Add an unmeasured stream using minimum constraint

There is another way to use the minimum flow rate usefully to handle unmeasured, sporadic flows. By sporadic flow, we mean that there is no measurement on this stream but the flow for this stream is discontinuous. That is, on some days there may be no flow but on others there is some. In such cases, you wish to treat the flow as exactly zero on some days while allowing a reconciled, nonzero value to be assigned on other days.

Add an unmeasured stream (U_STREAM) to the flowsheet and reconcile again.

In our example, the reconciled value of this unmeasured stream is 0.2 ton/day after reconciliation.

Let us assume that flows less than 0.5 ton/day are unrealistically small and should be treated as zero (and therefore treated as out of service).

To achieve this treatment, define a minimum flow rate of 0.5 ton/day in this unmeasured stream.

This unmeasured stream is reconciled as out of service after running data reconciliation.

As you have seen, configuration of the minimum flow rate for an unmeasured stream can be useful in preventing unrealistic flowing with no measurement. Sometimes, the same technique can be applied to a measured stream that may have false measurement which means its measurement value is not quite zero even when there is no flow.