRefP Display The pressure for the HOR specified by the user in the reaction file.
Rqd_dH(Rct/Set) Input The required Heat Of Reaction value of the reaction at reference conditions, either the value typed in on the reaction file (Rct) or changed in the access window (Set). If user requires the value to revert back to that of the reaction file value, simply enter * into the field and press OK.
At Reaction Pressure
HoR@0 Calc The Heat of Reaction per unit mass of specified species at 0 degrees C.
mlHoR@0 Calc The Heat of Reaction per unit mole of specified species at 0 degrees C.
HsGain@0 Calc The total change in enthalpy for this specific reaction at 0 dC and Reaction Pressure.
The following fields will only become visible if the 'Extra Info' and/or 'Change Vars' options are selected. The fields that are visible will depend on the Option selected.
HoR@Fd Calc The Heat of Reaction per unit mass of specified species at the Feed temperature. HoR@Fd = HoR@Ref + Integral of Cp from Ref to Feed T. (mass based)
HoR@Pr Calc The Heat of Reaction per unit mass of specified species at the Product temperature. HoR@Pr = HoR@Ref + Integral of Cp from Ref to Product T. (mass based)
mlHoR@Fd Calc The Heat of Reaction per mole of specified species at the Feed temperature. mlHoR@Fd = mlHoR@Ref + Integral of Cp from Ref to Feed T (mole based).
mlHoR@Pr Calc The Heat of Reaction per mole of specified species at the Product temperature. mlHoR@Pr = mlHoR@Ref + Integral of Cp from Ref to Product T (mole based).
HsGain@0 Calc The total change in enthalpy for this specific reaction at 0 degrees C.
HsGain@Fd Calc The total change in enthalpy for this specific reaction at Feed temperature.
HsGain@Pr Calc The total change in enthalpy for this specific reaction at Product temperature.
At Reference (0C 101.325kPa No Partial Pressure) These fields will only become visible if the ExtraInfo list box is set to Include refInfo/All.
HoR@Ref Output The Heat of Reaction per unit mass of specified species at the reference conditions, 0 degrees C and 101.325kPa.
mlHoR@Ref Calc The Heat of Reaction per mole of specified species at the reference conditions, 0 degrees C and 101.325kPa.
HsGain@Ref Calc The total change in enthalpy for this specific reaction at the reference conditions, 0 degrees C and 101.325kPa..
At User Defined Temperature and Pressure These fields will only become visible if the ExtraInfo list box is set to Include UsrDefInfo/All.
HoR@UsrDef Calc The change in enthalpy / kg of specified species that is reacted. Calculated using Heat of formation values defined in the SysCAD.mdb file @ user specified temperature (UsrDefT), unless Heat of Reaction value is specified in the Rqd_dH field.
mlHoR@UsrDef Calc The change in enthalpy / kgmol of specified species that is reacted. Calculated using Heat of formation values defined in the SysCAD.mdb file @ user specified temperature (UsrDefT), unless Heat of Reaction value is specified in the Rqd_dH field.
HsGain@UsrDef Calc The total change in enthalpy for this specific reaction at user specified temperature (UsrDefT).
The following will only become visible if the ChangeVars list box is set to Include Mass/All.
RB.Rx.MsChg
Reactant1 Calc Mass of Reactant1 being consumed. (negative number)
Reactantx Calc Mass of Reactantx being consumed. (negative number)
Product1 Calc Mass of Product1 being produced. (positive number)
Productx Calc Mass of Productx being consumed. (positive number)
The following will only become visible if the ChangeVars list box is set to Include Mole/All.
RB.Rx.MlChg
Reactant1 Calc Mole of Reactant1 being consumed. (negative number)
Reactantx Calc Mole of Reactantx being consumed. (negative number)
Product1 Calc Mole of Product1 being produced. (positive number)
Productx Calc Mole of Productx being consumed. (positive number)

Source Data Fields

Tag / Symbol Input / Calc / Options Description
If the user has specified a source of material within the reaction file, the following block(s) will appear. (More than one species may be added as a source in the rct file.)
Reaction Display Source: Species Name
On Tick Box This may be used to enable or disable the Source.
TypeID Display Source
Species i Calc The mass of species i required for the Reaction Block. The mass of each species specified in the source will be displayed in a separate field.
Source.SetTandP Tick Box This may be used to set the temperature and pressure of the Source. If this is Not enabled, then the Feed temperature and Pressure are used.
Source.T Input The required temperature of the Source. This field is only visible if Source.SetTandP is enabled.
Source.P Input The required pressure of the Source (usually only important for vapours). This field is only visible if Source.SetTandP is enabled.
HsGain Calc The total enthalpy added via the source species, calculated at the source temperature and pressure.
HfGain Calc The total enthalpy, including Heat of formation, added via the source species, calculated at the source temperature and pressure.


Sink Data Fields

Tag / Symbol Input / Calc / Options Description
If the user has specified a sink of material within the reaction file, the following fields will appear. (More than one species may be removed via a sink in the rct file.)
Reaction Display Sink: Species Name(s)
On Tick Box This may be used to enable or disable the Sink.
TypeID Display Sink
Species i Calc The mass of species i that will be discarded in the Sink. The mass of each species specified in the Sink will be displayed in a separate field.
HsGain Calc The total enthalpy removed via the sink species.
HfGain Calc The total enthalpy removed via the sink species.


Heat Exchange Data Fields

Tag / Symbol Input / Calc / Options Description
If the user has specified a heat exchange with the reaction file, then the amount of heat that is added, or removed, from the unit will also be shown here.
On Tick Box This may be used to enable or disable the Heat Exchange.
Heat Exchange Display The Heat Exchange method chosen in the reaction file will be displayed in this field.
1. FinalT Method
FinalTRqd Input The targeted Final temperature required.
HeatGain Calc The amount of heat added or subtracted is given as the Heat Gain. Heat added to the reaction block is given as a positive number.
2. ApproachT Method
TargetT Input The target temperature.
ApproachT Input The extent in which the unit approaches the target temperature (%)
HeatGain Calc The amount of heat added or subtracted is given as the Heat Gain. Heat added to the reaction block is given as a positive number.
3. Approach Ambient Method
Ambient Input The ambient temperature.
ApproachAmbient Input The extent in which the unit approaches the ambient temperature (%)
HeatGain Calc The amount of heat added or subtracted is given as the Heat Gain. Heat added to the reaction block is given as a positive number.
4. Power Method
PowerInput Input Power supplied to the unit.
HeatGain Calc The amount of heat added or subtracted is given as the Heat Gain. Heat added to the reaction block is given as a positive number.
5. Electrolysis Method
ElectEff (%) Input The cell efficiency (%)
HeatGain Calc The amount of heat added or subtracted is given as the Heat Gain. Heat added to the reaction block is given as a positive number.

Hints and Comments

  1. By default, reactions will solve in a sequential order, the order is defined by how they appear in the reaction file. However, the user can change the sequence order by inserting a sequence number per reaction or reaction set.
    For simultaneous reactions, user must provide the same sequence number to all the reactions to be solved at the same time. All reactions found under a specified sequence number will be assigned the same sequence number and thus solved simultaneously.
  2. For simultaneous reactions, problems may arise if a component act both as a reactant and a product, for the reacting amount available comes solely from the feed, and not from the reactions. This is not a problem for sequential equations.
  3. Heat of formation information must be entered for all components involved in reactions. If Hf information is missing, then Heat of Reaction values should be provided. If neither is present, then SysCAD will give a warning and the Heat of Reaction value calculated will be incorrect (any missing Hf's are assumed to be +100 kJ/mol).
  4. If multi reactions are present in single reaction block, the Final Concentration method may not work correctly.
  5. Make sure -> is used instead of = or <-> when writing reactions that are non-reversible.
  6. If the order of the reactions is changed, SysCAD will remember any overridden extents and still associate them with the old reaction number. Eg. if the extent of the old R2 was overridden to be 10%, then the extent of the new R2 will also be manually overridden to 10%.
  7. The outlet temperature from the reaction block (Prod.T) will be set to no less than 10 degrees below the project minimum temperature and no more than 10 degrees above the project maximum temperature. This may cause an energy imbalance across the unit. These temperature limits can be set in the Project Configuration file.
  8. If the user uses a reaction source which is the extent species, then the extent achieved may not be calculated correctly and the user may receive a warning that the extent has not been achieved.
  9. When writing equations, there is a trick to keep the SysCAD Access Window fields RB.R1.mlXfer and RB.R1.msXfer conversion units meaningful. To do this, the user should write the controlling reactant as the first reactant in the equation.

For Example:

\mathbf{\mathit{CaS(s) + 2O2(g) = CaSO4(aq)}} Extent: Fraction \mathbf{\mathit{CaS(s) = 0.9}}

When the reaction is written this way, the fields displayed will be

RB.R1.mlXfer (kmol/s.CaS(s)) and RB.R1.msXfer (kg/s.CaS(s)), which is meaningful.

However, if the reaction is written like this:

\mathbf{\mathit{2O2(g) + CaS(s) = CaSO4(aq)}} Extent: Fraction \mathbf{\mathit{CaS(s) = 0.9}}

The fields displayed will be RB.R1.mlXfer (kmol/s.O2(g)) and RB.R1.msXfer (kg/s.O2(g))

This is not meaningful as we are interested in CaS, not O2.

NOTE: In SysCAD 92, the above reaction can be written in both ways, and the result in SysCAD Access window will be displayed correctly as kg/s (CaS(s)).

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