  We study heat transport in quasi-one-dimensional spin-chain systems by
considering the model of one-dimensional bosonic spin excitations interacting
with three-dimensional phonons and impurities in the limit of weak spin-lattice
coupling and fast spin excitations. A combined effect of the phonon and
impurity scatterings yields the following spin-boson thermal conductivity
behavior: kappa_s ~ T^2 at low, kappa_s ~ 1/T at intermediate, and kappa_s =
const at higher temperatures. Our results agree well with the existing
experimental data for Sr2CuO3. We predict an unusual dependence on the impurity
concentration for a number of observables and propose further experiments.
