Reading in a saved UTCHEM simulation will delete any UTCHEM simulation that is already in memory. If a current 3D grid is in memory and the incoming 3D grid does not match, the current 3D grid will also be deleted.
The current UTCHEM interface includes many, but not all, of the features included in the UTCHEM executable. GMS is able to read UTCHEM simulations that were not saved by GMS, but certain features included in the input file will not be available. GMS will alert you with messages to features in the input file that are not in the UTCHEM interface.
Related Links:
UTCHEM options not supported by GMS
New Simulation
Building a UTCHEM model
Delete Simulation
Running UTCHEM