f Excel is closed while it is connected to the ControlShell then an orphaned
Excel process remains in memory. The reason lies in the COM architecture.
There is no way around it.
Such an orphan process may be removed from Windows Task Manager. To avoid
creation of an orphaned Excel process, either close the ControlShell before
closing Excel or disconnect the Excel instance from the ControlShell by
pressing <Ctrl>+<Delete> at the addin prompt.