Dynamic Project Overall Mass Balance

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Related Links: Example PGMs for Dynamic Projects

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The following examples show how the Tag Select Class could be used to perform a simple mass balance in a dynamic project.

• This is best performed after the last iteration using the Terminate Solution sub-routine.
• It can also be performed every iteration for debugging.
• The main difference to the steady-state mass balance shown above is that is needs to take account of material in surges and tears (in dynamic, tears can have surge).

Notes:

• This mass balance only takes account of feeders and makeup sources as possible sources and sinks of material and tanks and tear blocks as possible surges of material.
• It ignores any reaction block sources and sinks and other units such as conveyor belts, multi-storage units (stockpiles) and tailings dams.

Example: Dynamic Project Mass Balance

PageLabel "MassBal" 
   Textbreak
   TagSelect Inputs, Outputs, Surges, Tears
   Array     InputList, OutputList, SurgeList, TearList
   Textbreak
   real      MassIn@("M","t"), MassOut@("M","t")
   real      StartSurgeMass@("M","t"), SurgeMass@("M","t"), TearMass@("M","t")
   real      MassBalanceError@("M","t"), RelativeError@("Frac", "Frac")
   real      Preset_surge, Preset_acc
   Checkbox  OK@, Recalc@
	
Sub InitMassBalance()
  ;find all true feeders (not connected) and makeup sources
    OK = Inputs.Exec("([UnitType]=='FeederSink' AND [State]==1 AND [Active]==1) OR [UnitType] == 'MakeupSource'", false, false)
  ;find all true sinks (not connected)
    OK = Outputs.Exec("[UnitType]=='FeederSink' AND [State]==2 AND [Active]==1",false, false)
  ;find all surges (tanks)
    OK = Surges.Exec("[UnitType]=='Tank-1' AND [Active]==1", false, false)
  ;find all Tears
    OK = Tears.Exec("[UnitType]=='Flange' AND [SubClass]=='Tear' AND [Active]==1", false, false)
  ;initialise masses
    MassIn = 0.0
    MassOut = 0.0
    StartSurgeMass = 0.0
    SurgeMass = 0.0
    TearMass = 0.0
    MassBalanceError = 0.0
    RelativeError = 0.0
  ;check if recalculation of initial masses will be required because Preset is used
    Recalc = iif(["$Solver.Dyn.Scenario.Start.Preset"]==1, TRUE, FALSE)
EndSub

Sub CalcStartMass()
  ;sum all Contents 
   StartSurgeMass = 0.0
   Surges.GetValues(".Content.Mt (t)", SurgeList)
   StartSurgeMass = SurgeList.Sum()
EndSub

Sub ReCalcStartMass()
  ; sum all Contents, recalculation after first iteration (due to Preset being used) 
  StartSurgeMass = 0
   Surges.GetValues(".Content.Mt (t)", SurgeList)
   Preset_surge = SurgeList.Sum()
   Surges.GetValues(".QmAcc (t/s)", SurgeList)
   Preset_acc = SurgeList.Sum()
   StartSurgeMass = StartSurgeMass + Preset_surge - (Preset_acc*DeltaTime())
EndSub

Sub CalcMassBalance()
  ; sum all inputs 
   MassIn = 0.0
   Inputs.GetValues(".QProd.Total.Mt (t)", InputList)
   MassIn = InputList.Sum()
  ; sum all Outputs 
   MassOut = 0.0
   Outputs.GetValues(".QProd.Total.Mt (t)", OutputList)
   MassOut = OutputList.Sum()
  ; sum all Tank Surge 
   SurgeMass = 0.0
   Surges.GetValues(".Content.Mt (t)", SurgeList)
   SurgeMass = SurgeList.Sum()
  ; sum all Tears  
   TearMass = 0.0
   Tears.GetValues(".Tear.Accum.Mt (t)", TearList)
   TearMass = TearList.Sum()
  ; perform mass balance
   MassBalanceError = MassIn - MassOut + StartSurgeMass - SurgeMass + TearMass
   RelativeError = MassBalanceError/Max(MassIn,MassOut)
EndSub

Sub PreStart() 
   ;--- Logic executed early before first iteration
   InitMassBalance()
EndSub

Sub InitialiseSolution() 
   ;--- Logic executed during initialisation before first iteration
   CalcStartMass()
EndSub

Sub TerminateSolution() 
   ;--- Logic executed after last iteration (when solver is stopped)
   CalcMassBalance()
EndSub

if Recalc
   ; recalculate initial mass because Preset used
   ReCalcStartMass()
   Recalc = FALSE
endif

CalcMassBalance() ; include this line to perform mass balance every iteration for debugging

$ ; --- end of file ---