Method for circularly pyrolyzing tar

The invention relates to a method for circularly pyrolyzing tar, which comprises the steps of low-temperature preheating of organic solid wastes, high-temperature catalytic pyrolysis and medium-temperature zone circular pyrolysis, and specifically comprises the following steps of conveying the organic solid wastes to a pyrolysis zone by adopting a continuous sample injection mode, firstly preheating in a low-temperature zone of 100-300 DEG C, then pyrolyzing in a high-temperature zone of 500-550 DEG C, and finally entering a medium-temperature zone of 400-450 DEG C, meanwhile, enabling pyrolysis steam to be separated and flow back to the medium-temperature zone for cyclic catalytic pyrolysis, and enabling the pressure of the pyrolysis zone to be kept at 5-7 MPa in the whole heat treatment process. The conversion of tar to high-quality light fuel oil and clean combustible gas is realized by utilizing relatively low energy consumption, the tar conversion rate reaches 99.9%, the activity of a catalyst in the pyr