  Motivated by a recent experiment [S. Beattie, S. Moulder, R. J. Fletcher, and
Z. Hadzibabic, PRL 110, 025301 (2013)] we study the superflow of atomic spinor
Bose-Einstein condensates optically trapped in a ring-shaped geometry. Within a
dissipative mean-field approach we simulate a two-component condensate in
conditions adapted to the experiment. In qualitative agreement with the
experimental findings, we observe persistent currents, if the spin-population
imbalance is above some well-defined `critical' value. The triply charged
vortices decay in quantized steps. The vortex lines escape from the center of
the ring through dynamically created regions in the condensate annulus with
reduced density of one component filled by atoms of the other component. The
vortices then leave the ring-shaped high density region of the condensate and
finally decay into elementary excitations.
