A conveyor feeding system for reliably and continuously supplying particulate matter as feedstock, such as rubber tire chips, to a reactor or distillation unit. The feeding system includes a pair of inclined spiral augers having their lower ends submerged in oil or other liquid to provide a liquid seal, thereby preventing undesirable back flow of distillation gases through the feeding system. The push auger acts to push lightweight feedstock downward, submerging it through the liquid seal. The material thereafter is taken up by the partially submerged feed auger, for withdrawal up out of the liquid seal for delivery to further processing, such as a pyrolytic reactor. Buoyant material, which otherwise might float upon the liquid of the seal reservoir, accordingly may be effectively processed through the system. An inlet valve, through which feedstock is introduced into the push auger, can be opened and closed in coordination with the rotation of the push auger, so that material is fed smoothly into the liquid seal reservoir. The inlet valve also may be of a type which prevents back-flow of gas from the push auger to material inlet valve.