  Motivated by recent experiments on the material Ba_3NiSb_2O_9 we consider a
spin-one quantum antiferromagnet on a triangular lattice with the Heisenberg
bilinear and biquadratic exchange interactions and a single-ion anisotropy.
Using a fermionic "triplon" representation for spins, we study the phase
diagram within mean field theory. In addition to a fully gapped spin-liquid
ground state, we find a state where one gapless triplon mode with Fermi surface
coexists with d + id topological pairing of the other triplons. Despite the
existence of a Fermi surface, this ground state has fully gapped bulk spin
excitations. Such a state has linear in temperature specific heat and constant
in plane spin susceptibility, with an unusually high Wilson ratio.
