3 replies to this topic

[chrbac]

I'm running a Sep block in my model and just specifying split fractions for one of two outlet streams.  Basically I'm saying send 90% of the water to stream 1 and everything else to stream 2.  I keep getting this error

** ERROR

   BLOCK B1 IS NOT IN MASS BALANCE:

   MASS INLET FLOW = 0.28721682E+00, MASS OUTLET FLOW = 0.28521217E+00

   RELATIVE DIFFERENCE = 0.70286308E-02

   CHECK CHEMISTRY/MOLECULAR WEIGHTS

 

why is the block eating mass?  I dont understand how this happens.  There's no chemistry happening in the block and its just splitting the streams.

 

Thanks

[Bobby Strain]

Is this block in some recycle loop? Maybe a screen snapshot would get you some answers.

 

Bobby

[chrbac]

I've added it to a recycle loop, but this was happening before that.  This is my process, and the mass imbalance is only getting worse....

everything in the snapshot with an error is out of mass balance

 

Attached Files

•  Capture.PNG   176.29KB   15 downloads

[Lucian Gomoescu]

Hi,

 

1. Is stream "CO2OUT" specified as a tear stream @ Data Browser>>Convergence>>Tear>>Specifications ?
In my opinion, the best thing to do is to tear only stream "S1". In this way an estimation of components flow rates and P, T for this stream would be enough for solver of tears  to calculate the rest of ops and stream. In other words this decision involves the minimum number of tears to break all loops.

 

2. Make sure that there are coherent design specs, e.g. make up streams components flow rates are varied in order to suppliment the losses etc.

Try to track possible design specs which are missing (e.g. CO2 mole flow rate in stream "CO2" is not equal to sum of losses of CO2 with streams "BLEED", "PRODCRUD" etc) or are impossible to be fulfilled (contradictions, etc)

 

3. Reconcile streams (see Run>>Reconcile All Streams).